JP2006343697A - Display panel and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the response speed and display high quality images by suppressing image blurring in a display device using a medium which shows optical isotropy when no voltage is applied but shows optical anisotropy when a voltage is applied. <P>SOLUTION: An image display time Tw and black display time (reset time) Tr are provided within a one-frame period Tf. A voltage for image display is applied in the image display time Tw, and a voltage for black display (for resetting) is applied in the black display time Tr. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a display panel and a display device with high display quality that have high-speed response characteristics and wide viewing field characteristics and suppress moving image blur.

  The liquid crystal display device has an advantage that it is thin, lightweight, and consumes less power among various display devices. For this reason, it is widely used in image display devices such as TVs and monitors, OA (Office Automation) devices such as word processors and personal computers, video cameras, digital cameras, mobile phones and other information terminals. Yes.

  Conventionally, for example, twisted nematic (TN) mode using nematic liquid crystal, ferroelectric liquid crystal (FLC), or antiferroelectric liquid crystal (AFLC) is used as a liquid crystal display method of a liquid crystal display device. Known display modes, polymer dispersion type liquid crystal display modes, transverse electric field mode (IPS) modes in which an electric field in the horizontal direction with respect to the substrate surface is applied to the liquid crystal layer, and the like are known.

  Among these liquid crystal display methods, for example, a TN mode liquid crystal display device has been put to practical use. However, the liquid crystal display device using the TN mode has drawbacks such as a slow response and a narrow viewing angle, and these disadvantages greatly hinder CRT (cathode ray tube).

  Although the display mode using FLC or AFLC has advantages such as quick response and wide viewing angle, it has major drawbacks in terms of shock resistance, temperature characteristics, etc. It hasn't been done yet.

  Furthermore, the polymer dispersion type liquid crystal display mode using light scattering does not require a polarizing plate and can display a high luminance, but the viewing angle cannot be controlled by the phase plate, and the response characteristic is not necessary. There is little advantage over the TN mode.

  In any of these display methods, the liquid crystal molecules are aligned in a certain direction, and the appearance differs depending on the angle with respect to the liquid crystal molecules. Each of these display systems uses rotation of liquid crystal molecules due to application of an electric field, and the liquid crystal molecules rotate in an aligned manner, so that it takes time to respond. In the case of a display mode using FLC or AFLC, although it is advantageous in terms of response speed and viewing angle, irreversible alignment breakage due to external force becomes a problem.

  On the other hand, a display method based on electronic polarization using a secondary electro-optic effect has been proposed in contrast to these display methods utilizing the rotation of liquid crystal molecules by applying an electric field.

  The electro-optic effect is a phenomenon in which the refractive index of a substance is changed by an external electric field. The electro-optic effect includes an effect proportional to the first order of the electric field and an effect proportional to the second order, which are called the Pockels effect and the Kerr effect, respectively. In particular, the Kerr effect, which is a secondary electro-optic effect, has been applied to high-speed optical shutters from an early stage, and has been put to practical use in special measuring instruments.

  The Kerr effect was discovered by J. Kerr in 1875. To date, organic liquids such as nitrobenzene and carbon disulfide have been known as materials that exhibit the Kerr effect. These materials are used for, for example, the above-described optical shutter, light modulation element, light polarization element, or high electric field strength measurement of a power cable or the like.

  After that, it was shown that the liquid crystal material has a large Kerr constant, and a basic study for application to an optical modulation element, an optical deflection element, and an optical integrated circuit was conducted, and the Kerr constant exceeding 200 times that of the nitrobenzene was shown. Liquid crystal compounds have also been reported.

  In such a situation, application to a display device of the Kerr effect is being studied. Since the Kerr effect is proportional to the second order of the electric field, it can be expected to be driven at a relatively low voltage compared to the Pockels effect, which is proportional to the first order of the electric field, and is essentially several microseconds to several milliseconds. Therefore, application to a high-speed response display device is expected.

  For example, in Patent Document 1, as a display device using the Kerr effect, at least one of a pair of substrates that is transparent, a medium that includes a polar molecule in an isotropic state sandwiched between the pair of substrates, There is disclosed a display device including a polarizing plate disposed outside at least one of a pair of substrates and an electric field applying unit for applying an electric field to the medium.

  When a medium exhibiting the Kerr effect is applied to a display device, a hold-type display device can be considered like a conventional liquid crystal display device. Here, the hold-type display device is a display device in which written display data is held with little attenuation for a predetermined period. However, a hold-type display device has a problem that moving image blur tends to occur. In such a hold-type display element, even if the optical response of the liquid crystal is sufficiently fast, moving image blur tends to occur due to human visibility. That is, even if a medium having a high-speed response characteristic and exhibiting the Kerr effect is applied to a hold-type display device, moving image blur tends to occur.

  In Patent Document 3, as a method for improving the moving image display performance in the liquid crystal display device, only the display data is written to the liquid crystal pixels and the backlight is turned off in 2/3 time of one field period. In the remaining 1/3 time of one field period, the display data written with the backlight turned on is disclosed.

  Also, in the conventional liquid crystal display device, when the same gradation display is continued for a long time and then the next gradation display is performed, there is a case where the phenomenon of burn-in remains, which is affected by the previous gradation display. is there. Such a burn-in phenomenon in the conventional liquid crystal display device has two factors.

  One is the application of a DC voltage to the liquid crystal. When a TFT or the like is used as a switching element, a direct current component is generated as an effective voltage applied to the liquid crystal due to the parasitic capacitance of the element, and image sticking may appear. Therefore, in the conventional liquid crystal display device, the burn-in can be suppressed by reducing the direct current component as much as possible.

Another factor is ions in the liquid crystal layer attached to the alignment film interface due to the electric polarization of the alignment film. Therefore, in a conventional liquid crystal display device, image sticking is suppressed by suppressing ions remaining in the liquid crystal material and ions eluted and generated in the liquid crystal layer of the liquid crystal display device to a low level. It is also considered that the residual potential in the alignment film or in the insulating film on the electrode surface affects the adhesion of ions to the alignment film interface, and a liquid crystal material that suppresses the residual potential in the alignment film has been developed. Has been. In addition, it has been studied to suppress image sticking by forming an organic thin film that adsorbs free ions so as not to affect the electric field in the liquid crystal layer.
JP 2001-249363 A (publication date September 14, 2001) Japanese Patent Laid-Open No. 11-183937 (publication date July 9, 1999) JP 2000-293142 A (publication date October 20, 2000) Paul R. Gerber “Electro-Optical Effects of a Small-Pitch Blue-Phase System”, 1985, Mol. Cryst. Liq. Cryst., Vol. 116, p.197-206 Hirotsugu kikuchi, 4 others, "Polymer-stabilized liquid crystal blue phases", p. 64-68, [online], September 2, 2002, Nature Materials, vol. 1, [Search July 10, 2003], Internet <URL: https://www.nature.com/naturematerials> Kazuya Saito, Michio Tsuji, “Thermodynamics of unusual thermotropic liquid crystals that are optically isotropic”, Liquid Crystals, Vol. 5, No. 1, p. 20-27, 2001 Jun Yamamoto, "Liquid Crystal Microemulsion", Liquid Crystal, Vol.4, No.3, p.248-254, 2000 Yukihide Shiraishi and 4 others, “Palladium nanoparticles protected with liquid crystal molecules—Preparation and application to guest-host mode liquid crystal display devices”, Polymer Journal, Vol. 59, No. 12, p. 753-759, December 2002 `` Handbook of Liquid Crystals '', Vol.1, p.484-485, Wiley-VCH, 1998 Makoto Yoneya, “Searching for Nanostructured Liquid Crystal Phase by Molecular Simulation”, Liquid Crystal, Vol.7, No.3, p.238-245, 2003 `` Handbook of Liquid Crystals '', Vol.2B, p.887-900, Wiley-VCH, 1998 Jun Yamamoto, “Liquid Crystal Science Experiment Course 1st: Identification of Liquid Crystal Phase: (4) Lyotropic Liquid Crystal”, Liquid Crystal, Vol. 6, No. 1, p.72-82 Eric Grelet, 3 others "Structural Investigations on Smectic Blue Phases", PHYSICAL REVIEW LETTERS, The American Physical Society, 23 APRIL 2001, VOLUME 86, NUMBER 17, p.3791-3794 Shiro Matsumoto, 3 others "Fine droplets of liquid crystals in a transparent polymer and their response to an electric field", 1996, Appl. Phys. Lett., Vol.69, p.1044-1046 Norihiro Mizoshita, Kenji Hanabusa, Takashi Kato `` Fast and High-Contrast Electro-optical Switching of Liquid-Crystalline Physical Gels: Formation of Oriented Microphase-Separated Structure '', Advanced Functional Materials, APRIL 2003, Vol. 13, No. 4, p313 -317) Michi Nakata, 3 others "Blue phases induced by doping chiral nematic liquid crystals with nonchiral molecules", PHYSICAL REVIEW E, The American Physical Society, 29 October 2003, VOLUME 68, NUMBER 4, p.04710-1 to 04701-6 Chandrasekar, Hatsuo Kimura, Mamoru Yamashita, “Physics of Liquid Crystal (Original Book 2nd Edition)”, 1995, Yoshioka Shoten, p.330 Physics Dictionary Editorial Committee, “Physics Dictionary”, 1992, Baifukan, p.631

  However, as shown in Non-Patent Document 1, a display device using a medium exhibiting the Kerr effect has a problem that the response behavior deteriorates at low temperatures because the temperature dependence of the response speed is large.

  Further, a display device using a medium exhibiting the Kerr effect generally has a problem that the drive voltage is high. Note that Patent Document 1 describes liquid crystal materials exhibiting a large Kerr constant, but even when these liquid crystal materials are used, a driving voltage of several tens of volts or more is required. Therefore, it is conceivable to increase the dielectric anisotropy in order to reduce the drive voltage. Here, the dielectric anisotropy (Δε) is a value represented by Δε = εe−εo, where εe is the dielectric constant in the major axis direction of the liquid crystal molecules and εo is the dielectric constant in the minor axis direction of the liquid crystal molecules. It is. However, a liquid crystal material having a high dielectric anisotropy easily takes in impurity ions, and when used in a display device, there is a concern that the reliability may deteriorate due to the impurity ions taken into the liquid crystal material.

  In addition, the hold type display device using the Kerr effect has a problem that moving image blur tends to occur. In order to eliminate the motion blur, the method of intermittently lighting the backlight as in Patent Document 3 requires that the signal input timing to the display element and the intermittent lighting timing of the lighting device be precisely matched. It is difficult to perform accurate timing control accurately.

  Further, the inventors of the present invention have studied in detail the moving image blur and the burn-in factor in the display device using the medium exhibiting the Kerr effect, and as a result, the moving image blur and the burn-in in the display device using the medium exhibiting the Kerr effect are Thus, it has been clarified that there is an expression factor different from the conventional liquid crystal display element. Therefore, in order to suppress the moving image blur and the burn-in in the display device using the medium exhibiting the Kerr effect, a countermeasure different from the countermeasure against the moving image blur and the burn-in phenomenon in the conventional liquid crystal display device is required.

  Thus, conventionally, a method for improving the response characteristic at the low temperature of the Kerr effect has not been clarified. In addition, in a display device using a medium exhibiting the Kerr effect, no technology has been disclosed in the past for solving the reliability deterioration due to impurity ions. In addition, a method of intermittently lighting the lighting device has been proposed in order to eliminate moving image blur in the display device. However, in such a method, the signal input timing to each pixel and the intermittent lighting timing of the lighting device are There is a problem that timing control is difficult because it is necessary to precisely match.

  The present invention has been made in view of the above problems, and its object is to provide a display panel using a medium that exhibits optical isotropy when no voltage is applied and exhibits optical anisotropy when a voltage is applied. An object of the present invention is to display a high-quality image with improved response speed and suppressed moving image blur and burn-in.

  In order to solve the above problems, a display panel of the present invention includes a pair of substrates at least one of which is transparent, a material layer sandwiched between the two substrates, and a pixel electrode for applying an electric field to the material layer. And a counter electrode, and a display panel that performs display by applying an electric field to the substance layer, wherein the substance layer exhibits optical isotropy when no electric field is applied, and the orientation direction of molecules by applying the electric field And a medium in which the degree of optical anisotropy changes, and after applying a voltage for image display between the pixel electrode and the counter electrode, the following is performed between the pixel electrode and the counter electrode: Before applying an image display voltage, the potential of the pixel electrode and the potential of the counter electrode are made substantially equal.

  Here, changing the degree of optical anisotropy means changing the shape of the refractive index ellipsoid. That is, the display panel of the present invention realizes different display states by utilizing the change in the shape of the refractive index ellipsoid when no electric field is applied and when an electric field is applied.

  On the other hand, in the conventional liquid crystal display panel, the major axis direction of the refractive index ellipsoid remains unchanged when the electric field is applied and when no electric field is applied. That is, in the conventional liquid crystal display panel, different display states are realized by changing the major axis direction of the refractive index ellipsoid when no electric field is applied and when an electric field is applied. Therefore, the display principle of the present invention and the conventional liquid crystal display panel are greatly different.

  A medium that exhibits optical isotropy when no electric field is applied and exhibits optical anisotropy when an electric field is applied is different from a liquid crystal that has been used in conventional display panels. The change in the orientation state of the film or the change in the orientation state from when an electric field is applied to when no electric field is applied are different. In other words, the medium used in the display panel having the above configuration is optically isotropic, unlike conventional liquid crystals, when no electric field is applied. And the change from the state which shows optical isotropy to the state which shows optical anisotropy is accompanied by a big orientation change. Further, the change from the state exhibiting optical anisotropy to the state exhibiting optical isotropy is accompanied by a larger alignment change than the conventional liquid crystal. Since such an orientation change is accompanied by a state change of a large orientation defect, the orientation change moves slowly at a low temperature. Also, a change from a state exhibiting optical anisotropy to a state exhibiting optical isotropy as compared to a state exhibiting optical anisotropy to a state exhibiting optical anisotropy (relaxation process) In particular, the movement of the orientation change becomes slow.

  The inventors of the present invention examined in detail the change in orientation during this relaxation process. As a result, it has been found that a phenomenon such as a kind of memory effect occurs in the above relaxation process (relaxation phenomenon). In other words, by applying an electric field for a long time and maintaining the state where the alignment state completely changed from the state showing optical isotropy to the state showing optical anisotropy for a long time, even if the electric field application is stopped, It was discovered that the relaxation to the optically isotropic state occurs slower than when no electric field is applied for a long time. Due to such a memory effect, in a display panel using a medium that exhibits optical isotropy when no electric field is applied and exhibits optical anisotropy when an electric field is applied, if the same grayscale voltage is continuously applied, The response speed becomes slow when changing to gradation.

  On the other hand, according to the above configuration, after a voltage for image display is applied between the pixel electrode and the counter electrode, the next voltage for image display is applied between the pixel electrode and the counter electrode. Before the application, the potential of the pixel electrode is made substantially equal to the potential of the counter electrode. Thereby, the orientation state of the molecules of the medium constituting the material layer is changed to an orientation state exhibiting optical isotropy after the voltage for image display is applied and before the voltage for next image display is applied. Reset. As a result, since the medium sealed in the material layer is not maintained in the same orientation for a long time, the influence of the memory effect as described above can be suppressed. Accordingly, it is possible to prevent the response speed from being lowered when the next image is displayed, that is, when the voltage for the next image display is applied. Further, when the next image is displayed, the influence of the arrangement state of the dielectric material in the previous frame is reduced or prevented, and the flow and tailing of the image can be prevented.

  Even in the conventional liquid crystal display panel, when the same gradation display is continued for a long time and then the next gradation display is performed, the phenomenon of so-called burn-in appears, in which the influence of the previous gradation display remains. There is a case. There are two factors in the image sticking phenomenon in the liquid crystal display panel. One is the application of a DC voltage to the liquid crystal. When a TFT or the like is used as a switching element, a direct current component is generated as an effective voltage applied to the liquid crystal due to the parasitic capacitance of the element, and image sticking may appear. Therefore, burn-in can be suppressed by reducing the direct current component as much as possible.

  Another factor is the electric polarization of the alignment film or ions in the liquid crystal layer attached to the alignment film interface. Therefore, in the conventional liquid crystal display panel, the burn-in is suppressed by suppressing the remaining of ions in the liquid crystal material and the elution and generation of ions in the liquid crystal layer of the liquid crystal display panel to a low level. In addition, it is considered that the residual potential in the alignment film or in the insulating film on the electrode surface affects the ions in the liquid crystal layer, and liquid crystal materials have been developed to suppress the residual potential in the alignment film. It has also been studied to suppress image sticking by forming an organic thin film that adsorbs free ions so as not to affect the electric field in the liquid crystal layer.

  However, unlike the conventional image sticking phenomenon of the liquid crystal display panel, the memory effect as described above is considered to be caused by a change in the alignment state of the molecules constituting the medium. However, different countermeasures are required.

  Moreover, although the dielectric material which shows a big Kerr constant is described in patent document 1, the drive voltage was several tens of volts or more. Therefore, it is conceivable to increase the dielectric anisotropy in order to further reduce the drive voltage. Here, the dielectric anisotropy (Δε) is a value represented by Δε = εe−εo, where εe is the dielectric constant in the major axis direction of the liquid crystal molecules and εo is the dielectric constant in the minor axis direction of the liquid crystal molecules. It is. However, a dielectric material having a high dielectric anisotropy tends to take in impurity ions. Further, the medium exhibiting the Kerr effect is easier to capture impurity ions than the liquid crystal material used in the conventional liquid crystal display panel, and there is a concern about reliability problems when used as a display panel.

  On the other hand, according to the above configuration, after a voltage for image display is applied between the pixel electrode and the counter electrode, a voltage for the next image display is applied between the pixel electrode and the counter electrode. Before the operation, the potential of the pixel electrode and the potential of the counter electrode are made substantially equal to reset the accumulation of the impurity ions to the pixel electrode or the counter electrode even when impurity ions are present in the medium. be able to. As a result, the impurity ions do not adversely affect the driving, a good driving can be performed, and the reliability can be improved.

  Further, the display panel of the present invention supplies a first switching element connected to the pixel electrode and a scanning signal connected to the first switching element for driving and controlling the first switching element. A first signal signal that is connected to the scanning signal line and the first switching element and supplies a first data signal to the pixel electrode via the first switching element when the first switching element is on. Data signal lines, and a drive control means for controlling a scan signal supplied to the scan signal line and a first data signal supplied to the first data signal line, wherein the drive control means has one frame period. An image display period in which a voltage for image display is applied between the pixel electrode and the counter electrode, and a reset period in which the potential of the pixel electrode and the potential of the counter electrode are substantially equal It may be provided with.

  According to the above configuration, the drive control unit applies an image display voltage between the pixel electrode and the counter electrode during one frame period, and the potential of the pixel electrode is opposed to the pixel electrode. There is provided a reset period in which the potential of the electrode is substantially equal. Thereby, the medium sealed in the material layer is not maintained in the same orientation state for a long time, so that the influence of the memory effect as described above can be suppressed. Accordingly, it is possible to prevent the response speed from being lowered during driving in the next frame, and it is possible to prevent image flow and tailing. Further, even when impurity ions are present in the medium, accumulation of impurity ions in the pixel electrode or the counter electrode can be reset. As a result, the impurity ions do not adversely affect the driving, a good driving can be performed, and the reliability can be improved.

  In this case, the drive control means turns on the first switching element connected to the scanning signal line in the image display period, and in that state, the image is applied from the first data signal line to the pixel electrode. A selection period in which a voltage for image display is applied between the pixel electrode and the counter electrode by supplying a first data signal for display, and a first switching element connected to the scanning signal line And a non-selection period in which the voltage between the pixel electrode and the counter electrode is held at the voltage applied in the selection period, and the first connected to the scanning signal line is provided in the reset period. The switching element may be turned on, and in this state, the first data signal having substantially the same potential as the counter electrode may be supplied from the first data signal line to the pixel electrode.

  According to the above configuration, an appropriate image corresponding to the first data signal supplied from the first data signal is printed by printing a voltage for image display on the material layer in the selection period and the non-selection period. Can be displayed.

  The pixel electrode, the counter electrode, and the plurality of scanning signal lines, the plurality of first data signal lines, and the combination of the scanning signal line and the first data signal line. A first switching element; and the drive control means includes a first switching element for each of the scanning signal lines, and the first of each pixel connected to the scanning signal line during the selection period. In this state, the first data signal corresponding to the image to be displayed on each pixel is supplied from the first data signal line to the pixel electrode of each pixel. The first switching element of each pixel connected to the scanning signal line is turned off, and the first switching element of each pixel connected to the scanning signal line is turned on during the reset period. The first Over from data signal line to the pixel electrode of each pixel may be configured to supply a first data signal of the counter electrode and substantially the same potential.

  According to the above configuration, for each pixel (pixel position) connected to the same scanning signal line (one line), before the selection period of the next frame is started, The reset period is provided so that the alignment state (arrangement state) of the molecules constituting the pixel medium becomes optically isotropic. Thereby, it is possible to prevent the molecules constituting the medium from being maintained in the same orientation for a long time and to suppress the expression of the memory effect, thereby improving the response characteristics. In addition, since the influence of the orientation state of the molecules constituting the medium in the immediately preceding frame can be reduced or prevented during driving in the next frame, image flow and tailing can be prevented. Further, even when impurity ions are included in the material layer, impurity ions can be prevented from being accumulated in the pixel electrode or the counter electrode.

  In addition, a third switching element that is provided so as to connect the pixel electrode and the counter electrode and that is driven and controlled by a signal different from the first switching element is provided, and the drive control unit includes the image display period. The first switching element connected to the scanning signal line is turned on, and the first data signal for image display is supplied from the first data signal line to the pixel electrode in that state. A selection period in which a voltage for image display is applied between the pixel electrode and the counter electrode, and the first switching element connected to the scanning signal line is turned off, and the pixel electrode and the counter electrode are A non-selection period for holding the voltage at the voltage applied in the selection period, and in the reset period, the third switching element is turned on, and the pixel electrode and the counter electrode are By causing pass, it may be configured to the potential of the potential and the counter electrode of the pixel electrodes substantially equal.

  According to the above configuration, the drive control unit turns on the third switching element and conducts the pixel electrode and the counter electrode in the reset period, thereby substantially reducing the potential of the pixel electrode and the potential of the counter electrode. Make equal. Thereby, it is possible to prevent the molecules constituting the medium from being maintained in the same orientation for a long time and to suppress the expression of the memory effect, thereby improving the response characteristics. In addition, since the influence of the orientation state of the molecules constituting the medium in the immediately preceding frame can be reduced or prevented during driving in the next frame, image flow and tailing can be prevented. Further, even when impurity ions are included in the material layer, impurity ions can be prevented from being accumulated in the pixel electrode or the counter electrode.

  In this case, the drive control unit may supply a rectangular wave that is inverted with respect to the potential of the counter electrode as the first data signal to the pixel electrode during the selection period.

  The pixel electrode, the counter electrode, and the plurality of scanning signal lines, the plurality of first data signal lines, and the combination of the scanning signal line and the first data signal line. A pixel including a first switching element and a third switching element, and the drive control circuit connects the third switching element in each pixel to a pixel adjacent to the pixel. A driving control may be performed by a scanning signal for driving and controlling the first switching element.

  According to the above configuration, the first switching element in each pixel on one line is connected to one scanning signal line, and the third switching element in each pixel on another line adjacent to the one line. Is connected. Therefore, by performing scanning of one scanning signal line, a writing operation (driving operation in an image display period) is performed on each pixel in which the first switching element is connected to the scanning signal line, and A reset operation (driving operation during a reset period) can be performed on each pixel connected to the first switching element. That is, the pixel column (element column) on which the writing operation is performed and the pixel column on which the reset operation is performed can be driven simultaneously. Thereby, an increase in driving frequency can be prevented.

  In this case, the drive control means may be configured to alternately repeat the supply of the active signal to the odd-numbered scanning signal lines and the scanning of the active signal to the even-numbered scanning signal lines for each frame. .

  According to the above configuration, the time ratio between the image display period (hold period; gradation display period by input of gradation signal) and the reset period (blanking period) in each pixel is 1: 1, and good intermittent display is achieved. (Intermittent lighting) can be performed.

  In addition to the above configuration, the second data signal line for supplying the second data signal to the counter electrode, which is provided substantially in parallel and alternately with the first data signal line, and the counter A second switching element that connects the electrode and the second data signal line, and is driven and controlled by a scanning signal common to the first switching element, and the drive control means includes: The first switching element and the second switching element of each pixel connected to the scanning signal line are turned on, and in this state, the pixel of each pixel from the first data signal line and the second data signal line By supplying the first data signal and the second data signal corresponding to the image displayed on each pixel to the electrode and the counter electrode, respectively, the pixel electrode and the counter electrode in each pixel A selection period in which a voltage for image display is applied between the first switching element and the second switching element of each pixel connected to the scanning signal line is turned off, so that in each of the pixels in the selection period A non-selection period for holding a voltage applied between the pixel electrode and the counter electrode may be provided.

  According to the above configuration, the image display is appropriately performed by controlling the potential of the pixel electrode and the potential of the counter electrode by each data signal supplied from the first data signal line and the second data signal line. It can be carried out. In the reset period, the third switching element is turned on to electrically connect the pixel electrode and the counter electrode, whereby the potential difference between these electrodes can be made substantially equal.

  Further, in this case, the drive control means uses the potentials of the first data signal and the second data signal in the selection period when the potential difference between the pixel electrode and the counter electrode becomes substantially equal in the reset period. It is good also as a structure which sets to the reverse electric potential on the basis of the electric potential of the said both electrodes. Here, the reverse potential is a potential in which the magnitude relationship with respect to the reference potential is opposite and the absolute values of the difference from the reference potential are equal to each other.

  According to the above configuration, the potentials of the first data signal and the second data signal in the selection period are the same when the potential difference between the pixel electrode and the counter electrode is substantially equal in the reset period. The reverse potential is set with respect to the potential. As a result, compared to the writing voltage (the difference between the potential of each of the first and second data signals and the reference potential) for each of the pixel electrode and the counter electrode, a voltage twice that applied to the material layer is applied. be able to. That is, even when a switching element and a data signal circuit having the same withstand voltage as in the conventional case are used, it is possible to apply twice the voltage to the material layer as compared with the conventional case. Therefore, high voltage driving is possible, and intermittent display with improved response characteristics can be performed.

  A storage capacitor line; a first storage capacitor formed between the pixel electrode and the storage capacitor line; a second storage capacitor formed between the counter electrode and the storage capacitor line; It is good also as a structure provided with.

  According to said structure, the influence of the leakage current in the said 1st and 2nd switching element can be made small by providing the 1st and 2nd auxiliary capacity.

  In addition, the pixel electrode and the counter electrode are provided on the same substrate, and the storage capacitor line is provided on the substrate on which the pixel electrode and the counter electrode are provided, with respect to the pixel electrode and the counter electrode. In addition, a configuration in which an insulating layer is interposed therebetween may be employed.

  The capacitance value of the first auxiliary capacitor and the capacitance value of the second auxiliary capacitor may be substantially equal.

  According to the above configuration, even if the potential fluctuation of the auxiliary capacitance line occurs, the potential fluctuation value generated in each of the first and second data electrodes becomes substantially equal. Therefore, the target applied voltage is appropriately applied to the material layer. Display unevenness due to potential fluctuations can be suppressed.

  A capacitance value of a parasitic capacitance formed between the pixel electrode and a scanning signal line connected to the first switching element and the second switching element; the counter electrode; the first switching element; A capacitance value of a parasitic capacitance formed between the scanning signal line connected to the second switching element may be substantially equal.

  According to the above configuration, even if the potential fluctuation of the scanning signal line occurs, the value of the potential fluctuation generated in each of the pixel electrode and the counter electrode becomes equal, so that the target applied voltage can be appropriately applied to the material layer. , Display unevenness due to potential fluctuations can be suppressed.

  Further, a capacitance value of a first parasitic capacitance formed between the pixel electrode and the first data signal line, and a second value formed between the counter electrode and the first data signal line. A parasitic capacitance, a capacitance value of a third parasitic capacitance formed between the pixel electrode and the second data signal line, the counter electrode and the second data signal line, The capacitance values of the fourth parasitic capacitances formed between the two may be substantially equal.

  According to the above configuration, even if potential variations occur in the pixel electrode and the counter electrode, the potential variation values generated in both electrodes are equal. That is, the movement of electric charges in the first to fourth parasitic capacitances accompanying the potential fluctuations of the pixel electrode and the counter electrode is various except for the display unit capacitance (capacitance formed by the pixel electrode, the material phase, and the counter electrode). Therefore, the target applied voltage can be appropriately applied to the material layer, and display unevenness due to potential fluctuations can be suppressed.

  The capacitance values of the first to fourth parasitic capacitances are the capacitance value of the fifth parasitic capacitance formed between the pixel electrode and the scanning signal line, and the counter electrode and the scanning signal. It is good also as a structure larger than the capacitance value of the 6th parasitic capacitance formed between lines.

  According to the above configuration, the potentials of the pixel electrode and the counter electrode are further stabilized by making the first to fourth parasitic capacitances larger than the fifth parasitic capacitance and the sixth parasitic capacitance. Can do. Thereby, at the time of switching of the switching element, the change in the electric field of the display capacitor portion (capacity formed by the pixel electrode, the material phase, and the counter electrode) can be suppressed, and the occurrence of flicker can be suppressed.

  The image display voltage may include a discharge unit that discharges the charge accumulated between the pixel electrode and the counter electrode.

  According to said structure, the electric charge accumulate | stored in the said both electrodes by the voltage for image display applied between the said pixel electrode and a counter electrode can be discharged by the said discharge means. That is, after an image display voltage is applied between the pixel electrode and the counter electrode, the image display voltage is applied before a next image display voltage is applied between the pixel electrode and the counter electrode. The electric charge accumulated in both the electrodes can be discharged by the voltage. Thereby, the medium sealed in the material layer is not maintained in the same orientation state for a long time, so that the influence of the memory effect as described above can be suppressed. Accordingly, it is possible to prevent the response speed from being lowered when the next image is displayed, that is, when the voltage for the next image display is applied. Further, when the next image is displayed, the influence of the arrangement state of the molecules constituting the medium in the previous frame is reduced or prevented, and the flow and tailing of the image can be prevented. Further, even when impurity ions are present in the medium, accumulation of impurity ions in the pixel electrode or the counter electrode can be reset. As a result, the impurity ions do not adversely affect the driving, a good driving can be performed, and the reliability can be improved.

  Note that the discharge unit may be a resistance element provided so as to connect the pixel electrode and the scanning signal line.

  The pixel electrode, the counter electrode, and the plurality of scanning signal lines, the plurality of first data signal lines, and the combination of the scanning signal line and the first data signal line. A pixel including a first switching element is provided on one of the opposing substrates, and the discharging means includes a pixel electrode of each pixel and a first switching element of each pixel. It is also possible to adopt a configuration in which the resistor element is provided on the one substrate so as to connect to another scanning signal line arranged adjacent to the scanning signal line for controlling the above.

  In addition, a capacitive signal line connected to the pixel electrode via a capacitive element is provided, and the discharging means is a resistive element provided to connect the pixel electrode and the capacitive signal line. A certain configuration may be adopted.

  According to any one of the configurations described above, the resistance element functions as a discharge unit that discharges the charge accumulated between the pixel electrode and the counter electrode.

  In the configuration including any one of the resistance elements, the resistance value of the resistance element is the charge accumulated between the pixel electrode and the counter electrode, and the first data signal is supplied to the pixel electrode. After that, it is preferable to set the value to be discharged during the period until the next first data signal is supplied.

  According to the above configuration, the electric charge accumulated between the pixel electrode and the counter electrode can be discharged during the period until the next first data signal is supplied. It can suppress suitably.

  Further, the pixel electrode, the first switching element, and the discharge means may be provided on one of the pair of opposed substrates.

  In addition, the material layer may be provided with an alignment aid that promotes a change in the degree of optical anisotropy when an electric field is applied.

  According to said structure, the change of the grade of the optical anisotropy at the time of an electric field application is accelerated | stimulated with the said orientation auxiliary material. Thereby, optical anisotropy can be expressed in a wide temperature range. That is, by applying an electric field to a medium exhibiting optical isotropy when no electric field is applied, optical anisotropy can be expressed in a wide temperature range. In addition, as such an alignment auxiliary material, what superposed | polymerized the polymeric compound can be used, for example.

  The pixel electrode and the counter electrode may be arranged on at least one of the pair of substrates so as to generate an electric field in a direction parallel to the substrate surface.

  The pixel electrode and the counter electrode may be transparent.

  According to said structure, since the said pixel electrode and a counter electrode are transparent, the transmittance | permeability can be raised. For example, when forming an alignment aid polymerized by light irradiation in the material layer, a polymerizable compound that is polymerized by light irradiation is added to the material layer to form the pixel electrode and the counter electrode. By irradiating light from the substrate side, the region on both electrodes can be irradiated with ultraviolet light. Since unreacted polymerizable compounds can be reduced, it is possible to prevent deterioration in reliability such as a decrease in voltage holding ratio.

  The pixel electrode and the counter electrode may be provided on one of the pair of substrates, and a color filter may be formed on the substrate on which the pixel electrode and the counter electrode are formed.

  According to the above configuration, the pixel electrode and the counter electrode are formed only on one substrate. For this reason, compared with the case where these each electrodes are each installed in a different board | substrate, the precision of the alignment of both board | substrates requested | required in a manufacturing process becomes low.

  The pixel electrode and the counter electrode may be provided on one of the pair of substrates, and the other substrate on which the pixel electrode and the counter electrode are formed may be transparent.

  According to said structure, since the said other board | substrate is transparent and the electrode is not formed in the said other board | substrate, the transmittance | permeability can be raised. Also, for example, when forming an alignment aid polymerized by light irradiation in the material layer, a polymerizable compound that is polymerized by light irradiation is added to the material layer to form the pixel electrode and the counter electrode. By irradiating with light from the side of the substrate that is not exposed, the area where the substance layer can be exposed can be expanded, and unreacted polymerizable compounds can be reduced. For this reason, deterioration of the reliability of the display panel can be prevented. Moreover, the amount of light irradiation for polymerizing the polymerizable compound can be reduced.

  The pixel electrode and the counter electrode may be arranged to generate an electric field in the normal direction of the pair of opposing substrate surfaces.

  According to the above configuration, the change in the degree of optical anisotropy can be promoted not only in the vicinity of the interface between the substrate and the substrate in the material layer, but also in a region away from both substrates. The voltage can be lowered.

  In addition, a plurality of the scanning signal lines, a plurality of the first data signal lines, and the pixel electrodes provided for each combination of the scanning signal lines and the first data signal lines are connected to the pixel electrodes. And a pixel including a first switching element that is driven and controlled by a scanning signal supplied to the scanning signal line is formed on an active matrix substrate that is one of the pair of substrates, The counter electrode may be formed on the counter substrate, which is the other substrate of the pair of substrates, so as to face the pixel electrodes.

  According to the above configuration, active matrix driving can be performed at a low voltage in each pixel.

  Further, a color filter may be formed on the active matrix substrate.

  According to the above configuration, the color filter is formed on the active matrix substrate. In this case, compared with the case where the color filter is provided on the counter substrate, the accuracy of alignment between the two substrates required in the manufacturing process is lowered.

  Further, the counter substrate and the counter electrode may be transparent.

  According to said structure, since the said opposing board | substrate and counter electrode are transparent, the transmittance | permeability can be raised. For example, when forming an alignment aid polymerized by light irradiation in the material layer, a polymerizable compound that is polymerized by light irradiation is added to the material layer, and light irradiation is performed from the counter substrate side. The region where the substance layer can be exposed can be expanded, and unreacted polymerizable compounds can be reduced. Thereby, deterioration of the reliability of the display panel can be prevented. Moreover, the amount of light irradiation for polymerizing the polymerizable compound can be reduced.

  In addition, an auxiliary capacitor may be connected in parallel with the display unit capacitor formed by the pixel electrode, the counter electrode, and the material layer.

  According to the above configuration, since the capacitance formed between the pixel electrode and the counter electrode is increased, the influence of the leakage current in the first switching element and the material layer can be reduced.

  The medium may exhibit a cholesteric blue phase. Alternatively, a chiral agent may be added to the medium.

  Any of the above media is particularly likely to exhibit a memory effect. For this reason, when using these media, it is preferable to reduce the influence of the memory effect by adopting one of the above-described configurations.

  A display device according to the present invention includes any one of the display panels described above.

  According to the above configuration, since the medium sealed in the material layer is not maintained in the same orientation state for a long time, the influence of the memory effect as described above can be suppressed. Accordingly, it is possible to prevent the response speed from being lowered when the next image is displayed, that is, when the voltage for the next image display is applied. Further, when the next image is displayed, the influence of the arrangement state of the molecules constituting the medium in the previous frame is reduced or prevented, and the flow and tailing of the image can be prevented. Further, even when impurity ions are present in the medium, accumulation of impurity ions in the pixel electrode or the counter electrode can be reset. As a result, the impurity ions do not adversely affect the driving, a good driving can be performed, and the reliability can be improved. In addition, a display device using a medium in which the degree of optical anisotropy changes when an electric field is applied has a high response speed. Therefore, with the above configuration, the response speed is high, the reliability is high, and intermittent lighting is performed. Possible display devices can be realized.

  The display device of the present invention includes a pair of substrates, at least one of which is transparent, a material layer sandwiched between the substrates, a pixel electrode and a counter electrode for applying an electric field to the material layer, A display device that performs display by applying an electric field to the material layer, wherein the material layer exhibits optical isotropy when no electric field is applied, and the orientation direction of molecules changes due to the application of the electric field, resulting in optical differences. It consists of a medium whose degree of directionality changes, and after applying an image display voltage between the pixel electrode and the counter electrode, the next image display voltage is applied between the pixel electrode and the counter electrode. Before the operation, drive control means for controlling the potential of the pixel electrode and / or the counter electrode is provided so that the potential of the pixel electrode is substantially equal to the potential of the counter electrode. Here, the drive control means may be formed on any of the substrates, or may be provided outside the substrate. That is, the drive control means may be formed on a display panel constituted by the pair of opposing substrates and the material layer, or may be provided outside the display panel.

  According to the above configuration, since the medium sealed in the material layer is not maintained in the same orientation state for a long time, the influence of the memory effect as described above can be suppressed. Accordingly, it is possible to prevent the response speed from being lowered when the next image is displayed, that is, when the voltage for the next image display is applied. Further, when the next image is displayed, the influence of the arrangement state of the molecules constituting the medium in the previous frame is reduced or prevented, and the flow and tailing of the image can be prevented. Further, even when impurity ions are present in the medium, accumulation of impurity ions in the pixel electrode or the counter electrode can be reset. As a result, the impurity ions do not adversely affect the driving, a good driving can be performed, and the reliability can be improved.

  A first switching element connected to the pixel electrode; a scanning signal line connected to the first switching element for supplying a scanning signal for driving and controlling the first switching element; And a first data signal line that is connected to one switching element and supplies a first data signal to the pixel electrode through the first switching element when the first switching element is on. The drive control means substantially includes an image display period in which a voltage for image display is applied between the pixel electrode and the counter electrode, and a potential of the pixel electrode and a potential of the counter electrode during one frame period. A reset period that is equivalent may be provided.

  According to the above configuration, the drive control unit applies an image display voltage between the pixel electrode and the counter electrode during one frame period, and the potential of the pixel electrode is opposed to the pixel electrode. There is provided a reset period in which the potential of the electrode is substantially equal. Thereby, the medium sealed in the material layer is not maintained in the same orientation state for a long time, so that the influence of the memory effect as described above can be suppressed. Accordingly, it is possible to prevent the response speed from being lowered during driving in the next frame, and it is possible to prevent image flow and tailing. Further, even when impurity ions are present in the medium, accumulation of impurity ions in the pixel electrode or the counter electrode can be reset. As a result, the impurity ions do not adversely affect the driving, a good driving can be performed, and the reliability can be improved.

  In this case, the drive control means turns on the first switching element connected to the scanning signal line in the image display period, and in that state, the image is applied from the first data signal line to the pixel electrode. A selection period in which a voltage for image display is applied between the pixel electrode and the counter electrode by supplying a first data signal for display, and a first switching element connected to the scanning signal line And a non-selection period in which the voltage between the pixel electrode and the counter electrode is held at the voltage applied in the selection period, and the first connected to the scanning signal line is provided in the reset period. The switching element may be turned on, and in this state, the first data signal having substantially the same potential as the counter electrode may be supplied from the first data signal line to the pixel electrode.

  According to the above configuration, an appropriate image corresponding to the first data signal supplied from the first data signal is printed by printing a voltage for image display on the material layer in the selection period and the non-selection period. Can be displayed.

  The pixel electrode, the counter electrode, and the plurality of scanning signal lines, the plurality of first data signal lines, and the combination of the scanning signal line and the first data signal line. A first switching element; and the drive control means includes a first switching element for each of the scanning signal lines, and the first of each pixel connected to the scanning signal line during the selection period. In this state, the first data signal corresponding to the image to be displayed on each pixel is supplied from the first data signal line to the pixel electrode of each pixel. The first switching element of each pixel connected to the scanning signal line is turned off, and the first switching element of each pixel connected to the scanning signal line is turned on during the reset period. The first Over from data signal line to the pixel electrode of each pixel may be configured to supply a first data signal of the counter electrode and substantially the same potential.

  According to the above configuration, for each pixel (pixel position) connected to the same scanning signal line (one line), before the selection period of the next frame is started, The reset period is provided so that the alignment state (arrangement state) of the molecules constituting the pixel medium becomes optically isotropic. Thereby, it is possible to prevent the molecules constituting the medium from being maintained in the same orientation for a long time and to suppress the expression of the memory effect, thereby improving the response characteristics. In addition, since the influence of the orientation state of the molecules constituting the medium in the immediately preceding frame can be reduced or prevented during driving in the next frame, image flow and tailing can be prevented. Further, even when impurity ions are included in the material layer, impurity ions can be prevented from being accumulated in the pixel electrode or the counter electrode.

  In addition, a third switching element that is provided so as to connect the pixel electrode and the counter electrode and that is driven and controlled by a signal different from the first switching element is provided, and the drive control unit includes the image display period. The first switching element connected to the scanning signal line is turned on, and the first data signal for image display is supplied from the first data signal line to the pixel electrode in that state. A selection period in which a voltage for image display is applied between the pixel electrode and the counter electrode, and the first switching element connected to the scanning signal line is turned off, and the pixel electrode and the counter electrode are A non-selection period for holding the voltage at the voltage applied in the selection period, and in the reset period, the third switching element is turned on, and the pixel electrode and the counter electrode are By causing pass, it may be configured to the potential of the potential and the counter electrode of the pixel electrodes substantially equal.

  According to the above configuration, the drive control unit turns on the third switching element and conducts the pixel electrode and the counter electrode in the reset period, thereby substantially reducing the potential of the pixel electrode and the potential of the counter electrode. Make equal. Thereby, it is possible to prevent the molecules constituting the medium from being maintained in the same orientation for a long time and to suppress the expression of the memory effect, thereby improving the response characteristics. In addition, since the influence of the orientation state of the molecules constituting the medium in the immediately preceding frame can be reduced or prevented during driving in the next frame, image flow and tailing can be prevented. Further, even when impurity ions are included in the material layer, impurity ions can be prevented from being accumulated in the pixel electrode or the counter electrode.

  In this case, the drive control unit may supply a rectangular wave that is inverted with respect to the potential of the counter electrode as the first data signal to the pixel electrode during the selection period.

  The pixel electrode, the counter electrode, and the plurality of scanning signal lines, the plurality of first data signal lines, and the combination of the scanning signal line and the first data signal line. A pixel including a first switching element and a third switching element, and the drive control circuit connects the third switching element in each pixel to a pixel adjacent to the pixel. A driving control may be performed by a scanning signal for driving and controlling the first switching element.

  According to the above configuration, the first switching element in each pixel on one line is connected to one scanning signal line, and the third switching element in each pixel on another line adjacent to the one line. Is connected. Therefore, by performing scanning of one scanning signal line, a writing operation (driving operation in an image display period) is performed on each pixel in which the first switching element is connected to the scanning signal line, and A reset operation (driving operation during a reset period) can be performed on each pixel connected to the first switching element. That is, the pixel column (device column) on which the writing operation is performed and the pixel column on which the reset operation is performed can be driven simultaneously. Thereby, an increase in driving frequency can be prevented.

  In this case, the drive control means may be configured to alternately repeat the supply of the active signal to the odd-numbered scanning signal lines and the scanning of the active signal to the even-numbered scanning signal lines for each frame. .

  According to the above configuration, the time ratio between the image display period (hold period; gradation display period by input of gradation signal) and the reset period (blanking period) in each pixel is 1: 1, and good intermittent display is achieved. (Intermittent lighting) can be performed.

  In addition to the above configuration, the second data signal line for supplying the second data signal to the counter electrode, which is provided substantially in parallel and alternately with the first data signal line, and the counter A second switching element that connects the electrode and the second data signal line, and is driven and controlled by a scanning signal common to the first switching element, and the drive control means includes: The first switching element and the second switching element of each pixel connected to the scanning signal line are turned on, and in this state, the pixel of each pixel from the first data signal line and the second data signal line By supplying the first data signal and the second data signal corresponding to the image displayed on each pixel to the electrode and the counter electrode, respectively, the pixel electrode and the counter electrode in each pixel A selection period in which a voltage for image display is applied between the first switching element and the second switching element of each pixel connected to the scanning signal line is turned off, so that in each of the pixels in the selection period A non-selection period for holding a voltage applied between the pixel electrode and the counter electrode may be provided.

  According to the above configuration, the image display is appropriately performed by controlling the potential of the pixel electrode and the potential of the counter electrode by each data signal supplied from the first data signal line and the second data signal line. It can be carried out. In the reset period, the third switching element is turned on to electrically connect the pixel electrode and the counter electrode, whereby the potential difference between these electrodes can be made substantially equal.

  Further, in this case, the drive control means is configured such that the potentials of the first data signal and the second data signal in the selection period are substantially equal to each other in the potential difference between the pixel electrode and the counter electrode in the reset period. It is good also as a structure which sets to the reverse electric potential on the basis of the electric potential of the said both electrodes.

  According to the above configuration, the potentials of the first data signal and the second data signal in the selection period are the same when the potential difference between the pixel electrode and the counter electrode is substantially equal in the reset period. The reverse potential is set with respect to the potential. As a result, compared to the writing voltage (the difference between the potential of each of the first and second data signals and the reference potential) for each of the pixel electrode and the counter electrode, a voltage twice that applied to the material layer is applied. be able to. That is, even when a switching element and a data signal circuit having the same withstand voltage as in the conventional case are used, it is possible to apply twice the voltage to the material layer as compared with the conventional case. Therefore, high voltage driving is possible, and intermittent display with improved response characteristics can be performed.

  As described above, in the display panel or display device of the present invention, after a voltage for image display is applied between the pixel electrode and the counter electrode, the next image display is displayed between the pixel electrode and the counter electrode. Before applying the above voltage, the potential of the pixel electrode is made substantially equal to the potential of the counter electrode.

  Thereby, the medium sealed in the material layer is not maintained in the same orientation state for a long time, so that the influence of the memory effect as described above can be suppressed. Accordingly, it is possible to prevent the response speed from being lowered when the next image is displayed, that is, when the voltage for the next image display is applied. Further, when the next image is displayed, the influence of the arrangement state of the molecules constituting the medium in the previous frame is reduced or prevented, and the flow and tailing of the image can be prevented.

  Further, even when impurity ions are present in the medium, accumulation of impurity ions in the pixel electrode or the counter electrode can be reset. As a result, the impurity ions do not adversely affect the driving, a good driving can be performed, and the reliability can be improved.

Embodiment 1
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view illustrating a schematic configuration of one pixel in a display element (display panel) 190 provided in the display device according to the present embodiment. The display device includes a plurality of such display elements 190.

  As shown in FIG. 1, the display element 190 includes a material layer 103 sandwiched between two substrates 101 and 102. The material layer 103 is encapsulated with a medium that exhibits optical isotropy (may be macroscopically isotropic) when no electric field is applied and exhibits optical anisotropy when an electric field is applied. The medium sealed in the material layer 103 will be described later.

  A data electrode 104 and a common electrode 105 for applying an electric field to the material layer 103 are disposed opposite to each other on the surface of the substrate 101 facing the substrate (counter substrate) 102. An insulating film 106 is formed between the data electrode 104 and the common electrode 105. Further, polarizing plates 107 and 108 are provided on the surfaces of the substrates 101 and 102 opposite to the opposing surfaces of the two substrates, respectively. In the following description, the substrate 101 and each member formed on the substrate 101 are referred to as an active matrix substrate 100.

  This display device performs display by changing the alignment direction of the liquid crystal in the material layer 103 by an electric field formed by applying a voltage between the data electrode 104 and the common electrode 105. 6A shows a state in which no voltage is applied between the data electrode 104 and the common electrode (drain electrode) 105 (voltage non-application state (off state)). FIG. Represents a state in which a voltage is applied between the data electrode 104 and the common electrode 105 (voltage application state (ON state)).

  FIG. 7 is an explanatory diagram showing the arrangement of the data electrode 104 and the common electrode 105 and the absorption axis directions of the polarizing plates 107 and 108. As shown in this figure, the electrode 104 and the electrode 105 in the display element 190 are composed of comb-shaped electrodes formed in a comb-teeth shape, and are opposed to each other. Further, the polarizing plates 107 and 108 provided on both the substrates 101 and 102 have absorption axes orthogonal to each other, the absorption axes of the polarizing plates 107 and 108, and the electrodes of the comb teeth portions of the electrodes 104 and 105, respectively. The extending direction (the direction perpendicular to the electric field application direction) forms an angle of about 45 degrees. For this reason, the absorption axis in each of the polarizing plates 107 and 108 forms an angle of about 45 degrees with respect to the direction of electric field application by the electrodes 105 and 106.

  FIG. 5 is a schematic plan view of the active matrix substrate 100. As shown in this figure, the active matrix substrate 100 has drive circuit regions 14A and 14B and a display region 119 on a substrate 101. In the present embodiment, the drive circuit regions 14A and 14B are provided on the substrate 101. However, the present invention is not limited to this, and a drive signal is supplied from a drive circuit provided outside the substrate 101. There may be.

  The display region 119 is provided with a plurality of scanning signal lines 111 arranged substantially parallel to each other and a plurality of data signal lines 110 orthogonal to each scanning signal line 111. A pixel as shown in FIG. 1 is formed for each section surrounded by two adjacent scanning signal lines 111 and two adjacent data signal lines 110. 5 is an equivalent circuit diagram for one pixel of the display element 190 and is the same as the circuit diagram shown in FIG. Details of the equivalent circuit diagram will be described later.

  FIG. 2 is a plan view showing a schematic configuration of one pixel in the display element 190. 1 described above is a cross-sectional view taken along the d-d ′ section shown in FIG. 2. As shown in this figure, the display element 190 includes a TFT (Thin Film Transistor) 109 as a switching element in each pixel. The data electrode 104 is connected to the drain electrode of the TFT 109, the data signal line 110 is connected to the source electrode of the TFT 109, and the scanning signal line 111 is connected to the gate electrode of the TFT 109. The common electrode 105 is connected to the common signal line 112. Thus, in the display element 190, the data signal line driving circuit and the scanning signal line driving circuit (both not shown) provided in the driving circuit regions 14B and 14A, respectively, send signals to the data signal lines 110 and the scanning signal lines 111. It is possible to perform active driving by inputting.

  FIG. 3 is an equivalent circuit diagram of one pixel of the display element 190, which is the same as the transmission circuit diagram described in the lower part of FIG. As shown in this figure, a display capacitor 120 exists between the TFT 109 and the common signal line 112. The display unit capacitor 120 is a capacitor that exists between the data electrode 104 and the common electrode 105. Further, an auxiliary capacitance 121 (capacity existing between the data electrode 104 and the common signal line 112) exists between the TFT 109 and the common signal line 112, and a parasitic capacitance 122 exists between the TFT 109 and the scanning signal line 111. The parasitic capacitance 123 exists between the TFT 109 and the data signal line 110.

  In the display device according to the present embodiment, a signal input from the data signal line 110 is next transmitted from the data signal line 110 by the display unit capacitor 120 formed of the material layer 103 and the auxiliary capacitor 121 formed in parallel thereto. Is held for a period until the signal is input.

  Next, a method for manufacturing the display element 190 will be described.

  First, a metal material made of tantalum or the like is formed on a glass substrate 101 by a sputtering method, patterned, and then subjected to anodic oxidation, whereby the scanning signal line 111, the gate electrode of the TFT 109, and the common electrode 105 are formed. The common signal line 112 was formed.

  Next, a silicon nitride film as a gate insulating film 106 and a silicon film as a semiconductor layer constituting a channel layer of the TFT 109 were formed by a plasma CVD method, and patterning was performed.

  Further, a metal material made of aluminum or the like was formed by sputtering and patterned, whereby the source electrode and the drain electrode of the TFT 109, the data signal line 110, and the data electrode 104 were formed at the same time.

  In the display element 190, glass substrates are used as the substrates 101 and 102. However, the material of the substrates 101 and 102 is not limited to this, and at least one of the substrates 101 and 102 may be a transparent substrate. That's fine. In this embodiment, the distance between the two substrates in the display element 190, that is, the thickness of the material layer 103 is 10 μm. However, the distance between the two substrates is not limited to this, and may be set arbitrarily. .

  In the present embodiment, as shown in FIG. 7, the electrodes 104 and 105 are comb-shaped electrodes formed in a comb-like shape and are arranged to face each other. However, the shapes of the electrodes 104 and 105 are limited to the comb-shaped electrodes. It is not a thing and you may change suitably. In the present embodiment, the electrode 104 and the electrode 105 are formed with a line width of 5 μm and a distance between electrodes (electrode spacing) of 5 μm. However, the present invention is not limited to this, for example, according to the gap between the substrate 101 and the substrate 102. Can be set arbitrarily. In addition, the materials of the electrodes 104 and 105 are not limited to the above-mentioned materials, and various conventionally known materials can be used as electrode materials such as transparent electrode materials such as ITO (indium tin oxide) and metal electrode materials other than those described above. Can be used.

  In addition, an organic thin film for adsorbing free ions in the material layer 103 or an alignment film for assisting the orientation of the medium enclosed in the material layer 103 is applied to the surface of the substrates 101 and 102 on the material layer 103 side. (Not shown). As such an alignment film, for example, an organic thin film such as polyimide that has been rubbed in advance may be used.

  In the present embodiment, a mixture in which the following compounds are mixed in the following proportions is used as the medium enclosed in the material layer 103.

JC-1041xx 44.73 mol% (46.931 wt%)
5CB 43.43 mol% (35.1 wt%)
ZLI-4572 4.9 mol% (10.3 wt%)
EHA 4.0 mol% (2.4 wt%)
RM257 2.61 mol% (5.0 wt%)
DMPAP 0.33 mol% (0.27 wt%)
Here, JC1041xx (manufactured by Chisso) is a nematic liquid crystal mixture, 5CB (4-cyano-4'-pentyl biphenyl, Aldrich) is nematic liquid crystal, and ZLI-4572 (manufactured by Merck) is Chiral agent, EHA (2-ethylhexyl acrylate, Aldrich) is monoacrylate, RM257 (Merck) is diacrylate monomer, DMPAP (2,2-dimethoxy-2-phenyl acetophenon, Aldrich) is It is a photopolymerization initiator. The chemical structural formula of 5CB is shown below.

  The above mixture exhibited a cholesteric blue phase in the temperature range of 326.3K to 319.5K.

  Next, while adjusting the temperature so that the above mixture always became a cholesteric blue phase, without applying an electric field, the mixture was irradiated with ultraviolet rays to polymerize EHA and RM257. The medium thus obtained stably exhibited a cholesteric blue phase from 326.4K to 260K or less.

  8 and 9 show the schematic structure of the cholesteric blue phase. As shown in these figures, the cholesteric blue phase has a highly symmetric structure. In addition, the cholesteric blue phase has an order less than the optical wavelength (ordered structure, orientation order), and thus is a substantially transparent substance (a substance exhibiting optical isotropy) in the optical wavelength range, When applied, the degree of orientation order changes and optical anisotropy appears (the degree of optical anisotropy changes). That is, the cholesteric blue phase is optically almost isotropic when no electric field is applied, but the liquid crystal molecules tend to face in the electric field direction when the electric field is applied, so that the lattice is distorted and optical anisotropy is exhibited. Therefore, by using the above mixture as a medium for encapsulating the material layer 103, the temperature range that can be used for display can be greatly expanded as compared with a conventional display device using the Kerr effect.

  Next, a method for driving the display device according to the present embodiment will be described. FIG. 4 is an explanatory diagram for explaining a driving method of the display device according to the present embodiment, and shows the voltage waveform applied to the material layer 103 and the light transmittance characteristics of the material layer 103 that change according to the voltage waveform. Show. FIG. 4 shows a result obtained by repeatedly applying a voltage to the display element 190 by the polarity inversion driving method. That is, FIG. 4 shows a result when a voltage is directly applied to the data electrode 104 and the common electrode 105 without connecting the TFT (switching element) 109 to the data electrode (pixel electrode) 104.

  The period Tf shown in FIG. 4 corresponds to one frame in active matrix driving. In this embodiment, Tf = 16.7 ms is set. The length of this period Tf corresponds to the length of one frame at the time of 60 Hz driving used in the conventional active matrix driving.

  A period Tw in FIG. 4 corresponds to an image display period in active matrix driving, that is, a selection period and a subsequent non-selection period (holding period, holding period). In this embodiment, as shown as a period Tr in FIG. 4, a reset period (black display period) is provided. That is, during one frame period Tf, an image display period (selection period and non-selection period) Tw and a reset period Tr that is a black display period are set.

  As shown in FIG. 4, a voltage V or −V (the absolute value of V is larger than the threshold value of the material layer 103) is applied to the material layer 103 over the period Tw. In active matrix driving, all pixel switches connected to one scanning signal line 111 are turned on over a selection period, and in this state, a data voltage corresponding to each pixel is supplied to each data signal line 110. A voltage is applied to the material layer 103 of each pixel connected to the one scanning signal line 111. Thereafter, all the pixel switches connected to the one scanning signal line are turned off. The subsequent period is a non-selection period, but the voltage (data voltage) V or −V supplied during the selection period is applied to the material layer 103 of each pixel connected to the one scanning signal line 111. Since it is held by the display unit capacitor 120 formed of the layer 103 and the auxiliary capacitor 121 formed in parallel thereto, the display state is maintained (held) and an image display period is set.

  Thereafter, all the pixel switches connected to the one scanning signal line 111 are turned on again. In this state, the potential of the data electrode 104 of each pixel connected to each data signal line 110 is set to the same potential as the potential of the common electrode 105 via each data signal line 110. Note that the potential of the data electrode 104 is not necessarily exactly the same as the potential of the common electrode 105, and may be any potential that can be regarded as substantially the same. In other words, any potential can be used as long as the transmittance of the pixel can be made substantially zero and a black display state can be substantially realized.

  As a result, as shown in FIG. 4, in the reset period Tr, the relaxation starts so that the transmittance of the pixel approaches 0, and the relaxation almost ends within the reset period Tr (a state where the transmittance is almost 0). become). As a result, before the selection period of the next frame is started, the state of the material layer 103 in the image display period Tw of the previous frame is substantially optically isotropic (transmittance is substantially zero). Is canceled (reset).

  Therefore, when a voltage is applied to the material layer 103 during the selection period of the next frame, the molecules (dielectric molecules) contained in the material layer 103 do not start to move from the orientation state in the previous frame, As shown in FIG. 4, the transition is always started from the state where the transmittance is 0 (or almost 0). For this reason, phenomena (moving image blur) such as tailing and flow of images on the screen can be suppressed.

  Note that when the material layer 103 is kept at 273 K, the one frame period Tf is fixed and the reset period Tr is changed. As the image display period Tw is shortened (the reset period Tr is lengthened), the relaxation time is shortened. became. More specifically, one frame Tf = 16.7 ms is set, and the image display period Tw is changed to 16.7 ms, 11.2 ms, 8.3 ms, 5, 5 ms (the reset period Tr is set to 0 second, 5 seconds). As a result, the relaxation times were 6 ms, 4 ms, 3 ms, and 2 ms, respectively. This indicates that the longer the image display period Tw, that is, the longer the period during which the same voltage is applied to the material layer 103, the longer the relaxation time.

  This is because when an electric field is applied for a long time, the orientation state changes from a state showing optical isotropy to a state showing optical anisotropy for a long time. It means that a phenomenon (relative to the “memory effect” in the present specification) occurs that the relaxation to the objective isotropic state becomes slower than when the electric field is not applied for a long time. Further, from the above results, the influence of the memory effect becomes larger as the period of time during which the orientation state is changed from the state showing optical isotropy to the state showing optical anisotropy becomes longer, and the relaxation time becomes longer. It turns out that it becomes long.

  As described above, the present embodiment uses a medium that exhibits optical isotropy when no electric field is applied and exhibits optical anisotropy when an electric field is applied. Therefore, the change in the alignment state between application of an electric field and application of no electric field is different from that of a liquid crystal used in a conventional liquid crystal display element. That is, in the display device according to the present embodiment, unlike the conventional liquid crystal display device, the medium sealed in the material layer 103 is optically isotropic when no electric field is applied. Then, by applying an electric field to this medium, the medium changes from a state exhibiting optical isotropy to a state exhibiting optical anisotropy.

  Such a change from a state exhibiting optical isotropy to a state exhibiting optical anisotropy is accompanied by a larger alignment change than the conventional liquid crystal display device. Similarly, a change from a state exhibiting optical anisotropy to a state exhibiting optical isotropy is accompanied by a larger alignment change than the conventional liquid crystal display device.

  Such an orientation change is accompanied by a state change of a large orientation defect, and the movement of the orientation change becomes slow at a low temperature. In particular, a change from a state exhibiting optical anisotropy to a state exhibiting optical isotropic (relaxation process) compared to a state exhibiting optical anisotropy to a state exhibiting optical anisotropy Will slow down the movement of orientation change.

  The inventors of the present invention have examined in detail the orientation change in the relaxation process, and as a result, found that a phenomenon such as a kind of memory effect occurs in the above relaxation process (relaxation phenomenon). In other words, by applying an electric field for a long time and maintaining the state where the alignment state completely changed from the state showing optical isotropy to the state showing optical anisotropy for a long time, even if the electric field application is stopped, It was discovered that the relaxation to the optically isotropic state occurs slower than when no electric field is applied for a long time. For this reason, in a display element using a medium that exhibits optical isotropy when no electric field is applied and exhibits optical anisotropy when an electric field is applied, if the same gradation voltage is continuously applied, The response speed becomes slow when changing.

  Therefore, in this embodiment, in order to avoid a decrease in response speed due to such a memory effect, a black display period (reset period Tr) is provided in one frame. Thereby, the medium sealed in the material layer 103 is not maintained in the same orientation for a long time, so that the influence of the memory effect as described above can be suppressed. Therefore, it is possible to prevent the response speed from decreasing when an image is displayed in the next frame.

  For example, after applying (displaying) a gradation voltage (gradation voltage 1) for displaying a certain bright state for a long time, next applying (displaying) gradation voltage 2 for displaying a slightly dark state. If the memory effect is remarkable, the response to the display in a slightly dark state (gradation voltage 2) is remarkably delayed. In such a case, providing a black display period within one frame may increase the response speed. That is, the gradation voltage 1 is reduced from the gradation voltage 1 by applying the gradation voltage 1 → black → the gradation voltage 2 to the gradation voltage 2 after the gradation effect is reduced. There are cases where the response speed becomes faster when applied.

  As described above, in the display device according to the present embodiment, by providing the reset period Tr in one frame, the response speed is increased, and the material layer in the image display period of the previous frame is driven when driving in the next frame. The influence of the arrangement state of the medium enclosed in 103 can be suppressed or prevented, and the flow and tailing of images can be suppressed.

  Note that the conventional liquid crystal display element is not accompanied by a large change in alignment unlike the medium used in the present display element, and therefore it is considered that the above memory effect due to the change in the state of alignment defects does not occur. That is, even if the same gradation voltage is applied for a long time, the relaxation phenomenon due to the state change of the alignment defect does not slow down. Therefore, in the conventional liquid crystal display element, even if the black display period is provided in one frame, the response speed is not expected to be increased. Therefore, when the voltage is applied as described above, the response is considered to be delayed. That is, in the conventional liquid crystal display device, it is considered that the response is slower when the voltage of gradation voltage 1 → black → gradation voltage 2 is applied than gradation voltage 1 → gradation voltage 2.

  Here, the difference in display principle between the display device according to the present embodiment (a display device in which the degree of optical anisotropy of the medium changes by applying an electric field) and the conventional liquid crystal display device will be described in detail. FIG. 12 is an explanatory diagram for explaining the difference in display principle between the display element according to the present embodiment and the liquid crystal display device of the conventional display method, and shows the refractive index ellipsoid when the electric field is applied and when no electric field is applied. The shape and direction are schematically shown. FIG. 12 shows the display principle in the TN method, VA (Vertical Alignment) method, and IPS (In Plane Switching) method as a conventional liquid crystal display method.

  As shown in this figure, the TN liquid crystal display element has a configuration in which a liquid crystal layer is sandwiched between opposing substrates, and transparent electrodes (electrodes) are provided on both substrates. When no electric field is applied, the major axis direction of the liquid crystal molecules in the liquid crystal layer is twisted and aligned while the major axis direction of the liquid crystal molecules is aligned along the electric field direction when the electric field is applied. As shown in FIG. 12, the average refractive index ellipsoid in this case has the major axis direction parallel to the substrate surface when no electric field is applied, and the major axis direction is the normal direction of the substrate surface when an electric field is applied. Turn to. That is, the shape of the refractive index ellipsoid is an ellipse when no electric field is applied and when an electric field is applied, and the major axis direction changes (the refractive index ellipsoid rotates) when the electric field is applied. Further, the shape of the refractive index ellipsoid is almost the same when no voltage is applied and when a voltage is applied.

  Similarly to the TN mode, the VA mode liquid crystal display element has a configuration in which a liquid crystal layer is sandwiched between opposing substrates, and transparent electrodes (electrodes) are provided on both substrates. However, in the VA mode liquid crystal display element, when no electric field is applied, the major axis direction of the liquid crystal molecules in the liquid crystal layer is aligned in a direction substantially perpendicular to the substrate surface. The axial direction is oriented in a direction perpendicular to the electric field. In the average refractive index ellipsoid in this case, as shown in FIG. 12, the major axis direction is normal to the substrate surface when no electric field is applied, and the major axis direction is parallel to the substrate surface when an electric field is applied. Turn to. That is, the shape of the refractive index ellipsoid is an ellipse when no electric field is applied and when an electric field is applied, and the major axis direction (direction of the refractive index ellipsoid) changes with the electric field applied (the refractive index ellipsoid rotates). To do). Note that the shape of the refractive index ellipsoid is almost the same between when no electric field is applied and when an electric field is applied.

  In addition, the IPS liquid crystal display element includes a pair of electrodes facing each other on a single substrate, and a liquid crystal layer is formed in a region between both electrodes. The orientation direction of the liquid crystal molecules is changed by applying an electric field, and different display states can be realized when no electric field is applied and when an electric field is applied. Therefore, even in an IPS liquid crystal display element, as shown in FIG. 12, the shape of the refractive index ellipsoid is an ellipse between when no electric field is applied and when an electric field is applied, and the major axis direction changes (refractive index ellipse). Body rotates). Further, the shape of the refractive index ellipsoid is almost the same between when no electric field is applied and when an electric field is applied.

  As described above, in the liquid crystal display element of the conventional display system, the liquid crystal molecules are aligned in some direction (typically one direction) even when no electric field is applied. In such a state, the orientation direction is changed all at once, and display (modulation of transmittance) is performed. Further, the shape of the refractive index ellipsoid is almost the same between when no electric field is applied and when an electric field is applied. That is, in the conventional display type liquid crystal display element, the shape of the refractive index ellipsoid is an ellipse when no electric field is applied and when an electric field is applied, and the major axis direction changes depending on the electric field applied (refractive index ellipsoid). Display using the fact that the For this reason, the major axis direction of the refractive index ellipsoid is not always perpendicular or parallel to the electric field application direction. On the other hand, in the display device according to the present embodiment, as will be described later, the direction of the refractive index ellipsoid is perpendicular or parallel to the electric field application direction.

  As described above, in the liquid crystal display element of the conventional display method, the degree of alignment order of liquid crystal molecules beyond visible light is substantially constant, and display is performed by changing the alignment direction.

  In contrast to these display methods, in the display element according to the present embodiment, molecules are directed in all directions when no electric field is applied. However, since these molecules have an order (ordered structure, orientation order) less than the wavelength scale of light, optical anisotropy does not appear (the degree of orientation order on a scale of visible light or higher = 0) Unlike the conventional liquid crystal display element, the refractive index ellipsoid is spherical as shown in FIG.

  However, when an electric field is applied, each molecule has positive dielectric anisotropy, so that the orientation state changes in the direction in the substrate plane (direction parallel to the substrate surface). Further, at this time, distortion occurs in the ordered structure of less than the optical wavelength, and optical anisotropy (orientation order degree on a scale of visible light or higher> 0) appears, and the refractive index ellipsoid becomes elliptical. At this time, the major axis direction of the refractive index ellipsoid is parallel to the electric field direction. More specifically, when the dielectric anisotropy of the medium sealed in the material layer 103 is positive, the major axis direction of the refractive index ellipsoid is parallel to the electric field direction, and the dielectric anisotropy of the medium sealed in the material layer 103 is Is negative, the major axis direction of the refractive index ellipsoid is perpendicular to the electric field direction. That is, in the display element using the above-described mixed system, the shape of the refractive index ellipsoid is isotropic (nx = ny = nz) when no electric field is applied, and the shape of the refractive index ellipsoid is anisotropic when the electric field is applied. (Nx> ny) is expressed. Here, nx, ny, and nz respectively represent refractive indexes with respect to the substrate surface and the left-right direction in FIG. 12, the substrate surface parallel to the depth direction in FIG. 12, and the direction perpendicular to the substrate surface.

  Note that the degree of orientation order in visible light or more ≈ 0 (there is almost no order of orientation), when viewed on a scale smaller than visible light, the proportion of liquid crystal molecules arranged in a certain direction is large (orientation). However, when viewed on a scale larger than visible light, the orientation direction is averaged, meaning that there is no orientation order.

  In other words, in this embodiment, the degree of orientation order on a scale equal to or greater than the wavelength of visible light is approximately zero, and the degree of orientation order has no effect on light in the visible light wavelength region and light having a wavelength larger than the visible light wavelength region. Indicates that it is small enough. For example, a state where black display is realized under crossed Nicols is shown. On the other hand, in this embodiment, the degree of orientation order on a scale of visible light wavelength or more> 0 indicates that the degree of orientation order on a scale of visible light wavelength or more is larger than a substantially zero state. The state where white display is realized under two cols is shown. (In this case, gray which is a gradation display is also included).

  Further, in the display element according to the present embodiment, since the material layer 103 has positive dielectric anisotropy, the major axis direction of the refractive index ellipsoid when the electric field is applied is always parallel to the electric field direction. It becomes. (If the material layer 203 has negative dielectric anisotropy, the major axis direction of the refractive index ellipsoid is perpendicular to the electric field direction.) In contrast, the conventional liquid crystal display Since the element performs display by rotating the major axis direction of the refractive index ellipsoid by applying an electric field, the major axis direction of the refractive index ellipsoid is not always perpendicular or parallel to the electric field direction.

  Thus, in the display element according to the present embodiment, the direction of optical anisotropy is constant (the electric field application direction does not change), and display is performed by modulating the degree of orientation order above visible light. . That is, in the display element using the above-described mixed system, the degree of optical anisotropy (or orientation order above visible light) of the medium itself changes. Therefore, the display principle of the display element according to the present embodiment is greatly different from the display principle of the conventional liquid crystal display device.

  Further, in the display element according to the present embodiment, display is performed using distortion generated in a structure exhibiting optical isotropy, that is, a change in the degree of optical anisotropy in the medium. A wide viewing angle characteristic can be realized as compared with a conventional liquid crystal display element that performs display by changing. Furthermore, in the display element according to the present embodiment, the direction in which birefringence occurs is constant and the optical axis direction does not change, so a wider viewing angle characteristic can be realized.

  Further, in the display element according to the present embodiment, display is performed using anisotropy that appears due to distortion of the structure of a micro region (lattice like a crystal). Therefore, unlike the conventional display principle, there is no problem that the inherent viscosity of the liquid crystal greatly affects the response speed, and a high-speed response of about 1 ms can be realized. That is, in the display principle of the conventional method, the change in the alignment direction of the liquid crystal molecules was used, and thus the inherent viscosity of the liquid crystal greatly influenced the response speed. However, in the display device according to the present embodiment, the structure of the minute region is Since the strain is used, the influence of the inherent viscosity of the liquid crystal is small and a high-speed response can be realized. Therefore, since the display device according to the present embodiment has high-speed response, it is also suitable for, for example, a field sequential color display device.

  In the present embodiment, the mixture (medium) sealed in the material layer 103 contains a monomer and a photopolymerization initiator. This stabilizes the molecular orientation and promotes the change in molecular orientation when an electric field is applied, thus widening the driving temperature range and changing the degree of optical anisotropy when an electric field is applied. Can be promoted.

  Here, when the mixture (medium) enclosed in the material layer 103 contains a monomer, a photopolymerization initiator, or the like, the polymerization is incomplete even after polymerization (curing) of the monomer by ultraviolet irradiation. In some cases, ions remain in the material layer 103 due to a cause such as. In order to reduce the driving voltage, it is effective to use a mixture having a high dielectric anisotropy as the above mixture. In this case, the mixture easily takes in ions. If the same driving voltage is continuously applied for a long time as in the conventional driving method, ions remaining in such a medium or ions taken into the medium adhere to and accumulate on one electrode, adversely affecting it. There was a problem of affecting.

  On the other hand, by providing a reset period within one frame as in this embodiment, even if residual ions are present, the residual ions can be reset. Thus, residual ions do not adversely affect driving, and the next gradation voltage application is performed satisfactorily. In other words, by providing a black display period (reset period) in one frame period, accumulation of impurity ions in the data electrode (or common electrode) can be reset, and good driving can be performed. Can be improved.

  In the present embodiment, the above-described mixture is used as a medium to be enclosed in the material layer 103, but the medium to be enclosed in the material layer 103 is not limited to this, and an optical difference is applied by applying an electric field. It is sufficient if the degree of directionality changes.

  In the present embodiment, the medium enclosed in the material layer 103 contains an acrylate monomer. An acrylate monomer is a photopolymerizable monomer (polymerizable compound), and is polymerized (cured) by irradiation with ultraviolet rays (light) to form a polymer chain (alignment aid). By forming such a polymer chain in the material layer 103, the molecular orientation can be stabilized and the change in the degree of optical anisotropy when an electric field is applied can be promoted. Note that the polymerizable compound added to the medium sealed in the material layer 103 is not limited to that used in the above mixture. For example, a polymerizable compound (compound A) having the following structural formula can be used as the polymerizable compound added to the medium sealed in the material layer 103.

  Here, X represents a hydrogen atom or a methyl group. N is an integer of 0 or 1. Moreover, the 6-membered rings A, B, and C independently represent 1,4-phenylene group, 1,4-transcyclohexyl group, or any of the following functional groups. That is, the 6-membered rings A, B, and C may be different or the same among the following functional groups. In the following functional groups, m represents an integer of 1 to 4.

Y1 and Y2 are each independently a single bond, —CH ₂ CH ₂ —, —CH ₂ O—, —OCH ₂ —, —OCO—, —COO—, —CH═CH—, —C≡. C—, —CF═CF—, — (CH ₂ ) ₄ —, —CH ₂ CH ₂ CH ₂ O—, —OCH ₂ CH ₂ CH ₂ —, —CH═CHCH ₂ CH ₂ O—, —CH ₂ CH ₂ represents CH═CH—. Y1 and Y2 may also be a linear or branched alkyl or alkenyl group having up to 10 carbon atoms, one CH ₂ group present in this group or adjacent. Two non-CH ₂ groups may be replaced by —O—, —S—, —CO—O— and / or —O—CO—. Y1 and Y2 may or may not contain a chiral carbon. Y1 and Y2 may be the same or different as long as they have any of the structures described above.

  Y3 represents a single bond, —O—, —OCO—, or —COO—. R3 represents an alkyl group having 1 to 20 carbon atoms that does not contain a chiral carbon. Note that these compounds exhibit a liquid crystal phase and thus have a high ability to impart alignment regulating force and are suitable as a medium to be enclosed in the material layer 103. An example of such a compound is RM257 described above.

  Other compounds include liquid crystalline (meth) acrylate (polymerizable compound) having the following structural formula.

  In addition, when using a liquid crystalline (meth) acrylate having a liquid crystal skeleton and a polymerizable functional group in the molecule, in order to achieve both halftone display and low voltage driving, a gap between the liquid crystal skeleton and the polymerizable functional group is required. A monofunctional, bifunctional or trifunctional liquid crystalline acrylate having no methylene spacer is preferred. That is, monofunctional, bifunctional, or trifunctional acrylates that are acrylic acid or methacrylic acid esters of compounds having a liquid crystal skeleton having two or three six-membered rings as a partial structure are preferable.

  Such a monofunctional acrylate does not have a flexible linking group such as an alkylene group or an oxyalkylene group between the acryloyloxy group and the liquid crystal skeleton. For this reason, the main chain of the polymer obtained by polymerizing this type of acrylate has a rigid liquid crystal skeleton directly integrated without a linking group, and the thermal motion of the liquid crystal skeleton is limited by the polymer main chain. Therefore, the orientation of the liquid crystal molecules affected by the main chain can be further stabilized. Since these compounds also exhibit a liquid crystal phase near room temperature, they have a high ability to impart alignment regulating force and are suitable as a medium to be enclosed in the dielectric material layer 103.

  Moreover, it is preferable to use an acrylate monomer as a photopolymerizable monomer (photoreactive monomer). In particular, a mixed system of a liquid crystalline diacrylate monomer and a non-liquid crystalline acrylate monomer is preferable. This is because in the case of a mixed system of a liquid crystalline diacrylate monomer and a liquid crystalline acrylate monomer, the expansion range of the temperature range showing the cholesteric blue phase becomes small. For example, 46.2 mol% of JC1041xx, 44.7 mol% of 5CB, 5.0 mol% of ZLI-4572, 6CBA (liquid crystalline acrylate monomer; 6- (4′-cyanobiphenyl-4-yloxy) hexyl acrylate) When the composition was 8 mol%, RM257 was 1.1 mol%, and DMPAP was 0.2 mol%, the temperature range showing the cholesteric blue phase was in the range of 329.8K to 327.7K.

  As the non-liquid crystalline monomer, an acrylate monomer having an acryloyl group or a methacryloyl group in the molecular structure is preferable, and a branched structure acrylate monomer having an alkyl group as a side chain is particularly preferable. The alkyl group preferably has 1 to 4 carbon atoms, and preferably has at least one side chain composed of such an alkyl group per monomer unit. Examples of such a monomer include TMHA (3,5,5-trimetthylhexyl acrylate, manufactured by Aldrich) in addition to EHA. In addition, when photopolymerization is performed with an acrylate monomer having no branched structure, the expansion range of the temperature range of the cholesteric blue phase may be reduced. For example, JC1041xx is 44.1 mol%, 5CB is 44.3 mol%, ZLI-4572 is 5.2 mol%, and HA (an acrylate monomer having no branched structure; n-hexyl acrylate, manufactured by Aldrich) is 4.0 mol. %, RM257 was prepared in a composition of 2.0 mol%, and DMPAP was prepared in a composition of 0.3 mol%, the temperature range showing a cholesteric blue phase was in the range of 326.2K to 318.0K. However, even when HA is used, the range of expansion of the temperature range of the cholesteric blue phase can be expanded by increasing the proportion of HA. When using an acrylate monomer having no branched structure, it is preferable to use a monomer having a long alkyl chain. If such an acrylate monomer is used, the same effect as that of an acrylate having a branched structure can be obtained. An example is n-OA (n-octyl acrylate, manufactured by Aldrich).

Further, the photopolymerizable monomer (polymerizable compound) is not limited to the achiral substance as described above, and a chiral substance may be used. Since the chiral photopolymerizable monomer itself is chiral, it spontaneously takes a twisted structure, and therefore has good compatibility with the twisted structure of the cholesteric blue phase and high stability.
As the photopolymerizable monomer exhibiting chirality, for example, a polymerizable compound having the following structural formula can be used.

  Here, R1 represents a C3-C20 alkyl group having a chiral carbon and including a branched chain structure. R2 represents an alkyl group having 1 to 20 carbon atoms and may or may not contain a chiral carbon. Note that these compounds exhibit a liquid crystal phase and thus have a high ability to impart alignment regulating force and are suitable as a medium to be enclosed in the material layer 103. Examples of such compounds include the following compounds.

This compound exhibits a cholesteric phase in the range of 69 ° C to 97 ° C.

  Further, the quantity ratio of each substance is not limited to the above-described quantity ratio. However, when the content of the photopolymerizable monomer (monomer) is small, the molecular orientation regulating force may not be sufficiently exhibited. For example, when a cholesteric blue phase is used as a medium sealed in the material layer 103 as in the present embodiment, the temperature range showing the costelic blue phase is not so wide when the content of the photopolymerizable monomer (monomer) is small. For example, JC1041xx is 45.1 mol%, 5CB is 45.8 mol%, ZLI-4572 is 5.1 mol%, EHA is 2.4 mol%, RM257 is 1.5 mol%, and DMPAP is 0.2 mol%. ) In this case (in this case, the photoreactive monomer content is 3.9 mol%), the cholesteric blue phase is in the range of 326.3K to 319.5K, and the above ratio (JC-1041xx is 44.73 mol%). 5CB 43.43 mol%, ZLI-4572 4.9 mol%, EHA 4.0 mol%, RM257 2.61 mol%, and DMPAP 0.33 mol%). The temperature range was narrower than Further, when the monomer content is high, when used as a display element, the portion contributing to the change in optical anisotropy is reduced when an electric field is applied compared to when no electric field is applied, and the driving voltage is increased. Therefore, the content of the photopolymerizable monomer (photoreactive monomer) is preferably in the range of 2 mol% to 20 mol%, more preferably in the range of 3 mol% to 15 mol%, and 5 mol% to 11 mol%. More preferably.

  Further, the phase transition temperature between the liquid crystal phase and the solid phase is preferably −10 ° C. or lower, and more preferably −30 ° C. or lower. That is, it is preferable to determine the quantity ratio of the mixed substance so that the phase transition temperature of the liquid crystal phase-solid phase is −10 ° C. or lower, more preferably −30 ° C. or lower.

  Further, epoxy acrylate may be used as a photopolymerizable monomer to be added to the medium sealed in the material layer 103. Examples of the epoxy acrylate include bisphenol A type epoxy acrylate, brominated bisphenol A type epoxy acrylate, and phenol novolac type epoxy acrylate. Epoxy acrylate has both an acrylic group that is polymerized by light irradiation, a carbonyl group that is polymerized by heating, and a hydroxyl group in one molecule. For this reason, the light irradiation method and the heating method can be used together as the curing method. In this case, there is a high possibility that at least one of the functional groups reacts and is polymerized (cured). Therefore, there are fewer unreacted parts and sufficient polymerization can be performed.

  In this case, it is not always necessary to use the light irradiation method and the heating method in combination, and either method may be used. That is, the present display element is not limited to a method of polymerizing a photopolymerizable monomer by ultraviolet light (light), and a method of polymerizing may be appropriately selected according to the characteristics of the polymerizable compound to be used. In other words, in the present display element, the polymerizable compound added to the medium is not limited to a photopolymerizable monomer that is polymerized by light irradiation, but may be a polymerizable monomer that is polymerized by a method other than light irradiation. For example, a thermopolymerizable monomer may be used.

  In addition, the phase transition temperature of the isotropic phase-liquid crystal phase may be lowered by addition of a monomer and ultraviolet light (UV) irradiation. For this reason, it is preferable that the phase transition temperature of the isotropic phase-liquid crystal phase of the liquid crystal mixture before containing the monomer is 55 ° C. or higher so that the use temperature range does not become too narrow when used as a display element. That is, it is preferable to determine the quantity ratio of the mixed material so that the phase transition temperature between the isotropic phase and the liquid crystal phase of the liquid crystal mixture before containing the monomer is 55 ° C. or higher. When the display element is actually used by applying it to a product such as a television, there is generally no problem if the phase transition temperature of the isotropic phase-liquid crystal phase of the liquid crystal mixture before the monomer is contained is 55 ° C. or more. For example, when JC1041xx is prepared with a composition of 48.2 mol%, 5CB of 47.4 mol%, and ZLI-4572 of 4.4 mol%, and then irradiated with ultraviolet light, the phase transition temperature of the isotropic phase-liquid crystal phase is It was 331.8K, but JC1041xx was 44.7 mol%, 5CB was 43.4 mol%, ZLI-4572 was 4.9 mol%, EHA was 4 mol%, RM257 was 2.6 mol%, and DMPAP was 0.33 mol%. When prepared with the composition and then irradiated with ultraviolet light, the phase transition temperature of the isotropic phase-liquid crystal phase was reduced to 326.4K.

  Further, the polymerizable compound is preferably one that can assist (promote) the orientation of molecules by application of a voltage, such as a network polymer (network polymer material), a cyclic polymer (cyclic polymer material), etc. There may be.

  In this embodiment, DMPAP (2,2-dimethoxy-2-phenyl acetophenon, manufactured by Aldrich) is used as the polymerization initiator, but the present invention is not limited to this. As the polymerization initiator, in addition to DMPAP, for example, methyl ethyl ketone peroxide, benzoyl peroxide, cumene hydroxide peroxide, tertiary butyl peroxide, dicumyl peroxide, benzoyl alkyl ether, acetophenone, benzophenone , Xanthone-based benzoin ether-based, benzyl ketal-based polymerization initiators, and the like can be used. Note that commercially available products include, for example, Darocur 1173, 1116 manufactured by Merck, Irgacure 184, 369, 651, 907 manufactured by Ciba Chemical Co., Kayacure DETX, EPA, ITA manufactured by Nippon Kayaku Co., DMPAP manufactured by Aldrich, DMPA or the like (both are registered trademarks) can be used as they are or in an appropriate mixture.

  Moreover, in this embodiment, although the polymerization initiator is added, the polymerization initiator does not necessarily need to be added. However, in order to polymerize the polymerizable compound by, for example, light or heat, it is preferable to add a polymerization initiator. Polymerization can be carried out rapidly by adding a polymerization initiator.

  Moreover, it is preferable that the addition amount of a polymerization initiator is 10 wt% or less with respect to a polymeric compound. This is because if it is added more than 10 wt%, the polymerization initiator acts as an impurity, and the specific resistance of the display element is lowered.

Further, in order to promote a change in the degree of optical anisotropy due to electric field application, the material layer 103 may include a porous structure. For example, a porous inorganic material may be used as the porous structure. In this case, for example, a sol-gel material (porous inorganic material) such as barium titanate may be added in advance to a medium (dielectric liquid) sealed in the substance layer 103. As another example, a porous inorganic layer may be formed using polystyrene fine particles and SiO ₂ fine particles. For example, a glass substrate with a transparent electrode having a slit is immersed in an aqueous solution in which polystyrene fine particles having a particle size of 100 nm and SiO ₂ fine particles having a particle size of 5 nm are mixed and dispersed, and the self-assembly phenomenon of the mixed fine particles is utilized by a pulling method. After forming a film thickness of several μm, the substrate having a porous inorganic layer having a reverse opal structure having 100 nm pores can be obtained by baking at a high temperature to vaporize polystyrene. Then, a cell may be formed by injecting a dielectric material after filling the substrates into a cell and filling the hole with the dielectric material. Even when these porous inorganic materials are used, the same effects as those obtained when the material layer 103 includes the polymer chain (polymerizable compound) can be obtained.

  Further, a hydrogen bond network (hydrogen bond) can also be used for the material layer 103 in order to promote a change in the degree of optical anisotropy due to application of an electric field. Here, the hydrogen bond network means a bonded body formed not by chemical bonds but by hydrogen bonds.

  Such a hydrogen bond network can be obtained by, for example, mixing a gelling agent (hydrogen bonding material) with a medium encapsulated in the substance layer 103. As the gelling agent, a gelling agent containing an amide group is preferable, and a gelling agent containing at least two amide groups in one molecule, a urea-based or lysine-based gelling agent is more preferable. For example, a gelling agent (gelling agent A or gelling agent B) having the following structural formula can be used.

These gelling agents can be gelled by mixing a dielectric material such as a liquid crystalline material with a small amount of gelling agent.

  In addition, for example, a gel material (hydrogen-bonding material) and Lys18 (see the following structural formula) described in Non-Patent Document 12 (p.314, FIG. 2) are set in a medium in which the substance layer 103 is sealed. It is obtained by mixing 15 mol%.

  That is, a hydrogen bonding network showing a Gel (gel) state as shown in Non-Patent Document 12 (p.314, Fig.1) realized by mixing Lys18 with 0.15 mol% in a medium is optically applied by applying an electric field. It can be used to promote changes in the degree of mechanical anisotropy. Even when these hydrogen bonding networks are used, the same effects as those obtained by including the polymer chain (polymerizable compound) in the material layer 103 can be obtained.

  In the case of polymer networks, there are concerns such as increased process of UV irradiation, material deterioration due to UV irradiation, and decreased reliability due to unreacted groups, but these have the advantage that they do not occur in the case of gelling agents. .

  Further, fine particles may be used for the material layer 103 in order to promote a change in the degree of optical anisotropy due to electric field application. In a system in which fine particles are dispersed in the material layer 103, a dielectric material such as liquid crystal molecules is oriented under the influence of the fine particle interface. Therefore, in the system in which the fine particles are dispersed, the orientation state of the dielectric substance is stabilized due to the dispersion state.

  In this case, the substance layer 103 is formed by enclosing a dielectric material such as a liquid crystalline substance and fine particles. Each of the dielectric substance and the fine particles is composed of one or more kinds. Further, it is desirable that fine particles are dispersed in the dielectric material so that the fine particles are dispersed in the dielectric material layer.

  In this case, it is preferable to use fine particles having an average particle size of 0.2 μm or less. By using fine particles having an average particle diameter of 0.2 μm or less, the dispersibility in the material layer 103 is stabilized, and the fine particles are not aggregated or phases are not separated even after a long time. Therefore, for example, since the fine particles are precipitated and local unevenness of the fine particles is generated, the unevenness of the display element can be sufficiently suppressed.

  In addition, when light is incident on three-dimensionally distributed particles, diffracted light is generated at a certain wavelength. By suppressing the generation of this diffracted light, the optical isotropy is improved and the contrast of the display element is increased. Although the diffracted light by the three-dimensionally distributed particles depends on the incident angle, the diffracted wavelength λ is given by λ = 2d. Here, d is a distance between particles. In general, it is said that the lower limit of the wavelength visible to humans is about 400 nm. Therefore, the interparticle distance d of the fine particles is preferably 200 nm or less, which is half of the visible light (400 nm). In addition, the International Lighting Commission CIE (Commission Internationale de l'Eclairage) stipulates that the wavelength that cannot be recognized by human eyes is 380 nm or less. Therefore, the interparticle distance d of the fine particles is more preferably 190 nm or less, which is half of 380 nm.

  The concentration (content) of the fine particles in the material layer 103 is preferably 0.05 wt% or more and 20 wt% or less with respect to the total weight of the fine particles and the medium enclosed in the material layer 103. By adjusting the concentration of the fine particles in the material layer 103 to be 0.05 wt% or more and 20 wt% or less, aggregation of the fine particles can be suppressed.

  Note that the fine particles encapsulated in the material layer 103 are not particularly limited, and may be transparent or opaque. The fine particles may be organic fine particles such as a polymer, inorganic fine particles, metallic fine particles, or the like.

  When using organic fine particles, it is preferable to use fine particles in the form of polymer beads such as polystyrene beads, polymethyl methacrylate beads, polyhydroxy acrylate beads, and divinylbenzene beads. In this case, it may be cross-linked or may not be cross-linked. When using inorganic fine particles, it is preferable to use fine particles such as glass beads and silica beads. When metal-based fine particles are used, alkali metals, alkaline earth metals, transition metals, and rare earth metals are preferable. For example, it is preferable to use fine particles in the form of titania, alumina, palladium, silver, gold, copper or oxides of these metal elements. These metal-based fine particles may be used with only one kind of metal, or may be formed by alloying and compounding two or more kinds of metals. For example, the silver particles may be covered with palladium. If the metal fine particles are composed only of silver particles, the characteristics of the display element may change due to the oxidation of silver, but the oxidation of silver can be prevented by covering the surface with a metal such as palladium. Further, the fine particles in the form of beads may be used as they are, or those that have been heat-treated or those provided with an organic substance on the surface of the beads may be used. As the organic substance to be imparted, those showing liquid crystallinity are preferable. By applying an organic substance exhibiting liquid crystallinity to the bead surface, the medium (dielectric substance) in the peripheral portion is easily aligned along the liquid crystal molecules. For example, a compound having the following structural formula is preferred.

Here, n is an integer of 0-2.
Here, the 6-membered ring A is preferably any of the following functional groups.

The 6-membered rings B and C independently represent a 1,4-phenylene group, a 1,4-transcyclohexyl group, or any of the following functional groups (see the following structural formula).

Here, m represents an integer of 1 to 4. That is, the 6-membered rings B and C may be different or the same among the following functional groups.

Here, Y1, Y2, and Y3 are each independently a single bond, —CH ₂ CH ₂ —, —CH ₂ O—, —OCH ₂ —, —OCO—, —COO—, —CH═CH—, —C≡C—, —CF═CF—, — (CH ₂ ) ₄ —, —CH ₂ CH ₂ CH ₂ O—, —OCH ₂ CH ₂ CH ₂ —, —CH═CHCH ₂ CH ₂ O—, — CH ₂ CH ₂ CH═CH— is represented. Y 1, Y 2 and Y 3 may be a linear or branched alkyl group or alkenyl group having up to 10 carbon atoms, and one CH ₂ group present in this group or Two non-adjacent CH ₂ groups may be replaced by —O—, —S—, —CO—O— and / or —O—CO—. Y1, Y2, and Y3 may or may not contain a chiral carbon. Y1, Y2, and Y3 may be the same or different as long as they have any of the structures described above.

  R represents a hydrogen atom, a halogen atom, a cyano group, an alkyl group having 1 to 20 carbon atoms, an alkenyl group, or an alkoxyl group.

  The amount of these organic substances imparted to the surface of the metal fine particles is preferably in a ratio of 1 mol to 50 mol with respect to 1 mol of the metal.

  The metal-based fine particles to which the organic material is added can be obtained by dissolving or dispersing metal ions in a solvent, mixing with the organic material, and reducing this. Water, alcohols, and ethers can be used as the solvent.

  Further, as the fine particles to be dispersed, those formed of fullerene and / or carbon nanotubes may be used. Any fullerene may be used as long as carbon atoms are arranged in a spherical shell. For example, a fullerene having a stable structure having 24 to 96 carbon atoms is preferable. Examples of such fullerene include a C60 spherical closed-shell carbon molecule group composed of 60 carbon atoms. Further, as the carbon nanotube, for example, a cylindrical nanotube with a several atomic layer thick graphite-like carbon atom surface rounded is preferable.

  The shape of the fine particles is not particularly limited. For example, a spherical shape, an ellipsoidal shape, a lump shape, a columnar shape, a conical shape, a form having protrusions in these forms, or a form in which holes are opened in these forms. It may be. Further, the surface form of the fine particles is not particularly limited, and may be, for example, smooth or may have irregularities, holes, and grooves.

  The content of the fine particles is preferably 0.05 wt% or more and 20 wt% or less with respect to the total weight of the fine particles and the dielectric substance. If the amount is less than 0.05 wt%, the mixing ratio of the fine particles is small, so that there is a possibility that the effect of the fine particles as an alignment aid is not sufficiently exhibited. Aggregation may cause light to scatter.

  A microporous film such as a membrane filter may be used. As the microporous film, for example, Millipore (Nippon Millipore) can be used.

  In addition, the material of the microporous film includes polycarbonate, polyolefin, cellulose mixed ester, cellulose acetate, polyvinylidene fluoride, acetylcellulose, a mixture of cellulose acetate and cellulose nitrate, a liquid crystalline substance to be sealed in the microporous film, etc. A material made of a material that does not react with the dielectric material is preferable. The size (diameter) of the micropores is optically isotropic when encapsulating the dielectric material, and in order to realize a system capable of immobilizing the dielectric material, 1 / wavelength of visible light It is preferably 4 or less, and more preferably 50 nm or less. As a result, the dielectric material layer can exhibit a sufficiently transparent state with respect to visible light. Further, the thickness of the microporous film is preferably 50 μm or less, and more preferably 10 μm or less.

  In the above description, the structure for fixing the molecular orientation order structure in the medium exhibiting the costelic blue phase has been described. However, the medium to be fixed is not limited to this. In the case of using another medium (medium showing a phase having another ordered structure) described later, the molecular ordered structure may be fixed. Thereby, the use temperature range in the case of using as a display element can be expanded greatly. Further, in the case of using such a medium, a structure in which the molecular ordered structure is fixed when an electric field is not applied to the material layer 103 after the medium is sealed in the material layer 103 may be employed.

  The microporous film may have a twisted structure such as a spiral crystal. For example, a polyolefin film, a polypeptide film, etc. are mentioned. The polypeptide film having a twisted structure is preferably a synthetic polypeptide having a helical structure, that is, an α-helix forming ability. Examples of the synthetic polypeptide capable of forming α-helix include polyglutamic acid derivatives such as poly-γ-benzyl-L-glutamate. These synthetic polypeptides can be used as they are commercially available or manufactured according to the method described in the literature etc. as they are or diluted with a poorly water-soluble helical solvent such as 1,2-dichloroethane. Examples of commercially available synthetic polypeptides capable of forming α-helix include poly-γ-methyl-L-glutamate such as Ajicoat A-2000, XB-900 [manufactured by Ajinomoto Co., Inc.].

  When a film with a twisted structure is used, when the dielectric medium exhibits chirality, large distortion does not occur if the twisted structure of the dielectric medium and the twisted structure of the film are close, so the stability of the dielectric medium Will increase. In addition, even when the dielectric medium does not exhibit chirality, the dielectric medium is oriented according to the twisted structure of the film, so that the dielectric medium exhibits properties similar to a medium exhibiting chirality.

  As another substance to be sealed in the substance layer 103, for example, ZLI-2293 (mixed liquid crystal, manufactured by Merck & Co., Inc.) is 67.1 wt% and P8PIMB (1,3-phenylene bis [4- (4-8-alkylphenyliminomethyl- A substance in which 15 wt% of benzoate, banana type (bending type) liquid crystal, see the following structural formula) and 17.9 wt% of MLC-6248 (chiral agent, manufactured by Merck & Co., Inc.) may be used. A cholesteric blue phase is exhibited in a temperature range of 2 ° C. to 82.1 ° C. Further, the mixing ratio of each of the above-mentioned substances may be changed as appropriate, for example, ZLI-2293 is 69.7 wt% and P8PIMB is 15 wt. %, MLC-6248 (chiral agent) 15.3 wt% mixed material exhibits a cholesteric blue phase in the temperature range of 80.8 ° C. to 81.6 ° C.

  Further, as another substance to be encapsulated in the substance layer 103, for example, ZLI-2293 (mixed liquid crystal, manufactured by Merck & Co., Inc.) 67.1 wt%, MHPOBC (4- (1-methylheptyloxycarbonyl) phenyl-4'-octylcarboxybiphenyl-4-) A substance in which 15 wt% of carboxylate, linear liquid crystal, see the following structural formula) and 17.9 wt% of MLC-6248 (chiral agent, manufactured by Merck & Co., Inc.) may be used. This material exhibits a cholesteric blue phase in the temperature range of 83.6 ° C. to 87.9 ° C. Moreover, you may change and use suitably the mixing ratio of said each substance. For example, a material in which ZLI-2293 is mixed at 69.7 wt%, MHPOBC at 15 wt%, and MLC-6248 (chiral agent) at 15.3 wt% shows a cholesteric blue phase in the temperature range of 87.8 ° C to 88.4 ° C. .

  Although cholesteric blue phase could not be expressed only by mixing ZLI-2293 and MLC-6248, cholesteric blue was obtained by adding banana-shaped (bent) liquid crystal P8PIMB or linear liquid crystal MHPOBC. Phase showed.

  In the above example, a racemic body is used as the linear liquid crystal. However, the liquid crystal is not necessarily limited to a racemic body, and a chiral body may be used. In addition, when using a linear liquid crystal, it is preferable to use a liquid crystal having a reclined structure (facing different directions for each layer) such as a linear liquid crystal MHPOBC.

  Further, the banana type (bent type) liquid crystal is not limited to P8PIMB. For the bent portion, not only a benzene ring such as a phenylene group but also a banana type (bent type) liquid crystal bonded with a naphthalene ring or a methylene chain may be used. Alternatively, a banana (bent) liquid crystal containing an azo group may be used. For example, examples of the banana-type (bent type) liquid crystal other than P8PIMB include Azo-8O, 8Am5, and 14OAm5 (see the following structural formula).

  In addition, a polymerizable monomer, or a polymerizable monomer and a polymerization initiator may be added to these mixed substances. That is, the orientational order structure of the molecules constituting the medium made of the mixed material may be fixed by forming a large number of small regions (fine domains) in the material layer 103 with the polymerizable compound. Further, in this case, after the medium is sealed in the material layer 103, the molecular ordering structure may be fixed when an electric field is not applied to the material layer 103.

  In addition, the substance to be sealed in the substance layer 103 preferably has a structure having an optical wavelength or less. Since the cholesteric blue phase suitable for the present invention has a defect order equal to or less than the optical wavelength, it is generally transparent in the optical wavelength region and optically isotropic. Here, optically generally isotropic means that the cholesteric blue phase exhibits a color reflecting the spiral pitch of the liquid crystal, and therefore, when the spiral pitch is not in the visible range, it does not exhibit color, but in the visible range. In some cases, this means that a color corresponding to the wavelength is displayed.

  Here, when having a selective reflection wavelength region of 400 nm or more or a helical pitch, the cholesteric blue phase (blue phase) is colored in a color reflecting the helical pitch. That is, since visible light is reflected, the color presented thereby is recognized by the human eye. Therefore, for example, when full-color display is realized by the display element of the present invention and applied to a television or the like, it is not preferable that the reflection peak is in the visible range.

  The selective reflection wavelength also depends on the incident angle with respect to the helical axis of the medium. For this reason, when the structure of the medium is not one-dimensional, that is, when it has a three-dimensional structure such as a cholesteric blue phase, the incident angle of light on the spiral axis has a distribution. Therefore, the width of the selective reflection wavelength can also be distributed.

  For this reason, it is preferable that the selective reflection wavelength region or the helical pitch of the blue phase is not more than the visible region, that is, not more than 400 nm. If the selective reflection wavelength region or the helical pitch of the blue phase is 400 nm or less, the above coloration is hardly recognized by human eyes.

  In addition, the International Lighting Commission CIE (Commission Internationale de l'Eclairage) stipulates that the wavelength that human eyes cannot recognize is 380 nm or less. Therefore, it is more preferable that the selective reflection wavelength region or the helical pitch of the blue phase is 380 nm or less. In this case, it is possible to reliably prevent the above coloration from being recognized by human eyes.

  The coloration as described above is related not only to the helical pitch and the incident angle but also to the average refractive index of the medium. At this time, the colored light is light having a wavelength width Δλ = PΔn with the wavelength λ = nP as the center. Here, n is the average refractive index and P is the helical pitch. Δn is the anisotropy of the refractive index.

  Δn varies depending on the material. For example, when a liquid crystal material is used as a material for sealing the material layer 103, the average refractive index of the liquid crystal material is about 1.5 and Δn is about 0.1. In order that the color to be colored is not in the visible range, when the spiral pitch P is λ = 400, P = 400 / 1.5 = 267 nm. Δλ is Δλ = 0.1 × 267 = 26.7. Therefore, in order to prevent the above coloration from being recognized by human eyes, the spiral pitch of the medium should be set to 253 nm or less obtained by subtracting 13.4 nm, which is approximately half of 26.7 nm, from 267 nm. That's fine. That is, in order to prevent the above coloration, the spiral pitch of the medium is preferably 253 nm or less.

  Further, in the above description, in the relationship of λ = nP, λ is 400 nm. However, when λ is 380 nm, which is determined by the International Lighting Commission CIE as a wavelength that cannot be recognized by human eyes, color is displayed. The spiral pitch for making the color out of the visible range is 240 nm or less. That is, when the spiral pitch of the medium is 240 nm or less, the above coloration can be surely prevented.

  For example, a sample prepared with a composition of 50.0 wt% JC1041xx, 38.5 wt% 5CB, and 11.1 wt% ZLI-4572 will undergo a phase transition from an isotropic phase to a blue phase at about 53 ° C. It was not visible because it was below the visible range.

  Further, 87.1 wt% of the above mixed sample, 5.4 wt% of TMPTA (trimethylolpropane triacrylate, manufactured by Aldrich), 7.1 wt% of RM257, and DMPA (2,2-dimethoxy-2-phenyl-acetophenone) of 0. A sample in which 4 wt% is mixed and UV-irradiated while keeping the optical isotropic phase in the vicinity of the cholesteric-optical isotropic phase, the photoreactive monomer is polymerized, has a wide temperature range showing the optical isotropic phase. became.

  In addition, a sample in which each compound having the following structural formula is mixed at the ratio shown on the right side of the structural formula causes a phase transition from the isotropic phase to the blue phase at about 20 ° C. or less, but the helical pitch is below the visible range. There was no coloration. In this mixed system, 30 wt% of a chiral agent was mixed as shown in the following structural formula (lowermost structural formula).

  As described above, the cholesteric blue phase suitable for the present invention has a defect order less than the optical wavelength. Since the defect structure is caused by the fact that neighboring molecules are largely twisted, the dielectric medium (medium) exhibiting a cholesteric blue phase needs to exhibit chirality in order to develop a large twisted structure. In order to develop a large twisted structure, it is preferable to add a chiral agent to the dielectric medium. The concentration of the chiral agent is preferably 8 wt% or 4 mol% or more although it depends on the twisting force of the chiral agent. When expanding the temperature range showing the cholesteric blue phase by polymer network (photopolymerization of photoreactive monomer), if the proportion of the chiral agent in the dielectric medium is 8 wt% or 4 mol% or more, the cholesteric blue phase The temperature range was about 1 ° C. or higher, and photopolymerization by ultraviolet irradiation could be performed while adjusting the temperature. When the ratio of the chiral agent was less than 8 wt% or 4 mol%, the temperature range of the cholesteric blue phase was narrowed, and it was difficult to adjust the temperature during photopolymerization.

  The concentration of the chiral agent is more preferably 15 wt% or more. When a cholesteric blue phase is expressed by adding a banana type (bending type) liquid crystal or a linear liquid crystal having a tilted structure, the temperature range of the cholesteric blue phase is about 1 if the concentration of the chiral agent is 15 wt% or more. It became ℃. Moreover, the temperature range of the cholesteric blue phase was further expanded by increasing the concentration of the chiral agent to 17.9 wt%.

  The concentration of the chiral agent is more preferably 30 wt% or more. When each compound consisting of the above structural formula is mixed in the proportion shown on the right side of the structural formula (when the concentration of the chiral agent is 30 wt%), the cholesteric blue phase is present because the helical pitch is below the visible range. Did not color. This is probably because the helical pitch was shortened by containing a large amount of chiral agent. In the cholesteric blue phase, since the color reflects the helical pitch, it is not preferable that the reflection peak is in the visible range when full color display is realized and applied to a television or the like. Further, when the concentration of the chiral agent was reduced from 30 wt%, the temperature range of the cholesteric blue phase became narrow.

  Thus, it is preferable that the concentration of the chiral agent is high because the cholesteric blue phase is easily developed and the helical pitch of the cholesteric blue phase is shortened. However, when the amount of the chiral agent added is excessive, there is a problem that the liquid crystallinity of the entire material layer 103 is lowered. The lack of liquid crystallinity leads to a decrease in the degree of optical anisotropy when an electric field is applied, leading to a decrease in function as a display element. Further, the liquid crystallinity is lowered, leading to a decrease in the stability of the cholesteric blue phase, and the expansion of the temperature range of the cholesteric blue phase cannot be expected. For the above reasons, the upper limit of the concentration of the chiral agent is determined, and according to the analysis by the present inventors, it has been found that the upper limit is 80 wt%. That is, the concentration of the chiral agent is preferably 80 wt% or less.

  In the above description, the effect of adding the chiral agent in the cholesteric blue phase has been described. However, the effect of adding the chiral agent is not limited to the cholesteric blue phase, and a dielectric medium exhibiting a smectic blue phase, a nematic phase, or the like. In this case, substantially the same effect can be obtained.

  By adding the chiral agent, the helical twist power of the chiral agent can be effectively acted, and a short-range-order can be exerted between the molecules. That is, when no voltage is applied, the molecules in the medium can be made to respond to the dielectric medium having optical isotropy as a small group (cluster) by applying the voltage. As a result, even in a dielectric medium that originally exhibits optical anisotropy only in a very narrow temperature range, the temperature range in which optical anisotropy can be exhibited can be expanded by adding a chiral agent.

  In addition, in a dielectric medium to which a chiral agent is added, optical rotation occurs in incident light due to unidirectional twist caused by the spontaneous twisting direction of the chiral agent, so that light can be efficiently extracted.

Also, molecules that do not have asymmetric carbon atoms like banana-type (flexible) liquid crystals (the molecules themselves do not have chirality), but have chirality as a system due to anisotropy of molecular shape and packing structure A medium containing may be used. An example of the banana type (bending type) liquid crystal is P8PIMB. Further, the banana type (bending type) liquid crystal is not limited to P8PIMB. The bent portion may be bonded not only by a benzene ring such as a phenylene group but also by a naphthalene ring or a methylene chain. For example, banana type (bending type) liquid crystals other than P8PIMB include 8Am5 and 14OAm5. Also in this case, a twisted structure of either left-handed twist or right-handed twist can be induced, and the transmittance can be improved.
The medium sealed in the material layer 103 is typically optically isotropic when no voltage is applied, and may be a medium in which optical modulation is induced by voltage application. In other words, it may be a substance that typically increases the degree of orientation of molecules or molecular aggregates (clusters) with voltage application. Moreover, it is preferable that it is a medium with positive dielectric anisotropy.

  As described above, the medium sealed in the material layer 103 may be any medium that changes the degree of optical anisotropy when an electric field is applied. As a medium to be enclosed in the material layer 103, for example, a liquid crystal phase having an ordered structure of an optical wavelength or less and optically isotropic and having a positive or negative dielectric anisotropy is applied. be able to. Alternatively, a system that is optically isotropic can be used, in which liquid crystal molecules are filled with aggregates that are radially aligned with a size equal to or smaller than the wavelength of light. By applying an electric field to these, it is possible to distort the fine structure of molecules or aggregates and induce optical modulation. In addition, when these media are used, molecular orientation changes can be promoted by forming alignment aids such as polymerizable compounds, hydrogen bonds, porous structures, and fine particles. It becomes possible to do.

  Hereinafter, examples of such a medium other than those described above will be described as medium examples. However, the medium examples shown below are examples of usable media and do not limit the media applicable to the display device according to the present embodiment.

[Medium example 1]
As a medium enclosed in the material layer 103, for example, a cubic phase (cubic phase, cubic) having an ordered structure having cubic symmetry (symmetry of cubic crystal) having a scale of less than an optical wavelength (less than the wavelength of visible light). A medium exhibiting a crystal phase can be used.

  An example of such a medium is BABH8 described in Non-Patent Documents 6 and 7. The structural formula of this BABH8 is

It is represented by

  Further, BABH8 exhibits a cubic phase composed of an ordered structure having a scale of less than the optical wavelength (less than the wavelength of visible light) at 136.7 ° C. or more and 161 ° C. or less. Non-Patent Document 6 discloses a cubic phase structural model as shown in FIGS. 8, 10, and 11.

  As described above, BABH8 is transparent because its lattice constant is about 6 nm, which is one order of magnitude smaller than the optical wavelength, and the ordered structure (orientation order) is less than the optical wavelength. That is, in the above temperature range, it is optically isotropic when no electric field is applied. Therefore, when BABH8 is applied to this display element, good black display can be performed under crossed Nicols.

  On the other hand, when an electric field is applied between the electrodes 104 and 105 while controlling the temperature of the material layer 103 to 136.7 ° C. or more and 161 ° C. or less, distortion occurs in the structure having cubic symmetry, and optical anisotropy is exhibited. To do. That is, BABH8 is optically isotropic when no electric field is applied in the above temperature range, and exhibits optical anisotropy when an electric field is applied.

  In this manner, in the display device having the above-described configuration, distortion is generated in the structure having cubic symmetry by applying an electric field, and birefringence is generated, so that a good white display can be performed. Note that the direction in which birefringence occurs is constant, and its magnitude changes with the application of an electric field. Further, the voltage transmittance curve indicating the relationship between the voltage applied between the electrodes 104 and 105 and the transmittance is a stable curve in the wide temperature range as described above. That is, in the display device having the above configuration, a stable voltage transmittance curve can be obtained in a temperature range of about 20 K between 136.7 ° C. and 161 ° C., and temperature control becomes extremely easy.

  In the case of using BABH8, as in the case of using the above-described mixture (see FIG. 12), the display is performed using the distortion generated in the structure having cubic symmetry, that is, the change in the degree of optical anisotropy in the medium. Do. Therefore, a wider viewing angle characteristic can be realized than a conventional liquid crystal display device that performs display by changing the alignment direction of liquid crystal molecules. In addition, since the direction in which birefringence occurs is constant and the optical axis direction does not change, a wider viewing angle characteristic can be realized.

[Medium example 2]
As a medium sealed in the material layer 103, a medium composed of molecules exhibiting a smectic D phase (SmD) which is one of liquid crystal phases can be applied.

  An example of a liquid crystalline material exhibiting a smectic D phase is ANBC16. As for ANBC16, Non-Patent Document 3 (p.21, FIG. 1, Structure 1 (n = 16)), Non-Patent Document 8 (p.888, Table 1, Compound (compound no.) 1, Compound 1a, Compound 1a-1). These molecular structures are shown below.

4'n-alkoxy-3'-nitro-biphenyl-4-carboxylic acids
n-15 Cr 127 SmC 187 Cub 198 SmA 204 I
This liquid crystalline substance (ANBC16, n = 16 in the chemical structural formula) exhibits a smectic D phase in a temperature range of 171.0 ° C. to 197.2 ° C. In the smectic D phase, a plurality of molecules form a three-dimensional lattice such as jungle gym (registered trademark), and the lattice constant thereof is several tens of nm or less and less than the optical wavelength. ANBC16 shown in this embodiment is about 6 nm. That is, the smectic D phase has an ordered structure in which the molecular arrangement exhibits cubic symmetry. For this reason, the smectic D phase is optically isotropic.

  In addition, when an electric field is applied to the material layer 103 made of ANBC16 in the above temperature range where the ANBC 16 exhibits a smectic D phase, the molecule itself has a dielectric anisotropy, so that the molecule tends to move in the electric field direction and has a lattice structure. Distortion occurs. That is, optical anisotropy appears in the material layer 103.

  Therefore, the ANBC 16 can be applied as a medium encapsulating the material layer 103 of the display element. Note that not only the ANBC 16 but a substance exhibiting a smectic D phase changes the degree of optical anisotropy between when an electric field is applied and when no electric field is applied, so that the medium enclosed in the material layer 103 of the display element As applicable.

[Medium Example 3]
A liquid crystal microemulsion can be applied as a medium to be enclosed in the material layer 103. Here, liquid crystal microemulsion is an O / W type microemulsion named by Yamamoto et al. (Oil is a continuous phase in which water is dissolved in oil in the form of water droplets with a surfactant) Is a generic term for a system (mixed system) in which oil molecules are replaced with thermotropic liquid crystal molecules (see Non-Patent Document 4).

  Specific examples of the liquid crystal microemulsion include, for example, Pentylcyanobiphenyl (5CB), which is a thermotropic liquid crystal (temperature transition liquid crystal) showing a nematic liquid crystal phase, and a lyotropic liquid crystal showing a reverse micelle phase (described in Non-Patent Document 4). There is a mixed system with an aqueous solution of Didodecyl ammonium bromide (DDAB), which is a lyotropic liquid crystal, a concentration transition liquid crystal, or a lyotropic liquid crystal. This mixed system has a structure represented by schematic diagrams as shown in FIGS.

  In this mixed system, the diameter of reverse micelles is typically about 50 mm, and the distance between the reverse micelles is about 200 mm. These scales are about an order of magnitude smaller than the optical wavelength. In addition, reverse micelles exist randomly in three-dimensional space, and 5CB are radially oriented around each reverse micelle. Therefore, the above mixed system is optically isotropic.

  When an electric field is applied to the medium composed of the above-mentioned mixed system, since the dielectric anisotropy exists in 5CB, the molecule itself tends to go in the direction of the electric field. That is, orientation anisotropy appears in a system that is optically isotropic because it is oriented radially around a reverse micelle, and optical anisotropy appears. Therefore, the above mixed system can be applied as a medium to be enclosed in the material layer 103 of the display device. Note that the liquid crystal microemulsion whose degree of optical anisotropy changes depending on whether no electric field is applied or when an electric field is applied is not limited to the above-described mixed system, and can be applied as a medium sealed in the material layer 103 of the display device. .

[Medium Example 4]
As a medium sealed in the material layer 103, lyotropic liquid crystal (lyotropic liquid crystal) having a specific phase can be used. Here, the lyotropic liquid crystal generally means a liquid crystal of another component system in which main molecules forming the liquid crystal are dissolved in a solvent having other properties (such as water or an organic solvent). The specific phase is a phase in which the degree of optical isotropy changes between when an electric field is applied and when no electric field is applied. Examples of such a specific phase include a micelle phase, a sponge phase, a cubic phase, and a reverse micelle phase described in Non-Patent Document 9. FIG. 15 shows a classification diagram of the lyotropic liquid crystal phase.

  Surfactants that are amphiphilic substances include substances that develop a micelle phase. For example, an aqueous solution of sodium decyl sulfate, which is an ionic surfactant, an aqueous solution of potassium palmitate, and the like form spherical micelles. Further, in a mixed solution of polyoxyethylene nonylphenyl ether, which is a nonionic surfactant, and water, micelles are formed by the nonylphenyl group acting as a hydrophobic group and the oxyethylene chain acting as a hydrophilic group. In addition, micelles are formed even in an aqueous solution of a styrene-ethylene oxide block copolymer.

  For example, spherical micelles exhibit a spherical shape by packing molecules in all spatial directions (forming a molecular assembly). In addition, since the size of the spherical micelle is equal to or smaller than the optical wavelength, it appears isotropic without showing anisotropy in the optical wavelength region. However, when an electric field is applied to such spherical micelles, the spherical micelles are distorted, so that anisotropy is expressed. Therefore, a lyotropic liquid crystal exhibiting a spherical micelle phase can be used as a medium sealed in the material layer 103 of the display device. It should be noted that not only the spherical micelle phase but also other shapes of micelle phases, that is, a lyotropic liquid crystal showing a string micelle phase, an elliptical micelle phase, a rod-like micelle phase, etc., is sealed in the material layer 103 to have substantially the same effect. Can be obtained.

  Further, it is generally known that reverse micelles in which a hydrophilic group and a hydrophobic group are exchanged are formed depending on the conditions of concentration, temperature, and surfactant. Such reverse micelles optically show the same effects as micelles. Therefore, by applying a lyotropic liquid crystal exhibiting a reverse micelle phase as a medium encapsulated in the material layer 103, an effect equivalent to that obtained when a lyotropic liquid crystal exhibiting a micelle phase is used. The liquid crystal microemulsion described in the medium example 3 is an example of a lyotropic liquid crystal exhibiting a reverse micelle phase (reverse micelle structure).

Further, the aqueous solution of the nonionic surfactant pentaethylene glycol-dodecyl ether (Pentaethylenglychol-dodecylether, C ₁₂ E ₅ ) has a concentration and temperature range showing a sponge phase and a cubic phase as shown in FIG. To do. Such a sponge phase or cubic phase is a transparent substance in the optical wavelength region because it has an order (ordered structure, orientation order) less than the optical wavelength. That is, a medium composed of these phases is optically isotropic. When an electric field is applied to a medium composed of these phases, distortion occurs in the ordered structure (orientation order), and optical anisotropy appears. Therefore, a lyotropic liquid crystal exhibiting a sponge phase or a cubic phase can also be used as a medium sealed in the material layer 103 of the display device.

[Medium Example 5]
Liquid crystal fine particle dispersion showing a phase in which the degree of optical isotropy changes between when an electric field is applied and when no electric field is applied, such as a micelle phase, a sponge phase, a cubic phase, and a reverse micelle phase, as a medium to be enclosed in the material layer 103 The system can be applied. Here, the liquid crystal fine particle dispersion is a mixed system in which fine particles are mixed in a solvent (liquid crystal).

As such a liquid crystal fine particle dispersion system, for example, a latex having a surface of about 100 mm and a surface modified with an aqueous solution of a nonionic surfactant pentaethylene glycol-dodecyl ether (C ₁₂ E ₅ ) with a sulfate group. There is a liquid crystal fine particle dispersion system in which particles are mixed. In this liquid crystal fine particle dispersion system, a sponge phase is developed. Therefore, as in the case of the medium example 4, the liquid crystal fine particle dispersion system can be applied as a medium sealed in the material layer 103 of the display device.

  By replacing the latex particles with DDAB in the liquid crystal microemulsion of medium example 3, the same orientation structure as that of the liquid crystal microemulsion of medium example 3 can be obtained.

[Medium Example 6]
A dendrimer (dendrimer molecule) can be used as a medium enclosed in the material layer 103. Here, the dendrimer is a three-dimensional highly branched polymer having a branch for each monomer unit.

  Since dendrimers have many branches, they have a spherical structure when the molecular weight exceeds a certain level. Since this spherical structure has an order equal to or less than the optical wavelength, the spherical structure is a transparent material in the optical wavelength region, and the orientation order is changed by application of a voltage to exhibit optical anisotropy. Therefore, the dendrimer can be applied as a medium encapsulated in the material layer 103 of the display device.

[Example 7 of medium]
As a medium enclosed in the material layer 103, a medium made of molecules exhibiting a smectic blue (BP _Sm ) phase can be applied.

  Like the cholesteric blue phase, the smectic blue phase has a highly symmetric structure. In addition, since it has an order (ordered structure, orientation order) equal to or less than the optical wavelength, it is a substantially transparent substance in the optical wavelength region, and the orientation order is changed by application of voltage, and optical anisotropy is exhibited. That is, the smectic blue phase is almost optically isotropic, and the liquid crystal molecules tend to move in the electric field direction when an electric field is applied, so that the lattice is distorted and anisotropy is expressed. Therefore, a medium including molecules exhibiting a smectic blue phase can be used as a medium sealed in the substance layer 103 of the display device.

In addition, as a substance which shows a smectic blue phase, there exists FH / FH / HH-14BTMHC described in the nonpatent literature 10, for example. This material exhibits BP _Sm 3 phase at 74.4 ° C. to 73.2 ° C., BP _Sm 2 phase at 73.2 ° C. to 72.3 ° C., and BP _Sm 1 phase at 72.3 ° C. to 72.1 ° C. .

  When a medium exhibiting a smectic blue phase is used, the selective reflection wavelength region or helical pitch of the blue phase is preferably 400 nm or less, as in the case of using a medium exhibiting a costic blue phase, and is preferably 380 nm or less. It is more preferable. Further, the helical pitch is preferably 253 nm or less, and more preferably 240 nm or less.

  Further, not limited to the above-described examples of mediums, a polymerizable compound, a hydrogen bond, a porous structure, even if the medium has a large ordered structure size and is not likely to be applied to the display device according to the present embodiment. By forcibly fixing to fine domains with fine particles or the like, it can be applied to the display element according to this embodiment. For example, if a microstructure consisting of the above-described polymer network, gelling agent, microporous film, etc. is formed in the medium, even a nematic or cholesteric phase is almost optically isotropic. Can create a unique state.

  As the polymer network, for example, a fine polymer network formed in the isotropic phase by mixing acrylate monomer in 5CB and irradiating ultraviolet rays in the isotropic phase can be used. After forming the polymer network in this manner, if the nematic phase is precipitated by lowering the temperature, the fine polymer network is filled with orientation defects. That is, if the polymer network is formed with a scale of less than or equal to the optical wavelength, an optically isotropic nematic phase can be obtained instead of the usual uniaxially oriented nematic orientation. Further, when a complete optical isotropic phase cannot be obtained and light is slightly scattered, a chiral agent may be mixed in advance. Thereby, since a twisted structure can be induced in the fine domain formed in the polymer network, the optical anisotropy of the fine domain can be reduced. As a result, light scattering can be suppressed.

  When the material layer 103 includes any one of the above-described media, different display states can be realized when a voltage is applied and when no voltage is applied.

[Embodiment 2]
Other embodiment of this invention is described based on figures. For convenience of explanation, members having the same functions as those described in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  In the display device according to the first embodiment, the signal for the reset period (for black display) is transmitted from the data signal line driving circuit and the scanning signal line driving circuit to the scanning signal line 111 and the data signal line 110 in the reset period Tr. In other words, by supplying a signal having substantially the same potential as that of the common electrode 105 to the data electrode 104, the memory effect generated in the medium is alleviated. On the other hand, the display device according to the present embodiment has an effect on the display characteristics of the memory effect generated in the medium without supplying a black display signal from the data signal line driving circuit and the scanning signal line driving circuit. It can be reduced.

  FIG. 16 is an explanatory diagram illustrating a schematic configuration of the display device according to the present embodiment. This figure is drawn corresponding to the actual geometric arrangement. The circuit diagram shown in the lower part of FIG. 16 is an equivalent circuit diagram for one pixel in the display element (display panel) 191 provided in the display device.

  As shown in this figure, the display device according to the present embodiment includes an active matrix substrate 100 having drive circuit regions 14A and 14B and a display region 119 on a substrate 101, similarly to the display device according to the first embodiment. I have. In the present embodiment, the drive circuit regions 14A and 14B are provided on the substrate 101. However, the present invention is not limited to this, and a drive signal is supplied from a drive circuit provided outside the substrate 101. There may be.

  The display area 119 is provided with a plurality of scanning signal lines (gate signal lines) 111 arranged substantially parallel to each other and a plurality of data signal lines 110 orthogonal to the respective scanning signal lines 111. A pixel is formed for each section surrounded by two adjacent scanning signal lines 111 and two adjacent data signal lines 110. That is, a rectangular area surrounded by the data signal lines 110 and the scanning signal lines 111 is a pixel area, and a display unit is configured by a set of these pixel areas.

  In addition, as shown in FIG. 16, one end of each scanning signal line 111 extends to one side (left side in the figure) of the substrate 101, and the extending portion is a semiconductor mounted in the drive circuit region 14B of the substrate 101. It is connected to a vertical scanning circuit (scanning signal line driving circuit) composed of an integrated circuit. One end of each data signal line is also extended to one side (upper side in the drawing) of the substrate 101, and the extending portion is a video signal drive circuit made of a semiconductor integrated circuit mounted on the drive circuit region 14A of the substrate 101. It is connected to (data signal line driving circuit).

  Further, the substrate 102 is disposed opposite to the substrate 101 so as to avoid the region where the semiconductor circuit is mounted in the drive circuit regions 14A and 4B, and has a smaller area than the substrate 101. The substrate 102 is fixed to the substrate 101 by a sealing material formed around the substrate 102, and this sealing material serves as a medium (dielectric material) constituting the material layer 103 between the substrate 101 and the substrate 102. It also serves as a sealing function.

  In the display element 191, the data electrode (pixel electrode) 104 is provided on the substrate 101, and the counter electrode (common electrode) 147 is provided on the substrate 102 side. That is, the display element 191 is a so-called vertical electric field type display element that performs display using an electric field in the normal direction of the substrate surface.

  As shown in FIG. 16, each pixel region (display element 191) includes a TFT (Thin Film Transistor) 109 as a switching element. A data electrode 104 (not shown in FIG. 16) is connected to the drain electrode of the TFT 109, a data signal line 110 is connected to the source electrode of the TFT 109, and a scanning signal line 111 a is connected to the gate electrode of the TFT 109. It is connected. As a result, a scanning signal (voltage) is supplied from the scanning signal line driving circuit provided in the driving circuit region 14 </ b> B to the gate electrode of the TFT 109 via the scanning signal line 111. When the TFT 109 is turned on by this scanning signal, a video signal (voltage) supplied from the data signal line drive circuit provided in the drive circuit area 14A to the source electrode of the TFT 109 via the data signal line 110 is displayed. It is supplied to the data electrode 104 of the element 191.

  Further, as shown in FIG. 16, a storage capacitor element (auxiliary capacitor) 121b is formed between the data electrode 104 and the scan signal line 111b adjacent to the scan signal line 111a. Note that the scanning signal line 111 a and the scanning signal line 111 b are separated with the data electrode 104 interposed therebetween. The storage capacitor 121b has a function or the like that works to reduce the influence of a change in gate potential on, for example, the midpoint potential (data electrode potential) when the TFT 109 switches. Note that the scanning signal line 111b controls the supply of a video signal to the data electrode 104 of another pixel adjacent to the pixel shown in FIG.

  Further, as shown in FIG. 16, in the display element 191, the data electrode 104 and the scanning signal line 111b are connected through a resistance element 129.

  The resistance element 129 is for discharging the charge of the display unit capacitor 120 through the scanning signal line 111b when the video signal from the data signal line 110 is supplied to the data electrode 104 via the TFT 109. This prevents the charge of the video signal from being accumulated (residual) for a long time in the partial capacitor 120. That is, the resistance value of the resistance element 129 is set to a value for discharging the video signal supplied to the data electrode 104 during one frame period. In other words, the time constant CR determined by the product of the resistance value R of the resistance element 129 and the capacitance C of the scanning signal line 111 is set smaller than the period of one frame.

  Note that, in the conventional display element in which the resistance element 129 is not formed, the storage capacitor element 121b is connected to the data electrode 104 during the period in which the TFT 109 is turned on in addition to the above-described functions. Although it has a function of storing the supplied video signal for one frame period, such a storage function is reduced by providing the resistance element 129.

  The data electrode 104 in each pixel region generates an electric field with the counter electrode 147 provided on the opposite substrate 102 with the material layer 103 interposed therebetween. In the display device according to the present embodiment, the light transmittance of the medium (dielectric substance) between the two electrodes is thereby controlled. Note that the counter electrode 147 is formed in common on each pixel region on the surface of the substrate 102 on the material layer 103 side.

  FIG. 17 is a cross-sectional view showing a schematic configuration of one pixel in a display element (display panel) 191 provided in the display device according to the present embodiment.

  As shown in this figure, a scanning signal line 111a (conductive layer g1) is formed on the surface of the substrate 101 on the material layer 103 side. In addition, a light shielding film 128 (conductive layer g1) made of the same material as the scanning signal line 111a is formed in the pixel region. The light-shielding film 128 is for shielding extraneous light incident on the resistance element 129 made of a semiconductor layer, which will be described later, formed on the upper surface thereof through the substrate 101.

  An insulating film 106 is formed so as to cover the scanning signal line 111a and the light shielding film 128. The insulating film 106 functions as an interlayer insulating film between the scanning signal line 111a and a data signal line 110 described later, a gate insulating film of a TFT 109 described later, and a dielectric film of a storage capacitor element 121b described later. . The material of the insulating film 106 is not particularly limited, but for example, SiN can be used.

  As shown in FIG. 17, a semiconductor layer 131 is formed in a portion overlapping the scanning signal line 111a when viewed from the normal direction of the substrate surface of the substrate 101. This semiconductor layer 131 is an i-type (intrinsic: conductivity type determining impurity is not doped) semiconductor layer made of, for example, a-Si.

  In addition, a drain electrode 132 and a source electrode 133 are formed on the upper surface of the semiconductor layer 131, whereby a MOS type TFT 109 having a part of the scanning signal line 111a as a gate electrode is formed.

  A semiconductor layer 134 made of the same material as the semiconductor layer 131 is formed in a portion overlapping the light shielding film 128 when viewed from the normal direction of the substrate surface of the substrate 101. In this embodiment, the semiconductor layer 134 is also formed in the formation region of the data signal line 110 integrally with the semiconductor layer 131 of the TFT 109. This is to enhance the functions of the interlayer insulating film together with the insulating film 106. A pair of electrodes 135 and 136 are formed on the upper surface of the semiconductor layer 134 formed on the light shielding film 128. Thereby, a resistance element 129 using the semiconductor layer 134 as a resistance material is formed.

  Further, the source electrode 133, the drain electrode 132 of the TFT 109, and the pair of electrodes 135 and 136 of the resistance element 129 are formed simultaneously with the data signal line 110 formed on the insulating film 106. That is, when the data signal line 110 (conductive film d1) is formed, a part of the data signal line 110 is formed to extend to the upper surface of the semiconductor layer 131, so that a part of the extension part is the TFT 109. The drain electrode 132 is formed. In addition, an electrode formed apart from the drain electrode 132 becomes the source electrode 133. Similarly, when the data signal line 110 (conductive film d1) is formed, a part of the extended portion is formed by extending a part of the data signal line 110 to the upper surface of the semiconductor layer 134. The electrode 135 is formed. In addition, an electrode formed apart from the electrode 135 is an electrode 136.

  Note that the source electrode 133 is connected to a data electrode 104 (to be described later), and in order to secure the connection portion, the source electrode 133 has a pattern (shape) having an extension portion slightly extended to the center side of the pixel region. Yes. In addition, the electrode 135 formed on the semiconductor layer 134 in the formation region of the resistance element 129 is connected to the data electrode 104, and is slightly extended to the central portion of the pixel region in order to secure the connection portion. It has a pattern (shape) having an extending portion.

  The electrode 136 formed on the semiconductor layer 134 is connected to the scanning signal line 111b adjacent to the semiconductor layer 134, and extends slightly toward the scanning signal line 111b in order to secure the connection portion. It has a pattern (shape) having an extended portion. Note that a semiconductor layer doped with impurities is formed at the interface between the drain electrode 132 and the source electrode 133 of the TFT 109 and the semiconductor layer 131 of the resistor 129 and the semiconductor layer 134 of the electrodes 135 and 136 of the resistance element 129. This semiconductor layer functions as a contact layer.

  That is, after the semiconductor layers 131 and 134 are formed, a thin semiconductor layer doped with impurities is formed on the surface thereof, and the drain electrode 132, the source electrode 133, and the electrodes 135 and 136 are formed. By using the electrode as a mask, the semiconductor layer doped with impurities exposed therefrom is etched to obtain the above-described configuration.

  Thus, on the surface of the substrate 101 on which the data signal line 110, the drain electrode 132, the source electrode 133, and the electrodes 135 and 136 are formed, a medium (dielectric property) sealed in the TFT 109 and the material layer 103 so as to cover them. A protective film 139 made of, for example, SiN is formed to avoid direct contact with the substance.

  The protective film 139 exposes a contact hole for exposing a part of the extended portion of the source electrode 133 of the TFT 109 and a part of the extended portions of the electrodes 135 and 136 of the resistance element 129. Contact holes for scanning, a scanning signal line 111a (scanning signal line for driving the TFT 109), and a contact hole for exposing a part of the scanning signal line 111b (date signal line adjacent to the scanning signal line 111a) are formed. ing.

  A transparent data electrode 104 made of, for example, an ITO film is formed on the upper surface of the protective film 139 so as to cover most of the pixel region. The data electrode 104 covers a part of the scanning signal line 111a for driving the TFT 109 and a part of the scanning signal line 111b adjacent to the scanning signal line 111a (as viewed from the normal direction of the substrate surface of the substrate 101). Arranged so as to overlap. Further, a storage capacitor element 121b having a protective film 139 and an insulating film 106 as a dielectric film is formed between the data electrode 104 and the scanning signal line 111b.

  Further, the data electrode 104 is formed so as to cover a contact hole for exposing a part of the source electrode 133 of the TFT 109 in the protective film 139 and a contact hole for exposing a part of the electrode 135 of the resistance element 129. Has been. Therefore, the data electrode 104 is connected to the source electrode 133 of the TFT 109 and to one electrode 136 of the resistance element 129.

  A wiring layer 137 is formed so as to cover a contact hole for exposing part of the electrode 135 of the resistance element 129 and a contact hole for exposing part of the scanning signal line 111b in the protective film 139. . Thereby, the wiring layer 137 connects the electrode 136 of the resistance element 129 and the scanning signal line 111b. The wiring layer 137 may be formed in the same process as the data electrode 104 using the same material as the data electrode 104.

  Further, an alignment film is formed on the surface (contact surface with the material layer 103) of the substrate 101 on which the data electrodes 104 and the like are formed in such a manner as to cover the data electrodes 104 and the like. As this alignment film, for example, an organic thin film subjected to a rubbing process can be used.

  On the other hand, a black matrix (not shown) is formed on the surface of the substrate 102 on the dielectric material side so as to define each pixel region. This black matrix is provided in order to prevent the light incident from the outside from being applied to the TFT 109 and the resistance element 129 and to improve the display contrast. Further, a color filter (not shown) having a color corresponding to each pixel region is formed in an opening portion of the black matrix (a region through which light is transmitted and a substantial pixel region).

  Further, on the surface of the substrate 102 facing the substrate 101, a flattened film formed by applying, for example, an organic thin film is formed so as to cover the black matrix and the color filter. This flattening film is for preventing the steps due to the black matrix and the color filter from becoming obvious.

  Further, a counter electrode 147 formed in common in each pixel region is provided on the surface of the planarizing film. The counter electrode 147 generates an electric field corresponding to a video signal (voltage) between the data electrode 104 in each pixel region, and thereby the light of the medium sandwiched between the data electrode 104 and the counter electrode 147. It controls the transmittance. The counter electrode 147 is made of a transparent material such as ITO.

  Further, an alignment film (not shown) is formed on the surface of the substrate 102 on which the counter electrode 147 is thus formed so as to cover the counter electrode 147. As this alignment film, for example, an organic thin film subjected to a rubbing process can be used.

  In the display element 191, a mixture obtained by mixing the following compounds in the following ratio is enclosed in the material layer 103.

  To this mixture, a compound (liquid crystal (meth) acrylate, polymerizable compound) composed of the above-mentioned compound A which is a photopolymerizable monomer (polymerizable compound), and an initiator (polymerization initiator, Methyl ethyl ketone peroxide (not shown) was added.

  As shown in FIG. 17, polarizing plates 107 and 108 are bonded to the surfaces of the substrates 101 and 102 opposite to the surface on the material layer 103 side. The absorption axes of the polarizing plates 107 and 108 are orthogonal to each other, and the polarizing axes 107 and 108 are bonded so that the absorption axis forms an angle of 45 degrees with the rubbing direction of the alignment films provided on both substrates. Yes.

  In addition, enclosure of the said mixture is performed as follows, for example. That is, the substrates 101 and 102 are adjusted via a spacer (not shown) such as plastic beads so that the distance between them (the thickness of the material layer 103) is 5 μm, and a sealing material (not shown) is used. Seal and fix the surrounding area. At this time, a portion that becomes an injection port (not shown) of a medium (dielectric liquid) to be injected later is opened without being sealed. In addition, the material of a spacer and a sealing material is not specifically limited, The thing conventionally used for the liquid crystal display element can be used.

  Next, between the two substrates, a mixture obtained by adding the above liquid crystal (meth) acrylate as a photopolymerizable monomer and methyl ethyl ketone peroxide as a polymerization initiator to the above mixture is injected. Here, the addition amount of the photopolymerizable monomer is preferably 0.05 wt% (wt%) or more and 15 wt% or less. This is because when the ratio of the polymerizable monomer is high, the driving voltage increases. Moreover, it is preferable that the addition amount of a polymerization initiator shall be 10 wt% or less.

  Next, the cell (display element 191) is irradiated with ultraviolet rays while maintaining the temperature of both substrates at 100 ° C. by an external heating device (not shown). As a result, the photopolymerizable monomer injected into the material layer 103 is polymerized (cured) to form a polymer chain. In addition, said mixture shows a negative type nematic liquid crystal phase below 113 degreeC, and shows an isotropic phase at the temperature beyond it. That is, in the present embodiment, a polymer chain is formed by polymerizing a photopolymerizable monomer in a state where the medium enclosed in the material layer 103 exhibits a liquid crystal phase.

  Thus, in a state where the medium sealed in the material layer 103 exhibits a liquid crystal phase, the liquid crystal molecules in this medium are aligned along the rubbing direction under the influence of rubbing applied to the alignment film. Therefore, by polymerizing the photopolymerizable monomer in this state, the ratio of the portion of the polymer chain obtained by polymerization along the alignment direction of the liquid crystal molecules increases. That is, the polymer chain has a structural anisotropy so that the ratio of the liquid crystal molecules oriented in the alignment direction of the original liquid crystal molecules aligned by the influence of rubbing increases.

  The display element 191 thus obtained is maintained at a temperature just above the nematic-isotropic phase transition point (a temperature slightly higher than the phase transition temperature, for example, +0.1 K) by an external heating device. By applying a voltage between the electrodes 104 and 147, the transmittance of the material layer 103 changes. That is, the medium enclosed in the material layer 103 is kept in an isotropic phase state by maintaining a temperature slightly higher than the liquid crystal phase-isotropic phase transition point of the medium, and a voltage is applied between the electrodes 104 and 147. Thus, the transmittance of the material layer 103 can be changed. Note that in the display element 191, the maximum transmittance was obtained when the voltage applied between both electrodes was 110V.

  Next, the drive state of the display device according to the present embodiment will be described. FIG. 41 shows an input signal (video signal) supplied via the data signal line 110, an input signal (scanning signal) supplied via the scanning signal line 111a, and an input signal supplied via the scanning signal line 111b. (Scanning signal), voltage applied to the display section capacitor 120 (between the data electrode 104 and the counter electrode 147), and the same as the display element 191 except that the conventional display element (the resistance element 129 and the storage capacitor element 121b is not provided). FIG. 6 is a waveform diagram of a voltage applied to the display unit capacitance of the conventional display element when each of the input signals is given to the display element having the configuration of FIG.

  As shown in this figure, a scanning signal for turning on the TFT 109 in a period t1 is input to the scanning signal line 111a. Note that a period obtained by combining the period 1 and the subsequent period 2 corresponds to one frame period.

  When a scanning signal for turning on the TFT 109 is input in the period t1, in the conventional display element, a voltage corresponding to a video signal supplied via the data signal line 110 is applied to the display unit capacitor, and the display unit capacitor is applied. The applied voltage is held at the same voltage (voltage corresponding to the video signal) throughout the period t1 and the period t2 (hold period). That is, the potential of the data electrode 104 is held at the same potential throughout the periods t1 and t2.

  On the other hand, in the display element 191 according to the present embodiment, the voltage applied to the display unit capacitor 120 becomes a voltage corresponding to the video signal supplied via the data signal line 110 in the period t1, and then the passage of time. It decreases with time and becomes almost zero at the end of the period t2. This is because a signal (video signal) supplied to the data electrode 104 is discharged by the resistance element 129.

  As described above, in the display element 191, the voltage applied to the display unit capacitor 120 becomes a voltage corresponding to the video signal in the period t1, and then attenuates to almost 0 in one frame period. As a result, the time for which the voltage corresponding to the video signal supplied to the data electrode 104 is accumulated in the display unit capacitor 120 is shorter than that of the conventional liquid crystal display device. That is, unlike the conventional case, the same alignment state is not maintained for a long time, so that the influence of the “memory effect” as described above can be reduced. As a result, the response speed can be improved. Further, when driving in the next frame, the influence of the orientation state (arrangement state) of the medium (dielectric material) in the previous frame can be reduced or prevented, and the flow and tailing of the image can be suppressed.

  FIG. 18A is a diagram showing luminance response characteristics in each pixel region when the resistance element 129 is not provided as in the prior art, and FIG. 18B is a pixel region of the display element 191 according to the present embodiment. It is the graph which showed the response characteristic of the brightness | luminance in. As shown in these drawings, the response speed can be improved by providing the resistance element 129 like the display element 191.

  In this embodiment, the resistance element 129 is connected to the scanning signal line 111b for driving a pixel adjacent to the pixel including the resistance element 129, but the present invention is not limited to this. For example, even when the resistance element 129 is connected to the scanning signal line 111a for driving the pixel including the resistance element 129, substantially the same effects as those described above can be obtained. FIG. 42 is an equivalent circuit diagram of the display element 191 in this case.

  In this embodiment, the semiconductor layer 134 is used as the material of the resistance element 129, but the present invention is not limited to this. When the semiconductor layer 134 is used, the semiconductor layer 131 of the TFT 109 can be formed at the same time as the semiconductor layer 131. However, if the increase in the number of manufacturing steps can be allowed, the semiconductor layer 131 is not particularly limited. Because.

  Further, in this embodiment, the data electrode 104 is formed on one substrate 101 side, and the counter electrode 147 is formed on the other substrate 102 side through the material layer 103. Although the configuration in which the electric field in the vertical direction is applied to the substrate surfaces 101 and 102 has been described, the present invention is not limited to this. For example, as in Embodiment 1, an electric field in a direction parallel to the substrate surface may be applied. In this case, for example, the data electrode 104 and the counter electrode 147 are formed on the substrate 101 side. Therefore, the material layer 103 may be a medium whose light transmittance can be controlled by a component substantially parallel to the substrate surfaces of the substrates 101 and 102 among the electric fields applied by both electrodes. In this case, a so-called counter signal line is formed on the substrate 101 side so as to connect the counter electrode 147 of each pixel region in common, but the resistance element 129 whose one end is connected to the data electrode 104 is formed. The other end may be connected to the counter electrode 147 or the counter voltage signal line.

  Further, as described above, the display device according to the present embodiment can improve the display characteristics of the memory effect generated in the medium without supplying the black display signal from the data signal line driving circuit and the scanning signal line driving circuit. The influence can be reduced. However, the display device according to the present embodiment is not limited to such a configuration, and the black display signal may be supplied from the data signal line driving circuit and the scanning signal line driving circuit as in the first embodiment. Good. That is, drive signals corresponding to the image display period Tw and the reset period Tr may be supplied from the data signal line drive circuit and the scanning signal line drive circuit.

  Further, in this embodiment, as a method of developing a liquid crystal phase when forming a polymerizable compound, a nematic phase is caused to appear at a temperature lower than the phase transition temperature of the liquid crystal phase-isotropic phase, but this method is not limited. It is not a thing. For example, by applying a high voltage that is not normally used for display, that is, a voltage much higher than the driving voltage of the display device, without forcing a temperature lower than the phase transition temperature of the liquid crystal phase to the isotropic phase, It may be aligned to develop a liquid crystal phase. That is, in order to develop the liquid crystal phase, an external field such as a temperature (typically lower than the liquid crystal phase-isotropic phase transition temperature) or an electric field may be applied. In addition, it is preferable that the external field given in order to express a liquid crystal phase shall be an environment different from the environment at the time of display.

  Further, the liquid crystal phase to be developed when forming the polymerizable compound is not limited to the nematic phase. Any state that exhibits optical anisotropy by applying an external field different from the driving state of the display element may be used, for example, a smectic (smectic) phase, a crystal phase, a cholesteric blue phase, a smectic blue phase, an isotropic phase. It may be.

  As another medium to be enclosed in the material layer 103, for example, among liquid crystalline materials as described in Patent Document 1, a mixture of 3HPFF, 5HPFF, and 7HPFF (1,2-difluoro-4- [ Trans-4- (trans-4-n-propylcyclohexyl) cyclohexyl] benzene, 1,2-difluoro-4- [trans-4- (trans-4-n-pentylcyclohexyl) cyclohexyl] benzene, and 1,2 -Difluoro-4- [trans-4- (trans-4-n-heptylcyclohexyl) cyclohexyl] benzene)) and the like may be applied. This material exhibits negative dielectric anisotropy.

  The medium enclosed in the material layer 103 is typically optically approximately isotropic when no electric field is applied, and may be a medium in which optical modulation is induced by applying an electric field. That is, it may be a substance that typically increases the degree of orientation of molecules or molecular aggregates (clusters) with the application of an electric field.

  In addition, as a medium to be enclosed in the material layer 103, for example, a liquid crystal phase having an ordered structure less than an optical wavelength and optically isotropic and having a negative dielectric anisotropy is applied. Can do. Alternatively, a system that is optically isotropic can be used, in which liquid crystal molecules are filled with aggregates that are radially aligned with a size equal to or smaller than the wavelength of light. By applying an electric field to these, it is possible to distort the fine structure of molecules or aggregates and induce optical modulation. In addition, even when these media are used, molecular orientation can be promoted by including a polymerizable compound, a hydrogen bond, a porous structure, or fine particles, so that driving at a low voltage is possible. It becomes possible.

  As such a medium, for example, a mixed system of 3HPFF, 5HPFF, and 7HPFF can be used. This mixed system has negative dielectric anisotropy.

  As described above, the mixed system of 3HPFF, 5HPFF, and 7HPFF is transparent because the ordered structure is less than the optical wavelength. That is, it is optically isotropic when no electric field is applied. Therefore, when this mixed system is applied to the display element according to the present embodiment, good black display can be performed under crossed Nicols.

  On the other hand, if an electric field is applied between the electrodes 104 and 147 while the above mixed system is controlled to a temperature range that exhibits optical isotropy when no electric field is applied, the structure exhibiting optical isotropy is distorted and optical Anisotropy develops (the degree of optical anisotropy changes). That is, the above mixed system is optically isotropic when no electric field is applied, and exhibits optical anisotropy when an electric field is applied.

  As described above, in the display device having the above-described structure, distortion is generated in the structure exhibiting optical isotropy by applying an electric field, and birefringence is generated, so that a good white display can be performed. Note that the direction in which birefringence occurs is constant, and its magnitude changes with the application of an electric field. Further, the voltage transmittance curve showing the relationship between the voltage (electric field) applied between the electrodes 104 and 147 and the transmittance is a stable curve. That is, in the display device having the above configuration, a stable voltage transmittance curve can be obtained in a temperature range exhibiting optical isotropy when no electric field is applied, and temperature control becomes extremely easy.

  Further, the medium sealed in the material layer 103 may be any compound shown in the first embodiment. In addition, a single compound may exhibit liquid crystallinity, or may exhibit liquid crystallinity by mixing a plurality of substances. Alternatively, other non-liquid crystalline substances may be mixed therein.

  Moreover, in the display element 191, although the board | substrates 101 and 102 were comprised with the glass substrate, it does not restrict to this. Moreover, although the space | interval between both board | substrates in the display element 191 was 5 micrometers, it is not limited to this, What is necessary is just to set arbitrarily. The electrodes 104 and 147 are made of ITO. However, the invention is not limited to this, and at least one of the electrodes 104 and 147 may be a transparent electrode material.

  In the display element 191, an alignment film made of an organic thin film is used, but the material of the alignment film is not particularly limited. For example, an organic thin film such as polyimide may be used, or an alignment film made of polyamic acid may be used. Alternatively, polyvinyl alcohol, a silane coupling agent, polyvinyl cinnamate, or the like may be used. When polyamic acid or polyvinyl alcohol is used, rubbing treatment may be performed after these materials are applied on the substrate to form an alignment film. Further, when a silane coupling agent is used, it may be formed by a pulling method like an LB film. Further, when polyvinyl cinnamate is used, UV (ultraviolet) irradiation may be performed after coating the polyvinyl cinnamate on the substrate.

  In the display element 191, the rubbing direction applied to the alignment film provided on each substrate is not particularly limited. For example, the rubbing directions of the substrates may be antiparallel to each other, and the rubbing directions of the substrates may be mutually different. The directions may be parallel and the same (parallel direction), or the rubbing directions of the substrates may be different from each other. Further, only one of them may be rubbed.

  In this embodiment, an alignment film subjected to rubbing treatment is used as the alignment film, but the present invention is not limited to this. For example, an alignment film that has been irradiated with light may be used. In this case, the irradiation light may be irradiated with polarized light or non-polarized light may be irradiated obliquely. Further, it may be a horizontal alignment film or a vertical alignment film. However, when a horizontal alignment film is used, an alignment film material that has been used in a liquid crystal display element or the like and that is very compatible with a liquid crystal material can be used as it is. In addition, unlike the vertical alignment film, it is possible to use the strong alignment regulating force in the in-plane direction of the substrate that the horizontal alignment film gives to the liquid crystal molecules, which can further promote the development of optical anisotropy during voltage application. It becomes possible.

  Further, the photopolymerizable monomer (polymerizable compound) is not limited to the above-described compound, and may be, for example, another liquid crystal (meth) acrylate having a liquid crystal skeleton and a polymerizable functional group in the molecule. The main chain of the polymer obtained by polymerizing this kind of monofunctional (meth) acrylate has a rigid liquid crystal skeleton directly integrated without a linking group, and the thermal movement of the liquid crystal skeleton is caused by the polymer main chain. Since it is limited, the orientation of the liquid crystal molecules affected by the main chain can be further stabilized.

  Further, epoxy acrylate may be used as a photopolymerizable monomer to be added to the medium sealed in the material layer 103. In addition, when any of the above-described polymerizable compounds is used, the amount of the polymerizable compound added is preferably in the range of 0.05 wt% or more and 15 wt% or less. This is because when the concentration of the cured portion is less than 0.05 wt%, the alignment assisting function provided by the polymerizable compound is reduced (alignment regulating force is weak), and when it is more than 15 wt%, the electric field applied to the polymerizable compound is reduced. This is because the ratio increases and the drive voltage increases.

  Further, by applying the present invention to a display device using the Kerr effect, a display device that exhibits high-speed response characteristics can be realized. In the manufacturing method described above, the electrodes 104 and 147 and the alignment film are formed on the opposing surfaces of the substrates 101 and 102, and the polarizing plate is formed on the surface of the substrates 101 and 102 opposite to the surface on which the electrodes 104 and 147 are formed. 107 and 108 are bonded together, a medium containing a photopolymerizable monomer and a polymerization initiator is sealed between both substrates, and then the photopolymerizable monomer is polymerized by irradiating with ultraviolet rays. However, the present invention is not limited to this. .

  For example, ultraviolet irradiation may be performed in a state where a color filter is attached to the substrate 102 and the TFT 109 is formed on the substrate 101. However, in this case, if exposure (ultraviolet irradiation) is performed from the front side of the panel (display element 191) (the side of the substrate 102 to which the color filter is attached) (ultraviolet irradiation), a considerable proportion of ultraviolet light is absorbed by the color filter. Photopolymerization cannot be performed effectively. For this reason, a much stronger ultraviolet ray is required as compared with the case of not passing through a color filter, which is a big problem. The color filter has red, green, and blue regions depending on the pixel, but the transmittance of ultraviolet light differs greatly in each of the red, green, and blue regions, so photopolymerization is performed by irradiating ultraviolet light through the color filter. As a result, large unevenness occurs for each pixel.

  Therefore, the exposure may be performed from the back side of the panel (display element 191) (the substrate 101 side on which the TFT 109 is formed). However, when exposure is performed from the back side of the panel, there are light shielding portions such as signal lines, scanning lines, and TFTs 109. These portions are difficult to form with a transparent electrode (transparent material). This is because transparent electrodes such as ITO have higher resistance than metals such as aluminum, copper, and tantalum, and thus are not suitable for use in signal lines and scanning lines. In particular, in the case of a large-sized and large-screen display element such as a liquid crystal television, since signal lines and scanning lines become enormous, it is unsuitable to make them transparent. Therefore, when exposure is performed from the back side of the panel, regions on the signal lines, scanning lines, and TFTs become light-shielding portions, and the media in those regions cannot perform photopolymerization. For this reason, it is necessary to cover the edge of the signal line, the scanning line, and the TFT 109 with a light shielding film, which causes a decrease in the aperture ratio. Furthermore, unreacted photopolymerizable monomers and initiators in the region of the light-shielding portion may cause reliability deterioration such as a decrease in voltage holding ratio, and therefore it is not preferable that there is an unreacted portion.

  In order to solve these problems, a color filter and a light-shielding film may be formed on the substrate 101 (substrate on which the TFT 109 is formed) side and exposed from the opposite substrate 102 side. Accordingly, it is not necessary to irradiate light through the TFT 109 (switching element), the color filter, the light shielding film, and the like, so that a wider area of the material layer 103 can be exposed. Accordingly, since the light shielding portion is eliminated, the material layer 103 can be exposed entirely. Therefore, it is not necessary to cover the edge portion as described above with a light shielding film, so that the aperture ratio is improved. Furthermore, since no unreacted polymerizable monomer, polymerization initiator, etc. remain, reliability deterioration can be prevented.

  In this case, it is preferable that the opposite substrate (the substrate 102 to which a color filter is conventionally attached) and the electrode 147 formed on the opposite substrate are formed of a transparent material. Thereby, the irradiation amount of an ultraviolet-ray can be reduced.

[Embodiment 3]
Still another embodiment of the present invention will be described. For convenience of description, members having the same functions as those described in the first or second embodiment are denoted by the same reference numerals and description thereof is omitted.

  FIG. 19 is a cross-sectional view and an equivalent circuit diagram showing a schematic configuration of one pixel of the display element 192 provided in the display device according to the present embodiment. The display element 192 is different from the display element 191 according to the second embodiment in the configuration of the resistance element 129. That is, the display element 191 according to the second embodiment is formed so that the resistance element 129 overlaps the light shielding film 128 when viewed from the normal direction of the substrate surface, as shown in FIG. On the other hand, as shown in FIG. 19, the display element 192 according to the present embodiment is formed at a position overlapping the scanning signal line 111b when viewed from the normal direction of the substrate surface. Note that the scanning signal line 111b is a scanning signal line for driving the TFT 109 of the adjacent pixel, and the scanning signal line 111a for driving the TFT 109 of the pixel including the resistance element 129 is the data electrode 104 of the pixel. It is arranged so as to be adjacent to each other. Note that the connection of one electrode 135 of the resistance element 129 to the data electrode 104 and the connection of the other electrode 136 to the scanning signal line 111b are contact holes formed in the protective film 139, as in FIG. It is made through.

  Accordingly, the scanning signal line 111b of the adjacent pixel functions as a light-shielding film that shields the resistance element 129 using the semiconductor layer 134 as a resistance material from external light incident from the substrate 101 side. Further, since the resistance element 129 is not formed in the pixel region (display region) surrounded by the scanning signal lines 111a and 111b and the data signal lines 110 and 110, it is possible to suppress a decrease in the aperture ratio.

  The equivalent circuit diagram of the display element 192 according to the present embodiment is substantially equal to the equivalent circuit diagram of the display element 191 according to the second embodiment shown in FIG. However, in the present embodiment, the resistance value of the resistance element 129 varies depending on the potential of the scanning signal line 111b of the pixel adjacent to the pixel including the resistance element 129.

  In a certain frame period, a gate signal (a signal for turning on the TFT 109) is supplied to the scanning signal line 111b (the (n−1) th row (previous stage) scanning signal line) and the scanning signal line 111a (the nth row scanning signal line). ), The potential of the data electrode 104 to which the video signal is supplied by the scanning signal of the n-th scanning signal line 111a in the frame period can be reset by the scanning signal of the preceding scanning signal line 111b. Also in this case, a graph showing the luminance response characteristics in each pixel region in relation to one frame period is as shown in FIG. Further, the state of the input signal waveform to the display element 192 and the voltage applied to the display section capacitor 120 in the display element 192 are as shown in FIG.

  In this embodiment, the resistance element 129 is connected to the scanning signal line 111b for driving a pixel adjacent to the pixel including the resistance element 129. However, the present invention is not limited to this. For example, even if the resistance element 129 is connected to the scanning signal line 111a for driving the pixel including the resistance element 129, the substantially same effect as the above configuration can be obtained. An equivalent circuit diagram of each pixel in this case is as shown in FIG.

  In this embodiment, the semiconductor layer 134 is used as the material of the resistance element 129, but the present invention is not limited to this. When the semiconductor layer 134 is used, the semiconductor layer 131 of the TFT 109 can be formed at the same time as the semiconductor layer 131. However, if the increase in the number of manufacturing steps can be allowed, the semiconductor layer 131 is not particularly limited. Because.

  Further, in this embodiment, the data electrode 104 is formed on one substrate 101 side, and the counter electrode 147 is formed on the other substrate 102 side through the material layer 103. Although the configuration in which the electric field in the vertical direction is applied to the substrate surfaces 101 and 102 has been described, the present invention is not limited to this. For example, as in Embodiment 1, an electric field in a direction parallel to the substrate surface may be applied. In this case, for example, the data electrode 104 and the counter electrode 147 are formed on the substrate 101 side. Therefore, the material layer 103 may be a medium whose light transmittance can be controlled by a component substantially parallel to the substrate surfaces of the substrates 101 and 102 among the electric fields applied by both electrodes.

[Embodiment 4]
Still another embodiment of the present invention will be described. For convenience of explanation, members having the same functions as those described in any of Embodiments 1 to 3 are denoted by the same reference numerals and description thereof is omitted.

  FIG. 20 is a cross-sectional view and an equivalent circuit diagram showing a schematic configuration for one pixel of a display element (display panel) 193 provided in the display device according to the present embodiment. The display element 193 is configured such that the resistance element 129 and the storage capacitor element b are connected to the capacitor line 138 instead of the scanning signal line 111b of the adjacent pixel. This is different from the display element 192 according to the third embodiment. The capacitor line 138 (conductive layer g1) is in the same layer as each scanning signal line 111 (111a, 111b).

  As shown in FIG. 20, the insulating film 106 and the protective film 139 are formed on the upper layer of the capacitor line 138, and the data electrode 104 is formed on the upper layer. As a result, a storage capacitor element 121 b is formed between the capacitor line 138 and the data electrode 104 using the insulating film 106 and the protective film 139 as a dielectric film.

  In addition, as illustrated in FIG. 20, the resistance element 129 is formed in a region overlapping with the capacitor line 138 when viewed from the normal direction of the substrate surface of the substrate 101. One electrode 135 of the resistance element 129 is connected to the data electrode 104 through a contact hole provided in the protective film 139. The other electrode 136 of the resistance element 129 is connected to the capacitor line 138 by the wiring layer 137 through a contact hole provided in the protective film 139. Note that the resistance element 129 overlaps with part of a region overlapping with the capacitor line 138 when viewed from the normal direction of the substrate surface of the substrate 101, and the data electrode 104 is not formed in the overlapping region. That is, the data electrode 104 is formed so as to avoid the resistance element 129, and the resistance element 129 and the capacitance line 138 are formed in a region overlapping with the capacitance line 138 when viewed from the normal direction of the substrate surface of the substrate 101. In the non-overlapping region, the data electrode 104 and the capacitor line 138 overlap.

  In such a configuration, the video signal supplied to the data electrode 104 is discharged to the capacitor line 138 side through the resistance element 129. Therefore, also in this case, a graph showing the luminance response characteristics in each pixel region in relation to one frame period is as shown in FIG.

  In the present embodiment, the semiconductor layer 134 is used as the material of the resistance element 129, but the present invention is not limited to this. When the semiconductor layer 134 is used, the semiconductor layer 131 of the TFT 109 can be formed at the same time as the semiconductor layer 131. However, if the increase in the number of manufacturing steps can be allowed, the semiconductor layer 131 is not particularly limited. Because.

  Further, in this embodiment, the data electrode 104 is formed on one substrate 101 side, and the counter electrode 147 is formed on the other substrate 102 side through the material layer 103. 101, the configuration in which the electric field in the vertical direction is applied to the substrate surface of the substrate 102 has been described, but the present invention is not limited to this. For example, as in Embodiment 1, an electric field in a direction parallel to the substrate surface may be applied. In this case, for example, the data electrode 104 and the counter electrode 147 are formed on the substrate 101 side. Therefore, the material layer 103 may be a medium whose light transmittance can be controlled by a component substantially parallel to the substrate surfaces of the substrates 101 and 102 among the electric fields applied by both electrodes.

[Embodiment 5]
Still another embodiment of the present invention will be described. For convenience of explanation, members having the same functions as those described in any of Embodiments 1 to 4 are given the same reference numerals, and descriptions thereof are omitted.

  FIG. 21 is a plan view showing a schematic configuration showing a schematic configuration for one pixel of a display element (display panel) 194 provided in the display device according to the present embodiment. FIG. 22 is a cross-sectional view taken along the line c-c ′ of the display element 194 shown in FIG. 21.

  In the display element 194, pixels are formed in regions surrounded by the first data signal line 110A and the second data signal line 110B and the adjacent two scanning signal lines 111a and 111b, respectively. In the following description, when attention is paid to a certain pixel, it is necessary to distinguish a scanning signal line existing in the pixel from a scanning signal line existing on the next stage of the pixel. A signal line is identified as a scanning signal line 111a, and a scanning signal line existing on the next stage side of the target pixel is distinguished as a scanning signal line 111b.

  As shown in FIG. 21, each pixel of the display element 194 includes a first data electrode 104A, a second data electrode 104B, a first TFT 109A, a second TFT 109B, and a third TFT 109C.

  The first data signal line 110A is connected to the first data electrode 104A via the first TFT 109A, and the second data signal line 110B is connected to the second data electrode 104B via the second TFT 109B. Connected with. The first data electrode 104A and the second data electrode 104B are connected via the source-drain of the third TFT 109C. The gate electrodes of the first TFT 109A and the second 109B are connected to the scanning signal line 111a. The gate electrode of the third TFT 109C is connected to the scanning signal line 111b.

  As shown in FIG. 22, the display element 194 includes a material layer 103 sandwiched between two substrates 101 and 102, and a dielectric material (medium) is sealed in the material layer 103. Note that the structure shown in FIG. 21 is formed on the surface of the substrate 101 facing the substrate 102.

  An insulating film 106 is formed between the first data signal line 110A and the second data signal line 110B and the scanning signal line 111a. Further, polarizing plates 107 and 108 are provided on the surfaces of the substrates 101 and 102 opposite to the opposing surfaces of the two substrates, respectively.

  Then, the display element 194 has an optical anisotropic property of the medium sealed in the material layer 103 by an electric field formed by applying a voltage between the first data electrode 104A and the second data electrode 104B. The display is performed by changing the degree of sex.

  FIG. 23 is an equivalent circuit diagram showing one pixel of the display element 194. FIG. 24 is an explanatory diagram showing a schematic configuration of the display element 194. As shown in this figure, the display element 194 has a large number of pixels shown in FIG. 23 arranged in a matrix. In FIG. 24, X represents a scanning signal line, Y1 represents a first data signal line, and Y2 represents a second data signal line.

  As shown in FIG. 23, in the display element 194, a display unit capacitor 120 exists between the first TFT 109A and the second TFT 109B. The display unit capacitor 120 is a capacitor that exists between the first data electrode 104A and the second data electrode 104B.

  In the display element 194, since the first TFT 109A and the second TFT 109B are connected to the same scanning signal line 111a, the same scanning signal is input to the first TFT 109A and the second TFT 109B, and switching is performed simultaneously. Is done. When the first TFT 109A and the second TFT 109B are turned on, the display portion capacitor 120 formed between the first data electrode 104A and the second data electrode 104B has a first data signal line 110A. And a voltage of a potential difference between the first data signal line 110B and the second data signal line 110B.

  In the display device according to the present embodiment, the potential supplied from the first data signal line 110A and the second data signal line 110B to the first data electrode 104A and the second data electrode 104B is the first The relationship is a reverse potential with reference to the gradation potential when the potential difference between the first data electrode 104A and the second data electrode 104B is 0V. Therefore, in the display device according to the present embodiment, the display is compared with the configuration illustrated in FIG. 1 (the configuration in which the reference potential is supplied to the common electrode 105 and the potential corresponding to the video signal is supplied to the data electrode 104). A double voltage can be applied to the partial capacitor 120. Therefore, even when a TFT and a data signal circuit having the same breakdown voltage as in the conventional case are used, a voltage twice as high as that in the conventional case can be applied to the material layer 103.

  On the other hand, the third TFT 109C has a gate electrode connected to the scanning signal line 111b, and a source electrode and a drain electrode connected to the first data electrode 104A and the second data electrode 104B, respectively. For this reason, when the third TFT 109C is turned on, the first data electrode 104A and the second data electrode 104B are short-circuited, and the potential difference between these electrodes (the display capacitor 120) becomes 0V.

  That is, in the display device according to the present embodiment, in accordance with the potential difference between the first data electrode 104A and the second data electrode 104B in a state where the scanning signal line 111a is on and the scanning signal line 111b is off. Gray scale display can be performed. Further, in a state where the scanning signal line 111b is turned on, the potential difference between the first data electrode 104A and the second data electrode 104B is set to 0 V, and black display can be performed by combining with the normally black mode. .

  That is, in the display device according to the present embodiment, writing control is performed when the scanning signal line 111a is turned on for the element rows for one line connected to the same scanning signal line, and collectively when the scanning signal line 111b is turned on. Black display. Thereby, in the display device according to the present embodiment, the medium sealed in the material layer 103 is prevented from being maintained in the same orientation for a long time, and the memory effect can be suppressed. Therefore, it is possible to prevent the response speed from decreasing when an image is displayed in the next frame. Further, intermittent display can be realized without using a method of intermittently lighting the backlight (illuminating device). Thereby, a moving image blur can be suppressed appropriately.

  Note that in the configuration shown in FIG. 21, the first TFT 109A and the second TFT 109B in each pixel of the element column driven by the scanning signal line, and the preceding element column of one scanning signal line A third TFT 109C in each pixel is connected. In this configuration, each scanning signal line functions as the scanning signal line 111b for the preceding element column and functions as the scanning signal line 111a for the next element column.

  Thus, in each scanning signal line, the function of the scanning signal line 111a (function of applying a voltage corresponding to the video signal to the display unit capacitor 120) and the function of the scanning signal line 111b (function of discharging the charge of the display unit capacitor 120). ), It is possible to simultaneously switch pixels for two lines adjacent to the scanning signal line by scanning one scanning signal line. That is, by scanning one scanning signal line, it is possible to input a gradation signal (voltage corresponding to the video signal) to the pixels on one line and input 0 V to the pixels on the other line. .

  As a result, two lines of pixels can be scanned simultaneously with one scanning signal line, so that intermittent display is performed with the conventional configuration (configuration in which one line of pixels is scanned with one scanning signal line). Compared to the case, it is possible to secure twice the on-time of the TFT. Therefore, even when the capacitance value of the display portion capacitor 120 is increased due to the relative dielectric constant of the material layer 103 compared to the liquid crystal material used in the conventional liquid crystal display element, It is possible to obtain sufficient writing ability.

  Note that the configuration is not limited to the above, and for each scanning signal line, the third TFT 109C in each pixel in the previous element column of the element column driven by the scanning signal line and the element column driven by the scanning signal line The first TFT 109 and the second TFT 109B in each pixel may be connected. In this case as well, the same effects as the above configuration can be obtained.

  In the present embodiment, the configuration in which the function of the scanning signal line 111a and the function of the scanning signal line 111b are shared by one scanning signal line has been described, but the present invention is not limited to this. That is, the function of the scanning signal line 111a and the function of the scanning signal line 111b may be realized by separate scanning signal lines.

  In the display device according to the present embodiment, the scanning signal line driving circuit (not shown) scans the odd-numbered scanning signal lines (supplying an active signal for controlling the switching elements) and the even-numbered scanning signal lines. The scanning may be alternately performed for each frame. In this case, each pixel sequentially repeats input of a gradation signal (video signal corresponding to an image to be displayed) and input of 0 V (black display signal) for each frame. Therefore, in each pixel, the time ratio of the hold period (gradation display period by the input of the gradation signal) and blanking period (black display period by the input of 0 V) is 1: 1, and satisfactory intermittent display is performed. be able to.

  Here, when a gradation signal is input to each pixel, the first TFT 109A and the second TFT 109B are driven. In order to set the input to each pixel to 0 V, the third TFT 109C is used. Only will be driven. For this reason, it is originally desirable that the third TFT 109C has a charging capability (on-current) that is twice that of the first TFT 109A and the second TFT 109B. However, in practice, even if the third TFT 109C has a charging capability (on-current) equal to or lower than that of the first TFT 109A and the second TFT 109B, from the viewpoint of visibility, there is a problem with intermittent display. This is not expected to occur. The reason is as follows.

  First, consider a case where a transition is made from a gradation display state of a low gradation (a gradation close to black) to a black display state. In this case, since the voltage applied to the pixel performing gradation display is small, the charge stored in the display unit capacitor 120 is also small, and even if the charging capability (ON current) of the third TFT 109C is small, the predetermined voltage is not limited. It is sufficiently possible to set the applied voltage of the pixel to 0 V (intermittent display) within this period.

  On the other hand, when shifting from a gradation display state with a high gradation (a gradation close to white) to a black display state, the applied voltage to the pixel performing the gradation display is large, so the display unit capacitance If the charge stored in 120 is large and the charging capability (ON current) of the third TFT 109C is small, the applied voltage of the pixel may not be completely 0V within a predetermined period. However, when it is in a high gradation state, that is, in a high luminance state, the human pupil who observes it is narrowed down, so even if the black state at the time of intermittent display is slightly floating, the luminance is recognized to be sufficiently dark. In terms of visibility, intermittent display is established.

  Thus, according to the display device according to the present embodiment, intermittent display suitable for a display element having a material layer 103 having a large relative dielectric constant or a display element having a material layer 103 that requires a high driving voltage. Is possible.

  Here, the configuration of the display element 194 will be described in more detail. FIG. 25A and FIG. 25B are cross-sectional views showing a schematic configuration of 194.

  In the display element 194, the material layer 103 which is an optical modulation layer is sandwiched between two opposing substrates (substrates 101 and 102). In addition, on the surface of the substrate 101 facing the substrate 102, the first data electrode 104A and the second data electrode 104B, which are electric field applying means for applying an electric field to the material layer 103, are arranged to face each other. Furthermore, polarizing plates 107 and 108 are provided on the surfaces of the substrates 101 and 102 opposite to the opposing surfaces of both substrates, respectively.

  25A shows a state in which no voltage is applied between the data electrodes 104A and 104B (no voltage applied state (off state)), and FIG. 25B shows a state between the data electrodes 104A and 104B. This represents a state in which a voltage is applied (voltage application state (on state)).

  The substrates 101 and 102 are made of glass substrates. However, the material of the substrates 101 and 102 is not limited thereto, and at least one of the substrates 101 and 102 may be a transparent substrate. Note that the distance between the substrates in the display element 190, that is, the thickness of the material layer 103 was 10 μm. However, the distance between the two substrates is not limited to this, and may be set arbitrarily.

  FIG. 26 is a diagram for explaining the arrangement of the first data electrode 104A and the second data electrode 104B and the absorption axis directions of the polarizing plates 107 and 108. FIG. As shown in this figure, the first data electrode 104A and the second data electrode 104B in the display element 194 are composed of comb-shaped electrodes formed in a comb-teeth shape and are arranged to face each other. In the display element 194, the first data electrode 104A and the second data electrode 104B are formed with a line width of 5 μm and an interelectrode distance (electrode interval) of 5 μm. It can be arbitrarily set according to the gap with the terminal 102. In addition, as the material of the first data electrode 104A and the second data electrode 104B, various conventionally known materials can be used as the electrode material, such as a transparent electrode material such as ITO and a metal electrode material such as aluminum. Further, the shapes of the first data electrode 104 and the second data electrode 104B are not limited to the comb electrodes, and may be changed as appropriate.

  Further, as shown in FIG. 26, the polarizing plates 107 and 108 provided on both the substrates 101 and 102 have the absorption axes orthogonal to each other, and the absorption axes and the respective data in the respective polarizing plates 107 and 108. The electrodes 104 </ b> A and 104 </ b> B are formed so as to form an angle of about 45 degrees with the electrode extension direction (direction orthogonal to the electric field application direction) of the comb-teeth portion. For this reason, the absorption axis in each of the polarizing plates 107 and 108 forms an angle of about 45 degrees with respect to the direction of electric field application by the data electrodes 104A and 104B.

  The material layer 103 is filled with the same compound as in the first embodiment. Note that the display device may include a heating unit (not shown) for heating the display element 194 (or the material layer 103) to a certain temperature. This heating means may be, for example, a heater provided around the display element 194, or a sheet-like heater directly bonded to the display element 194.

  In addition, an organic thin film may be formed on the opposing surfaces of both the substrates 101 and 102 as necessary. In this case, the organic thin film formed on the substrate 101 side may be formed so as to cover the first data electrode 104A and the second data electrode 104B.

  FIG. 27A shows the first data electrode 104A and the second data electrode 104B in a state where the material layer 103 is kept at a temperature exhibiting an optical isotropic phase in the display device according to the present embodiment. It is explanatory drawing which shows the orientation state of a molecule | numerator when not applying a voltage in between. FIG. 27B shows a voltage between the first data electrode 104A and the second data electrode 104B in the display device according to the present embodiment in a state where the temperature is maintained at an optically isotropic phase. It is explanatory drawing which shows the orientation state of a molecule | numerator at the time of applying.

  As shown in these drawings, in the display device according to the present embodiment, the transmittance can be changed by applying a voltage while keeping the material layer 103 at a temperature exhibiting an optical isotropic phase. That is, as shown in FIG. 27A, in the state where no voltage is applied, the material layer 103 is optically isotropic and is in a black display state. On the other hand, when a voltage is applied, as shown in FIG. 27B, in the region where an electric field is applied, the major axis direction of the molecules of the dielectric substance (medium) is oriented in the electric field direction, so that birefringence appears. Transmittance can be modulated.

  FIG. 27C shows a display device according to this embodiment in which the material layer 103 is applied between the first data electrode 104A and the second data electrode 104B while maintaining a temperature exhibiting an optical isotropic phase. It is a graph which shows a voltage transmittance | permeability curve at the time of changing the voltage to perform. Note that the horizontal axis represents the voltage applied between the first data electrode 104A and the second data electrode 104B, and the vertical axis represents the transmittance of the display element 194. As shown in this figure, the display device according to the present embodiment has a normally black mode in which the transmittance of the display element 194 can be changed according to the applied voltage, and black display is obtained when 0 V is applied. It is possible.

  Note that in the case where the temperature of the material layer 103 is maintained at a temperature exhibiting an optical isotropic phase, the transmittance can be modulated to a practically sufficient level by a voltage of about 0 V to 100 V. However, at a temperature sufficiently far from the phase transition temperature from the optical isotropic phase to the isotropic phase (a temperature sufficiently higher than the phase transition temperature), the necessary voltage increases as described below.

That is, according to Non-Patent Document 6, the birefringence generated by applying an electric field is
Δn = λBE ²
It can be described by. Λ is the wavelength of light, B is the Kerr constant, and E is the applied electric field strength.

And this Kerr constant B is
B∝ (T-Tni) ^-1
Is proportional to Here, Tni is the temperature of the transition point, and T is the temperature of the medium.

  Therefore, even if it can be driven with a weak electric field strength in the vicinity of the transition point (Tni), the required electric field strength increases rapidly as the temperature (T) rises. For this reason, at the temperature immediately above the phase transition, the transmittance can be sufficiently modulated with a voltage of about 100 V or less, but at a temperature sufficiently far from the phase transition temperature, the voltage required for modulating the transmittance becomes large. . Therefore, in the display element using the Kerr effect immediately above the phase transition temperature, high-precision temperature control is necessary, and the lower the temperature control accuracy, the higher the drive voltage is required.

  Next, a method for manufacturing the display element 194 will be described.

  First, a metal material made of tantalum or the like was formed on the substrate 101 by a sputtering method, patterned, and then anodized to form each scanning signal line and each TFT gate electrode. Next, a silicon nitride film as a gate insulating film 106 and a silicon film as a semiconductor layer for forming a channel layer or the like were formed by plasma CVD, and patterning was performed. Furthermore, a metal material made of aluminum or the like was formed by sputtering and patterned to form a TFT source electrode and drain electrode, and a data signal line and a data electrode at the same time.

  Next, FIG. 28 shows a waveform of an input signal to the display element 194 and a voltage state applied to the display section capacitor 120 of the display element 194. Note that the broken lines shown in the input signal waveforms of the first data signal line 110A and the second data signal line 110B indicate that the potential difference between the first data electrode 104A and the second data electrode 104B is 0V. (Reference potential). As shown in this figure, the input signals of the first data signal line 110A and the second data signal line 110B have opposite potentials with respect to the potential indicated by the broken line.

  As shown in this figure, when the scanning signal for the scanning signal line 111a is turned on in the period t1, the first TFT 109A and the second TFT 109B are turned on, and the first data electrode 104A and the second data electrode 104B are turned on. Are at the same potential as the first data signal line 110A and the second data signal line 110B. This potential is held in the first data electrode 104A and the second data electrode 104B even during the period t2 (hold period). Therefore, during the periods t1 and t2, a voltage corresponding to the potential difference between the first data electrode 104A and the second data electrode 104B is applied to the display unit capacitor 120.

  Next, in a period t3, when the scanning signal with respect to the scanning signal line 111b is turned on, the third TFT 109C is turned on, and the first data electrode 104A and the second data electrode 104B are connected. As a result, the potential difference between the first data electrode 104A and the second data electrode 104B becomes 0V. As a result, in the period t3 and the subsequent period t4, the voltage applied to the display unit capacitor 120 becomes 0 V, and the display element 194 displays black (blanking period).

  By driving the display element 194 as described above, a sufficient voltage necessary for driving the display element 194 (to perform appropriate display using the display element 194) is applied to the material layer 103. Could be applied. By using the above-described dielectric material as a medium to be enclosed in the substance layer 103, a display device having high-speed response characteristics and high viewing angle characteristics can be realized.

  FIG. 29 is an explanatory diagram showing a signal waveform of a scanning signal for each scanning signal line. In this embodiment, as shown in this figure, scanning of odd-numbered scanning signal lines and scanning of even-numbered scanning signal lines are alternately performed for each frame. Thereby, for each pixel, the input of the gradation signal and the input of 0 V are sequentially repeated for each frame. Therefore, it is possible to prevent the medium enclosed in the material layer 103 from being maintained in the same orientation for a long time, and to suppress the influence of the memory effect. Therefore, it is possible to prevent the response speed from decreasing when an image is displayed in the next frame. Further, intermittent display can be realized without using a method of intermittently lighting the backlight (illuminating device). Thereby, a moving image blur can be suppressed appropriately.

  Further, according to the above driving method, it is possible to simultaneously scan pixels for two rows by the same scanning. For this reason, it is possible to secure twice the on-time of each TFT as compared with the case of intermittent display in the conventional configuration (configuration in which one line of pixels is scanned by one scanning signal line). Therefore, each TFT can have a sufficient writing ability to the display unit capacitor 120, and a good display without display unevenness can be obtained.

  In addition to the display element 194 having the above structure, an auxiliary capacitor 121 connected in parallel to the display unit capacitor 120 (the first data electrode 10A and the second data electrode 104B) may be provided. FIG. 30 is an equivalent circuit diagram of the display element 194 when the auxiliary capacitor 121 is provided.

  The auxiliary capacitor 121 is inevitably formed when the substrate 101 in the region between the first data electrode 104A and the second data electrode 104B is made of a dielectric material. In particular, in the configuration, the capacitance value of the auxiliary capacitor 121 is increased by increasing the relative dielectric constant of the substrate 101. As described above, by increasing the capacitance value of the auxiliary capacitor 121, the influence of the leakage current in the first to third TFTs 109A, 109B, and 109C and the material layer 103 can be reduced.

  By the way, in the case where a monomer or a photopolymerization initiator is contained in the medium sealed in the material layer 103, even after polymerization (curing) is performed by ultraviolet irradiation, the material layer 103 is caused by incomplete polymerization or the like. Ions may remain. In addition, when the material layer 103 has high dielectric anisotropy, ions are easily taken into the material layer 103. If such ions remain in or are taken into the material layer 103, the voltage holding ratio of the material layer 103 tends to be low. That is, the leak current tends to increase. However, by providing the auxiliary capacitor 121 as described above, the influence of the leakage current in the material layer 103 can be reduced.

  In the present embodiment, the same compound as in the first embodiment described above is used as the medium sealed in the material layer 103, but the present invention is not limited to this, and other dielectric materials may be used. .

[Embodiment 6]
Still another embodiment of the present invention will be described. For convenience of explanation, members having the same functions as those described in any of Embodiments 1 to 5 are denoted by the same reference numerals and description thereof is omitted.

  FIG. 31 is an equivalent circuit diagram for one pixel of the display element 194 provided in the display device according to the present embodiment. The configuration of the display element 194 according to the present embodiment is substantially the same as the configuration of the display element 194 described in the sixth embodiment, but in this embodiment, each scanning signal line, data signal line, and each data In consideration of the parasitic capacitance generated between the electrodes, the effect of these parasitic capacitances on the display is further suppressed.

  Therefore, the equivalent circuit diagram shown in FIG. 31 shows parasitic capacitances 149 to 156 in addition to the equivalent circuit diagram shown in FIG. 30 in the sixth embodiment. That is, the equivalent circuit diagram of the display element 194 illustrated in FIG. 31 is obtained by adding parasitic capacitances 149 to 156 to the equivalent circuit diagram of the display element 194 illustrated in FIG.

  Here, the parasitic capacitance 149 is a parasitic capacitance generated between the scanning signal line 111a and the first data electrode 104A. Further, the parasitic capacitance 150 is a parasitic capacitance generated between the scanning signal line 111a and the second data electrode 104B. The parasitic capacitance 151 is a parasitic capacitance generated between the scanning signal line 111b and the first data electrode 104A. The parasitic capacitance 152 is a parasitic capacitance generated between the scanning signal line 111b and the second data electrode 104B. The parasitic capacitance 153 (first parasitic capacitance) is a parasitic capacitance generated between the data signal line 110A and the first data electrode 104A. The parasitic capacitance 154 (second parasitic capacitance) is a parasitic capacitance generated between the data signal line 110A and the second data electrode 104B. The parasitic capacitance 155 (third parasitic capacitance) is a parasitic capacitance generated between the data signal line 110B and the first data electrode 104A. The parasitic capacitance 156 (fourth parasitic capacitance) is a parasitic capacitance generated between the data signal line 110B and the second data electrode 104B.

  In this embodiment, as shown in FIG. 21, the interval between the scanning signal line 111a and the first data electrode 104A and the interval between the scanning signal line 111a and the second data electrode 104B are made equal to each other. The interval between the line 111b and the first data electrode 104A is set equal to the interval between the scanning signal line 111b and the second data electrode 104B. Thereby, the capacitance value of the parasitic capacitance 149 and the capacitance value of the parasitic capacitance 150 are equal, and the capacitance value of the parasitic capacitance 151 and the capacitance value of the parasitic capacitance 152 are equal. Therefore, the capacitance values of the parasitic capacitances 149 and 151 (fifth parasitic capacitance) are equal to the capacitance values of the parasitic capacitances 150 and 152 (sixth parasitic capacitance).

  When the capacitance value of the parasitic capacitance 149 and the capacitance value of the parasitic capacitance 150, or the capacitance value of the parasitic capacitance 151 and the capacitance value of the parasitic capacitance 152 are different, the first data electrode changes when the potential of the scanning signal line 111a or 111b varies. The potentials of 104A and the second data electrode 104B are affected by the potential fluctuation of the scanning signal line 111a or 111b and fluctuate due to the parasitic capacitances 149 to 152.

  On the other hand, in the present embodiment, as described above, the capacitance value of the parasitic capacitance 149 and the capacitance value of the parasitic capacitance 150 are equal, and the capacitance value of the parasitic capacitance 151 and the capacitance value of the parasitic capacitance 152 are the same. Therefore, even if the potential variation of the scanning signal line 111a or 111b occurs, the potential variation values applied to the first data electrode 104A and the second data electrode 104B are equal. Therefore, the potential difference between the first data electrode 104A and the second data electrode 104B (the voltage applied to the display portion capacitor 120) does not fluctuate. For this reason, a target applied voltage can be appropriately applied to the material layer 103.

  In the present embodiment, as shown in FIG. 21, the interval between the data signal line 110A and the first data electrode 104A is made equal to the interval between the data signal line 110A and the second data electrode 104B. The interval between the data signal line 110B and the first data electrode 104A is made equal to the interval between the data signal line 110B and the second data electrode 104B. As a result, the capacitance value of the parasitic capacitance 153 and the capacitance value of the parasitic capacitance 156 are equal, and the capacitance value of the parasitic capacitance 154 and the capacitance value of the parasitic capacitance 155 are equal.

  When the capacitance value of the parasitic capacitance 153 and the capacitance value of the parasitic capacitance 156, or the capacitance value of the parasitic capacitance 154 and the capacitance value of the parasitic capacitance 155 are different, depending on the display content (depending on the input signal of each data signal line), crosstalk May occur.

  On the other hand, in this embodiment, as described above, the interval between the data signal line 110A and the first data electrode 104A and the interval between the data signal line 110A and the second data electrode 104B are made equal. The interval between the data signal line 110B and the first data electrode 104A is made equal to the interval between the data signal line 110B and the second data electrode 104B. As a result, it is possible to perform a good display in which crosstalk is suppressed.

  Further, the capacitance values of the parasitic capacitances 153 to 156 (first to fourth parasitic capacitances) are changed to the capacitance values of the parasitic capacitances 149 and 151 (fifth parasitic capacitance), and the parasitic capacitances 150 and 152 (sixth capacitance). The capacitance of the first data electrode 104A and the second data electrode 104B can be further stabilized by increasing the capacitance value of the parasitic capacitance. Thereby, the change in the electric field of the display capacitor 120 due to the fluctuation of the potential of the scanning signal line during the switching of the TFT can be suppressed, and the occurrence of flicker can be suppressed.

  Further, as shown in FIG. 32, in addition to the configuration of FIG. 31, an auxiliary capacitance line 157 is provided, and an auxiliary capacitance 158 is provided between the auxiliary capacitance line 157 and the first data electrode 104A. An auxiliary capacitor 159 may be provided between the second data electrode 104B.

  FIG. 33 is a plan view of the display element 194 provided with the auxiliary capacitance line 157, and FIG. 34 is a cross-sectional view of the display element 194 in this case. As shown in FIG. 34, the storage capacitor line 157 can be formed in the same process and in the same step in the same layer as the scanning signal line 111a.

  As described above, by providing the auxiliary capacitors 158 and 159, an effect of suppressing the potential fluctuation of the first data electrode 104A and the second data electrode 104B can be obtained. Note that the potential of the auxiliary capacitance line 157 can basically be set freely. However, in the case of the present embodiment, since the auxiliary capacitance line 157 and the data signal lines 110A and 110B intersect, the gradation when the potential difference between the data electrode 104A and the data electrode 104B is 0V. It is the condition that the best display state can be maintained that it is equal to the potential.

[Embodiment 7]
Still another embodiment of the present invention will be described. For convenience of explanation, members having the same functions as those described in any of Embodiments 1 to 6 are given the same reference numerals, and descriptions thereof are omitted.

  35 is a plan view showing a schematic configuration of one pixel of the display element 195 provided in the display device according to the present embodiment, FIG. 36 is a sectional view thereof, and FIG. 37 is an equivalent circuit diagram thereof. FIG. 38 is an explanatory diagram showing the configuration of the display element 195. As shown in this figure, the display element 195 includes a large number of pixels shown in FIGS. 35 to 37 in a matrix. In FIG. 38, X represents a scanning signal line, Y represents a data signal line, and C represents an auxiliary capacitance line.

  As shown in FIG. 35, the display element 195 includes a data signal line 110, a first scanning signal line 111a, a second scanning signal line 111b, a common signal line 161, a first TFT 109A, a third TFT 109C, and a data electrode. 104 and a common electrode 162 are provided.

  The data electrode 104 is connected to the data signal line 110 via the drain-source of the first TFT 109. The gate electrode of the first TFT 109A is connected to the scanning signal line 111a. The data electrode 104 is connected to the source electrode of the third TFT 109C, the gate electrode of the third TFT 109C is connected to the scanning signal line 111b, and the drain electrode is connected to the common electrode 162. Note that the common electrode 162 is connected to the common signal line 161.

  Thereby, in the display element 195, an electric field is generated between the data electrode 104 and the common electrode 162 (see FIG. 36), thereby changing the transmittance of the material layer 103 to perform display. Therefore, a display region (that is, a display unit capacitor 120) is formed by the data electrode 104, the common electrode 162, and the material layer 103 between these electrodes.

  As shown in the equivalent circuit diagram of FIG. 37, in the display element 195, the display unit capacitor 120 exists between the first TFT 109A and the common signal line 161. The display unit capacitance 120 is a capacitance that exists between the data electrode 104 and the common electrode 162. Further, a parasitic capacitance 164 exists between the data electrode 104 and the scanning signal line 111 a, and a parasitic capacitance 165 exists between the data electrode 104 and the data signal line 110, and the data electrode 104 and the common signal line 161. There is a parasitic capacitance 166 between the two.

  Further, in the display element 195, the first TFT 109A of each pixel in the element row that controls the input of the video signal from the data signal line 110 by the scanning signal line 111a to the scanning signal line 111a, and the next stage of the element row. The third TFT 109C of each pixel in the element row is connected. That is, the display device according to the present embodiment includes a plurality of scanning signal lines and a plurality of data signal lines orthogonal to each scanning signal line as shown in FIG. 38, and includes the scanning signal lines and the data signal lines. Pixels are formed in each region partitioned in a matrix. Each scanning signal line is connected to a first TFT 109A in each pixel on one line and a third TFT 109C in each pixel on a line subsequent to the above line.

  Next, a method for manufacturing the display element 195 will be described.

  First, a metal material made of tantalum or the like is formed on the substrate 101 by a sputtering method and patterned to form the common signal line 161 and the common electrode 162, and then anodization is performed. Scanning signal lines and gate electrodes of the TFTs 109A and 109C were formed. Next, a silicon nitride film was formed as the gate insulating film 106 by plasma CVD, and a silicon film was further formed as a semiconductor layer for forming the channel layers of the TFTs 109A and 109C, followed by patterning. Further, in order to connect the drain electrode of the third TFT 109C and the common electrode 162, patterning for forming a contact hole in the insulating film 106 was performed. At this time, the insulating film 106 over the common electrode 162 may be removed at the same time. Alternatively, the insulating film 106 in the display region (the region between the data electrode 104 and the common electrode 162) may be removed at the same time to have a structure as shown in FIG. Thereby, it is possible to prevent a drop in applied voltage between the data electrode 104 and the common electrode 162 due to the influence of the insulating film 106.

  Next, a metal material made of aluminum or the like was formed by sputtering and patterned, whereby the source and drain electrodes, the data signal line 110, and the data electrode 104 of the TFTs 109A and 109C were formed at the same time. In addition, a medium similar to that shown in Embodiment Mode 1 was used as the medium sealed in the material layer 103.

  40 is an explanatory diagram showing a waveform of an input signal to the display element 195 and a voltage state applied to the display unit capacitance 120 of the display element 195. FIG. Note that the broken line shown in the input signal waveform for the data signal line 110 indicates the potential of the common electrode 162.

  As shown in this figure, the input signal to the data signal line 110 is a rectangular wave whose polarity is reversed with the potential of the common electrode 162 as a reference.

  In a period t1, when the scanning signal for the scanning signal line 111a is turned on, the potential of the data electrode 104 becomes the same as the potential of the data signal line 110. This potential is held in the data electrode 104 even during the period t2 (hold period). That is, during the periods t1 and t2, a voltage corresponding to the potential difference between the common electrode 162 and the potential supplied from the data signal line 110 to the data electrode 104 in the period t1 is continuously applied to the display unit capacitor 120.

  Next, in a period t3, when the scanning signal for the scanning signal line 111b is turned on, the third TFT 109C is turned on, and the data electrode 104 and the common electrode 162 are connected. As a result, the potential of the data electrode 104 becomes equal to the potential of the common electrode 162, and the potential difference between the data electrode 104 and the common electrode 162 becomes 0V. That is, the voltage applied to the display unit capacitor 120 is 0V. Therefore, in the period t3 and the subsequent period t4, the display element 195 displays black (blanking period).

  In the present embodiment, similarly to FIG. 29 described in the fifth embodiment, scanning of odd-numbered scanning signal lines and scanning of even-numbered scanning signal lines are alternately performed for each frame. Is preferred. In the case of driving in this way, each pixel sequentially repeats the input of the gradation signal and the input of 0V for each frame. Therefore, it is possible to prevent the medium sealed in the material layer 103 from being maintained in the same orientation for a long time, and to suppress the memory effect. Therefore, it is possible to prevent the response speed from decreasing when an image is displayed in the next frame. Further, intermittent display can be realized without using a method of intermittently lighting the backlight (illuminating device). Thereby, a moving image blur can be suppressed appropriately.

  Further, according to the above driving method, it is possible to simultaneously scan pixels for two rows by the same scanning. For this reason, it is possible to secure twice the on-time of each TFT as compared with the case of intermittent display in the conventional configuration (configuration in which one line of pixels is scanned by one scanning signal line). Therefore, each TFT can have a sufficient writing ability to the display unit capacitor 120, and a good display without display unevenness can be obtained. The display element 195 according to the present embodiment has a smaller number of TFTs than the display element 194 according to the fifth embodiment. For this reason, it is possible to improve the yield rate in the display element manufacturing process.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. Embodiments are also included in the technical scope of the present invention.

  The present invention is widely applied to image display devices such as televisions and monitors, OA devices such as word processors and personal computers, or image display devices provided in information terminals such as video cameras, digital cameras, and mobile phones. Can do.

It is a cross-sectional schematic diagram which shows schematic structure of the display panel concerning one Embodiment of this invention. It is a top view which shows schematic structure of the display panel concerning one Embodiment of this invention. It is an equivalent circuit diagram of the display panel. It is a characteristic view which shows the applied voltage to the material layer, and the transmittance | permeability at that time in the display panel concerning one Embodiment of this invention. FIG. 3 is an equivalent circuit diagram of an active matrix substrate and pixels of the display panel. FIG. 6A is a cross-sectional view of the display panel when no voltage is applied, and FIG. 6B is a cross-sectional view of the display panel when a voltage is applied. It is a top view for demonstrating arrangement | positioning of the electrode and polarizing plate in the said display panel. It is a model figure of various phase structures. It is explanatory drawing which shows the cholesteric blue phase and the mechanism of the immobilization in one Embodiment of this invention. It is a structural model (rod network model) of a cubic phase. It is a structural model of a cubic phase. It is explanatory drawing for demonstrating the difference in the display principle in the display panel concerning one Embodiment of this invention, and the conventional liquid crystal display panel. It is a schematic diagram which shows the structure of a liquid crystal microemulsion. It is a schematic diagram which shows the structure of a liquid crystal microemulsion. It is a classification diagram of a lyotropic liquid crystal phase. 1 is an equivalent circuit diagram of an active matrix substrate and pixels of a display panel according to an embodiment of the present invention. 1 is a schematic cross-sectional view and an equivalent circuit diagram of a display panel according to an embodiment of the present invention. It is explanatory drawing which shows the effect of the display panel by one Embodiment of this invention. 1 is a schematic cross-sectional view and an equivalent circuit diagram of a display panel according to an embodiment of the present invention. 1 is a schematic cross-sectional view and an equivalent circuit diagram of a display panel according to an embodiment of the present invention. It is a top view which shows schematic structure of the display panel concerning one Embodiment of this invention. It is a cross-sectional schematic diagram which shows schematic structure of the display panel concerning one Embodiment of this invention. It is a display panel equivalent circuit schematic concerning one Embodiment of this invention. 1 is an equivalent circuit diagram of a display panel according to an embodiment of the present invention. FIG. 25A is a cross-sectional view of a display panel according to an embodiment of the present invention in a voltage non-application state, and FIG. 25B is a cross-sectional view of the display panel in a voltage application state. It is a top view for demonstrating arrangement | positioning of an electrode and a polarizing plate in the display panel concerning one Embodiment of this invention. FIG. 27A is a cross-sectional view showing the orientation state of the medium in the voltage-less application state of the display panel according to one embodiment of the present invention, and FIG. FIG. 27C is a graph showing a voltage-transmittance curve of the display panel. It is a waveform diagram which shows the input signal waveform to the display panel concerning one Embodiment of this invention, and the electric potential state in the display panel. It is a wave form diagram which shows the input signal to each scanning signal line in the display panel concerning one Embodiment of this invention. FIG. 24 is an equivalent circuit diagram in the case where an auxiliary capacitor is provided in addition to the display panel shown in FIG. FIG. 31 is an equivalent circuit diagram when a parasitic capacitance is further added to the display panel shown in FIG. 30. 1 is an equivalent circuit diagram of a display panel according to an embodiment of the present invention. It is a top view which shows schematic structure of the display panel concerning one Embodiment of this invention. It is sectional drawing which shows schematic structure of the display panel concerning one Embodiment of this invention. It is a top view which shows schematic structure of the display panel concerning one Embodiment of this invention. It is sectional drawing which shows schematic structure of the display panel concerning one Embodiment of this invention. 1 is an equivalent circuit diagram of a display panel according to an embodiment of the present invention. 1 is an equivalent circuit diagram of a display panel according to an embodiment of the present invention. FIG. 36 is a cross-sectional view showing another configuration example of the display panel shown in FIG. 35. It is a waveform diagram which shows the input signal waveform to the display panel concerning one Embodiment of this invention, and the electric potential state in this display panel. It is a waveform diagram which shows the input signal waveform to the display panel which can be provided in the display apparatus concerning one Embodiment of this invention, and the electric potential state of the display panel. It is an equivalent circuit diagram which shows the modification of the display panel concerning one Embodiment of this invention.

Explanation of symbols

14A, 14B Drive circuit area 101 substrate (active matrix substrate)
102 Substrate (counter substrate)
103 Material layer 104, 104A Data electrode (pixel electrode)
104B Data electrode (counter electrode)
105 Common electrode (counter electrode)
106 Insulating film 109, 109A TFT (first switching element)
109B TFT (second switching element)
109C TFT (third switching element)
110, 110A Data signal line (first data signal line)
110B data signal line (second data signal line)
111, 111a, 111b Scanning signal line 112 Common signal line 120 Display unit capacity 121, 121b Auxiliary capacity 122, 123 Parasitic capacity 128 Light shielding film 129 Resistance element 138 Capacity line (capacitance signal line)
147 Counter electrode 149 Parasitic capacitance (fifth parasitic capacitance)
150 Parasitic capacitance (sixth parasitic capacitance)
151 Parasitic capacitance (fifth parasitic capacitance)
152 Parasitic capacitance (sixth parasitic capacitance)
153 Parasitic capacitance (first parasitic capacitance)
154 Parasitic capacitance (second parasitic capacitance)
155 Parasitic capacitance (third parasitic capacitance)
156 Parasitic capacitance (fourth parasitic capacitance)
157 Auxiliary capacitance line 158, 159 Auxiliary capacitance 161, 162 Common electrode (counter electrode)
164, 165, 166 Parasitic capacitance 190-195 Display element (display panel)

Claims (46)

A pair of substrates, at least one of which is transparent, a material layer sandwiched between the substrates, a pixel electrode and a counter electrode for applying an electric field to the material layer, and applying an electric field to the material layer A display panel for displaying with
The material layer is optically isotropic when no electric field is applied, and is composed of a medium in which the degree of optical anisotropy is changed by changing the orientation direction of molecules by applying an electric field,
After applying an image display voltage between the pixel electrode and the counter electrode, before applying a next image display voltage between the pixel electrode and the counter electrode, the potential of the pixel electrode A display panel characterized in that the potential of the counter electrode is substantially equal. A first switching element connected to the pixel electrode;
A scanning signal line connected to the first switching element and supplying a scanning signal for driving and controlling the first switching element;
A first data signal line connected to the first switching element and supplying a first data signal to the pixel electrode via the first switching element when the first switching element is on; ,
Drive control means for controlling a scanning signal supplied to the scanning signal line and a first data signal supplied to the first data signal line;
The drive control means includes
In one frame period, an image display period in which a voltage for image display is applied between the pixel electrode and the counter electrode, and a reset period in which the potential of the pixel electrode is substantially equal to the potential of the counter electrode The display panel according to claim 1, wherein the display panel is provided. The drive control means includes
In the above image display period,
The first switching element connected to the scanning signal line is turned on, and in this state, the first data signal for image display is supplied from the first data signal line to the pixel electrode. And a selection period in which a voltage for image display is applied between the counter electrode and the counter electrode,
A first switching element connected to the scanning signal line is turned off, and a non-selection period for holding a voltage between the pixel electrode and the counter electrode at a voltage applied in the selection period is provided.
In the reset period, the first switching element connected to the scanning signal line is turned on, and in this state, the first data signal having substantially the same potential as the counter electrode is transferred from the first data signal line to the pixel electrode. The display panel according to claim 2, wherein the display panel is supplied. The pixel electrode, the counter electrode, and the first electrode provided for each of the plurality of scanning signal lines, the plurality of first data signal lines, and the combination of the scanning signal line and the first data signal line. And a switching element.
The drive control means for each scanning signal line,
In the selection period, the first switching element of each pixel connected to the scanning signal line is turned on, and the pixel is displayed on the pixel electrode of the pixel from the first data signal line in that state. Supplying a first data signal corresponding to the image;
In the non-selection period, the first switching element of each pixel connected to the scanning signal line is turned off,
In the reset period, the first switching element of each pixel connected to the scanning signal line is turned on, and in this state, the pixel electrode of each pixel is substantially the same as the counter electrode from the first data signal line. 4. The display panel according to claim 3, wherein a first data signal having a potential is supplied. A third switching element which is provided so as to connect the pixel electrode and the counter electrode and is driven and controlled by a signal different from the first switching element;
The drive control means includes
In the above image display period,
The first switching element connected to the scanning signal line is turned on, and in this state, the first data signal for image display is supplied from the first data signal line to the pixel electrode. And a selection period in which a voltage for image display is applied between the counter electrode and the counter electrode,
A first switching element connected to the scanning signal line is turned off, and a non-selection period for holding a voltage between the pixel electrode and the counter electrode at a voltage applied in the selection period is provided.
In the reset period, the potential of the pixel electrode and the potential of the counter electrode are made substantially equal by turning on the third switching element and conducting the pixel electrode and the counter electrode. The display panel according to claim 2. The drive control means includes
6. The display panel according to claim 5, wherein a rectangular wave that is inverted with respect to the potential of the counter electrode is supplied to the pixel electrode as the first data signal during the selection period. The pixel electrode, the counter electrode, and the first electrode provided for each of the plurality of scanning signal lines, the plurality of first data signal lines, and the combination of the scanning signal line and the first data signal line. A switching element and a third switching element.
The drive control circuit is
7. The drive control of the third switching element in each pixel is performed by a scanning signal for driving and controlling the first switching element in a pixel adjacent to each pixel. Display panel. The drive control means includes
8. The display panel according to claim 7, wherein the active signal supply to the odd-numbered scanning signal lines and the scanning of the active signal to the even-numbered scanning signal lines are alternately repeated for each frame. A second data signal line for supplying a second data signal to the counter electrode, which is provided substantially in parallel and alternately with the first data signal line;
A second switching element that connects the counter electrode and the second data signal line and is driven and controlled by a common scanning signal with the first switching element;
The drive control means includes
In the above image display period,
The first switching element and the second switching element of each pixel connected to the scanning signal line are turned on, and in this state, the pixel electrode of each pixel from the first data signal line and the second data signal line And supplying the first data signal and the second data signal corresponding to the image to be displayed on each pixel to the counter electrode, respectively, for displaying an image between the pixel electrode and the counter electrode in each pixel. A selection period for applying the voltage;
By turning off the first switching element and the second switching element of each pixel connected to the scanning signal line, the voltage applied between the pixel electrode and the counter electrode in each pixel during the selection period is changed. The display panel according to claim 7, further comprising a non-selection period to be held. The drive control means includes
The potentials of the first data signal and the second data signal in the selection period are reversed with reference to the potentials of the two electrodes when the potential difference between the pixel electrode and the counter electrode becomes substantially equal in the reset period. The display panel according to claim 9, wherein the display panel is set as follows. An auxiliary capacitance line;
A first auxiliary capacitance formed between the pixel electrode and the auxiliary capacitance line;
The display panel according to claim 10, further comprising a second auxiliary capacitor formed between the counter electrode and the auxiliary capacitor line. The pixel electrode and the counter electrode are provided on the same substrate,
12. The auxiliary capacitance line is formed on a substrate provided with the pixel electrode and the counter electrode with an insulating layer interposed between the pixel electrode and the counter electrode. The display panel described in 1.   The display panel according to claim 11 or 12, wherein a capacitance value of the first auxiliary capacitor and a capacitance value of the second auxiliary capacitor are substantially equal. A capacitance value of a parasitic capacitance formed between the pixel electrode and a scanning signal line connected to the first switching element and the second switching element;
14. A capacitance value of a parasitic capacitance formed between the counter electrode and a scanning signal line connected to the first switching element and the second switching element is substantially equal. The display panel according to any one of the above. A capacitance value of a first parasitic capacitance formed between the pixel electrode and the first data signal line;
A capacitance value of a second parasitic capacitance formed between the counter electrode and the first data signal line;
A capacitance value of a third parasitic capacitance formed between the pixel electrode and the second data signal line;
15. The capacitance value of the fourth parasitic capacitance formed between the second counter electrode and the second data signal line is substantially equal to any one of claims 10 to 14. Display panel. Each capacitance value of the first to fourth parasitic capacitances is
From the capacitance value of the fifth parasitic capacitance formed between the pixel electrode and the scanning signal line, and the capacitance value of the sixth parasitic capacitance formed between the counter electrode and the scanning signal line The display panel according to claim 15, wherein the display panel is also large.   2. The display panel according to claim 1, further comprising discharge means for discharging charges accumulated between the upper pixel electrode and the counter electrode by the image display voltage.   18. The display panel according to claim 17, wherein the discharge means is a resistance element provided so as to connect the pixel electrode and the scanning signal line. The pixel electrode, the counter electrode, and the first electrode provided for each of the plurality of scanning signal lines, the plurality of first data signal lines, and the combination of the scanning signal line and the first data signal line. And a pixel including the switching element is provided on one of the opposing substrates,
The discharge means connects the pixel electrode of each pixel to the other scanning signal line arranged adjacent to the scanning signal line that controls the first switching element of each pixel. The display panel according to claim 17, wherein the display panel is a resistive element. A capacitive signal line connected to the pixel electrode via a capacitive element;
18. The display panel according to claim 17, wherein the discharge means is a resistance element provided so as to connect the pixel electrode and the capacitive signal line.   The resistance value of the resistance element is the charge accumulated between the pixel electrode and the counter electrode, and the first data signal is supplied to the pixel electrode after the first data signal is supplied to the pixel electrode. The display panel according to any one of claims 18 to 20, wherein the value is set to a value to be discharged in a period up to.   The display panel according to any one of claims 17 to 21, wherein the pixel electrode, the first switching element, and the discharge means are provided on one of the pair of opposed substrates. .   The display panel according to any one of claims 1 to 22, wherein the material layer is provided with an alignment auxiliary material that promotes a change in the degree of optical anisotropy when an electric field is applied. .   The display panel according to claim 23, wherein the material layer contains a polymerizable compound.   The pixel electrode and the counter electrode are disposed on at least one of the pair of substrates so as to generate an electric field in a direction parallel to the substrate surface. Display panel.   The display panel according to claim 25, wherein the pixel electrode and the counter electrode are transparent. The pixel electrode and the counter electrode are provided on one of the pair of substrates,
27. The display panel according to claim 25, wherein a color filter is formed on the substrate on which the pixel electrode and the counter electrode are formed. The pixel electrode and the counter electrode are provided on one of the pair of substrates,
27. The display panel according to claim 25, wherein the other substrate on which the pixel electrode and the counter electrode are formed is transparent.   The said pixel electrode and a counter electrode are arrange | positioned so that an electric field may be generate | occur | produced in the normal direction of the substrate surface of a pair of said opposing board | substrate, The Claim 1 characterized by the above-mentioned. Display panel. A plurality of the scanning signal lines, a plurality of the first data signal lines, and the pixel electrodes provided for each combination of the scanning signal lines and the first data signal lines; A pixel including a first switching element driven and controlled by a scanning signal supplied to the scanning signal line is formed on an active matrix substrate which is one of the pair of substrates;
30. The display panel according to claim 29, wherein the counter electrode is formed on a counter substrate which is the other substrate of the pair of substrates so as to oppose each of the pixel electrodes.   The display panel according to claim 30, wherein a color filter is formed on the active matrix substrate.   32. The display panel according to claim 30, wherein the counter substrate and the counter electrode are transparent.   The display panel according to claim 1, wherein an auxiliary capacitor is connected in parallel with a display unit capacitor formed by the pixel electrode, the counter electrode, and the material layer.   The display panel according to claim 1, wherein the medium exhibits a cholesteric blue phase.   The display panel according to claim 1, wherein a chiral agent is added to the medium.   A display device comprising the display panel according to claim 1. A pair of substrates, at least one of which is transparent, a material layer sandwiched between the substrates, a pixel electrode and a counter electrode for applying an electric field to the material layer, and applying an electric field to the material layer A display device for displaying on
The material layer is optically isotropic when no electric field is applied, and is composed of a medium in which the degree of optical anisotropy is changed by changing the orientation direction of molecules by applying an electric field,
After applying an image display voltage between the pixel electrode and the counter electrode, before applying a next image display voltage between the pixel electrode and the counter electrode, the potential of the pixel electrode A display device comprising drive control means for controlling the potential of the pixel electrode and / or the counter electrode so that the potential of the counter electrode is substantially equal. A first switching element connected to the pixel electrode;
A scanning signal line connected to the first switching element and supplying a scanning signal for driving and controlling the first switching element;
A first data signal line connected to the first switching element and supplying a first data signal to the pixel electrode via the first switching element when the first switching element is on; With
The drive control means includes
In one frame period, an image display period in which a voltage for image display is applied between the pixel electrode and the counter electrode, and a reset period in which the potential of the pixel electrode is substantially equal to the potential of the counter electrode The display device according to claim 37, wherein the display device is provided. The drive control means includes
In the above image display period,
The first switching element connected to the scanning signal line is turned on, and in this state, the first data signal for image display is supplied from the first data signal line to the pixel electrode. And a selection period in which a voltage for image display is applied between the counter electrode and the counter electrode,
A first switching element connected to the scanning signal line is turned off, and a non-selection period for holding a voltage between the pixel electrode and the counter electrode at a voltage applied in the selection period is provided.
In the reset period, the first switching element connected to the scanning signal line is turned on, and in this state, the first data signal having substantially the same potential as the counter electrode is transferred from the first data signal line to the pixel electrode. The display device according to claim 38, wherein the display device is supplied. The pixel electrode, the counter electrode, and the first electrode provided for each of the plurality of scanning signal lines, the plurality of first data signal lines, and the combination of the scanning signal line and the first data signal line. And a switching element.
The drive control means for each scanning signal line,
In the selection period, the first switching element of each pixel connected to the scanning signal line is turned on, and the pixel is displayed on the pixel electrode of the pixel from the first data signal line in that state. Supplying a first data signal corresponding to the image;
In the non-selection period, the first switching element of each pixel connected to the scanning signal line is turned off,
In the reset period, the first switching element of each pixel connected to the scanning signal line is turned on, and in this state, the pixel electrode of each pixel is substantially the same as the counter electrode from the first data signal line. 40. The display device according to claim 39, wherein a first data signal having a potential is supplied. A third switching element which is provided so as to connect the pixel electrode and the counter electrode and is driven and controlled by a signal different from the first switching element;
The drive control means includes
In the above image display period,
The first switching element connected to the scanning signal line is turned on, and in this state, the first data signal for image display is supplied from the first data signal line to the pixel electrode. And a selection period in which a voltage for image display is applied between the counter electrode and the counter electrode,
A first switching element connected to the scanning signal line is turned off, and a non-selection period for holding a voltage between the pixel electrode and the counter electrode at a voltage applied in the selection period is provided.
In the reset period, the potential of the pixel electrode and the potential of the counter electrode are made substantially equal by turning on the third switching element and conducting the pixel electrode and the counter electrode. The display device according to claim 38. The drive control means includes
42. The display device according to claim 41, wherein a rectangular wave that is inverted with reference to the potential of the counter electrode is supplied to the pixel electrode as the first data signal during the selection period. The pixel electrode, the counter electrode, and the first electrode provided for each of the plurality of scanning signal lines, the plurality of first data signal lines, and the combination of the scanning signal line and the first data signal line. A switching element and a third switching element.
The drive control circuit is
43. The drive control of the third switching element in each pixel is performed by a scanning signal for driving and controlling the first switching element in a pixel adjacent to each pixel. Display device. The drive control means includes
44. The display device according to claim 43, wherein the supply of the active signal to the odd-numbered scanning signal lines and the scanning of the active signal to the even-numbered scanning signal lines are alternately repeated for each frame. A second data signal line for supplying a second data signal to the counter electrode, which is provided substantially in parallel and alternately with the first data signal line;
A second switching element that connects the counter electrode and the second data signal line and is driven and controlled by a common scanning signal with the first switching element;
The drive control means includes
In the above image display period,
The first switching element and the second switching element of each pixel connected to the scanning signal line are turned on, and in this state, the pixel electrode of each pixel from the first data signal line and the second data signal line And supplying the first data signal and the second data signal corresponding to the image to be displayed on each pixel to the counter electrode, respectively, for displaying an image between the pixel electrode and the counter electrode in each pixel. A selection period for applying the voltage;
By turning off the first switching element and the second switching element of each pixel connected to the scanning signal line, the voltage applied between the pixel electrode and the counter electrode in each pixel during the selection period is changed. 43. The display device according to claim 41, wherein a non-selection period to be held is provided. The drive control means includes
The potentials of the first data signal and the second data signal in the selection period are reversed with reference to the potentials of the two electrodes when the potential difference between the pixel electrode and the counter electrode becomes substantially equal in the reset period. 44. The display device according to claim 43, wherein the display device is set as follows.

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