JP2009156962A - Liquid crystal optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that in a conventional PDLC, the whole surface thereof becomes transparent at the same time when a voltage is applied, because a fixed potential is applied to an ITC, while the whole surface becomes scattered at the same time when the voltage application is stopped, and that it is difficult to display a variety of display images due to simple operation. <P>SOLUTION: In this liquid crystal optical device, the resistance of ITOs 2a and 3a on glass substrates 2 and 3 are increased, a voltage is applied to one end, while the other end is grounded to change a potential along a current flowing direction in each of ITOs. A high potential area quickly becomes transparent, and a low potential area gradually becomes transparent or partially becomes transparent. The control flexibility is increased, to apply the PDLC 1 in a wide range with expanded functions. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal system called PDLC (Polymer Dispersed Liquid Crystal) or polymer dispersed liquid crystal, and more particularly to a method for driving the PDLC.

  Conventional PDLC does not require rubbing treatment and injects a monomer (not having liquid crystallinity) and a photoreaction initiator added into the liquid crystal. When the ultraviolet rays are uniformly irradiated, the monomer is polymerized and phase-separated into a liquid crystal portion and a polymer portion (micro phase separation). Since the liquid crystal part and the polymer part have different refractive indexes, the transmitted light is confused when no voltage is applied (uniform turbulence). When a voltage is applied, the liquid crystal rises in the direction of the electric field, and the refractive index ratio between the polymer and the liquid crystal. Becomes smaller and becomes transparent.

Therefore, in the conventional liquid crystal display device, since members such as a polarizing plate and an alignment plate are required, there is a problem that the amount of incident light is reduced due to these members. Since no alignment plate is used, it is said that a brighter screen can be realized with less power (including backlight).
JP 2005-060703 A

  However, in the conventional PDLC described above, the entire surface of the display surface is made transparent or scattered. A transparent electrode (ITO) is formed on the entire surface of at least two portions of the two substrates facing each other. When the voltage is applied to the electrode in advance, the entire surface of the display surface becomes transparent, and if the application is stopped, the entire surface of the display surface is in a scattering state, so there is no difficulty.

  In addition, if a transparent electrode is formed on two substrates in a state where only a part of the display surface is divided, for example, left and right, for example, if a voltage is applied to the transparent electrode of only the left half, the left half Since only the portion becomes transparent and the right half portion is in a scattering state, the control of the power source applied to the electrode is only complicated, and no difficulty is generated.

  Here, for example, when a display surface in which the periphery of the display portion is in a scattered state and the central portion is transparent is required, a transparent electrode (ITO) cannot be provided on the outer edge of the substrate, and only the central portion is provided. Since a transparent electrode must be provided on the viewing surface and power must be supplied to the transparent electrode on the viewing surface side, problems such as the power supply terminal being visible from the viewing surface side must be solved. There is a problem that becomes impossible.

  Furthermore, at present, means such as controlling the scattering property at a desired location, such as shifting between the scattered state portion and the transparent state portion with gradation, are extremely difficult. Thus, the problem arises that the expressiveness of PDLC must be restricted.

  In the present invention, as a specific means for solving the above-described conventional problems, a transparent electrode is provided on the inner side of the substrate, and high-resistance ITO is adopted as the transparent electrode, and the high resistance of the ITO A liquid crystal optical element capable of applying a partially different voltage value to the inside of the element by using a voltage gradient due to the dielectric constant anisotropy and refractive index anisotropy inside the element. A liquid crystal material having a property, a monomer, and a photopolymerization initiator for polymerizing the monomer are sealed and produced by irradiating the device with ultraviolet rays to polymerize the monomer. The problem is solved by providing a liquid crystal optical element that is characterized.

  According to the present invention, a transparent electrode (ITO) having a relatively high resistance (500 Ω □ or more) is laid on at least one of the substrates, and power sources of different voltages are connected to both ends of the transparent electrode. The applied voltage is inclined according to the position, and the place where it is transparent on the display surface and the place where it is scattered can be freely set, giving freedom to display, and expanding the expression capability of this kind of PDLC It has an excellent effect.

  1 shows a PDLC according to the present invention. A pair of glass substrates 2 and 3 on which transparent electrodes such as ITO are formed (ITO thickness: 500 mm, glass plate thickness: 0.7 mm, glass Material: Blue plate glass). Then, ITO 2a is patterned into a desired pattern on a glass substrate (back substrate) 2 on one side, for example, a landscape seen from a window.

  The pattern of ITO 3a on the counter substrate (front substrate) 3 may be solid (see FIG. 1B) or may be appropriately patterned separately. An alignment film (not shown) was formed on the surfaces of the ITO 2a and the ITO 3a, and an alignment process such as rubbing was performed so that the alignment direction between the upper and lower substrates 2 and 3 was antiparallel.

  In PDLC, alignment processing such as alignment film formation or rubbing may or may not be performed. Moreover, TN orientation may be sufficient. Patterned ITO 2a and 3a were used for the transparent electrode of the light control portion (pixel portion in the case of display). The resistance of the ITOs 2a and 3a is not limited to the above (500Ω □ or more).

  Further, a low resistance ITO 3a may be used for a substrate on one side, for example, the substrate 3. Further, ITO having partially different resistance values may be used. In particular, if the resistance of the part of the display figure that corresponds to the part to be noticed is lowered, it is possible to express a display in which the part to be noticed first scatters first and then gradually spreads to the end part. It is. However, in order to obtain the above operations and effects, patterning and ITO film formation must be performed twice or more, and they are not used here.

  Next, a main sealant containing 2.5 wt% of a gap control agent was formed on one glass substrate 3 (lower substrate). (Formation method: screen printing or dispenser) The material of the gap control agent is selected so that the liquid crystal layer is 5 to 150 μm. In this first embodiment, the liquid crystal layer is 15 μm. A 15 μm glass fiber was chosen.

  3% by weight of this glass fiber was added to Mitsui Chemicals sealant ES-7500 to obtain a main sealant. A gap control agent was sprayed on the other glass substrate 2 (upper substrate). Here, 15 μm plastic balls were spread using a dry gap spreader.

  These glass substrates were overlaid, and heat treatment was performed with a pressure applied at a constant pressure by a press machine or the like to cure the main sealant. Here, heat treatment was performed at 150 ° C. for 3 hours. Thus, an empty cell having a cell thickness of 15 microns was produced.

  A mixture of a liquid crystal, a chiral agent, a liquid crystalline monomer (UCL • 001) (manufactured by Dainippon Ink & Chemicals), and a photopolymerization initiator was vacuum-injected into the cell. As the host liquid crystal, a liquid crystal having a positive Δε (Δn: 0.298, Tni = 128 ° C .: manufactured by Omemoto Ink Chemical Co., Ltd.) was used. The chiral agent S-811 was added to 0.376 wt% (pitch 28 microns) with respect to the host liquid crystal. The chiral agent is not limited to S-811.

  Moreover, the same effect is acquired not only in this value but in the range of about 0.02 wt% to about 5 wt%. However, the smaller the amount added, the lower the scattering property at the time of voltage application. On the other hand, if the amount added is too large, there may be problems such as hysteresis in the VT characteristics and poor transparency when no voltage is applied.

The relationship between the amount of chiral agent added, the tendency of scattering and the chiral pitch cannot be generally stated depending on the liquid crystal material or chiral material. Is desirable. To this chiral liquid crystal, 0.5 to 40 wt% of an acrylate monomer was added.

  Although depending on the material used, if the monomer addition amount is 2 wt% or less, there is a tendency that a polymer network is not sufficiently formed, and if it is 15 wt% or more, the responsiveness of the liquid crystal due to voltage tends to be deteriorated. Degree is desirable. In the examples, 5 wt% was added for the experiment.

  Furthermore, the initiator in which 0.1 to 0.5 wt% of a photopolymerization reaction initiator is added to the monomer is not particularly limited as long as it is a material sensitive to ultraviolet rays (around 365 nm). In this first example, Irgacure made by Ciba Chemicals was used. After the injection, an end sealant was applied to the injection port and sealed.

At this time, if a photocurable end seal is used, a light shielding mask may be used so that the cell is not directly irradiated with ultraviolet rays. Further, a thermosetting end seal agent or a two-component mixed end seal agent may be used.

The injected liquid crystal cell was irradiated with strong ultraviolet light through a photomask. For light irradiation, a photo-alignment device manufactured by Megilo Predation was used. The light source used here is a high-pressure mercury lamp, but a xenon lamp, a metal halide lamp, a low-pressure mercury lamp, or the like may be used. The irradiation intensity is 80 mW / cm ² (350 nm), and irradiation is performed for 30 seconds (irradiation The amount is 2.5 W / cm ² ).

  The photomask uses a 20 μm / 20 μm line / space pattern (stripe pattern). The mask pattern is not limited to a stripe pattern, and may be a lattice pattern, a concentric pattern, a random pattern, or the like. The transmittance may be changed depending on the location. Further, although the case where the pattern size is 20 μm (40 μm pitch) has been described, it is not limited thereto.

  However, liquid crystal cells having a cell thickness of 15 μm have been found to be difficult to obtain high scattering properties with a pattern size of 50 μm or more, and preferably 40 μm or less. Although the case where the irradiation time of ultraviolet rays is 30 seconds was demonstrated, it is not restricted to it. However, it has been confirmed that if the irradiation time is short, it is difficult to obtain a high scattering property, and even if the irradiation time is increased to 30 seconds or more, the scattering property does not change.

  The power supply to be used needs to be capable of applying a higher voltage than a normal LCD drive power supply. Although a power supply capable of applying a maximum of 50 V is used here, the required power supply capacity varies depending on the ITO resistance, pattern, and cell size. The state of transmittance change can also be changed depending on the terminal (position where the electrodes are connected). For example, when the terminal is attached to the lower side as in the case of a solid electrode, the scattering state gradually decreases diagonally from the lower left side due to voltage application. It can express changes in transmittance that spread.

  On the contrary, when it is attached to the upper side, it changes from the upper left side, but due to the counter electrode, the transmittance changes so that the scattering state gradually spreads in the lateral direction.

  FIG. 2 shows a second embodiment of the present invention, a pair of glass substrate back substrate 4 on which a transparent electrode such as ITO is formed, front substrate 5 (ITO thickness: 500 mm, glass plate thickness: 0.7 mm, Glass material: Blue plate glass) is prepared. The ITO patterns 4a and 5a on both substrates were solid (however, partial patterning was performed so that both ITO patterns 4a and 5a did not exist in the seal portion).

  An alignment film was formed on the ITO surface, and alignment treatment such as rubbing was performed so that the alignment directions of the upper and lower substrates were antiparallel. An alignment process such as alignment film formation or rubbing may or may not be performed. Moreover, TN orientation may be sufficient. Solid ITO was used for the transparent electrode of the light control portion (pixel portion in the case of a display). The resistance of ITO is not limited to the value of the first embodiment. Moreover, you may use low resistance ITO for the board | substrate of one side. Alternatively, ITO having partially different resistance values may be used.

  Next, a main sealant containing 2.5 wt% of a gap control agent was formed on one glass substrate (for example, the back substrate 4) (formation method: green printing or dispenser). The diameter of the gap control agent was The material is selected so that the liquid crystal layer is 5 to 150 microns. In this example, since the liquid crystal layer has a thickness of 15 μm, a glass fiber having a gap control agent diameter of 15 μm microns was selected. 3% by weight of this glass fiber was added to Mitsui Chemicals sealant ES-7500 to obtain a main sealant.

  A gap control agent was sprayed on the other glass substrate (front substrate 5). Here, 15 micron plastic balls were spread using a dry gap spreader. These glass substrates were superposed and heat-treated with a pressure applied at a constant pressure using a press or the like to cure the main sealant. Here, heat treatment was performed at 150 ° C. for 3 hours. Thus, an empty cell having a cell thickness of 15 microns was produced.

  A mixture of a liquid crystal, a chiral agent, a liquid crystalline monomer (UCL-001: manufactured by Dainippon Ink & Chemicals), and a photopolymerization initiator was vacuum-injected into the cell. A liquid crystal having a positive Δε (Δn = 0.298, Tni = 128 ° C .: manufactured by Dainippon Ink & Chemicals) was used as the host liquid crystal. The chiral agent S-811 was added to 0.376 wt% (pitch 28 microns) with respect to the host liquid crystal.

  The chiral agent is not limited to S-811. The addition amount is not limited to this value, and the same effect can be obtained in the range of about 0.02 wt% to about 5 wt%. However, the smaller the amount added, the lower the scattering property when a voltage is applied. On the other hand, if the amount added is too large, there may be problems such as hysteresis in the VT characteristics and poor transparency when no voltage is applied.

  The relationship between the amount of chiral agent added, the tendency of scattering and the chiral pitch cannot be generally stated depending on the liquid crystal material or chiral material, but the amount of added chiral agent is about 0.1 wt% to 3 wt% for the liquid crystal material used this time. Is desirable. To this chiral liquid crystal, 0.5 to 40 wt% of an acrylate monomer was added.

  Although depending on the materials used, there is a tendency that a polymer network is not sufficiently formed when the monomer addition weight is 2 wt% or less, and when it is 15 wt% or more, there is a tendency that the response of the liquid crystal is deteriorated due to voltage. % Is desirable. In the examples, 5 wt% was added for the experiment.

  Further, 0.1 to 0.5 wt% of a photopolymerization initiator was added to the monomer. The initiator is not particularly limited as long as it is a material having sensitivity to ultraviolet rays (around 365 nm). In the examples, Irgacure made by Ciba Chemicals was used. After the injection, an end sealant was applied to the inlet and sealed. At this time, if a photocurable end seal is used, a light shielding mask is preferably used so that the cell 1 is not directly irradiated with ultraviolet rays. Further, a thermosetting end seal agent or a two-component mixed end seal agent may be used.

The injected liquid crystal cell was irradiated with strong ultraviolet light through a photomask. For light irradiation, a photo-alignment device made by Megilo Precision was used. The light source used here is a high pressure mercury lamp, but a xenon lamp, a methanol halide lamp, a low pressure mercury lamp, or the like may be used. The irradiation intensity was 80 mW / cm ² (350 nm), and irradiation was performed for 30 seconds (the irradiation amount was 2.5 W / cm ² ).

  A 20 μm / 20 μm line / space pattern (stripe pattern) was used as the photomask. The mask pattern is not limited to a stripe pattern, and may be a lattice pattern, a concentric pattern, a random pattern, or the like. Moreover, although the case where the pattern size is 20 microns (40 micron pitch) has been described, it is not limited thereto.

  However, for liquid crystal cells having a cell thickness of 15 microns, it has been found that high scattering properties are difficult to obtain with a pattern size of 50 microns or more, and 40 microns or less is desirable. Although the case where the irradiation time of ultraviolet rays is 30 seconds was demonstrated, it is not restricted to it. However, it has been confirmed that if the irradiation time is short, it is difficult to obtain high scattering properties, and even if the irradiation time is increased to 30 seconds or more, the scattering properties are not changed.

  In the configuration of FIG. 2, two terminals (total of four terminals) can be taken from both substrates 4 and 5. Various scattering states can be expressed by arranging different AC power sources for each. The power supply to be used needs to be capable of applying a higher voltage than a normal LCD drive power supply. Although a power supply capable of applying a maximum of 50 V is used here, the required power supply capacity differs depending on the ITO resistance and cell size.

  The transmittance state when different voltages are applied to the respective terminals in FIG. 2 is shown in FIGS. Here, the threshold is about 10 V and the driving frequency is 300 Hz. When 30V and 0V are applied to the respective terminals, transparent portions are formed diagonally as shown in FIG.

  When different voltages are applied to the four terminals, a complicated pattern is shown as shown in FIG. In this way, various scattering patterns can be drawn depending on how the voltage is applied to each terminal. Note that the effective voltage varies depending on the applied frequency, and a more complicated pattern may be produced.

  As described above, according to the present invention, in addition to the driving method for simply turning on and off the conventional PDLC, the speed of transition from the transparent side to the diffusing side can be changed depending on the location, or On the contrary, the speed at which the transition from the diffusing side to the transparent side can be freely changed depending on the location, and the expressibility of this kind of PDLC is increased.

  In addition, it is possible to change the degree of diffusion depending on the location and to perform a novel display that has not been possible in the past, which is effective in expanding the application of this type of PDLC.

It is explanatory drawing which shows 1st Example of PDLC which is a liquid crystal optical device which concerns on this invention. It is explanatory drawing which similarly shows the 2nd Example of PDLC which concerns on this invention. It is explanatory drawing which shows an example of the display in a 2nd Example. It is explanatory drawing which shows another example of a display in a 2nd Example.

Explanation of symbols

1 ... PDLC
2 ... Back substrate 2a ... Patterning ITO
3 ... front substrate 3a ... solid ITO
4 ... Back substrate 4a ... Solid ITO
5 ... Front substrate 5a ... Solid ITO

Claims (4)

  A transparent electrode is provided on the inner side of the substrate, and high-resistance ITO is adopted for the transparent electrode, and a voltage value that is partially different inside the element using a voltage gradient due to the high resistance of the ITO. A liquid crystal optical element capable of providing a liquid crystal material and a monomer having dielectric anisotropy and refractive index anisotropy inside the element, and photopolymerization start for polymerizing the monomer A liquid crystal optical element, wherein the liquid crystal optical element is sealed by containing an agent, and is produced by irradiating the element with ultraviolet rays to polymerize the monomer.   2. The liquid crystal optical device according to claim 1, wherein at least one of the transparent electrodes is provided with a power supply for applying different voltages at least between both ends of the transparent electrode.   3. The liquid crystal optical element according to claim 1, wherein the liquid crystal material is sealed in a state where a chiral agent having a property of twisting liquid crystal molecules is contained.   The liquid crystal optical device according to claim 1, wherein the monomer is a liquid crystal monomer.

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