JP2006066513A - Light emitting device and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device that can emit light rays of a plurality of colors with a simple optical system. <P>SOLUTION: In the light emitting device 2, a light shielding film 20 has recesses corresponding to each picture element. A plurality of light emitting elements 32, 34, 36, for example, the light emitting elements of three primary colors R, G, and B, are buried in each recess. For the light emitting elements 32, 34, and 36, LEDs or organic EL elements can be used. A cathode 38 supplies electric power to each light emitting element 32, 34, and 36. Transparent insulating films 40 seal the plurality of light emitting elements 32, 34, and 36 and electrodes in the recesses. The light shielding film 20 is formed of a conductive material and used as the ground-side common electrode. The plurality of light emitting elements 32, 34, and 36 are arranged along the light projecting direction in each recess. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light emitting device that can be used as a light source such as a liquid crystal projector, and a display device using the light emitting device.

  In recent years, liquid crystal projectors have become widespread. Liquid crystal projectors can be made smaller and lighter than CRT (Cathode Ray Tube) projectors, and portable types have also been put into practical use. FIG. 1 of Patent Document 1 discloses a liquid crystal projector including an optical system and a liquid crystal panel for each of red, green, and blue (hereinafter referred to as R, G, and B).

FIG. 55 of Patent Document 1 discloses a display device in which three semiconductor lasers are sequentially turned on in a time division manner, and a liquid crystal panel modulates light generated in synchronization with the time division lighting.
International Publication No. 99/49358

  However, the display device disclosed in FIG. 55 of Patent Document 1 requires an array lens for converting into parallel rays and a deformed curved lens for uniformizing the luminance distribution, which increases the number of components and makes it complicated. An optical system is required. In addition, since three semiconductor lasers serving as light sources are arranged in parallel with the display surface for each pixel, it is difficult to increase the resolution.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a light emitting device capable of irradiating light of a plurality of colors with a simple optical system and a display device using the light emitting device.

  A light-emitting device according to an aspect of the present invention includes a light-shielding film having a recess corresponding to each pixel, a plurality of light-emitting elements embedded in each recess, and a transparent insulating film that seals the plurality of light-emitting elements in the recess. Prepare. An LED or an organic EL element may be used as the “light emitting element”. The “plurality of light-emitting elements” may be R, G, and B light-emitting elements, and may be circulated at high speed, for example, at a speed that exceeds human visual time resolution.

  According to this aspect, light of a plurality of colors can be emitted for each pixel. In addition, since each pixel is partitioned by a light shielding film, it is possible to suppress mixing of light between pixels without using a complicated optical system.

  Another embodiment of the present invention is also a light emitting device. This device seals a light shielding film having a recess corresponding to each pixel, a plurality of light emitting elements embedded in each recess, an electrode for supplying power to each light emitting element, and a plurality of light emitting elements and electrodes in the recess. A light-shielding film made of a conductive material to form a common electrode on the ground side. The “electrode” may be made of transparent indium tin oxide (ITO).

  According to this aspect, light of a plurality of colors can be emitted for each pixel. Further, since the light shielding film is grounded, wiring can be simplified.

  The plurality of light emitting elements may be installed along the light irradiation direction in the recess. According to this, the area of each pixel can be reduced, and a high-resolution image can be handled.

  Another embodiment of the present invention is a display device. This device includes the light-emitting device of the above-described aspect and a liquid crystal panel that controls the transmittance of light from the light-emitting device for each pixel. Ferroelectric liquid crystal or semi-ferroelectric liquid crystal may be used as the “liquid crystal”. “Transmittance” includes 0%, that is, the light shielding state.

  According to this aspect, the light emitting elements of different colors can be circulated and lit, so that an image can be obtained by transmitting monochromatic light with a different transmittance for each pixel at a certain high speed, for example, at a speed exceeding the human visual time resolution. An image with high color purity can be obtained.

  According to the present invention, it is possible to obtain an apparatus that can emit light of a plurality of colors with a simple optical system.

  FIG. 1 is a side sectional view of a display device 1 according to the present invention. The display device 1 includes a light emitting device 2 and a liquid crystal panel 10. The light emitting device 2 is mainly generated from the light shielding film 20, the first light emitting element 32, the second light emitting element 34, the third light emitting element 36, and the insulating film 40. The light shielding film 20 is formed of tungsten W, silicon tungsten WSi, copper Cu, aluminum Al, titanium Ti, or the like, and serves as a common electrode on the ground side of the first light emitting element 32, the second light emitting element 34, and the third light emitting element 36. Used. The light shielding film 20 can be formed by a sputtering method. Moreover, when using tungsten W etc., you may form into a film by CVD (Chemical Vapor Deposition) method.

  The light shielding film 20 is provided with a recess for each pixel. The first light emitting element 32, the second light emitting element 34, and the third light emitting element 36 are embedded in each recess. The first light emitting element 32, the second light emitting element 34, and the third light emitting element 36 correspond to the three primary colors of R, G, and B. For these light emitting elements 32, 24 and 36, LEDs (Light Emitting Diodes) can be used. By using the LED, low power consumption can be achieved. Furthermore, heat generation can be suppressed, leading to a reduction in the cooling mechanism such as a fan, and miniaturization and noise reduction can be achieved. The lifetime is also semi-permanent.

  The three primary color light emitting elements 32, 34, and 36 can be arranged in arbitrary positions in the recess. Even among the light emitting elements that do not conform to the specification, the luminance can be adjusted by adjusting the distance of each light emitting element with respect to the display surface. In FIG. 1, the light emitting elements 32, 34, and 36 of the three primary colors in the recess are arranged side by side in a direction perpendicular to the display surface. One pixel can be made smaller and the resolution can be increased as it is linearly arranged in the direction perpendicular to the display surface.

The three primary color light emitting elements 32, 34, and 36 embedded in the respective recesses are provided with electrodes (not shown). In the case where an electrode is provided at a position where light emitted from the light emitting elements 34 and 36 behind the display surface is blocked, a transparent electrode may be used. After electrodes are provided on the light emitting elements 32, 34, and 36 of the three primary colors, an insulating film 40 is formed in each recess in order to fill the recess. The insulating film 40 may be a transparent silicon oxide SiO ₂ film. The silicon oxide SiO ₂ film can be formed by a plasma CVD method or the like.

  The liquid crystal panel 10 transmits the light from the light emitting device 2 with a predetermined transmittance and displays an image. The liquid crystal panel 10 may use a general TN (Twisted Nematic) liquid crystal, but may use a ferroelectric liquid crystal. The response time of a general ferroelectric liquid crystal is 10 to several hundreds [us], and some of them have been developed with several hundreds [ns]. Although the detailed operation of the display device 1 will be described later, since the display device 1 switches between R, G, and B monochromatic display at high speed and synthesizes three colors in the human brain, A more accurate image can be generated by using liquid crystal. However, if the response time is about 5 [ms], it exceeds the human visual time resolution, so that it appears as an image in which three colors are combined.

  In the liquid crystal panel 10, data lines and scanning lines are arranged in a matrix, and a region surrounded by the lines corresponds to a pixel. This pixel corresponds to the pixel of the light emitting device 2. In the liquid crystal panel 10, the data lines and the scanning lines are controlled by passive matrix driving or active matrix driving, and the molecular orientation of the liquid crystal is controlled for each pixel. With this molecular orientation, the light from the light emitting device 2 is transmitted with changing the transmittance for each pixel to generate an image. In the case of active matrix driving, a thin film transistor (TFT) may be used as a switching element of each pixel.

  FIG. 2 is a front sectional view of the light emitting device 2 according to the present invention. When viewed from the front, it is well understood that the light-shielding film 20 has a lattice-shaped recess corresponding to one pixel. As described above, the light emitting elements 32, 34, and 36 of the three primary colors can be arbitrarily arranged in the recess. The upper left pixel in FIG. 2 is an example in which the first light emitting element 32, the second light emitting element 34, and the third light emitting element 36 are arranged in this order in the direction perpendicular to the display surface as shown in FIG. is there. However, although it arrange | positions on the same surface of the light shielding film 20, it does not arrange | position on the same straight line, but arrange | positions so that it may not overlap on the same straight line. Depending on the size and type of the first light-emitting element 32 and the second light-emitting element 34, the light emitted from the second light-emitting element 34 and the third light-emitting element 36 that are distant from the display surface is blocked, and a light loss that cannot be ignored. May occur. In that case, the optical loss can be reduced by such an arrangement.

  As shown in FIG. 1, the pixel on the right of the pixel is arranged in the order of the first light emitting element 32, the second light emitting element 34, and the third light emitting element 36 on the same straight line in the direction perpendicular to the display surface. This is an example. When the first light emitting element 32 and the second light emitting element 34 are sufficiently small, or the first light emitting element 32 and the second light emitting element 34 are transparent, they may be arranged on the same straight line. In that case, the size of the pixel can be minimized and the resolution can be increased.

  Further, the pixel on the right of the above pixel is an example in which the light emitting elements 32, 34, and 36 of the three primary colors are arranged on the bottom surface of the recess. Thus, even when they are arranged on the same surface facing the display surface, since the pixels are partitioned by the light shielding film 20, mixing of light between the pixels can be prevented.

  FIG. 3 is a side sectional view of a light emitting device 2 using an organic EL (ElectroLuminescent) according to the present invention. In the light emitting device 2 in FIG. 1, the example in which LEDs are used as the light emitting elements 32, 34, and 36 has been described. In this regard, in the light emitting device 2 of FIG. 3, an example in which organic EL elements are used as the light emitting elements 32, 34 and 36 will be described. An organic EL device injects electrons and holes from the cathode and anode into the light emitting layer, respectively, and these recombine at the interface between the light emitting layer and the hole transport layer or inside the light emitting layer near the interface to excite organic molecules. When the organic molecule returns from the excited state to the ground state, it emits fluorescence. By selecting a material used for the light emitting layer, an organic EL element that emits an appropriate color can be obtained. An organic EL element is generally easily affected by water molecules and oxygen molecules, and thus is preferably formed by a vacuum deposition method.

  In FIG. 3, when the light shielding film 20 is used as a common anode, the cathode 38 is located at a position facing the organic layer (in FIG. 3 to FIG. 5, corresponding to the light emitting elements 32, 34, and 36). Is provided. The cathode 38 is a transparent electrode made of ITO. The organic layer has a structure in which a hole transport layer, a light emitting layer, and an electron transport layer are laminated in this order from the bottom. The thickness of the organic layer is preferably about 0.2 [μm].

The insulating film 42 is formed around the organic layer formed on the light shielding film 20 using a transparent SiO ₂ film or the like. A cathode 38 using ITO is formed on the insulating film 42 and each organic layer. The thickness of ITO is preferably about 1000 angstroms. In order to insulate from the upper, lower, left, and right concave portions, an insulating film 40 is formed in the space in each concave portion, and the light emitting elements 32, 34, and 36 and the cathode 38 in each concave portion are sealed.

  FIG. 4 is a cross-sectional view of the upper surface of the light emitting device 2 using the organic EL according to the present invention. In FIG. 4, the light shielding films 20 other than the portions where the insulating films 40 and 42 and the organic layer are laminated are omitted. The arrows in the figure indicate the direction of light irradiation. ITO used for the cathode 38 is wired in the direction of the bottom surface of the recess. It can be seen that the three organic layers corresponding to the three primary colors are independently controlled by different power supply lines.

  FIG. 5 is a front sectional view of the light emitting device 2 using the organic EL according to the present invention. In the concave portion corresponding to each pixel, the three light emitting elements 32, 34, and 36 are arranged on the same straight line with respect to the light irradiation direction. The insulating film 42 is formed around each organic layer and protects each organic layer. ITO is formed on the organic layer. In this state, each recess is sealed with the insulating film 40, and each pixel is insulated.

  It will be understood by those skilled in the art that the light emitting device 2 shown in FIGS. 3 to 5 can be manufactured by a general process technique. For example, pixels for one row of the matrix may be generated and stacked for the number of columns of the matrix. For example, it can be manufactured as follows. First, the light shielding film 20 is formed on the substrate by sputtering or the like, and is appropriately etched to generate a threshold with an adjacent pixel or an organic layer base. Further, in order to make the back surface closed by the light shielding film 20 with respect to the irradiation direction, when generating a mask pattern on the light shielding film 20, the mask pattern may be generated so that the portion forming the back surface grows more. Good. Further, the portion may be formed independently.

Then, around the position where each of the organic layers are laminated, the SiO ₂ film is deposited by a CVD method, or vacuum deposition method in each of the SiO ₂ film forming an organic layer. The organic layer can be protected by this SiO ₂ film. Next, ITO is formed on the organic layer and the SiO ₂ film by sputtering or the like. Finally, a SiO ₂ film is formed in the space allocated to each pixel by a CVD method or the like, and the organic layer and ITO of each pixel are sealed. Through these steps, one row of pixels can be generated. This process is repeated for the number of columns in the matrix.

  Then, a hole for wiring is made in the light shielding film 20 on the back surface. The wiring from the ITO of each organic layer may be taken out from the hole formed in the light shielding film 20 on the back surface while being insulated. These wirings are integrated into three systems for each of R, G, and B, and are controlled by three types of power supplies and a light emission control unit 60 described later. In this way, the light emitting device 2 can be manufactured. In addition, also when using LED for the light emitting elements 32, 34, and 36, it can manufacture by the same process fundamentally. In this case, the process of forming the organic layer is simplified. The light emitting device 2 using an organic EL element can be made thinner than that using an LED. In addition, as will be described later, it is possible to perform control in which luminance control is performed on the light emitting device 2 side.

  When the light emitting elements 32, 34, and 36 of the three primary colors are arranged on the bottom surface of the concave portion as in the upper right pixel in FIG. 2, the light shielding elements 20 are stacked from the bottom surface of the concave portion, that is, the irradiation direction. It is good to go. In this case, the light shielding film 20 is formed on the substrate and etched to generate a matrix-like threshold for all the pixels, so that the recesses for all the pixels can be easily formed.

  Next, a usage example of the light emitting device 2 according to the present invention will be described. FIG. 6 is a block diagram showing a first configuration example of the display device 1 using the light emitting device 2 according to the present invention. The liquid crystal panel 10 uses a region surrounded by a plurality of data lines provided at a predetermined interval in the column direction and a plurality of scanning lines provided at a predetermined interval in the row direction as pixels. This pixel corresponds to the pixel of the light emitting device 2 partitioned by the light shielding film 20.

  The panel control unit 50 includes a data line driving circuit 52 and a scanning line driving circuit 54, and receives image data and a synchronization signal. The panel control unit 50 processes the input image data, and applies the R, G, B image data from the data line driving circuit 52 to the data lines (not shown) of the liquid crystal panel 10 in a predetermined order. The predetermined order corresponds to the cyclic lighting control of the light emitting device 2 by the light emission control unit 60. Each of the R, G, and B image data is 8-bit digital data to express 256 gradations, and the data line driving circuit 52 performs PWM (Pulse Width Modulation) control on the digital data, and the data line To give. Each image data may be composed of other bits such as 6 bits.

  The scanning line driving circuit 54 controls to output the image data given to the liquid crystal panel 10 by the data line driving circuit 52 from the pixels of the specific scanning line in accordance with the synchronization signal. For example, when the light emission control unit 60 performs the cyclic lighting control of the light emitting device 2 within 1/60 [s], the scanning line driving circuit 54 switches the scanning line at the same timing. Corresponding to this, the data line driving circuit 52 gives the R, G, B image data to be output from the pixels of the scanning line to the data line. Those pixels of the liquid crystal panel 10 transmit light from the light emitting device 2 at a transmittance according to each image data. As a result, the R, G, B three-color image data is displayed within 1/60 [s] from the specific scanning line, but the human visual time resolution is exceeded. It looks like a color-synthesized image. Note that when the liquid crystal panel 10 having a slow response time is used, the subjective image quality deteriorates.

  In the light emitting device 2, as described in FIGS. 1 to 5, pixels configured by an assembly of a plurality of light emitting elements 32, 34, and 36 are formed in the respective concave portions partitioned by the light shielding film 20. The light emission control unit 60 circulates and lights the light emitting elements 32, 34, and 36 of each pixel of the light emitting device 2. A synchronization signal for synchronizing with the control of the liquid crystal panel 10 is given from the synchronization generation circuit 70 to the light emission controller 60. The light emission control unit 60 turns on the light emitting elements 32, 34, and 36 in the order of R, G, and B within 1/60 [s], for example, in accordance with the synchronization signal. Instantaneously, one of R, G, and B is turned on.

  The pixel to be lit is based on the wiring of the light emitting elements 32, 34 and 36. When all the light emitting elements 32, 34, and 36 of the light emitting device 2 are connected by the same power line for each color, the entire light emission is controlled for each color. In this case, the power supply control system can be simplified. In addition, when each color is connected by the same power supply line in the row direction corresponding to the scanning line of the liquid crystal panel 10 and power control is possible in units of rows, the row corresponding to the scanning of the scanning line, or the number before and after the row A row may be lit. In this case, power consumption can be reduced.

  The synchronization generation circuit 70 supplies a synchronization signal to the panel control unit 50 and the light emission control unit 60. The circulation lighting control of R, G, and B by the light emitting device 2, the supply of image data to the data lines of the liquid crystal panel 10, and the scanning line control must be synchronized. The synchronization generation circuit 70 generates a signal for achieving this synchronization and supplies it to both.

  As described above, according to the display device 1 having the first configuration, it is possible to obtain an image with high color purity by switching the monochromatic display of R, G, and B at such a high speed that humans cannot recognize. Further, in order to improve the contrast ratio, a turn-off time may be provided for each of the R, G, and B monochrome displays. Specifically, the light emission control unit 60 may insert an extinguishing period when the light emitting elements 32, 34, and 36 are switched when the three primary color light emitting elements 32, 34, and 36 are turned on. As another method, when the scanning line driving circuit 54 selects one scanning line, a light shielding period may be inserted each time R, G, and B colors are displayed. According to these, there is an effect equivalent to inserting a black display, and the contrast ratio is improved.

  FIG. 7 is a block diagram showing a second configuration example of the display device 1 using the light emitting device 2 according to the present invention. Unlike the display device 1 having the first configuration, the display device 1 in the second configuration example is an example in which image data is written not by the liquid crystal panel 10 but by the light emitting device 2. In the second configuration example, organic EL elements may be used as the light emitting elements 32, 34, and 36 in order to write image data on the light emitting device 2 side. The light emitting elements 32, 34, and 36 in the pixels formed in the light emitting device 2 are connected in the column direction by data lines for each color.

  The light emission control unit 60 of the second configuration example includes a data line driving circuit 62 and receives image data and a synchronization signal. The light emission control unit 60 processes the input image data, and supplies the R, G, and B image data from the data line driving circuit 62 to the corresponding color data lines. The data line driving circuit 62 sequentially switches from one color data line to another color data line in accordance with the synchronization signal in order to turn on the light emitting device 2 in a circulating manner. At this time, if the image data is a digital value, the luminance of each color is adjusted by PWM control.

  The liquid crystal panel 10 of the second configuration example has no data lines and is provided with a plurality of scanning lines at predetermined intervals in the row direction. Unlike the first configuration example, the panel control unit 50 of the second configuration example has a configuration in which the data line driving circuit 52 is removed. A synchronization signal is input to the panel control unit 50. The scanning line driving circuit 54 controls the light from the light emitting device 2 to be transmitted from the pixels of the specific scanning line in accordance with the synchronization signal. For example, when the data line driving circuit 62 switches the data line that supplies the image data within 1/60 [s], the scanning line is switched at the same timing to transmit the light from the light emitting device 2. . Other configurations are the same as those of the first configuration example.

  As described above, according to the second configuration example, similarly to the first configuration example, it is possible to obtain an image with high color purity by switching the monochromatic display of R, G, and B at such a high speed that humans cannot recognize. . Further, since the data lines for writing and displaying the image data and the scanning lines are arranged separately in the light emitting device 2 and the liquid crystal panel 10, wiring can be simplified.

  Note that the light emission control unit 60 may insert a turn-off period when switching from one color data line to another color data line. Further, when the scanning line driving circuit 54 selects one scanning line, a light shielding period may be inserted each time R, G, and B colors are displayed. According to these, there is an effect equivalent to inserting a black display, and the contrast ratio can be improved.

  Note that the second configuration example is not limited to the light-emitting device 2 in which the plurality of light-emitting elements 32, 34, and 36 are embedded in the recesses, and a configuration in which the plurality of light-emitting elements 32, 34, and 36 are provided corresponding to the pixels. It may be. For example, a plurality of light emitting elements 32, 34, and 36 may be arranged corresponding to each pixel on a flat substrate.

  FIG. 8 is a diagram showing an example in which the display device 1 of the present invention is applied to a projector 100. The light from the light emitting device 2 passes through the liquid crystal panel 10 and enters the projection lens 80. The projection lens 80 enlarges the incident light and projects it onto the screen 90.

  Thus, according to the projector 100, an image with high color purity can be obtained by switching the monochromatic display of R, G, and B at such a high speed that humans cannot recognize. Unlike conventional projectors, there is no need to provide three liquid crystal panels and optical systems corresponding to R, G, and B, respectively. Moreover, since it is not necessary to generate light of each color from a light source such as a high-pressure mercury lamp using a color filter, the light efficiency does not decrease.

  The present invention has been described above based on the embodiments. The present invention is not limited to these embodiments, and various modifications thereof are also effective as aspects of the present invention. The light emitting device 2 of the present invention can also be used as a light source of a display such as a mobile phone, a notebook PC, a PDA (Personal Digital Assistants).

It is sectional drawing of the side surface of the display apparatus which concerns on this invention. It is sectional drawing of the front of the light-emitting device which concerns on this invention. It is sectional drawing of the side surface of the light-emitting device using the organic EL which concerns on this invention. It is sectional drawing of the upper surface of the light-emitting device using the organic EL which concerns on this invention. It is sectional drawing of the front of the light-emitting device using organic EL which concerns on this invention. It is a figure which shows the block diagram which shows the 1st structural example of the display apparatus using the light-emitting device which concerns on this invention. It is a figure which shows the block diagram which shows the 2nd structural example of the display apparatus using the light-emitting device which concerns on this invention. It is a figure which shows the example which applied the display apparatus of this invention to the projector.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Display apparatus, 2 Light-emitting device, 10 Liquid crystal panel, 20 Light shielding film, 32, 34, 36 Light emitting element, 38 Cathode, 40, 42 Insulating film.

Claims (4)

A light shielding film having a recess corresponding to each pixel;
A plurality of light-emitting elements embedded in each recess,
A transparent insulating film that seals the plurality of light emitting elements in the recess;
A light emitting device comprising: A light shielding film having a recess corresponding to each pixel;
A plurality of light-emitting elements embedded in each recess,
Electrodes for supplying power to each light emitting element;
A transparent insulating film that seals the plurality of light emitting elements and the electrodes in the recess,
A light-emitting device, wherein the light-shielding film is formed of a conductive material and serves as a common electrode on the ground side.   The light-emitting device according to claim 1, wherein the plurality of light-emitting elements are installed in the concave portion along a light irradiation direction. A light emitting device according to any one of claims 1 to 3,
A display device comprising: a liquid crystal panel that controls the transmittance of light from the light emitting device for each of the pixels.

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