JP2007187696A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device which does not require processing of high accuracy, is high in area coverage of a display region and uses a lateral electric field. <P>SOLUTION: The display device has a plurality of laminated display layers each having a plurality of the display regions. The display regions of the respective display layers cooperatively constitute a dot matrix. More preferably, each display layer has counter substrates, a plurality of first electrodes which are formed on one side of the counter substrates, respectively include a plurality of display regions, extend in a first direction, and are arranged in parallel along a second direction intersecting with the first direction, a plurality of second electrodes which are formed on the other of the counter substrates, respectively extend in a second direction while surrounding the circumferences of the plurality of the display regions, and are arranged in parallel along the first direction, ribs which are arranged between the counter substrates so as to surround the respective display regions and delineate the distances between the counter substrates, and working media which are housed in the respective spaces delineated by the counter substrates and the ribs. The substrates, electrodes, and ribs which ought to transmit the display of other layers are transparent. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a display device, and more particularly to a thin display device that can be electrically controlled.

  Liquid crystal display devices and plasma display devices are known as thin display devices. These display devices can display high-definition moving images and still images, but have a high manufacturing cost and require power for display. It cannot be folded. There is also a need for a still image display device that can be used more simply, such as paper.

  There is known a display device in which particles are dispersed in a dielectric fluid such as liquid crystal and the distribution state of the particles is controlled by a lateral electric field. The display can be switched by forming an electrode for generating a horizontal electric field on the counter substrate and applying an electric field in the reverse direction. In a state where particles are present in the display area, incident light is reflected and scattered by the particles, and white display or black display according to the color of the particles is performed. In the state where particles exist outside the display area, the incident light is transmitted. When a light absorption plate or a reflection plate is disposed outside the counter substrate, incident light is absorbed and reflected, and black display, white display, and the like can be performed. By selecting white display or black display for each display area distributed in the form of a dot matrix, display in an arbitrary shape is possible. Such a display device has a memory property and maintains display even when the electric field is turned off. An MFPD (mobile fine particle display) that controls the position of fine particles by the movement of a fluid, an apparatus that uses electrophoresis, and the like are known.

JP 2003-98556 A JP, 2004-294623, A The electrochromic technique can also control reflectance and transmittance electrically. As a configuration, almost the same configuration as that of a liquid crystal display device or the like can be used, an electrochromic material layer is formed on one electrode of a display region, and an electrolyte is used as a medium.

  These display devices are as thin as paper and have the potential to realize a display device that can maintain display even when the power is disconnected. By using a plastic substrate, it is expected that bending to some extent is possible.

  In order to perform display with a large amount of information that can be arbitrarily changed, it is desirable to arrange pixels in a dot matrix. In the liquid crystal display device, an active matrix substrate in which a thin film transistor (TFT) is arranged for each pixel is used. It is not easy to form TFTs on a plastic substrate. In a liquid crystal display device, it is difficult to maintain display even when the power is disconnected. The liquid crystal display device can hardly be bent.

  For example, a simple matrix substrate in which an X-direction electrode is formed on one substrate and a Y-direction electrode is formed on the other substrate is not suitable for moving image display with a low duty ratio, but has a memory property When displaying a still image with, the image switching time can be lengthened and used without any problem.

  In order to electrically separate the electrodes arranged in parallel, a predetermined gap is necessary between adjacent electrodes. The gap becomes a non-display area. In order to narrow the gap, high-precision processing is required.

  When a horizontal electric field is used, electrodes are arranged inside and outside the display area. If the electrode outside the display area is enlarged, the area occupancy of the display area is lowered and the image quality is lowered. In order to narrow the electrode outside the display area, the processing has high accuracy, the manufacturing cost is increased, and the yield is also reduced.

  An object of the present invention is to provide a display device which does not require high-precision processing and has a high area occupancy ratio of a display region.

  Another object of the present invention is to provide a thin display device that can use a plastic substrate.

According to one aspect of the present invention,
A plurality of stacked display layers, each having a plurality of display areas;
A display device is provided in which the display areas of the display layers cooperate to form a dot matrix.

Preferably, each display layer is
A counter substrate;
A plurality formed on one of the counter substrates, each including a plurality of display areas, extending in a first direction, and arranged in parallel along a second direction intersecting the first direction; A first electrode of
A plurality of second electrodes formed on the other side of the counter substrate, extending in the second direction, and arranged in parallel along the first direction;
Ribs arranged between the opposing substrates so as to surround each display region, and defining a distance between the opposing substrates;
A working medium accommodated in each space defined by the counter substrate and the rib;
Have
The substrate, the electrode, and the rib are transparent if they should transmit the display of the other layer.

  Since the dot matrix is composed of a plurality of layers, the burden per layer is reduced. Even if high-precision processing is not performed, display with a high area occupancy ratio of the display region is possible.

  Embodiments of the present invention will be described below with reference to the drawings.

  1A1, 1B1, and 1C1 are plan views showing a manufacturing process of a lower substrate of a display device according to a first embodiment of the present invention, and FIGS. 1A2, 1B2, and 1C2 are cross sections taken along a dashed line in FIGS. 1A1, 1B1, and 1C1. The figure is shown. 1A1 and 1A2 are collectively referred to as FIG. 1A. Others have the same name. In the figure, the horizontal direction is called the X direction, and the vertical direction is called the Y direction. As an example, the pitch of the dot matrix to be formed is 450 μm in both the X direction and the Y direction.

  As shown in FIG. 1A, a plurality of striped transparent lower electrodes 12 are formed on a transparent substrate 11. The transparent substrate 11 is a plastic substrate or a glass substrate, and the transparent lower electrode 12 is formed of indium-tin oxide (ITO), for example. The transparent lower electrode 12 is formed by sputtering an ITO film and patterning it using photolithography, or by a printing method such as screen printing. When using a printing method, a paste in which ITO or metal particles are dispersed is used. A conductive polymer can also be used. In the figure, electrodes extending in the Y direction are arranged in parallel in the X direction. For example, stripe electrodes having a width of 450 μm are arranged at intervals of 450 μm. A display area is defined on the transparent lower electrode.

  As shown in FIG. 1B, a lattice frame or rib 13 is formed of low melting point glass or transparent plastic material so as to surround the display area of the transparent lower electrode 12. For example, Pb-containing low-melting glass to which 4 wt% of a plastic ball (spacer) having a diameter of 75 μm is added is screen-printed to form a grid-like rib having a height of 75 μm and having 400 μm square openings distributed in a matrix. The opening of the rib 13 includes each display area.

As shown in FIG. 1C, the working medium 14 in which fine particles are dispersed in the opening of the rib 13 is dropped by a dispenser. For example, a mixed fluid in which fine particles are added to the fluid is dropped with a dispenser. The dripping amount is controlled to be equal to the volume to be filled. The fluid rises from the upper surface of the rib 13 due to surface tension. As the fluid, it is preferable to use an insulating dielectric material such as liquid crystal. In the case of liquid crystal, the dielectric anisotropy may be positive or negative. The behavior of the fine particles is affected by the dielectric anisotropy of the liquid crystal, and the larger the absolute value of the dielectric anisotropy, the faster the movement speed of the fine particles. For example, RDP-00333 (Dainippon Ink) is used as the liquid crystal. The addition amount of the fine particles dispersed in the liquid crystal is about 1 to 50 wt%, desirably about 10 to 30 wt%. For example, 20 wt% of fine particles are added. The particle diameter of the fine particles is about 0.5 to 100 μm, preferably about 2 to 20 μm. For example, fine particles having a particle diameter of 6 μm are used. As the material of the fine particles, for example, oxides such as TiO ₂ , SiO ₂ , ZnO, and organic substances such as styrene balls can be used. Solid particles or hollow particles can be used. You may add a white pigment, a black pigment, etc.

  FIG. 1D shows a manufacturing process of the upper substrate. A transparent electrode 22 having an opening is formed on the transparent substrate 21. The opening is aligned with the display area. For example, the upper electrodes 22 including a plurality of openings of 450 μm square and extending in the X direction are arranged in parallel in the Y direction. Like the lower substrate, the transparent upper substrate 21 is formed of a plastic substrate or a glass substrate, and the transparent upper electrode 22 is formed of, for example, indium-tin oxide (ITO). The opening of the transparent upper electrode 22 defines a display area on the transparent lower electrode.

  FIG. 1E shows a state in which the upper substrate is overlaid on the lower substrate. The opening of the transparent upper electrode 22 of the upper substrate 21 is disposed in the opening of the rib 13 on the transparent lower electrode 12 of the lower substrate to define a display area. The working medium 14 is accommodated in the display area. In order not to generate bubbles, for example, the upper substrate can be superposed on the lower substrate in a vacuum and thermocompression bonded. For example, both substrates are set with appropriate spacers sandwiched in a vacuum pack, the inside of the vacuum pack is evacuated to vacuum, the spacers are extracted, and both substrates are pressure-bonded and returned to the atmosphere.

  FIG. 1F shows a state where the upper substrate and the lower substrate are overlapped with each other as seen through the top surface. The working medium is accommodated below the opening (display area) of the upper electrode 22 arranged in parallel in the horizontal direction, and the lower electrode 12 is arranged so as to connect the display areas arranged in the vertical direction. With this structure, one display layer is formed. Other display layers are also produced by the same process, and four display layers are prepared. The display area of each display layer is arranged so as to be shifted in the horizontal direction / vertical direction by the display area.

  Each display area is surrounded by grid ribs. Accordingly, the working medium is also divided into display areas. If the rib is made of a material that does not allow the passage of fine particles, the movement of the fine particles from pixel to pixel is prevented.

  2A and 2B are a plan view and a cross-sectional view showing a state in which four display layers are stacked and assembled.

  As shown in FIG. 2A, the display areas D1 and D2 are alternately arranged in the horizontal direction, and the display areas D3 and D4 are alternately arranged one line below. The display areas D1 to D4 are display areas of the first display layer to the fourth display layer. A cross section taken along the one-dot chain line of FIG. 2A is shown in FIG. 2B. The uppermost display layer DL1 includes a lower substrate 11-1, a lower electrode 12-1, a rib 13-1, a working medium 14-1, an upper electrode 22-1, an upper substrate 21-1, and is formed of a black insulating material or the like. The black matrix BM is included. The second display layer DL2, the third display layer DL3, and the fourth display layer DL4 have the same configuration as the first display layer DL1 except that the black matrix BM is not included. The fourth display layer DL4 has a light absorption layer ABS above or below the lower substrate 11-4.

  Note that the upper electrode and the working medium are not shown in the third display layer DL3 and the fourth display layer DL4, but this is the position where the first display layer DL1 and the second display layer DL2 perform display in this section. This is because the third display layer DL3 and the fourth display layer DL4 are positions where no display is performed. If the cross section of one row is taken, the first display layer DL1 and the second display layer DL2 are arranged without the upper electrode and the working medium, and the third display layer DL3 and the fourth display layer DL4 are the upper electrode and the working medium. It becomes the composition which has. The display areas of the first display layer DL1 and the second display layer DL2 are shifted by one pixel in the horizontal direction. The display areas of the third display layer DL3 and the fourth display layer DL4 have the same configuration.

  Since dot matrix display is performed with the display layers stacked in four layers, in each display layer, display regions may be formed every other pixel in the horizontal (X) direction and the vertical (Y) direction. Since the electrode can be arranged using the vacant area, the positional accuracy becomes remarkably gentle. For example, when the size of one pixel is 450 μm □, the lower electrode shown in FIG. 1A may be formed easily by using screen printing or the like by arranging striped electrodes having a width of 450 μm with an interval of 450 μm.

  The upper electrode shown in FIG. 1D also has an opening of 450 μm □, but the distance between the openings is 450 μm, and even if electrodes having a width of 150 μm are formed on both sides of the opening, the distance between the electrodes is about 100 μm. Can be created using technology.

  In the case of an MFPD display device, the cell gap (distance between substrates or distance between electrodes) is about 10 μm to 200 μm. For example, when the distance between the substrates is 75 μm, the ribs 13 have a height of 75 μm, but even in a region having a lattice shape and a narrow width, the width is about 400 μm. Therefore, it can be formed by a printing method, and sufficient self-holding ability can be easily provided.

  As shown in FIG. 2A, when the four layers are stacked, the dot matrix display is a square matrix, and a known driving method can be used. For the manufacturing method of the MFPD apparatus and the like, the disclosure of [Embodiments of the invention] in Patent Documents 1 and 2 can be referred to.

  3A and 3B are cross-sectional views schematically showing driving of MFPD display. FIG. 3A shows a state in which white fine particles are distributed in the display region. When light enters from above, the incident light is reflected and scattered by the white fine particles, and an observer observing from above feels the display area white. The alignment films 16 and 26 are formed on the substrate so as to cover the surfaces of the lower electrode 12 and the upper electrode 22.

  FIG. 3B shows a state in which white fine particles are removed from the lower electrode. When the white fine particles no longer exist in the display area, the incident light from above passes through the working medium, passes through the lower electrode, and enters and is absorbed by the light absorbing plate ABS disposed below the display layer. An observer observing from above feels the display area black.

  The display principle of the display device is not limited to MFPD.

  3C and 3D show the case of an electrochromic display device. An electrochromic material layer 18 is disposed on the lower electrode 12, and the working medium 14 is an electrolyte instead of a liquid crystal containing fine particles. Since the working medium 14 for each pixel is separated by the rib 13, interference between pixels can be prevented. The upper electrode 22 does not need to have an opening, and can be disposed opposite to the lower electrode like a liquid crystal display device. FIG. 3C shows a state in which the electrochromic material layer 18 is colored due to the interaction of the working medium 14 with the electrolyte. An observer who observes from above feels that the display in the display area is colored.

  FIG. 3D shows a state in which the electrochromic material layer 18 has become colorless due to the interaction with the working medium 14. Incident light from above passes through the electrochromic material layer 18 and the lower electrode 12 and is reflected by the white reflector REF disposed below. An observer observing from above feels the display area white. The electrochromic display device may have a display principle in which the electrochromic material is dispersed in the electrolyte without forming the electrochromic material layer, and the working medium itself is made transparent or colored. In this embodiment, the electrochromic material layer is provided on the lower substrate. However, the electrochromic material layer may be provided on the upper substrate and observed without using the working medium. In this case, a reflective display device that does not require an external reflection plate can be obtained by dispersing a white pigment or the like in the working medium. By providing a reflective display device in the lowermost layer of a multilayer configuration, the multilayer display device can also be configured as a reflective type.

  According to the four-layer laminated structure, the clearance margin in the X direction and the Y direction is significantly increased. The laminated structure is not limited to a four-layer laminated structure.

  When performing dot matrix display, for example, the row direction pitch and the column direction pitch are selected to be the same value. In FIG. 2A, a case where the row direction pitch and the column direction pitch of the display area D are 500 μm and the minimum rule (width and interval) of the pattern is 100 μm is considered. First, consider a case where a dot matrix is formed with a single display layer. The lower electrode as shown in FIG. 1A has a stripe shape extending in the Y direction. If the X direction interval is 100 μm, electrodes having an X direction width of 400 μm can be arranged in all rows. The width of the display area in the X direction can be 400 μm.

  The upper electrode as shown in FIG. 1D needs to have an opening in the display area and be disposed outside the display area. If the distance between the electrodes is 100 μm, electrodes with a minimum width of 100 μm are further required on both sides of the opening, for a total of 300 μm. When 300 μm is subtracted from the pitch of 500 μm, the opening, that is, the width of the display area in the Y direction becomes 200 μm. A display region of 400 μm × 200 μm is formed in a unit area of 500 μm × 500 μm, and the area occupancy of the display region is 8/25 = 0.32. The electrodes on both sides of the opening of the upper electrode have a total width of 200 μm, which may increase the resistance. If the electrode width is increased, the opening becomes even narrower.

  According to the first embodiment, four display layers are combined, and division is performed in the X direction and the Y direction. Even if the electrode width is sufficient, each display area can be 500 μm × 500 μm, and the area occupancy of the display area is 1. If you want to increase the area occupancy but do not want to stack up to 4 layers, you can divide only in one direction (Y direction) that greatly reduces the area occupancy and stack two layers. it can.

  FIG. 4A is a plan view showing an electrode arrangement of one display layer of the two-layer stacked display device. The lower electrodes 12 extending in the Y direction have a width of 400 μm and are arranged in parallel in the X direction with an interval of 100 μm. The upper electrodes extending in the X direction are arranged every other row, have openings of width 400 μm × height 500 μm, have electrodes of width 200 μm on both sides of the openings, and are parallel to the Y direction at intervals of 100 μm. Be placed. A total electrode width of 400 μm is obtained on both sides of the opening, and the balance with the lower electrode width of 400 μm is good. The other layer is formed in a shape shifted in the Y direction by a half pitch (500 μm).

  FIG. 4B is a plan view of a state in which two layers are stacked. Since the Y direction is divided into the display area D1 and the display area D2, when the two layers are combined, the display area is continuous in the Y direction. Each display area has a width in the X direction of 400 μm and a height in the Y direction of 500 μm. The area occupation ratio of the display area is 400 × 500/500 × 500 = 0.8. Compared with the area occupancy rate of 0.32 when formed with a single layer, the improvement is more than twice.

  The above numerical values are merely examples and are not limiting. Various changes can be made as required. Although the area occupying ratio also changes, it can be understood that a significant improvement can be obtained as compared with the case where the display device is configured with a single layer. An electrochromic display device can be formed with a similar structure. In the case of an electrochromic display device, it is not necessary to provide an opening in the electrode, and the electrode arrangement becomes easier.

  Although the case of a four-layer stacked structure and a two-layer stacked structure has been described, the total number of stacked structures is not limited to four or two. Arbitrary plural layers can be laminated to form a display device.

  FIG. 5 shows an example of a display device having a three-layer structure. Each of the display layers DL1, DL2, and DL3 performs red (R) display, green (G) display, and blue (B) display. A display DIS in which three layers of displays are superimposed performs RGB color display. For example, three colors are displayed by electrochromic display.

  6A and 6B are a cross-sectional view and a plan view showing a case where an overlap is provided between stacked electrodes. Even when the display device is observed obliquely, more reliable display can be performed. The number of stacked layers is not limited to 2, 3, and 4. Further, the manufacturing method of the display device is not limited to the above.

  FIG. 6C shows the case where the rib is formed by forming a resist pattern on the substrate and sandblasting. A rib-shaped resist pattern RP is formed on the substrate 11, and sandblasting is performed using the resist pattern as a mask. The substrate 11 is scraped by the sand 30 at a portion not covered with the resist pattern RP, and the remaining portion forms a rib.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

1A1, 1B1, and 1C1 are plan views of the lower substrate, FIGS. 1A2, 1B2, and 1C2 are cross-sectional views of the lower substrate, FIG. 1D is a plan view of the upper substrate, and FIG. 1E is a cross-sectional view in which the upper and lower substrates are stacked. FIG. 1F is a perspective plan view of the superimposed substrate. 2A is a plan view of the multilayer display device, and FIG. 2B is a cross-sectional view of the multilayer display device. 3A and 3B are schematic cross-sectional views showing the operation principle of MFPD display, and FIGS. 3C and 3D are schematic cross-sectional views showing the operation principle of electrochromic display. 4A and 4B are plan views showing the electrode arrangement of one display layer and the display area arrangement of the laminated structure of the two-layer laminated display device. FIG. 5 is a perspective view illustrating an example of a three-layer stacked display device. 6A and 6B are a cross-sectional view and a plan view showing a configuration example in which an overlap is provided between electrodes. FIG. 6C is a cross-sectional view showing selective sandblasting, which is another method of forming ribs.

Explanation of symbols

11 Lower substrate 12 Lower electrode 13 Rib 14 Working medium 21 Upper substrate 22 Upper electrode BM Black matrix ABS Absorbing material layer 16, 26 Alignment film
18 Electrochromic material layer REF Reflector D Display area

Claims (10)

A plurality of stacked display layers, each having a plurality of display areas;
A display device in which display areas of the display layers cooperate to form a dot matrix. Each of the display layers is
A counter substrate;
A plurality formed on one of the counter substrates, each including a plurality of display areas, extending in a first direction, and arranged in parallel along a second direction intersecting the first direction; A first electrode of
A plurality of second electrodes formed on the other side of the counter substrate, extending in the second direction, and arranged in parallel along the first direction;
Ribs arranged between the opposing substrates so as to surround each display region, and defining a distance between the opposing substrates;
A working medium accommodated in each space defined by the counter substrate and the rib;
Have
The display device according to claim 1, wherein the substrate, the electrode, and the rib are transparent to transmit a display of another layer.   The display device according to claim 2, wherein the plurality of display layers are four layers.   4. The display device according to claim 3, wherein display areas of the four display layers form a square matrix, and each display layer is disposed alternately in the first direction and the second direction.   The display device according to claim 2, wherein the plurality of display layers are two layers.   6. The display device according to claim 5, wherein each of the two display layers constitutes every other display area along the first direction.   The display device according to claim 2, wherein the substrate is a plastic substrate.   The display device according to claim 2, wherein the rib is formed using low-melting glass or plastic.   The display device according to claim 2, wherein the working medium is a medium in which fine particles are dispersed in a dielectric fluid made of liquid crystal. An electrochromic material layer disposed on at least the display region of the first electrode;
The display device according to claim 2, further comprising: an electrolyte.

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