JP2007133013A - Particle movement type display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device of which the visual field angle is switched according to the intended purpose of a user, and which is furnished with a function as a memory. <P>SOLUTION: The particle movement type display is provided with: a substrate; a closed space including a plurality of particles of at least one kind arranged on the substrate; and a reflecting layer which reflects light which is made incident to the closed space, wherein the reflecting condition of the incident light on the reflecting layer is varied by diffusing the particles in the direction of the face of the substrate, or concentrating the particles to at least a part of the closed space, thus at least two displaying states, bright and dark, are formed. The particle movement type display is provided with diffusion reflecting means of which the visual field angle characteristic is designed for every pixel. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a particle movement display device and a display method thereof.

  In recent years, mobile devices such as mobile phones, PDAs, and e-books have become more multifunctional, and it has become possible to send and receive e-mails, browse the Internet and photos, etc., regardless of location. However, with portable devices that can be carried around like this, there is a possibility that the contents displayed on the display may be viewed by a third party other than the operator, for example, on a train or airplane, which has a privacy problem. . In addition, there is an increasing demand for usage that widens or narrows the viewing angle as required so that the operator can view sentences and images displayed on the display in a free posture. Among them, for example, as disclosed in Document 1, a portable terminal device that can selectively switch the viewing angle of a display device is known. As a technique for controlling the viewing angle, a plurality of techniques using liquid crystals have been proposed. For example, a liquid crystal display device as shown in Document 2 is known. In addition, mobile terminals are often used outdoors because of their use, and low power consumption and space saving are also desired. However, in this respect, since many liquid crystals do not have so-called memory properties, it is necessary to continue to apply voltage to the liquid crystals during the display period, and further reduction in power consumption is an issue. On the other hand, it is difficult to ensure the reliability of liquid crystal having a memory property when it is assumed to be used in various environments outdoors, and has not yet been put into practical use.

Therefore, a particle movement type display device is known as one of thin and light display systems having memory properties. For example, an electrophoretic display device which is one of particle movement type display devices can be given (see Document 3). However, in the conventional particle movement type display device, it has been a problem to control the viewing angle characteristics according to the usage conditions of the operator.
Japanese Patent Laid-Open No. 2004-062094 Japanese Patent Laid-Open No. 9-6289 Patent Registration No. 3421494

  The present invention solves the above problem, and an object of the present invention is to provide a particle movement type display device having a memory property and having a function that allows an operator to adjust the viewing angle range according to the application. is there.

  The present invention has been made to solve the above-described problems, and includes a substrate, a closed space in which at least one kind of a plurality of particles arranged on the substrate surface is included, and light incident on the closed space. A reflecting layer for reflecting, and changing the reflection condition of incident light in the reflecting layer by diffusing the plurality of particles in the substrate surface direction or by integrating the plurality of particles in at least a part of the closed space. In the particle movement type display device that forms at least two bright and dark display states, the particle movement type display device is provided with diffuse reflection means whose viewing angle characteristics are designed for each pixel.

  As described above, in the particle movement type display device of this embodiment, it is possible to switch between the wide viewing angle state and the narrow viewing angle state. Further, since the particle movement type display device has a memory property, the display state is maintained even when the signal from the outside is turned off. As a result, a particle movement type display device that is lightweight and thin, has low power consumption, and can switch the viewing angle according to the use of the operator can be obtained.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

  Hereinafter, a typical embodiment of the particle movement type display device of the present invention will be described with reference to FIG. 1 and FIG.

  FIG. 1 is a schematic configuration diagram showing an example of a particle movement type display device in the present embodiment. In FIG. 1, a plurality of pixel groups 103 each including a pixel A101 and a pixel B102 are provided. Each pixel is provided with a switching element (not shown), and a gate line 104 and a source line 105 are connected to the switching element. ing. Here, the pixel A101 and the pixel B102 are designed to have different viewing angle characteristics. For example, the viewing angle of the pixel A101 has a wider viewing angle characteristic than the pixel B102. Each pixel has a switching element, and the display state can be controlled independently by an external signal.

  The display operation of the particle movement type display device having the pixel configuration as described above will be described below.

  First, when displaying at a wide viewing angle, a display signal is applied to the source lines 105 of the pixels A101 and B102 constituting the pixel group, and an arbitrary image is formed by matching the viewing direction of the pixel A101 and the viewing direction of the pixel B102. . On the other hand, when performing display with a narrow viewing angle, the pixel A101 designed to have a wide viewing angle characteristic applies a display signal for performing black level display to the source line 105 and a display signal to the pixel B102. Here, for the sake of simplicity of explanation, the pixel group 103 composed of two pixels is taken as an example, but the essence of the present invention is not limited to this, and the number of pixels is further increased to 1 One pixel group may be configured. In the wide viewing angle display, a display signal is applied to both the pixel A101 and the pixel B102. However, a black level display signal is applied to the pixel B102 having a relatively narrow viewing angle depending on the use of the operator. Anyway. In addition, although the viewing angle mode has been described with two types of narrow viewing angle and wide viewing angle, more viewing angle modes may be provided depending on the application of the display device.

  Next, an example of the pixel structure of the particle movement type display device having the viewing angle characteristics as described above will be described. However, in the present invention, the essence of the present invention is the same when only the charged particles are included between the rear substrate and the front substrate and when the particles dispersed in the insulating liquid are further included. Therefore, a typical embodiment of the electrophoretic display device will be described below with reference to FIG.

  The electrophoretic display device according to the present embodiment includes a thin film transistor on a rear substrate 10 and a concavo-convex structure layer 13 made of a photosensitive material on a rear substrate 10 as shown by a single pixel portion in FIG. The common electrode 12 is disposed in a region corresponding to the periphery of the pixel on the insulating layer 14 provided on the reflective electrode 11. On the common electrode 12, a partition wall 15 is provided so as to partition the pixels. The charged particles 30 dispersed in the insulating liquid 31 are filled between the rear substrate 10 and the front substrate 20 disposed so as to face the rear substrate 10, and although the periphery is not shown, the rear substrate 10 and the front substrate 20 are Sealed with adhesive and sealed. The viewing angle characteristics in the diffuse reflection means can be controlled by arbitrarily designing the concavo-convex shape in the concavo-convex structure layer 13. For example, there are methods for adjusting the inclination angle and height of the convex portion, the area and shape of the convex structure in the surface of the rear substrate 10, and the arrangement method of the individual convex portions or concave portions.

  Next, the display operation will be described.

  Here, the insulating liquid 31 is colorless and transparent, and the charged particles 30 are black. Further, the common electrode 12 has light absorptivity, and prevents incident light from being reflected by the common electrode 12. Light incident from the front substrate 20 is absorbed by the charged particles 30 distributed in the insulating liquid 31, and passes through the insulating liquid 31, reaches the reflective electrode 11, and is reflected by the reflective electrode 11 surface. Some light is directed forward. Therefore, the observer 50 can visually recognize a predetermined reflection intensity determined according to the distribution of the charged particles 31. Display is made according to the distribution of the charged particles 30 controlled in pixel units in this way. The distribution of the charged particles 30 in the insulating liquid 31 is controlled by the voltage applied to the reflective electrode 11 and the common electrode 12. For example, if the charged particles 30 dispersed in the insulating liquid 31 are positively charged, applying a positive polarity voltage to the reflective electrode 11 and a negative polarity voltage to the common electrode 12 causes the charged particles 30 to be common. Since they gather on the electrode 12 side, the light incident from the front is substantially reflected by the reflective electrode 11. Thereby, a bright pixel can be formed. On the other hand, when a negative polarity voltage is applied to the reflective electrode 11 and a positive polarity voltage is applied to the common electrode 12, the charged particles 30 move so as to cover the reflective electrode 11, so that the incident light is absorbed by the charged particles 30, The pixel can display the color of the charged particles 30. In the above embodiment, since the charged particle 30 is black, the pixel forms a black display. Further, if the charged particles 30 have other colors, it is possible to display colors according to the colors. The insulating liquid 31 may be colored in an arbitrary color. Although not shown, color display can also be performed by patterning a color filter on the reflective electrode 11 or patterning a color filter on the front substrate.

  Next, an example of a method for manufacturing an electrophoretic display device including a thin film transistor (hereinafter referred to as TFT) according to the present embodiment will be described.

  In this embodiment, the rear substrate 10 is made of alkali-free glass, and a source line 45 and a drain electrode 46 made of a molybdenum alloy are provided via a gate line 41 made of an aluminum alloy and molybdenum and an interlayer insulating layer 42 made of silicon nitride. A bottom gate type TFT comprising a semiconductor layer 43 made of amorphous silicon and a doped layer 44 which is a semiconductor film doped with P (phosphorus) at a high concentration at the intersection of the gate electrode 41 and the source electrode 45 is arranged in a matrix. Forming. An inorganic protective layer 47 made of silicon nitride is formed thereon. A predetermined resist pattern is formed on this protective layer 47 by irradiating with ultraviolet rays using a photoresist and a predetermined photomask, and then the protective layer 47 is etched by dry etching using fluorine gas, A contact hole is formed in the protective layer 47 located at the position. On the protective layer 47, the uneven structure layer 13 is formed. For the production of the concavo-convex structure layer 13, exposure, development, and a technique of melting by heating using a photoresist and a predetermined photomask are employed. Before hot melting, ultraviolet rays are irradiated to increase the crosslinking rate of the photoresist. After that, a 1000 Å thick aluminum film was formed on the concavo-convex structure layer 13 under a substrate temperature of 135 ° C., and a predetermined resist pattern was formed by irradiating ultraviolet rays using a photoresist and a predetermined photomask, Thereafter, wet etching is performed with a phosphoric acid-based etchant to form the reflective electrode 11. The reflective electrode 11 is electrically connected to the drain electrode 15. An insulating layer 14 is laminated on the entire surface including the reflective electrode 22. On the insulating layer 14, chromium oxide and chromium are continuously vapor-deposited, and a resist pattern is formed by irradiating ultraviolet rays using a photoresist and a predetermined photomask, and then wet etching is performed using a nitric acid-based etchant. The electrode 12 is disposed near the periphery of the reflective electrode 11. Each film thickness is adjusted so that the laminated film of chromium oxide and chromium is almost black. On the common electrode 12, a high-viscosity negative resist is patterned to form partition walls 15 having a height of 15 μm and a width of 5 μm. Thereafter, each pixel surrounded by the partition wall 24 is filled with a predetermined amount of a transparent insulating liquid 31 in which charged particles 30 are dispersed at a predetermined concentration, and the front substrate 20 is brought into close contact with the partition wall 15 to thereby each pixel. A transparent insulating liquid 31 in which charged particles 30 are dispersed is sealed, and although the periphery is not shown, the rear substrate 10 and the front substrate 20 are sealed with an adhesive. An active matrix type electrophoretic display device having an amorphous silicon TFT is manufactured.

  Here, as the insulating liquid 31, water, methanol, ethanol, acetone, hexane, toluene, aromatic hydrocarbons such as benzene having a long chain alkyl group, etc., or other various oils alone or these A mixture of a surfactant and the like can be used. The charged particles 30 are organic or inorganic particles having a property of moving by electrophoresis due to a potential difference in a dispersion medium. Examples of the charged particles 30 include black pigments such as aniline black and carbon black, titanium dioxide, One or more of white pigments such as antimony trioxide, azo pigments, and other colored pigments can be used. Furthermore, these pigments include electrolytes, surfactants, resins, rubbers, oil-based charge control agents, titanium-based coupling agents, aluminum-based coupling agents, silane-based coupling agents, and the like as necessary. Dispersants, lubricants, stabilizers and the like can be added.

Example 1
As shown in FIG. 1, the particle movement type display device according to the present embodiment has a gate line 104 as a scanning line, a source line 105 as a signal line, and an additional capacitance (Cs) line (not shown). is doing. The Cs wiring is for forming an additional capacitance by a later-described reflective electrode 11 and an overlapping portion (Cs on Com method), and is formed simultaneously with the gate line 104. Near the intersection of the gate line 104 and the source line 105, a bottom gate TFT (not shown) as a switching element is formed. As shown in FIG. 2, the TFT includes a gate electrode 41, an interlayer insulating layer 42, a semiconductor layer 43, a doped layer 44, a source electrode 45 and a drain electrode 46 formed on a rear substrate 10 made of glass. Yes. The pixel group 103 includes two pixels, a pixel A101 and a pixel B102, and the pixel A101 and the pixel B102 are designed to have different viewing angle characteristics. Specifically, the pixel A101 is set to have a wider viewing angle characteristic than the pixel B102.

  2 includes a concavo-convex structure layer 13, a reflective electrode 11, an insulating layer 14, a common electrode 12, and a partition wall 15 formed on the protective layer 47. The pixel portion shown in FIG. On the surface of the reflective electrode 11, a concavo-convex structure layer 13 having a concavo-convex shape designed in a desired shape is disposed under the reflective electrode 11 so that micro-order concavo-convex can be formed. The reflective electrode 11 is formed of aluminum (Al) having a thickness of 100 nm, and the concavo-convex structure layer 13 is connected to the drain electrode 45 of the TFT through a contact hole. The insulating film 14 is made of a transparent insulating resin having a transmittance of 90% and a thickness of 500 nm, and is disposed between the reflective electrode 11 and the common electrode 12 to insulate the two electrodes. The common electrode 12 includes a double film of chromium oxide and chromium having a thickness of 150 nm, and is stacked on the insulating film 14. The common electrode 12 formed near the periphery of the reflective electrode 11 also has a function as a black matrix for the purpose of improving display contrast. That is, a region surrounded by the common electrode 12 corresponds to a pixel opening. Further, in the particle movement type display device in the present embodiment, a transparent insulating liquid 31 in which a large number of black charged particles 30 containing carbon black are dispersed is filled between the rear substrate 10 and the front substrate 20, and the insulating property is increased. The electrophoretic display device is configured to move the charged particles 30 in the liquid 31 according to an electric field. The concavo-convex structure layer 13 is designed to have a concavo-convex shape so that the pixel A101 and the pixel B102 shown in FIG. 1 have different viewing angle characteristics. The concavo-convex structure layer 13 is formed using a photosensitive resist. The size of the concavo-convex structure layer 13 is a hexagonal convex pattern having a diameter of 1 to 10 μm within the substrate surface. It is laid down.

  The operation of the particle movement type display device having the above configuration will be described below.

  In the above particle movement type display device, each signal sent from the outside is selectively inputted to the TFT, so that it is in a wide viewing angle state when used in an office or a presentation, and from other people when used in an airplane or train. Narrow viewing angle so that it cannot be seen. First, when a wide viewing angle state is set, a display signal is applied to the source lines 105 of the pixels A101 and B102 constituting the pixel group, and an arbitrary image is obtained by matching the viewing direction of the pixel A101 and the viewing direction of the pixel B102. Form. The common electrode 12 is inputted with a voltage of 0V. On the other hand, when performing display with a narrow viewing angle, the pixel A101 designed to have a wide viewing angle characteristic applies a display signal for performing black level display to the source line 105 and a display signal to the pixel B102. In this case, since an image is formed only with the pixel B102 having a relatively narrow viewing angle, an image with a narrow viewing angle can be displayed. In the display state described above, even if the input signal is turned off, the particle movement display device itself has a memory property, so that the displayed image is maintained without being erased.

  As described above, the particle movement type display device of this embodiment includes a pixel group composed of pixels having different viewing angle characteristics, and the reflection electrode potential of each pixel can be independently controlled by the TFT. Therefore, it is possible to switch between the wide viewing angle state and the narrow viewing angle state. Further, since the particle movement type display device has a memory property, the display state is maintained even when the signal from the outside is turned off. As a result, a particle movement type display device that is lightweight and thin, has low power consumption, and can switch the viewing angle according to the use of the operator can be obtained.

(Example 2)
The present embodiment is a particle movement type display device having a pixel group composed of four pixels. Each of the four pixels includes a TFT in the same manner as in the first embodiment, and each pixel can be independently controlled by an external signal. Further, in the particle movement type display device in this embodiment, a color filter is provided on the reflective electrode 11 in order to perform color display. Although the color filter is not shown in FIG. 2, the color filter is laminated between the insulating layer 14 and the reflective electrode 11. The pixel group is composed of pixels capable of displaying red, blue, green, and white colors, and color filters made of a resin material containing a pigment are disposed in the red, blue, and green pixels. The concavo-convex structure layer of each pixel is designed so that the white pixel has a wider viewing angle than the other three pixels.

  By the way, in designing the viewing angle characteristics of the white pixel, the following matters are taken into consideration. Unlike the red, blue, and green pixels, the white pixel has no color filter and thus has a relatively high reflection efficiency for incident light. For this reason, when the viewing angle characteristics of white pixels are the same as those of red, blue, and green pixels, the entire image is likely to be blurred white. For this reason, in the white pixel, the viewing angle characteristics are designed by adjusting the display color balance. Further, in the same manner as in the first embodiment, in order to perform display in which the viewing angle characteristic is controlled according to the use of the operator, the red angle is compared with the viewing angle characteristic of the image when the display including white pixels is performed. Display made only of blue, green pixels has narrower viewing angle characteristics.

  The operation of the particle movement type display device having the above configuration will be described below.

  In the above particle movement type display device, each signal sent from the outside is selectively inputted to the TFT, so that it is in a wide viewing angle state when used in an office or a presentation, and from other people when used in an airplane or train. Narrow viewing angle so that it cannot be seen. First, when a wide viewing angle state is set, a display signal is added to the source lines of all pixels including white pixels constituting the pixel group, and an arbitrary image is obtained by matching the viewing directions of all pixels included in the pixel group. Form.

  The common electrode 12 is inputted with a voltage of 0V. On the other hand, when displaying a narrow viewing angle, a white pixel designed to have a wide viewing angle characteristic applies a display signal for displaying a black level to the source line, and applies a display signal to the other pixels. In this case, since an image is formed only with pixels having a relatively narrow viewing angle, an image with a narrow viewing angle can be displayed. In the display state described above, even if the input signal is turned off, the particle movement display device itself has a memory property, so that the displayed image is maintained without being erased.

  As described above, the particle movement type display device of this embodiment includes a pixel group composed of pixels having different viewing angle characteristics, and the reflection electrode potential of each pixel can be independently controlled by the TFT. Furthermore, by providing white pixels, it is possible to switch between a bright wide viewing angle state and a narrow viewing angle state. Further, since the particle movement type display device has a memory property, the display state is maintained even when the signal from the outside is turned off. As a result, a particle movement type display device that is lightweight and thin, has low power consumption, and can switch the viewing angle according to the use of the operator can be obtained.

The figure for demonstrating the structure of the particle movement type display apparatus which concerns on this invention. FIG. 7 is a diagram for explaining a pixel structure of a particle movement type display device according to the invention.

Explanation of symbols

10 Back board
11 Reflective electrode
12 Common electrode
13 Uneven structure layer
14 Insulating layer
15 Bulkhead
20 Front board
30 charged particles
31 Insulating liquid
41 Gate electrode
42 Interlayer insulation layer
43 Semiconductor layer
44 doped layer
45 Source electrode
46 Drain electrode
47 Protective layer
101 pixels A
102 pixels B
103 pixel group
104 Gate line
105 source line

Claims (15)

  A substrate, a closed space containing at least one kind of a plurality of particles disposed on the substrate surface, and a reflective layer that reflects light incident on the closed space, wherein the plurality of particles are arranged in the substrate surface direction. In a particle movement type display device that diffuses or accumulates the plurality of particles in at least a part of the closed space to change a reflection condition of incident light in the reflection layer, thereby forming at least two bright and dark display states. A particle movement type display device comprising: a diffuse reflection means in which a viewing angle characteristic is designed for each pixel of a pixel group composed of a plurality of pixels.   2. The particle movement type display device according to claim 1, wherein in the diffuse reflection means, at least one pixel in the pixel group has a viewing angle characteristic different from that of other pixels.   3. The particle movement type display device according to claim 1, wherein in the pixel group, only a pixel displaying a specific color has a viewing angle characteristic different from that of other pixels.   4. The particle movement type display device according to claim 3, wherein only the pixel displaying white has a wider viewing angle than the other pixels.   The particle movement display device according to claim 1, wherein the pixel group includes a plurality of pixels that display the same color and have different viewing angle characteristics.   2. The particle movement type display device according to claim 1, wherein the display is performed by switching the viewing angle characteristics.   7. The particle movement type display device according to claim 6, wherein display is performed using only pixels having a narrow viewing angle characteristic.   7. The particle movement display device according to claim 6, wherein display is performed using only pixels having a wide viewing angle characteristic.   7. The particle movement type display device according to claim 6, wherein display is performed using pixels having a plurality of viewing angle characteristics.   2. The particle movement type display device according to claim 1, wherein the plurality of particles are charged particles and are dispersed in an insulating liquid and disposed in the closed space.   2. The particle movement type display device according to claim 1, further comprising at least one color filter, wherein the color filter is formed on at least a part of the reflective layer.   The particle movement type display device according to claim 1, wherein the at least one kind of particles is substantially black.   The particle movement type display device according to claim 1, wherein a forward scattering layer is provided on an observer side.   14. The particle movement type display device according to claim 1, wherein the reflective layer is a metal electrode formed on the substrate.   The substrate includes a scanning line and a signal line arranged so as to cross each other, and a switching element arranged in the vicinity of the intersection of the scanning line and the signal line, and the metal electrode is electrically connected to the switching element. The particle movement type display device according to any one of claims 1 to 14, wherein the particle movement type display device is connected.

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