JP5572282B2 - Display device and manufacturing method thereof - Google Patents

Description

At least one of them forms a cell with a dispersed system in which charged or magnetized fine particles are dispersed in a liquid, liquid crystal or gas medium between transparent substrates, and the fine particles are moved by a transverse electric field or a transverse magnetic field. In order to move the fine particles in a horizontal direction in a lateral particle movement type display device that changes the light transmittance in the vertical direction to the substrate of the cell by modulating the amount of the fine particles in a dispersed state, The drive electrode and the common electrode are composed of a pair of comb-shaped parallel plate electrodes whose main surfaces are opposed to each other, and are configured to form a substantially uniform lateral electric field between the electrodes. An area ratio defined by a value obtained by dividing the light shielding area by the electrode in one pixel by the pixel area of the flat plate electrode is 20% or less, and the area of the plane parallel to the substrate of the flat plate electrode (Δs)
The area ratio (Δs / Δz) of the area (Δz) of the principal surface perpendicular to the surface is 0.2 or less, the pitch P between the parallel plate electrodes is 5 to 100 μm, and the cell gap d is 0.5 to 2.0 of the pitch P. It is a display device characterized in that it is set to double, and it is an enlarged projection display that uses a high-definition small panel as a light valve, a small to meter-size direct-view display device, thin flexible black and white and full-color electronic paper display, It can be applied to a wide range of display sizes up to a very large display device in which a large number of basic cells or basic panels are arranged two-dimensionally, and also relates to a display device applicable to reflection only, transmission only, or both reflection and transmission, and its manufacturing method. is there.

A typical thin display device is a liquid crystal display device, which is provided with a three-color filter of monochrome, red (R), green (G), and blue (B), and changes the transmittance of the corresponding liquid crystal layer. It is operated as a shutter, and a full color is realized by a color adding method of R, G, B light. A transmissive color liquid crystal device provided with a white backlight behind is widely used for liquid crystal TVs, personal computer monitors, mobile phone display devices, and the like. However, a serious difficulty of the liquid crystal display device is an optical loss of more than 50% due to the use of the polarizing plate, and an R, G, B color filter is juxtaposed for realizing a full color display, and further 2/3 rays. It is a loss.

As another display device, there has been proposed a horizontal electric field particle movement display method in which light transmittance is changed by moving and accumulating fine particles dispersed in a transparent liquid or gas body in a horizontal direction with respect to a display surface (Patent Document). 1-13). As shown in FIGS. 1A and 1B, a dispersion system in which charged fine particles are dispersed between a transparent substrate 1 provided with a transparent counter electrode 3 and a substrate 2 provided with a collect electrode 4 is provided. The light transmittance of the cell is changed depending on whether a particle is deposited on the counter electrode 3 by applying a voltage between the electrodes 3 and 4 or accumulated on the collect electrode 4 having a small area. It is said. That is, when the fine particles are black light-absorbing, the dark state is obtained in (A) and the light state is obtained in (B). FIGS. 1C and 1D show a case where the transparent counter electrode 3 is formed on the same plane as the collect electrode 4, and the operation is the same as (A) and (B).

Other configurations are shown in Figure 2. Here, the collect electrode 4 is formed of a mesh electrode, and the particles are deposited on the transparent counter electrode 3, or in a dark state when dispersed, and in a bright state when deposited on the mesh collect electrode 4 .

The electrode configuration and the display mode as shown in FIGS. 1 and 2 have serious problems in that the drive voltage increases and the response speed decreases. Further, the most important light transmittance and light blocking rate as an electronic shutter have not been sufficiently considered. In the conventional configuration of FIG. 1, the particles in the middle of the collect electrodes 4 at both ends (that is, the cell center) have a weak electric field and are long to bring these particles on the collect electrode or the counter electrode center during light and dark. It is necessary to move the distance, and there is a problem that the switching time (response speed) between light and dark is extremely deteriorated. In addition, since it is difficult to deposit particles uniformly on a solid transparent counter electrode having a large area in a non-uniform electric field, it has been difficult to realize a display with excellent contrast. The electrode configuration and display mode as shown in FIG. 2 are excellent in that the electric field strength is surely made uniform in the pixel plane. In addition, the use of a state in which particles are not uniformly accumulated on the counter electrode but a state in which particles are dispersed substantially uniformly is also used for improving the responsiveness. However the electrode area ratio of the mesh electrode is an important parameter in order to provide excellent bright state transmittance, the cross-sectional shape, the electrode pitch of the electrode, the dispersion particle amount, high contrast because they have not been sufficiently studied cell thickness, etc. Therefore, it could not be a practical display device that realizes high transmittance, low voltage drive, and high-speed response.
JP 49-24695 A Japanese Patent Laid-Open No. 03-91722 USP 5,745,094 JP 9-2111499 A JP2001-201770 JP2004-20818 Special Table 2005-500572 JP-A-2002-333643 JP2003-248244 JP2005-3964 JP2004-258615A JP 2004-252277 A JP 2002-122890 A

It is desirable for the display device to have a high response speed. In the case of the particle movement display method, an electric field strength of about 0.2 to 2 V / μm is usually required to realize a practical response speed. There are various sizes of pixels of a display device depending on applications. Since the light valve used for enlarged projection requires small size and high definition, the pixel size may be 10 μm or less. On the other hand, in a public display installed indoors or outdoors, there are cases where the pixels are in the order of centimeters. In this application , the horizontal particle movement display is applied to pixels of all sizes , and the practical characteristics are improved by optimizing important characteristics as a display such as transmittance, contrast, and response speed with a practical driving voltage. It has been made .

In order to solve the above-mentioned problems, the present invention is a particle movement display method using a transverse electric field or a transverse magnetic field as in the prior art, but it is a novel method that improves the response speed, reduces the driving voltage, and particularly improves the transmittance and contrast. The present invention proposes a cell configuration and relates to the improvement of the inventor's Japanese Patent Application No. 2007-506602.

As shown in FIGS. 3A and 3B, the basic cell of the present invention is shown in a cross-sectional view and a partial perspective view in FIG. A cell 8 is constituted by a partition wall 20 provided therebetween, and the cell is filled with a dispersion system 7 in which fine particles 5 are dispersed in a transparent medium, and a pair of narrow and long plate-like electrodes 6-1; 6-2 is provided on the entire surface of each cell to constitute a cell 8. As shown in FIG. 3A, in the state where black light absorbing fine particles 5 such as carbon black or white high light scattering fine particles 5 such as titanium dioxide are dispersed in the cell 8, light incident from the transparent substrate 2 is If the hiding power of the fine particles 5 is sufficient, the incident light is blocked by the fine particles and becomes black.

If a DC voltage is applied between the electrodes 6-1 and 6-2 as shown in FIG.
, 6-2, the fine particles 5 move along the electric lines of force, and accumulate on the side surface of the negative electrode 6-1 when positively charged. The regions other than the electrode 6-1 on which the particles are integrated and the electrode 6-2 on which the particles are not integrated have nothing to block light and are transparent. Here, an appropriate D of opposite polarity between 6-1 and 6-2
When a C voltage pulse or an AC voltage is applied, the fine particles on 6-1 redistribute in the cell 8 after leaving the electrode, and the cell 8 becomes opaque again. In this way, by changing the amount of dispersed particles in the cell 8 (and hence the amount of particles accumulated in the 6-1), the transmittance in the direction perpendicular to the substrate of the cell 8 can be continuously changed. The display has a memory property in order to maintain the state after being cut. The dispersion system 7 includes a transparent liquid, a transparent liquid crystal body, and a gas body in which positively or negatively charged fine particles are dispersed. When the dispersion medium is a liquid or liquid crystal, the movement of the particles is called electrophoresis. The electrodes 6-1 and 6-2 are used in a comb-like configuration as shown in the front view of FIG. Both in even plane parallel narrow the substrate, side features there Ru that is equally large area substantially cell gap height.

In the present invention, the electrode 6-1 for accumulating particles is called a drive electrode, and the other electrode 6-2 is called a common electrode. Plate-like drive electrodes are present on the entire surface of the cell, and particles can be repeatedly accumulated and dispersed depending on the direction and the charged polarity of the particles by a substantially uniform lateral electric field between the common electrodes 6-2. This particle movement display method is termed a horizontal (lateral) electric field type particle movement display method. As is clear from FIG. 3B, it is an important feature that the fine particles can be deposited on both side surfaces of the driving electrode having a large area. If the pitch between the electrodes is appropriately selected, low voltage driving can be achieved particularly when the pixels are larger than in the case of FIG. 1 in which electrodes are provided only in the periphery of the cell.

As shown in FIG. 5, the area of the plane parallel to the substrate of one plate-like drive electrode 6-1 on which particles can be deposited is Δs, the area of the plane perpendicular to the substrate is Δz, and in this application, Δs / Δz is driven. This is called the electrode aspect ratio. It is also the ratio of the plate thickness to the height. The present application is characterized by the use of a drive electrode having a low aspect ratio, and in the particle deposition state (bright state), dispersed particles are thinly deposited on the side surface (Δz) of the large area of the drive electrode. Since the shielding effect is small, a high transmittance of the cell can be realized. When the pixel area excluding the partition wall is S and the number of electrodes in one pixel is n, Δs × n is the light shielding area by the electrodes themselves. The ratio of pixel area of the light shielding area due to the electrode that have named in the present application as electrode area ratio. For example, a pixel area of 100 μm square, an electrode thickness of 2 μm, and a height of 100 μm (Δs = 200 μm)
Electrode area ratio if ²⁾ if provided this 4 is 8%. In the cell configuration of the present application, a common electrode with a small aspect ratio is opposed to the drive electrode, so the light shielding by the common electrode is small, and the uniformity of the electric field between both electrodes is also good, so high-speed, high transmittance display This is a configuration suitable for realizing the above. The thickness of the plate electrode depends on the pixel size, cell gap, manufacturing method, and mechanical strength, but is usually 0.1-30 μm, preferably 0.2-20 μm. The cell thickness is 5 to 150 μm, preferably 10 to 100 μm as described later, and therefore the aspect ratio Δs / Δz is suitably 0.2 or less.

In FIG. 3, it is assumed that the particles have positive or negative single polarity. Certainly, in the conventional configuration shown in FIG. 1, it is clear that satisfactory bright transmittance and display contrast cannot be obtained unless the particles have a single polarity, and the use of a single particle system was an essential condition. However, in the case of the present application in which the particle dispersion state is the dark state with the configuration of FIG. 3, a bipolar dispersion system in which positive and negative particles are mixed can be used effectively. That is, positive and negative particles are deposited on both side surfaces of the electrodes 6-1 and 6-2 except for the electrodes provided on the partition wall in the bright state, and the deposited area is large, so that the thickness of the adhered particle layer can be reduced. High transmittance can be realized in the state. Since Δs is small, an opaque material can be used for the common electrode, and the degree of freedom in selecting an electrode material is increased. In (0010), the electrode on which particles are deposited is defined as the drive electrode. However, in the bipolar dispersion system, the common electrode also deposits particles. In this case, the common electrode also becomes the drive electrode.

When the dispersion medium is a so-called aerosol dispersion system in which the dispersion medium is a gas, the charge of the particles is mainly frictional charge between the particles. Therefore, the bipolar dispersion system is superior in the charge stability of the particles. One of the advantages.

As a method for forming an electrode having a small width and a small aspect ratio in the cell thickness direction on the substrate surface side as shown in FIG. 5, electroforming, conductive polymer or conductive fine particles dispersed in resin Various technologies such as micro-shaping of conductive paint and micro-processing of metal foil and metal thin film can be used.

As an example, as shown in FIG. 6, an electrode and a wiring pattern are formed in advance on the substrate 2 (A), a resist pattern is formed thereon (B), and a resist-free hole on the electrode pattern is formed by electroforming. A method of filling with metal (C) and then removing the resist (D) can be used. In general, LIGA process (meaning fine processing by Lithographie, electroplating (Galvanoformung), forming (Abformung) using X-ray in German) as a method of making a narrow hole in the vertical direction in a thick resist What is called is effective. In other words, irradiate a portion of the thick resin layer, such as polymethyl methacrylate (PMMA), where there is no metal mask layer with synchrotron radiation that has high transparency and excellent straightness, to make PMMA low-molecular and easily soluble. Thus, a fine and sharp hole can be provided in the substrate in the vertical direction. After filling the hole with metal by electroforming, the PMMA may be dissolved and removed leaving a partition wall as shown in FIG.

Using FIG. 6 (D), a new mold with a new thin film electrode can be used to produce a large number of replicas of FIG. 6 (D) by electromolding.

The male layer as shown in FIG. 6 (D) made of a rigid substrate such as ceramic, glass, metal, etc. is made using the LIGA process instead of directly using FIG. 6 (D), and the heat-softened resin layer or uncured UV resin The resin layer is pressed into a female shape, and after the resin layer is cured, the residual resin on the electrode is removed by RIE (reactive ion etching) and post-electroforming is performed, as shown in FIG. A male electrode configuration may be realized. Of course, when the height of the electrode is not large, it is possible to form a perforated resist pattern as shown in FIG. 6B by employing a normal photoresist or an electron beam exposure process.

On the other hand, the porous resin layer as shown in FIG. 6B is filled with a conductive polymer or conductive paint instead of electroforming and cured, and then the original resin layer is dissolved and removed to form the electrode with the cured conductive resin. You can also

A female die as shown in FIG. 6B is made using a substrate having high heat resistance such as ceramic or glass, and the hole is filled with fine metal powder or conductive toner fine powder, and then heated and melted to form a conductive structure. May be transferred to a substrate provided with a thin film electrode.

The second method of forming the plate electrode is to provide a conductive resin or conductive paint layer before curing on a substrate provided with a thin film wiring, and press a female die directly on this to process it into a male shape. The conductive resin layer is removed and then cured by heating or UV irradiation to form an electrode structure as shown in FIG. In order to improve the releasability of the resin from the mold, it is necessary that the inner surface of the mold is subjected to a release treatment such as a fluorine treatment.

As shown in FIG. 7, the third method for forming the plate-like electrode is to prepare a female die 30 having a recess at a predetermined location on a rigid substrate. This is covered with a metal foil, or the metal thin film 31 provided on another release substrate is transferred to the female mold 30 (A). Next, it is pressed from above with a specially designed male mold, and the metal film is bent at right angles to the electrode shape. Of course, it is also preferable to partially pattern the metal film before pressing so that the metal film can be easily bent by photoetching, laser drawing, or a punching die. Next, the hole portion is filled with resin, and unnecessary resin or metal film on the surface is removed by etching or polishing, and then a metal film is provided by vapor deposition or sputtering, and necessary electrodes are interconnected. Then, after transferring to the substrate 2 provided with an adhesive layer, the resist remaining between the electrodes is dissolved and removed, whereby an electrode structure on the substrate 2 as shown in FIG. 6D can be formed.

A fourth method for forming the plate-like electrode is a printing transfer method. In other words, a low-viscosity conductive resin or paint is filled in the concave part of a female mold made of a rigid body with a squeegee or the like (under reduced pressure if necessary), and then temporarily cured, and printed and transferred to a substrate on which metal wiring is formed. It is suitable for mass productivity by post-heating or UV-curing. Mold release treatment is indispensable.

In the fifth method, a block is formed by laminating a large number of sheets each provided with an electrode and a wiring film on a film via an adhesive layer. The laminated surface is polished and attached to a substrate provided with an adhesive, and sliced to a thickness corresponding to a cell gap of several tens of μm. An electrode thin film is formed on the slice surface and patterned, and then transferred to the final substrate to obtain the structure of FIG. Thereafter, the film may be dissolved and removed.

As mentioned above, narrow and tall plate electrodes were provided not only for electroforming of metals and metal alloys such as nickel, chromium, gold and copper, but also for printing of conductive resins and conductive paints, ink-jet drawing, etc. Photoetching of conductive thick films, microembossing, metal mold micromolding, and electrode structure printing and transferring methods can be used effectively.

When the fine particles are accumulated on the drive electrode, it is not preferable that the fine particles adhere to and remain on the inner surfaces of the upper and lower substrates because the light transmittance in the bright state of the cell is inhibited. Therefore, it is desirable that this portion of the cell is coated with a low surface tension substance such as a fluorine compound or the like so as to prevent the fine particles from sticking, or in the case of a single particle system, a surface treatment is performed so as to be charged to the same polarity as the particles. Further, when the dispersion medium is a liquid, it is desirable that the specific gravity of the fine particles and the liquid be as close as possible because it is difficult for the particles to settle or float.

In the present invention, the particle dispersion state that creates a dark state is a colloid state in which fine particles are stably dispersed uniformly in the liquid regardless of the specific gravity due to Brownian motion. This includes a state in which the particles are loosely adhered and a state in which the particles are loosely aggregated to form a three-dimensional network structure between the two substrates or between the two electrodes. The fine particles need not be of one type, and various types of fine particles may be mixed in order to optimize the optical characteristics.

The fine particles 5 are usually light-absorbing, but it is also possible to use white reflective ones such as titanium dioxide. In the case of using white reflective particles, if the back substrate 2 side of the cell 8 is black, for example, a reflective display device that is in a bright state in a fine particle dispersed state and a dark state in a state where particles are accumulated on an electrode. Can be realized.

In a passive display device such as the present application, what determines display performance is transmittance, contrast, color purity, response speed, resolution, viewing angle, and the like, and driving voltage and power consumption are also important factors for the device. In the display device as shown in FIG. 3, the transmission contrast is determined by the transmittance in the particle dispersion state (dark) and the transmittance in the particle accumulation state (bright). In particular, creating a sufficiently dark state is an essential requirement for improving contrast. In order to achieve a contrast of 1000: 1, 100: 1, 10: 1 or more, the transmittance in the particle dispersion state of the cell is 0.1% (optical density 3 or higher), 1% (optical density 2 or higher), 10 % (Optical density of 1 or more). In the cell configuration of the present application, it is very easy to set the transmittance in the dispersed state to the above value by increasing the particle concentration of the dispersed system. However, increasing the particle concentration generally causes problems such as slowing of the moving speed of the particles and easy deterioration of the light transmittance, so it is not a good idea to increase the particle concentration unnecessarily.

The cell transmittance in the bright state at the time of particle accumulation in this display device will be described with reference to FIG. Assume that all the particles in a dispersion system in which fine particles are dispersed at a concentration that provides sufficient penetration are accumulated on the upper substrate (assuming that all particles are accumulated on one side substrate anyway even if the particles are bipolar). The thickness of the particle layer at this time is h, and the area of the pixel is S (A). In the bright state where the total area of the electrodes for depositing particles in one pixel is Δz × n (where n is the number of surfaces on which particles can be deposited in one pixel) and all dispersed particles are accumulated in Δz × n, The thickness e of the particle layer on the electrode is h * S / Δz / n (B). For example, the penetration force of normal carbon black is measured to be 9300 cm ² / g. Since the density is about 1.7, the solid layer is only 0.63 μm. In an actual deposited particle layer, there are inter-particle voids and the like, so the thickness of the particle layer is considerably larger than this, but at most several μm thick. Even if the particle layer thickness h = 3 μm (porosity = 78%), in the cell configuration with S≈Δz and n = 4, only e = h / 4 = 0.75 μm. That is, in the example of the 100 μm square cell described in (0011), the light transmittance of the cell is (100 ² −2) because the 2 μm thick electrode is equivalent to 2.75 μm thick in the bright state at the time of particle deposition. .75 × 100 × 4) / 100 ² = 89% A preferable high transmittance can be realized. When the electrode thickness is 0.5 .mu.m and 5 .mu.m, transmittances of 95% and 77% are obtained, respectively, so that high contrast can be realized at the same time. Of course, it should be noted that the smaller the pixel, the thinner the electrode thickness.

Lowering the particle concentration generally increases the moving speed of the particles. If the dispersion system is thickened , the hiding property can be increased even at a low particle concentration (g / cm ³ ), and high speed and high contrast can be easily realized. However, the thicker the cell and the narrower the electrode pitch, the greater the absorption loss of obliquely incident light and the lowering of luminance due to parallax.

FIG. 9A shows the relationship among the cell gap d (approximately the electrode height), the electrode pitch P, the backlight radiation angle θ, and the lower substrate thickness H. The dispersion system is bipolar, and the particles are driven and deposited on both sides of the common electrode. Also, only the component in the plane perpendicular to the inner electrode surface of the emitted light is discussed. Components of θ1, θ2,... Θn are deposited in light rays exceeding the angle θ (= tan ⁻¹ (P / (H + d))) from the internal line of the backlight radiated light from the point A on the lower surface of the lower substrate. It is absorbed by the particle layer and cannot be emitted to the outside, resulting in a loss. As is clear from FIGS. 9B and 9C, the smaller the substrate thickness H, the thicker the gap d, the smaller the θ, that is, the narrower the viewing angle, unless the electrode pitch P is increased. In the case of using the reflection type, if the substrate 2 is made reflective, the light beam that becomes reflected light from the point B and becomes a loss is reflected light that exceeds θR (> θ). , Tan (θR) = P / d, the gap d is large and θR is small. If the pitch P is not increased, the viewing angle becomes narrow and the loss increases. When used in transmission, the light loss is greatly improved if the backlight is converted into parallel light with a prism sheet (<θ = tan ⁻¹ (P / (H + d))) as used in a liquid crystal display.

The dependence of the viewing angle characteristics of the luminance of the display device on the cell gap d and the electrode pitch P will be described with reference to FIG. As shown in FIG. 10, when the display device is viewed from the direction of the angle θ from the perpendicular to the electrode substrate surface (assuming that the backlight radiated light or reflected light is completely diffused light), FIG. The ΔP region (corresponding to the Δθ region in the figure) in the inter-electrode region P of FIG. When the ratio (ΔP / P) of the shaded area ΔP with respect to the interelectrode area P is the luminance reduction ratio F, F = d × tan (θ) / P. Naturally, as seen in FIGS. 10B and 10C, the luminance loss F increases as the angle θ increases, the pitch P decreases, and the gap d increases. This indicates that there is a limit to increasing the cell gap in order to achieve high speed and high contrast at a low particle dispersion concentration, and there is also a limit to reducing the electrode gap for low voltage and high speed driving. As a compromise, the cell thickness is preferably about 100 μm or less, and the electrode pitch p is preferably 0.5 to 2 times the cell gap d.

FIG. 11 shows an example of a voltage waveform applied between the drive electrode and the common electrode in order to create a particle dispersion state from the particle accumulation state. When the dispersion system is a single particle system, a reverse voltage having an appropriate pulse width with which the particles leave the drive electrode is applied (A). An AC voltage (B) that gradually increases in frequency regardless of a single particle system or a twin particle system, and an AC voltage (C) that attenuates the peak value. A combination of (B) and (C) is also effective.

In FIG. 3, the particles are confined inside the cell by the partition wall 20 in order to prevent the fine particles from moving to the adjacent cell and to maintain the particle concentration in each pixel constant. Further, as long as the cell is made small, there is a merit that the specific gravity difference between the dispersion medium and the particles does not become an obstacle.

Instead of confining the dispersion system in the cell with the partition walls, the dispersion system may be confined inside the capsule particles. FIG. 12 shows a display device of the present invention using capsule particles. A display sheet having an excellent aperture ratio can be obtained by transforming substantially spherical capsule particles into a rectangular parallelepiped as shown in the figure using a spacer material of an appropriate size. In the display sheet of FIG. 12, the electrode is not in direct contact with the dispersion system. However, as in FIG. 3, the particles can be collected on the inner wall of the capsule corresponding to the side surface of the electrode or dispersed in the capsule particle to modulate the transmittance. However, since the capsule wall and the binder resin layer are interposed between the electrode and the dispersion system, voltage attenuation occurs somewhat, leading to an increase in driving voltage. Therefore, it is desirable to keep these insulating or semiconductive layers as thin as possible. In FIG. 12, without using the upper substrate 1, the capsule particles may be deformed by covering the capsule particle layer and the binder particles may be cured by UV irradiation. After that, the rigid substrate is peeled off and a protective film is applied. A single substrate display sheet can be formed.

Particularly in the case of a flexible sheet display using a film as a substrate, it is preferable that both substrates are bonded to each other through a partition wall. In the case of the capsule particle system, since the binder resin is filled between the capsule particles, if the binder resin is cured with UV or the like after being sandwiched between the two substrates, it plays a role of bonding the two substrates.

In the present invention, a cell refers to a region in which a dispersion system is confined by a partition wall or a capsule. A pair of electrodes as shown in FIG. 4 may be provided in one cell, or may be provided in one set for many cells as in the case of a capsule particle system. A pixel refers to a region having a pair of electrodes as shown in FIG. 4 and may be a single cell or a number of cells.

A full-color display panel can be constructed by stacking three layers of cells as shown in FIGS. However, the three layers of fine particles 5 are C (cyan), M (magenta), and Y (yellow). FIG. 13 shows a cross section of a full-color display panel using a C, M, Y capsule particle system. Here, one pixel is composed of 3 × 3 × 3 capsule particles, and it is assumed that an electrode pair as shown in FIG. 4A is used for each color modulation electrode. If Y and M particles are in a moderately dispersed state and C particles are in an electrode-integrated state, that portion is R (red), and if C and M particles are in a moderately dispersed state and Y particles are in an electrode-integrated state, the same subtractive color mixture Thus, B (blue), Y, and C particles become G (green) in a dispersed state. Of course, only C particles, M particles, and Y particles have C, M, and Y colors in a dispersed state, respectively. In addition to the C, M, and Y panels, a fourth color modulation layer that can be modulated to white-black in order to block light more completely may be added to form a four-layer structure. Further, the cell stacking order can be arbitrarily selected. When the white backlight 13 is turned off, it can be used as a reflective color panel or a transmissive color panel with a white diffuser and white backlight. In multi-color display, a two-layer structure of dispersed systems having different colors may be used.

In the color panel of FIG. 13 excluding the intermediate substrate, in addition to the loss due to the electrodes of each layer, the angle of the light beam that can pass through the three layers is limited and the viewing angle becomes a problem, so the cell thickness is reduced. The electrode pitch must be increased. The use of a light-reflecting reflector with increased reflection intensity in the vertical direction as a reflector is a desirable means for obtaining a bright color image at the expense of viewing angle characteristics.

In a display device in which a large number of cells are stacked, attention should be paid to interface reflection. Interface reflection always occurs at interfaces having different refractive indexes. Multilayer display cells consist of a large number of layers (substrate, dispersion medium, capsule wall, binder resin, etc.). Of course, they are made of materials with the same refractive index as much as possible to reduce unnecessary interface reflections. It is important to.

There are (1) static (2) simple matrix (3) two-terminal active matrix (4) three-terminal active matrix and the like as a driving method of a display device composed of a large number of pixels.

FIG. 14 shows an example of a process for manufacturing a panel having a simple matrix configuration. An electrode thin film made of aluminum, chromium, gold or the like is provided on a substrate 2 such as glass or plastic by vapor deposition or sputtering, and a column electrode Ci and a drive electrode 6-1 connected thereto as shown in FIG. Form. Next, the insulating layer 23 is formed at least at a predetermined position of the column electrode, and then the common electrode 6-2 and the row electrode Ri are formed (B). Hereinafter, various methods can be applied to the method of forming the plate-like electrode as shown in FIG. For example, after forming a perforated resist layer as shown in FIG. 6B at a predetermined portion of the electrode film made of fine wires, the electrode film is grown in the vertical direction by electrolysis or electroless plating, and then dissolved and removed leaving the partition wall. A simple matrix display panel is formed by filling the dispersion with the upper substrate. In the case of using the method of transferring an electrode structure provided on a separate substrate in advance to the thin film electrode surface in FIG. 14B, the electrode surface must be previously subjected to a treatment such as solder plating. A signal is applied to the column electrode Ci, and a scanning signal is applied to the linear common electrode Ri, so that display is performed in a line sequential manner. Although the panel configuration is simple, there is an advantage that it can be manufactured at a low cost. However, since each pixel is required to have a threshold characteristic, it cannot normally be used for applications with a large display capacity.

In order to increase the display capacity, it is necessary to adopt an active matrix (hereinafter abbreviated as AM) configuration. FIG. 15 shows a manufacturing process of a two-terminal AM array composed of a so-called MIM (Metal Insulator Metal) element in which an anodized film is sandwiched between metal electrodes. After forming parallel linear column electrodes Ci on a substrate with a metal thin film such as aluminum or tantalum, the column electrodes Ci are anodized to form an oxide film on the surface (A). Then, a metal film is provided by vapor deposition or sputtering to form, for example, a comb drive electrode 6-1 (B). A two-terminal element 21 is formed in a region where the drive electrode and the column electrode intersect. Next, the insulating layer 23 is formed at least at a position where the column electrode intersects the row electrode later, and then the common electrode 6-2 and the scanning electrode Ri are formed (C) to form a two-terminal AM array. The display panel is constructed by driving the common electrode in the vertical direction on the substrate with electrodes thus obtained as described in (0042) and sandwiching the dispersed system or capsule particles between the upper substrate. Instead of MIM, a two-terminal AM array can also be formed by sandwiching a non-linear resistance element in which a semiconductor such as zinc oxide is dispersed in a resin at the intersection of electrodes 6-1 and Ci.

Next, a configuration of an AM panel in which each pixel is provided with a TFT switching element is shown. TFT (Thin) as shown in FIG.
film transistor) to form a three-terminal element AM array. The drive electrode 6-1 separated from the signal line Ci by an insulating layer is connected to a drain (D) electrode, and the source (S) electrode is a part of the column electrode Ci, and a semiconductor between S and D is a semiconductor. The gate insulating film is laminated. A three-terminal AM array is formed by providing an interlayer insulating film in the column electrode portion and then providing a row electrode Ri (gate electrode). The common electrode 6-2 is separated from the column electrode and the row electrode by an insulating layer, and extends over the entire panel like the column electrode or the row electrode, and is taken out of the panel as one terminal common to all pixels. A panel can be formed in the same manner as described above after driving and common electrodes are grown on the AM array layer thus obtained as described in (0042). In FIG. 16, the TFT is shown as a staggered type, but an inverted staggered type TFT is of course possible.

There are roughly three methods for manufacturing an active matrix panel having a color modulation layer laminated structure as shown in FIG. That is, (1) the C, M, Y capsule particle driving AM array is all formed on the substrate 2 (in the case of an opaque TFT, it is desirable to be provided under the partition wall or spacer portion in order to improve the aperture ratio). Next, (a) formation of a holed resist layer for growing the first layer electrode and the next layer drain terminal (b) removing the resist after growing the first color electrode and drain terminal, and (c) filling the first color capsule particles between the electrodes. (D) Smooth layer formation (e) Second color drain terminal portion opening (f) Metal film formation (g) Second layer drive, common electrode patterning Thereafter, the above (a) and subsequent steps are repeated for the number of colors. (2) AM array and capsule particle layer filling ⇒ Method of laminating smooth layer formation in sequence for each color (3) After peeling layer, AM, electrode, capsule particle filling and smoothing on transfer rigid substrate, bonding A method such as laminating three layers by sequentially transferring each color panel to the final substrate side provided with layers is used.

For example, a large-sized display system composed of M × m × N × n pixels can be constructed by arranging basic panels composed of vertical M pixels and horizontal N pixels as described above, for example, m vertical and n horizontal panels. It is possible to construct a low-power, high-definition full-color large-sized display system for both reflection and transmission of a curved surface type and several tens of meters in size.

FIG. 17 shows an AM reflection type light valve using a silicon substrate for use in a projector or the like. Forming an AM array of FET elements on the silicon substrate 15 ⇒ Forming an insulating smooth layer, forming a reflective film on the pixel section ⇒ Forming a transparent insulating layer ⇒ Opening a drain terminal portion of the FET ⇒ Forming a drive / common electrode (drive electrode and drain terminal) Through hole connection) ⇒ Growth in the vertical direction of the drive and common electrode ⇒ Dissolve and remove the resin leaving the partition walls ⇒ Fill the cell between the transparent substrate with the dispersion system. Thus, the partition wall type reflection light valve is formed. For example, when a light valve of 1 inch size and full HD (1920 × 1440 pixels) is configured, the pixel pitch is about 11 μm. If one drive electrode having a width of about 1 μm is provided at the center of the pixel and a common electrode is provided on the inner surfaces of both side partition walls, a light valve that can be driven at 10 V or less can be configured. It is desirable to make the partition wall 20 insulative black or to form a black matrix film between the upper substrate and the partition wall.

The reflection type light valve shown in FIG. 17 is configured by replacing the liquid crystal in a liquid crystal light valve called LCOS (liquid-crystal-on-silicon) with a fine particle dispersion system. Similar to LCOS, a white light source such as an ultra-high pressure mercury lamp is separated into R, G, B light by a dichroic mirror or prism, and R, G, B color light images obtained by irradiating each color light to the light valve in FIG. A full color image can be obtained by magnifying and synthesizing the image on a screen. If an LED or a semiconductor laser is used as the light source, a small projector can be configured. In addition to the front projector, a rear projector is possible by bending the optical path along the way. Although the pixel pitch is 1/3 of monochrome, it is possible to construct a single-plate color light valve by providing a color filter on the front surface, and if a three-layer laminated panel as shown in FIG. A single-plate color light bulb can be configured. As the dispersion system, either a partition wall type or a capsule type may be used. In the reflection type, the light beam passes through the dispersion layer twice, so that the particle concentration of the dispersion system is ½ that of the transmission type, and a high-speed response is possible.

Instead of the silicon substrate, an AM substrate in which an AM array is formed of polysilicon or the like on heat-resistant glass such as quartz, or a low-temperature polysilicon AM array formed on a glass substrate is used. A plate-type high-definition transmission type light valve can be configured.

FIG. 18 shows a sectional view of a transmission type full color panel using R, G, B juxtaposed color filters. The liquid crystal as the light valve of the current liquid crystal color panel is replaced with a dispersion system 7 in which fine particles capable of modulating transmittance in black and white are dispersed. The drive electrode of each pixel is connected to the drain terminal of the AM array, and the common electrode is connected to a common terminal for all pixels. If a backlight with a high degree of parallelism is used, the electrode pitch can be reduced and the cell gap can be increased. However, since the viewing angle is sacrificed, it is desirable to diffuse light at the front surface.

Although the configuration in which the R, G, and B color filters are provided in adjacent pixels has been described in FIG. 18, the dispersion medium of each cell may be colored in R, G, and B instead of using the color filters. However, it is necessary to provide each color cell in a stripe shape or a dot shape.

The color panel shown in FIG. 18 uses R, G, B juxtaposed color filters or R, G, B coloring liquids, so there is a defect that 2/3 of white incident light to the light modulation element is lost. The TFT array mass production process and equipment have the advantage that they can be used almost as they are, and they can be manufactured in any size from small to over 100 inches. Unlike a liquid crystal color panel, a viewing angle widening film, a polarizing plate, an alignment film, an alignment treatment process, etc. are unnecessary, and in addition to simplifying the process and reducing the number of members, a polarizing plate and a transparent electrode are unnecessary. Therefore, brighter display can be realized.

There are uses for electronic price tags, message displays, and the like that do not necessarily require full color display. FIG. 19 describes an example in which multi-color display is performed without using a color filter in a single-layer dispersion system. A dispersion system in which fine particles having different colors and moving speeds are mixed and dispersed in a transparent dispersion medium is used. That is, if a DC voltage is applied between the electrodes 6-1 and 6-2 (first pulse) and particles are deposited on one electrode (described in the case of particles of the same polarity) (FIG. 19A), The cell appears transparent (white when the reflector is white when viewed in reflection). If a reverse polarity DC pulse (second pulse) with an appropriate width or peak value is applied here, particles with fast moving speed (first particle: black) first leave the electrode and become dispersed. If is stopped, the cell looks black, which is a dispersed state of particles having a high moving speed (FIG. 19B). In the case of a reverse polarity pulse having a width or peak value larger than that of the second pulse, the first particles are accumulated on the counter electrode 6-2, and only the second particles having a slow speed (red) are dispersed in the dispersion system. Therefore, the cell looks almost red (FIG. 19C). If an appropriate AC voltage is applied between the electrodes, the first and second particles are both dispersed, and a red-black color, which is a mixture of these, is presented. That is, four colors can be selected on the single-layer panel. Even if fine particles having different colors have different polarities, they can be used as long as their moving speeds are different.

In FIG. 19, an example of multi-color display using the difference in the moving speed of the particles is described. However, depending on the properties of the particles, the dispersion medium and the electrodes, the particles deposited on the electrodes can be desorbed from the electrodes by applying a reverse polarity voltage. A threshold characteristic may appear. This threshold property difference between different color microparticles can be used effectively. The threshold values of the first and second particles are V1 and V2 (V1> V2), respectively. When the voltage V is V1> V> V2, only the second particles can be dispersed. When the voltage V is V> V1, the first particles are mainly used. This is because only a dispersed state can be produced. In addition, a mixed dispersion color can be obtained with an AC voltage of V> V1, and a difference in threshold value as well as a difference in migration speed can be effectively utilized for selective dispersion of particles, and a multi-color display can be achieved with a simple configuration panel. It becomes possible.

When forming a panel or laminated panel using thin film substrates, alignment of both substrates and each panel becomes difficult due to expansion and contraction due to the temperature and tension of the film. Both film substrates are pasted in advance on a rigid substrate such as glass with a size that assumes single or multiple pieces, and after forming processes such as electrodes, switch elements, partition walls, and spacers, between both films In addition, if the method of peeling the panel from the rigid substrate after filling the dispersion and forming the panel is taken, the difficulty of the process such as the vertical alignment of the electrodes due to the thinness of the film and stretchability is reduced. .

Even if the panel itself is flexible, if a drive circuit, a battery, or the like is mounted, the paper-like property of the display panel tends to be impaired. Since the display panel of the present invention has a memory property, once the display is updated, the display is maintained even if the driver is disconnected. Therefore, it is possible to adopt a panel / signal source separation method in which the panel electrode terminal portion or the signal supply circuit portion is exposed and connected to the signal supply source only when the display is updated, and the cost is low because no driver is mounted. This ensures the flexibility of the panel. Of course, if a thin film drive circuit is also provided on the film substrate, the number of terminals for supplying signals can be drastically reduced, which is convenient.

When a plastic film is used as the transparent substrate of the light modulation element used in the present invention, the feature of continuous mass production by roll-to-roll can be exhibited. For example, electrode film formation on lower film, patterning, conductive resin layer coating, electrode shaping with female die roll, removal of unnecessary resin layer on electrode, formation of insulating partition, filling with dispersion system between upper film, panel Resin sealing at the periphery, forming individual panels by punching, removing the peripheral film with a laser or cutter, and exposing the electrode extraction part. AM forming processes such as organic and inorganic TFTs that can be processed at a low temperature are compatible with the roll-to-roll process, and can be effectively applied to the formation of flexible AM panels.

Film materials include vinyl polyethylene, polyvinyl chloride, polyvinylidene chloride, polypropylene, polystyrene, fluororesin, polyamide polycarbonate, polyethylene terephthalate, polyamide nylon, heat-resistant engineering plastic, polyimide, poly Various materials such as sulfone, polyether sulfone, polyphenylene sulfide, polyether ketone, and polyetherimide can be used.

In general, a polymer film is more permeable to gas than glass. In order to improve the reliability of the film panel, it is effective to provide a gas barrier layer on the film surface. As the gas barrier layer, it is known that thin films such as silicon oxide and silicon nitride, and laminated films of these films and organic films such as vinyl alcohol-containing polymers are known.

The example using an electric field for the movement of fine particles has been described above. If the fine particles have magnetism, magnetic force can be used for the accumulation and dispersion of the particles.

For example, in the configuration of FIG. 3, a dispersion in which fine particles having magnetism are dispersed in a dispersion system is used. As shown in FIG. 20, for example, a drive electrode having a thin film coil formed on the surface of a film sheet is used. When the particles are moved in the lateral direction by magnetic force, an opposing common electrode is not necessary. As for the common electrode, it is only necessary that one end of the coil is connected by a thin line in common to all pixels. Here, the pitch P between the drive electrode and the common electrode means the pitch between the drive electrodes. In the example of FIG. 20, one end of the coil is taken out from the back of the film and connected to a transparent electrode strip provided on the substrate 2 as a common electrode wiring. The other end of the coil of each pixel is connected to the drain terminal of the AM array. Since the coil is formed on the surface perpendicular to the substrate, when a pulse current is passed through the coil, a horizontal magnetic field is generated and the magnetic particles can be moved in the horizontal direction. The magnetic particles are deposited on both surfaces of the drive electrode. Whether the deposited fine particles on the coil substrate are redispersed or maintained in the deposited state when the current is turned off depends on the redispersion force and the strength of the intermolecular adhesion force between the fine particles and the coil substrate. When using a material with strong redispersion force such as a magnetic fluid, the dispersion medium has thixotropic properties, and when a transverse magnetic field is generated by applying a current pulse, the viscosity is reduced and particles are rapidly accumulated on the electrode. It is desirable that when the external magnetic field disappears, the particles are slowly redispersed and the cell becomes opaque. Although the memory is lost, it can be effectively used for moving image display, still image display by refresh, and the like.

A magnetic fluid is obtained by wrapping ferromagnetic fine particles such as iron oxide in a surfactant and colloidally dispersing it in an aqueous or non-aqueous dispersion medium. Excellent dispersion stability and sufficient light shielding effect. A water-based magnetic fluid may be used if an insulating film is provided on the coil surface.

In order to form a small thin film coil on a vertical substrate, for example, as described in FIG. 7, a sheet in which a metal thin film is formed on a metal foil provided with a resin film or an insulating film in advance and a large number of coils are patterned by a photo process is used. It can be formed by vertically bending a predetermined portion with a mold.

In the display element of the present invention, since the light transmittance of the partition wall portion does not change, it is desirable to minimize the width of this portion in the light transmission direction and to increase the aperture ratio of the pixel portion as much as possible. The LIGA method is useful in that a narrow partition can be formed. If the partition wall portion is transparent, light leakage occurs and the contrast is lowered. Therefore, it is desirable to make this portion black-absorbing. In order to achieve a transmittance modulation of 1000: 1 or more, it is necessary to suppress the light transmittance of the cell in the fine particle dispersion state including the partition wall to less than 0.1%. This can be achieved by providing a matrix (BM) layer and preventing it, and then selecting the concentration of fine particles contained in the cell.

The material used for this invention is described. As described above, it is desirable that the fine particles have as high a hiding power as possible. For black and white, carbon black, pigment black, graphite or the like, or a so-called toner in which these are embedded in a resin can be used. C, M, Y fine particles include various organic pigments such as azo, phthalocyanine, nitro, and nitroso pigments used in printing ink, color copier toner, and ink jet ink, iron oxide, cadmium yellow, and cadmium red. Various things such as inorganic pigments can be used. Y color fine particles such as Hansa Yellow, Benzidine Yellow, and Quinoline Yellow, M Color Fine Particles such as Pigment Red, Rhodamine B, Rose Bengal, and Dimethylquinacridone, and C Color Fine Particles such as aniline blue, phthalocyanine blue, and Pigment Blue K are black. As the fine particles, C, M, and Y fine particles may be mixed and used.

The fine particles are not limited to simple substances, but may be capsule fine particles containing dyes, pigments and some color materials, magnetic materials, etc. together with resins and liquids in order to optimize chargeability, magnetism and color tone. As for the shape of the particles, any of a spherical shape, a needle shape, a rod shape, a scale shape and the like can be used. The size of the fine particles is desirably about 5 nm to 5 μm. Fine particles can be surface-modified by surface coating at the atomic or molecular level, or can be charged and have good dispersibility using a dispersant, surfactant, etc. Must be adjusted to be redistributed.

In the panel of FIG. 3 of the present application, it has been described that the drive electrode 6-1 and the common electrode 6-2 are both exposed to the dispersion system. In some cases, it is coated with a conductive, semiconductive or insulating film.

Because it will be exposed to strong light for outdoor use, it is especially suitable for the materials used (substrate, adhesive, fine particles, dispersion medium, dispersant, capsule wall material, binder resin, partition material, electrode, AM, etc.) It is necessary to use one that is excellent in light resistance and heat resistance. For outdoor use, it is desirable to use a film or surface coated with a UV absorber. An antireflection film is also useful for improving visibility.

When the medium is liquid, various types of highly insulating solvents such as silicon-based, petroleum-based and halogenated hydrocarbons can be used. Liquid crystal is also a useful fine particle dispersion medium, and it is known that threshold characteristics are exhibited in the desorption of particles from electrodes due to the dielectric anisotropy of the liquid crystal, and can be effectively used in a dispersion system for a simple matrix panel.

As the non-linear element material, as described above, a semiconductor such as MIM, a chalcogenite compound, zinc oxide, etc., in which a thin film of Ta, Al or the like is anodized and sandwiched with the other metal can be used, and a-Si, An inorganic semiconductor such as a-InGaZnO or polysilicon, or a low molecular or high molecular organic semiconductor such as pentacene, polyfluorene, or polyhexylthiophene is used.

The present invention has the following effects. A horizontal particle movement display device that changes the light transmission by moving fine particles with a transverse magnetic field without a transverse electric field, adopting narrow and vertically long plate-like electrodes with a small aspect ratio, both sides of the plate-like electrodes particulate amount of cells in conjunction are use a particle deposition to the electrode pitch, the cell thickness, in particular therefore a high contrast at a low voltage plus discussed driving electrode area ratio, to achieve a high transmittance, high definition for extended projection It can be applied to a wide range of display sizes, from small light valves, small to meter-sized direct-view display devices, thin flexible black and white and full-color electronic paper, and super-large display devices exceeding several tens of meters. A display device applicable to both transmission was realized.

Is a cross-sectional view showing the principle of a conventional horizontal electric field particle movement type display device Is another cross-sectional view showing the principle of a conventional horizontal electric field particle movement type display device (A), (B) is a cross-sectional view showing the principle of the lateral electric field particle movement type display device of the present invention, (C) is a perspective view. These are front views of electrodes used in the display device of the present invention. FIG. 3 is a perspective view of a plate electrode of the display device of the present invention. Is an example of an electrode forming process used in the display device of the present invention Is another example of the electrode forming process used in the display device of the present invention FIG. 3 is a principle diagram showing light transmittance in a bright state of the display device of the present invention. FIG. 4 is a view showing viewing angle characteristics in a backlight type or a reflection mode of the display device of the present invention; FIG. 4 is a diagram showing the cell parameter dependence of the viewing angle of the display device of the present invention. Example of applied voltage waveform for creating a particle dispersion state in the display device of the present invention Cross-sectional view of the display device of the present invention composed of capsule particles Sectional view of C, M, Y dispersion type laminated color panel of the present invention Front view of electrode manufacturing process and electrode configuration of simple matrix panel of the present invention Front view of 2-terminal AM array manufacturing process and electrode configuration of the invention The front view of the electrode structure of the pixel part of 3 terminal TFTAM panel of this invention Sectional view of a reflective AM light valve using the silicon integrated circuit of the present invention as a lower substrate Sectional view of color panel with color filter of the present invention Sectional drawing which shows the operation principle of the single layer multi-color panel of this invention Configuration perspective view (A) and plan view (B) of the drive electrode used in the display device using the magnetic particle dispersion system of the present invention.

DESCRIPTION OF SYMBOLS 1 Transparent upper substrate 2 Lower substrate 3 Counter electrode 4 Collect electrode 5 Fine particle 6 Electrode 6-1 Drive electrode 6-2 Common electrode 7 Dispersion system 8 Cell 9 Spacer 10 Capsule particle 11 Adhesive 12 White diffuser plate 13 White backlight 13a
Color filter 13b Black matrix 13c
XY active matrix array 13d
XY active matrix array 14 for three colors Reflector 15 Silicon substrate 16 Binder 17 Backlight unit 18
C1, C2, C3, ……… Column electrode terminal 19
R1, R2, R3,... Row electrode terminal 20 Bulkhead 21 Two-terminal element 22 TFT element 23 Insulating film 24 Stacked cell 25 FET array 26 Resin 27 Reflective film 28 Mask layer 29 Metal 30 Mold 31 Metal thin film 32 Wiring

Claims (1)

At least one of them forms a cell with a dispersed system in which charged or magnetized fine particles are dispersed in a liquid, liquid crystal or gas medium between transparent substrates, and the fine particles are moved by a transverse electric field or a transverse magnetic field. In order to move the fine particles in a horizontal direction in a lateral particle movement type display device that changes the light transmittance in the vertical direction to the substrate of the cell by modulating the amount of the fine particles in a dispersed state, The drive electrode and the common electrode are composed of a pair of comb-shaped parallel plate electrodes whose main surfaces are opposed to each other, and are configured to form a substantially uniform lateral electric field between the electrodes. An area ratio defined by a value obtained by dividing the light shielding area by the electrode in one pixel of the flat plate electrode by the pixel area is 20% or less, and the area (Δs) of the plane parallel to the substrate of the flat plate electrode Area of vertical main surface (Δz) The area ratio (Δs / Δz) is 0.2 or less, the pitch P between the parallel plate electrodes is set to 5 to 100 μm, and the cell gap d is set to 0.5 to 2.0 times the pitch P. Display device