JP2003121887A - Electrophoresis display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high contrast without considering a difference in the refractive index between a colorless, transparent insulating substrate and a dispersing layer. SOLUTION: A convex and colorless, transparent insulating substrate 4 having a convex lens function is arranged so as to be opposed to a lower electrode 3 arranged on a lower substrate 2. An upper electrodes 6 are arranged on both sides or around the insulating substrate 4, and upper substrates 5 supporting the upper electrodes 6 have a light shading property. The upper electrodes 6 and the lower electrode 3 are almost in parallel, to uniformalize electric field strength when voltage is applied. A space 10 partitioned by partitions 8 between the upper and lower electrodes 3, 6, and the insulating substrate 4 is filled with a colorless, transparent fluid 11 containing electrophoretic particles 12. The side faces 8a of the partitions 8 are set to a tilt angle θsmaller than a critical angle. The respective electrophoretic particles 12 have equal electric charges, and are colored. A colored insulating layer 9 is provided on the lower electrode 3 and the side faces 8a of the partitions 8, color them in a color contrasted with the electrophoretic particles 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophoretic display device used for a reflective display device, which has low power consumption and is easy on the eyes.

[0002]

2. Description of the Related Art Conventionally, a reflection type display device using a liquid crystal has been mainly developed. However, a general liquid crystal cell using the optical rotatory power of a liquid crystal always needs a polarizer, It must pass through the polarizer at least twice. As a result, the reflected light is attenuated by 50% or more, which is a fatal factor such as a decrease in the screen brightness that greatly affects the characteristics of the reflective display device. On the other hand, the reflective display device using the electrophoretic display device has advantages such as low power consumption and reduced eye fatigue. The reflective display device using the electrophoretic display device is used, for example, as a signboard such as a guide display, a temporary output display for a personal computer, a display for a mobile communication device or a mobile terminal, an advertisement display, a newspaper, a book, etc. The fields such as display devices can be mentioned.

As an electrophoretic display device used in such a reflective display device, for example, Japanese Patent No. 90096
No. 3,255,1783, and US Pat.
Devices such as those described in the publication are known. In these electrophoretic display devices, a dispersion layer made of an insulating liquid in which electrophoretic particles and a dye are dissolved is sandwiched between two electrodes, and an image is obtained by a contrasting color of the electrophoretic particles and the dye. That is, in each pixel, when the electrophoretic particles adhere to the surface of one electrode close to the observer, the color of the electrophoretic particles can be visually observed, and the electrophoretic particles adhere to the surface of the other electrode far from the observer. In some cases, the color of the electrophoretic particles is hidden by the insulating liquid and the color of the insulating liquid can be visually observed. Then, with a large number of these pixels arranged in the horizontal direction (horizontal direction), the display color of each pixel can be selected to display a monochrome image or the like on the entire display device. Further, in order to display a color image, each pixel in which the electrophoretic particles or the insulating fluid is set to cyan, magenta, yellow and black may be arranged.

These electrophoretic display devices have a wide viewing angle,
Despite the advantages of high contrast and low power consumption, adsorption of dye dissolved in an insulating liquid to electrophoretic particles and insulation between the electrode surface on which electrophoretic particles are adsorbed and electrophoretic particles Due to adverse effects such as permeation of volatile liquids,
There is a big problem that it is difficult to achieve both high reflectance, that is, brightness and high contrast. In the case of matrix display, the electrophoretic particle migration time must be shortened to speed up the response. For that purpose, it is necessary to shorten the distance between the electrodes, but when this is shortened, the ability to absorb or shield the color of the electrophoretic particles by the colored insulating liquid is reduced, and the contrast is reduced due to the hiding property being lowered. was there.

As a means for solving these problems, Japanese Patent Laid-Open No. 2001-174853 discloses an electrophoretic display device having an upper substrate having a concave lens function for each pixel.
In this method, the insulating liquid is made colorless and transparent, and the electrophoretic particles and the colored layers or coloring filters arranged on the side surfaces of the partition walls are used to obtain color contrast. Moreover, a high-speed response and high contrast can be obtained by forming the upper electrode into a curved structure and keeping the distance between the two electrodes that adsorb the electrophoretic particles constant. Further, since the upper substrate provided on the outer side of the curved upper electrode plays the role of a concave lens, the lower electrode appears to be small and the electrophoretic particles adsorbed on this electrode are inconspicuous.

[0006]

However, in the above-mentioned electrophoretic display device, since the concave lens function is merely used to improve the contrast, the concealment of the electrophoretic particles adsorbed on the lower electrode is not sufficient. There is a limit to the expression of contrast, and there is a big problem that the contrast is inevitably inferior to the method using the concealment of electrophoretic particles. Also, in order to make the upper substrate on the observation side have a concave lens function, the refractive index of the insulating liquid in the dispersion layer is set to be smaller than that of the upper substrate, but it is effectively a colorless and transparent insulating layer such as glass or plastic. There is also a practical problem that it is extremely difficult from a material point of view to obtain an insulating fluid having a very small refractive index as compared with the upper substrate. The present invention has been made in view of the above circumstances, and an object thereof is to provide an electrophoretic display device having high contrast.

[0007]

An electrophoretic display device according to the present invention is an electrophoretic display device having a plurality of pixels, in which each pixel is provided on a first substrate and a first substrate. No. 1 electrode, a colorless and transparent insulating substrate provided facing the first electrode and having a convex curved surface structure on the first electrode side, and a second substrate provided adjacent to the insulating substrate. A second electrode disposed on the second substrate so as to face the first electrode, a colorless transparent fluid between the first and second electrodes, and colored electricity having an electric charge of the same polarity. It comprises a dispersion layer containing electrophoretic particles and a partition wall for separating pixels, imparts a light-shielding property to the second substrate or the second electrode, and
At least the surface of the first electrode has a color that can be compared with the electrophoretic particles. Therefore, the first and second
If the electrophoretic particles are adsorbed to the first electrode by applying voltages of different polarities to the electrodes, the color of the electrophoretic particles can be magnified and observed through the insulating substrate having a convex lens function. If the electrophoretic particles are adsorbed on the second electrode, the color of the surface of the first electrode (and the side surface of the partition wall) can be observed under magnification. Therefore, in any case, high contrast can be obtained, and the fluid can be selected without being limited to a material having a smaller refractive index than a colorless and transparent insulating substrate such as glass or plastic. By providing not only the surface of the first electrode but also the side surface of the partition wall with a color that can be compared with the electrophoretic particles, only the same color can be provided regardless of the angle of the viewing direction when viewing through the insulating substrate. It is visible and has high contrast regardless of the viewing angle.

The side surface of the partition wall may be located between the first electrode and the second electrode, and the distance between the facing side surfaces may be gradually reduced as the side surface approaches the first electrode. In addition to high contrast, the area occupied by each pixel can be reduced. The first electrode can be smaller than each pixel area. Further, the distance between the first electrode and the second electrode may be substantially constant. At the time of applying a voltage to the first and second electrodes and switching the polarities, the adsorbed electrophoretic particles are prevented from concentrating on a part of each electrode and the electrodes are almost uniformly covered, so that the contrast can be enhanced. .

In the color display, the electrophoretic particles of each pixel may be white, and the surface of the first electrode and the side surface of the partition wall (and the second substrate) may be black. Alternatively, the electrophoretic particles of each pixel may be black, and the surface of the first electrode and the side surface of the partition wall (and the second substrate) may be white. Monochrome display is possible for each pixel. Further, in each of the plurality of pixels, each electrophoretic particle is white, and the surface of the first electrode, the side surface of the second substrate and the partition wall (and the second substrate).
May include respective pixels of cyan, magenta, yellow, and black, and these respective pixels may be laterally arranged. A color image can be displayed by the large number of pixels in the entire electrophoretic display device. In addition, a plurality of pixels each of which has cyan, magenta, yellow, and black electrophoretic particles is vertically stacked, and at least the second substrate of at least the uppermost pixel of the plurality of pixels is white. In the bottom pixel, the surface of the first electrode and the side surface of the partition wall are white, and in the other pixels, the first substrate, the first electrode, the second electrode and the partition wall are colorless and transparent. May be. A color image can be displayed with a configuration in which a plurality of pixels are stacked and arranged.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional view of one pixel in an electrophoretic display device according to an embodiment of the present invention. An electrophoretic display device 1 according to the embodiment shown in FIG. 1 shows a vertical cross section of a single pixel, and includes a lower electrode 3 on a lower substrate 2 (first substrate) made of an arbitrary insulating material.
(First electrode) is provided, and the lower electrode 3 is, for example, a metal film patterned in a line shape or a dot shape. A colorless and transparent insulating substrate 4 having a convex curved shape toward the lower electrode 3 is provided at a position facing the lower electrode 3. The insulating substrate 4 has, for example, a convex curved plate shape having the same thickness, and has a convex lens function by having a configuration in which it is convex toward the lower substrate 2. This insulating substrate 4 is formed in a cylindrical peripheral surface shape when the lower electrode 3 is, for example, a line shape, and is a spherical shape when it is a dot shape. An upper substrate 5 having a light shielding property is provided on both sides or the periphery of the insulating substrate 4, and an upper electrode 6 (second electrode) having a polarity opposite to that of the lower electrode 3 is provided below the upper substrate 5. ing. For each pixel, the upper electrode 6 is formed in a substantially ring shape around the insulating substrate 4 when the insulating substrate 4 has, for example, a spherical shape. When the insulating substrate 4 has a cylindrical peripheral surface, the upper electrode 6 sandwiches the insulating substrate 4. It is formed separately on both sides.

The lower electrode 3 and the upper electrode 6 are arranged so as to face each other and are substantially parallel to each other.
It is preferable that the upper electrodes 6 that are separated from each other and have a width of L / 2 have the same area with a width of L / 2. The upper electrode 6 preferably has a smaller area than the lower electrode 3. Further, the insulating substrate 4 is located so that a part of the convex curved surface shape protrudes toward the lower electrode 3 side from the upper electrode 6. The lower electrode 3 and the upper electrode 6 are separated from each other by a partition wall 8, and the side surface 8 a inside the partition wall 8 is divided.
Are inclined outward from both ends of the lower electrode 3 toward both ends of the upper electrode 6, and the inclination angle is set to an appropriate value θ. The partition wall 8 plays a role of maintaining the gap (distance) between the electrodes 3 and 6 and insulation, and when the inclination angle θ of the side surface 8a becomes a critical angle (usually about 41 °), incident light incident from the outside When the light is refracted by the insulating substrate 4 and the fluid 11 (which can be said to have generally the same refractive index) and reflected by the side wall 8a, the reflected light must be totally reflected unless it passes through the insulating substrate 4 to the outside. It becomes a dead space because it cannot be seen from the outside. If a dead space is formed due to the total reflection of the reflected light, the contrast is lowered. Therefore, in order to avoid this, it is preferable to set the tilt angle θ to a value smaller than the critical angle. For example, the refractive index of air is n1 (≈1), and the refractive index of the insulating substrate 4 such as plastic or glass and the colorless and transparent fluid 11 is n2 (≈1.
5), the critical angle is arcsin (n1 / n2)
Can be obtained with. Therefore, to prevent total reflection, θ <arcsi
It may be set to n (n1 / n2). Generally, the critical angle is 4
Since it is 1 °, the inclination angle θ may be set to less than 41 °.

In addition, it is preferable that the distance between the electrodes 3 and 6 is short in order to speed up the response speed and reduce the viewing angle dependency when switching the images and turning the electrodes on and off. It is preferably as low as possible. Partition wall 8
The side surface 8a and the surface of the lower electrode 3 are colored with an appropriate color, and in the present embodiment, the colored insulating layer 9 is covered. A dispersion layer 13 including a colorless transparent fluid 11 and a colored electrophoretic element 12 is enclosed in a space 10 partitioned by the upper and lower electrodes 3, 6, the partition wall 8 and the insulating substrate 4. The electrophoretic particles 12 and the colored insulating layer 9 are set in colors that can be compared with each other, such as black and white. The plurality of colored electrophoretic particles 12 are dispersed in the fluid 11 with electric charges of the same polarity. The fluid 11 has good transparency to light in the visible range, has a small dissolving power for the electrophoretic particles 12, can stably disperse the electrophoretic particles 12, and does not contain ions and does not generate ions when a voltage is applied. desirable. Further, in order to prevent the electrophoretic particles 12 from floating and sinking, it is preferable that the specific gravity is almost equal to that of the electrophoretic particles 12 and that the electrophoretic particles 12 have a low viscosity in order to promote the rapid movement of the electrophoretic particles 12 when a voltage is applied. The lower electrode 3 and the upper electrode 6 are electrically connected to the electric circuit 14, so that application and disconnection of voltage, switching of polarities, and the like are appropriately performed at both electrodes 3 and 6. Even if the voltage application is interrupted after the electrophoretic particles 12 are once adsorbed to the lower electrode 3 or the upper electrode 6, the electrophoretic particles 12 have a memory function of being held in that position.

The lower substrate 2 and the upper substrate 5 are not particularly limited as long as they have sufficient insulation and microscopic planarity and strength enough to maintain a sufficient structure. A flexible substrate may be used as long as the cell structure is maintained.
As a specific material, glass, plastic, or ceramic is preferable. The electrode material forming the lower electrode 3 and the upper electrode 6 is preferably a material having good conductivity such as aluminum, copper, silver, gold, or platinum. Further, as the transparent electrode material, it is preferable to use a thin film of tin oxide, indium oxide, ITO, ATO, copper iodide or the like. The electrodes can be formed by a usual method such as vapor deposition, sputtering and photolithography. As the colorless and transparent insulating substrate 4 having a convex curved surface shape, it is assumed that the insulating substrate 4 has sufficient insulating properties and colorless and transparent properties, and can form a convex lens structure. As a specific material, glass, plastic, or ceramic is preferable. Further, as the processing method, a stamper molding method, a dry etching method, a wet etching method, a template method or the like can be used depending on the material. In the case of the light-shielding upper substrate 5 on which the upper electrode 6 is arranged, or on the lower substrate 2 on which the lower electrode 3 is arranged, electrophoretic particles 12 are formed.
In the case of bearing a color contrasting with, a substrate obtained by mixing an appropriate pigment or dye with glass, plastic or ceramic, or a colored ceramic can be used. When the upper substrate 5 is colorless and transparent, a colored electrode having a light-shielding property may be provided as the upper electrode 6, or on the surface of the upper substrate 5 on the opposite side of the upper electrode 6 for providing the light-shielding property. The colored insulating layer 9 may be provided.

The material of the partition wall 8 is preferably an insulating material such as glass, plastic or ceramic. Further, when the partition 8 itself is provided with a contrasting color with the electrophoretic particles 12 without providing the colored insulating layer 9, it is preferable to use a mixture of glass, plastic or ceramic with an appropriate pigment or dye, or a colored ceramic. it can. Electrophoretic particles 12
As the colored insulating layer 9 which bears the contrasting color, it is possible to use the insulating layer itself having a contrasting color, or a mixture of a pigment and a dye carrying a contrasting color in this insulating layer. The material and thickness of the colored insulating layer 9 are not particularly limited as long as a sufficient voltage is applied to the dispersion layer 13 and display unevenness does not occur. Examples of the material for the colored insulating layer 9 include inorganic substances such as titanium oxide, silicon oxide and aluminum oxide, or polyethylene, polystyrene, phenol resin, polyamide, polyimide, polypropylene, epoxy resin, polyvinyl chloride, fluororesin, silicone resin and the like. The organic substance of can be used. When a pigment or dye that bears a contrasting color with the electrophoretic particles 12 is mixed, the material is not particularly limited, but a material that is stably and uniformly held by the colored insulating layer 9 is selected. In order to form the insulating layer on the electrodes 3 and 6 or the substrates 2 and 5, usual methods such as sputtering, vapor deposition, solution coating, solution dipping, spin coating, and Langmuir-Blodgett method can be used depending on the material. . The thickness of the dielectric layer is
For example, several nm to several μm can be considered. In order to prevent the irreversible adsorption of the electrophoretic particles 12 on the electrode surface and the electrochemical reaction of impurities such as water on the electrode surface, it is necessary not only on the lower electrode 3 but also on the upper electrode 6 surface. Accordingly, it is desirable to provide an insulating layer such as a fluororesin.

Further, it is desirable that the electrophoretic particles 12 are stably dispersed in the fluid 11, have a single polarity, and have a small particle size distribution from the viewpoint of the life, contrast, resolution, etc. of the display device. The particle size is 0.1
The thickness is preferably from 5 μm to 5 μm. Within this range, the light scattering efficiency does not decrease, and a sufficient response speed is obtained when a voltage is applied. The material of the electrophoretic particles 12 is not particularly limited, such as an organic pigment and an inorganic pigment, but examples of the organic pigment include azo pigments, polycondensed azo pigments, metal complex azo pigments, flavanthron pigments, and phthalocyanine pigments. , Quinacridone pigments, anthraquinone pigments, anthrapyridine pigments, pyranthrone pigments, dioxazine pigments, perylene pigments, perinone pigments, isoindolinone pigments, quinophthalone pigments,
Examples include thioindigo pigments and indanthrene pigments.
Examples of the inorganic pigment include zinc white, titanium oxide, zinc oxide, zirconium oxide, antimony white, carbon black, iron black, red iron oxide, mapico yellow, red lead, cadmium yellow, zinc sulfide, lithopone, barium sulfide, cadmium selenide, Barium sulfate, lead chromate, lead sulfate,
Examples thereof include barium carbonate, calcium carbonate, lead white, and alumina white.

As the fluid 11 which is an insulating liquid that can be used for the above-mentioned electrophoretic particle material, for example, without considering the difference in refractive index from the colorless and transparent insulating substrate 4 such as glass or plastic, for example, , Hexane, decane, dodecane, hexadecane, dodecylbenzene, kerosene, toluene, xylene, olive oil, soybean oil, sesame oil, tricresyl phosphate, isopropanol, trichlorotrifluoroethane, dibromotetrafluoroethane, tetrachloroethylene, silicone oil, fluorocarbon, fluorinated Typical insulating liquids such as polyether and pure water can be mentioned. A mixed fluid may be used as the fluid 11 when specific gravity matching with the electrophoretic particles 12 is performed to prevent the electrophoretic particles 12 from floating and sinking. In the present embodiment, the mixing weight ratio in the dispersion layer 13 including the electrophoretic particles 12 and the fluid 11 is
It is not particularly limited as long as the electrophoretic property of the electrophoretic particles 12 is not hindered and the reflection control of the dispersion layer 13 can be sufficiently performed, but for example, 1 wt% to 20 wt% is preferable.

Further, in order to increase the electric charge of the electrophoretic particles 12 or to make them have the same polarity, an additive such as a resin or a surfactant can be added to the fluid 11 if necessary. The thickness of the dispersion layer 13 is larger than the outer diameter of the electrophoretic particles 12 and is not particularly limited as long as the movement of the electrophoretic particles 12 is not hindered, but the response speed when a voltage is applied is increased and the viewing angle dependence is increased. In order to make it small, it is desirable to be as thin as possible. From such a viewpoint, the dispersion layer 13
The preferred thickness of is from 5 μm to 200 μm. In the present embodiment, the electric circuit 14 is not particularly limited, but for example, the maximum rated voltage is 100 V and the power supply capacity is 1
It is possible to use a power supply having a 0 mA power supply and the polarity of which can be arbitrarily set.

When active matrix driving is performed using this electrophoretic display device 1, switching elements (TFT, etc.) are formed on the lower substrate 2 and a large number of upper electrodes 6 are formed.
The signal electrode group constituting the above and the scanning electrode group constituting the plurality of lower electrodes 3 are provided substantially orthogonal to each other. In the case of the reflective display, it is not necessary to consider the aperture ratio as compared with the transmissive display device, so that there is a spatial margin in the design of the switching element on the lower substrate 2. Further, in order to perform passive matrix driving, the signal electrode group and the scanning electrode group may be arranged substantially orthogonally.

Since each pixel of the electrophoretic display device 1 according to the present embodiment has the above-described structure, a voltage having a polarity different from that of the electrophoretic particles 12 is applied to the lower electrode 3 and the upper electrode 6 is applied. When the same polarity as that of the electrophoretic particles 12 is applied, the electrophoretic particles 12 are adsorbed and collected on the lower electrode 3. When this is visually observed from the outside through the insulating substrate 4 having the convex curved surface portion, the electrophoretic particles 12 adsorbed on the lower electrode 3 are seen in an enlarged state due to the convex lens effect of the colorless and transparent insulating substrate 4, and the entire pixel is electrically charged. The coloring of the electrophoretic particles 12 will be displayed. In this case, the side surface 8 of the partition wall 8
Although the color of the colored insulating layer 9 provided in a is a contrasting color different from the color of the electrophoretic particles 12, it is hardly visible because it is located outside the field of view of the enlarged image through the insulating substrate 4. When a voltage having a polarity different from that of the electrophoretic particles 12 is applied to the upper electrode 6 and a voltage having the same polarity as that of the electrophoretic particles 12 is applied to the lower electrode 3, the electrophoretic particles 12 are applied to the back surface of the upper substrate 5 having a light shielding property. Since it is adsorbed to the upper electrode 6 located, it is hidden by the upper substrate 5. Therefore, when viewed from the outside through the insulating substrate 4, the color of the colored insulating layer 9 covering the surface of the lower electrode 3 and the side wall 8a appears to be enlarged. Moreover, by setting the distance between the lower electrode 3 and the upper electrode 6 to be constant, the strength of the electric field can be made constant when a voltage is applied between the electrodes 3 and 6 as shown in FIG. The line of electric force can be made constant. Therefore, the electrophoretic particles 12 do not concentrate on a part where the distance between the electrodes 3 and 6 is short, the movement of the electrophoretic particles 12 between the electrodes 3 and 6 is quick and smooth, and the electrophoretic particles 12 are uniformly electrophoresed over the entire electrodes. The particles 12 are adsorbed and high contrast can be obtained.

Therefore, according to the present embodiment, basically, a high contrast can be obtained from the color of the electrophoretic particles 12 and the color of the colored insulating layer 9 such as the surface of the lower electrode 3. In addition, for each pixel of the electrophoretic display device 1, the height of the partition wall 8 is reduced to shorten the distance between the electrodes 3 and 6, so that the response speed can be increased without causing the problem of the shielding property. In addition, the electrophoretic particles 12 are attached to the lower electrode 3
It is possible to prevent the colored insulating layer 9 on the side surface 8a separated from the electrophoretic particles 12 from being visually recognized due to an angle (viewing angle) viewed through the insulating substrate 4 having a convex curved surface shape when adsorbed on the substrate, and thus to prevent viewing angle dependence. Can be made smaller. Further, by making the distance between the upper electrode 6 and the lower electrode 3 constant, the strength of the electric field can be made constant and the lines of electric force can be made constant. 6 is not adsorbed, and the contrast can be improved also from this point.

Next, the overall structure of the electrophoretic display device (reference numeral 20 will be used for convenience) provided with a plurality of one pixel structures of the electrophoretic display device 1 according to the above-described embodiment will be described with reference to FIG. In the electrophoretic display device 20 according to the present embodiment, a plurality of configurations for one pixel shown in FIG. 1 are arranged in the lateral direction, that is, the plane direction. Such an electrophoretic display device 20 includes a lower substrate 10 as shown in FIG.
2 (lower substrate 2), a scanning electrode group 103 forming a plurality of lower electrodes 3 is formed, and the colored insulating layer 10 is formed on the surface thereof.
9 is provided. Each side surface 10 is on the lower substrate 102.
A partition 108 (partition 8) provided with a colored insulating layer 109 is provided in 8a, and the partition 108 has a plurality of spaces 110.
(Space 10) is arranged so as to extend in a direction substantially orthogonal to the scanning electrode group 103, and each space 110 is a pair of side walls 10.
It is partitioned by 8a and 108a (side wall 8a). Partition 1
An upper substrate 105 (upper substrate 5) having a signal electrode group 106 constituting a plurality of upper electrodes 6 and an insulating substrate 104 (insulating substrate 4) is provided on the upper part of 08. Insulation layer 1
Reference numeral 04 has a convex curved surface portion located at the upper part of the space 110 and having a cylindrical peripheral surface-shaped convex lens structure continuous in the extending direction, and a pair of signal electrode groups along the insulating substrate 104 on both sides thereof. 106 are continuously provided. The scan electrode group 103 extends so as to be substantially orthogonal to the signal electrode group 106, and simple matrix drive is possible. The space 110 between the scan electrode 103 and the signal electrode 106
A dispersion layer 13 containing electrophoretic particles 12 and a fluid 11 (not shown) is enclosed in the inside.

The electrophoretic display device 20 shown in FIG. 3 has a structure for obtaining a monochrome display image. For example, the electrophoretic particles 12 in each pixel are colored white and the scanning electrode 1 is used.
03 (lower electrode 2), the colored insulating layer 109 on the side surface 108a of the partition wall 108, and the upper substrate 105 are made black. As another method, conversely, the electrophoretic particles 12 in each pixel are made black, and the colored insulating layer 1 on the scanning electrode 103 (lower electrode 2) and the side surface 108a of the partition 108 is formed.
09 and the upper substrate 105 may be white. In the case of monochrome image display, one space 11
A plurality of scan electrodes 103 (lower electrodes 3) are arranged along the extending direction of 0 to form a plurality of pixels in one row corresponding to the number of scan electrodes 103. It is not partitioned by 108. In this case, the electrophoretic particles 12 may be adsorbed to the electrodes of the adjacent pixels, but since they have the same color, there is no problem such as reduction in contrast. On the other hand, in order to obtain a color display image on the electrophoretic display device 20, since the colors of the electrophoretic particles 12 may be different between adjacent pixels, it is necessary to partition each pixel with a partition 108. There is.

As one method for obtaining a color display image in the electrophoretic display device 20, each electrophoretic particle 12 in a plurality of pixels is white, and the surface of the scanning electrode 103 (lower electrode 3) and the side surface 108a of the partition 108 are formed. There is a method in which the colored insulating layer 109 and the upper substrate 105 are set to cyan, magenta, yellow, and black for each pixel, and the pixels are arranged in the horizontal direction (horizontal direction). Alternatively, the electrophoretic particles 12 and the colored insulating layer 1 such as the scanning electrode 103
The color scheme with 09 or the like may be reversed. As still another method, in a plurality of pixels, the electrophoretic particles 12 are cyan, magenta, yellow, and black, respectively. The pixels are sequentially arranged in the vertical direction (stacking direction), and at least the uppermost part of the stacked pixels is arranged. The upper substrate 105 in each pixel
Is white, the surface of the scanning electrode 103 (lower electrode 3) and the side surface 108a of the partition wall 108 are the white colored insulating layer 109 only in the lowermost pixel, and in the other pixels, the lower substrate 10 is used.
2, a method of making the scanning electrode 103 and the partition 108 colorless and transparent can be mentioned. In this case, the colored insulating layer 109 may not be provided.

[0024]

EXAMPLES Specific examples of the present invention will be described below. In an electrophoretic display device 20 in which one pixel has a structure similar to that of the electrophoretic display device 1 shown in FIG. 1 and moreover has a structure similar to that shown in FIG. Formation and setting were performed as follows. The lower substrate 2 is a colorless and transparent glass substrate 102 having a thickness of 1 mm,
The lower electrode 3 was ITO patterned to have a width of 30 μm and an interval of 50 μm. The upper substrate 5 is made of polycarbonate, and the upper electrode 6 is ITO patterned to have a width of 30 μm and a gap of 50 μm. A black insulating layer pattern for light shielding was provided on the surface of the upper substrate 5 opposite to the upper electrode 6 by screen printing. Then, based on the structure of FIG. 1, a width of 50 μm and a recess depth of 10 μm in the central portion are formed between the black insulating layers by using a stamper forming method.
A colorless and transparent insulating substrate 4 formed as a convex lens structure having a cylindrical peripheral surface was manufactured.

The partition wall 8 is formed of a low-melting glass by using a screen printing method, and the height of the partition wall 8 in FIG. 1 is set so that the inclination angle θ of the side surface 8a is about 30 degrees in order to avoid the critical condition. It was set to 17 μm. The interval between the partition walls 8 sandwiching the dispersion layer 13 in the vertical cross section shown in FIG. 1 was 50 μm. The colored insulating layer 9 was formed by dip-coating a fine powder of barium sulfate mixed with a fluororesin on the side surface 8a with a thickness of about 0.5 μm. A black resin toner (particle size 1 μm) is used as the electrophoretic particles 12, and isopropanol is used as the transparent fluid 11, and both are mixed so that the mixing weight ratio of the electrophoretic particles 12 is 10%. A small amount of a surfactant was added to improve the dispersion layer 13. In this case, the surface of the electrophoretic particles 12 is negatively charged.

The operation of one pixel of the electrophoretic display device 1 thus obtained will be described below. First, the electric circuit 10
When a DC voltage of 30 V is applied so that the lower electrode 3 and the upper electrode 6 become the positive electrode and the negative electrode, respectively, the negatively charged electrophoretic particles 12 move to the lower electrode 3 and the colored insulating layer 9 is formed.
Adsorbed on the surface. At this time, when observed from the outside through the colorless and transparent insulating substrate 4, the black color of the electrophoretic particles 12 was enlarged and observable due to the convex lens effect of the insulating substrate 4.
In this state, the electrical connection between the electric circuit 10 and the electrode is cut off,
This was continued even after the voltage application was cut off, showing that the electrophoretic display device 1 has a memory function. Next, a voltage was applied with the polarity reversed from that in the previous case. That is, when a DC voltage of 30 V is applied so that the lower electrode 3 becomes the negative electrode and the upper electrode 6 becomes the positive electrode, the electrophoretic particles 12 are adsorbed by the upper electrode 6 and are thus hidden by the light-shielding upper substrate 5.
The observer was able to visually recognize the white color of the colored insulating layer 9 due to the effect of the convex lens by the insulating substrate 4. Also in this case, the adsorption state of the electrophoretic particles 12 was maintained even after the electrical connection between the electric circuit 10 and the electrodes was cut off, and it was confirmed that the electrophoretic display device 1 has a memory function. The optical reflection characteristics in white display and black display are substantially the same as those of the colored insulating layer 9 and the electrophoretic particles 6 alone, and the electrophoretic display device provides a wide viewing angle, brightness, and high contrast. I was able to confirm.

When the height of the partition wall 8 and the area of the lower electrode 3 are set so that only the lower electrode 3 can be viewed through the insulating substrate 4, the colored insulating layer 9 is the lower electrode 3 only. It suffices to cover it, and it is not necessary to provide the colored insulating layer 9 for the partition wall 8. Further, the colored insulating layer 9 is not necessarily provided, and the partition wall 8 and the lower electrode 3 themselves may be colored. In either case, the side surface of the partition wall 8 and the surface of the lower electrode 3 should be visible in a colored state. In addition,
The present invention is not limited to the above-described embodiments, and various modifications can be made based on the spirit of the present invention, and these modifications are not excluded from the scope of the present invention.

[0028]

As described above, in the electrophoretic display device according to the present invention, each pixel is colorless and transparent and is provided so as to face the first electrode and has a convex curved surface structure on the first electrode side. An insulating substrate, a second electrode disposed on the second substrate adjacent to the insulating substrate and facing the first electrode, a colorless transparent fluid, and a colored liquid having an electric charge of the same polarity. A dispersion layer containing electrophoretic particles and partition walls for separating pixels, imparts a light-shielding property to the second substrate or the second electrode, and the surfaces of the first electrodes and the side surfaces of the partition walls are electrophoretic particles. Since it has a color that can be compared with, it is not limited to the use of a dispersion layer having a small refractive index, and it is possible to obtain an electrophoretic display device which can be magnified and observed and has high contrast.

Further, the side surface of the partition wall is located between the first electrode and the second electrode, and the distance between the side surfaces facing each other is gradually reduced toward the first electrode, so that the contrast is high. Moreover, the area occupied by each pixel can be reduced. Further, since the distance between the first electrode and the second electrode is set to be substantially constant, the electrophoretic particles are concentrated on a part of each electrode when the voltage is applied to the first and second electrodes or the polarity is switched. It is possible to prevent this from happening and to coat the electrodes almost uniformly to enhance the contrast.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of one pixel of an electrophoretic display device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an electric field when a voltage is applied to electrodes of the electrophoretic display device shown in FIG.

FIG. 3 is an exploded perspective view showing an overall configuration of an electrophoretic display device provided with a plurality of pixel structures shown in FIG.

[Explanation of symbols]

1,20 Electrophoretic display device 2 Lower substrate (first substrate) 3 Lower electrode (first electrode) 4 insulating substrate 5 Upper substrate (second substrate) 6 Upper electrode (second electrode) 8,108 partition wall 8a, 108a side surface 9 Colored insulation layer 10 electric circuits 11 fluid 12 Electrophoretic particles 103 scan electrode group 106 signal electrode group

Claims (7)

[Claims] 1. An electrophoretic display device having a plurality of pixels, wherein each pixel includes a first substrate, a first electrode provided on the first substrate, and the first electrode. A colorless and transparent insulating substrate provided facing each other and having a convex curved surface structure on the first electrode side; a second substrate provided adjacent to the insulating substrate; and a second substrate on the second substrate. A second electrode disposed opposite to the first electrode, and a dispersion layer between the first and second electrodes, containing a colorless transparent fluid and colored electrophoretic particles having the same polarity charge. And a partition wall separating the pixels, and imparts a light-shielding property to the second substrate or the second electrode, and at least the surface of the first electrode has a color that can be compared with the electrophoretic particles. Electrophoresis display device. 2. A side surface of the partition wall is located between the first electrode and the second electrode, and a distance between the side surfaces facing each other is gradually reduced toward the first electrode. The electrophoretic display device described. 3. The electrophoretic display device according to claim 1, wherein the distance between the first electrode and the second electrode is substantially constant. 4. The electrophoretic display device according to claim 1, wherein the electrophoretic particles are white, and the surfaces of the first electrode, the second substrate, and the side walls of the partition are black. 5. The electrophoretic particles are white, and the surface of the first electrode, the side surface of the second electrode, and the side surface of the partition wall are composed of cyan, magenta, yellow, and black pixels, respectively, and the pixels are arranged horizontally. The electrophoretic display device according to claim 1, wherein the electrophoretic display device is provided. 6. The electrophoretic display device according to claim 1, wherein the electrophoretic particles are black, and the surfaces of the first electrode, the second substrate, and the side walls of the partition are white. 7. In each pixel in which the electrophoretic particles are formed of cyan, magenta, yellow, and black and are vertically stacked, at least the second substrate in the uppermost pixel is white, and the first substrate is white. 4. The surface of the electrode and the side surface of the partition wall are white only in the lowermost pixel, and in the other pixels, the first substrate, the first electrode, the second electrode, and the partition wall are colorless and transparent. Electrophoretic display device.