JP2013222024A - Electrophoretic display device and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophoretic display device including a partition wall, the device capable of being improved in responsiveness and reduced in electric power consumption, and an electronic apparatus.SOLUTION: An electrophoretic display device includes a first substrate having first electrodes on a first surface, a second substrate arranged away from the first substrate and facing the first surface, a second electrode arranged between the first substrate and the second substrate so as to be spaced from the first electrodes and partition walls arranged in an interval between the first substrate and the second substrate and partitioning the interval into a plurality of cells, a dispersion liquid filled in each of the cells and having electrophoretic particles, and a particle passing member arranged between the first electrode and the second electrode and allowing the electrophoretic particles to pass therethrough. The particle passing member is colored in a color different from that of the electrophoretic particles. The first electrodes each include a protrusion which protrudes toward the second substrate side and at which an electric field in the cell is concentrated when an electric field is applied to between the first electrode and the second electrode.

Description

  The present invention relates to an electrophoretic display device and an electronic apparatus.

FIG. 11 is a cross-sectional view schematically illustrating a configuration example of an electrophoretic display (EPD) 90 according to a conventional example.
As shown in FIG. 11, the electrophoretic display device 90 includes a pixel substrate 1, a counter substrate 3, a dispersion liquid 5, and a pair of electrodes (pixel electrode 2 and common electrode 4) that apply an electric field to the dispersion liquid 5. And partition walls 8 that form a plurality of cells 12. The dispersion 5 includes at least electrophoretic particles 6 and a dispersion medium 7 (mixed solution of a solvent 7a and a dispersant).

  When performing monochrome display using the above-described electrophoretic display device 90, for example, two types of electrophoretic particles 6 are used: black particles 6a and white particles 6b. At this time, in order to control the migration of the electrophoretic particles 6, one of the two types of particles (for example, the black particles 6a) is negatively charged and the other particle (for example, the white particles 6b) is charged. ) Is charged positively. Then, for example, a positive potential is applied to the pixel electrode 2 and a negative potential is applied to the common electrode 4. As a result, one particle migrates to the pixel electrode 2 side and the other particle migrates to the common electrode 4 side to separate the two types of particles, enabling monochrome display. In FIG. 11, the white particles 6 b have moved to the counter substrate 3 side, and white color is displayed through the counter substrate 3. In addition, as such a prior art, there exist some which were disclosed by patent document 1, for example.

JP 2003-66494 A

  By the way, in principle, the electrophoretic display device has a faster response speed (that is, a higher speed operation is possible) as the charged amount of the electrophoretic particles increases. Further, in order to increase the charge amount of the electrophoretic particles, it is necessary to increase the concentration of ions contained in the solvent (that is, the concentration of counter ions). However, when the ion concentration in the solvent is increased, leakage current generated during operation of the electrophoretic display device may increase, and power consumption may increase.

  In addition, when two or more types of electrophoretic particles are used to increase the contrast of the electrophoretic display device, if the charge amount of the electrophoretic particles is increased for the purpose of improving the responsiveness of the display device, the particles aggregate. It becomes easy. This is because particles charged with different signs attract each other by electrostatic interaction. When the particles aggregate, the contrast of the electrophoretic display device may not increase.

As described above, in the electrophoresis method used in the conventional electrophoretic display device, “high-speed response” and “low power consumption” have a so-called trade-off relationship, and it is extremely difficult to achieve both. It was. Also, “fast response” and “high contrast” are in a trade-off relationship, and it has been extremely difficult to achieve both.
Therefore, the present invention has been made in view of the above circumstances, and is an electrophoretic display device having a partition wall so that responsiveness can be improved and power consumption can be reduced. It is an object of the present invention to provide an electrophoretic display device and an electronic apparatus.

  An electrophoretic display device according to one embodiment of the present invention for solving the above problems includes a first substrate having a first electrode on a first surface, and a second substrate facing the first surface. A second electrode disposed between the first substrate and the second substrate and spaced apart from the first electrode; and between the first substrate and the second substrate. Partitioning into a plurality of cells, a dispersion liquid having electrophoretic particles filled in each of the plurality of cells, and between the first electrode and the second electrode, A sheet-like particle passing member through which the migrating particles can pass, wherein the particle passing member is colored in a different color from the electrophoretic particles, and the first electrode is disposed on the second substrate side. A protrusion that protrudes and concentrates an electric field applied between the first electrode and the second electrode. And butterflies. Here, the sheet form means a film form or a plate form.

  With such a configuration, when an electric field is applied between the first electrode and the second electrode, the electric field concentrates on the convex portion. Thereby, the convection of the solvent can be generated starting from the convex portion, and the solvent can be circulated toward the first electrode side or the second electrode side in each of the plurality of cells. Further, the flow velocity of the convection can be made faster than the migration speed due to the Coulomb force (electric attractive force or repulsive force) of the electrophoretic particles.

  Thus, in each of the plurality of cells, the electrophoretic particles are transported by solvent convection. In addition, among the electrophoretic particles transported by the convection, the particles approaching the first electrode or the second electrode are moved to the first electrode or the second electrode by the Coulomb force acting between the particles and the electrode. It can be attracted to and absorbed. Thus, according to the electrophoretic display device according to the above aspect, solvent convection can be intentionally generated. The electrophoretic particles can be moved by actively utilizing not only the Coulomb force but also the convection of the solvent. For this reason, the “fast response” of the electrophoretic particles becomes possible.

  Further, compared with the prior art, in order to increase the responsiveness of the electrophoretic particles, it is not necessary to increase the charge amount of the electrophoretic particles and it is not necessary to increase the concentration of ions contained in the solvent. For this reason, it is possible to reduce the leakage current generated during the operation of the electrophoretic display device, thereby enabling “low power consumption”. Therefore, the trade-off relationship between “high-speed response” and “low power consumption” can be eliminated, and both can be achieved (that is, the responsiveness can be improved and the power consumption can be reduced).

Further, according to the electrophoretic display device according to the above aspect, the particle passing member is disposed between the first electrode and the second electrode, and the particle passing member is colored in a color different from that of the electrophoretic particle. Has been. For this reason, by applying an electric field to each of the plurality of cells, the color of the electrophoretic particles (first color) and the color of the particle passing member (second color) can be selectively displayed. .
For example, assume that the second substrate is a substrate on the display surface side. At this time, when the electrophoretic particles are attracted toward the second electrode, many electrophoretic particles gather between the particle passage member and the second substrate. For this reason, the display surface displays the color (first color) of the electrophoretic particles. On the other hand, when the electrophoretic particles are attracted toward the first electrode, almost no electrophoretic particles exist between the particle passage member and the second substrate. For this reason, the display surface displays the color (second color) of the particle passing member.

  Thus, according to the electrophoretic display device according to the aspect described above, the first color and the second color can be selectively displayed using the electrophoretic particles and the particle passing member. The electrophoretic particles may be of a single color, and it is not necessary to dispose electrophoretic particles of different colors in the same cell, so that “high contrast” is possible. Therefore, the trade-off relationship between “high-speed response” and “high contrast” can be eliminated, and both of them can be satisfied (that is, responsiveness can be improved and high contrast can be realized). Moreover, since it is not necessary to prepare electrophoretic particles of a plurality of colors, it is possible to contribute to a reduction in manufacturing cost of the electrophoretic display device.

  In addition, as the above-mentioned “first substrate”, for example, “pixel substrate 1” described later corresponds. As the “first surface”, for example, “surface 1a” described later corresponds. As the “first electrode”, for example, “pixel electrode 2” described later corresponds. The “second substrate” corresponds to, for example, “opposing substrate 3” described later. As the “second electrode”, for example, “common electrode 4” described later corresponds. As the “particle passage member”, for example, “colored plate 15” described later corresponds.

  In the electrophoretic display device described above, the electrophoretic particles may be charged only in one of positive and negative. With such a configuration, the plurality of electrophoretic particles arranged in the same cell are all charged to the same sign. For this reason, the particles are not attracted by the Coulomb force, but rather repel each other, so that the particles can be prevented from aggregating.

  In the electrophoretic display device, the second electrode may be disposed apart from the second substrate and may have an opening through which the electrophoretic particles can pass. With such a configuration, even if the second substrate is a substrate on the display surface side, it is not necessary to configure the second electrode with a transparent member. For this reason, it is not necessary to use an expensive transparent member such as ITO (indium tin oxide) for the second electrode. For this reason, the manufacturing cost of the electrophoretic display device can be reduced. In addition, since the second electrode is separated from the second substrate, it is possible to suppress display quality from being deteriorated due to light absorption of the second electrode. Furthermore, since the distance between the first electrode and the second electrode can be shortened, the electric field between the first electrode and the second electrode can be easily increased.

In the electrophoretic display device, the structure of the particle passage member is a structure in which a plurality of sheets having a plurality of through holes having a diameter larger than that of the electrophoretic particles are stacked in the thickness direction of the particle passage member. This may be a feature. With such a configuration, it is easy to manufacture the particle passing member.
In the electrophoretic display device, the first cell and the second cell of the plurality of cells may be characterized in that the particle passing member is colored in a different color. With such a configuration, a color image can be displayed by combining a plurality of cells having different colors of the particle passing member. For example, the particle passing member of the first cell among the plurality of cells is colored red (R), the particle passing member of the second cell adjacent to the first cell is colored green (G), When the particle passing member of the third cell adjacent to one cell or the second cell is colored blue (B), the combination of the first to third cells is regarded as one pixel for color display. can do.

In the electrophoretic display device, the convex portion may be a weight, and the apex of the cone may be directed to the inside of the cell. With such a configuration, when an electric field is applied between the first electrode and the second electrode, the electric field can be efficiently concentrated on the apex of the weight body. Therefore, solvent convection can be generated efficiently.
In the electrophoretic display device described above, the convex portion may be a column. If it is such a structure, when an electric field is applied between the 1st electrode and the 2nd electrode, it is closest to the 2nd electrode among the fields or sides which constitute this column The electric field can be efficiently concentrated on the portion. Therefore, solvent convection can be generated efficiently.

In the electrophoretic display device described above, an electric field is applied between the first electrode and the second electrode, thereby causing convection of the dispersion liquid in the cell with the convex portion as a base point. This may be a feature. With such a configuration, since the convection of the dispersion occurs in the cell, the electrophoretic particles can be efficiently flowed as compared with the case where the convection of the dispersion does not occur. For this reason, among the electrophoretic particles transported by this convection, the particles approaching the first electrode or the second electrode are moved to the first electrode or the second electrode by the Coulomb force acting between the particles. It can be attracted and attracted to the electrode.
An electrophoretic display device according to another aspect of the present invention includes the above-described electrophoretic display device. With such a configuration, since the above-described electrophoretic display device is provided, it is possible to realize an electronic device that achieves both high-speed response and low power consumption with respect to the display function.

1 is a diagram illustrating a configuration example of an electrophoretic display device 10 according to a first embodiment of the present invention. The figure which shows an example of the common electrode 4 which concerns on 1st Embodiment of this invention. The figure which shows an example of the positional relationship of the convex part 9 and the common electrode 4 Section showing an example of the structure of the colored plate 15 The figure which shows typically the mechanism in which the electrophoretic display device 10 operate | moves. The figure which shows the modification of the common electrode 4 which concerns on 1st Embodiment of this invention. The figure which shows the modification of the convex part 9 typically. The figure which shows the 1st structural example of the electrophoretic display apparatus 20 which concerns on 2nd Embodiment of this invention. The figure which shows the 2nd structural example of the electrophoretic display apparatus 20 which concerns on 2nd Embodiment of this invention. The figure which shows the structural example of the electronic paper 100 which concerns on 3rd Embodiment of this invention. The figure which shows the structural example of the electrophoretic display apparatus 90 which concerns on a prior art example.

Embodiments of the present invention will be described below with reference to the drawings. Note that in the drawings to be described below, portions having the same configuration and function are denoted by the same reference numerals, and repetitive description thereof is omitted.
(1) First embodiment (configuration)
FIG. 1 is a cross-sectional view schematically showing a configuration example of an electrophoretic display device 10 according to the first embodiment of the present invention. As shown in FIG. 1, the electrophoretic display device 10 includes a pixel substrate 1, a pixel electrode 2, a counter substrate 3, a common electrode 4, a dispersion liquid 5, a partition wall 8, and a coloring plate 15. Yes. First, the configuration of the electrophoretic display device 10 will be described.

  The pixel substrate 1 is a substrate including a pixel electrode 2 and a drive circuit (not shown) for controlling a voltage applied to the pixel electrode 2. The material of the pixel substrate 1 is, for example, glass or flexible plastic. The shape of the pixel substrate 1 is, for example, a flat plate shape. The pixel substrate 1 has a surface 1a and a surface 1b opposite to the surface 1a. A pixel electrode 2 is formed on the surface 1 a of the pixel substrate 1. Further, a drive circuit (not shown) may be formed on the surface 1b side of the pixel substrate 1. The drive circuit includes, for example, a plurality of thin film transistors (hereinafter referred to as TFTs). The TFT functions as a switching element for applying a voltage independently to each of the plurality of pixel electrodes.

  In the electrophoretic display device 10, the pixel substrate 1 is disposed, for example, on the side opposite to the display surface (that is, the surface on the image display side). For this reason, the pixel substrate 1 is not limited to being transparent (that is, colorless and transparent or colored and transparent and capable of transmitting visible light), and may be non-transparent. The TFT may be an organic TFT. In the case of an organic TFT, high-temperature heat treatment is not required in the manufacturing process. Therefore, an inexpensive, lightweight, and flexible plastic substrate can be used for the pixel substrate 1. The material and shape of the pixel substrate 1 are not limited to the above.

  The pixel electrode 2 is an electrode for applying a driving voltage to each of the plurality of cells partitioned by the partition walls. The pixel electrode 2 includes a plate-like electrode member (hereinafter, also simply referred to as “base”) 2 a and a convex portion 9 disposed on the base 2 a. Each of the plurality of pixel electrodes 2 corresponds to, for example, one pixel for monochrome display, and a voltage is applied independently by turning on and off the TFT. The pixel electrode 2 is formed of, for example, a laminate of nickel plating and gold plating in this order on a Cu (copper) foil, or a conductor such as Al (aluminum) or ITO (indium tin oxide). .

  The pixel electrodes 2 are arranged on the surface 1a of the pixel substrate 1 so as to form a plurality of columns in the vertical direction and the horizontal direction (that is, the horizontal direction) at equal intervals (that is, arranged in a dot matrix). ing.). Alternatively, the pixel electrodes 2 may be arranged in segments on the surface 1a of the pixel substrate. In addition, the pixel electrode 2 should just be formed with the conductor, and a material and a shape are not specifically limited. Further, the distance between the pixel electrodes 2 is not particularly limited.

  The counter substrate 3 is a substrate disposed to face the surface 1 a of the pixel substrate 1. In the electrophoretic display device 10, the counter substrate 3 is disposed on the display surface side, for example. For this reason, the counter substrate 3 needs to be transparent. The material of the counter substrate 3 is, for example, glass or flexible plastic. The shape of the counter substrate 3 is, for example, a flat plate shape. The counter substrate 3 only needs to be transparent, and the material and shape are not limited to the above.

  The common electrode 4 is an electrode for applying a common voltage to each of the plurality of cells 12 partitioned by the partition walls, and is connected to, for example, a ground potential or a fixed potential. The common electrode 4 is disposed between the pixel substrate 1 and the counter substrate 3 and at positions away from the pixel substrate 1 and the counter substrate 3. The common electrode 4 is a grid electrode, for example, and has an opening 4a through which the electrophoretic particles 6 can pass.

  FIG. 2 is a plan view showing an example of the common electrode 4 according to the first embodiment. As shown in FIG. 2A, the common electrode 4 is a grid electrode, for example, a mesh electrode having an opening 4a. The shape of the opening 4a is, for example, a quadrangle in a plan view or a rounded quadrangle in a plan view. Further, as shown in FIG. 2B, the common electrode 4 may be a flat electrode having an opening 4a, for example. FIG. 2B illustrates a case where the shape of the opening 4a is a circular shape in plan view, but the shape of the opening 4a is not limited to this, and is rectangular in plan view. May be triangular or polygonal. Furthermore, the common electrode 4 may be, for example, a ring-shaped electrode (not shown).

In addition, when the common electrode 4 is a grid electrode, the common electrode 4 should just be formed with the electroconductive member, The material and shape are not specifically limited. That is, it does not matter whether it is transparent or non-transparent. For example, aluminum (Al) can be used as a member of the common electrode 4. When the common electrode 4 is a grid electrode, the common electrode 4 is fixed to the partition wall 8, for example.
Returning to FIG. 1, the dispersion 5 includes the electrophoretic particles 6 and the dispersion medium 7. The dispersion 5 is filled in each of a plurality of cells 12 surrounded by the pixel substrate 1, the counter substrate 3, and a partition wall 8 described later. The dispersion 5 is in contact with, for example, the pixel electrode 2 and the common electrode 4.

The electrophoretic particles 6 are particles that can migrate in the dispersion medium 7 when an electric field is applied between the pixel electrode 2 and the common electrode 4, and are either positive (positive) or negative (negative). It is a charged particle. In FIG. 1, as the electrophoretic particles 6, for example, white particles that are positively charged are illustrated.
The dispersion medium 7 includes a solvent 7a and a dispersant (not shown). The solvent 7a is a non-aqueous solvent, for example, and is a solvent containing so-called counter ions. Furthermore, it is an insulating solvent. When the solvent 7a is a non-aqueous solvent, compared with the case where the solvent 7a is an aqueous solvent, water can be prevented from entering the cell, and the cell can be expanded by absorbing moisture (swelling). ) And corrosion of the electrode and the like due to moisture can be prevented. For this reason, the reliability of the electrophoretic display device 10 can be improved. The dispersant is a substance for uniformly dispersing the electrophoretic particles 6 in the solvent 7a.

  The partition wall 8 is a wall for partitioning the pixel substrate 1 and the counter substrate 3 into a plurality of cells 12. The partition wall 8 can prevent the electrophoretic particles 6 from sedimenting in the lateral direction (that is, moving to the adjacent cell 12). In FIG. 1, a partition having a smooth surface is illustrated as the partition 8. The partition wall 8 is disposed between the pixel electrodes 2 so as to surround each of the plurality of pixel electrodes 2 in plan view. As illustrated in FIG. 2 described later, the shape of the portion surrounding the pixel electrode 2 of the partition wall 8 in plan view (hereinafter referred to as planar shape) is, for example, a square. The part surrounding the pixel electrode 2 of the partition wall 8 is also a part surrounding the convex part 9 and is also a part constituting the outline of each cell 12. An epoxy resin can be used as a material for the partition wall 8. In addition, the shape and material of the partition 8 are not limited to the above.

  The protrusion 9 is a protrusion provided in the pixel electrode 2, and is formed of, for example, a conductive material, like the base 2a. The convex portion 9 protrudes toward the surface 3 a of the counter substrate 3. The convex portion 9 is for concentrating the electric field when an electric field is applied between the pixel electrode 2 and the common electrode 4 (that is, making the strength of the electric field locally in the cell). By concentrating the electric field around the convex portion 9, convection of the solvent 7a can be efficiently generated. The convex portion 9 is made of, for example, a quadrangular pyramid, and its bottom surface is in contact with the base portion 2a, and its apex 9a is arranged so as to face the inside of the cell 12 (that is, the common electrode 4 side). The apex 9 a of the convex portion 9 is a portion where the electric field is particularly concentrated when an electric field is applied between the pixel electrode 2 and the common electrode 4.

FIG. 3 is a diagram illustrating an example of a positional relationship between the convex portion 9 and the common electrode 4. 3A is a cross-sectional view, and FIG. 3B is a plan view viewed from the counter substrate side. In FIG. 3B, only the convex portion 9, the common electrode 4, and the partition wall 8 are shown so that the positional relationship can be easily grasped.
In the first embodiment, as shown in FIG. 3A, a virtual line (center line) that passes through the vertex 9a of the convex portion 9 and is orthogonal to the bottom surface of the convex portion 9 in the cross-sectional view is the center of the opening 4a. It is preferable that the positional relationship between the convex portion 9 and the common electrode 4 is adjusted so as to pass through. That is, as shown in FIG. 3B, in a plan view, the positional relationship between the convex portion 9 and the common electrode 4 is adjusted so that the vertex 9a of the convex portion 9 and the center of the opening 4a overlap. Is preferred. Thereby, the convection of the solvent 7a, which will be described later, can be made to be nearly symmetrical in a sectional view with the convex portion 9 as the center, and it becomes easy to ensure the symmetry of the convection.

  Returning to FIG. 1, the colored plate 15 is disposed between the pixel electrode 1 and the common electrode 4 and has a plurality of holes (or gaps) having a diameter larger than that of the electrophoretic particles 6. As a result, the colored plate 15 can pass the electrophoretic particles 6 from one surface thereof to the other surface through holes or the like. The colored plate 15 is made of an insulating member. The colored plate 15 is colored in a different color from the electrophoretic particles 6. For example, when the electrophoretic particles 6 are white, the colored plate 15 is colored in a color other than white (for example, black). When the electrophoretic particles 6 are black, the colored plate 15 is colored in a color other than black (for example, white). For example, the coloring plate 15 is fixed to the partition wall 8.

  FIG. 4 is a cross-sectional view illustrating a configuration example of the coloring plate 15. As shown in FIG. 4A, the colored plate 15 has a sheet shape and a structure in which a fibrous insulating material is knitted. Or as shown in FIG.4 (b), the colored board 15 may be porous structures, such as a sheet form and foaming urethane. Further, as shown in FIG. 4 (c), the colored plate 15 has a plurality of sheets 15a, 15b, 15c,... With holes 16, so that the positions of the holes 16 are staggered (that is, the colored plate 15). In the thickness direction, a stacked structure may be used so that the holes 16 overlap and communicate with each other. In particular, the laminated structure of the sheets shown in FIG. 4 (c) is easy to adjust the size and shape of the holes 16 of the sheets 15a, 15b, 15c..., And the sheets 15a, 15b, 15c. By doing so, there is an advantage that the thickness of the colored plate 15 and the ease of passage of the electrophoretic particles 6 can be adjusted. Next, an operation example of the electrophoretic display device 10 will be described.

(Operation)
FIG. 5 is a cross-sectional view schematically showing a mechanism in which the electrophoretic display device 10 described in FIG. 1 operates. FIG. 5A is a diagram schematically showing the electrophoretic display device 10 in a state where no electric field is applied between the pixel electrode 2 and the common electrode 4 (that is, no electric field). As shown in FIG. 5A, the electrophoretic particles 6 are dispersed in the dispersion medium 7 when no electric field is applied between the pixel electrode 2 and the common electrode 4.

  FIGS. 5B and 5D are diagrams schematically showing the electrophoretic display device 10 in an initial state in which an electric field is applied between the pixel electrode 2 and the common electrode 4. Here, FIG. 5B shows a state in which a negative potential is applied to the pixel electrode 2 and a positive potential is applied to the common electrode 4. Since an electric field is applied between the pixel electrode 2 and the common electrode 4, the electrophoretic particles 6 are affected by the electric field and attempt to migrate toward the pixel electrode 2.

  At the same time, the electric field concentrates on the apex 9a of the convex portion 9, and the electric field strength at the apex 9a is increased. This local strong electric field interacts with ions (mainly counter ions) contained in the solvent 7a, so that the solvent 7a is uniform in the direction away from the vertex 9a (the common electrode 4 side) starting from the vertex 9a. It flows (convection of the solvent 7a occurs). The convection of the solvent 7a is continuously generated while an electric field is applied from the outside. Therefore, the solvent 7a circulates in each of the plurality of cells 12. The flow rate of this convection can be made faster than the migration speed due to the electrical action of the electrophoretic particles 6.

  In each of the plurality of cells 12, convection in a circulating direction is generated in the solvent 7 a, and the electrophoretic particles 6 are transported in each cell 12 by this convection. At this time, the electrophoretic particles 6 are transported through the holes 16 of the colored plate 15 (for example, see FIG. 4C). The electrophoretic particles 6 transported along the convection direction of the solvent 7a are selectively attracted to the surface of the pixel electrode 2 or the surface of the common electrode 4 by the Coulomb force. As described above, in this example, since the electrophoretic particles 6 are positively charged, they are attracted to the surface of the pixel electrode 2. By repeating the movement by the convection (that is, when the dispersion liquid 5 circulates), many electrophoretic particles 6 are adsorbed on the pixel electrode 2. As a result, as shown in FIG. 5C, the electrophoretic particles 6 hardly exist between the common electrode 4 and the counter substrate as the display surface. Thereby, the electrophoretic display device 10 displays the color of the colored plate 15 on the display surface.

  On the other hand, FIG. 5D shows a state in which a positive potential is applied to the pixel electrode 2 and a negative potential is applied to the common electrode 4. Since an electric field is applied between the pixel electrode 2 and the common electrode 4, the electrophoretic particles 6 are affected by the electric field and attempt to migrate toward the common electrode 4. At the same time, the electric field concentrates on the convex portion 9 and the electric field strength at the pixel electrode 2 increases.

For this reason, convection of the solvent 7a is generated in the opposite direction to the case of FIG. 5B, and the electrophoretic particles 6 are transported in each cell 12 by this convection. Also at this time, the electrophoretic particles 6 are transported through the holes 16 of the colored plate 15 or the like. And many electrophoretic particles 6 are adsorbed to the common electrode 4 by repeating movement by convection. As a result, as shown in FIG. 5E, many electrophoretic particles 6 gather between the common electrode 4 and the counter substrate which is the display surface. Thereby, the electrophoretic display device 10 displays the color of the electrophoretic particles 6 on the display surface.
Note that after the electric field is applied, the display state shown in FIG. 5C or FIG. 5E can be maintained by the electric mirror image force even in the state where no electric field is applied from the outside.

(Effect of 1st Embodiment)
As described above, according to the electrophoretic display device 10 according to the first embodiment of the present invention, the pixel electrode 2 includes the convex portion 9 that protrudes toward the common electrode 4, and thus is common to the pixel electrode 2. When an electric field is applied between the electrode 4 and the electrode 4, the electric field concentrates on the convex portion 9. Thereby, convection of the solvent 7a can be generated starting from the convex portion 9, and the solvent 7a can be circulated toward the pixel electrode 2 side or the common electrode 4 side in each of the plurality of cells 12. . The flow velocity of the convection can be made faster than the migration speed due to the Coulomb force of the electrophoretic particles 6.

Thus, in each of the plurality of cells 12, the electrophoretic particles 6 are transported by the convection of the solvent 7a. In addition, among the electrophoretic particles 6 transported by convection, particles approaching the pixel electrode 2 or the common electrode 4 are selectively attracted to any electrode by the Coulomb force acting between the particles. Adsorb.
Thus, according to the electrophoretic display device 10 according to the first embodiment of the present invention, the convection of the solvent 7 a can be intentionally generated and used for the movement of the electrophoretic particles 6. The electrophoretic particles 6 can be moved by actively utilizing not only the Coulomb force but also the convection of the solvent 7a. For this reason, the responsiveness of the electrophoretic particles 6 can be improved, and a “high-speed response” is possible.

  Further, compared with the prior art, in order to increase the responsiveness of the electrophoretic particles 6, it is not necessary to increase the charge amount of the electrophoretic particles 6 and it is not necessary to increase the concentration of ions contained in the solvent 7a. For this reason, it is possible to reduce the leakage current generated during the operation of the electrophoretic display device 10 and to achieve “low power consumption”. Therefore, the trade-off relationship between “high-speed response” and “low power consumption” can be eliminated, and both can be achieved.

Further, according to the electrophoretic display device 10 according to the first embodiment of the present invention, the colored plate 15 is disposed between the pixel electrode 2 and the common electrode 4, and the colored plate 15 is connected to the electrophoretic particles 6. Are colored differently. Therefore, by selectively applying an electric field to each of the plurality of cells 12, the color of the electrophoretic particles 6 (first color) and the color of the coloring plate 15 (second color) can be selectively displayed. Can do. The electrophoretic particles 6 may be of a single color, and it is not necessary to dispose the electrophoretic particles 6 of different colors in the same cell 12, so that “high contrast” is possible. Therefore, the trade-off relationship between “high-speed response” and “high contrast” can be eliminated, and both can be achieved.
Moreover, since it is not necessary to prepare electrophoretic particles of a plurality of colors, it is possible to contribute to a reduction in manufacturing cost of the electrophoretic display device.

(First modification)
In the first embodiment, the case where the common electrode 4 is disposed between the colored plate 15 and the counter substrate 3 and at positions away from the colored plate 15 and the counter substrate 3 has been described. Moreover, the common electrode 4 demonstrated the case where it was a grid electrode which has the opening part 4a. However, in the first embodiment of the present invention, the arrangement and form of the common electrode 4 are not limited to this. Hereinafter, this point will be described with an example.

  FIG. 6 is a cross-sectional view schematically showing a modification of the common electrode 4. As shown in FIG. 6A, when the common electrode 4 is a grid electrode, the common electrode 4 may be in contact with the colored plate 15. That is, the common electrode 4 may be disposed between the coloring plate 15 and the counter substrate 3, in contact with the coloring plate 15, and at a position away from the counter substrate 3. Further, the common electrode 4 may not only be in contact with the colored plate 15 but may be fixed to the surface of the colored plate 15. Even in such a case, the common electrode 4 functions as an electrode. The colored plate 15 can also pass the electrophoretic particles 6.

Furthermore, when the common electrode 4 and the colored plate 15 are in contact (including the case where they are fixed), they can be fixed to the partition wall 8 in a lump. For example, as shown in FIG. 6A, a case is assumed in which the partition wall 8 includes a partition wall lower portion 8a fixed to the surface 1a of the pixel substrate 1 and a partition wall upper portion 8b fixed to the surface 3a of the counter substrate 3. . In this case, the common electrode 4 and the colored plate 15 can be fixed to the partition 8 together by sandwiching the common electrode 4 and the colored plate 15 between the partition lower portion 8a and the partition upper portion 8b. For this reason, it becomes easy to fix the common electrode 4 and the colored plate 15 to the partition wall 8.
As another modified example, as shown in FIGS. 6B and 6C, the common electrode 4 may be formed entirely or partially on the surface 3 a of the counter substrate 3. In this case, the common electrode 4 is made of a transparent conductive film such as ITO. Even in such a case, the common electrode 4 functions as an electrode.

(Second modification)
In the first embodiment described above, a case has been described in which one convex portion 9 is arranged in each of the plurality of cells 12, and the convex portion 9 is formed of a quadrangular pyramid with the apex 9 a facing the inside of the cell 12. However, in the embodiment of the present invention, the arrangement and shape of the convex portions are not limited to this. In the embodiment of the present invention, a plurality of convex portions 9 may be arranged in one cell 12. Moreover, the convex part 9 may be comprised with cones other than a quadrangular pyramid, such as a cone, a triangular pyramid, and a hexagonal pyramid. Or the convex part 9 may be comprised by column bodies, such as a triangular prism, a square pole, a hexagonal pillar, and a cylinder. Hereinafter, this point will be described.

FIG. 7 is a perspective view and a cross-sectional view schematically showing a modified example of the convex portion 9. As shown in FIGS. 7A and 7B, the convex portion 9 may be formed of a cone. If the convex portion 9 is arranged so that the bottom surface of the cone is in contact with the base portion 2a and the apex 9a of the cone faces the common electrode 4, the electric field can be concentrated on the apex 9a of the cone.
Moreover, as shown to FIG.7 (c) and (d), the convex part 9 may be comprised by the cylinder. If one end face of the cylinder is in contact with the base portion 2a and the other end face 9b of the cylinder faces the common electrode 4, the electric field can be concentrated on the end face 9b.

  Moreover, the convex part 9 may be linear. Specifically, as shown in FIGS. 7E and 7F, the line-shaped convex portion 9 is formed of a triangular prism, and the triangular prism is arranged so as to be tilted on the base 2a (that is, three triangular prisms). It may be arranged such that one of the side surfaces is in contact with the base 2a. In this case, when an electric field is applied between the pixel electrode 2 and the common electrode 4, the electric field can be concentrated on the side 9c closest to the common electrode 4 among the sides of the triangular prism.

  Further, as shown in FIGS. 7 (g) and (h), the line-shaped convex portion is formed of a quadrangular column, and the quadrangular column is arranged so as to be tilted on the base 2a (that is, the four side surfaces of the quadrangular column). One of them may be arranged so as to be in contact with the base portion 2a). In this case, when an electric field is applied between the pixel electrode 2 and the common electrode 4, the electric field can be concentrated on the side surface 9d closest to the common electrode 4 among the side surfaces of the quadrangular prism.

In the embodiment of the present invention, as the convex portion 9, for example, the above examples may be combined. For example, as shown in FIGS. 7 (i) and 7 (j), as the convex portion 9, a triangular prism line shape and a quadrangular prism line shape may be arranged separately. In this case, when an electric field is applied between the pixel electrode 2 and the common electrode 4, the electric field can be concentrated on the side 9c of the triangular prism and the side surface 9d of the quadrangular prism.
Although not shown, when a plurality of convex portions 9 are arranged in one cell, some of them are arranged directly on the surface 1a (for example, see FIG. 1) of the pixel substrate 1 instead of on the base portion 2a. You may make it do. In FIGS. 7A, 7C, 7E, 7G, and 7I, the description of the counter substrate 3 and the common electrode 4 is omitted.

(2) Second Embodiment In the first embodiment described above, as an example, the case where the electrophoretic particles 6 are white and the colored plate 15 is colored in a color other than white (as an example, black) has been described. Alternatively, the case where the electrophoretic particles 6 are black and the colored plate 15 is colored in a color other than black (for example, white) has been described. However, in the embodiment of the present invention, the colors of the electrophoretic particles 6 and the colored plate 15 are not limited to the above, and any color can be selected. In the embodiment of the present invention, the color of the coloring plate 15 may be different between the first cell 12 and the second cell 12 among the plurality of cells 12. For example, if the colored plate 15 is colored in a different color between a plurality of adjacent cells 12, three or more colors can be displayed. In the second embodiment, an electrophoretic display device capable of color display will be described.

(First configuration)
FIG. 8 is a conceptual diagram showing a first configuration example of the electrophoretic display device 20 according to the second embodiment of the present invention. The electrophoretic display device 20 according to the second embodiment is different from the electrophoretic display device 10 described in the first embodiment in that the color of the colored plate 15 is different among the plurality of cells 12. Other configurations are the same as those of the electrophoretic display device 10 described in the first embodiment.

  FIG. 8A shows a case where the electrophoretic particles 6 are black and the colored plates 15 of the four adjacent cells 12 are colored in different colors. For example, among the plurality of cells 12, the colored plate 15 of the first cell 12 is colored red (R), the colored plate 15 of the second cell 12 is colored green (G), and the third cell 12 The colored plate 15 is colored blue (B), and the colored plate 15 of the fourth cell 12 is colored white (W).

  The first cell 12 can selectively display red (R) of the colored plate 15 and black of the electrophoretic particles 6. The second cell 12 can selectively display green (G) of the colored plate 15 and black of the electrophoretic particles 6. Similarly, the third cell 12 can selectively display blue (B) and black, and the fourth cell can selectively display white (W) and black. Therefore, in FIG. 8A, for example, one pixel for color display can be configured by the first to fourth cells 12. Then, by selectively displaying the three primary colors of red (R), green (G), and blue (B), white (W), or black of particles in each cell 12 constituting one pixel, the color is changed. It is possible to mix and display a color image of a wide range of colors using a plurality of pixels.

  Or as shown in FIG.8 (b), the color of a coloring board may be three colors instead of four colors. For example, among the plurality of cells 12, the colored plate 15 of the first cell 12 is colored red (R), the colored plate 15 of the second cell 12 is colored green (G), and the third cell 12 The colored plate 15 is colored blue (B), and the first to third cells 12 may constitute one pixel for color display. Even in such a case, colors can be mixed by selectively displaying the three primary colors of RGB or the black color of the particles in each cell 12 constituting one pixel, and a color image using a plurality of pixels. Can be displayed.

(Second configuration)
In the second embodiment of the present invention, color images may be displayed using the three primary colors cyan (C), magenta (M), and yellow (Y) instead of the three primary colors RGB.
FIG. 9 is a conceptual diagram showing a second configuration example of the electrophoretic display device 20 according to the second embodiment of the present invention. FIG. 9A shows a case where the electrophoretic particles 6 are white and the colored plates 15 of the four adjacent cells 12 are colored in different colors. For example, among the plurality of cells 12, the colored plate 15 of the first cell 12 is colored cyan (C), the colored plate 15 of the second cell 12 is colored magenta (M), and the third cell 12 is colored. The colored plate 15 is colored yellow (Y), and the colored plate 15 of the fourth cell 12 is colored black (Bk).

  The first cell 12 can selectively display cyan (C) of the colored plate 15 and white of the electrophoretic particles 6. The second cell 12 can selectively display the magenta (M) of the colored plate 15 and the white color of the electrophoretic particles 6. Similarly, the third cell 12 can selectively display yellow (Y) and white, and the fourth cell can selectively display black (Bk) and white. For this reason, in FIG. 9A, the first to fourth cells 12 can constitute one color pixel. Then, by selectively displaying the three primary colors of cyan (C), magenta (M), yellow (Y), black (Bk), or white of particles in each cell 12, colors can be mixed, A wide range of color images can be displayed using a plurality of pixels.

  Or as shown in FIG.9 (b), the color of a colored plate may be three colors instead of four colors. That is, among the plurality of cells 12, the colored plate 15 of the first cell 12 is colored cyan (C), the colored plate 15 of the second cell 12 is colored magenta (M), and the third cell 12 is colored. The colored plate 15 is colored yellow (B), and the first to third cells 12 may constitute one color pixel. Even in such a case, colors can be mixed by selectively displaying the three primary colors of CMY or white in each cell 12, and a color image can be displayed using a plurality of pixels. is there.

(Effect of 2nd Embodiment)
According to 2nd Embodiment of this invention, there exists an effect of 1st Embodiment mentioned above. In addition, a color image can be displayed.
(3) Third Embodiment Next, a case where the electrophoretic display devices 10 and 20 according to the first and second embodiments are applied to an electronic device will be described.
(Constitution)
FIG. 10A is a perspective view showing a configuration example of the electronic paper 100 according to the third embodiment of the present invention. The electronic paper 100 includes any one of the electrophoretic display devices 10 and 20 described in the first and second embodiments in the display area 101. Since the pixel substrate 1 and the counter substrate 3 are each made of a flexible material, the electronic paper 100 is flexible, and is made of a rewritable sheet having the same texture and flexibility as conventional paper. The main body 102 is provided.

  FIG. 10B is a perspective view illustrating a configuration example of the electronic notebook 200. An electronic notebook 200 is obtained by bundling a plurality of the electronic papers 100 and sandwiching them between covers 201. The cover 201 includes display data input means (not shown) for inputting display data sent from an external device, for example. Thereby, according to the display data, the display content can be changed or updated while the electronic paper is bundled.

(Effect of the third embodiment)
The electronic paper 100 and the electronic notebook 200 according to the third embodiment of the present invention include the electrophoretic display device 10 according to the first embodiment of the present invention or the electrophoretic display device 20 according to the second embodiment. . For this reason, the same effects as those of the first and second embodiments can be obtained, and an electronic apparatus including a display unit having excellent image retention characteristics and excellent display quality can be obtained. Note that the electronic paper 100 and the electronic notebook 200 described above are examples of the electronic apparatus according to the present invention, and do not limit the scope of application of the present invention. For example, the electrophoretic display devices 10 and 20 can be suitably used for display portions of electronic devices such as mobile phones and portable audio devices.

1 pixel substrate, 1a, 1b, 3a plane, 2 pixel electrode, 2a base, 3 counter substrate, 4 common electrode, 4a opening, 5 dispersion, 6 electrophoretic particles, 7 dispersion medium, 7a solvent 8 partition, 8a partition Lower part, 8b Partition upper part, 9 convex part, 9a vertex, 9b end face, 9c side, 9d side face, 10, 20 electrophoretic display device, 12 cells, 15 colored plate, 15a, 15b, 15c sheet, 16 holes, 100 electronic paper , 101 display area, 102 main body, 200 electronic notebook, 201 cover

Claims (9)

A first substrate having a first electrode on a first surface;
A second substrate facing the first surface;
A second electrode disposed between the first substrate and the second substrate and spaced from the first electrode;
A partition partitioning a plurality of cells between the first substrate and the second substrate;
A dispersion having electrophoretic particles filled in each of the plurality of cells;
A sheet-like particle passing member disposed between the first electrode and the second electrode, through which the electrophoretic particles can pass,
The particle passage member is colored in a different color from the electrophoretic particles,
The electrophoretic display, wherein the first electrode has a convex portion that protrudes toward the second substrate and concentrates an electric field applied between the first electrode and the second electrode. apparatus.   The electrophoretic display device according to claim 1, wherein the electrophoretic particles are charged only in one of positive and negative.   The electrophoretic display according to claim 1, wherein the second electrode is disposed away from the second substrate and has an opening through which the electrophoretic particles can pass. apparatus.   The structure of the particle passage member is a structure in which a plurality of sheets having a plurality of through holes having a diameter larger than that of the electrophoretic particles are stacked in the thickness direction of the particle passage member. 4. The electrophoretic display device according to any one of items 3.   The first cell and the second cell of the plurality of cells are colored in different colors by the particle passing member. Electrophoretic display device.   The electrophoretic display device according to claim 1, wherein the convex portion is formed of a weight, and the apex of the cone is directed to the inside of the cell.   The electrophoretic display device according to claim 1, wherein the convex portion is a column.   The convection of the dispersion liquid is generated in the cell from the convex portion as a base point by applying an electric field between the first electrode and the second electrode. The electrophoretic display device according to any one of items 7.   An electronic apparatus comprising the electrophoretic display device according to any one of claims 1 to 8.

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