JP2009192637A - Electrophoretic display sheet, electrophoretic display device and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophoretic display sheet capable of exhibiting superior color display property, an electrophoretic display device and an electronic apparatus. <P>SOLUTION: The electrophoretic display device 1 has a dispersion medium 5 containing first particles A and second particles B which are charged negatively, and third particles C which are charged positively. The first particles A have larger electrophoretic mobility than the second particles B, and smaller charge density than the second particles B. A voltage such that an upper electrode 7 is positive and a lower electrode 8 is negative is applied to obtain a first state wherein the first particles A are disposed on the side of the upper electrode 7 more than the second particles B by using the difference in electrophoretic mobility, and in the first state, a voltage such that a pair of electrode pieces 71 and 72 alternate in having high and low potentials is applied between the electrode pieces 71 and 72 to obtain a second state wherein the position relation between the first particles A and second particles B is inverted of that in the first state by using the difference in charge density. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

For example, an electrophoretic display using particle electrophoresis is known as an image display unit of electronic paper (see, for example, Patent Document 1). The electrophoretic display has excellent portability and power saving, and is particularly suitable as an image display unit of electronic paper.
Patent Document 1 discloses an electrophoretic display device that constitutes a pixel of an electrophoretic display. The electrophoretic display device includes a cell, and in the cell, a transparent insulating liquid, positively charged white electrophoretic particles (hereinafter simply referred to as “white particles”), and negatively charged black Electrophoretic particles (hereinafter simply referred to as “black particles”) are enclosed. Further, a transparent electrode is installed on one side of the cell, and a colored plate is installed on the other side. Furthermore, the 1st electrode and the 2nd electrode are provided on the colored plate (refer FIG. 3 of patent document 1).

Such an electrophoretic display device has a white color by applying a voltage between the transparent electrode and the first and second electrodes, or applying a voltage between the first electrode and the second electrode. The desired color is displayed by causing the particles and the black particles to migrate in the transparent insulating liquid, thereby causing the white particles and the black particles to be unevenly distributed at desired portions.
Here, in the electrophoretic display device of Patent Document 1, when a voltage is applied to the first electrode and the second electrode, for example, black particles are unevenly distributed in the vicinity of the first electrode, and white particles are in the vicinity of the second electrode. Is unevenly distributed.

  At this time, when the inside of the cell is visually recognized through the transparent electrode, the color plate has a larger area than the total area of the aggregate of white particles and the aggregate of black particles. It becomes. However, since white particles and black particles are unevenly distributed between the transparent electrode and the colored plate, the white particles and the black particles are affected, and the color purity of the colored plate is lowered. It becomes difficult to display colors.

JP 2005-31345 A

  An object of the present invention is to provide an electrophoretic display sheet, an electrophoretic display device, and an electronic apparatus that can exhibit excellent color display properties.

Such an object is achieved by the present invention described below.
The electrophoretic display sheet of the present invention includes a filling portion filled with a dispersion medium in which at least two kinds of particles having different colors are dispersed;
A first electrode provided on one side of the filling portion and having a pair of electrode pieces that can be visually recognized in the filling portion;
A second electrode provided on the other side of the filling portion,
The at least two types of particles include negatively charged first particles and second particles,
The first particles have a higher electrophoretic mobility than the second particles and a lower charge density than the second particles;
By applying a voltage in which the first electrode is positive and the second electrode is negative, a difference in the electrophoretic mobility is obtained when the first particles and the second particles are unevenly distributed on the first electrode side. A first state in which the first particles are located closer to the first electrode than the second particles, and the pair of electrode pieces of the first electrode between the pair of electrode pieces from the first state. By applying a voltage that alternately switches the potential level of the electrode piece, the second particle is located closer to the second electrode than the second particle using the difference in charge density. A state in which the color in the filling portion visually recognized through the first electrode is changed by selecting either the first state or the second state. It is characterized by being.
Thereby, the electrophoretic display sheet which can exhibit the outstanding color display property can be provided.

In the electrophoretic display sheet of the present invention, it is preferable that a positive voltage is applied to each of the pair of electrode pieces to alternately switch the potential level of the pair of electrode pieces.
Thereby, the positional relationship between the first particles and the second particles can be reversed while the first particles and the second particles are positioned in the vicinity of the first electrode. Therefore, switching from the first state to the second state can be performed smoothly.

In the electrophoretic display sheet of the present invention, in addition to the at least two kinds of particles, positively charged third particles are included,
By applying a voltage in which the first electrode is negative and the second electrode is positive, the third particles are unevenly distributed on the first electrode side, and the first particles and the second particles are unevenly distributed on the second electrode side. It is preferable to change the color by selecting one of the first state, the second state, and the third state.
As a result, the colors of the three types of particles can be clearly displayed.

In the electrophoretic display sheet of the present invention, when the voltage is applied between the pair of electrode pieces of the first electrode so that the potential level of the pair of electrode pieces is alternately switched, It is preferable to apply a voltage that causes the third particles to be unevenly distributed on the second electrode side.
Thereby, the positional relationship between the first particles and the second particles can be reversed while the third particles are positioned in the vicinity of the second electrode. Therefore, the color display characteristics are improved.

In the electrophoretic display sheet of the present invention, when the voltage applied to one of the pair of electrode pieces is V1, the voltage applied to the other is V2, and the voltage applied to the second electrode is V3, V3 Preferably satisfies the relationship of V1, V2> V3.
Thereby, the positional relationship between the first particles and the second particles can be reversed while the third particles are positioned in the vicinity of the second electrode more reliably. Therefore, the color display characteristics are further improved.

The electrophoretic display sheet of the present invention includes a filling portion filled with a dispersion medium in which at least two kinds of particles having different colors are dispersed;
A first electrode provided on one side of the filling portion and having a pair of electrode pieces that can be visually recognized in the filling portion;
A second electrode provided on the other side of the filling portion,
The at least two kinds of particles include positively charged first particles and second particles,
The first particles have a higher electrophoretic mobility than the second particles and a lower charge density than the second particles;
By applying a voltage that makes the first electrode negative and the second electrode positive, the difference in the electrophoretic mobility is caused when the first particles and the second particles are unevenly distributed on the first electrode side. A first state in which the first particles are located closer to the first electrode than the second particles, and the pair of electrode pieces of the first electrode between the pair of electrode pieces from the first state. By applying a voltage that alternately switches the potential level of the electrode piece, the second particle is located closer to the second electrode than the second particle using the difference in charge density. A state in which the color in the filling portion visually recognized through the first electrode is changed by selecting either the first state or the second state. It is characterized by being.
Thereby, the electrophoretic display sheet which can exhibit the outstanding color display property can be provided.

In the electrophoretic display sheet of the present invention, it is preferable that a negative voltage is applied to each of the pair of electrode pieces to alternately switch the potential level of the pair of electrode pieces.
Thereby, the positional relationship between the first particles and the second particles can be reversed while the first particles and the second particles are positioned in the vicinity of the first electrode. Therefore, switching from the first state to the second state can be performed smoothly.

In the electrophoretic display sheet of the present invention, in addition to the at least two kinds of particles, negatively charged third particles are included,
By applying a voltage in which the first electrode is positive and the second electrode is negative, the third particles are unevenly distributed on the first electrode side, and the first particles and the second particles are unevenly distributed on the second electrode side. It is preferable to change the color by selecting one of the first state, the second state, and the third state.
As a result, the colors of the three types of particles can be clearly displayed.

In the electrophoretic display sheet of the present invention, when the voltage is applied between the pair of electrode pieces of the first electrode so that the potential level of the pair of electrode pieces is alternately switched, It is preferable to apply a voltage that causes the third particles to be unevenly distributed on the second electrode side.
Thereby, the positional relationship between the first particles and the second particles can be reversed while the third particles are positioned in the vicinity of the second electrode. Therefore, the color display characteristics are improved.

In the electrophoretic display sheet of the present invention, when the voltage applied to one of the pair of electrode pieces is V1, the voltage applied to the other is V2, and the voltage applied to the second electrode is V3, V3 Preferably satisfies the relationship of V1, V2 <V3.
Thereby, the positional relationship between the first particles and the second particles can be reversed while the third particles are positioned in the vicinity of the second electrode more reliably. Therefore, the color display characteristics are further improved.

In the electrophoretic display sheet of the present invention, it is preferable that one of the first particles and the third particles is a black particle and the other is a white particle.
As a result, monochrome display is possible, and visibility, particularly contrast, is improved.
In the electrophoretic display sheet of the present invention, it is preferable that the first particles are black particles and the third particles are white particles.
As a result, monochrome display is possible, and visibility, particularly contrast, is improved. Further, excellent white display characteristics can be exhibited.

In the electrophoretic display sheet of the present invention, it is preferable that the second particles are chromatic particles.
Thereby, color display becomes possible and versatility of the electrophoretic display device is enhanced.
The electrophoretic display device of the present invention includes the electrophoretic display sheet of the present invention and a substrate provided on the other side of the filling portion.
Thus, an electrophoretic display device that can exhibit excellent display characteristics can be provided.
An electronic apparatus according to the present invention includes the electrophoretic display device according to the present invention.
Thereby, an electronic device that can exhibit excellent display characteristics can be provided.

Hereinafter, an electrophoretic display sheet, an electrophoretic display device, and an electronic apparatus according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
<Electrophoretic display device>
<< First Embodiment >>
First, a first embodiment of an electrophoretic display device (electrophoretic display device of the present invention) to which the electrophoretic display sheet of the present invention is applied will be described.

FIG. 1 is a schematic longitudinal sectional view showing a first embodiment of the electrophoretic display device of the present invention, FIG. 2 is a diagram showing an example of drive waveforms of the electrophoretic display device shown in FIG. 1, and FIGS. These are schematic longitudinal cross-sectional views showing the operation of the electrophoretic display device, respectively. In the following, for convenience of explanation, the upper side in FIGS. 1 and 3 to 6 is referred to as “upper”, the lower side is referred to as “lower”, the right side is referred to as “right”, and the left side is referred to as “left”.
An electrophoretic display device 1 shown in FIG. 1 includes a circuit board (back plane) 9 and an electrophoretic display sheet 2 bonded to the upper surface of the circuit board 9. Hereinafter, the structure of each part is demonstrated sequentially.
The circuit board 9 has a flat base 91 and a circuit (not shown) including a switching element such as a TFT provided on the base 91.

On the other hand, the electrophoretic display sheet 2 includes a base 3 in which a plurality of recesses 31 are regularly formed on the upper surface, and a lid 4 provided on the upper surface of the base 3 so as to close the upper opening of the recess 31. have. The base 3 and the lid 4 are joined in a liquid-tight manner.
A liquid-tight space formed by the inner wall of the recess 31 and the lid portion 4 is filled with a dispersion medium 5 containing three types of particles A to C. Hereinafter, this liquid-tight space is referred to as “filling portion 6”.
A plurality of upper electrodes (first electrodes) 7 are provided on the upper surface of the lid 4 so as to correspond to the respective recesses 31. Such an upper electrode 7 is composed of a pair of electrode pieces 71 and 72 spaced apart from each other.

On the other hand, a plurality of lower electrodes (second electrodes) 8 are provided on the lower surface of the base 3 so as to correspond to the respective recesses 31. That is, the upper electrode 7 and the lower electrode 8 are disposed to face each other with the filling portion 6 interposed therebetween.
In the electrophoretic display device 1 of the present embodiment, each filling unit 6 constitutes one pixel, and each pixel has the same configuration as each other. P ”) will be described as a representative, and description of other pixels will be omitted.

  The substrate 3 has insulating properties and impermeability of the dispersion medium 5. The constituent material of the substrate 3 is not particularly limited. For example, various resin materials such as an epoxy resin, an acrylic resin, a urethane resin, a melamine resin, and a phenol resin, silica, alumina, titania, and the like. These ceramic materials can be used, and one or more of them can be used in combination.

The lid part 4 is substantially colorless and transparent, and has a function as a visual recognition part for visually recognizing the inside of the filling part 6 from the outside of the filling part 6 (hereinafter, the lid part 4 is referred to as “visual recognition part 4”). Also called). In addition, as the cover part 4, if the inside of the filling part 6 can be visually recognized from the exterior of the filling part 6, it may not be colorless and transparent, and may be colored.
Such a lid 4 has insulating properties and impermeability of the dispersion medium 5. The constituent material of the lid 4 is not particularly limited. For example, polyolefin such as polyethylene, polypropylene, and ethylene-vinyl acetate copolymer, modified polyolefin, polyamide (eg, nylon 6, nylon 66), styrene Various thermoplastic elastomers such as polyvinyl chloride, polyurethane, polyester, fluororubber, chlorinated polyethylene, etc., or copolymers, blends, polymer alloys, etc. mainly composed of these. One or two or more of them can be used in combination.
The separation distance between the upper surface of the lid 4 and the lower surface of the base 3, ie, the separation distance between the upper electrode 7 and the lower electrode 8, is not particularly limited, but is preferably about 10 to 500 μm, and about 20 to 100 μm. More preferably.

Next, the upper electrode 7 and the lower electrode 8 will be described.
As described above, the upper electrode 7 includes a pair of electrode pieces 71 and 72. Such electrode pieces 71 and 72 have substantially the same shape, and are provided so as to cover substantially the entire upper opening of the recess 31 when the electrophoretic display device 1 is viewed from the upper side in FIG. It has been. With such a configuration, as will be described later, since the entire region of the visual recognition unit 4 can be covered with any of the particles A to C, the color display characteristics are improved.
The electrode pieces 71 and 72 are substantially colorless and transparent, respectively. Thereby, the inside of the filling part 6 can be visually recognized from the outside of the electrophoretic display device 1 through the upper electrode 7 and the visual recognition part 4. The electrode pieces 71 and 72 may not be colorless and transparent as long as the inside of the filling unit 6 can be visually recognized from the outside of the electrophoretic display device 1 and may be colored.

The constituent material of the electrode pieces 71 and 72 is not particularly limited as long as it is substantially conductive. For example, a metal material such as copper, aluminum or an alloy containing these, carbon such as carbon black, etc. Ions such as NaCl, LiClO ₄ , KCl, LiBr, LiNO ₃ , and LiSCN in a matrix material such as an electroconductive polymer material such as polyacetylene, polypyrrole, or derivatives thereof, or a matrix resin such as polyvinyl alcohol, polycarbonate, or polyethylene oxide. Conductive oxidation of ion conductive polymer material in which conductive material is dispersed, indium tin oxide (ITO), fluorine-doped tin oxide (FTO), tin oxide (SnO ₂ ), indium oxide (IO), etc. Various conductive materials such as physical materials, and one or more of these materials It can be used in combination.
The lower electrode 8 is provided so as to cover the entire bottom surface 311 of the recess 31. The lower electrode 8 may not be provided so as to cover the entire area of the bottom surface 311 of the recess 31 as in the present embodiment. For example, the lower electrode 8 may be provided only at the center of the bottom surface 311, The bottom surface 311 may be provided so as to exclude the central portion.

On the other hand, the lower electrode 8 may be opaque or transparent.
The constituent material of the lower electrode 8 is not particularly limited as long as it is substantially conductive. For example, the same material as the constituent material of the electrode pieces 71 and 72 described above can be used.
Such a lower electrode 8 is electrically connected to the circuit formed on the circuit board 9. The electrophoretic display device 1 is configured to control ON / OFF of voltage application to the lower electrode 8 by a TFT (switching element) included in the circuit.

The electrophoretic display device 1 is configured such that a voltage can be applied independently to the electrode pieces 71 and 72 and the lower electrode 8 by a voltage application unit (not shown). In addition, the electrophoretic display device 1 can appropriately change the strength of the voltage applied to each electrode (the electrode pieces 71 and 72 and the counter electrode 8) by the voltage applying unit.
Specifically, when the voltage applied to the electrode piece 71 is V1, the voltage applied to the electrode piece 72 is V2, and the voltage applied to the lower electrode 8 is V3, for example, the strength of V1, V2, and V3 is V1. >V2> V3, V1>V3> V2, V2>V1> V3, V2>V3> V1, V3>V1> V2, V3>V2> V1, V1> V2 = V3, V1 <V2 = V3, etc. can do.

Next, the dispersion medium 5 filled in the filling unit 6 will be described.
The dispersion medium 5 is preferably substantially colorless and transparent. As such a dispersion medium 5, a medium having a relatively high insulating property is preferably used. Examples of the dispersion medium 5 include various types of water (distilled water, pure water, ion-exchanged water, etc.), alcohols such as methanol, ethanol, and butanol, cellosolves such as methyl cellosolve, and esters such as methyl acetate and ethyl acetate. , Ketones such as acetone and methyl ethyl ketone, aliphatic hydrocarbons such as pentane, alicyclic hydrocarbons such as cyclohexane, and aromatic hydrocarbons such as benzene having a long-chain alkyl group such as benzene and toluene , Halogenated hydrocarbons such as methylene chloride and chloroform, aromatic heterocycles such as pyridine and pyrazine, nitriles such as acetonitrile and propionitrile, amides such as N, N-dimethylformamide, carboxylates, Mineral oils such as liquid paraffin, vegetable oils such as linoleic acid, linolenic acid and oleic acid, dimethyl silyl Silicone oils such as hydrogen oil, methylphenyl silicone oil, and methyl hydrogen silicone oil, fluorine-based liquids such as hydrofluoroether, and other various oils, and other various oils. It can be used alone or as a mixture.

Further, in the dispersion medium 5, if necessary, for example, a charge control agent composed of particles of electrolyte, surfactant, metal soap, resin material, rubber material, oils, varnish, compound, etc., titanium-based coupling You may make it add various additives, such as dispersing agents, lubricants, stabilizers, such as an agent, an aluminum coupling agent, and a silane coupling agent.
Such a dispersion medium 5 contains three types of particles A to C, respectively, as described above. The three types of particles A to C may be contained in the dispersion medium 5, respectively, but are preferably dispersed in the dispersion medium 5.

The three types of particles A to C are respectively positive or negatively charged first particle A, second particle B charged to the same polarity as the first particle A, and opposite polarity of the first particle A. The third particles C are charged.
In the present embodiment, the case where the first particles A and the second particles B are negatively charged and the third particles C are positively charged will be described. The three types of particles A to C are also simply referred to as “electrophoretic particles”.

As described above, the first particles A and the second particles B are particles having negative charges, respectively. Therefore, the first particles A and the second particles B are adsorbed to the electrode to which a positive voltage is applied (that is, the electrode having the higher potential) out of the upper electrode 7 and the lower electrode 8. Thus, the particles migrate in the dispersion medium 5 toward the electrode.
On the other hand, the third particle C is a particle having a positive charge. Therefore, the third particles C are dispersed toward the upper electrode 7 and the lower electrode 8 so as to be adsorbed to the electrode to which a negative voltage is applied (that is, the electrode having the lower potential). The particles migrate in the medium 5.

Further, the first particle A has a higher electrophoretic mobility than the second particle B, and a lower charge density than the second particle B. In the present invention, the difference in electrophoretic mobility between the first particles and the second particles is used to make a black display state (first state) described later, and the charge density between the first particles and the second particles. By using the difference between the two, a yellow display state (second state), which will be described later, is set.
For example, the electrophoretic mobility of the first particle A can be selected by selecting (setting) the relationship between the charge density and the particle size of the first particle A and the relationship between the charge density and the particle size of the second particle B, respectively. Can be made larger than the electrophoretic mobility of the second particles B.

Hereinafter, in order to make the electrophoretic mobility of the first particle A larger than the electrophoretic mobility of the second particle B, the relationship between the charge density and the particle size of the first particle A, and the charge density of the second particle B An example will be given to explain how the relationship between the particle size and the particle size should be set. In the following, for convenience of explanation, the case where the first particles A and the second particles B are each spherical will be described.
First, if the electrophoretic mobility of the first particles A and mu _A, mu _A is represented by the formula (1) shown below.

［式（１）中のε_ｒは分散媒５の比誘電率であり、ε_０は真空の誘電率であり、ηは分散媒５の粘性率であり、ｆ（ｋａ_Ａ）は、Ｈｅｎｒｒｙ関数であり、Ψ_Ａ（０）は、第１粒子Ａの表面電位である。］

[Ε _r in the formula (1) is the relative permittivity of the dispersion medium 5, ε ₀ is the vacuum permittivity, η is the viscosity of the dispersion medium 5, and f (ka _A ) is the Henry function. Ψ _A (0) is the surface potential of the first particle A. ]

That is, ε _r , ε ₀ and η are elements due to the dispersion medium 5.
F (ka _A ) in the formula (1) is represented by the following formula (2), and Ψ _A (0) is represented by the following formula (3) because the first particles A are spherical. The

［式（２）中のκはＤｅｂｙｅ−Ｈｕｃｋｅｌパラメータであり、ａ_Ａは第１粒子Ａの粒径である。また、式（３）中のσ_Ａは第１粒子Ａの電荷密度である。］

[Κ in Equation (2) is the Debye-Huckel parameter, and a _A is the particle size of the first particle A. Further, σ _A in the formula (3) is the charge density of the first particles A. ]

Κ in the formula (2) is a value specific to the dispersion medium 5.
Σ _A in the formula (3) is represented by the following number (4) because the first particles A are spherical.

［式（４）中のＱ_Ａは第１粒子Ａの持つ電荷量(帯電量)である。］

[Q _A in the formula (4) is the charge amount (charge amount) of the first particles A. ]

From the above formulas (1) to (4), the electrophoretic mobility μA of the first particles _A is expressed by the following formula (5).

Similarly to the formula (5), the electrophoretic mobility μ _B of the second particle _B is represented by the following formula (6).

［式（６）中のａ_Ｂは第２粒子Ｂの粒径であり、σ_Ｂは第２粒子Ｂの電荷密度である。］

[A _B in the formula (6) is the particle size of the second particle B, and σ _B is the charge density of the second particle B. ]

From equation (6), it can be seen that the particle parameters that determine the electrophoretic mobility μ and the charge density σ are the particle diameter a and the charge amount Q. Therefore, first, in the case where Q _A = Q _B , ie, the charge amount ratio Q _B / Q _A = 1, the electrophoretic mobility ratio μ _B / μ _A when the particle size ratio a _B / a _A is changed. Then, let us see the change in the charge density ratio σ _B / σ _A. FIG. 7 is a graph of this.

In FIG. 7, since the charge amount ratio Q _B / Q _A = 1, when the particle size ratio a _B / a _A = 1, the first particles A and the second particles B are exactly the same as the particles. It shows the characteristics, and it can be seen that the electrophoretic mobility ratio μ _B / μ _A = 1 and the charge density ratio σ _B / σ _A = 1.
When a _B / a _A > 1, μ _B / μ _A <1 and σ _B / σ _A <1. Therefore, when than the particle size a _A of the first particles A is the particle size a _B of the second particles B large, electrophoretic mobility of the first particles A than electrophoretic mobility mu _B of the second particles B mu _A It is large and that the direction of the charge density sigma _a of the first particle a from charge density sigma _B of the second particles B increases seen towards the.

On the other hand, when a _B / a _A <1, μ _B / μ _A > 1 and σ _B / σ _A > 1. Therefore, when the particle size a _A of the first particles A than the particle size a _B of the second particles B is large, electrophoretic mobility mu _B than electrophoretic mobility mu _A of the first particles A second particles B is large and is can be seen that significantly better charge density sigma _B than the charge density sigma _a of the first particle a second particles B towards the. At this time, it can be seen that there is no particle diameter ratio a _B / a _A that satisfies the electrophoretic mobility ratio μ _B / μ _A <1 and the charge density ratio σ _B / σ _A > 1.

Here, let us consider a case where the charge amount ratio Q _B / Q _{A is changed} to Q _B / Q _A <1 and Q _B / Q _A > 1. FIG. 8 shows an example in which Q _B / Q _A <1. In the case of Q _B / Q _A = 0.1, electrophoresis is performed when the particle size ratio a _B / a _A is changed as in FIG. FIG. 5 is a graph showing changes in mobility ratio μ _B / μ _A and charge density ratio σ _B / σ _A. FIG. According to FIG. 8, as in FIG. 7, there may be no particle diameter ratio a _B / a _A satisfying the electrophoretic mobility ratio μ _B / μ _A <1 and the charge density ratio σ _B / σ _A > 1. I understand.

On the other hand, FIG. 9 shows an example in which Q _B / Q _A > 1 and, for Q _B / Q _A = 10, electrophoresis is performed when the particle size ratio a _B / a _A is changed as in FIG. FIG. 5 is a graph showing changes in mobility ratio μ _B / μ _A and charge density ratio σ _B / σ _A. FIG. According to FIG. 9, the particle size ratio a _B / a _A satisfying the electrophoretic mobility ratio μ _B / μ _A <1 and the charge density ratio σ _B / σ _A > 1 exists in the range of a _B / a _A > 1. (Region T shown in FIG. 9).

As described above, the charge mobility is adjusted so that Q _B / Q _A > 1, and the electrophoretic mobility ratio μ _B when the particle size ratio a _B / a _A is changed based on the determined charge volume. and / mu _a, by graphing the change in charge density ratio σ _{B /} σ _a, it is possible to know may be in what extent the particle size ratio a _{B /} a _a.
Considering the charge amount ratio that can be practically prepared, the charge amount ratio is preferably such that Q _B / Q _A is greater than 1 and 100 or less, and considering the particle size ratio accordingly, the particle size ratio a _B / a _A is preferably greater than 1 and 10 or less.

The first particles A, the second particles B, and the third particles C as described above have different colors. The colors of the first particle A, the second particle B, and the third particle C are not particularly limited, respectively. From among achromatic colors such as white, black, and gray, and chromatic colors such as red, blue, and green, Three colors can be arbitrarily selected.
Further, the combination of the type of particles (first particle A, second particle B, third particle C) and the color of the particles (white, black, blue, red, yellow, etc.) is not limited. First particle A is a white particle, second particle B is a black particle, third particle C is a combination of yellow particles, first particle A is a blue particle, second particle B is a white particle, third A combination of particles in which the particles C are black can be mentioned.

  As the electrophoretic particles, any particles can be used as long as they satisfy the above-mentioned conditions, and are not particularly limited. However, pigment particles, resin particles, ceramic particles, metal particles, metal oxide particles are used. Alternatively, at least one of these composite particles is preferably used. These particles have the advantage that they are easy to manufacture and the charge can be controlled relatively easily.

  Examples of pigments constituting the pigment particles include black pigments such as aniline black, carbon black, and titanium black, white pigments such as titanium dioxide, antimony trioxide, zinc sulfide, and zinc white, and azo series such as monoazo, disazo, and polyazo. Pigments, yellow pigments such as isoindolinone, yellow lead, yellow iron oxide, cadmium yellow and titanium yellow, azo pigments such as monoazo, disazo and polyazo, red pigments such as quinacridone red and chrome vermilion, phthalocyanine blue and indanthrene Blue pigments such as blue, bitumen, ultramarine, and cobalt blue, green pigments such as phthalocyanine green, and the like can be used, and one or more of these can be used in combination.

Examples of the resin material constituting the resin particles include acrylic resin, urethane resin, urea resin, epoxy resin, rosin resin, polystyrene, polyester, AS resin copolymerized with styrene and acrylonitrile, and the like. These can be used alone or in combination of two or more.
The composite particles are, for example, composed of pigment particles whose surfaces are coated with a resin material, resin particles whose surfaces are coated with a pigment, or a mixture of a pigment and a resin material mixed in an appropriate composition ratio. Particles and the like.

  In addition, for the purpose of improving the dispersibility of the electrophoretic particles in the dispersion medium 5, a polymer highly compatible with the dispersion medium 5 is physically adsorbed on the surfaces of the particles A to C. Or chemically bonded. Among these, those in which the polymer is chemically bonded are particularly preferable because of the problem of detachment from the surface of the electrophoretic particles. With such a configuration, the affinity of the electrophoretic particles in the dispersion medium 5, that is, the dispersibility can be improved by acting in a direction in which the apparent specific gravity of the electrophoretic particles is reduced.

In this case, the number of bonds of the polymer is preferably about 300 to 2500 (pieces / μm ² ) in one positively charged particle B, more preferably about 500 to 1600 (pieces / μm ² ). preferable. By setting the number of polymer bonds within the above range, the affinity of the electrophoretic particles for the dispersion medium 5 can be increased and the dispersibility can be improved. In addition, it is possible to prevent a decrease in Coulomb force due to the charge on the surface of the electrophoretic particles being covered with the polymer.

  Examples of such a polymer include a polymer having a group reactive with the electrophoretic particle and a chargeable functional group, a group reactive with the electrophoretic particle, a long chain alkyl chain, a long chain ethylene oxide chain, and a long chain. Polymers having a chain fluorinated alkyl chain, a long dimethylsilicone chain, etc., groups having reactivity with electrophoretic particles, a chargeable functional group, a long alkyl chain, a long ethylene oxide chain, a long fluorinated alkyl chain And a polymer having a long-chain dimethyl silicone chain.

  In the polymer as described above, examples of groups having reactivity with the electrophoretic particles (hereinafter referred to as reactive groups) include, for example, epoxy groups, thioepoxy groups, alkoxysilane groups, silanol groups, alkylamide groups, aziridines. Group, oxazone group, isocyanate group and the like, and one or more of these can be selected and used, but depending on the type of electrophoretic particles to be used, etc. Good.

The average particle size of the electrophoretic particles is not particularly limited, but is preferably about 0.1 to 10 μm, and more preferably about 0.1 to 7.5 μm. If the average particle size of the electrophoretic particles is too small, a sufficient concealment rate cannot be obtained mainly in the visible light range, and as a result, the display contrast of the electrophoretic display device 1 may be reduced. If the average particle size of the electrophoretic particles is too large, depending on the type or the like, the particles may easily settle in the dispersion medium 5, which may cause problems such as deterioration in display quality of the electrophoretic display device 1.
The non-charged particles A, the positively charged particles B, and the negatively charged particles C have been described above. The dispersion of the three particles A to C in the dispersion medium 5 can be performed by, for example, a paint shaker method, a ball mill method, a media mill, or the like. Method, ultrasonic dispersion method, stirring dispersion method and the like can be used alone or in combination of two or more.

  Next, the operation of the electrophoretic display device 1 will be described with reference to FIGS. Needless to say, FIGS. 1 and 3 to 6 are schematically illustrated for convenience of explanation, and the number and size of each of the particles A to C are greatly different from actual ones. Hereinafter, the color in the filling portion 6 when viewed from the upper electrode 7 side is referred to as “display color”. In the present embodiment, the first particles A are negatively charged black particles, the second particles B are negatively charged yellow particles, and the third particles are positively charged white particles. Particles.

<1> Black Display First, the black display state (first state) will be described.
For example, as shown in FIG. 2A, by applying a voltage V1, a voltage V2, and a voltage V3 to the electrode piece 71, the electrode piece 72, and the lower electrode 8, respectively, the electrode pieces 71, 72 are positive and lower electrodes. 8 becomes negative. As a result, the first particles A and the second particles B are electrically adsorbed by the electrode pieces 71 and 72 (that is, the upper electrode 7), respectively, so that the dispersion medium 5 moves toward the upper electrode 7. At this time, due to the difference in electrophoretic mobility between the first particle A and the second particle B, the first particle A reaches the upper electrode 7 before the second particle B.

  Therefore, as shown in FIG. 3, the first particle A and the second particle B respectively correspond to the upper electrode 7 so that the first particle A is located on the upper electrode 7 side with respect to the second particle B. (That is, it is unevenly distributed in the visual recognition part 4). In other words, in order from the upper electrode 7 side, a first particle layer formed by aggregating a large number of first particles A and a second particle layer formed by aggregating a large number of second particles B It will be in the state which laminated | stacked.

On the other hand, the third particles C migrate toward the lower electrode 8 in the dispersion medium 5 so as to be electrically adsorbed by the lower electrode 8. As a result, as shown in FIG. 3, the third particles C are unevenly distributed in a portion corresponding to the lower electrode 8 (that is, the bottom surface 311).
In this state, since the visual recognition part 4 is covered with the first particles A, black is visually recognized as the display color.

  In such an electrophoretic display device 1, even if the voltage application to the upper electrode 7 and the lower electrode 8 is stopped, the first particle A, the second particle B, and the third particle C are not applied with voltage. It has the characteristic of maintaining the state immediately before being stopped. That is, after the black display state is reached, the black display state can be maintained even if the voltage application is stopped. The same applies to a yellow display state, a white display state, and the like described later.

<2> Yellow Display State Next, the yellow display state (second state) will be described.
First, the black display state described above is set. In this state, as shown in FIG. 2B, by applying the voltage V1, the voltage V2, and the voltage V3 to the electrode piece 71, the electrode piece 72, and the lower electrode 8, respectively, the first particle A and the second particle Due to the difference in charge density from B, the positional relationship between the first particles A and the second particles B is reversed. Thereby, the visual recognition part 4 will be covered with the 2nd particle | grains B, Therefore, yellow is visually recognized as a display color.

Here, prior to describing the specific movement (migration) of the first particle A, the second particle B, and the third particle C, the voltages V1 to V3 shown in FIG. 2B will be described. The voltage V1 and the voltage V2 are the same as each other except that the phases are shifted by 180 degrees. Therefore, the voltage V1 is described as a representative, and the description of the voltage V2 is omitted.
The voltage V1 is a square voltage that changes periodically. More specifically, the state S1 having the maximum potential and the state S2 having the minimum potential are switched at equal time intervals. As is clear from FIG. 2B, the voltage V1 is positive in both the state S1 and the state S2.
As the frequency of the voltage V1, but are not limited to, 1 × is preferably ^{10 2 ~1 × 10 9 [Hz} ], and more is 1 × ¹⁰ 2 ~1 × ¹⁰ 6 in the range of [Hz] Preferably, it is 1 × 10 ² to 1 × 10 ³ [Hz]. Thereby, as will be described later, the positional relationship between the first particles A and the second particles B can be reversed more smoothly.

On the other hand, the voltage V3 is negative. Therefore, as will be described later, the positions of the first particles A and the second particles B can be reversed while the third particles C are unevenly distributed near the lower electrode 8. The voltage V3 is not particularly limited as long as the relationship of V1, V2> V3 is satisfied, that is, as long as it is smaller than the voltage V1 and the voltage V2, and may be a positive voltage, for example.
Next, specific movement (migration) of the first particle A, the second particle B, and the third particle C when the voltages V1 to V3 are applied to the corresponding electrodes will be described.

First, at time T1, since the potential of the electrode piece 71 is higher than that of the electrode piece 72, the first particles A and the second particles B are adsorbed to the electrode piece 71 so that the electrode piece 71 passes through the dispersion medium 5. Run to the side.
On the contrary, at time T2, since the potential of the electrode piece 72 is higher than that of the electrode piece 71, the first particle A and the second particle B are adsorbed by the electrode piece 72, and the electrode piece 72 passes through the dispersion medium 5. Electrophoresis toward the 72 side.

  When the time T1 and the time T2 as described above are periodically repeated, the first particles A and the second particles B migrate in the dispersion medium 5 so as to reciprocate in the left-right direction. Here, as described above, since the frequencies of the voltages V1 and V2 are relatively high, the migration distance of the first particles A and the second particles B at the times T1 and T2 is extremely short. Therefore, the first particles A and the second particles B substantially vibrate slightly in the vicinity of the upper electrode 7.

The second particle B has a higher charge density than the first particle A, and the electrostatic force (Coulomb force) with the upper electrode 7 is stronger than that of the first particle A. Therefore, when the vibration continues, the second particle B Passes between a large number of first particles A and gradually moves to the upper electrode 7 side.
Accordingly, the second particles B as shown in FIG. 5 become the first particles A through the state in which the first particles A and the second particles B as shown in FIG. On the other hand, it will be in the state located in the transparent electrode 7 side. That is, a state (second state) in which the positional relationship between the first particles A and the second particles B is reversed with respect to the black display state (first state).

  Note that when the positional relationship between the first particle A and the second particle B is reversed by the vibration, the first particle A and the second particle B have a short migration distance as described above. The difference in electrophoretic mobility between A and the second particle B has little influence, and the difference in electric density between the first particle A and the second particle B has a dominant influence. Therefore, the second particles B having a charge density higher than that of the first particles A are surely moved to the upper electrode 7 side than the first particles A.

In addition, as described above, since the voltages V1 and V2 are both positive, the first particles A and the second particles are kept in the vicinity of the upper electrode 7 while the negatively charged first particles A and second particles B are positioned in the vicinity of the upper electrode 7. B can be vibrated, and the positions of the first particles A and the second particles B can be reversed smoothly and quickly.
In this state, since the visual recognition part 4 is covered with the second particles B, yellow is visually recognized as the display color.
At this time, since the voltage V3 is applied to the lower electrode 8, even if the positions of the first particle A and the second particle B are being reversed, the third particle C is applied to the lower electrode 8. It can be located in the vicinity, whereby excellent color display characteristics can be exhibited.

<3> White Display Next, the white display state (third state) will be described.
For example, as shown in FIG. 2C, when the voltage V1, the voltage V2, and the voltage V3 are applied to the electrode piece 71, the electrode piece 72, and the lower electrode 8, respectively, the upper electrode 7 becomes negative and the lower electrode 8 becomes positive. . Thus, the first particles A and the second particles B migrate in the dispersion medium 5 toward the lower electrode 8 so as to be electrically adsorbed by the lower electrode 8. As a result, as shown in FIG. 6, the first particles A and the second particles B are unevenly distributed at portions corresponding to the lower electrode 8.

On the other hand, the third particles C migrate toward the upper electrode 7 in the dispersion medium 5 so as to be electrically adsorbed by the upper electrode 7. Thereby, as shown in FIG. 6, the third particles C are unevenly distributed in the portion corresponding to the transparent electrode 7.
In this state, since the visual recognition part 4 is covered with the third particles C, white is visually recognized as the display color.
Although the black display state, the yellow display state, and the white display state have been described in detail above, the electrophoretic display device 1 can further display an intermediate color between black and yellow. That is, the electrophoretic display device 1 can express yellow gradation. Hereinafter, a case where an intermediate color between black and yellow is displayed will be described.

<4> Intermediate Color Display between Black and Yellow As described above, when a voltage as shown in FIG. 2B is applied in the black display state, the state shown in FIG. That is, when switching from the black display state to the yellow display state, the display color gradually changes from black to yellow.

  Here, as described above, even when the voltage application is stopped, the electrophoretic display device 1 maintains the first particle A, the second particle B, and the third particle C in a state immediately before the voltage application is stopped. Then, it has an ugly property. If such a property is used, a voltage as shown in FIG. 2 (b) is applied. For example, when the voltage application is stopped when the state shown in FIG. 4 is reached, as shown in FIG. Therefore, it is possible to display an intermediate color between yellow and black, that is, yellow having a lower brightness than the yellow display state.

The operation of the electrophoresis table device 1 has been described in detail above.
In the present embodiment, the first particles A are black particles and the third particles are white particles, so that the reactivity of black and white display can be particularly improved. Specifically, in order to obtain the yellow display state, it is necessary to go through the black display state as described above, but the black display state and the white display state are not in other states. It can be. Therefore, switching between the black display state and the white display state can be performed quickly, and the black and white display reactivity is excellent. Such an effect is also exhibited when the first particles A are white particles and the third particles are black particles.

  Moreover, the display color (white) in a white display state can be made into a desired thing by making the 1st particle | grains A into black particles and making the 3rd particles into white particles. Specifically, the third particle C is the only positively charged particle among the three types of particles A to C. Therefore, in the white display state as shown in FIG. 5, only the third particles C are unevenly distributed above the filling part 6 so as to cover the visual recognition part 4.

  Here, in the electrophoretic display device composed of only normal black and white particles, there is a problem that the luminance of white display cannot be increased because black particles exist below the white particles. In the lower part of the white particles, the second particles B are not black particles. As a result, the luminance in white display can be improved with respect to the electrophoretic display device composed of only ordinary black and white particles.

On the other hand, for example, when the first particle A is a white particle, that is, when the state shown in FIG. 3 is a white display state, the first particle A varies depending on the content and the particle size of the first particle A. However, a part of incident light may be absorbed by the second particles B, and a desired white color may not be displayed.
Further, since the second particles B are chromatic particles, color display is possible in addition to black and white display. Thereby, the versatility of the electrophoretic display device 1 is enhanced.

<< Second Embodiment >>
Next, a second embodiment of the electrophoretic display device of the present invention will be described.
FIG. 10 is a schematic longitudinal sectional view showing a second embodiment of the electrophoretic display device of the present invention.
Hereinafter, the electrophoretic display device according to the second embodiment will be described with a focus on differences from the above-described embodiments, and description of similar matters will be omitted.

The electrophoretic display device according to the second embodiment of the present invention is the same as the electrophoretic display device of the first embodiment except that the configuration of the pixels is different. In addition, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment mentioned above.
As shown in FIG. 10, the pixel P includes three filling portions 61, 62, and 63 arranged in parallel in the left-right direction.

The first particles A and the third particles C contained in the dispersion medium 5 filled in the filling portions 61, 62, and 63 are the same as those in the first embodiment. That is, the first particles A contained in each dispersion medium 5 are negatively charged black particles, and the third particles C are positively charged white particles.
The second particles contained in the dispersion medium 5 filled in the filling unit 61 are negatively charged cyan particles, and the second particles contained in the dispersion medium 5 filled in the filling unit 62 are negative. The second particles B, which are charged magenta particles and are contained in the dispersion medium 5 filled in the filling portion 63, are negatively charged yellow particles.

That is, the pixel P includes a filling unit 61 capable of displaying cyan as a display color, a filling unit 62 capable of displaying magenta, and a filling unit 63 capable of displaying yellow. According to such a pixel P, full color display is possible by arbitrarily combining the display colors of the three filling portions 61, 62, and 63.
For example, when displaying black, all three filling parts 61, 62, 63 may be in a black display state (a state where the first particles A cover the visual recognition part 4), and when magenta is desired to be displayed. The filling portion 62 is in a magenta display state (a state where the second particles B cover the visual recognition portion 4), and the filling portions 61 and 63 are in a white display state (a state where the third particles cover the visual recognition portion 4). In order to display an intermediate color between cyan and magenta, the filling unit 61 may be set to the cyan display state, the filling unit 62 may be set to the magenta display state, and the filling unit 63 may be set to the white display state.

In addition, the arrangement | positioning, shape, etc. of the filling parts 61, 62, and 63 in such a pixel P are not specifically limited.
Further, the color of the second particles B contained in the dispersion medium 5 filled in the filling portion 61 is cyan, the color of the second particles B contained in the dispersion medium 5 filled in the filling portion 62 is magenta, The second particles B contained in the dispersion medium 5 filled in the filling unit 63 have been described as yellow, but the present invention is not limited to this. For example, the dispersion medium 5 filled in the filling unit 61 may The color of the second particles B contained is red (R), the color of the second particles B contained in the dispersion medium 5 filled in the filling part 62 is green (G), and the filling part 63 is filled. The color of the second particles B contained in the dispersion medium 5 may be blue (B). This also enables full color display as in the present embodiment.

According to the second embodiment as described above, the same effect as that of the first embodiment can be exhibited.
The electrophoretic display device 1 as described above can be incorporated into various electronic devices. As an electronic apparatus of the present invention provided with an electrophoretic display device, for example, an electronic paper, an electronic book, a television, a viewfinder type, a monitor direct view type video tape recorder, a car navigation device, a pager, an electronic notebook, a calculator, an electronic newspaper, Examples include a word processor, a personal computer, a workstation, a videophone, a POS terminal, and a device equipped with a touch panel.

Of these electronic devices, an electronic paper will be described as an example for specific description.
FIG. 11 is a perspective view showing an embodiment when the electronic apparatus of the present invention is applied to electronic paper.
An electronic paper 600 shown in FIG. 11 includes a main body 601 composed of a rewritable sheet having the same texture and flexibility as paper, and a display unit 602.
In such an electronic paper 600, the display unit 602 includes the electrophoretic display device 1 as described above.

Next, an embodiment when the electronic apparatus of the present invention is applied to a display will be described.
FIG. 12 is a diagram showing an embodiment when the electronic apparatus of the present invention is applied to a display. Among these, (a) in FIG. 12 is a sectional view and (b) is a plan view.
A display (display device) 800 shown in FIG. 12 includes a main body 801 and an electronic paper 600 that is detachably attached to the main body 801. The electronic paper 600 has the same configuration as described above, that is, the configuration shown in FIG.

  The main body 801 has an insertion port 805 into which the electronic paper 600 can be inserted on the side (right side in FIG. 12), and two pairs of conveying rollers 802a and 802b are provided inside. When the electronic paper 600 is inserted into the main body 801 through the insertion port 805, the electronic paper 600 is installed in the main body 801 in a state of being sandwiched between the pair of conveyance rollers 802a and 802b.

  A rectangular hole 803 is formed on the display surface side of the main body 801 (the front side in FIG. 12B), and a transparent glass plate 804 is fitted into the hole 803. . Thereby, the electronic paper 600 installed in the main body 801 can be viewed from the outside of the main body 801. That is, in the display 800, the display surface is configured by visually recognizing the electronic paper 600 installed in the main body 801 on the transparent glass plate 804.

Further, a terminal portion 806 is provided at the leading end portion (left side in FIG. 12) of the electronic paper 600 in the insertion direction, and the terminal is provided inside the main body portion 801 with the electronic paper 600 installed on the main body portion 801. A socket 807 to which the unit 806 is connected is provided. A controller 808 and an operation unit 809 are electrically connected to the socket 807.
In such a display 800, the electronic paper 600 is detachably installed on the main body 801, and can be carried and used while being detached from the main body 801.

  The electrophoretic display sheet, electrophoretic display device, and electronic apparatus of the present invention have been described above based on the illustrated embodiments, but the present invention is not limited to these. For example, in the electrophoretic display sheet, the electrophoretic display device, and the electronic apparatus of the present invention, the configuration of each part can be replaced with an arbitrary configuration that exhibits the same function, and an arbitrary configuration is added. You can also

Further, in the above-described embodiment, the filling portion has been described as being formed by the lid portion and the concave portion formed in the base body. However, the present invention is not limited to this. For example, a so-called microcapsule may be used as the filling portion. .
In the above-described embodiment, the electrophoretic display device has been described as having a plurality of pixels. However, the number of pixels is not particularly limited, and may be one, for example.

In the above-described embodiment, the dispersion medium contains three types of particles, that is, the first particles, the second particles, and the third particles. However, at least the first particles and the second particles are included. The third particles may be omitted as long as they are contained.
In the above-described embodiment, the first particle and the second particle are each negatively charged particles, and the third particle is a positively charged particle. However, the opposite is true. That is, the first particles and the second particles may be positively charged particles, and the third particles may be negatively charged particles. In this case, a voltage opposite to the voltage shown in FIG. 2 may be applied. Also by this, the same effect as the above-described embodiment can be exhibited.

1 is a schematic longitudinal sectional view showing a first embodiment of an electrophoretic display device of the present invention. It is a figure which shows an example of the drive waveform of the electrophoretic display apparatus shown in FIG. It is a typical longitudinal cross-sectional view which shows the action | operation of the electrophoretic display apparatus shown in FIG. It is a typical longitudinal cross-sectional view which shows the action | operation of the electrophoretic display apparatus shown in FIG. It is a typical longitudinal cross-sectional view which shows the action | operation of the electrophoretic display apparatus shown in FIG. It is a typical longitudinal cross-sectional view which shows the action | operation of the electrophoretic display apparatus shown in FIG. Changes in electrophoretic mobility ratio μ _B / μ _A and charge density ratio σ _B / σ _A when the particle size ratio a _B / a _A is changed when the charge amount ratio Q _B / Q _A = 1 It is a graph which shows. When the charge amount ratio Q _B / Q _A = 0.1, the electrophoretic mobility ratio μ _B / μ _A and the charge density ratio σ _B / σ _A when the particle size ratio a _B / a _A is changed It is a graph which shows the change of. Changes in the electrophoretic mobility ratio μ _B / μ _A and the charge density ratio σ _B / σ _A when the particle size ratio a _B / a _A is changed when the charge amount ratio Q _B / Q _A = 10 It is a graph which shows. It is a typical longitudinal section showing a 2nd embodiment of an electrophoretic display device of the present invention. It is a perspective view which shows embodiment at the time of applying the electronic device of this invention to electronic paper. It is a figure which shows embodiment at the time of applying the electronic device of this invention to a display.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electrophoretic display device 2 ... Electrophoretic display sheet 3 ... Base | substrate 31 ... Recessed part 311 ... Bottom face 4 ... Cover part (viewing part) 5 ... Dispersion medium 6, 61-63 ... Filling part 7 ... Upper electrode (first electrode) 71, 72 ... Electrode piece 8 ... Lower electrode (second electrode) 9 ... Circuit board 91 ... Base 600 ... Electronic paper 601 ... Main body 602 ... Display unit 800 …… Display 801 …… Main body 802a, 802b …… Conveying roller pair 803 …… Hole 804 …… Transparent glass plate 805 …… Insertion slot 806 …… Terminal 807 …… Socket 808 …… Controller 809 …… Operation unit A ... 1st particle B ... 2nd particle C ... 3rd particle

Claims (15)

A packed portion filled with a dispersion medium in which at least two kinds of particles having different colors are dispersed;
A first electrode provided on one side of the filling portion and having a pair of electrode pieces that can be visually recognized in the filling portion;
A second electrode provided on the other side of the filling portion,
The at least two types of particles include negatively charged first particles and second particles,
The first particles have a higher electrophoretic mobility than the second particles and a lower charge density than the second particles;
By applying a voltage in which the first electrode is positive and the second electrode is negative, a difference in the electrophoretic mobility is obtained when the first particles and the second particles are unevenly distributed on the first electrode side. A first state in which the first particles are located closer to the first electrode than the second particles, and the pair of electrode pieces of the first electrode between the pair of electrode pieces from the first state. By applying a voltage that alternately switches the potential level of the electrode piece, the second particle is located closer to the second electrode than the second particle using the difference in charge density. A state in which the color in the filling portion visually recognized through the first electrode is changed by selecting either the first state or the second state. An electrophoretic display sheet characterized by comprising:   The electrophoretic display sheet according to claim 1, wherein a positive voltage is applied to each of the pair of electrode pieces to alternately switch the potential level of the pair of electrode pieces. In addition to the at least two types of particles, positively charged third particles are included,
By applying a voltage in which the first electrode is negative and the second electrode is positive, the third particles are unevenly distributed on the first electrode side, and the first particles and the second particles are unevenly distributed on the second electrode side. The color can be changed by selecting any one of the first state, the second state, and the third state. The electrophoretic display sheet as described.   When the voltage is applied between the pair of electrode pieces of the first electrode such that the potential level of the pair of electrode pieces is alternately switched, the third electrode is applied to the second electrode. The electrophoretic display sheet according to claim 3, wherein a voltage that causes uneven distribution to the side is applied.   When the voltage applied to one of the pair of electrode pieces is V1, the voltage applied to the other is V2, and the voltage applied to the second electrode is V3, V3 is V1, V2> V3. The electrophoretic display sheet according to claim 4, wherein: A packed portion filled with a dispersion medium in which at least two kinds of particles having different colors are dispersed;
A first electrode provided on one side of the filling portion and having a pair of electrode pieces that can be visually recognized in the filling portion;
A second electrode provided on the other side of the filling portion,
The at least two kinds of particles include positively charged first particles and second particles,
The first particles have a higher electrophoretic mobility than the second particles and a lower charge density than the second particles;
By applying a voltage that makes the first electrode negative and the second electrode positive, the difference in the electrophoretic mobility is caused when the first particles and the second particles are unevenly distributed on the first electrode side. A first state in which the first particles are located closer to the first electrode than the second particles, and the pair of electrode pieces of the first electrode between the pair of electrode pieces from the first state. By applying a voltage that alternately switches the potential level of the electrode piece, the second particle is located closer to the second electrode than the second particle using the difference in charge density. A state in which the color in the filling portion visually recognized through the first electrode is changed by selecting either the first state or the second state. An electrophoretic display sheet characterized by comprising:   The electrophoretic display sheet according to claim 6, wherein a negative voltage is applied to each of the pair of electrode pieces to alternately switch the potential level of the pair of electrode pieces. In addition to the at least two types of particles, negatively charged third particles are included,
By applying a voltage in which the first electrode is positive and the second electrode is negative, the third particles are unevenly distributed on the first electrode side, and the first particles and the second particles are unevenly distributed on the second electrode side. The color change can be performed by selecting any one of the first state, the second state, and the third state. The electrophoretic display sheet as described.   When the voltage is applied between the pair of electrode pieces of the first electrode such that the electric potential level of the pair of electrode pieces is alternately switched, the third electrode is applied to the second electrode. The electrophoretic display sheet according to claim 8, wherein a voltage that causes uneven distribution to the side is applied.   When the voltage applied to one of the pair of electrode pieces is V1, the voltage applied to the other is V2, and the voltage applied to the second electrode is V3, V3 is V1, V2 <V3. The electrophoretic display sheet according to claim 9, wherein:   11. The electrophoretic display sheet according to claim 3, wherein one of the first particles and the third particles is a black particle, and the other is a white particle.   The electrophoretic display sheet according to claim 11, wherein the first particles are black particles, and the third particles are white particles.   The electrophoretic display sheet according to claim 1, wherein the second particles are chromatic color particles.   An electrophoretic display device comprising: the electrophoretic display sheet according to claim 1; and a substrate provided on the other side of the filling portion.   An electronic apparatus comprising the electrophoretic display device according to claim 14.

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