JP2005241784A - Electrophoretic display device, and microcapsule and dispersion liquid used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophoretic display device having electrophoretic particles which have charge larger than before and of which the charge polarity and the charge distribution are uniform, and to provide microcapsules and a dispersion liquid used therefor. <P>SOLUTION: The electrophoretic display device 30 has a dispersion medium 46 and the electrophoretic particles 48 dispersed in the dispersion medium 46. The electrophoretic particle 48 has an inorganic particle and an ionic atom group which is bonded to the surface of the inorganic particle via a chemical bond and which has divalent or higher charge. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a display device using electrophoresis, a microcapsule and a dispersion used therefor.

  Electrophoretic display devices have recently attracted attention as electronic paper. Electronic paper is an electronic display that can be easily handled like paper. Electronic paper is required to be easy to see like paper, easy to erase and write on the display, and low in energy required for display maintenance. For example, Non-Patent Document 1 describes various types of electronic paper.

  For example, Patent Document 1 discloses an electrophoretic display device having a pair of electrodes and an electrophoretic dispersion liquid enclosed between them. The electrophoretic dispersion liquid includes a dispersion medium colored with a dye and white particles (electrophoretic particles) dispersed in the dispersion medium. White particles are positively charged particles. When a potential difference is applied between a pair of electrodes, the charged particles are attracted to one of the electrodes depending on the direction of the electric field, and the observer is given the white color of the charged particles or the color of the dye. appear. Therefore, an image can be displayed by controlling the voltage applied to the electrode.

  Patent Document 2 discloses a display device having a configuration in which an electrophoretic dispersion is filled in a cellular microcapsule (hereinafter sometimes referred to as a microcapsule type electrophoretic display device). FIG. 6 is a diagram for explaining the microcapsule-type electrophoretic display device of Patent Document 2. In FIG.

  In the display device of Patent Document 2, a pair of microcapsules 10 filled with a dispersion liquid including a dispersion medium 2, white charged particles 4 (electrophoretic particles), and black charged particles 6 (electrophoretic particles) are provided. Located between the electrodes 12 and 14. The white charged particles 4 and the black charged particles 6 have opposite charge characteristics. Therefore, when a potential difference is applied between a pair of electrodes, the charged particles are attracted to one of the electrodes depending on the direction of the electric field. It is done.

  When the white particles 4 are positively charged and the black particles 6 are negatively charged, when a voltage is applied as shown in FIG. 6A, the white particles 4 are placed on the viewer's electrode 12 side in the microcapsule 10. Since the positive charged particles 4 are attracted, white is observed by the observer. On the other hand, when a voltage is applied as shown in FIG. 6B, black negative charged particles 6 are attracted to the side of the observer-side electrode 12 in the microcapsule 10, so that the observer is black. Observed. As described above, an image can be displayed by controlling the voltage applied to the electrode.

The electrophoretic particles in the dispersion medium have a charge. Patent Document 1 discloses that an organosilane derivative is bonded to inorganic particles such as silica to form charged particles in which positive monovalent ionic atomic groups are chemically bonded. On the other hand, Patent Document 2 discloses forming positive and negative charged particles 4 and 6 by using a charge control agent (CCA).
US Pat. No. 4,680,103 JP 2001-516467 A "Does electronic paper replace paper?", Nikkei Science 2002 February (released on December 25, 2001), pages 42-51 (Original: "The Electronic Paper Chase", Scientific American, November 2001, Steve Dittle)

  However, the charged particles described in Patent Document 1 in which a positive monovalent ionic atomic group is chemically bonded have insufficient charge amount. In addition, when particle charging is performed using a charge control agent as in Patent Document 2, the charge amount of the particles is insufficient, and the charge polarity and charge amount distribution are not uniform.

  When the charge amount of the particles is not sufficient, it is necessary to increase the driving voltage of the electrophoretic display device, which causes a problem that the life of the display device is shortened. There is also a problem that high-speed response is difficult. If the distribution of the charge polarity and charge amount is not uniform, there is a problem that high-quality display cannot be performed.

  In view of the above problems, the present invention provides an electrophoretic display device having electrophoretic particles having a larger charge amount than the prior art and a uniform charge polarity and charge amount distribution, and microcapsules and dispersions used therefor. For the purpose.

  The electrophoretic display device of the present invention is a display device having a dispersion medium and electrophoretic particles dispersed in the dispersion medium, and the electrophoretic particles are chemically bonded to inorganic particles and the surfaces of the inorganic particles. And an ionic atomic group having a charge of two or more valences bonded via a hydrogen atom.

  The dispersion medium may include a liquid crystal material having positive dielectric anisotropy.

  The dispersion medium may include a lyotropic liquid crystal.

  The dispersion medium may include a conductive polymer.

  A dye molecule may be bonded to the ionic atomic group via a chemical bond.

  A microcapsule wall may be further included, and the dispersion medium and the electrophoretic particles may be filled in the microcapsule wall to constitute a microcapsule.

  The microcapsule of the present invention is a microcapsule having a microcapsule wall and a dispersion medium and electrophoretic particles filled in the microcapsule wall, wherein the electrophoretic particles include inorganic particles and the inorganic particles And an ionic atomic group having a charge of two or more valences bonded to the surface of the substrate via a chemical bond.

  The dispersion for electrophoretic display device of the present invention is a dispersion for electrophoretic display device comprising a dispersion medium and electrophoretic particles dispersed in the dispersion medium, wherein the electrophoretic particles include inorganic particles, It has an ionic atomic group having a divalent or higher charge bonded to the surface of the inorganic particle through a chemical bond.

  In the electrophoretic display device of the present invention, the electrophoretic particles have inorganic particles and divalent or higher ionic atomic groups X bonded to the surface of the inorganic particles through chemical bonds. The charge amount of the particles is large, and the distribution of charge polarity and charge amount is uniform. For this reason, lower voltage driving, higher speed response and higher image quality display are possible.

  As shown in FIG. 1, an electrophoretic display device 30 according to an embodiment of the present invention is arranged between substrates 36 and 38 each having electrodes 32 and 34 formed of, for example, ITO, and between the electrodes 32 and 34. The microcapsule type electrophoretic display device having the microcapsules 42A and 42B. The microcapsules 42 </ b> A and 42 </ b> B are held by an insulating layer 52 (for example, a polymer resin layer) disposed between the electrode 32 and the electrode 34.

  The electrodes 34 and 32 are formed in stripes on the surfaces of the viewer side substrate 36 and the back side substrate 38 so as to cross each other.

  Each of the microcapsules 42A and 42B contains a dispersion liquid containing a transparent dispersion medium 46, white electrophoretic particles 48W dispersed in the dispersion medium 46, and black electrophoretic particles 48B inside the microcapsule wall. Filled. For example, the white electrophoretic particles 48W are positively charged, and the black electrophoretic particles 48B are negatively charged. The dispersion medium 46 is an organic solvent.

  When a predetermined voltage is applied between the opposing electrode 32 and the electrode 34, when the electrode 32 is positive, the black electrophoretic particles 48B are attracted to the electrode 32 side, and the white electrophoretic particles 48W are attracted to the electrode 34 side. Therefore, white color can be displayed (microcapsule 42A). Conversely, when the electrode 32 is a negative electrode, the white electrophoretic particles 48W are attracted to the electrode 32 side and the black electrophoretic particles 48B are attracted to the electrode 34 side, so that black can be displayed (microcapsule 42B).

Each of the electrophoretic particles (charged particles) 48W and 48B includes inorganic particles and divalent or higher ionic atomic groups X bonded to the surfaces of the inorganic particles through chemical bonds. The divalent or higher ionic atomic group X is bonded to the surface of the inorganic particle via, for example, a polymer or low molecular compound having a functional group A that forms a chemical bond with the surface of the inorganic particle. Examples of the divalent or higher ionic atomic group X include, for example, an anion such as —PhPO ₄ ³⁻ , — (CH ₂ ) ₆ OPO ₃ ³⁻ , —BO ₃ ³⁻ , —SO ₄ ²⁻ , —S ₂ O ₃ ²⁻ or the like can be used, and as the cation, aluminum, quinolinol complex (Alq3), copper phthalocyanine, zinc complex, or the like can be used.

As the functional group A that forms a chemical bond with the surface of the inorganic particles, —COO, —SiR ₃ , —TiR ₃ , —AlR ₃ (R: for example, alkoxy, acetoxy, halogen, H) or the like can be used. Such a polymer is, for example, a copolymer of a monomer unit having an atomic group X ′ that generates a divalent or higher ionic atomic group X and a monomer unit having a functional group A ′ that generates the functional group A. It is. Such a low-molecular compound has, for example, an ionic atomic group X and a functional group A ′ that generates the functional group A.

  The electrophoretic particles 48W and 48B have a charge amount larger than that of the conventional electrophoretic particles because the valence of the ionic atomic group X bonded to the surface of the inorganic particle through a chemical bond is 2 or more. And the distribution of charge amount is uniform. Therefore, it can be driven at a lower voltage than the conventional electrophoretic display device, and the lifetime of the display device can be made longer than before. In addition, when a voltage equal to that of the conventional electrophoretic display device is applied, the electrophoretic particles can be moved at a high speed, so that a faster response than that of the conventional electrophoretic display device is possible.

  Moreover, since the ionic organic substance is charged on the surface of the inorganic particle through a chemical bond, the electrophoretic particle can be produced without using a charge control agent. Here, the chemical bond is preferably a covalent bond, but is not limited thereto, and may be a hydrogen bond, an ionic bond, or the like. Therefore, the problem that the charge amount of the electrophoretic particles is insufficient due to the use of the charge control agent and the charge polarity and the charge amount distribution cannot be made uniform can be avoided. Is possible.

  The dispersion medium 46 preferably contains a liquid crystal material having positive dielectric anisotropy. This is because when the voltage is applied, the major axis of the liquid crystal molecules is parallel to the direction of the electric field, so that isotropic diffusion of the electrophoretic particles is suppressed and the electrophoretic particles can be moved at a higher speed. The liquid crystal material may be lyotropic liquid crystal. Further, the dispersion medium 46 may include a conductive polymer. This is because the conductive polymer is rigid, so that the same effect as described above can be obtained.

  The configuration of the electrophoretic display device 30 of the present embodiment is not limited to the above. The electrophoretic display device can also perform color display. 2 and 3 are diagrams showing the configuration of the color electrophoretic display device. The color electrophoretic display device 30B of FIG. 2 has three types of microcapsules 42C, 42D, and 42E. The microcapsule 42C is filled with a dispersion liquid containing a transparent dispersion medium 46, white electrophoretic particles 48W and red electrophoretic particles 48CR dispersed in the dispersion medium 46 inside the microcapsule wall. The microcapsule 42D is filled with a dispersion liquid containing a transparent dispersion medium 46, white electrophoretic particles 48W and green electrophoretic particles 48CG dispersed in the dispersion medium 46 inside the microcapsule wall. The microcapsule 42E is filled with a dispersion liquid containing a transparent dispersion medium 46, white electrophoretic particles 48W and blue electrophoretic particles 48CB dispersed in the dispersion medium 46 inside the microcapsule wall. For example, the white electrophoretic particles 48W are positively charged, and the red, green, and blue electrophoretic particles 48CR, 48CG, and 48CB are all negatively charged.

  When a predetermined voltage is applied between the opposing electrode 32 and the electrode 34, when the electrode 32 is a positive electrode, the red, blue, and green electrophoretic particles 48CR, 48CG, and 48CB are attracted to the electrode 32 side, and the white electrophoretic particles Since 48W is attracted to the electrode 34 side, white can be displayed. Conversely, when the electrode 32 is a negative electrode, the white electrophoretic particles 48W are attracted to the electrode 32 side, and the red, blue, and green electrophoretic particles 48CR, 48CG, and 48CB are attracted to the electrode 34 side. , Green can be displayed. Therefore, color display by additive color mixing is possible by controlling the applied voltage. Even if the microcapsules 42C, 42D, and 42E have black electrophoretic particles 48B instead of the white electrophoretic particles 48W, color display by additive color mixture is possible.

  Further, if the microcapsules 42C, 42D, and 42E have cyan, magenta, and yellow electrophoretic particles in place of the red, blue, and green electrophoretic particles 48CR, 48CG, and 48CB, respectively, color by subtractive color mixing Display is possible.

  As will be described later, the electrophoretic particles colored in red, blue, green, cyan, magenta, or yellow can be prepared by binding dye molecules to the ionic organic substances on the surface of the inorganic particles through chemical bonds. it can.

  Although the case where each of the microcapsules has two types of electrophoretic particles has been described above, the microcapsule may be formed using one type of electrophoretic particle. Specifically, as shown in the electrophoretic display device 30C of FIG. 3, the microcapsule wall is filled with, for example, white electrophoretic particles 48W and a dispersion medium 46C colored in a predetermined color. When the white electrophoretic particles 48W are negatively charged, when the electrode 34 is a positive electrode, the electrophoretic particles 48W are attracted to the electrode 34, so that white can be displayed. Conversely, when the electrode 34 is a negative electrode, the electrophoretic particles 48W are attracted to the electrode 32 side, so that the color of the dispersion medium 46C can be displayed. If a dispersion medium colored, for example, yellow, magenta, or cyan is used for each microcapsule, color display can be performed.

  The electrophoretic display device 30 of the present embodiment is not limited to a microcapsule type electrophoretic display device, and can also be applied to an electrophoretic display device that does not use microcapsules. For example, as shown in the display device 30D of FIG. 4, a dispersion medium 46 and electrophoretic particles 48 colored in a predetermined color are disposed between the electrodes 32 and 34 facing each other. When the electrophoretic particle 48 is negatively charged, when the electrode 32 is a positive electrode, the electrophoretic particle 48 is attracted to the electrode 32 side, so that the color of the dispersion medium can be displayed. Conversely, when the electrode 32 is a negative electrode, the electrophoretic particles 48 are attracted to the electrode 34 side, so that the color of the particles 48 can be displayed. However, the use of microcapsules has the advantage that the dispersion can be easily handled and the dispersion can be applied to electrode substrates of any material and shape.

  The electrophoretic display device 30 of the present embodiment can also be applied to an in-plane type electrophoretic display device. FIG. 5 is a diagram illustrating a configuration of an in-plane type electrophoretic display device. The details of the electrophoretic display device are described in, for example, Japanese Patent Application Laid-Open No. 11-202804.

  The electrophoretic display device 30E of FIG. 5 includes a viewer-side substrate 36 and a back-side substrate 38, and a dispersion liquid disposed therebetween. On the substrate 38 on the back side, a white display electrode 34W (for example, formed of ITO), an insulating layer 33 (for example, formed of polyimide) formed on the electrode 34W, and one of the insulating layers 33 The black display electrode 32B formed in the part is provided. The white display electrode 34W and the black display electrode 32B are provided in the same substrate 38, and the black display electrode 32B has a smaller area than the white display electrode 34W.

  The dispersion includes a transparent insulating dispersion medium 46 and black charged electrophoretic particles 48.

  When the black charged electrophoretic particles 48 are positively charged, when the black display electrode 32B is a negative electrode, the electrophoretic particles 48 are attracted onto the electrode 32B, so that white can be displayed. Conversely, when the black display electrode 32B is a positive electrode, the electrophoretic particles 48 are attracted onto the white display electrode 34W, so that black can be displayed.

  In this display device, the positively charged particles 48 are attracted to the electrode 32B or the electrode 34W by electrostatic attraction or electrostatic repulsion due to the capacitance formed between the electrode 32B and the electrode 34W even when voltage application is stopped. Therefore, it has excellent memory characteristics and can reduce power consumption.

  Hereinafter, a method for manufacturing the electrophoretic display device of this embodiment will be exemplified.

  First, a method for producing a microcapsule will be described. The microcapsule has a dispersion medium 46 and electrophoretic particles 48W and 48B in the microcapsule wall.

  As the dispersion medium 46, for example, any one of organic solvents such as chloroform, dichloromethane, tetrachloromethane, toluene, xylene, NMP, THF, and dioxane, or a mixture thereof can be used. The dispersion medium 46 is colored by mixing a known azo dye, anthraquinone dye, triphenylmethane dye, metal dye, or the like, if necessary.

  The dispersion medium 46 preferably contains a liquid crystal material having positive dielectric anisotropy. As the liquid crystal material, for example, those represented by the following chemical formulas (Chemical Formula 1), (Chemical Formula 2), and (Chemical Formula 3) can be used. Note that the dispersion medium 46 as a whole may be mixed with an organic solvent as long as it has orientation.

  A lyotropic liquid crystal such as a surfactant, phospholipid, or non-phospholipid may be used as the liquid crystal material. Further, the dispersion medium 46 may include a conductive polymer such as polythiophene, polyphenylene, polyphenylene vinylene, polyaniline, polythienylene instead of the liquid crystal material. The degree of polymerization of the conductive polymer is preferably in the range of 2 or more and 200 or less. If the degree of polymerization is 2 or more, the movement of the electrophoretic particles can be sufficiently fast due to the rigidity of the polymer, and if it is 200 or less, the molecular weight distribution (polymerization degree distribution) of the polymer can be sufficiently controlled. Because. The concentration of the polymer in the dispersion medium 46 is preferably in the range of 0.001% by mass to 5% by mass. If it is 0.001% by mass or more, the movement of the electrophoretic particles can be sufficiently fast due to the anisotropy of the polymer solution. If it is 5% by mass or less, the electrophoretic particles are moved by the viscosity of the solution. It is because it is not suppressed.

  The electrophoretic particles include inorganic particles and ionic organic substances bonded to the surfaces of the inorganic particles through chemical bonds. As the inorganic particles, silica, titanium, titanium oxide, alumina particles, or the like can be used.

  For example, electrophoretic particles can be produced using the inorganic particles and the polymer material. Hereinafter, a method for producing electrophoretic particles in which negative polyvalent ionic atomic groups are chemically bonded to the surface of the particles will be specifically described.

As shown in the following chemical formula _{4, the} monomer unit (1) (styrene phosphoric acid) having an atomic group PhPO ₄ H ₂ that generates a multivalent ionic atomic group PhPO ₄ ^3- and a functional group capable of chemically bonding to the silica surface A monomer unit (2) (acrylic acid chloride) having a functional group COCl group that generates a group COO group is copolymerized to synthesize a polymer (3).

As shown in chemical formula 6 below, the polymer (3) is reacted with OH groups on the silica surface. In addition, as shown in Chemical formula 5, the silica particles may be subjected to alkali treatment in advance. The obtained composite (5) is subjected to an alkali treatment to obtain electrophoretic particles (6) in which the negative trivalent charged ionic atomic group PhPO ₄ ^3- is chemically bonded to the surface of the silica particles.

  Electrophoretic particles can be produced using a low molecular weight compound.

As shown in the chemical formula 7 below, the silyl group (7) is reacted with OH groups on the surface of the silica particles. The silylating agent (7) has a polyvalent ionic atomic group (CH ₂ ) ₆ OPO ₃ ^3- and a functional group SiCl ₃ that generates a functional group SiO ₃ that can be chemically bonded to the silica surface. Silica (8) may be subjected to alkali treatment in advance as required as shown in Chemical Formula 5 above. The obtained composite is subjected to alkali treatment to obtain electrophoretic particles (9) in which negatively trivalent charged ionic atomic groups (CH ₂ ) ₆ OPO ₃ ^3- are chemically bonded to the surface of silica particles. it can.

  Hereinafter, a specific example of a method for producing an electrophoretic particle in which a positive multivalent ionic atomic group is chemically bonded to the surface of the particle will be described.

  As shown in the following chemical formula 8, the monomer unit (10) (ruthenium (II) pyridinium methacrylate) having an atomic group that generates a polyvalent ionic atomic group ruthenium (II) pyridinium, and a functional group capable of chemically bonding to the silica surface A monomer unit (11) (acrylic acid chloride) having a functional group COCl group that generates a group COO group is copolymerized to synthesize a polymer (12).

  This polymer (12) is reacted with OH groups on the silica surface. The silica particles may be subjected to alkali treatment in advance as required as shown in Chemical Formula 5 above. The obtained synthetic product is subjected to an alkali treatment, and electrophoretic particles in which the positively divalent charged ionic atomic group ruthenium (II) pyridinium shown in Chemical Formula 9 is chemically bonded to the surface of the silica particles can be obtained.

  Electrophoretic particles can be colored by chemically bonding a dye molecule to an ionic organic substance. As the dye molecule, for example, naphthylmethylmethacrylamide and a soluble monomer containing a dye molecule other than naphthalene (a monomer containing a dye such as anthracene, phenanthrene, pyrene, and perylene) can be used. Hereinafter, a specific example of the manufacturing method will be described.

As shown in the chemical formula 10 below, the monomer unit (13) (styrene phosphoric acid) having the atomic group PhPO ₄ H ₂ used in the chemical formula ₄ described above and the functional group that generates a functional group COO group that can be chemically bonded to the silica surface. A monomer unit (15) (acrylic acid chloride) having a group COCl group and a dye molecule naphthylmethyl methacrylamide (14) are copolymerized to synthesize a polymer (16). The obtained polymer (16) can be subjected to an alkali treatment to obtain colored electrophoretic particles (17).

  Conventionally, it has been difficult to produce colored electrophoretic particles. Specifically, for example, aluminum, silver, and gold layers are deposited on inorganic particles by physical vapor deposition, and then the metal layer is colored in colors such as red, blue, and green to produce colored electrophoretic particles. (For example, refer to Patent Document 2). Alternatively, colored electrophoretic particles have been produced by chemically bonding a dye compound to particles made of a crosslinked polymer material (see, for example, JP-A No. 2003-117434).

  In contrast, in the present embodiment, as described above, electrophoretic particles can be colored by chemically bonding a dye molecule to an ionic organic substance. Therefore, it is easier to perform colored electrophoresis than conventional methods using existing inorganic particles. Particles can be made.

  The dispersion obtained by mixing the electrophoretic particles obtained above and a dispersion medium is mixed with a known method such as a phase separation method such as a complex coacervation method, an interfacial polymerization method, an in-situ method, or a solution dispersion cooling method. It encloses in the microcapsule wall to be created. If necessary, the diameter distribution of the produced microcapsules is controlled by an arbitrary method such as sieving or specific gravity separation. As a diameter of a microcapsule, 1-300 micrometers is desirable, More preferably, it is 5-200 micrometers.

  The microcapsule is disposed at a desired position on the substrate 38 on which the electrode 32 is formed by using, for example, a photolithography method. Details of the arrangement method of the microcapsules are described in, for example, Japanese Patent Application Laid-Open No. 11-20284. The film thickness of the microcapsule layer composed of the polymer resin layer 3 and the microcapsules is preferably 1 to 300 μm, more preferably 5 to 200 μm.

  An electrophoretic display device 30 is manufactured by bonding a substrate 36 on which an electrode 34 made of, for example, ITO is formed on the microcapsule layer. For the substrates 36 and 38, a plastic film substrate such as polyethylene terephthalate, polycarbonate, and polyethersulfone can be suitably used in addition to the glass substrate.

  The electrophoretic display device of the present invention is widely applicable to a microcapsule electrophoretic display device, an in-plane electrophoretic display device, and other electrophoretic display devices.

It is a figure for demonstrating the electrophoretic display device 30 of one Embodiment of this invention. It is a figure for demonstrating the electrophoretic display device 30B of one Embodiment of this invention. It is a figure for demonstrating the electrophoretic display device 30C of one Embodiment of this invention. It is a figure for demonstrating the electrophoretic display device 30D of one Embodiment of this invention. It is a figure for demonstrating the electrophoretic display device 30E of one Embodiment of this invention. It is a figure for demonstrating the conventional electrophoretic display device.

Explanation of symbols

2 Dispersion medium 4 White charged particle 6 Black charged particle 10 Microcapsule 12 Electrode 14 Electrode 30 Electrophoretic display device 30B Electrophoretic display device 30C Electrophoretic display device 30D Electrophoretic display device 30E Electrophoretic display device 32 Electrode 34 Electrode 32B Electrode 34W Electrode 36 Viewer side substrate 38 Back side substrate 42A Microcapsule 42B Microcapsule 46 Dispersion medium 48CB Blue electrophoretic particles 48CG Green electrophoretic particles 48CR Red electrophoretic particles 48B Black electrophoretic particles 48W White electrophoretic particles Particle 52 Insulating layer

Claims (8)

A display device having a dispersion medium and electrophoretic particles dispersed in the dispersion medium,
The electrophoretic particle is an electrophoretic display device having inorganic particles and an ionic atomic group having a charge of two or more valences bonded to the surface of the inorganic particles through a chemical bond.   The electrophoretic display device according to claim 1, wherein the dispersion medium includes a liquid crystal material having positive dielectric anisotropy.   The electrophoretic display device according to claim 1, wherein the dispersion medium includes a lyotropic liquid crystal.   The electrophoretic display device according to claim 1, wherein the dispersion medium includes a conductive polymer.   The electrophoretic display device according to claim 1, wherein a dye molecule is bonded to the ionic atomic group through a chemical bond. A microcapsule wall;
The electrophoretic display device according to claim 1, wherein the microcapsule wall is filled with the dispersion medium and the electrophoretic particles to constitute a microcapsule. A microcapsule wall,
A microcapsule having a dispersion medium and electrophoretic particles filled in the microcapsule wall,
The electrophoretic particle is a microcapsule comprising inorganic particles and an ionic atomic group having a charge of two or more valences bonded to the surface of the inorganic particles through a chemical bond. A dispersion for an electrophoretic display device comprising a dispersion medium and electrophoretic particles dispersed in the dispersion medium,
The electrophoretic display device dispersion liquid for electrophoretic display devices, wherein the electrophoretic particles include inorganic particles and an ionic atomic group having a divalent or higher charge bonded to the surface of the inorganic particles through a chemical bond.

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