JP5644601B2 - Electrophoretic particles, electrophoretic particle dispersion, display medium, and display device - Google Patents

Description

  The present invention relates to an electrophoretic particle, an electrophoretic particle dispersion, a display medium, and a display device.

  An electrophoretic display medium has been actively studied as a display having image maintenance (so-called memory property). In this display method, electrophoretic particles charged in a liquid are used, and the electrophoretic particles are placed in the cell by applying an electric field (a configuration in which two electrode substrates are stacked and the electrophoretic material is enclosed with a dispersion medium between them). And display is performed by moving back and forth alternately.

  In general, in an electrophoretic display medium, the electrophoretic particles have a surface charge due to adsorption of ions from the dispersion medium or a surface dissociation reaction in the dispersion medium, and the electrophoretic particles in the dispersion medium have a charge state. Display is performed by moving the electrophoretic particles by utilizing the force acting on the electrophoretic particles.

For example, in Patent Document 1, in order to impart charging characteristics, color, and fluidity to micron-order particles called mother particles, a plurality of types of sub-micron to nano-order fine particles are applied to the surface of the mother particle by mechanical and chemical methods. Techniques have been proposed in which mixed particles are made to adhere to display an image.
The present technology has composite particles composed of mother particles and small particles. One of the particles is urethane particles (average particle size 5.8 μm) as mother particles, carbon (average particle size 0.03 μm) as small particles, and borontron no. 7 are mixed, and the small particles and the charge control agent are immobilized on the surface of the mother particles by the mechano-fusion method. Then, by applying a voltage between the electrodes of both substrates and applying an electric field between both the substrates, the small particles impart charging characteristics and fluidity to the mother particles.

JP 2003-233092 A

  The subject of this invention is providing the electrophoretic particle which suppressed adhesion to a to-be-contacted object.

The above problem is solved by the following means. That is,
The invention according to claim 1
A display medium according to claim 4 or 5 , and
Voltage application means for applying a voltage between the pair of substrates or the pair of electrodes of the display medium;
A display device comprising:

The invention according to claim 2
2. The electrophoresis according to claim 1, wherein an electrolyte layer in which an anionic electrolyte material and a cationic electrolyte material are alternately stacked in the radial direction of the electrophoretic particle body as the electrolyte material is provided on a surface of the electrophoretic particle body. particle.

The invention according to claim 3
The electrophoretic particle according to claim 1, wherein the electrolyte material is an electrolyte polymer.

The invention according to claim 4
A dispersion medium;
Electrophoretic particles dispersed in the dispersion medium, wherein the electrophoretic particles according to any one of claims 1 to 3,
An electrophoretic particle dispersion comprising:

The invention according to claim 5
A pair of substrates, at least one of which is translucent,
The electrophoretic particle dispersion according to claim 4 enclosed between the pair of substrates;
A display medium comprising:

The invention according to claim 6
A pair of electrodes, at least one of which is translucent,
A region having an electrophoretic particle dispersion according to claim 4 provided between the pair of electrodes;
A display medium comprising:

The invention according to claim 7 provides:
A display medium according to claim 5 or 6,
Voltage application means for applying a voltage between the pair of substrates or the pair of electrodes of the display medium;
A display device comprising:

According to the first and second aspects of the present invention, one of the anionic electrolyte material and the cationic electrolyte material as the electrolyte material has an irregular shape as compared with the case where one of them is attached to the surface of the electrophoretic particle body alone. However, it is possible to provide the electrophoretic particles in which the adhesion to the contacted object is suppressed.

According to the inventions according to claims 3 , 4, 5, and 6, the electrophoretic particles are more firmly fixed to the contacted object than when the electrophoretic particles having no electrolyte material attached to the surface of the electrophoretic particle main body are applied. A suppressed electrophoretic particle dispersion, a display medium, and a display device can be provided.

1 is a schematic configuration diagram of a display device according to a first embodiment. It is explanatory drawing which shows typically the movement aspect of a particle group when a voltage is applied between the board | substrates of the display medium of the display apparatus which concerns on 1st Embodiment. It is a schematic block diagram of the display apparatus which concerns on 2nd Embodiment. It is a diagram which shows typically the relation between the applied voltage and the amount of movement of particles (display density) in the display device concerning a 2nd embodiment. It is explanatory drawing which shows typically the relationship between the voltage aspect applied between the board | substrates of a display medium, and the movement aspect of particle | grains.

  Hereinafter, embodiments of the present invention will be described.

(Electrophoretic particles, electrophoretic particle dispersion)
The electrophoretic particles according to the present embodiment include an electrophoretic particle main body and an electrolyte material attached to the surface of the electrophoretic particle main body.

Here, the electrophoretic particles used in the display medium generally use a pulverization method, an emulsion polymerization method, or the like, and charge control is performed by adding a charge control agent. Since it is difficult to form on the surface, the surface charge density of the particles tends to vary. For this reason, sticking to an object to be contacted with the electrophoretic particles (for example, other than the dispersion medium, the electrophoretic particles, the substrate, the electrode, the gap member (spacer), etc.) may occur. As a result, accurate driving cannot be achieved, and control and image stability are often lacking. In addition, when the charge control agent is adhered to the surface of the electrophoretic particles as particles, if the adhesion strength is not sufficient, the home appliance control agent particles peel off due to collision or friction between the electrophoretic particles as they are repeatedly displayed. , It migrates to the surface of other electrophoretic particles and electrodes. As a result, the charge control, which is the original purpose, cannot be controlled, the electrophoretic particles are not driven sufficiently, the desired display density is not generated, and the image retention characteristics are deteriorated. There is a tendency for the characteristics to deteriorate.
In contrast, the electrophoretic particles according to the present embodiment are considered to form a high-density charged layer with little variation on the particle surface due to the above-described configuration. In addition to the dispersion medium, adhesion to the electrophoretic particles, the substrate, the electrode, the gap member (spacer), etc.) is suppressed.
In particular, when an electrolyte polymer is used as the electrolyte material, this layer is considered to have excellent adsorption stability, and thus image retention characteristics tend to be stable even when driven for a long time.
When an electrolyte polymer is used as the electrolyte material, a nano-order structure is formed on the surface. As a result, it is considered that the super-water-repellent effect is exhibited, and as a result, the contacted object with which the electrophoretic particles come into contact (for example, other than the dispersion medium, the electrophoretic particles, the substrate, the electrode, the gap member (spacer), etc.) The sticking to is further suppressed.

  In addition, since the electrophoretic particles according to the present embodiment are considered to have the electrolyte material exposed on the surface of the electrophoretic particle, the electrophoretic particles correspond to the polarity (anionic or cationic) of the electrolyte material exposed on the surface. Charge polarity is also imparted, and electrophoretic properties as electrophoretic particles are ensured.

  Each element of the electrophoretic particles will be described in detail.

The electrolyte material will be described.
The electrolyte material is a material having charged groups (separable functional groups) in the side chain or main molecular structure.

  Examples of the electrolyte material include organic electrolyte materials (for example, electrolyte polymer (electrolyte polymer), electrolyte low molecule (electrolyte monomer)), and inorganic electrolyte materials (for example, inorganic oxide particles having an ionizing group on the surface). .

  Examples of the electrolyte polymer include cationic electrolyte polymers (for example, polyallylamine hydrochloride, polyallylamine amide sulfate, polydiallylamine hydrochloride, polyallylamine acetate, polymethyldiallylamine hydrochloride, polymethyldiallylamine amide sulfate). . Anionic electrolyte polymers (for example, polyacrylic acid, polydiallyldimethylammonium chloride, sodium polyacrylate, etc.) can be mentioned.

Examples of the weight average molecular weight of the electrolyte polymer include a range of 1000 to 500,000 (preferably 5000 to 300,000).
The weight average molecular weight is measured by a static light scattering method or size exclusion column chromatography, and the numerical values described in this specification are measured by the method. The same applies hereinafter.

Examples of the electrolyte small molecule include a cationic electrolyte small molecule (for example, titanium (IV) bis (ammonium lactato) dihydroxide), an anionic electrolyte polymer (for example, acrylic acid, methacrylic acid, 2-acrylamide-2- Methyl propane sulfonic acid etc.).
As a weight average molecular weight of electrolyte low molecule, the range of 50 or more and 500 or less (desirably 100 or more and 400 or less) is mentioned, for example.

Examples of inorganic oxide particles having an ionizing group on the surface include cationic inorganic oxide particles (for example, Fe ₂ O ₃ , Al ₂ O _3, etc.), anionic inorganic oxide particles (for example, TiO ₂ , SiO _2, etc.). ) And the like.

Among these, the electrolyte material is preferably an electrolyte polymer. The electrolyte polymer tends to adhere in a layered manner so as to cover the surface of the electrophoretic particle main body, and there is a tendency that variation in the charging property of the electrophoretic particles is suppressed (that is, the charge distribution becomes narrow).
Particularly, among electrolyte polymers, strong electrolyte polymers (for example, polydiallyldimethylammonium chloride, diallylamine hydrochloride / sulfur dioxide copolymer, diallylmethylethylammonium ethyl sulfate / sulfur dioxide copolymer, methyldiallylamine hydrochloride / Sulfur dioxide copolymer, etc.) is preferable. The strong electrolyte polymer further suppresses the variation in chargeability of the electrophoretic particles (that is, the charge distribution becomes narrower), and when applied to a display medium, the display density is improved and is easily maintained.

The electrolyte material is attached to the surface of the electrophoretic particle body. Specifically, for example, the electrolyte material is electrostatically adsorbed on the surface of the electrophoretic particle body to form an electrolyte layer (molecular layer or particle layer). It is attached with.
In particular, it is preferable that an anionic electrolyte material and a cationic electrolyte material as the electrolyte material are attached to the surface of the electrophoretic particle body in an electrolyte layer in which the electrophoretic particle body is alternately laminated in the radial direction.
That is, it is preferable that two or more anionic electrolyte layers of the anionic electrolyte material and a cationic electrolyte layer of the cationic electrolyte material are alternately laminated on the surface of the electrophoretic particle body.

Thereby, shape control of the electrophoretic particles is realized.
As will be described later, an electrolyte material is formed by alternately laminating an anionic electrolyte material and a cationic electrolyte material by electrostatic adsorption to form an electrolyte layer having a thickness, and this electrolyte material is alternately electrostatically adsorbed. At this time, electrolyte layers having partially different thicknesses can be formed by partially absorbing and adsorbing them. For this reason, regardless of the shape of the electrophoretic particle body itself, the shape of the electrophoretic particle can be selected from a spherical shape to an irregular shape by the electrolyte layer. For example, when emphasis is placed on drive controllability, the particles may be made small and the particles have a smooth surface. In addition, when it is desired to prevent the electrophoretic particles from adhering to and adhering to an object to be contacted, the particles may be large and the particles may have a complicated structure. Thus, it becomes easy to realize particle shape selection in accordance with the difference in driving method and display method.
In addition, since a thick electrolyte layer is formed, even if the shape of the electrophoretic particles is not spherical but irregular, the variation in charging polarity is suppressed and the electrophoretic particles come into contact. Sticking to an object (for example, other than a dispersion medium, between electrophoretic particles, a substrate, an electrode, a gap member (spacer), etc.) is suppressed, and when applied to a display medium, the display density is improved and is easily maintained. .
The charging polarity is selected by selecting the polarity of the electrolyte material (its electrolyte layer) located on the outermost side of the electrophoretic particles.

The adhesion amount of the electrolyte material is 0.001% by mass or more and 5% by mass or less (preferably 0.01% by mass or more and 1% by mass or less, more preferably 0.05% by mass or more and 0.0% by mass or less) with respect to the electrophoretic particle body. 1% by mass or less).
By making the adhesion amount of the electrolyte material within the above range, the adhesion of the electrophoretic particles to the contacted object is suppressed.

The electrophoretic particle body will be described.
Examples of the electrophoretic particle body include metal oxide particles (for example, insulating properties such as glass beads, alumina, and titanium oxide), thermoplastic or thermosetting resin particles, and a colorant fixed on the surface of these resin particles. And particles containing a colorant in a thermoplastic or thermosetting resin, and metal colloidal particles having a plasmon coloring function.

As the thermoplastic resin constituting the electrophoretic particle body, for example,
Styrenes (eg, styrene, chlorostyrene, etc.), monoolefins (eg, ethylene, propylene, butylene, isoprene, etc.), vinyl esters (eg, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, etc.), α-methylene Aliphatic monocarboxylic esters (eg methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate) Homopolymers of vinyl ethers (eg, vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether, etc.), vinyl ketones (eg, vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone, etc.), Two or more of these copolymers.

  Examples of the thermosetting resin constituting the electrophoretic particle main body include a crosslinked copolymer mainly composed of divinylbenzene and a crosslinked resin such as crosslinked polymethyl methacrylate, a phenol resin, a urea resin, a melamine resin, a polyester resin, and a silicone resin. Is mentioned. Particularly representative binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer. Examples of the polymer include polyethylene, polypropylene, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, and paraffin wax.

Examples of the colorant include organic pigments, inorganic pigments, oil-soluble dyes, etc., for example, magnetic powders such as magnetite and ferrite, carbon black, titanium oxide, magnesium oxide, zinc oxide, phthalocyanine copper-based cyan colorants, azo-based materials Known colorants such as a yellow color material, an azo magenta color material, a quinacridone magenta color material, a red color material, a green color material, and a blue color material can be used.
Specific examples of the colorant include aniline blue, calcoyl blue, chrome yellow, ultramarine blue, dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. Blue 15: 1, C.I. I. Pigment Blue 15: 3, etc. are exemplified as typical examples.

  If necessary, a charge control agent may be mixed in the resin constituting the electrophoretic particle body. As the charge control agent, known materials used for toner materials for electrophotography can be used. For example, cetylpyridyl chloride, BONTRON P-51, BONTRON P-53, BONTRON E-84, BONTRON E-81 (above, Quaternary ammonium salts such as Orient Chemical Industry Co., Ltd., salicylic acid metal complexes, phenol condensates, tetraphenyl compounds, metal oxide particles, and metal oxide particles surface-treated with various coupling agents.

A magnetic material may be mixed into the inside or the surface of the electrophoretic particle body as necessary. As the magnetic material, a color-coated inorganic magnetic material or organic magnetic material is used as necessary. Further, a transparent magnetic material, in particular, a transparent organic magnetic material does not hinder the color development of the color pigment, and the specific gravity is smaller than that of the inorganic magnetic material, so that it is more desirable.
As the colored magnetic material (magnetic powder), for example, a small-diameter colored magnetic powder described in JP-A-2003-131420 may be used. A material provided with magnetic particles serving as nuclei and a colored layer laminated on the surface of the magnetic particles is used. The colored layer may be selected by coloring the magnetic powder opaque with a pigment or the like, but it is desirable to use, for example, a light interference thin film. This optical interference thin film is a thin film having a thickness equivalent to the wavelength of light made of an achromatic material such as SiO ₂ or TiO ₂ , and reflects light in a wavelength selective manner by optical interference in the thin film. is there.

  Hereinafter, a method for producing electrophoretic particles according to the present embodiment will be described.

First, an example of a method for producing an electrophoretic particle body will be described.
Any conventionally known method may be used as a method for producing the electrophoretic particle body. For example, as described in JP-A-7-325434, the resin, the pigment, and the charge control agent are weighed so as to have a target mixing ratio, and after the resin is heated and melted, the pigment is added, mixed, dispersed, After cooling, a method is used in which particles are prepared using a pulverizer such as a jet mill, a hammer mill, a turbo mill, and the obtained particles are then dispersed in a dispersion medium. Also, particles containing a charge control agent are prepared by polymerization methods such as suspension polymerization, emulsion polymerization, dispersion polymerization, coacervation, melt dispersion, emulsion aggregation, and then dispersed in a dispersion medium. A particle dispersion medium may be produced. Furthermore, the resin, the colorant, and the charge control agent may have a plasticity, the dispersion medium does not boil, and the temperature is lower than the decomposition point of at least one of the resin, the charge control agent, and the colorant. And a method using an appropriate apparatus for dispersing and kneading the raw material of the dispersion medium. Specifically, the pigment, the resin, and the charge control agent are heated and melted in a dispersion medium with a meteor mixer, a kneader, etc., and the molten mixture is cooled with stirring using the temperature dependence of the solvent solubility of the resin. Solidify / precipitate to produce particles.

  Furthermore, the above raw materials are put into a suitable container equipped with granular media for dispersion and kneading, for example, a heated vibration mill such as an attritor or a heated ball mill, and the container is placed in a desired temperature range, for example, 80 You may use the method of disperse | distributing and knead | mixing at 150 degreeC or more. As granular media, steels such as stainless steel and carbon steel, alumina, zirconia, silica and the like are desirably used. In order to produce migrating particles by this method, the raw material that has been previously fluidized is further dispersed in a container by granular media, and then the dispersion medium is cooled to precipitate a resin containing a colorant from the dispersion medium. The granular media generates a shear and / or impact to reduce the particle size while maintaining a motion state during and after cooling.

Next, an example of a method for attaching an electrolyte material to the surface of the electrophoretic particle main body will be described.
Here, when a member having a charged surface is immersed in a solution in which a material having an opposite charge is dissolved or dispersed, an electrostatic interaction (electrostatic adsorption action) works between the member and the material, and the surface of the member is affected. A layer of this material is formed. This electrostatic interaction (electrostatic adsorption action) is considered to act by the interaction of the Debye length, van der Waals force, entropy, etc. of the adsorption target.

That is, the method of attaching the electrolyte material to the surface of the electrophoretic particle body utilizes this electrostatic interaction (electrostatic adsorption action).
For example, depending on the electrophoretic particle body whose surface is charged, an electrolyte material having a counter charge (when the surface of the electrophoretic particle is positively charged, an anionic electrolyte material, when the surface of the electrophoretic particle is negatively charged, By selecting (electrolytic electrolyte material), the electrolyte material can be adsorbed (attached) to the surface of the electrophoretic particles.
Moreover, even if there is a variation in the chargeability of the surface of the electrophoretic particles (that is, a variation in density at the charged site), for example, by adjusting the Ph of the solution in which the electrolyte material is dissolved or dispersed, the effect of the Debye length is increased. When the zeta potential of the electrophoretic particles as a whole is positive (positively charged) or negative (negatively charged), the electrolyte material having the counter charge can be adsorbed (attached).
And after adsorption | suction (after adhesion), the electrophoretic particle by which the electrolyte layer was formed with the thickness on the surface of the electrophoretic particle main body by washing with pure water is obtained.

Specifically, for example, when the obtained electrophoretic particles are to have a negative charge (negative charge), the electrolyte material is placed in pure water in which the zeta potential of the electrophoretic particle body is adjusted to a ph concentration having a positive potential. After the electrolyte layer is formed on the surface of the electrophoretic particle main body by dissolving or dispersing and mixing the solution and the electrophoretic particle main body, the fine particles may be washed in pure water.
On the other hand, when the resulting electrophoretic particles are to have a positive charge (positive charge), the cationic electrolyte material is dissolved or dispersed in pure water in which the zeta potential of the electrophoretic particles is adjusted to a ph concentration having a -potential. Then, after the electrolyte layer is formed on the surface of the electrophoretic particle main body by mixing the solution and the electrophoretic particle main body, the fine particles may be washed in pure water.

Further, when an electrolyte layer in which an anionic electrolyte material and a cationic electrolyte material are alternately laminated in the radial direction of the electrophoretic particle main body as the electrolyte material is formed, the above operation is repeated.
Here, when alternately forming an electrolyte layer of an anionic electrolyte material and an electrolyte layer of a cationic electrolyte material, in order to control the shape of the electrophoretic particles obtained by partially varying the thickness of each electrolyte layer For example, if weak electrolyte anions and strong electrolyte cations are alternately laminated, the weak electrolyte anion has a low degree of dissociation, so that minute irregularities are formed on the surface, and by repeating the lamination, a particle shape with controlled irregularities can be obtained. It is done.

Hereinafter, the electrophoretic particles according to the present embodiment will be described.
The electrophoretic particle dispersion according to the present embodiment includes a dispersion medium and electrophoretic particles dispersed in the dispersion medium.
And the electrophoretic particle which concerns on the said this embodiment is applied as an electrophoretic particle.

  The electrophoretic particle dispersion according to the present embodiment may be one in which one type of electrophoretic particle is dispersed in a dispersion medium, but 1) an electrophoretic particle having a different charge polarity and 2) a charge polarity. Even if they are the same, a plurality of types of electrophoretic particles may be dispersed in a dispersion medium by combining electrophoretic particles having different voltages necessary for movement in accordance with an electric field.

The dispersion medium will be described.
The dispersion medium in which the electrophoretic particles are dispersed is preferably an insulating liquid. Here, “insulating” indicates that the volume resistivity is 10 ¹¹ Ωcm or more. The same applies hereinafter.

  Specific examples of the insulating liquid include hexane, cyclohexane, toluene, xylene, decane, hexadecane, kerosene, paraffin, isoparaffin, silicone oil, high-purity petroleum, ethylene glycol, alcohols, ethers, esters, dimethylformamide, dimethyl Acetamide, dimethyl sulfoxide, 1-methyl-2-pyrrolidone, N-methylformamide, acetonitrile, tetrahydrofuran, propylene carbonate, ethylene carbonate, benzine, diisopropylnaphthalene, olive oil, trichlorotrifluoroethane, tetrachloroethane, dibromotetrafluoroethane, etc. Those mixtures are preferably used. Among these, silicone oil is preferably applied.

Moreover, water (so-called pure water) is also preferably used as a dispersion medium by removing impurities so as to have the following volume resistance value. The volume resistance value is preferably 10 ³ Ωcm or more, more preferably 10 ⁷ Ωcm or more and 10 ¹⁹ Ωcm or less, and further preferably 10 ¹⁰ Ωcm or more and 10 ¹⁹ Ωcm or less. By setting the volume resistance value within this range, it is possible to more effectively apply an electric field to the electrophoretic particles and suppress the generation of bubbles due to the electrolysis of the liquid due to the electrode reaction. The electrophoretic properties are not impaired, and excellent repeated stability is imparted.

  If necessary, the insulating liquid may contain acid, alkali, salt, dispersion stabilizer, stabilizer for anti-oxidation or ultraviolet absorption, antibacterial agent, preservative, etc. It is desirable to add so that it may become the range of the specific volume resistance value shown above.

  For insulating liquids, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, fluorosurfactants, silicone surfactants, metal soaps as charge control agents Alkyl phosphate esters, succinimides and the like may be added and used.

  More specific examples of the ionic and nonionic surfactants are as follows. Nonionic activators include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, And fatty acid alkylolamide. Examples of the anionic surfactant include alkylbenzene sulfonate, alkylphenyl sulfonate, alkyl naphthalene sulfonate, higher fatty acid salt, sulfate of higher fatty acid ester, sulfonic acid of higher fatty acid ester, and the like. Examples of the cationic surfactant include primary to tertiary amine salts and quaternary ammonium salts. These charge control agents are desirably 0.01% by mass or more and 20% by mass or less, and particularly desirably 0.05% by mass or more and 10% by mass or less with respect to the solid content of the particles. If it is less than 0.01% by mass, the desired charge control effect may be insufficient, and if it exceeds 20% by mass, it may cause an excessive increase in the conductivity of the developer, making it difficult to use. Because.

  In addition, the dispersion medium may use a polymer resin together with the insulating liquid. It is also desirable that the polymer resin is a polymer gel, a polymer polymer or the like.

  Examples of polymer resins include agarose, agaropectin, amylose, sodium alginate, propylene glycol ester alginate, isolikenan, insulin, ethyl cellulose, ethyl hydroxyethyl cellulose, curdlan, casein, carrageenan, carboxymethyl cellulose, carboxymethyl starch, callose, agar, chitin, Chitosan, silk fibroin, kuer gum, quince seed, crown gall polysaccharide, glycogen, glucomannan, keratan sulfate, keratin protein, collagen, cellulose acetate, gellan gum, schizophyllan, gelatin, elephant palm mannan, tunisin, dextran, dermatan sulfate, starch, Tragacanth gum, nigeran, hyaluronic acid, hydroxyethylcellulose, hydroxypropyl Examples include polymer gels derived from natural polymers such as pill cellulose, pustulan, funolan, decomposed xyloglucan, pectin, porphyran, methylcellulose, methyl starch, laminaran, lichenan, lentinan, locust bean gum, and synthetic polymers. Includes almost all polymer gels.

  In addition, polymers containing functional groups of alcohol, ketone, ether, ester, and amide in the repeating unit are exemplified. For example, polyvinyl alcohol, poly (meth) acrylamide and derivatives thereof, polyvinyl pyrrolidone, polyethylene oxide, and the like. Examples include copolymers containing molecules.

  Among these, gelatin, polyvinyl alcohol, poly (meth) acrylamide and the like are desirably used from the viewpoints of production stability, electrophoretic characteristics and the like.

  Further, by mixing the following colorant in the dispersion medium, for example, a color different from the color of the electrophoretic particles is displayed on the display medium. For example, when the color of the electrophoretic particles is black by mixing a colorant showing white as the colorant, for example, white and black are displayed in the display medium.

  Colorants to be mixed with the dispersion medium include carbon black, titanium oxide, magnesium oxide, zinc oxide, phthalocyanine copper-based cyan color material, azo-based yellow color material, azo-based magenta color material, quinacridone-based magenta color material, and red color material. And known colorants such as green color material and blue color material. Specifically, aniline blue, calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. Blue 15: 1, C.I. I. Pigment Blue 15: 3 is a typical example.

  In the electrophoretic particle dispersion according to the present embodiment, an acid, an alkali, a salt, a dispersant, a dispersion stabilizer, a stabilizer for anti-oxidation or ultraviolet absorption, an antibacterial agent, an antiseptic, and the like, if necessary May be added. In addition, a charge control agent may be added to the electrophoretic particle dispersion according to this embodiment.

  The concentration of the electrophoretic particles in the electrophoretic particle dispersion according to the present embodiment is variously selected depending on display characteristics, response characteristics, or use thereof, but is selected in a range of 0.1% by mass to 30% by mass. Is desirable. When mixing particles having different colors, the total amount of the particles is preferably within the above range.

The electrophoretic particles (the dispersion liquid) according to the present embodiment described above are used for an electrophoretic display medium, an electrophoretic light control medium (light control element), a liquid toner of a liquid development type electrophotographic system, and the like. Is done. In addition, as an electrophoretic display medium and an electrophoretic light control medium (light control element), a known method of moving a particle group in a direction opposite to an electrode (substrate) surface, unlike the electrode (substrate), There is a method of moving in a direction along a plane (so-called in-plane type element), or a hybrid element combining these.
In the electrophoretic particle dispersion liquid according to the present embodiment, when a plurality of types of particles having different colors and charging polarities are mixed and used as the electrophoretic particles, a display medium capable of realizing color display can be obtained.

(Display medium, display device)
Hereinafter, examples of the display medium and the display device according to the embodiment will be described.

-First embodiment-
FIG. 1 is a schematic configuration diagram of a display device according to the first embodiment. FIG. 2 is an explanatory diagram schematically illustrating a movement mode of the particle group when a voltage is applied between the substrates of the display medium of the display device according to the first embodiment.

The display device 10 according to the first embodiment is a mode in which the electrophoretic particle dispersion according to the present embodiment is applied as a particle dispersion including the dispersion medium 50 and the particle group 34 of the display medium 12 (that is, In this embodiment, the electrophoretic particle dispersion according to this embodiment is applied as the particle group 34).
Specifically, as the particle group 34, a particle group 34A and a particle group 34B that exhibits a different color from the particle group 34A and has a different charging polarity are applied.

  As shown in FIG. 1, the display device 10 according to the present embodiment includes a display medium 12, a voltage application unit 16 that applies a voltage to the display medium 12, and a control unit 18.

  The display medium 12 includes a display substrate 20 that serves as an image display surface, a rear substrate 22 that faces the display substrate 20 with a gap, and holds a space between these substrates at a specific interval, and between the substrates of the display substrate 20 and the rear substrate 22. The gap member 24 is configured to include a reflective particle group 36 having optical reflection characteristics different from that of the particle group 34 enclosed in each cell.

  The cell indicates a region surrounded by the display substrate 20, the back substrate 22, and the gap member 24. A dispersion medium 50 is enclosed in the cell. The particle group 34 is composed of a plurality of particles. The particle group 34 is dispersed in the dispersion medium 50 and reflects between the display substrate 20 and the back substrate 22 according to the electric field strength formed in the cell. Move through the gap.

  In addition, the gap member 24 is provided so as to correspond to each pixel when the image is displayed on the display medium 12, and cells are formed so as to correspond to each pixel, so that the display medium 12 can display each pixel. It may be configured to do.

  Further, in the present embodiment, in order to simplify the description, the present embodiment will be described using a diagram focusing on one cell. Hereinafter, each configuration will be described in detail.

  First, the pair of substrates will be described. The display substrate 20 has a configuration in which a surface electrode 40 and a surface layer 42 are sequentially laminated on a support substrate 38. The back substrate 22 has a configuration in which a back electrode 46 and a surface layer 48 are laminated on a support substrate 44.

  The display substrate 20 or both the display substrate 20 and the back substrate 22 are translucent. Here, the translucency in the present embodiment indicates that the visible light transmittance is 60% or more.

  Examples of the material of the support substrate 38 and the support substrate 44 include glass and plastics such as polyethylene terephthalate resin, polycarbonate resin, acrylic resin, polyimide resin, polyester resin, epoxy resin, and polyethersulfone resin.

  As materials for the front electrode 40 and the back electrode 46, oxides such as indium, tin, cadmium and antimony, composite oxides such as ITO, metals such as gold, silver, copper and nickel, organic materials such as polypyrrole and polythiophene, etc. Is mentioned. The surface electrode 40 and the back electrode 46 may be any of these single-layer films, mixed films, and composite films. The thicknesses of the front electrode 40 and the back electrode 46 are preferably, for example, 100 mm or more and 2000 mm or less. The back electrode 46 and the surface electrode 40 may be formed in a matrix shape or a stripe shape, for example.

  Further, the surface electrode 40 may be embedded in the support substrate 38. Further, the back electrode 46 may be embedded in the support substrate 44. In this case, the materials of the support substrate 38 and the support substrate 44 are selected according to the composition of each particle of the particle group 34 and the like.

  The back electrode 46 and the surface electrode 40 may be separated from the display substrate 20 and the back substrate 22 and disposed outside the display medium 12.

  In the above description, the case where both the display substrate 20 and the back substrate 22 are provided with electrodes (the front electrode 40 and the back electrode 46) has been described. However, only one of them is provided, and active matrix driving is performed. Also good.

  In order to perform active matrix driving, the support substrate 38 and the support substrate 44 may include a TFT (Thin Film Transistor) for each pixel. The TFT is preferably provided on the back substrate 22 instead of the display substrate.

  Next, the surface layer will be described. The surface layer 42 and the surface layer 48 are formed on the surface electrode 40 and the back electrode 46, respectively. Examples of the material constituting the surface layer 42 and the surface layer 48 include polycarbonate, polyester, polystyrene, polyimide, epoxy, polyisocyanate, polyamide, polyvinyl alcohol, polybutadiene, polymethyl methacrylate, copolymerized nylon, ultraviolet curable acrylic resin, fluorine Examples thereof include resins.

  The surface layer 42 and the surface layer 48 may be configured to include the above-described resin and a charge transport material, or may be configured to include a self-supporting resin having a charge transport property.

  Next, the gap member will be described. The gap member 24 for holding a gap between the display substrate 20 and the back substrate 22 is made of, for example, a thermoplastic resin, a thermosetting resin, an electron beam curable resin, a photocurable resin, rubber, metal, or the like. The

The gap member 24 may be integrated with either the display substrate 20 or the back substrate 22. In this case, the support substrate 38 or the support substrate 44 is manufactured by performing etching processing, laser processing processing, press processing processing, printing processing, or the like using a previously manufactured mold.
In this case, the gap member 24 is fabricated on either the display substrate 20 side, the back substrate 22 side, or both.

  The gap member 24 may be colored or colorless, but is preferably colorless and transparent. In that case, the gap member 24 is made of, for example, a transparent resin such as polystyrene, polyester, or acrylic.

The particulate gap member 24 is also preferably transparent, and glass particles are used in addition to transparent resin particles such as polystyrene, polyester, or acrylic.
Note that “transparent” means having a transmittance of 60% or more with respect to visible light.

  Next, the reflective particle group will be described. The reflective particle group 36 is composed of reflective particles having optical reflection characteristics different from that of the particle group 34, and functions as a reflective member that displays a color different from that of the particle group 34. And it also has a function as a gap member to move without hindering movement between the display substrate 20 and the back substrate 22. That is, each particle of the particle group 34 is moved from the back substrate 22 side to the display substrate 20 side or from the display substrate 20 side to the back substrate 22 side through the gap between the reflective particle groups 36. As the color of the reflective particle group 36, for example, white or black is preferably selected so as to be the background color, but other colors may be used. The reflective particle group 36 may be an uncharged particle group (that is, a particle group that does not move in response to an electric field) or a charged particle group (a particle group that moves in response to an electric field). May be. In the present embodiment, the case where the reflective particle group 36 is an uncharged particle group and is white is described, but the present invention is not limited to this.

  The particles of the reflective particle group 36 include, for example, a white pigment (for example, titanium oxide, silicon oxide, zinc oxide), a resin (for example, polystyrene resin, polyethylene resin, polypropylene resin, polycarbonate resin, polymethyl methacrylate resin (PMMA), acrylic resin). Resin, phenol resin, formaldehyde condensate, etc.). Moreover, when applying particles other than white as the particles of the reflective particle group 36, for example, the above-described resin particles containing a pigment or dye of a desired color may be used. If the pigment or dye is, for example, RGB or YMC color, a general pigment or dye used for printing ink or color toner can be used.

  In order to enclose the reflective particle group 36 between the substrates, for example, an inkjet method or the like is performed. Further, when the reflective particle group 36 is fixed, for example, after the reflective particle group 36 is sealed, the particle group surface layer of the reflective particle group 36 is melted by heating (and pressurizing if necessary). It is performed while maintaining the gap.

  The size of the cell in the display medium 12 is closely related to the resolution of the display medium 12, and the smaller the cell, the higher the resolution of the display medium 12 can be produced. The length of the display substrate 20 in the plate surface direction is about 10 μm or more and 1 mm or less.

  In order to fix the display substrate 20 and the back substrate 22 to each other through the gap member 24, fixing means such as a combination of bolts and nuts, a clamp, a clip, and a substrate fixing frame are used. Also, fixing means such as an adhesive, heat melting, and ultrasonic bonding may be used.

  The display medium 12 configured as described above includes, for example, a bulletin board, a circulation version, an electronic blackboard, an advertisement, a signboard, a flashing sign, an electronic paper, an electronic newspaper, an electronic book, and a copier / printer in which images are stored and rewritten. Used for document sheets etc.

  As described above, the display device 10 according to the present embodiment includes the display medium 12, the voltage application unit 16 that applies a voltage to the display medium 12, and the control unit 18 (FIG. 1). reference).

  The voltage application unit 16 is electrically connected to the front electrode 40 and the back electrode 46. In the present embodiment, the case where both the front electrode 40 and the back electrode 46 are electrically connected to the voltage application unit 16 will be described. However, one of the front electrode 40 and the back electrode 46 is grounded. The other may be connected to the voltage application unit 16.

  The voltage application unit 16 is connected to the control unit 18 so as to exchange signals.

  The control unit 18 stores in advance various programs such as a CPU (Central Processing Unit) that controls the operation of the entire apparatus, a RAM (Random Access Memory) that temporarily stores various data, and a control program that controls the entire apparatus. Further, it may be configured as a microcomputer including a ROM (Read Only Memory).

  The voltage application unit 16 is a voltage application device for applying a voltage to the front electrode 40 and the back electrode 46, and applies a voltage according to the control of the control unit 18 between the front electrode 40 and the back electrode 46.

  Next, the operation of the display device 10 will be described. This operation will be described according to the operation of the control unit 18.

  Here, among the particle groups 34 enclosed in the display medium 12, the case where the particle group 34B is negatively charged and the particle group 34B is positively charged will be described. In the following description, it is assumed that the dispersion medium 50 is transparent and the reflective particle group 36 is white. That is, in the present embodiment, a case will be described in which the display medium 12 displays the colors presented by the movement of the particle group 34A and the particle group 34B, and displays white as the background color.

First, an initial operation signal indicating that a voltage is applied for a specific time so that the surface electrode 40 is a negative electrode and the back electrode 46 is a positive electrode is output to the voltage application unit 16. When a negative electrode and a voltage equal to or higher than the threshold voltage at which the concentration variation ends is applied between the substrates, the particles constituting the particle group 34A charged on the negative electrode move to the back substrate 22 side, (See FIG. 2A). On the other hand, particles constituting the particle group 34B charged to the positive electrode move to the display substrate 20 side and reach the display substrate 20 (see FIG. 2A).
At this time, as the color of the display medium 12 visually recognized from the display substrate 20 side, white as the color of the reflective particle group 36 is used as the background color, and the color exhibited by the particle group 34B is visually recognized. Note that the particle group 34 </ b> A is concealed by the reflective particle group 36 and is difficult to be visually recognized.

  The T1 time may be stored in advance in a memory such as a ROM (not shown) in the control unit 18 as information indicating the voltage application time in the voltage application in the initial operation. Then, information indicating this specific time may be read when the process is executed.

Next, the polarity of the voltage applied between the substrates is reversed between the surface electrode 40 and the back electrode 46, and when the voltage is applied with the surface electrode 40 as the positive electrode and the back electrode 46 as the negative electrode, the negative electrode is charged. The moving particle group 34A moves to the display substrate 20 side and reaches the display substrate 20 side (see FIG. 2B). On the other hand, the particles constituting the particle group 34B charged to the positive electrode move to the back substrate 22 side and reach the back substrate 22 (see FIG. 2B).
At this time, as the color of the display medium 12 visually recognized from the display substrate 20 side, white as the color of the reflective particle group 36 is used as the background color, and the color exhibited by the particle group 34A is visually recognized. The particle group 34 </ b> B is concealed by the reflective particle group 36 and is difficult to be visually recognized.

  Thus, in the display device 10 according to the present embodiment, the display is performed when the particle group 34 (particle group 34A, particle group 34B) reaches the display substrate 20 or the back substrate 22 and adheres thereto.

-Second Embodiment-
The display device according to the second embodiment will be described below. FIG. 3 is a schematic configuration diagram of a display device according to the second embodiment. FIG. 4 is a diagram schematically showing a relationship between an applied voltage and a moving amount (display density) of particles in the display device according to the second embodiment. FIG. 5 is an explanatory diagram schematically showing the relationship between the voltage mode applied between the substrates of the display medium and the particle movement mode in the display device according to the second embodiment.

  The display device 10 according to the second embodiment is a form in which two or more types of particle groups are applied. Two or more kinds of particle groups are all charged with the same polarity.

As shown in FIG. 3, the display device 10 according to the second embodiment includes a display medium 12, a voltage application unit 16 that applies a voltage to the display medium 12, and a control unit 18.
Note that the display device 10 according to the present embodiment has substantially the same configuration as the display device 10 described in the first embodiment, and thus the same reference numerals are given to the same configuration and detailed description thereof is omitted.

The display medium 12 holds the display substrate 20 serving as an image display surface, the back substrate 22 facing the display substrate 20 with a gap, and holds the substrate between the display substrate 20 and the back substrate 22 at a predetermined interval. A gap member 24 that partitions the substrate into a plurality of cells, a particle group 34 enclosed in each cell, and a reflective particle group 36 having optical reflection characteristics different from the particle group 34 are configured.
The opposing surfaces of the display substrate 20 and the back substrate 22 are charged as described in the first embodiment, and the surface layer 42 and the surface layer 48 are provided on the opposing surfaces.

  In the present embodiment, as the particle group 34, a plurality of types of particle groups 34 having different colors are dispersed in the dispersion medium 50.

In the present embodiment, as the three types of particle groups 34, particle groups 34 having different colors, that is, yellow yellow particle group 34Y, magenta magenta particle group 34M, and cyan cyan particle group 34C are dispersed. However, it is not limited to three types.
The plurality of types of particle groups 34 are particle groups that perform electrophoresis between substrates, and the absolute value of the voltage required to move in accordance with the electric field is different for each color particle group. That is, each color particle group 34 (yellow particle group 34Y, magenta particle group 34M, and cyan particle group 34C) has a voltage range necessary for moving each color particle group 34 for each color. Are different.

  As each particle of the plurality of types of particle groups 34 having different absolute values of voltages necessary to move in accordance with the electric field, for example, the type of resin that constitutes the particles among the materials that constitute the aforementioned migrating particles It can be obtained by preparing particle dispersions containing particles having different charge amounts by changing the concentration, the amount of charge, the amount of charge control agent, etc., and mixing them.

  Here, as described above, the yellow particle group 34Y, the magenta particle group 34M, and the cyan particle group 34C having different colors are dispersed as the three types of particle groups 34 in the display medium 12 according to the present embodiment. These plural kinds of particle groups 34 have different absolute values of voltages necessary for moving in accordance with the electric field in the respective color particle groups.

  In the present embodiment, the absolute value of the voltage when each of the three color particle groups, the magenta magenta particle group 34M, the cyan cyan particle group 34C, and the yellow yellow particle group 34Y, starts moving. In the following description, it is assumed that the magenta magenta particle group 34M is | Vtm |, the cyan cyan particle group 34C is | Vtc |, and the yellow yellow particle group 34Y is | Vty |. Further, the absolute value of the maximum voltage for moving all the three color particle groups of the magenta particle group 34M, the cyan cyan particle group 34C, and the yellow yellow particle group 34Y of each color particle group 34 is used. In the following description, it is assumed that the magenta magenta particle group 34M is | Vdm |, the cyan cyan particle group 34C is | Vdc |, and the yellow yellow particle group 34Y is | Vdy |.

  Note that the absolute values of Vtc, -Vtc, Vdc, -Vdc, Vtm, -Vtm, Vdm, -Vdm, Vty, -Vty, Vdy, and -Vdy described below are | Vtc | <| Vdc | <| Description will be made assuming that the relationship is Vtm | <| Vdm | <| Vty | <| Vdy |.

  Specifically, as shown in FIG. 4, for example, the three types of particle groups 34 are all dispersed in the dispersion medium 50 in a state of being charged with the same polarity, and are necessary for moving the cyan particle groups 34C. Absolute value of voltage range | Vtc ≦ Vc ≦ Vdc | (absolute value of Vtc or more and Vdc or less), absolute value of voltage range necessary for moving magenta particle group 34M | Vtm ≦ Vm ≦ Vdm | The absolute value of the value below Vdm) and the absolute value of the voltage range necessary to move the yellow particle group 34Y | Vty ≦ Vy ≦ Vdy | (the absolute value of the value between Vty and Vdy) overlap in this order. It is set to become large without doing.

  Further, in order to independently drive each color particle group 34, the absolute value | Vdc | of the maximum voltage for moving all the cyan particle groups 34C is the absolute value of the voltage range necessary for moving the magenta particle group 34M. | Vtm ≦ Vm ≦ Vdm | (the absolute value of a value between Vtm and Vdm) and the absolute value of the voltage range necessary to move the yellow particle group 34Y | Vty ≦ Vy ≦ Vdy | (a value between Vty and Vdy) Is set smaller than the absolute value). Further, the absolute value | Vdm | of the maximum voltage for moving all the magenta particle groups 34M is the absolute value of the voltage range necessary for moving the yellow particle group 34Y | Vty ≦ Vy ≦ Vdy | (Vty or more, Vdy or more Is set to be smaller than the absolute value).

  That is, in this embodiment, the voltage groups necessary for moving the color particle groups 34 are set so as not to overlap, so that the particle groups 34 for each color are independently driven.

The “voltage range necessary for moving the particle group 34” means the voltage necessary for the particle to start moving and the change in display density even if the voltage and voltage application time are further increased from the start of movement. It shows the voltage range until it disappears and the display density is saturated.
Further, the “maximum voltage necessary for moving all the particle groups 34” means a voltage at which the display density does not change and the display density is saturated even if the voltage and the voltage application time are further increased from the start of the movement. Indicates.
In addition, “all” includes the fact that the characteristics of some of the particle groups 34 are different to the extent that they do not contribute to the display characteristics due to the variation in characteristics of the particle groups 34 of the respective colors. That is, even if the voltage and the voltage application time are further increased from the start of the movement described above, the display density does not change and the display density is saturated.
The “display density” is measured between the display surface side and the back side while measuring the color density on the display surface side with a reflection densitometer of optical density (Optical Density = OD) of X-rite. Apply a voltage and gradually change this voltage in the direction of increasing the measured concentration (increase or decrease the applied voltage) to saturate the concentration change per unit voltage, and in that state, adjust the voltage and voltage application time. Even when the density is increased, the density does not change, and the density is shown when the density is saturated.

  In the display medium 12 according to the present embodiment, the voltage applied between the substrates is gradually increased by applying a voltage from 0 V between the display substrate 20 and the back substrate 22 to increase the voltage value of the applied voltage. When the value exceeds + Vtc, the display density starts to change due to the movement of the cyan particle group 34C in the display medium 12. Further, when the voltage value is increased and the voltage applied between the substrates becomes + Vdc, the change in display density due to the movement of the cyan particle group 34C in the display medium 12 stops.

  When the voltage value is further increased and the voltage applied between the display substrate 20 and the back substrate 22 exceeds + Vtm, a change in display density due to the movement of the magenta particle group 34M starts to appear in the display medium 12. When the voltage value is further increased and the voltage applied between the display substrate 20 and the back substrate 22 becomes + Vdm, the change in display density due to the movement of the magenta particle group 34M in the display medium 12 stops.

  Further, when the voltage value is increased and the voltage applied between the substrates exceeds + Vty, a change in display density due to the movement of the yellow particle group 34Y starts to appear in the display medium 12. When the voltage value is further increased and the voltage applied between the substrates becomes + Vdy, the change in display density due to the movement of the yellow particle group 34Y in the display medium 12 stops.

  On the other hand, if the negative voltage from 0V is applied between the display substrate 20 and the back substrate 22 to gradually increase the absolute value of the voltage and the absolute value of the voltage −Vtc applied between the substrates is exceeded. In the display medium 12, the display density starts to change due to the movement of the cyan particle group 34C between the substrates. Furthermore, when the absolute value of the voltage value is increased and the voltage applied between the display substrate 20 and the rear substrate 22 becomes −Vdc or more, the change in display density due to the movement of the cyan particle group 34C in the display medium 12 occurs. Stop.

  When the negative voltage is further applied by increasing the absolute value of the voltage value, and the voltage applied between the display substrate 20 and the rear substrate 22 exceeds the absolute value of −Vtm, the magenta particles are displayed on the display medium 12. A change in display density due to movement of the group 34M begins to appear. When the absolute value of the voltage value is further increased and the voltage applied between the display substrate 20 and the back substrate 22 becomes −Vdm, the change in display density due to the movement of the magenta particle group 34M in the display medium 12 stops. .

  When the absolute value of the voltage value is further increased to apply a negative voltage, and the voltage applied between the display substrate 20 and the back substrate 22 exceeds the absolute value of −Vty, yellow particles are displayed on the display medium 12. The display density starts to change due to the movement of the group 34Y. When the absolute value of the voltage value is further increased and the voltage applied between the substrates becomes −Vdy, the change in display density due to the movement of the yellow particle group 34Y in the display medium 12 stops.

  That is, in the present embodiment, as shown in FIG. 4, the voltage applied between the substrates is within the range of −Vtc to + Vtc (voltage range | Vtc | or less). When applied between the substrates, the particle groups 34 (cyan particle group 34C, magenta particle group 34M, and yellow particle group 34Y) move so much that the display density of the display medium 12 changes. I can say no. When a voltage higher than the absolute values of the voltage + Vtc and the voltage −Vtc is applied between the substrates, the display density of the display medium 12 is changed with respect to the cyan particle group 34C among the three color particle groups 34. The display density starts to change for the first time, and when the voltage −Vdc and a voltage greater than the absolute value | Vdc | of the voltage Vdc are applied, the display density per unit voltage does not change.

  Furthermore, when a voltage that is applied between the substrates is between −Vtm and + Vtm (voltage range | Vtm | or less) is applied between the display substrate 20 and the back substrate 22, the display medium Thus, it can be said that the magenta particle group 34M and the yellow particle group 34Y do not move so much that the display density of 12 changes. When a voltage higher than the absolute value of the voltage + Vtm and the voltage −Vtm is applied between the substrates, the display density of the display medium 12 is changed for the magenta particle group 34M of the magenta particle group 34M and the yellow particle group 34Y. The display density per unit voltage begins to change to the extent that particles are generated to the extent that they are generated, and when a voltage greater than the absolute value | Vdm | of the voltage −Vdm and the voltage Vdm is applied, the display density changes. Disappear.

  In addition, when a voltage that is applied between the substrates is between −Vty and + Vty (voltage range | Vty | or less) is applied between the display substrate 20 and the back substrate 22, the display medium 12. It can be said that the movement of the particles of the yellow particle group 34Y has not occurred to the extent that the display density changes. When a voltage higher than the absolute value of the voltage + Vty and the voltage −Vty is applied between the substrates, the yellow particle group 34Y starts to move and display a particle that causes a change in the display density of the display medium 12. When the density starts to change and a voltage greater than the absolute value | Vdy | of the voltage −Vdy and the voltage Vdy is applied, the display density does not change.

  Next, with reference to FIG. 5, the mechanism of particle movement when an image is displayed on the display medium 12 will be described.

  For example, the display medium 12 will be described assuming that the yellow particle group 34Y, the magenta particle group 34M, and the cyan particle group 34C described with reference to FIG.

  In the following, the voltage applied between the substrates that is larger than the absolute value of the voltage necessary for the particles constituting the yellow particle group 34Y to start moving and less than or equal to the maximum voltage of the yellow particle group 34Y is referred to as “large voltage”. The voltage applied between the substrates that is larger than the absolute value of the voltage necessary for the particles constituting the magenta particle group 34M to start moving and is equal to or less than the maximum voltage of the magenta particle group 34M is referred to as “medium voltage”. The voltage applied between the substrates that is larger than the absolute value of the voltage required for the particles constituting the cyan particle group 34C to start moving and below the maximum voltage of the cyan particle group 34C is referred to as a “small voltage”. To do.

  Further, when a higher voltage is applied to the display substrate 20 side than the back substrate 22 side between the substrates, the respective voltages are respectively “+ large voltage”, “+ medium voltage”, and “+ small voltage”. Called. When a voltage higher than that on the display substrate 20 side is applied to the rear substrate 22 side between the substrates, the respective voltages are respectively “−large voltage”, “−medium voltage”, and “−small voltage”. Will be described.

  As shown in FIG. 5A, when all of the magenta particle group 34M, the cyan particle group 34C, and the yellow particle group 34Y as all the particle groups are positioned on the back substrate 22 side in the initial state (white display). State), when a “+ large voltage” is applied between the display substrate 20 and the back substrate 22 from this initial state, all the particle groups include a magenta particle group 34M, a cyan particle group 34C, and a yellow particle group 34Y. Moves to the display substrate 20 side. In this state, even if the voltage application is canceled, each particle group does not move while adhering to the display substrate 20 side, and subtractive color mixing (magenta) by the magenta particle group 34M, the cyan particle group 34C, and the yellow particle group 34Y. In this case, the black color is displayed by the subtractive color mixture of cyan and yellow. (See FIG. 5B).

  Next, when “−medium voltage” is applied between the display substrate 20 and the back substrate 22 from the state of FIG. 5B, the magenta particle group 34 </ b> M among the particle groups 34 of all colors and cyan The particle group 34 </ b> C moves to the back substrate 22 side. For this reason, since only the yellow particle group 34Y is attached to the display substrate 20 side, yellow display is performed (see FIG. 5C).

  Further, when “+ small voltage” is applied between the display substrate 20 and the back substrate 22 from the state of FIG. 5C, the magenta particle group 34M and the cyan particle group 34C moved to the back substrate 22 side. The cyan particle group 34C moves to the display substrate 20 side. For this reason, the yellow particle group 34Y and the cyan particle group 34C are attached to the display substrate 20 side, and green is displayed by the subtractive color mixture of yellow and cyan (see FIG. 5D).

  In addition, when a “−small voltage” is applied between the display substrate 20 and the back substrate 22 from the state of FIG. 5B, among all the particle groups 34, the cyan particle group 34 C is on the back substrate 22 side. Move to. For this reason, since the yellow particle group 34Y and the magenta particle group 34M are attached to the display substrate 20 side, red display is performed by additive mixing of cyan and magenta (see FIG. 5I).

  On the other hand, when “+ medium voltage” is applied between the display substrate 20 and the back substrate 22 from the initial state shown in FIG. 5A, all the particle groups 34 (magenta particle group 34M, cyan particle group 34C) are applied. , And the yellow particle group 34Y), the magenta particle group 34M and the cyan particle group 34C move to the display substrate 20 side. For this reason, since the magenta particle group 34M and the cyan particle group 34C are attached to the display substrate 20 side, blue is displayed by the subtractive color mixing of magenta and cyan (see FIG. 5E).

When a “−small voltage” is applied between the display substrate 20 and the back substrate 22 from the state of FIG. 5E, the magenta particle group 34M and the cyan particle group 34C adhering to the display substrate 20 side. Among them, the cyan particle group 34C moves to the back substrate 22 side.
Therefore, only the magenta particle group 34M is attached to the display substrate 20 side, so that a magenta color is displayed (see FIG. 5F).

When a “−high voltage” is applied between the display substrate 20 and the back substrate 22 from the state of FIG. 5F, the magenta particle group 34M adhering to the display substrate 20 side is moved to the back substrate 22 side. Moving.
For this reason, since nothing is adhered to the display substrate 20 side, white is displayed as the color of the reflective particle group 36 (see FIG. 5G).

  When a “+ small voltage” is applied between the display substrate 20 and the back substrate 22 from the initial state shown in FIG. 5A, all the particle groups 34 (magenta particle group 34M, cyan particle group) are applied. 34C and the yellow particle group 34Y), the cyan particle group 34C moves to the display substrate 20 side. For this reason, the cyan particle group 34C adheres to the display substrate 20 side, so that a cyan color is displayed (see FIG. 5H).

Further, when a “−large voltage” is applied between the display substrate 20 and the back substrate 22 from the state shown in FIG. 5I, all the particle groups 34 are back as shown in FIG. Moving to the substrate 22 side, white display is performed.
When a “−large voltage” is applied between the display substrate 20 and the back substrate 22 from the state shown in FIG. 5D, all the particle groups 34 are transferred to the back as shown in FIG. Moving to the substrate 22 side, white display is performed.

In the present embodiment, by applying a voltage corresponding to each particle group 34 between the substrates, the target particles are selectively moved according to the electric field generated by the voltage, so that particles of a color other than the target color are used. Is suppressed from moving in the dispersion medium 50, color mixing of colors other than the target color is suppressed, and color display is performed while suppressing deterioration in image quality of the display medium 12.
In addition, if the absolute value of the voltage required for each particle group 34 to move according to the electric field is different from each other, even if the voltage ranges necessary for moving according to the electric field overlap with each other, clear color display is possible. However, when the voltage ranges are different from each other, color mixing is further suppressed and color display is realized.

  Further, by dispersing the three color particle groups 34 of cyan, magenta, and yellow in the dispersion medium 50, cyan, magenta, yellow, blue, red, green, and black are displayed, and for example, white reflective particles It is realized that the group 36 displays white and performs a specific color display.

  In the display medium 12 and the display device 10 according to any of the above embodiments, the surface electrode 40 is provided on the display substrate 20 and the back electrode 46 is provided on the back substrate 22, and a voltage is applied between the electrodes (ie, between the substrates). In the above description, the particle group 34 is moved and displayed between the substrates. However, the present invention is not limited to this, and the embodiment moves between the electrodes (electrophoretic particle dispersion medium between the electrodes). On the other hand, an electrode may be provided on the gap member, and a voltage may be applied between the electrodes to move the particle group 34 between the display substrate 20 and the gap member for display.

  In the display medium 12 and the display device 10 according to any of the above embodiments, the display medium 12 is described by providing the display substrate 20 with the surface electrode 40 and the back substrate 22 with the back electrode 46. The form arrange | positioned outside the display medium 12 may be sufficient.

  In the display medium 12 and the display device 10 according to any of the above-described embodiments, the mode in which two or three kinds (two colors or three colors) of particle groups (34A, 34B) are applied as the particle group 34 has been described. One type (one color) of particle groups may be applied, or four types (four colors) or more of particle groups may be applied.

  Hereinafter, the present invention will be described more specifically with reference to examples.

[Example 1]
(Preparation of magenta particle dispersion)
-Preparation of dispersion A-
The following components were mixed, and ball milling was performed for 20 hours with 10 mmφ zirconia balls to prepare dispersion A.
<Composition>
-Cyclohexyl methacrylate: 53 parts by mass-Magenta pigment (Kermin 6B: manufactured by Dainichi Seika Co., Ltd.): 3 parts by mass-Charge control agent (COPY CHARGE NY VP2351, manufactured by Clariant Japan): 2 parts by mass-Cyclohexane: 5 parts by mass

-Preparation of charcoal dispersion B-
The following components were mixed and finely pulverized with a ball mill in the same manner as described above to prepare a charcoal dispersion B.
<Composition>
-Calcium carbonate: 40 parts by mass-Water: 60 parts by mass

-Preparation of mixture C-
The following components were mixed, degassed with an ultrasonic machine for 10 minutes, and then stirred with an emulsifier to prepare a mixed solution C.
<Composition>
-2% by mass serogen aqueous solution (Daiichi Kogyo Seiyaku Co., Ltd.): 4.3g
Charcoal cal dispersion B: 8.5g
・ 20% by mass saline solution: 50 g

35 g of dispersion A, 1 g of divinylbenzene, and polymerization initiator AIBN (azobisisobutyronitrile): 0.35 g were weighed and mixed thoroughly, and deaerated by an ultrasonic machine for 10 minutes.
This was added to the mixed solution C and emulsified with an emulsifier.
Next, this emulsified liquid was put in a bottle, put into a silicone bottle, sufficiently degassed under reduced pressure using an injection needle, and sealed with nitrogen gas. Next, it was reacted at 60 ° C. for 10 hours to prepare particles. After cooling, cyclohexane was removed from the dispersion with a freeze dryer at −35 ° C. and 0.1 Pa for 2 days. The obtained particles were dispersed in ion-exchanged water, calcium carbonate was decomposed with aqueous hydrochloric acid, and filtered. Then, after washing with distilled water, 10-2 stirring the ^{M /} pH 7.5 polyallylamine hydrochloride solution particles in an aqueous solution of 3 hours, to adsorb the polyallylamine hydrochloride to the particle surface. After drying the obtained particles, 2 parts by mass were added to 98 parts by mass of dimethyl silicone oil (KF-96L-1cs manufactured by Shin-Etsu Silicone) together with 2 parts by mass of the nonionic surfactant polyoxyethylene alkyl ether, A magenta particle dispersion was prepared by stirring and dispersing. The volume average particle diameter of the magenta particles was 1 μm.
The charging polarity of the magenta particles in this dispersion was positively charged as a result of enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

[Example 2]
(Preparation of cyan particle dispersion)
Polyallylamine hydrochloride was adsorbed on the particle surface in the same manner as in Example 1 except that a cyan pigment (cyanine blue 4933M; manufactured by Dainichi Seika Co., Ltd.) was used instead of the magenta pigment.
Next, the particles were stirred in a 10 ⁻² M / pH 3.5 polyacrylic acid aqueous solution to adsorb the polyanions to the surface particles for one hour. After drying the obtained particles, 2 parts by mass were added to 98 parts by mass of dimethyl silicone oil (KF-96L-1cs manufactured by Shin-Etsu Silicone) together with 2 parts by mass of the nonionic surfactant polyoxyethylene alkyl ether, Cyan dispersion was prepared by stirring and dispersing. The volume average particle diameter of the cyan particles was 1 μm.
The charged polarity of the cyan particles in this dispersion was negatively charged as a result of enclosing the dispersion between the electrode substrates and applying a DC voltage to evaluate the migration direction.

[Example 3]
Magenta particles were produced in the same manner as in Example 1 except that polydiallyldimethylammonium chloride, which is a strong electrolyte, was used instead of polyallylamine hydrochloride.
The charging polarity of the magenta particles in this dispersion was positively charged as a result of enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

[Example 4]
In Example 3, a cyan pigment was used instead of a magenta pigment to adsorb polydiallyldimethylammonium chloride, and then the particles were stirred in a 50% aqueous solution of titanium (IV) bis (ammonium lactato) dihydroxide. The small electrolyte molecules were adsorbed on the surface particles for 1 hour. Thereafter, a cyan particle dispersion was prepared in the same manner as in Example 2.
The charged polarity of cyan particles in this dispersion was negatively charged as a result of evaluating the migration direction by enclosing the dispersion between two electrode substrates and applying a DC voltage.

[Example 5]
In Example 2, Al ₂ O ₃ particles 1%, pH 3.5 aqueous solution was used instead of polyallylamine hydrochloride, TiO ₂ particles 1%, pH 7.5 aqueous solution was used instead of polyacrylic acid aqueous solution, and Al ₂ O ₃ aqueous solution was used. A cyan particle dispersion was prepared in the same manner except that TiO ₂ was alternately adsorbed. The charged polarity of cyan particles in this dispersion was negatively charged as a result of evaluating the migration direction by enclosing the dispersion between two electrode substrates and applying a DC voltage.

[Example 6]
When the shape of the magenta particles of the magenta particle dispersion prepared in Example 1 was observed, it was spherical. Further, the shape of the particles before adsorbing (adhering) the electrolyte material was also spherical.
In contrast, in Example 1, After adsorption of the polyallylamine hydrochloride to the particle surface, the particles stirred microparticles in 10 -2 ^{M /} pH 3.5 aqueous polyacrylic acid, surface an hour polyanions Adsorbed on particles. Similarly, 10 layers of polyallylamine hydrochloride / polyacrylic acid were alternately adsorbed, and finally polyacrylamine hydrochloride was adsorbed on the surface. Observation of the magenta particles produced in this manner revealed an unusual shape (specifically, an uneven shape).

[Example 7]
0.1 part by mass of the magenta particle dispersion liquid prepared in Example 1 (solid content 0.1 parts by mass) and 0.1 part by mass of the cyan electrophoretic particle dispersion liquid prepared in Example 2 (0.1 parts by mass solids) And the mixed electrophoretic particle dispersion was prepared.
Then, in the same manner as in Examples 1 and 2, the fixation of the electrophoretic particles and the display color density were evaluated. As a result, no color mixture was observed in each color (magenta display, cyan display). Similar results were obtained.

[Comparative Example 1]
A cyan particle dispersion was prepared in the same manner as in Example 2 except that the treatment for adsorbing polyallylamine hydrochloride on the particle surface was not performed.
The charged polarity of the cyan particles in the dispersion was positively charged as a result of encapsulating the dispersion between the electrode substrates and applying a DC voltage to evaluate the migration direction.

[Evaluation]
(Preparation of display medium)
A display medium having the same configuration as that of the first embodiment was manufactured as follows (see FIG. 1). An ITO film having a thickness of 50 nm was formed as an electrode on a supporting substrate made of glass having a thickness of 0.7 mm by a sputtering method. After applying a layer to the back substrate composed of this ITO / glass substrate using CYTOP (manufactured by Asahi Glass Co., Ltd., CTL809M), a gap member having a height of 50 μm and a width of 20 μm is obtained by performing exposure and wet etching. Formed.

  After forming a heat-fusible adhesive layer (not shown) on the top of the gap member, it was filled with the following white particle group and electrophoretic particle dispersion obtained in each example, and was produced in the same manner as the back substrate / A display medium made of glass and having a treatment layer formed thereon is bonded to the back substrate so that the surfaces (electrode surfaces) on which the treatment layers are formed face each other, and heat is applied to produce a display medium did.

  In this way, a display medium was produced.

(Preparation of white particles)
-Preparation of dispersion A-
The following components were mixed, and ball milling was performed for 20 hours with 10 mmφ zirconia balls to prepare dispersion A.
<Composition>
・ Cyclohexyl methacrylate: 53 parts by mass. Titanium oxide 1 (white pigment) (primary particle size 0.3 μm, Type CR63: manufactured by Ishihara Sangyo Co., Ltd.): 45 parts by mass. Cyclohexane: 5 parts by mass.

-Preparation of charcoal dispersion B-
The following components were mixed and finely pulverized with a ball mill in the same manner as described above to prepare a charcoal dispersion B.
<Composition>
-Calcium carbonate: 40 parts by mass-Water: 60 parts by mass

-Preparation of mixture C-
The following components were mixed, degassed with an ultrasonic machine for 10 minutes, and then stirred with an emulsifier to prepare a mixed solution C.
<Composition>
-2% by mass serogen aqueous solution (Daiichi Kogyo Seiyaku Co., Ltd.): 4.3g
Charcoal cal dispersion B: 8.5g
・ 20% by mass saline solution: 50 g

  35 g of dispersion A, 1 g of divinylbenzene, and polymerization initiator AIBN (azobisisobutyronitrile): 0.35 g were weighed and mixed thoroughly, and deaerated by an ultrasonic machine for 10 minutes. This was added to the mixed solution C and emulsified with an emulsifier. Next, this emulsified liquid was put into a bottle, put into a silicone bottle, used with an injection needle, sufficiently degassed under reduced pressure, and sealed with nitrogen gas. Next, it was reacted at 65 ° C. for 15 hours to prepare particles. After cooling, cyclohexane was removed from the dispersion with a freeze dryer at −35 ° C. and 0.1 Pa for 2 days. The obtained particle powder was dispersed in ion-exchanged water, calcium carbonate was decomposed with hydrochloric acid water, and filtered. Thereafter, it was washed with sufficient distilled water, and passed through a nylon sieve having openings of 20 μm and 25 μm to make the particle sizes uniform. This was dried to obtain a white particle group having a volume average particle diameter of 20 μm. This was defined as white particles (reflecting particle group).

(Evaluation)
Using the produced display medium, a voltage of 50 V is applied to both electrodes so that the electrode of the display substrate is positive and the electrode of the rear substrate is negative. The electrode of the display substrate is negative and the electrode of the rear substrate is positive. A voltage of 50 V was applied to both electrodes so that the following was repeated, and by repeating this operation, the particles were moved between the display substrate and the back substrate, and the operation of displaying / not displaying the color of the electrophoretic particles was performed.
Note that when the color of the electrophoretic particles is not displayed, the display medium is white due to white particles (reflecting particle group).

-Electrophoretic particle fixation-
For the fixation of the electrophoretic particles, the display operation of display / non-display is performed once, 100 times, and 500 times, and then the display medium is disassembled to display each surface (cell) of the display substrate, the back substrate, and the gap member. The structural surface) was observed and evaluated with an optical microscope. The evaluation criteria are as follows. The results are shown in Table 1.
◎: Particles are not fixed ○: Particles are slightly fixed, but there is no problem in practical use ×: A large amount of particles are observed and clearly visible by visual inspection

-Display color density-
Regarding the display color density of the electrophoretic particles, the display / non-display operation is performed once, 100 times, and 500 times, and then the display color density exhibited by the electrophoretic particles is determined by X-Rite 530 (X-Rite). It was measured. Then, using the first display color density as the initial density, the ratio of the display color density after 100 times and 500 times with respect to the initial density was examined. The evaluation criteria are as follows.
A: 98% or more with respect to the initial density B: 90% or more and less than 98% with respect to the initial density Δ +: 85% or more and less than 90% with respect to the initial density Δ−: 75% or more with respect to the initial density 85% Less than x: Less than 75% of the initial concentration

  From the above results, it can be seen that in this example, better results were obtained for the fixation of electrophoretic particles and the display color density than in the comparative example.

DESCRIPTION OF SYMBOLS 10 Display apparatus 12 Display medium 16 Voltage application part 18 Control part 20 Display board | substrate 22 Back board | substrate 24 Gap member 34 (34A, 34B, 34Y, 34C, 34M) Particle group 36 Reflective particle group 38 Support substrate 40 Surface electrode 42 Surface layer 44 Support substrate 46 Back electrode 48 Surface layer 50 Dispersion medium

Claims (6)

An electrophoretic particle body;
Electrophoresis with an electrolyte layer and an electrolyte material adhering to the surface an anionic inorganic oxide particles and cationic inorganic oxide particles are alternately stacked toward the radial direction of the electrophoretic particle body of the electrophoretic particle body particle. The electrophoretic particle according to claim 1, wherein the anionic inorganic oxide particles are iron (III) oxide or aluminum oxide, and the cationic inorganic oxide particles are titanium oxide or silicon dioxide . A dispersion medium;
Electrophoretic particles dispersed in the dispersion medium, wherein the electrophoretic particles according to claim 1 or 2 ;
An electrophoretic particle dispersion comprising: A pair of substrates, at least one of which is translucent,
The electrophoretic particle dispersion according to claim 3 , encapsulated between the pair of substrates,
A display medium comprising: A pair of electrodes, at least one of which is translucent,
A region having an electrophoretic particle dispersion according to claim 3 provided between the pair of electrodes;
A display medium comprising: A display medium according to claim 4 or 5 , and
Voltage application means for applying a voltage between the pair of substrates or the pair of electrodes of the display medium;
A display device comprising: