JP2009037185A - Particle dispersion liquid, display medium, and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide particle dispersion liquid capable of suppressing variation in charging characteristics of dispersed particles, a display medium using the same, and a display device. <P>SOLUTION: The particle dispersion liquid includes: a first solvent for dispersing a particle group moving in response to an electric field and containing at least one of silicone oil and a paraffin-based hydrocarbon solvent; and an amino-modified silicone oil. The display medium using the dispersion particle dispersion liquid and the display device are also provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

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

  Conventionally, a display technique using electrophoresis has been proposed as a display medium that can be rewritten repeatedly.

As such a display technique, for example, a display medium having a configuration in which a dispersion liquid is sealed between a pair of substrates and a group of charged particles is dispersed in the dispersion liquid is known.
In such a display medium, by applying a voltage according to an image between the substrates, the charged particles are moved to display the image as the color contrast of the particles (for example, Patent Documents 1 to 4). reference).

  In such display technology, particles moving between the substrates are enclosed between the substrates in a state of being dispersed in the dispersion medium as described above. As this dispersion medium, for example, an aromatic hydrocarbon solvent, an isoparaffin hydrocarbon solvent, a halogenated hydrocarbon solvent, an oily polysiloxane such as silicone oil, or a highly insulating solvent such as high-purity petroleum is used. ing.

JP 2004-333589 A JP-A-2005-107146 JP 2005-128141 A JP 2003-005228 A

As described above, since the particles moving between the substrates move in the dispersion medium according to the electric field formed between the substrates, the image is displayed as the color contrast of the particles. If the charging characteristics fluctuate due to changes over time, it may be difficult to display a desired image.
An object of the present invention is to provide a particle dispersion capable of suppressing a change in charging characteristics of dispersed particles, a display medium using the particle dispersion, and a display device.

  The above problem is solved by the following means. That is,

  The invention according to claim 1 contains a first solvent containing at least one of a silicone oil and a paraffinic hydrocarbon solvent, and an amino-modified silicone oil, in which particles moving according to an electric field are dispersed. A particle dispersion characterized by the following.

  The invention according to claim 2 is the particle dispersion according to claim 1, wherein the amino-modified silicone oil is a side-chain amino-modified silicone oil having an amino group in a side chain.

  The invention according to claim 3 is the particle dispersion according to claim 1, wherein the particle group contains an anionic resin as a main component.

  The invention according to claim 4 is the particle dispersion according to claim 1, wherein the particle group contains a cationic resin as a main component.

  The invention according to claim 5 is the particle dispersion according to claim 1, wherein the second particle group that is smaller than the volume average primary particle size of the particle group and adheres to the surface of the particle group is further dispersed. It is a liquid.

  The invention according to claim 6 is a pair of substrates, at least one of which is translucent, a first solvent that is sealed between the pair of substrates and includes at least one of silicone oil and paraffinic hydrocarbon solvent, A display medium comprising: a particle dispersion containing amino-modified silicone oil; and a particle group dispersed in the particle dispersion and moving according to an electric field.

  The invention according to claim 7 is the display medium according to claim 6, wherein the amino-modified silicone oil is a side-chain type amino-modified silicone oil having an amino group in a side chain.

  The invention according to claim 8 is the display medium according to claim 6, wherein the particle group contains an anionic resin as a main component.

  The invention according to claim 9 is the display medium according to claim 6, wherein the particle group includes a cationic resin as a main component.

  The invention according to claim 10 further comprises a second particle group that is dispersed in the particle dispersion and that is smaller than the volume average primary particle size of the particle group and adheres to the surface of the particle group. The display medium according to claim 6.

  The invention according to claim 11 is characterized in that the particle group is composed of a plurality of types of particles having different absolute values of voltages necessary for moving according to an electric field and colored in different colors. The display medium according to claim 6.

  The invention according to claim 12 is characterized in that the plurality of types of particles have a voltage range necessary for moving according to the electric field for each type, and the voltage ranges are different from each other. It is a display medium of description.

  The invention according to claim 13 is a pair of substrates, at least one of which has translucency, and a first solvent that is sealed between the pair of substrates and includes at least one of silicone oil and paraffinic hydrocarbon solvent, A display medium comprising: a particle dispersion containing amino-modified silicone oil; and particles dispersed in the particle dispersion and moving in response to an electric field; and a voltage between the pair of substrates of the display medium. And a voltage applying means for applying.

  The invention according to claim 14 is the display device according to claim 13, wherein the amino-modified silicone oil is a side-chain amino-modified silicone oil having an amino group in a side chain.

  The invention according to claim 15 is the display device according to claim 13, wherein the particle group contains an anionic resin as a main component.

  The invention according to claim 16 is the display device according to claim 13, wherein the particle group contains a cationic resin as a main component.

  The invention according to claim 17 further includes a second particle group in which the display medium is dispersed in the particle dispersion and is smaller than the volume average primary particle size of the particle group and adheres to the surface of the particle group. The display device according to claim 13.

  The invention according to claim 18 is characterized in that the particle group is composed of a plurality of types of particles that have different absolute values of voltages necessary for moving according to an electric field and are colored in different colors. The display device according to claim 13.

  The invention according to claim 19 is characterized in that the plurality of types of particles have a voltage range necessary for moving according to the electric field for each type, and the voltage ranges are different from each other. It is a display apparatus of description.

  According to the first aspect of the present invention, there is an effect that it is possible to suppress the change in the charging characteristics of the dispersed particles as compared with the case where no amino-modified silicone oil is contained.

  According to the invention concerning Claim 2, there exists an effect of suppressing the change of the charging characteristic of the dispersed particle efficiently.

  According to the third aspect of the invention, there is an effect that the negative electrode charging can be stabilized as the charging characteristics of the dispersed particles.

  According to the fourth aspect of the invention, there is an effect that the positive electrode charging can be stabilized as the charging characteristics of the dispersed particles.

  According to the invention which concerns on Claim 5, there exists an effect that the further stabilization of the charging characteristic of the disperse | distributed particle | grain can be aimed at.

  According to the invention concerning Claim 6, compared with the case where amino-modified silicone oil is not contained, there exists an effect that the display medium which can suppress the change of the electrical charging characteristic of the disperse | distributed particle | grains is obtained.

  According to the invention concerning Claim 7, there exists an effect that the display medium which suppresses the change of the charging characteristic of the disperse | distributed particle | grain efficiently is obtained.

  According to the invention of claim 8, there is an effect that a display medium in which the negative electrode charging is stabilized as the charging characteristics of the dispersed particles can be obtained.

  According to the ninth aspect of the present invention, there is an effect that a display medium in which the positive electrode charging is stabilized as the charging characteristics of the dispersed particles can be obtained.

  According to the tenth aspect of the invention, there is an effect that a display medium in which the charging characteristics of dispersed particles are further stabilized can be obtained.

  According to the invention which concerns on Claim 11, there exists an effect that a color display is carried out by a single pixel.

  According to the invention which concerns on Claim 12, there exists an effect that color mixing is suppressed and color display is carried out.

  According to the thirteenth aspect of the present invention, it is possible to obtain a display device capable of suppressing the change in the charging characteristics of the dispersed particles as compared with the case where no amino-modified silicone oil is contained.

  According to the fourteenth aspect of the invention, there is an effect that a display device that efficiently suppresses a change in charging characteristics of dispersed particles can be obtained.

  According to the fifteenth aspect of the invention, there is an effect that a display device including a display medium in which the negative electrode charging is stabilized as the charging characteristics of the dispersed particles can be obtained.

  According to the sixteenth aspect of the invention, there is an effect that a display device including a display medium in which the positive electrode charging is stabilized as the charging characteristics of the dispersed particles can be obtained.

  According to the seventeenth aspect of the invention, there is an effect that a display device including a display medium in which the charging characteristics of dispersed particles are further stabilized can be obtained.

  According to the eighteenth aspect of the invention, there is an effect that color display is performed with a single pixel.

  According to the nineteenth aspect, there is an effect that color mixing is suppressed and color display is performed.

  Hereinafter, embodiments of the present invention will be described.

(First embodiment)
The particle dispersion according to the present embodiment disperses particles moving according to an electric field, and includes a first solvent containing at least one of a silicone oil and a paraffinic hydrocarbon solvent, and an amino-modified silicone oil. is doing.

In the present embodiment, the particle group that moves according to the electric field has charging characteristics in a state where it is dispersed in the particle dispersion. For this reason, the particle group moves in the particle dispersion according to the formed electric field by forming an electric field in the particle dispersion.
In this particle group, as described above, by being dispersed in a particle dispersion containing at least one of a silicone oil and a paraffinic hydrocarbon solvent and an amino-modified silicone oil. The change in charging characteristics with time is suppressed.

  First, the particle group dispersed in the particle dispersion will be described.

  As described above, the particle group has specific charging characteristics in a state of being dispersed in the particle dispersion. Here, in the present embodiment, the charge characteristics indicate the charge polarity and charge amount of the particles. When an electric field corresponding to the charging characteristics of the dispersed particle groups is formed in the particle dispersion, the particle groups move according to the charging characteristics of the formed electric field.

  In this embodiment, resin particles made of a cationic, nonionic, or anionic resin can be used as this particle group. Furthermore, what fixed the coloring agent on the surface of these resin particles, what contained the coloring agent in these resin particles, etc. are mentioned.

  As this particle group, in this embodiment, resin particles mainly composed of a cationic resin, resin particles mainly composed of an anionic resin, or resin particles mainly composed of a nonionic resin are used. . Furthermore, what fixed the coloring agent on the surface of these resin particles, what contained the coloring agent in these resin particles, etc. are mentioned.

  The “resin particles containing a cationic resin as a main component” indicate that the resin particles exhibit a cationic property when configured as resin particles constituting the particle group. By using the resin particles mainly composed of the cationic resin as a particle group that moves by an electric field, a positively charged particle group is prepared.

  Similarly, the “resin particles having an anionic resin as a main component” indicate that the resin particles exhibit an anionic property when configured as the resin particles constituting the particle group. By using the resin particles containing the anionic resin as a main component as a particle group that moves by an electric field, a negatively charged particle group is prepared.

  In addition, the “resin particles mainly composed of a nonionic resin” indicate that the resin particles exhibit nonionic properties when configured as resin particles constituting the particle group.

  For the production of resin particles containing the cationic resin as a main component, that is, resin particles exhibiting cationic properties when configured as resin particles constituting a particle group, a homopolymer of a basic monomer, or at least A copolymer composed of a monomer containing one kind of basic monomer is used.

  The basic monomer is a compound having at least one cationic group, and in the present embodiment, the cationic group refers to an amino group and an ammonium base.

Examples of the basic monomer used in the present embodiment include the following. Specifically, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dibutylaminoethyl (meth) acrylate, N, N-hydroxyethylaminoethyl (meta) ) Acrylate, N-ethylaminoethyl (meth) acrylate, N-octyl-N-ethylaminoethyl (meth) acrylate, N, N-dihexylaminoethyl (meth) acrylate and other aliphatic amino groups (meth) Acrylates, N-methyl acrylamide, N-octyl acrylamide, N-phenyl methyl acrylamide, N-cyclohexyl acrylamide, N-phenyl acrylamide, Np-methoxy-phenyl acrylamide, N, N-dimethyl acrylamide, N, N-dibutyl acrylate (Meth) acrylamides such as rilamide, N-methyl-N-phenylacrylamide, aromatic substituted ethylene monomers having a nitrogen-containing group such as dimethylaminostyrene, diethylaminostyrene, dimethylaminomethylstyrene, dioctylaminostyrene,
Vinyl-N-ethyl-N-phenylaminoethyl ether, vinyl-N-butyl-N-phenylaminoethyl ether, triethanolamine divinyl ether, vinyl diphenylaminoethyl ether, N-vinylhydroxyethylbenzamide, m-aminophenyl vinyl ether And nitrogen-containing vinyl ether monomers.

  More suitable basic monomers include nitrogen-containing heterocyclic compounds, among which pyrroles such as N-vinylpyrrole, N-vinyl-2-pyrroline, N-vinyl-3-pyrroline, etc. Pyrrolines, N-vinylpyrrolidine, vinylpyrrolidineaminoether, pyrrolidines such as N-vinyl-2-pyrrolidone, imidazoles such as N-vinyl-2-methylimidazole, imidazolines such as N-vinylimidazoline, N -Indoles such as vinylindole, Indolines such as N-vinylindoline, N-vinylcarbazole, carbazoles such as 3,6-dibromo-N-vinylcarbazole, 2-vinylpyridine, 4-vinylpyridine, 2-methyl Pyridines such as -5-vinylpyridine, (meth) acrylic piperidine, N-vinylpiperide , Piperidines such as N-vinylpiperazine, quinolines such as 2-vinylquinoline and 4-vinylquinoline, pyrazoles such as N-vinylpyrazole and N-vinylpyrazoline, oxazoles such as 2-vinyloxazole, 4-vinyl Oxazines such as oxazine and morpholinoethyl (meth) acrylate are particularly preferred.

  For the production of the resin particles mainly composed of the anionic resin, that is, the resin particles exhibiting anionic property when constituted as each resin particle constituting the particle group, a homopolymer of an anionic monomer, or at least A copolymer composed of a monomer containing one kind of anionic monomer is used.

  The anionic monomer is a compound having at least one anionic group, and in the present embodiment, the anionic group includes a hydroxyl group, a carboxyl group, a carboxylate group, a sulfonate group, a sulfonate group, It refers to a phosphate group and a phosphate group.

Examples of the anionic monomer used in the present embodiment include the following.
Specifically, among the anionic monomers, the carboxylic acid monomers include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, or anhydrides thereof and monoalkyl esters thereof. And vinyl ethers having a carboxyl group such as carboxyethyl vinyl ether and carboxypropyl vinyl ether.

  Examples of the sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acyclic acid ester, bis- (3-sulfopropyl) -itaconic acid ester, and the like. And its salts. In addition, there are sulfuric acid monoesters of 2-hydroxyethyl (meth) acrylic acid and salts thereof.

  Further, as phosphoric acid monomers, vinyl phosphonic acid, vinyl phosphate, acid phosphoxyethyl (meth) acrylate, acid phosphoxypropyl (meth) acrylate, bis (methacryloxyethyl) phosphate, diphenyl-2-methacryloyloxyethyl phosphate Diphenyl-2-acryloyloxyethyl phosphate, dibutyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, dioctyl-2- (meth) acryloyloxyethyl phosphate, and the like.

A thermoplastic resin or a thermosetting resin is used for the production of the resin particles containing the nonionic resin as a main component.
Examples of the thermoplastic resin used for the production of resin particles mainly composed of nonionic resin include styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene, and isoprene, vinyl acetate, vinyl propionate, Vinyl esters such as vinyl benzoate and vinyl butyrate, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate Α-methylene aliphatic monocarboxylic esters such as vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether, and other vinyl ethers, vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone, etc. S, can be exemplified homopolymers or copolymers of vinyl pyrrolidones.

  In addition, as thermosetting resins used for the production of resin particles mainly composed of nonionic resins, crosslinked resins mainly composed of divinylbenzene, crosslinked resins such as crosslinked polymethyl methacrylate, phenol resins, urea Examples thereof include resins, melamine resins, polyester resins, and silicone resins. 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 thereof include a polymer, polyethylene, polypropylene, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, and paraffin wax.

  As the colorant, organic or inorganic pigments, oil-soluble dyes, etc. can be used, magnetic powders such as magnetite and ferrite, carbon black, titanium oxide, magnesium oxide, zinc oxide, phthalocyanine copper-based cyan colorant, Known colorants such as an azo 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 given. 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, etc. can be exemplified as typical ones.

  If necessary, a charge control agent may be mixed in the resin constituting the resin particles. 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 fine particles, and metal oxide fine particles surface-treated with various coupling agents. .

A magnetic material may be mixed in the inside or the surface of the particles 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, and is more desirable.
As the colored magnetic powder, for example, a small-diameter colored magnetic powder described in JP-A-2003-131420 can 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 appropriately selected, for example, coloring the magnetic powder opaque with a pigment or the like, but it is preferable to use a light interference thin film, for example. 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 selectively reflects the wavelength of light by optical interference in the thin film. It is.

  An external additive may be attached to the surface of the particles as necessary. The color of the external additive is preferably transparent so as not to affect the color of the particles.

  As the external additive, inorganic fine particles such as metal oxides such as silicon oxide (silica), titanium oxide, and alumina are used. In order to adjust the chargeability, fluidity, environment dependency, etc. of the fine particles, these can be surface-treated with a coupling agent or silicone oil.

  Coupling agents include positively chargeable ones such as aminosilane coupling agents, aminotitanium coupling agents, nitrile coupling agents, and silanes that do not contain nitrogen atoms (consisting of atoms other than nitrogen). Coupling agents, titanium-based coupling agents, epoxy silane coupling agents, acrylic silane coupling agents, etc., silicone oils include amino-modified silicone oil, dimethyl silicone oil, alkyl-modified silicone oil, α-methylsulfone-modified silicone oil, Examples thereof include methylphenyl silicone oil, chlorophenyl silicone oil, and fluorine-modified silicone oil. These are selected according to the desired resistance of the external additive.

Among such external additives, well-known hydrophobic silica and hydrophobic titanium oxide are preferable. In particular, TiO (OH) ₂ described in JP-A-10-3177 and a silane compound such as a silane coupling agent are used. The titanium compound obtained by the reaction with is suitable. As the silane compound, any of chlorosilane, alkoxysilane, silazane, and a special silylating agent can be used. This titanium compound is produced by reacting TiO (OH) ₂ produced in a wet process with a silane compound or silicone oil and drying it. Since it does not pass through the firing step of several hundred degrees, strong bonds between Ti are not formed, there is no aggregation, and the fine particles are almost in the state of primary particles. Furthermore, since the silane compound or silicone oil reacts directly with TiO (OH) ₂ , the amount of silane compound or silicone oil treated can be increased, and the charging characteristics can be controlled by adjusting the amount of silane compound treated. The charging ability that can be imparted and can be imparted can be significantly improved over that of conventional titanium oxide.

  The primary particles of the external additive are generally 5 nm to 100 nm, preferably 10 nm to 50 nm, but are not limited thereto.

  The blending ratio of the external additive and the particles is appropriately adjusted based on the balance between the particle size of the particles and the particle size of the external additive. If the amount of the external additive added is too large, a part of the external additive is liberated from the particle surface and adheres to the surface of the other particle, so that desired charging characteristics cannot be obtained. Generally, the amount of the external additive is 0.01 part by weight or more and 3 parts by weight or less, more preferably 0.05 part by weight or more and 1 part by weight or less with respect to 100 parts by weight of the particles.

  The external additive may be added only to any one of a plurality of types of particles, or may be added to a plurality of types or all types of particles. When an external additive is added to the surface of all particles, it is desirable that the external additive is driven into the particle surface with an impact force, or the particle surface is heated to firmly fix the external additive to the particle surface. As a result, the external additive is released from the particles, and the external additive of different polarity is strongly aggregated to prevent the formation of an aggregate of the external additive that is difficult to dissociate with an electric field. Is prevented.

  As a method for producing the particle group, any conventionally known method may be used. For example, as described in JP-A-7-325434, a resin, a pigment, and a charge control agent are weighed to a predetermined mixing ratio, and after the resin is heated and melted, the pigment is added, mixed, dispersed, and cooled. After that, a method of preparing fine particles using a pulverizer such as a jet mill, a hammer mill, a turbo mill, etc., and then dispersing the obtained particles in a dispersion medium can be used. 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 may be prepared. Furthermore, the resin, the colorant, the charge control agent, and the dispersion can be plasticized, the dispersion medium does not boil, and the temperature is lower than the decomposition point of the resin, the charge control agent and / or the colorant. There is a method using an appropriate apparatus capable of dispersing and kneading the raw material of the 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. The particles can be produced by solidification / precipitation.

  Furthermore, the raw materials described above are put into a suitable container equipped with granular media for dispersion and kneading, for example a heated vibration mill such as an attritor, a heated ball mill, and the container is placed in a preferred temperature range, for example A method of dispersing and kneading at 80 ° C. or higher and 160 ° C. or lower can be used. As granular media, steels such as stainless steel and carbon steel, alumina, zirconia, silica and the like are preferably used. In order to produce particles by this method, a raw material that has been sufficiently fluidized is dispersed in a container with 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.

  As described above, the particle dispersion for dispersing the particle group is a liquid containing the first solvent containing at least one of silicone oil and paraffinic hydrocarbon solvent and amino-modified silicone oil.

  Specific examples of the silicone oil contained in the first solvent include dimethyl silicone oil in which a hydrocarbon group is bonded to a siloxane bond, diethyl silicone oil, methyl ethyl silicone oil, methyl phenyl silicone oil, diphenyl silicone oil, and fluorine-modified. Examples thereof include silicone oil, epoxy-modified silicone oil, and alcohol-modified silicone oil. Among these, dimethyl silicone is particularly desirable from the viewpoints of high safety, chemical stability, long-term reliability, and high resistivity.

  The viscosity of the silicone oil is desirably 0.1 mPa · s or more and 20 mPa · s or less, and more desirably 0.1 mPa · s or more and 2 mPa · s or less in an environment at a temperature of 20 ° C. By setting the viscosity within the above range, the moving speed of particles, that is, the display speed can be improved. In addition, Tokyo Keiki B-8L type | mold viscosity meter is used for the measurement of this viscosity.

  Examples of the paraffinic hydrocarbon solvent include normal paraffinic hydrocarbons and isoparaffinic hydrocarbons having 20 or more carbon atoms (boiling point of 80 ° C. or higher). For reasons of safety and volatility, use isoparaffins. Is preferred. Specifically, Shell Sol 71 (manufactured by Shell Petroleum), Isopar O, Isopar H, Isopar K, Isopar L, Isopar G, Isopar M (Isopar is a trade name of Exxon), IP Solvent (manufactured by Idemitsu Petrochemical), etc. Can be mentioned.

  The content of the paraffinic hydrocarbon solvent in the first solvent is not particularly limited as long as the desired hue is obtained, and the cell thickness (that is, between the substrate between the display substrate and the back substrate) is not limited. It is effective for the display medium to adjust the content by the distance). That is, in order to obtain a desired hue, the content can be increased as the cell becomes thicker, and the content can be reduced as the cell becomes thinner. Generally, it is 50 wt% or more and 99.99 wt% or less.

  When the first solvent is composed only of silicone oil, the content of particles in the particle dispersion of silicone oil is not particularly limited as long as it is a concentration at which a desired hue can be obtained. It is effective for the display medium to adjust the content by the distance (that is, the distance between the display substrate and the back substrate). That is, in order to obtain a desired hue, the content decreases as the cell becomes thicker, and the content can increase as the cell becomes thinner. Generally, it is 0.01 wt% or more and 50 wt% or less.

  On the other hand, when the first solvent is composed only of the paraffinic hydrocarbon solvent, the content of the particles in the particle dispersion of the paraffinic hydrocarbon solvent is not particularly limited as long as the desired hue is obtained. However, it is effective for the display medium to adjust the content by the cell thickness (that is, the distance between the display substrate and the back substrate). That is, in order to obtain a desired hue, the content decreases as the cell becomes thicker, and the content can increase as the cell becomes thinner. Generally, it is 0.01 wt% or more and 50 wt% or less.

  Further, when the first solvent is a mixed solution of silicone oil and paraffinic hydrocarbon solvent, it can be used by mixing at an arbitrary ratio depending on the viscosity and conductivity of the solution.

  Specifically, the amino-modified silicone oil contained in the particle dispersion has a compound represented by the following general formula (1) having an amino group in the side chain of the polysiloxane, and an amino group at one end of the polysiloxane. A compound represented by the following general formula (2), a compound represented by the following general formula (3) having amino groups at both ends of the polysiloxane, and an amino group at both the side chain and both ends of the polysiloxane. The at least 1 compound chosen from the group which consists of a compound represented by following General formula (4) is mentioned.

In the general formula (1), R ^{1 to} R ⁹ each independently represents an alkyl group having 1 to 3 carbon atoms, m represents an integer of 1 to 40, and n represents an integer of 1 to 40. Indicates.
Further, in the above general formula ^{(2), R} 10 ~R ¹⁶ represents an alkyl group having 1 to 3 carbon atoms each independently, n is an integer of 1 or more and 40 or less.

In the general formula (3), R ^{17 to} R ²² each independently represents an alkyl group having 1 to 3 carbon atoms, and n represents an integer of 1 to 40.

Further, in the general formula ^{(4), R} 23 ~R ²⁹ represents an alkyl group having 1 to 3 carbon atoms each independently, m is an integer of 1 or more and 40 or less, n is 1 or more and 40 or less of Indicates an integer.

  Among these compounds, when having an amino group at the terminal as in the general formula (2) or the general formula (3) because of having a large amount of amino group in 1 mol of amino-modified silicone. In the formula, the number of amino groups in one molecule is 1 to 2 regardless of the number of n, but when having an amino group in the side chain as in the general formula (1) or (4) In the formula, there are as many amino groups as n in the formula, and the change in the charging characteristics of the dispersed particles is efficiently suppressed. Therefore, it is preferable to use a side chain type amino-modified silicone oil having an amino group in the side chain as represented by the general formula (1) or the general formula (4).

  The amine equivalent of the amino-modified silicone oil is desirably in the range of 350 g / mol to 4,000 g / mol.

  When the amine equivalent of the amino-modified silicone oil is in the range of 350 g / mol to 4,000 g / mol, an effect can be obtained by adding a small amount of amino-modified silicone oil.

  The amine equivalent is a value obtained by dividing the total molecular weight of the amino-modified silicone oil by the number of amino groups.

  The amine equivalent was measured by weighing amino-modified silicone oil, adding a 1: 1 mixture of isopropyl alcohol and toluene, dissolving with stirring, and then titrating with 0.1N hydrochloric acid solution using an automatic titrator. The amine equivalent can be measured by the following formula.

[Formula 1]
Amine equivalent (g / mol) = silicone oil amount (g) × 1,000 / {hydrochloric acid consumption (ml) × 0.1}

  The particle dispersion contains the amino-modified silicone oil with respect to the first solvent, so that an effect of suppressing change in charging characteristics appears. However, the amine equivalent contains amino groups contained in the modified silicone oil. Since the amount is different, the content of the amino-modified silicone oil can be adjusted according to the size of the amine equivalent. For example, in the case of an amine equivalent of 350 g / mol, it is preferable to contain 0.01% by weight or more, more preferably 0.05% by weight or more, and more preferably 0.1% by weight or more to more significantly increase the charging characteristics. It is more preferable because a change suppressing effect appears. In addition, when the amine equivalent is, for example, 4000 g / mol, it is preferably contained in an amount of 0.1% by weight or more, and the inclusion of 0.5% by weight or more shows a remarkable effect of suppressing change in charging characteristics. More preferred.

  As described above, since the amount of amino groups contained in the amino-modified silicone oil varies depending on the size of the amine equivalent, it is effective to adjust the content depending on the amine equivalent of the amino-modified silicone oil to be used.

  When the particle dispersion contains 0.01% by weight or more of the amino-modified silicone oil having an amine equivalent of 350 g / mol with respect to the first solvent, the charging property of the particles dispersed in the particle dispersion is improved. When the change is suppressed and the content is less than 0.01% by weight, the change in the charging characteristics of the particle group may be insufficient.

  The content of the amino-modified silicone oil in the particle dispersion is as described above with respect to the first solvent, for example, if the amino-modified silicone oil having an amine equivalent of 350 g / mol is 0.01% by weight or more. Although it is possible to effectively suppress the change in the charging characteristics of the particles dispersed in the particle dispersion, the power consumption is reduced when the display medium is configured using this particle dispersion, as will be described in detail later. For this reason, the particle dispersion preferably contains 5% by weight or less of the amino-modified silicone oil based on the first solvent, more preferably 1% by weight or less, and 0.5% by weight or less. It is particularly preferable to do this. As described above, since the amount of amino groups contained in the amino-modified silicone oil varies depending on the size of the amine equivalent, it is effective to adjust the content depending on the amine equivalent of the amino-modified silicone oil to be used.

The particle dispersion is preferably insulative for reasons such as reduction in power consumption. Specifically, the volume resistance value is preferably 10 ³ Ωcm or more, more preferably 10 ⁷ Ωcm or more and 10 ¹⁹ Ωcm. Or less, more preferably 10 ¹⁰ Ωcm or more and 10 ¹⁹ Ωcm or less. By setting such a volume resistance value, the amount of current that flows when a voltage is applied is suppressed.

  In the particle dispersion, each particle of the particle group that is smaller than the volume average primary particle size of the particle group that moves according to the electric field (so-called electrophoresis) and is dispersed in the particle dispersion liquid. The structure which further included the 2nd particle group adhering to the surface of this may be sufficient.

  Each particle constituting the second particle group is preferably 1/100 to 1/2 times the volume average primary particle size of the electrophoretic particle group, and is 1/50 to 1/5. It is preferable that it is less than 2 times. In addition, as a particle group to be electrophoresed, when a plurality of types of particle groups having different volume average primary particle sizes are dispersed in the particle dispersion, the volume average primary particle size of the plurality of types of particle groups is the largest. The volume average particle size of the small particle group may be 1/100 times to 1/2 times, preferably 1/50 times to 1/5 times.

  Further, the second particle group is preferably substantially colorless or white when contained in the particle dispersion. Note that “substantially colorless” means coloring that lowers the color purity of the hue (BGR or the like), that is, has no absorption in the visible range, and has excellent light transmittance. Specifically, it has a wavelength of 400 nm or more. It means not having an absorption coefficient of 1000 or more (the same applies in this specification).

Furthermore, as described above, the second particle group has an adhesion property that it adheres to the surface of each particle of the electrophoretic particle group dispersed in the particle dispersion.
In order to have such adhesion properties, the second particle group is a group of particles that are dispersed in a continuous particle dispersion in the same system and that are charged with a positive electrode. Is configured as particles charged on the negative electrode, and when the electrophoretic particle group is a particle group charged on the negative electrode, the positive electrode may be charged.
When such a second particle group is charged to the positive electrode or the negative electrode, the charging characteristics of the second particle group dispersed in the continuous particle dispersion in the same system are expressed as What is necessary is just to set it as the structure charged with the same charge amount as the total charge amount of the said particle group to be electrophoresed dispersed in the particle dispersion liquid in the same system, and reverse polarity.

  As the second particles having the above characteristics, inorganic particles, organic particles, or mixed particles thereof are used.

  Specific examples of the inorganic particles include fumed silica, colloidal silica, fumed alumina, and fumed titania.

  Specific examples of the organic particles include polystyrene and styrene copolymer, (meth) acrylic resin and (meth) acrylic copolymer, polyvinyl chloride, polyacetal, saturated polyester, polyamide, polyimide, and polycarbonate. , Phenoxy resin, polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene polyolefin, olefin copolymer, and melamine resin, preferably (meth) acrylic resin and (meth) Acrylic copolymer, polyvinyl chloride, polyacetal, saturated polyester, polyamide, polyimide, polycarbonate, phenoxy resin, polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene polyolefin and olefin copolymer Body, and the like.

Further, when the second particle group is configured as a resin particle, the second particle group is dispersed in the particle dispersion liquid by including a silicon graft chain in an amount of 0.01 to 80 parts by weight. Improves.
As the silicon graft chain contained in the second particle group, for example, organosiloxane (for example, Chisso Silaplane FM-0711, FM-0721, FM-0725, etc.) is preferably used.

  Further, in order to adjust the adhesion property of the second particle group, the charge amount is the same as the total charge amount of the electrophoretic particle group dispersed in the particle dispersion liquid in the same system and is charged in the opposite polarity. In order to achieve the above-described configuration, specifically, the resin constituting the second particle group may be prepared so as to have a polar group.

As a method for adjusting the second particle group, for example, when the second particle group is configured as a resin particle, a monomer such as the basic monomer or the anionic monomer is suspended in the suspension. It is preferable to adjust by polymerization by a combination method or an emulsion polymerization method.
Furthermore, a reverse phase suspension polymerization method which is a kind of suspension polymerization method is more preferably used.

  The content of the second particle group in the particle dispersion varies depending on the charge amount and concentration of the electrophoretic particle group dispersed in the continuous particle dispersion in the same system. In order not to inhibit the electrophoretic properties of the particle group, the amount is preferably in the range of 0.1 to 100 parts by weight with respect to 100 parts by weight of the electrophoretic particle group, and preferably 1 to 10 parts by weight. More preferably, it is in the range.

In addition, to the particle dispersion, an acid, an alkali, a salt, a dispersion stabilizer, a stabilizer for anti-oxidation or ultraviolet absorption, an antibacterial agent, an antiseptic, and the like can be added, if necessary. It is preferable to add so that it may become the range of the specific volume resistance value shown above.
In the particle dispersion, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, a fluorosurfactant, a silicone surfactant, a metal soap as a charge control agent , Alkyl phosphate esters, succinimides and the like can be added.
It has ionic and nonionic surfactants, block or graft copolymers consisting of lipophilic and hydrophilic parts, and also has a polymer chain skeleton such as cyclic, star-like, and dendritic polymers (dendrimers). Further, compounds selected from metal complexes of salicylic acid, metal complexes of catechol, metal-containing bisazo dyes, tetraphenylborate derivatives and the like can be 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 preferably 0.01% by weight or more and 20% by weight or less, and particularly preferably 0.05% by weight or more and 10% by weight or less, based on the solid content of the particles. If the amount is less than 0.01% by weight, the desired charge control effect is insufficient. If the amount exceeds 20% by weight, the conductivity of the particle dispersion is excessively increased, making it difficult to use.

  The particle group dispersed in the particle dispersion is a resin particle mainly composed of a nonionic resin in the above-described particle group, and a colorant fixed on the surface of a resin particle mainly composed of a nonionic resin. In the case where a resin particle containing a nonionic resin as a main component and containing a colorant is used, the resin particle is negatively charged in the particle dispersion, and the polarity changes after a lapse of time. And the change in charging characteristics with time is suppressed.

In addition, as a particle group dispersed in the particle dispersion liquid, a colorant is fixed to the surface of the resin particle mainly composed of a cationic resin and the resin particle mainly composed of a cationic resin in the particle group described above. In the case of using a resin particle containing a cationic resin as a main component and containing a colorant, the resin particle is charged positively in the particle dispersion and remains polar after a lapse of time. Is suppressed, and the change in charging characteristics with time is suppressed.
This is presumably because the charge amount increases due to the amino-modified silicone adsorbed around the particle group. Therefore, the positive charge amount of the positively charged particle group can be stabilized by dispersing the resin particles containing the cationic resin as a main component in a particle dispersion described later.

Similarly, as a particle group dispersed in the particle dispersion, a resin is mainly composed of an anionic resin in the particle group described above, and a colorant is added to the surface of the resin particle mainly composed of an anionic resin. In the case of using a fixed one or a resin particle containing an anionic resin as a main component and containing a colorant, the resin particle is negatively charged in the particle dispersion, and after a lapse of time. The change in polarity is suppressed, and the change in charging characteristics with time is suppressed.
This is presumably because the amino-modified silicone acts as a counter ion of the particle group to promote acid-base dissociation. For this reason, the negative charge amount of the negatively charged particle group can be stabilized by dispersing the resin particles containing the anionic resin as a main component in a particle dispersion described later.

  Furthermore, the second particle group adheres to the surface of each particle of the electrophoretic particle group by including the second particle group in the particle dispersion. Then, the second particle group adheres to the surface of each particle of the electrophoretic particle group, so that the positive charge and the negative charge in the particle dispersion are balanced, and the system becomes neutral and electrophoreses. The charging characteristics of the particle group can be further stabilized.

  The particle dispersion according to the present embodiment is used as a particle dispersion of particles in an electrophoretic display medium. Since this particle dispersion suppresses the change in the charging characteristics of the dispersed particles, it can be applied particularly to each field using a dispersion for dispersing charged particles.

(Second Embodiment)
FIG. 1 is a schematic configuration diagram showing a display device according to this embodiment of the present invention.
The display device 10 according to the present embodiment applies the particle dispersion described in the first embodiment as the particle dispersion 50 that disperses the particle groups 34 corresponding to the particle groups described in the first embodiment. It is a form to do.
By applying the particle dispersion described in the first embodiment as the particle dispersion 50, a change in the charging characteristics of the particle group 34 dispersed in the display medium 12, which will be described in detail later, is suppressed, and the display medium 12 to suppress image quality degradation.

  As shown in FIG. 1, the display device 10 according to the second embodiment includes a display medium 12, a voltage application unit 16, and a control unit 18. The control unit 18 is connected to the voltage application unit 16 so as to be able to exchange signals.

  The control unit 18 includes a CPU (central processing unit) that controls the operation of the entire device, a RAM (Random Access Memory) that temporarily stores various data, and a control program that controls the entire device and a program indicated by a processing routine. The microcomputer includes a ROM (Read Only Memory) in which various programs are stored in advance.

  The display medium 12 corresponds to the display medium of the present invention, the display device 10 corresponds to the display device of the present invention, and the voltage application unit 16 corresponds to the voltage applying means of the display device of the present invention. The particle dispersion 50 corresponds to the particle dispersion of the present invention, and the particle group 34 corresponds to the particle group of the particle dispersion, the display medium, and the display device of the present invention.

  The voltage application unit 16 is electrically connected to a front electrode 40 (details will be described later) and a back electrode 46 (details will be described later). In this 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 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.

  As shown in FIG. 1, the display medium 12 includes a display substrate 20 serving as an image display surface, a rear substrate 22 that faces the display substrate 20 with a gap, and holds these substrates at a predetermined interval. It includes a gap member 24 that divides the back substrate 22 into a plurality of cells, and a 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. In this cell, a particle dispersion 50 is enclosed. The particle group 34 corresponds to the particle group described in the first embodiment, and has specific charging characteristics so as to move in the particle dispersion 50 according to the electric field. Then, when an electric field is formed in the cell in a state in which the particle group 34 is dispersed in the particle dispersion 50, the particle group 34 passes through the particle dispersion 50 according to the formed electric field strength, that is, the display substrate. It moves between 20 and the back substrate 22.

  It is to be noted that the gap member 24 is provided so as to correspond to each pixel when an image is displayed on the display medium 12, and cells are formed so as to correspond to each pixel, whereby the display medium 12 displays the color for each pixel. May be configured to be possible.

In the present embodiment, a plurality of types of particle groups 34 having different colors are dispersed as the particle groups 34 dispersed in the particle dispersion 50 of the display medium 12. In the present embodiment, as the three types of particle groups 34, the yellow color yellow particle group 34Y, the magenta magenta particle group 34M, and the cyan color cyan particle group 34C are dispersed as the particle groups 34 having different colors. 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.

  As each particle of the plurality of types of particle groups 34 having different absolute values of voltages necessary to move according to the electric field, among the materials constituting the particle groups described in the first embodiment, For example, by changing the type of resin, the type of resin, the type of functional group in the resin, the amount of charge control agent or magnetic powder, etc. It is obtained by mixing.

  Here, the content (% by mass) of the particle group 34 with respect to the total mass in the cell is not particularly limited as long as a desired hue can be obtained, and the content is adjusted by the thickness of the cell. This is effective as the display medium 12. That is, in order to obtain a desired hue, the content may be small when the cell is thick, and the content may be increased when the cell is thin. Generally, it is 0.01 mass% or more and 50 mass% or less.

Each cell may further include the second particle group described in the first embodiment. In this case, the content (% by mass) of the second particle group with respect to the total mass in the cell is such that the particles displayed on the display medium 12 by the particle group 34 are not affected and are electrophoresed. The display medium 12 is effective to adjust the content according to the charge amount of the second particle group as long as the charge amount of the group is kept stable. Specifically, it is 0.1 mass% or more and 50 mass% or less.

  Hereinafter, each component of the display medium 12 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 structure in which a back electrode 46 and a surface layer 48 are sequentially laminated on a support substrate 44.

  Examples of the support substrate 38 and the support substrate 44 include glass and plastics such as polycarbonate resin, acrylic resin, polyimide resin, polyester resin, epoxy resin, and polyether sulfone resin.

  For the back electrode 46 and the surface electrode 40, oxides such as indium, tin, cadmium and antimon, composite oxides such as ITO, metals such as gold, silver, copper and nickel, organic conductive materials such as polypyrrole and polythiophene, etc. May be used. These can be used as a single layer film, a mixed film or a composite film, and are formed by vapor deposition, sputtering, coating, or the like. Moreover, the thickness is normally 100 angstroms or more and 2000 angstroms or less according to the vapor deposition method and the sputtering method. The back electrode 46 and the front electrode 40 are formed in a desired pattern, for example, a matrix shape or a stripe shape that enables passive matrix driving, by a conventionally known means such as etching of a conventional liquid crystal display element or a printed circuit board.

  Further, the surface electrode 40 may be embedded in the support substrate 38. Similarly, the back electrode 46 may be embedded in the support substrate 44. In this case, since the materials of the support substrate 38 and the support substrate 44 may affect the charging characteristics and fluidity of each particle of the particle group 34, the material is appropriately selected according to the composition of each particle of the particle group 34.

  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 this case, since the display medium 12 is sandwiched between the back electrode 46 and the surface electrode 40, the inter-electrode distance between the back electrode 46 and the surface electrode 40 increases and the electric field strength decreases. In order to obtain a desired electric field strength, it is necessary to devise measures such as reducing the thickness of the support substrate 38 and the support substrate 44 of the display medium 12 and reducing the distance between the support substrate 38 and the support substrate 44.

  In the above description, the case where both the display substrate 20 and the back substrate 22 are provided with the electrodes (the front electrode 40 and the back electrode 46) has been described.

  In order to enable active matrix driving, the support substrate 38 and the support substrate 44 may include a TFT (thin film transistor) for each pixel. The TFTs are preferably formed not on the display substrate but on the back substrate 22 because wiring can be easily laminated and components can be easily mounted.

  If the display medium 12 is a simple matrix drive, the structure of the display device 10 having the display medium 12 described later can be simplified, and the active matrix drive using TFTs is simpler than the simple matrix drive. Display speed.

  When the surface electrode 40 and the back electrode 46 are formed on the support substrate 38 and the support substrate 44, respectively, the electrodes between the electrodes that cause breakage of the surface electrode 40 and the back electrode 46 and adhesion of each particle of the particle group 34 are obtained. In order to prevent the occurrence of leakage, it is preferable to form a surface layer 42 and / or a surface layer 48 as a dielectric film on each of the surface electrode 40 and the back electrode 46 as necessary.

As the material for forming the surface layer 42 and / or the surface layer 48, polycarbonate, polyester, polystyrene, polyimide, epoxy, polyisocyanate, polyamide, polyvinyl alcohol, polybutadiene, polymethyl methacrylate, copolymer nylon, ultraviolet curable acrylic resin Alternatively, an organic layer such as a fluororesin or an inorganic layer such as a SiO ₂ film may be used.

  In addition to the insulating material described above, an insulating material containing a charge transport material may be used. Inclusion of a charge transport material improves particle chargeability by injecting particles into the particle, and when the charge amount of the particle becomes extremely large, the charge of the particle is leaked and the charge amount of the particle is stabilized. An effect is obtained.

Examples of the charge transport material include a hydrazone compound, a stilbene compound, a pyrazoline compound, and an arylamine compound that are hole transport materials. Further, a fluorenone compound, a diphenoquinone derivative, a pyran compound, zinc oxide, or the like, which is an electron transport material, may be used. Further, a self-supporting resin having a charge transporting property may be used.
Specific examples thereof include polyvinyl carbazole and polycarbonate obtained by polymerization of a specific dihydroxyarylamine and bischloroformate described in US Pat. No. 4,806,443. Since the dielectric film may affect the charging characteristics and fluidity of the particles, it is appropriately selected according to the composition of the particles. Since the display substrate which is one of the substrates needs to transmit light, it is preferable to use a transparent one of the above materials.

  The gap member 24 for holding the gap between the display substrate 20 and the back substrate 22 is formed so as not to impair the transparency of the display substrate 20, and is made of a thermoplastic resin, a thermosetting resin, an electron beam curable resin, a photocuring agent. It is made of resin, rubber, metal or the like.

  The gap member 24 includes a cell type and a particle type. An example of the cellular type is a net. Since the net is easy to obtain and inexpensive, and the thickness is relatively uniform, it is useful when manufacturing an inexpensive display medium 12. The net is unsuitable for displaying fine images, and is preferably used for a large display device that does not require high resolution. In addition, as other cellular spacers, a sheet in which holes are formed in a matrix by etching, laser processing, or the like can be cited. In this sheet, the thickness, the shape of the holes, the size of the holes, etc. are compared with the net. Easy to adjust. For this reason, the sheet is used for a display medium for displaying a fine image, and is effective in improving the contrast.

The gap member 24 may be integrated with any one of the display substrate 20 and the back substrate 22, and the support substrate 38 or the support substrate 44 is etched, laser processed, or using a prefabricated mold, The support substrate 38 or the support substrate 44 having the cell pattern of any size and the gap member 24 are produced by printing or the like.
In this case, the gap member 24 can be 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 so as not to adversely affect the display image displayed on the display medium 12, and in this case, for example, transparent such as polystyrene, polyester, or acrylic A resin or the like may be used.

  The particulate gap member 24 is preferably transparent, and glass particles are also used in addition to transparent resin particles such as polystyrene, polyester or acrylic.

  In the display medium 12, insulating particles 36 are enclosed in each cell. The insulating particles 36 are different in color and insulative particles from the particle group 34 enclosed in the same cell, and have a gap through which each particle of the particle group 34 can pass. And the display substrate 20 are arranged along a direction substantially orthogonal to the facing direction. Further, between the insulating particles 36 and the back substrate 22 and between the display substrate 20 and the insulating particles 36, each particle of the particle group 34 included in the same cell is connected to the back substrate 22 and the display substrate 20. In the opposite direction, a plurality of intervals are provided so as to be stacked.

  That is, each particle of the particle group 34 is moved through the gap between the insulating particles 36 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. As the color of the insulating particles 36, for example, white or black is preferably selected so as to be a background color.

  Insulating particles 36 include spherical particles of benzoguanamine / formaldehyde condensate, spherical particles of benzoguanamine / melamine / formaldehyde condensate, spherical particles of melamine / formaldehyde condensate, (Nippon Shokubai Co., Ltd. poster), titanium oxide-containing crosslinking Spherical fine particles of polymethyl methacrylate (MBX-white manufactured by Sekisui Plastics Co., Ltd.), spherical fine particles of cross-linked polymethyl methacrylate (Kemisnow MX manufactured by Soken Chemical Co., Ltd.), fine particles of polytetrafluoroethylene (Lublon L manufactured by Daikin Industries, Ltd.) , Shamrock Technologies Inc. SST-2), fluorocarbon fine particles (CF-100 manufactured by Nippon Carbon Co., Ltd., CFGL, CFGM manufactured by Daikin Industries), silicone resin fine particles (Tospearl manufactured by Toshiba Silicone Co., Ltd.), titanium dioxide Microparticles containing polyester (Nippon Paint Co. Biryushia PL1000 White T), fine particles (manufactured by NOF Corporation Konagi No181000 white) of the titanium oxide-containing polyester-acrylic, silica spherical fine particles (Ube-Nitto Kasei Ltd. Haipureshika), and the like. Without limitation to the above, a white pigment such as titanium oxide may be mixed and dispersed in a resin, and then pulverized and classified to a desired particle size.

  Since these insulating particles 36 are provided between the display substrate 20 and the rear substrate 22 as described above, the insulating particles 36 are １ ／ the length of the cell in the opposing direction between the display substrate 20 and the rear substrate 22. It is preferable that the volume average primary particle diameter is 1 to 50, and the content is 1 volume% to 50 volume% with respect to the volume of the cell.

  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 display medium can be made. Usually, the size is about 10 μm to 1 mm.

  In order to fix the display substrate 20 and the back substrate 22, fixing means such as a combination of bolts and nuts, a clamp, a clip, and a substrate fixing frame can be used. Also, fixing means such as an adhesive, heat melting, and ultrasonic bonding can be used.

  The display medium 12 includes a bulletin board capable of storing and rewriting images, a circulation version, an electronic blackboard, an advertisement, a signboard, a flashing sign, an electronic paper, an electronic newspaper, an electronic book, and a document sheet that can be shared with a copier / printer. Can be used for

  In this display medium 12, different colors are displayed by changing the applied voltage (V) applied between the display substrate 20 and the back substrate 22.

  In the display medium 12, each pixel of the image data is moved for each cell corresponding to each pixel of the display medium 12 by moving the particle group 34 according to the electric field formed between the display substrate 20 and the back substrate 22. The color according to can be displayed.

  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 of 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. 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 the color particle group 34 for each color. Are different.

  In the present embodiment, the absolute value of the voltage when each of the three color particle groups of the magenta magenta particle group 34M, the cyan cyan particle group 34C, and the yellow yellow particle group 34Y starts moving. Assuming 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 |. Also, the absolute value of the maximum voltage for moving almost all of 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. Assuming 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 |.

  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. 2, for example, three types of particle groups 34 are all dispersed in the particle dispersion 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 a value between Vtc and Vdc), absolute value of voltage range necessary for moving magenta particle group 34M | Vtm ≦ Vm ≦ Vdm | Absolute value of the value between Vtm and 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), It is set to be large without overlapping in this order.

  Further, in order to independently drive the particle groups 34 of the respective colors, the absolute value | Vdc | of the maximum voltage for moving almost all the cyan particle groups 34C is the absolute value of the voltage range necessary for moving the magenta particle group 34M. Value | 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 | (Vty to Vdy The absolute value of the value between) is set smaller. In addition, the absolute value | Vdm | of the maximum voltage for moving almost all of the magenta particle group 34M is the absolute value of the voltage range necessary for moving the yellow particle group 34Y | Vty ≦ Vy ≦ Vdy | (from Vty to Vdy). 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.
The “maximum voltage required to move almost all the particle groups 34” means that even if the voltage and the voltage application time are further increased from the start of the movement, the display density does not change and the display density is saturated. Indicates voltage.
Further, “almost all” means that there is a variation in the characteristics of the particle groups 34 of the respective colors, so that some of the characteristics of the particle groups 34 are different to the extent that they do not contribute to the display characteristics. 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.
“Display density” is the color density on the display surface side measured with the optical density (Optical Density = 0D) reflection densitometer X-rite's reflection densitometer. 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. 2, the voltage applied between the substrates is in the range of −Vtc to Vtc (voltage range | Vtc | or less). When applied between the substrate 22 and the substrate 22, the movement of the particles 34 (cyan particle group 34 C, magenta particle group 34 M, and yellow particle group 34 Y) to such a degree that the display density of the display medium 12 changes. Is not occurring. When a voltage greater than the absolute value of the voltage + Vtc and the voltage −Vtc is applied between the substrates, the degree of change in the display density of the display medium 12 for the cyan particle group 34C among the three color particle groups 34 occurs. The display density starts to change for the first time, and when a voltage equal to or higher than the absolute value | Vdc | of the voltage −Vdc and the voltage Vdc is applied, the display density per unit voltage does not change.

  Further, when a voltage is applied between the display substrate 20 and the back substrate 22 so that the voltage applied between the substrates is within a range of −Vtm to Vtm (voltage range | Vtm | or less), It can be said that the movement of the particles of the magenta particle group 34M and the yellow particle group 34Y to the extent that the display density of the display medium 12 changes does not occur. 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 and the magenta particle group 34M of the yellow particle group 34Y. The display density per unit voltage starts to change to the extent that particles are generated, and when the voltage −Vdm and voltage Vdm absolute value | Vdm | or more are applied, the display density changes. Disappear.

  Further, when a voltage is applied between the display substrate 20 and the back substrate 22 so that the voltage applied between the substrates is within the range of −Vty to Vty (voltage range | Vty | or less), the display It can be said that the movement of the particles of the yellow particle group 34Y to the extent that the display density of the medium 12 changes does not occur. 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 equal to or higher 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. 3, the mechanism of particle movement when an image is displayed on the display medium 12 of the present invention 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 between the substrates on the display substrate 20 side than the back substrate 22 side, the respective voltages are referred to as “+ large voltage”, “+ medium voltage”, and “+ small voltage”, respectively. . Further, when a higher voltage is applied to the back substrate 22 side than the display substrate 20 side, the respective voltages are referred to as “−large voltage”, “−medium voltage”, and “−small voltage”, respectively. I will explain.

  As shown in FIG. 3A, if 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, When “+ large voltage” is applied between the display substrate 20 and the back substrate 22 from the state, the magenta particle group 34M, the cyan particle group 34C, and the yellow particle group 34Y are displayed on the display substrate 20 side as all particle groups. Move to. 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. 3B).

  Next, when “−medium voltage” is applied between the display substrate 20 and the back substrate 22 from the state of FIG. 3B, 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. Therefore, since only the yellow particle group 34Y is attached to the display substrate 20 side, yellow display is performed (see FIG. 3C).

  Further, when “+ small voltage” is applied between the display substrate 20 and the back substrate 22 from the state of FIG. 3C, 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. 3D).

  3B, when a “−small voltage” is applied between the display substrate 20 and the back substrate 22, the cyan particle groups 34C of all the particle groups 34 move to the back substrate 22 side. To do. 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. 3I).

  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. 3A, 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, the magenta particle group 34M and the cyan particle group 34C adhere to the display substrate 20 side, so that blue is displayed by the subtractive color mixing of magenta and cyan (see FIG. 3E).

When a “−small voltage” is applied between the display substrate 20 and the back substrate 22 from the state of FIG. 3E, 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. 3F).

When a “−large voltage” is applied between the display substrate 20 and the back substrate 22 from the state of FIG. 3F, 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 insulating particles 36 (see FIG. 3G).

  When a “+ small voltage” is applied between the display substrate 20 and the back substrate 22 from the initial state shown in FIG. 3A, 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. 3H).

Further, when a “−large voltage” is applied between the display substrate 20 and the back substrate 22 from the state shown in FIG. 3I, all the particle groups 34 appear on the back surface as shown in FIG. Moving to the substrate 22 side, white display is performed.
Similarly, when a “−large voltage” is applied between the display substrate 20 and the back substrate 22 from the state shown in FIG. 3D, all the particle groups 34 are formed as shown in FIG. Moving to the back substrate 22 side, white display is performed.

  Thus, in the present embodiment, by applying a voltage according to each particle group 34 between the substrates, the desired particles are selectively moved according to the electric field due to the voltage, so that a color other than the desired color can be obtained. The particles can be prevented from moving in the particle dispersion liquid 50, color mixing of colors other than the desired color can be suppressed, and color display can be performed while image quality deterioration of the display medium 12 is suppressed. 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 required to move according to the electric field overlap each other, each particle group 34 is a single pixel. Color display can be realized. 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 particle dispersion liquid 50, cyan, magenta, yellow, blue, red, green, and black can be displayed, and white White can be displayed by the insulating particles 36, and a desired color display can be performed.

Here, when the charging characteristics of each color particle group 34 (yellow particle group 34Y, magenta particle group 34M, and cyan particle group 34C) dispersed in the particle dispersion 50 change with the passage of time from the production of the display medium 12. Even if the same voltage or the same polarity voltage is applied to the display medium 12, it may be difficult to display a desired color on the display medium 12.
However, according to the display medium 12 and the display device 10 of the present embodiment, the particle group 34 in the display medium 12 is dispersed in the particle dispersion 50 described in the first embodiment. Changes in charging characteristics are suppressed. Therefore, a change in charging characteristics of the particle group 34 that moves in accordance with the electric field dispersed in the display medium 12 is suppressed, and deterioration in image quality of the display medium 12 can be suppressed.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples. In addition, unless otherwise indicated, a part shows a weight part.

[Example A]
Hereinafter, embodiments of the present invention will be described in detail.

(Example A1)
-Preparation of insulating particles 36-
Insulating particles 36 were prepared by the following procedure.
First, the following components were mixed, and ball milling with 10 mmφ zirconia balls was performed for 20 hours to prepare dispersion AA.
<Composition>
• 53 parts by weight of cyclohexyl methacrylate • Titanium oxide 1 (white pigment) (primary particle size 0.3 μm, Type CR63: manufactured by Ishihara Sangyo Co., Ltd.) 45 parts by weight • 5 parts by weight of cyclohexane

Next, the following components were mixed, and finely pulverized with a ball mill in the same manner as described above to prepare a charcoal dispersion AB.
<Composition>
・ 40 parts by weight of calcium carbonate ・ 60 parts by weight of water

The following components were mixed, degassed with an ultrasonic machine for 10 minutes, and then stirred with an emulsifier to prepare a mixed liquid AC.
<Composition>
・ 4.3g of 2% serogen
-Charcoal dispersion AB 8.5g
・ 20% saline 50g

  35 g of the dispersion AA prepared above, 1 g of divinylbenzene, and polymerization initiator AIBN: 0.35 g were weighed and mixed sufficiently, and deaeration was performed for 10 minutes with an ultrasonic machine. This was added to the mixed liquid AC prepared above 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 filtration was performed. Thereafter, it was washed with sufficient distilled water, and passed through a nylon sieve having openings of 25 μm and 20 μm to make the particle sizes uniform. This was dried to obtain a group of white particles having an average particle diameter of 20 μm. This was designated as insulating particles 36.

-Preparation of particle group 34M-
As the particle group 34, a magenta-colored magenta particle group 34M was prepared.

The following components were mixed and ball milling was performed for 20 hours with 10 mmφ zirconia balls to prepare dispersion BA.
<Composition>
• 53 parts by weight of cyclohexyl methacrylate • 3 parts by weight of magenta pigment (Kermin 6B: manufactured by Dainichi Seika Co., Ltd.) • 2 parts by weight of charge control agent (COPY CHARGE PSY VP2038: manufactured by Clariant Japan) • 5 parts by weight of cyclohexane

The following components were mixed, and finely pulverized with a ball mill in the same manner as above to prepare a charcoal dispersion BB.
<Composition>
・ 40 parts by weight of calcium carbonate ・ 60 parts by weight of water

The following components were mixed, degassed with an ultrasonic machine for 10 minutes, and then stirred with an emulsifier to prepare a mixed solution BC.
<Composition>
・ 4.3g of 2% serogen aqueous solution
-Charcoal cal dispersion BB 8.5g
・ 20% saline 50g

  35 g of the prepared dispersion BA, 1 g of divinylbenzene, and polymerization initiator AIBN: 0.35 g were weighed and mixed thoroughly, and deaerated with an ultrasonic machine for 10 minutes. This was added to the mixed solution BC 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 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 fine particle powder was dispersed in ion exchange water, calcium carbonate was decomposed with hydrochloric acid water, and filtration was performed. Thereafter, it was washed with sufficient distilled water and dried. 2 parts by weight of the obtained particles are put into 98 parts by weight of silicone oil (corresponding to the first solvent) together with 2 parts by weight of the surfactant polyoxyethylene alkyl ether, and stirred and dispersed to obtain the magenta particle group 34M and the magenta particle group. A 34M dispersion was prepared. The volume average particle diameter of the magenta particle group 34M was 1 μm. The magenta particle group 34M thus produced was negatively charged.

The following display medium was produced using the produced magenta particle group 34M, the first solvent, the dispersion, and the insulating particles 36.
In Example A1, the particle dispersion liquid in which the magenta particle group 34M is dispersed in the display medium 12 is 5% with respect to 100% by weight of the first solvent (silicone oil) prepared as amino-modified silicone oil. A liquid containing wt% side chain type amino-modified silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: KF393, amine equivalent: 350 g / mol) was used. Details are shown below.

  ―Production of image display media―

In this embodiment, the display medium 12 uses a support substrate made of transparent glass of 70 mm × 50 mm × 1.1 mm as the support substrate 44, and ITO is used as the back electrode 46 on the support substrate by sputtering to a thickness of 50 nm. A film was formed with a thickness.
At this time, when the color density of this substrate was measured by X-Rite (X-Rite 404A, manufactured by X-Rite), the L * value was 93.

Similarly, a support substrate made of transparent glass of 70 mm × 50 mm × 1.1 mm is used for the support substrate 38, and ITO is formed on the support substrate 38 as a surface electrode 40 with a thickness of 50 nm by a sputtering method. Filmed.
At this time, when the color density of this substrate was measured by X-Rite, the L * value was 93.

  Thereafter, a layer is applied on the back electrode 46 of the support substrate 44 using a photosensitive polyimide varnish to produce the back substrate 22 as the surface layer 48, and then exposed and exposed on the surface layer 48 of the back substrate 22. A partition wall having a height of 100 μm and a width of 20 μm was formed as the gap member 24 by wet etching.

  After forming a heat-fusible adhesive layer (not shown) on the gap member 24, the prepared insulating particles 36, the prepared magenta particle group 34M, and a dispersion of the magenta particle group 34M, 5% by weight of a side chain amino-modified silicone oil (Shin-Etsu Chemical Co., Ltd .: KF393, amine equivalent: 350 g / mol) with respect to 100% by weight of the silicone oil (first solvent) contained in the dispersion of the magenta particle group 34M. ).

  That is, in Example A1, as a particle dispersion, 5% by weight of amino-modified silicone oil was mixed with 100% by weight of the first solvent in a dispersion containing the first solvent (silicone oil) prepared above. The resulting solution was used as a particle dispersion.

  Next, a layer is applied on the surface electrode 40 of the support substrate 38 using a photosensitive polyimide varnish to form a surface layer 48 to produce the display substrate 20. The display medium 20 was produced by applying heat to the display substrate 20 attached to the back substrate 22 via the gap member 24 so that the back electrode 46 of the substrate 22 faced.

Using the display medium 12 manufactured in Example A1 in this way, a voltage of 40 V was applied to both electrodes for 2 seconds so that the surface electrode 40 on the display substrate 20 side was positive and the back electrode 46 on the back substrate 22 was negative. Applied. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the display substrate 20 side by an electric field generated by voltage application, and the display medium 12 displayed a magenta color.
When the concentration of the display substrate 20 immediately after the voltage of 40 V was applied for 2 seconds was measured with a densitometer (X-Rite 404A, manufactured by X-Rite), a * was 39 and b * was 0.

  Thereafter, a voltage of 40 V was applied to both electrodes so that the surface electrode 40 of the display substrate 20 was negative and the back electrode 46 of the back substrate 22 was positive. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the back substrate 22 side by an electric field generated by voltage application, and the display medium 12 displayed white.

Further, after repeating the magenta color display and the white display 1000 times, the display medium 12 is further left in an environment of 25 ° C. and 40% RH for 240 hours. A voltage of 40 V was applied to both electrodes for 2 seconds so that the back electrode 46 of the substrate 22 was negative. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the display substrate 20 side by an electric field generated by voltage application, and the display medium 12 displayed a magenta color.
When the concentration of the display substrate 20 was measured with a densitometer (X-Rite 404A) immediately after applying a voltage of 40 V for 2 seconds after being left in this 25 ° C. 40% RH environment for 240 hours, a * was 39, b * was 0, and no change in concentration was observed.

  Further, after applying a voltage of 40 V to both electrodes so that the surface electrode 40 of the display substrate 20 is negative and the back electrode 46 of the rear substrate 22 is positive, the display substrate 20 is peeled off and the color density of the display substrate 20 is increased. As a result, the L * value was 93, no change from before the voltage application, and no adhesion of the magenta particle group 34M was observed.

  For this reason, the magenta particle group 34M in the display medium 12 produced in Example A1 shows no change in charging characteristics even after being rewritten 1000 times and left in an environment of 25 ° C. and 40% RH for 240 hours. Thus, it can be said that the change in the charging characteristics could be suppressed.

(Example A2)
The display medium 12 was manufactured using the magenta particle group 34M prepared in Example A1, the first solvent, the dispersion, and the insulating particles 36.
In Example A2, the dispersion containing the first solvent (silicone oil) prepared in Example A1 used as the particle dispersion in Example A1 is used as the particle dispersion to be enclosed in the display medium 12. Instead of the solution in which 5% by weight of amino-modified silicone oil is mixed with 100% by weight of the first solvent, the first solvent is added to the dispersion containing the first solvent prepared in Example A1. A display medium 12 was prepared in the same manner as in Example A1 except that a solution in which 1% by weight of side chain type amino-modified silicone oil was mixed with 100% by weight was evaluated in the same manner as in Example A1. went.

Using the display medium 12 produced in Example A2, a voltage of 40 V was applied to both electrodes for 2 seconds so that the surface electrode 40 on the display substrate 20 side was positive and the back electrode 46 on the back substrate 22 was negative. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the display substrate 20 side by an electric field generated by voltage application, and the display medium 12 displayed a magenta color.
When the concentration of the display substrate 20 immediately after the voltage of 40 V was applied for 2 seconds was measured with a densitometer (X-Rite 404A, manufactured by X-Rite), a * was 39 and b * was 0.

  Thereafter, a voltage of 40 V was applied to both electrodes so that the surface electrode 40 of the display substrate 20 was negative and the back electrode 46 of the back substrate 22 was positive. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the back substrate 22 side by an electric field generated by voltage application, and the display medium 12 displayed white.

  Further, after repeating the magenta color display and the white display 1000 times, the display medium 12 is further left in an environment of 25 ° C. and 40% RH for 240 hours. A voltage of 40 V was applied to both electrodes for 2 seconds so that the back electrode 46 of the substrate 22 was negative. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the display substrate 20 side by an electric field generated by voltage application, and the display medium 12 displayed a magenta color. When the concentration of the display substrate 20 was measured with a densitometer (X-Rite 404A) immediately after applying a voltage of 40 V for 2 seconds after being left in this 25 ° C. 40% RH environment for 240 hours, a * was 39, b * was 0, and no change in concentration was observed.

  Further, after applying a voltage of 40 V to both electrodes so that the surface electrode 40 of the display substrate 20 is negative and the back electrode 46 of the rear substrate 22 is positive, the display substrate 20 is peeled off and the color density of the display substrate 20 is increased. Was measured with the above densitometer, the L * value was 92, which was almost the same as before voltage application, and adhesion of the magenta particle group 34M was not observed.

  For this reason, the magenta particle group 34M in the display medium 12 produced in Example A2 has charging characteristics even after being rewritten 1000 times and left in an environment of 25 ° C. and 40% RH for 240 hours in the same manner as Example A1. Thus, it can be said that the change in charging characteristics could be suppressed.

(Example A3)
The display medium 12 was produced using the magenta particle group 34M prepared in Example A1 above, the first solvent, and the insulating particles 36.
In Example A3, the dispersion containing the first solvent (silicone oil) prepared in Example A1 used as the particle dispersion in Example A1 is used as the particle dispersion to be sealed in the display medium 12. Instead of the solution in which 5% by weight of amino-modified silicone oil is mixed with 100% by weight of the first solvent, the first solvent is added to the dispersion containing the first solvent prepared in Example A1. A display medium 12 was prepared in the same manner as in Example A1, except that a solution in which 0.1% by weight of the side chain type amino-modified silicone oil was mixed with respect to 100% by weight. Evaluation was performed.

Using the display medium 12 produced in Example A3, a voltage of 40 V was applied to both electrodes for 2 seconds so that the surface electrode 40 on the display substrate 20 side was positive and the back electrode 46 on the back substrate 22 was negative. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the display substrate 20 side by an electric field generated by voltage application, and the display medium 12 displayed a magenta color.
When the concentration of the display substrate 20 immediately after the voltage of 40 V was applied for 2 seconds was measured with a densitometer (X-Rite 404A, manufactured by X-Rite), a * was 38 and b * was 0.

  Thereafter, a voltage of 40 V was applied to both electrodes so that the surface electrode 40 of the display substrate 20 was negative and the back electrode 46 of the back substrate 22 was positive. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the back substrate 22 side by an electric field generated by voltage application, and the display medium 12 displayed white.

  Further, after repeating the magenta color display and the white display 1000 times, the display medium 12 is further left in an environment of 25 ° C. and 40% RH for 240 hours. A voltage of 40 V was applied to both electrodes for 2 seconds so that the back electrode 46 of the substrate 22 was negative. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the display substrate 20 side by an electric field generated by voltage application, and the display medium 12 displayed a magenta color. When the concentration of the display substrate 20 was measured with a densitometer (X-Rite 404A) immediately after applying a voltage of 40 V for 2 seconds after being left in this 25 ° C. 40% RH environment for 240 hours, a * was 38, b * was 0, and no change in concentration was observed.

  Further, after applying a voltage of 40 V to both electrodes so that the surface electrode 40 of the display substrate 20 is negative and the back electrode 46 of the rear substrate 22 is positive, the display substrate 20 is peeled off and the color density of the display substrate 20 is increased. As a result, the L * value was 91 and the value was lower than that before voltage application, but adhesion of the magenta particle group 34M was hardly known.

  For this reason, the magenta particle group 34M in the display medium 12 produced in Example A3 shows a change in charging characteristics even after being left in an environment of 25 ° C. and 40% RH for 240 hours, as in Example A1. In other words, it can be said that the change in charging characteristics could be suppressed.

(Example A4)
The display medium 12 was produced using the magenta particle group 34M prepared in Example A1 above, the first solvent, and the insulating particles 36.
In Example A4, the particle dispersion to be sealed in the display medium 12 is a dispersion containing the first solvent (silicone oil) prepared in Example A1 and used as the particle dispersion in Example A1. Instead of the solution in which 5% by weight of amino-modified silicone oil is mixed with 100% by weight of the first solvent, the first solvent is added to the dispersion containing the first solvent prepared in Example A1. A display medium 12 was produced in the same manner as in Example A1, except that a solution in which 6% by weight of a side chain amino-modified silicone oil was mixed with 100% by weight. Evaluation was performed in the same manner as in Example A1. went.

Using the display medium 12 produced in Example A4, a voltage of 40 V was applied to both electrodes for 2 seconds so that the surface electrode 40 on the display substrate 20 side was positive and the back electrode 46 on the back substrate 22 was negative. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the display substrate 20 side by an electric field generated by voltage application, and the display medium 12 displayed a magenta color.
When the concentration of the display substrate 20 immediately after the voltage of 40 V was applied for 2 seconds was measured with a densitometer (X-Rite 404A, manufactured by X-Rite), a * was 39 and b * was 0.

  Thereafter, a voltage of 40 V was applied to both electrodes so that the surface electrode 40 of the display substrate 20 was negative and the back electrode 46 of the back substrate 22 was positive. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the back substrate 22 side by an electric field generated by voltage application, and the display medium 12 displayed white.

  Further, after repeating the magenta color display and the white display 1000 times, the display medium 12 is further left in an environment of 25 ° C. and 40% RH for 240 hours. A voltage of 40 V was applied to both electrodes for 2 seconds so that the back electrode 46 of the substrate 22 was negative. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the display substrate 20 side by an electric field generated by voltage application, and the display medium 12 displayed a magenta color. When the concentration of the display substrate 20 was measured with a densitometer (X-Rite 404A) immediately after applying a voltage of 40 V for 2 seconds after being left in this 25 ° C. 40% RH environment for 240 hours, a * was 39, b * was 0, and no change in concentration was observed.

  Further, after applying a voltage of 40 V to both electrodes so that the surface electrode 40 of the display substrate 20 is negative and the back electrode 46 of the rear substrate 22 is positive, the display substrate 20 is peeled off and the color density of the display substrate 20 is increased. Was measured, and the L * value was 93, which was the same as before voltage application, and adhesion of the magenta particle group 34M was not observed.

For this reason, the magenta particle group 34M in the display medium 12 produced in Example A4 is charged even after being rewritten 1000 times and left in an environment of 25 ° C. and 40% RH for 240 hours as in Example A1. It can be said that no change in the characteristics was observed and the change in the charging characteristics could be suppressed.
In Example A4, the conductivity of the particle dispersion was calculated from the value of the current flowing when a voltage was applied, and it was 1 × 10 ⁻⁹ S / cm. Therefore, it can be said that the display media produced in Examples A1 to A3 are more suitable for practical use than the display media produced in Example A4.

(Example A5)
The display medium 12 was produced using the magenta particle group 34M prepared in Example A1 above, the first solvent, and the insulating particles 36.
In Example A5, the particle dispersion to be enclosed in the display medium 12 is a dispersion containing the first solvent (silicone oil) prepared in Example A1 and used as the particle dispersion in Example A1. Instead of the solution in which 5% by weight of amino-modified silicone oil is mixed with 100% by weight of the first solvent, the first solvent is added to the dispersion containing the first solvent prepared in Example A1. A display medium 12 was produced in the same manner as in Example A1, except that a solution in which 0.005% by weight of the side chain type amino-modified silicone oil was mixed with respect to 100% by weight. Evaluation was performed.

Using the display medium 12 produced in Example A5, a voltage of 40 V was applied to both electrodes for 2 seconds so that the surface electrode 40 on the display substrate 20 side was positive and the back electrode 46 on the back substrate 22 was negative. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the display substrate 20 side by an electric field generated by voltage application, and the display medium 12 displayed a magenta color.
When the concentration of the display substrate 20 immediately after the voltage of 40 V was applied for 2 seconds was measured with a densitometer (X-Rite 404A, manufactured by X-Rite), a * was 38 and b * was 0.

  Thereafter, a voltage of 40 V was applied to both electrodes so that the surface electrode 40 of the display substrate 20 was negative and the back electrode 46 of the back substrate 22 was positive. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the back substrate 22 side by an electric field generated by voltage application, and the display medium 12 displayed white.

  Further, after repeating the magenta color display and the white display 1000 times, the display medium 12 is further left in an environment of 25 ° C. and 40% RH for 240 hours. A voltage of 40 V was applied to both electrodes for 2 seconds so that the back electrode 46 of the substrate 22 was negative. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the display substrate 20 side by an electric field generated by voltage application, and the display medium 12 displayed a magenta color. When the concentration of the display substrate 20 was measured with a densitometer (X-Rite 404A) immediately after applying a voltage of 40 V for 2 seconds after being left in this 25 ° C. 40% RH environment for 240 hours, a * was 37, b * was 0, and almost no change in concentration was observed.

  Further, after applying a voltage of 40 V to both electrodes so that the surface electrode 40 of the display substrate 20 is negative and the back electrode 46 of the rear substrate 22 is positive, the display substrate 20 is peeled off and the color density of the display substrate 20 is increased. Was measured, the L * value was 90, the difference from before the voltage application was slight, and adhesion of the magenta particle group 34M was hardly observed.

  For this reason, the magenta particle group 34M in the display medium 12 produced in Example A5 was rewritten 1000 times as in Example A1, and after being left in an environment of 25 ° C. and 40% RH for 240 hours. Although a change in charging characteristics was observed as compared with Examples A1 to A4, the color change by visual observation was at an acceptable level, and it can be said that the change in charging characteristics could be suppressed.

(Example A6)
The display medium 12 was produced using the magenta particle group 34M prepared in Example A1 above, the first solvent, and the insulating particles 36.
In Example A6, the dispersion containing the first solvent (silicone oil) prepared in Example A1 used as the particle dispersion in Example A1 is used as the particle dispersion to be enclosed in the display medium 12. Instead of the solution in which 5% by weight of amino-modified silicone oil is mixed with 100% by weight of the first solvent, the first solvent is added to the dispersion containing the first solvent prepared in Example A1. Example A1 except that a solution in which 0.01% by weight of a double-terminal amino-modified silicone oil (XX-22-161B manufactured by Shin-Etsu Chemical Co., Ltd., amine equivalent: 1500 g / mol) was mixed with 100% by weight was used. A display medium 12 was produced in the same manner as described above and evaluated in the same manner as in Example A1.

Using the display medium 12 produced in Example A6, a voltage of 40 V was applied to both electrodes for 2 seconds so that the surface electrode 40 on the display substrate 20 side was positive and the back electrode 46 on the back substrate 22 was negative. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the display substrate 20 side by an electric field generated by voltage application, and the display medium 12 displayed a magenta color.
When the concentration of the display substrate 20 immediately after the voltage of 40 V was applied for 2 seconds was measured with a densitometer (X-Rite 404A, manufactured by X-Rite), a * was 39 and b * was 0.

  Thereafter, a voltage of 40 V was applied to both electrodes so that the surface electrode 40 of the display substrate 20 was negative and the back electrode 46 of the back substrate 22 was positive. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the back substrate 22 side by an electric field generated by voltage application, and the display medium 12 displayed white.

  Further, after repeating the magenta color display and the white display 1000 times, the display medium 12 is further left in an environment of 25 ° C. and 40% RH for 240 hours. A voltage of 40 V was applied to both electrodes for 2 seconds so that the back electrode 46 of the substrate 22 was negative. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the display substrate 20 side by an electric field generated by voltage application, and the display medium 12 displayed a magenta color. When the concentration of the display substrate 20 was measured with a densitometer (X-Rite 404A) immediately after applying a voltage of 40 V for 2 seconds after being left in this 25 ° C. 40% RH environment for 240 hours, a * was 38, b * was 0, and no change in concentration was observed.

  Further, after applying a voltage of 40 V to both electrodes so that the surface electrode 40 of the display substrate 20 is negative and the back electrode 46 of the rear substrate 22 is positive, the display substrate 20 is peeled off and the color density of the display substrate 20 is increased. Was measured, and the L * value was 92, which was almost the same as before voltage application, and no adhesion of the magenta particle group 34M was observed.

  For this reason, the magenta particle group 34M in the display medium 12 produced in Example A6 is charged even after being rewritten 1000 times and left in an environment of 25 ° C. and 40% RH for 240 hours, as in Example A1. It can be said that no change in the characteristics was observed and the change in the charging characteristics could be suppressed.

(Example A7)
The display medium 12 was produced using the magenta particle group 34M prepared in Example A1 above, the first solvent, and the insulating particles 36.
In Example A7, the particle dispersion to be enclosed in the display medium 12 is a dispersion containing the first solvent (silicone oil) prepared in Example A1 and used as the particle dispersion in Example A1. Instead of the solution in which 5% by weight of amino-modified silicone oil is mixed with 100% by weight of the first solvent, the first solvent is added to the dispersion containing the first solvent prepared in Example A1. Except for using a solution in which 1% by weight of both ends-type amino-modified silicone oil (KF-8010 manufactured by Shin-Etsu Chemical Co., Ltd., amine equivalent: 450 g / mol) was mixed with respect to 100% by weight, the same as Example A1 was used. A display medium 12 was produced and evaluated in the same manner as in Example A1.

Using the display medium 12 produced in Example A7, a voltage of 40 V was applied to both electrodes for 2 seconds so that the surface electrode 40 on the display substrate 20 side was positive and the back electrode 46 of the back substrate 22 was negative. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the display substrate 20 side by an electric field generated by voltage application, and the display medium 12 displayed a magenta color.
When the concentration of the display substrate 20 immediately after the voltage of 40 V was applied for 2 seconds was measured with a densitometer (X-Rite 404A, manufactured by X-Rite), a * was 38 and b * was 0.

  Thereafter, a voltage of 40 V was applied to both electrodes so that the surface electrode 40 of the display substrate 20 was negative and the back electrode 46 of the back substrate 22 was positive. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the back substrate 22 side by an electric field generated by voltage application, and the display medium 12 displayed white.

  Further, after repeating the magenta color display and the white display 1000 times, the display medium 12 is further left in an environment of 25 ° C. and 40% RH for 240 hours. A voltage of 40 V was applied to both electrodes for 2 seconds so that the back electrode 46 of the substrate 22 was negative. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the display substrate 20 side by an electric field generated by voltage application, and the display medium 12 displayed a magenta color. When the concentration of the display substrate 20 was measured with a densitometer (X-Rite 404A) immediately after applying a voltage of 40 V for 2 seconds after being left in this 25 ° C. 40% RH environment for 240 hours, a * was 37, b * was 0, and no change in concentration was observed.

  Further, after applying a voltage of 40 V to both electrodes so that the surface electrode 40 of the display substrate 20 is negative and the back electrode 46 of the rear substrate 22 is positive, the display substrate 20 is peeled off and the color density of the display substrate 20 is increased. As a result, the L * value was 90, and although the value was lower than before voltage application, adhesion of the magenta particle group 34M was hardly recognized.

  For this reason, the magenta particle group 34M in the display medium 12 produced in Example A7 has the charging characteristics even after being rewritten 1000 times and left in an environment of 25 ° C. and 40% RH for 240 hours as in Example A1. Thus, it can be said that the change in charging characteristics could be suppressed.

(Comparative Example A1)
The display medium 12 was produced using the magenta particle group 34M prepared in Example A1 above, the first solvent, and the insulating particles 36.
In this comparative example A1, the particle dispersion to be enclosed in the display medium 12 is 5 with respect to 100% by weight of the first solvent adjusted in Example A1 used as the particle dispersion in Example A1. A solution in which the first solvent prepared in Example A1 was not mixed with the first solvent prepared in Example A1, that is, the first solvent was used as the particle dispersion 50 in place of the solution in which the amino acid-modified silicone oil by weight% was mixed. The display medium 12 was produced in the same manner as in Example A1, and evaluated in the same manner as in Example A1.

Using the display medium 12 produced in Comparative Example A1, a voltage of 40 V was applied to both electrodes for 2 seconds so that the surface electrode 40 on the display substrate 20 side was positive and the back electrode 46 on the back substrate 22 was negative. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the display substrate 20 side by an electric field generated by voltage application, and the display medium 12 displayed a magenta color.
When the concentration of the display substrate 20 immediately after the voltage of 40 V was applied for 2 seconds was measured with a densitometer (X-Rite 404A, manufactured by X-Rite), a * was 37 and b * was 0.

  Thereafter, a voltage of 40 V was applied to both electrodes so that the surface electrode 40 of the display substrate 20 was negative and the back electrode 46 of the back substrate 22 was positive. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the back substrate 22 side by an electric field generated by voltage application, and the display medium 12 displayed white.

  Further, after repeating the magenta color display and the white display 1000 times, the display medium 12 is further left in an environment of 25 ° C. and 40% RH for 240 hours. A voltage of 40 V was applied to both electrodes for 2 seconds so that the back electrode 46 of the substrate 22 was negative. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the display substrate 20 side by an electric field generated by voltage application, and the display medium 12 displayed a magenta color. When the concentration of the display substrate 20 was measured with a densitometer (X-Rite 404A) immediately after applying a voltage of 40 V for 2 seconds after being left in this 25 ° C. 40% RH environment for 240 hours, a * was 33, b * was 0, and the concentration was significantly reduced.

  Further, after applying a voltage of 40 V to both electrodes so that the surface electrode 40 of the display substrate 20 is negative and the back electrode 46 of the rear substrate 22 is positive, the display substrate 20 is peeled off and the color density of the display substrate 20 is increased. Was measured, and the L * value was 82, and adhesion of the magenta particle group 34M was observed.

  For this reason, it can be said that in the magenta particle group 34M in the display medium 12 manufactured in Comparative Example A1, particles whose polarity is reversed are generated over time, and the charging characteristics are changed.

(Example A8)
A display medium 12 was produced using the first solvent, the insulating particles 36, and the particle dispersion prepared in Example A1.
In Example A8, the following cyan cyan particle group 34C mainly composed of a cationic resin was used as the particle group 34 instead of the magenta particle group 34M prepared in Example A1. Further, as the amino-modified silicone oil, TSF4708 manufactured by GE Toshiba Silicone, which is a side chain type amino-modified silicone oil, was used. Except for these two points, the display medium 12 was produced in the same manner as in Example A1, and evaluated in the same manner as in Example A1.

-Preparation of particle group 34C-
As the particle group 34, a cyan cyan particle group 34C was prepared.

A silicone-modified acrylic polymer KP545 (manufactured by Shin-Etsu Chemical Co., Ltd.) (5 parts by weight) dissolved in dimethyl silicone oil (KF-96-2CS) (95 parts by weight) was prepared as a continuous phase.
Next, as a resin, cationized polyvinyl alcohol (7 parts by weight of Nippon Synthetic Chemical Co., Ltd. K-210), cyan pigment dispersion (corresponding to 3 parts by weight of pigment solids) (3 parts by weight) and water (63 parts by weight) Was prepared as a dispersed phase. Further, 80 parts by weight of the continuous phase and 20 parts by weight of the dispersed phase were added and emulsified. The emulsification was performed for 10 minutes with an ultrasonic crusher (UH-600S manufactured by SMT).

  The obtained emulsified liquid was put into an eggplant flask, and the water was removed by heating (65 ° C.) and reducing the pressure with an evaporator while stirring to prepare cyan particle group 34C as blue electrophoretic particles.

The volume average primary particle size of the adjusted cyan particle group 34 was measured by HORIBA LB-550 (dynamic light scattering type particle size distribution measuring device) and found to be 330 nm.
Further, when this adjusted cyan particle group 34 was observed with an optical microscope, it was found that particles having a size of 1 mm or more were not observed, and an agglomerate could not be confirmed, so that the dispersion stability was excellent. Moreover, spherical particles were observed when observed with a scanning electron microscope (FE-SEM S-5500, manufactured by Hitachi).

  2 parts by weight of the adjusted cyan particle group 34C and 2 parts by weight of the surfactant polyoxyethylene alkyl ether are added to 98 parts by weight of silicone oil (corresponding to the first solvent), and dispersed by stirring to disperse the cyan particle group 34C. A dispersion was prepared. The cyan particle group 34C thus produced was positively charged.

Using the display medium 12 produced in Example A8, a voltage of 40 V was applied to both electrodes for 2 seconds so that the surface electrode 40 on the display substrate 20 side was negative and the back electrode 46 on the back substrate 22 was positive. As a result, it was observed that the positively charged cyan particle group 34C was moved to the display substrate 20 side by the electric field generated by the voltage application, and the display medium 12 displayed cyan.
When the density of the display substrate 20 immediately after the voltage of 40 V was applied for 2 seconds was measured with a densitometer (X-Rite 404A, manufactured by X-Rite), a * was −38 and b * was −40.

  Thereafter, a voltage of 40 V was applied to both electrodes so that the surface electrode 40 of the display substrate 20 was positive and the back electrode 46 of the back substrate 22 was negative. As a result, it was observed that the positively charged cyan particle group 34 </ b> C moved to the back substrate 22 side by an electric field by voltage application, and the display medium 12 displayed white.

  Further, after the cyan display and the white display are repeated 1000 times, the display medium 12 is further allowed to stand in an environment of 25 ° C. and 40% RH for 240 hours, and then the surface electrode 40 on the display substrate 20 side is negative again. A voltage of 40 V was applied to both electrodes for 2 seconds so that the back electrode 46 of the substrate 22 was positive. As a result, it was observed that the positively charged cyan particle group 34C was moved to the display substrate 20 side by the electric field generated by the voltage application, and the display medium 12 displayed cyan. When the concentration of the display substrate 20 was measured with a densitometer (X-Rite 404A) immediately after applying a voltage of 40 V for 2 seconds after being left in this 25 ° C. 40% RH environment for 240 hours, a * was −38, b * was −39, and no change in concentration was observed.

  Further, after applying a voltage of 40 V to both electrodes so that the front electrode 40 of the display substrate 20 is positive and the back electrode 46 of the rear substrate 22 is negative, the display substrate 20 is peeled off, and the color density of the display substrate 20 is increased. Was measured, and the L * value was 93, which was not changed before voltage application. Further, no adhesion of the cyan particle group 34C was observed, and no aggregation of particles was observed.

  For this reason, the cyan particle group 34C in the display medium 12 produced in Example A8 has the charging characteristics even after being rewritten 1000 times and left in an environment of 25 ° C. and 40% RH for 240 hours, as in Example A1. Thus, it can be said that the change in charging characteristics could be suppressed.

(Example A9)
Display medium 12 was fabricated using the first solvent, insulating particles 36, and particle dispersion prepared in Example A8.
In Example A9, the following cyan cyan particle group 34C mainly composed of a cationic resin different from the cyan particle group 34C prepared in Example A8 was used as the particle group 34. Except for this one point, the display medium 12 was produced in the same manner as in Example A8 and evaluated in the same manner as in Example A1.

-Preparation of particle group 34-
As the particle group 34, a cyan cyan particle group 34C was prepared as follows.

A silicone-modified acrylic polymer KP545 (manufactured by Shin-Etsu Chemical Co., Ltd.) (5 parts by weight) dissolved in dimethyl silicone oil (KF-96-2CS) (95 parts by weight) was prepared as a continuous phase.
Next, polyallylamine (7 parts by weight of Nittobo PAA-15C), cyan pigment dispersion (corresponding to 3 parts by weight of pigment solids) (3 parts by weight) and water (63 parts by weight) were mixed as the resin. Was prepared as a dispersed phase. Further, 80 parts by weight of the continuous phase and 20 parts by weight of the dispersed phase were added and emulsified. The emulsification was performed for 10 minutes with an ultrasonic crusher (UH-600S manufactured by SMT).
The obtained emulsified liquid was put into an eggplant flask, and the water was removed by heating (65 ° C.) and reducing the pressure with an evaporator while stirring to prepare cyan particle group 34C as blue electrophoretic particles.

The volume average primary particle size of the adjusted cyan particle group 34 was measured with a HORIBA LB-550 (dynamic light scattering particle size distribution measuring device), and found to be 356 nm.
Further, when this adjusted cyan particle group 34 was observed with an optical microscope, it was found that particles having a size of 1 mm or more were not observed, and an agglomerate could not be confirmed, so that the dispersion stability was excellent. Further, when observed with a scanning electron microscope (FE-SEM S-5500, manufactured by Hitachi), spherical particles were observed.

  2 parts by weight of this adjusted cyan particle group 34 and 2 parts by weight of a surfactant polyoxyethylene alkyl ether are added to 98 parts by weight of silicone oil (corresponding to the first solvent), and dispersed by stirring to disperse cyan particle group 34C. A dispersion was prepared. The cyan particle group 34C thus produced was positively charged.

Using the display medium 12 produced in Example A9, a voltage of 40 V was applied to both electrodes for 2 seconds so that the surface electrode 40 on the display substrate 20 side was negative and the back electrode 46 on the back substrate 22 was positive. As a result, it was observed that the positively charged cyan particle group 34C was moved to the display substrate 20 side by the electric field generated by the voltage application, and the display medium 12 displayed cyan.
When the density of the display substrate 20 immediately after the voltage of 40 V was applied for 2 seconds was measured with a densitometer (X-Rite 404A, manufactured by X-Rite), a * was −38 and b * was −40.

  Thereafter, a voltage of 40 V was applied to both electrodes so that the surface electrode 40 of the display substrate 20 was positive and the back electrode 46 of the back substrate 22 was negative. As a result, it was observed that the positively charged cyan particle group 34 </ b> C moved to the back substrate 22 side by an electric field by voltage application, and the display medium 12 displayed white.

  Further, after the cyan display and the white display are repeated 1000 times, the display medium 12 is further allowed to stand in an environment of 25 ° C. and 40% RH for 240 hours, and then the surface electrode 40 on the display substrate 20 side is negative again. A voltage of 40 V was applied to both electrodes for 2 seconds so that the back electrode 46 of the substrate 22 was positive. As a result, it was observed that the positively charged cyan particle group 34C was moved to the display substrate 20 side by the electric field generated by the voltage application, and the display medium 12 displayed cyan. When the concentration of the display substrate 20 was measured with a densitometer (X-Rite 404A) immediately after applying a voltage of 40 V for 2 seconds after being left in this 25 ° C. 40% RH environment for 240 hours, a * was −38, b * was −39, and no change in concentration was observed.

  Further, after applying a voltage of 40 V to both electrodes so that the front electrode 40 of the display substrate 20 is positive and the back electrode 46 of the rear substrate 22 is negative, the display substrate 20 is peeled off, and the color density of the display substrate 20 is increased. Was measured, and the L * value was 93, which was not changed before voltage application. Further, no adhesion of the cyan particle group 34C was observed, and no aggregation of particles was observed.

  For this reason, the cyan particle group 34C in the display medium 12 manufactured in Example A9 has the charging characteristics even after being rewritten 1000 times and left in a 25 ° C. 40% RH environment for 240 hours, as in Example A1. Thus, it can be said that the change in charging characteristics could be suppressed.

(Example A10)
Display medium 12 was fabricated using the first solvent, insulating particles 36, and particle dispersion prepared in Example A8.
In Example A10, the following cyan cyan particle group 34C mainly composed of a cationic resin different from the cyan particle group 34C prepared in Example A8 was used as the particle group 34C. Except for this one point, the display medium 12 was produced in the same manner as in Example A8 and evaluated in the same manner as in Example A1.

-Preparation of particle group 34-
As the particle group 34, a cyan cyan particle group 34C was prepared as follows.

A silicone-modified acrylic polymer KP545 (manufactured by Shin-Etsu Chemical Co., Ltd.) (5 parts by weight) dissolved in dimethyl silicone oil (KF-96-2CS) (95 parts by weight) was prepared as a continuous phase.
Next, as a resin, dimethylamine / epichlorohydrin polymer (7 parts by weight of Kayomaster PD-10 manufactured by Yokkaichi Gosei Co., Ltd.), cyan pigment dispersion (equivalent to 3 parts by weight of pigment solids) (3 parts by weight) and water (63 parts) (Part by weight) was prepared as a dispersed phase. Further, 80 parts by weight of the continuous phase and 20 parts by weight of the dispersed phase were added and emulsified. Emulsification was carried out for 10 minutes with an ultrasonic crusher (UH-600S manufactured by SMT).
The obtained emulsified liquid was put into an eggplant flask, and the water was removed by heating (65 ° C.) and reducing the pressure with an evaporator while stirring to prepare cyan particle group 34C as blue electrophoretic particles.

The volume average primary particle size of the adjusted cyan particle group 34C was measured by HORIBA LB-550 (dynamic light scattering type particle size distribution measuring device) and found to be 310 nm.
Further, when this adjusted cyan particle group 34C was observed with an optical microscope, particles of 1 mm or more were not observed, and no agglomerates could be confirmed, indicating that the dispersion stability was excellent. Moreover, spherical particles were observed when observed with a scanning electron microscope (FE-SEM S-5500, manufactured by Hitachi).

  2 parts by weight of the adjusted cyan particle group 34C and 2 parts by weight of the surfactant polyoxyethylene alkyl ether are added to 98 parts by weight of silicone oil (corresponding to the first solvent), and dispersed by stirring to disperse the cyan particle group 34C. A dispersion was prepared. The cyan particle group 34C thus produced was positively charged.

Using the display medium 12 produced in Example A10, a voltage of 40 V was applied to both electrodes for 2 seconds so that the surface electrode 40 on the display substrate 20 side was negative and the back electrode 46 on the back substrate 22 was positive. As a result, it was observed that the positively charged cyan particle group 34C was moved to the display substrate 20 side by the electric field generated by the voltage application, and the display medium 12 displayed cyan.
When the density of the display substrate 20 immediately after the voltage of 40 V was applied for 2 seconds was measured with a densitometer (X-Rite 404A, manufactured by X-Rite), a * was −38 and b * was −40.

  Thereafter, a voltage of 40 V was applied to both electrodes so that the surface electrode 40 of the display substrate 20 was positive and the back electrode 46 of the back substrate 22 was negative. As a result, it was observed that the positively charged cyan particle group 34 </ b> C moved to the back substrate 22 side by an electric field by voltage application, and the display medium 12 displayed white.

  Further, after the cyan display and the white display are repeated 1000 times, the display medium 12 is further allowed to stand in an environment of 25 ° C. and 40% RH for 240 hours, and then the surface electrode 40 on the display substrate 20 side is negative again. A voltage of 40 V was applied to both electrodes for 2 seconds so that the back electrode 46 of the substrate 22 was positive. As a result, it was observed that the positively charged cyan particle group 34C was moved to the display substrate 20 side by the electric field generated by the voltage application, and the display medium 12 displayed cyan. When the concentration of the display substrate 20 was measured with a densitometer (X-Rite 404A) immediately after applying a voltage of 40 V for 2 seconds after being left in this 25 ° C. 40% RH environment for 240 hours, a * was −38, b * was −39, and no change in concentration was observed.

  Further, after applying a voltage of 40 V to both electrodes so that the front electrode 40 of the display substrate 20 is positive and the back electrode 46 of the rear substrate 22 is negative, the display substrate 20 is peeled off, and the color density of the display substrate 20 is increased. Was measured, and the L * value was 93, which was not changed before voltage application. Further, no adhesion of the cyan particle group 34C was observed, and no aggregation of particles was observed.

  For this reason, the cyan particle group 34C in the display medium 12 produced in Example A10 has the charging characteristics even after being rewritten 1000 times and left in an environment of 25 ° C. and 40% RH for 240 hours, as in Example A1. Thus, it can be said that the change in charging characteristics could be suppressed.

(Example A11)
A display medium 12 was produced using the first solvent, the insulating particles 36, and the particle dispersion prepared in Example A3.
In Example A11, as the particle group 34, the cyan particle group 34C prepared in Example A8 containing a cationic resin as a main component was used instead of the magenta particle group 34M prepared in Example A3. . Further, as the amino-modified silicone oil, TSF4708 manufactured by GE Toshiba Silicone, which is a side chain type amino-modified silicone oil, was used. Except for these two points, the display medium 12 was produced in the same manner as in Example A3 and evaluated in the same manner as in Example A3.

Using the display medium 12 produced in Example A11, a voltage of 40 V was applied to both electrodes for 2 seconds so that the surface electrode 40 on the display substrate 20 side was negative and the back electrode 46 of the back substrate 22 was positive. As a result, it was observed that the positively charged cyan particle group 34C was moved to the display substrate 20 side by the electric field generated by the voltage application, and the display medium 12 displayed cyan.
When the density of the display substrate 20 immediately after the voltage of 40 V was applied for 2 seconds was measured with a densitometer (X-Rite 404A, manufactured by X-Rite), a * was −38 and b * was −40.

  Thereafter, a voltage of 40 V was applied to both electrodes so that the surface electrode 40 of the display substrate 20 was positive and the back electrode 46 of the back substrate 22 was negative. As a result, it was observed that the positively charged cyan particle group 34 </ b> C moved to the back substrate 22 side by an electric field by voltage application, and the display medium 12 displayed white.

  Further, after the cyan display and the white display are repeated 1000 times, the display medium 12 is further allowed to stand in an environment of 25 ° C. and 40% RH for 240 hours, and then the surface electrode 40 on the display substrate 20 side is negative again. A voltage of 40 V was applied to both electrodes for 2 seconds so that the back electrode 46 of the substrate 22 was positive. As a result, it was observed that the positively charged cyan particle group 34C was moved to the display substrate 20 side by the electric field generated by the voltage application, and the display medium 12 displayed cyan. When the concentration of the display substrate 20 was measured with a densitometer (X-Rite 404A) immediately after applying a voltage of 40 V for 2 seconds after being left in this 25 ° C. 40% RH environment for 240 hours, a * was −38, b * was −38, and almost no change in concentration was observed.

  Further, after applying a voltage of 40 V to both electrodes so that the front electrode 40 of the display substrate 20 is positive and the back electrode 46 of the rear substrate 22 is negative, the display substrate 20 is peeled off, and the color density of the display substrate 20 is increased. Was measured, and the L * value was 93, which was not changed before voltage application. Further, no adhesion of the cyan particle group 34C was observed, and no aggregation of particles was observed.

For this reason, the cyan particle group 34C in the display medium 12 produced in Example A11 has the charging characteristics even after being rewritten 1000 times and left in an environment of 25 ° C. and 40% RH for 240 hours, as in Example A1. Thus, it can be said that the change in charging characteristics could be suppressed.

(Example A12)
Display medium 12 was fabricated using the first solvent, insulating particles 36, and particle dispersion prepared in Example A8.
In Example A12, the following cyan cyan particle group 34C mainly composed of an anionic resin was used as the particle group 34 instead of the cyan particle group 34C prepared in Example A8. Except for this one point, the display medium 12 was produced in the same manner as in Example A8 and evaluated in the same manner as in Example A8.

-Preparation of particle group 34-
As the particle group 34, a cyan cyan particle group 34C was prepared.

A solution BA was prepared by dissolving 5 parts by weight of a silicone-modified acrylic polymer (KP545 manufactured by Shin-Etsu Chemical Co., Ltd.) in 95 parts by weight of dimethyl silicone oil (KF-96-2CS manufactured by Shin-Etsu Chemical Co., Ltd.). Next, 7 parts by weight of an anionic acrylic resin (AW-36H manufactured by Starlight PMC), 3 parts by weight of cyan pigment dispersion (Emacol manufactured by Sanyo Dye Co., Ltd .: equivalent to 20 parts by weight of pigment solid content), and 63 parts by weight of water were added. Solution BB was prepared by mixing. 80 parts by weight of the solution BA and 20 parts by weight of the solution BB were mixed and emulsified with an ultrasonic crusher (UH-600S manufactured by SMT Corporation) for 10 minutes.
Next, the obtained emulsion was heated (65 ° C.) and reduced pressure (10 mPa) with an evaporator while stirring to obtain a particle dispersion in which cyan cyan particle group 34C was dispersed in silicone oil. The obtained cyan particle group 34C had a volume average particle size of 500 nm. The cyan particle group 34C thus produced was negatively charged.

Using the display medium 12 produced in Example A12, a voltage of 50 V was applied to both electrodes for 2 seconds so that the surface electrode 40 on the display substrate 20 side was positive and the back electrode 46 on the back substrate 22 was negative. As a result, it was observed that the negatively charged cyan particle group 34C was moved to the display substrate 20 side by the electric field generated by the voltage application, and the display medium 12 displayed cyan.
When the concentration of the display substrate 20 immediately after the 50 V voltage was applied for 2 seconds was measured with a densitometer (X-Rite 404A, manufactured by X-Rite), a * was −38 and b * was −40.

  Thereafter, a voltage of 50 V was applied to both electrodes so that the surface electrode 40 of the display substrate 20 was negative and the back electrode 46 of the back substrate 22 was positive. As a result, it was observed that the negatively charged cyan particle group 34C was moved to the back substrate 22 side by the electric field by voltage application, and the display medium 12 displayed white.

  Further, after the cyan display and the white display are repeated 1000 times, the display medium 12 is further allowed to stand in an environment of 25 ° C. and 40% RH for 240 hours, and then the surface electrode 40 on the display substrate 20 side is added again. A voltage of 50V was applied to both electrodes for 2 seconds so that the back electrode 46 of the substrate 22 was negative. As a result, it was observed that the negatively charged cyan particle group 34C was moved to the display substrate 20 side by the electric field generated by the voltage application, and the display medium 12 displayed cyan. When the concentration of the display substrate 20 was measured with a densitometer (X-Rite 404A) immediately after applying a voltage of 50 V for 2 seconds after being left in this 25 ° C. and 40% RH environment for 240 hours, a * was −38, b * was −38, and no change in concentration was observed.

  Further, after applying a voltage of 50 V to both electrodes so that the surface electrode 40 of the display substrate 20 is negative and the back electrode 46 of the rear substrate 22 is positive, the display substrate 20 is peeled off and the color density of the display substrate 20 is increased. Was measured, and the L * value was 93, which was not changed before voltage application. Further, no adhesion of the cyan particle group 34C was observed, and no aggregation of particles was observed.

  For this reason, the cyan particle group 34C in the display medium 12 produced in Example A12 has the charging characteristics even after being rewritten 1000 times and left in an environment of 25 ° C. and 40% RH for 240 hours as in Example A1. Thus, it can be said that the change in charging characteristics could be suppressed.

(Example A13)
The display medium 12 was prepared in the same manner as in Example A12 except that each cell (in the particle dispersion) of the display medium 12 produced in Example A12 described above further contained the following particles as second particles. It produced and evaluated similarly to Example A12.

-Adjustment of the second particle group-
The following particles were prepared as the second particle group.

  Solution A (continuous phase) by dissolving 5 parts by weight of silicone-modified acrylic polymer (KP545 manufactured by Shin-Etsu Chemical Co., Ltd.) as an emulsifier in 95 parts by weight of dimethyl silicone oil (KF-96-2CS manufactured by Shin-Etsu Chemical Co., Ltd.) as a poor solvent. Adjusted. Next, 7 parts by weight of cationized polyvinyl alcohol (K-210 manufactured by Nippon Synthetic Chemical Co., Ltd.) and 100 parts by weight of water as a good solvent were mixed to prepare Solution B (dispersed phase). Emulsification was carried out by mixing 80 parts by weight of Solution A and 20 parts by weight of Solution B to prepare an emulsion. The emulsification was performed for 20 minutes with an ultrasonic crusher (UH-600S manufactured by SMT).

  Next, the obtained emulsion is put into an eggplant flask and heated (65 ° C.) / Depressurized (10 mPa) with an evaporator while stirring to remove moisture (good solvent), and colorless particles are dispersed in silicone oil. A particle dispersion was obtained. The particle dispersion was centrifuged and precipitated, and then redispersed in the silicone oil to obtain a particle dispersion in which the second particle group was dispersed in the silicone oil. The obtained second particle group had a volume average particle diameter of 50 nm. Further, this second particle group was positively charged.

  The above-prepared second particle group was observed with an optical microscope, but particles of 1 mm or more were not observed, and agglomerates could not be confirmed. Therefore, the prepared second particle group was excellent in dispersion stability. I found out. When observed with a scanning electron microscope (FE-SEM S-5500, manufactured by Hitachi), spherical particles were observed. Moreover, when measured by HORIBA LB-550 (dynamic light scattering type particle size distribution measuring device), the average particle size was 50 nm.

Using the display medium 12 produced in Example A13, a voltage of 50 V was applied to both electrodes for 2 seconds so that the surface electrode 40 on the display substrate 20 side was positive and the back electrode 46 on the back substrate 22 was negative. As a result, it was observed that the negatively charged cyan particle group 34C was moved to the display substrate 20 side by the electric field generated by the voltage application, and the display medium 12 displayed cyan.
When the concentration of the display substrate 20 immediately after the 50 V voltage was applied for 2 seconds was measured with a densitometer (X-Rite 404A, manufactured by X-Rite), a * was −38 and b * was −40.

  Thereafter, a voltage of 50 V was applied to both electrodes so that the surface electrode 40 of the display substrate 20 was negative and the back electrode 46 of the back substrate 22 was positive. As a result, it was observed that the negatively charged cyan particle group 34C was moved to the back substrate 22 side by the electric field by voltage application, and the display medium 12 displayed white.

  Further, after the cyan display and the white display are repeated 1000 times, the display medium 12 is further allowed to stand in an environment of 25 ° C. and 40% RH for 240 hours, and then the surface electrode 40 on the display substrate 20 side is added again. A voltage of 50V was applied to both electrodes for 2 seconds so that the back electrode 46 of the substrate 22 was negative. As a result, it was observed that the negatively charged cyan particle group 34C was moved to the display substrate 20 side by the electric field generated by the voltage application, and the display medium 12 displayed cyan. When the concentration of the display substrate 20 was measured with a densitometer (X-Rite 404A) immediately after applying a voltage of 50 V for 2 seconds after being left in this 25 ° C. and 40% RH environment for 240 hours, a * was −38, b * was −40, and almost no change in concentration was observed.

  Further, after applying a voltage of 50 V to both electrodes so that the surface electrode 40 of the display substrate 20 is negative and the back electrode 46 of the rear substrate 22 is positive, the display substrate 20 is peeled off and the color density of the display substrate 20 is increased. Was measured, and the L * value was 93, which was not changed before voltage application. Further, no adhesion of the cyan particle group 34C was observed, and no aggregation of particles was observed.

  For this reason, the cyan particle group 34C in the display medium 12 produced in Example A13 has the charging characteristics even after being rewritten 1000 times and left in an environment of 25 ° C. and 40% RH for 240 hours, as in Example A1. Thus, it can be said that the change in charging characteristics could be suppressed.

(Example A14)
The display medium 12 was prepared in the same manner as in Example A8, except that each cell (in the particle dispersion) of the display medium 12 produced in Example A8 described above further contained the following particles as second particles. It produced and evaluated like Example A8.

-Adjustment of the second particle group-
The following particles were prepared as the second particle group.

  Solution A (continuous phase) by dissolving 5 parts by weight of silicone-modified acrylic polymer (KP545 manufactured by Shin-Etsu Chemical Co., Ltd.) as an emulsifier in 95 parts by weight of dimethyl silicone oil (KF-96-2CS manufactured by Shin-Etsu Chemical Co., Ltd.) as a poor solvent. Adjusted. Next, 7 parts by weight of anionic polyvinyl alcohol “Poval KM-618” and 100 parts by weight of water as a good solvent were mixed to prepare Solution B (dispersed phase). Emulsification was carried out by mixing 80 parts by weight of Solution A and 20 parts by weight of Solution B to prepare an emulsion. The emulsification was performed for 20 minutes with an ultrasonic crusher (UH-600S manufactured by SMT).

  Next, the obtained emulsion is put into an eggplant flask and heated (65 ° C.) / Depressurized (10 mPa) with an evaporator while stirring to remove moisture (good solvent), and colorless particles are dispersed in silicone oil. A particle dispersion was obtained. The particle dispersion was centrifuged and precipitated, and then redispersed in the silicone oil to obtain a particle dispersion in which the second particle group was dispersed in the silicone oil. The obtained second particle group had a volume average particle diameter of 30 nm. In addition, this second particle group was negatively charged.

  The above-prepared second particle group was observed with an optical microscope, but particles of 1 mm or more were not observed, and agglomerates could not be confirmed. Therefore, the prepared second particle group was excellent in dispersion stability. I found out. When observed with a scanning electron microscope (FE-SEM S-5500, manufactured by Hitachi), spherical particles were observed. Moreover, when measured by HORIBA LB-550 (dynamic light scattering type particle size distribution measuring device), the average particle size was 30 nm.

Using the display medium 12 produced in Example A14, a voltage of 50 V was applied to both electrodes for 2 seconds so that the surface electrode 40 on the display substrate 20 side was negative and the back electrode 46 on the back substrate 22 was positive. As a result, it was observed that the positively charged cyan particle group 34C was moved to the display substrate 20 side by the electric field generated by the voltage application, and the display medium 12 displayed cyan.
When the concentration of the display substrate 20 immediately after the 50 V voltage was applied for 2 seconds was measured with a densitometer (X-Rite 404A, manufactured by X-Rite), a * was −38 and b * was −40.

  Thereafter, a voltage of 50 V was applied to both electrodes so that the surface electrode 40 of the display substrate 20 was positive and the back electrode 46 of the back substrate 22 was negative. As a result, it was observed that the positively charged cyan particle group 34 </ b> C moved to the back substrate 22 side by an electric field by voltage application, and the display medium 12 displayed white.

  Further, after the cyan display and the white display are repeated 1000 times, the display medium 12 is further allowed to stand in an environment of 25 ° C. and 40% RH for 240 hours, and then the surface electrode 40 on the display substrate 20 side is negative again. A voltage of 50 V was applied to both electrodes for 2 seconds so that the back electrode 46 of the substrate 22 was positive. As a result, it was observed that the positively charged cyan particle group 34C was moved to the display substrate 20 side by the electric field generated by the voltage application, and the display medium 12 displayed cyan. When the concentration of the display substrate 20 was measured with a densitometer (X-Rite 404A) immediately after applying a voltage of 50 V for 2 seconds after being left in this 25 ° C. and 40% RH environment for 240 hours, a * was −38, b * was −40, and no change in concentration was observed.

  Further, after applying a voltage of 50 V to both electrodes so that the surface electrode 40 of the display substrate 20 is positive and the back electrode 46 of the rear substrate 22 is negative, the display substrate 20 is peeled off, and the color density of the display substrate 20 is increased. Was measured, and the L * value was 93, which was not changed before voltage application. Further, no adhesion of the cyan particle group 34C was observed, and no aggregation of particles was observed.

  For this reason, the cyan particle group 34C in the display medium 12 manufactured in Example A14 has the charging characteristics even after being rewritten 1000 times and left in an environment of 25 ° C. and 40% RH for 240 hours as in Example A1. Thus, it can be said that the change in charging characteristics could be suppressed.

(Example A15)
Example A1 except that the second particles obtained in Example A13 were further contained as the second particles in each cell (in the particle dispersion) of the display medium 12 produced in Example A1. A display medium 12 was produced in the same manner as in Example 1, and evaluated in the same manner as in Example A1.

Using the display medium 12 produced in Example A15, a voltage of 50 V was applied to both electrodes for 2 seconds so that the surface electrode 40 on the display substrate 20 side was positive and the back electrode 46 on the back substrate 22 was negative. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the display substrate 20 side by an electric field generated by voltage application, and the display medium 12 displayed a magenta color.
When the concentration of the display substrate 20 immediately after the 50 V voltage was applied for 2 seconds was measured with a densitometer (X-Rite 404A, manufactured by X-Rite), a * was 39 and b * was 0.

  Thereafter, a voltage of 50 V was applied to both electrodes so that the surface electrode 40 of the display substrate 20 was negative and the back electrode 46 of the back substrate 22 was positive. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the back substrate 22 side by an electric field generated by voltage application, and the display medium 12 displayed white.

  Further, after repeating the magenta color display and the white display 1000 times, the display medium 12 is further left in an environment of 25 ° C. and 40% RH for 240 hours. A voltage of 50V was applied to both electrodes for 2 seconds so that the back electrode 46 of the substrate 22 was negative. As a result, it was observed that the negatively charged magenta particle group 34M was moved to the display substrate 20 side by an electric field generated by voltage application, and the display medium 12 displayed a magenta color. When the concentration of the display substrate 20 was measured with a densitometer (X-Rite 404A) immediately after applying a voltage of 50 V for 2 seconds after being left in this 25 ° C. and 40% RH environment for 240 hours, a * was 39, b * was 0, and no change in concentration was observed.

  Further, after applying a voltage of 50 V to both electrodes so that the surface electrode 40 of the display substrate 20 is negative and the back electrode 46 of the rear substrate 22 is positive, the display substrate 20 is peeled off and the color density of the display substrate 20 is increased. Was measured, and the L * value was 93, which was not changed before voltage application. Further, no adhesion of the magenta particle group 34M was observed, and no aggregation of particles was observed.

  For this reason, the magenta particle group 34M in the display medium 12 produced in Example A15 has the charging characteristics even after being rewritten 1000 times and left in an environment of 25 ° C. and 40% RH for 240 hours as in Example A1. Thus, it can be said that the change in charging characteristics could be suppressed.

  The results are summarized in Table 1 below.

[Example B]
(Example B1)
As shown below, an image display device having the same configuration as that of the image display device according to the second embodiment was manufactured (see FIG. 1).

-Preparation of particle dispersion of yellow particle group 34Y-
A particle dispersion liquid in which the yellow particle group 34Y was dispersed in silicone oil was produced in the same manner as in Example A1, except that Microlith Y-4G-K (manufactured by Ciba) was used as the yellow pigment.

-Preparation of Cyan Particle Group 34C Particle Dispersion-
A particle dispersion in which cyan particle group 34C was dispersed in silicone oil was prepared in the same manner as in Example A1, except that cyanine blue 4933M (manufactured by Dainichi Seika Co., Ltd.) was used as the cyan pigment.

-Preparation of particle dispersion of magenta particle group 34M-
As the particle dispersion liquid of the magenta particle group 34M, the dispersion liquid of the magenta particle group 34M produced in Example A1 was used.

  Instead of the magenta particle group 34M and the first solvent prepared in Example A1, the particle dispersion of the yellow particle group 34Y, the particle dispersion of the cyan particle group 34C, and the particle dispersion of the magenta particle group 34M were prepared. A display medium 12 was produced in the same manner as in Example A1 using the insulating particles 36 prepared in Example A1 except that was used.

  Next, the electrode of the display substrate of the obtained display medium 12 was connected to a product name Trek 610C manufactured by Trek as the voltage application unit 16, and the electrode of the back substrate was grounded. Further, a personal computer (trade name CF-R1 manufactured by Panasonic Corporation) was connected to the voltage application unit 16 as a machine having the function of the control unit 18.

An image display device was produced as described above.
Here, the absolute value | Vty | of the voltage when the yellow particle group 34Y starts moving was 50V, and the absolute value | Vdy | of the maximum voltage for moving almost all of the yellow particle group 34Y was 53V. .
Further, the absolute value | Vtm | of the voltage when the magenta particle group 34M starts moving was 34V, and the absolute value | Vdm | of the maximum voltage for moving almost all the magenta particle group 34M was 38V.
Further, the absolute value | Vtc | of the voltage when the cyan particle group 34C starts moving was 20V, and the absolute value | Vdc | of the maximum voltage for moving almost all the cyan particle group 34C was 24V.
Then, as described with reference to FIG. 3, when the voltage applied between the substrates is controlled, the particle group 34 of each color is selectively moved according to the color to be displayed, and a desired color can be displayed. It was.

  Further, after the display medium 12 manufactured in Example B1 was left in an environment of 25 ° C. and 40% RH for 240 hours, the voltage applied between the substrates was controlled in the same manner as described above. The particles 34 were selectively moved to display a desired color.

It is a schematic block diagram of the display medium and display apparatus which concern on 2nd Embodiment. It is a diagram which shows typically the relationship between the voltage to apply and the moving amount (display density | concentration) of particle | grains. 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.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Display apparatus 12 Display medium 16 Voltage application part 34 Particle group 34C Cyan particle group 34Y Yellow particle group 34M Magenta particle group 50 Particle dispersion

Claims (19)

  A particle dispersion characterized by containing a first solvent containing at least one of a silicone oil and a paraffinic hydrocarbon solvent, and an amino-modified silicone oil, in which a group of particles moving according to an electric field is dispersed.   The particle dispersion according to claim 1, wherein the amino-modified silicone oil is a side-chain amino-modified silicone oil having an amino group in a side chain.   The particle dispersion according to claim 1, wherein the particle group includes an anionic resin as a main component.   The particle dispersion according to claim 1, wherein the particle group includes a cationic resin as a main component.   2. The particle dispersion according to claim 1, wherein a second particle group that is smaller than the volume average primary particle size of the particle group and adheres to a surface of the particle group is further dispersed. A pair of substrates, at least one of which is translucent,
A particle dispersion containing a first solvent encapsulated between the pair of substrates and containing at least one of at least one of a silicone oil and a paraffinic hydrocarbon solvent; and an amino-modified silicone oil;
A group of particles dispersed in the particle dispersion and moving according to an electric field;
A display medium comprising:   The display medium according to claim 6, wherein the amino-modified silicone oil is a side-chain amino-modified silicone oil having an amino group in a side chain.   The display medium according to claim 6, wherein the particle group includes an anionic resin as a main component.   The display medium according to claim 6, wherein the particle group includes a cationic resin as a main component.   The display according to claim 6, further comprising a second particle group that is dispersed in the particle dispersion and is smaller than a volume average primary particle size of the particle group and adheres to a surface of the particle group. Medium.   7. The particle group according to claim 6, wherein the particle group includes a plurality of kinds of particles colored in different colors while having different absolute values of voltages necessary for moving according to an electric field. Display medium.   The display medium according to claim 11, wherein the plurality of types of particles have a voltage range necessary for moving according to an electric field for each type, and the voltage ranges are different from each other. A pair of substrates, at least one of which has translucency, a first solvent that is sealed between the pair of substrates and includes at least one of a silicone oil and a paraffinic hydrocarbon solvent, and an amino-modified silicone oil A display medium comprising: a particle dispersion liquid; and particles dispersed in the particle dispersion liquid and moving according to an electric field;
Voltage applying means for applying a voltage between the pair of substrates of the display medium;
A display device comprising:   The display device according to claim 13, wherein the amino-modified silicone oil is a side-chain amino-modified silicone oil having an amino group in a side chain.   The display device according to claim 13, wherein the particle group includes an anionic resin as a main component.   The display device according to claim 13, wherein the particle group includes a cationic resin as a main component.   The display medium further includes a second particle group that is dispersed in the particle dispersion and is smaller than the volume average primary particle size of the particle group and adheres to a surface of the particle group. The display device described in 1.   14. The particle group according to claim 13, wherein the particle group includes a plurality of types of particles that have different absolute values of voltages necessary for moving according to an electric field and are colored in different colors. Display device.   19. The display device according to claim 18, wherein the plurality of types of particles have a voltage range necessary for moving according to an electric field for each type, and the voltage ranges are different from each other.