JP5499438B2 - Display particles and manufacturing method thereof, display particle dispersion, display medium, and display device - Google Patents

Description

  The present invention relates to a display particle and a method for producing the same, a display particle dispersion, a display medium, and a display device.

  An electrophoretic display medium has been actively studied as a display having a memory property. In this display method, an electrophoretic material in which charged display particles (electrophoretic particles) are dispersed in a liquid is used, and the electrophoretic particles are placed in the cell by applying an electric field (two electrophoretic substrates are stacked between the electrophoretic materials). The display can be performed by alternately moving to the viewing surface and the back surface of the structure in which is enclosed.

  In the present technology, the electrophoretic material is an important element, and various technical developments have been made. In addition, as a liquid for dispersing particles, a material having low volatility and high safety as a chemical substance is desired. Such highly safe liquids include paraffinic hydrocarbon solvents that are petroleum-derived high-boiling components (including commercially available products such as Isopar materials manufactured by Exxon), silicone oils, fluorine-based liquids, etc. Therefore, a material that is stably dispersed in such a liquid and has excellent chargeability and electrophoretic properties is required. In particular, silicone oil is useful because it has low volatility and flammability and high safety.

However, at present, a material system that is stably dispersed in silicone oil and has stable charging characteristics is not well known. As a prior art, for example, a technique using a silicone-based charge control polymer dispersant has been proposed in Patent Documents 1 and 2, and as an electrophoretic particle using a coacervation method, Patent Document 3 is known, A configuration containing a charge adjusting agent as electrophoretic particles dispersed in silicone oil is disclosed.
Japanese Patent No. 3936588 JP 2002-212423 A JP 2004-279732 A

  For example, in a technique using a silicone-based charge control polymer dispersant, it is difficult to achieve both dispersion and charge stability because the dispersant functions as a uniform dispersion of particles and at the same time as a counter ion of migrating particles. It was. In order to realize a system in which a plurality of color particles having different charging polarities are mixed in the same system for the purpose of multicolor display (some display particles are positively charged and display particles of a different color are negatively charged) Dispersing agents with different polar groups (acids and bases) are mixed with particles with different charging polarities, which may cause acid-salt reactions between the dispersing agents, causing the particles to aggregate or deteriorate the charging characteristics. is there. On the other hand, in the technology using the coacervation method, it is essential to include a charge control agent in the particles. However, the charge control agent is eluted in the silicone oil as a dispersion medium, and the distribution in the particles is biased. This may cause the charging characteristics to become unstable. Furthermore, electrophoretic materials composed of particles of conventional polymer materials have an improved method of introducing a crosslinked structure because the heat resistance of the particles used is low, but there is a problem that the degree of freedom in material design and manufacturability are reduced. It was.

  An object of the present application is to provide display particles having stable dispersibility, charging characteristics, and heat resistance, and a method for producing the same. Another object of the present invention is to provide a display particle dispersion, a display medium, and a display device using the display particles.

The above problem is solved by the following means. That is,
The invention according to claim 1
Containing a water-soluble polymer having a charged group and a colorant;
The display particles are characterized in that the water-soluble polymer comprises at least a monomer component that becomes a silicone chain at a mass ratio of 20% or less with respect to the whole polymer as a copolymer component.

The invention according to claim 2
A group of particles that move in response to an electric field and include the display particles according to claim 1;
Silicone oil as a dispersion medium for dispersing the particles;
A particle dispersion for display, comprising:

The invention according to claim 3
The display particle dispersion according to claim 2, wherein the dispersion medium is a silicone oil in which a hydrocarbon group is bonded to a siloxane bond, or a modified silicone oil .

The invention according to claim 4
The display particle dispersion according to claim 2, wherein the particle group is composed of a plurality of types of display particles having different charging polarities.

The invention according to claim 5
The plurality of types of display particles child includes the display particles containing the water-soluble polymer having a quaternary ammonium group as the charging group, the water-soluble polymer having a salt of an acid group as the charging group The display particle dispersion according to claim 4, comprising the display particles.

The invention according to claim 6
A pair of substrates, at least one of which is translucent,
The display particle dispersion according to any one of claims 2 to 5, encapsulated between the pair of substrates,
A display medium comprising:

The invention according to claim 7 provides:
A pair of electrodes, at least one of which is translucent,
The display particle dispersion according to any one of claims 2 to 5, which is held between the pair of electrodes,
A display medium comprising:

The invention according to claim 8 provides:
A display medium according to claim 6;
Voltage applying means for applying a voltage between the pair of substrates of the display medium;
A display device comprising:

The invention according to claim 9 is:
And a water-soluble polymer having a charging group, a colorant, an emulsifier, a first solvent consisting of silicone oil, the boiling point than the first solvent incompatible is the first solvent low and the charging group A step of stirring and emulsifying a mixed solution containing a second solvent that dissolves the aqueous polymer having
Removing the second solvent from the emulsified mixed solution;
Have
A method for producing display particles, characterized in that the water-soluble polymer comprises at least a monomer component that becomes a silicone chain as a copolymer component.

The invention according to claim 10 is:
The method for producing display particles according to claim 9, wherein the first solvent is a silicone oil in which a hydrocarbon group is bonded to a siloxane bond, or a modified silicone oil .

The invention according to claim 1 provides display particles having stable dispersibility, charging characteristics, and heat resistance.
According to the second aspect of the invention, a display particle dispersion having stable dispersibility, charging characteristics and heat resistance is provided.
According to the third aspect of the invention, in particular, a display particle dispersion in which deterioration of charging characteristics is suppressed is provided.
The invention according to claim 4 provides a display particle dispersion having stable dispersibility and charging characteristics even in a system in which a plurality of types of display particles having different charging polarities are mixed. According to the invention of claim 5, in particular, among the plurality of types of display particles having different charging polarities, the display particles having different charging polarities due to the quaternary ammonium group and the acid group salt as the charging group are used. Thus, a display particle dispersion having stable dispersibility and charging characteristics is provided.
According to the invention which concerns on Claim 6, the display medium which can be displayed repeatedly and stably is provided.
According to the invention which concerns on Claim 7, the display medium which can display stably repeatedly is provided.
According to the eighth aspect of the present invention, there is provided a display device capable of displaying repeatedly and stably.
According to the invention of claim 9, display particles having stable dispersibility and charging characteristics can be obtained. Further, the dispersion medium can be used as a silicone oil display particle dispersion without undergoing washing and drying processes.
According to the tenth aspect of the invention, in particular, a display particle dispersion in which deterioration of charging characteristics is suppressed can be obtained.

  Hereinafter, embodiments of the present invention will be described.

(Display particles, display particle dispersion)
The display particle dispersion according to this embodiment includes a particle group including display particles that move in response to an electric field, and silicone oil as a dispersion medium for dispersing the particle group. The display particles (display particles according to this embodiment) include a water-soluble polymer having a charged group and a colorant, and the water-soluble polymer includes at least a monomer component having the charge group. It comprises a monomer component that becomes a silicone chain as a copolymer component.
However, in the particle dispersion for display according to the present embodiment (display particles according to the present embodiment), the monomer component to be a silicone chain has a mass ratio of 20% or less with respect to the whole polymer and is highly soluble in water. Included in the molecule as a copolymerization component.

The display particles according to the present embodiment are particles that move according to an electric field, have charging characteristics when dispersed in a dispersion medium, and move within the dispersion medium according to the formed electric field. is there. The display particles (display particle dispersion) according to the present embodiment are particles having stable dispersibility, charging characteristics, and heat resistance by adopting the above configuration. Here, the charging characteristics indicate the charge polarity and charge amount of the particles. In this embodiment, fluctuations in the charge polarity and charge amount are suppressed and stabilized.

  Here, since the display particles according to the present embodiment have the above characteristics, in the display particle dispersion, the particle group including the particles includes a plurality of types of display particles having different charging polarities, that is, the present embodiment. Whether the display particles are composed of a plurality of types of display particles having different charging polarities or a system in which a plurality of types of display particles having different charging polarities are mixed, stable dispersibility and charging characteristics are maintained. A plurality of types of display particles having different charging polarities can be obtained, for example, by changing the charging group of a polymer having a charging group described later.

  And as a plurality of types of display particles having different charging polarities, the display particles containing the water-soluble polymer having a quaternary ammonium group as the charging group, and a water-soluble high particle having an acid group salt as the charging group. When the display particles containing molecules are used, particularly stable dispersibility and charging characteristics are maintained.

  First, the display particles will be described. The display particles include a water-soluble polymer having a charged group, a colorant, and, if necessary, other compounding materials.

  The water-soluble polymer having a charged group is a polymer having, for example, a cationic group or an anionic group as a charged group. Examples of the cationic group as the charged group include an amine group and a quaternary ammonium group (including salts of these groups), and positively charged polarity is imparted to the particles by the cationic group. On the other hand, examples of the anionic group as the charging group include a carboxyl group, a carboxylate group, a sulfonate group, a sulfonate group, a phosphate group, and a phosphate group (including salts of these groups). The negatively charged polarity is imparted to the particles by the anionic group.

  And the water-soluble polymer which has a charging group is comprised including the monomer component used as a silicone chain as a copolymerization component at least. Specifically, the water-soluble polymer having a charged group includes, for example, a monomer component that becomes a silicone chain, a monomer component having a charged group, and another monomer component as at least a copolymer component. Examples include polymers that are constructed. That is, the water-soluble polymer having a charging group is preferably a copolymer obtained by copolymerizing a monomer that becomes a silicone chain, a monomer having a charging group, and another monomer component. .

  Examples of the monomer that becomes a silicone chain include a silicone-based monomer, for example, a silicone macromonomer that is a structure having a long-chain silicone chain and a polymerizable group (vinyl group). Various methods for synthesizing macromonomers have been proposed and can be synthesized by living polymerization or group transfer polymerization. In addition, silicone compounds having a reactive epoxy group or amino group at the terminal can also be mentioned. Among these, dimethyl silicone monomers having a methacrylate group at one end (for example, manufactured by Chisso: Silaplane “FM-0711”, “FM-0721”, from the point that stable dispersibility and charging characteristics can be imparted) “FM-0725”, etc., manufactured by Shin-Etsu Chemical Co., Ltd .: “X-22-174DX”, “X-22-2426”, “X-22-2475”, etc.), silicone monomers having an epoxy group at one end (for example, Shin-Etsu Chemical Co., Ltd .: “X-22-173DX” and the like).

  Examples of the monomer having a charging group include a monomer having a cationic group (hereinafter referred to as a cationic monomer) and a monomer having an anionic group (hereinafter referred to as an anionic monomer).

Examples of the cationic monomer 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, aromatic substituted ethylene monomers having nitrogen-containing groups 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 Nitrogen-containing vinyl ether monomers such as
Pyrrols such as N-vinylpyrrole, pyrrolines such as N-vinyl-2-pyrroline and N-vinyl-3-pyrroline, pyrrolidines such as N-vinylpyrrolidine, vinylpyrrolidine aminoether, and N-vinyl-2-pyrrolidone Imidazoles such as N-vinyl-2-methylimidazole, imidazolines such as N-vinylimidazoline, indoles such as N-vinylindole, indolines such as N-vinylindoline, N-vinylcarbazole, 3, 6 -Carbazoles such as dibromo-N-vinylcarbazole, pyridines such as 2-vinylpyridine, 4-vinylpyridine, 2-methyl-5-vinylpyrazine, (meth) acrylic piperidine, N-vinylpiperidone, N-vinylpiperazine, etc. Piperidines, 2-vinylquinoline, 4-vinylquinoline Particularly preferred are quinolines such as N-vinylpyrazole and N-vinylpyrazoline, oxazoles such as 2-vinyloxazole, oxazines such as 4-vinyloxazine and morpholinoethyl (meth) acrylate.
Moreover, as a particularly preferable cationic monomer from versatility, (meth) acrylates having an aliphatic amino group such as N, N-dimethylaminoethyl (meth) acrylate and N, N-diethylaminoethyl (meth) acrylate In particular, it is preferable to use a quaternary ammonium salt structure before or after polymerization. Quaternary ammonium chloride can be obtained by reacting the above compound with alkyl halides or tosylate esters.

On the other hand, as an anionic monomer, the following are mentioned, for example.
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) click acid ester, bis- (3-sulfopropyl) -itaconic acid ester, and salts thereof. There is. In addition, there are sulfuric acid monoesters of 2-hydroxyethyl (meth) acrylic acid and salts thereof.
Examples of phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, acid phosphoxyethyl (meth) acrylate, acid phosphoxypropyl (meth) acrylate, bis (methacryloxyethyl) phosphate, diphenyl-2-methacryloyloxyethyl phosphate, diphenyl There are 2-acryloyloxyethyl phosphate, dibutyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, dioctyl-2- (meth) acryloyloxyethyl phosphate, and the like.
Preferred anionic monomers are those having (meth) acrylic acid or sulfonic acid, and more preferably those having a structure in which an ammonium salt is formed before or after polymerization. Ammonium salts can be prepared by reacting with tertiary amines or quaternary ammonium hydroxides.

  Examples of other monomers include water-soluble monomers (for example, monomers having a hydroxyl group). Specific examples include hydroxyethyl (meth) acrylate and hydroxybutyl (meta ) Acrylate, glyceryl (meth) acrylate, monomers having ethylene oxide-based units (for example, (meth) acrylate of alkyloxyoligoethylene glycol such as tetraethylene glycol monomethyl ether (meth) acrylate, one-end (meth) acrylate of polyethylene glycol), Examples include dimethyl (meth) acrylamide, (meth) acrylamide, vinyl pyrrolidone, vinyl pyridine and the like. It is also possible to copolymerize a predetermined amount of other monomers having low water solubility other than these, and other well-known nonionic such as (meth) acrylic acid alkyl esters, styrene, styrene derivatives, etc. Monomer.

Here, “water-soluble” of a water-soluble polymer having a charged group is defined as a property that does not cause precipitation when dissolved at 10% by mass in water at 20 ° C. Depending on the type of water-soluble polymer, it may become cloudy, but if it does not precipitate, it is in a dissolved state.
In order for the water-soluble polymer having a charged group to be water-soluble, in particular, the mass ratio of the monomer component serving as a silicone chain to the entire polymer is 20% or less, preferably 15%. The following is desirable. On the other hand, from the viewpoint of imparting stable dispersibility and charging characteristics to the particles, the monomer component serving as the silicone chain is 1% or more, preferably 5% or more in terms of the mass ratio of the whole polymer. desirable.
Further, in the water-soluble polymer having a charged group, the ratio of the monomer component having a charged group and the other monomer component contained together with the monomer component that becomes a silicone chain is the mass ratio (a single unit that becomes a silicon chain). Monomer component: charged monomer group component: other monomer component) in the range of 1: 1: 98 to 20: 80: 0, preferably 5: 5: 90 to 20: 80: 0. A range is desirable. The charge amount of the desired particles is adjusted by the ratio of the monomer component having a charging group. Further, the water solubility of the desired polymer is adjusted by the ratio of the water-soluble monomer component as the other monomer component.

  The weight average molecular weight of the polymer having a charging group is preferably from 1,000 to 1,000,000, more preferably from 10,000 to 200,000.

  The polymer having a charged group may be obtained by copolymerizing the above monomers together, or may be prepared by previously copolymerizing other monomers (monomers having a charged group, other monomers). After polymerization, a monomer that becomes a silicone chain may be polymerized (bonded).

  Next, the colorant will be described. 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.

  The blending amount of the colorant is desirably 10% by mass or more and 99% by mass or less, and desirably 30% by mass or more and 99% by mass or less with respect to the polymer having a charging group.

Next, other compounding materials will be described. Examples of other compounding materials include a charge control agent and a magnetic material.
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. .

As the magnetic material, an inorganic magnetic material or an organic magnetic material color-coated as necessary is used. Further, a transparent magnetic material, in particular, a transparent organic magnetic material does not hinder the color development of the color pigment, and the specific gravity is smaller than that of the inorganic magnetic material, so that it is more desirable.
As a colored magnetic material (color-coated material), 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.

Next, a method for producing display particles according to the present embodiment will be described.
The method for producing display particles according to this embodiment includes a water-soluble polymer having a charging group, a colorant, a first solvent composed of a silicone oil, and an incompatible with the first solvent, and a boiling point of the first solvent. And an emulsifying step of emulsifying and emulsifying a mixed solution containing a second solvent that dissolves the polymer having a charged group and having a low charge group, and a step of removing the second solvent from the emulsified mixed solution. Is preferred. When display particles are produced by a so-called liquid drying method, display particles having particularly stable dispersibility and charging characteristics can be obtained.

  In addition, this method is used as a display particle dispersion containing display particles and a dispersion medium as it is by using a dispersion medium used for the display medium as the first solvent. Thereby, in the manufacturing method of the display particle which concerns on this embodiment, the display particle dispersion liquid which used the 1st solvent which consists of silicone oil as a dispersion medium by passing through the said process does not pass through a washing | cleaning and drying process. Easy to make. Hereinafter, it demonstrates according to a process.

  In addition, the manufacturing method of the display particles according to the present embodiment is not limited to the above-described manufacturing method. For example, the method is adopted by a well-known method (coacervation method, dispersion polymerization method, suspension polymerization method, etc.). May be.

  Hereinafter, the details of the method for producing display particles according to the present embodiment will be described. Hereinafter, it demonstrates according to a process.

-Emulsification process-
In the emulsification step, the first solvent composed of a polymer having a charging group, a colorant, and silicone oil and the first solvent are incompatible with each other and have a boiling point lower than that of the first solvent and a polymer having a charging group. The mixed solution containing the second solvent is stirred and emulsified. Further, in the mixed solution to be emulsified, other compounding materials (emulsifier, charge control agent, etc.) other than the above materials are blended as necessary.

  In the emulsification step, the second solvent forms a dispersed phase and is emulsified in the continuous phase of the first solvent by stirring the mixed solution. The emulsifier is dissolved or dispersed in the continuous phase, and the water-soluble polymer having a charged group and the colorant are dissolved or dispersed in the dispersed phase.

  In the emulsification step, each material may be sequentially mixed in the mixed solution. For example, first, a first mixed solution in which a water-soluble polymer having a charging group, a colorant, and a second solvent are mixed, A second mixed solution is prepared by mixing a solvent and, if necessary, an emulsifier and a solvent. And it is good to emulsify so that a 1st mixed solution may be disperse | distributed and mixed in a 2nd mixed solution, and a 1st mixed solution may be disperse | distributed in a particulate form in a 2nd mixed solution.

  Stirring for emulsification is performed using, for example, a known stirring device (for example, a homogenizer, a mixer, an ultrasonic crusher, etc.). In order to suppress an increase in temperature during emulsification, the temperature of the mixed solution during emulsification is desirably maintained at 0 ° C. or higher and 50 ° C. or lower. For example, the stirring speed of a homogenizer or mixer for emulsification, the output intensity of the ultrasonic crusher, and the emulsification time are set according to the desired particle diameter.

Next, the first solvent will be described.
Specifically, the silicone oil as the first solvent is a silicone oil in which a hydrocarbon group is bonded to a siloxane bond (for example, dimethyl silicone oil, diethyl silicone oil, methyl ethyl silicone oil, methyl phenyl silicone oil, diphenyl silicone oil, etc.) And modified silicone oil (for example, fluorine-modified silicone oil, amine-modified silicone oil, carboxyl-modified silicone oil, epoxy-modified silicone oil, alcohol-modified silicone oil, etc.). Among these, nonionic silicone oil, particularly dimethyl silicone is desirable from the viewpoints of high safety, chemical stability, good 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.

Next, the second solvent will be described.
The second solvent is used as a good solvent that can form a dispersed phase in the mixed solution. Further, a material that is incompatible with the first solvent, has a boiling point lower than that of the first solvent, and dissolves a polymer having a charged group is selected. Here, incompatible means a state in which a plurality of substance systems exist in independent phases without being mixed. Moreover, dissolution refers to a state where the residue of the dissolved material is not visually confirmed.

  Specific examples of the second solvent include water, lower alcohols having 5 or less carbon atoms (eg, methanol, ethanol, propanol, isopropyl alcohol, etc.), tetrahydrofuran, and acetone, but are not limited thereto. In particular, water is preferable from the viewpoint of imparting stable dispersibility, thermal stability, and charging characteristics to the particles.

  The second solvent is selected from those having a boiling point lower than that of the first solvent because it can be removed from the mixed solution system, for example, by heating under reduced pressure. The boiling point is, for example, from 50 ° C. to 200 ° C. Desirably, more desirably, it is 50 ° C or higher and 150 ° C or lower.

Next, the emulsifier will be described. Preferable examples of the emulsifier include silicone-modified resins and modified silicone oils.
Examples of the silicone-modified resin include a silicone-modified acrylic resin, a silicone-modified polyurethane resin, and a silicone-modified epoxy resin. Among these, a silicone-modified acrylic resin is preferable as the silicone-modified resin from the viewpoint of improving the dispersion stability of the obtained particles.

  Examples of the silicone-modified acrylic resin include acrylic esters (for example, acrylic acid, alkyl acrylate, etc.), methacrylic esters (acrylamide, acrylonitrile, methacrylic acid, alkyl methacrylate, etc.), methacrylamide, and methacrylonitrile. Examples thereof include those obtained by modifying a silicone with respect to a homopolymer of a selected monomer or two or more types of copolymers.

  Specific examples of the silicone-modified acrylic resin include “KP545: manufactured by Shin-Etsu Silicone”, “FA-4001CM: manufactured by Toray Dow Silicone”, “Symac: manufactured by Toa Gosei Co., Ltd.”, and the like.

  On the other hand, examples of the modified silicone oil include carboxyl-modified silicone oil, fluorine-modified silicone oil, alcohol-modified silicone oil, epoxy-modified silicone oil, and amine-modified silicone oil. Among these, amine-modified silicone oil is preferable as the modified silicone oil from the viewpoint of improving the dispersion stability of the obtained particles.

  Specific examples of the modified silicone oil include “TSF4708: manufactured by GE Toshiba Silicone”, “TSF4709: manufactured by GE Toshiba Silicone”, and the like.

  Here, it is particularly preferable to apply a polymer having a dendritic structure as an emulsifier. By applying a polymer having a dendritic structure as an emulsifier, the dispersion stability of the obtained particles is particularly improved. The polymer having a dendritic structure is a polymer having a molecular structure in which side chains connected to the main chain are regularly branched (a molecular structure called a dendmary structure). Thus, as the polymer having a dendritic structure, a silicone-modified acrylic resin represented by “FA-4001CM: manufactured by Toray Dow Silicone” (for example, “FA-4001CM: manufactured by Toledo Silicone”) is suitable. Can be mentioned. In this silicone-modified acrylic resin, the side chain silicone linked to the acrylic main chain is composed of an oligomer in which a large number of trimethylsiloxane groups are regularly branched to form a sphere. Of course, the polymer having a dendritic structure is not limited thereto.

  The blending amount of the emulsifier is desirably 3% by mass or more and 40% by mass or less, and desirably 5% by mass or more and 20% by mass or less with respect to the first solvent.

-Second solvent removal step-
Next, in the second solvent removal step, the second solvent (low boiling point solvent) is removed from the mixed solution emulsified in the emulsification step. By removing the second solvent, the water-soluble polymer having a charged group is precipitated and formed into particles while adhering other materials to the inclusion or the surface in the dispersed phase formed by the second solvent. Display particles are obtained. Further, the polymer forming the particles may contain various additives such as pigment dispersants and weathering stabilizers. For example, a commercially available pigment dispersion contains a polymer substance and a surfactant for dispersing the pigment. When this is used, the colored particles are used together with a resin for controlling charging, as well as these resins. Substance will be included.

Here, examples of the method for removing the second solvent include a method of heating the mixed solution and a method of reducing the pressure of the mixed solution, and these methods may be combined.
When the mixed solution is heated to form the second solvent, the heating temperature is preferably 30 ° C. or higher and 200 ° C. or lower, and more preferably 50 ° C. or higher and 180 ° C. or lower.
On the other hand, when the mixed solution is depressurized to remove the second solvent, the depressurization pressure is preferably 0.01 mPa to 200 mPa, and more preferably 0.01 mPa to 20 mPa.

  Through the above steps, display particles or a display particle dispersion containing the display particles can be obtained. In addition, acids, alkalis, salts, dispersion stabilizers, stabilizers for the purpose of preventing oxidation or absorbing ultraviolet rays, antibacterial agents, preservatives, etc. may be added to the resulting display particle dispersion as necessary. May be.

  An anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, a fluorine surfactant, a silicone surfactant as a charge control agent for the obtained display particle dispersion. Silicone cationic compounds, silicone anionic compounds, metal soaps, alkyl phosphate esters, succinimides, and the like may be added.

Charge control agents include ionic or nonionic surfactants, block or graft copolymers composed of a lipophilic part and a hydrophilic part, polymers such as cyclic, star-like or dendritic polymers (dendrimers) Compounds with chain skeletons, metal complexes of salicylic acid, metal complexes of catechol, metal-containing bisazo dyes, tetraphenylborate derivatives, copolymers of polymerizable silicone macromers (Tisso: Silaplane) and anionic monomers or cationic polymers, etc. Is mentioned.
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 mass or more and 20% by mass or less, and particularly preferably 0.05% by mass or more and 10% by mass or less with respect to the solid content of the particles.

Moreover, you may dilute with respect to the obtained particle dispersion liquid for display with the 1st solvent (The 1st solvent containing an emulsifier (dispersing agent as needed)) as needed.
The concentration of the display particles in the display particle dispersion can be variously selected depending on the display characteristics, response characteristics, and use thereof, but is preferably selected in the range of 0.1 mass% to 30 mass%. When mixing multi-particles having different colors, the total amount of the particles is preferably within this range. When the amount is less than 0.1% by mass, the display density becomes insufficient. When the amount is more than 30% by mass, there is a problem that the display speed becomes slow or aggregation easily occurs.
It is also preferable to obtain a color display by mixing a plurality of types of particles having different colors and charging polarities. Furthermore, as a plurality of types of display particles having different charging polarities, the display particles containing the water-soluble polymer having a quaternary ammonium group as the charging group, and a water-soluble high particle having an acid group salt as the charging group. When the display particles containing molecules are used, particularly stable dispersibility and charging characteristics can be maintained.

  The display particles and the display particle dispersion according to the present embodiment are used for an electrophoretic display medium, a liquid toner of a liquid developing electrophotographic system, and the like.

Here, other display particles will be described below.
Other display particles contain a water-insoluble polymer having a charging group and a colorant, and the polymer contains at least a silicone-based macromonomer component as a copolymer component. Other display particles are particles that move in response to an electric field, have charging characteristics when dispersed in a dispersion medium, and move in the dispersion medium in response to the formed electric field. The other display particles are also particles having stable dispersibility and charging characteristics by adopting the above configuration. Here, the charging characteristics indicate the charge polarity and charge amount of the particles. In this embodiment, fluctuations in the charge polarity and charge amount are suppressed and stabilized.

  Here, since the other display particles have the above characteristics, in the display particle dispersion, the particle group including the particles is composed of a plurality of types of display particles having different charge polarities, that is, charged as other display particles. Stable dispersibility and charging characteristics are maintained regardless of whether the display particles are composed of a plurality of types of display particles having different polarities or a system in which a plurality of types of display particles having different charge polarities are mixed. A plurality of types of display particles having different charging polarities can be obtained, for example, by changing the charging group of a polymer having a charging group described later.

Moreover, you may comprise the display particle dispersion liquid made into the particle group containing the other display particle and the display particle which concerns on the said this embodiment. This makes it possible to obtain a particle dispersion in which different types of particles operate while maintaining their respective charging characteristics.

  The other display particles include a polymer having a charged group, a colorant, and, if necessary, other compounding materials.

  The polymer having a charging group includes a silicone-based macromonomer component as at least a copolymer component. Specific examples of the polymer having a charging group include a polymer comprising at least a silicone-based macromonomer component and a monomer component having a charging group as a copolymerization component. That is, the water-insoluble polymer having a charging group is preferably a copolymer obtained by copolymerizing a silicone macromonomer and a monomer having a charging group. Here, the “macromonomer” is a generic term for an oligomer having a polymerizable functional group (degree of polymerization of about 2 or more and about 300 or less) or a polymer, and has both properties of a polymer and a monomer (monomer). Is.

  Examples of the silicone-based macromonomer include dimethyl silicone monomers having a methacrylate group at one end similar to those described above (for example, manufactured by Chisso Corporation: Silaplane “FM-0711”, “FM-0721”, “FM-0725”). Etc., manufactured by Shin-Etsu Chemical Co., Ltd .: “X-22-174DX”, “X-22-2426”, “X-22-2475”, etc.), silicone monomers having an epoxy group at one end (for example, manufactured by Shin-Etsu Chemical Co., Ltd.) : "X-22-173DX"). Among these, dimethyl silicone monomers having a methacrylate group at one end (for example, manufactured by Chisso: Silaplane “FM-0711”, “FM-0721”, from the point that stable dispersibility and charging characteristics can be imparted) “FM-0725”, manufactured by Shin-Etsu Chemical Co., Ltd .: “X-22-174DX”, “X-22-2426”, “X-22-2475” and the like) are preferable examples.

  In addition, the water-insoluble polymer having a charging group includes, in addition to the monomer having a charging group, other monomer components (monomer components having no charging group) such as (meth) acrylates, Hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, N-vinylpyrrolidone, styrene, a styrene derivative, or the like may be included as a copolymerization component.

Here, it is desirable that the polymer having a charging group is 3% to 60%, preferably 5% to 40% by mass ratio of the silicone macromonomer component to the whole polymer. By setting it within this range, other characteristics (charging polarity imparting and charge amount control) can be realized while imparting stable dispersibility and charging characteristics to the particles.
Moreover, in the polymer having a charged group, the ratio of the monomer component having a charged group contained together with the silicone-based macromonomer component is the mass ratio (monomer component that becomes a silicon chain: monomer component having a charged group). ) In the range of 100: 1 to 1:10, preferably in the range of 100: 5 to 5: 100. The charge amount of the desired particles is adjusted by the ratio of the monomer component having a charging group.

  The weight average molecular weight of the polymer having a charging group is preferably from 1,000 to 1,000,000, more preferably from 10,000 to 200,000.

Next, another method for producing display particles will be described.
Other display particle manufacturing methods include, for example, a water-insoluble polymer having a charging group (a polymer that is a copolymer having at least a silicone-based macromonomer component as a copolymer component), a colorant, and an organic solvent. A step of preparing a colorant-containing polymer solution, a step of dripping the colorant-containing polymer solution into silicone oil, emulsifying the colorant-containing polymer solution in silicone oil, and emulsifying the colorant And removing the organic solvent from the polymer solution. When other display particles are produced by the so-called coacervation method, display particles having particularly stable dispersibility and charging characteristics can be obtained.

  In addition, this technique uses a dispersion medium (silicone oil) used as a display medium as a solvent for dropping the colorant-containing polymer solution, and as a display particle dispersion containing display particles and a dispersion medium as it is. Used. As a result, in other display particle manufacturing methods, through the above steps, a display particle dispersion using the first solvent made of silicone oil as a dispersion medium can be easily prepared without going through a washing / drying step. Is done. Hereinafter, it demonstrates according to a process.

  In addition, the manufacturing method of other display particles is not limited to the above-described manufacturing method, and for example, a method may be employed by a well-known method (dispersion polymerization method, suspension polymerization method, or the like).

  Hereinafter, the detail of the manufacturing method of the other display particle is demonstrated. Hereinafter, it demonstrates according to a process.

-Colorant-containing polymer solution preparation process-
In the colorant-containing polymer solution preparation step, the polymer having a charging group and the colorant are mixed in an organic solvent and stirred to dissolve the polymer and disperse the colorant to obtain a colorant-containing polymer solution. In addition, a monomer (including a macromonomer) as a constituent component of a polymer having a charged group is added to an organic solvent for polymerization, and then a colorant (or a dispersion thereof) is added to form a colorant-containing polymer. A solution may be made.

  Examples of the organic solvent include a solvent that dissolves a polymer having a charged group and is compatible or incompatible with silicone oil. As a result, any solvent may be used as long as the resin can be precipitated when the silicone oil is dropped into the solution while the resin is dissolved. Thereafter, it is only necessary that a solvent other than silicone oil can be removed by drying under reduced pressure or the like under the condition that the silicone oil is not evaporated. Examples of the organic solvent include isopropyl alcohol (IPA), methanol, ethanol, butanol, tetrahydrofuran, ethyl acetate, butyl acetate and the like. Among these, isopropyl alcohol (IPA) is desirable from the viewpoint of providing stable dispersion stability and charging characteristics.

-Emulsification process-
In the emulsification step, the colorant-containing polymer solution is dropped into the silicone oil, and the colorant-containing polymer solution is emulsified in the silicone oil. Further, in the silicone oil, other blending materials (emulsifier, charge control agent, etc.) other than the above materials are blended as necessary.

  In the emulsification step, the colorant-containing polymer solution is dropped into silicone oil and stirred to form a dispersed phase in which the silicone solvent is a poor solvent and the organic solvent of the colorant-containing polymer solution is a good solvent. And emulsified. The polymer having the charging group and the colorant are dissolved or dispersed in the dispersed phase composed of the colorant-containing polymer solution.

  The colorant-containing polymer solution for emulsification is stirred while dropping, and this stirring is performed using, for example, a known stirring device (for example, a homogenizer, a mixer, an ultrasonic crusher, etc.). In order to suppress the temperature rise during emulsification, the temperature of the mixed solution during emulsification is desirably maintained at 0 ° C. or more and 25 ° C. or less. For example, the stirring speed of a homogenizer or mixer for emulsification, the output intensity of the ultrasonic crusher, and the emulsification time are set according to the desired particle diameter.

-Removal process-
Next, in the removing step, the organic solvent (good solvent) is removed from the colorant-containing polymer solution emulsified in the emulsifying step. By removing this organic solvent, a polymer having a charged group is precipitated and formed into particles while adhering other materials to the content or surface in the dispersed phase formed by the organic solvent, and the display particles Is obtained.

Here, examples of the method for removing the organic solvent include a method of heating a silicone oil solution in which a colorant-containing polymer solution is emulsified, and a method of reducing the pressure of the silicone oil. May be.
When the organic solvent is heated for heating, the heating temperature is preferably 60 ° C. or higher and 200 ° C. or lower, and more preferably 60 ° C. or higher and 180 ° C. or lower.
On the other hand, when the second solvent is removed by reducing the pressure of the organic solvent, the reduced pressure is preferably 0.01 mPa to 200 mPa, and more preferably 0.01 mPa to 20 mPa.

  Through the above steps, other display particles or a display particle dispersion containing the same are obtained.

  The other display particles (display dispersion liquid containing the display particles) have been described above. Since the display particles other than the above are the same as the display particles (display particle dispersion liquid) according to the above embodiment, the description thereof is omitted. .

(Display medium, display device)
The electrophoretic material of the present invention can be applied to optical elements such as display elements and light control elements. When applied to a display element, a known method of moving a particle group in a direction perpendicular to the electrode (substrate) surface, or a so-called in-plane type element that moves in a horizontal direction, or a hybrid that combines these methods. It is possible to apply to an element.

  FIG. 1 is an example of a schematic configuration diagram illustrating a display device according to the present embodiment. The display device of the present invention is not limited to the configuration described below.

The display device 10 according to the present embodiment includes a display medium including the display particles and the dispersion medium (first solvent) as the particle dispersion liquid including the dispersion medium 50 and the particle group 34 of the display medium 12. In this embodiment, the display particle dispersion according to the embodiment is applied. The same applies to the other display particles described above (display particle dispersion liquid in which the dispersion medium is silicone oil).

  As shown in FIG. 1, the display device 10 according to the present 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 apparatus, a RAM (Random Access Memory) that temporarily stores various data, and a program indicated by a control program and a processing routine for controlling the entire apparatus. 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 voltage application unit 16 is electrically connected to the front electrode 40 and the back electrode 46. 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.

  Hereinafter, the display medium 12 will be described in detail.

  As shown in FIG. 1, the display medium 12 includes a display substrate 20 serving as a display surface, a rear substrate 22 that faces the display substrate 20 with a gap, and holds the substrates at a predetermined interval. It includes a gap member 24 that divides the 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. A dispersion medium 50 is enclosed in this cell. Particle groups 34 (details will be described later) are dispersed in the dispersion medium 50 and move between the display substrate 20 and the back substrate 22 in accordance with the electric field strength formed in the cell.

  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 addition to the cell shown in FIG. 1, the cell can also be formed by holding a capsule in which a dispersion medium is enclosed in a substrate. In this case, the substrate need not be a pair but may be one.

  A plurality of types of particle groups 34 having different colors are dispersed in the dispersion medium 50 of the display medium 12. The plurality of types of particle groups 34 are particles that are electrophoresed between the 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 for movement according to the electric field, the display particles according to the above-described embodiment (or the display particle dispersion containing the display particles) are used. ), For example, by changing the kind of the “polymer” to produce display particles having different charge amounts (or display particle dispersions containing them), and mixing them.

  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.

  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 Fluorine resin or the like 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 given. 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 that a plurality of layers can 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 made by Nippon Carbon, CFGL, CFGM made by Daikin Industries), fine particles of silicone resin (Tospearl made by Toshiba Silicone Co., Ltd.), polyester containing titanium oxide Fine particles (Nippon Paint Bilucia PL1000 Wight T), fine particles (manufactured by NOF Corporation Konak No181000 white titanium oxide-containing polyester acrylate), 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 the 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, by moving according to the electric field formed between the display substrate 20 and the back substrate 22, the color corresponding to each pixel of the image data for each cell corresponding to each pixel of the display medium 12 Can be displayed.

  Here, in the display medium 12, as shown in FIG. 2, in the particle group 34, for each color, the particle group 34 moves in accordance with the electric field at the time of electrophoresis between the substrates. The absolute values of the required voltages are different. Each color particle group 34 has a voltage range necessary for moving each color particle group 34 for each color, and the voltage range is different. In other words, the absolute value of the voltage has the voltage range, and the voltage range is different for each color of the particle group 34.

  In the present embodiment, as the particle group 34 enclosed in the same cell of the display medium 12, as shown in FIG. 1, a magenta magenta particle group 34M, a cyan cyan particle group 34C, and The description will be made assuming that the three color particle groups 34 of the yellow color yellow particle group 34Y are enclosed.

  The magenta magenta magenta particle group 34M, the cyan cyan particle group 34C, and the yellow color yellow particle group 34Y are magenta magenta as absolute values of voltages when the three color particle groups start moving. In the following description, it is assumed that the 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 |.

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

  Specifically, as shown in FIG. 2, for example, all the particle groups 34 are charged with the same polarity, and the absolute value of the voltage range necessary to move the cyan particle group 34C | Vtc ≦ Vc ≦ Vdc | (Vtc Absolute value of a value between Vtm and Vdm), absolute value of voltage range necessary to move the magenta particle group 34M | Vtm ≦ Vm ≦ Vdm | (absolute value of a value between Vtm and Vdm), and yellow particles The absolute value of the voltage range necessary to move the group 34M | Vty ≦ Vy ≦ Vdy | (the absolute value of the value between Vty and Vdy) is set to be large without overlapping in this order. Yes.

  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 34M is the absolute value of the voltage range necessary for moving the magenta particle group 34M. Value | Vtm ≦ Vm ≦ Vdm | (the absolute value of the value between Vtm and Vdm) and the absolute value of the voltage range necessary to move the yellow particle group 34M | Vty ≦ Vy ≦ Vdy | (Vty to Vdy The absolute value of the value between) is set smaller. Further, the absolute value | Vdm | of the maximum voltage for moving almost all of the magenta particle group 34M is equal to the absolute value | Vty ≦ Vy ≦ Vdy | (Vty to Vdy) of the voltage range necessary for moving the yellow particle group 34M. 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 this embodiment, the voltage applied between the substrates is gradually increased by applying a voltage from 0 V between the front substrate 20 and the rear 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 34 in the display medium 12 stops.

  When the voltage value is further increased and the voltage applied between the front substrate 20 and the rear 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 front substrate 20 and the rear 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 electrode voltage is applied from 0 V to the substrate between the front substrate 20 and the rear 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 yellow particle group 34C between the substrates. Further, when the absolute value of the voltage value is increased and the voltage applied between the front substrate 20 and the rear substrate 22 becomes −Vdc or more, the display density changes due to the movement of the cyan particle group 34C in the display medium 12. Stop.

  When the negative voltage is further applied by increasing the absolute value of the voltage value and the voltage applied between the front 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 front substrate 20 and the rear 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 negative voltage is further applied by increasing the absolute value of the voltage value and the voltage applied between the front substrate 20 and the rear 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 34 </ b> C in the display medium 12 stops.

  In other words, in the present embodiment, as shown in FIG. 2, the voltage applied between the substrates is within 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 front substrate 20 and the rear substrate 22 such that the voltage applied between the substrates is in the 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 front substrate 20 and the rear substrate 22 so that the voltage applied between the substrates is within a range of −Vty to Vty (voltage range | Vty | or less), the display is performed. 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 dispersion medium 50, color mixing with colors other than the desired color is suppressed, and color display is 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 necessary for moving according to the electric field overlap with each other, clear color display is possible. However, when the voltage ranges are different from each other, color mixing is further suppressed and color display is realized.

  Further, by dispersing the three color particle groups 34 of cyan, magenta, and yellow in the dispersion medium 50, cyan, magenta, yellow, blue, red, green, and black can be displayed, and white insulation can be displayed. The white particles can be displayed by the active particles 36, and a desired color display can be performed.

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

Example 1
First, N-vinylpyrrolidone as another monomer: 90 parts by mass, Silaplane “FM-0721” as a monomer to be a silicone chain: 5 parts by mass, and methacrylic acid as a monomer having a charging group: 5 parts by mass A part was mixed with 100 parts by mass of isopropyl alcohol, and 0.2 parts by mass of AIBN was dissolved as a polymerization initiator, and polymerization was performed at 70 ° C. for 6 hours under nitrogen. The product was purified using cyclohexane as a reprecipitation solvent and dried to obtain a polymer.
When the obtained polymer was dissolved in distilled water, it was dissolved even at 30% by mass and no precipitation was observed, indicating that it was a water-soluble polymer.

Next, Ciba's water-dispersed pigment solution (Unisperse cyan color: pigment concentration 26% by mass) is mixed with 1 part by mass of 3% by mass of a 10% by mass aqueous solution of the above polymer to obtain an aqueous solution containing the polymer and the pigment. Prepared. Next, a 3 mass% silicone solution of KP545 was prepared by adding silicone-modified acrylic polymer KP545 (manufactured by Shin-Etsu Chemical Co., Ltd.) as an emulsifier to dimethyl silicone oil (KF-96-2CS manufactured by Shin-Etsu Silicone Co., Ltd.). And after mixing the said aqueous solution with 10 mass parts of 3 mass% silicone solutions of KP545, this is disperse | distributed with an ultrasonic crusher (SMT Co., Ltd. UH-600S), and the aqueous solution containing a polymer and a pigment is made into silicone oil ( A suspension dispersed in a viscosity of 2 cs) was prepared.
Next, this suspension was decompressed (2 KPa), heated (70 ° C.) for 2 hours to remove moisture, and display particles dispersed with display particles containing polymer and pigment in silicone oil. A liquid was obtained. A chemically equimolar amount of trihexylamine was added to the obtained display particle dispersion to form a salt with methacrylic acid, which is a polymer monomer component.
It was 8.1 mass% when solid content concentration of the produced particle dispersion was measured from the mass measurement before and behind drying of silicone oil. Further, the volume average particle size of the migrating particles in the dispersion was measured (Holiba LA-300: laser light scattering / diffraction particle size measuring device), and as a result, it was 310 nm.
The charged polarity of the electrophoretic particles in this dispersion was determined by enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction. .

(Example 2)
First, 2-hydroxyethyl acrylate as another monomer: 85 parts by mass, Silaplane “FM-0721” as a silicone chain monomer: 10 parts by mass, and methacrylic acid as a monomer having a charging group: 5 A mass part is mixed with 100 parts by mass of isopropyl alcohol, and AIBN (2,2′-azobis (isobutyronitrile)): 0.2 part by mass as a polymerization initiator is dissolved, and 70 ° C. under nitrogen for 6 hours. Polymerization was performed. The product was purified using cyclohexane as a reprecipitation solvent and dried to obtain a polymer.
When the obtained polymer was dissolved in distilled water, it was dissolved even at 30% by mass and no precipitation was observed, indicating that it was a water-soluble polymer.

Next, Ciba's water-dispersed pigment solution (Unisperse magenta color: pigment concentration 16% by mass) is mixed with 3 parts by mass of a 10% by mass aqueous solution of the above polymer in 1 part by mass to obtain an aqueous solution containing the polymer and the pigment. Prepared. Next, a 3 mass% silicone solution of KP545 was prepared by adding silicone-modified acrylic polymer KP545 (manufactured by Shin-Etsu Chemical Co., Ltd.) as an emulsifier to dimethyl silicone oil (KF-96-2CS manufactured by Shin-Etsu Silicone Co., Ltd.). Then, the aqueous solution was mixed with 10 parts by mass of a 3% by mass silicone solution of KP545, and this was dispersed by an ultrasonic crusher, and the aqueous solution containing the polymer and the pigment was dispersed in silicone oil (viscosity 2 cs). A suspension was prepared.
Next, this suspension was decompressed (2 KPa), heated (70 ° C.) for 2 hours to remove moisture, and display particles dispersed with display particles containing polymer and pigment in silicone oil. A liquid was obtained. A chemically equimolar amount of trihexylamine was added to the obtained display particle dispersion to form a salt with methacrylic acid, which is a polymer monomer component.
It was 7.2 mass% when solid content concentration of the produced particle dispersion liquid was measured from the mass measurement before and behind drying of silicone oil. Further, the volume average particle size of the migrating particles in the dispersion was measured (Holiba LA-300: laser light scattering / diffraction particle size measuring device), and as a result, it was 280 nm.
The charged polarity of the electrophoretic particles in this dispersion was determined by enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction. .

(Example 3)
First, N-vinylpyrrolidone as another monomer: 85 parts by mass, Silaplane “FM-0721” as a monomer to be a silicone chain: 10 parts by mass, Diethylaminoethyl methacrylate as a monomer having a charging group: 5 Part by mass was mixed with 100 parts by mass of isopropyl alcohol, and 0.2 parts by mass of AIBN was dissolved as a polymerization initiator, and polymerization was performed at 70 ° C. for 6 hours under nitrogen. The product was purified using cyclohexane as a reprecipitation solvent and dried to obtain a polymer.
When the obtained polymer was dissolved in distilled water, it was dissolved even at 30% by mass and no precipitation was observed, indicating that it was a water-soluble polymer.

Next, 3 parts by mass of a 10% by mass aqueous solution of the above polymer is mixed with 1 part by mass of a Ciba water-dispersed pigment solution (Unisperse cyan color: pigment concentration 26% by mass) to obtain an aqueous solution containing the polymer and the pigment. Prepared. Next, a 3 mass% silicone solution of KP545 was prepared by adding silicone-modified acrylic polymer KP545 (manufactured by Shin-Etsu Chemical Co., Ltd.) as an emulsifier to dimethyl silicone oil (KF-96-2CS manufactured by Shin-Etsu Silicone Co., Ltd.). Then, the aqueous solution was mixed with 10 parts by mass of a 3% by mass silicone solution of KP545, and this was dispersed by an ultrasonic crusher, and the aqueous solution containing the polymer and the pigment was dispersed in silicone oil (viscosity 2 cs). A suspension was prepared.
Next, the suspension was depressurized (2 KPa) and heated (70 ° C.) to remove moisture, thereby obtaining a display particle dispersion in which display particles containing a polymer and a pigment were dispersed in silicone oil. . 0.1 parts by mass of ethyl bromide is added to the obtained display particle dispersion, and the dispersion is heated at 80 ° C. for 2 hours to quaternize the amino group of diethylaminoethyl methacrylate, which is a polymer monomer component. And then unreacted ethyl bromide was removed under reduced pressure.
It was 8.2 mass% when solid content concentration of the produced particle dispersion was measured from the mass measurement before and behind drying of silicone oil. Further, the volume average particle size of the migrating particles in the dispersion was measured (Holiba LA-300: laser light scattering / diffraction particle size measuring device), and as a result, it was 260 nm.
The charge polarity of the electrophoretic particles in this dispersion was positively charged as a result of being obtained by enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

(Example 4)
First, 2-hydroxyethyl acrylate as another monomer: 90 parts by mass, Silaplane “FM-0721” as a monomer to be a silicone chain: 5 parts by mass, and diethylaminoethyl methacrylate as a monomer having a charging group: 5 parts by mass was mixed with 100 parts by mass of isopropyl alcohol, and 0.2 parts by mass of AIBN was dissolved as a polymerization initiator, and polymerization was performed at 70 ° C. for 6 hours under nitrogen. The product was purified using cyclohexane as a reprecipitation solvent and dried to obtain a polymer.
When the obtained polymer was dissolved in distilled water, it was dissolved even at 30% by mass and no precipitation was observed, indicating that it was a water-soluble polymer.

Next, 3 parts by mass of a 10% by mass aqueous solution of the above polymer is mixed with 1 part by mass of a Ciba water-dispersed pigment solution (Unisperse / magenta color: pigment concentration 16% by mass) to obtain an aqueous solution containing the polymer and the pigment. Prepared. Next, a 3 mass% silicone solution of KP545 was prepared by adding silicone-modified acrylic polymer KP545 (manufactured by Shin-Etsu Chemical Co., Ltd.) as an emulsifier to dimethyl silicone oil (KF-96-2CS manufactured by Shin-Etsu Silicone Co., Ltd.). Then, the aqueous solution was mixed with 10 parts by mass of a 3% by mass silicone solution of KP545, and this was dispersed by an ultrasonic crusher, and the aqueous solution containing the polymer and the pigment was dispersed in silicone oil (viscosity 2 cs). A suspension was prepared.
Next, the suspension was depressurized (2 KPa) and heated (70 ° C.) to remove moisture, thereby obtaining a display particle dispersion in which display particles containing a polymer and a pigment were dispersed in silicone oil. . 0.1 parts by mass of ethyl bromide is added to the obtained display particle dispersion, and the dispersion is heated at 80 ° C. for 2 hours to quaternize the amino group of diethylaminoethyl methacrylate, which is a polymer monomer component. And then unreacted ethyl bromide was removed under reduced pressure.
The solid content concentration of the prepared particle dispersion was measured by mass measurement before and after drying the silicone oil and found to be 7.3% by mass. Further, the volume average particle size of the migrating particles in the dispersion was measured (Holiba LA-300: laser light scattering / diffraction particle size measuring device), and as a result, it was 290 nm.
The charge polarity of the electrophoretic particles in this dispersion was positively charged as a result of being obtained by enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

(Example 5)
Using the water-soluble resin prepared in Example 1, a magenta color display particle dispersion was prepared using only the pigment and the same magenta pigment as in Example 2. The solid content concentration was 7.0%, and the volume average particle size was 300 nm.
The charged polarity of the electrophoretic particles in this dispersion was determined by enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction. .

(Example 6)
Using the water-soluble resin prepared in Example 2, only the pigment was used to prepare a cyan display particle dispersion using the same cyan pigment as in Example 1. Moreover, solid content concentration was 8.1% and the volume average particle diameter was 280 nm.
The charged polarity of the electrophoretic particles in this dispersion was determined by enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction. .

(Example 7)
Using the water-soluble resin produced in Example 3, only the pigment was used to produce a magenta color display particle dispersion using the same magenta pigment as in Example 4. The solid content concentration was 7.2%, and the volume average particle size was 300 nm.
The charge polarity of the electrophoretic particles in this dispersion was positively charged as a result of being obtained by enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

(Example 8)
Using the water-soluble resin prepared in Example 4, only the pigment was used to prepare a cyan display particle dispersion using the same cyan pigment as in Example 3. The solid content concentration was 8.2%, and the volume average particle size was 270 nm.
The charge polarity of the electrophoretic particles in this dispersion was positively charged as a result of being obtained by enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

(Comparative Example 1)
N-vinylpyrrolidone: 95 parts by mass as another monomer, methacrylic acid: 5 parts by mass as a monomer having a charging group, are mixed with 100 parts by mass of isopropyl alcohol, and AIBN: 0.2 mass as a polymerization initiator. Part was dissolved and polymerization was carried out at 70 ° C. for 6 hours under nitrogen. The product was purified and dried using cyclohexane as a reprecipitation solvent to obtain a polymer having no silicone chain. A cyan display particle dispersion was prepared in the same manner as in Example 1 except that this polymer was used. The solid content concentration was 8.1%, and the volume average particle size was 300 nm.
The charged polarity of the electrophoretic particles in this dispersion was determined by enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction. It was a mixture of particles.

(Comparative Example 2)
A magenta color display particle dispersion was prepared in the same manner using only the pigment of the water-soluble polymer prepared in Comparative Example 1 and a magenta pigment. The solid content concentration was 7.0%, and the volume average particle size was 290 nm.
The charged polarity of the electrophoretic particles in this dispersion was determined by enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction. It was a mixture of particles.

(Comparative Example 3)
2-hydroxyethyl methacrylate: 95 parts by mass as another monomer, diethylaminoethyl methacrylate: 5 parts by mass as a monomer having a charging group, and 100 parts by mass of isopropyl alcohol are mixed, and AIBN: 0. 2 parts by mass was dissolved, and polymerization was performed at 70 ° C. for 6 hours under nitrogen. The product was purified and dried using cyclohexane as a reprecipitation solvent to obtain a polymer having no silicone chain. A magenta color display particle dispersion was prepared in the same manner as in Example 4 except that this polymer was used. The solid content concentration was 8.1%, and the volume average particle size was 300 nm.
The charged polarity of the electrophoretic particles in this dispersion was determined by enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction. It was.

(Comparative Example 4)
A cyan color particle dispersion for display was prepared in the same manner using the water-soluble polymer prepared in Comparative Example 3 with only a pigment and a cyan pigment. Moreover, solid content concentration was 7.1% and the volume average particle diameter was 320 nm.
The charged polarity of the electrophoretic particles in this dispersion was determined by enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction. It was.

(Evaluation)
-Dispersion stability-
The particle dispersion stability of the particle dispersions obtained in the above Examples and Comparative Examples was evaluated. For dispersion stability, a solution in which the solid content concentration of the dispersion liquid was adjusted to 2% by mass was placed in a sample bottle, the sedimentation state after 24 hours was visually evaluated, and the particle diameter of the particle dispersion liquid was further measured to be initial. Judged from the presence or absence of difference. The results are shown below.
Example 1: Good (no sedimentation, no change in particle size)
Example 2: Good (no sedimentation, no change in particle size)
Example 3: Good (no sedimentation, no change in particle size)
Example 4: Good (no sedimentation, no change in particle size)
Example 5: Good (no sedimentation, no change in particle size)
Example 6: Good (no sedimentation, no change in particle size)
Example 7: Good (no sedimentation, no change in particle size)
Example 8: Good (no sedimentation, no change in particle size)
Comparative Example 1: Slightly poor (there is sedimentation, the particle size increases)
Comparative Example 2: Slightly poor (there is sedimentation, the particle size increases)
Comparative Example 3: Slightly poor (there is sedimentation, the particle size increases)
Comparative Example 4: Slightly poor (there is sedimentation, the particle size increases)

  From the above results, it can be seen that in this example, the dispersion stability is superior to the comparative example.

-Initial charging polarity-
Although described in Examples and Comparative Examples, the initial charging polarities were as follows.
Example 1: Almost negative charge (with a small amount of positive charge)
Example 2: Almost negative charge (with a small amount of positive charge)
-Example 3: Positive charge-Example 4: Positive charge-Example 5: Almost negative charge (with a small amount of positive charge)
Example 6: almost negative charge (with a small amount of positive charge)
Example 7: Positive charging Example 8: Positive charging Comparative example 1: Positive / negative mixed (slightly negatively charged)
・ Comparative example 2: Positive / negative mixed (slightly negatively charged)
Comparative Example 3: Almost positive charge (with a little negative charge)
Comparative Example 4: Almost positive charge (with a little negative charge)

  From the above results, it can be seen that in this example, the initial charge polarity controllability is superior to the comparative example.

-Charging stability-
The charging stability of the particles was evaluated for the particle dispersions obtained in the above Examples and Comparative Examples. The charging stability shows the following results obtained by evaluating the polarity of the electrophoretic particles having the dispersion liquid sandwiched between the electrodes after one week and judging by the change in the charging polarity before and after one week.
-Example 1: Good-Example 2: Good-Example 3: Good-Example 4: Good-Example 5: Almost good (with a very small amount of negative charge)
-Example 6: Good-Example 7: Good-Example 8: Good-Comparative Example 1: Poor (positively charged particles increased)
Comparative Example 2: Poor (positively charged particles increased)
Comparative Example 3: Somewhat bad (a small amount of negatively charged particles are generated)
Comparative Example 4: Slightly poor (a small amount of negatively charged particles are generated)

  From the above results, it can be seen that in this example, the charging stability is superior to the comparative example.

-Particle mixing evaluation-
The dispersion stability and charging stability of each particle when two particles of different colors and band electrodes were mixed were evaluated. Evaluation was made by mixing each dispersion prepared in Examples and Comparative Examples at a concentration of 1% by mass, and determining from the dispersibility 24 hours after mixing and the electrophoretic properties of each particle by the above-described evaluation by sandwiching between electrodes. The results are shown below.
-Mixing of Example 1 to Example 4: Good (no aggregation of 2 particles, each particle maintains its polarity)
-Example 2-Example 3 mixing: good (no aggregation of 2 particles, each particle maintains its own polarity)
Example 5-Mixing of Example 8: Good (no aggregation of 2 particles, each particle maintains its polarity)
-Example 6-Mixing of Example 7: Good (no aggregation of 2 particles, each particle maintains its polarity)
-Mixing of Comparative Example 1 to Comparative Example 4: Poor (2 particle aggregation occurrence, positively charged aggregate)
Comparative Example 2—Mixing of Comparative Example 3: Poor (2 particle agglomeration, positively charged agglomerate)

  From the above results, it can be seen that this example is superior in dispersion stability and charging stability when two particles having different polarities are mixed as compared with the comparative example.

(Example 9: Production and evaluation of optical element model)
Prepare an ITO glass substrate (5 cm x 10 cm, thickness 2 mm) one by one, form an offset shape with a part of the electrode surface for wiring, and form a tape spacer on the outer periphery (partial opening is formed) As a result, a plurality of cell structures (empty cells) in which two substrates were bonded at an interval of 100 μm with the electrode substrate surfaces facing each other were produced.
From the opening of this cell (empty cell), the two-particle mixed dispersion of Example 1 and Example 4, the two-particle mixed dispersion of Example 2 and Example 3, and the two particles of Example 5 and Example 8 were used. The dispersion and the two-particle mixed dispersions of Example 6 and Example 7 were each injected by the reduced pressure method, and four types of evaluation optical elements with the openings sealed were produced.
When a DC voltage having a polarity of 10 V was applied to the manufactured optical element, both elements could alternately express magenta color and cyan color. Repeatability was also stable over 100,000 times.
From the above results, it can be seen that the optical element produced in this example exhibits good and stable light control characteristics.

[Reference example]
(Reference Example 1)
First, hydroxyethyl methacrylate: 65 parts by mass as another monomer, silaplane “FM-0721”: 30 parts by mass as a silicone-based macromonomer, methacrylic acid: 5 parts by mass as a monomer having a charging group, isopropyl The mixture was mixed with 100 parts by mass of alcohol, 0.2% by mass of AIBN was dissolved as a polymerization initiator, and polymerization was performed at 70 ° C. for 6 hours under nitrogen. A chemically equimolar amount of trihexylamine was added thereto, and the product formed with methacrylic acid and a salt was purified using cyclohexane as a reprecipitation solvent and dried to obtain a polymer.

Next, 0.5 g of the above polymer was added to 9 g of isopropyl alcohol and dissolved, then 0.5 g of cyan pigment (Cyanine Blue 4973) made by Sanyo Dye was added, and 0.5 mmφ zirconia balls were used for 48 hours. Dispersion was performed to obtain a pigment-containing polymer solution.
3 g of this pigment-containing polymer solution was taken out, and 12 g of 2CS silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: KF96) was added dropwise and emulsified while applying ultrasonic waves, and then heated to 60 ° C. And dried under reduced pressure to evaporate IPA to obtain display particles containing a polymer and a pigment. Thereafter, the particles are settled with a centrifuge, the supernatant is removed, 5 g of the silicone oil is added, ultrasonic waves are applied, washed, the particles are settled with a centrifuge, the supernatant is removed, 5 g of the above silicone oil was added to obtain a display particle dispersion. The average particle diameter of the obtained display particles was 0.2 μm (cyan) as a result of measurement with a particle size measuring machine.

(Reference Example 2)
First, hydroxyethyl methacrylate: 65 parts by mass as another monomer, silaplane “FM-0721”: 30 parts by mass as a silicone-based macromonomer, diethylaminoethyl methacrylate: 5 parts by mass as a monomer having a charging group, Mixing with 100 parts by mass of isopropyl alcohol, 0.2 parts by mass of AIBN as a polymerization initiator was dissolved, and polymerization was performed at 70 ° C. for 6 hours under nitrogen. The product was purified using cyclohexane as a reprecipitation solvent and dried to obtain a polymer.

Next, 0.5 g of the above polymer was added to 9 g of isopropyl alcohol and dissolved, then 0.5 g of Sanyo Dye Magenta Pigment (Pigment Red 3090) was added, and 0.5 mmΦ zirconia balls were used for 48 hours. Dispersion was performed to obtain a pigment-containing polymer solution.
3 g of this pigment-containing polymer solution was taken out, and 12 g of 2CS silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: KF96) was added dropwise and emulsified while applying ultrasonic waves, and then heated to 60 ° C. And dried under reduced pressure to evaporate IPA to obtain display particles containing a polymer and a pigment. Thereafter, the particles are settled with a centrifuge, the supernatant is removed, 5 g of the silicone oil is added, ultrasonic waves are applied, washed, the particles are settled with a centrifuge, the supernatant is removed, 5 g of the above silicone oil was added to obtain a display particle dispersion. The average particle size of the obtained display particles was 0.3 μm (magenta) as a result of measurement with a particle size measuring machine.

(Reference Example 3)
Particles were produced in the same manner as in Reference Example 2 except that hydroxy acrylate was used as a monomer to obtain 0.4 μm magenta particles.

(Reference Example 4)
In Reference Example 1, a silicone macromer was prepared by the same method except that silaplane “FM-0725”: 20 parts by mass and hydroxyethyl methacrylate: 75 parts by mass were obtained, and 0.4 μm cyan particles were obtained.

(Reference Comparative Example 1)
In preparing the polymer, a polymer was prepared in the same manner as in Example 1 except that methacrylic acid was not used, and a display particle dispersion was prepared using the polymer.

(Evaluation)
-Dispersion stability-
With respect to the particle dispersions obtained in the above Reference Examples and Reference Comparative Examples, the dispersion stability of the particles was evaluated in the same manner as in the above Examples. The results are shown below.
-Reference Example 1: Good-Reference Example 2: Good-Reference Example 3: Good-Reference Example 4: Good-Reference Comparative Example 1: Good

  From the above results, it can be seen that in this example, the dispersion stability is superior to the comparative example.

-Charging stability-
For the particle dispersions obtained in the above Reference Examples and Reference Comparative Examples, the charging stability of the particles was evaluated in the same manner as in the above Examples. The results are shown below.
-Reference Example 1: Good-Reference Example 2: Good-Reference Example 3: Good-Reference Example 4: Good-Reference Comparative Example 1: Many reverse polarities of charging occur, resulting in failure

  From the above results, it can be seen that the charging stability is superior in this reference example as compared with the comparative example.

[Evaluation of device characteristics]
Using the display particle dispersions prepared in the above Examples, Reference Examples, Comparative Examples, etc., according to the following table, the display particle dispersion alone, a mixed dispersion of display particle dispersions (denoted as Dispersions 1 and 2) ) Or a particle dispersion for display with white particles added, and a device sample sealed between a pair of glass substrates on which indium tin oxide (TIO) electrodes are formed is prepared, and the following evaluation is performed. It was.

-Element characteristic evaluation method-
A voltage (± 10 V) was applied to both electrodes of the device sample, and the display particles were moved while switching between positive and negative, and evaluated as follows. The degree of color mixing of the display colors when the display was switched to 50 times after the display was switched was performed by sensory evaluation, and the following judgments were made.
○: Slightly mixed color level △: Although there is a mixed color level, color can be judged ×: Clearly mixed color is recognized

  In addition, the white particle to add was produced with the following method.

-White particles (light colored particles)-
-Preparation of Dispersion A1 The following ingredients were mixed and ball milling was performed for 20 hours with 10 mmφ zirconia balls to prepare Dispersion A1.
<Composition>
Cyclohexyl methacrylate 61 parts by weight Divinyldimethoxysilane 1 part by weight Titanium oxide 1 (white pigment) 35 parts by weight (primary particle size 0.3 μm, Taipei CR63: manufactured by Ishihara Sangyo Co., Ltd.)
Hollow particles (primary particle size: 0.3 μm) 3 parts by mass (SX866 (A): manufactured by JSR)
Charge control agent (SBT-5-0016: manufactured by Orient Kogyo Co., Ltd.) 1 part by mass

-Preparation of Charcoal Cal Dispersion B1 The following components were mixed and finely pulverized with a ball mill in the same manner as above to prepare Charcoal Cal Dispersion B1.
<Composition>
Calcium carbonate 40 parts by weight Water 60 parts by weight

-Preparation of liquid mixture C1 The following components were mixed, deaerated with an ultrasonic machine for 10 minutes, and then stirred with an emulsifier to prepare liquid mixture C1.
<Composition>
Charcoal Cal Dispersion B1 8.5g
20% saline 50g

  Next, the dispersion A1: 35 g, ethylene glycol dimethacrylate 1 g, and polymerization initiator AIBN: 0.35 g were weighed and mixed sufficiently, followed by deaeration with an ultrasonic machine for 2 minutes. This was added to the mixed solution C1 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. In this state, particles were produced by reacting at 65 ° C. for 15 hours. 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 to obtain unclassified white particles. Subsequently, the openings were passed through nylon sieves of 10 μm and 15 μm to make the particle sizes uniform. This was dried to obtain white particles having a volume average particle diameter of 13 μm and a specific gravity of 1.7.

  The results of evaluation are summarized in Table 1.

  From the above results, the particle dispersion prepared in this example, this reference example, alone or in combination, even in a system mixed with white particles, compared to the particle dispersion prepared in the comparative example and reference comparative example, It can be seen that the display characteristics are good.

It is a schematic block diagram of the display apparatus which concerns on this 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 20 Display substrate 22 Back substrate 24 Gap member 34 Particle group 34C Cyan particle group 34Y Yellow particle group 34M Magenta particle group 36 Insulating particle 38 Support substrate 40 Surface electrode 42 Surface layer 44 Support substrate 46 Back electrode 48 Surface layer 50 Dispersion medium

Claims (10)

Containing a water-soluble polymer having a charged group and a colorant;
The display particles are characterized in that the water-soluble polymer comprises at least a monomer component that becomes a silicone chain at a mass ratio of 20% or less with respect to the whole polymer as a copolymer component. A group of particles that move in response to an electric field and include the display particles according to claim 1;
Silicone oil as a dispersion medium for dispersing the particles;
A particle dispersion for display, comprising:   The display particle dispersion according to claim 2, wherein the dispersion medium is a silicone oil in which a hydrocarbon group is bonded to a siloxane bond, or a modified silicone oil.   The display particle dispersion according to claim 2, wherein the particle group is composed of a plurality of types of display particles having different charging polarities. The plurality of types of display particles child includes the display particles containing the water-soluble polymer having a quaternary ammonium group as the charging group, the water-soluble polymer having a salt of an acid group as the charging group The display particle dispersion according to claim 4, comprising the display particles. A pair of substrates, at least one of which is translucent,
The display particle dispersion according to any one of claims 2 to 5, encapsulated between the pair of substrates,
A display medium comprising: A pair of electrodes, at least one of which is translucent,
The display particle dispersion according to any one of claims 2 to 5, which is held between the pair of electrodes,
A display medium comprising: A display medium according to claim 6;
Voltage applying means for applying a voltage between the pair of substrates of the display medium;
A display device comprising: And a water-soluble polymer having a charging group, a colorant, an emulsifier, a first solvent consisting of silicone oil, the boiling point than the first solvent incompatible is the first solvent low and the charging group A step of stirring and emulsifying a mixed solution containing a second solvent that dissolves the aqueous polymer having
Removing the second solvent from the emulsified mixed solution;
Have
A method for producing display particles, characterized in that the water-soluble polymer comprises at least a monomer component that becomes a silicone chain as a copolymer component.   The method for producing display particles according to claim 9, wherein the first solvent is a silicone oil in which a hydrocarbon group is bonded to a siloxane bond, or a modified silicone oil.