JP2012042497A - Particle dispersion liquid for display, display medium and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a particle dispersion liquid for a display, which comprises a system including first particles that move in accordance with an electric field and have a first functional group on the surfaces thereof, and a dispersant having a second functional group in the opposite polarity to that of the first functional group and further includes second particles, and which suppresses color mixing of a color by the first particles and a color by the second particles, compared to a particle dispersion liquid that does not use the above second particles.SOLUTION: The particle dispersion liquid for a display includes: first particles that move in accordance with an electric field and have a first functional group on the surfaces of the particles; a dispersant having a second functional group in an opposite polarity to that of the first functional group; second particles that move in accordance with an electric field, have a color and charging characteristics different from those of the first particles, and have at least one group selected from a phenyl group, a hydroxyl group and an alkyl group on the surfaces thereof; and a dispersion medium.

Description

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

  An electrophoretic display medium has been studied. In the display method using the electrophoretic display medium, display is performed by dispersing charged particles (electrophoretic particles) in a liquid and forming an electric field in the liquid to move the electrophoretic particles. It is.

  Patent Document 1 shows an electrophoretic medium including a plurality of charged particles and a polymer, and each of the charged particles and the polymer has a functional group that forms a complex. It has been proposed to provide a display medium with improved image stability without increasing the driving voltage.

Special table 2009-544051 gazette

  The subject of this application is in the system containing the 1st particle | grains which have the 1st functional group on the surface which moves according to an electric field, and the dispersing agent which has a 2nd functional group of the opposite polarity to this 1st functional group. As compared with the case where the second particles in the present invention are not used as particles having different colors and charging characteristics from the first particles, color mixing of the colors of the first particles and the colors of the second particles is suppressed. And providing a display particle dispersion.

The above problem is solved by the following means. That is,
The invention according to claim 1
A first particle that moves in response to an electric field and has a first functional group on the surface;
A dispersant having a second functional group having a polarity opposite to that of the first functional group;
A second particle that moves in response to an electric field, has different color and charging characteristics from the first particle, and has at least one group selected from the group consisting of a phenyl group, a hydroxyl group, and an alkyl group on the surface;
A dispersion medium;
A particle dispersion for display comprising

The invention according to claim 2 is the display particle dispersion according to claim 1, wherein the second particle group has at least an alkyl group on its surface.
The invention according to claim 3 includes a pair of substrates, at least one of which has translucency, and the display particle dispersion according to claim 1 or 2 enclosed between the pair of substrates. Display medium.

According to a fourth aspect of the present invention, there is provided a display device comprising the display medium according to the third aspect and voltage applying means for applying a voltage between the pair of substrates of the display medium.

According to the first, third, and fourth aspects of the invention, the first particle having the first functional group on the surface that moves in response to the electric field, and the first functional group having a polarity opposite to that of the first functional group. In a system including a dispersant having a bifunctional group, the color of the first particle is different from that of the first particle as a particle having a color and charging property different from that of the first particle. And color mixing by the second particles are suppressed.
According to the invention which concerns on Claim 2, compared with the case where a 2nd particle group does not have an alkyl group on the surface, the color mixture with the color by a 1st particle and the color by a 2nd particle is further suppressed.

It is a schematic block diagram of the display apparatus which concerns on this embodiment. It is explanatory drawing which shows typically the movement aspect of a particle group when a voltage is applied between the board | substrates of the display medium of the display apparatus which concerns on this embodiment. (A) (B) It is explanatory drawing which shows typically the movement aspect of a particle group when a voltage is applied between the board | substrates of the display medium of the display apparatus which concerns on this embodiment.

  Hereinafter, an embodiment of the present invention will be described.

(Particle dispersion for display)
In the dispersion liquid for display of the present embodiment, in the dispersion medium, the first particles having the first functional group on the surface and the dispersant having the second functional group having the opposite polarity to the first functional group are included. A second electrophoretic particle dispersed and having at least one group selected from the group consisting of a phenyl group, a hydroxyl group, and an alkyl group on the surface as an electrophoretic particle having a different color and charging polarity from the first particle. A particle dispersion liquid for display in which particles are dispersed.

  Thus, the second particles having at least one group selected from the group consisting of a phenyl group, a hydroxyl group, and an alkyl group on the surface as electrophoretic particles having different colors and charging polarities from the first particles. When used, a display particle dispersion in which color mixing of the color of the first particles and the color of the second particles is suppressed as compared to the case where the second particles having such a configuration are not used is provided. Conceivable.

  Note that in this specification, particles that move in response to an electric field (including first particles and second particles) may be referred to as electrophoretic particles.

Here, the display particle dispersion is applied to the display medium, and an electric field is generated between the substrates of the display medium, in which the first particles move to one of the substrates and the second particles move to the other substrate. Once formed, the first and second particles move in opposite directions. For this reason, the color of the first particle and the color of the second particle are selectively displayed on the display medium.
In addition, it is thought that repulsive force acts between the 1st particles because the charge polarity is the same polarity. However, due to the attractive interaction (acid-base interaction) between the first functional group of the first particle and the second functional group of the dispersant, the first particle is given a cohesive force. It is considered that the color display maintainability is improved. When the electric field is formed in the display particle dispersion liquid, the first particles constrained by the cohesive force are released from the constraining force according to the electric field strength and are separated from each other in the dispersion medium. Moving.

Here, as the electrophoretic particles having different colors and charging characteristics from the first particles, the second particles in the present embodiment (at least one selected from the group consisting of phenyl groups, hydroxyl groups, and alkyl groups on the surface). In the case of using conventional particles different from the second particles having the above group, conventional particles having a color different from that of the first particles may adhere to the first particles. In some cases, color mixing with conventional particles has occurred.
However, in the display particle dispersion liquid of the present embodiment, the second particles having at least one group selected from the group consisting of a phenyl group, a hydroxyl group, and an alkyl group on the surface as the second particles. When used, a display particle dispersion in which color mixing of the color of the first particles and the color of the second particles is suppressed as compared to the case where the second particles having such a configuration are not used is provided. Conceivable.

  Hereinafter, the display particle dispersion according to this embodiment will be described in detail.

―First particle―
As described above, the first particle is an electrophoretic particle that moves in response to an electric field, and has a first functional group.

  As this 1st particle | grain, the structure containing a coloring agent and the polymer which has a 1st functional group is mentioned, It is set as the structure containing the other compounding material as needed. The first particles may be particles in which a colorant is dispersed and blended in a polymer having a first functional group (hereinafter referred to as a first polymer). The particle | grains coat | covered with the 1st polymer | macromolecule may be sufficient, and the particle | grains which the 1st polymer | macromolecule couple | bonded with the particle | grain surface of a coloring agent may be sufficient.

  Note that “bonding” means binding of a reactive group in the first polymer (the reactive group may also serve as the first functional group) and a functional group on the surface of the colorant. “Coating” means that a reactive group in the first polymer causes a reaction such as polymerization with a functional group on the surface of the colorant or a chemical substance added to the system separately to form a layer on the surface of the colorant. The first polymer is used as an emulsifier in the state of covering the colorant surface or at the time of particle preparation, and the first polymer covers the colored particle by physical adsorption or chemical adsorption on the outermost layer of the particle. It shows the state.

  The first functional group is a group having a plus or minus polarity, and specifically includes an acid group (hereinafter referred to as a cationic group) or a base (hereinafter referred to as an anionic group). Here, the first functional group may be a group that functions as a charging group, or may be a group that functions as a charging group, although it may be provided separately from a group that functions as a charging group. .

When a cationic group is used as the first functional group in the first polymer, examples of the cationic group include an amino group and a quaternary ammonium group (including salts of these groups). By using a cationic group as the first functional group, positive charge polarity is imparted to the first particles including the first polymer having the first functional group (cationic group).
On the other hand, when an anionic group is used as the first functional group in the first polymer, examples of the anionic group include a phenol group, a carboxyl group, a carboxylic acid group, a sulfonic acid group, a sulfonic acid group, a phosphorus group, and the like. Examples include acid groups, phosphate groups, and tetraphenylboron groups (including salts of these groups). By using an anionic group as the first functional group, negative charge polarity is imparted to the first particles including the first polymer having the first functional group (anionic group).

  Specific examples of the first polymer include a homopolymer of the monomer having the first functional group, a monomer having the first functional group, and another monomer (functional group (charged group)). And a copolymer with a monomer that does not have. The description such as “(meth) acrylate” is an expression including both “acrylate” and “methacrylate”. The same applies hereinafter.

  Examples of the monomer having the first functional group include a monomer having a cationic group (hereinafter, cationic monomer) or a monomer having an anionic group (hereinafter, anionic monomer). Can be mentioned.

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 vinylamine, pyrroles such as N-vinylpyrrole, pyrrolines such as N-vinyl-2-pyrroline and N-vinyl-3-pyrroline, N-vinylpyrrolidine, vinylpyrrolidine aminoether Pyrrolidines such as N-vinyl-2-pyrrolidone, imidazoles such as N-vinyl-2-methylimidazole, imidazolines such as N-vinylimidazoline, indoles such as N-vinylindole, N-vinylindoline, etc. India Phosphorus, N-vinylcarbazole, carbazoles such as 3,6-dibromo-N-vinylcarbazole, pyridines such as 2-vinylpyridine, 4-vinylpyridine, 2-methyl-5-vinylpyridine, (meth) acrylic Piperidines such as piperidine, N-vinylpiperidone and N-vinylpiperazine, quinolines such as 2-vinylquinoline and 4-vinylquinoline, pyrazoles such as N-vinylpyrazole and N-vinylpyrazoline, and oxazoles such as 2-vinyloxazole , Oxazines such as 4-vinyloxazine and morpholinoethyl (meth) acrylate.

  Among them, as the cationic monomer, (meth) acrylates having an aliphatic amino group such as N, N-dimethylaminoethyl (meth) acrylate and N, N-diethylaminoethyl (meth) acrylate are used. It is particularly desirable 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, examples of the anionic monomer include a carboxylic acid monomer, a sulfonic acid monomer, and a phosphoric acid monomer.
Examples of the carboxylic acid monomer include (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and their anhydrides and their monoalkyl esters, carboxyl groups such as carboxyethyl vinyl ether and carboxypropyl vinyl ether. And vinyl ethers having
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 the like. Salt. Moreover, the sulfuric monoester of 2-hydroxyethyl (meth) acrylic acid and its salt are mentioned.
Examples of the phosphoric acid monomer include vinylphosphonic acid, vinyl phosphate, acid phosphoxyethyl (meth) acrylate, acid phosphoxypropyl (meth) acrylate, bis (methacryloxyethyl) phosphate, diphenyl-2-methacryloyloxyethyl phosphate, Examples thereof include diphenyl-2-acryloyloxyethyl phosphate, dibutyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, dioctyl-2- (meth) acryloyloxyethyl phosphate, and the like.

  Among the above, preferable anionic monomers are those having (meth) acrylic acid or sulfonic acid, and more preferably those having a structure of ammonium salt before or after polymerization. This ammonium salt is produced by reacting with tertiary amines or quaternary ammonium hydroxides.

  Other monomers include nonionic monomers (nonionic monomers) such as (meth) acrylonitrile, (meth) acrylic acid alkyl esters, (meth) acrylamide, ethylene, propylene. , Butadiene, isoprene, isobutylene, N-dialkyl substituted (meth) acrylamide, styrene, vinyl carbazole, styrene, styrene derivatives, polyethylene glycol mono (meth) acrylate, vinyl chloride, vinylidene chloride, isoprene, butadiene, vinyl pyrrolidone, hydroxyethyl ( Examples include meth) acrylate and hydroxybutyl (meth) acrylate.

  The copolymerization ratio between the monomer having the first functional group and the other monomer is appropriately changed according to the target charge amount of the first particles. For example, the copolymerization ratio of the monomer having the first functional group and the other monomer is selected in the range of 1: 100 or more and 100: 0 or less in terms of the molar ratio.

  The weight average molecular weight of the first polymer, which is a polymer having the first functional group, is preferably 1,000 to 1,000,000, and more preferably 10,000 to 200,000.

  Further, the content of the first functional group contained in the first polymer of the first particle is, for example, 0.1% by mass or more and 10% by mass with respect to the total amount of monomers constituting the first polymer. The following is desirable, and 2 mass% or more and 5 mass% or less are more desirable.

  The content of the first particles in the display particle dispersion according to the present embodiment may be an amount capable of obtaining a predetermined color density. For example, 0.01% by mass with respect to the dispersion medium (100% by mass). % To 10% by mass is desirable, and 0.5% to 5% by mass is more desirable.

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

  The blending amount of the colorant contained in the first particles is preferably 10% by mass to 99% by mass, more preferably 30% by mass to 99% by mass with respect to the first polymer contained in the first particle. desirable.

  Next, other compounding materials contained in the first particles will be described. Examples of other compounding materials include a charge control material and a magnetic material. In addition to the charging group, the charging characteristics such as the charging amount and charging polarity of the first particles are adjusted by adjusting the type and blending amount of the charge control material and magnetic material. Note that the charging characteristics can also be adjusted by adjusting the particle size of the first particles.

  As the charge control material, known materials used for electrophotographic toner materials are 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 Industries, 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, a color-coated inorganic magnetic material or organic magnetic material is used as necessary. Further, a transparent magnetic material, in particular, a transparent organic magnetic material does not hinder the color development of the color pigment, and the specific gravity is smaller than that of the inorganic magnetic material, and is more desirable.
As a colored magnetic material (color-coated material), for example, a small-diameter colored magnetic powder described in JP-A-2003-131420 is used. Specifically, examples of the colored magnetic material include those provided with magnetic particles serving as nuclei and a colored layer laminated on the surface of the magnetic particles. The colored layer may be selected as appropriate, for example, by coloring the magnetic powder opaque with a pigment or the like. For example, it is desirable to use a light interference thin film. This optical interference thin film is a thin film having a thickness equivalent to the wavelength of light made of an achromatic material such as SiO ₂ or TiO ₂ and selectively reflects the wavelength of light by optical interference in the thin film. It is.

―Dispersant―
Next, the dispersant will be described.
As described above, the dispersant has a second functional group having a polarity opposite to that of the first functional group in the first particle. As this dispersant, when the first functional group of the first particles is a cationic group, the dispersant has an anionic group as the second functional group. Moreover, when the 1st functional group in the said 1st particle | grain is an anionic group, a dispersing agent is set as the structure which has a cationic group as a 2nd functional group.

Examples of the dispersant used in the present embodiment include a polymer dispersant.
Specifically, examples of the polymer dispersant having a cationic group as the second functional group include monomers selected from monomers having amino groups and monomers having quaternary ammonium groups. Examples thereof include a polymer or a copolymer of these with another monomer (nonionic monomer). About each monomer, since it is the same as that of the said 1st polymer | macromolecule, description is abbreviate | omitted.

  On the other hand, examples of the polymer dispersant having an anionic group as the second functional group include a monomer having a carboxyl group, a monomer having a carboxylate group, a monomer having a sulfonate group, and a sulfonate group. A monomer polymer selected from a monomer having a phosphate group, a monomer having a phosphate group, and a monomer having a phosphate group, or a copolymer of these with another monomer (nonionic) A polymer etc. are mentioned. About each monomer, since it is the same as that raised with the said 1st polymer | macromolecule, description is abbreviate | omitted.

  Further, as the dispersant, for example, when the dispersion medium is silicone oil, a silicone-based polymer described later may be applied. That is, the dispersant may be a copolymer of the monomer and a silicone chain component (monomer thereof) constituting the silicone polymer.

The content of the second functional group in the dispersant is desirably 0.5% by mass or more and 20% by mass or less, for example, and preferably 2% by mass or more and 10% by mass or less with respect to the total amount of monomers constituting the dispersant. More desirable.
Further, the weight average molecular weight of the dispersant is preferably, for example, 10,000 or more and 1,000,000 or less, more preferably 50,000 or more and 300,000 or less.
The content of the polymer dispersant in the display particle dispersion of the present embodiment is preferably 0.0001% by mass or more and 5% by mass or less, more preferably 0.01% by mass with respect to 100% by mass of the dispersion medium. % To 1% by mass.

-Second particle-
Next, the second particle will be described.
As described above, the second particles are particles that move in response to an electric field, and are different in color and charging characteristics from the first particles, and are selected from the group consisting of phenyl groups, hydroxyl groups, and alkyl groups on the surface. Having at least one group.

  Note that “the charging characteristics are different” means that at least one of the charge amount and the polarity of the electrophoretic particles is different. That is, electrophoretic particles having different charging characteristics are different in at least one of a moving voltage value (electric field strength) and a moving voltage polarity.

  The second particles may have at least one group selected from the group consisting of a phenyl group, a hydroxyl group, and an alkyl group, but have at least an alkyl group from the viewpoint of further suppressing color mixing. Is desirable.

  In addition, from the viewpoint of further suppressing color mixing, the second particles do not have acid groups and bases at least on the surface (the amount of acid groups and bases in the second particles is 1% by mass of the total weight of the particles in monomer units). The following is desirable:

In addition, from the viewpoint of further multicolor display, the second particles include a plurality of types of particles (particle groups) that are different in color and charging characteristics from the first particles and that have different colors and charging characteristics. It is good.
In addition, in the case where the second particle includes the plurality of types of particles, in order to adjust the charging characteristics so as to be different from each other, the type and amount of the charging group to be contained, the charge control material to be contained, and the magnetic property What is necessary is just to combine and adjust 1 or more of the kind and quantity of material, and the magnitude | size of particle | grains.

The second particles include a colorant and a polymer having at least one group selected from the group consisting of a phenyl group, a hydroxyl group, and an alkyl group (hereinafter referred to as a second polymer). The composition includes other compounding materials as required.
The second particles may be particles in which a colorant is dispersed and blended in the second polymer, or particles in which the surface of the colorant is coated with the second polymer. The particle | grains which the 2nd polymer couple | bonded with the particle | grain surface of a coloring agent may be sufficient.

  Specific examples of the second polymer include a homopolymer of a monomer having at least one group selected from the group consisting of a phenyl group, a hydroxyl group, and an alkyl group. The second polymer is, for example, a copolymer of these monomers and other monomers (monomers having no polar group, phenyl group, hydroxyl group, or alkyl group). May be. The second polymer includes a monomer having at least one group selected from the group consisting of a phenyl group, a hydroxyl group, and an alkyl group, and a phenyl group, a hydroxyl group, and an alkyl group. It may be a copolymer of a monomer having a group different from the monomer.

  Examples of the monomer having a phenyl group include the following. Specific examples include styrene, phenoxyethylene glycol acrylate, phenoxy polyethylene glycol acrylate, 2-hydroxy-3-phenoxypropyl acrylate, and phenoxyethylene glycol methacrylate. Among these, it is desirable to use phenoxyethylene glycol methacrylate.

  Examples of the monomer having a hydroxyl group include the following. Specifically, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, allyl alcohol, and the like are obtained by copolymerizing a monomer having a glycidyl group and then ring-opening, and have t-butoxy. Examples thereof include those in which OH groups are introduced by polymerizing monomers and then hydrolyzing them. Among these, it is desirable to use hydroxyethyl methacrylate.

  Examples of the monomer having an alkyl group include methyl (meth) acrylate, stearyl (meth) acrylate, and isostearyl (meth) acrylate. Among these, it is desirable to use methyl methacrylate.

  The alkyl group is preferably an alkyl group having 1 to 36 carbon atoms, and more preferably an alkyl group having 1 to 18 carbon atoms. The alkyl group may be substituted or unsubstituted, but is preferably unsubstituted.

  Other monomers (monomers having no acid group, base, phenyl group, hydroxyl group, and alkyl group) include nonionic monomers (nonionic monomers). And an amide group.

  Here, a monomer having at least one group selected from the group consisting of a phenyl group, a hydroxyl group, and an alkyl group, and another monomer (functional group (charging group), phenyl group, hydroxyl group, And the copolymerization ratio with the monomer having no alkyl group are appropriately changed according to the charge amount and the charge polarity.

  The total content of phenyl groups, hydroxyl groups, and alkyl groups contained in the second polymer of the second particles is, for example, 0.001 with respect to the total amount of monomers constituting the second polymer. The mass% is preferably 90% by mass or less and more preferably 0.1% by mass or more and 50% by mass or less.

  The content of the second particles in the display particle dispersion of the present embodiment may be an amount that provides a predetermined color density. For example, 0.01% with respect to the dispersion medium (100% by mass). The mass is preferably from 10% by mass to 10% by mass, and more preferably from 0.5% by mass to 5% by mass.

  In addition, since the other structure (a coloring agent, a magnetic agent, etc.) in a 2nd particle is the same as that of a 1st polymer | macromolecule, description is abbreviate | omitted.

  The first particles and the second particles described above may be particles each having a surface bonded or coated with a silicone-based polymer. Further, the silicone polymer may have a functional group contained in each of the first particle and the second particle, and may be used in place of the polymer constituting the first particle and the second particle. That is, a copolymer of each monomer and a silicone component (monomer) may be used as the first polymer and the second polymer constituting each of the first particle and the second particle. .

  The silicone polymer is, for example, a polymer compound having a silicone chain, and more specifically a compound having a silicone chain (silicone graft chain) as a side chain with respect to the main chain of the main polymer compound. Is good.

  As one of the silicone-based polymers, for example, at least a silicone chain component and, if necessary, a reactive component, a copolymer component having a charged group, and other copolymer components (a copolymer component having no charged group) are included. The copolymer which copolymerized 1 type is mentioned suitably. In addition, a monomer may be used for the raw material of the copolymerization component (especially silicone chain component) in the said copolymer, and a macromonomer may be used. This "macromonomer" is a generic term for oligomers having a polymerizable functional group (degree of polymerization of about 2 or more and about 300 or less) or polymers, and has the properties of both polymers and monomers. is there.

  As the silicone chain component, a dimethyl silicone monomer having a (meth) acrylate group at one end (for example, manufactured by Chisso: Silaplane: FM-0711, FM-0721, FM-0725, etc., Shin-Etsu Silicone Co., Ltd .: X -22-174DX, X-22-2426, X-22-2475, etc.).

  Examples of the reactive component include glycidyl (meth) acrylate having an epoxy group, and isocyanate monomers having an isocyanate group (Showa Denko: Karenz AOI, Karenz MOI).

  As a copolymer component having a charged group and other copolymer components (a copolymer component having no charged group), the monomer having the functional group described above or another monomer (having no functional group) Monomer) and monomers having at least one group selected from the group consisting of a phenyl group, a hydroxyl group, and an alkyl group.

  In the silicone polymer, the mass ratio of the silicone chain component to the whole polymer is 3% or more and 60% or less, preferably 5% or more and 40% or less. By setting it within this range, for example, other properties (charging polarity imparting and charge amount control) are realized while imparting stable dispersibility to the particles.

  Examples of the silicone polymer include a silicone compound having an epoxy group at one end (silicone compound represented by the following structural formula 1) in addition to the copolymer. Examples of the silicone compound having an epoxy group at one end include X-22-173DX manufactured by Shin-Etsu Silicone Co., Ltd.

In Structural Formula 1, R ₁ ′ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. n represents a natural number (for example, 1 to 1000, preferably 3 to 100). x represents an integer of 1 to 3.

  Examples of the silicone polymer include a dimethyl silicone monomer having a (meth) acrylate group at one end (silicone compound represented by the following structural formula 2: manufactured by Chisso Corporation: Silaplane: FM-0711, FM-0721, FM -7725, Shin-Etsu Silicone Co., Ltd .: X-22-174DX, X-22-2426, X-22-2475, etc.) and glycidyl (meth) acrylate or isocyanate monomer (Showa Denko: Karenz AOI, Karenz MOI) A copolymer comprising at least two components is also preferred.

In Structural Formula 2, R ₁ represents a hydrogen atom or a methyl group. R ₁ ′ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. n represents a natural number (for example, 1 to 1000, preferably 3 to 100). x represents an integer of 1 to 3.

  The weight average molecular weight of the silicone polymer is desirably 500 or more and 1,000,000 or less, and more desirably 1,000 or more and 1,000,000 or less.

―Dispersion medium―
Next, the dispersion medium will be described.
The dispersion medium is an insulating liquid and may be a liquid that disperses the first particles, the dispersant, and the second particles described above. In the present specification, “insulating” indicates that the volume resistivity is 10 ⁷ Ωcm or more.

  Specifically, hexane, cyclohexane, toluene, xylene, decane, hexadecane, kerosene, paraffin, isoparaffin, silicone oil, dichloroethylene, trichloroethylene, perchloroethylene, high-purity petroleum, ethylene glycol, alcohols, ether , Esters, dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, 2-pyrrolidone, N-methylformamide, acetonitrile, tetrahydrofuran, propylene carbonate, ethylene carbonate, benzine, diisopropylnaphthalene, olive oil, isopropanol, trichlorotrifluoro Preferable use of ethane, tetrachloroethane, dibromotetrafluoroethane, etc. and their mixtures It is. Among these, it is desirable to apply silicone oil.

  When silicone oil is used as the dispersion medium, the dispersion medium may be a mixed solvent of silicone oil and a solvent other than silicone oil.

  Specific examples of the silicone oil include silicone oils 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.). . Of these, dimethyl silicone is particularly desirable.

  Examples of the solvent other than silicone oil include other petroleum-derived high-boiling solvents such as paraffinic hydrocarbon solvents and fluorine-based liquids.

  A desirable combination of the first functional group of the first particles and the second functional group of the dispersant in the display particle dispersion according to the present embodiment is the first functional group from the viewpoint of obtaining cohesive force. Examples include a combination in which the group is an amino group and the second functional group is a carboxyl group, and a combination in which the first functional group is carboxyl and the second functional group is an amino group. Among these, a combination in which the first functional group is amino and the second functional group is a carboxyl group is particularly desirable.

  In addition, the first functional group of the first particle, the second functional group of the dispersant, and the surface group of the second particle (phenyl group, hydroxyl group, and alkyl) in the display particle dispersion according to the present embodiment. And at least one group selected from the group consisting of groups), the first functional group is an amino group, the second functional group is a carboxyl group, and the surface group of the second particle is an alkyl group. The combination which is is mentioned.

Next, a method for producing electrophoretic particles (the first particles and the second particles) will be described.
As a method for producing the electrophoretic particles according to the present embodiment, for example, a polymer (first polymer or second polymer, hereinafter referred to simply as “polymer” in the description of the production method) and coloring are used. A second solvent (forming a dispersed phase) that is incompatible with the first solvent (a poor solvent capable of forming a continuous phase) and has a lower boiling point than the first solvent and dissolves the polymer. A step of stirring and emulsifying the mixed solution containing the obtained good solvent), and removing the second solvent from the emulsified mixed solution, and coloring particles (display particles) containing the polymer and the colorant And a step of generating a known method. This manufacturing method is a so-called submerged drying method.

  This production method uses a dispersion medium (for example, silicone oil) used for the display particle dispersion as the first solvent, and as it is, as a display particle dispersion containing the first particles or the second particles and the dispersion medium. May be used. Thereby, in the manufacturing method of the electrophoretic particle which concerns on this embodiment, the display particle dispersion liquid which used the 1st solvent as a dispersion medium is obtained through a washing | cleaning and drying process by passing through the said process. Further, washing of the electrophoretic particles (removal of ionic impurities) or replacement of the dispersion medium may be performed.

  In addition, the manufacturing method of electrophoretic particles is not limited to the above-described manufacturing method. For example, a method of forming electrophoretic particles by a known method (such as a pulverization method, a coacervation method, a dispersion polymerization method, a suspension polymerization method). Is adopted. In each method, a dispersion medium used for the display particle dispersion is used as a solvent (a solvent finally remaining in the manufacturing method), and is used as a display particle dispersion containing the electrophoretic particles and the dispersion medium after production. Also good. Thus, in the method for producing electrophoretic particles, a display particle dispersion using the solvent to be used as a dispersion medium can be obtained without going through a washing / drying step by going through each production step.

  Through the above steps, electrophoretic particles are obtained, and a display particle dispersion containing the same is obtained. Here, the obtained display particle dispersion may be diluted with, for example, a dispersion medium (solvent) as necessary.

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

  The display particle dispersion according to this embodiment is used for an electrophoretic display medium, an electrophoretic light control medium (light control element), a liquid toner of a liquid developing electrophotographic system, and the like. In addition, as an electrophoretic display medium and an electrophoretic light control medium (light control element), a method of moving electrophoretic particles in a direction opposite to a known electrode (substrate) surface, an electrode (substrate) is different. ) A method of moving in a direction along the plane (so-called in-plane type element), or a hybrid element combining these.

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

As shown in FIG. 1, the display device 10 includes a book including the electrophoretic particles and the dispersion medium according to the above embodiment as a display particle dispersion liquid including the dispersion medium 50 of the display medium 12 and the electrophoretic particles 34. This is a form to which the display particle dispersion according to the embodiment is applied. Specifically, among the electrophoretic particles 34, the first particle is applied as the particle group 34A, the second particle is applied as the particle group 34B that exhibits a different color from the particle group 34A and has a different charging polarity. It is.

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

  The display medium 12 includes a display substrate 20 that serves as an image display surface, a rear substrate 22 that faces the display substrate 20 with a gap, and holds a space between these substrates at a specific interval, and between the substrates of the display substrate 20 and the rear substrate 22. A plurality of cells, a gap member 24, an electrophoretic particle 34 enclosed in each cell, a dispersing agent 35, and a reflecting particle group 36 having optical reflection characteristics different from the electrophoretic particle 34. Yes.

  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. The electrophoretic particles 34 (details will be described later) are composed of a plurality of particles. The electrophoretic particles 34 are dispersed in the dispersion medium 50, and the distance between the display substrate 20 and the back substrate 22 is changed according to the electric field strength formed in the cell. Is moved through the gap between the reflective particle groups 36.

  In addition, 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, so that the display medium 12 can display each pixel. You may comprise so that it may become possible.

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

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

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

  The surface electrode 40 may be embedded in the support substrate 38. Further, the back electrode 46 may be embedded in the support substrate 44. Further, the back electrode 46 and the surface electrode 40 may be separated from the display substrate 20 and the back substrate 22 and disposed outside the display medium 12.

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

  In order to realize active matrix driving, the support substrate 38 and the support substrate 44 may include a TFT (thin film transistor) for each pixel. Since it is easy to laminate wiring and mount components, it is desirable to form the TFT on the back substrate 22 instead of the display substrate.

  In addition, when the display medium 12 is a simple matrix drive, the configuration of a display device 10 having the display medium 12 described later is simplified, and when the active matrix drive using TFTs is used, the display speed is higher than that of the simple matrix drive. Will be faster.

  Next, the gap member will be described. 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 light-transmitting property of the display substrate 20. The gap member 24 may be integrated with either the display substrate 20 or the back substrate 22. The gap member 24 may be colored or colorless, but is desirably colorless and transparent so as not to adversely affect the display image displayed on the display medium 12.

  Note that “transparent” means having a transmittance of 60% or more with respect to visible light.

  Next, the reflective particle group 36 will be described. The reflective particle group 36 is a non-charged particle group (non-electrophoretic particle group), is composed of reflective particles having optical reflection characteristics different from that of the particle group 34, and displays a color different from that of the particle group 34. It functions as a reflecting member. And it has the function as a space | gap member which has the hole which these electrophoretic particle 34 moves, without inhibiting the movement of the electrophoretic particle 34 between the board | substrates of the display substrate 20 and the back substrate 22. FIG. That is, each particle of the electrophoretic particles 34 moves through the gap between the reflective particle groups 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 reflective particle group 36, for example, it is desirable to select white or black so as to be the background color. In the present embodiment, the case where the reflective particle group 36 is white is described, but the present invention is not limited to this color.

  The size of the cell in the display medium 12 is closely related to the resolution of the display medium 12, and a display medium 12 capable of displaying a high-resolution image is produced as the cell is smaller. The length of the substrate 20 in the plate surface direction is about 10 μm or more and 1 mm or less.

  The display medium 12 configured as described above includes, for example, a bulletin board capable of storing and rewriting images, a circulation version, an electronic blackboard, an advertisement, a signboard, a flashing sign, electronic paper, an electronic newspaper, an electronic book, and a copier / printer. Used for document sheets that are shared with other companies.

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

  The voltage application unit 16 is electrically connected to the front electrode 40 and the back electrode 46. In the present embodiment, the case where both the front electrode 40 and the back electrode 46 are electrically connected to the voltage application unit 16 will be described. However, one of the front electrode 40 and the back electrode 46 is grounded. The other may be connected to the voltage application unit 16. Moreover, the voltage application part 16 is connected to the control part 18 so that signal transmission / reception is possible.

  The control unit 18 stores in advance various programs such as a CPU (Central Processing Unit) that controls the operation of the entire apparatus, a RAM (Random Access Memory) that temporarily stores various data, and a control program that controls the entire apparatus. The ROM includes a read only memory (ROM) and a bus (not shown) for connecting them.

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

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

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

First, an initial operation signal indicating that a voltage is applied for a specific time so that the surface electrode 40 is a negative electrode and the back electrode 46 is a positive electrode is output to the voltage application unit 16. When the surface electrode 40 becomes a negative electrode and the back electrode 46 becomes a positive electrode and a voltage having a voltage value that causes electrophoresis of the particle group 34A and the particle group 34B is applied, the particles constituting the particle group 34A charged on the negative electrode It moves to the substrate 22 side and reaches the back substrate 22 (see FIG. 2). On the other hand, the particles constituting the particle group 34B charged to the positive electrode move to the display substrate 20 side and reach the display substrate 20 (see FIG. 2).
At this time, as the color of the display medium 12 visually recognized from the display substrate 20 side, white as the color of the reflective particle group 36 is used as the background color, and the color exhibited by the particle group 34B is visually recognized. Note that the particle group 34 </ b> A is concealed by the reflective particle group 36 and is difficult to be visually recognized.

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

  Here, the dispersion medium 50 contains a dispersant 35. As described above, when a voltage is applied between the display substrate 20 and the back substrate 22, the particle group 34 </ b> A (first particles) and the dispersing agent 35 dispersed in the dispersion medium 50 (see FIG. 3). (See (A)), and moves to one of the substrates (for example, the display substrate 20 side) (FIG. 3B). Then, each particle constituting the particle group 32 </ b> A as the first particle that has moved to the display substrate 20 side is aggregated via the dispersant 35. For this reason, the color display by the particle group 32A (first particle) is maintained.

  And since each particle (2nd particle) which comprises particle group 34B as 2nd particle | grains is set as the structure mentioned above, it is suppressed that it adheres to particle group 34A (1st particle). For this reason, it is thought that the color mixture of the color by the particle group 34B (second particle) and the color by the particle group 34A (first particle) is suppressed.

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

[Examples and comparative examples]

<Production of first particles>
The following first particles (magenta color) were prepared.

-Production of first particle 1 (first particle having acid group as first functional group: negatively charged particle)-
First, Silaplane “FM-0721”: 4.5 parts by mass as a monomer that becomes a silicone chain, and 0.5 parts by mass of methacrylic acid as a monomer having a charging group are mixed with 10 parts by mass of isopropyl alcohol. As a polymerization initiator, AIBN (2,2′-azobis (isobutyronitrile)): 0.02 part by mass was dissolved and polymerized under nitrogen at 70 ° C. for 6 hours to obtain a polymer.

Next, Ciba water-dispersed pigment solution (magenta color: pigment concentration 16% by mass) was mixed with 1 part by mass of 3 parts by mass of a 10% by mass aqueous solution of polyvinyl alcohol to prepare an aqueous solution containing a polymer and a pigment. Next, a 3 mass% silicone solution of the above polymer was prepared as an emulsifier in 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 the said polymer, this is disperse | distributed with an ultrasonic crusher, and the aqueous solution containing a polymer and a pigment is disperse | distributed in silicone oil (viscosity 2cs). 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. The resulting display particle dispersion was centrifuged to remove the supernatant, and the operation of adding a new solvent was repeated three times for washing.
It was 7.2 mass% when solid content concentration of the produced 1st 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 550 nm.
The charged polarity of the first particles 1 in this dispersion was negatively charged as a result of enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

-Production of first particles 2-
First, Silaplane “FM-0721”: 27 parts by mass as a monomer that forms a silicone chain, and 3 parts by mass of diethylaminoethyl methacrylate as a monomer having a charged group are mixed with 100 parts by mass of isopropyl alcohol, and polymerization is started. AIBN (2,2′-azobis (isobutyronitrile)): 0.2 part by mass as an agent was dissolved and polymerized at 70 ° C. for 6 hours under nitrogen to obtain a polymer.

  Next, Ciba water-dispersed pigment solution (magenta color: pigment concentration 16% by mass) was mixed with 1 part by mass of 3 parts by mass of a 10% by mass aqueous solution of polyvinylpyrrolidone to prepare an aqueous solution containing a polymer and a pigment. Next, a 3 mass% silicone solution of the above polymer was prepared as an emulsifier in 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 the said polymer, this is disperse | distributed with an ultrasonic crusher, and the aqueous solution containing a polymer and a pigment is disperse | distributed in silicone oil (viscosity 2cs). 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. The obtained particle dispersion for display was centrifuged to remove the supernatant, and the operation of adding a new solvent was repeated three times for washing.
It was 7.2 mass% when solid content concentration of the produced 1st particle dispersion liquid was measured from the mass measurement before and behind drying of silicone oil. Further, the volume average particle diameter 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 680 nm.
The charged polarity of the first particles 2 in this dispersion was positively charged as a result of enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

<Preparation of dispersant>
The following dispersant was prepared.

-Preparation of Dispersant 1 (dispersant having a base as the second functional group)-
-Silaplane FM-0711 (manufactured by Chisso Corporation) 4.5 parts by mass-Diethylaminoethyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.) 0.5 parts by mass
・ Solvent: 10 parts by mass of isopropyl alcohol Same as above ・ Polymerization initiator: V-65 (azobisdimethylvaleronitrile) 0.02 parts by mass manufactured by Wako Pure Chemical Industries, Ltd. The reaction was performed for 24 hours. After completion of the polymerization, the resultant was dried under reduced pressure to remove and purify the solvent and unreacted monomer, thereby obtaining Dispersant 1. The yield was 98%. As a result of measuring the molecular weight by GPC, the weight average molecular weight was 120,000 in terms of polystyrene standard.

-Production of Dispersant 2 (Dispersant with Acid Group as Second Functional Group)-
-Silaplane FM-0711 (manufactured by Chisso Corporation) 4.5 parts by mass-Methacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd .: monomer having an acid group) 0.5 parts by mass-Isopropyl alcohol (solvent) 10 Part by mass / V-65 (azobisdimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd .: polymerization initiator) 0.02 part by mass The above composition was mixed and reacted at 55 ° C. for 24 hours after sufficient nitrogen substitution. . After completion of the polymerization, the resultant was dried under reduced pressure to remove and purify the solvent and unreacted monomers, thereby obtaining a dispersant 2. The yield was 98%. As a result of measuring the molecular weight by GPC, the weight average molecular weight was 120,000 in terms of polystyrene standard.

<Preparation of second particles>
The following second particles (cyan) were adjusted.
(Particles produced using submerged drying method)
-Preparation of comparative second particle A1 (Comparative second particle having acid group)-
Poly (acrylamido-2-methylpropanesulfonic acid): PAMPS (weight average molecular weight 210,000) was synthesized by ordinary radical solution polymerization, and a 10 mass% aqueous solution thereof was prepared. Next, 1 part by mass of Ciba's water-dispersed pigment solution (Unisperse cyan color: pigment concentration of 26% by mass), 3 parts by mass of a 10% aqueous solution of PAMPS, and a stoichiometric amount of triethylamine for neutralizing the same. The mixed solution is mixed with 10 parts by mass of a 3% by mass silicone solution of the following silicone polymer A, stirred with an ultrasonic crusher, and an aqueous solution containing a polymer and a pigment is used as a base material. A suspension dispersed and emulsified therein was prepared.

  Next, the suspension was decompressed (2 KPa) and heated (70 ° C.) for 1 hour to remove moisture, and the silicone oil in which the magenta colored particles containing the polymer and the pigment were dispersed in the silicone oil. A dispersion was obtained. Furthermore, this dispersion was heated at 100 ° C. for 3 hours to cause the following silicone polymer A to react with and bind to the surface of the colored particles. After the reaction, the particles were settled using a centrifugal separator and purified by repeating washing with silicone oil. Furthermore, the density | concentration was adjusted with silicone oil and the 2nd particle dispersion liquid (cyan color) whose solid content density | concentration of comparative 2nd particle | grains A1 was 1 mass% was produced.

It was 550 nm as a result of measuring the volume average particle diameter of the comparison 2nd particle | grains A1 in this dispersion liquid (Holiba LA-300: Laser light scattering and a diffraction type particle size measuring apparatus).
The charging polarity of the comparative second particles A1 in this dispersion was negatively charged as a result of enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

-Preparation of silicone polymer A (second polymer with carboxyl group)-
Silaplane FM-0711 (manufactured by Chisso Corporation) which is a silicone monomer: 4.8 parts by mass, methacrylic acid as a monomer having a carboxyl group (manufactured by Wako Pure Chemical Industries, Ltd.): 0.2 parts by mass of dimethyl silicone oil ( Mixed with 10 parts by mass of Shin-Etsu Silicone KF-96L-2CS), 0.4 parts by mass of azobisvaleronitrile as a polymerization initiator was added, polymerization was performed, and a silicone polymer A having a carboxyl group ( Second polymer) was prepared. The weight average molecular weight was 400,000.

-Preparation of second particle A3 (second particle having an alkyl group)-
Instead of 0.2 parts by weight of methacrylic acid used in the preparation of the second comparative particle A1, methyl methacrylate: 5 parts by weight (manufactured by Wako Pure Chemical Industries, Ltd.) and glycidyl methacrylate: 0.5 parts by weight (Wako Pure) The second particle dispersion liquid of the second particle A3 was obtained under the same conditions and the same manufacturing method as the comparative second particle A1, except that Yakuhin Co., Ltd. was used.

  It was 1 mass% when solid content concentration of this dispersion liquid was measured from the mass measurement before and behind drying of silicone oil. Further, the volume average particle diameter of the comparative second particles A2 in the dispersion was measured (Holiba LA-300: laser light scattering / diffraction particle size measuring device), and as a result, it was 550 nm. Further, the charged polarity of the comparative second particle A2 in the present dispersion was negatively charged as a result of enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

-Preparation of second particles A1 (second particles having hydroxyl groups on the surface)-
In the production of the comparative second particle A1, instead of methacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd.) used as a monomer having a carboxyl group, hydroxyethyl methacrylate (Wako Pure Chemical Industries, Ltd.), which is a monomer having a hydroxyl group, was used. )): A display particle dispersion of the second particles A1 was obtained under the same conditions and the same production method as those of the comparative second particles A1, except that 5 parts by mass were used.
It was 8 mass% when solid content concentration of this dispersion liquid was measured from the mass measurement before and behind drying of silicone oil. Moreover, as a result of measuring the volume average particle diameter of the second particles A1 in the dispersion (Holiba LA-300: laser light scattering / diffraction particle size measuring device), it was 300 nm. Further, the charging polarity of the second particles A1 in the present dispersion was negatively charged as a result of enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

-Preparation of second particles A2 (second particles having phenyl groups on the surface)-
AMP10G (Shin Nakamura Chemical Co., Ltd.), which is a monomer having a phenyl group, was used instead of methacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd.) used as a monomer having a carboxyl group in the preparation of the comparative second particle A1. The second particle dispersion liquid of the second particle A2 was obtained under the same conditions and the same production method as those of the comparative second particle A1, except for using the same product.
It was 8 mass% when solid content concentration of this dispersion liquid was measured from the mass measurement before and behind drying of silicone oil. Moreover, as a result of measuring the volume average particle diameter of the second particles A2 in the dispersion (Holiba LA-300: laser light scattering / diffraction particle size measuring device), it was 500 nm. The charging polarity of the second particles A2 in this dispersion was negatively charged as a result of encapsulating the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

-Production of second particles C1 (second particles having phenyl groups on the surface)-
First, to 30 parts by mass of isopropanol, two kinds of dimethyl silicone monomers (FM0725 (manufactured by Chisso: Silaplane) 5 parts by mass, FM0721 (manufactured by Chisso: Silaplane) 5 parts by mass), 2-hydroxyethyl methacrylate (HEMA) 5 parts by mass, 2 parts by mass of octafluoropentyl methacrylate (Tokyo Chemical Industry Co., Ltd.), and 2 parts by mass of AMP10G (manufactured by Shin-Nakamura Chemical Co., Ltd.) as a monomer having a phenyl group, a polymerization initiator (azo 0.02 parts by mass of bisdimethylvaleronitrile “V-65” (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved, oxygen was removed by nitrogen bubbling, and polymerization was carried out at 55 ° C. for 8 hours. After the polymerization, purification treatment and drying were performed to prepare a polymer dispersant A1.

Next, 3 parts by mass of the polymer dispersant A adjusted as described above was dissolved in 97 parts by mass of dimethyl silicone oil (KF-96-2CS manufactured by Shin-Etsu Silicone Co., Ltd.) as an insulating solvent to prepare a continuous phase. Subsequently, 10 parts by mass of a cationic dimethylamine / epochrohydrin polymer as a polymer having a functional group which is a constituent component of the mother particle, a cyan pigment dispersion as a colorant (Emacol manufactured by Sanyo Dye Co., Ltd .: pigment solids) A dispersion phase was prepared by mixing 5 parts by mass) (equivalent to 20 parts by mass) and 85 parts by mass of water as a good solvent. The continuous phase and the dispersed phase were mixed and emulsified for 10 minutes using an ultrasonic crusher (UH-600S manufactured by SMT).
Next, the obtained emulsion is put into an eggplant flask, water is removed by heating (65 ° C.) and reducing pressure (10 mPa) with an evaporator while stirring, and the cyan second particles C1 are dispersed in the silicone oil. A second particle dispersion was obtained.

  It was 8 mass% when solid content concentration of this dispersion liquid was measured from the mass measurement before and behind drying of silicone oil. Further, the volume average particle diameter of the second particles C1 in the dispersion was measured (Holiba LA-300: laser light scattering / diffraction particle size measuring device), and as a result, it was 550 nm. Further, the charging polarity of the second particles C1 in the present dispersion was negatively charged as a result of enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

-Production of comparative second particles C1 (second particles having phosphate groups and carboxyl groups on the surface)-
In the production of the second particle C1, in place of AMP10G (manufactured by Shin-Nakamura Chemical Co., Ltd.) used as a monomer having a phenyl group, 2- (phosphoric acid), a monomer having a phosphate group and a carboxyl group, is used. (Methacryloyloxy) ethyl (manufactured by Aldrich): 2 parts by mass and methacrylic acid: 2 parts by mass of the second particle C1 of the comparative second particle C1 under the same conditions and the same production method as the second particle C1. Got.
It was 7 mass% when solid content concentration of this dispersion liquid was measured from the mass measurement before and behind drying of silicone oil. Moreover, as a result of measuring the volume average particle diameter of the comparative second particles C1 in the dispersion (Holiba LA-300: laser light scattering / diffraction particle size measuring device), it was 250 nm. Further, the charged polarity of the comparative second particle C1 in the present dispersion was negatively charged as a result of encapsulating the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

-Production of comparative second particles C2 (second particles having amino groups on the surface)-
In the production of the second particle C1, instead of AMP10G (manufactured by Shin-Nakamura Chemical Co., Ltd.) used as a monomer having a phenyl group, diethylaminoethyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.) which is a monomer having an amino group is used. : Except having used 2 mass parts, the 2nd particle dispersion liquid of comparative 2nd particle | grains C2 was obtained on the same conditions and the same manufacturing method as said 2nd particle | grains C1.
It was 5 mass% when solid content concentration of this dispersion liquid was measured from the mass measurement before and behind drying of silicone oil. Moreover, as a result of measuring the volume average particle diameter of the comparative second particles C2 in the dispersion (Holiba LA-300: laser light scattering / diffraction particle size measuring device), it was 220 nm. Further, the charged polarity of the comparative second particle C2 in the present dispersion was negatively charged as a result of enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

Further, the following second particles (cyan) were adjusted.
(Particles produced using submerged drying method)
-Preparation of comparative second particle a1 (Comparison second particle having base)-
Polyvinylpyrrolidone (manufactured by K90 Wako Pure Chemical Industries, Ltd.): PVP (weight average molecular weight 360,000) was synthesized by ordinary radical solution polymerization, and a 10% by mass aqueous solution thereof was prepared. Next, 3 parts by mass of a 10% aqueous solution of PVP and 3 parts by mass of silicone polymer B shown below are added to 1 part by mass of a Ciba water-dispersed pigment solution (Unisperse cyan color: pigment concentration of 26 mass%). The suspension was mixed with 10 parts by mass of the solution and stirred with an ultrasonic crusher to prepare a suspension in which an aqueous solution containing a polymer and a pigment was dispersed and emulsified in silicone oil as a base material.

  Next, the suspension was decompressed (2 KPa) and heated (70 ° C.) for 1 hour to remove moisture, and the silicone oil in which the magenta colored particles containing the polymer and the pigment were dispersed in the silicone oil. A dispersion was obtained. Further, this dispersion was heated at 100 ° C. for 3 hours to cause the following silicone polymer B to react with and bind to the surface of the colored particles. After the reaction, the particles were settled using a centrifugal separator and purified by repeating washing with silicone oil. Furthermore, the density | concentration was adjusted with silicone oil and the 2nd particle dispersion liquid (cyan color) whose solid content concentration of the comparison 2nd particle | grains a1 is 1 mass% was produced.

It was 600 nm as a result of measuring the volume average particle diameter of the comparison 2nd particle | grains a1 in this dispersion liquid (Holiba LA-300: laser light scattering and diffraction type particle size measuring apparatus).
The charged polarity of the comparative second particles a1 in this dispersion was positively charged as a result of encapsulating the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

-Preparation of silicone polymer B (second polymer with amino group)-
Silaplane FM-0711 (manufactured by Chisso Corporation) which is a silicone monomer: 4.8 parts by mass, diethylaminoethyl methacrylate as a monomer having an amino group (manufactured by Wako Pure Chemical Industries, Ltd.): 0.2 parts by mass Silicone oil (KF-96L-2CS manufactured by Shin-Etsu Silicone Co., Ltd.) is mixed with 10 parts by mass, 0.4 part by mass of azobisvaleronitrile is added as a polymerization initiator, polymerization is performed, and a silicone-based polymer having a carboxyl group is added. Molecule B (second polymer) was prepared. The weight average molecular weight was 200,000.

-Preparation of comparative second particle a2 (Comparative second particle having acid group)-
Diethylaminoethyl methacrylate used in the preparation of the comparative second particle a1: The same conditions and the same as the comparative second particle a1 except that methacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of 0.2 part by mass. A second particle dispersion of the comparative second particle a2 was obtained by the manufacturing method.

-Production of second particles a1 (second particles having hydroxyl groups on the surface)-
In the production of the comparative second particle a1, in place of diethylaminoethyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.) used as a monomer having an amino group, hydroxyethyl methacrylate (Wako Pure Chemical ( Ltd.): A display particle dispersion of the second particles a1 was obtained under the same conditions and the same production method as those of the comparative second particles a1, except that 5 parts by mass was used.
It was 8 mass% when solid content concentration of this dispersion liquid was measured from the mass measurement before and behind drying of silicone oil. Further, the volume average particle diameter of the second particles a1 in the dispersion was measured (Holiba LA-300: laser light scattering / diffraction particle size measuring device), and as a result, it was 300 nm. Further, the charging polarity of the second particles a1 in the present dispersion was positively charged as a result of enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

-Production of second particles a2 (second particles having phenyl groups on the surface)-
In the production of the comparative second particle a1, in place of diethylaminoethyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.) used as a monomer having an amino group, AMP10G (Shin Nakamura Chemical Co., Ltd.), which is a monomer having a phenyl group, was used. The second particle dispersion liquid of the second particles a2 was obtained under the same conditions and the same production method as those of the comparative second particles a1, except that (made by KK) was used.
It was 8 mass% when solid content concentration of this dispersion liquid was measured from the mass measurement before and behind drying of silicone oil. Further, the volume average particle diameter of the second particles a2 in the dispersion was measured (Holiba LA-300: laser light scattering / diffraction particle size measuring device), and as a result, it was 630 nm. The charged polarity of the second particles a2 in this dispersion was positively charged as a result of encapsulating the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

-Preparation of second particles a3 (second particles having an alkyl group)-
Instead of 0.2 parts by mass of diethylaminoethyl methacrylate used in the preparation of the comparative second particles a1, methyl methacrylate: 5 parts by mass (manufactured by Wako Pure Chemical Industries, Ltd.) and glycidyl methacrylate: 0.5 parts by mass (sum) The second particle dispersion liquid of the second particles a3 was obtained under the same conditions and the same manufacturing method as those of the comparative second particles a1, except that Kogyo Pharmaceutical Co., Ltd. was used.

  It was 4 mass% when solid content concentration of this dispersion liquid was measured from the mass measurement before and behind drying of silicone oil. Further, the volume average particle diameter of the second particles a3 in the dispersion liquid was measured (Holiba LA-300: laser light scattering / diffraction particle size measuring apparatus), and as a result, it was 480 nm. Further, the charging polarity of the second particles a3 in this dispersion was positively charged as a result of enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

-Production of second particles c1 (second particles having phenyl groups on the surface)-
First, to 30 parts by mass of isopropanol, two kinds of dimethyl silicone monomers (FM0725 (manufactured by Chisso: Silaplane) 5 parts by mass, FM0721 (manufactured by Chisso: Silaplane) 5 parts by mass), 2-hydroxyethyl methacrylate (HEMA) 5 parts by mass and 2 parts by mass of AMP10G (manufactured by Shin-Nakamura Chemical Co., Ltd.) as a monomer having a phenyl group, and a polymerization initiator (azobisdimethylvaleronitrile “V-65”, manufactured by Wako Pure Chemical Industries, Ltd.) 0.02 part by mass was dissolved, oxygen was removed by nitrogen bubbling, and polymerization was carried out at 55 ° C. for 8 hours. After the polymerization, purification treatment and drying were performed to prepare polymer dispersant A2.

Next, 3 parts by mass of the polymer dispersant A2 prepared as described above was dissolved in 97 parts by mass of dimethyl silicone oil (KF-96-2CS manufactured by Shin-Etsu Silicone) as an insulating solvent to prepare a continuous phase. Subsequently, 10 parts by mass of a cationic dimethylamine / epochrohydrin polymer as a polymer having a functional group which is a constituent component of the mother particle, a cyan pigment dispersion as a colorant (Emacol manufactured by Sanyo Dye Co., Ltd .: pigment solids) A dispersion phase was prepared by mixing 5 parts by mass) (equivalent to 20 parts by mass) and 85 parts by mass of water as a good solvent. The continuous phase and the dispersed phase were mixed and emulsified for 10 minutes using an ultrasonic crusher (UH-600S manufactured by SMT).
Next, the obtained emulsion is put into an eggplant flask, and water is removed by heating (65 ° C.) and reducing pressure (10 mPa) with an evaporator while stirring, whereby the cyan second particles c1 are dispersed in the silicone oil. A second particle dispersion was obtained.

  It was 8 mass% when solid content concentration of this dispersion liquid was measured from the mass measurement before and behind drying of silicone oil. Further, the volume average particle size of the second particles c1 in the dispersion was measured (Holiba LA-300: laser light scattering / diffraction particle size measuring device), and as a result, it was 350 nm. Further, the charging polarity of the second particles c1 in this dispersion was positively charged as a result of enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

-Preparation of comparative second particles c1 (second particles having amino groups on the surface)-
In the production of the second particle c1, instead of AMP10G (manufactured by Shin-Nakamura Chemical Co., Ltd.) used as a monomer having a phenyl group, diethylaminoethyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.) which is a monomer having an amino group is used. : Except having used 2 mass parts, the 2nd particle dispersion liquid of the comparative 2nd particle c1 was obtained on the same conditions and the same manufacturing method as the said 2nd particle c1.
It was 5 mass% when solid content concentration of this dispersion liquid was measured from the mass measurement before and behind drying of silicone oil. Further, the volume average particle diameter of the comparative second particles c1 in the dispersion was measured (Holiba LA-300: laser light scattering / diffraction particle size measuring device), and as a result, it was 280 nm. Further, as a result of evaluating the charging polarity of the comparative second particles c1 in the present dispersion liquid by enclosing the dispersion liquid between two electrode substrates and applying a DC voltage to evaluate the migration direction, it was positively charged.

(Examples and comparative examples)
-Preparation of particle dispersion for display-
Each of the first particle dispersion, the dispersant, and the second particle dispersion adjusted as described above is mixed so that the content in the display particle dispersion is the content shown in Table 5 and Table 6, A display particle dispersion and a comparative particle dispersion were prepared.

-Production of display media-
A display medium having the structure shown in FIG. 1 was produced as follows (see FIG. 1). More specifically, ITO was formed as a film with a thickness of 50 nm on a support substrate made of glass having a thickness of 0.7 mm by sputtering. A gap layer having a height of 50 μm and a width of 20 μm is obtained by applying a surface layer to the back substrate composed of this ITO / glass substrate using CYTOP (manufactured by Asahi Glass Co., Ltd., CTL809M), followed by exposure and wet etching. Formed.

  After forming a heat-fusible adhesive layer (not shown) on the upper part of the gap member, it is filled with the following white particle group, the obtained display particle dispersion and comparative particle dispersion, and the same as the back substrate. A display substrate made of ITO / glass and having a surface layer formed is bonded to the back substrate so that the surfaces (electrode surfaces) on which the surface layers are formed face each other, and heat is applied. A display medium was prepared for each display particle dispersion and each comparative particle dispersion.

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

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

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

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

[Mixed color evaluation]
By using the produced display medium, a voltage of 15 V is applied to both electrodes for 5 seconds (hereinafter referred to as a first voltage) so that the electrode of the display substrate is positive and the electrode of the back substrate is negative. Either one of the particles (comparative first particle) and the second particle (comparative second particle) was migrated to the display substrate side, and the other was migrated to the back substrate side (moved in directions opposite to each other). Next, by applying a voltage (hereinafter referred to as a second voltage) whose polarity is reversed or whose applied voltage is 15 V (the application time is the same), the first particles (comparative first particles) are opposite to the moving direction. ) And the second particles (comparative second particles), and the first particles (comparative first particles) and the second particles (comparative second particles) in the direction opposite to the moving direction when the first voltage is applied immediately before. ) Were moved (moved in opposite directions).

A series of voltage application processes for applying the second voltage after the application of the first voltage are repeated 10 times in succession, and then applying one of the first voltage and the second voltage, First particles or comparative first particles (cyan) were moved to the display substrate side. And about 10 points including the edge part and center part of the whole area | region of the surface of a display board, the average value which measured the optical density was evaluated using the densitometer (X-Rite404A made from X-Rite). The optical density when cyan of the target display medium was displayed was used.

In addition, as a reference display medium used for color mixture evaluation, a display medium exactly the same as the display medium to be evaluated is prepared for each display medium to be evaluated except that the second particles (or comparative second particles) are not included. The first particles or the comparative first particles (cyan) were moved to the display substrate side by applying one of the first voltage and the second voltage once. And about 10 points including the edge part and center part of the whole area | region of the surface of a display substrate, the average value which measured the optical density using the densitometer (X-Rite404A made from X-Rite) was used as the standard. The optical density when displaying the magenta color of the display medium was used.

  Then, based on the cyan optical density when the magenta color is displayed on the reference display medium and the cyan optical density when the magenta color is displayed on the evaluation target display medium, the color mixture is evaluated. went. The evaluation criteria were as follows. The evaluation results are shown in Tables 5 and 6.

-Evaluation criteria for color mixing-
G1: The difference between the measurement result of the cyan optical density when the magenta color is displayed on the reference display medium and the measurement result of the cyan optical density when the magenta color is displayed on the evaluation target display medium is 10 %Less than.
G2: The difference between the measurement result of the cyan optical density when the magenta color is displayed on the reference display medium and the measurement result of the cyan optical density when the magenta color is displayed on the display medium to be evaluated is 10 % To 30%.
G3: The difference between the measurement result of the cyan optical density when the magenta color is displayed on the reference display medium and the measurement result of the cyan optical density when the magenta color is displayed on the display medium to be evaluated is 30 % To 50%.
G4: The difference between the measurement result of the cyan optical density when the magenta color is displayed on the reference display medium and the measurement result of the cyan optical density when the magenta color is displayed on the display medium to be evaluated is 50 %more than.

DESCRIPTION OF SYMBOLS 10 Display apparatus, 12 Display medium, 16 Voltage application part, 18 Control part, 20 Display substrate, 22 Back substrate, 34A particle group, 34B particle group, 35 Dispersant, 50 Dispersion medium

Claims (4)

A first particle that moves in response to an electric field and has a first functional group on the surface;
A dispersant having a second functional group having a polarity opposite to that of the first functional group;
A second particle that moves in response to an electric field, has different color and charging characteristics from the first particle, and has at least one group selected from the group consisting of a phenyl group, a hydroxyl group, and an alkyl group on the surface;
A dispersion medium;
A particle dispersion for display comprising:   The display particle dispersion according to claim 1, wherein the second particle group has at least an alkyl group on a surface thereof. A pair of substrates, at least one of which is translucent,
The display particle dispersion liquid according to claim 1 or 2, encapsulated between the pair of substrates,
A display medium comprising: A display medium according to claim 3;
Voltage applying means for applying a voltage between the pair of substrates of the display medium;
A display device comprising: