JP5316062B2 - Display particle dispersion, display medium, and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a particle dispersion liquid for display wherein a cohesive force is given between particles for display having the same polarity in comparison with the use of two kinds of polymer dispersants different in charge polarities in a system wherein at least two kinds of particles for display different in charge polarities are mixed. <P>SOLUTION: The particle dispersion liquid for display includes: (a dispersion medium 50) which contains a main dispersion medium. an additive dispersion medium having a solubility parameter (SP value) different from that of the main dispersion medium and of which the difference in solubility parameter (SP value) from particles for display is larger than the difference in solubility parameter (SP value) between the main dispersion medium and particles for display; and a first particle for display (a particle group 34A thereof) which is dispersed in the dispersion medium and moves in accordance with an electric field and has a first polymer dispersant deposited on the surface thereof and has a functional group immiscible to the main dispersion medium in the surface thereof or the first polymer dispersant. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to 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, display particles (electrophoretic particles) charged in a liquid are used, and the electrophoretic particles are enclosed in a cell by applying an electric field (two electrode substrates are stacked and an electrophoretic material is enclosed with a dispersion medium therebetween). Display is performed by alternately moving to the viewing surface and back surface of the configuration.

  In the present technology, the display particles (electrophoretic particles) are important elements, and various technical developments have been made. For example, for the purpose of imparting the cohesive force of the display particles, there has been proposed a method for making the particles easy to aggregate by adjusting the compatibility of the polymer shell around the display particles together with the display particles (for example, , Patent Document 1)

Special Table 2007-508588

  The problem of the present application is to provide a display particle dispersion in which cohesion between display particles is given to the main dispersion medium in which display particles are dispersed, compared to the case where a specific additive dispersion medium is not added. It is.

The above problem is solved by the following means. That is,
The invention according to claim 1
The main dispersion medium and an additive dispersion medium having a solubility parameter (SP value) different from that of the main dispersion medium are included. The difference in solubility parameter (SP value) between the main dispersion medium and the following display particles is used for the following display. A mixed dispersion medium having a large difference in solubility parameter (SP value) from the particles;
First display particles that are dispersed in the dispersion medium and move in response to an electric field, the first polymer dispersant being attached to the surface, and the main dispersion medium on the surface or the first polymer dispersant First display particles having a functional group incompatible with
A particle dispersion for display comprising:

The invention according to claim 2
The main dispersion medium is silicone oil;
The display particle dispersion according to claim 1, wherein the functional group incompatible with the main dispersion medium is selected from a hydroxyl group, a carboxyl group, and a phenyl group.

The invention according to claim 3
The main dispersion medium is silicone oil;
The display particle dispersion according to claim 1, wherein the additive dispersion medium is selected from a modified silicone oil and a compound having a phenyl group.

The invention according to claim 4
As the display particles,
First display particles that are dispersed in the mixed dispersion medium and move in response to an electric field, the first polymer dispersant being attached to the surface, and the main dispersion on the surface or the first polymer dispersant First display particles having a functional group incompatible with the medium;
Second display particles that are dispersed in the mixed dispersion medium, move in response to an electric field, and have a different charge polarity from the first display particles, and a second polymer dispersant is attached to the surface. The display particle dispersion according to claim 1, further comprising second display particles having functional groups incompatible with the main dispersion medium on the surface or the second polymer dispersant.

The invention according to claim 5
A pair of substrates, at least one of which is translucent,
The display dispersion liquid according to any one of claims 1 to 4, wherein the display dispersion liquid is sealed between the pair of substrates.
A display medium comprising:

The invention according to claim 6
A pair of electrodes, at least one of which is translucent,
A region having a display dispersion liquid according to any one of claims 1 to 4, which is provided between the pair of electrodes.
A display medium comprising:

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

According to the first aspect of the present invention, the cohesion between display particles having the same charge polarity is imparted to the main dispersion medium in which the display particles are dispersed, as compared with the case where no specific additive dispersion medium is added. The
According to the second aspect of the present invention, the cohesion between display particles having the same charge polarity is given compared to the case where the main dispersion medium and the functional group incompatible with the main dispersion medium are not specified. The
According to the third aspect of the present invention, the cohesion between display particles having the same charge polarity is imparted compared to the case where the main dispersion medium and the dispersion medium are not specified.
According to the invention of claim 4, in a system in which at least two kinds of display particles having different charging polarities are mixed, a specific additive dispersion medium is not added to the main dispersion medium in which the display particles are dispersed. In contrast to this, aggregation of display particles having different charging polarities is suppressed, and aggregating force between display particles having the same charging polarity is imparted.
According to the invention which concerns on Claim 5, the maintainability of a display is provided compared with the case where it does not have this structure.
According to the invention which concerns on Claim 6, the maintainability of a display is provided compared with the case where it does not have this structure.
According to the invention which concerns on Claim 7, the maintainability of a display is provided compared with the case where it does not have this structure.

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. It is a schematic diagram for demonstrating the presumed effect | action of the dispersion liquid for a display which concerns on this embodiment.

  Hereinafter, embodiments of the present invention will be described.

(Particle dispersion for display)
The display particle dispersion according to the present embodiment includes a dispersion medium and display particles (a group thereof) that are dispersed in the dispersion medium and move according to an electric field. As the display particles, a polymer dispersant is attached to the surface thereof, and display particles having a functional group incompatible with the main dispersion medium are applied to the surface or the polymer dispersant. The dispersion medium is a main dispersion medium and a mixed dispersion medium of an added dispersion medium having a solubility parameter (SP value) different from that of the main dispersion medium, and the solubility parameter (SP value) of the main dispersion medium and display particles. A mixed dispersion medium having a larger solubility parameter (SP value) difference from the first display particles than the difference is applied.

  Further, the display particle dispersion according to the present embodiment has the first polymer dispersant attached to the surface as display particles and is incompatible with the main dispersion medium on the surface or the first polymer dispersant. The first display particles having a functional group and the first display particles are second display particles having different charging polarities, and the second polymer dispersant is attached to the surface, and the surface or the second display particle. It may be in a form in which at least two kinds of display particles having different charge polarities are applied to the polymer dispersant having the second display particles having a functional group incompatible with the main dispersion medium. .

  In the display particle dispersion according to this embodiment, the main dispersion medium is provided with a functional group incompatible with the main dispersion medium, either directly or indirectly through the polymer dispersion medium. Maintain the dispersibility of the particles. On the other hand, a mixed dispersion medium and a polymer dispersant obtained by adding an additive dispersion medium to the main dispersion medium by adding an additive dispersion medium having a solubility parameter (SP value) different from that of the main dispersion medium. The difference in solubility parameter between the display particles to which is attached is larger than the solubility parameter difference between the main dispersion medium and the display particles to which the polymer dispersant is attached. When the solubility parameter difference between the dispersion medium and the display particles (display particles to which the polymer dispersion medium is attached) widens, the display particles to which the polymer dispersant is attached aggregates between particles having the same chargeability. It tends to occur. This is because as the solubility parameter difference between the display particles to which the dispersion medium and the polymer dispersant are attached increases, the molecular chains of the polymer dispersant tend to extend outward from the display particles as shown in FIG. A certain state (FIG. 3A) is a state in which the molecular chain of the polymer dispersant is curved and contracts or tends to move toward the display particles (FIG. 3B), and has the same charging polarity. This is probably because the distance between the display particles is shortened.

  For this reason, in the display particle dispersion according to the present embodiment, the display particles having the same charge polarity are compared with each other as compared with the case where the main dispersion medium and the functional group incompatible with the main dispersion medium are not specified. Cohesive force is imparted. On the other hand, the display particles constrained by the cohesive force are released when the particles are kept at a certain distance by movement according to the electric field, and the display particles are separated from each other in the dispersion liquid. Moving.

  When the display particle dispersion according to this embodiment is applied to a display medium or a display device, when display particles having the same polarity gather together for display (for example, move to the display substrate side), Since the condensing force acts on the display particles having the same polarity, the constraint due to the condensing force is difficult to be released, and display maintainability, that is, memory property is imparted.

  Further, in the display particle dispersion according to the present embodiment, a system in which at least two kinds of display particles having different charging polarities are mixed (the second display particles having different charging polarities together with the first display particles). In the applied system), the aggregation of display particles having different charge polarities is suppressed and the same charge polarity as compared with the case where a specific additive dispersion medium is not added to the main dispersion medium in which the display particles are dispersed. The agglomeration force between the display particles having is given. This is because the solubility parameter of the dispersion medium itself is not changed by adding a functional group to the display particles or the polymer dispersion medium, but the solubility parameter difference between the dispersion medium and the display particles to which the polymer dispersant is attached. From the viewpoint of the relationship between the first display particles and the second display particles having different charging polarities, it is considered that an element (for example, a functional group) that acts attraction is not provided.

  First, display particles (first display particles and second display particles having a different charging polarity from the first display particles) will be described.

  The display particles include, for example, a colorant and a polymer, and may include other compounding materials as necessary. The display particles may be particles in which a colorant is dispersed and blended in a polymer, or may be particles in which the colorant particle surface is coated with a polymer.

The display particles preferably have a functional group incompatible with the main dispersion medium on the surface thereof. The functional group may also serve as the charged group. Here, the functional group is incompatible with the main dispersion medium means that the functional group is incompatible with the main dispersion medium as a component constituting a polymer having a functional group incompatible with the main dispersion medium. It means that a monomer having a compatible functional group is present in an independent phase without being mixed with the main dispersion medium.
Specifically, when the main dispersion medium is silicone oil, examples of the functional group include a carboxyl group, a hydroxyl group, an amino group, a polyether group, and a phenyl group. Among these, a hydroxyl group, a carboxyl group, or a phenyl group is preferable.
Examples of the functional group include a carboxyl group, a hydroxyl group, an amino group, a polyether group, or a phenyl group when the main dispersion medium is a paraffinic hydrocarbon solvent.
When the polymer dispersant attached to the display particles has the functional group, the display particles need not have the functional group.

The display particles preferably have a charged group on the surface. Depending on the type of the charged group, positively charged particles or negatively charged particles are obtained. Examples of the charged group include a base or an acid group. Among the base (hereinafter referred to as a cationic group) or acid group (hereinafter referred to as an anionic group) that functions as a charged group, examples of the cationic group that functions as a charged group include an amino group and a quaternary ammonium group. Including the salt of the group), this cationic group generally imparts positively charged polarity to the particles. On the other hand, examples of the anionic group as the charging group include a phenol group, a carboxyl group, a carboxylate group, a sulfonate group, a sulfonate group, a phosphate group, a phosphate group, and a tetraphenylboron group (these groups). In general, the anionic group imparts negatively charged polarity to the particles.
When the polymer dispersant attached to the display particles has a charged group, the display particles need not have a charged group.

  In order to provide the display particles with the above-described charged group or a functional group incompatible with the main dispersion medium, it is preferable to apply a polymer containing these groups as the polymer constituting the display particles.

  Specific examples of the polymer constituting the display particles include a homopolymer of a monomer having a charged group, a homopolymer of a monomer having a functional group incompatible with the main dispersion medium, and the like. (Monomers having no functional group incompatible with the charging group or the main dispersion medium) or copolymers thereof.

  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). The description such as “(meth) acrylate” is an expression including both “acrylate” and “methacrylate”. The same applies hereinafter.

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.
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, for example, by reacting the 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, carboxylic acid monomers include (meth) acrylic 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, and salts thereof.
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.
Preferable anionic monomers are those having (meth) acrylic acid or sulfonic acid, and more preferably those having a structure that becomes an ammonium salt before or after polymerization. The ammonium salt is produced, for example, by reacting with a tertiary amine or quaternary ammonium hydroxide.

  Examples of the monomer having a functional group incompatible with the main dispersion medium include hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, ( Examples include meth) acrylic acid, maleic acid, styrene, styrene derivatives, phenoxyethylene glycol (meth) acrylate, vinyl naphthalene, and fluorine-substituted alkyl esters of (meth) acrylic acid.

  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, etc. It is done.

  Here, when a monomer having a charging group is used as the polymer, the ratio is appropriately changed according to, for example, the charge amount of the desired particles. Further, when a monomer having an incompatible functional group is used in the main dispersion medium, the ratio is appropriately changed according to, for example, the charge amount of desired particles.

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

  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 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 material and a magnetic material.
As the charge control material, known materials used for electrophotographic toner materials 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, 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. 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, the polymer dispersant will be described.
The polymer dispersant is, for example, bonded or coated on the surface of the colored particles and attached to the surface of the colored particles. In addition, the polymer dispersant may be constituted by adhering (chemically bonding or coating) the surface of the colorant instead of the polymer constituting the colored particle to constitute the colored particle.

  The polymer dispersant may have a charged group as in the polymer constituting the colored particles, or may have a functional group incompatible with the main dispersion medium.

Examples of polymer dispersants include poly (meth) acrylate polymers and copolymers having hydrophilic groups, silicone polymers and copolymers having hydrophilic groups, and long-chain alkyl compounds having hydrophilic groups. Examples thereof include a polymer, a copolymer, a copolymer of a monomer having a hydrophilic group and styrene, and a styrene-butadiene copolymer. Among these, a silicone polymer or copolymer having a hydrophilic group, or a long-chain alkyl polymer or copolymer having a hydrophilic group is preferably exemplified.
In addition, by using a polymer dispersant with a reactive component, it is effective for dispersion stability and electrophoretic properties of particles by forming a chemical bond such as a covalent bond with the particle surface and a coating layer on the particle surface. Is also expected.

  The silicone-based polymer or copolymer having a hydrophilic group is, for example, a polymer compound having a silicone chain and a hydrophilic group, and more specifically, for example, a compound having a silicone chain as a main chain. Alternatively, the main chain of the main polymer compound may be a compound having a silicone chain (silicone graft chain) as a side chain.

  Examples of the silicone-based polymer include, for example, a silicone chain component, a hydrophilic component, a reactive component if necessary, a copolymer component having a charged group, and a functional group incompatible with the main dispersion medium. A copolymer obtained by copolymerizing at least one of a functional group and other copolymer components (a copolymer component having no functional group incompatible with the charging group or the main dispersion medium) is preferable. 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 hydrophilic components include polyethylene glycol mono (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, (meth) acrylic acid and salts thereof, Maleic acid and its salt, dialkylaminoethyl (meth) acrylate and its salt, (meth) acrylamide, vinylpyrrolidone and the like can be mentioned.

  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 the copolymerization component having a charging group and other copolymerization components (copolymerization components having no charging group), the monomer having a charging group described in the polymer having a charging group, other monomers ( Those mentioned in (monomers not having a charging group) are applied. Further, the copolymer component having a charging group may be the same as the hydrophilic component described above.

  In the silicone polymer, the mass ratio of the silicone chain component to the whole polymer is 10% or more and 98% or less, preferably 20% or more and 95% 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 2 or more and 5 or less.

  Examples of the silicone polymer having a reactive group 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-0725, etc., 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) Copolymers comprising at least two components with AOI and Karenz MOI) are 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 2 or more and 5 or less.

  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.

On the other hand, the long-chain alkyl polymer having a reactive group has a structure similar to, for example, the above-mentioned silicone copolymer, and a long-chain alkyl (meth) as a long-chain alkyl component instead of the silicone chain component. The thing using an acrylate is mentioned. Specific examples of the long-chain alkyl (meth) acrylate are preferably those having an alkyl chain having 4 or more carbon atoms, such as butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and dodecyl (meth). Examples include acrylate and stearyl (meth) acrylate. Among these, at least two components of long-chain alkyl (meth) acrylate and glycidyl (meth) acrylate, or an isocyanate monomer (Showa Denko: Karenz AOI, Karenz MOI) from the viewpoint of excellent reactivity and surface activity. A copolymer consisting of is preferred. The composition ratio of the components in the copolymer is selected from the same range as that of the silicone polymer.
The “long chain” of the long-chain alkyl polymer means, for example, a polymer having an alkyl chain having 4 to 30 carbon atoms in the side chain.

  The weight average molecular weight of the long-chain alkyl polymer is preferably 1,000 to 1,000,000, and more preferably 10,000 to 1,000,000.

  These polymer dispersants are bonded or coated on the surface of the colored particles. Here, the “bond” refers to the reactive group of the polymer dispersant and the functional group (the functional group is charged as described above) on the surface of the colored particles. “Coating” means that the reactive group of the polymer dispersant is polymerized by a functional group on the surface of the colored particles or a chemical substance added to the system separately. It shows a state in which a reaction is caused to form a layer on the particle surface to cover the colored particle surface. As a method of selectively performing bonding and coating, for example, when bonding, a polymer dispersant (for example, a silicone polymer) having a reactive group that actively bonds to a functional group (charged group) as described above. Or a long-chain alkyl polymer) (for example, an acid group, an acid group, an alcoholate group, a phenolate group as a functional group on the particle, and an epoxy group or an isocyanate group as a reactive group) Select the polymer to which the reactive groups of the polymer dispersant (eg, silicone polymer or long-chain alkyl polymer) are bonded using the functional group (charged group) as a catalyst (eg, functional group (charged group)) For example, an amino group, an ammonium group, and an epoxy group as a reactive group).

  A method of bonding or coating a polymer dispersant (for example, a silicone polymer or a long-chain alkyl polymer) on the surface of the colored particles is performed by heating or the like. Further, the binding amount and the coating amount are preferably in the range of 2% by mass to 200% by mass with respect to the mass of the particles in view of dispersibility. When the amount is less than 2% by mass, the particle dispersant is inferior, and when the amount is more than 200% by mass, the charge amount of the particles is reduced.

  The bonding amount and the coating amount are obtained as follows. One is to calculate the amount of increase with respect to the amount of the particle material by centrifuging the produced particles and measuring their mass. In addition, it may be calculated from the composition analysis of the particles.

Next, the dispersion medium will be described. The dispersion medium is a mixed dispersion medium of a main dispersion medium and an additive dispersion medium. Here, the main dispersion medium means a dispersion medium containing 70% by mass or more based on the entire mixed dispersion medium.
Examples of the main dispersion medium include petroleum-derived high-boiling solvents such as paraffinic hydrocarbon solvents, silicone oils, and fluorinated liquids, but the type of colored particles (mainly polymer dispersants) to which the polymer dispersant is attached. It is selected according to. Specifically, for example, when colored particles having a silicone polymer attached thereto are used as the polymer dispersion medium, silicone oil is preferably selected as the main dispersion medium. In addition, when applying colored particles to which a long-chain alkyl polymer is attached as a polymer dispersant, it is preferable to select a paraffin hydrocarbon solvent.

  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.). Among these, dimethyl silicone is particularly desirable from the viewpoint of high safety, chemical stability, long-term reliability, and high resistivity.

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

  Examples of the paraffinic hydrocarbon solvent include normal paraffinic hydrocarbons and isoparaffinic hydrocarbons having 20 or more carbon atoms (boiling point of 80 ° C. or higher), but it is desirable to use isoparaffins for reasons such as safety and volatility. . 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.

  On the other hand, the added dispersion medium is a dispersion medium having a solubility parameter (SP value) different from that of the main dispersion medium, and the solubility parameter (SP value) of the entire dispersion medium is changed to change the main dispersion medium and display particles (polymer dispersion). Compared to the difference in solubility parameter (SP value) from the display particles to which the agent is attached, the mixed dispersion medium (dispersion liquid in which the additive dispersion medium is added to the main dispersion medium) and the display particles (indication to which the polymer dispersant is attached) Is a dispersion medium that increases the difference in solubility parameter (SP value) from

Examples of the additive dispersion medium include, when the main dispersion medium is silicone oil, modified silicone oil, a compound having a phenyl group, and a hydrocarbon compound. Among these, modified silicone oils and compounds having a phenyl group are preferable.
Examples of the modified silicone oil include a modified silicone oil having a polar group. Specifically, for example, a hydroxy-modified silicone oil having a hydroxy group, a carboxy-modified silicone oil having a carboxyl group, and an amino-modified having an amino group. Examples thereof include silicone oil, modified silicone oil having a phenyl group, and modified silicone oil having a polyether group.
Examples of the compound having a phenyl group include substituted aromatic compounds. Examples of substituted aromatic compounds include alkyl-substituted benzenes such as toluene, xylene, mesitylene, and ethylbenzene; halogen-substituted benzenes such as benzyl alcohol, chlorobenzene, fluorobenzene, chlorotoluene, and fluorotoluene; toluene, aniline, methylaniline, and dimethyl And aromatic esters such as aniline and ethyl benzoate, and aromatic ethers.

Further, examples of the additive dispersion medium include alcohols and aromatic compounds when the main dispersion medium is a paraffinic hydrocarbon solvent.
Examples of alcohols include alcohols having 1 to 20 carbon atoms, ethylene glycol, glycerin, oligo or polyethylene glycol.
Examples of the aromatic compound include those described above as the substituted aromatic compound added to the silicone oil.

  The addition amount of the added dispersion medium is selected according to the solubility parameter of the target mixed dispersion medium. For example, it is 1% by mass or more and 99% by mass with respect to the total dispersion medium (main dispersion medium + added dispersion medium). It is preferable that the content be 10% by mass or more and 50% by mass or less.

  Here, a mixed dispersion medium in which the solubility parameter (SP value) of the entire dispersion medium is increased by adding an additional dispersion medium to the main dispersion medium may be used, or a mixed dispersion medium in which the solubility is decreased. However, the solubility parameter difference between the mixed dispersion medium and the display particles to which the polymer dispersant is attached is larger than the solubility parameter difference between the main dispersion medium and the display particles to which the polymer dispersant is attached. Next, each dispersion medium type is selected.

Specifically, the solubility parameter of the main dispersion medium is preferably 6 or more and 10 or less (preferably 7 or more and 8 or less).
The solubility parameter of the added dispersion medium is preferably 6 or more and 15 or less (preferably 6 or more and 12 or less).
The solubility parameter of the mixed dispersion medium is, for example, preferably 6 or more and 15 or less (preferably 7 or more and 12 or less).
The solubility parameter of the colored particles to which the polymer dispersant is attached may be, for example, 6 or more and 10 or less (preferably 7 or more and 8 or less).
The solubility parameter difference between the main dispersion medium and the colored particles to which the polymer dispersant is attached is, for example, 0 or more and 2 or less (preferably 0 or more and 1 or less).
The solubility parameter difference between the mixed dispersion medium and the colored particles to which the polymer dispersant is attached is, for example, 0 or more and 3 or less (preferably 0 or more and 2 or less).

The display particles to which the polymer dispersant is attached and the solubility parameter (SP value) of each dispersion medium are determined as follows.
The SP value of each dispersion medium is determined by calculating from the evaporation energy (Δei) and molar volume (Δvi) of chemical structure atoms or atomic groups by the Fedor formula: SP value δ = (ΣΔei / ΣΔvi) ^1/2. .
When the solubility of the added dispersion medium in the dispersion medium is small, the SP value δ _M of the mixed dispersion medium is calculated from the SP values δ ₁ and δ ₃ and the volume fraction of each dispersion medium by Φ ₁ and Φ _3. : Δ _M = Φ ₁ δ ₁ + Φ ₃ δ ₃
Further, the SP value of the display particles to which the polymer dispersant is attached is defined as the SP value of the polymer dispersant present on the surface. The SP value of the polymer dispersant can be similarly calculated using the above-mentioned Fedor formula. This value is the SP value of the display particles. As other methods for calculating the SP value of a polymer, there are calculation formulas of Small and Hoy. These calculate the SP value from the chemical structure, specific gravity, and molecular weight of the polymer based on empirical values (Group Molecular Attraction Constants) of each atom and functional group from the heat of vaporization measurement.

Next, an example using a submerged drying method will be described as an example of a method for producing display particles.
The method for producing display particles includes a polymer, a colorant, a polymer dispersant (for example, a silicone polymer or a long-chain alkyl polymer), a first solvent, and the first solvent that are incompatible with the first solvent. Stirring and emulsifying a mixed solution containing a second solvent having a boiling point lower than that of one solvent and dissolving the polymer; removing the second solvent from the emulsified mixed solution; and It is preferable to have a step of producing colored particles containing a colorant and a step of reacting the polymer dispersant to bond or cover the surface of the colored particles. 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, the present technique may be 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, the display particle dispersion liquid using the first solvent as the dispersion medium is easily produced through the above steps without passing through the washing / drying step. Of course, in order to improve electrical characteristics, it is also possible to carry out cleaning of particles (removal of ionic impurities) and replacement of the dispersion medium as appropriate.

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

-Emulsification process-
In the emulsification step, for example, a solution composed of a polymer dispersant and a first solvent, a polymer, a colorant, and the first solvent are incompatible with each other, have a lower boiling point than the first solvent, and dissolve the polymer. Two solutions of the second solvent and the second solvent are mixed, stirred and emulsified. Moreover, it is also possible to mix | blend other compounding materials (a charge control agent, a pigment dispersant, etc.) other than the said material in the mixed solution to emulsify as needed.

  In the emulsification step, the mixed solution is stirred to disperse the low-boiling point second solvent in the form of droplets in the continuous phase using the high-boiling point solution (first solvent + reactive polymer) as the first solvent. A phase is formed and emulsified. The polymer dispersant is dissolved in the continuous phase of the first solvent, and the polymer and the colorant are dissolved or dispersed in the second solvent.

  In the emulsification step, each material may be sequentially mixed in the mixed solution. For example, first, a first mixed solution in which a polymer, a colorant, and a second solvent are mixed, a polymer dispersant and a first solvent are mixed. To prepare a second mixed solution. 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. In addition, the second mixed solution is also preferably prepared by adding each monomer constituting the polymer dispersant to the first solvent and then polymerizing to obtain the polymer dispersant.

  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 the temperature rise 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.

  Here, as a 1st solvent, it is used as a poor solvent which can form a continuous phase in a mixed solution, for example, the said mixed solvent is mentioned.

On the other hand, the second solvent is used as a good solvent capable of forming a dispersed phase in the mixed solution. Further, a material that is incompatible with the first solvent, has a lower boiling point than the first solvent, and dissolves the polymer 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, acetone, and other organic solvents (eg, toluene, dimethylformamide, dimethyl). Acetamide), but is not limited thereto.
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, 50 ° C. or more and 200 ° C. or less. Desirably, more desirably, it is 50 ° C or higher and 150 ° C or lower.

-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 polymer is precipitated while being encapsulated with other materials in the dispersed phase formed by the second solvent, and colored 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 contain these substances. .

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. In addition, you may make a polymer dispersing agent react with the particle | grain surface by the heating in the removal process of this 2nd solvent. 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.

-Bonding or coating process-
In the bonding or coating step, the polymer dispersant is reacted in the solution (first solvent) in which the colored particles are generated, and bonded or coated on the surface of the colored particles. In addition, although reaction may have advanced by the heat processing in the above-mentioned 2nd solvent removal process, more reliable reaction is implement | achieved by this process.

Here, examples of the method of reacting the polymer dispersant to bond or coat the surface of the colored particles include a method of heating a solution according to the type of the polymer dispersant.
When the solution is heated, the heating temperature is preferably 50 ° C. or higher and 200 ° C. or lower, and more preferably 60 ° C. or higher and 150 ° C. or lower.

  In addition, the manufacturing method of the display particles is not limited to the above-described manufacturing method, and for example, colored particles (display particles) by a known method (pulverization method, coacervation method, dispersion polymerization method, suspension polymerization method, or the like). The method of forming is adopted.

  Further, the method for attaching (bonding or coating) the polymer dispersant to the display particles is not limited to the above, and for example, a method using a coacervation method may be adopted. Specifically, for example, the produced display particles are dispersed in a first solvent in which a polymer dispersant is dissolved, the second solvent is dropped into the second solvent and emulsified, and then the first solvent is added. And the polymer dispersant is deposited on the colored particles and reacted to adhere (bond or cover) to the surface of the display particles. Suitable examples of the first solvent include isopropyl alcohol (IPA), methanol, ethanol, butanol, tetrahydrofuran, ethyl acetate, and butyl acetate. Among these, isopropyl alcohol (IPA) is desirable from the viewpoint of providing stable dispersion stability and charging characteristics. On the other hand, as the second solvent, the above mixed dispersion medium is preferably exemplified.

  Through each step of the above production method, display particles or a display particle dispersion containing the display particles can be obtained. Further, in each step of the above production method, the main dispersion medium may be used as the finally remaining solvent, and after the display particle dispersion liquid is obtained, the additive dispersion medium may be added to the main dispersion medium. .

  The method for producing the display particles (or dispersion thereof) is an example using a submerged drying method. Besides this, surface graft polymerization to pigments or colored polymer particles, pigment particles, Various known techniques such as surface coating by a coacervation method of a polymer or a dispersant, and an encapsulation method using a pigment polymer or a dispersant can be applied.

  Here, the obtained display particle dispersion may be diluted with a dispersion medium (solvent), for example, 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 the display particle dispersion according to the present embodiment, as a charge control agent, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, a fluorine-based surfactant, a silicone-based interface. Activators, 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.

The concentration of the display particles in the display particle dispersion according to the present embodiment is variously selected depending on display characteristics, response characteristics, or use thereof, but is selected in a range of 0.1% by mass to 30% by mass. Is desirable. When mixing multi-particles having different colors, the total amount of the particles is preferably within this range. When the content is less than 0.1% by mass, the display density becomes insufficient. When the content is more than 30% by mass, the display speed may become slow or aggregation may easily occur.
It is also preferable to obtain a color display by mixing a plurality of types of particles having different colors and charging polarities.

  The display particle dispersion according to the present embodiment is obtained by preparing first display particles (dispersion liquid) and second display particles (dispersion liquid), respectively, and mixing them.

  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 known method of moving particles in a direction perpendicular to the electrode (substrate) surface is different from the horizontal direction. There is a method of moving to (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.

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

  The display device 10 according to the present embodiment is a form in which the display particle dispersion according to the present embodiment is applied as a particle dispersion including the dispersion medium 50 of the display medium 12 and the particle group 34. Specifically, among the particle groups 34, the first display particles are applied as the particle groups 34A, the second display particles are displayed as the particle groups 34B that exhibit a color different from that of the particle groups 34A and have different charging polarities. It is an applied form. Then, the mixed dispersion medium is applied as the dispersion medium 50.

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

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

  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 particle group 34 (described in detail later) is composed of a plurality of particles. The particle group 34 is dispersed in the dispersion medium 50 and passes between the display substrate 20 and the back substrate 22 according to the electric field strength formed in the cell. It moves 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.

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

  For the surface electrode 40 and the back electrode 46, oxides such as indium, tin, cadmium and antimon, composite oxides such as ITO, metals such as gold, silver, copper and nickel, organic materials such as polypyrrole and polythiophene are used. Is done. 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 to 2000 mm according to the vapor deposition method and the sputtering method. The back electrode 46 and the front electrode 40 may be formed in a desired pattern, for example, a matrix shape or a stripe shape enabling a passive matrix drive, by a conventionally known means such as etching of a conventional liquid crystal display medium or a printed circuit board. Good.

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

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

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

  In order to enable 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.

  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.

  Next, the gap member will be described. 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, a surface layer 42 and a surface layer 48 as dielectric films are formed on the surface electrode 40 and the back electrode 46, respectively, as necessary.

  As materials for forming the surface layer 42 and the surface layer 48, polycarbonate, polyester, polystyrene, polyimide, epoxy, polyisocyanate, polyamide, polyvinyl alcohol, polybutadiene, polymethyl methacrylate, copolymerized nylon, ultraviolet curable acrylic resin, fluororesin Etc. 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 desirable to use a transparent one of the above materials.

  Next, the gap member will be described. The gap member 24 for maintaining a 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, and is a thermoplastic resin, a thermosetting resin, or an electron beam curing. It is made of resin, photo-curing resin, rubber, metal or the like.

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

  The gap member 24 may be colored or colorless, but is preferably colorless and transparent 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 Resin or the like is used.

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

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

  Next, the reflective particle group will be described. The reflective particle group 36 is an uncharged particle group, is composed of reflective particles having optical reflection characteristics different from that of the particle group 34, and functions as a reflective member that displays a color different from that of the particle group 34. is there. And it also has a function as a gap member to move without hindering movement between the display substrate 20 and the back substrate 22. That is, each particle of the particle group 34 is moved from the back substrate 22 side to the display substrate 20 side or from the display substrate 20 side to the back substrate 22 side through the gap between the reflective particle groups 36. As the color of the reflective particle group 36, for example, 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.

  As the reflective particle group 36, for example, particles in which a white pigment such as titanium oxide, silicon oxide, or zinc oxide is dispersed in polystyrene, polyethylene, polypropylene, polycarbonate, PMMA, acrylic resin, phenol resin, formaldehyde condensate, or the like are used. . Moreover, when applying particles other than white as the reflective particle group 36, for example, the above-described resin particles containing a pigment or dye of a desired color may be used. If the pigment or dye is, for example, RGB or YMC color, a general pigment or dye used for printing ink or color toner may be used.

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

  The size of the cell in the display medium 12 is closely related to the resolution of the display medium 12, and the display medium 12 capable of displaying a high-resolution image as the cell is smaller can be manufactured. The length of the twelve display substrates 20 in the plate surface direction is about 10 μm to 1 mm.

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

  The display medium 12 configured as described above includes, for example, a bulletin board 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 etc.

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

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

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

  The control unit 18 stores in advance various programs such as a CPU (Central Processing Unit) that controls the operation of the entire apparatus, a RAM (Random Access Memory) that temporarily stores various data, and a control program that controls the entire apparatus. It is also possible to configure as a microcomputer including a ROM (Read Only Memory).

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

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

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

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

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

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

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

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

[Example A]
(Comparative Example A1)
First, a silicone-based polymer A (polymer dispersing agent) having a hydroxyl group incompatible with the main dispersion medium (dimethylsilicone oil) was produced as follows. Silaplane FM0711 (manufactured by Chisso) as a silicone-based macromer: 8 parts by mass, 1.5 parts by mass of 2-hydroxyethyl methacrylate and 0.5 parts by mass of glycidyl methacrylate, azobisdimethylvaleronitrile as a radical polymerization initiator: 0. A silicone polymer A (polymer dispersing agent) was prepared by copolymerization by solution free radical thermal polymerization using 05 parts by mass as isopropyl alcohol and 20 parts by mass as a solvent. The weight average molecular weight was 100,000. And the 3 mass% silicone oil solution of the silicone type polymer A was prepared by diluting with silicone oil. In addition, as silicone oil, dimethyl silicone oil (KF-96L 2cs manufactured by Shin-Etsu Silicone) was used.

  Next, a polymer α1 having a carboxylate group (anionic group) as a charging group was produced as follows. N-vinylpyrrolidone: 8.5 parts by mass, methacrylic acid triethylamine salt: 1.5 parts by mass as a radical polymerization initiator, azobisdimethylvaleronitrile: 0.05 parts by mass, isopropyl alcohol: 20 parts by mass as a solvent After copolymerization by solution free radical thermal polymerization, the solvent and unreacted monomer were removed under reduced pressure to obtain a solid copolymer.

Next, a 10% by mass aqueous solution of polymer α1 was prepared. Then, 3 parts by mass of a 10% by mass aqueous solution of the polymer α1 is mixed with 1 part by mass of a Ciba water-dispersed pigment solution (Unisperse / magenta color: pigment concentration 16% by mass), and this mixed solution is mixed with the silicone polymer. The mixture is mixed with 10 parts by mass of a 3% by weight silicone oil solution of A, stirred for 10 minutes with an ultrasonic crusher (UH-600S manufactured by SMT), and an aqueous solution containing a polymer having a charged group and a pigment is added to the silicone oil. A suspension dispersed and emulsified in was prepared.
Next, the suspension was decompressed (2 KPa) and heated (70 ° C.) for 1 hour to remove moisture, and magenta colored particles containing a polymer having a charged group and a pigment were dispersed in silicone oil. A silicone oil dispersion was obtained. Further, this dispersion was heated at 100 ° C. for 3 hours to cause the reactive 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. Further, the concentration was adjusted with silicone oil to prepare a 5% by mass display particle dispersion. As a result of measuring the binding amount of the silicone-based polymer A by elemental analysis, it was 16% by mass with respect to the mass of the particles. It was 450 nm as a result of measuring the volume average particle diameter of the particle | grains of the produced particle dispersion liquid (Holiba LA-300: Laser light scattering and a diffraction type particle size measuring apparatus).
Thus, a base / magenta particle dispersion A1 to which dimethyl silicone oil was applied as the main dispersion medium was produced.

(Comparative Example A2)
Next, a polymer α2 having a triethylammonium group (cation group) as a charging group was produced as follows. N-vinylpyrrolidone: 9 parts by mass, diethylaminoethyl methacrylate: 1 part by mass as a radical polymerization initiator and azobisdimethylvaleronitrile: 0.05 part by mass as isopropyl alcohol: 20% by mass as a solvent by free radical thermal polymerization After copolymerization, 1 part by mass of ethyl iodide was added to the solution and reacted at 70 ° C. for 2 hours to quaternize the diethylamino group to a triethylammonium group. After completion of the reaction, the solvent and unreacted monomer were removed under reduced pressure to obtain a solid copolymer.

The polymer α2 is applied instead of the polymer α1, and the Ciba water dispersion pigment solution (Unisperse cyan color: pigment) is used instead of the Ciba water dispersion pigment solution (Unisperse magenta color: pigment concentration 16% by mass). A 5% by mass base / cyan particle dispersion A2 was prepared in the same manner as in Comparative Example A1 (base / magenta particle dispersion A1) except that the concentration was 26% by mass.
It was 400 nm as a result of measuring the volume average particle diameter of the particle | grains of the produced particle dispersion (Holiba LA-300: Laser light scattering and a diffraction type particle size measuring apparatus).

(Comparative Example A3)
1 part by mass of the base / magenta particle dispersion A1 prepared in Comparative Example A1 and 1 part by mass of the base / cyan particle dispersion A2 prepared in Comparative A2 were mixed to prepare a mixed particle dispersion. .

(Comparative Example A4)
As magenta-colored positively charged display particles (volume average particle diameter: 450 nm), a silicone copolymer (manufactured by Chisso Silaplane, MMA, hydroxybutyl methacrylate copolymer) containing magenta pigment as an OH group-containing monomer. Using particles coated with 5% by weight of hydroxybutyl methacrylate in the copolymer (manufactured by Sekisui Chemical Co., Ltd .: sample name XX-367W), a dimethyl silicone dispersion containing 5% by weight of these particles was prepared. did. In this way, a base / magenta particle dispersion A4 to which dimethyl silicone oil was applied as the main dispersion medium was prepared.

(Examples A1 to A6)
According to Table 1, an additive dispersion medium was added to the base / magenta particle dispersion A1 to prepare magenta particle dispersions, respectively. In Table 1, phenyl-modified silicone (Shin-Etsu Silicone KF-50-100cs) was used as the phenyl-modified silicone.

(Example A7)
According to Table 1, an additive dispersion medium was added to the mixed particle dispersion prepared in Comparative Example A3 to prepare mixed particle dispersions, respectively.

[Example B]
(Comparative Example B1)
First, a silicone polymer B (polymer dispersant) having a phenyl group incompatible with the main dispersion medium (dimethylsilicone oil) was prepared as follows. Silaplane FM0711 (manufactured by Chisso) as a silicone-based macromer: 8.5 parts by mass, phenoxyethylene glycol monoacrylate (AMP-10G, manufactured by Shin-Nakamura Chemical): 1 part by mass and 0.5 parts by mass of glycidyl methacrylate, start of radical polymerization A silicone polymer B (polymer dispersing agent) was prepared by copolymerization by solution free radical thermal polymerization using 0.05 parts by mass of azobisdimethylvaleronitrile as a solvent and 20 parts by mass of isopropyl alcohol as a solvent. The weight average molecular weight was 120,000. And the 3 mass% silicone oil solution of the silicone type polymer A was prepared by diluting with silicone oil. In addition, as silicone oil, dimethyl silicone oil (KF-96L 2cs manufactured by Shin-Etsu Silicone) was used.

Comparative Example A1 (base / magenta particle dispersion), except that the silicone polymer B was used instead of the silicone polymer A, and the polymer α1 prepared above was used as a resin having an anion group as a charging group. In the same manner as in liquid A1), 5% by mass of base / magenta particle dispersion B1 was prepared.
It was 400 nm as a result of measuring the volume average particle diameter of the particle | grains of the produced particle dispersion (Holiba LA-300: Laser light scattering and a diffraction type particle size measuring apparatus).

(Comparative Example B2)
Polymer α2 is applied instead of polymer α1, and Ciba water dispersion pigment solution (Unisperse cyan color: pigment concentration 26) instead of Ciba water dispersion pigment solution (Unisperse magenta color: pigment concentration 16% by mass). 5% by mass of base / cyan particle dispersion B2 was prepared in the same manner as in Comparative Example B1 (base / magenta particle dispersion B1) except that the following was used.
It was 410 nm as a result of measuring the volume average particle diameter of the particle | grains of the produced particle dispersion liquid (Holiba LA-300: Laser light scattering and a diffraction type particle size measuring apparatus).

(Comparative Example B3)
1 part by mass of the base / magenta particle dispersion B1 prepared in Comparative Example B1 and 1 part by mass of the base / cyan particle dispersion B2 prepared in Comparative Example B2 were mixed to prepare a mixed particle dispersion. .

(Examples B1 to B2)
According to Table 2, an additive dispersion medium was added to the base / magenta particle dispersion B1 to prepare magenta particle dispersions, respectively.

(Example B3)
According to Table 2, an additive dispersion medium was added to the mixed particle dispersion prepared in Comparative Example B3 to prepare magenta particle dispersions, respectively.

[Example C]
(Comparative Example C1)
As magenta positively-charged display particles (volume average particle diameter: 500 nm), a silicone copolymer (manufactured by Chisso Silaplane, MMA, methacrylic acid copolymer: co-polymer) containing a magenta pigment as a component of a carboxyl group-containing monomer. Particles coated with methacrylic acid in the polymer (5% by mass) (manufactured by Sekisui Plastics Co., Ltd .: sample name XX-366W) were used to prepare a dimethyl silicone dispersion containing 5% by mass of these particles. In this way, a base / magenta particle dispersion C1 to which dimethyl silicone oil was applied as the main dispersion medium was prepared.

(Examples C1 to C2)
According to Table 2, an additive dispersion medium was added to the base / magenta particle dispersion C1 to prepare magenta particle dispersions, respectively. In Table 2, phenyl-modified silicone (Shin-Etsu Silicone KF-50-100cs) was used as the phenyl-modified silicone.

[Comparative example]
(Comparative Example 1)
First, a comparative silicone polymer (polymer dispersant) was prepared as follows. Silaplane FM0711 (manufactured by Chisso Corporation): 9.5 parts by mass as a silicone-based macromer, and 0.5 parts by mass of glycidyl methacrylate, 0.05 parts by mass of azobisdimethylvaleronitrile as a radical polymerization initiator: 20 parts by mass of isopropyl alcohol Silicone polymer D (polymer dispersant) was prepared by copolymerization by solution free radical thermal polymerization using a part as a solvent. The weight average molecular weight was 110,000. And the 3 mass% silicone oil solution of the silicone type polymer A was prepared by diluting with silicone oil. In addition, as silicone oil, dimethyl silicone oil (KF-96L 2cs manufactured by Shin-Etsu Silicone) was used.

Then, 5% by mass of Comparative Base / Magenta Particle Dispersion 1 was used in the same manner as Comparative Example A1 (Base / Magenta Particle Dispersion A) except that Comparative Silicone Polymer was used instead of Silicone Polymer A. Was made.
It was 350 nm as a result of measuring the volume average particle diameter of the particle | grains of the produced particle dispersion liquid (Holiba LA-300: laser light scattering and a diffraction type particle size measuring apparatus).

(Comparative Example 2)
As magenta positively charged electrophoretic particles (volume average particle diameter: 600 nm), particles (manufactured by Sekisui Chemical Co., Ltd.) coated with a magenta pigment with a silicone copolymer (a copolymer of Chisso Silaplane and MMA): Sample name XX-158W) was used to prepare a silicone dispersion containing 5% by weight of the particles. In this way, a base / magenta particle dispersion 21 was prepared in which dimethyl silicone oil was applied as the main dispersion medium.

(Comparative Example 3)
According to Table 2, an additive dispersion medium was added to the comparative base / magenta particle dispersion 1 prepared in Comparative Example 1 to prepare magenta particle dispersions, respectively.

[Example: Display element]
-Production of display media-
A display medium having the same configuration as that of the present embodiment was manufactured as follows (see FIG. 1). An ITO film having a thickness of 50 nm was formed as an electrode on a supporting substrate made of glass having a thickness of 0.7 mm by a sputtering method. After applying a layer using a photosensitive polyimide varnish (manufactured by Fuji Hunt Electronics Technology Co., Ltd., PROBIMIDE 7005) to the back substrate composed of this ITO / glass substrate, a height of 100 μm is obtained by performing exposure and wet etching. A gap member having a width of 20 μm was formed.

  After forming a heat-fusible adhesive layer (not shown) on the upper part of the gap member, it was filled with the following white particle group and the particle dispersion prepared in each example, and ITO / A display medium made of glass and having a treatment layer formed thereon was bonded to the back substrate so that the surfaces (electrode surfaces) on which the treatment layers were formed face each other, and heated to produce a display medium. .

  In this way, a display medium was produced. Using the produced display medium, a voltage of 50 V was applied to both electrodes so that the electrode of the display substrate was positive and the electrode of the back substrate was negative. As a result, it is observed that the negatively charged magenta particles are moved to the display substrate by the electric field due to voltage application, and the positively charged cyan particles are moved to the back substrate by the electric field due to voltage application. Observed, the display medium displayed a magenta color.

  Next, a voltage of 300 V was applied to both electrodes for 60 seconds so that the display substrate electrode was negative and the back substrate electrode was positive. A voltage of 300 V was applied to both electrodes for 60 seconds so that the electrode on the display substrate was positive and the electrode on the back substrate was negative. By repeating this operation, the particles of each color were moved to the display substrate and the back substrate, and each color was displayed. As a result, display was performed with good display maintainability (memory property).

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

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

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

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

[Evaluation]
The display sustainability (memory property) of the particle dispersions produced in the above examples was examined. Display sustainability (memory property) was examined as a measure of how much an image is held when no electric field is applied after applying an electric field. Specifically, it evaluated according to the following operation. The results are shown in Tables 1 and 2.
(1) A parallel plate electrode in which a particle dispersion with a particle concentration of about 0.5 wt% (diluted 10 times) is put in a small plastic container called a disposable cell, and a Cytop (AGC amorphous fluororesin) coat is made of an ITO glass substrate. Insert a pair.
(2) A voltage (100 V / 300 V) is applied to the electrode pair for a certain time (10 s / 60 s) and then left open or short-circuited.
(3) After 1 hour, the electrode substrate was taken out and dried, the color density of particles remaining on the substrate was observed, and the memory property was evaluated by comparing this with the state when taken out immediately after voltage application.
The evaluation criteria are as follows.
G5: Very good (color density change rate of 0 or more and less than 0.05)
G4: Good (color density change rate 0.05 to less than 0.1)
G3: Normal (color density change rate 0.1 to less than 0.2)
G2: Slightly bad (color density change rate 0.2 or more and less than 0.5)
G1: Poor (color density change rate of 0.5 or more and less than 1)

  From the obtained results, it can be seen that in this example, a result excellent in display maintainability was obtained as compared with the comparative example.

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

Claims (7)

The main dispersion medium and an additive dispersion medium having a solubility parameter (SP value) different from that of the main dispersion medium are included. The difference in solubility parameter (SP value) between the main dispersion medium and the following display particles is used for the following display. A mixed dispersion medium having a large difference in solubility parameter (SP value) from the particles;
First display particles that are dispersed in the dispersion medium and move in response to an electric field, the first polymer dispersant being attached to the surface, and the main dispersion medium on the surface or the first polymer dispersant First display particles having a functional group incompatible with
A particle dispersion for display comprising: The main dispersion medium is silicone oil;
The display particle dispersion according to claim 1, wherein the functional group incompatible with the main dispersion medium is selected from a hydroxyl group, a carboxyl group, and a phenyl group. The main dispersion medium is silicone oil;
The display particle dispersion according to claim 1, wherein the additive dispersion medium is selected from a modified silicone oil and a compound having a phenyl group. As the display particles,
First display particles that are dispersed in the mixed dispersion medium and move in response to an electric field, the first polymer dispersant being attached to the surface, and the main dispersion on the surface or the first polymer dispersant First display particles having a functional group incompatible with the medium;
Second display particles that are dispersed in the mixed dispersion medium, move in response to an electric field, and have a different charge polarity from the first display particles, and a second polymer dispersant is attached to the surface. The display particle dispersion according to claim 1, further comprising second display particles having functional groups incompatible with the main dispersion medium on the surface or the second polymer dispersant. A pair of substrates, at least one of which is translucent,
The display dispersion liquid according to any one of claims 1 to 4, wherein the display dispersion liquid is sealed between the pair of substrates.
A display medium comprising: A pair of electrodes, at least one of which is translucent,
A region having a display dispersion liquid according to any one of claims 1 to 4, which is provided between the pair of electrodes.
A display medium comprising: A display medium according to claim 5 or 6,
Voltage applying means for applying a voltage between the pair of substrates of the display medium;
A display device comprising: