JP5387437B2 - Display particle dispersion, display medium, and display device - Google Patents

Description

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

  In Patent Document 1, at least two kinds of charged particles having the same color and different volume average particle diameter and mobility are used as the charged particles, and the mobility of the charged particles having a small volume average particle diameter is set to the volume average particle diameter. An electrophoretic display element in which the mobility of large charged particles is smaller has been proposed.

  In Patent Document 2, as charged particles, at least two kinds of charged particles having the same color and different volume average particle diameter and mobility are used, and the mobility of charged particles having a small volume average particle diameter is set to a large volume average particle diameter. An electrophoretic display element has been proposed in which the mobility of charged particles is larger.

  In Patent Document 3, at least two kinds of particles having different colors are packed, and the at least two kinds of particles are a first particle charged on the negative electrode, and a negative electrode having lower mobility and higher charge density than the first particles. There has been proposed an electrophoretic display sheet containing second particles that are electrically charged.

  Patent Document 4 discloses a colored particle that moves in a dispersion medium in response to an electric field applied from the outside, a colored particle that does not move in the dispersion medium with respect to a constant electric field applied from the outside, and a dispersion medium. There has been proposed an electrophoretic display solution containing.

JP 2006-292879 A JP 2006-292880 A JP 2009-116041 A JP 2001-188269 A

  The subject of this invention is compared with the case where the 1st white particle and 2nd white particle in this invention are not included as a white particle in the system with which 2 types of colored particles from which polarity differs, and a white particle are mixed. It is another object of the present invention to provide a display particle dispersion that realizes clear multicolor display.

The above problem is solved by the following means. That is,
The invention according to claim 1 is a display medium comprising a pair of substrates , at least one of which has translucency, and a display particle dispersion liquid sealed between the pair of substrates, wherein the display particle dispersion The liquid is charged on the positive electrode and moves in response to an electric field, and the first colored particles are colored in a first color different from white, and the negative electrode is charged and moves in response to the electric field. Second colored particles colored in a second color different from the first color, and charged in the positive electrode, move according to an electric field, and have a volume from the first colored particles and the second colored particles. White first white particles having a small average particle diameter and a moving speed slower than that of the first colored particles and the second colored particles, and charged to the negative electrode, move according to an electric field, The volume average particle size is smaller than the colored particles and the second colored particles, and the first White white particles having a slower moving speed than the colored particles and the second colored particles, the first colored particles, the second colored particles, the first white particles, and the second white particles A display medium, which is a display particle dispersion containing a dispersion medium for dispersing particles.

Invention, the display particle dispersion further comprises a white third white particles that do not move in response to an electric field, the display medium of claim 1 according to claim 2.

The invention according to claim 3 is the display particle dispersion, wherein the first colored particles include a colorant and a first resin containing a structural unit derived from a vinyl monomer having a phenyl group. And the second colored particles comprise a colorant and a second resin containing a structural unit derived from a first monomer having at least one of a carboxylic acid group and a fluorine group, The first white particles include a white color material and a third resin including a structural unit derived from the vinyl monomer, and the second white particles include a white color material and the first color material. The display medium of Claim 1 or Claim 2 comprised including the 4th resin containing the structural unit derived from the monomer of this.

The invention according to claim 4 is a display comprising: the display medium according to any one of claims 1 to 3; and a voltage applying device that applies a voltage between a pair of substrates included in the display medium. Device.

According to the invention according to claim 1 and claim 4 , in a system in which two types of colored particles having different polarities and white particles are mixed, the first white particles and the second white particles in the present invention are used as white particles. There is an effect that clear multicolor display is realized as compared with the case where white particles are not included.

  According to the invention concerning Claim 2, compared with the case where the 3rd white particle in this invention is not included, there exists an effect that white display with high whiteness is implement | achieved.

  According to the invention of claim 3, as the first colored particles, the second colored particles, the first white particles, and the second white particles, compared to the case where the configuration of the present invention is not used, There is an effect that a change in the charge amount is suppressed.

It is a schematic block diagram of the display apparatus which concerns on this embodiment. It is a schematic block diagram of the display apparatus which concerns on this embodiment. It is a schematic block diagram of the display apparatus which concerns on this embodiment. It is a schematic block diagram of the display apparatus which concerns on this embodiment. It is a schematic block diagram of the display apparatus which concerns on this embodiment. (A)-(D) It is a diagram which shows the relationship between the charge amount of the white particle contained in the particle dispersion for display, and the number of particles.

  Hereinafter, embodiments of the present invention will be described.

(Particle dispersion for display)
The display particle dispersion according to the present embodiment includes first colored particles colored in a first color different from white charged on the positive electrode, and white and first color charged on the negative electrode. Second colored particles colored in the second color, white first white particles charged on the positive electrode, white second white particles charged on the negative electrode, and dispersion for dispersing these particles Medium.

  The first color and the second color may be different from white and different from each other, and examples thereof include yellow, magenta, cyan, red, green, blue, and black.

  These first colored particles, second colored particles, first white particles, and second white particles are electrophoretic particles that move in a dispersion medium in response to an electric field. And the moving speed according to the electric field of a 1st white particle and a 2nd white particle is slower than a 1st colored particle and a 2nd colored particle. Furthermore, the first white particles and the second white particles have a volume average particle size smaller than that of the first colored particles and the second colored particles.

Therefore, a display medium (details will be described later) is configured using this display particle dispersion, and the first colored particles charged on the positive electrode and the first white particles charged on the positive electrode are displayed on the display medium. An electric field that moves the second colored particles charged on the negative electrode and the second white particles charged on the negative electrode to the back side (the side opposite to the display surface) is moved between the substrates of the display medium. When formed, the first colored particles having a high moving speed reach the display surface side faster than the first white particles, and the first white particles move to the display surface side behind the first colored particles.
Since the volume average particle diameter of the first white particles is smaller than that of the first colored particles, the voids between the particles of the first colored particles that have reached the display surface side are displayed behind the first colored particles. The first white particles reaching the surface side are filled with the first white particles, and the back side of the layer of the first colored particles positioned on the display surface side is shielded by the first white particles.

Further, on the back substrate side, the second colored particles having a high moving speed reach the back side faster than the second white particles, and the second white particles move to the back side behind the second colored particles. .
Since the volume average particle diameter of the first white particles is smaller than that of the first colored particles, the voids between the particles of the second colored particles that have reached the back side are delayed behind the second colored particles. The display surface side of the layer formed of the second colored particles located on the back side is shielded by the second white particles.

For this reason, in this state, when the display medium is visually recognized from the display surface side, the color of the first colored particles positioned on the display surface side is visually recognized, and the back side (display medium side) of the first colored particles is observed. The side opposite to the display surface side) is shielded by the first white particles, and the color of the second colored particles positioned on the back side is shielded by the second white particles. .
Therefore, it is considered that the color by the first colored particles is clearly displayed.

  Conversely, the first colored particles charged on the positive electrode and the first white particles charged on the positive electrode are moved to the back side of the display medium, and the second colored particles charged on the negative electrode and the negative electrode are charged. When an electric field for moving the second white particles thus formed to the display surface side is formed between the substrates of the display medium, the first colored particles having a high moving speed reach the back side faster than the first white particles, and The first white particles move to the back surface side behind the one colored particle. In addition, the second colored particles having a high moving speed reach the display surface side faster than the second white particles, and the second white particles move to the display surface side after the second colored particles. The volume average particle diameters of the first white particles and the second white particles are smaller than the first colored particles and the second colored particles.

Therefore, in this state, when the display medium is visually recognized from the display surface side, the color of the second colored particles positioned on the display surface side is visually recognized, and the back side of the second colored particles is the second white color. The color of the first colored particles positioned on the back side is shielded by the first white particles.
Therefore, it is considered that the color by the second colored particles is clearly displayed.

  Further, the first colored particles or the second colored particles located on the display surface side move to the back side from the state where the color by the first colored particles or the color by the second colored particles is displayed. When the electric field having the strength to be formed is formed between the substrates of the display medium, the first colored particles or the second colored particles arranged on the display surface side are changed from the first white particles and the first colored particles due to the difference in moving speed. It is considered that the display surface side of the layer made of these colored particles is covered with the first white particles and the second white particles, reaching the back side before the white particles of 2. For this reason, the color by the 1st colored particle and the 2nd colored particle located in the back side from the 1st white particle and the 2nd white particle is shielded by the 1st white particle and the 2nd white particle. It is considered that a white display with high whiteness is realized.

  Therefore, it is considered that a clear multicolor display is realized by using the display particle dispersion liquid of the present embodiment.

  In addition, since the color of the colored particles (first colored particles and second colored particles) is shielded by the first white particles and the second white particles, white is displayed. Compared to the case where the display particle dispersion without the configuration of the embodiment is used, the white particle (the first white particles and the second white particles) in the display particle dispersion is small in whiteness and white. It is considered that a high-quality white display is realized.

  In addition, as described above, since the filling rate of the white particles (first white particles and second white particles) dispersed in the display particle dispersion is suppressed, the viscosity improvement of the dispersion medium is suppressed, It is considered that the speed required for changing the display color can be improved.

In addition, in the display particle dispersion liquid of the present embodiment, as the white particles, in addition to the first white particles and the second white particles, third white particles that do not move in response to an electric field are further included. An added configuration may be used.
This “does not move in response to an electric field” means that when a display medium in which a display particle dispersion liquid is filled between substrates is constituted, electrophoresis that is dispersed in the same dispersion liquid between the substrates of the display medium. Even if an electric field in which the particles to be moved (in this embodiment, the first colored particles, the second colored particles, the first white particles, and the second white particles) move is formed, the third white particles Shows a state where the substrate does not move from one side of the pair of substrates to the other side.
Specifically, the charge amount of the third white particles is 0 or close to 0. This “state where the charge amount is 0 or close to 0” means a state in which neither the positive electrode nor the negative electrode is charged, or even if either the positive electrode or the negative electrode is charged, it does not move according to the electric field. It shows a state having only a charge amount of. Therefore, at least one of the first colored particles, the second colored particles, the first white particles, and the second white particles is interposed between the substrates of the display medium filled with the display particle dispersion. Even if the electric field to be moved is formed, the moving speed of the third white particles is zero or infinitely close to zero.

  In addition to the first white particles and the second white particles that move according to the electric field, the third white particles that do not move according to the electric field are added to the display particle dispersion as white particles. It is considered that white display with higher whiteness is realized by light scattering by the third white particles dispersed in the dispersion medium.

  The specific action when the display particle dispersion is filled in the display medium will be described later in detail.

  Next, the display particle dispersion of the present embodiment will be described in detail.

(First colored particles)
First, the first colored particles will be described.
As described above, the first colored particles are particles that are charged to the positive electrode, move according to the electric field, and are colored in a first color different from white.
The first colored particles include a colorant and a first resin. The first colored particles may include other compounding materials as necessary.
The first colored particles may have a configuration in which a colorant is dispersed or blended in the first resin, or may have a configuration in which the surface of the colorant is coated with the first resin. .

  Here, “coated” the particle surface of the colorant with the first resin indicates a state where the first resin covers the surface of the colorant. Hereinafter, “coating” has the same meaning.

  As described above, the first colored particles are particles charged to the positive electrode. The first resin, which is a constituent component of the first colored particles, is a polymer having a basic group functioning as a charging group or an electron donating group (hereinafter sometimes referred to as a cationic group). It is comprised including.

Examples of the cationic group that functions as a charging group include an amino group, a quaternary ammonium group, a phenyl group, a heterocyclic ring containing an N atom, an amide group, and the like (including salts of these groups). This cationic group imparts the polarity of the positive electrode to the first colored particles.

  The polymer having a cationic group may be a polymer containing a structural unit derived from a monomer having a cationic group, and may be a homopolymer of a monomer having a cationic group or a cationic group. And a monomer that does not have a charging group. As a result, the first colored particles may be configured to be particles charged to the positive electrode.

Examples of the monomer having a cationic group 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, vinylpyrrolidineaminoe Ether, 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. Inn 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.

  Nonionic monomers (nonionic monomers) that constitute a copolymer with a monomer having a cationic group and that do not have a charging group include, for example, (meth) acrylonitrile, (meth) acrylic. Acid alkyl ester, (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, chloride Examples include vinylidene, isoprene, butadiene, vinyl pyrrolidone, hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, and the like.

In the present embodiment, descriptions such as “(meth) acrylate” are expressions including both “acrylate” and “methacrylate”. The same applies hereinafter.

The copolymerization ratio between the monomer having a cationic group and the monomer having no charging group is appropriately changed according to the charge amount of the desired particles. Usually, the copolymerization ratio of the monomer having a cationic group and another monomer is selected in the range from 1: 100 to 100: 0 in terms of the molar ratio.

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

  The first resin may further include a polymer dispersant in addition to the polymer having the cationic group. The polymer dispersant may have a structure having the cationic group as a charging group.

  Examples of the polymer dispersant include poly (meth) acrylate polymers and copolymers, silicone polymers and copolymers, long-chain alkyl polymers and copolymers, and monomers and styrene copolymers. And a styrene-butadiene copolymer. 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 polymer is, for example, a polymer compound having a silicone chain, and more specifically, a compound having a silicone chain (silicone graft chain) as a side chain with respect to the main chain of the main polymer compound. Is good.

  As one of the silicone-based polymers, for example, at least a silicone chain component and, if necessary, a reactive component, a copolymer component having a charged group, and other copolymer components (a copolymer component having no charged group) are included. And a copolymer obtained by copolymerizing one kind. 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 Chemical Co., Ltd.) X-22-174DX, X-22-2426, X-22-2475, etc.).

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

  As the copolymerization component having a charging group and other copolymerization components (copolymerization components having no charging group), the monomer having the cationic group described above, the monomer having the anionic group described later, Monomers without the described charging groups are applied.

  The silicone polymer preferably has a silicone chain component in a mass ratio of 3% to 60%, or 5% to 40%. 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 Chemical Co., Ltd.

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

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

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

  Examples of the weight average molecular weight of the silicone-based polymer include 500 to 1,000,000 and 1,000 to 1,000,000.

Next, the colorant contained in the first colored particles will be described.
As the colorant used for the first colored particles, a colorant exhibiting a color other than white is selected. Examples of the colorant used in the first colored particles include organic or inorganic pigments, oil-soluble dyes, and the like, for example, magnetic powder such as magnetite and ferrite, carbon black, magnesium oxide, and phthalocyanine copper-based cyan color. Examples thereof include known colorants such as materials, azo yellow color materials, azo magenta color materials, quinacridone magenta color materials, red color materials, green color materials, and blue color materials. 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 238, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 74, C.I. I. Pigment blue 15: 1, C.I. I. Pigment Blue 15: 3, etc. are exemplified as typical examples.

  As a compounding quantity of a coloring agent, 10 mass% or more and 99 mass% or less with respect to the said 1st resin contained in 1st colored particle, 30 mass% or more and 99 mass% or less are mentioned.

Next, other compounding materials will be described.
Examples of other compounding materials contained in the first colored particles 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, an inorganic magnetic material or an organic magnetic material color-coated as necessary is used. Further, a transparent magnetic material, in particular, a transparent organic magnetic material does not hinder the color development of the color pigment, and the specific gravity is smaller than that of the inorganic magnetic material, so that it is more desirable.
Examples of the colored magnetic material (color-coated material) include small-diameter colored magnetic powder described in JP-A-2003-131420. A material provided with magnetic particles serving as nuclei and a colored layer laminated on the surface of the magnetic particles is used. The colored layer may be selected as appropriate, such as coloring the magnetic powder opaque with a pigment or the like. For example, a light interference thin film may be used. 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.

(Second colored particles)
Next, the second colored particles will be described.
The second colored particles include a colorant and a second resin. In addition, about the 2nd colored particle, the structure containing the other compounding material may be sufficient as needed.
Further, the second colored particles may have a configuration in which a colorant is dispersed or blended in the second resin, or the surface of the colorant may be coated with the second resin. Good.

  As described above, the second colored particles are particles charged on the negative electrode. The second resin, which is a constituent component of the second colored particles, includes a polymer having an acidic group that functions as a charging group (hereinafter sometimes referred to as an anionic group).

Examples of the anionic group that functions as the charging group include electron withdrawing groups such as a fluorine group, a carboxyl group, a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, and a tetraphenylboron group (of these groups). Including salt). This anionic group imparts the polarity of the negative electrode to the second colored particles.

  The polymer having an anionic group may be a polymer containing a structural unit derived from a monomer having an anionic group, and may be a homopolymer of a monomer having an anionic group or an anionic group. It is sufficient that the second colored particle is a particle charged to the negative electrode as a result.

  Examples of the monomer having an anionic group include the following.

Examples of the monomer having a fluorine group include a (meth) acrylate monomer having a fluorine group, specifically, trifluoroethyl (meth) acrylate, pentafluoropropyl (meth) acrylate, and perfluoroethyl (meth) acrylate. Perfluorobutylethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate, perfluorodecylethyl (meth) acrylate, trifluoromethyltrifluoroethyl (meth) acrylate, hexafluorobutyl (meth) acrylate, and the like. .

Examples of the monomer having a carboxylic acid group include (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, and anhydrides thereof and monoalkyl esters thereof, carboxyethyl vinyl ether, and carboxypropyl vinyl ether. Examples include vinyl ethers having a carboxyl group.
Examples of the monomer having a sulfonic acid group include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) acyclic acid ester, bis- (3-sulfopropyl) -itaconic acid ester, and the like. And its salts. In addition, there are sulfuric acid monoesters of 2-hydroxyethyl (meth) acrylic acid and salts thereof.

  Monomers having a phosphoric acid group include vinylphosphonic acid, vinyl phosphate, acid phosphoxyethyl (meth) acrylate, acid phosphoxypropyl (meth) acrylate, bis (methacryloxyethyl) phosphate, diphenyl-2-methacryloyloxyethyl Examples include phosphate, diphenyl-2-acryloyloxyethyl phosphate, dibutyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, dioctyl-2- (meth) acryloyloxyethyl phosphate, and the like.

  Nonionic monomers (nonionic monomers) that can form a copolymer with a monomer having an anionic group include a nonionic monomer (nonionic monomer), such as (meth) acrylonitrile, (meth) acrylic. Acid alkyl ester, (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, chloride Examples include vinylidene, isoprene, butadiene, vinyl pyrrolidone, hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, and the like.

  The copolymerization ratio between the monomer having an anionic group and the monomer having no charging group is appropriately changed according to the charge amount of the desired particles. Usually, the copolymerization ratio of the monomer having an anionic group and the monomer having no charging group is selected in the range from 1: 100 to 100: 0 in terms of the molar ratio.

  The weight average molecular weight of the monomer having an anionic group is preferably from 1,000 to 1,000,000, more preferably from 10,000 to 200,000.

  In addition to the polymer having the anionic group, the second resin contained in the second colored particles may further include a polymer dispersant. The polymer dispersant may have a configuration having the anionic group as a charging group. Examples of the polymer dispersant include the polymer dispersants described above.

  As the colorant contained in the second colored particles, the color of the second colored particles indicates a color other than white and is different from the first color which is the color of the first colored particles. The second color is selected. The colorant used for the second colored particles is specifically the colorant used for the first colored particles from among the colorants listed above as the colorant used for the first colored particles. A color different from the agent may be selected.

  The blending amount of the colorant in the second colored particles is 10% by mass to 99% by mass and 30% by mass to 99% by mass with respect to the second resin contained in the second colored particles. Can be mentioned.

  Furthermore, examples of other compounding materials contained in the second colored particles include the above-described charge control materials and magnetic materials.

  The volume average particle diameters of the first colored particles and the second colored particles may be larger than those of the first white particles and the second white particles. Further, the volume average particle diameters of the first colored particles and the second colored particles may be the same or different. The volume average particle diameter of the first colored particles and the second colored particles varies depending on the size of the display medium to be applied, and examples thereof include 0.3 μm or more and 30 μm or less, and 0.3 μm or more and 20 μm or less. .

  In the present embodiment, when the particle diameter to be measured is 2 μm or more, a Coulter counter TA-II type (manufactured by Beckman-Coulter) is used as the measuring device, and the electrolyte is ISOTON-II (manufactured by Beckman-Coulter). Is used to measure the volume average particle size.

  As a measurement method, 0.5 mg to 50 mg of a measurement sample is added to 2 ml of a 0.5% aqueous solution of a surfactant as a dispersant, more preferably sodium alkylbenzenesulfonate, and this is added to 100 ml to 150 ml of the electrolyte solution. Added to. The electrolytic solution in which the measurement sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for 1 minute. Using the Coulter counter TA-II type, an aperture having an aperture diameter of 100 μm is used. The particle size distribution of the particles in the range may be measured. The number of particles to be measured is 50,000.

  On the other hand, when the particle diameter to be measured is less than 2 μm, it may be measured using a laser scattering particle size distribution measuring device (FPAR1000: manufactured by Otsuka Electronics Co., Ltd.).

(First white particles)
Next, the first white particles will be described.
As described above, the first white particles are charged to the positive electrode, move according to the electric field, have a smaller particle diameter than the first colored particles and the second colored particles, and the first colored particles and the first colored particles. It is a white particle having a slower moving speed according to the electric field than the colored particles.

  The first white particles include a white color material and a third resin. Note that the first white particles may be configured to include other compounding materials as described above, if necessary. The first white particles may have a configuration in which a white color material is dispersed or blended in the third resin, or the surface of the white color material is covered with the third resin. There may be.

The third resin, which is a constituent component of the first white particles, includes a polymer having a cationic group that functions as a charging group. Examples of the cationic group that functions as the charging group include the cationic groups listed above.

  The polymer having a cationic group may be a polymer including a structural unit derived from a monomer having a cationic group, and may be a homopolymer of a monomer having a cationic group, or may be cationic. It may be a copolymer of a monomer having a group and a monomer having no charging group. In addition, the polymer having a cationic group contained in the third resin that is a constituent component of the first white particles is derived from both a monomer having a cationic group and a monomer having an anionic group. The constitutional unit may be included, and as a result, the type of the charged group, the number of charged groups, the cationic group, and the like so that the first white particles become particles charged to the positive electrode. It is only necessary that the polarity of the third resin be adjusted to the positive electrode by adjusting the ratio with the anionic group and the like.

  In addition, since the polarity of the third resin only needs to be adjusted so that the first white particles become particles charged to the positive electrode, the third resin constituting the first white particles is It may be configured to include both a polymer having a cationic group and a polymer having an anionic group.

  As specific examples of the monomer having a cationic group, the monomer having an anionic group, and the monomer having no charging group, the specific examples given as the monomers contained in the first resin of the first colored particles. An example is given.

  In addition to the polymer having the cationic group, the third resin may further include the above-described polymer dispersant.

  Here, as described above, the third resin, which is a constituent component of the first white particles, is a resin including a polymer including a structural unit derived from a monomer having a cationic group. It is preferable that the cationic group contained in the resin and the cationic group contained in the first resin that is a constituent component of the first colored particles are the same group.

Furthermore, the third resin of the first white particles is a structural unit derived from a monomer having a cationic group contained in a polymer having a cationic group contained in the first resin of the first colored particles. It is preferable to have.
Further, the third resin of the first white particles may be composed of the first resin of the first colored particles.

A configuration in which the third resin, which is a constituent component of the first white particles, is derived from a monomer having a cationic group contained in a polymer having a cationic group contained in the first resin of the first colored particles. By including the unit, it is considered that the change in the charge amount of the first white particles and the first colored particles when left for a long period of time is suppressed.

  Next, the white color material contained in the first white particles will be described.

  Examples of the white color material include white pigments such as titanium oxide (rutile type titanium oxide and anatase type titanium oxide), calcium carbonate, barium carbonate, zinc white, lead white, zinc sulfide, aluminum oxide, silicon oxide, and zirconium oxide. It is done.

  Of these, titanium oxide having high specific gravity and high whiteness is desirable. Among these titanium oxides, rutile type titanium oxide is desirable. For the purpose of adjusting the zeta potential, other white color materials (for example, calcium carbonate, barium carbonate, etc.) may be used in combination with titanium oxide.

  The white color material is also used for the second white particles and the third white particles, but the white color material used for the first white particles, the second white particles, and the third white particles is The same kind of color material may be used, or different white color materials may be used.

  Moreover, as a white color material, the linear or cyclic | annular polysilane compound which has the polysilane structure shown by the following general formula (I), and its halogen substituted compound (Hereinafter, both may be called a specific polysilane compound.). Since the material has a high refractive index (for example, a material with a refractive index of 1.65 or more) and a specific gravity is small (for example, a material with a specific gravity of 1.2 or less), particle sedimentation is suppressed and whiteness is improved. For this reason, a specific polysilane compound is particularly suitable as the white color material applied to the third white particles that do not move according to the electric field.

  In general formula (I), A represents a phenyl group. B represents an alkyl group or a phenyl group. n represents a natural number. The weight average molecular weight is preferably 10,000 or more and 100,000 or less.

  Examples of the alkyl group represented by B include an alkyl group having 1 to 22 carbon atoms, desirably an alkyl group having 1 to 12 carbon atoms, and more desirably an alkyl group having 1 to 6 carbon atoms. The alkyl group may be a linear alkyl group or a branched alkyl group. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an n-butyl group, a sec-butyl group, a hexyl group, an octyl group, a decyl group, and a stearyl group.

  The specific polysilane compound may be a chain polysilane compound or a cyclic polysilane compound.

  The chain polysilane compound is preferably a chain polysilane compound having a structure represented by the following structural formula (I-1A). Here, in Structural Formula (I-1A), n represents a natural number, and the weight average molecular weight is preferably 10,000 or more and 100,000 or less.

  The cyclic polysilane compound may be a cyclic polysilane compound represented by the following structural formula (I-2A). The cyclic polysilane compound is a compound having six structures represented by the general formula (I), and other five compounds are also preferable.

  The specific polysilane compound may be a halogen-substituted compound of a chain or cyclic polysilane compound having a polysilane structure represented by the general formula (I), and the halogen-substituted compound is represented by the general formula (I). Among the polysilane structures, a polysilane compound in which at least one of the polysilane structures has a phenyl group substituted by halongen (for example, fluorine or chlorine). This halogen-substituted compound has an improved refractive index compared to an unsubstituted compound. Specific examples of the halogen-substituted compound of the polysilane compound include a chain polysilane compound represented by the following structural formula (I-1B) and a cyclic polysilane compound represented by the following structural formula (I-2B). Here, in structural formulas (I-1B) and (I-2B), R represents halogen. n is synonymous with n in Structural Formula (I-1A).

  The content of the white color material in the first white particles is 10% by mass to 99% by mass, or 30% by mass to 99% by mass with respect to the third resin contained in the first white particles. . Moreover, about content of the white color material in the 2nd white particle mentioned later, 10 mass% or more and 99 mass% or less, or 30 mass% or more 99 mass% with respect to 4th resin contained in the 2nd white particle. It is below mass%. Moreover, about content of the white color material in the 3rd white particle mentioned later, 10 mass% or more and 99 mass% or less with respect to 5th resin contained in the 3rd white particle, or 30 mass% or more 99 It is below mass%.

  Examples of other compounding materials in the first white particles include the above-described charge control agents and magnetic materials. As the charge control agent, known ones used for electrophotographic toner materials are used.

(Second white particles)
Next, the second white particles will be described.
As described above, the second white particles are charged on the negative electrode, move according to the electric field, have a smaller particle diameter than the first colored particles and the second colored particles, and the first colored particles and the first colored particles. It is a white particle having a slower moving speed according to the electric field than the colored particles.

  The second white particles include a white color material and a fourth resin. Note that the second white particles may also include other compounding materials as necessary. The second white particles may have a configuration in which a white color material is dispersed or blended in the fourth resin, or the surface of the white color material is covered with the fourth resin. There may be.

Examples of the white color material contained in the second white particles include the above-described white color material. Moreover, the other compounding material mentioned above is mentioned also about another compounding material.

The fourth resin, which is a constituent component of the second white particles, includes a polymer having an anionic group that functions as a charging group. Examples of the anionic group that functions as the charging group include the anionic groups described above.

  The polymer having an anionic group may be a polymer including a structural unit derived from a monomer having an anionic group, and may be a homopolymer of a monomer having an anionic group or an anionic group. It may be a copolymer of a monomer having a group and a monomer having no charging group. In addition, the polymer having an anionic group contained in the fourth resin, which is a component of the second white particles, is derived from both a monomer having an anionic group and a monomer having a cationic group. The constitutional unit may be included, and as a result, the type of the charged group, the number of charged groups, the cationic group, and the like so that the second white particles are particles charged to the negative electrode. The polarity of the 4th resin should just be adjusted to the negative electrode by adjusting the ratio etc. with an anionic group.

  In addition, since the polarity of the fourth resin only needs to be adjusted so that the second white particles become particles charged to the negative electrode, the fourth resin constituting the second white particles is: The structure may include both a polymer having an anionic group and a polymer having a cationic group.

  Specific examples of the monomer having an anionic group, the monomer having a cationic group, and the monomer not having a charging group include the above-described monomer having an anionic group, a monomer having a cationic group, and a charging group. Monomers that do not have

  The fourth resin may further include a polymer dispersant. The polymer dispersant may also have a charged group. Examples of the polymer dispersant include the polymer dispersants described above.

  The fourth resin, which is a constituent component of the second white particles, is a resin containing a polymer containing a structural unit derived from a monomer having an anionic group as described above. It is preferable that the anionic group contained in and the anionic group contained in the second resin that is a constituent component of the second colored particle are the same group.

Further, the fourth resin of the second white particles is a structural unit derived from a monomer having an anionic group contained in a polymer having an anionic group contained in the second resin of the second colored particle. It is preferable to contain.
Further, the fourth resin of the second white particles may be composed of the second resin of the second colored particles.

A configuration in which the fourth resin, which is a constituent component of the second white particles, is derived from a monomer having an anionic group contained in a polymer having an anionic group contained in the second resin of the second colored particle. By including the unit, it is considered that the change in the charge amount of the second white particles and the second colored particles when left for a long period of time is suppressed.

Here, the first colored particles, the second colored particles, the first white particles, and the second white particles dispersed in the same dispersion medium are converted into each particle by gelation of the resin contained in each particle. The colorant and white particles contained may be exposed to the outside of the resin.
Therefore, the first resin contained in the first colored particles contains a structural unit derived from a vinyl monomer having a phenyl group, and the third resin contained in the first white particles is made of this vinyl monomer (first And the second resin contained in the second colored particles has a structural unit derived from the same vinyl monomer as the vinyl monomer having a phenyl group contained in the resin of at least one of a carboxylic acid group and a fluorine group And the fourth resin contained in the second white particles contains a structural unit derived from the first monomer. It is desirable.

  As described above, the first colored particles, the second colored particles, the first white particles, and the second white particles are included in each particle dispersed in the same dispersion medium by having the above configuration. It is considered that the gelation of the resin is suppressed, the decrease in the coverage by the resin of the colorant or the white color material is suppressed, and the further reduction in the charge amount is realized. The second colored particles and the second It is considered that the dispersibility of the particles in the dispersion medium can be improved by making the white particles contain a fluorine group.

(Third white particles)
Next, the third white particles will be described.
The third white particles are white particles that do not move according to the electric field. The third white particles include a white color material and a fifth resin. Note that the third white particles may also include the above-described other compounding materials as necessary. The third white particles may have a configuration in which a white color material is dispersed or blended in the fifth resin, or the surface of the white color material is covered with the fifth resin. There may be. As this white color material, the white color material mentioned above is mentioned.

As this 5th resin, a thermoplastic resin and a thermosetting resin are mentioned, for example. Thermoplastic resins include styrenes (eg, styrene, chlorostyrene, etc.), monoolefins (eg, ethylene, propylene, butylene, isoprene, etc.), vinyl esters (eg, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, etc.) Α-methylene aliphatic monocarboxylic acid esters (for example, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, methacrylic acid) Single weight of vinyl ethers (eg vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether), vinyl ketones (vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone, etc.) Body, or a copolymer thereof.

  Examples of the thermosetting resin include cross-linked resins (for example, cross-linked copolymers based on divinylbenzene and cross-linked polymethyl methacrylate), phenol resins, urea resins, melamine resins, polyester resins, silicone resins, and the like.

  The fifth resin may contain a polymer having a charging group. In this case, the number of charged groups and the ratio of the cationic group and the anionic group may be adjusted so that the third white particles have a charge amount that does not move according to the electric field.

  When the fifth resin contained in the third white particles includes a charged group, the charged group is added to the first resin, the second resin, the third resin, and the fourth resin. The charged group may be the same as the charged group contained.

In addition, as described above, the resin containing the structural unit derived from the vinyl monomer having a phenyl group is used as the resin contained in the first colored particles and the first white particles, and the second colored particles and the second white particles are used. When a resin containing a structural unit derived from a monomer having at least one of a carboxylic acid group and a fluorine group is used as the resin contained in the particles, as the fifth resin contained in the third white particles, It is desirable to include a structural unit derived from both a monomer having at least one of a carboxylic acid group and a fluorine group and a vinyl monomer having a phenyl group. By adopting such a configuration, it is considered that the coverage of each particle contained in the same display particle dispersion can be improved, the change in charge amount can be suppressed, and the dispersibility of each particle can be improved.

The volume average particle diameters of the first white particles and the second white particles are smaller than the first colored particles and the second colored particles.
More specifically, the volume average particle diameter of the first white particles fills the voids generated between the first colored particles when a plurality of the first colored particles having the same polarity are present. The size may be, for example, within the range of 1/10 to 3/5 times the volume average particle diameter of the first colored particles, or within the range of 1/5 to 1/2 times Can be mentioned.

  In addition, the volume average particle diameter of the second white particles is such that when a plurality of second colored particles having the same polarity are present together, the voids generated between these second colored particles are filled. For example, it may be in the range of 1/10 to 3/5 times the volume average particle diameter of the second colored particles, or in the range of 1/5 to 1/2 times.

  The volume average particle size of the first white particles and the second white particles is, for example, 0.1 μm or more and 0.5 μm or less, 0.1 μm or more and 0.3 μm or less, or 0.1 μm or more and 0.2 μm. The following are mentioned.

The volume average particle diameter of the third white particles may be the same volume average particle diameter as the first colored particles and the second colored particles, but depending on the dispersibility in the dispersion medium and the electric field. From the viewpoint of obtaining floating properties that do not move, it is desirable that the volume average particle size is smaller than the first colored particles and the second colored particles.

  Examples of the volume average particle size of the third white particles include 0.1 μm to 0.5 μm, 0.1 μm to 0.3 μm, and 0.1 μm to 0.2 μm.

  In addition, it is essential that the moving speed according to the electric field of the first white particles and the second white particles is slower than that of the first colored particles and the second colored particles.

As a method of adjusting the moving speed so as to satisfy this relationship, the surface area (that is, the size) of the first colored particles, the second colored particles, the first white particles, and the second white particles, these particles The amount of charged groups contained in the particles, the ratio of cationic groups and anionic groups as charged groups, the types and amounts of charge control agents contained in these particles, and the types and amounts of magnetic materials can be adjusted. However, it is not limited to these.

  This moving speed is measured by forming a partition wall on two transparent glass substrates with ITO electrodes and bonding them together to produce an empty cell. Then, a dispersion liquid in which particles to be measured are dispersed in a dispersion medium is injected into this empty cell, and the voltage of the voltage value determined for measurement is continued between the ITO electrodes for the time determined for measurement. Then, the state of migration of particles when applied is taken using a high-speed photography camera, and the obtained image is analyzed to calculate the movement distance of the particles per unit time.

(Dispersion medium)
Next, the dispersion medium contained in the display particle dispersion of the present embodiment will be described.

  Examples of the dispersion medium contained in the display particle dispersion of the present embodiment include petroleum-derived high-boiling solvents such as paraffinic hydrocarbon solvents, silicone oils, and fluorine-based liquids.

  Specifically, silicone oils having hydrocarbon groups bonded to siloxane bonds (for example, dimethyl silicone oil, diethyl silicone oil, methyl ethyl silicone oil, methyl phenyl silicone oil, diphenyl silicone oil, etc.), modified silicone oil ( For example, fluorine-modified silicone oil, amine-modified silicone oil, carboxyl-modified silicone oil, epoxy-modified silicone oil, alcohol-modified silicone oil, and the like. 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.

(Method for producing particles)
Next, a method for producing the first colored particles, the second colored particles, the first white particles, the second white particles, and the third white particles will be described.

  Examples of the method for producing the first colored particles, the second colored particles, the first white particles, the second white particles, and the third white particles include a method using a coacervation method. .

Specifically, for example, as a method for producing the first colored particles, the colorant used for the first colored particles, the first resin, the other compounding material, and the first dissolving the resin are used. Two kinds of liquids, that is, a mixed solution of the first solvent, and a second solvent having a lower boiling point than the first solvent for the colorant, the first resin, and the first solvent. After mixing and stirring to emulsify, the first solvent is removed, and the first resin dissolved in the first solvent is precipitated on the surface of the colorant, whereby the colorant and the first First colored particles containing a resin are produced. In addition, you may mix | blend other compounding materials other than the said material in the said mixed solution as needed.
The second colored particles are also produced by the above-described manufacturing method by replacing the colorant with the second colorant and replacing the first resin with the second resin.

Examples of the first solvent include isopropyl alcohol (IPA), methanol, ethanol, butanol, tetrahydrofuran, ethyl acetate, butyl acetate and the like. Among these, isopropyl alcohol (IPA) is desirable from the viewpoint of providing stable dispersion stability and charging characteristics. On the other hand, as the second solvent, a dispersion medium contained in the display particle dispersion according to the present embodiment may be used, and among these, silicone oil is preferable.

  In the case where the first white particles, the second white particles, and the third white particles are produced by the coacervation method, for example, a white color material, the third resin, and the fourth resin are used. And the first solvent that dissolves these resins, and the two liquids of the second solvent and the second solvent are mixed and stirred to emulsify, and then the first solvent is removed and the first solvent is removed. The resin dissolved in the solvent is deposited on the surface of the white color material. In addition, you may mix | blend other compounding materials other than the said material in the said mixed solution as needed.

As a result, the first white particles, the second white particles, and the third white particles are adjusted in the same mixed solution.

  For example, the resin dissolved in the first solvent is deposited on the surface of the white color material, thereby producing a plurality of types of white particles having different ratios of cationic groups and anionic groups contained in the resin. Will be. For example, by producing white particles by the above-described manufacturing method, the ratio of the cationic group and the anionic group contained in the resin of each white particle, as shown in the diagram 70 of FIG. A plurality of white particles having a distribution ranging from the charge amount to the charge amount of plus a are produced. Of the plurality of white particles, a white particle that indicates the positive electrode and has a charge amount that moves according to the electric field is defined as a first white particle. Of the plurality of white particles, a white particle that exhibits a negative electrode and has a charge amount that moves in accordance with an electric field is defined as a second white particle. In addition, among the plurality of white particles, white particles exhibiting a charge amount that does not move in accordance with the electric field are set as third white particles.

  Note that the distribution of the charge amount of the white particles produced by the above-described manufacturing method is in the range of minus a to plus a in the example shown by the diagram 70 in FIG. This range is appropriately adjusted by adjusting the resin used for production. For example, as shown in a diagram 72 in FIG. 6B, the distribution of the charge amount of the white particles produced by the above manufacturing method is from minus b to plus b (where | a | <| b |). A range of white particles may be adjusted.

  Further, the distribution of the charge amount of the white particles produced by the above-described manufacturing method shows the positive electrode and moves according to the electric field as shown in FIG. 6C by adjusting the resin used for producing the white particles. Charge distribution of the first white particles having a charge amount (line 80A), charge distribution of the second white particles having a negative charge and moving according to the electric field (line 80B), and electric field The distribution may be such that the third white particles that do not move in accordance with (line 80C) do not overlap.

  In addition, as shown in FIG. 6D, the resin used for producing the white particles is adjusted so that only the first white particles (diagram 80A) and the second white particles (diagram 80B) are adjusted. You may adjust.

  The method for producing the first white particles is not limited to the above method, and the first white particles may be produced by the coacervation method using only the first resin of the first resin and the second resin. Good. In addition, the second white particles may be produced by the coacervation method using only the second resin of the first resin and the second resin.

  As described above, the moving speed of the first white particles and the second white particles according to the electric field is slower than that of the first colored particles and the second colored particles, but the first white particles and the second white particles It is preferable that there is a difference between the absolute value of the charge amount of the white particles and the absolute value of the charge amounts of the first colored particles and the second colored particles. The more the absolute value of the charge amount is different, the moving speed according to the electric fields of the first white particles and the second white particles, and the moving speed according to the electric fields of the first colored particles and the second colored particles, Are preferable from the viewpoint of improving image quality.

  Through the above steps, first colored particles, second colored particles, first white particles, second white particles, and third white particles are produced.

  Then, the first colored particles, the second colored particles, the first white particles, the second white particles, and the third white particles that are produced as described above are mixed with a dispersion medium for display. A particle dispersion is obtained. In addition, for the obtained display particle dispersion, acid, alkali, salt, dispersant, dispersion stabilizer, stabilizer for anti-oxidation or ultraviolet absorption, antibacterial agent, preservative, etc., if necessary May be added.

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

Charge control agents include ionic or nonionic surfactants, block or graft copolymers composed of a lipophilic part and a hydrophilic part, polymers such as cyclic, star-like or dendritic polymers (dendrimers) Compounds with a chain skeleton, 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 desirably 0.01% by mass or more and 20% by mass or less, and particularly desirably 0.05% by mass or more and 10% by mass or less with respect to the solid content of the particles.

  Moreover, you may dilute with respect to the obtained particle dispersion liquid for display with the 1st solvent (the 1st solvent containing a dispersing agent as needed) as needed.

  The concentration of the first colored particles, the second colored particles, the first white particles, the second white particles, and the third white particles in the display particle dispersion is the display characteristics, response characteristics, or use thereof. The total amount of these particles is preferably selected in the range of 0.1% by mass or more and 30% by mass or less.

  As described above, in the display particle dispersion liquid of the present embodiment, the white particles (first white particles, second white particles, and third white particles) in the display particle dispersion liquid. Although it is considered that a white display with high whiteness is realized with a small filling rate, specifically, the total amount of white particles in the display particle dispersion is 8% by mass or more and 43% by mass or less, or 13% by mass. It is suppressed to the range of 38 mass% or less.

  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, examples of the display medium and the display device according to the embodiment will be described.

  As shown in FIG. 1, the display device 10 of the present embodiment includes a dispersion medium 50, first colored particles 34, second colored particles 36, first white particles 38 </ b> A, and second in the display medium 12. The display particle dispersion 52 according to the present embodiment is applied as the display particle dispersion 52 including the white particles 38B.

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

  The display medium 12 includes a display substrate 20 that serves as an image display surface, a rear substrate 22 that faces the display substrate 20 with a gap, and holds a space between these substrates at a specific interval, and between the substrates of the display substrate 20 and the rear substrate 22. A gap member (not shown) that divides the cell into a plurality of cells and a display particle dispersion liquid 52 sealed in each cell are included.

  The cell indicates a region surrounded by the display substrate 20, the back substrate 22, and a gap member (not shown). In this cell, a display particle dispersion 52 is sealed.

  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 may be selected according to the type of each material included in the display particle dispersion 52.

  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.

  When the surface electrode 40 and the back electrode 46 are formed on the support substrate 38 and the support substrate 44, respectively, leakage between the electrodes that causes damage to the surface electrode 40 and the back electrode 46 or adhesion of each particle of the particle group. In order to prevent the occurrence of this, a surface layer 42 and a surface layer 48 as dielectric films are respectively formed on the surface electrode 40 and the back electrode 46 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.

The gap member (not shown) is formed so as not to impair the translucency of the display substrate 20, and is formed of a thermoplastic resin, a thermosetting resin, an electron beam curable resin, a photocurable resin, rubber, metal, or the like.

  The gap member 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 is produced on either the display substrate 20 side, the back substrate 22 side, or both.

  The gap member 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, a transparent resin such as polystyrene, polyester, or acrylic Etc. are used.

  The particulate gap member 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 70% or more with respect to visible light.

  The display particle dispersion 52 includes the dispersion medium 50, the first colored particles 34, the second colored particles 36, the first white particles 38A, and the second white particles 38B.

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

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

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

  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.

  In the following description, the first colored particles 34 are particles colored red, and the second colored particles 36 are particles colored blue.

First, under the control of the control unit 18, the first colored particles 34 and the second colored particles are transferred from the voltage application unit 16 to the surface electrode 40 and the back electrode 46 so that the surface electrode 40 becomes a negative electrode and the back electrode 46 becomes a positive electrode. A voltage with such an intensity that each of the particles 36 moves between the substrates is continuously applied for a period of time until the particles reach the display substrate 20 side or the back substrate 22 side.
As a result, the first colored particles 34 charged on the positive electrode and the first white particles 38A charged on the positive electrode move to the display substrate 20 side. Then, the second colored particles 36 charged on the negative electrode and the second white particles 38B charged on the negative electrode move to the back substrate 22 side.

Here, the moving speed according to the electric field of the first white particles 38 </ b> A is slower than that of the first colored particles 34. For this reason, as shown in FIG. 1, the first colored particles 34 reach the display substrate 20 side faster than the first white particles 38A by the application of the voltage, and reach the display substrate 20 side. The first white particles 38 </ b> A are positioned on the back substrate 22 side of the layer of the first colored particles 34 so as to fill the gaps between the particles of the first colored particles 34. For this reason, when viewed from the display substrate 20 side, the gap between the particles of the first colored particles 34 positioned on the display substrate 20 side is positioned on the back substrate 22 side of the first colored particles 34. It will be in the state shielded by the 1st white particle 38A.
Further, the moving speed according to the electric field of the second white particles 38 </ b> B is slower than that of the second colored particles 36. For this reason, as shown in FIG. 1, the second colored particles 36 reach the back substrate 22 side faster than the second white particles 38B by the application of the voltage, and reach the back substrate 22 side. The second white particles 38 </ b> B are positioned on the display substrate 20 side from the layer of the two colored particles 36 so as to fill the gaps between the particles of the second colored particles 36. Therefore, when viewed from the display substrate 20 side, the gap between the particles of the second colored particles 36 positioned on the back substrate 22 side is positioned on the display substrate 20 side of the second colored particles 36. It will be in the state shielded by the 2nd white particle 38B.

  For this reason, when the display medium 12 is visually recognized from the display substrate 20 side as the display surface, the color of the second colored particles 36 is shielded by the second white particles 38B, and the layer of the first colored particles 34 is formed. The gap between the particles on the back substrate 22 side is shielded by the first white particles 38A, and the color (here, red) by the first colored particles 34 is clearly displayed.

Next, under the control of the control unit 18, the first colored particles 34 and the second colored particles 16 and the second electrode 46 are transferred from the voltage application unit 16 to the surface electrode 40 and the back electrode 46 so that the surface electrode 40 becomes a positive electrode and the back electrode 46 becomes a negative electrode. A voltage with such an intensity that each of the colored particles 36 moves between the substrates is continuously applied for a period of time until the particles reach the display substrate 20 side or the back substrate 22 side.
As a result, the first colored particles 34 charged on the positive electrode and the first white particles 38A charged on the positive electrode move to the back substrate 22 side. Then, the second colored particles 36 charged on the negative electrode and the second white particles 38B charged on the negative electrode move to the display substrate 20 side (see FIG. 2).

Here, the moving speed according to the electric field of the first white particles 38A is slower than that of the first colored particles 34, and the moving speed according to the electric field of the second white particles 38B is slower than that of the second colored particles 36. .
Therefore, as in the case of the red display (color display by the first colored particles 34), when the voltage is applied, the display is performed when viewed from the display substrate 20 side as shown in FIG. A gap between the particles of the second colored particles 36 positioned on the substrate 20 side is shielded by the second white particles 38B positioned on the back substrate 22 side of the second colored particles 36.
Further, by applying the voltage, as shown in FIG. 2, the first colored particles 34 reach the back substrate 22 side faster than the first white particles 38A, and reach the back substrate 22 side. The first white particles 38 </ b> A are positioned on the display substrate 20 side from the layer of the colored particles 34 so as to fill the gaps between the particles of the first colored particles 34. Therefore, when viewed from the display substrate 20 side, the gap between the particles of the first colored particles 34 positioned on the back substrate 22 side is positioned closer to the display substrate 20 than the first colored particles 34. It will be in the state shielded by the 1st white particle 38A.

  For this reason, when the display medium 12 is viewed from the display substrate 20 side on which the display surface is formed, the color due to the first colored particles 34 is shielded by the first white particles 38A and the layer due to the second colored particles 36. The gap between the particles on the back substrate 22 side is shielded by the second white particles 38B, and the color (blue in this case) by the second colored particles 36 is clearly displayed.

  Further, under the control of the control unit 18, for example, the back electrode 46 is grounded with respect to the display medium 12 in the red display state shown in FIG. The electric field in which the first colored particles 34 that have been moved move toward the back substrate 22 generates a voltage having a strength that is formed between the display substrate 20 and the back substrate 22, and the first colored particles 34 have the back substrate 22. Apply continuously for the time to reach the side.

  As a result, the second colored particles 36 located on the back substrate 22 side remain arranged on the back substrate 22 side, and the first colored particles 34 located on the display substrate 20 side move to the back substrate 22 side. Moving. Further, the first white particles 38A located on the display substrate 20 side also move to the back substrate 22 side at a speed slower than the moving speed of the first colored particles 34 (see FIG. 3).

When the voltage is viewed from the display substrate 20 side as shown in FIG. 3, the second colored particles 36 and the first colored particles 34 are located on the back substrate 22 side. The gap between the colored particles moves to the back substrate 22 side behind the first white particles 38A, thereby being shielded by the first white particles 38A disposed on the display substrate 20 side from these colored particles. It becomes a state.
For this reason, when the display medium 12 is viewed from the display substrate 20 side as the display surface, both the color (red) by the first colored particles 34 and the color (blue) by the second colored particles 36 are These colored particles are shielded by the white particles (the first white particles 38A and the second white particles 38B) positioned on the display substrate 20 side, and the first white particles 38A and the second white particles are blocked. The white color by 38B is clearly displayed, and white color with high whiteness is displayed.

  Therefore, according to the display medium 12 and the display device 10 of the present embodiment, clear multicolor display is realized.

In the above embodiment, the case where the two colored particles of the first colored particles 34 and the second colored particles 36 are used as the particles colored in a color other than white has been described. As the particles 34, two or more kinds of colored particles having the same polarity (positive electrode) and different in moving speed and color may be used, and as the second colored particles 36, the moving speed and moving each other with the same polarity (negative electrode). Two or more kinds of colored particles having different speeds may be used.
For example, red colored particles and yellow colored particles having different moving speeds are used as the first colored particles 34, and blue moving colors having different moving speeds are used as the second colored particles 36. Colored particles colored in black and colored particles colored in black may be used.

  With such a configuration, it is considered that further multicolor display is realized with clear colors.

  In the example shown in FIGS. 1 to 3, the first colored particles 34, the second colored particles 36, the first white particles 38 </ b> A, and the second white particles 38 </ b> B are used as the display particle dispersion 52. And the display particle dispersion liquid containing the dispersion medium 50 has been described. As shown in FIG. 4, the display further includes the third white particles 38C as the third white particles described above. The particle dispersion liquid 52A may be used.

  Further, by further including the third white particles 38C, the third white particles 38C include the third white particles that are white particles that do not move according to the electric field, as described above. By including, when displaying the color by the 1st colored particle 34 or the color by the 2nd colored particle 36, a further clear color display is implement | achieved. Further, it is considered that the whiteness can be further improved when displaying white.

Specifically, under the control of the control unit 18, the first colored particles 34 and the first colored particles 34 and the back electrode 46 are transferred from the voltage application unit 16 to the surface electrode 40 and the back electrode 46 so that the surface electrode 40 becomes a negative electrode and the back electrode 46 becomes a positive electrode. A voltage having such an intensity that each of the two colored particles 36 moves between the substrates is continuously applied until the particles reach the display substrate 20 side or the back substrate 22 side.
By applying this voltage, as shown in FIG. 4, the first colored particles 34 charged on the positive electrode and the first white particles 38A charged on the positive electrode move to the display substrate 20 side. Then, the second colored particles 36 charged on the negative electrode and the second white particles 38B charged on the negative electrode move to the back substrate 22 side.
Here, since the third white particles 38 </ b> C are particles that do not move in response to the electric field, they exist in a suspended state in the dispersion medium 50.

  For this reason, when the display medium 12 is visually recognized from the display substrate 20 side as the display surface, the color of the second colored particles 36 is shielded by the second white particles 38B, and the layer of the first colored particles 34 is formed. Since the gap between the particles on the back substrate 22 side is shielded by the first white particles 38A, and the third white particles 38C are floating in the dispersion medium 50, the first colored particles 34 are present. And the 2nd colored particle 36 will be shielded more. For this reason, the color (here red) by the first colored particles 34 is clearly displayed.

  And although illustration is omitted, in the case where the color by the second colored particles 36 is displayed, similarly, the first colored particles 34 and the second colored particles 36 are further shielded by the third white particles 38C. The Rukoto. For this reason, the color (here blue) by the second colored particles 36 is also displayed more clearly.

Further, it is considered that the whiteness is further improved during white display.
Specifically, the first colored particles 34 and the second colored particles 34 and the second electrode 46 are controlled by the control unit 18 from the voltage application unit 16 to the surface electrode 40 and the back electrode 46 so that the surface electrode 40 becomes a positive electrode and the back electrode 46 becomes a negative electrode. A voltage having such an intensity that each of the colored particles 36 moves between the substrates is continuously applied for a period of time until the particles reach the display substrate 20 side or the back substrate 22 side.
As a result, the first colored particles 34 charged on the positive electrode and the first white particles 38A charged on the positive electrode move to the back substrate 22 side. Then, the second colored particles 36 charged on the negative electrode and the second white particles 38B charged on the negative electrode move to the display substrate 20 side (see FIG. 5).

  When the display medium 12 is viewed from the display substrate 20 side, which is the display surface, the color of the first colored particles 34 is shielded by the first white particles 38A, and the layer of the second colored particles 36 is formed. The gap between the particles on the back substrate 22 side is shielded by the second white particles 38B. Further, since the third white particles 38C are suspended in the dispersion medium 50, white is clearly displayed by light scattering by the third white particles 38C suspended in the dispersion medium 50, Further, a white color with a high degree of whiteness is displayed.

  Accordingly, by including the third white particles 38C, a clearer multicolor display is realized.

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

<Example 1>
(Adjustment of dispersion of white particles (first white particles, second white particles, and third white particles))
-Preparation of resin A (cationic polymer)-
Hydroxyethyl methacrylate: 32 parts by mass, silaplane FM-0721 which is a silicone monomer, 50 parts by mass, and AMP10G having a phenyl group as a cationic group: 17.8 parts by mass are mixed with 200 parts by mass of isopropyl alcohol. Then, 0.2 parts by mass of AIBN as a polymerization initiator was dissolved, and polymerization was performed at 70 ° C. for 6 hours under nitrogen.

-Preparation of resin B (anionic polymer)-
Hydroxyethyl methacrylate: 32 parts by mass, silaplane FM-0721 which is a silicone monomer, 50 parts by mass, MMA (methyl methacrylate) as an anionic monomer having a carboxylic acid ester: 13.8 parts by mass, anionic having a fluorine group OFPMA (1H, 1H, 5H-octafluoropentyl methacrylate) as a monomer: 4 parts by mass is mixed with 200 parts by mass of isopropyl alcohol, and AIBN: 0.2 part by mass as a polymerization initiator is dissolved, and 70 ° C. under nitrogen. Polymerization was carried out for 6 hours.

-Preparation of white particle dispersion-
To 14 g of isopropyl alcohol (IPA), 0.5 g of the resin A and 0.5 g of the resin B were added and sufficiently dissolved. Further, 3.0 g of titanium oxide (TTO-55S, manufactured by Ishihara Sangyo Co., Ltd.) was added as a white color material, and 0.5 mmφ zirconia balls were used and dispersed for 48 hours to obtain a mixed liquid A1 of white particles. .

12 g of this white particle mixed liquid A1 was taken out, and 10 g of 2CS (viscosity 2 centistokes) silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) was added dropwise and emulsified while applying ultrasonic waves. Next, this solution was heated to 60 ° C. and dried under reduced pressure to remove (evaporate) IPA. After this, the white particles are settled with a centrifuge, and after removing the supernatant, 5 g of silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) is added, washed with ultrasonic waves, and white with a centrifuge. The particles were allowed to settle and the supernatant liquid was removed. Furthermore, 5 g of the above silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) was added.
As a result, a dispersion A1 of white particles having a volume average particle diameter of 0.23 μm was obtained.

  The obtained white particle dispersion A1 was sealed between two electrode substrates, and a DC voltage was applied to evaluate the migration direction. As a result, white particles charged to the positive electrode (first white particles), Three types of white particles were confirmed: white particles charged to the negative electrode (second white particles) and white particles that did not move in response to the electric field (third white particles).

(Adjustment of the first colored particle dispersion)
1.0 g of the above resin A was added to 14 g of isopropyl alcohol (IPA) and sufficiently dissolved. Furthermore, as a red colorant, 0.5 g of a red pigment (trade name: Red 3090, manufactured by Sanyo Dye) is added, and 0.5 mmφ zirconia balls are used and dispersed for 48 hours to obtain a mixture of red particles. It was.

10 g of the mixed solution of red particles was taken out, and 10 g of 2CS (viscosity 2 centistokes) silicone oil (trade name: KF96) was added dropwise and emulsified while applying ultrasonic waves. Next, this solution was heated to 60 ° C. and dried under reduced pressure to remove (evaporate) IPA. Thereafter, red particles are settled with a centrifuge, and after removing the supernatant, 5 g of silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) is added, washed with ultrasonic waves, and red with a centrifuge. The particles were allowed to settle and the supernatant liquid was removed. Furthermore, 5 g of the above silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) was added.
As a result, a dispersion of red particles having a volume average particle size of 0.4 μm was obtained.

  The obtained red particle dispersion was sealed between two electrode substrates, and a DC voltage was applied to evaluate the migration direction. As a result, it was confirmed that the positive electrode was charged.

(Adjustment of second colored particle dispersion)
1.0 g of the above resin B was added to 14 g of isopropyl alcohol (IPA) and sufficiently dissolved. Further, as a blue colorant, 0.5 g of a cyan pigment (product names: Cyan 3020, manufactured by Sanyo Dye) was added, and 0.5 mmφ zirconia balls were used and dispersed for 48 hours to obtain a blue particle mixture. Obtained.

10 g of this blue particle mixture was taken out, and 10 g of 2CS (viscosity 2 centistokes) silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) was added dropwise and emulsified while applying ultrasonic waves. Next, this solution was heated to 60 ° C. and dried under reduced pressure to remove (evaporate) IPA. Thereafter, the blue particles are settled with a centrifuge and the supernatant liquid is removed. Then, 5 g of silicone oil (trade name: KF96, manufactured by Shin-Etsu Chemical Co., Ltd.) is added, washed with ultrasonic waves, and blue with a centrifuge. The particles were allowed to settle and the supernatant liquid was removed. Furthermore, 5 g of the above silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) was added.
As a result, a dispersion of blue particles having a volume average particle size of 0.3 μm was obtained.

  The obtained dispersion of blue particles was sealed between two electrode substrates, and a DC voltage was applied to evaluate the migration direction. As a result, it was confirmed that the negative electrode was charged.

(Adjustment of particle dispersion for display)
Silicone oil (Shin-Etsu Chemical Co., Ltd.) as a dispersion medium so that the adjusted white particle dispersion A1 20% by weight, the red particle dispersion 0.5% by weight, and the blue particle dispersion 0.5% by weight are prepared. (Product name: KF-96-2S) was adjusted and mixed. Thus, the display particle dispersion A1 was prepared.

(Preparation of display medium)
The display particle dispersion A1 prepared as described above is placed between a pair of glass substrates on which indium tin oxide (ITO) electrodes are formed (a Teflon (registered trademark) sheet having a thickness of 50 μm as a gap member between the pair of glass substrates). A display medium A1 encapsulated in the interposed cell) was produced.

<Example 2>
A display medium A2 was produced under the same conditions and the same manufacturing method as in Example 1 except that the following white particle dispersion A2 was used instead of the white particle dispersion A1 prepared in Example 1.

(Adjustment of dispersion of white particles (first white particles, second white particles, and third white particles))
-Preparation of resin C (polymer having cationic and anionic groups)-
Hydroxyethyl methacrylate: 32 parts by mass, silaplane FM-0721 which is a silicone monomer, 50 parts by mass, AMP10G having a phenyl group as a cationic group: 10.6 parts by mass, and an anionic monomer having a carboxylic acid MA (methacrylic acid): 2.0 parts by mass and OFPMA (1H, 1H, 5H-octafluoropentyl methacrylate): 3 parts by mass as an anionic monomer having a fluorine group are mixed with 200 parts by mass of isopropyl alcohol. Then, 0.4 parts by mass of AIBN as a polymerization initiator was dissolved, and polymerization was performed at 70 ° C. for 6 hours under nitrogen.

-Preparation of white particle dispersion-
To 14 g of isopropyl alcohol (IPA), 1.0 g of the above resin C was added and sufficiently dissolved. Further, 3.0 g of titanium oxide (TTO-55S, manufactured by Ishihara Sangyo Co., Ltd.) was added as a white color material, and 0.5 mmφ zirconia balls were used and dispersed for 48 hours to obtain a mixed liquid A2 of white particles. .

12 g of this white particle mixture A2 was taken out, and 10 g of 2CS (viscosity 2 centistokes) silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) was added dropwise and emulsified while applying ultrasonic waves. Next, this solution was heated to 60 ° C. and dried under reduced pressure to remove (evaporate) IPA. After this, the white particles are settled with a centrifuge, and after removing the supernatant, 5 g of silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) is added, washed with ultrasonic waves, and white with a centrifuge. The particles were allowed to settle and the supernatant liquid was removed. Furthermore, 5 g of the above silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) was added.
As a result, a dispersion A2 of white particles having a volume average particle size of 0.24 μm was obtained.

  The obtained white particle dispersion A2 was sealed between two electrode substrates, and a DC voltage was applied to evaluate the migration direction. As a result, white particles charged to the positive electrode (first white particles), Three types of white particles were confirmed: white particles charged to the negative electrode (second white particles) and white particles that did not move in response to the electric field (third white particles). In addition, it was confirmed that the moving speeds of the first white particles and the second white particles in Example 2 are slower than those of the first white particles and the second white particles in Example 1.

<Example 3>
A display medium A3 was produced under the same conditions and the same manufacturing method as in Example 1 except that the following white particle dispersion A3 was used instead of the white particle dispersion A1 prepared in Example 1.

-Preparation of white particle dispersion-
To 14 g of isopropyl alcohol (IPA) and 5 g of tetrahydrofuran (THF), 2.0 g of the resin A was added and sufficiently dissolved. Further, 3.0 g of titanium oxide (TTO-55S, manufactured by Ishihara Sangyo Co., Ltd.) was added as a white color material, and 0.5 mmφ zirconia balls were used and dispersed for 48 hours to obtain a white particle mixed liquid A3. .

  12 g of this white particle mixed liquid A3 was taken out, and 10 g of 2CS (viscosity 2 centistokes) silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) was added dropwise and emulsified while applying ultrasonic waves. Next, this solution was heated to 60 ° C. and dried under reduced pressure to remove (evaporate) IPA and THF. After this, the white particles are settled with a centrifuge, and after removing the supernatant, 5 g of silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) is added, washed with ultrasonic waves, and white with a centrifuge. The particles were allowed to settle and the supernatant liquid was removed. Furthermore, 5 g of the above silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) was added. As a result, a dispersion A3-1 of white particles having a volume average particle diameter of 0.21 μm was obtained.

Similarly, only by replacing the resin A with the resin B, a white particle dispersion A3-2 having a volume average particle size of 0.23 μm was obtained.
Dispersion A3 was obtained by mixing these dispersions A3-1 and A3-2 in the same amount.

  The obtained white particle dispersion A3 was sealed between two electrode substrates, and a migration direction was evaluated by applying a DC voltage. As a result, it was found that there was no white particle that did not respond to an electric field.

<Example 4>
A display medium A4 was produced under the same conditions and the same manufacturing method as in Example 1 except that the following white particle dispersion A4 was used instead of the white particle dispersion A1 prepared in Example 1.

-Adjustment of resin D-
Hydroxyethyl methacrylate: 32 parts by mass, silaplane FM-0721: 35 parts by mass, silaplane FM0725: 15 parts by mass, AMP10G having a phenyl group as a cationic group: 10.6 parts by mass MMA (methyl methacrylate): 2.0 parts by mass as an anionic monomer having a carboxylic acid ester is mixed with 200 parts by mass of isopropyl alcohol, and AIBN: 0.4 part by mass is dissolved as a polymerization initiator. Polymerization was performed at 70 ° C. for 6 hours under nitrogen.

-Preparation of white particle dispersion-
To 14 g of isopropyl alcohol (IPA) and 2 g of tetrahydrofuran (THF), 1.0 g of the resin D was added and sufficiently dissolved. Furthermore, as a white color material, 3.0 g of titanium oxide (TTO-55S, manufactured by Ishihara Sangyo) was added and dispersed using a zirconia ball having a diameter of 0.5 mm for 48 hours to obtain a mixed liquid A4 of white particles. .

12 g of this white particle mixed liquid A4 was taken out, and 10 g of 2CS (viscosity 2 centistokes) silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) was added dropwise and emulsified while applying ultrasonic waves. Next, this solution was heated to 60 ° C. and dried under reduced pressure to remove (evaporate) IPA and THF. After this, the white particles are settled with a centrifuge, and after removing the supernatant, 5 g of silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) is added, washed with ultrasonic waves, and white with a centrifuge. The particles were allowed to settle and the supernatant liquid was removed. Furthermore, 5 g of the above silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) was added.
As a result, a dispersion A4 of white particles having a volume average particle size of 0.0.22 μm was obtained.

  The obtained white particle dispersion A4 was sealed between two electrode substrates, and a DC voltage was applied to evaluate the migration direction. As a result, white particles charged to the positive electrode (first white particles), Three types of white particles were confirmed: white particles charged to the negative electrode (second white particles) and white particles that did not move in response to the electric field (third white particles). In addition, it was confirmed that the moving speeds of the first white particles and the second white particles in Example 2 are slower than those of the first white particles and the second white particles in Example 1.

<Example 5>
A display medium A5 was produced under the same conditions and the same manufacturing method as in Example 1 except that the following white particle dispersion A5 was used instead of the white particle dispersion A1 prepared in Example 1.

-Adjustment of resin E-
Hydroxyethyl methacrylate: 32 parts by mass, silaplane FM-0721 which is a silicone-based monomer, AMP10G having a phenyl group as a cationic group: 10.6 parts by mass, and an anionic monomer having sulfonic acid Vinylsulfonic acid (VSA-H manufactured by Asahi Kasei Finechem): 1.0 part by mass, and an anionic monomer having a fluorine group, OFPMA (1H, 1H, 5H-octafluoropentyl methacrylate): 3 parts by mass, isopropyl alcohol It mixed with 200 mass parts, AIBN: 0.4 mass part was melt | dissolved as a polymerization initiator, and superposition | polymerization was performed at 70 degreeC under nitrogen for 6 hours.

-Preparation of white particle dispersion-
To 14 g of isopropyl alcohol (IPA) and 2 g of tetrahydrofuran (THF), 1.0 g of the resin E was added and sufficiently dissolved. Further, 3.0 g of titanium oxide (TTO-55S, manufactured by Ishihara Sangyo Co., Ltd.) was added as a white color material, and 0.5 mmφ zirconia balls were used and dispersed for 48 hours to obtain a white particle mixed liquid A5. .

12 g of this white particle mixed liquid A5 was taken out, and 10 g of 2CS (viscosity 2 centistokes) silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) was added dropwise and emulsified while applying ultrasonic waves. Next, this solution was heated to 60 ° C. and dried under reduced pressure to remove (evaporate) IPA. After this, the white particles are settled with a centrifuge, and after removing the supernatant, 5 g of silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) is added, washed with ultrasonic waves, and white with a centrifuge. The particles were allowed to settle and the supernatant liquid was removed. Furthermore, 5 g of the above silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) was added.
As a result, a dispersion A5 of white particles having a volume average particle size of 0.23 μm was obtained.

  The obtained white particle dispersion A5 was sealed between two electrode substrates, and a DC voltage was applied to evaluate the migration direction. As a result, white particles charged to the positive electrode (first white particles), Three types of white particles were confirmed: white particles charged to the negative electrode (second white particles) and white particles that did not move in response to the electric field (third white particles). In addition, it was confirmed that the moving speeds of the first white particles and the second white particles in Example 2 are slower than those of the first white particles and the second white particles in Example 1.

<Comparative Example 1>
A display medium B1 was produced under the same conditions and the same manufacturing method as in Example 1 except that the following white particle dispersion B1 was used instead of the white particle dispersion A1 prepared in Example 1.

(Preparation of dispersion of white particles (first white particles))
1.0 g of the above resin A was added to 14 g of isopropyl alcohol (IPA) and sufficiently dissolved. Further, 3.0 g of titanium oxide (TTO-55S, manufactured by Ishihara Sangyo Co., Ltd.) was added as a white color material, and 0.5 mmφ zirconia balls were used and dispersed for 48 hours to obtain a white particle mixed solution B1. .

12 g of this white particle mixture B1 was taken out, and 10 g of 2CS (viscosity 2 centistokes) silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) was added dropwise and emulsified while applying ultrasonic waves. Next, this solution was heated to 60 ° C. and dried under reduced pressure to remove (evaporate) IPA. After this, the white particles are settled with a centrifuge, and after removing the supernatant, 5 g of silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) is added, washed with ultrasonic waves, and white with a centrifuge. The particles were allowed to settle and the supernatant liquid was removed. Furthermore, 5 g of the above silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) was added.
As a result, a dispersion B1 of white particles having a volume average particle diameter of 0.23 μm was obtained.

  The obtained white particle dispersion B1 was sealed between two electrode substrates, and a DC voltage was applied to evaluate the migration direction. As a result, only the white particles (first white particles) charged on the positive electrode were found. confirmed.

<Comparative example 2>
A display medium B2 was produced under the same conditions and the same manufacturing method as in Example 1 except that the following white particle dispersion B2 was used instead of the white particle dispersion A1 prepared in Example 1.

-Adjustment of resin F-
Vinyl pyrrolidone: 33.5 parts by mass, Silaplane FM-0721: 50 parts by mass of silicone monomer, Silaplane FM0725: 15, 1 part by mass of ethylene glycol dimethacrylate are mixed with 200 parts by mass of isopropyl alcohol. AIBN: 0.5 part by mass was dissolved as a polymerization initiator, and polymerization was performed at 70 ° C. for 6 hours under nitrogen.

-Preparation of white particle dispersion-
To 14 g of isopropyl alcohol (IPA) and 5 g of tetrahydrofuran (THF), 2.0 g of the resin F was added and sufficiently dissolved. Further, 3.0 g of titanium oxide (TTO-55S, manufactured by Ishihara Sangyo Co., Ltd.) was added as a white color material, and 0.5 mmφ zirconia balls were used and dispersed for 48 hours to obtain a white particle mixed solution B2. .

  12 g of this white particle mixture B2 was taken out, and 10 g of 2CS (viscosity 2 centistokes) silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) was added dropwise and emulsified while applying ultrasonic waves. Next, this solution was heated to 60 ° C. and dried under reduced pressure to remove (evaporate) IPA and THF. After this, the white particles are settled with a centrifuge, and after removing the supernatant, 5 g of silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) is added, washed with ultrasonic waves, and white with a centrifuge. The particles were allowed to settle and the supernatant liquid was removed. Furthermore, 5 g of the above silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: trade name KF96) was added. As a result, a dispersion B2 of white particles having a volume average particle size of 0.21 μm was obtained.

  The obtained dispersion B2 of white particles was sealed between two electrode substrates, and the direction of migration was evaluated by applying a DC voltage. As a result, white particles that did not respond to an electric field or responded very slowly. I found out.

[Evaluation]
The resulting display medium was evaluated for the clarity of each color during white display, blue display, and red display, the display color switching speed, the change over time in the charge amount of the particles, and the dispersibility.

―Visibility assessment―
Particles were moved by applying DC (direct current) at a voltage of 30 V for 5 seconds between the electrode substrates (inter-substrate distance: 50 μm) of the display medium prepared above, and switching the polarity. When a positive electrode voltage was applied to the display-side electrode at 30 V for 2 seconds, blue particles moved to the display-side glass substrate, and blue was displayed.
On the other hand, when a negative electrode voltage was applied to the display-side electrode at 30 V for 2 seconds, the red particles moved to the display-side glass substrate and displayed red.

  Furthermore, when the positive electrode voltage was applied to the display side electrode at 7 V for 3 seconds in the state where the red color was displayed, the red particles moved to the glass substrate on the back side, and white color was displayed.

(Blue display)
With respect to the display medium in which the blue color was displayed, the display color on the display substrate side was measured using X939 manufactured by X-Rite, and the blue sharpness (C density) was evaluated. The evaluation criteria were as follows. The evaluation results are shown in Table 1.
G1: When 0.8 or more.
G2: When 0.6 or more and less than 0.8.
G3: When it is 0.3 or more and less than 0.6.
G4: When less than 0.3.

(Displayed in red)
With respect to the display medium in which the red color was displayed, the display color on the display substrate side was measured using X939 manufactured by X-Rite, and the redness (M density) was evaluated. The evaluation criteria were as follows. The evaluation results are shown in Table 1.
G1: When 0.8 or more.
G2: When 0.6 or more and less than 0.8.
G3: When it is 0.3 or more and less than 0.6.
G4: When less than 0.3.

(White display)
About the display medium in a state where the white color is displayed, a color meter WMS-1 (manufactured by Murakami Color Research Laboratory Co., Ltd.) was used to determine whiteness. The evaluation criteria were as follows. The evaluation results are shown in Table 1.
G1: When 40% or more.
G2: 30% or more and less than 40%.
G3: When it is 20% or more and less than 30%.
G4: When it is less than 20%.

-Display color switching speed-
Switching between red display, blue display, and white display performed in the sharpness evaluation described above, time required from red display to blue display, time required from blue display to white display, required from white display to red display Each time was measured and the average value was determined. The time required for this display change is measured by measuring the change in color density on the display substrate side with a color meter X-Rite 939 (manufactured by X-Rite) after applying a voltage for displaying each color. The time until the change in density per unit time became 0.1 or less was determined as the time required for the change in display color. The evaluation criteria were as follows. The evaluation results are shown in Table 1.
G1: When it is less than 2 seconds.
G2: When it is 2 seconds or more and less than 5 seconds.
G3: When it is 5 seconds or more and less than 10 seconds.
G4: When it is 10 seconds or more.

-Change in charge of particles over time-
In the presence of mixed particles, it is impossible to measure the charge amount of each color, so by monitoring the change in display color density that is directly related to the charge amount, and evaluating the display stability, The change over time in the amount of charge was evaluated.
Evaluation is made between the electrode substrates at 50 μm, and the electrode substrate surfaces are opposed to each other, and the dispersion liquid prepared in the above-mentioned Examples and Comparative Examples is enclosed, switched at voltage + − (30 V), and displayed in red and blue, M density | concentration and C density | concentration were measured by X-Rite939 for every frequency | count, and each color density change was calculated compared with the initial stage. Then, the number of times of display when the change in either color density was 0.2 was obtained. The evaluation criteria were as follows. The evaluation results are shown in Table 1.
G1: When it is 300 times or more.
G2: When it is 200 times or more and less than 300 times.
G3: When it is 100 times or more and less than 200 times.
G4: When it is less than 100 times.

-Dispersibility of particles-
The dispersion prepared in each of the above Examples and Comparative Examples was sealed in a 3 mΦ (inner diameter) glass tube so as to have a height of 50 mm and allowed to stand at room temperature for 20 days. The height of the uncolored liquid of this dispersion was measured in millimeters. Thereby, the dispersibility of the particles was evaluated. The evaluation criteria were as follows. The evaluation results are shown in Table 1.
G1: When it is less than 3 mm.
G2: When it is 3 mm or more and 5 mm or less.
G3: When it is 5 mm or more and 7 mm or less.
G4: When it is 7 mm or more.

  As shown in Table 1, in the example, a display medium having a higher color sharpness than that of the comparative example was provided.

DESCRIPTION OF SYMBOLS 10 Display apparatus, 12 Display medium, 16 Voltage application part, 18 Control part, 34 1st colored particle, 36 2nd colored particle, 38A 1st white particle, 38B 2nd white particle, 38C 3rd white Particle, 50 Dispersion medium

Claims (4)

A display medium comprising a pair of substrates, at least one of which has translucency, and a display particle dispersion encapsulated between the pair of substrates, the display particle dispersion comprising:
First colored particles that are charged to the positive electrode, move according to an electric field, and are colored in a first color different from white,
Second colored particles that are charged to the negative electrode, move according to an electric field, and are colored white and a second color different from the first color;
Charged to the positive electrode, moves in response to an electric field, has a volume average particle size smaller than that of the first colored particles and the second colored particles, and moves faster than the first colored particles and the second colored particles. First white particles of slow white,
The negative electrode is charged, moves in accordance with an electric field, has a volume average particle size smaller than that of the first colored particles and the second colored particles, and a moving speed than the first colored particles and the second colored particles. Second white particles that are slow white,
A dispersion medium for dispersing the first colored particles, the second colored particles, the first white particles, and the second white particles;
A display particle dispersion comprising,
Display medium . The display particle dispersion further comprises a white third white particles that do not move in response to an electric field, the display medium of claim 1. In the display particle dispersion,
The first colored particles are configured to include a colorant and a first resin including a structural unit derived from a vinyl monomer having a phenyl group,
The second colored particles are configured to include a colorant and a second resin including a structural unit derived from a first monomer having at least one of a carboxylic acid group and a fluorine group,
The first white particles are configured to include a white color material and a third resin including a structural unit derived from the vinyl monomer.
The second white particles are configured to include a white color material and a fourth resin including a structural unit derived from the first monomer.
The display medium according to claim 1 or 2. The display medium according to any one of claims 1 to 3 ,
A voltage applying unit for applying a voltage between a pair of substrates provided in the display medium,
A display device comprising: