JP2011027781A - Particle dispersion liquid for display, display medium and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a particle dispersion liquid for display that prevents variations in reversible aggregation and redispersion characteristics of a particle for display. <P>SOLUTION: The particle dispersion liquid for display includes: a dispersion medium 50 composed of silicone oil; the particle for display (its particle assemblage 34) moving according to an electric field; and a polymer dispersant having at least one monomer as a copolymerization constituent. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  An electrophoretic display medium has been actively studied as a display having a memory property. In this display method, display particles (electrophoretic particles) charged in a liquid are used, and the electrophoretic particles are enclosed in a cell by applying an electric field (two electrode substrates are stacked and an electrophoretic material is enclosed with a dispersion medium therebetween). Display is performed by alternately moving to the viewing surface and back surface of the configuration.

  In the present technology, the display particles (electrophoretic particles) are important elements, and various technical developments have been made. For example, for the purpose of imparting cohesive force and charging stability of display particles, a technique using an additive having a charge polarity different from the charge polarity of the display particles has been proposed (for example, patents). References 1 and 2)

JP 2007-121570 A Japanese Patent No. 3936588

  The problem of the present application is that the display particles are reversible compared to the case where a polymer dispersant that does not contain at least one monomer represented by the following general formulas (I) and (II) as a copolymer component is applied. It is an object to provide a display particle dispersion liquid in which fluctuations in agglomeration / redispersion characteristics are suppressed.

The above problem is solved by the following means. That is,
The invention according to claim 1
Display particles that move in response to an electric field;
A polymer dispersant containing at least one monomer represented by the following general formulas (I) and (II) as a copolymerization component;
A dispersion medium comprising silicone oil;
A particle dispersion for display.

(In the general formulas (I) and (II), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₉ and R ₁₀ are each independently a hydrogen atom or 1 or more carbon atoms. Represents an alkyl group having 4 or less, or a fluoroalkyl group having 1 to 4 carbon atoms, R ₈ represents a hydrogen atom or a methyl group, and n, l, and m are each independently an integer of 1 to 1000. X represents an integer of 1 to 3.

The invention according to claim 2
The display particles are display particles having a base;
The polymer dispersant is a polymer dispersant containing at least one monomer represented by the general formulas (I) and (II) and a monomer having an acid group as at least a copolymerization component. The display particle dispersion according to claim 1.

The invention according to claim 3
The display particles are display particles having an acid group,
The polymer dispersant is a polymer dispersant containing at least one monomer represented by the general formulas (I) and (II) and a monomer having a base as at least a copolymerization component. Item 4. The display particle dispersion according to Item 1.

The invention according to claim 4
A pair of substrates, at least one of which is translucent,
The particle dispersion for display according to any one of claims 1 to 3, encapsulated between the pair of substrates,
A display medium comprising:

The invention according to claim 5
A pair of electrodes, at least one of which is translucent,
A region having the display particle dispersion according to any one of claims 1 to 3 provided between the pair of electrodes;
A display medium comprising:
The invention according to claim 6
A display medium according to claim 4 or 5, and
Voltage application means for applying a voltage between the pair of substrates or the pair of electrodes of the display medium;
Display device with

According to the first aspect of the present invention, compared to a system including a polymer dispersant that does not have at least one monomer represented by the general formulas (I) and (II) as a copolymer component, the display Fluctuations in reversible agglomeration and redispersion characteristics of the particles for use are suppressed.
According to the inventions according to claims 2 and 3, the charging polarity of the display particles is higher than that of a system in which the functional group of the display particles and the functional group of the polymer dispersant do not exert acid-base interaction. Fluctuations are suppressed.
According to the invention of claim 4, there is provided a display particle dispersion containing a polymer dispersant that does not contain at least one monomer represented by the general formulas (I) and (II) as a copolymer component. Compared to the case where it is applied, stable repeated display is realized.
According to the invention of claim 5, there is provided a display particle dispersion containing a polymer dispersant that does not contain at least one monomer represented by the general formulas (I) and (II) as a copolymer component. Compared to the case where it is applied, stable repeated display is realized.
According to the invention which concerns on Claim 6, the particle dispersion for a display containing the polymer dispersing agent which does not contain at least 1 sort (s) of the monomer shown by the said general formula (I) and (II) as a copolymer component. Compared to the case where it is applied, stable repeated display is realized.

1 is a schematic configuration diagram of a display device according to a first embodiment. It is explanatory drawing which shows typically the movement aspect of a particle group when a voltage is applied between the board | substrates of the display medium of the display apparatus which concerns on 1st Embodiment. In an Example, it is a schematic diagram which shows the drive waveform for evaluating repetition stability.

  Hereinafter, embodiments of the present invention will be described.

(Particle dispersion for display)
The display particle dispersion according to this embodiment includes display particles (a group thereof) that move according to an electric field, a polymer dispersant, and a dispersion medium that includes silicone oil. The polymer dispersant is a specific polymer dispersant containing at least one monomer represented by the following general formulas (I) and (II) as a copolymerization component.

  Here, when the aggregating force is applied between the display particles via the polymer dispersant for controlling the aggregating force between the display particles, the aggregation between the display particles may progress over time. As the aggregation progresses, the reversible aggregation / redispersion characteristics of the display particles vary greatly, resulting in a change in electric field response (threshold characteristics) and display unevenness.

On the other hand, in the display particle dispersion according to the present embodiment, a single amount represented by the following general formulas (I) and (II) is used as a polymer dispersant for controlling the cohesive force between display particles. By applying a specific polymer dispersant containing at least one kind of body, even if reversible aggregation / redispersion of display particles is repeated, the progress of aggregation between the display particles over time is suppressed. Therefore, the change in reversible aggregation / redispersion characteristics of the display particles of the display particles is suppressed.
Then, when the display particle dispersion according to the present embodiment is applied to a display medium or a display device, it is considered that the progress of aggregation between the display particles over time can be suppressed, so that stable repeated display is realized. Is done.

The display particle dispersion according to the present embodiment is preferably in a form in which the functional groups of the display particles and the functional groups of the polymer dispersant exert an acid-base interaction.
In other words, 1) a polymer dispersion containing display particles having a base, at least one monomer represented by the following general formulas (I) and (II) and a monomer having an acid group as at least a copolymerization component 2) Display particles having an acid group, at least one monomer represented by the following general formulas (I) and (II) and a monomer having a base at least. It is preferable that the polymer dispersant contained as a polymerization component is combined.

In the display particle dispersion according to the present embodiment, when the above form is adopted, fluctuations in the charging polarity of the display particles that move according to the electric field are suppressed. In particular, a negatively charged particle having a base as display particles having a base, at least one monomer represented by the following general formulas (I) and (II) and a monomer having an acid group are at least a copolymerization component. In combination with the polymer dispersant contained as the above, the display particles are stabilized by negative charge.
When the display particle dispersion according to the present embodiment is applied to a display medium or a display device, fluctuations in the charge polarity of the display particles are suppressed, that is, the display particles (group) having the same charge polarity. Among them, since the presence of display particles having reverse polarity is reduced, mixed color display is suppressed.

The display particles will be described.
The display particles include, for example, a colorant and a polymer and, if necessary, include other compounding materials. The display particles may be particles in which a colorant is dispersed and blended in a polymer, or the particle surface of the colorant is coated with a polymer, or the particle surface of the colorant is a low molecular compound (for example, Particles treated with a monomer having a charging group) may be used.

The polymer preferably has a base or acid group as a functional group. Here, in the polymer, the functional group may be a group that functions as a charging group, or may be a group that functions separately from a group that functions as a charging group, but is a group that functions as a charging group. Is good. When the polymer has a base or an acid group separately from a group that functions as a charging group, the charging group includes a fluorine group.
The polymer having a functional group that functions as a charging group will be described as a polymer having a charging group.

  In the polymer having a charged group, among the base (hereinafter referred to as a cationic group) or the acid group (hereinafter referred to as an anionic group) that functions as a charged group, the cationic group that functions as a charged group is, for example, an amino group, 4 Examples include quaternary ammonium groups (including salts of these groups). For example, the cationic group imparts positively charged polarity to the particles. On the other hand, examples of the anionic group as the charging group include a phenol group, a carboxyl group, a carboxylate group, a sulfonate group, a sulfonate group, a phosphate group, a phosphate group, and a tetraphenylboron group (these groups). For example, this anionic group imparts negatively charged polarity to the particles.

  Specifically, the polymer having a charging group may be, for example, a homopolymer of a monomer having a charging group, or a monomer having a charging group and another monomer (charging group). And monomers having no monomer). The description such as “(meth) acrylate” is an expression including both “acrylate” and “methacrylate”. The same applies hereinafter.

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

Examples of the cationic monomer include the following. Specifically, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dibutylaminoethyl (meth) acrylate, N, N-hydroxyethylaminoethyl (meta) ) Acrylate, N-ethylaminoethyl (meth) acrylate, N-octyl-N-ethylaminoethyl (meth) acrylate, N, N-dihexylaminoethyl (meth) acrylate and other aliphatic amino groups (meth) Acrylates, aromatic substituted ethylene monomers having nitrogen-containing groups such as dimethylaminostyrene, diethylaminostyrene, dimethylaminomethylstyrene, dioctylaminostyrene,
Vinyl-N-ethyl-N-phenylaminoethyl ether, vinyl-N-butyl-N-phenylaminoethyl ether, triethanolamine divinyl ether, vinyl diphenylaminoethyl ether, N-vinylhydroxyethylbenzamide, m-aminophenyl vinyl ether Nitrogen-containing vinyl ether monomers such as vinylamine, pyrroles such as N-vinylpyrrole, pyrrolines such as N-vinyl-2-pyrroline and N-vinyl-3-pyrroline, N-vinylpyrrolidine, vinylpyrrolidine aminoether Pyrrolidines such as N-vinyl-2-pyrrolidone, imidazoles such as N-vinyl-2-methylimidazole, imidazolines such as N-vinylimidazoline, indoles such as N-vinylindole, N-vinylindoline, etc. India Phosphorus, N-vinylcarbazole, carbazoles such as 3,6-dibromo-N-vinylcarbazole, pyridines such as 2-vinylpyridine, 4-vinylpyridine, 2-methyl-5-vinylpyridine, (meth) acrylic Piperidines such as piperidine, N-vinylpiperidone and N-vinylpiperazine, quinolines such as 2-vinylquinoline and 4-vinylquinoline, pyrazoles such as N-vinylpyrazole and N-vinylpyrazoline, and oxazoles such as 2-vinyloxazole , Oxazines such as 4-vinyloxazine and morpholinoethyl (meth) acrylate.
Moreover, as a particularly preferable cationic monomer from versatility, (meth) acrylates having an aliphatic amino group such as N, N-dimethylaminoethyl (meth) acrylate and N, N-diethylaminoethyl (meth) acrylate In particular, it is preferable to use a quaternary ammonium salt structure before or after polymerization. Quaternary ammonium chloride can be obtained, for example, by reacting the compound with alkyl halides or tosylate esters.

As an anionic monomer, the following are mentioned, for example.
Specifically, among the anionic monomers, carboxylic acid monomers include (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, citraconic acid, or anhydrides thereof and monoalkyl esters thereof. And vinyl ethers having a carboxyl group such as carboxyethyl vinyl ether and carboxypropyl vinyl ether.
Examples of the sulfonic acid monomer include styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 3-sulfopropyl (meth) click acid ester, bis- (3-sulfopropyl) -itaconic acid ester, and salts thereof. There is. In addition, there are sulfuric acid monoesters of 2-hydroxyethyl (meth) acrylic acid and salts thereof.
Examples of phosphoric acid monomers include vinylphosphonic acid, vinyl phosphate, acid phosphoxyethyl (meth) acrylate, acid phosphoxypropyl (meth) acrylate, bis (methacryloxyethyl) phosphate, diphenyl-2-methacryloyloxyethyl phosphate, diphenyl There are 2-acryloyloxyethyl phosphate, dibutyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, dioctyl-2- (meth) acryloyloxyethyl phosphate, and the like.
Desirably, the anionic monomer has (meth) acrylic acid or sulfonic acid, and more desirably has an ammonium salt structure before or after polymerization. The ammonium salt is prepared by, for example, reacting with a tertiary amine or quaternary ammonium hydroxide.

  As a monomer having a fluorine group that functions as a charging group other than an acid group and a base, a monomer component having fluorine includes, for example, a (meth) acrylate monomer having a fluorine group, specifically, trifluoro Ethyl (meth) acrylate, pentafluoropropyl (meth) acrylate, perfluoroethyl (meth) acrylate, perfluorobutylethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate, perfluorodecylethyl (meth) acrylate, tri Examples thereof include fluoromethyltrifluoroethyl (meth) acrylate and hexafluorobutyl (meth) acrylate.

  On the other hand, examples of other monomers include nonionic monomers (nonionic monomers). 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, vinylidene chloride, isoprene, butadiene, vinyl pyrrolidone, hydroxyethyl ( Examples include meth) acrylate and hydroxybutyl (meth) acrylate.

  Here, the copolymerization ratio between the monomer having a charging group and another monomer is changed according to the charge amount of the desired particles. Usually, the copolymerization ratio of the monomer having a charged group and another monomer is selected in the range of 1: 100 to 100: 0 in terms of the molar ratio.

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

  Here, the negatively charged particles having a base as the display particles will be described in detail. For the negatively charged particles having a base, a polymer having a base is used as the polymer. In negatively charged particles having a base, since the base is not a group that functions as a charged group, it is preferable to have a group that functions as a charged group separately. Examples of the charging group include a fluorine group, a carboxyl group, a carboxylic acid group, a sulfonic acid group, a sulfonic acid group, a phosphoric acid group, and a phosphoric acid group, and a fluorine group is preferable.

  That is, the negatively charged particles having a base are preferably a polymer having a base as a polymer and a fluorine group as a charged group. As the polymer having a base and a fluorine group, a monomer having a base, a monomer having a fluorine group, and other monomers (nonionic monomers) as necessary may be used. A polymer is mentioned. About these monomers, it is the same as that of what was illustrated by the monomer which comprises the said polymer | macromolecule.

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

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

Next, other compounding materials will be described. Examples of other compounding materials include a charge control material and a magnetic material.
As the charge control material, known materials used for electrophotographic toner materials can be used. For example, cetylpyridyl chloride, BONTRON P-51, BONTRON P-53, BONTRON E-84, BONTRON E-81 (above, Quaternary ammonium salts such as Orient Chemical Industry Co., Ltd.), salicylic acid metal complexes, phenol condensates, tetraphenyl compounds, metal oxide particles, and metal oxide particles surface-treated with various coupling agents.

As the magnetic material, a color-coated inorganic magnetic material or organic magnetic material is used as necessary. Further, a transparent magnetic material, in particular, a transparent organic magnetic material is more preferable because it hardly inhibits the coloring of the colored pigment and has a smaller specific gravity than the inorganic magnetic material.
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 such that the magnetic powder is opaquely colored with a pigment or the like, but it is preferable to use, for example, a light interference thin film. This optical interference thin film is a thin film having a thickness equivalent to the wavelength of light made of an achromatic material such as SiO ₂ or TiO ₂ and selectively reflects the wavelength of light by optical interference in the thin film. It is.

  Here, the display particles may be particles having a silicone polymer adhered (for example, bonded or coated) to the surface thereof. Further, the silicone polymer may have a charged group similar to the polymer constituting each of the display particles, and may be used in place of the above polymer constituting the display particles.

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

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

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

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

  As the copolymerization component having a charging group and other copolymerization components (copolymerization components having no charging group), the monomer having a charging group described in the polymer having a charging group, other monomers ( Those mentioned in (monomers not having a charging group) are applied.

  In the silicone polymer, the mass ratio of the silicone chain component to the whole polymer is 3% or more and 60% or less, preferably 5% or more and 40% or less.

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

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

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

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

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

Next, the polymer dispersant will be described.
The polymer dispersant is a specific polymer dispersant containing at least one monomer represented by the general formulas (I) and (II) as a copolymerization component. The polymer dispersant is a polymer dispersion medium that is soluble in silicone oil. Note that the term “soluble” means that the polymer dispersant is dissolved by 1% by mass or more in the silicone oil at 25 ° C.

  Specifically, as the polymer dispersant, at least one monomer represented by the general formulas (I) and (II) and a monomer having an acid group or a base are included as at least a copolymer component. It is preferably a molecular dispersant, and may contain a monomer having no acid group and base as a copolymerization component, if necessary.

  That is, the polymer dispersant includes, for example, at least one monomer represented by the general formulas (I) and (II), and, if necessary, a monomer having an acid group or a base, an acid group, and You may be comprised from the copolymer of the monomer which does not have a base.

  The monomers represented by the general formulas (I) and (II) will be described.

In the general formulas (I) and (II), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₉ and R ₁₀ are each independently a hydrogen atom, 1 to 4 carbon atoms. The following alkyl groups or fluoroalkyl groups having 1 to 4 carbon atoms are represented.
R ₈ represents a hydrogen atom or a methyl group.
n, l, and m each independently represent an integer of 1 or more and 1000 or less.
x represents an integer of 1 to 3.

In general formula (I), preferably
R ₁ and R ₅ each independently represent a butyl group,
R ₂ , R ₃ , R ₄ , R ₆ , and R ₇ each independently represent a methyl group,
R ₈ represents a methyl group,
n and m each independently represent an integer of 1 to 5,
x represents an integer of 1 to 3.

On the other hand, in general formula (II), desirably
R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₉ and R ₁₀ each independently represent a methyl group;
R ₈ represents a methyl group,
n, l, and m each independently represent an integer of 1 to 3,
x represents an integer of 1 to 3.

  Hereinafter, although the specific example of the monomer shown by general formula (I) and (II) is shown, it is not restricted to this.

Next, the monomer having an acid group or a base will be described.
Examples of the monomer having an acid group include a monomer having a carboxyl group, a monomer having a carboxylate group, a monomer having a sulfonate group, a monomer having a sulfonate group, and a phosphate group. And monomers having a phosphate group. Examples of the respective monomers are the same as those exemplified as the anionic monomer in the polymer constituting the display particles, and thus the description thereof is omitted.
Examples of the monomer having a base include a monomer having an amino group and a monomer having a quaternary ammonium group. Examples of each monomer are the same as those exemplified as the cationic monomer in the polymer constituting the display particles, and thus the description thereof is omitted.

Next, a monomer having no acid group and base will be described.
Examples of the monomer having no acid group and base include nonionic monomers (nonionic monomers). For example, (meth) acrylonitrile, (meth) acrylic acid alkyl ester, (meth) Acrylamide, ethylene, propylene, butadiene, isoprene, isobutylene, N-dialkyl substituted (meth) acrylamide, styrene, vinylcarbazole, styrene, styrene derivatives, polyethylene glycol mono (meth) acrylate, vinyl chloride, vinylidene chloride, isoprene, butadiene, vinyl Examples include pyrrolidone, hydroxyethyl (meth) acrylate, and hydroxybutyl (meth) acrylate.

In the polymer dispersant, at least one component of the monomers represented by the general formulas (I) and (II) is 80% or more and 99.9% or less in terms of mass ratio to the whole polymer, preferably It is desirable that it is 90% or more and 99.9% or less.
Further, when the polymer dispersant includes a monomer component having an acid group or a base, the monomer component is preferably 0.5% or more and 20% or less in terms of a mass ratio to the whole polymer. Is preferably 0.5% or more and 10% or less.

  The weight average molecular weight of the polymer dispersant is preferably, for example, 10,000 or more and 1,000,000 or less, more preferably 50,000 or more and 300,000 or less.

  The content of the polymer dispersant is desirably 0.0001% by mass to 5% by mass with respect to the dispersion medium, and more desirably 0.01% by mass to 1% by mass.

Next, the dispersion medium will be described.
The dispersion medium is configured to include silicone oil. Of course, the dispersion medium may be a mixed solvent of silicone oil and a solvent other than silicone oil.

  Specific examples of the silicone oil include silicone oils in which a hydrocarbon group is bonded to a siloxane bond (for example, dimethyl silicone oil, diethyl silicone oil, methyl ethyl silicone oil, methyl phenyl silicone oil, diphenyl silicone oil, etc.). Of these, dimethyl silicone is particularly desirable.

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

Next, a method for producing display particles will be described.
Examples of the method for producing display particles according to the present embodiment include a polymer, a colorant, a first solvent (a poor solvent capable of forming a continuous phase), and the first solvent incompatible with the first solvent. A step of stirring and emulsifying a mixed solution containing a second solvent having a boiling point lower than that of the solvent and dissolving the polymer (a good solvent capable of forming a dispersed phase), and the second solvent from the emulsified mixed solution. And a step of producing colored particles (display particles) containing the polymer and the colorant by removal. This manufacturing method is a so-called submerged drying method.

  In this production method, a dispersion medium (silicone oil) used for a display medium as a first solvent may be used as it is as a display particle dispersion containing display particles and a dispersion medium. Thereby, in the manufacturing method of the display particle which concerns on this embodiment, the particle dispersion liquid for display which used the 1st solvent as the dispersion medium is obtained by passing through the said process, without passing through a washing | cleaning and drying process. Further, the particles may be washed (removal of ionic impurities) or the dispersion medium may be replaced.

  In addition, the manufacturing method of the display particles is not limited to the above-described manufacturing method, and for example, colored particles (display particles) by a known method (pulverization method, coacervation method, dispersion polymerization method, suspension polymerization method, or the like). The method of forming is adopted. In each method, a dispersion medium used for a display medium may be used as a solvent (a solvent finally remaining in the manufacturing method), and the display medium may be used as a display particle dispersion liquid including display particles and a dispersion medium after production. Thereby, in the manufacturing method of the display particle, the display particle dispersion liquid using the solvent to be used as the dispersion medium can be obtained through the manufacturing process without passing through the washing / drying process. Further, the particles may be washed (removal of ionic impurities) or the dispersion medium may be replaced.

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

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

The concentration of the display particles in the display particle dispersion according to the present embodiment is variously selected depending on display characteristics, response characteristics, or use thereof, but is selected in a range of 0.1% by mass to 30% by mass. Is desirable. When mixing multi-particles having different colors, the total amount of the particles is preferably within this range.
It is also possible to obtain a color display by mixing a plurality of types of particles having different colors and charging polarities.

  The display particle dispersion according to this embodiment may include two or more display particles as display particles. Examples of the two or more kinds of display particles include display particles having different charging polarities and combinations of display particles having different electric field strengths that start moving by an electric field.

  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 a particle group in a direction opposite to an electrode (substrate) surface, unlike the electrode (substrate), There is a method of moving in a direction along a plane (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.

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

  The display device 10 according to the present embodiment includes the display particle dispersion according to the present embodiment as a particle dispersion including the dispersion medium 50 of the display medium 12, the particle group 34, and a linear polymer (not shown). Is a form to apply.

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

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

  The cell indicates a region surrounded by the display substrate 20, the back substrate 22, and the gap member 24. A dispersion medium 50 is enclosed in this cell. The particle group 34 is composed of a plurality of particles. The particle group 34 is dispersed in the dispersion medium 50 and reflects between the display substrate 20 and the back substrate 22 according to the electric field strength formed in the cell. Move through the gap.

  In addition, the gap member 24 is provided so as to correspond to each pixel when the image is displayed on the display medium 12, and cells are formed so as to correspond to each pixel, so that the display medium 12 can display each pixel. It may be configured to do.

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

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

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

  Examples of the material 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.

  As materials for the front electrode 40 and the back electrode 46, oxides such as indium, tin, cadmium and antimony, composite oxides such as ITO, metals such as gold, silver, copper and nickel, organic materials such as polypyrrole and polythiophene, etc. Is mentioned. The surface electrode 40 and the back electrode 46 may be any of these single-layer films, mixed films, and composite films. The thicknesses of the front electrode 40 and the back electrode 46 are preferably, for example, 100 mm or more and 2000 mm or less. The back electrode 46 and the surface electrode 40 may be formed in a matrix shape or a stripe shape, for example.

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

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

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

  In order to perform active matrix driving, the support substrate 38 and the support substrate 44 may include a TFT (Thin Film Transistor) for each pixel. The TFT is preferably provided on the back substrate 22 instead of the display substrate.

  Next, the surface layer will be described. The surface layer 42 and the surface layer 48 are formed on the surface electrode 40 and the back electrode 46, respectively. Examples of the material constituting the surface layer 42 and the surface layer 48 include polycarbonate, polyester, polystyrene, polyimide, epoxy, polyisocyanate, polyamide, polyvinyl alcohol, polybutadiene, polymethyl methacrylate, copolymerized nylon, ultraviolet curable acrylic resin, fluorine Examples thereof include resins.

  The surface layer 42 and the surface layer 48 may be configured to include the above-described resin and a charge transport material, or may be configured to include a self-supporting resin having a charge transport property.

  Next, the gap member will be described. The gap member 24 for holding a gap between the display substrate 20 and the back substrate 22 is made of, for example, a thermoplastic resin, a thermosetting resin, an electron beam curable resin, a photocurable resin, rubber, metal, or the like. The

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

  The gap member 24 may be colored or colorless, but is preferably colorless and transparent. In that case, the gap member 24 is made of, for example, a transparent resin such as polystyrene, polyester, or acrylic.

The particulate gap member 24 is also preferably transparent, and glass particles are used in addition to transparent resin particles such as polystyrene, polyester, or acrylic.
Note that “transparent” means having a transmittance of 60% or more with respect to visible light.

  Next, the reflective particle group will be described. The reflective particle group 36 is composed of reflective particles having optical reflection characteristics different from that of the particle group 34, and functions as a reflective member that displays a color different from that of the particle group 34. And it also has a function as a gap member to move without hindering movement between the display substrate 20 and the back substrate 22. That is, each particle of the particle group 34 is moved from the back substrate 22 side to the display substrate 20 side or from the display substrate 20 side to the back substrate 22 side through the gap between the reflective particle groups 36. As the color of the reflective particle group 36, for example, white or black is preferably selected so as to be the background color, but other colors may be used. The reflective particle group 36 may be an uncharged particle group (that is, a particle group that does not move in response to an electric field) or a charged particle group (a particle group that moves in response to an electric field). May be. In the present embodiment, the case where the reflective particle group 36 is an uncharged particle group and is white is described, but the present invention is not limited to this.

  The particles of the reflective particle group 36 include, for example, a white pigment (for example, titanium oxide, silicon oxide, zinc oxide), a resin (for example, polystyrene resin, polyethylene resin, polypropylene resin, polycarbonate resin, polymethyl methacrylate resin (PMMA), acrylic resin). Resin, phenol resin, formaldehyde condensate, etc.). Moreover, when applying particles other than white as the particles of the reflective particle group 36, for example, the above-described resin particles containing a pigment or dye of a desired color may be used. If the pigment or dye is, for example, RGB or YMC color, a general pigment or dye used for printing ink or color toner can be used.

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

  The size of the cell in the display medium 12 is closely related to the resolution of the display medium 12, and the smaller the cell, the higher the resolution of the display medium 12 can be produced. The length of the display substrate 20 in the plate surface direction is about 10 μm or more and 1 mm or less.

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

  The display medium 12 configured as described above includes, for example, a bulletin board, a circulation version, an electronic blackboard, an advertisement, a signboard, a flashing sign, an electronic paper, an electronic newspaper, an electronic book, and a copier / printer in which images are stored and rewritten. Used for document sheets etc.

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

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

  The voltage application unit 16 is connected to the control unit 18 so as to 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. Further, it may be configured as a microcomputer including a ROM (Read Only Memory).

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

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

Here, a case where the particle group 34 enclosed in the display medium 12 is positively charged will be described. In the following description, it is assumed that the dispersion medium 50 is transparent and the reflective particle group 36 is white. That is, in the present embodiment, a case will be described in which the display medium 12 displays the color exhibited by the movement of the particle group 34 and displays white by the reflective particle group 36 as the background color.
In addition, the following operation | movement demonstrates the operation | movement from the state in which the particle group 34 adhered to the back substrate 22 side on description.

  First, an operation signal indicating that the voltage is applied so that the front electrode 40 becomes a negative electrode and the back electrode 46 becomes a positive electrode for a specific time is output to the voltage application unit 16. When the voltage applied between the electrodes is increased from the state shown in FIG. 2A and a voltage equal to or higher than the threshold voltage at which the surface electrode 40 is a negative electrode and the concentration fluctuation ends is applied, the cohesive force of the particle group 34 is increased. In a reduced state, the particles constituting the particle group 34 charged to the positive electrode move to the display substrate 20 side and reach the display substrate 20 (see FIG. 2B).

  When the application between the electrodes is finished, the particle group 34 is constrained on the surface substrate 20 side, and the color exhibited by the particle group 34 is viewed from the display substrate 20 side with the white color as the color of the reflective particle group 36 being the background color. The color of the display medium 12 is visually recognized.

  Next, an operation signal indicating that a voltage is applied between 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 for a specific time is applied to the voltage application unit 16. Output to. When the voltage applied between the electrodes is increased and a voltage equal to or higher than the threshold voltage at which the surface electrode 40 is the positive electrode and the concentration fluctuation ends is applied, the positive electrode is charged in a state where the cohesive force of the particle group 34 is reduced. The particles constituting the particle group 34 move to the back substrate 22 side and reach the back substrate 22 (see FIG. 2A).

  When the application between the electrodes is finished, the particle group 34 is constrained on the back substrate 22 side, while white as the color of the reflective particle group 36 is the color of the display medium 12 visually recognized from the display substrate 20 side. As visible. In addition, the particle group 34 is concealed by the reflective particle group 36 and is difficult to be visually recognized.

  Here, the voltage application time between the electrodes may be stored in advance in a memory such as a ROM (not shown) in the control unit 18 as information indicating the voltage application time in voltage application during operation. Then, information indicating the voltage application time may be read when the process is executed.

  Thus, in the display device 10 according to the present embodiment, the display is performed by the particle group 34 reaching the display substrate 20 or the back substrate 22 and adhering / aggregating.

  In the display medium 12 and the display device 10 according to the present embodiment, the surface electrode 40 is provided on the display substrate 20, the back electrode 46 is provided on the back substrate 22, and a voltage is applied between the electrodes (that is, between the substrates). Although the embodiment has been described in which the particle group 34 is moved between the substrates for display, the present invention is not limited thereto. For example, while the surface electrode 40 is provided on the display substrate 20, the gap member is provided with electrodes, and the voltage between the electrodes is The particle group 34 may be moved and displayed between the display substrate 20 and the gap member.

  Further, in the display medium 12 and the display device 10 according to the above-described embodiment, a mode in which one type (one color) of particle groups is applied as the particle group 34 is described, but the present invention is not limited to this, and two types (two colors) are used. The form which applied the above particle group may be sufficient.

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

[Example A]
(Example A1)
-Production of cyan particles-
As cyan particles A (display particles using a polymer having a base: negatively charged particles), particles (XX426W) manufactured by Sekisui Plastics Co., Ltd. were prepared. This was dispersed in dimethyl silicone oil (KF-96-2CS manufactured by Shin-Etsu Silicone) to obtain a cyan particle dispersion.
The charged polarity of the cyan particles in this dispersion was positively charged as a result of enclosing the dispersion between two electrode substrates and applying a DC voltage to evaluate the migration direction.

-Production of polymer dispersant A1-
MCS-M11 (manufactured by Amax Co., Ltd .: monomer of general formula (I)) 4.5 parts by mass Methacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd .: monomer having an acid group) 0.5 Parts by mass, isopropyl alcohol (solvent) 10 parts by mass, V-65 (azobisdimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd .: polymerization initiator) 0.02 parts by mass The reaction was later performed at 55 ° C. for 24 hours. After completion of the polymerization, the polymer was dried under reduced pressure to remove and purify the solvent and unreacted monomers, thereby obtaining a polymer dispersant A1. The yield was 98%. As a result of measuring the molecular weight by GPC, the weight average molecular weight was 120,000 in terms of polystyrene standard.

-Preparation of particle dispersion for display-
0.5 parts by mass of the polymer dispersant A1 was added to 100 parts by mass of the obtained cyan particle dispersion A (solid content concentration 1.5%) to obtain a display particle dispersion.

(Examples A-2 to A-4, Examples A2-1 to A2-4, Comparative Examples A-1 to A-4)
According to Table 1, a polymer dispersant was prepared in the same manner as in Example A1, except that the type and concentration of the polymer dispersant were changed. The polymer dispersant used is shown below.

-Production of polymer dispersant A2-
MTT-1011 (manufactured by Amax Co., Ltd .: monomer of general formula (II)) 4.5 parts by weight Methacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd .: monomer having an acid group) 0.5 Parts by mass, isopropyl alcohol (solvent :) 10 parts by mass, V-65 (azobisdimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd .: polymerization initiator) 0.02 parts by mass Mixing the above composition, sufficient nitrogen After substitution, the reaction was carried out at 55 ° C. for 24 hours. After completion of the polymerization, the polymer was dried under reduced pressure to remove and purify the solvent and unreacted monomer to obtain a polymer dispersant A2. The yield was 98%. As a result of measuring the molecular weight by GPC, the weight average molecular weight was 120,000 in terms of polystyrene standard.

-Production of Polymer Dispersant A for Comparative Example-
-Silaplane FM0711 (manufactured by Chisso) 4.5 parts by mass-Methacrylic acid (manufactured by Wako Pure Chemical Industries, Ltd.) 0.5 parts by mass-10 parts by mass of isopropyl alcohol (solvent)-V-65 (azobisdimethylvaleronitrile) ) (Wako Pure Chemical Industries, Ltd .: polymerization initiator) 0.02 parts by mass The above composition was mixed and reacted at 55 ° C. for 24 hours after sufficient nitrogen substitution. After completion of the polymerization, the polymer was dried under reduced pressure to remove and purify the solvent and unreacted monomers, and a comparative polymer dispersant A was obtained. The yield was 98%. As a result of measuring the molecular weight by GPC, the weight average molecular weight was 120,000 in terms of polystyrene standard.

[Example B]
(Example B1)
-Production of magenta particles B (display particles having acid groups: negatively charged particles)-
First, 2-hydroxyethyl acrylate as another monomer: 85 parts by mass, Silaplane “FM-0721” as a silicone chain monomer: 10 parts by mass, and methacrylic acid as a monomer having a charging group: 5 A mass part is mixed with 100 parts by mass of isopropyl alcohol, and AIBN (2,2′-azobis (isobutyronitrile)): 0.2 part by mass as a polymerization initiator is dissolved, and 70 ° C. under nitrogen for 6 hours. Polymerization was performed. The product was purified using cyclohexane as a reprecipitation solvent and dried to obtain a polymer.
When the obtained polymer was dissolved in distilled water, it was dissolved even at 30% by mass and no precipitation was observed, indicating that it was a water-soluble polymer.

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

-Production of polymer dispersant B1-
MCS-M11 (manufactured by Amax Co., Ltd .: monomer of general formula (I)) 4.5 parts by mass Diethylaminoethyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd .: monomer having a base) 0.5 Part by mass: Isopropyl alcohol (solvent) 10 parts by mass V-65 (azobisdimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd .: polymerization initiator) 0.02 parts by mass Mixing the above composition with sufficient nitrogen After substitution, the reaction was carried out at 55 ° C. for 24 hours. After completion of the polymerization, the polymer was dried under reduced pressure to remove and purify the solvent and unreacted monomers to obtain a polymer dispersant B1. The yield was 98%. As a result of measuring the molecular weight by GPC, the weight average molecular weight was 120,000 in terms of polystyrene standard.

-Preparation of particle dispersion for display-
0.5 parts by mass of the polymer dispersant B1 was added to 100 parts by mass of the obtained magenta particle dispersion B (solid content concentration 1.5%) to obtain a display particle dispersion.

(Examples B-2 to B-4, Examples B2-1 to B2-4, Comparative Examples B-1 to B-4)
According to Table 1, a polymer dispersant was produced in the same manner as in Example B1, except that the type and concentration of the polymer dispersant were changed. The polymer dispersant used is shown below.

-Production of polymer dispersant B2-
RTT-1011 (manufactured by Amax Co., Ltd .: monomer of general formula (II)) 4.5 parts by mass Diethylaminoethyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd .: monomer having a base) 0.5 Parts by mass, isopropyl alcohol (solvent) 10 parts by mass, V-65 (azobisdimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd .: polymerization initiator) 0.02 parts by mass The reaction was later performed at 55 ° C. for 24 hours. After completion of the polymerization, the polymer was dried under reduced pressure to remove and purify the solvent and unreacted monomer to obtain a polymer dispersant B2. The yield was 98%. As a result of measuring the molecular weight by GPC, the weight average molecular weight was 120,000 in terms of polystyrene standard.

-Production of Polymer Dispersant B for Comparative Example-
-Silaplane FM0711 (manufactured by Chisso) 4.5 parts by mass-Diethylaminoethyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.) 0.5 parts by mass-10 parts by mass of isopropyl alcohol (solvent)-V-65 (azobisdimethylvalero) Nitrile) (manufactured by Wako Pure Chemical Industries, Ltd .: polymerization initiator) 0.02 parts by mass The above composition was mixed and reacted at 55 ° C. for 24 hours after sufficient nitrogen substitution. After completion of the polymerization, the polymer was dried under reduced pressure to remove and purify the solvent and unreacted monomers, and a comparative polymer dispersant B was obtained. The yield was 98%. As a result of measuring the molecular weight by GPC, the weight average molecular weight was 120,000 in terms of polystyrene standard.

[Evaluation]
-Production of display media-
A display medium having the same configuration as that of the first embodiment was manufactured as follows (see FIG. 1). An ITO film having a thickness of 50 nm was formed as an electrode on a supporting substrate made of glass having a thickness of 0.7 mm by a sputtering method. After applying a layer to the back substrate composed of this ITO / glass substrate using CYTOP (manufactured by Asahi Glass Co., Ltd., CTL809M), a gap member having a height of 50 μm and a width of 20 μm is obtained by performing exposure and wet etching. Formed.

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

  In this way, a display medium was produced. Using the produced display medium, a voltage of 20 V is applied to both electrodes so that the electrode of the display substrate is positive and the electrode of the rear substrate is negative. By repeating this, particles are moved to the display substrate and the rear substrate, The color of the display particles was displayed.

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

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

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

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

-Repetitive stability-
The repeated stability of cyan and magenta colors (change in threshold electric field strength of display particles) in the obtained display medium was evaluated as follows. The results are shown in Table 1.

-Repetitive stability-
The repeated stability was evaluated by the fluctuation of the threshold electric field strength. Specifically, as shown in the drive waveform shown in FIG. 3, first, the threshold electric field strength was calculated from a charge-electric field (QE) hysteresis curve when a voltage was applied with a triangular wave. The electric field strength at which the differential value of the charge Q in the Q-E hysteresis curve takes the maximum value was defined as the threshold electric field strength. Further, after the threshold electric field strength was measured, it was repeatedly driven with a rectangular wave for 100 cycles, and the threshold electric field strength was again measured with a triangular wave. And this operation was performed continuously and the fluctuation | variation of the threshold electric field intensity at the time of driving a total of 10,000 cycles with a rectangular wave was investigated.

  From the above results, it can be seen that Examples A and B have better repeatability than the comparative example.

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

Claims (6)

Display particles that move in response to an electric field;
A polymer dispersant containing at least one monomer represented by the following general formulas (I) and (II) as a copolymerization component;
A dispersion medium comprising silicone oil;
A particle dispersion for display.
(In the general formulas (I) and (II), R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₉ and R ₁₀ are each independently a hydrogen atom or 1 or more carbon atoms. Represents an alkyl group having 4 or less, or a fluoroalkyl group having 1 to 4 carbon atoms, R ₈ represents a hydrogen atom or a methyl group, and n, l, and m are each independently an integer of 1 to 1000. X represents an integer of 1 to 3. The display particles are display particles having a base;
The polymer dispersant is a polymer dispersant containing at least one monomer represented by the general formulas (I) and (II) and a monomer having an acid group as at least a copolymerization component. The display particle dispersion according to claim 1. The display particles are display particles having an acid group,
The polymer dispersant is a polymer dispersant containing at least one monomer represented by the general formulas (I) and (II) and a monomer having a base as at least a copolymerization component. Item 4. The display particle dispersion according to Item 1. A pair of substrates, at least one of which is translucent,
The particle dispersion for display according to any one of claims 1 to 3, encapsulated between the pair of substrates,
A display medium comprising: A pair of electrodes, at least one of which is translucent,
A region having the display particle dispersion according to any one of claims 1 to 3 provided between the pair of electrodes;
A display medium comprising: A display medium according to claim 4 or 5, and
Voltage application means for applying a voltage between the pair of substrates or the pair of electrodes of the display medium;
A display device comprising: