JP6098324B2 - Colored particles and production method thereof, colored particle dispersion, display medium, and display device - Google Patents

Description

  The present invention relates to colored particles and a method for producing the same, a colored 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 system, an electrophoretic material in which colored particles (electrophoretic particles) charged in a liquid are dispersed is used, and the electrophoretic particles are placed in a cell by applying an electric field (two electrode substrates are stacked and the electrophoretic material is placed between them). Display can be performed by alternately moving to the viewing surface and back surface of the encapsulated configuration.

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

However, at present, a material system that is stably dispersed in silicone oil and has stable charging characteristics is not well known. As a conventional technique, for example, a technique using a silicone-based charge control polymer dispersant is disclosed in Patent Documents 1 and 2, and as an electrophoretic particle using a coacervation method, Patent Document 3 is known, A configuration containing a charge adjusting agent as electrophoretic particles dispersed in silicone oil is disclosed.
Further, in Patent Document 4, for the purpose of imparting stable dispersibility and charging characteristics, a display in which a reactive silicone polymer or a reactive long-chain alkyl polymer is bonded to or coated on the surface of a charged colored particle. Particles are disclosed.

Japanese Patent No. 3936588 JP 2002-212423 A JP 2004-279732 A JP 2009-186808 A

By the way, as represented by colored particles used in display technology using electrophoresis, it is important that the colored particles having charging properties have stable dispersibility and charging characteristics.
For example, in a technique using a silicone-based charge control polymer dispersant, the dispersant functions as a uniform dispersion of colored particles and at the same time serves as a counter ion of the colored particles, so that both dispersion and charge stability can be achieved. was difficult. In order to realize a system in which multiple colored particles with different charging polarities are mixed in the same system for the purpose of multicolor display (some colored particles are positively charged and colored particles of a different color are negatively charged) Dispersants with different polar groups (acids and bases) are mixed with different colored particles, so that the dispersants may cause acid-salt reaction, causing the colored particles to aggregate or charge characteristics to deteriorate. is there. On the other hand, in the technique using the coacervation method, it is essential that the charge control agent is contained in the colored particles. However, the charge control agent is eluted in the silicone oil as a dispersion medium, or is distributed in the colored particles. There is a risk that bias may occur and charging characteristics may become unstable.

  Under such circumstances, the present inventors further examined the display particles described in Patent Document 4, and had a problem that dispersion stability and chargeability were still insufficient. all right. In particular, it has been found that in colored particles bonded or coated with a reactive polymer having a glycidyl group in the side chain, the proportion of colored particles having a polarity opposite to that of the desired charge increases.

The present invention has been made in view of the above, and an object of the present invention is to provide colored particles having stable dispersibility and charging characteristics.
Another object of the present invention is to provide a colored particle dispersion, a display medium, and a display device using the colored particles.

The above problem is solved by the following means. That is,
<1>
Core particles containing a first polymer having a chargeable group and a colorant , wherein the colorant is dispersed using the first polymer as a base material ;
A coating layer covering the surface of the core particle, comprising a monomer unit A having a silicone chain as a side chain and an ethylenically unsaturated group, a vinyloxy group, a hydroxymethyl group, an alkoxymethyl group, an oxazolyl group, and an alkoxysilyl group A monomer unit B having at least one self-crosslinkable group selected from the group consisting of a side chain, and the self-crosslinkable group of the monomer unit B is a functional group that does not generate a hydroxyl group by crosslinking. A coating layer containing a crosslinked polymer;
Colored particles having

< 2 >
The colored particles according to <1>, wherein the self-crosslinking group of the monomer unit B of the second polymer is a vinyloxy group.

< 3 >
The second polymer further has a monomer unit C having a functional group crosslinkable with the self-crosslinkable group of the monomer unit B, and the self-crosslinkable group of the monomer unit B and the functional group of the monomer unit C The colored particles according to <1> or <2> , wherein a hydroxyl group is not generated by crosslinking.

< 4 >
< 3 > The colored particles according to < 3 >, wherein the self-crosslinkable group of the monomer unit B is a vinyloxy group or an oxazolyl group, and the functional group of the monomer unit C of the second polymer is a carboxyl group.

< 5 >
The colored particles according to any one of <1> to < 4 >, wherein the first polymer further includes a monomer unit α having a functional group capable of crosslinking with a self-crosslinkable group of the monomer unit B of the second polymer in a side chain. .

< 6 >
<1> to < 5 > a particle group containing the colored particles according to any one of the above,
A dispersion medium for dispersing the particles,
A colored particle dispersion having:

< 7 >
The colored particle dispersion according to <6>, wherein the dispersion medium is silicone oil or a paraffinic hydrocarbon solvent.

< 8 >
The colored particle dispersion liquid according to < 6 > or < 7 >, wherein the particle group is composed of a plurality of types of colored particles having different charging polarities.

< 9 >
A pair of substrates, at least one of which is translucent,
The colored particle dispersion liquid according to any one of < 6 > to < 8 >, encapsulated between a pair of substrates,
A display medium comprising:

< 10 >
< 9 > a display medium according to
Voltage applying means for applying a voltage between a pair of substrates of the display medium;
A display device comprising:

< 11 >
A pair of electrodes, at least one of which is translucent,
A region having the colored particle dispersion according to any one of < 6 > to < 8 > provided between a pair of electrodes;
A display medium comprising:

< 12 >
< 11 > a display medium according to
Voltage applying means for applying a voltage between a pair of electrodes of the display medium;
A display device comprising:

< 13 >
A first polymer having a chargeable group, a colorant, a first solvent, and a first polymer having a chargeability group that is incompatible with the first solvent and has a lower boiling point than the first solvent. A step of stirring and emulsifying the mixed solution containing the second solvent,
Removing the second solvent from the emulsified mixed solution to produce core particles containing the first polymer having the chargeable group and the colorant;
At least one selected from the group consisting of the core particles, a monomer unit A having a silicone chain as a side chain, and an ethylenically unsaturated group, vinyloxy group, hydroxymethyl group, alkoxymethyl group, oxazolyl group, and alkoxysilyl group And a second polymer having a monomer unit B having a self-crosslinkable group in the side chain, and the self-crosslinkable group of the monomer unit B being a functional group that does not generate a hydroxyl group by crosslinking, Coating the surface of the core particle with a crosslinked body of the second polymer by crosslinking two polymers;
The manufacturing method of the colored particle which has this.

< 14 >
The method for producing colored particles according to < 13 >, wherein the first solvent is a silicone oil or a paraffinic hydrocarbon solvent.

  According to the present invention, colored particles having stable dispersibility and charging characteristics can be provided. In addition, according to the present invention, a colored particle dispersion, a display medium, and a display device using the colored particles can be provided.

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

Hereinafter, the present invention will be described in detail.
In the present specification, “(meth) acryl” is a notation of both “acryl” and “methacryl”. “(Meth) acrylo” is a notation for both “acrylo” and “methacrylo”. “(Meth) acrylate” is a notation for both “acrylate” and “methacrylate”.

[Colored particles]
The colored particles of the present invention have core particles and a coating layer that covers the surface of the core particles. The core particles contain a first polymer having a chargeable group and a colorant. The coating layer has a monomer unit A having a silicone chain as a side chain and a monomer unit B having a self-crosslinkable group as a side chain, and the self-crosslinkable group of the monomer unit B does not generate a hydroxyl group by crosslinking. It contains a crosslinked product of the second polymer that is a functional group.
The colored particles of the present invention have charging characteristics when dispersed in a dispersion medium. For example, when the colored particles of the present invention are applied to display particles (electrophoretic particles), the colored particles of the present invention move in the dispersion medium according to the electric field.

The colored particles of the present invention are colored particles having stable dispersibility and charging characteristics by adopting the above configuration. Here, the charging characteristics indicate the charging polarity and the charge amount of the colored particles. In the colored particles of the present invention, fluctuations in the charging polarity and the charge amount are suppressed, and the charging characteristics are stabilized. Specifically, in the colored particles of the present invention, desired charging is ensured and the generation of colored particles of reverse polarity is suppressed, and the charging characteristics are stabilized.
The reason for this is not clear, but by introducing the monomer unit B into the second polymer that coats the core particles, there is no hydroxyl group in the vicinity of the crosslinking point of the crosslinked body of the second polymer (that is, the monomer of the second polymer). This is because it is considered that a hydroxyl group is not generated in the vicinity of the crosslinking point in association with crosslinking of the self-crosslinking group of the unit B (crosslinking reaction of the self-crosslinking group).

  Hereinafter, the colored particles of the present invention will be described in detail.

(Core particles)
The core particle includes a first polymer having a chargeable group, a colorant, and, if necessary, other compounding materials.

-First polymer-
The first polymer having a chargeable group is a polymer having, for example, a cationic group or an anionic group as the chargeable group. Examples of the cationic group as the charging group include an amino group and a quaternary ammonium group (including salts of these groups), and a positively charged polarity is imparted to the colored particles by the cationic group. 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). The anionic group imparts negatively charged polarity to the colored particles.

  Specifically, as a polymer having a charging group, a polymer comprising a monomer unit having a charging group, a polymer having a monomer unit having a charging group and another monomer unit (a monomer unit having no charging group) Etc.

  As monomers for constituting a monomer unit having a charging group, a monomer having a cationic group (hereinafter referred to as a cationic monomer), a monomer having an anionic group (hereinafter referred to as an anionic monomer). Mer).

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 (meth) acrylate having an aliphatic amino group , Aromatic substituted ethylene monomers having a nitrogen-containing group such as dimethylaminostyrene, diethylaminostyrene, dimethylaminomethylstyrene, dioctylaminostyrene, vinyl-N-ethyl-N-phenylaminoethyl ether, vinyl-N -Butyl-N-phenylamino Nitrogen-containing vinyl ether monomers such as ethyl ether, triethanolamine divinyl ether, vinyl diphenylaminoethyl ether, N-vinylhydroxyethylbenzamide, m-aminophenyl vinyl ether, pyrroles such as vinylamine and N-vinylpyrrole, N- Pyrrolines such as vinyl-2-pyrroline and N-vinyl-3-pyrroline, N-vinylpyrrolidine, vinylpyrrolidine amino ether, pyrrolidines such as N-vinyl-2-pyrrolidone, N-vinyl-2-methylimidazole and the like Imidazoles, imidazolines such as N-vinylimidazoline, indoles such as N-vinylindole, indolines such as N-vinylindoline, carbazoles such as N-vinylcarbazole and 3,6-dibromo-N-vinylcarbazole, -Pyridines such as vinylpyridine, 4-vinylpyridine, 2-methyl-5-vinylpyrazine, piperidines such as (meth) acrylic piperidine, N-vinylpiperidone, N-vinylpiperazine, 2-vinylquinoline, 4-vinylquinoline, etc. Quinolines, pyrazoles such as N-vinylpyrazole and N-vinylpyrazoline, oxazoles such as 2-vinyloxazole, oxazines such as 4-vinyloxazine and morpholinoethyl (meth) acrylate, and the like.
Moreover, as a particularly preferable cationic monomer from versatility, (meth) acrylates having an aliphatic amino group such as N, N-dimethylaminoethyl (meth) acrylate and N, N-diethylaminoethyl (meth) acrylate In particular, it is preferable to use a quaternary ammonium salt structure before or after polymerization. Quaternary ammonium chloride can be obtained by reacting the above compound with alkyl halides or tosylate esters.

On the other hand, as an anionic monomer, the following are mentioned, for example.
Specifically, among the anionic monomers, 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. Can be mentioned. Other examples include 2-hydroxyethyl (meth) acrylic acid monoester and its salts.
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 Examples include 2-acryloyloxyethyl phosphate, dibutyl-2-methacryloyloxyethyl phosphate, dibutyl-2-acryloyloxyethyl phosphate, dioctyl-2- (meth) acryloyloxyethyl phosphate, and the like.
Preferred anionic monomers are those having (meth) acrylic acid or sulfonic acid, and more preferably those having a structure in which an ammonium salt is formed before or after polymerization. Ammonium salts can be prepared by reacting with tertiary amines or quaternary ammonium hydroxides.

  Other monomers for constituting other monomer units include nonionic monomers (nonionic monomers), (meth) acrylonitrile, (meth) acrylic acid alkyl esters, (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.

The first polymer has, in addition to the monomer unit having a chargeable group and other monomer units, a functional group capable of crosslinking with the self-crosslinkable group of the monomer unit B of the second polymer constituting the coating layer described later. It is preferable to further have a monomer unit α. By having this monomer unit α, the second polymer (the coating layer containing it) is fixed, and the dispersibility of the colored particles is easily stabilized.
The monomer constituting the monomer unit α is selected according to the self-crosslinkable group of the monomer unit B of the second polymer. Specifically, the monomer unit C of the second polymer is selected as the monomer unit α. The monomer illustrated by the monomer for comprising is mentioned. However, the monomer unit α may also serve as a monomer unit having a charging group.

Here, in the first polymer, the ratio of the monomer unit having a chargeable group to another monomer unit (copolymerization ratio of the monomer having a chargeable group to another monomer) is a desired colored particle. The amount is appropriately changed according to the charge amount. Usually, this ratio (copolymerization ratio between the monomer having a chargeable group and another monomer) is in the range of 1:99 to 100: 0 in molar ratio (preferably 10:90 to 100: (Range up to 0).
When the first polymer has a monomer unit α different from the monomer unit having a charging group, the ratio of the monomer having the charging group to the monomer unit α (the monomer polymerization ratio) is the molar ratio. In the range of 1:99 to 99: 1 (preferably in the range of 10:90 to 99: 1).

The weight average molecular weight of the first polymer having a chargeable group is preferably 1,000 or more and 1,000,000 or less, and more preferably 10,000 or more and 200,000 or less.
Here, the weight average molecular weight is measured by gel permeation chromatography (GPC) using polystyrene as a standard substance. The method for measuring the weight average molecular weight of other polymers is the same.

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

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

-Other ingredients-
Other compounding materials will be described.
Examples of other compounding materials include a charge control agent, a magnetic material, and a crosslinking agent.
As the charge control agent, known materials used for toner materials for electrophotography can be used, such as cetylpyridyl chloride, BONTRON P-51, BONTRON P-53, BONTRON E-84, BONTRON E-81 (orientated chemistry). Quaternary ammonium salts such as those manufactured by Kogyo Co., Ltd., salicylic acid metal complexes, phenol condensates, tetraphenyl compounds, metal oxide particles, metal oxide particles surface-treated with various coupling agents, and the like.

Examples of the magnetic material include inorganic magnetic materials and organic magnetic materials that are color-coated as necessary. Further, a transparent magnetic material, in particular, a transparent organic magnetic material does not hinder the color development of the color pigment, and the specific gravity is smaller than that of the inorganic magnetic material, 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 appropriately selected, for example, coloring the magnetic powder opaque with a pigment or the like, but it is preferable to use a light interference thin film, for example. This optical interference thin film is a thin film having a thickness equivalent to the wavelength of light made of an achromatic material such as SiO ₂ or TiO ₂ and selectively reflects the wavelength of light by optical interference in the thin film. It is.
In addition, you may include in the inside of a colored particle, and you may adhere to the surface.

  As the crosslinking agent, a compound having a plurality of ethylenically unsaturated groups in the molecule; a compound having a plurality of isocyanate groups in the molecule; a group selected from an imino group, a methylol group, and an alkoxymethyl group in the molecule One type of melamine compound or guanamine compound; In order to promote the crosslinking reaction of these crosslinking agents, an acid, a base, a salt, a polymerization initiator, or the like may be added.

(Coating layer)
The coating layer that covers the surface of the core particles will be described.
The coating layer contains a crosslinked product of the second polymer. And the 2nd polymer has the monomer unit A which has a silicone chain in a side chain, and the monomer unit B which has a self-crosslinkable group in a side chain. The 2nd polymer may have other monomer units (monomer unit C, monomer unit D, etc.) other than monomer units A and B as needed.

Specific examples of the second polymer include (meth) acrylic resins, styryl resins, polyurethane resins, polyvinyl alcohol resins, polyvinyl formal resins, polyamide resins, polyester resins, and epoxy resins. In particular, (meth) acrylic resins and styryl resins are preferable, and (meth) acrylic resins are more preferable.
That is, the second polymer has monomer units A and B as monomer units constituting these resins, and other monomer units (monomer unit C, monomer unit D, etc.) as necessary.

  Note that the silicone chain or each functional group has a side chain means that the polymer chain of the second polymer (polymerized chain by ethylenic double bond, urethane bond or amide bond, etc.) is the main chain, and branched from this main chain. It shows having a silicone chain or each functional group at the site.

-Monomer unit A-
The monomer unit A is a monomer unit having a silicone chain in the side chain. Specific examples of the monomer unit A include monomer units having a structure represented by the following general formula (S) in the side chain as a silicone chain.

In general formula (S), R ¹¹ and R ¹² each independently represents an alkyl group or an aryl group. The alkyl group represented by R ¹¹ and R ¹² is preferably an alkyl group having 1 to 4 carbon atoms, and may have a substituent. Specific examples of the alkyl group include a methyl group and an ethyl group. The aryl group represented by R ¹¹ and R ¹² is preferably an aryl group having 6 to 20 carbon atoms and may have a substituent. Specific examples of the aryl group include a phenyl group and a naphthyl group. R ¹¹ and R ¹² preferably each independently represent a methyl group or a phenyl group, and more preferably a methyl group.
p represents an integer of 2 to 500, preferably 5 to 350, and more preferably 8 to 250.

Monomer units having a structure represented by the general formula (S) in the side chain are described in J.P. Appl. Polym. Sci. 2000, 78, 1955, JP-A-56-28219, etc., a reactive group (with respect to a polymer having a reactive group such as an epoxy group, a hydroxyl group, a carboxyl group, an acid anhydride group) Synthesis by a method of introducing a polysiloxane having one end of an amino group, mercapto group, carboxyl group, hydroxyl group, etc. with respect to an epoxy group or an acid anhydride group by a polymer reaction or a method of polymerizing a polysiloxane-containing macromer can do.
Here, the polysiloxane-containing macromer is specifically a dimethyl silicone monomer having a (meth) acrylate group at one end (silicone compound represented by the following structural formula (1): manufactured by JNC: Silaplane: FM-0711 , FM-0721, FM-0725, etc., manufactured by Shin-Etsu Chemical Co., Ltd .: X-22-174DX, X-22-2426, X-22-2475, etc.).

In the structural formula (1), R ¹ represents a hydrogen atom or a methyl group. R ² 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.

-Monomer unit B-
The monomer unit B is a monomer unit having a self-crosslinkable group in the side chain. The self-crosslinkable group is a functional group that does not generate a hydroxyl group by crosslinking of the self-crosslinkable group (crosslinking reaction of the self-crosslinkable group). Here, the self-crosslinkable group refers to a group capable of self-crosslinking between functional groups under a certain condition without adding a crosslinking agent.

  Examples of self-crosslinkable groups include ethylenically unsaturated groups (vinyl group, allyl group, styryl group, (meth) acryloyl group, (meth) acrylamide group, etc.), vinyloxy group, hydroxymethyl group, alkoxymethyl group, oxazolyl group, And at least one group selected from the group consisting of alkoxysilyl groups. Among these, a vinyloxy group is preferable as the self-crosslinkable group from the viewpoint of stable dispersibility and charging characteristics.

  As monomers for constituting the monomer unit B, ethylene (di) methacrylate, divinylbenzene, 2-hydroxyethyl (meth) acrylate and 2-isocyanatoethyl (meth) acrylate are added reaction products. , Allyl (meth) acrylate, 2-vinyloxyethyl (meth) acrylate, 2- (2-vinyloxyethoxy) ethyl (meth) acrylate, N-methylolacrylamide, N-butoxymethylacrylamide, 2-vinyl-2- Examples thereof include oxazoline and 3- (trimethoxysilyl) propyl (meth) acrylate.

-Monomer unit C-
The monomer unit C is a monomer unit having a functional group capable of crosslinking with the self-crosslinkable group of the monomer unit B in the side chain.
And a hydroxyl group is not produced by the bridge | crosslinking of the self-crosslinkable group of the monomer unit B, and the functional group of the monomer unit C. That is, the self-crosslinkable group of the monomer unit B and the functional group of the monomer unit C are groups that do not generate a hydroxyl group due to a mutual crosslinking reaction.
By introducing the monomer unit C into the second polymer, the crosslinking density of the second polymer is increased, and the dispersibility of the colored particles is easily increased. In addition, with the crosslinking (crosslinking reaction) between the self-crosslinkable group of the monomer unit B and the functional group of the monomer unit C, a hydroxyl group is not generated near the crosslinking point (that is, near the crosslinking point of the crosslinked body of the second polymer). Since it does not have a hydroxyl group), desired charging is ensured, generation of colored particles with reverse polarity is suppressed, and the charging characteristics of the colored particles are easily stabilized.

As the functional group of the monomer unit C, when the self-crosslinkable group of the monomer unit B is a (meth) acryloyl group or an acrylamide group, an active hydrogen-containing group capable of Michael addition reaction to the (meth) acryloyl group (primary amino group) Group, secondary amino group, malonate ester group, acetoacetate ester group, malonamide group, acetoacetamide group, etc.).
Examples of the monomer for constituting the monomer unit C having an active hydrogen-containing group include 2-acetoacetoxyethyl (meth) acrylate and 2-ethoxymalonyloxyethyl (meth) acrylate.

Examples of the functional group of the monomer unit C include active hydrogen-containing groups such as an alcoholic hydroxyl group and an acetoacetate group when the self-crosslinkable group of the monomer unit B is a hydroxymethyl group or an alkoxymethyl group.
Examples of the monomer for constituting the monomer unit C having an active hydrogen-containing group include 2-hydroxyethyl (meth) acrylate and 3-hydroxypropyl (meth) acrylate.

The functional group of the monomer unit C includes a carboxyl group when the self-crosslinkable group of the monomer unit B is a vinyloxy group or an oxazolyl group.
Monomers constituting the monomer unit C having a carboxyl group include (meth) acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, 4-vinylbenzoic acid, 2-methacryloyloxyethyl succinic acid. , 2-methacryloyloxyethyl hexahydrophthalic acid and the like.

Here, the combination of the monomer unit B and the monomer unit C is preferably a combination of the monomer unit B having a vinyloxy group or oxazolyl group in the side chain and the monomer unit C having a carboxyl group in the side chain. That is, the self-crosslinking group of the monomer unit B is preferably a vinyloxy group or an oxazolyl group, and the functional group of the monomer unit C of the second polymer is preferably a carboxyl group.
By introducing the monomer unit C having a carboxyl group in the side chain into the second polymer, the adsorptivity of the cross-linked product of the second polymer to the surface of the core particle is improved, and the coating amount of the second polymer between the core particles is increased. The variation is reduced, and the charge amount of the colored particles is stabilized.

-Monomer unit D-
Monomers for constituting the monomer unit D include (meth) acrylic acid alkyl esters such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate and butyl (meth) acrylate; hydroxyethyl (Meth) acrylic acid hydroxyalkyl esters such as (meth) acrylate and hydroxybutyl (meth) acrylate; and monomers for constituting the monomer unit D include (meth) acrylate (tetraethylene glycol monomethyl) having an ethylene oxide unit. (Meth) acrylate of alkyloxyoligoethylene glycol such as ether (meth) acrylate, one-terminal (meth) acrylate of polyethylene glycol, etc.); (meth) acrylic acid; maleic acid; N, N-dialkyla Roh (meth) acrylate; and the like.

-Ratio of monomer units of the second polymer-
In the second polymer, among the monomer units, the monomer units A and B are essential components, and the monomer units C and D are optional components.
The ratio (copolymerization ratio) of the monomer units A is preferably 50% by mass or more and 999.9% by mass or less, more preferably 60% by mass or more and 99.8% by mass or less, and particularly preferably 70% by mass with respect to all monomer units. It is not less than 99.7% by mass. When the ratio (polymerization ratio) of the monomer unit A is in the above range, the dispersibility of the colored particles in the dispersion medium is easily stabilized.
The ratio of monomer units B (copolymerization ratio) is preferably 0.1% by mass or more and 50% by mass or less, more preferably 0.2% by mass or more and 40% by mass or less, and particularly preferably 0%, based on all monomer units. It is 3 mass% or more and 30 mass% or less. When the ratio (copolymerization ratio) of the monomer units B is 50% by mass or less, thickening or gelation is easily suppressed when the second polymer is synthesized. When the ratio of monomer units B (copolymerization ratio) is 0.1% by mass or more, the coating amount of the second polymer crosslinked to the surface of the core particles is sufficient, and the dispersibility of the colored particles in the dispersion medium is stable. It becomes easy to do.

  The ratio of monomer units C (copolymerization ratio) is preferably 0% by mass or more and 25% by mass or less, more preferably 0.1% by mass or more and 20% by mass or less, and particularly preferably 0.5% by mass with respect to all monomer units. It is not less than 15% by mass. When the ratio of the monomer units C (polymerization ratio) is in the above range, the coating amount of the crosslinked body of the second polymer on the surface of the core particles is sufficient, and the dispersibility of the colored particles in the dispersion medium is easily stabilized.

-Weight average molecular weight of the second polymer-
The weight average molecular weight (Mw) of the second polymer is preferably from 2,000 to 1,000,000, and preferably from 2,000 to 500,000, from the viewpoint of handling during synthesis and dispersibility of the colored particles. More preferably, it is particularly preferably 8,000 to 300,000.

  Hereinafter, although the specific example of a 2nd polymer is shown, this invention is not limited to these. In addition, the composition ratio of the monomer unit which comprises a 2nd polymer represents a mass percentage. In the specific examples, “n” represents a natural number (for example, 1 to 1000, preferably 3 to 100).

-Other components for forming the coating layer-
In the coating layer, in addition to the crosslinked product of the second polymer, a compound having one or more functional groups capable of crosslinking with the self-crosslinkable group of the second polymer (monomer unit B) and not generating a hydroxyl group upon crosslinking May be optionally added as a crosslinking agent.
Specifically, for example, when the self-crosslinkable group of the monomer unit B of the second polymer is an ethylenically unsaturated group, a compound having at least one ethylenically unsaturated bond, preferably two or more, as a crosslinking agent. It may be added.
For example, when the self-crosslinkable group of the monomer unit B of the second polymer is a vinyloxy group, a compound having one, preferably two or more carboxyl groups may be added as a crosslinking agent.

−Coating layer coverage−
The coating amount of the crosslinked body of the second polymer on the surface of the core particle is preferably in the range of 1% by mass to 250% by mass with respect to the mass of the core particle from the viewpoint of stable dispersibility and charging characteristics. More preferably, it is in the range of 2% by mass or more and 200% by mass or less. When the coating amount is 1% by mass or more, the dispersibility of the colored particles is likely to increase, and when the coating amount is 250% by mass or less, the decrease in the charge amount of the colored particles is easily suppressed.

  This coating amount is obtained as follows. One is to calculate the amount of increase with respect to the amount of the particle material by centrifuging the produced colored particles and measuring the mass thereof. In addition, calculation from a composition analysis of particles can also be applied.

-Average particle diameter of colored particles-
The average particle size (volume average particle size) of the colored particles of the present invention is, for example, 0.1 μm or more and 10 μm or less, but is selected according to the application and is not limited thereto.
The average particle size is measured using a Photo FPAR-1000 (dynamic light scattering particle size distribution measuring device) manufactured by Otsuka Electronics Co., Ltd., and analyzed by the MARQUAARD method.

[Method for producing colored particles]
The method for producing colored particles according to the present invention includes a first polymer having a chargeable group, a colorant, a first solvent, an incompatible with the first solvent, a lower boiling point than the first solvent, and a chargeable group. A step of stirring and emulsifying a mixed solution containing a second solvent that dissolves the first polymer having a first solvent, and removing the second solvent from the emulsified mixed solution to thereby color the first polymer having a charging group A core particle containing an agent, a core particle, a monomer unit A having a silicone chain as a side chain and a monomer unit B having a self-crosslinkable group as a side chain, and self-crosslinking of the monomer unit B It is preferable to have a step of coating the surface of the core particle by mixing the second polymer, which is a functional group in which the functional group does not generate a hydroxyl group by crosslinking, and then crosslinking the second polymer. When colored particles are produced by a so-called in-liquid drying method, colored particles having particularly stable dispersibility and charging characteristics can be obtained.

  Here, when the colored particles of the present invention are applied to display particles (electrophoretic particles), dispersion of the obtained colored particles can be achieved by using a dispersion medium used for the display medium as the first solvent in the above method. The liquid can be used as it is as a display particle dispersion containing display particles and a dispersion medium. Thereby, in the manufacturing method of the colored particle of this invention, the display particle dispersion liquid which used the 1st solvent as the dispersion medium can also be easily produced through the said process, without passing through a washing | cleaning and drying process. . Of course, it is also possible to appropriately carry out cleaning of colored particles (removal of ionic impurities) and replacement of the dispersion medium in order to improve electrical characteristics. Hereinafter, it demonstrates according to a process.

  In addition, the manufacturing method of the colored particles of the present invention is not limited to the above manufacturing method, and after forming the core particles by a known method (coacervation method, dispersion polymerization method, suspension polymerization method, etc.) After mixing the core particles with the second polymer, a method may be employed in which the surface of the core particles is coated with a crosslinked body of the second polymer by crosslinking the second polymer.

  Hereafter, the detail of the manufacturing method of the colored particle of this invention is demonstrated according to process.

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

  In the emulsification step, by stirring the mixed liquid, the low-boiling point second solvent forms a droplet-like dispersed phase in the continuous phase of the high-boiling point first solvent and is emulsified. Note that the second polymer is dissolved in the continuous phase of the first solvent, and the first polymer having a chargeable group and the colorant are dissolved or dispersed in the dispersed phase of the second solvent.

In the emulsification step, each material may be sequentially mixed in the mixed solution. For example, first, a first mixed solution in which a first polymer having a charging group, a colorant, and a second solvent are mixed, A second mixed solution in which the polymer and the first solvent are mixed is prepared. And it is good to emulsify so that a 1st mixed solution may be disperse | distributed and mixed in a 2nd mixed solution, and a 1st mixed solution may be disperse | distributed in a particulate form in a 2nd mixed solution. The second mixed solution is also preferably prepared by adding each monomer constituting the second polymer to the first solvent and then polymerizing it to obtain the second polymer.
Here, the first mixed solution in which the first polymer having a chargeable group, the colorant, and the second solvent are mixed and dispersed in the first solvent in which the second polymer is not mixed, and the emulsification step and later described. The second solvent removal step is performed to prepare the core particles, and then the second mixed solution containing the second polymer and the first solvent is mixed with the obtained core particle dispersion to crosslink the second polymer. It is also a suitable technique to coat the surface of the core particle with a crosslinked body of the second polymer.

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

Next, the first solvent will be described.
The first solvent is used as a poor solvent that can form a continuous phase in a mixed solution, and includes petroleum-derived high-boiling solvents such as paraffinic hydrocarbon solvents, silicone oils, and fluorinated liquids, but is not limited thereto. Absent. In particular, silicone oil or paraffinic hydrocarbon solvent is preferably applied from the viewpoint of obtaining colored particles having stable dispersibility and charging characteristics.

  Specific examples of silicone oils include silicone oils in which hydrocarbon groups are bonded to siloxane bonds (dimethylsilicone oil, diethylsilicone oil, methylethylsilicone oil, methylphenylsilicone oil, diphenylsilicone oil, etc.), modified silicone oils (fluorine-modified). Silicone oil, amine-modified silicone oil, carboxyl-modified silicone oil, epoxy-modified silicone oil, alcohol-modified silicone oil, etc.). Among these, dimethyl silicone is particularly desirable from the viewpoint of high safety, chemical stability, long-term reliability, and high resistivity. In addition, as commercially available silicone oil, Shin-Etsu Chemical Co., Ltd. KF-96 series etc. are mentioned.

  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, when the colored particles are applied to the display particles, the moving speed of the display particles, that is, the display speed can be improved. In addition, Tokyo Keiki B-8L type | mold viscosity meter is used for the measurement of this viscosity.

  Examples of the paraffinic hydrocarbon solvent include normal paraffinic hydrocarbons and isoparaffinic hydrocarbons having 20 or more carbon atoms (boiling point of 80 ° C. or higher). For reasons of safety and volatility, use isoparaffins. Is preferred. Specifically, Shell Sol 71 (manufactured by Shell Petroleum), Isopar O, Isopar H, Isopar K, Isopar L, Isopar G, Isopar M (Isopar is a trade name of Exxon), IP Solvent (manufactured by Idemitsu Petrochemical), etc. Can be mentioned.

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

  Specific examples of the second solvent include water, lower alcohols having 5 or less carbon atoms (eg, methanol, ethanol, propanol, isopropyl alcohol, etc.), tetrahydrofuran, acetone, and other organic solvents (eg, toluene, dimethylformamide, dimethylacetamide). However, it is not limited to this.

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

-Second solvent removal step-
Next, in the second solvent removal step, the second solvent (low boiling point solvent) is removed from the mixed solution emulsified in the emulsification step. By removing the second solvent, the first polymer having the chargeable group is precipitated and encapsulated in the dispersed phase formed by the second solvent while encapsulating other materials, and the core particles are formed. can get. Further, the first polymer forming the core particles may contain various additives such as a pigment dispersant and a weathering stabilizer. For example, a commercially available pigment dispersion contains a polymer substance or a surfactant for dispersing the pigment. When this is used, the core particle is not only a resin for controlling the charge, but also these resins. Substance will be included.

Here, examples of the method for removing the second solvent include a method of heating the mixed solution and a method of reducing the pressure of the mixed solution, and these methods may be combined.
When the mixed solution is heated to form the second solvent, the heating temperature is preferably 30 ° C. or higher and 200 ° C. or lower, and more preferably 50 ° C. or higher and 180 ° C. or lower. In addition, the crosslinking reaction of the second polymer may be carried out by heating in the removal step of the second solvent, and the surface of the core particles may be coated with the crosslinked body of the second polymer. A catalyst may be added. On the other hand, when the mixed solution is depressurized to remove the second solvent, the depressurization pressure is preferably 0.01 mPa to 200 mPa, and more preferably 0.01 mPa to 20 mPa.

-Coating process-
In the coating step, the second polymer is crosslinked in the solution (first solvent) in which the core particles are generated, and the surface of the core particles is coated with a crosslinked body of the second polymer. That is, the coating layer containing the crosslinked body of the second polymer is formed on the surface of the core particle. In addition, although reaction may have progressed by the heat processing in an above described 2nd solvent removal process, more reliable reaction is realizable by this process.

  Here, as a method of causing the second polymer to undergo a crosslinking reaction and coating the surface of the core particles with a crosslinked body of the second polymer, for example, a method of heating a solution according to the type of the second polymer can be mentioned. It is done. When the solution is heated, the heating temperature is preferably 50 ° C. or higher and 200 ° C. or lower, and more preferably 60 ° C. or higher and 150 ° C. or lower. Further, depending on the type of the second polymer, a crosslinking agent may be added separately, and an acid, a base, a salt, a polymerization initiator, or the like may be optionally added to accelerate the reaction.

Through the above steps, colored particles or a colored particle dispersion containing the same is obtained.
In addition, you may dilute with the 1st solvent (The 1st solvent containing a dispersing agent as needed), for example with respect to the obtained colored particle dispersion liquid as needed.

[Particle dispersion]
The colored particle dispersion of the present invention has a particle group containing the colored particles of the present invention and a dispersion medium for dispersing the particle group.

Here, since the colored particles of the present invention have the above characteristics, in the colored particle dispersion of the present invention, a system in which the particle group containing the colored particles is composed of a plurality of types of colored particles having different charging characteristics, That is, even in a system in which a plurality of types of colored particles having different charging characteristics are mixed, stable dispersibility and charging characteristics are maintained. A plurality of types of colored particles having different charging characteristics can be obtained, for example, by changing the chargeable group or the amount of the first polymer having a chargeable group.
The colored particles having different charging characteristics are colored particles having different charge polarities and charge amounts.

The dispersion medium is not particularly limited, but a low dielectric solvent (for example, a dielectric constant of 5.0 or less, desirably 3.0 or less) may be selected. The dispersion medium may use a solvent other than the low dielectric solvent, but preferably contains 50% by volume or more of the low dielectric solvent. In addition, the dielectric constant of a low dielectric constant is calculated | required with a dielectric constant meter (made by Nippon Luft).
Examples of the low dielectric solvent include petroleum-derived high-boiling solvents such as paraffinic hydrocarbon solvents, silicone oils, and fluorinated liquids. Specific examples of the paraffinic hydrocarbon solvent and the silicone oil are the same as those described for the first solvent in the method for producing colored particles of the present invention.

  If necessary, the colored particle dispersion of the present invention may be added with 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. May be.

  The colored particle dispersion of the present invention includes an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, a fluorosurfactant, a silicone surfactant, a silicone as a charge control agent. A cationic compound, a silicone anion compound, a metal soap, an alkyl phosphate ester, a succinimide, or 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) Copolymerization of a compound having a chain skeleton, a metal complex of salicylic acid, a metal complex of catechol, a metal-containing bisazo dye, a tetraphenylborate derivative, a polymerizable silicone macromer (manufactured by JNC: Silaplane) and an anionic monomer or a cationic polymer Examples include coalescence.
More specific examples of the ionic and nonionic surfactants are as follows. Nonionic activators include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, And fatty acid alkylolamide. Examples of the anionic surfactant include alkylbenzene sulfonate, alkylphenyl sulfonate, alkyl naphthalene sulfonate, higher fatty acid salt, sulfate of higher fatty acid ester, sulfonic acid of higher fatty acid ester, and the like. Examples of the cationic surfactant include primary to tertiary amine salts and quaternary ammonium salts. These charge control agents are preferably 0.01% by mass or more and 20% by mass or less, and particularly preferably 0.05% by mass or more and 10% by mass or less based on the solid content of the particles.

In the colored particle dispersion of the present invention, the concentration of the colored particles can be variously selected depending on the application, but is preferably selected in the range of 0.1% by mass to 50% by mass.
Specifically, when the colored particles are applied to the display particles, the concentration of the colored particles in the colored particle dispersion is in the range of 0.1% by mass or more and 30% by mass or less depending on the display characteristics and response characteristics. It is desirable to be selected. When mixing multi-particles having different colors, the total amount of the particles is preferably within this range. When the concentration of the colored particles is 0.1% by mass or more, a sufficient display density is easily secured, and when the concentration of the colored particles is 30% by mass or less, a decrease in display speed and aggregation of the colored particles are easily suppressed.

[Use of colored particles (dispersion liquid) of the present invention]
The colored particles of the present invention (dispersions thereof) are particles for display such as electrophoretic display media, electrophoretic light control media (light control elements), liquid toners of liquid developing electrophotographic systems (dispersions thereof) ), Paints, ink compositions 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.

  In the colored particles (dispersion liquid) of the present invention, it is also preferable to use a mixture of a plurality of types of colored particles having different colors and charging polarities. In order to obtain a colored particle dispersion containing two or more kinds of the colored particles of the present invention, these dispersions may be prepared and then mixed.

[Display medium, display device]
A display medium according to a first aspect of the present invention includes a pair of substrates having at least one of light-transmitting properties and the colored particle dispersion of the present invention sealed between the pair of substrates. And the display apparatus of 1st this invention is equipped with the display medium of 1st this invention, and the voltage application means which applies a voltage between a pair of board | substrates of a display medium.

  On the other hand, the display medium of the second aspect of the present invention includes a pair of electrodes having at least one of translucency, and a region having the colored particle dispersion of the present invention provided between the pair of electrodes. The display medium of the second aspect of the present invention and voltage applying means for applying a voltage between the pair of electrodes of the display medium are provided.

  Hereinafter, an exemplary embodiment of a display medium and a display device of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a display device according to the present embodiment. FIG. 2 is an explanatory diagram schematically illustrating a movement mode of the particle group when a voltage is applied between the substrates of the display medium of the display device according to the present embodiment.
The display device 10 according to the present embodiment is a mode in which the colored particle dispersion of the present invention is applied as a particle dispersion including the dispersion medium 50 of the display medium 12 and the particle group 34. That is, the colored particles of the present invention are dispersed in the dispersion medium 50 as the particles of the particle group 34.

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

  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, plastic, polyethylene terephthalate resin, polycarbonate resin, acrylic resin, polyimide resin, polyester resin, epoxy resin, and polyethersulfone resin.

  Examples of the material for the surface electrode 40 and the back electrode 46 include 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 resin, and the like. Is mentioned.

  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 a thermoplastic resin, a thermosetting resin, an electron beam curable resin, a photocurable resin, rubber, metal, or the like.

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

  The gap member 24 may be colored or colorless, but is preferably colorless and transparent. In this case, the gap member 24 is made of 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 a color of the reflective particle group 36, for example, white or black is preferably selected so as to be a 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 (titanium oxide, silicon oxide, zinc oxide, etc.), resin (polystyrene resin, polyethylene resin, polypropylene resin, polycarbonate resin, polymethyl methacrylate resin (PMMA), acrylic resin, For example, particles dispersed in phenol resin, formaldehyde condensate, etc.) or resin particles (polystyrene particles, polyvinyl naphthalene particles, bismelamine particles, polyvinyl biphenyl particles, 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.

  The reflective particle group 36 is sealed between the substrates by an ink jet method or the like. 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.

Next, other configurations of the display medium will be described.
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 that 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 addition, the content (% by mass) of the particle group 34 with respect to the total mass in the cell is not particularly limited as long as a desired hue can be obtained, and the cell thickness (that is, the display substrate 20 and It is effective for the display medium 12 to adjust the content by the distance between the substrate and the back substrate). That is, in order to obtain a desired hue, the content can be decreased as the cell becomes thicker, and the content can be increased as the cell becomes thinner. Generally, it is 0.01 mass% or more and 50 mass% 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 frame for fixing the substrate are used. Also, fixing means such as an adhesive, heat melting, and ultrasonic bonding may be used.

  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, the mode in which one type (one color) of particle group is applied as the particle group 34 has been described. It may be a form in which two or more types (two colors) of particle groups are applied in different combinations of voltages.
Specifically, for example, as the particle group 34, a positively chargeable first particle group, a negatively chargeable second particle group, and a positively chargeable particle having a threshold voltage different from those of the first particle group, The form which applied the 3rd particle group with a big diameter is mentioned.

[Electronic devices equipped with a display medium (display device)]
The display medium (display device) of the present invention is provided in an electronic device, a display medium, a card medium, and the like.
Specifically, the image display device of the present invention includes, for example, an electronic bulletin board capable of storing and rewriting images, an electronic circulation version, an electronic blackboard, an electronic advertisement, an electronic signboard, a flashing sign, electronic paper, an electronic newspaper, and an electronic book. Electronic document sheets that can be shared with copiers and printers, portable computers, tablet computers, mobile phones, smart cards, signature devices, watches, shelf labels, flash drives, etc.

  Hereinafter, the present invention will be described more specifically with reference to examples. Hereinafter, the present invention will be described more specifically with reference to examples. However, these examples do not limit the present invention. In the text, “part” and “%” mean “part by mass” and “% by mass” unless otherwise specified.

[Synthesis of second polymer]
(Synthesis of polymer (P-1))
In a 500 ml three-necked flask equipped with a nitrogen inlet tube, a condenser and a stirring rod, 96 parts by mass of silaplane FM-0721 (weight average molecular weight of about 5000; manufactured by JNC) as a silicone monomer, 4 parts by mass of allyl methacrylate, 100 of toluene A mass part was mixed and stirred and mixed for 10 minutes under a nitrogen stream. 0.4 parts by mass of azobisvaleronitrile (manufactured by Wako Pure Chemicals: V-65) was added as a polymerization initiator, and polymerization was carried out at 65 ° C. for 6 hours. Toluene is distilled off from the reaction solution under reduced pressure and diluted with a silicone oil “KF-96L-2cs (manufactured by Shin-Etsu Chemical Co., Ltd.)”), and a polymer having a silicone chain and a self-crosslinkable group in the side chain (P-1 10 mass% silicone oil solution was obtained. The weight average molecular weight was 100,000.

(Synthesis of polymer (P-10) In a 500 ml three-necked flask equipped with a nitrogen inlet tube, a condenser and a stirring rod, 96 parts by mass of Silaplane FM-0721 (weight average molecular weight: about 5000; manufactured by JNC) as a silicone monomer, 3 parts by mass of 2- (2-vinyloxyethoxy) ethyl acrylate (VEEA, manufactured by Nippon Shokubai), 1 part by mass of methacrylic acid, and 100 parts by mass of toluene were mixed and stirred for 10 minutes under a nitrogen stream. As an initiator, 0.4 part by mass of azobisvaleronitrile (manufactured by Wako Pure Chemicals: V-65) was added, and polymerization was carried out at 65 ° C. for 6 hours. KF-96L-2cs (manufactured by Shin-Etsu Chemical Co., Ltd.))), a polymer having a silicone chain and a self-crosslinking group in the side chain (P-10) Of 10 mass% silicone oil solution was obtained. The weight average molecular weight was 120,000.

  In addition, the synthesis | combination of the other 2nd polymer used in the Example shown below was synthesize | combined similarly.

[Production of core particles]
(Preparation of core particle dispersion A-1)
45 parts by mass of a styrene / acrylic resin (“X-345” manufactured by Seiko PMC) as the first polymer having a chargeable group, and a melamine compound (“Nicarac MW-390 (manufactured by Sanwa Chemical Co., Ltd.)”) as a crosslinking agent ”5 An aqueous dispersion was prepared by adding 50 parts by mass of cyan pigment (“H524F (manufactured by Sanyo Dye))” as a colorant to water so that the total amount was 15% by mass.
Next, the obtained aqueous dispersion was used as a dispersed phase, and a silicone oil ("KF-96L-2cs (Shin-Etsu)" added with 1% by mass of a silicone oil solution (surfactant "KF-6028 (manufactured by Shin-Etsu Chemical Co., Ltd.)") was used. Made by Chemical Industry Co., Ltd.))) as a continuous phase, these were mixed at a mass ratio (continuous phase: dispersed phase) of 10: 1 and emulsified with a homogenizer to prepare an emulsion.
Next, the obtained emulsion is dried by an evaporator at 60 ° C. for 6 hours, water in the emulsion is removed, and the core containing the first polymer having a chargeable group in the silicone oil and the pigment A silicone oil dispersion in which particles were dispersed was obtained. The obtained particles had an average particle size of 0.6 μm and C.I. V. The value (index indicating monodispersity: Coefficient of Variation: CV [%] = (σ / D) × 100 (σ: standard deviation, D: average particle diameter)) was 25%.
And the core particle disperse | distributed in the liquid was wash | cleaned with silicone oil using the centrifuge, and 1 mass% core particle dispersion liquid A-1 was prepared.

(Preparation of core particle dispersion A-2)
The core particle dispersion liquid is the same as the core particle dispersion liquid A-1, except that a commercially available product (manufactured by Wako Pure Chemical Industries, Ltd.) polymethacrylic acid (weight average molecular weight 50,000) is used as the first polymer having a chargeable group. A-2 was prepared.

[Example 1]
(Core particle coating process)
Next, a 10% by mass silicone oil solution of a polymer (P-1) having a silicone chain and a self-crosslinkable group in the side chain as a second polymer in 50 parts by mass of the 1% by mass core particle dispersion (A-1). After adding 10 parts by mass and mixing for 10 minutes under a nitrogen stream, 0.01 part by mass of azobisvaleronitrile (manufactured by Wako Pure Chemicals: V-65) was added as a crosslinking catalyst, and 70 parts under a nitrogen stream. A crosslinking reaction was carried out at 0 ° C. for 6 hours to coat the surface of the core particles with a crosslinked product of the polymer (P-1) [second polymer] to form a coating layer. After cooling, the supernatant is removed by a centrifuge, and 2-propanol and silicone oil “KF-96L-2cs (manufactured by Shin-Etsu Chemical Co., Ltd.)”) are mass ratio to remove unreacted polymer (P-1). The particles were washed with a centrifuge using the liquid mixed at 1: 1. Thereafter, until the unreacted polymer (P-1) is not detected by GPC, the particles are settled using a centrifugal separator and purified by repeating the addition of silicone oil and sedimentation washing, and finally the particle solid content is 5 A mass% display particle dispersion was prepared. As a result of measuring the coating amount of the coating layer by elemental analysis, it was 4% by mass with respect to the mass of the particles.

Further, the dispersion stability of the particles was evaluated as follows. A solution containing 5% by mass of the prepared migrating particles was dispersed with an ultrasonic disperser for 10 minutes, and then the state of particle sedimentation and particle aggregation of the dispersion before and after standing for 24 hours in a stationary state was expressed as Horiba LA-300: Laser The particle size was measured by a light scattering / diffraction particle size measuring device.
Further, the display particle dispersion was sealed between the two electrode substrates, and the charge polarity of the display particles (electrophoretic particles) was evaluated by observing the migration direction under application of a DC voltage.

[Example 2]
In the core particle coating step, a display particle dispersion was obtained in the same manner as in Example 1 except that 0.2 parts by mass of ethylene glycol diacrylate was added as a crosslinking agent to carry out a crosslinking reaction. As a result of measuring the coating amount of the coating layer by elemental analysis, it was 5% by mass with respect to the mass of the particles.

[Example 3]
In the coating step of the core particle, the same as Example 1 except that the polymer (P-2) was used as the second polymer instead of the polymer (P-1) having a silicone chain and a self-crosslinkable group in the side chain. Thus, a display particle dispersion was obtained. As a result of measuring the coating amount of the coating layer by elemental analysis, it was 5% by mass with respect to the mass of the particles.

[Example 4]
In the core particle coating step, a display particle dispersion was obtained in the same manner as in Example 3 except that 0.2 parts by mass of ethylene glycol diacrylate was added as a crosslinking agent to carry out a crosslinking reaction. As a result of measuring the coating amount of the coating layer by elemental analysis, it was 6% by mass with respect to the particle mass.

[Example 5]
The same procedure as in Example 1 except that the polymer (P-3) was used as the second polymer in place of the polymer (P-1) having a silicone chain and a self-crosslinkable group in the side chain in the core particle coating step. Thus, a display particle dispersion was obtained. As a result of measuring the coating amount of the coating layer by elemental analysis, it was 5% by mass with respect to the mass of the particles.

[Example 6]
In the coating step of the core particles, the same as Example 1 except that the polymer (P-4) was used as the second polymer instead of the polymer (P-1) having a silicone chain and a self-crosslinkable group in the side chain. Thus, a display particle dispersion was obtained. As a result of measuring the coating amount of the coating layer by elemental analysis, it was 7% by mass with respect to the particle mass.

[Example 7]
In the core particle coating step, as the second polymer, the polymer (P-5) is used instead of the polymer (P-1) having a silicone chain and a self-crosslinking group in the side chain, and azobisvaleronitrile is used as the crosslinking catalyst. A display particle dispersion was obtained in the same manner as in Example 1, except that 0.01 parts by mass of p-toluenesulfonic acid monohydrate was used. As a result of measuring the coating amount of the coating layer by elemental analysis, it was 5% by mass with respect to the mass of the particles.

[Example 8]
In the coating step of the core particles, the same as Example 7 except that the polymer (P-6) was used as the second polymer instead of the polymer (P-5) having a silicone chain and a self-crosslinkable group in the side chain. Thus, a display particle dispersion was obtained. As a result of measuring the coating amount of the coating layer by elemental analysis, it was 7% by mass with respect to the particle mass.

[Example 9]
In the coating step of the core particles, the same as Example 7 except that the polymer (P-7) was used as the second polymer instead of the polymer (P-5) having a silicone chain and a self-crosslinkable group in the side chain. Thus, a display particle dispersion was obtained. As a result of measuring the coating amount of the coating layer by elemental analysis, it was 5% by mass with respect to the mass of the particles.

[Example 10]
In the coating step of the core particle, the same as Example 7 except that the polymer (P-8) was used as the second polymer instead of the polymer (P-5) having a silicone chain and a self-crosslinkable group in the side chain. Thus, a display particle dispersion was obtained. As a result of measuring the coating amount of the coating layer by elemental analysis, it was 4% by mass with respect to the mass of the particles.

[Example 11]
In the coating step of the core particle, the same as Example 7 except that the polymer (P-9) was used as the second polymer instead of the polymer (P-5) having a silicone chain and a self-crosslinkable group in the side chain. Thus, a display particle dispersion was obtained. As a result of measuring the coating amount of the coating layer by elemental analysis, it was 6% by mass with respect to the particle mass.

[Example 12]
In the coating step of the core particle, the same as Example 7 except that the polymer (P-10) was used as the second polymer instead of the polymer (P-5) having a silicone chain and a self-crosslinkable group in the side chain. Thus, a display particle dispersion was obtained. As a result of measuring the coating amount of the coating layer by elemental analysis, it was 10% by mass with respect to the mass of the particles.

[Example 13]
In the core particle coating step, the second polymer was the same as Example 7 except that the polymer (P-11) was used instead of the polymer (P-5) having a silicone chain and a self-crosslinkable group in the side chain. Thus, a display particle dispersion was obtained. As a result of measuring the coating amount of the coating layer by elemental analysis, it was 9% by mass with respect to the mass of the particles.

[Example 14]
In the core particle coating step, a display particle dispersion was obtained in the same manner as in Example 3, except that the core particle dispersion (A-2) was used instead of the core particle dispersion (A-1). As a result of measuring the coating amount of the coating layer by elemental analysis, it was 4% by mass with respect to the mass of the particles.

[Example 15]
In the core particle coating step, a display particle dispersion was obtained in the same manner as in Example 12 except that the core particle dispersion (A-2) was used instead of the core particle dispersion (A-1). As a result of measuring the coating amount of the coating layer by elemental analysis, it was 8% by mass with respect to the mass of the particles.

[Example 16]
In the core particle coating step, the same as Example 7 except that the polymer (P-12) was used as the second polymer instead of the polymer (P-5) having a silicone chain and a self-crosslinkable group in the side chain. Thus, a display particle dispersion was obtained. As a result of measuring the coating amount of the coating layer by elemental analysis, it was 4% by mass with respect to the mass of the particles.

[Example 17]
In the coating step of the core particles, the same as Example 7 except that the polymer (P-13) was used as the second polymer instead of the polymer (P-5) having a silicone chain and a self-crosslinkable group in the side chain. Thus, a display particle dispersion was obtained. As a result of measuring the coating amount of the coating layer by elemental analysis, it was 4% by mass with respect to the mass of the particles.

[Example 18]
In the coating step of the core particles, the same as Example 7 except that the polymer (P-14) was used as the second polymer instead of the polymer (P-5) having a silicone chain and a self-crosslinkable group in the side chain. Thus, a display particle dispersion was obtained. As a result of measuring the coating amount of the coating layer by elemental analysis, it was 4% by mass with respect to the mass of the particles.

[Example 19]
In the coating step of the core particles, the same as Example 7 except that the polymer (P-15) was used as the second polymer instead of the polymer (P-5) having a silicone chain and a self-crosslinkable group in the side chain. Thus, a display particle dispersion was obtained. As a result of measuring the coating amount of the coating layer by elemental analysis, it was 7% by mass with respect to the particle mass.

[Comparative Example 1]
Example 7 except that the comparative polymer (R-1) was used as the second polymer in place of the polymer (P-5) having a silicone chain and a self-crosslinkable group in the side chain in the core particle coating step. In the same manner, a display particle dispersion was obtained. As a result of measuring the coating amount of the coating layer by elemental analysis, it was 6% by mass with respect to the particle mass.

[Comparative Example 2]
The core particle dispersion (A-1) was used as a display particle dispersion as it was without being coated with the crosslinked body of the second polymer.

[Comparative Example 3]
In the core particle coating step, a display particle dispersion was obtained in the same manner as in Comparative Example 1, except that the core particle dispersion (A-2) was used instead of the core particle dispersion (A-1). As a result of measuring the coating amount of the coating layer by elemental analysis, it was 5% by mass with respect to the mass of the particles.

[Comparative Example 4]
The core particle dispersion (A-2) was used as a display particle dispersion as it was without being coated with the crosslinked body of the second polymer.

[Evaluation]
Using the display particle dispersion obtained in each example, 20% by mass of white particles and 1% by mass of display particles (electrophoretic particles (cyan particles)) in KF-96L-2cs in a continuous phase. A dispersion liquid was prepared and used as an electrophoretic particle dispersion liquid.
However, white particles prepared as follows were used.

-Production of white particles-
45 parts by mass of Silaplane FM-0721, 45 parts by mass of 2-vinylnaphthalene, 240 parts by mass of silicone oil “KF-96L-1cs (manufactured by Shin-Etsu Chemical Co., Ltd.)” and 2 parts by mass of lauroyl peroxide are placed in a flask and stirred. Then, nitrogen was bubbled at a flow rate of 0.2 L / min for deoxygenation, followed by heating in an oil bath at 70 ° C. for 10 hours to obtain a dispersion of white fine particles. The obtained dispersion was centrifuged and the supernatant was discarded, 400 ml of KF-96L-2cs was added, and the dispersion was returned to the dispersed state by ultrasonic irradiation. This was repeated 3 times, washing and replacement with KF-96L-2cs were performed to obtain a white particle dispersion.
The resulting white particles had an average particle size of 0.5 μm and C.I. V. The value was 10%.
The white particles did not migrate when an electric field of ± 20 V was applied.

Next, the obtained electrophoretic particle dispersion is placed in a cell with a 50 μm spacer (gap member) interposed between a pair of glass substrates on which indium tin oxide (ITO) electrodes are formed. A device sample enclosed in () was produced. The spacer (gap member) was formed by applying a spin coat on the electrode forming surface of one glass substrate with CYTOP (Asahi Glass Co., Ltd., CTL809M), followed by heating at 200 ° C. for 4 hours.
Then, using the obtained element sample, a voltage of ± 15 V is applied between the electrodes of the element sample by a function generator (power source manufactured by NF is driven by LabView manufactured by NATIONAL INSTRUMENTS), and an ammeter (manufactured by KEITHLEY) and The charge amount of display particles (electrophoretic particles) and the abundance ratio of reverse polarity particles were examined using an optical measuring device (USB2000 manufactured by Ocean Optics). Specifically, it is as follows.

-Charge amount-
The charge amount (initial charge amount) of the display particles (electrophoretic particles) was obtained by applying a rectangular wave of 0V-15V and integrating the charge amount up to the time when the current value became constant.

-Ratio of particles with opposite polarity-
The abundance ratio of reverse polarity particles (initial abundance ratio) in the display particles (electrophoretic particles) was measured by calibrating white in a standard sample and black in a dark state with an optical measurement device.

From the above results, it can also be seen that the display particles of this example have better dispersibility in the silicone oil and a lower proportion of the opposite polarity particles compared to the display particles of the comparative example.
This shows that the colored particles of the present invention have stable dispersibility and charging characteristics.

  In the above evaluation, as the white particles, using the white particles W1 obtained by the following production method, an electrophoretic particle dispersion and a device sample were prepared, and the same evaluation was performed using this. In each example, the same evaluation results as described above were obtained.

-Production of white particles W1-
4-vinylbiphenyl (manufactured by Nippon Steel Chemical Co., Ltd.): 1 part by mass Silaplane FM-0721 (manufactured by JNC, weight average molecular weight Mw = 5000: structural formula (1) [R ¹ = methyl group, R ² = Butyl group, n = 68, x = 3]): 1 part by mass-Lauroyl peroxide (manufactured by Aldrich): 0.03 part by mass-Isopar M (Isopar M: registered trademark, manufactured by ExxonMobil): 10 parts by mass・ Hexane (manufactured by Kanto Chemical Co., Inc.): 2 parts by massToluene (manufactured by Kanto Chemical Co., Ltd.): 2 parts by mass The above composition was mixed and heated at 65 ° C. for 18 hours, and then dimethyl silicone oil (Shin-Etsu Chemical Co., Ltd.) The solvent was replaced with KF-96L-2cs (viscosity 2cs).
Thereby, the dispersion liquid of the white particle W1 comprised with the copolymer which contains 4-vinylbiphenyl as a polymerization component was obtained. The volume average particle size of the white particles W1 was 0.53 μm.

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 (14)

Core particles containing a first polymer having a chargeable group and a colorant , wherein the colorant is dispersed using the first polymer as a base material ;
A coating layer covering the surface of the core particle, comprising a monomer unit A having a silicone chain as a side chain and an ethylenically unsaturated group, a vinyloxy group, a hydroxymethyl group, an alkoxymethyl group, an oxazolyl group, and an alkoxysilyl group A monomer unit B having at least one self-crosslinkable group selected from the group consisting of a side chain, and the self-crosslinkable group of the monomer unit B is a functional group that does not generate a hydroxyl group by crosslinking. A coating layer containing a crosslinked polymer;
Colored particles having   The colored particles according to claim 1, wherein the self-crosslinking group of the monomer unit B of the second polymer is a vinyloxy group. The second polymer further has a monomer unit C having a functional group capable of cross-linking with the self-crosslinkable group of the monomer unit B, and the self-crosslinkable group of the monomer unit B and the monomer unit C The colored particles according to claim 1 or 2 , wherein a hydroxyl group is not generated by crosslinking with a functional group. The colored particles according to claim 3 , wherein the self-crosslinkable group of the monomer unit B is a vinyloxy group or an oxazolyl group, and the functional group of the monomer unit C of the second polymer is a carboxyl group. The colored particles according to any one of claims 1 to 4 , wherein the first polymer further includes a monomer unit α having a functional group capable of crosslinking with a self-crosslinkable group of the monomer unit B of the second polymer in a side chain. . A group of particles containing the colored particles according to any one of claims 1 to 5 ,
A dispersion medium for dispersing the particle group;
A colored particle dispersion having: The colored particle dispersion according to claim 6 , wherein the dispersion medium is a silicone oil or a paraffinic hydrocarbon solvent. The colored particle dispersion according to claim 6 or 7 , wherein the particle group is composed of a plurality of types of colored particles having different charging polarities. A pair of substrates, at least one of which is translucent,
The colored particle dispersion liquid according to any one of claims 6 to 8 , encapsulated between the pair of substrates,
A display medium comprising: A display medium according to claim 9;
Voltage applying means for applying a voltage between the pair of substrates of the display medium;
A display device comprising: A pair of electrodes, at least one of which is translucent,
A region having the colored particle dispersion according to any one of claims 6 to 8 , provided between the pair of electrodes,
A display medium comprising: A display medium according to claim 11 ;
Voltage applying means for applying a voltage between the pair of electrodes of the display medium;
A display device comprising: A first polymer having a chargeable group, a colorant, a first solvent, and a first polymer having a chargeability group that is incompatible with the first solvent and has a lower boiling point than the first solvent. A step of stirring and emulsifying the mixed solution containing the second solvent,
Removing the second solvent from the emulsified mixed solution to produce core particles containing the first polymer having the chargeable group and the colorant;
At least one selected from the group consisting of the core particles, a monomer unit A having a silicone chain as a side chain, and an ethylenically unsaturated group, vinyloxy group, hydroxymethyl group, alkoxymethyl group, oxazolyl group, and alkoxysilyl group And a second polymer having a monomer unit B having a self-crosslinkable group in the side chain, and the self-crosslinkable group of the monomer unit B being a functional group that does not generate a hydroxyl group by crosslinking, Coating the surface of the core particle with a crosslinked body of the second polymer by crosslinking two polymers;
The manufacturing method of the colored particle which has this. The method for producing colored particles according to claim 13 , wherein the first solvent is a silicone oil or a paraffinic hydrocarbon solvent.