JP5251940B2 - Method for producing electrophoretic particles - Google Patents

Description

  The present invention relates to a method for producing electrophoretic particles, a method for producing an electrophoretic particle dispersion, and an image display medium and an image display device using the electrophoretic particle dispersion produced by the method for producing an electrophoretic particle dispersion. About.

  There is a great need for a paper-like image display medium that can be rewritten with the advantages of both display and hard copy. Among these, those using electrophoretic elements are excellent in terms of display quality and power consumption during display operation. An electrophoretic display medium is formed by enclosing a dispersion liquid in which a plurality of electrophoretic particles having a color different from the color of a dispersion medium are dispersed in a colored dispersion medium between a pair of transparent electrodes. . In this case, the electrophoretic particles (hereinafter also referred to as “electrophoretic particles”) have a charge on the surface in the dispersion medium, and a voltage opposite to the charge of the electrophoretic particles is applied to one of the transparent electrodes. In such a case, the migrating particles are deposited there, and the color of the migrating particles is observed. When a voltage having the same direction as the charge of the migrating particles is applied, the migrating particles move to the opposite side, so the color of the dispersion medium changes. Observed. As a result, display can be performed.

  The electrophoretic particles are required to have optical properties such as white and coloring relating to display and non-display states, and good charging performance to move quickly in response to an external electric field. Of these, various kinds of organic pigments and inorganic pigments have been conventionally used as the particles having the above optical properties, and these are used as they are or after adding an additive such as a particle dispersant to improve dispersion stability. (See Patent Document 1). However, the pigment is generally not a perfect insulator, and its volume resistivity is smaller than that of an insulator. Therefore, it is difficult to migrate well along the direction of the electric field in the range of the external electric field in electrophoretic display, and in particular, it is inferior in terms of repeated stability of display switching.

  On the other hand, various kinds of polymers are preferable as the insulating charged particles, and many particles migrate well even with an external electric field. However, polymers do not have white or colored particles with satisfactory optical functions as display materials. In order to satisfy these two requirements, it has been conventionally performed to use a composite of the above pigment and polymer by heating and melting (see Patent Document 2). However, in this case, the above problem cannot be solved because the pigment is not completely encapsulated in the polymer but is also present on the surface to some extent.

  As an attempt to solve the above problem, a dispersion composition in which a particulate material is dispersed in an organic solvent and a self-dispersing polymer compound is adsorbed on the outer surface of the particulate material is disclosed ( (See Patent Document 3). However, this particle dispersion composition is prepared by adding a particulate material to the polymer compound dissolved in the good solvent in the production method, and further adding a poor solvent for the polymer compound to precipitate the polymer compound. Therefore, it is difficult to control the equilibrium of dissolution and precipitation in the two-solvent system of the polymer compound, and in order to stably disperse the polymer compound in the poor solvent without aggregation, There is a problem that the composition is very limited and the room for selecting a good solvent is limited.

  On the other hand, a method has been reported in which a pigment and a monomer are added to an organic solvent and a reaction is performed in the organic solvent to form a polymer layer on the pigment surface (see Non-Patent Document 1). However, in this case, the reaction solvent used is methanol, which is a polar organic solvent, and the resulting particles are particles that are stably dispersed in methanol. Therefore, it is difficult to stably disperse with an insulating organic solvent used in electrophoretic display, and if a particle dispersant is added for stabilization, a very large amount of use is required. There is a problem that the electrophoretic properties are impaired.

  This invention is made | formed in view of this present condition, and makes it a subject to solve the said various problems in the past and to achieve the following objectives. That is, the present invention provides a method for producing an electrophoretic particle, a method for producing an electrophoretic particle dispersion, and the electrophoretic particle capable of easily producing an electrophoretic particle excellent in dispersion stability and chargeability. It is an object of the present invention to provide an image display medium and an image display device that use an electrophoretic particle dispersion produced by a method for producing a dispersion.

  As a result of intensive studies to solve the above problems, the present inventor used a particle dispersant having both a pigment-adsorptive functional group and a solvent-affinity site, and the particle dispersant was adsorbed on solid particles. It has been found that solid particles are stably dispersed in the nonpolar solvent without agglomeration due to the steric effect resulting from the solvent affinity site of the dispersant. When the polymerization reaction of the monomer soluble in the solvent is carried out in the solid particle dispersion in such a state, when both the generated polymer particles and the particle dispersant have an acidic group, the generated polymer fine particles are formed on the surface of the solid particles. Adsorbed, composite particles with a solid particle surface coated with a polymer fine particle layer are obtained, and this composite particle has good dispersion stability and insulation due to the steric effect of the outer polymer particle layer in a nonpolar solvent. It has been found that it has good charging characteristics. In addition, since the solid particles are initially dispersed in the state of primary particles, the resulting composite particles become a composite particle having a fine particle size with the primary particles of the solid particles as nuclei, and the composite particles dispersed by dispersing the composite particles When the liquid is used for an image display medium utilizing an electrophoretic phenomenon, it has been found that an image display medium capable of responding at high speed with a low voltage can be obtained because it has good chargeability and is not easily subjected to viscous resistance accompanying migration.

The present invention is based on the above findings of the present inventors, and means for solving the above problems are as follows. That is,
<1> A pigment dispersion step in which a pigment is dispersed in the nonpolar solvent using a particle dispersant that is soluble in at least a nonpolar solvent and has both a pigment-adsorbing functional group and a solvent affinity site; And a polymer generation step of adding a monomer soluble in at least the nonpolar solvent to carry out a polymerization reaction and generating an insulating polymer having the same functional group as the particle dispersant insoluble in the nonpolar solvent. A method for producing electrophoretic particles, wherein the polymer obtained is heteroaggregated on the pigment surface. In the method for producing electrophoretic particles according to <1>, since the insulating polymer is aggregated on the surface of the pigment, it is possible to easily produce the electrophoretic particles having excellent dispersion stability and chargeability. it can.
<2> The method for producing electrophoretic particles according to <1>, wherein the pigment has basicity and the particle dispersant has an acidic group. In the method for producing electrophoretic particles according to <2>, insulating polymer particles having an acidic group are aggregated on the surface of a basic pigment. Thereby, electrophoretic particles excellent in dispersion stability and chargeability can be produced.
<3> The method for producing electrophoretic particles according to any one of <1> to <2>, wherein the pigment is a metal oxide treated with a silane coupling agent having a basic group. In the method for producing electrophoretic particles according to <3>, the efficiency of aggregation of polymer fine particles on the surface of metal oxide particles is increased. As a result, electrophoretic particles having more excellent dispersion stability and chargeability can be produced.
<4> The method for producing electrophoretic particles according to <1>, wherein the pigment is a metal oxide, and the particle dispersant and the monomer both contain at least an amino group. In the method for producing electrophoretic particles according to <4>, since the pigment is a metal oxide and both the particle dispersant and the at least one monomer contain an amino group, the polymer is high on the surface of the metal oxide. Aggregate with aggregation efficiency. This makes it possible to produce a particle dispersion in which a metal oxide that is difficult to stably disperse in a nonpolar solvent is stably dispersed with good chargeability.
<5> The method for producing electrophoretic particles according to any one of <1> to <4>, wherein a monomer having at least one functional group of the same type as the functional group of the particle dispersant is used. In the method for producing electrophoretic particles according to <5>, since a monomer having a functional group of the same type as the particle-adsorbing functional group of the particle dispersant is used, the efficiency of polymer aggregation on the pigment surface is increased. As a result, electrophoretic particles having more excellent dispersion stability and chargeability can be produced.
<6> The method for producing electrophoretic particles according to any one of <1> to <5>, wherein the produced polymer is a copolymer containing a compatible monomer that is compatible with a nonpolar solvent. In the method for producing electrophoretic particles according to <6>, since the produced polymer is a copolymer having a monomer that is soluble in a nonpolar solvent as a component, the surface of the electrophoretic particles is partially compatible with the solvent. Electrophoretic particles that have a soluble component, have the steric effect, and have excellent dispersion stability can be produced.
<7> The method for producing electrophoretic particles according to <6>, wherein the compatible monomer is a macromer. In the method for producing electrophoretic particles according to <7>, since the compatible monomer is a macromer, the solvent-compatible site has a comb structure, and thus the steric effect is further increased. As a result, electrophoretic particles having further excellent dispersion stability can be produced.
<8> The electrophoretic particle according to any one of <6> to <7>, wherein the nonpolar solvent is silicone oil, and the compatible monomer is a silicone macromer represented by the following structural formula (1): It is a manufacturing method. In the method for producing electrophoretic particles according to <8>, the nonpolar organic solvent is a silicone oil, and the compatible monomer is a silicone macromer represented by the general formula (I). Thereby, it is possible to produce electrophoretic particles having excellent dispersion stability and chargeability with respect to an electrophoretic display medium using silicone oil as a dispersion medium.
However, 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. n represents a natural number, and x represents an integer of 1 to 3.

<9> A method for producing an electrophoretic particle dispersion, comprising the step of producing an electrophoretic particle according to any one of <1> to <8>, and a step of dispersing the electrophoretic particle in a nonpolar organic solvent. .
<10> The method for producing an electrophoretic particle dispersion liquid according to <9>, further including a particle dispersant that disperses the electrophoretic particles. In the electrophoretic particle dispersion liquid produced by the production method according to <10>, the electrophoretic particle dispersion liquid further contains a particle dispersing agent that disperses the electrophoretic particles. An electrophoretic particle dispersion that can be stably dispersed can be provided.
<11> The method for producing an electrophoretic particle dispersion according to any one of <9> to <10>, wherein the nonpolar organic solvent is colored by dissolving a dye having a different color from the electrophoretic particles.
<12> The method for producing an electrophoretic particle dispersion according to any one of <9> to <11>, wherein two or more electrophoretic particles having different colors and charges are dispersed in a colorless and transparent nonpolar organic solvent. It is.

<13> A pair of electrode substrates, and an electrophoretic particle dispersion produced by the method for producing an electrophoretic particle dispersion according to any one of <9> to <12> between at least one pair of electrode substrates An image display medium comprising a liquid. The image display medium according to <13> includes a particle dispersion in which electrophoretic particles excellent in dispersion stability and chargeability are dispersed. Therefore, an image excellent in long-term stability and display response. A display medium can be provided.
<14> The image display medium according to <13>, wherein the electrophoretic particle dispersion is contained in a microcapsule.

  <15> An image display device using the image display medium according to <14> as a display unit. In the image display device according to <15>, since it contains a particle dispersion in which electrophoretic particles excellent in dispersion stability and chargeability are dispersed, an image excellent in long-term stability and display response. A display device can be provided.

  According to the present invention, various problems in the prior art can be solved, and an electrophoretic particle manufacturing method and an electrophoretic particle dispersion manufacturing method that can easily manufacture electrophoretic particles excellent in dispersion stability and chargeability, In addition, it is possible to provide an image display medium and an image display device that use the electrophoretic particle dispersion produced by the method for producing the electrophoretic particle dispersion.

FIG. 1 is a cross-sectional view of an image display medium showing an embodiment of the present invention. FIG. 2 is a cross-sectional view of an image display medium showing another embodiment of the present invention. FIG. 3 is a schematic diagram of an image display device showing an embodiment of the present invention.

(Production method of composite particles and composite particle dispersion)
The method for producing composite particles of the present invention comprises a solid particle dispersion step and a polymer production step, and further comprises other steps as necessary.
In the present invention, the solid particles are dispersed in the nonpolar solvent without being aggregated by the particle dispersant. In this state, a monomer that is soluble in a nonpolar solvent is added for polymerization, and when a polymer insoluble in the nonpolar solvent is precipitated at the interface between the solid particles and the nonpolar solvent, the polymer is heteroaggregated on the surface of the solid particles. Composite particles are obtained.
The composite particle dispersion of the present invention is obtained by dispersing composite particles produced by the method for producing composite particles of the present invention in a nonpolar solvent.
Hereinafter, the details of the composite particle dispersion of the present invention will be clarified through the description of the method for producing composite particles of the present invention.

-Solid particle dispersion process-
The solid particle dispersion step is a step of dispersing solid particles in the nonpolar solvent using a particle dispersant soluble in the nonpolar solvent.

  The nonpolar solvent is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include paraffinic hydrocarbons such as pentane, hexane, heptane, octane, nonane, decane and dodecane; isohexane, isooctane and isododecane. Isoparaffin hydrocarbons such as liquid paraffin; alkyl naphthene hydrocarbons such as liquid paraffin; aromatic hydrocarbons such as benzene, toluene, xylene, alkylbenzene, and solvent naphtha; and silicone oil. These nonpolar solvents can be used alone or in combination of two or more.

Preferred examples of the silicone oil include dialkyl silicone oils such as dimethyl silicone oil; cyclic dialkyl silicone oils; alkylphenyl silicone oils; cyclic alkylphenyl silicone oils; alkyl aralkyl silicone oils, and the like.
Examples of the alkylphenyl silicone oil include methylphenyl silicone oil, ethylphenyl silicone oil, propylphenyl silicone oil, butylphenyl silicone oil, hexylphenyl silicone oil, octylphenyl silicone oil, laurylphenyl silicone oil, stearylphenyl silicone oil, Etc.
Examples of the cyclic alkylphenyl silicone oil include cyclic polymethylphenylsiloxane, cyclic polyethylphenylsiloxane, cyclic polybutylphenylsiloxane, cyclic polyhexylphenylsiloxane, cyclic polymethylchlorophenylsiloxane, and cyclic polymethylbromophenylsiloxane. Can be mentioned.

  As the solid particles, various organic pigments and inorganic pigments having surface basicity can be used. Here, the basicity of the solid particles is a measure of the acid basicity of the particles that can be examined by a back titration method (see, for example, Color Material Association Vol. 61 p. 692, 1988). In the present invention, the solid particles are particles in which a base is detected by the above method, but are preferably particles in which the equivalent of the base is larger than the equivalent of the acid.

  It is preferable that the solid particles have basicity and the particle dispersant has an acidic group. For solid particles having basic properties, the solid particles having basicity can be dispersed stably in a solvent because the dispersant having an acidic group is strongly adsorbed by acid-base interaction. Insulating polymer particles having acidic groups on the surface thereof aggregate to provide composite particles excellent in dispersion stability and chargeability.

  Moreover, it is preferable that the said solid particle is what processed the metal oxide with the silane coupling agent which has a basic group. When the solid particles are those obtained by treating a metal oxide with a silane coupling agent having a basic group, the efficiency of aggregation of polymer fine particles on the surface of the metal oxide particles is increased, and the dispersion stability and chargeability are more excellent. Composite particles can be provided.

  Examples of the silane coupling agent having a basic group include N-2 (aminoethyl) 3-aminopropylmethyldimethoxysilane, N-2 (aminoethyl) 3-aminopropyltrimethoxysilane, and N-2 (amino Ethyl) 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N-phenyl- 3-aminopropyltrimethoxysilane, and the like.

  Examples of the metal oxide include silicon dioxide, aluminum oxide, titanium oxide, and zinc oxide. The coupling treatment can clearly impart basicity to the surface of the metal oxide particles, and polymer fine particles having acidic groups are adsorbed well on the surface of the solid particles to obtain organic / inorganic composite particles containing an inorganic substance. be able to. In addition, since both the particle dispersant and the polymer particle have an acidic group, the interaction between the two is small, and the particle dispersant does not act as an aggregating agent for the polymer particle, so that it is well dispersed in a nonpolar organic solvent. Composite particles are obtained.

In the composite particle manufacturing method, it is preferable that the solid particle is a metal oxide, and both the particle dispersant and a monomer described later contain at least an amino group. This is because the particle dispersant and the amino group of the polymer are favorably adsorbed on the surface of the metal oxide, making it possible to obtain composite particles having the primary particles of the metal oxide as nuclei.
As said metal oxide, the same thing as the above can be used.

As the solid particles, colored solid particles can be used, and the color of the colored solid particles is not particularly limited and can be appropriately selected according to the purpose. For example, white particles, black particles, color particles , Etc. These may be used individually by 1 type and may use 2 or more types together.
As the white particles, the metal oxide can be used.
As the black colored particles, for example, carbon black, aniline black, furnace black, lamp black and the like can be used.
Examples of the color particles include cyan colored particles, magenta colored particles, yellow colored particles, and the like. Examples of the cyan colored particles include phthalocyanine blue, methylene blue, Victoria blue, methyl violet, aniline blue, and ultramarine blue. Examples of the magenta colored particles include rhodamine 6G lake, dimethylquinacridone, watching red, rose bengal, rhodamine B, alizarin lake, and the like. Examples of the yellow colored particles include chrome yellow, benzidine yellow, hansa yellow, naphthol yellow, molybdenum orange, quinoline yellow, and tartrazine.

  There is no restriction | limiting in particular in the average particle diameter of the said solid particle, According to the objective, it can select suitably, 0.1-10 micrometers is preferable.

  The particle dispersant is a compound that is soluble in a solvent in a particle dispersion and has an adsorptivity to the particles when the particles are present, and the particles are aggregated due to electrostatic repulsion or the steric effect of the dispersant molecules. It is something to prevent. In the non-aqueous solvent, the particles are stably dispersed, and a particle dispersion having good dispersibility can be obtained. As the particle dispersant, among surfactants used as known particle dispersants, those soluble in a nonpolar solvent can be used, and polymer dispersants are preferable. This is because the dispersion stability of the particles particularly in the nonpolar organic solvent system is largely due to the steric effect of the polymer compound.

Preferred examples of the polymer dispersant include a polymer dispersant having an acidic group and a polymer dispersant having a basic group.
Examples of the polymeric dispersant having an acidic group include (meth) acrylic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, fumaric acid, cinnamic acid, crotonic acid, vinylbenzoic acid, 2 -Methacryloxyethyl succinic acid, 2-methacryloxyethyl maleic acid, 2-methacryloxyethyl hexahydrophthalic acid, 2-methacryloxyethyl trimellitic acid, vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, 2-sulfoethyl At least one monomer having an acidic group such as methacrylate, 2-acrylamido-2-methylpropanesulfonic acid, 3-chloroamidophosphoxypropyl methacrylate, 2-methacryloxyethyl acid phosphate, hydroxystyrene, and the like (meth) described later Alkyl ester of acrylic acid A polymer obtained from at least one of the ether or aryl ester, and the like.
In addition, these can synthesize | combine resin soluble in a nonpolar organic solvent by adjusting suitably the kind of monomer to combine, and the compounding ratio at the time of superposition | polymerization.
Examples of the polymeric dispersant having a basic group include N-methylaminoethyl (meth) acrylate, N-ethylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N , N-diethylaminoethyl (meth) acrylate, N, N-dibutylaminoethyl acrylate, N, N-di-tert-butylaminoethyl acrylate, N-phenylaminoethyl methacrylate, N, N-diphenylaminoethyl methacrylate, aminostyrene , Dimethylaminostyrene, N-methylaminoethylstyrene, dimethylaminoethoxystyrene, diphenylaminoethylstyrene, N-phenylaminoethylstyrene, 2-N-piperidylethyl (meth) acrylate, 2-vinylpyridine, 4-vinylpi A polymer obtained from at least one monomer having a basic group such as gin and 2-vinyl-6-methylpyridine and at least one alkyl ester or aryl ester of (meth) acrylic acid described later, and the like. Can be mentioned.
In addition, these can synthesize | combine resin soluble in a nonpolar organic solvent by adjusting suitably the kind of monomer to combine, and the compounding ratio at the time of superposition | polymerization.

-Polymer production process-
The polymer generation step is a step of adding a monomer soluble in the nonpolar solvent to the dispersion and performing a polymerization reaction to generate a polymer insoluble in the nonpolar solvent.

  As the monomer soluble in the nonpolar solvent, at least one kind is a known thermoplastic resin whose homopolymer is insoluble in the nonpolar solvent, and is soluble in the nonpolar solvent among the monomers constituting the thermosetting resin. If the nonpolar solvent is a hydrocarbon solvent, for example, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, Lauryl (meth) acrylate, stearyl (meth) acrylate, vinyl laurate, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) Acrylate, phenyl (meth) acrylate, Len, vinyl toluene, vinyl acetate, divinyl benzene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol tri (meth) acrylate, butanediol di (meth) acrylate, 1,6-hexanediol di (Meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, dipropylene glycol di (meth) acrylate, trimethylolhexane tri (meth) acrylate, Pentaeri slit tetra (meth) acrylate, 1,3-dibutylene glycol di (meth) acrylate, trimethylolethane tri (meth) acrylate, etc. Can be mentioned. Moreover, the copolymer which combined several types of monomer may be sufficient. In addition, these can synthesize | combine a polymer insoluble in a nonpolar solvent by determining suitably the kind of monomer to combine, and the compounding ratio at the time of superposition | polymerization.

  In the method for producing the composite particle, by using a monomer having a functional group of the same type as the functional group adsorbed on the solid particle, the polymer is favorably adsorbed on the solid particle, and the particle dispersant and the polymer are of the same kind. This is because by having a functional group, the interaction between the two is small and the particle dispersant does not act as a polymer flocculant, so that composite particles that are well dispersed in a nonpolar solvent can be obtained.

  There is no restriction | limiting in particular as said adsorption functional group, According to the objective, it can select suitably, For example, polar groups, such as a carboxyl group, an amide group, a cyano group, an amino group, and a hydroxyl group, are mentioned. Examples of the monomer having an adsorptive functional group include 2-hydroxyethyl (meth) acrylate, 2,3-dihydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxy-3-propyl ( (Meth) acrylate, 2-chloroethyl (meth) acrylate, 2,3-dibromopropyl (meth) acrylate, (meth) acrylonitrile, isobutyl-2-cyanoacrylate, 2-cyanoethyl acrylate, ethyl-2-cyanoacrylate, methacrylacetone, Vinylpyrrolidone, N-acryloylmorpholine, tetrahydrofurfuryl methacrylate, trifluoroethyl methacrylate, p-nitrostyrene, acrylamide, methacrylamide, N, N-dimethylmethacrylamide, N, N -Dibutylmethacrylamide, the monomer which has the said acidic group, the monomer which has the said basic group, etc. are mentioned.

  In the method for producing composite particles, it is preferable that the generated polymer is a copolymer containing a compatible monomer that is compatible with a nonpolar solvent. This is because the polymer component on the surface of the composite particle produced thereby has a component that is partially compatible with the solvent, so that the dispersion stability of the composite particle is increased by the steric effect.

  In the method for producing the composite particles, the compatible monomer is preferably a macromer. The macromer is a polymer having reactivity. In particular, a polymer of a one-end reaction type radical polymerization macromer has a comb structure in which many side chains are bonded to the main chain. This is because when the comb structure portion has a property of being compatible with a solvent, a large steric effect is imparted to the resulting composite particles, and the dispersion stability is further increased.

  Examples of the macromer include, for the hydrocarbon solvent, one-end methacryloyl group-modified polymethyl methacrylate, one-end methacryloyl group-modified polyethyl methacrylate, one-end methacryloyl group-modified polybutyl methacrylate, one-end methacryloyl. Examples thereof include group-modified polyoctyl methacrylate, one-end methacryloyl group-modified polydecyl methacrylate, and the like.

  In the composite particle manufacturing method, it is preferable that the nonpolar solvent is a silicone oil and the compatible monomer is a silicone macromer represented by the following structural formula (1).

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, preferably having 1 to 4 carbon atoms, and examples thereof include a methyl group, an ethyl group, and a propyl group. n represents a natural number, for example, preferably 2 to 200, more preferably 5 to 100. x represents an integer of 1 to 3.

  Since both the nonpolar solvent and the macromer are silicone-based, composite particles having excellent dispersion stability and chargeability with respect to an electrophoretic display medium using silicone oil as the nonpolar solvent can be obtained. .

(Composite particle dispersion)
The composite particle dispersion of the present invention is obtained by dispersing composite particles produced by the above-described method for producing composite particles in a nonpolar organic solvent. The nonpolar organic solvent may be a solvent used in the manufacturing process of the composite particles, or may be a dispersion of the composite particles once recovered and dried in another nonpolar organic solvent. .

  The composite particle dispersion preferably further contains a particle dispersant for dispersing the composite particles. As the particle dispersant, among the surfactants used as known particle dispersants, those soluble in a nonpolar organic solvent can be used, and are preferably polymer dispersants. The same manufacturing process can be used.

  The nonpolar organic solvent differs depending on the composite particles used and cannot be defined unconditionally, but may be colorless and transparent, or may be colored by dissolving a dye having a color different from that of the composite particles. For example, (1) The nonpolar organic solvent is preferably colored by dissolving a dye having a color different from that of the composite particles from the viewpoint of increasing display contrast. (2) Two or more kinds of composite particles having different colors and chargeability are preferably dispersed in a colorless and transparent nonpolar organic solvent.

  Examples of the dye include azo dyes, anthraquinone dyes, phthalocyanine dyes, triallylmethane dyes, and the like. Examples of these dyes include spirit black (SB, SSBB, AB), nigrosine base (SA, SAP, SAPL, EE, EEL, EX, EXBP, EB), and oil yellow (105, 107, 129, 3G, GGS). , Oil Orange (201, PS, PR), Fast Orange, Oil Red (5B, RR, OG), Oil Scarlet, Oil Pink 312, Oil Violet # 730, Macrolex Blue RR, Sumiplast Green G, Oil Brown (GR 416), Sudan Black X60, Oil Green (502, BG), Oil Blue (613, 2N, BOS), Oil Black (HBB, 860, BS), Bali First Yellow (1101, 1105, 3108, 4120), Bali First o Orange (3209, 3210), Bali first red (1306, 1355, 2303, 3304, 3306, 3320), Bali first pink 2310N, Bali first brown (2402, 3405), Bali first blue (3405, 1501, 1603, 1605) 1607, 2606, 2610), Bali first violet (1701, 1702), Bali first black (1802, 1807, 3804, 3810, 3820, 3830), and the like.

(Image display medium)
The image display medium of the present invention comprises a pair of electrode substrates and at least the composite particle dispersion of the present invention between the pair of electrode substrates, and a voltage is applied between the pair of electrode substrates. An image is displayed by electrophoresis of composite particles.
In this case, it is preferable that at least one of the pair of electrode substrates is light transmissive.
In the image display medium of the present invention, the dispersion medium may be separated into a minute space between a pair of substrates by partition walls or microcapsules in order to suppress aggregation and bias of particles in the dispersion medium.

-Electrode substrate-
Although there is no restriction | limiting in particular as said electrode substrate, Usually, the electrode substrate etc. which formed the conductive layer on the board | substrate which consists of glass, plastics, etc. are mentioned.
Examples of the material of the plastic substrate include acrylic resin, polycarbonate resin, and epoxy resin.
There is no restriction | limiting in particular as said conductive layer, Although it can select suitably according to the objective, A transparent conductive layer is preferable. The conductive layer can be formed of, for example, indium oxide, indium tin oxide (ITO), tin oxide, or the like.

-Other components-
Examples of the other members include a metal reflection plate, a light diffusion plate, and an antireflection layer. These may be used alone or in combination of two or more.
A TFT or the like may be further attached to the electrode substrate (lower substrate).

  Here, an embodiment of the image display medium of the present invention will be described with reference to FIG. In FIG. 1, 1 and 2 are conductive layers, at least one of which is light transmissive. 3 is a microcapsule. However, the microcapsule is not an essential requirement, and may be an embodiment in which the particle dispersion is sealed in a cell provided with fine partition walls by photolithography or the like. Reference numeral 4 denotes white or colored particles. As the white or colored particles, composite particles produced by the method for producing composite particles of the present invention are used. Reference numeral 5 denotes a colored dispersion medium in which the nonpolar organic solvent is colored white or a color different from that of the colored composite particles. In order to control the dispersibility of the dispersed particles, a dispersant or the like may be added to the colored dispersion medium as necessary. Reference numeral 6 denotes an adhesive support layer, which preferably holds the microcapsule 3 between the conductive layers 1 and 2 and is transparent and excellent in electrical insulation. A solvent-free curable material is particularly preferable.

  If a power supply electrode is brought into contact with a part of the conductive layers 1 and 2, an electric field can be generated between the conductive layers 1 and 2, so that white or colored particles can move reliably. In order to perform the display, voltage applying means between the conductive layers 1 and 2 may be prepared, which is convenient. In any case, it is preferable to divide the two electrodes by a large number of fine cells because it can prevent the deviation of particles and the aggregation of particles due to gravity.

  FIG. 2 is a diagram showing another embodiment of the image display medium of the present invention. In FIG. 2, reference numerals 1 and 2 denote conductive layers, at least one of which is light transmissive. The same material as described above can be used for the conductive layer. 4a and 4b are white or colored particles, and the colors and charging polarities of 4a and 4b are different from each other. 7 is a nonpolar organic solvent, preferably colorless and transparent. This is because the contrast of the image based on the color difference between the white or colored particles 4a and 4b is not adversely affected. In order to control the dispersibility of the dispersed particles, a dispersant or the like is preferably added to the nonpolar organic solvent 7 as necessary. As the white or colored particles constituting the composite particle dispersion, composite particles produced by the method for producing composite particles of the present invention are used, and two different colored composite particles are used. If the power supply electrode is brought into contact with a part of the conductive layers 1 and 2, an electric field can be generated between the conductive layers 1 and 2, and the two kinds of particles 4 a and 4 b can reliably move in the opposite directions. In order to perform the display, voltage applying means between the conductive layers 1 and 2 may be prepared, which is convenient.

The image display medium of the present invention is produced, for example, by applying a mixture obtained by mixing the composite particle dispersion-containing microcapsules obtained above and an adhesive serving as an adhesive support layer to an electrode substrate and bonding the counter electrode substrate together. can do.
The coating method is not particularly limited and may be appropriately selected depending on the intended purpose. For example, a known coating film forming method such as blade, wire bar, dipping, spin coating can be used, and an image display medium can be easily used. It can be manufactured.

  In the image display medium of the present invention, since a particle dispersion in which composite particles having excellent dispersion stability and chargeability are dispersed is used, an image display medium having excellent long-term stability and display response is provided. Can do.

(Image display device)
The image display device of the present invention uses the image display medium of the present invention as a display means, and includes a drive circuit, an arithmetic circuit, an internal memory, a power source, and other means as required.
Since the image display device of the present invention contains a composite particle dispersion in which composite particles excellent in dispersion stability and chargeability are dispersed, an image display device excellent in long-term stability and display response is provided. be able to.
Here, FIG. 3 is a schematic view showing an example of the image display apparatus of the present invention. As shown in FIG. 3, the image display device 10 includes an image display medium 11, a housing 12, information input means 13, a drive circuit, an arithmetic circuit, an internal memory, a power source, and the like that are not shown. The electrodes in the image display medium 11 in FIG. 3 form a dot matrix, and can display an image as a whole by displaying ON a designated dot.

  The present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

Example 1
-Production of composite particles-
In a reaction vessel equipped with a stirrer, a thermometer and a reflux condenser, 200 parts by mass of hexane was accommodated and heated to 50 ° C. A solution consisting of 19 parts by weight of dodecyl methacrylate, 1 part by weight of dimethylaminoethyl methacrylate and 0.1 part by weight of azobisdimethylvaleronitrile was added dropwise thereto. When the reaction was terminated by stirring at 50 ° C. for 4 hours, a uniform and transparent amino group-containing resin solution was obtained.
Next, in a reaction vessel equipped with a stirrer, a thermometer, and a reflux condenser, 20 parts by mass of the amino group-containing resin solution, 75 parts by mass of hexane, and 5 parts by mass of titanium oxide (CR-90, manufactured by Ishihara Sangyo Co., Ltd.) The particle dispersions which were combined and dispersed with a homogenizer were added and heated to 50 ° C. A solution consisting of 8 parts by weight of methyl methacrylate, 1 part by weight of dodecyl methacrylate, 1 part by weight of dimethylaminoethyl methacrylate and 0.1 part by weight of azobisdimethylvaleronitrile was added dropwise thereto. Subsequently, it stirred at 50 degreeC for 4 hours, reaction was complete | finished, only the solid component was collect | recovered, and the titanium oxide-amino group containing resin composite particle was produced.

-Preparation of composite particle dispersion-
An aqueous solution in which 10 parts by mass of urea, 1 part by mass of resorcinol and 10 parts by mass of an ethylene-maleic anhydride copolymer were dissolved in 290 parts by mass of water was adjusted to pH 3.5 with an aqueous sodium hydroxide solution.
Separately, 1 part by mass of the titanium oxide-amino group-containing resin composite particle is added to 30 parts by mass of a saturated solution of an isoparaffin-based hydrocarbon solvent (Exxon Chemical Co., Ltd., Isopar H) dye (Bayer, Macrolex Blue RR), Ultrasonic dispersion was performed to prepare a particle dispersion. This particle dispersion was added to the above aqueous solution, and further 25 parts by mass of a formaldehyde solution was added, followed by heating and stirring at 50 ° C. for 3 hours to produce microcapsules. After completion of the reaction, the microcapsules were collected by suction filtration, washing with water and drying.

-Fabrication and operation of image display media-
The obtained microcapsules were dispersed in an ultraviolet curable epoxy resin (trade name: manufactured by ThreeBond Co., Ltd., 3121) and applied on a glass substrate with an ITO electrode with a wire bar. Next, the coating film was sandwiched with another ITO electrode so that the distance between the electrodes was 100 μm, and then cured by irradiation with ultraviolet rays. Thus, an image display medium was produced.

<Performance evaluation>
When a voltage of −100 V was applied to the upper ITO electrode of the obtained image display medium, the titanium oxide-amino group-containing resin composite particles were quickly electrodeposited on the upper electrode and looked white when viewed from the upper substrate surface. Next, when a voltage of +100 V is applied to the upper electrode, the titanium oxide-amino group-containing resin composite particles move to the lower electrode, and when viewed from the upper substrate side, the colored state caused by the color of the dye in the nonpolar organic solvent It was seen clearly. Further, these display changes were repeated 100 times, but no display deterioration was observed.

(Comparative Example 1)
-Fabrication and operation of image display media-
In Example 1, an image display medium was produced in the same manner as in Example 1 except that titanium oxide was used instead of the titanium oxide-amino group-containing resin composite particles.
<Performance evaluation>
With respect to the obtained image display medium, the display was switched by applying a voltage, but when it was repeated 10 times, the particles aggregated and did not migrate well in the electric field direction.

(Example 2)
-Production of composite particles-
In a reaction vessel equipped with a stirrer, a thermometer and a reflux condenser, 200 parts by mass of silicone oil (manufactured by Toray Dow Corning Silicone Co., Ltd., SH200 1cs) was taken and heated to 50 ° C. A solution consisting of 19 parts by weight of methacryloxypropyl-modified silicone, 1 part by weight of dimethylaminoethyl methacrylate, and 0.1 part by weight of azobisdimethylvaleronitrile was added dropwise thereto. When the reaction was terminated by stirring at this temperature for 4 hours, a uniform and transparent amino group-containing resin solution was obtained.
Next, in a reaction vessel equipped with a stirrer, a thermometer and a reflux condenser, 20 parts by mass of the amino group-containing resin solution, 75 parts by mass of silicone oil, and titanium oxide (CR-90, manufactured by Ishihara Sangyo Co., Ltd.) 5 A particle dispersion liquid in which the mass parts were combined and dispersed with a homogenizer was added and heated to 50 ° C. A solution consisting of 8 parts by weight of methyl methacrylate, 1 part by weight of methacryloxypropyl-modified silicone, 1 part by weight of dimethylaminoethyl methacrylate, and 0.1 part by weight of azobisdimethylvaleronitrile was added dropwise thereto. The reaction was terminated by stirring at this temperature for 4 hours, and only the solid component was recovered and dried to prepare titanium oxide-amino group-containing resin composite particles.

-Preparation of composite particle dispersion-
In a reaction vessel equipped with a stirrer, a thermometer and a reflux condenser, 200 parts by mass of silicone oil was taken and heated to 50 ° C. A solution consisting of 19.9 parts by weight of methacryloxypropyl-modified silicone, 0.1 part by weight of methacrylic acid, and 0.1 part by weight of azobisdimethylvaleronitrile was added dropwise thereto. When the reaction was terminated by stirring at this temperature for 4 hours, a uniform and transparent resin solution was obtained.
As a particle dispersion, 69 parts by mass of silicone oil and 20 parts by mass of the composite particle dispersant, 10 parts by mass of the titanium oxide-amino group-containing resin composite particles, and 1 part by mass of black titanium oxide (titanium black) are combined. A microcapsule was prepared in the same manner as in Example 1 except that an ultrasonic dispersion was added, and after completion of the reaction, the microcapsule was collected by suction filtration, washing with water and drying.

-Fabrication and operation of image display media-
The obtained microcapsules were dispersed in an ultraviolet curable epoxy resin (trade name: manufactured by ThreeBond Co., Ltd., 3121) and applied on a glass substrate with an ITO electrode with a wire bar. Next, the coating film was sandwiched with another ITO electrode so that the distance between the electrodes was 100 μm, and then cured by irradiation with ultraviolet rays. Thus, an image display medium was produced.

<Performance evaluation>
For the obtained image display medium, when a voltage of −100 V was applied to the upper ITO electrode, the composite particles were rapidly electrodeposited on the upper electrode and looked white when viewed from the upper substrate surface. Next, when a voltage of +100 V was applied to the upper electrode, the titanium oxide particles moved to the lower electrode, and when viewed from the upper substrate side, a black state due to the color of black titanium oxide was clearly seen. Further, even when these display changes were repeated 100 times, no display deterioration was observed.

(Comparative Example 2)
-Fabrication and operation of image display media-
In Example 2, an image display medium was produced in the same manner as in Example 2 except that titanium oxide was used instead of the composite particles.
<Performance evaluation>
The obtained image display medium was subjected to display switching by applying a voltage. However, titanium oxide and black titanium oxide aggregated, and display switching due to migration could not be confirmed.

(Example 3)
-Production of composite particles-
Into a reaction vessel equipped with a stirrer, a thermometer and a reflux condenser, 200 parts by mass of hexane was taken and heated to 50 ° C. A solution consisting of 19.9 parts by weight of dodecyl methacrylate, 0.1 part by weight of methacrylic acid, and 0.1 part by weight of azobisdimethylvaleronitrile was added dropwise thereto. When the reaction was terminated by stirring at this temperature for 4 hours, a uniform and transparent acidic group-containing resin solution was obtained.
In a reaction vessel equipped with a stirrer, a thermometer and a reflux condenser, 20 parts by mass of the acidic group-containing resin solution, 75 parts by mass of hexane, and 5 parts by mass of the treated titanium oxide are put together and dispersed in a homogenizer. And heated to 50 ° C. A solution consisting of 8.5 parts by weight of methyl methacrylate, 1 part by weight of dodecyl methacrylate, 0.5 part by weight of methacrylic acid and 0.1 part by weight of azobisdimethylvaleronitrile was added dropwise thereto. The reaction was terminated by stirring at this temperature for 4 hours, and only the solid component was collected and dried to produce titanium oxide-polymer composite particles.

-Preparation of composite particle dispersion-
A solution prepared by dissolving 10 parts by mass of urea, 1 part by mass of resorcinol and 10 parts by mass of an ethylene-maleic anhydride copolymer in 290 parts by mass of water was adjusted to pH 3.5 with an aqueous sodium hydroxide solution.
Separately, 1 part by mass of the above titanium oxide-polymer composite particles was added to 30 parts by mass of a saturated solution of isoparaffin hydrocarbon solvent (Exxon Chemical Co., Isopar H) dye (Bayer, Macrolex Blue RR) and ultrasonically dispersed. Was prepared as a particle dispersion. This dispersion was added to the above aqueous solution, and further 25 parts by mass of a formaldehyde solution was added, followed by heating and stirring at 50 ° C. for 3 hours to produce microcapsules. After completion of the reaction, the microcapsules were collected by suction filtration, washing with water and drying.

-Fabrication and operation of image display media-
The obtained microcapsules were dispersed in an ultraviolet curable epoxy resin (trade name: manufactured by ThreeBond Co., Ltd., 3121) and applied on a glass substrate with an ITO electrode with a wire bar. Next, the coating film was sandwiched with another ITO electrode so that the distance between the electrodes was 100 μm, and then cured by irradiation with ultraviolet rays. Thus, an image display medium was produced.

<Performance evaluation>
When a voltage of +100 V was applied to the upper ITO electrode of the obtained image display medium, the titanium oxide particles quickly electrodeposited on the upper electrode and looked white when viewed from the upper substrate surface. Next, when a voltage of −100 V was applied to the upper electrode, the titanium oxide particles moved to the lower electrode, and when viewed from the upper substrate side, the coloring state due to the color of the dye was clearly seen. In addition, display deterioration was not observed even when the display was switched 100 times.

(Comparative Example 3)
-Fabrication and operation of image display media-
In Example 3, an image display medium was produced in the same manner as in Example 3 except that titanium oxide was used instead of the composite particles.
<Performance evaluation>
The obtained image display medium was subjected to display switching by applying a voltage, but when it was repeated 10 times, the particles aggregated and did not migrate well in the electric field direction.

Example 4
-Production of composite particles-
Disperse 10 parts by mass of titanium oxide (CR-90, manufactured by Ishihara Sangyo Co., Ltd.) in a mixed solvent of 50 parts by mass of water and 50 parts by mass of ethanol in which 0.1 part by mass of 3-aminopropyltrimethoxysilane is dissolved. After leaving it to stand, it was washed and dried to prepare a coupled titanium oxide.
On the other hand, 200 parts by mass of silicone oil (manufactured by Toray Dow Corning Silicone Co., SH200, 1cs) was taken in a reaction vessel equipped with a stirrer, a thermometer and a reflux condenser, and heated to 50 ° C. A solution consisting of 19.9 parts by weight of methacryloxypropyl-modified silicone, 0.1 part by weight of methacrylic acid, and 0.1 part by weight of azobisdimethylvaleronitrile was added dropwise thereto. Subsequently, when the reaction was completed by stirring at 50 ° C. for 4 hours, a uniform and transparent acidic group-containing resin solution was obtained.
Particles dispersed in a homogenizer by combining 20 parts by mass of the acidic group-containing resin solution, 75 parts by mass of silicone oil, and 5 parts by mass of the coupling-treated titanium oxide in a reaction vessel equipped with a stirrer, a thermometer and a reflux condenser. The dispersion was added and heated to 50 ° C. A solution consisting of 8.9 parts by weight of methyl methacrylate, 1 part by weight of methacryloxypropyl-modified silicone, 0.1 part by weight of methacrylic acid, and 0.1 part by weight of azobisdimethylvaleronitrile was added dropwise thereto. Subsequently, it stirred at 50 degreeC for 4 hours, reaction was complete | finished, only the solid component was collect | recovered, and the titanium oxide-acid group containing resin composite particle was produced.

-Preparation of composite particle dispersion-
In a reaction vessel equipped with a stirrer, a thermometer and a reflux condenser, 200 parts by mass of silicone oil was taken and heated to 50 ° C. A solution consisting of 19 parts by weight of methacryloxypropyl-modified silicone, 1 part by weight of dimethylaminoethyl methacrylate, and 0.1 part by weight of azobisdimethylvaleronitrile was added dropwise thereto. When the reaction was terminated by stirring at this temperature for 4 hours, a uniform and transparent resin solution was obtained.
A solution prepared by dissolving 10 parts by mass of urea, 1 part by mass of resorcinol and 10 parts by mass of an ethylene-maleic anhydride copolymer in 290 parts by mass of water was adjusted to pH 3.5 with an aqueous sodium hydroxide solution.
Separately, 21 parts by mass of silicone oil is combined with 6 parts by mass of the resin solution as the composite particle dispersant, 3 parts by mass of the titanium oxide-acid group-containing resin composite particles, and 0.3 parts by mass of black titanium oxide (titanium black). A particle dispersion was prepared by ultrasonic dispersion. This particle dispersion was added to the above aqueous solution, and further 25 parts by mass of a formaldehyde solution was added, followed by heating and stirring at 50 ° C. for 3 hours to produce microcapsules. After completion of the reaction, the microcapsules were collected by suction filtration, washing with water and drying.

-Fabrication and operation of image display media-
The obtained microcapsules were dispersed in an ultraviolet curable epoxy resin (trade name: manufactured by ThreeBond Co., Ltd., 3121) and applied on a glass substrate with an ITO electrode with a wire bar. Next, the coating film was sandwiched with another ITO electrode so that the distance between the electrodes was 100 μm, and then cured by irradiation with ultraviolet rays. Thus, an image display medium was produced.

<Performance evaluation>
In the obtained image display medium, when a voltage of +100 V was applied to the upper ITO electrode, the composite particles were rapidly electrodeposited on the upper electrode and looked white when viewed from the upper substrate surface. Next, when a voltage of −100 V was applied to the upper electrode, the titanium oxide particles moved to the lower electrode, and when viewed from the upper substrate side, a black state due to the color of the black titanium oxide was clearly seen. In addition, display deterioration was not observed even when the display was switched 100 times.

(Comparative Example 4)
-Fabrication and operation of image display media-
In Example 4, an image display medium was produced in the same manner as in Example 4 except that titanium oxide was used instead of the composite particles.
<Performance evaluation>
The obtained image display medium was subjected to display switching by applying a voltage. However, titanium oxide and black titanium oxide aggregated, and display switching due to migration could not be confirmed.

  Since the image display medium using the composite particle dispersion of the present invention has good chargeability and is not easily subjected to viscous resistance accompanying migration, it can respond at low voltage and high speed, and has the advantages of both display and hard copy. It can be widely used as a paper-like image display medium that can be rewritten.

DESCRIPTION OF SYMBOLS 1 Conductive layer 2 Conductive layer 3 Microcapsule 4 White thru | or colored particle 4a White thru | or colored particle 4b White thru | or colored particle 5 Colored dispersion medium 6 Adhesive support layer 7 Dispersion medium 10 Image display apparatus 11 Image display medium 12 Housing 13 Information input means

Japanese Patent No. 2551783 Japanese Patent Publication No.51-46396 JP 2001-98206 A

9th International Display Workshop (IDW'02) Proceedings p. 1361 (2002)

Claims (2)

A pigment dispersion step Ru obtain an acid group and the solvent-affinity sites and dispersion pigment using a particle dispersant are dispersed in a non-polar solvent having both a pigment adsorbing functional group,
A polymer generation step of adding a monomer having at least an acidic group to the dispersion to perform a polymerization reaction, and generating a copolymer having an acidic group ,
Method of manufacturing an electrophoretic particles, characterized in that to heteroaggregation the copolymer was made fresh on the pigment surface. A pigment dispersion step of dispersing the pigment in a nonpolar solvent using a particle dispersant having both a basic group which is a pigment-adsorptive functional group and a solvent-affinity site;
A polymer production step of adding a monomer having at least a basic group to the dispersion to conduct a polymerization reaction to produce a copolymer having a basic group,
A method for producing electrophoretic particles, wherein the produced copolymer is heteroaggregated on the pigment surface.