JP2003275565A - Method for making microcapsule including electrophoretic particle dispersion and reversible display device using this capsule - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for making microcapsules including an electrophoretic particle dispersion capable of efficiently making microcapsules with a relatively large and uniform particle size by eliminating a classifying process step in order to enable a high-contrast display with a display device using the microcapsules including the electrophoretic particles and of making the content of the electrophoretic particles uniform and the display device using the same. <P>SOLUTION: The method for making the microcapsules including the electrophoretic particle dispersion comprises using the following agitating elements and a reactor: The ratio (d1/d2) of the element diameter (d1) of the agitating elements and the inner diameter (d2) of the reactor is 0.4 to 0.9; the ratio (d1/h1) of the element diameter (d1) of the agitating elements and the total (h1) of the heights of the agitating elements is 0.3 to 1.5; and the height (h2) of the liquid level of an agitating solution is ≥1.2 times the total (h1) of the heights of the agitating elements. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing microcapsules containing an electrophoretic particle dispersion solution, and more specifically, it contains an electrophoretic particle dispersion solution having a relatively large particle size and a narrow particle size distribution. And a display medium using the same.

[0002]

2. Description of the Related Art Microcapsules are used in many fields such as recording materials such as pressure-sensitive recording paper and heat-sensitive recording paper, agricultural chemicals, pharmaceuticals, fragrances, liquid crystals and adhesives. Many methods have been proposed for the production method, and typical microencapsulation methods include coacervation method, interfacial polymerization method,
The in-situ polymerization method and the like are known.

By the way, in recent years, along with the development of information equipment, the amount of data of various kinds of information is increasing, and the output of information also takes various forms. The form of information output is generally displayed on a display screen using a cathode ray tube or liquid crystal, but these displays are required to be portable and have low power consumption, and new displays are being actively developed. There is. As such a new display,
An electrophoretic display device having a structure in which a dispersion system in which electrophoretic particles are dispersed in a dispersion medium colored in a color different from that of the particles is encapsulated in microcapsules and the microcapsules are arranged between electrodes is Kaihei 1-86116 (Patent No. 2551783), US Pat. No. 6,241,92
No. 1 and US Pat. No. 6,262,706. This method reduces the burden on the user's eyes because it is a reflective display that does not require a backlight like liquid crystal displays, does not become difficult to see even if the viewing angle is changed, and the response time is compared. It is possible to rewrite as quickly as possible.Furthermore, the electrophoretic particles that have moved to the electrodes by applying a voltage have a memory property that maintains that state for a long period of time even if the voltage is removed. It is expected to have excellent performance as a display device such that it does not require electric power during the running time.

As a method for producing microcapsules containing electrophoretic particles, it is disclosed that a general microencapsulation method is used as described above. When displaying characters on a display using this microcapsule, the particle size of the microcapsule required to obtain sufficient resolution is 50 to 150 μm. Further, in order to improve the display contrast, it is necessary to make the particle diameters of the microcapsules as uniform as possible, but at present, the sieving by classification is mainly performed and the production efficiency is poor. Thus, it was difficult to stably manufacture microcapsules having a relatively large particle size and a narrow particle size distribution. Further, there is a problem that the content of the electrophoretic particles contained in the microcapsules becomes non-uniform, so that the contrast is lowered.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide a display device using microcapsules containing electrophoretic particles in order to enable high contrast display. Method for producing microcapsules containing electrophoretic particle-dispersed solution capable of efficiently producing capsules without classifying process and making uniform content of electrophoretic particles in the microcapsules, and display device using the same Is provided. That is, the particle size of the microcapsules necessary for displaying a high contrast is preferably 10 to 20.
The particle size distribution of the microcapsules is preferably 100% or less, more preferably 70% or less, in addition to 0 μm, more preferably 50 to 150 μm.

[0006]

Means for Solving the Problems As a result of diligent studies, the present inventors have found that the stirring blade diameter (d1) and the reaction vessel inner diameter (d2).
Ratio (d1 / d2) is 0.4 to 0.9, and the ratio (d1 / h1) of the blade diameter (d1) of the stirring blades and the total height (h1) of the stirring blades is 0.3 to Achieving the above object by using a stirring blade and a container whose height (h2) of the stirring solution is 1.2 times or more of the total height (h1) of the stirring blades. I found that I can do it.

That is, according to the present invention, the impeller blade diameter (d
The ratio (d1 / d2) of 1) to the inner diameter (d2) of the reaction vessel is 0.4 to 0.9, and the ratio of the blade diameter (d1) of the stirring blade and the total height (h1) of the stirring blade. (D1 / h1) is 0.
The electrophoretic property is 3 to 1.5 and the height (h2) of the liquid level of the stirring solution is 1.2 times or more the total height (h1) of the stirring blades and the reaction vessel. Electrophoretic property characterized by emulsifying and dispersing a hydrophobic dispersion liquid in which particles are dispersed in a hydrophobic medium in a hydrophilic medium containing a dispersion stabilizer, and emulsifying and dispersing the hydrophobic dispersion liquid into microcapsules. The present invention relates to a method for producing microcapsules containing a particle dispersion solution.

Further, the present invention is characterized in that the electrophoretic particles contain at least two kinds of colored particles having different color tones and electrophoretic properties, and the microcapsules containing the electrophoretic particle dispersion liquid are contained. Manufacturing method.

The present invention also relates to an electrophoretic particle dispersion-containing microcapsule produced by the method for producing an electrophoretic particle dispersion-containing microcapsule.

Further, according to the present invention, at least one of the microcapsules containing the electrophoretic particle dispersion liquid is transparent.
The present invention relates to a reversible display medium sandwiched between a pair of opposing electrodes.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The method for producing microcapsules containing electrophoretic particles according to the present invention comprises dispersing one or more kinds of electrophoretic particles having different color tones in a hydrophobic medium, and dispersing the hydrophobic dispersion in water. After the emulsification, microencapsulation is carried out, and it is characterized in that a stirring blade having a large stirring blade area is used in the emulsification step and the microencapsulation step. That is, the blade diameter (d1) of the stirring blade and the inner diameter (d
The ratio (d1 / d2) of 2) is 0.4 to 0.9, and the total of the blade diameter (d1) of the stirring blade and the height of the stirring blade (h
The ratio (d1 / h1) of 1) is 0.3 to 1.5, and the height (h2) of the liquid level of the stirring solution is 1.2 times or more the total height (h1) of the stirring blades. By using a stirring blade and a container, particles having a particle size in the range of 10 to 200 μm, a particle size distribution with a coefficient of variation of 100% or less, and electrophoretic particles in microcapsules uniformly entering are obtained.

Summarizing the above, the present invention is a method for producing microcapsules containing electrophoretic particles using a stirring blade having a large effective stirring area. Impeller diameter (d1)
And the ratio (d1 / d2) of the inner diameter (d2) of the reaction vessel is 0.
When it is 4 or less, the stirring speed must be increased in order to stir the whole system, and as a result, fine particles and large particles are formed, and microcapsules having a wide particle size distribution can be obtained.
Further, if it is 0.9 or more, the power required for stirring becomes large, but the desired effect is small, and further, the precision when manufacturing the reaction vessel is required.

When the ratio (d1 / h1) of the blade diameter (d1) of the stirring blades and the total height (h1) of the stirring blades is 0.3 or less, this reaction kettle becomes a substantially elongated product and is effective as a production facility. Not a thing. On the other hand, if it is 1.5 or more, a shape similar to that of a normal small-area stirring blade is approached, and the desired effect cannot be obtained. When the height (h2) of the liquid level of the stirring solution is 1.2 times or less of the total height (h1) of the stirring blades, the effective stirring area of the stirring blades cannot be fully utilized, resulting in poor efficiency.

Such a stirring blade and a container are disclosed in JP-A-8-281089, Max-Blend stirring apparatus manufactured by Sumitomo Heavy Industries, Ltd., and JP-A-5-49890. Shinzuna Pantec Co., Ltd. full-zone agitator, JP-A-9-7569
Hi-F of Soken Kagaku Co., Ltd.
Examples thereof include a mixer device and a stirring device manufactured by Mitsubishi Heavy Industries, Ltd., which is disclosed in JP-A-6-198155.

Next, constituent materials that can be used for producing the electrophoretic particle-containing microcapsules of the present invention will be described. First, as the hydrophobic dispersion medium, for example, aromatic hydrocarbons such as benzene, toluene, xylene, phenylxylylethane, diisopropylnaphthalene, naphthene hydrocarbons, hexane, dodecylbenzene, cyclohexane, kerosene, paraffin hydrocarbons, etc. Of aliphatic hydrocarbons, chloroform, trichlorethylene,
Halogenated hydrocarbons such as tetrachloroethylene, trifluoroethylene, tetrafluoroethylene, dichloromethane and ethyl bromide, tricresyl phosphate, trioctyl phosphate, octyl diphenyl phosphate, phosphate esters such as tricyclohexyl phosphate, dibutyl phthalate ,
Phthalates such as dioctyl phthalate, dilauryl phthalate, dicyclohexyl phthalate, butyl oleate, diethylene glycol dibenzoate, dioctyl sebacate, dibutyl sebacate, dioctyl adipate, trioctyl trimellitate, acetyltriethyl citrate, maleic acid Carboxylic esters such as octyl, dibutyl maleate, ethyl acetate, isopropyl biphenyl, isoamyl biphenyl, chlorinated paraffin, diisopropyl naphthalene, 1,1-ditolylethane, 1,2-ditolylethane, 2,4-ditertiaryaminophenol, N , N-dibutyl-2-butoxy-5
-Tertiary octyl aniline and the like, but not limited thereto. In addition, these organic solvents can be used alone or in combination of two or more.

The above-mentioned hydrophobic dispersion medium is colorless,
Any color can be used. When two kinds of particles such as positively charged particles and negatively charged particles or positively or negatively charged particles and uncharged particles are used as the electrophoretic particles, a colorless hydrophobic dispersion medium is used. When one kind of electrophoretic particles is used, a dispersion medium in which a dye is dissolved is used as a colored hydrophobic dispersion medium. As the dye that can be used in that case, an oil-soluble dye is used, for example, Spirit Black (SB, S
SBB, AB), Nigrosine base (SA, SAP, S
APL, EE, EEL, EX, EXBP, EB), Oil Yellow (105, 107, 129, 3G, GG)
S), 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, B
G), Oil Blue (613, 2N, BOS), Oil Black (HBB, 860, BS), Varifast Yellow (1101, 1105, 3108, 4120),
Bali Fast Orange (3209, 3210), Bali Fast Red (1306, 1355, 2303, 33)
04, 3306, 3320), Bali First Pink 2
310N, Bali First Brown (2402, 340
5), Bali First Blue (3405, 1501, 1
603, 1605, 1607, 2606, 2610),
Bali First Violet (1701, 1702),
Varifast Black (1802, 1807, 38
04, 3810, 3820, 3830) and the like can be used.

Inorganic pigment particles and organic pigment particles can be used as the electrophoretic particles that can be used in the method for producing the electrophoretic particle-encapsulated microcapsules of the present invention. Examples of the inorganic pigment particles include lead white, zinc white,
Lithopone, titanium dioxide, zinc sulfide, antimony oxide,
Calcium carbonate, kaolin, mica, barium sulfate, gloss white, alumina white, talc, silica, calcium silicate, cadmium yellow, cadmium lipoton yellow, yellow iron oxide, titanium yellow, titanium barium yellow, cadmium orange, cadmium lipoton orange. , Molybdate orange, red iron oxide, red lead,
Silver vermilion, cadmium red, cadmium lipotone red,
Amber, brown iron oxide, zinc iron chrome brown, chrome green, chrome oxide, viridian, cobalt green, cobalt chrome green, titanium cobalt green, navy blue, cobalt blue, ultramarine blue, cerulean blue,
Cobalt aluminum chrome blue, cobalt violet, mineral violet, carbon black, iron black, manganese ferrite black, cobalt ferrite black, copper chrome black, copper chrome manganese black, titanium black, aluminum powder, copper powder, lead powder, bell powder, zinc Powder or the like can be used.

Examples of the organic pigment particles include fast yellow, disazo yellow, condensed azo yellow,
Anthrapyrimidine yellow, isoindoline yellow, copper azomethine yellow, quinophthaloin yellow,
Benzimidazolone yellow, nickel dioxime yellow, monoazo yellow lake, dinitroaniline orange, pyrazolone orange, perinone orange, naphthol red, toluidine red, permanent carmine, brilliant fast scarlet, pyrazolone red, rhodamine 6G lake, permanent red, resole red , Bon lake red, lake red, brilliant carmine, bordeaux 10B, naphthol red, quinacridone magenta, condensed azo red, naphthol carmine, perylene scar red, condensed azo scar red, benzimidazolone carmine, anthraquinonyl red, perylene red, perylene maroon , Quinacridone maroon, quinacridone scarred, quinacridone red, diketopiro Pyrrole red, benzimidazolone Brown, phthalocyanine green, Victoria blue lake, phthalocyanine blue, fast sky blue, alkali blue toe toner, indanthrone blue, Rhodamine B lake, methyl violet lake,
Dioxazine violet, naphthol violet and the like can be used.

Further, fine polymer particles can be used as the electrophoretic particles. The polymer fine particles can be produced by a conventionally known method, and examples thereof include a method using emulsion polymerization, a seed emulsion polymerization method, a soap-free polymerization method, a dispersion polymerization method, and a suspension polymerization method. But,
It is not limited to those produced by these methods.

Examples of the material of the polymer fine particles include styrene type, styrene-acrylic type, styrene-isoprene type, divinylbenzene type, methyl methacrylate type, methacrylate type, ethyl methacrylate type, ethyl acrylate type, n-butyl acrylate type, Acrylic acid type, acrylonitrile type, acrylic rubber-methacrylate type, ethylene type, ethylene-acrylic acid type, nylon type, silicone type, urethane type, melamine type, benzoguanamine type, phenol type, fluorine (tetrachloroethylene) type, vinylidene chloride type, Quaternary pyridinium salt system,
Examples thereof include synthetic rubber, cellulose, cellulose acetate, chitosan, calcium alginate, etc., but are not limited to these polymer materials. Further, the above-mentioned polymer fine particles used in the present invention may be dyed with a dye as required, or may be colored by containing pigment particles before use.

Further, it is preferable to use these pigment components not only as fine particles of the pigment alone but also in the state of being subjected to various surface treatments. As the surface treatment method in this case, various methods that are usually carried out for pigment particles can be applied. For example, a pigment surface coated with various compounds including a polymer, a titanate-based silane-based coating, etc. Examples thereof include those subjected to coupling treatment with various coupling agents such as the above, and those subjected to graft polymerization treatment. Further, these pigment particles can be used even in a state of being subjected to mechanochemical treatment, and composite particles formed between pigment particles or between polymer particles and hollow polymer particles, and various resins. It can also be used in the form of composite particles or the like formed between and.

The particle size of these electrophoretic particles is preferably 0.01 to 10 μm, more preferably 0.05 to
The particle size is 5 μm, but is not limited to these particle sizes.

The hydrophobic dispersion medium used in the electrophoretic particle-encapsulating microcapsule of the present invention is conventionally used for the purpose of controlling the charge amount of the electrophoretic particles or enhancing the dispersibility. The various dispersants used can be used. Examples of these dispersants include nonionic (nonionic) surfactants and anionic surfactants, cationic surfactants, and amphoteric surfactants that can be dissolved or mixed in a dispersion medium. The ionic surfactants may be used alone or in combination of two or more.

Examples of nonionic surfactants as these dispersants include polyoxyethylene nonylphenol ether, polyoxyethylene dinonylphenol ether, polyoxyethylene octylphenol ether, polyoxyethylene styrenated phenol, polyoxypolyoxyethylene bisphenol A. , Polyoxyethylene nonylphenyl ethers, polyoxyethylene octylphenyl ethers, nonylphenol ethoxylates and other polyoxyalkylene alkylphenol ethers.

Polyoxyalkylene ethers such as polyoxyethylene castor oil, polyoxyalkylene block polymer, polyoxyethylene cetyl ether, polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether and polyoxypropylene ether. Monool type polyoxyalkylene glycol, diol type polyoxyalkylene glycol, triol type polyoxyalkylene glycol, monool type block type polyalkylene glycol, diol type block type polyalkylene glycol, random type polyalkylene glycol Glycols such as.

Primary linear alcohol ethoxylates such as octylphenol ethoxylate, oleyl alcohol ethoxylate, and lauryl alcohol ethoxylate, secondary linear alcohol ethoxylates, and alkyl alcohol ethers such as polynuclear phenol ethoxylates.

Polyoxyalkylene alkyl esters such as polyoxyethylene rosin ester, polyoxyethylene lauryl ester, polyoxyethylene oleyl ester and polyoxyethylene stearyl ester. Sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan dilaurate, sorbitan dipalmitate, sorbitan distearate, sorbitan sesquilaurate, sorbitan sesquipalmitate, sorbitan sesquistearate .

Polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate,
Polyoxyethylene sorbitan dilaurate, polyoxyethylene sorbitan dipalmitate, polyoxyethylene sorbitan distearate, polyoxyethylene sorbitan sesquilaurate, polyoxyethylene sorbitan sesquipalmitate, polyoxyethylene sorbitan sesquistearate, etc. Oxyethylene sorbitan esters.

Saturated fatty acid methyl ester, unsaturated fatty acid methyl ester, saturated fatty acid butyl ester, unsaturated fatty acid butyl ester, saturated fatty acid stearyl ester,
Fatty acid esters such as unsaturated fatty acid stearyl ester, saturated fatty acid octyl ester, unsaturated fatty acid octyl ester, stearic acid polyethylene glycol ester, oleic acid polyethylene glycol ester and rosin polyethylene glycol ester.

Fatty acids such as stearic acid, oleic acid, palmitic acid, lauric acid and myristic acid, and amidated compounds of these fatty acids. Polyoxyethylene alkylamines such as polyoxyethylene lauryl amine, polyoxyethylene alkyl amine, polyoxyethylene alkyl amine ether.

Higher fatty acid monoethanolamides such as lauric acid monoethanolamide and palm fatty acid diethanolamide, higher fatty acid diethanolamides, polyoxyethylenestearic acid amide, coconut diethanolamide (1-2 type / 1-1 type), Amide compounds such as alkylalkylolamide and alkanolamides. R
_{- (CH 2 CH 2 O)} mH (CH 2 CH 2 O) nH, R-N
Alkanolamines represented by H—C ₃ H ₆ —NH ₂ [R = oleyl octyl dodecyl tetradecyl hexadecyl ochradecyl coconut, beef tallow, soybean, etc.]. R
Primary amines represented by -NH ₂ [R = oleyl octyl dodecyl tetradecyl hexadecyl octadecyl coconut beef tallow soybean, etc.]. R1R2-NH [R1
-R2 = R = oleyl-octyl-dodecyl-tetradecyl-hexadecyl-octadecyl-coconut-beef tallow-soybean, etc.]. R1R2R3N [R1 ・
R2, R3 = oleyl, octyl, dodecyl, tetradecyl, hexadecyl, ochradecyl, coconut, beef tallow, soybean, etc.]. Various synthetic higher alcohols and various natural higher alcohols. Polymers such as acrylic acid-based compounds, polycarboxylic acid-based compounds, hydroxy fatty acid oligomers, modified hydroxy fatty acid oligomers, and oligomers can be used.

Examples of the anionic surfactants include polycarboxylic acid type polymer activators, polycarboxylic acid type anion activators, carboxylic acid salts such as special fatty acid soaps and rosin soaps. Castor oil sulfuric acid ester salt, lauryl alcohol sulfuric acid ester Na salt, lauryl alcohol sulfuric acid ester amine salt, natural alcohol sulfuric acid ester Na salt, higher alcohol sulfuric acid ester Na salt, and other alcoholic sulfuric acid ester salts, and lauryl alcohol ether sulfuric acid ester Amine salt, lauryl alcohol ether sulfate ester Na salt, synthetic higher alcohol ether sulfate ester amine salt, synthetic higher alcohol ether sulfate ester Na salt, alkyl polyether sulfate ester amine salt, alkyl polyether sulfate ester Na salt, natural alcohol EO (ethylene oxide) addition system sulfuric acid ester amine salt, natural alcohol EO (ethylene oxide)
Addition-based sulfate Na salt, synthetic alcohol EO (ethylene oxide) addition-based sulfate amine salt, synthetic alcohol EO (ethylene oxide) addition-based sulfate Na salt, alkylphenol EO (ethylene oxide) addition-based sulfate amine salt, alkylphenol EO (ethylene oxide) Addition system sulfate ester Na
Sulfuric acid such as salt, polyoxyethylene nonyl phenyl ether sulfuric acid ester amine salt, polyoxyethylene nonyl phenyl ether sulfuric acid ester Na salt, polyoxyethylene polycyclic phenyl ether sulfuric acid ester amine salt, polyoxyethylene polycyclic phenyl ether sulfuric acid ester Na salt, etc. Ester salts.

Various alkylallyl sulfonic acid amine salts,
Various alkyl allyl sulfonic acid Na salts, naphthalene sulfonic acid amine salts, naphthalene sulfonic acid Na salts, various alkyl benzene sulfonic acid amine salts, various alkyl benzene sulfonic acid Na salts, naphthalene sulfonic acid condensates,
Sulfonates such as naphthalene sulfonic acid formalin condensate. Polyoxyethylene nonyl phenyl ether sulfonic acid amine salt, polyoxyethylene nonyl phenyl ether sulfonic acid Na salt, polyoxyethylene special allyl ether sulfonic acid amine salt, polyoxyethylene special allyl ether sulfonic acid Na salt, polyoxyethylene tridecyl phenyl Polyoxyalkylene-based sulfonates such as amine salt of ether sulfonate, Na salt of polyoxyethylene tridecylphenyl ether sulfonate, amine salt of polyoxyethylene alkyl ether sulfonate, Na salt of polyoxyethylene alkyl ether sulfonate. Dialkyl sulfosuccinate amine salt, dialkyl sulfosuccinate Na salt, polycyclic phenyl polyethoxy sulfosuccinate amine salt, polycyclic phenyl polyethoxy sulfosuccinate Na salt, polyoxyethylene alkyl ether sulfosuccinic acid monoester amine salt,
Polyoxyethylene alkyl ether sulfosuccinate monoester Na salts and other sulfosuccinate ester salts.

Alkyl phosphates, alkoxyalkyl phosphates, higher alcohol phosphates,
Use of phosphates such as higher alcohol phosphates, alkylphenol phosphates, aromatic phosphates, polyoxyalkylene alkyl ether phosphates, polyoxyalkylene alkyl allyl ether phosphates, and phosphates be able to.

Examples of the cationic surfactant include R
-N (CH ₃₎ 3X alkyl trimethylamine based quaternary ammonium salts represented by [R = stearyl cetyl lauryl oleyl dodecyl coconut, soybean beef tallow / X = halogen amine, etc.]. Tetramethylamine salt,
Quaternary ammonium salts such as tetrabutylamine salt. (R
NH ₃ ) (CH ₃ COO) [R = stearyl / cetyl / lauryl / oleyl / dodecyl / coconut / soybean / beef tallow, etc.] Benzylamine quaternary ammonium salts such as lauryldimethylbenzylammonium salt (halogen / amine salt etc.), stearyldimethylbenzylammonium salt (halogen / amine salt etc.), dodecyldimethylbenzylammonium salt (halogen / amine salt etc.). R (CH ₃ ) N (C ₂ H ₄ O) mH (C ₂ H ₄ O) n
A polyoxyalkylene-based quaternary ammonium salt represented by X [R = stearyl / cetyl / lauryl / oleyl / dodecyl / coconut / soybean / beef tallow / X = halogen / amine or the like] can be used.

As the amphoteric surfactant, for example, various betaine type surfactants, various imidazoline type surfactants,
A β-alanine type surfactant, polyoctyl polyaminoethylglycine hydrochloride, etc. can be used. In addition, various other protective colloid agents can be used.

The in-situ conventionally used for the preparation of the electrophoretic particle-containing microcapsules of the present invention.
It can be prepared by a u method, an interfacial polymerization method, a coacervation method, or the like, and in that case, as the wall material of the microcapsule, polyurethane, polyurea, polyurea-polyurethane, amino resin, polyamide, acrylate ester , Methacrylic acid ester, vinyl acetate, gelatin and the like. Further, the size of the microcapsules used in the present invention is about 10 to 200 μm, preferably about 50 to 150 μm.

When producing microcapsules, it is first necessary to emulsify and disperse the hydrophobic dispersion in a hydrophilic medium. Water is most preferable as the hydrophilic medium, but in some cases, an organic solvent that dissolves in water, such as alcohols, may be added. In addition, a protective colloid such as a water-soluble polymer compound or inorganic fine particles is used for emulsion dispersion. As the water-soluble polymer compound, for example, acrylic acid polymer, (meth) acrylic acid copolymer (acrylic acid ester such as methyl acrylate, acrylic acid amide, acrylonitrile, 2-methylpropanesulfonic acid, styrenesulfonic acid, acetic acid Copolymers with vinyl etc.), maleic acid copolymers (styrene,
Copolymers of ethylene, propylene, methyl vinyl ether, vinyl acetate, isobutylene, butadiene and the like with maleic acid), carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, gelatin, gum arabic starch derivative, polyvinyl alcohol and the like can be used. As the inorganic fine particles, for example, talc, bentonite, organic bentonite, white carbon, colloidal silica, colloidal alumina, fine particle silica, calcium carbonate, calcium sulfate and the like can be used.

Further, other nonionic surfactants or ionic surfactants can be used to control the emulsified state.

A typical method for synthesizing the microcapsules used in the present invention is shown below. In the case of the in-situ method, the wall material is polyurethane, polyurea, polyurea-
Polyurethane, urea-formaldehyde resin, melamine-formaldehyde resin, acrylic acid ester, methacrylic acid ester, vinyl acetate and the like can be used.

As the polyvalent isocyanate compound used when polyurethane, polyurea, or polyurea-polyurethane is used as the wall material, an organic compound having two or more isocyanate groups in the molecule is first used. Examples of such a polyvalent isocyanate compound include m-phenylene diisocyanate, p-phenylene diisocyanate, 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, naphthalene-1,4-diisocyanate, diphenylmethane-4, 4'-diisocyanate, 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, 3,3'-dimethyldiphenylmethane-4,
4'-diisocyanate, xylylene-1,4-diisocyanate, 4,4'-diphenylpropane diisocyanate, trimethylene diisocyanate, hexamethylene diisocyanate, propylene-1,2-diisocyanate, butylene-1,2-diisocyanate, cyclohexylene-1 Diisocyanates such as 2,2-diisocyanate and cyclohexylene-1,4-diisocyanate, p
-Phenylene diisothiocyanate, xylylene-1,
Triisocyanates such as 4-diisothiocyanate and ethylidyne diisothiocyanate can be used, and tetraisocyanates such as 4,4′-dimethyldiphenylmethane-2,2 ′, 5,5′-tetraisocyanate can be used. As the polyvalent isocyanate compound, for example, an adduct of hexamethylene diisocyanate and hexanetriol, an adduct of 2,4-tolylene diisocyanate and prenzcatechol, an adduct of tolylene diisocyanate and hexanetriol, tolylene diisocyanate and trimethylol Polyvalent isocyanate prepolymers such as propane adducts, xylylene diisocyanate and trimethylolpropane adducts, hexamethylene diisocyanate and trimethylolpropane adducts, and the like can also be utilized.

Further, as a polyvalent isocyanate compound,
A prepolymerized compound can also be used. Further, two or more of the above-mentioned substances can be used in combination.
On the other hand, as the wall film forming substance having reactivity with the polyvalent isocyanate compound, polyhydric alcohols, hydroxypolyesters, hydroxypolyalkylene ethers, alkylene oxide adducts of polyvalent amines, polyvalent amines, etc. Examples thereof include substances having two or more active hydrogens.

The above polyhydric alcohols may be aliphatic, aromatic or alicyclic, and for example, catechol, resorcinol, 1,2-dihydroxy-4-methylbenzene, 1,3-dihydroxy-5. -Methylbenzene, 3,4-dihydroxy-1-methylbenzene, 3,5
-Dihydroxy-1-methylbenzene, 2,4-dihydroxyethylbenzene, 1,3-naphthalenediol,
1,5-naphthalene diol, 2,7-naphthalene diol, 2,3-naphthalene diol, o, o'-biphenol, p, p'-biphenol, bisphenol A, bis-
(2-hydroxyphenyl) methane, xylylenediol, ethylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,1,1-trimethylolpropane, hexanetriol, pentaerythritol, glycerin, sorbitol and the like can be used.

The hydroxy polyalkylene ethers include the above polyhydric alcohols and polycarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, maleic acid, isophthalic acid, terephthalic acid and gluconic acid. The resulting hydroxypolyesters may be mentioned. Examples of the hydroxypolyalkylene ethers include hydroxypolyalkylene ethers which are condensation products of the above polyhydric alcohols and alkylene oxides such as ethylene oxide, propylene oxide and butylene oxide. Examples of the alkylene oxide adducts of polyvalent amines include o-phenylenediamine, p-phenylenediamine, diaminonaphthalene, ethylenediamine, 1,3-propylenediamine,
Diethylenetriamine, triethylenetetramine, 1,
Examples thereof include those obtained by substituting at least one of hydrogens of amino groups of polyvalent amine such as 6-hexamethylenediamine with the above-mentioned alkylene oxide.

Examples of the polyvalent amines include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 1,6-hexamethylenediamine, 1,8
-Octamethylenediamine, 1,12-dodecamethylenediamine, o-phenylenediamine, p-phenylenediamine, m-phenylenediamine, o-xylylenediamine, p-xylylenediamine, m-xylylenediamine, menthanediamine, bis (4-amino-3-methylcyclohexylnomethane, isophoronediamine, 1,
3-diaminocyclohexane, a spiro acetal-type diamine, etc. can be used. Further, water can also be used as a wall film forming substance having reactivity with polyvalent isocyanate.

Basically, it comprises the following steps. An aqueous solution containing a protective colloid is prepared. When a water-soluble polymer is used as the protective colloid, 0.2 to 10 parts by weight, preferably 0.5 to 5 parts by weight, of the water-soluble polymer is used with respect to 100 parts by weight of water. When used, 0.1 to 100 parts by weight with respect to 100 parts by weight of water,
It is preferable to use 1 to 50 parts by weight.

Next, the hydrophobic dispersion medium is mixed with electrophoretic particles, a polyvalent isocyanate compound, a polyhydric alcohol and, in some cases, a polyvalent amine to prepare a hydrophobic dispersion liquid. This hydrophobic dispersion is emulsified and dispersed in the protective colloid aqueous solution prepared in the above step. Here, the amount of the electrophoretic particles used is 100 parts by weight of the hydrophobic dispersion.
It is in the range of 0.1 to 20 parts by weight, preferably 1 to 10 parts by weight. The amount of the polyvalent isocyanate compound used is 1 to 50 parts by weight, relative to 100 parts by weight of the hydrophobic dispersion.
The preferred range is 5 to 20 parts by weight. The amount of polyhydric alcohol or polyhydric amine used is in the range of 1 to 50 parts by weight, preferably 5 to 20 parts by weight, based on 100 parts by weight of the hydrophobic dispersion.

The obtained emulsified dispersion is heated to a predetermined temperature to react the polyvalent isocyanate with the polyvalent alcohol or the polyvalent amine to obtain the desired microcapsules.

When acrylic acid ester, methacrylic acid ester, vinyl acetate or the like is used as the wall material, examples of the radical polymerizable monomer usable in the present invention include styrene, α-methylstyrene,
Aromatic monomers such as p-methylstyrene, t-butylstyrene, chlorostyrene, benzyl acrylate, benzyl methacrylate and vinyltoluene.

Methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n acrylate -Acrylic acid alkyl esters such as octyl, decyl acrylate, dodecyl acrylate.

Methyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-methacrylate.
-Alkyl methacrylates such as octyl, decyl methacrylate, dodecyl methacrylate. Hydroxy group-containing monomers such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate. N-substituted acryl such as N-methylolacrylamide, N-butoxymethylacrylamide, N-methylolmethacrylamide, N-butoxymethylmethacrylamide,
Methacrylic monomers. Acrylic acid, methacrylic acid,
Polymerizable unsaturated carboxylic acids such as itaconic acid, maleic acid, fumaric acid and crotonic acid, and carboxyl group-containing monomers such as anhydrides thereof. Epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate, and one or more selected from acrylonitrile, methacrylonitrile, crotonnitrile, vinyl acetate, vinyl chloride, vinylidene chloride and the like can be selected.

Further, in the present invention, together with the above-mentioned radical-polymerizable monomer, polyfunctional and hence crosslinkable monomers such as methylenebisacrylamide, divinylbenzene, ethylene glycol dimethacrylate, tripropylene glycol diacrylate. , Bisphenol A diglycidyl ether diacrylate, trimethylolpropane triacrylate, acrylated cyanurate and the like can also be used.

When the above radical polymerizable monomer is used, the radical polymerization initiator that can be used in the present invention includes organic peroxides such as lauroyl peroxide, benzoyl peroxide, methyl ethyl ketone peroxide, cyclohexanone peroxide, and 2 , 2-bis (t-butylperoxy) valate, di-t-butylperoxide, dicumylperoxide, octanoylperoxide, etc., and azo compounds such as 2,2-azobis (2,4-dimethyl) Valeronitrile), 2,2-azobis (2-methylbutyronitrile), 1,1-azobis (cyclohexyl-1-carbonitrile), VA-06
1, VA-080, VR-110, V-601 (all are Wako Pure Chemical Industries, Ltd.) etc. can be used. Inorganic peroxides such as ammonium peroxide and sodium peroxide can also be used. These initiators may be used alone, or may be used in a redox type by being used in combination with a reducing agent such as Rongalit. As a chain transfer agent for adjusting the molecular weight, octyl thioglycolate, methoxybutyl thioglycolate, octyl mercaptopropionate,
Methoxybutyl mercaptopropionate, mercaptans such as stearyl mercaptan, and α-methylstyrene dimer can be used.

In the step, electrophoretic particles, radical polymerizable monomer, radical polymerization initiator, a hydrophobic dispersion medium,
Depending on the case, a hydrophobic dispersion liquid is prepared by mixing a chain transfer agent or the like. This hydrophobic dispersion is emulsified and dispersed in a protective colloid aqueous solution as described above. Here, the amount of the radical-polymerizable monomer used is in the range of 1 to 90 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts by weight of the hydrophobic dispersion liquid. The amount of the radical polymerization initiator used is not particularly limited, but is usually a radical polymerizable monomer.
It is in the range of 0.1 to 10 parts by weight, preferably 0.1 to 5 parts by weight, relative to 100 parts by weight.

In the case of radical polymerization by the in-situ method, it is possible not to mix the radically polymerizable monomer and the radical polymerization initiator into the hydrophobic dispersion medium, but to dissolve them in water and polymerize them. In this case, it is preferable to use the radically polymerizable monomer and the radical polymerization initiator to be used in a range that dissolves in water.

The obtained emulsified dispersion is heated to a predetermined temperature to initiate radical polymerization to obtain the desired microcapsules.

When an amino resin is used as the wall material, the components usable in the present invention are:
For example, melamine / formaldehyde prepolymer, urea /
Formaldehyde prepolymer, alkylated methylolurea alkylated methylolmelamine, N-alkylmelamine / formaldehyde prepolymer, guanamine / formaldehyde prepolymer, alkylurea / formaldehyde prepolymer, alkyleneurea / formaldehyde prepolymer, etc. are used. be able to.

In the step, electrophoretic particles are mixed with a hydrophobic dispersion medium to prepare a hydrophobic dispersion liquid. This hydrophobic dispersion is emulsified and dispersed in a protective colloid aqueous solution as described above. The amino resin component is used in an amount of 1 to 200 parts by weight, preferably 10 to 60 parts by weight, based on 100 parts by weight of the hydrophobic dispersion. When the amino resin component is a urea / formaldehyde prepolymer, this component may be gradually or once added to the system, or the raw material urea may be previously dissolved in an aqueous medium, and then gradually or once. Formaldehyde may be added to the system. The microencapsulation reaction is preferably under acidic conditions, ie the pH of the system.
Is 2.0 to 6.8, and more preferably 3.0 to 6.0. The conditions of the system may be appropriately adjusted depending on the type of amino resin component used. For example, in the case of melamine / formaldehyde prepolymer or alkylated methylol melamine,
A pH of 4.0 to 5.5 and a pH of 2.0 to 4.5 are suitable for urea / formaldehyde prepolymers. The pH of the system is adjusted to 3.0 to 6.8, and heating at a predetermined temperature causes polycondensation on the surface of the dispersed particles of the hydrophobic substance to obtain the desired microcapsules.

The amino resin component is an initial condensate of formaldehyde with urea, melamine, etc., and can be produced by a conventional method.

Next, in the case of the interfacial polymerization method, polyurethane, polyurea, polyurea-polyurethane, polyamide or the like can be used as the wall material. In the interfacial polymerization method, a hydrophobic monomer is added to a hydrophobic dispersion medium, the hydrophobic dispersion is emulsified and dispersed in water, and then a hydrophilic monomer is added to cause polymerization on the oil droplet surface. As the polyvalent isocyanate compound used when polyurethane, polyurea, or polyurea-polyurethane is used as the wall material, the polyvalent isocyanate, polyvalent alcohol, and polyvalent amine shown by the in-situ method can be used. . Generally, polyvalent isocyanate is used as the hydrophobic monomer, and polyhydric alcohol or polyvalent amine is used as the hydrophilic monomer. The amounts of these monomers used are the same as the amounts shown by the in-situ method.

When polyamide is used as the wall material, polybasic acid halide may be used as the hydrophobic monomer and polyvalent amine may be used as the hydrophilic monomer in place of the polyvalent isocyanate. As the polybasic acid halide, sebacoyl chloride, terephthaloyl chloride or the like can be used.

Next, in the case of the coacervation method, the well-known gelatin-acacia complex coacervation method can be used. In addition to gum arabic, gelatin can react with anions such as sodium alginate, carrageenan, carboxymethylcellulose, agar, polyvinylbenzenesulfonic acid, maleic anhydride copolymer, and other surfactants. After coacervating, it is common to cure with formaldehyde. As described above, by using the electrophoretic particle-containing microcapsules produced by various methods and materials as a display material, display with high contrast can be performed.

In the present invention, electrophoretic reversible display media using electrophoretic particle-containing microcapsules are provided. As a form of these electrophoretic reversible display media, for example, at least one is transparent. At least one of a pair of substrates has an electrode on one surface, and the electrode surface is placed in a space formed by facing the one substrate with or without a spacer. An electrophoretic reversible display medium filled with microcapsules containing electrophoretic particles of the invention. Alternatively, at least one of the pair of substrates, at least one of which is transparent, has an electrode on one surface, and the electrode surface is arranged to face the one substrate with or without a spacer. An electrophoretic reversible display medium in which the space formed in 1 is discontinuously divided by a matrix material and filled with the electrophoretic particle-encapsulating microcapsules of the present invention. Alternatively, an electrophoretic reversible display medium in which a coating layer made of the electrophoretic particle-encapsulating microcapsules of the present invention and a matrix material is formed on the electrode surface side of a transparent or opaque substrate having an electrode on one surface. Alternatively, a coating layer composed of the electrophoretic particle-encapsulating microcapsules of the present invention and a matrix material is formed on the electrode surface side of a transparent or opaque substrate having an electrode on one surface, and an overcoat is formed on the coating layer. Examples include electrophoretic reversible display media provided with layers. In addition, the substrate in the present invention indicates both a substrate having an electrode surface and a substrate not having an electrode surface.

FIG. 1 shows that the space formed by a pair of electrode substrates via a spacer is filled with the electrophoretic particle-encapsulating microcapsules of the present invention as a reversible display recording layer by using a matrix material, and electrophoresis is performed. A display medium is manufactured. The reversible display recording layer is prepared by dissolving, dispersing, suspending or emulsifying the electrophoretic particle-containing microcapsules of the present invention and a matrix material as a coating liquid, and the resulting coating liquid is wire bar coat, roll coat, It can be obtained by coating and drying on the electrode plate by a method such as blade coating, dip coating, spray coating, spin coating, or gravure coating. In this case, examples of the electrode plate include an electrode formed by forming a conductive film such as ITO on a glass plate or a plastic film, an electrode formed by forming a conductive metal film such as aluminum, copper, or gold. .

As the matrix material, the same material as the wall material of the microcapsules, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinyldene chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, polyvinyl alcohol, poly Ethylene oxide, polypropylene oxide, ethylene-vinyl alcohol copolymer, polyacetal, acrylic resin, methyl cellulose, ethyl cellulose, phenol resin,
Fluorine resin, silicone resin, diene resin, polystyrene-based thermoplastic elastomer, polyolefin-based thermoplastic elastomer, polyurethane-based thermoplastic elastomer,
Polyester thermoplastic elastomer, polyphenylene ether, polyphenylene sulfide, polyether sulfone, polyether ketone, polyarylate, aramid, polyimide, poly-p-phenylene, poly-p-xylene, poly-p-phenylene vinylene, polyhydantoin, polyparaban One or more materials selected from acids, polybenzimidazoles, polybenzothiazoles, polybenzooxadiazoles, polyquinoxalines, the above-mentioned thermosetting resins or active energy ray-curing resins, or mixtures thereof can be used. .

As a material for forming the overcoat layer, the material for forming the above matrix material can be used. The overcoat layer comprises a medium for dissolving, dispersing, suspending or emulsifying these materials, a curing agent, a protective layer material composition containing a catalyst and / or a cocatalyst, a wire bar coat, a roll on the display layer. Coat, blade coat, dip coat, spray coat, spin coat,
Alternatively, it is formed by a coating method such as a gravure coating, a sputtering method, a chemical vapor deposition method, or the like. The thickness of the overcoat layer is preferably as thin as possible within a range having a function of protecting the display layer, and is about 0.1 to 100 μm.
m, and more preferably 0.3 to 30 μm.

[0067]

EXAMPLES The present invention will be described below with reference to examples. In addition, "part" and "%" in an example show "weight part" and "weight%", respectively.

(Example 1) A hydrophobic dispersion medium colored by dissolving 1 part by weight of oil blue, an oil-soluble dye, in 150 parts by weight of paraffin hydrocarbon isoper (manufactured by Exxon Corporation) was prepared. To this hydrophobic dispersion medium, 5 parts by weight of titanium dioxide (Ti-PURE R104, manufactured by DuPont) that has been subjected to hydrophobic treatment as electrophoretic particles was added, and the mixture was dispersed for 10 minutes using an ultrasonic disperser to give a hydrophobic dispersion solution. It was made. On the other hand, an aqueous solution prepared by dissolving 20 parts by weight of a partially neutralized styrene-maleic anhydride resin as a water-soluble polymer in 1500 parts by weight of ion-exchanged water was prepared in a Maxblend stirrer (Sumitomo Heavy Industries, Ltd.). Next, the previously prepared hydrophobic dispersion was added to this aqueous solution, and stirring was continued while adjusting the number of revolutions so that the particle diameter was about 100 μm, and the hydrophobic dispersion was emulsified and dispersed in water. The particle size was obtained by observing with an optical microscope and averaging 100 particles. Separately, a mixed solution of 150 parts by weight of 37% formalin, 50 parts by weight of melamine, and 400 parts by weight of deionized water was adjusted to pH 9.0 with a caustic soda aqueous solution with stirring, and reacted at 60 ° C. for 20 minutes to give a transparent solution. melamine/
A formaldehyde condensate was obtained. This reaction liquid was added to the above emulsified dispersion liquid and reacted at 50 ° C. for 3 hours by an in-situ method. The obtained electrophoretic particle-encapsulated microcapsules had a particle diameter of 91 μm and a coefficient of variation of 55%.

Then, 20 g of the obtained electrophoretic particle-encapsulating microcapsules-1 was added to 80 g of a 10 wt% polyvinyl alcohol aqueous solution to prepare a dispersion coating solution. Using an applicator with a gap of 100 μm,
Coating on a glass plate with an ITO film (on the ITO film) and drying to form a microcapsule coating film containing electrophoretic particles,
Further, a glass plate with an ITO film (ITO film on the side of the microcapsule coating film) was placed thereon to prepare an electrophoretic display medium. When the electrophoretic display medium thus prepared is connected to a DC power source, the direction of the electric field is switched at a rectangular frequency of 10 Hz, and a voltage of ± 100 V is applied, whereby titanium dioxide particles are electrophoresed on the upper electrode. It was possible to display white (the electric field of the upper electrode was positive) and blue (the electric field of the lower electrode was positive) when the titanium dioxide particles were electrophoresed on the lower electrode.

In order to examine the display performance of the obtained electrophoretic display medium, Photonic MCPD-100 manufactured by Otsuka Electronics Co., Ltd.
0 was used to measure the reflected light intensities in white display and blue display, respectively, in the visible light region at 45 ° irradiation and 0 ° light reception, and the ratio of the reflectances of both display colors was obtained as the contrast. The contrast was 1 (blue): 6.1 (white).
By the way, the contrast between the solid blue print portion printed on the newspaper and the white background portion of the newspaper was 1 (blue): 7.4 (white), demonstrating that the electrophoretic display medium has a high display contrast.

Example 2 The same operation as in Example 1 was carried out except that the stirring device was changed to a Hi-F mixer device (manufactured by Soken Kagaku Co., Ltd.) to obtain electrophoretic particle-containing microcapsules. The particle size of this microcapsule is 107 μm,
The coefficient of variation was 48%. The contrast was measured with a display device using the microcapsules, and it was 1 (blue): 6.3 (white), which proved that the display contrast of the electrophoretic display medium was high.

(Example 3) A hydrophobic dispersion medium colored by dissolving 1 part by weight of oil blue, an oil-soluble dye, in 150 parts by weight of paraffin hydrocarbon isoper (manufactured by Exxon Corporation) was prepared. To this hydrophobic dispersion medium, 5 parts by weight of titanium dioxide (Ti-PURE R104, manufactured by DuPont) that has been subjected to hydrophobic treatment as electrophoretic particles was added, and the mixture was dispersed for 10 minutes using an ultrasonic disperser to give a hydrophobic dispersion solution. It was prepared, and 11.1 parts by weight of an adduct of 3 mol of tolylene diisocyanate and 1 mol of trimethylolpropane was added. On the other hand, an aqueous solution in which 15 parts by weight of polyvinyl alcohol as a water-soluble polymer was dissolved in 1500 parts by weight of ion-exchanged water was prepared in a Maxblend stirrer (Sumitomo Heavy Industries, Ltd.). Next, the previously prepared hydrophobic dispersion was added to this aqueous solution, and stirring was continued while adjusting the number of revolutions so that the particle diameter was about 100 μm, and the hydrophobic dispersion was emulsified and dispersed in water. Separately, 56 parts by weight of an aqueous solution containing 5.6 parts by weight of triethylenetetramine was prepared, added to the above emulsified dispersion liquid, and reacted at 50 ° C. for 5 hours by an interfacial polymerization method. The obtained electrophoretic particle-encapsulated microcapsules had a particle diameter of 83 μm and a coefficient of variation of 57%. The contrast was measured with a display device using the microcapsules, and it was 1 (blue): 6.0 (white), which proved that the display contrast of the electrophoretic display medium was high.

Example 4 A hydrophobic dispersion medium colored by dissolving 1 part by weight of oil-soluble dye oil blue in 150 parts by weight of paraffin hydrocarbon isoper (manufactured by Exxon Corporation) was prepared. To this hydrophobic dispersion medium, 5 parts by weight of titanium dioxide (Ti-PURE R104, manufactured by DuPont) that has been subjected to hydrophobic treatment as electrophoretic particles was added, and the mixture was dispersed for 10 minutes using an ultrasonic disperser to give a hydrophobic dispersion solution. It was prepared, and 3.5 parts by weight of methyl methacrylate, 3.5 parts by weight of isobutyl methacrylate, 0.5 parts by weight of ethylene glycol dimethacrylate, and 0.1 parts by weight of benzoyl peroxide were added and dissolved. On the other hand, an aqueous solution prepared by dissolving 5 parts by weight of polyvinyl alcohol as a water-soluble polymer in 500 parts by weight of ion-exchanged water was prepared in a Maxblend stirring device (Sumitomo Heavy Industries, Ltd.). Next, the previously prepared hydrophobic dispersion was added to this aqueous solution, and stirring was continued while adjusting the number of revolutions so that the particle diameter was about 100 μm, and the hydrophobic dispersion was emulsified and dispersed in water. This emulsified dispersion was reacted at 80 ° C. for 3 hours by the in-situ method. The obtained electrophoretic particle-encapsulated microcapsules had a particle diameter of 85 μm and a coefficient of variation of 61%. The contrast was measured with a display device using the microcapsules, and it was 1 (blue): 6.0 (white), which proved that the display contrast of the electrophoretic display medium was high.

(Example 5) A hydrophobic dispersion medium colored by dissolving 1 part by weight of oil blue, which is an oil-soluble dye, in 150 parts by weight of paraffin hydrocarbon isoper (manufactured by Exxon Corporation) was prepared. To this hydrophobic dispersion medium, 5 parts by weight of titanium dioxide (Ti-PURE R104, manufactured by DuPont) that has been subjected to hydrophobic treatment as electrophoretic particles was added, and the mixture was dispersed for 10 minutes using an ultrasonic disperser to give a hydrophobic dispersion solution. It was made. On the other hand, 10% in 2500 parts by weight of ion-exchanged water
An aqueous solution in which 500 parts by weight of an aqueous gelatin solution was dissolved was prepared in a Maxblend stirrer (manufactured by Sumitomo Heavy Industries, Ltd.) and heated to 50 ° C. Next, the previously prepared hydrophobic dispersion was added to this aqueous solution to emulsify and disperse the hydrophobic dispersion in water. To this emulsified dispersion, 500 parts by weight of a 10% aqueous solution of gum arabic was added, and the mixture was stirred while adjusting the number of revolutions so that the particle diameter was about 100 μm. While maintaining the temperature at 50 ° C., the pH of the system was gradually lowered to 4.2 using a 10% aqueous acetic acid solution to form a gelatin / acacia complex coacervation. Lower the system temperature to below 10 ℃ 3
20% by weight of 7% formalin was added, and the pH was adjusted to 9.0 with a 10% aqueous sodium hydroxide solution and cured. The obtained electrophoretic particle-encapsulating microcapsules had a particle size of 98 μm,
The coefficient of variation was 55%. The contrast was measured with a display device using the microcapsules, and it was 1 (blue): 6.1 (white), which proved that the display contrast of the electrophoretic display medium was high.

(Comparative Example 1) The stirring apparatus was equipped with a blade diameter (d
The ratio (d1 / d2) of 1) to the inner diameter (d2) of the reaction vessel is 0.35, and the ratio (d1 / h1) of the total diameter (h1) of the blade diameter (d1) of the stirring blade and the height of the stirring blade. ) Is 1.5 and the height (h2) of the liquid level of the stirring solution is 1.3 times the total height (h1) of the stirring blades. The same operation as in 1 was performed to obtain electrophoretic particle-containing microcapsules. The particle size of the microcapsules was 115 μm, and the coefficient of variation was 124%.
An electrophoretic display medium was prepared in the same manner as in Example 1, and the reflected light intensities at the time of white display and blue display were determined as the contrast. As a result, the contrast was 1 (blue): 3.1.
It was (white).

(Comparative Example 2) The stirring apparatus was equipped with a stirring blade having a blade diameter (d
The ratio (d1 / d2) of 1) to the inner diameter (d2) of the reaction vessel is 0.8, and the ratio (d1 / h1) of the total diameter (h1) of the stirring blade diameter (d1) and the stirring blade height. ) Is 0.25, and the height (h2) of the liquid level of the stirring solution is 1.3 times the total height (h1) of the stirring blades. The same operation as in 1 was performed to obtain electrophoretic particle-containing microcapsules. The particle size of the microcapsules was 123 μm, and the coefficient of variation was 115%.
An electrophoretic display medium was prepared in the same manner as in Example 1, and the reflected light intensities at the time of white display and blue display were determined as the contrast. As a result, the contrast was 1 (blue): 2.9.
It was (white).

[0077]

EFFECTS OF THE INVENTION According to the present invention, in order to enable high contrast display in a display device using a microcapsule containing electrophoretic particles, a step of classifying a microcapsule having a relatively large and uniform particle diameter. The present invention provides a method for producing microcapsules containing electrophoretic particle-dispersed solution in which the content of electrophoretic particles in the microcapsules can be made uniform, and a display device using the same, which can be produced efficiently without Is.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an electrophoretic display medium using the electrophoretic particle dispersion-containing microcapsules of the present invention.

[Explanation of symbols]

25. Substrate, 26. Electrode, 27. Transparent electrode, 28. Microcapsule filling layer (matrix layer), 29. Microcapsules containing electrophoretic particle dispersion liquid, 30. spacer

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4G005 AA01 AB14 BA03 BB08 BB09                       BB13 BB15 CA07 DA12X                       DC13Y DC50Y DD05Z DD13W                       DD33Z DD57W DE04 DE05                       DE06 EA06                 4G035 AB38 AB40                 4G078 AA02 AB20 BA05 DA30

Claims (4)

[Claims] 1. The ratio (d1 / d2) of the blade diameter (d1) of the stirring blade and the inner diameter (d2) of the reaction vessel is 0.4 to 0.9, and the blade diameter (d1) of the stirring blade and stirring are performed. Total height of wings (h
The ratio (d1 / h1) of 1) is 0.3 to 1.5, and the height (h2) of the liquid level of the stirring solution is 1.2 times or more the total height (h1) of the stirring blades. Using a stirring blade and a reaction vessel, a hydrophobic dispersion of electrophoretic particles dispersed in a hydrophobic medium is emulsified and dispersed in a hydrophilic medium containing a dispersion stabilizer,
A method for producing microcapsules containing an electrophoretic particle-dispersed solution, which comprises microencapsulating the emulsified and dispersed hydrophobic dispersion. 2. The electrophoretic particle-dispersed liquid-encapsulating microcapsules according to claim 1, wherein the electrophoretic particles are composed of at least two kinds of colored particles having different color tones and electrophoretic properties. Method. 3. An electrophoretic particle dispersion liquid-containing microcapsule produced by the method for producing an electrophoretic particle dispersion liquid-containing microcapsule according to claim 1. 4. A reversible display medium comprising the electrophoretic particle dispersion-containing microcapsules according to claim 3 sandwiched between two opposing electrodes, at least one of which is transparent.