JP4815844B2 - Method for producing microcapsules - Google Patents

Description

  The present invention relates to a method for producing a microcapsule, wherein a capsule wall is formed by a radical polymerization reaction. The microcapsules manufactured by the manufacturing method can be applied to a reversible display medium.

  Microcapsules are used in many fields such as recording materials such as pressure-sensitive recording paper and heat-sensitive recording paper, agricultural chemicals, medicines, fragrances, liquid crystals, adhesives and the like. Many methods have been proposed for the production method, and as a typical microencapsulation method, a coacervation method, an interfacial polymerization method, an in-situ polymerization method, or the like is known.

  Among them, the method of forming a microcapsule wall by an in-situ radical polymerization reaction has been used as a useful technique because it can easily control the particle diameter and the thickness of the capsule wall and can easily perform the capsule formation reaction. Furthermore, since there are many types of materials for encapsulation, it has an excellent feature that the properties of the capsule wall can be freely controlled according to the desired application.

  Such a microcapsule production method by radical polymerization involves a process of dissolving a monomer as a raw material of a capsule wall in a dispersion medium or a dispersoid and proceeding polymerization to form a capsule wall. This method has the advantage that any monomer can be used as long as it can be dissolved. However, since the monomer is uniformly distributed in the dispersion medium or the dispersoid, or both the dispersion medium and the dispersoid, there is a problem that the monomer concentration at the interface is low and efficient capsule wall formation cannot be achieved. In addition, when a monomer that is compatible with the dispersion medium is used as the monomer, polymerization also proceeds outside the capsule, so that a by-product is generated and a step for removing it is required, or the entire reaction system is gelled. There was a problem. On the other hand, when a monomer that is compatible with the dispersoid is used, the polymerization also proceeds inside the capsule, which causes problems such as a decrease in the transparency of the microcapsule and the encapsulation of the capsule inclusion. .

  In recent years, with the development of information equipment, the amount of data of various types of information has been steadily expanding, and information output has also taken various forms. The form of information output is generally displayed on a display screen using a cathode ray tube or liquid crystal. However, these displays are required to be portable and have low power, and new displays are being actively developed. Yes. As such a new display, a dispersion system in which electrophoretic particles are dispersed in a dispersion medium colored in a different color tone from the particles is enclosed in microcapsules, and these microcapsules are arranged between electrodes. An electrophoretic display device has been proposed (for example, Patent Documents 1 to 3).

  This method is a reflective display that does not require a backlight, such as a liquid crystal display, which reduces the burden on the user's eyes, does not become difficult to see even if the viewing angle is changed, and compares response times It can be rewritten as quickly as possible, and the electrophoretic particles that have moved onto the electrode by applying a voltage have a memory property that maintains its state for a long time even if the voltage is removed, thus maintaining a certain display. Excellent performance as a display device is expected, such as not requiring power for the time to do.

  As a method for producing a microcapsule encapsulating electrophoretic particles, it is disclosed to use a general microencapsulation method as described above. In particular, the preparation of microcapsules by radical polymerization utilizing a hydrophilic monomer is a useful technique because it does not have an adverse effect such as immobilization of inclusions. However, when a large amount of a hydrophilic monomer is used, the entire reaction system is gelled, which makes it difficult to isolate microcapsules.

JP-A-1-86116 US Pat. No. 6,241,921 US Pat. No. 6,262,706

  An object of the present invention is to provide a microcapsule production method using radical polymerization that does not involve gelation of a reaction system even when a large amount of a hydrophilic monomer is used, the microcapsule, and a reversible display medium using the microcapsule. Is to provide.

As a result of intensive investigations, the present inventors are a method in which capsule walls are formed by radical polymerization reaction, and the above problem is achieved by producing microcapsules using a hydrophilic monomer (A) and a polymerization inhibitor (B). It was found that can be solved.
That is, the present invention is a method for producing a microcapsule in which a capsule wall is formed by radical polymerization reaction of a polymerizable monomer at an interface between an oil-soluble solvent and a water-soluble solvent,
The oil-soluble solvent contains electrophoretic particles (C),
The water-soluble solvent contains a polymerizable monomer and a polymerization inhibitor (B), and
The polymerizable monomer contains 10 to 100% by weight of the hydrophilic monomer (A) based on the total polymerizable monomer, and
It is related with the manufacturing method of the microcapsule whose polymerization inhibitor (B) is 0.05-10 weight part with respect to 100 weight part of polymerizable monomers.

  Moreover, this invention relates to the manufacturing method of the said microcapsule whose polymerization inhibitor (B) is a water-soluble polymerization inhibitor.

  Moreover, this invention relates to the manufacturing method of the said microcapsule whose polymerization inhibitor (B) is nitrite.

  Moreover, this invention relates to the microcapsule manufactured by the said manufacturing method.

  The present invention also relates to a reversible display medium in which the microcapsule is sandwiched between two opposing electrodes, at least one of which is transparent.

  By using this production method, microcapsules can be produced and isolated using a large amount of a hydrophilic monomer without gelation of the reaction system. Therefore, especially when applied as an electrophoretic display device, the microcapsules can be isolated while minimizing the influence on the encapsulated electrophoretic particles, thereby inhibiting the electrophoretic properties of the electrophoretic particles. Therefore, it is possible to provide a reversible display medium that exhibits excellent electrophoretic display.

  The method for producing a microcapsule of the present invention comprises a microcapsule that forms a capsule wall and encloses a dispersoid by advancing a radical polymerization reaction using a dispersion containing a hydrophilic monomer (A) and a polymerization inhibitor (B). The capsule is manufactured. At this time, the dispersion medium and the dispersoid can use a solvent that is phase-separated from each other, but an oil-soluble solvent can be used as the dispersoid, and a water-soluble solvent can be used as the dispersion medium.

The present invention is described in detail below. As the hydrophilic monomer (A) used in the present invention, a water-soluble compound having an unsaturated double bond can be used. The hydrophilicity of the hydrophilic monomer (A) in the present invention means that the solubility in water at 20 ° C. is 1% by weight or more. More preferably, it is 3% by weight or more. By using such a hydrophilic monomer (A), the monomer concentration in the water-soluble solvent can be increased, and the capsule wall formation reaction can be performed more efficiently while suppressing the effect on the inclusion. preferable.
Examples of the hydrophilic monomer (A) include a compound having a nitrogen atom and a compound having a carboxyl group, which impart water solubility. Specifically, a compound having an unsaturated double bond on a nitrogen atom such as N-vinylcaprolactam and N-vinylcarbazole,

  (Meth) acrylic acid, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, aminoalkoxyalkyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, ethylene glycol mono (Meth) acrylate, diethylene glycol mono (meth) acrylate, triethylene glycol mono (meth) acrylate, tetraethylene glycol mono (meth) acrylate, propylene glycol mono (meth) acrylate, dipropylene glycol mono (meth) acrylate, tripropylene glycol Besides mono (meth) acrylate, tetrapropylene glycol mono (meth) acrylate, ethylene glycol di (meth) acrylate Polyethylene glycol di (meth) acrylate of having two or more alkylene oxide units (meth) acrylate compound,

  (Meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl methacrylamide, N, N-dimethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meta ) Acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, (meth) acryloylmorpholine, N-isopropyl (meth) acrylamide, N-diacetone (meth) acrylamide, methylenebis (meth) acrylamide (Meth) acrylamide compounds such as

  Vinyl ether compounds such as hydroxyethyl vinyl ether, triethylene glycol monovinyl ether, triethylene glycol divinyl ether,

  Dicarboxylate compound having an unsaturated double bond such as fumaric acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride, dimethylmaleic acid, dimethylmaleic anhydride, or the anhydride thereof,

  Maleimide, N- (2-hydroxyethyl) maleimide, N- (4-chlorophenyl) maleimide, N-methylmaleimide, N-ethylmaleimide, N-butylmaleimide, N-phenylmaleimide, citraconimide, N-methylcitraconimide, Maleimide compounds such as dimethylmaleimide,

  Crotonic acid derivatives such as crotonic acid and crotonic anhydride,

  Examples thereof include compounds having an unsaturated double bond on the nitrogen atom, such as N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone and N-vinylimidazole.

  Examples of the vinyl ether compound include hydroxyethyl vinyl ether, triethylene glycol monovinyl ether, and triethylene glycol divinyl ether, but are not limited thereto. Moreover, these hydrophilic monomers (A) can be used alone or in admixture of two or more.

  Furthermore, a polymerizable monomer other than the hydrophilic monomer (A) can be used for the purpose of controlling capsule formation efficiency, capsule strength, capsule wall thickness, gelation prevention properties, and the like. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, n-amyl (meta ) Acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate , Lauryl (meth) acrylate, hydroxybutyl (meth) acrylate, benzyl (meth) acrylate, phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, cyclohexyl (meth) acrylate, Bornyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, hexanediol di (meth) acrylate, nonanediol di (meth) acrylate, dicyclopenta (Meth) acrylate compounds such as dienyl di (meth) acrylate and acrylated cyanurate,

  Styrene derivatives such as styrene, α-methylstyrene, p-methylstyrene, t-butylstyrene, chlorostyrene, divinylbenzene,

  Nitrile compounds having an unsaturated double bond such as (meth) acrylonitrile, fumaronitrile, crotonnitrile,

  Carboxylic acid vinyl ester compounds such as vinyl acetate, vinyl monochloroacetate, vinyl pivalate,

  Dimethyl fumarate, diethyl fumarate, dibutyl fumarate, dimethyl maleate, diethyl maleate, dibutyl maleate, dimethyl itaconate, diethyl itaconate, dibutyl itaconate, dimethyl citraconate, diethyl citraconate, dibutyl citraconate A dicarboxylate compound having an unsaturated double bond such as

  Vinyl ether compounds such as methyl vinyl ether, ethyl vinyl ether, hydroxybutyl vinyl ether, 2-chloroethyl vinyl ether, isobutyl vinyl ether, dodecyl vinyl ether, cyclohexyl vinyl ether, butanediol divinyl ether, hexanediol divinyl ether,

  Halogenated olefin compounds such as vinyl chloride and vinylidene chloride,

  In addition to olefin compounds such as ethylene, butadiene, isobutylene, isoprene and cyclopentadiene, compounds having an allyl group can be exemplified, but the invention is not limited thereto. Moreover, these can be used individually by 1 type or in mixture of 2 or more types.

  The hydrophilic monomer (A) is preferably used in an amount of 10 to 100% by weight based on the entire polymerizable monomer. In particular, it can be preferably used in the region of 50 to 100% by weight of the whole polymerizable monomer that has not been used conventionally.

  As the polymerization inhibitor (B) used in the present invention, those capable of acting on monomer radicals, oligomer radicals, and polymer radicals during the progress of radical polymerization to stop further progress of the radical polymerization can be used. Specifically, quinones such as parabenzoquinone, p-naphthoquinone, 2,5-diphenyl p-benzoquinone,

  Phenols such as hydroquinone, hydroquinone monomethyl ether, hydroquinone monoethyl ether, hydroquinone monobutyl ether, mono t-butyl hydroquinone, di-t-butyl paracresol, naphthol,

  Ammonium salts such as triethylamine and dimethylaniline hydrochloride, acetate, carbonate,

  Thiocyanates such as ammonium thiocyanate, zinc thiocyanate, sodium thiocyanate, potassium thiocyanate, aluminum thiocyanate,

  Nitrites such as sodium nitrite, potassium nitrite, ammonium nitrite, calcium nitrite, silver nitrite, strontium nitrite, cesium nitrite, barium nitrite, magnesium nitrite, lithium nitrite, dicyclohexylammonium nitrite,

  Mercaptoethanol, monothiopropylene glycol, thioglycerol, thioglycolic acid, thiohydroacrylic acid, thiolactic acid, thiomalic acid, thioethanolamine, β-nitroethyl mercaptan, 1,2-dithioglycerol, 1,3-dithioglycerol, Dimercaptocarboxylic acid such as 1,3-dimercaptoacetone, β, β-dithioisobutyric acid, thioglycol, thiodiglycol, thiodiglycolic acid, β, β-thiodipropionic acid, thiodilactic acid, β-methylthiopropionaldehyde , Β-aminoethyl sulfide, nitro-substituted sulfide such as β-nitroethyl sulfide, and water-soluble sulfur-containing organic compounds such as β-mercaptoethyl sulfide,

    In addition, alkali metal salts such as isothiocyanic acid, alkaline earth metal salts, ammonium salts, alkali metal salts such as phosphinic acid, inorganic acid salts such as alkaline earth metal salts, bromides such as sodium and potassium, sodium, Non-limiting examples include halides such as iodides such as potassium, calcium, and ammonium, and transition metal ions. Moreover, these can be used individually by 1 type or in mixture of 2 or more types.

The polymerization inhibitor (B) is preferably a water-soluble polymerization inhibitor. More preferably, the water-soluble polymerization inhibitor has a solubility in water at 20 ° C. of 0.25% by weight or more. More preferably, it is 1% by weight or more. By using such a polymerization inhibitor (B), it is preferable because the amount of blending with respect to the dispersion medium can be increased, so that gelation of the reaction system can be efficiently suppressed.
Among water-soluble polymerization inhibitors, nitrite is particularly recommended because it has many components distributed in the dispersion medium and can effectively suppress the gel in the reaction system.

  The polymerization inhibitor (B) is preferably used in an amount of 0.05 to 10 parts by weight with respect to 100 parts by weight of the polymerizable monomer. If the amount is less than the above range, the effect of preventing gelation cannot be obtained. If the amount is not less than the above range, the polymerizability is lowered and the formation of microcapsules is inhibited. Therefore, it is preferably used within the above range. More preferably, it is 0.1-5 weight part, More preferably, it is 0.25-3 weight part.

  Examples of the oil-soluble solvent used in the present invention include aromatic hydrocarbons such as benzene, toluene, xylene, phenylxylylethane, diisopropylnaphthalene, naphthenic hydrocarbons,

Aliphatic hydrocarbons such as hexane, dodecylbenzene, cyclohexane, kerosene, paraffin hydrocarbons,

Halogenated hydrocarbons such as chloroform, trichloroethylene, tetrachloroethylene, trifluoroethylene, tetrafluoroethylene, dichloromethane, ethyl bromide,

Phosphate esters such as tricresyl phosphate, trioctyl phosphate, octyl diphenyl phosphate, tricyclohexyl phosphate,

Phthalic acid esters such as dibutyl phthalate, dioctyl phthalate, dilauryl phthalate, dicyclohexyl phthalate, butyl oleate, diethylene glycol dibenzoate, dioctyl sebacate, dibutyl sebacate, dioctyl adipate, trioctyl trimellitic acid, acetyl citrate Carboxylic acid esters such as triethyl, octyl maleate, dibutyl maleate, ethyl acetate,

Isopropylbiphenyl, isoamylbiphenyl, chlorinated paraffin, diisopropylnaphthalene, 1,1-ditolylethane, 1,2-ditolylethane, 2,4-ditertiaryaminophenol, N, N-dibutyl-2-butoxy-5-tertioctylaniline However, it is not limited to these. These organic solvents can be used alone or in combination of two or more.

  As the water-soluble solvent used in the present invention, a solvent that is incompatible with an oil-soluble solvent such as water can be used. Organic solvents such as methanol, acetone and acetonitrile can also be used, but ones that are not compatible with oil-soluble solvents must be selected. A water-soluble solvent is not limited to these, Each can be used individually or in mixture of 2 or more types.

  Further, a surfactant can be used to stabilize the dispersion state of the dispersoid in the dispersion medium. Surfactants include nonionic (nonionic) surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactant ions that can be dissolved or mixed in the dispersion medium. These surfactants can be used alone or in admixture of two or more. A reactive surfactant having one or more radically polymerizable unsaturated double bonds in the molecule can also be used.

As these surfactants, for example, polyoxyethylene nonylphenol ether, polyoxyethylene dinonylphenol ether, polyoxyethylene octylphenol ether, polyoxyethylene styrenated phenol, polyoxypolyoxyethylene bisphenol A, polyoxyethylene nonylphenol ether Polyoxyalkylene alkylphenol ethers such as oxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, and nonylphenol ethoxylate;
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; and alkyl alcohol ethers such as secondary linear alcohol ethoxylate and polynuclear phenol ethoxylate.
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, polyoxy Polyoxyethylene sorbitan esters such as ethylene sorbitan sesquilaurate, polyoxyethylene sorbitan sesquipalmitate, and polyoxyethylene sorbitan sesquistearate.

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, unsaturated fatty acid stearyl ester, saturated fatty acid octyl ester, unsaturated fatty acid octyl ester, stearic acid polyethylene glycol ester, Fatty acid esters such as oleic acid polyethylene glycol ester and rosin polyethylene glycol ester. Fatty acids such as stearic acid, oleic acid, palmitic acid, lauric acid, myristic acid, and amidated compounds of these fatty acids. Polyoxyethylene alkylamines such as polyoxyethylene laurylamine, polyoxyethylene alkylamine, and polyoxyethylene alkylamine ether.

Higher fatty acid monoethanolamides such as lauric acid monoethanolamide and palm fatty acid diethanolamide, higher fatty acid diethanolamides, polyoxyethylene stearic acid amide, coconut diethanolamide (1-2 type / 1-1 type), alkylalkylol Amide compounds such as amides and alkanolamides. _{R- (CH 2 CH 2 O)} mH (CH 2 CH 2 O) nH, R-NH-C 3 H 6 -NH 2 [R = oleyl octyl dodecyl tetradecyl, hexadecyl, octadecyl, coconut, beef tallow, soybean Etc., m and n are integers of 0 or more. ] The alkanolamines represented by these.

Primary amines represented by R—NH ₂ [R = oleyl, octyl, dodecyl, tetradecyl, hexadecyl, ocladesil, palm, beef tallow, soybean, etc.] Secondary amines represented by R ¹ R ² —NH [R ¹ · R ² = R = oleyl, octyl, dodecyl, tetradecyl, hexadecyl, ocladesil, palm, beef tallow, soybean, etc.] Tertiary amines represented by R ¹ R ² R ³ N [R ¹ , R ² , R ³ = oleyl, octyl, dodecyl, tetradecyl, hexadecyl, octadecyl, palm, beef tallow, soybean, etc.] Various synthetic higher alcohols and various natural higher alcohols. Polymers such as acrylic acid compounds, polycarboxylic acid compounds, hydroxy fatty acid oligomers, hydroxy fatty acid oligomer modified products, and oligomers can be used.

  Examples of anionic surfactants include carboxylates such as polycarboxylic acid type polymer surfactants, polycarboxylic acid type anionic surfactants, special fatty acid soaps, and rosin soaps. Castor oil sulfate ester salt, sulfate ester salt of lauryl alcohol, sulfate ester amine salt of lauryl alcohol, natural alcohol sulfate ester Na salt, sulfate alcohol ester of lauryl alcohol ether such as higher alcohol sulfate ester Na salt Amine salt, sulfate sodium salt of lauryl alcohol ether, sulfate amine salt of synthetic higher alcohol ether, sulfate ester Na salt of synthetic higher alcohol ether, alkyl polyether sulfate amine salt, alkyl polyether sulfate Na salt, natural alcohol EO (ethylene oxide) addition system sulfate ester amine salt, natural alcohol EO (ethylene oxide) addition system sulfate ester Na salt, synthetic alcohol EO (ethylene oxide) adduct Sulfate amine salt, synthetic alcohol EO (ethylene oxide) addition system sulfate ester Na salt, alkylphenol EO (ethylene oxide) addition system sulfate ester amine salt, alkylphenol EO (ethylene oxide) addition system sulfate ester Na salt, polyoxyethylene nonylphenyl ether sulfate Sulfate salts such as amine salts, polyoxyethylene nonylphenyl ether sulfate Na salt, polyoxyethylene polycyclic phenyl ether sulfate amine salt, polyoxyethylene polycyclic phenyl ether sulfate Na salt; Various alkyl allyl 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, naphthalene sulfone Sulfonates such as acid formalin condensates.

Polyoxyethylene nonylphenyl ether sulfonic acid amine salt, polyoxyethylene nonylphenyl ether sulfonic acid Na salt, polyoxyethylene special allyl ether sulfonic acid amine salt, polyoxyethylene special allyl ether sulfonic acid Na salt, polyoxyethylene tridecylphenyl Polyoxyalkylene sulfonates such as ether sulfonic acid amine salt, polyoxyethylene tridecyl phenyl ether sulfonic acid Na salt, polyoxyethylene alkyl ether sulfonic acid amine salt, and polyoxyethylene alkyl ether sulfonic acid Na salt. Dialkyl sulfosuccinate amine salt, dialkyl sulfosuccinate Na salt, polycyclic phenyl polyethoxy sulfosuccinate amine salt, polycyclic phenyl polyethoxy sulfosuccinate Na salt, polyoxyethylene alkyl ether sulfosuccinate monoester amine salt, poly Sulfosuccinic acid ester salts such as oxyethylene alkyl ether sulfosuccinic acid monoester Na salt. Alkyl phosphate ester, alkoxyalkyl phosphate ester, higher alcohol phosphate ester, higher alcohol phosphate, alkylphenol type phosphate ester, aromatic phosphate ester, polyoxyalkylene alkyl ether phosphate ester, polyoxyalkylene alkyl allyl ether Phosphate esters such as phosphate esters and phosphates can be used.

Examples of the cationic surfactant include alkyltrimethylamine represented by RN (CH ₃ ) 3X [R = stearyl, cetyl, lauryl, oleyl, dodecyl, palm, soybean, beef tallow, etc./X=halogen, amine, etc.] System quaternary ammonium salts. Quaternary ammonium salts such as tetramethylamine salts and tetrabutylamine salts. Acetates represented by (RNH ₃ ) (CH ₃ COO) [R = stearyl, cetyl, lauryl, oleyl, dodecyl, palm, 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 · X [R = stearyl cetyl lauryl oleyl dodecyl coconut, soybean beef tallow / X = halogen amine , M, and n are integers of 0 or more], and polyoxyalkylene-based quaternary ammonium salts can be used.

  Examples of amphoteric surfactants include various betaine surfactants, various imidazoline surfactants, β-alanine surfactants, polyoctyl polyaminoethylglycine hydrochloride, and the like. Various other protective colloid agents can also be used.

  Examples of reactive surfactants include sulfonate salts (for example, commercially available products Latemul S-120, S-180P, S-180A, Sanyo Kasei Co., Ltd., Eleminol JS-2, RS- 30 etc.) and alkylphenol ether type (as a commercial item, for example, Dairon Kogyo Seiyaku Co., Ltd. Aqualon HS-10, RN-20 etc.) can be used.

  More preferable as the surfactant is a reactive surfactant containing an unsaturated double bond. By containing an unsaturated double bond, the surfactant is also immobilized on the capsule wall by radical polymerization, which is preferable because a stronger microcapsule can be formed.

  Examples of the surfactant include a water-soluble acrylic resin, a water-soluble polyurethane resin, a water-soluble polyester resin, and a water-soluble epoxy resin. Further, it is more preferable that the monomer be selected and synthesized or modified so that an unsaturated double bond is contained in each resin skeleton, so that it can be used as a reactive surfactant. In addition, maleic acid copolymer (styrene, ethylene, propylene, methyl vinyl ether, vinyl acetate, isobutylene, butadiene copolymer with maleic acid, etc.), carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, gelatin, gum arabic starch derivative, Polyvinyl alcohol or the like can also be used as a surfactant.

  Further, other nonionic surfactants, ionic surfactants and inorganic fine particles for controlling the emulsified state include, for example, talc, bentonite, organic bentonite, white carbon, colloidal silica, colloidal alumina, fine particles. Silica, calcium carbonate, calcium sulfate and the like can be used in combination.

  Moreover, as a radical polymerization initiator, the compound which can generate a radical by heating can be used. Specifically, 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-hexylperoxy) cyclohexane, 1,1-bis (t-butyl) Peroxy) -3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, 1,1-bis (t-butylperoxy) cyclododecane, 2,2-bis (t- Butylperoxy) butane, n-butyl-4,4-bis (t-butylperoxy) valerate, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, p-menthane hydroper Oxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide , T-hexyl hydroperoxide, t-butyl hydroperoxide, t-butylcumyl peroxide, di-t-butyl peroxide, isobutyryl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide Oxide, lauroyl peroxide, stearoyl peroxide, succinic peroxide, m-toluoyl peroxide, benzoyl peroxide, di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, bis (4-t-butylcyclohexyl) ) Peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, di-2-methoxybutyl peroxydicarbonate, di 3-methyl-3-methoxybutyl) peroxydicarbonate, α, α'-bis (neodecanoylperoxy) diisopropylbenzene, cumylperoxyneodecanoate, 1,1,3,3-tetramethylbutylper Oxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, t-hexylperoxyneodecanoate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t -Butyl peroxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, t-hexylper Xyl-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-hexylperoxyisopropylmonocarbonate, t-butylperoxymaleic acid, t- Butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, 2,5-dimethyl-2,5-bis (m-toluoylperoxy) hexane, t-butylperoxyisopropyl Monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-bis (benzoylperoxy) hexane, t-butylperoxyacetate, t-butyl Peroxy-m-toluoyl benzoate, t-butyl pero Organic peroxides such as xylbenzoate and bis (t-butylperoxy) isophthalate,

2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis {N- (2-propenyl) -2-methylpropionamide}, 2,2′-azobis (N-butyl-2-methylpropionamide), 2,2′-azobis (N-cyclohexyl-2-methylpropionamide), dimethyl-2,2′-azobisisobutyrate, 2 Azo compounds such as 2,2′-azobis (2,4,4-trimethylpentane),

In addition, a redox initiator comprising a combination of an oxidizing agent such as sodium peroxodisulfate, potassium peroxodisulfate and ammonium peroxodisulfate and a reducing agent such as Rongalite can be used, but is not limited thereto. These polymerization initiators can be used alone or in combination of two or more.

  Also, use of mercaptans such as octyl thioglycolate, methoxybutyl thioglycolate, octyl mercaptopropionate, methoxybutyl mercaptopropionate, stearyl mercaptan, α-methylstyrene dimer, etc. as chain transfer agents for molecular weight adjustment Can do.

  In order to apply the microcapsule of the present invention as an electrophoretic display device, the electrophoretic particles (C) must be present in the capsule. The microcapsules encapsulating the electrophoretic particles (C) are produced by dispersing the electrophoretic particles (C) in the dispersoid in advance, further dispersing the dispersoid in a dispersion medium, and performing a radical polymerization reaction. can do.

  As the electrophoretic particles (C) used, inorganic pigment particles and organic pigment particles can be used. Examples of 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, and cadmium yellow. , Cadmium lipoton yellow, yellow iron oxide, titanium yellow, titanium barium yellow, cadmium orange, cadmium lipoton orange, molybdate orange, bengara, red lead, silver vermilion, cadmium red, cadmium lipoton red, amber, brown iron oxide, Zinc iron chrome brown, chrome green, chromium oxide, viridian, cobalt green, cobalt chrome green, titanium cobalt green, bitumen, cobalt blue, ultramarine, cerulean blue, cobalt aluminum chrome -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, etc. Can be used.

  Examples of 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, resol red, bon lake red, lake red, brilliant carmine, Bordeaux 10B, Naphthol Red, Quinacridone Magenta, Condensed Azo Red, Naphthol Carmine, Perylene Scar Red, Azo Scar Red, Benzimidazolone Carmine, Anthraquinonyl Red, Perylene Red, Perylene Maroon, Quinacridone Maroon, Quinacridone Scar Red, Quinacridone Red, Diketopyrrolopyrrole Red, Benzimidazolone Brown, Phthalocyanine Green, Victoria Blue Lake, Phthalocyanine Blue, fast sky blue, alkali blue toner, indanthrone blue, rhodamine B lake, methyl violet lake, dioxazine violet, naphthol violet and the like can be used.

  In addition, polymer fine particles can be used as the electrophoretic particles (C). 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. However, it is not limited to what was produced by these methods.

  Examples of the polymer fine particle material include styrene, styrene-acrylic, styrene-isoprene, divinylbenzene, methyl methacrylate, methacrylate, ethyl methacrylate, ethyl acrylate, n-butyl acrylate, and acrylic acid. , Acrylonitrile, acrylic rubber-methacrylate, ethylene, ethylene-acrylic acid, nylon, silicone, urethane, melamine, benzoguanamine, phenol, fluor (tetrachloroethylene), vinylidene chloride, quaternary pyridinium Examples thereof include a salt system, synthetic rubber, cellulose, cellulose acetate, chitosan, and calcium alginate, but are not limited to these polymer materials. The polymer fine particles used in the present invention may be dyed with a dye as necessary, or may be colored by containing pigment particles.

  Further, these pigment components are preferably used not only as fine particles of the pigment alone but also in various surface-treated states. As a surface treatment method in this case, various methods usually performed on pigment particles can be applied. For example, a pigment surface coated with various compounds such as a polymer, titanate-based, silane-based And the like, and those obtained by coupling treatment with various coupling agents such as those described above. In addition, these pigment particles can be used in a state of being subjected to mechanochemical treatment, such as composite particles formed between pigment particles or between polymer particles and hollow polymer particles, and various resins. It can also be used as a form of composite particles formed between the two.

  The particle diameter of these electrophoretic particles (C) is preferably 0.01 to 10 μm, more preferably 0.05 to 5 μm, but is not limited to these particle diameters.

  The dispersoid encapsulated in the microcapsule of the present invention may contain one or more additives for the purpose of enhancing the dispersibility of the electrophoretic particles (C) and controlling the charge amount. preferable. As these additives, the same surfactants as those described above can be used, and those which can be dissolved or mixed with the dispersoid are preferable.

  When microcapsules are used as an electrophoretic display device, the type and amount of electrophoretic particles (C) and additives may be adjusted so that the conductivity of the dispersoid solution is 0 to 20 pS / cm. preferable.

  Next, a typical method for synthesizing the microcapsules used in the present invention is shown. Oil-soluble solvent, water-soluble solvent, hydrophilic monomer (A), polymerization inhibitor (B), radical polymerization initiator, in some cases, polymerizable monomer other than hydrophilic monomer (A), surfactant, additive, chain A dispersion is prepared by mixing a transfer agent and the like. In some cases, the electrophoretic particles (C), additives, and the like are previously added to the oil-soluble solvent.

  The oil-soluble solvent is used in an amount of 1 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the water-soluble solvent. The polymerizable monomer is used in an amount of 1 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the water-soluble solvent. The radical polymerization initiator is used in an amount of 0.005 to 5 parts by weight, preferably 0.05 to 2.5 parts by weight, based on 100 parts by weight of the polymerizable monomer. The surfactant is suitably used in an amount of 0.2 to 10 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the water-soluble solvent. When forming microcapsules for the purpose of use as an electrophoretic display device, electrophoretic particles (C) are dispersed in an oil-soluble solvent. The electrophoretic particles (C) are used in an amount of 0.1 to 20 parts by weight, preferably 1 to 10 parts by weight, based on 100 parts by weight of the oil-soluble solvent.

  Next, the target microcapsules are obtained by heating the dispersion to a predetermined temperature in a nitrogen atmosphere to advance the radical polymerization reaction.

  Furthermore, in the present invention, an electric field responsive reversible display method is provided using microcapsules containing electrophoretic particles (C). Examples of the electrophoretic display medium include: Of a pair of substrates, at least one of which is transparent, at least one substrate has an electrode on one side, and the electrode surface is formed so as to face one substrate with or without a spacer. An electrophoretic reversible display medium in which the electrophoretic particles (C) encapsulating microcapsules of the present invention are filled in the formed space can be mentioned. Or at least one board | substrate has an electrode on one side among a pair of board | substrates with which at least one is transparent, and this electrode surface is arrange | positioned facing one board | substrate through and / or without a spacer. An electrophoretic reversible display medium in which the space formed in (1) is divided discontinuously by a matrix material and filled with the electrophoretic particle (C) -encapsulating microcapsules of the present invention. Alternatively, an electrophoretic reversible display medium in which an electrophoretic particle (C) -encapsulating microcapsule of the present invention and a coating layer made of a matrix material are formed on the electrode surface side of a transparent or opaque substrate having an electrode on one side Can be used. Alternatively, a coating layer composed of the electrophoretic particles (C) 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 side, and the coating layer is formed on the coating layer. And an electrophoretic reversible display medium provided with an overcoat layer. In addition, the board | substrate in this invention has shown both what has an electrode surface and what does not have.

  FIG. 1 shows an electrophoretic particle (C) -encapsulating microcapsule of the present invention filled in a space formed by a pair of electrode substrates with a spacer interposed therebetween as a reversible display recording layer. A display medium is produced. The reversible display recording layer is prepared by dissolving, dispersing, suspending or emulsifying the electrophoretic particles (C) encapsulating microcapsules of the present invention and a matrix material to prepare a coating solution, and coating the resulting coating solution with a wire bar coat, It is obtained by coating and drying on an electrode plate by a method such as roll coating, 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, and gold. .

  As the matrix material, the same material as the wall material of the microcapsule, or polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl butyral, polyvinyl alcohol, polyethylene oxide, polypropylene Oxide, ethylene-vinyl alcohol copolymer, polyacetal, acrylic resin, methyl cellulose, ethyl cellulose, phenol resin, fluorine resin, silicone resin, diene resin, polystyrene thermoplastic elastomer, polyolefin thermoplastic elastomer, polyurethane thermoplastic elastomer, polyester Thermoplastic elastomer, polyphenylene ether, polyphenylene sulfide, polyether sulfone, polyether ketone, Realylate, aramid, polyimide, poly-p-phenylene, poly-p-xylene, poly-p-phenylene vinylene, polyhydantoin, polyparabanic acid, polybenzimidazole, polybenzothiazole, polybenzooxadiazole, polyquinoxaline, as described above One or more materials selected from a thermosetting resin, an active energy ray curable resin, or a mixture thereof can be used.

  As a material for forming the overcoat layer, the material for forming the matrix material can be used. The overcoat layer comprises a protective layer material composition in which a medium, a curing agent, a catalyst and / or a co-catalyst for dissolving, dispersing, suspending or emulsifying these materials is added to the display layer. It is formed by a coating method such as coating, blade coating, dip coating, spray coating, spin coating, or gravure coating, or sputtering and chemical vapor deposition. The thickness of the overcoat layer is preferably as thin as possible within the range having the function of protecting the recording layer, and is about 0.1 to 100 μm, more preferably 0.3 to 30 μm.

  Hereinafter, the present invention will be described with reference to examples. In the examples, “parts” and “%” indicate “parts by weight” and “% by weight”, respectively.

Example 1
Dispersoid solution 1: 150 parts by weight of dodecane as an oil-soluble solvent, 5 parts by weight of titanium dioxide (DuPont, Ti-PURE R101) as electrophoretic particles (C), titanium black (black titanium manufactured by Ako Kasei) 5 parts by weight and 0.1 part of OLOA4382 (manufactured by Chevron) as an additive were added and dispersed for 10 minutes using an ultrasonic disperser. Further, 1.5 parts by weight of 2,2′-azobis (2,4-dimethylvaleronitrile) was added as a polymerization initiator and stirred to prepare a dispersoid solution.
Dispersion medium solution 1: 1500 parts by weight of ion-exchanged water as a water-soluble solvent, 15 parts by weight of Aqualon HS-10 (Daiichi Kogyo Seiyaku Co., Ltd.) as a reactive surfactant, and acrylic acid 80 as a hydrophilic monomer (A) The dispersion medium solution was prepared by adding and stirring 10 parts by weight of triethylene glycol diacrylate, 60 parts by weight of acrylonitrile as the other polymerizable monomer, and 1.5 parts by weight of sodium nitrite as the polymerization inhibitor (B). did.

  The dispersoid solution 1 was added to the dispersion medium solution 1 and the mixture was stirred at 25 ° C. for 10 minutes in a nitrogen atmosphere, then heated to 60 ° C. and reacted for 3 hours to obtain a microcapsule 1.

  Next, 20 g of the obtained microcapsule 1 was added to 80 g of a 10% by weight polyvinyl alcohol aqueous solution to prepare a dispersion coating solution. Using an applicator with a gap of 100 μm, this coating solution is applied onto an ITO film-coated glass plate (on the ITO film) and dried to form a microcapsule coating film. An electrophoretic display medium was prepared by placing the microcapsule coating side). The electrophoretic display medium thus created was connected to a DC power source, the electric field direction was switched at a rectangular frequency of 10 Hz, and a voltage of ± 100 V was applied to perform electrophoretic display. When titanium dioxide particles are electrophoresed on the top and titanium black particles are electrophoresed on the bottom electrode, white (the electric field of the top electrode is negative) is displayed, but the titanium black particles are electrophoresed on the top and the titanium dioxide particles are electrophoresed on the bottom electrode. In this case, it was possible to display black (the electric field of the upper electrode was positive at this time).

(Example 2)
Dispersion medium solution 2: 1500 parts by weight of ion-exchanged water as a water-soluble solvent, 15 parts by weight of Aqualon HS-10 (Daiichi Kogyo Seiyaku Co., Ltd.) as a reactive surfactant, and 80 parts by weight of acrylamide as a hydrophilic monomer (A) A dispersion medium solution was prepared by adding 10 parts by weight of ethylene glycol diacrylate, 60 parts by weight of acrylonitrile as the other polymerizable monomer, and 1.5 parts by weight of sodium nitrite as the polymerization inhibitor (B).

  The dispersoid solution 1 was added to the dispersion medium solution 2 and the mixture was stirred at 25 ° C. for 10 minutes in a nitrogen atmosphere, then heated to 60 ° C. and reacted for 3 hours to obtain microcapsules 2.

  When an electrophoretic display medium is prepared by the same method as in Example 1 and electrophoretic display is performed, both titanium dioxide particles and titanium black particles exhibit the same electrophoresis as in Example 1, and white and black can be displayed. there were.

(Example 3)
Dispersion medium solution 3: 1500 parts by weight of ion-exchanged water as a water-soluble solvent, 15 parts by weight of Aqualon HS-10 (Daiichi Kogyo Seiyaku Co., Ltd.) as a reactive surfactant, and acrylic acid 80 as a hydrophilic monomer (A) The dispersion medium solution was prepared by adding and stirring 10 parts by weight of triethylene glycol diacrylate, 60 parts by weight of acrylonitrile as the other polymerizable monomer, and 1.5 parts by weight of hydroquinone monomethyl ether as the polymerization inhibitor (B). did.

  The dispersoid solution 1 was added to the dispersion medium solution 3 and the mixture was stirred at 25 ° C. for 10 minutes in a nitrogen atmosphere, then heated to 60 ° C. and reacted for 3 hours to obtain a microcapsule 3.

  When an electrophoretic display medium is prepared by the same method as in Example 1 and electrophoretic display is performed, both titanium dioxide particles and titanium black particles exhibit the same electrophoresis as in Example 1, and white and black can be displayed. there were.

(Comparative Example 1)
Dispersion medium solution 4: 1500 parts by weight of ion-exchanged water as a water-soluble solvent, 15 parts by weight of Aqualon HS-10 (Daiichi Kogyo Seiyaku Co., Ltd.) as a reactive surfactant, and acrylic acid 80 as a hydrophilic monomer (A) A dispersion medium solution was prepared by adding 10 parts by weight of triethylene glycol diacrylate and 60 parts by weight of acrylonitrile as the other polymerizable monomer and stirring.

  The dispersion solution 1 was added to the dispersion medium solution 4 and stirred at 25 ° C. for 10 minutes in a nitrogen atmosphere, and then heated to 60 ° C. for 3 hours to obtain a microcapsule-containing dispersion. Gelation occurred and the microcapsules could not be isolated.

The schematic diagram of the electrophoretic display medium using the electrophoretic particle dispersion inclusion | inner_cover microcapsule of this invention is represented.

Explanation of symbols

1. Substrate, 2. Electrodes, 3. 3. transparent electrode; 4. Matrix material (microcapsule filling layer) 5. Microcapsules containing electrophoretic particle dispersion, spacer

Claims (5)

A method for producing a microcapsule in which a capsule wall is formed by a radical polymerization reaction of a polymerizable monomer at an interface between an oil-soluble solvent and a water-soluble solvent,
The oil-soluble solvent contains electrophoretic particles (C),
The water-soluble solvent contains a polymerizable monomer and a polymerization inhibitor (B), and
The polymerizable monomer contains 10 to 100% by weight of the hydrophilic monomer (A) based on the total polymerizable monomer, and
The manufacturing method of the microcapsule whose polymerization inhibitor (B) is 0.05-10 weight part with respect to 100 weight part of polymerizable monomers. The method for producing microcapsules according to claim 1, wherein the polymerization inhibitor (B) is a water-soluble polymerization inhibitor. The method for producing microcapsules according to claim 2, wherein the polymerization inhibitor (B) is nitrite. Microcapsules formed by manufactured by the method according to any one of claims 1 to 3. A reversible display medium comprising the microcapsule according to claim 4 sandwiched between two opposing electrodes, at least one of which is transparent.

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