JP4428032B2 - Display solution for electrophoretic display media - Google Patents

Description

  The present invention relates to a display liquid for an electrophoretic display medium, and relates to a display liquid for an electrophoretic display medium comprising alkenyl succinic anhydride having 4 to 40 carbon atoms in alkenyl.

  There are liquid crystal, electrochromic, electrophoresis, magnetophoresis and the like as display methods capable of reversibly changing the visual state by the action of an electric field, and active research and development has been conducted in recent years (see Non-Patent Document 1). A display medium using them includes a pair of electrode substrates and a display element inserted between them, and a drive circuit for applying a signal for displaying an image to each electrode is connected to the display medium.

  The present invention relates to an electrophoretic display device using the electrophoretic method and a display liquid thereof, and the technical trend thereof will be described below.

  Display liquids for electrophoretic display devices are roughly classified into two according to their operating principles. The first type is a display liquid for electrophoretic display devices in which a dye is dissolved in an electrically insulating solvent and colored, and pigment particles or pigment-resin composite particles are dispersed in the colored liquid. A display liquid for an electrophoretic display device in which pigment particles or pigment-resin composite particles of the above color tone are dispersed in a colorless electrically insulating solvent.

  In the invention using the display liquid for the first type of electrophoretic display device, the display liquid for the electrophoretic display device is enclosed in a microcapsule, and this microcapsule is used as a display element and is arranged between electrodes. There is an electrophoretic display device (see Patent Document 1). In this electrophoretic display device display liquid, an inorganic pigment having a high refractive index such as titanium dioxide is dispersed in a dispersion medium colored by dissolving a dye.

  As the second type, a display liquid for electrophoretic display device in which colored particles of two different colors having different polarities are dispersed is formed via a spacer between two opposing electrodes at least one of which is transparent. An electrophoretic display element enclosed in a cell is proposed (see Patent Documents 2 and 3), and an example in which a display liquid for an electrophoretic display device is included in a microcapsule is illustrated.

  As another method of the second type, at least one of the display liquids for electrophoretic display devices in which at least two types of electrophoretic particles having the same electric polarity, different color tone and electrophoretic speed are dispersed is transparent. There has been proposed an electrophoretic display element enclosed in a cell formed through a spacer between two counter electrodes (see Patent Document 4).

  On the other hand, as a means for preventing the aggregation of the electrophoretic particles having different charges of the second type, it has been proposed to use a steric or electrical repulsion effect by a steric hindrance agent or a charge control agent ( (See Patent Document 5).

  As another method of the second type, a display liquid for an electrophoretic display device has been proposed, which is composed of large concealing white particles composed of a resin and a white pigment, magnetic colored particles for display, and a solvent (patent). Reference 6).

Further, as an example including each of the first and second types, it is constituted by a dispersion medium containing at least one kind of charged particles and a surfactant, and at least one kind of the charged particles includes: Some contain at least a quaternary ammonium compound (see Patent Document 7).
The latest technology of digital paper, CMC, 2001 Patent No. 2551783 JP 62-269124 A International Publication No. 98/03896 Pamphlet JP-A 63-50886 Japanese National Patent Publication No. 8-510790 JP 10-149117 A JP 11-119704 A

  None of the methods described in the prior art is sufficient to prevent aggregation, the driving voltage is high, and the contrast is not sufficient. A polyisobutylene succinic anhydride having a molecular weight of several thousands to several hundreds of thousands described in JP-A-8-510790 is not preferred because the charge amount of the particles is lowered and the voltage required for electrophoresis is increased. In addition, in the system using a quaternary ammonium salt and a surfactant described in JP-A-11-119704, the surfactant inhibits the insulating properties of the insulating liquid dispersion medium, as the inventors have pointed out. It is clear that it is desirable not to be included in the system. In addition, due to the nature of the surfactant, the ionization is accelerated by the application of a voltage and changes its quality.

  In the present invention, an alkenyl succinic anhydride having 4 to 40 carbon atoms of alkenyl is added to a display liquid to prevent aggregation of charged particles, to improve chargeability, and to enable display with very good contrast It aims at providing the display liquid for apparatuses.

  Another object of the present invention is to provide a microcapsule containing the display liquid for the electrophoretic display medium.

  Furthermore, an object of the present invention is to provide an electrophoretic display medium using the display liquid or microcapsule for the electrophoretic display medium.

  The present invention is a display liquid for an electrophoretic display medium comprising an electrically insulating solvent, at least one kind of positively charged particles which are dispersed in the solvent, and alkenyl succinic anhydride, The present invention relates to a display liquid for an electrophoretic display medium, wherein the alkenyl has 4 to 40 carbon atoms.

  The present invention also relates to the display liquid for an electrophoretic display medium, wherein the alkenyl succinic anhydride is a reaction product of an olefin having a linear or branched chain having 4 to 40 carbon atoms and maleic anhydride.

  The present invention further relates to the display liquid for an electrophoretic display medium, further comprising negatively charged particles and alkenyl succinimide.

  The present invention also relates to the display liquid for an electrophoretic display medium, wherein the positively charged particles are titanium oxide surface-treated with a compound containing nitrogen.

  The present invention also relates to a microcapsule containing the display liquid for an electrophoretic display medium.

  The present invention also relates to an electrophoretic display medium in which the display liquid for electrophoretic display medium exists between two opposing electrodes, at least one of which is transparent.

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

  The electrophoretic display medium thus produced was connected to a power source, and the electric field direction was switched at a rectangular frequency of 0.5 Hz to apply a voltage with the highest contrast. The contrast ratio was measured by measuring reflected light intensity using a Photo MCPD-1000 manufactured by Otsuka Electronics, and measuring the contrast ratio from the reflectance ratio. As a result, by adding alkenyl succinic anhydride to the display solution, it can be used for both electrophoretic display media of cell type and capsule type, and there is no aggregation of particles, and it can be driven at a low voltage. A display liquid for an electrophoretic display medium having good contrast and an electrophoretic display medium using the same can be obtained.

  The present invention relates to a display liquid for an electrophoretic display medium comprising an electrically insulating solvent and at least one kind of positively charged particles that are dispersed in the solvent. Display liquids for electrophoretic display media are roughly classified into two types according to their operating principles. The first type is colored by dissolving a dye in an electrically insulating solvent and coloring charged particles. The display liquid for electrophoretic display medium is dispersed, and the second type is a display liquid for electrophoretic display medium in which charged particles of two different colors are dispersed in an electrically insulating solvent. The display liquid for electrophoretic display media of the present invention can be used for both the first type and the second type.

  The display liquid of the present invention includes positively charged particles, an electrically insulating solvent, and alkenyl succinic anhydride having 4 to 40 carbon atoms. The display liquid of the present invention may further contain particles charged to a negative charge. In the display liquid of the present invention, these positively charged or negatively charged particles exist in a state dispersed in an electrically insulating solvent.

  As the positively or negatively charged charged particles, inorganic pigment particles or 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, tin powder, zinc powder, etc. Can be used. In the present invention, titanium oxide or carbon black can be preferably used. In particular, titanium oxide can be preferably used as positively charged particles.

  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 rake, permanent red, resol red, bon rake red, rake 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 also be used as positively or negatively charged charged 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. However, it is not limited to what was produced by these methods.

  Examples of the polymer fine particle material include styrene, styrene- (meth) acrylic, styrene-isoprene, styrene-divinylbenzene, divinylbenzene, methyl methacrylate, methyl acrylate, ethyl methacrylate, and ethyl acrylate. , N-butyl methacrylate, n-butyl acrylate, methacrylic acid, acrylic acid, acrylonitrile, acrylic rubber-methacrylate, acrylic rubber-acrylate, ethylene, ethylene- (meth) acrylic acid, nylon , Silicone, urethane, melamine, benzoguanamine, phenol, fluorine (tetrafluoroethylene), vinylidene chloride, quaternary pyridinium salt, synthetic rubber, cellulose, cellulose acetate, chitosan, algi Calcium acid and the like, but not limited to polymeric 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. In the present invention, a styrene-divinylbenzene-based or ethylene- (meth) acrylic polymer can be preferably used. When the polymer fine particles contain a dye and / or pigment, the content of the dye and / or pigment is preferably 0.1 to 50 parts by weight with respect to 100 parts by weight of the polymer material.

  In addition, these pigment particles and polymer particles should be used not only as fine particles of pigment alone or polymer alone, but also in the form of composite particles formed with other compounds, various surface treatments, etc. Can do.

  As the form of composite particles, composite particles formed between pigment particles or polymer particles and pigment particles, composite particles formed between metal-containing dyes, polymer particles / hollow polymer particles It can be used in the form of formed composite particles and composite particles formed between various resins and polymers.

  In addition, as a surface treatment method, various methods usually performed on pigment particles or polymer fine particles can be applied. For example, various compounds including polymers are coated on the surface of pigment or polymer fine particles. And those subjected to coupling treatment with various coupling agents such as titanate and silane, those subjected to graft polymerization, and those subjected to mechanochemical treatment.

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

  In order to positively charge the particles, composite particles may be formed with a compound having a positive charge or a compound easily charged with a positive charge, or the surface of the particles may be treated with a compound having a positive charge.

  Examples of composite particles include basic dyes such as nigrosine dyes and triarylmethane dyes, electron donating substances such as quaternary ammonium salts, and charged trains such as polymethyl methacrylate, polyamide, and polyamine exhibit positive polarity. A positive charge can be imparted by combining a polymer with pigment particles or polymer particles. In the present invention, composite particles of a quaternary ammonium salt and pigment particles or polymer particles are preferably used.

As an example of a method of treating pigment particles or polymer fine particles with a compound having a positive charge, surface treatment with a compound containing nitrogen is particularly preferable from the viewpoint of charging to a positive charge. As the nitrogen-containing compound in the present invention, a silane coupling agent having an amino group such as 3-aminopropyltrimethoxysilane (shown by Formula 1. (In Formula 1, X ₁ , X ₂ and X ₃ are each represented by Independently, it represents an alkyl group that may have a substituent, an alkoxyl group that may have a substituent, or a halogen group, and R represents a hydrogen atom, an alkyl group that may have a substituent, or a substituent. X ₁ , X ₂ and X ₃ may be the same or different, n is an integer of 1 to 20)), amino-modified silicone oil, titanium having amino group Coupling agent (shown by Formula 2. (In Formula 2, X ₁ , X ₂ , and X ₃ are each independently an alkyl group that may have a substituent, an alkoxyl group that may have a substituent, or a halogen atom) Represents a group, R is a hydrogen atom, substituted The may have an alkyl group, or a may have a substituent aryl group .X _1, X _2, X ₃ is also the same, may be different .n is from 1 to 20 integer .)) And other reactive compounds such as stearylamine, unsaturated amines such as oleylamine, arylamines such as aniline, and amine compounds such as polyamines such as polyethyleneimine, and polymers such as acrylamide. Examples include, but are not limited to, materials. In the present invention, it is preferable to treat with an amine compound.

  Further, as an example of a method for treating the polymer fine particles with a compound having a positive charge, a method in which the surface of the polymer fine particles is subjected to a graft polymerization treatment with a compound having a positive charge is also preferably used. Examples of the positively charged compound include polyamide, polyvinyl alcohol, and polyamine. In the present invention, polymethacrylic acid is preferably used.

  In order to negatively charge the particles, composite particles may be formed with a compound having a negative charge or a compound that is easily charged with a negative charge, or the surface of the particles may be treated with a compound having a negative charge. Examples of composite particles include metal complexes of monoazo dyes, metal-containing dyes such as chromium-containing organic dyes (copper phthalocyanine green, chromium-containing monoazo dyes), and charged columns such as calixarenes or polytetrafluoroethylene having a negative polarity. Negative charge can be given by combining molecules.

  In the display liquid of the present invention, alkenyl succinic anhydride is used as a dispersing agent for positively charged particles. The alkenyl succinic anhydride has 4 to 40 carbon atoms, preferably 10 to 20 carbon atoms, and may be linear or branched.

  Alkenyl succinic anhydride is a method of reacting a conventionally known olefin and maleic anhydride at a temperature of 200 ° C. or more (Japanese Patent Publication No. 52-23669, Japanese Patent Publication No. 52-48639) and Japanese Patent Application Laid-Open No. 11-60568. The method can be synthesized. The olefin to be used is preferably 4 to 40 carbon atoms, more preferably 10 to 20 carbon atoms.

  When the carbon number exceeds 40, the particles start to aggregate and the contrast is remarkably lowered. Moreover, when the carbon number is less than 4, it tends to be difficult to obtain an effect as a dispersant. The amount added is preferably 1 to 500% by weight, more preferably 10 to 200% by weight, based on the particles. If the addition amount is less than 1% by weight, the dispersibility of the particles tends not to be improved, and if it exceeds 500% by weight, the conductivity of the display liquid tends to be high, and the particles tend to be difficult to electrophorese.

  When a mixture of positively charged particles and negatively charged particles is used, as long as the amount is small, a surfactant may be used in combination as a stabilizer or dispersant for the negatively charged particles. These stabilizers or dispersants include nonionic (nonionic) surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants that can be dissolved or mixed in a dispersion medium. Surfactant ionic surfactants can be used alone or in admixture of two or more.

  In the present invention, alkenyl succinimide is particularly preferable as a dispersant for negatively charged charged particles. An alkenyl succinimide can be obtained by reacting an alkenyl succinic anhydride with a polyamine such as polyethylene diamine. Examples include OLOA-1200 and OLOA-5096 manufactured by Chevron. The amount of alkenyl succinimide added is preferably 1 to 500% by weight, more preferably 10 to 200% by weight, based on the particles. If the addition amount is less than 1% by weight, the dispersibility of the particles tends not to be improved, and if it exceeds 500% by weight, the conductivity of the display liquid tends to be high, and the particles tend to be difficult to electrophorese.

  Next, the electrically insulating solvent is a hydrophobic dispersion medium such as benzene, toluene, xylene, phenylxylylethane, diisopropylnaphthalene, naphthene hydrocarbon, hexane, dodecylbenzene, cyclohexane, kerosene, paraffin hydrocarbon, Isopar G, H, L, M manufactured by Exxon Chemical Co., Ltd., Exol D30, D40, D80, D110, D130, Shellsol A, AB manufactured by Shell, Naphthesol L, M, H manufactured by Nippon Oil Co., Ltd. Aliphatic or aromatic hydrocarbons, halogenated hydrocarbons such as chloroform, trichloroethylene, tetrachloroethylene, trifluoroethylene, tetrafluoroethylene, dichloromethane, ethyl bromide, tricresyl phosphate, trioctyl phosphate, octyl diphenyl phosphate, phosphorus Such as tricyclohexyl acid Phthalic acid esters, dibutyl phthalate, dioctyl phthalate, dilauryl phthalate, dicyclohexyl phthalate, butyl oleate, diethylene glycol dibenzoate, dioctyl sebacate, dibutyl sebacate, dioctyl adipate, trimellitic acid Carboxylic acid esters such as trioctyl, acetyl triethyl citrate, octyl maleate, dibutyl maleate, ethyl acetate, isopropyl biphenyl, isoamyl biphenyl, chlorinated paraffin, diisopropyl naphthalene, 1,1-ditolyl ethane, 1,2-ditolyl ethane, 2 , 4-di-tert-aminophenol, N, N-dibutyl-2-butoxy-5-tert-octylaniline, and the like, but are not limited thereto. These hydrophobic dispersion media can be used alone or in combination of two or more.

  Further, as the above-mentioned electrically insulating solvent, either colorless or colored can be used. If two types of particles are used as electrophoretic particles, such as positively charged particles and negatively charged particles, or positively or negatively charged particles and uncharged particles, a colorless electrically insulating solvent is used. Although one type of charged 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 this case, an oil-soluble dye is used. For example, Spirit Black (SB, SSBB, AB), Nigrosine Base (SA, SAP, SAPL, EE, EEL, EX, EXBP, EB), Oil Yellow (105, 107, 129, 3G, GGS), oil orange (201, PS, PR), first orange, oil red (5B, RR, OG), oil scarlet, oil pink 312, oil violet # 730, macrolex blue RR, Sumiplast Green G, Oil Brown (GR, 416), Sudan Black X60, Oil Green (502, BG), Oil Blue (613, 2N, BOS), Oil Black (HBB, 860, BS), Bali First Yellow (1101, 1105, 108, 4120), Bali First Orange (3209, 3210), Bali First Red (1306, 1355, 2303, 3304, 3306, 3320), Bali First Pink 2310N, Bali First Brown (2402, 3405), Bali First Blue (3405) 1501, 1603, 1605, 1607, 2606, 2610), Bali First Violet (1701, 1702), Vari First Black (1802, 1807, 3804, 3810, 3820, 3830) and the like can be used.

  The display liquid for electrophoretic display medium of the present invention is a substance containing an electrically insulating solvent and at least one kind of positively charged particles that are dispersed in the solvent. The used amount of the particles is preferably 0.1 to 100 parts by weight, more preferably 1 to 50 parts by weight with respect to 100 parts by weight of the electrically insulating solvent. Furthermore, when the display liquid for electrophoretic display media contains particles charged to a negative charge, the usage amount of the particles charged to a negative charge is also 0.1 to 100 weights with respect to 100 parts by weight of the electrically insulating solvent. Parts, preferably 1 to 50 parts by weight. If the amount of positively charged particles or negatively charged particles is less than 0.1 parts by weight, sufficient concealing power cannot be obtained, and sufficient contrast cannot be obtained in an electrophoretic display medium. When the amount exceeds 100 parts by weight, there is a tendency that a high voltage is required for electrophoresis due to collision between particles or an increase in the viscosity of the display liquid.

  When the display liquid for electrophoretic display device of the present invention is used in a capsule electrophoretic display device, microcapsules can be obtained by the following method.

  The charged particle-encapsulating microcapsules of the present invention can be prepared by a conventionally used in-situ method, interfacial polymerization method, coacervation method, or the like. As examples, polyurethane, polyurea, polyurea-polyurethane, urea-formaldehyde resin, amino resin such as melamine-formaldehyde resin, polymer of radical polymerizable monomer such as polyamide, acrylate ester, methacrylate ester, vinyl acetate, gelatin Etc. Furthermore, the size of the microcapsules used in the present invention is 1 to 200 μm, more preferably 10 to 100 μm.

When producing microcapsules, first, a hydrophobic dispersion is emulsified and dispersed 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. For emulsification and dispersion, protective colloids such as water-soluble polymer compounds and inorganic fine particles are used. Examples of water-soluble polymer compounds include (meth) acrylic acid polymers, (meth) acrylic acid copolymers (acrylic acid esters such as methyl acrylate, acrylic acid amides, acrylonitrile, 2-methylpropanesulfonic acid, and styrene sulfone. Copolymer with acid, vinyl acetate, etc.), 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 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.
Furthermore, other nonionic surfactants and 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 in-situ method, the wall material is a radical polymer such as polyurethane, polyurea, polyurea-polyurethane, urea-formaldehyde resin, amino resin such as melamine-formaldehyde resin, acrylate ester, methacrylate ester, vinyl acetate, etc. Monomer polymerization products can be used.

  As the polyvalent isocyanate compound used when polyurethane, polyurea, or polyurea-polyurethane is used for the wall material, first, an organic compound having two or more isocyanate groups in the molecule is used. Examples of such polyvalent isocyanate compounds 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-1,2-diisocyanate, cyclohexylene-1,4-diisocyanate Diisocyanates such as p-phenylene diisothiocyanate, xylylene-1,4-diisothiocyanate, and ethylisidine diisothiocyanate, 4,4′-dimethyldiphenylmethane-2,2 ′, 5,5 ′ -Tetraisocyanate such as tetraisocyanate can be used. Examples of the polyvalent isocyanate compound include an adduct of hexamethylene diisocyanate and hexanetriol, an adduct of 2,4-tolylene diisocyanate and prenzcatechol, an adduct of tolylene diisocyanate and hexane triol, 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.

  Also, two or more of the above can be used in combination. On the other hand, the wall film-forming substance having reactivity with the polyvalent isocyanate compound includes polyhydric alcohols, hydroxy polyesters, hydroxy polyalkylene ethers, polyhydric amine alkylene oxide adducts, polyhydric amines, and the like. Examples thereof include substances having two or more active hydrogens.

  The polyhydric alcohols may be aliphatic, aromatic or alicyclic, such as catechol, resorcinol, 1,2-dihydroxy-4-methylbenzene, 1,3-dihydroxy-5-methylbenzene. 2,4-dihydroxyethylbenzene, 1,3-naphthalenediol, 1,5-naphthalenediol, 2,7-naphthalenediol, 2,3-naphthalenediol, 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, hexa Ntriol, pentaerythritol, glycerin, sorbitol and the like can be used.

  Hydroxy polyesters include hydroxy polyesters obtained from 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. Examples of hydroxy polyalkylene ethers include hydroxy polyalkylene ethers that are condensation products of the above polyhydric alcohols and alkylene oxides such as ethylene oxide, propylene oxide, and butylene oxide. As alkylene oxide adducts of polyvalent amines, o-phenylenediamine, p-phenylenediamine, diaminonaphthalene, ethylenediamine, 1,3-propylenediamine, diethylenetriamine, triethylenetetramine The thing which substituted at least 1 or more of the hydrogen of the amino group of polyvalent amines, such as 1, 6- hexamethylene diamine, with the above-mentioned alkylene oxide can be mention | raise | lifted.

  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-methylcyclohexyl) methane, isophoronediamine, 1,3 -Diaminocyclohexane, spiroacetal diamine, etc. can be used. Water can also be used as a wall film-forming substance reactive to polyvalent isocyanate.

  Basically, it consists of the following steps. An aqueous solution containing a protective colloid as a hydrophilic medium is prepared. When a water-soluble polymer compound 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 fine particles are used, it is appropriate to use 0.1 to 100 parts by weight, preferably 1 to 50 parts by weight with respect to 100 parts by weight of water.

  Next, a hydrophobic dispersion is prepared by mixing charged particles, a polyvalent isocyanate compound, a polyhydric alcohol, and in some cases a polyvalent amine, etc. in an electrically insulating solvent. This hydrophobic dispersion is emulsified and dispersed in the protective colloid aqueous solution prepared in the above step. For emulsification and dispersion, a high-speed rotary stirrer is used. For example, Claremix (M Technique Co., Ltd.) is used, and the mixture is stirred at 5000 rpm for 5 minutes for emulsification dispersion. The amount of the polyvalent isocyanate compound used is in the range of 1 to 50 parts by weight, preferably 5 to 20 parts by weight with respect to 100 parts by weight of the electrically insulating solvent. Moreover, the usage-amount of a polyhydric alcohol or a polyhydric amine is 1-50 weight part with respect to 100 weight part of said electrically insulating solvents, Preferably, it is the range of 5-20 weight part.

  The obtained emulsified dispersion is heated to a predetermined temperature and reacted with a polyvalent isocyanate and a polyhydric alcohol, a polyvalent amine, or the like to obtain a target microcapsule.

In addition, when using a polymer of a radical polymerizable monomer such as an acrylic ester, methacrylic ester or vinyl acetate as a wall material, examples of the radical polymerizable monomer that can be used in the present invention include the following. be able to. Aromatic monomers such as styrene, α-methylstyrene, p-methylstyrene, t-butylstyrene, chlorostyrene, benzyl acrylate, benzyl methacrylate, and vinyl toluene. Methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, Acrylic acid alkyl esters such as decyl acrylate and dodecyl acrylate. Methyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, decyl methacrylate, dodecyl methacrylate, etc. Methacrylic acid alkyl esters. Hydroxy group-containing monomers such as hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate. N-substituted acrylamides such as N-methylolacrylamide, N-butoxymethylacrylamide, N-methylolmethacrylamide and N-butoxymethylmethacrylamide. Carboxyl group-containing monomers such as polymerizable unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid and crotonic acid, and anhydrides thereof. One type or two or more types can be selected from epoxy group-containing monomers such as glycidyl acrylate and glycidyl methacrylate, and acrylonitrile, methacrylonitrile, crotonnitrile, vinyl acetate, vinyl chloride, vinylidene chloride and the like.

  Further, in the present invention, together with the above-mentioned radical polymerizable monomer, multifunctional and therefore crosslinkable monomers such as methylene bisacrylamide, divinylbenzene, tripropylene glycol diacrylate, bisphenol A diglycidyl ether diacrylate, Trimethylolpropane triacrylate, acrylated cyanurate, or the like can also be used.

  When using the above radical polymerizable monomer, 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) butane, n-butyl-4,4-bis (tert-butylperoxy) valerate, di-tert-butyl peroxide, dicumyl peroxide, octanoyl peroxide, etc., and azo compounds For example, 2,2-azobis (2,4-dimethylvaleronitrile), 2,2-azobis (2-methylbutyronitrile), 1,1-azobis (cyclohexyl-1-carbonitrile), VA-061, VA-080, VR-110, V-601 (all Wako Pure Chemical Industries It is possible to use a formula company), and the like. Inorganic peroxides such as ammonium peroxide and sodium peroxide can also be used. These initiators can be used alone, but may be used in a redox type in combination with a reducing agent such as Rongalite. 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.

  As the process, a hydrophobic dispersion is prepared by mixing charged particles, a radical polymerizable monomer, a radical polymerization initiator, and a chain transfer agent in some cases in an electrically insulating solvent. This hydrophobic dispersion is emulsified and dispersed in an aqueous protective colloid solution as described above. For emulsification and dispersion, a high-speed rotary stirrer is used. For example, Claremix (M Technique Co., Ltd.) is used, and the mixture is stirred at 5000 rpm for 5 minutes for emulsification dispersion. Here, the usage-amount of a radically polymerizable monomer is 1-90 weight part with respect to 100 weight part of said hydrophobic dispersion liquid, Preferably, it is the range of 10-50 weight part. The amount of the radical polymerization initiator used is not particularly limited, but is usually 0.1 to 10 parts by weight, preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the radical polymerizable monomer. It is a range.

In the case of radical polymerization by the in-situ method, it is also possible to perform polymerization by dissolving in water instead of mixing a radical polymerizable monomer and a radical polymerization initiator in an electrically insulating solvent. In this case, it is preferable to use the radically polymerizable monomer and the radical polymerization initiator used within 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, examples of the amino resin component that can be used in the present invention include melamine / formaldehyde initial polymer, urea / formaldehyde initial polymer, alkylated methylol urea alkylated methylol melamine, N -Alkylmelamine / formaldehyde prepolymer, guanamine / formaldehyde prepolymer, alkylurea / formaldehyde prepolymer, alkylene urea / formaldehyde prepolymer, etc. can be used.

  As a process, charged particles are mixed in an electrically insulating solvent to prepare a hydrophobic dispersion. This hydrophobic dispersion is emulsified and dispersed in an aqueous protective colloid solution as described above. For emulsification and dispersion, a high-speed rotary stirrer is used. For example, Claremix (M Technique Co., Ltd.) is used, and the mixture is stirred at 5000 rpm for 5 minutes for emulsification dispersion. Here, the amino resin component is used in an amount of 1 to 200 parts by weight, more preferably 10 to 60 parts by weight, based on 100 parts by weight of the electrically insulating solvent. When the amino resin component is a urea / formaldehyde prepolymer, this component may be added to the system gradually or all at once, or urea as the raw material may be dissolved in a hydrophilic medium in advance, and then gradually or Formaldehyde may be added to the system at once. Further, urea and formaldehyde as raw materials may be directly added to the system. The microencapsulation reaction is preferably carried out under acidic conditions, that is, the pH of the system is 2.0 to 6.8, more preferably 3.0 to 6.0. The conditions of the system may be appropriately adjusted depending on the type of amino resin component to be used. For example, in the case of melamine / formaldehyde initial polymer or alkylated methylol melamine, pH 4.0 to 5.5, urea / formaldehyde initial polymer The pH is suitably 2.0 to 4.5. By adjusting the pH of the system to 3.0 to 6.8 and heating to a predetermined temperature, polycondensation is performed on the surface of the dispersed particles of the hydrophobic substance to obtain the desired microcapsules.

  The amino resin component is an initial condensate such as formaldehyde, urea and melamine, and can be produced according to 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 an electrically insulating solvent, the hydrophobic dispersion is emulsified and dispersed in water, and then a hydrophilic monomer is added to cause polymerization on the surface of the oil droplets. Polyurethane, polyurea, polyisocyanate used in the case of using polyurea-polyurethane as a wall material, and a wall film-forming substance having reactivity with the polyvalent isocyanate compound include polyisocyanate shown by an in-situ method. Polyhydric alcohol, polyhydric amine, etc. can be used. Generally, a polyvalent isocyanate is used as the hydrophobic monomer, and a polyhydric alcohol, polyvalent amine, or the like is used as the hydrophilic monomer. About the usage-amount of these monomers, it is equivalent to the quantity shown by the in-situ method.

  When polyamide is used as a wall material, polybasic acid halides may be used as hydrophobic monomers instead of the above polyvalent isocyanates, and polyvalent amines may be used as hydrophilic monomers. As the polybasic acid halide, sebacoyl chloride, terephthaloyl chloride, or the like can be used.

  Next, in the case of the coacervation method, a well-known gelatin-gum arabic composite 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 coacervation, it is common to cure with formaldehyde. As described above, when the electrophoretic particle-containing microcapsules manufactured using various methods and materials are used as a display material, high-definition and high-contrast display can be performed.

Examples of the electrophoretic display medium using such a display liquid include the following forms.
(1) Create a space by placing a transparent electrode formed in a desired pattern on one of a pair of transparent members such as a glass substrate, with a spacer interposed therebetween, and fill the space with the display liquid of the present invention. To do.
(2) A discontinuous space is formed on the substrate on which the entire surface electrode has been formed by facing the insulating film through a number of spacers, and the space is filled with the display liquid of the present invention.
(3) A space is formed by placing a transparent electrode formed in a desired pattern on one of a pair of transparent members such as a glass substrate, with a spacer interposed therebetween, and the space is filled with the microcapsules of the present invention. To do. In this example, a binder may be present instead of the space.
(4) A discontinuous space is created by making an insulating film face each other through a large number of spacers on a substrate provided with a full-surface electrode, and the space is filled with the microcapsules of the present invention. In this example, a binder may be present instead of the space.
(5) The microcapsules of the present invention are applied together with a binder to a substrate having a full-surface electrode.

  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
Adjustment of display liquid for electrophoretic display medium: C.I. with respect to 150 parts by weight of paraffinic hydrocarbon isopar L (manufactured by Exxon Corporation) I. 5 parts by weight of titanium oxide (Ti-PURE R101, manufactured by DuPont) and 1 part by weight of octadecenyl succinic anhydride treated with an amine compound in an electrically insulating solvent colored by dissolving 2 parts by weight of Solvent Blue 14 In addition, an electrophoretic display liquid was prepared by dispersing for 60 minutes using an ultrasonic disperser.

(Example 2)
Adjustment of positively charged particle dispersion: 15 parts by weight of titanium oxide (DuPont, Ti-PURE R101) treated with an amine compound with respect to 115 parts by weight of paraffinic hydrocarbon isopar L (manufactured by Exxon Corporation) And 20 parts by weight of hexadecenyl succinic anhydride were added and dispersed for 60 minutes using an ultrasonic disperser to prepare an electrophoretic display liquid.
Preparation of negatively charged particle dispersion: 120 parts of carbon black after heating and kneading with 120 parts of carbon black and 480 parts of ethylene-methacrylic acid copolymer N1110H (made by Mitsui DuPont Polychemical Co., Ltd.) as a resin To give a colored chip. Next, it is pulverized with a pin mill while being cooled with liquid nitrogen (freeze pulverization), and is classified with a mesh having an opening of 150 μm and sharpened with an average particle size of 3 μm (SA-CP3L, centrifugal sedimentation type particle size distribution measuring machine manufactured by Shimadzu Corporation). A pulverized product having a uniform particle size distribution was obtained.
120 parts of the pulverized product, Isopar L (Exxon Chemical Co., Ltd.) 520 parts Bontron F-21 (Calixarene: Orient Chemical Industry Co., Ltd.) 10 parts were pulverized for 60 minutes to obtain a negatively charged particle mother liquid. To this solution, OLOA-1200 (alkenyl succinimide) is added, and the dispersion of negatively charged particles is adjusted with Isopar L so that the negatively charged particles are 4.0 wt% and OLOA-1200 is 2.0 wt%. Got.
An electrophoretic display liquid was prepared by mixing the positively charged particle dispersion and the negatively charged particle dispersion.

(Example 3)
Preparation of positively charged particle dispersion: 300 parts of titanium oxide treated with an amine compound (DuPont, Ti-PURE R101) and resin N1110H (Mitsui DuPont Polychemical Co., ethylene-methacrylic acid copolymer) 300 parts were heated and kneaded with two rolls and then coarsely pulverized to 1 to 10 mm square to obtain colored chips. Next, after pulverizing with a pin mill while cooling with liquid nitrogen, and classifying with a mesh of 150 μm mesh, a sharp particle size distribution with an average particle size of 46 μm (SA-CP3L, centrifugal sedimentation type particle size distribution measuring machine manufactured by Shimadzu Corporation) is obtained. A pulverized product was obtained. This pulverized product was mixed according to the following formulation, and wet pulverized with a DCP mill (Dryes Welke).
120 parts of the above-mentioned pulverized product, Isopar L (manufactured by Exxon Chemical Co., Ltd.) 520 parts, Bontron P-51 (quaternary ammonium salt produced by Orient Chemical Industry Co., Ltd.), 10 parts, are pulverized and the average particle size is 2.2 μm (MS2000, manufactured by Sysmex Corporation) A charged particle mother liquor was obtained. The dispersion time was 60 minutes. After adding 1 part by weight of dodecenyl succinic anhydride to the nonvolatile content 1 of this liquid, the nonvolatile content was adjusted to 4.0% with Isopar L to obtain a dispersion of positively charged particles.
An electrophoretic display liquid was prepared by mixing the positively charged particle dispersion and the negatively charged particle dispersion prepared in Example 2.

Example 4
Preparation of positively charged particle dispersion: 5 parts of styrene and 5 parts of divinylbenzene mixed with 100 parts of methanol, 0.5 parts of initiator 2,2-azobisisobutyronitrile (AIBN) accurately weighed and stabilized It was introduced into a closed container containing 2 parts of the agent poly (acrylic acid). The sealed container was replaced with nitrogen by bubbling nitrogen through the solution for several hours. The mixture was then spun at 60 ° C. for 8 hours at 30 revolutions per minute. After spinning for 8 hours, the second stage monomer, methacrylic acid, was poured into the vessel and continued to rotate under the same reaction conditions. The final product produced by this two-stage dispersion polymerization method had poly (methacrylic acid) grafted on the surface as the second stage monomer. The final particles were uniform in size and were in the range of 0.2-2 μm depending on the reaction medium used. The produced | generated particle | grains were 1 micrometer of average particle | grains Keiga, and showed favorable whiteness.
After the polymerization step, 4 parts by weight of particles treated with the above method and solvent-washed and 4 parts by weight of octadecenyl succinic anhydride are dispersed in 95 parts by weight of Isopar L using an ultrasonic disperser for 15 minutes to disperse positively charged particles. A liquid was obtained.
An electrophoretic display liquid was prepared by mixing the positively charged particle dispersion and the negatively charged particle dispersion prepared in Example 2.

(Example 5)
Microencapsulation was performed with reference to JP-A-51-9079.
15 parts by weight of the electrophoretic display liquid obtained in Example 1 in an aqueous solution obtained by dissolving 5 parts by weight of a methyl vinyl ether-maleic anhydride copolymer having a weight average molecular weight of 2.4 million as a water-soluble polymer in 150 parts by weight of purified water, urea 15 parts by weight, resorcinol 1.5 parts by weight, 37% formaldehyde aqueous solution 35 parts by weight are added with stirring, and reacted at 50 ° C. for 3 hours to synthesize and classify microcapsules, thereby classifying the microparticles having a particle size of 70 μm ± 20 μm. The capsule was removed.

(Example 6)
Using the electrophoretic display liquid of Example 2, microencapsulation was performed in the same manner as in Example 5.

(Example 7)
Using the electrophoretic display liquid of Example 3, microencapsulation was performed in the same manner as in Example 5.

(Example 8)
Microencapsulation was performed in the same manner as in Example 5 using the electrophoretic display liquid of Example 4.

(Comparative Example 1)
Positively charged particle dispersion: An electrically insulating solvent colored by dissolving 2 parts by weight of oil blue, an oil-soluble dye, was prepared with respect to 150 parts by weight of paraffinic hydrocarbon isopar L (manufactured by Exxon Corporation). An electrophoretic display solution was prepared by adding 5 parts by weight of hydrophobically treated titanium dioxide (DuPont, Ti-PURE R101) as charged particles to this electrically insulating solvent and dispersing for 15 minutes using an ultrasonic disperser.

(Comparative Example 2)
An electrophoretic display solution was prepared in the same manner as in Example 2 except that polyisobutenyl succinic anhydride (Chebron OLOA-15500, polyisobutenyl having about 80 carbon atoms) was added instead of hexadecenyl succinic anhydride.

(Comparative Example 3)
Using the electrophoretic display liquid of Comparative Example 1, microencapsulation was performed in the same manner as in Example 5.

(Comparative Example 4)
Using the electrophoretic display liquid of Comparative Example 2, microencapsulation was performed in the same manner as in Example 5.

Production of Display Medium Electricity produced in Examples 1, 2, 3, 4 and Comparative Examples 1 and 2 in a cell in which one side is a stainless steel electrode and the other is a glass electrode on which ITO is deposited and the gap between the electrodes is 0.1 mm. An electrophoresis cell was prepared by enclosing each of the electrophoresis display solutions.
Further, 20 g of charged particle-containing microcapsules prepared in Examples 5, 6, 7, and 8 and Comparative Examples 3 and 4 were 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, this coating solution is coated on an ITO film-coated glass plate (ITO film) and dried to form a charged particle-encapsulating microcapsule coating, and further on the ITO film-coated glass plate An electrophoretic display medium was produced by placing (ITO film on microcapsule coating side).

  The electrophoretic display medium thus produced was connected to a power source, and the electric field direction was switched at a rectangular frequency of 0.5 Hz to apply a voltage with the highest contrast. The contrast ratio was measured by measuring reflected light intensity using a Photo MCPD-1000 manufactured by Otsuka Electronics, and measuring the contrast ratio from the reflectance ratio. As a result, by adding alkenyl succinic anhydride to the display solution, it can be used for both electrophoretic display media of cell type and capsule type, and there is no aggregation of particles, and it can be driven at a low voltage. A display liquid for an electrophoretic display medium having good contrast and an electrophoretic display medium using the same can be obtained.

Claims (7)

A display liquid for an electrophoretic display medium, comprising: an electrically insulating solvent; at least one kind of positively charged particles that are dispersed in the solvent; and alkenyl succinic anhydride, A display liquid for an electrophoretic display medium, wherein the number is 4 to 40. The display liquid for an electrophoretic display medium according to claim 1, wherein the alkenyl succinic anhydride is a reaction product of an olefin having a linear or branched chain having 4 to 40 carbon atoms and maleic anhydride. The display liquid for an electrophoretic display medium according to claim 1, further comprising particles charged to a negative charge and alkenyl succinimide. The display liquid for electrophoretic display media according to claim 1, wherein the positively charged particles are titanium oxide surface-treated with a compound containing nitrogen. The microcapsule containing the display liquid for electrophoretic display media in any one of Claims 1-4. An electrophoretic display medium in which the display liquid for an electrophoretic display medium according to any one of claims 1 to 4 exists between two opposing electrodes, at least one of which is transparent. An electrophoretic display medium in which the microcapsules according to claim 5 are present between two opposing electrodes, at least one of which is transparent.