JP2006308739A - Liquid electrostatic developer and method for manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a positive charging liquid electrostatic developer that can disperse pigment particles in a high concentration in a low dielectric carrier such as vegetable oil to increase image density and that achieves both long-term storage stability and desired charge holding property, and to provide a method for manufacturing the developer. <P>SOLUTION: The liquid electrostatic developer is prepared by dispersing microcapsule pigment particles in a low dielectric carrier liquid. The microcapsule pigment particles are produced by encapsulating pigment particles having an anionic group on the surface with an encapsulating resin having a polymerizable surfactant having a cationic group, a hydrophobic group and a radical polymerizable group in one molecule as a repeating unit, and exhibit self positive charging property. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid electrostatic developer used in an electrophotographic image forming apparatus used for a copying machine, a printer, and the like, and a method for manufacturing the same.

  In electrophotography, a wet development method is known as a method for developing an electrostatic latent image, and an electrostatic latent image is formed on a photoreceptor by charging and image exposure, and a resin and a colorant are the main components. An electrostatic latent image is developed using a liquid electrostatic developer in which toner particles are usually dispersed in an aliphatic hydrocarbon such as Isopar, and the resulting toner image is transferred and fixed on a transfer paper. To be formed. In such a wet development method, toner particles of submicron to several μm are dispersed in a highly insulating carrier such as an aliphatic hydrocarbon to form a liquid electrostatic developer. Since the particle size can be made smaller than that of the dry development method, it is possible to obtain high resolution and gradation.

  However, in a liquid electrostatic developer, colored particles tend to settle, and when a charge control agent (CCA) is added to impart charge, the storage stability becomes unstable, the viscosity increases during long-term storage, and the liquid static In some cases, it may be difficult to perform the function as an electro-developer, and the addition of CCA causes a problem that the resistance of the carrier liquid is lowered, and dot reproducibility and fine line reproducibility during development are lowered. To solve this problem, pigment particles are coated by melt-kneading with resin, or microencapsulated by interfacial polymerization of polar monomers in the presence of pigment particles to give colored resin particles with polarity. It is known (Patent Documents 1 to 6), however, since the polymer to be coated is not removed at all, the content of the pigment is limited from the viewpoint of dispersion stability, and the pigment particles are highly concentrated in the carrier. However, it is difficult to obtain the problem that the image density cannot be increased, the image density cannot be increased, and the long-term storage stability and the desired charge retention.

  In addition, a liquid containing an aqueous medium and a coloring material component by adding a non-aqueous solvent to the coloring material that covalently bonds the polymer component or an aqueous medium in which the monomer and the coloring material forming the polymer are emulsified and dispersed. It is known that a liquid electrostatic developer having excellent dispersibility can be obtained by forming droplets and interfacial polymerization or by removing aqueous solvent to form colored resin particles (Patent Documents 7 and 8). The charge stability is due to the addition of a charge control agent, and the above-described problems due to the addition of CCA still remain.

  In Patent Documents 1 to 8, volatile aliphatic hydrocarbons are used as the carrier liquid, and when the toner image is fixed, the carrier liquid contained in the toner is volatilized or evaporated by means such as heating. Although it is necessary, there is a problem of deteriorating the use environment. Further, even if a means for collecting the aliphatic hydrocarbons volatilized in the vicinity of the fixing device is provided in consideration of the use environment, it is disadvantageous for downsizing the image forming apparatus.

  In addition, attempts have been made to respond to the demands for consideration for the use environment and miniaturization by using non-volatile silicone oil or liquid paraffin instead of volatile aliphatic hydrocarbons as the carrier liquid. Since the liquid is excellent in chemical stability, it will continue to exist on the transfer paper for a long time, resulting in a decrease in the print quality texture, a decrease in the stamping property, and a decrease in the writing property using water-based ink. There's a problem.

Further, it is known that the use of vegetable oil as a carrier does not cause environmental pollution as compared with volatile aliphatic hydrocarbons, and can reduce the risk of fire (Patent Document 9). It is also known that a modified product (unsaturated higher fatty acid ester) is used as a carrier liquid (Patent Document 10), and it is particularly required to use vegetable oil as a carrier as an environmentally friendly liquid electrostatic developer. According to the study by the present inventors, the vegetable oil itself may be negatively charged, and both positive and negative polarities are obtained by the pigment as a liquid electrostatic developer by dispersing it in the vegetable oil. It turns out that there is a case to show. When vegetable oil is used as the carrier liquid, the use of CCA is indispensable to obtain the desired polarity. However, the addition of CCA basically lowers the resistance of the carrier liquid, and the dot reproducibility and fine line reproducibility during development are improved. There is a problem that the storage stability of the dispersion becomes unstable, the viscosity increases when stored for a long time, and it becomes difficult to perform the function as a liquid electrostatic developer.
JP-A-8-30040 Japanese Patent Laid-Open No. 9-218540 JP-A-9-311506 JP 2005-10528 A Japanese Patent Laid-Open No. 2004-2501 JP 2001-31900 A JP 2002-212302 A Japanese Patent Laid-Open No. 2002-226591 JP 2000-19787 A JP 2001-98197 A

  The present invention can disperse pigment particles in a high concentration in a low dielectric carrier to increase the image density, and at the same time can provide long-term storage stability and desired charge retention at the same time. An object is to provide a liquid electrostatic developer and a method for producing the same, and in particular, to provide a positively chargeable liquid electrostatic developer using vegetable oil as a carrier and a method for producing the same.

  The liquid electrostatic developer according to the present invention is a liquid developer in which microencapsulated pigment particles are dispersed in a low dielectric carrier liquid, and the microencapsulated pigment particles have one molecule of pigment particles having an anionic group on the surface. It is microencapsulated with an encapsulating resin containing a polymerizable surfactant having a cationic group, a hydrophobic group, and a radically polymerizable group in the inside as a repeating structural unit, and exhibits self-positive charging. Features.

Cationic polymerizable surfactant
General formula R _{[4- (l + m + n)]} R ¹ _l R ² _m R ³ _n N ⁺ · X ⁻
Wherein R is a radical polymerizable group, R ¹ , R ² and R ³ are selected from hydrogen, alkyl group, aryl group, aralkyl group and alkylaryl group, at least one of which is a hydrophobic group , X is Cl, Br or I, l, m and n are 1 or 0 and are not 0 at the same time.)
It is a compound represented by these.

  The encapsulating resin contains at least one monomer selected from a hydrophobic monomer, a crosslinkable monomer, a monomer represented by the following general formula (1), or a hydrophilic monomer as a copolymerization component. .

(In the formula, R ¹ is a hydrogen atom or a methyl group, R ² is a bulky group, and represents a t-butyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or a heterocyclic group, and m is 0. -3, n represents an integer of 0 or 1.)
The pigment particles having an anionic group on the surface are derived from an inorganic pigment or an organic pigment.

The anionic group on the pigment particle surface is a sulfonic acid group (—SO ₃ H), a sulfinic acid group (—RSO ₂ H) (wherein R is an alkyl group having 1 to 12 carbon atoms which may have a substituent). Or a phenyl group), or at least one selected from carboxylic acid groups (—COOH).

From a sulfonic acid group (—SO ₃ H), a sulfinic acid group (—RSO ₂ H) (wherein R represents an alkyl group having 1 to 12 carbon atoms which may have a substituent, or a phenyl group). The introduction amount of at least one kind selected is 0.01 mmol / g to 0.15 mmol / g.

  The anionic group on the pigment particle surface is a carboxylic acid group (—COOH), and the active hydrogen content is 1.0 mmol / g to 6.0 mmol / g.

  The microencapsulated pigment particles are microencapsulated with 40 to 900 parts by mass of an encapsulating resin with respect to 100 parts by mass of pigment particles having an anionic group on the surface.

  The glass transition point (Tg) of the encapsulated resin is -20 ° C to 90 ° C.

  The volume average particle size of the microencapsulated pigment particles is 0.2 μm to 1 μm.

The low dielectric carrier liquid is composed of a vegetable oil containing an unsaturated group or an unsaturated fatty acid ester, and has a volume resistance of 10 ⁹ Ω · cm or more and a dielectric constant of 3.6 or less.

  Vegetable oil selected from safflower oil, sunflower oil, soybean oil, corn oil, cottonseed oil, or linseed oil containing at least 50% linolenic acid component in a low dielectric carrier liquid containing at least 50% linoleic acid component It is characterized by being.

  It is characterized by containing 2 mass% to 50 mass% of microencapsulated pigment particles.

In the method for producing a liquid electrostatic developer of the present invention, after dispersing pigment particles having an anionic group on the surface thereof in an aqueous dispersion medium, a cationic polymerizable surfactant is added and heated under dispersion treatment. Adding a polymerization initiator and emulsion polymerization to form microencapsulated pigment particles;
The microencapsulated pigment particles are filtered from the aqueous medium in the step and then dispersed in a low dielectric carrier liquid.

The method for producing a liquid electrostatic developer of the present invention comprises a step of dispersing a pigment particle having an anionic group on the surface thereof in an aqueous dispersion medium, adding a cationic polymerizable surfactant, and dispersing the pigment particles.
Adding a hydrophobic monomer, a crosslinkable monomer, at least one monomer selected from the monomers represented by the general formula (1), and a dispersion treatment;
A step of adding a cationic polymerizable surfactant and sequentially carrying out each step of the dispersion treatment, followed by heating and adding a polymerization initiator and emulsion polymerization to form microencapsulated pigment particles;
The microencapsulated pigment particles are filtered from the aqueous medium in the step and then dispersed in a low dielectric carrier liquid.

The method for producing a liquid electrostatic developer of the present invention comprises a step of dispersing a pigment particle having an anionic group on the surface thereof in an aqueous dispersion medium, adding a cationic polymerizable surfactant, and dispersing the pigment particles.
Adding a hydrophobic monomer, a crosslinkable monomer, at least one monomer selected from the monomers represented by the general formula (1), and a dispersion treatment;
Add the hydrophilic monomer together with the cationic polymerizable surfactant and perform each step of the dispersion process in sequence, then heat and add the polymerization initiator, and emulsion polymerization to form microencapsulated pigment particles The process of
The microencapsulated pigment particles are filtered from the aqueous medium in the step and then dispersed in a low dielectric carrier liquid.

  The liquid electrostatic developer of the present invention is an admicelle state in which a cationic polymerizable surfactant is ionically bonded to pigment particles having an anionic group on the surface in a low dielectric carrier using the cationic group. Then, self-positively charged microencapsulated pigment particles obtained by emulsion polymerization of the polymerizable group in the cationic polymerizable surfactant are dispersed, and the surfactant of the cationic polymerizable surfactant is dispersed. Thus, the pigment particles can be dispersed at a high concentration without agglomeration in the carrier liquid, and the image density can be increased. Further, the addition of CCA is unnecessary, and long-term storage stability and desired charge retention can be obtained at the same time. In addition, when vegetable oil is used as a carrier liquid, long-term storage stability and desired charge retention as a liquid electrostatic developer can be obtained at the same time regardless of the polarity of the vegetable oil itself. A liquid electrostatic developer using a carrier liquid that does not cause a problem can be obtained.

  In addition, according to the method for producing a liquid electrostatic developer of the present invention, the pigment particles having an anionic group dispersed in an aqueous dispersion medium on the surface are added with a cationic polymerizable surfactant. Group is ionically bonded, and the outermost surface of the pigment can be admixed into a state where the cationic groups are aligned. Therefore, when the cationic polymerizable surfactant is emulsion-polymerized, the outermost surface of the pigment is aligned with the cationic groups. Can be modified. Therefore, when dispersed in a low dielectric carrier liquid, it can be a self-positive liquid electrostatic developer without adding a fixing resin, a charge control agent, etc., and the repulsion of the cationic group on the pigment surface. Therefore, even when vegetable oil is used as a carrier liquid, long-term storage stability can be obtained, and a positively chargeable liquid electrostatic developer that simultaneously satisfies desired charge retention can be produced.

  The microencapsulated pigment particle in the present invention is a “cationic polymerizable surfactant” having a cationic particle, a hydrophobic group and a radical polymerizable group in at least one molecule of pigment particles having an anionic group on the surface. Are encapsulated with an encapsulating resin having repeating structural units.

  The pigment particles having an anionic group on the surface are derived from an inorganic pigment or an organic pigment, and can be suitably produced by surface treatment with an anionic (hydrophilic) group imparting agent. The pigment needs to be a pigment that does not dissolve in the anionic (hydrophilic) group-providing agent described later, and examples thereof include the following pigments.

  Examples of the inorganic pigment include carbon blacks such as furnace black, lamb black, acetylene black, and channel black (C.I. Pigment Black 7), iron oxide pigments, and the like. Organic pigments include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments), and polycyclic pigments (eg, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments). Thioindigo pigments, isoindolinone pigments, or quinofuranone pigments), dye chelates (such as basic dye-type chelates or acidic dye-type chelates), nitro pigments, nitroso pigments, or aniline black.

  Examples of carbon black include No. manufactured by Mitsubishi Chemical. 2300, no. 900, MCF88, No. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, or No2200B, etc .; Columbia-made Raven5750, Raven5250, Raven5000, Raven3500, Raven1255, Raven700, etc .; 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc .; or Color Black FW1, Color Black FW2, Bck, Col Black FW2, Cck W200, Color Black S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, can be used Printex 140U, Special Black 6, Special Black 5, Special Black 4A, or Special Black 4 and the like. Further, as the organic pigment for black, a black organic pigment such as aniline black (C.I. Pigment Black 1) can be used.

  Further, as organic pigments for yellow, C.I. l. Pigment Yellow 1 (Hansa Yellow), 2, 3 (Hansa Yellow 10G), 4, 5 (Hansa Yellow 5G), 6, 7, 10, 11, 12, 13, 14, 16, 17, 24 (Flavantron Yellow) , 34, 35, 37, 53, 55, 65, 73, 74, 75, 81, 83, 93, 94, 95, 97, 98, 99, 108 (anthrapyrimidine yellow), 109, 110, 113, 117 ( Copper complex pigment), 120, 124, 128, 129, 133 (quinophthalone), 138, 139 (isoindolinone), 147, 151, 153 (nickel complex pigment), 154, 167, 172, 180, etc. it can.

  Further, organic pigments for magenta include C.I. l. Pigment Red 1 (Para Red), 2, 3 (Toluidine Red), 4, 5 (lTRRed), 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38 (pyrazolone red), 40, 41, 42, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 88 (thioindigo), 112 ( Naphthol AS system), 114 (naphthol AS system), 122 (dimethylquinacridone), 123, 144, 146, 149, 150, 166, 168 (antanthrone orange), 170 (naphthol AS system), 171, 175, 176, 177, 178, 179 (berylene maroon), 184, 185, 187, 202, 209 (dichloroquinacridone), 219, 224 (vector) Ren-based), 245 (Naphthol AS-based), or, C. I. Pigment violet 19 (quinacridone), 23 (dioxazine violet), 32, 33, 36, 38, 43, 50, and the like.

  Further, as an organic pigment for cyan, C.I. l. Pigment Blue 1, 2, 3, 15, 15: 1, 15: 2, 15: 3, 15:34, 15: 4, 16 (metal-free phthalocyanine), 18 (alkali blue toner), 22, 25, 60 ( Slen Blue), 65 (Biolantron), 66 (Indigo), C.I. l. Vat blue 4, 60 etc. can be mentioned.

  Examples of organic pigments used in color developers other than magenta, cyan or yellow include C.I. I. Pigment green 7 (phthalocyanine green), 10 (green gold), 36, 37; C.I. I. Pigment brown 3, 5, 25, 26; I. Pigment orange 1, 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, 63, and the like.

  In the macroencapsulated pigment according to the present invention, the above pigments can be used alone or in combination of two or more.

  The inorganic pigment or organic pigment used in the present invention may be produced from the synthesis stage, and after synthesis, a known wet method such as a pole mill, a bead mill, a sand mill, or an attritor is used to adjust the structure and polarity of the pigment. Accordingly, an anionic dispersant, a cationic dispersant or a nonionic dispersant is added at a ratio of 0.1% by mass with respect to the pigment, and the primary average particle diameter is 10 nm to 1000 nm, preferably 20 nm to 900 nm. It is good to grind | pulverize to a primary average particle diameter.

Next, examples of the anionic (hydrophilic) group imparting agent that introduces an anionic group into the pigment particle include a sulfonating agent and a carboxylating agent.
The sulfonating agent is at least one anionic (hydrophilic) group of a sulfonic acid group (—SO ₃ H) or a sulfinic acid group (—RSO ₂ H) (hereinafter simply referred to as a sulfonic acid group (hydrophilic group)). Is a treatment agent for imparting to the surface of pigment particles. In addition, R in a sulfinic acid group is a C1-C12 alkyl group or a phenyl group, and may have a substituent.

  Examples of the sulfonating agent include sulfur-containing treatment agents such as sulfuric acid, fuming sulfuric acid, sulfur trioxide, chlorosulfuric acid, fluorosulfuric acid, amidosulfuric acid, sulfonated pyridine salt, and sulfamic acid. A pyridine salt, sulfamic acid, or the like is preferable, and one or a mixture of two or more can be used.

  The solvent for the sulfonation may be selected from those that do not react with the sulfonating agent and that the pigment is insoluble or sparingly soluble, such as sulfolane, N-methyl-2-pyrrolidone, dimethylacetamide, quinoline, hexamethyl Examples thereof include phosphoric triamide, chloroform, dichloroethane, tetrachloroethane, tetrachloroethylene, dichloromethane, nitromethane, nitrobenzene, liquid sulfur dioxide, carbon disulfide, and trichlorofluoromethane.

  In addition, when sulfuric acid, fuming sulfuric acid, sulfur trioxide, chlorosulfuric acid, fluorosulfuric acid, etc. are used alone, the reactivity is too high, and the pigment itself may be decomposed or altered, or the reaction control becomes difficult. Therefore, it is preferable to remove moisture as much as possible in the system to which the sulfonating agent is added. Moreover, it is good to use the solvent which can form a complex with a sulfonating agent, for example, N, N- dimethylformamide, a dioxane, a pyridine, a triethylamine, a trimethylamine, nitromethane, acetonitrile etc. are illustrated. The solvent capable of forming a complex with the sulfonating agent may be used by mixing with a solvent that does not react with the above-described sulfonating agent.

  In order to introduce a sulfonic acid group (hydrophilic group) to the surface of the pigment particle, the pigment is added to a solvent insoluble or hardly soluble in the pigment and sheared at high speed with a high speed mixer or the like to obtain a slurry dispersion. Alternatively, a slurry dispersion may be obtained by impact dispersion using a bead mill or a jet mill. Next, after removing water from the slurry-like dispersion as much as possible, a sulfonating agent is added, and the reaction is preferably performed for 3 to 10 hours under heating at 60 to 200 ° C. The solvent and the remaining sulfonating agent are removed by heat treatment. After removing and subjecting to a treatment such as washing with water, ultrafiltration, reverse osmosis, centrifugation, filtration, etc., if necessary, it may be dried and pulverized.

  The amount of sulfonic acid groups (hydrophilic groups) introduced is such that pigment particles having sulfonic acid groups (hydrophilic groups) introduced on the surface are absorbed into the 0.3% hydrogen peroxide aqueous solution by the oxygen flask combustion method. After that, the content of sulfate ion (divalent) is quantified by ion chromatography (Dionesque, 2000i), and this value may be converted to the amount of sulfonic acid group, and the amount of millimoles per 1 g of pigment (mmol / g). Indicated by

  The amount of sulfonic acid group (hydrophilic group) introduced is preferably 0.01 mmol / g or more. When the introduction amount of the sulfonic acid group is less than 0.01 mmol / g, the dispersibility in the aqueous solvent is low, the microencapsulation of the pigment particles becomes insufficient, and resin particles containing no pigment are by-produced, It is not preferable because aggregates of the pigment particles themselves are easily generated. Even if it exceeds 0.15 mmol / g, the effect accompanying the increase in the amount of introduced sulfonic acid groups is not observed.

  Next, the carboxylating agent is a treatment agent for imparting a carboxylic acid group (—COOH) to the pigment surface. Examples of the carboxylating agent include hypohalites such as sodium hypochlorite and potassium hypochlorite. Hypohalite breaks a part of the bond (C = C, C—C) on the pigment particle surface and oxidizes it to introduce a carboxylic acid group (—COOH) onto the pigment particle surface. Further, a carboxylic acid group (hydrophilic group) may be introduced by physical oxidation such as plasma treatment.

  An example of treatment with a carboxylating agent is effective after high-speed shear dispersion of pigment particles in an aqueous medium with a high-speed mixer or the like, or impact dispersion with a bead mill or jet mill to make a slurry dispersion. Hypohalite having a halogen concentration of 10 to 30% is added, and the mixture is reacted at 60 to 80 ° C. for 5 to 10 hours, preferably 10 hours or more with appropriate stirring. After the reaction, heat treatment is performed to remove the solvent and the remaining carboxylating agent from the slurry, and after being subjected to treatment such as washing with water, ultrafiltration, reverse osmosis, centrifugation, filtration, etc., if necessary, Dry and pulverize.

  Since the amount of carboxylic acid groups (—COOH) introduced is difficult to measure, the amount of active hydrogen on the pigment surface is measured, and the measured amount is taken as the amount of carboxylic acid groups (—COOH) introduced. The amount of active hydrogen on the pigment surface can be measured using the Zeisel method. That is, after all active hydrogen on the surface of the pigment particles is exchanged with methyl groups using a diazomethane solution, hydroiodic acid having a specific gravity of 1.7 is added and heated to vaporize the methyl groups as methyl iodide. The methyl iodide is then trapped with a silver nitrate solution and precipitated as silver silver iodide. The amount of the original methyl group, that is, the amount of active hydrogen, is measured by the weight of the obtained methyl silver iodide, and is expressed in millimolar amount (mmol / g) per 1 g of pigment.

  The active hydrogen content in the pigment is preferably 1.0 mmol / g or more, and more preferably 1.5 mmol / g or more. If it is less than 1.0 mmol / g, the dispersibility in an aqueous solvent is low, the microencapsulation of pigment particles becomes insufficient, resin particles containing no pigment are by-produced, and aggregates of pigment particles are easily generated. It is not preferable. The active hydrogen content is at most 6.0 mmol / g.

  The average particle size of the pigment particles having an anionic group (hydrophilic group) on the surface is preferably 1000 nm or less from the viewpoint of dispersibility and concealing property, and the average particle size is more preferably 50 nm to 800 nm. In order to make the average particle diameter of the pigment particles having an anionic group (hydrophilic group) in this range within this range, the primary particle diameter of the pigment, the kind of the hydrophilic group imparting agent, the anionic group (hydrophilic group) An introduction amount or the like may be appropriately selected. By making the average particle size 1000 nm or less, it is possible to obtain a microencapsulated pigment that has excellent dispersion stability in an aqueous medium and can increase the image density. The pigment particle size is measured using a laser Doppler type particle size distribution measuring instrument “Microtrac UPA150” manufactured by Leeds & Northrop.

  Next, the cationic polymerizable surfactant will be described. Cationic polymerizable surfactants are those that simultaneously contain a hydrophilic group consisting of a radical polymerizable group, a hydrophobic group, and a cationic group in one molecule by a covalent bond, and a polymerization function by the radical polymerizable group, It has a function as a surfactant composed of a hydrophilic group composed of a cationic group and a hydrophobic group.

Cationic polymerizable surfactants are, for example,
General formula R _{[4- (l + m + n)]} R ¹ _l R ² _m R ³ _n N ⁺ · X ⁻
Wherein R is a radical polymerizable group, R ¹ , R ² and R ³ are selected from hydrogen, alkyl group, aryl group, aralkyl group and alkylaryl group, at least one of which is a hydrophobic group , X is Cl, Br or I, l, m and n are 1 or 0 and are not 0 at the same time.)
The compound represented by these is illustrated.

  In the formula, R is a radical polymerizable group, and is selected from the group consisting of unsaturated hydrocarbon groups such as vinyl group, allyl group, acryloyl group, methacryloyl group, propenyl group, vinylidene group, vinylene group, acryloyl group, A methacryloyl group is preferred.

R ¹ , R ² and R ³ are hydrogen, an alkyl group, an aryl group, an aralkyl group, and an alkylaryl group. The aralkyl group is an alkyl group substituted with an aromatic hydrocarbon, and the alkylaryl group is an alkyl group substituted. Aromatic hydrocarbon groups are exemplified.

Specific examples include dimethylaminoethyl methyl chloride {(methacryloyloxyethyltrimethylammonium chloride) [CH ₂ ═C (CH ₃ ) COOCH ₂ CH ₂ N (CH ₃ ) ₃ ] ⁺ Cl ⁻ }, dimethylamino methacrylate Examples thereof include ethyl benzyl chloride, diallyl dimethyl ammonium chloride, 2-hydroxy-3-methacryloxypropyl trimethyl ammonium chloride and the like. Commercially available products include Acryester DMC (Mitsubishi Rayon Co., Ltd.), Acryester DML60 (Mitsubishi Rayon Co., Ltd.), C-1615 (Daiichi Kogyo Seiyaku Co., Ltd.), etc., alone or in combination. May be used.

Moreover, the general formula X is described in Japanese Patent Kokoku ^{_{4-65824 - · (R 1 R 2}} R 3) N + CH 2 CH (OH) CH 2 OCH 2 C (R 4) = CH 2
(Wherein R ₁ represents a hydrocarbon group having 8 to 22 carbon atoms, R ₂ and R ₃ represent an alkyl group having 1 to ₃ carbon atoms, R ₄ represents a hydrogen atom or a methyl group, and X ⁻ represents a monovalent group. Represents the negative ion.)
A cationic polymerizable surfactant represented by the formula is also preferably exemplified.

  Next, a method for producing a microencapsulated pigment will be described. The “aqueous solvent” used in the production method means a solvent mainly composed of water, and may further contain a water-soluble solvent such as glycerin or glycol.

  The first method for producing a microencapsulated pigment is to disperse pigment particles having an anionic group on the surface in an aqueous dispersion medium, then add a cationic polymerizable surfactant, and heat and polymerize under dispersion treatment. An initiator is added and emulsion polymerization is performed.

  The second production method of the microencapsulated pigment includes (1) a step of dispersing a pigment particle having an anionic group on the surface thereof in an aqueous dispersion medium, and then adding a cationic polymerizable surfactant for dispersion treatment. 2) A step of adding a dispersion treatment liquid to at least one monomer selected from a hydrophobic monomer, a crosslinkable monomer, and a monomer represented by the following general formula (1), and (3) a dispersion treatment liquid. The step of adding a cationic polymerizable surfactant to the dispersion and carrying out the dispersion treatment in this order is carried out in this order, and then (4) the obtained dispersion treatment liquid is heated and a polymerization initiator is added to carry out emulsion polymerization.

  The third production method of the microencapsulated pigment includes (1) a step of dispersing a pigment particle having an anionic group on the surface thereof in an aqueous dispersion medium, and then adding a cationic polymerizable surfactant for dispersion treatment. 2) A step of adding a dispersion treatment liquid to add at least one monomer selected from a hydrophobic monomer, a crosslinkable monomer, and a monomer represented by the general formula (1), and (3) a dispersion treatment liquid. Then, after carrying out a dispersion treatment in this order by adding a hydrophilic monomer together with the cationic polymerizable surfactant, (4) the obtained dispersion treatment liquid is heated and a polymerization initiator is added to emulsify. Polymerize.

  In the method for producing the microencapsulated pigment particles described above, the pigment particles having an anionic group on the surface are dispersed in an aqueous medium in an amount of 10% by mass to 30% by mass, and then the cation as described in each of the above production methods. The polymerizable polymerizable surfactant and each monomer are sequentially added and dispersed. The dispersion method may be an ultrasonic dispersion treatment, a dispersion treatment using a homogenizer, etc., preferably an ultrasonic dispersion treatment. . As ultrasonic dispersion, ultrasonic waves of 1 MHz to 5 MHz are used, and processing conditions are preferably set to 5 minutes to 30 minutes.

  As the formation mechanism of the microencapsulated pigment particles in the first production method, when a cationic polymerizable surfactant is added to an aqueous dispersion of a pigment having an anionic group on the surface, Some of the cationic groups are immobilized by ionically bonding the cationic groups with anionic groups on the pigment surface, and the remaining cationic polymerizable surfactants are polymerized with the cationic groups facing the aqueous phase. It is considered that the functional group side is admixed in a form covering the polymerizable group side of the cationic polymerizable surfactant fixed on the surface of the pigment particles. When a radical polymerization initiator is added to the admicelle state under heating, emulsion polymerization occurs between the polymerizable groups, and the cationic polymerizable surfactant itself is polymerized, and the obtained encapsulated pigment particles are The microencapsulated pigment particles have a cationic group on the surface.

  The encapsulating resin may contain a functional monomer such as a hydrophobic monomer, a crosslinkable monomer, and a monomer represented by the general formula (1) as a copolymerization component. The second and third production methods are cases where a function-imparting monomer is contained. In the second and third production methods, as in the first production method, first, a cationic polymerizable surfactant is added and dispersed in a dispersion in which a pigment having an anionic group on the surface is dispersed in water. In addition, as a post-treatment, a cationic polymerizable surfactant or, if necessary, a hydrophilic monomer is further added and dispersed, and the resulting encapsulated pigment particles are: As in the first production method, the microencapsulated pigment particles have a cationic group or a hydroxyl group on the surface together with the cationic group.

  The formation mechanism of the microencapsulated pigment particles in the second and third production methods is such that the pigment is dispersed in the order of addition described above, so that the cationic polymerizable surfactant or monomer present around the pigment particles is dispersed. The arrangement form can be controlled to a very high degree, and an admicelle state in which cationic groups are oriented toward the aqueous phase is formed in the outermost shell. Under heating, a polymerization initiator is added to this admicelle state and emulsion polymerization is carried out to polymerize in a highly controlled admicelle state, and the obtained encapsulated pigment particles are microcapsules having a cationic group on the surface. It becomes a pigmented pigment particle.

  According to the production method of the present invention, the arrangement form of the cationic polymerizable surfactant and the monomer existing around the pigment particles can be controlled to a very high degree, so that a by-product having no pigment particles (oligomer or (Polymer) can be reduced, the viscosity of the resulting dispersion can be reduced, and purification steps such as microfiltration can be facilitated.

  The addition amount of the cationic polymerizable surfactant to the pigment particles having an anionic group on the surface is the total number of moles of anionic groups in the pigment particles {anionic groups on the pigment surface (mol / g) × pigment weight (g). }, A range of 0.5 to 2 times mol, preferably 0.8 to 1.2 times mol is preferable. If the amount is less than 0.5 times mol, the purpose of adding the cationic polymerizable surfactant cannot be achieved. On the other hand, if it exceeds 2 moles, an unadsorbed cationic polymerizable surfactant is generated in the pigment particles, and a by-product of a polymer containing no pigment particles is generated, which is not preferable.

  In the second and third microencapsulated pigment particle manufacturing methods, the amount of the cationic polymerizable surfactant that forms the outermost shell of the capsule is 0.5 times the amount of the cationic polymerizable surfactant added first. The molar amount is 5 to 5 times, preferably 1 to 2 times. If the amount is less than 0.5 times mol, there is a problem in the dispersibility of the microencapsulated pigment particles due to the influence of a hydrophobic monomer or the like, and if it exceeds 2 times mol, polymer particles containing no pigment particles are generated.

  The cationic polymerizable surfactant is preferably 10 to 100 mol% in the encapsulated resin. Moreover, in the microencapsulated pigment particles produced by the second and third production methods, the content of the cationic polymerizable surfactant may be appropriately selected within the above range.

  Next, functional monomers such as a hydrophobic monomer, a crosslinkable monomer, and a monomer represented by the general formula (1), which are copolymerization components in the second and third production methods, will be described.

  The hydrophobic monomer is copolymerized for the purpose of improving the fixability, scratch resistance, water resistance, and carrier liquid resistance of the recorded matter. The hydrophobic monomer has at least a hydrophobic group and a radical polymerizable group in one molecule. Hydrophobic groups include aliphatic hydrocarbon groups such as methyl, ethyl and propyl, alicyclic hydrocarbon groups such as cyclohexyl, dicyclopentenyl, dicyclopentanyl and isobornyl, benzyl and phenyl And aromatic hydrocarbon groups such as naphthyl group and the like. Examples of the radical polymerizable group include unsaturated hydrocarbon groups such as vinyl group, allyl group, acryloyl group, methacryloyl group, propenyl group, vinylidene group and vinylene group.

Examples of hydrophobic monomers include styrene derivatives such as styrene, methylstyrene, dimethylstyrene, chlorostyrene, dichlorostyrene, bromostyrene, p-chloromethylstyrene, and divinylbenzene; methyl acrylate, ethyl acrylate, n-butyl acrylate, Butoxyethyl acrylate, benzyl acrylate, phenyl acrylate, phenoxyethyl acrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, etc. Monofunctional acrylic acid esters: methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, butoxime Methacrylates, benzyl methacrylate, phenyl methacrylate, phenoxyethyl methacrylate, cyclohexyl methacrylate, dicyclopentanyl methacrylate, dicyclopentenyl methacrylate, dicyclopentenyloxyethyl methacrylate, tetrahydrofurfuryl methacrylate, isobornyl methacrylate, etc. Functional methacrylate esters; allyl compounds such as allylbenzene, allyl-3-cyclohexanepropionate, 1-allyl-3,4-dimethoxybenzene, allylphenoxyacetate, allylphenylacetate, allylcyclohexane, allyl polycarboxylate; Acid, maleic acid, itaconic acid ester cheeks; monomers having radically polymerizable groups such as N-substituted maleimides and cyclic olefins It is below.
The copolymerization ratio of the hydrophobic monomer is 30 mol% to 50 mol% in the encapsulated resin.

  Next, the crosslinkable monomer forms a crosslinked structure in the encapsulated resin, and is added for the purpose of improving resistance to the carrier liquid and the like. When the carrier liquid penetrates into the interior of the polymer that coats the pigment particles, the polymer may swell, deform, and the like, which may reduce the dispersion stability of the microencapsulated pigment. By forming a crosslinked structure in the encapsulated resin, the carrier liquid resistance of the microencapsulated pigment is improved, and the dispersion stability can be further improved.

The crosslinkable monomer has a compound having two or more unsaturated hydrocarbon groups selected from vinyl group, allyl group, acryloyl group, methacryloyl group, propenyl group, vinylidene group and vinylene group, and ethylene glycol. Diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, allyl acrylate, bis (acryloxyethyl) hydroxyethyl isocyanurate, bis (acryloxyneopentyl glycol) adipate, 1, 3-butylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, propylene glycol diacrylate, Propylene glycol diacrylate, 2-hydroxy-1,3-diaacryloxypropane, 2,2-bis [4- (acryloxy) phenyl] propane, 2,2-bis [4- (acryloxyethoxy) phenyl] propane, 2,2-bis [4- (acryloxyethoxy diethoxy) phenyl] propane, 2,2-bis [4- (acryloxyethoxy polyethoxy) phenyl] propane, hydroxypentyl glycol neopentyl glycol diacrylate, 1, 4-butanediol diacrylate, dicyclopentanyl diacrylate, dipentaerythritol hexaacrylate, dipentaerythritol monohydroxypentaacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate, Labromobisphenol A diacrylate, triglycerol diacrylate, trimethylolpropane triacrylate, tris (acryloxyethyl) isocyanurate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol Dimethacrylate, propylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, 2-hydroxy -1,3-dimethacryloxypropane, 2,2-bis [4 Mono (methacryloxy) phenyl] propane, 2,2-bis [4- (methacryloxyethoxy) phenyl] propane, 2,2-bis [4- (methacryloxyethoxydiethoxy) phenyl] propane, 2,2-bis [ 4- (methacryloxyethoxypolyethoxy) phenyl] propane, tetrabromobisphenol A dimethacrylate, dicyclopentanyl dimethacrylate, dipentaerythritol hexamethacrylate, glycerol dimethacrylate, hydroxypentyl glycol dimethacrylate, dipentaerythritol Monohydroxypentamethacrylate, ditrimethylolpropane tetramethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, triglyceride Roll dimethacrylate, trimethylolpropane trimethacrylate, tris (methacryloxyethyl) isocyanurate, allyl methacrylate, divinylbenzene, diallyl phthalate, diallyl terephthalate, diallyl isophthalate, diethylene glycol bis allyl carbonate.
The copolymerization ratio of the crosslinkable monomer is 0.1 mol% to 5.0 mol% in the encapsulated resin.

  Further, the encapsulating resin may further have a repeating structural unit derived from a monomer represented by the following general formula (1).

(In the formula, R ¹ represents a hydrogen atom or a methyl group. R ² represents a bulky group, and represents a t-butyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or a heterocyclic group, m Represents 0 to 3, and n represents an integer of 0 or 1.)
The bulky group may be selected from a branched alkyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or a heterocyclic group, and the mobility is increased when the bulky group is contained in the encapsulating resin. Is restrained, the mechanical strength, heat resistance and carrier liquid resistance can be improved, and microencapsulated pigment particles having excellent abrasion resistance and durability can be obtained. In general formula (1), when m is 0, n is also 0.

  Examples of the branched alkyl group, alicyclic hydrocarbon group, and aromatic hydrocarbon group include a t-butyl group, a cycloalkyl group, a cycloalkenyl group, a benzyl group, a phenyl group, an isobornyl group, a dicyclopentanyl group, Examples include a dicyclopentenyl group, an adamantane group, a tetrahydrofuran group, and a naphthyl group.

  Moreover, the following are mentioned as a specific example of the monomer represented by the said General formula (1).

  The copolymerization ratio of the monomer represented by the general formula (1) is 20 mol% to 60 mol% in the encapsulated resin.

  In addition, a polymer derived from a crosslinkable monomer or a polymer derived from the monomer represented by the general formula (1) has an advantage of high Tg and excellent mechanical strength, heat resistance, and solvent resistance. The plasticity of the encapsulating resin becomes insufficient, and it tends to be in a state where it is difficult to adhere to the recording medium, and as a result, the fixability and abrasion resistance of the microcapsule pigment to the recording medium may be lowered. On the other hand, a polymer composed of the above-mentioned hydrophobic monomer (for example, a hydrophobic monomer having a long-chain alkyl group as a hydrophobic group) gives a polymer having excellent flexibility. Therefore, a crosslinkable monomer or a monomer represented by the general formula (1) It is good to contain a hydrophobic monomer in the ratio of 0.5 mol-170 mol with respect to 1 mol. As a result, an encapsulated resin having mechanical strength and carrier liquid resistance can be obtained as long as the plasticity is not impaired, and it is easy to adhere to the recording medium, has excellent fixing properties, and has carrier liquid resistance. In addition, excellent microencapsulated pigment particles can be obtained.

  Next, the hydrophilic monomer has a hydrophilic group and a radical polymerizable group in one molecule, and examples of the hydrophilic group include a hydroxyl group, an ethylene oxide group, an amide group, and an amino group. In addition, it is good to add with a cationic polymerizable surfactant as a monomer which forms the outermost outline of a microencapsulated pigment particle. Similar to the cationic group in the cationic polymerizable surfactant, the hydrophilic group in the hydrophilic monomer is considered to form an admicelle state toward the aqueous phase side. Since it is easy to form a hydrogen bond with the OH group of the fiber, it is a monomer that forms the outermost surface of the microencapsulated pigment particle.

  Examples of hydrophilic monomers include 2-hydroxyethyl methacrylate having a hydroxyl group, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, and the like, and ethyl diethylene glycol acrylate having an ethylene oxide group, polyethylene glycol monomethacrylate, methoxypolyethylene glycol methacrylate, and the like. Acrylamide having an amide group, N, N-dimethylacrylamide, etc., N-methylaminoethyl methacrylate containing amino group, N-methylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl methacrylate, diethylaminoethyl methacrylate, etc. Alkylamino esters of acrylic acid or methacrylic acid Unsaturated amides having an alkylamino group such as N- (2-dimethylaminoethyl) acrylamide, N- (2-dimethylaminoethyl) methacrylamide, N, N-dimethylaminopropylacrylamide and the like, and monovinylpyridine such as vinylpyridine And vinyl ethers having an alkylamino group such as dimethylaminoethyl vinyl ether; vinyl imidazole, N-vinyl-2-pyrrolidone and the like.

  The hydrophilic monomer may have a copolymerization ratio of 0.5 mol to 1.0 mol with respect to 1 mol of the cationic polymerizable surfactant that forms the outermost contour of the microencapsulated pigment particles.

  In the emulsion polymerization reaction, it is preferable to use a reaction vessel equipped with an ultrasonic generator, a stirrer, a reflux condenser, a dropping funnel and a temperature controller, and the polymerization initiator is activated while ultrasonically dispersing the aqueous dispersion. It is good to heat at 60 to 90 degreeC, and to dripping polymerization-initiator aqueous solution.

  As the polymerization initiator, a water-soluble radical polymerization initiator is preferable, and potassium persulfate, ammonium persulfate, sodium persulfate, 2,2-azobis- (2-methylpropionamidine) dihydrochloride, or 4,4-azobis- ( 4-cyanovaleric acid) and the like, and a catalytic amount is added to the dispersion. After completion of the polymerization, the pH of the dispersion liquid is adjusted to around 6, and the microencapsulated pigment particles are preferably finely filtered and collected as wet fine particles.

  The microencapsulated pigment particles of the present invention are 40 mass parts to 900 mass parts, preferably 50 mass parts to 850 mass parts of encapsulated resin with respect to 100 mass parts of pigment particles having an anionic group on the surface. It should be coated.

  The glass transition point (Tg) of the encapsulated resin is -20 ° C to 90 ° C, preferably -10 ° C to 80 ° C. Tg is measured using a thermal operation calorimeter (differential operation calorimeter, DSC) DSC200 (manufactured by Seiko Electronics Co., Ltd.). By making Tg within this temperature range, the recorded matter can be excellent in fixability and scratch resistance. When Tg is lower than −20 ° C., the carrier liquid resistance is lowered, and when it is higher than 90 ° C., the burden on the fixing device is increased, which is not preferable as a fixing device for energy saving.

  As will be described later, in the production of the liquid electrostatic developer of the present invention, the wet fine particles obtained above are dried at room temperature, then dispersed in a carrier liquid (vegetable oil), and water is distilled off by distillation under reduced pressure. The liquid electrostatic developer. When the glass transition point of the encapsulating resin is low and the drying conditions are severe, coalescence and aggregation of the microencapsulated pigment particles occur.

  The primary volume average particle diameter of the wet fine particles is 0.2 μm to 1 μm, preferably 0.2 μm to 0.8 μm.

  The particle size distribution is a value measured by a laser Doppler type particle size distribution measuring instrument “Microtrac UPA150” manufactured by Leeds & Northrop.

Next, the liquid electrostatic developer of the present invention will be described. The liquid electrostatic developer is made into a liquid electrostatic developer by dispersing microencapsulated pigment particles in a low dielectric carrier liquid. The low dielectric carrier liquid can be a known carrier liquid such as an aliphatic hydrocarbon, silicone oil, vegetable oil or the like having a volume resistance of 10 ⁹ Ω · cm or more and a dielectric constant of 3.6 or less. The microencapsulated pigment particles in the present invention are suitable for a liquid electrostatic developer using a vegetable oil or a fatty acid ester as a carrier liquid without causing the problem of environmental pollution (VOC).

  The vegetable oil is preferably selected from safflower oil, sunflower oil, soybean oil, corn oil, cottonseed oil containing at least 50% linoleic acid component, and linseed oil containing at least 50% linolenic acid component. The linoleic acid component contains two unsaturated bonds and the linolenic acid component contains three molecules. Such vegetable oils themselves have oxidative polymerization properties and are curable when fixed on transfer paper. Therefore, it is necessary to provide particularly positive fixing means after an image is formed on a recording medium. Therefore, the image can be fixed on the transfer paper, and the size and cost of the copying machine can be reduced. The vegetable oil may be purified by activated carbon treatment as a pretreatment for use. The amount (% by mass) of the acid component contained in the vegetable oil is shown in Table 1 below.

  Since the microencapsulated pigment particles in the present invention have a low Tg of the encapsulated resin, wet microparticles obtained in the preparation of the microencapsulated pigment particles are used at room temperature to be dispersed in a carrier liquid to form a liquid electrostatic developer. After drying, it may be dispersed in a carrier liquid (vegetable oil), and a liquid electrostatic developer in which microencapsulated pigment particles are dispersed while maintaining the particle size of wet fine particles can be obtained.

  In addition, after the wet fine particles are dried at room temperature, they are dispersed in a carrier liquid (vegetable oil) to form a liquid electrostatic developer. When the liquid electrostatic developer is subjected to dehydration using a vacuum distillation, a desiccant or the like, The water content is preferably 0.5% by mass or less, preferably 0.1% by mass or less.

  The microencapsulated pigment particles can be excellent in dispersibility even when contained up to 50% by mass with respect to the vegetable oil. However, the liquid electrostatic developer is 2% by mass to 45% by mass, preferably 3% by mass to 35%. It is good to contain by mass%.

  An antioxidant may be added for the purpose of preventing the carrier liquid from being oxidized. Examples of the antioxidant include t-butylhydroquinone, butylhydroxyanisole, isopropyl citrate and the like, and it is preferable to add 0.05% by mass to 2.0% by mass in the liquid electrostatic developer. If it is more than 2.0% by mass, it is not preferable because it affects the curing of the image during fixing.

When vegetable oil itself is used as a carrier liquid, it exhibits negative chargeability, and in order to make a positively chargeable liquid electrostatic developer, it is essential to add a charge control agent, but the microencapsulated pigment particles in the present invention are contained in vegetable oil. The liquid electrostatic developer can reliably function as a positively chargeable liquid electrostatic developer. In the microencapsulated pigment particles according to the present invention, the cationic groups are regularly and densely oriented in the outermost contour of the pigment particles. Therefore, when used as a liquid electrostatic developer, it is effective between adjacent microencapsulated pigment particles. The electrostatic repulsive force is generated, and the steric hindrance caused by the encapsulating resin can prevent the aggregation of the microencapsulated pigment particles in the liquid electrostatic developer, and exhibits excellent dispersion stability. The microencapsulated pigment particles contain an encapsulated resin, and the encapsulated resin can be used as a fixing resin.
In addition, the outermost surface of the microencapsulated pigment particles has a hydrophilic cationic group or a hydrophilic group derived from a hydrophilic polymer arranged therein, and the plain paper is interacted with the cellulose fibers of the plain paper. It is easily adsorbed on cellulose fibers, a high image density is obtained, and the occurrence of bleeding is suppressed.

  Moreover, even if inexpensive acidic paper is used as the recording medium, it shows a catalytic action when the vegetable oil adheres to the paper and undergoes oxidative polymerization after recording, and the microencapsulated pigment particles have quaternary ammonium on the surface. Since it has a cationic group composed of a basic group such as a group, it acts in the direction of neutralizing the pH of the paper in the recording portion, and the storage stability of the image after recording can be increased.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these Examples. “Part” means “part by mass”.

(Preparation of black pigment particles “Bk1” having sulfonic acid groups on the surface)
Carbon black (Mitsubishi Chemical "MA-7", particle size 24nm) 15 parts is mixed in sulfolane 200 parts, Eiger motor mill M250 type (Eiger Japan Co., Ltd.), bead filling rate 70% and rotation speed 5000rpm For 1 hour under the following conditions. The obtained pigment paste was transferred to an evaporator and heated to 120 ° C. while reducing the pressure to 30 mmHg or less, and water contained in the system was distilled off as much as possible.

  Next, the mixture was heated to 150 ° C., added with 25 parts of sulfur trioxide and reacted for 6 hours, washed several times with sulfolane, poured into water, and the black pigment particles into which sulfonic acid groups had been introduced were collected by filtration. . The obtained black pigment particles Bk1 had a particle size of 85 nm and an introduction amount of sulfonic acid groups of 0.12 mmol / g.

(Preparation of black pigment particles Bk2 having carboxylic acid groups on the surface)
After mixing 300 g of acidic carbon black (Mitsubishi Chemical Corporation, MA-100, particle size 24 nm) well with 1000 ml of water, 450 g of sodium hypochlorite (effective chlorine concentration: 12%) was added dropwise at 80 ° C. for 15 hours. Stir. The obtained slurry was Toyo Filter Paper No. While filtering through 2, the sample was repeatedly washed with ion-exchanged water. As a guideline for completion of washing with water, the test was carried out until the cloudiness disappeared when a 0.1 N aqueous solution of silver nitrate was added to the ion-exchanged water that passed through the paper. This pigment slurry was re-dispersed in 2500 ml of water, desalted with a reverse osmosis membrane until the conductivity was 0.2 microsiemens or less, and further concentrated to a pigment concentration of about 15% by mass. The obtained surface-treated pigment dispersion was acid-treated (acidified with aqueous hydrochloric acid), concentrated, dried, and finely pulverized to obtain black pigment particles Bk2 into which carboxylic acid groups had been introduced. The black pigment particle Bk2 had a particle size of 88 nm and an active hydrogen group content of 2.8 mmol / g.

(Preparation of cyan pigment particles C1 having sulfonic acid groups on the surface)
20 parts of a phthalocyanine pigment (CI Pigment Blue 15: 3, particle size 130 nm) are mixed with 500 parts of quinoline, conditions of Eiger Motor Mill M250 type (manufactured by Eiger Japan) with a bead filling rate of 70% and a rotation speed of 5000 rpm Then, the mixture was dispersed for 2 hours, and the dispersed mixture of the pigment paste and the solvent was transferred to a rotary evaporator, and heated to 120 ° C. while reducing the pressure to 30 mmHg or less, thereby removing as much water as possible in the system.

  Next, 20 parts of a sulfonated pyridine complex was added under heating at 160 ° C. and reacted for 8 hours. After completion of the reaction, the mixture was washed several times with quinoline and poured into water, and cyan pigment particles C1 having sulfonic acid groups on the surface. Got. The cyan pigment particle C1 had a particle size of 150 nm and a sulfonic acid group introduction amount of 0.04 mmol / g.

(Preparation of yellow pigment particles Y1 having sulfonic acid groups on the surface)
In the production of cyan pigment particles C1, 20 parts of “phthalocyanine pigment (CI Pigment Blue 15: 3)” were replaced with 20 parts of “isoindolinone pigment (CI Pigment Yellow 110, particle size 93 nm)”. Except for the above, yellow pigment particles Y1 having sulfonic acid groups on the surface were obtained by the same treatment method. The yellow pigment particle Y1 had a particle size of 111 nm, and the amount of sulfonic acid groups introduced was 0.045 mmol / g.

(Preparation of magenta pigment particles M1 having sulfonic acid groups on the surface)
In the production of cyan pigment particles C1, except that “parts of phthalocyanine pigment (CI Pigment Blue 15: 3) 20 parts” was replaced with “parts of quinacridone pigment (CI Pigment Red 122, particle size 138 nm)”, By the same treatment method, magenta pigment particles M1 having sulfonic acid groups on the surface were obtained. The magenta pigment particle M1 had a particle size of 149 nm and an introduction amount of sulfonic acid groups of 0.06 mmol / g.

Example 1
(Production of microencapsulated pigment MCPBk1 and production of liquid developer)
0.81 g of dimethylaminoethyl methyl chloride methacrylate as a cationic polymerizable surfactant was added to and mixed with an aqueous dispersion in which 20 g of black pigment particles Bk1 having sulfonic acid groups on the surface thereof were dispersed in 80 g of ion-exchanged water. Then, it processed by irradiating with an ultrasonic wave for 15 minutes. Next, 2.45 g of isobornyl methacrylate and 2.55 g of lauryl methacrylate were mixed and mixed with stirring. Further, 1.0 g of dimethylaminoethyl methyl chloride methacrylate was added and mixed, and then ultrasonication was performed again for 30 minutes. .

  The obtained dispersion was put into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a temperature controller, a nitrogen introduction tube and an ultrasonic generator. After raising the internal temperature of the reaction vessel to 80 ° C., an aqueous solution in which 0.3 g of 2,2′-azobis (2-methylpropionamidine) dihydrochloride as a polymerization initiator was dissolved in 20 g of ion exchange water, Polymerization was performed for 6 hours while introducing nitrogen at 80 ° C. After the completion of the polymerization reaction, the pH was adjusted to around 6 with disodium citrate, and microfiltration was performed to obtain wet microparticles of microencapsulated pigment MCPBk1.

  The obtained wet fine particles were measured for volume average particle size distribution using a laser Doppler type particle size distribution analyzer, Microtrac UPA150, manufactured by Leeds & Northrop Co., and found to be 100 nm to 850 nm. The obtained wet fine particles were dried at room temperature, and the glass transition point of the film polymer was measured using a heat-operated calorimeter (differential operation calorimeter, DSC) DSC200 (manufactured by Seiko Electronics Co., Ltd.). Met.

  Next, 10 g of the obtained wet fine particles was added to 170 g of sunflower oil containing 0.1 mass% of TBHQ (t-butylhydroquinone) as an antioxidant, and mixed by irradiation with ultrasonic waves. It moved to the rotary evaporator and water contained in the system was distilled off over 5 hours at the temperature of 120 degreeC, reducing pressure to 30 mmHg or less. Subsequently, it moved to the stainless steel beaker, and ultrasonic developer was irradiated for 10 minutes, and liquid developer MCPBk1 was produced.

  With respect to the liquid developer MCPBk1, the volume average particle size distribution was measured by the same method as that for the above-mentioned wet fine particles, and it was 100 nm to 850 nm, and it was confirmed that the particle size was maintained.

(Preparation of black liquid developer of comparative example)
6 parts of carbon black (Mitsubishi Chemical Corporation, MA-7, particle size 24 nm) is added to 100 g of sunflower oil containing 0.1% of the above-mentioned antioxidant TBHQ (t-butylhydroquinone) and ultrasonic Was dispersed and mixed to prepare Comparative Example Bk1.

(Evaluation of toner charge by electrophoresis)
The charging behavior of the liquid electrostatic developer was examined using an electrophoresis experimental apparatus. FIG. 1 is a diagram illustrating a measurement cell for charging characteristics of a liquid electrostatic developer, FIG. 1 (A) is a perspective view illustrating the measurement cell, and FIG. 1 (B) illustrates an electrode portion. It is a perspective view.

  In the measurement cell 1, an anode side electrode part 3 and a cathode side electrode part 4 are installed in a container 2 made of an electrically insulating member such as glass or synthetic resin. The anode terminal 5 provided on the anode side electrode section 3 is connected to a power feeding anode side lead wire 6 coupled to a current supply device (not shown), and is provided on the cathode side electrode section 4. A cathode-side lead wire 8 coupled to a current supply device (not shown) is connected to the cathode terminal 7. The anode-side electrode portion 3 and the cathode-side electrode portion 4 are provided with a holding member mounting groove 9 for holding both electrode portions at a predetermined interval on the upper portion thereof. Is held at a predetermined interval. In addition, a flow groove 10 is provided below the anode electrode portion 3 and the cathode electrode portion 4 so that the liquid electrostatic developer is smoothly supplied.

  FIG. 1B illustrates the anode electrode portion, and the cathode electrode portion is also formed of the same structure and members. The anode electrode portion 2 is formed of a molded body in which a protrusion 11 for anode engagement is provided on a resin having high oil resistance and solvent resistance, such as polyacetal resin (POM). An anode 12 is attached to the anode engaging projection 11 together with a spacer 13 made of an insulating member that maintains a constant distance from the counter electrode. The anode 12 is preferably formed on a transparent glass plate by forming a transparent conductive film 14 such as ITO that does not elute due to the applied current when a current is applied. By using a transparent conductive film formed on a transparent glass plate, it is easy to optically observe and measure the pigment deposited on the anode removed from the anode electrode after electrophoresis for a predetermined time. Can be performed. Alternatively, the pigment concentration may be measured with a reflection densitometer or the like after the anode removed from the anode electrode portion is pressed against a transfer material such as paper or a synthetic resin film to transfer the pigment. For each of the anode and the cathode, it is possible to determine whether it has a positive or negative charge characteristic by comparing the deposited pigment or its transferred image.

  In the electrophoresis experiment apparatus, a 300V DC voltage was applied for 10 seconds to adhere the electrophoretic particles to the positive and negative ITO transparent electrodes, and then both electrodes were removed from the measurement cell, and the particles adhering to the electrodes were removed. It was pressed and transferred onto transfer paper (J paper manufactured by Fuji Xerox Office Supply Co., Ltd.) to obtain a colored solid image.

  After standing for 1 day, the density of the colored solid image was measured as a reflection density using a reflection densitometer (model 520 type spectral densitometer manufactured by X-Rite Co.). From the reflection density value, it was determined whether the colored dispersed fine particles were positive, negative, or neutral (the amount of adhesion was positive and negative, meaning the same amount), and the results are shown in Table 2.

  The liquid developer MCPBk1 of the present invention clearly showed positive chargeability, but the comparative example Bk1 rather showed negative chargeability.

(Measurement of zeta potential of liquid developer)
The zeta potential of the liquid developer was measured at a room temperature of 25 ° C. and an applied voltage of DC 35 V by diluting the liquid developer 3000 times with methyl oleate using a zeta electrometer (Zeta Sizer, manufactured by Sysmex Corporation). The measurement results are also shown in Table 2.

  The liquid developer MCPBk1 of the present invention showed 93 mV, but the comparative example Bk1 showed negative chargeability of −29 mV.

(Example 2)
(Production of microencapsulated pigment MCPM1 and production of liquid developer)
To an aqueous dispersion in which 100 g of magenta pigment particles M1 having sulfonic acid groups on the surface are dispersed in 500 g of ion-exchanged water, 1.25 g of dimethylaminoethyl methyl chloride methacrylate as a cationic polymerizable surfactant was added and mixed. Then, ultrasonic waves were irradiated for 15 minutes. Next, 12 g of benzyl methacrylate and 8 g of dodecyl methacrylate were mixed and stirred and mixed, 1.5 g of dimethylaminoethylmethyl chloride methacrylate was further added, and ultrasonic waves were irradiated again for 30 minutes.

  The obtained dispersion was put into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a temperature controller, a nitrogen introduction tube and an ultrasonic generator. After raising the internal temperature of the reaction vessel to 80 ° C., an aqueous solution in which 0.6 g of 2,2′-azobis (2-methylpropionamidine) dihydrochloride as a polymerization initiator was dissolved in 20 g of ion exchange water was added dropwise, Polymerization was carried out at 80 ° C. for 6 hours while introducing nitrogen. After the completion of the polymerization reaction, the pH was adjusted to around 6 with disodium citrate and fine filtration was performed to obtain wet fine particles of the microencapsulated pigment MCPMI.

  The volume average particle size distribution of the obtained wet fine particles was measured using a laser Doppler type particle size distribution analyzer “Microtrac UPA150” manufactured by Leeds & Northrop Co. As a result, it was 100 nn to 530 nm.

  The obtained wet fine particles were dried at room temperature, and the glass transition point of the film polymer was measured using a thermal operation calorimeter (differential operation calorimeter, DSC) DSC200 (manufactured by Seiko Denshi KK). ° C.

  Next, 10 g of the obtained wet fine particles were added to 170 g of sunflower oil containing 0.1 mass% of TBHQ (t-butylhydroquinone) as an antioxidant and mixed by irradiating with ultrasonic waves. The liquid was transferred to a rotary evaporator, while maintaining the temperature at 120 ° C. for 5 hours while reducing the pressure to 30 mmHg or less, water contained in the system was distilled off, and then transferred to a stainless steel beaker, and ultrasonic waves were applied for 10 minutes. Irradiated to prepare a magenta toner liquid developer MCPMI.

(Preparation of Comparative Magenta Liquid Developer)
6 parts of quinacridone pigment (CI Pigment Red 122) is added to 100 g of sunflower oil containing 0.1% by mass of the above-mentioned antioxidant TBHQ (t-butylhydroquinone) and dispersed by irradiating with ultrasonic waves. By mixing, a magenta toner liquid developer (Comparative Example M1) of Comparative Example was produced.

  Using the prepared liquid developer of the present invention and a comparative developer, the toner charge was evaluated by electrophoresis as described in Example 1, and the zeta potential of the liquid developer was measured. The results are also shown in Table 2.

  According to the results, the liquid developer MCPMI of the present invention clearly showed positive chargeability, but the comparative example M1 was charged positively and negatively, rather, it was a developer close to neutrality. When the zeta potential was observed, the liquid developer MCPMI of the present invention showed 105 mV, but the comparative example M1 was 5 mV.

(Example 3)
(Production of microencapsulated pigment MCPM2 and production of liquid developer)
To an aqueous dispersion in which 100 g of magenta pigment particles M1 having sulfonic acid groups on the surface are dispersed in 500 g of ion-exchanged water, 1.25 g of dimethylaminoethyl methyl chloride methacrylate as a cationic polymerizable surfactant was added and mixed. Then, ultrasonic waves were irradiated for 15 minutes. Next, 12 g of benzyl methacrylate and 8 g of dodecyl methacrylate were added and mixed by stirring. Further, 0.5 g of 2-hydroxyethyl methacrylate and 1.5 g of dimethylaminoethyl methyl chloride methacrylate were mixed and added, and ultrasonic waves were irradiated again for 30 minutes.

  This dispersion was put into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a temperature controller, a nitrogen introduction tube and an ultrasonic generator. After raising the internal temperature of the reaction vessel to 80 ° C., an aqueous solution in which 0.6 g of 2,2′-azobis (2-methylpropionamidine) dihydrochloride as a polymerization initiator was dissolved in 20 g of ion exchange water was added dropwise, Polymerization was started at 80 ° C. for 6 hours while introducing nitrogen. After the completion of the polymerization reaction, the pH was adjusted to around 6 with disodium citrate and microfiltration was performed to obtain wet fine particles of microencapsulated pigment MCPM2.

  The obtained wet fine particles were measured for a volume average particle size distribution using a laser Doppler type particle size distribution analyzer Microtrac UPA150 manufactured by Leeds & Northrop Co. As a result, it was 100 nm to 540 nm.

  The obtained wet fine particles were dried at room temperature, and the glass transition point of the film polymer was measured using a heat-operated calorimeter (differential operation calorimeter, DSC) DSC200 (manufactured by Seiko Denshi KK). ° C.

  Next, 170 g of safflower oil containing 0.1% by mass of antioxidant TBHQ (t-butylhydroquinone) in 10 g of the obtained wet fine particles (200 parts by mass of commercially available safflower oil with 20 mass of activated carbon). The mixture was stirred for 1 hour and then filtered and used) and mixed by irradiation with ultrasonic waves. This mixed liquid was transferred to a rotary evaporator, and maintained at a temperature of 120 ° C. for 5 hours while reducing the pressure to 30 mmHg or less, thereby distilling off water contained in the system. Subsequently, it moved to the stainless steel beaker and irradiated with the ultrasonic wave for 10 minutes, and produced liquid developer MCPM2 of this invention.

  Using the prepared liquid developer of the present invention, the evaluation of toner charge by electrophoresis described in Example 1 and the zeta potential of the liquid developer were measured. The results are shown in Table 2.

According to the results, the liquid developer MCPM2 of the present invention clearly showed positive chargeability, and the zeta potential showed 100 mV.
Example 4
(Production of microencapsulated pigment MCPC1 and production of liquid developer)
1.0 g of dimethylaminoethyl methyl chloride as a cationic polymerizable surfactant was added to and mixed with an aqueous dispersion obtained by dispersing 100 g of cyan pigment particles C1 having sulfonic acid groups on the surface thereof in 500 g of ion-exchanged water. Then, ultrasonic waves were irradiated for 15 minutes. Next, 17.3 g of benzyl methacrylate, 7.7 g of dodecyl methacrylate and 0.05 g of diethylene glycol dimethyl methacrylate were added and mixed with stirring. Further, 1.5 g of dimethylaminoethyl methyl chloride methacrylate was added, and ultrasonic waves were irradiated again for 30 minutes. .

  The obtained dispersion was charged into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a temperature controller, a nitrogen introduction tube and an ultrasonic generator. After raising the internal temperature of the reaction vessel to 80 ° C., an aqueous solution in which 0.6 g of 2,2′-azobis (2-methylpropionamidine) dihydrochloride as a polymerization initiator was dissolved in 20 g of ion exchange water was added dropwise, Polymerization was carried out at 80 ° C. for 6 hours while introducing nitrogen. After the completion of the polymerization reaction, the pH was adjusted to around 6 with disodium citrate and microfiltration was performed to obtain wet fine particles of microencapsulated pigment MCPC1.

  The obtained wet fine particles were measured for a volume average particle size distribution using a laser Doppler type particle size distribution analyzer Microtrac UPA150 manufactured by Leeds & Northrop Co. As a result, it was 210 nm to 450 nm.

  The obtained wet fine particles were dried at room temperature, and the glass transition point of the film polymer was measured using a heat-operated calorimeter (differential operation calorimeter, DSC) DSC200 (manufactured by Seiko Electronics Co., Ltd.). Met.

  Next, 170 g of corn oil containing 10 g of the obtained wet fine particles and 0.1 mass% of TBHQ (t-butylhydroquinone) as an antioxidant (200 parts by mass of commercially available corn oil, 20 parts by mass of activated carbon). The mixture was stirred for 1 hour and then filtered and used) and mixed by irradiation with ultrasonic waves. This mixed liquid was transferred to a rotary evaporator, and maintained at a temperature of 120 ° C. for 5 hours while reducing the pressure to 30 mmHg or less, thereby distilling off water contained in the system. Subsequently, it moved to the stainless steel beaker and irradiated with the ultrasonic wave for 10 minutes, and produced liquid developer MCPC1 of this invention.

(Preparation of Comparative Cyan Liquid Developer)
In addition to 100 g of the above-mentioned activated carbon-treated corn oil containing 0.1% by mass of the above-mentioned antioxidant TBHQ (t-butylhydroquinone) 6 parts of phthalocyanine pigment (CI Pigment Blue 15: 3) A cyan toner liquid developer (Comparative Example C1) of Comparative Example was prepared by dispersing and mixing with sonic waves.

  Using the prepared liquid developer of the present invention and the comparative developer, the toner charge was evaluated by electrophoresis as described in Example 1, and the zeta potential of the liquid developer was measured. The results are also shown in Table 2.

  According to the results, the liquid developer MCPC1 of the present invention clearly showed positive chargeability, and the zeta potential was found to be 110 mV, but Comparative Example C1 had a liquid electrostatic developer on the positive and negative electrodes. The zeta potential was 11 mV.

(Example 5)
(Production of microencapsulated pigment MCPY1 and production of liquid developer)
After adding 2.8 g of methacryloyloxyethyltrimethylammonium chloride as a cationic polymerizable surfactant to an aqueous dispersion in which 150 g of yellow pigment particles Y1 having sulfonic acid groups on the surface are dispersed in 800 g of ion-exchanged water, and mixing. Ultrasonic waves were irradiated for 15 minutes. Next, 12 g of isobornyl methacrylate, 0.05 g of 1,6-hexanediol dimethacrylate and 8 g of dodecyl methacrylate were added and mixed by stirring. Further, 2.9 g of methacryloyloxyethyltrimethylammonium chloride was added, and ultrasonic waves were again applied for 30 minutes. Irradiated.

  The obtained dispersion was charged into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a temperature controller, a nitrogen introduction tube and an ultrasonic generator. After raising the internal temperature of the reaction vessel to 80 ° C., an aqueous solution in which 0.6 g of 2,2′-azobis (2-methylpropionamidine) dihydrochloride as a polymerization initiator was dissolved in 20 g of ion exchange water was added dropwise, Polymerization was carried out at 80 ° C. for 6 hours while introducing nitrogen. After completion of the polymerization, the pH was adjusted to around 6 with disodium citrate, and microfiltration was performed to obtain wet fine particles of the microencapsulated pigment MCPY1.

  The obtained wet fine particles were measured for volume average particle size distribution using a laser Doppler type particle size distribution analyzer, Microtrac UPA150, manufactured by Leeds & Northrop Co., and found to be 350 nm to 680 nm.

  The obtained wet fine particles were dried at room temperature, and the glass transition point of the film polymer was measured at 2 ° C. using a thermal operation calorimeter (differential operation calorimeter, DSC) DSC200 (manufactured by Seiko Electronics Co., Ltd.). Met.

  Next, 170 g of linseed oil containing 0.1 mass% of TBHQ (t-butylhydroquinone) as an antioxidant was added to 10 g of the obtained wet fine particles (20 mass parts of activated carbon was added to 200 mass parts of commercially available corn oil). The mixture was stirred for 1 hour and then used after filtration) and mixed by irradiation with ultrasonic waves. This mixed liquid was transferred to a rotary evaporator, and water contained in the system was distilled off at a temperature of 120 ° C. for 5 hours while reducing the pressure to 30 mmHg or less. Subsequently, it moved to the stainless steel beaker and irradiated with the ultrasonic wave for 10 minutes, and produced liquid developer MCPY1.

(Preparation of a yellow liquid developer of a comparative example)
Ultrasonic waves were added to 100 g of the above-mentioned activated carbon-treated flaxseed oil containing 6 parts of isoindolinone pigment (CI Pigment Yellow 110) containing 0.1% by mass of an antioxidant TBHQ (t-butylhydroquinone). Were dispersed and mixed to prepare a yellow toner liquid developer of comparative example (Comparative Example Y1).

  Using the prepared liquid developer of the present invention and a comparative developer, the toner charge was evaluated by electrophoresis as described in Example 1, and the zeta potential of the liquid developer was measured. The results are also shown in Table 2.

  According to the results, the liquid developer MCPY1 of the present invention clearly showed positive chargeability, and the zeta potential was determined to be 95 mV. The toner of the liquid developer of the comparative example was −1 mV, and the toner migrated to the positive and negative electrodes.

(Example 6)
(Production of microencapsulated pigment MCPBk2 and production of liquid developer)
0.81 g of dimethylaminoethyl methyl chloride methacrylate as a cationic polymerizable surfactant was added to and mixed with an aqueous dispersion in which 20 g of black pigment particles Bk2 having carboxylic acid groups on the surface thereof were dispersed in 80 g of ion-exchanged water. Then, ultrasonic waves were irradiated for 15 minutes. Next, 2.45 g of isobornyl methacrylate and 2.55 g of lauryl methacrylate were added and mixed with stirring, 1.0 g of dimethylaminoethylmethyl chloride methacrylate was further added, and ultrasonic waves were irradiated again for 30 minutes.

  The obtained dispersion was charged into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a temperature controller, a nitrogen introduction tube and an ultrasonic generator. After raising the internal temperature of the reaction vessel to 80 ° C., an aqueous solution in which 0.3 g of 2,2′-azobis (2-methylpropionamidine) dihydrochloride as a polymerization initiator was dissolved in 20 g of ion-exchanged water was dropped. Polymerization was carried out at 80 ° C. for 6 hours while introducing nitrogen. After the completion of the polymerization reaction, the pH was adjusted to around 6 with disodium citrate and microfiltration was performed to obtain wet microparticles of microencapsulated pigment MCPBk2.

  The obtained wet fine particles were measured for a volume average particle size distribution using a laser Doppler type particle size distribution analyzer Microtrac UPA150 manufactured by Leeds & Northrop Co. As a result, it was 100 nm to 870 nm.

  The obtained wet fine particles were dried at room temperature, and the glass transition point of the film polymer was measured using a thermal operation calorimeter (differential operation calorimeter, DSC) DSC200 (manufactured by Seiko Electronics Co., Ltd.). Met.

  Next, 10 g of the obtained wet fine particles were added with 170 g of soybean oil containing 0.1 mass% of TBHQ (t-butylhydroquinone) as an antioxidant (200 parts by mass of commercially available soybean oil and 20 parts by mass of activated carbon). The mixture was stirred for 1 hour and then filtered and used) and mixed by irradiation with ultrasonic waves. This mixed liquid was transferred to a rotary evaporator, and water contained in the system was distilled off at a temperature of 120 ° C. for 5 hours while reducing the pressure to 30 mmHg or less. Subsequently, it moved to the stainless steel beaker and irradiated with the ultrasonic wave for 10 minutes, and produced liquid developer MCPY1.

(Preparation of black liquid developer of comparative example)
6 parts of carbon black (manufactured by Mitsubishi Chemical Corporation, MA-7) is added to 100 g of the activated carbon-treated soybean oil containing 0.1% by mass of antioxidant TBHQ (t-butylhydroquinone), and ultrasonic waves are added. Irradiated and dispersed and mixed to prepare a black toner liquid developer of comparative example (Comparative Example Bk2).

  Using the prepared liquid developer of the present invention and a comparative developer, the toner charge was evaluated by electrophoresis as described in Example 1, and the zeta potential of the liquid developer was measured. The results are also shown in Table 2.

  According to the results, the liquid developer MCPY1 of the present invention clearly showed positive chargeability, but the comparative example Bk2 rather showed negative chargeability. Further, when the zeta potential was determined, the toner of the liquid electrostatic developer of the present invention showed 90 mV, but the comparative example Bk2 showed negative chargeability of -16 mV.

(Example 7)
Development, transfer, cleaning, and fixing were performed using a liquid development type image forming apparatus shown in FIG. The liquid developing type image forming apparatus will be described. A single layer type positively charged organic photosensitive member is used as the photosensitive member 1, and the developing roller 2 is made of an elastic member. First, the surface of the photoreceptor 1 is charged to +650 V by the scorotron 3 and a laser beam 4 controlled by an image signal is irradiated to form a latent image. Next, development is performed by applying a developing bias of +600 V to the elastic developing roller 2. The developing roller 2 is supplied with a liquid developer whose layer thickness is regulated by the regulating blade 6 while the anilox roller 5 rotates in contact with the developing roller 2 in the same direction. The anilox roller 5 is supplied with a liquid developer from a supply roller 7 which is a sponge-like elastic roller. The transfer bias is −950 V, and the transfer paper 8 is supplied in the left direction as indicated by the arrow while synchronizing the transfer timing by a pair of rollers from the lower right direction of the photosensitive member. The transfer roller 9 is composed of an elastic roller, and the above-described transfer bias is applied through a control system.

  The transferred paper passes between the heat fixing rollers 10 made of an oil repellent material and is fixed. The fixing temperature was set to 90 ° C. Fixing is performed to such an extent that the toner image developed and transferred from the transfer paper does not transfer to another contact object (transfer paper, finger, device peripheral member, etc.) from the transfer paper at this temperature. The fixing temperature can be set to be optimum depending on the viscosity, and the process speed of the image forming jig is set to 200 mm / second.

  When the transfer residual toner is generated, the illustrated cleaning elastic roller 11 is in contact with the photosensitive member, and is scraped off by the cleaning blade 12 positioned on the upper side while moving the liquid developer slightly adhering from the photosensitive member. . The cleaned photoreceptor 1 can form a monochromatic image while repeating the cycle of charging, exposure, development, transfer and cleaning again. Using the liquid developers of Examples 1 to 6 and Comparative Examples, 5% originals and solid images were printed out.

The evaluation of the fixability is performed by applying a mending tape (12 mm width) manufactured by Sumitomo 3M Co., Ltd. on the printed matter formed on the transfer paper (J paper manufactured by Fuji Xerox Office Supply Co., Ltd.) The density of the printed matter remaining on the transfer paper was expressed as a percentage of the initial density, and the results are shown together with the solid initial image density in Table 3. Note that the fog toner on the photoconductor has a transfer bias of −950 V, so in principle. When the image was not transferred onto the transfer paper but moved as a stain in some cases, it was evaluated as print image quality.
The reflection density of the printed matter was measured using a reflection densitometer (manufactured by X-Rite).

  According to the results, the liquid developer of the present invention has a high density in the image area, and no adhesion of toner to the non-image-copying area is seen, giving good print quality. In addition, these liquid developers were allowed to stand for one week and the dispersion stability was observed, and then the printed images were reproduced by placing them in the developing section of the image forming jig. However, the liquid developer of the present invention also showed sedimentation. The print quality was unchanged from the initial state. The liquid developer of the comparative example was severely settled, and the reproduction print quality was deteriorated from the initial stage, making it difficult to interpret 5% original characters.

  In addition, in preparation of the liquid electrostatic developer MCPM1 in Example 2, 170 g of cottonseed oil (20 parts by weight of activated carbon is added to 200 parts by weight of commercially available cottonseed oil and filtered after stirring for 1 hour) is used as a carrier liquid. In the same manner, the liquid developer of the present invention was prepared, and printing was performed in the same manner with the image forming apparatus of the liquid development system shown in FIG. Similarly, in Comparative Example M1, only the carrier liquid was replaced with cottonseed oil, printing was performed in the same manner, and a comparative evaluation was performed based on the presence or absence of microencapsulation. The fixability was 90% with the liquid electrostatic developer of the present invention and 48% in the comparative example. In addition, toner adhesion to the non-image area was not observed in the present invention, but toner was adhered in the comparative example.

  The liquid electrostatic developer of the present invention is useful as a liquid electrostatic developer used in an electrophotographic image forming apparatus used for a copying machine, a printer or the like.

FIG. 1 is a diagram for explaining an electrophoresis experimental apparatus for measuring the charging behavior of a liquid electrostatic developer. FIG. 2 is a diagram for explaining a liquid developing type image forming apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 21 ... Photoconductor, 22 ... Developing roller, 23 ... Scorotron, 24 ... Laser light controlled by image signal, 25 ... Anilox roller, 26 ... Restricting blade, 27 ... Supply roller, 28 ... transfer paper, 29 ... transfer roller, 30 ... thermal fixing roller, 31 ... cleaning elastic roller, 32 ... cleaning blade

Claims (16)

In a liquid developer in which microencapsulated pigment particles are dispersed in a low dielectric carrier liquid, the microencapsulated pigment particles include pigment particles having an anionic group on the surface, a cationic group and a hydrophobic group in one molecule. A liquid electrostatic developer, which is microencapsulated with an encapsulating resin containing a polymerizable surfactant having a radical polymerizable group as a repeating structural unit, and exhibits self-positive charge. Cationic polymerizable surfactant
General formula R _{[4- (l + m + n)]} R ¹ _l R ² _m R ³ _n N ⁺ · X ⁻
Wherein R is a radical polymerizable group, R ¹ , R ² and R ³ are selected from hydrogen, alkyl group, aryl group, aralkyl group and alkylaryl group, at least one of which is a hydrophobic group , X is Cl, Br or I, l, m and n are 1 or 0 and are not 0 at the same time.)
The liquid electrostatic developer according to claim 1, wherein the liquid electrostatic developer is represented by the formula: The encapsulating resin contains at least one monomer selected from a hydrophobic monomer, a crosslinkable monomer, a monomer represented by the following general formula (1), or a hydrophilic monomer as a copolymerization component. The liquid electrostatic developer according to claim 1.

(In the formula, R ¹ is a hydrogen atom or a methyl group, R ² is a bulky group, and represents a t-butyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or a heterocyclic group, and m is 0. -3, n represents an integer of 0 or 1.) 2. The liquid electrostatic developer according to claim 1, wherein the pigment particles having an anionic group on the surface are derived from an inorganic pigment or an organic pigment. The anionic group on the surface of the pigment particle is a sulfonic acid group (—SO ₃ H) or a sulfinic acid group (—RSO ₂ H).
(In the formula, R represents an optionally substituted alkyl group having 1 to 12 carbon atoms or a phenyl group.)
The liquid electrostatic developer according to claim 1, wherein the liquid electrostatic developer is at least one selected from the group consisting of carboxylic acid groups (—COOH). Sulfonic acid group (—SO ₃ H), sulfinic acid group (—RSO ₂ H)
(In the formula, R represents an optionally substituted alkyl group having 1 to 12 carbon atoms or a phenyl group.)
The liquid electrostatic developer according to claim 5, wherein an introduction amount of at least one selected from is from 0.01 mmol / g to 0.15 mmol / g. 6. The liquid electrostatic development according to claim 5, wherein the anionic group on the surface of the pigment particle is a carboxylic acid group (—COOH), and the active hydrogen content is 1.0 mmol / g to 6.0 mmol / g. Agent. 2. The liquid according to claim 1, wherein the microencapsulated pigment particles are microencapsulated by 40 to 900 parts by mass of an encapsulating resin with respect to 100 parts by mass of the pigment particles having an anionic group on the surface. Electrodeveloper. The liquid electrostatic developer according to claim 1, wherein the encapsulating resin has a glass transition point (Tg) of -20 ° C to 90 ° C. The liquid electrostatic developer according to claim 1, wherein the volume average particle diameter of the microencapsulated pigment particles is 0.2 μm to 1 μm. The low dielectric carrier liquid comprises a vegetable oil containing an unsaturated group or an unsaturated fatty acid ester, and has a volume resistance of 10 ⁹ Ω · cm or more and a dielectric constant of 3.6 or less. The liquid electrostatic developer described. Vegetable oil selected from safflower oil, sunflower oil, soybean oil, corn oil, cottonseed oil, or linseed oil containing at least 50% linolenic acid component in a low dielectric carrier liquid containing at least 50% linoleic acid component The liquid electrostatic developer according to claim 11, wherein 2. The liquid electrostatic developer according to claim 1, wherein the microencapsulated pigment particles are contained in an amount of 2% by mass to 50% by mass. After dispersing pigment particles having an anionic group on the surface in an aqueous dispersion medium, a cationic polymerizable surfactant is added, heated under dispersion treatment, a polymerization initiator is added, and emulsion polymerization is performed to form microcapsules. Forming the pigmented pigment particles,
A method for producing a liquid electrostatic developer, comprising filtering out microencapsulated pigment particles from an aqueous medium in the step and then dispersing the particles in a low dielectric carrier liquid. A step of dispersing a pigment particle having an anionic group on the surface thereof in an aqueous dispersion medium, and then adding a cationic polymerizable surfactant, followed by a dispersion treatment;
A step of adding and dispersing a hydrophobic monomer, a crosslinkable monomer, at least one monomer selected from monomers represented by the following general formula (1),
A step of adding a cationic polymerizable surfactant and sequentially carrying out each step of the dispersion treatment, followed by heating and adding a polymerization initiator and emulsion polymerization to form microencapsulated pigment particles;
A method for producing a liquid electrostatic developer, comprising filtering out microencapsulated pigment particles from an aqueous medium in the step and then dispersing the particles in a low dielectric carrier liquid.

(In the formula, R ¹ is a hydrogen atom or a methyl group, R ² is a bulky group, and represents a t-butyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or a heterocyclic group, and m is 0. -3, n represents an integer of 0 or 1.) A step of dispersing a pigment particle having an anionic group on the surface thereof in an aqueous dispersion medium, and then adding a cationic polymerizable surfactant, followed by a dispersion treatment;
A step of adding and dispersing a hydrophobic monomer, a crosslinkable monomer, at least one monomer selected from monomers represented by the following general formula (1),
Add the hydrophilic monomer together with the cationic polymerizable surfactant and perform each step of the dispersion process in sequence, then heat and add the polymerization initiator, and emulsion polymerization to form microencapsulated pigment particles The process of
A method for producing a liquid electrostatic developer, comprising filtering out microencapsulated pigment particles from an aqueous medium in the step and then dispersing the particles in a low dielectric carrier liquid.

(In the formula, R ¹ is a hydrogen atom or a methyl group, R ² is a bulky group, and represents a t-butyl group, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or a heterocyclic group, and m is 0. -3, n represents an integer of 0 or 1.)

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