JP5079598B2 - Toner for electrostatic charge development and method for producing the same - Google Patents

Description

  The present invention relates to a toner for developing an electrostatic charge used in an image forming apparatus such as an electrophotographic method, an electrostatic recording method, and an electrostatic printing method, and a manufacturing method thereof, and more specifically, has excellent chargeability and dispersibility. The present invention relates to an electrostatic charge developing toner characterized by a modification method for improving dispersion stability and a method for producing the same, and more particularly to a liquid developing toner capable of giving a high resolution image.

In electrophotography, the surface of the photoreceptor is uniformly charged (charging process), an electrostatic latent image is formed on the surface of the photoreceptor by exposure (exposure process), and the formed electrostatic latent image is colored resin. Developing with toner composed of particles (development process), transferring the toner image to a recording medium such as paper or an OHP sheet (transfer process), fixing the transferred toner to the recording medium (fixing process), and printing How to get.
The electrostatic charge developing toner includes a dry developing toner in which toner particles composed of a material containing a colorant such as a pigment and a binder resin are used in a dry state, and a liquid developing toner in which the toner particles are dispersed in an electrically insulating liquid. It is roughly divided into

In recent years, there is an increasing need for colorization of image forming apparatuses such as copiers, facsimiles, and printers using electrophotography. In color printing, for example, image printing with high resolution and high image quality such as a photograph that requires reproduction of a clear color tone is performed. Therefore, a color toner that can meet these requirements is demanded.
Since the toner for dry development deals with toner in a solid state, it currently occupies the mainstream of toner for electrostatic charge development because of the advantage in handling. In order to obtain a high-resolution and high-quality image, first, an appropriate charging property and an environment such as temperature and humidity for attaching an amount of toner according to the charge density of the electrostatic latent image formed on the photoreceptor. From the standpoint of preventing image deterioration due to changes, there is a problem with the environmental stability of the chargeability, and the toner for dry development tends to agglomerate the toner particles during storage and the like, and there is a problem with the uniformity when the toner particles are dispersed. It was. In addition, these characteristics become more prominent when the toner particle diameter is relatively small with the aim of high resolution and due to the powder as described above.

  On the other hand, since the liquid developing toner uses an electrically insulating liquid as a medium, the problem of agglomeration of toner particles in the liquid developing toner during storage is less likely to occur compared to the dry developing toner, and a fine toner is used. Can be used. As a result, the toner for liquid development has better reproducibility of fine line images, better gradation reproducibility, better color reproducibility than dry development toner, and also as a high-speed image forming method. It has the feature of being excellent. Development of a high-quality, high-speed digital printing apparatus using electrophotographic technology using a liquid developing toner, which takes advantage of these excellent features, is becoming popular. Under such circumstances, development of a liquid developing toner having better characteristics is demanded.

  As a method for producing such a toner for liquid development, a wet pulverization method for producing a toner for liquid development by pulverizing a material containing a colorant and a resin in an electrically insulating liquid (for example, Patent Document 1: Japanese Patent Application Laid-Open No. Hei 11 (1994)). 8-36277) or a polymerization method in which a monomer component is polymerized in an electrically insulating liquid to form resin particles insoluble in the insulating liquid (for example, Patent Document 2: Japanese Patent Publication No. 8-7470). Publication) A method for producing a toner for liquid development using a difference in solubility by dissolving or dispersing a resin, a colorant, and other materials in a solvent (for example, Patent Document 3: No. 3712434). ) Etc. are known.

However, the conventional method for producing a toner for liquid development has the following problems.
That is, it is difficult to pulverize the toner particles to a sufficiently small size by the wet pulverization method. To make the toner particles sufficiently small, a very large pulverization energy is required for a very long time. In short, the productivity of the liquid developer was extremely low. Further, in the method as described above, the particle size distribution of the toner particles tends to be widened. As a result, variations in characteristics (for example, charging characteristics) among the toner particles tend to increase.
In the polymerization method, toner particles having a desired size and the particle size distribution of the toner particles can be made relatively narrow. However, conventional polymerization methods cannot remove impurities such as dispersants and unreacted substances. As a result, the toner quality tends to be low in stability and reliability.
Further, in the conventional method as described above, it has been difficult to obtain a liquid developing toner having sufficiently high dispersibility of toner particles. When the dispersibility of the toner particles is poor, there is a problem that when left for a long time, the toner particles settle, and the toner particles aggregate. In addition, once the particles settle and agglomerate or the like in this manner, even if they are stirred again to disperse (redispersibility), it becomes difficult to disperse, and the toner particles are uniformly distributed during image formation. There was a problem that it could not be supplied.

In Patent Document 4 (Japanese Patent Laid-Open No. 2004-93706), toner particles, mercapto-modified silicone oil, amino-modified silane coupling agent, and organic are contained in an electrically insulating liquid for the purpose of improving the dispersibility of toner particles. A liquid developer obtained by adding an aluminum compound has been proposed. However, in such a method, the mercapto-modified silicone oil and the amino-modified silane coupling agent partially react with the hydrolysis group and amino group, which are impurities on the toner particle surface, but most of the toner particle surface is absorbed by adsorption. In the method of improving dispersibility by coating, it is necessary to add a large amount of mercapto-modified silicone oil and amino-modified silane coupling agent, and further an organoaluminum compound is added. These additives cause the problem that the chargeability of the liquid developer becomes extremely unstable and causes background staining, fogging, and the like.
As described above, when using the toner for liquid development, uniformity of characteristics (for example, particle size, charging characteristics, etc.) among the respective chargeable particles, and dispersibility of the chargeable particles in the electrically insulating liquid・ Redispersibility, these improvements are strongly desired.

In recent years, since it is possible to perform image formation by reducing the amount of discharge products such as ozone, development of a method for forming an image using a positively charged liquid developer has been promoted (for example, (Patent Document 5: JP-A-10-319646). In the positively chargeable toner for liquid development described in this patent publication, the chargeable particles are made positively charged by adding a charge control agent. By the way, as the resin material constituting the conventional toner particles, negatively chargeable ones are generally widely used from the viewpoint of fixability and charging characteristics. In this way, it is conceivable to add a charge control material to the toner particles using the negatively chargeable resin material so as to be positively charged, but it is difficult to obtain a sufficient charge amount. Although it is conceivable to use a positively chargeable resin material as a constituent material of toner particles, a positively chargeable resin material has low stability of the resin itself and is difficult to apply as a material constituting toner particles. Met.
JP-A-9-3354 of Patent Document 6 discloses a polymer having a carboxyl group-containing carbon black and an epoxy group, anisidyl group, or thioepoxy group that is reactive with a polysiloxane structure portion and a carboxyl group. Although a colorant composition containing a colorant formed by grafting is described, this is characterized by the grafting of carbon black itself, and colored particles comprising a resin and a colorant are modified with epoxy-modified silicone. Is basically different from

JP-A-8-36277 Japanese Patent Publication No.8-7470 Japanese Patent No. 3712434 JP 2004-93706 A JP 10-319646 A JP-A-9-3354

The present invention has been made in view of the above circumstances, and provides an electrostatic charge developing toner having excellent chargeability and charge stability of colored particles and having good dispersibility and dispersion stability. Further, the present invention provides an electrostatic charge developing toner excellent in redispersibility. In particular, the present invention provides a toner for developing an electrostatic charge having positive chargeability.

The object is (1) “ a liquid developer containing toner particles in an electrically insulating liquid, wherein the toner particles contain at least a binder resin and a colorant and have an acidic group on the surface. A liquid developer obtained by chemically modifying colored particles using epoxy-modified silicone and having a relative standard deviation (CV value) of particle size distribution of 30% or less ",
(2) “The liquid developer according to item (1), wherein the acidic group is a carboxyl group or a sulfonic acid group”;
(3) “The liquid developer according to (1) or (2) above, wherein the average particle diameter of the colored particles is 0.3 to 5 μm”,
(4) “A method for producing a liquid developer containing toner particles in an electrically insulating liquid, comprising at least a binder resin and a colorant, and a relative standard deviation (CV value) of particle size distribution of 30% or less The surface of the colored particles is chemically modified with the epoxy-modified silicone under ultrasonic dispersion in an electrically insulating liquid containing at least colored particles having acidic groups on the surface and epoxy-modified silicone. A method for producing a liquid developer ",
(5) “The method for producing a liquid developer according to ( 4 ) above, wherein the electrically insulating liquid is a silicone oil having a kinematic viscosity at 25 ° C. in the range of ² to 100 mm ² / s”. ,
(6) “The colored particles having an acidic group on the surface thereof are produced by a polymerization method,” which is achieved by the method for producing a liquid developer described in ( 4 ) or ( 5 ) above. .

According to the present invention, an electrostatic charge developing toner (dry toner and dry toner and toner containing toner particles obtained by chemically modifying an epoxy-modified silicone with colored particles having at least a binder resin and a colorant and having acidic groups on the surface thereof. Liquid toner). In this toner, colored particles in which silicone groups are directly bonded and coated are formed on the surface of the toner particles for electrostatic charge development. A small amount of epoxy-modified silicone is used to minimize the influence on charging characteristics and the like. By suppressing it to a low level, the electrostatic properties are excellent, and the dispersibility between the colored particles is greatly improved.
Further, according to the production method of the present invention, in the electrically insulating liquid having an acidic group on the surface and the epoxy group-modified colored particles, the colored particles having an acidic group on the surface are dispersed under ultrasonic dispersion. By carrying out the reaction treatment, it is possible to produce toner particles for electrostatic charge development that are very simply and uniformly coated with a silicone group directly bonded to and coated with colored particles. In the case of producing a toner for liquid development, it can be used as it is in the above-mentioned electrically insulating liquid. Further, when the electrically insulating liquid is silicone oil, the dispersibility of the liquid developing toner is dramatically improved.
Furthermore, the toner particles for electrostatic development of the present invention can be obtained by separating and drying the toner particles by distilling off or filtering the organic solvent after the main treatment, and then drying the toner particles.

  As will be apparent from the following detailed and specific description, according to the present invention, a toner in which colored particles containing at least a binder resin and a colorant and having acidic groups on the surface are chemically modified using epoxy-modified silicone. An electrostatic charge developing toner containing particles is provided. The electrostatic charge developing toner has excellent electrostatic characteristics such as charging characteristics, and greatly improves dispersibility among colored particles, dispersion stability and redispersibility. Therefore, it is excellent in durability and has a stable function. In addition, the electrostatic charge developing toner particles can be produced by an ultrasonic dispersion treatment in an electrically insulating liquid by a simple method with a very wide application range.

Hereinafter, preferred embodiments of the electrostatic charge developing toner of the present invention and the production method thereof will be described in detail.
The manufacturing method of the colored particle which has an acidic group on the surface of this invention is demonstrated.
First, a method for introducing an acidic group on the surface of the colored particles will be described. As a method for introducing the acidic group, a conventionally known method can be appropriately used. For example, a method of granulating using a difference in solubility with respect to a resin having an acidic group, specifically, a method of dissolving a resin having an acidic group in a solvent and dropping the resin having an acidic group into a poor solvent In particular, a method in which a resin having an acidic group is dissolved in a solvent and granulated in an aqueous continuous phase is preferable in that an acidic group that is a polar group is specifically formed on the particle surface. In this case, an auxiliary such as a dispersion stabilizer may be added to the aqueous continuous phase as necessary (coacervation method). In addition to the colorant, various additives such as a dispersant, a heat stabilizer, an antioxidant, and an ultraviolet absorber are uniformly dissolved and dispersed in the resin or the resin-containing dispersion as necessary. You may do it.

  Examples of the resins include synthetic resins such as acrylic resins, styrene resins, epoxy resins, urethane resins, vinyl resins, phenol resins, polyester resins, polyamide resins, and melamine resins, and natural resins such as gelatin, casein, and cellulose starch. Any of these resins may be used as long as the resin has a carboxyl group, a sulfonic acid group, a phenolic hydroxyl group, a methylol group, or a salt thereof as an active hydrogen group-containing acidic group. it can. Further, these resins may have a crosslinked structure formed according to the purpose of use.

  Furthermore, there is a polymerization method as a method for introducing acidic groups to the surface of the particles. In the polymerization method, various additions such as a polymerization initiator and, if necessary, a colorant and a crosslinking agent are added to a polymerizable monomer or a polymerization precursor (such as an oligomer) or a dispersion medium obtained by dispersing these. Fine particles having a desired particle diameter can be obtained by adjusting a polymerizable composition uniformly dissolved or dispersed together with the agent and polymerizing at a high temperature. Moreover, you may add various additives, such as a chain transfer agent, a wax, and a charge control agent, as needed. The polymerization method is suitably used for applications that require more uniformity, because particles having a narrow particle size distribution can be obtained as compared with the coacervation method.

Since the particle size distribution of the particles is reflected in the particle size distribution of the toner particles for electrostatic charge development of the present invention to be produced, those having high monodispersibility are preferable, and the relative standard deviation (CV value) is 30%. The following is preferable. When the relative standard deviation (CV value) exceeds 30%, the particle size distribution of the electrostatic charge developing toner particles produced from the above particles widens, and the properties of the particles resulting from the non-uniformity of the particle size are significantly impaired. Differences in electrostatic characteristics such as chargeability arise and become a problem.
The relative standard deviation (CV value) is calculated by the following mathematical formula (1).

（式中、ｓｄは粒子径の標準偏差を、ｍは平均径である。）
なお、上記ｓｄ、及びｍは、粒径アナライザー（ＦＰＡＲ−１０００:大塚電子社製）による動的光散乱法により得られる数値である。

(In the formula, sd is the standard deviation of the particle diameter, and m is the average diameter.)
The above sd and m are numerical values obtained by a dynamic light scattering method using a particle size analyzer (FPAR-1000: manufactured by Otsuka Electronics Co., Ltd.).

The method for producing the colored particles having an acidic group may be any one obtained by any production method, for example, by precipitation in an aqueous medium in the presence of colored particles obtained by a pulverization method or a dispersion stabilizer. Colored particles obtained by a wet method such as a polymerization method or a polymerization method can be used, and among them, a polymerization method in which the uniformity of the obtained particles is most excellent is preferable.
The polymerization method for obtaining the colored particles having an acidic group can be appropriately used in dispersion polymerization, suspension, or emulsion polymerization. However, as a method for producing colored particles having an acidic group on the surface, polymerization in an aqueous medium is preferable. As a method for producing colored particles having an average particle diameter of 0.3 to 5 μm, dispersion polymerization in an aqueous medium is more preferable.

The aqueous medium means an aqueous solution of a hydrophilic organic solvent. The hydrophilic organic solvent means an organic solvent having a solubility in water at 20 ° C. of 2% or more. Examples of hydrophilic organic solvents include methyl alcohol, ethyl alcohol, modified ethyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, sec-butyl alcohol, tert-amyl alcohol, 3-pentanol, and benzyl alcohol. , Cyclohexanol, ethylene glycol, glycerin, diethylene glycol and other alcohols, methyl cellosolve, ethyl cellosolve, isopropyl cellosolve, butyl cellosolve, ether alcohols such as diethylene glycol monomethyl ether and diethylene glycol monoethyl ether, ethers such as tetrahydrofuran, ethylene glycol dimethyl ether and dioxane Atoms, nitrogen atoms such as pyridine, dimethylformamide Including chromatic organic solvents. These organic solvents can be used singly or as a mixture of two or more. Of these, lower alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol are more preferable. With the mixed solvent of these hydrophilic organic solvent and water, the particle size and particle size distribution can be controlled while maintaining the polymerization stability. The mixing ratio of the hydrophilic organic solvent and water when adjusting the aqueous medium is preferably a weight ratio of 99: 1 to 5:95. When the ratio of the hydrophilic organic solvent exceeds 99, coalescence of the produced polymer may occur, and when it is less than 5, the dispersion stability is lowered and the particle size and particle size distribution may not be controlled. Further, organic solvents other than the above-mentioned hydrophilic organic solvent positions can be used in combination as long as the produced polymer is not dissolved in order to control the particle size, particle size distribution, and dispersion stability. As these organic solvents to be used in combination, hydrocarbons such as hexane, octane, decane, hexadecane, cyclohexane, petroleum ether, toluene, xylene, halogenated hydrocarbons such as carbon tetrachloride, trichloroethylene, tetrabromoethane, acetone, methyl ethyl ketone, Examples thereof include ketones such as methyl isobutyl ketone and cyclohexanone, and esters such as ethyl acetate and butyl acetate. Further, the polymerization may be carried out in the presence of inorganic ions such as SO ₄ ²⁻ , PO ₄ ³⁻ , Cl ⁻ , Na ⁺ , K ⁺ , Mg ²⁺ , Ca ²⁺ , or the pH of the aqueous medium. You can go.

Next, in detail when adopting the dispersion polymerization method in an aqueous medium, a predetermined polymerizable monomer, a colorant, and a polymerization initiator are sequentially added to and dispersed in the aqueous medium, and the polymerization is advanced by heating. A plurality of polymerizable monomers may be added separately, or a plurality of polymerizable monomers may be mixed and added in advance. Further, the polymerizable monomer may be added as it is, or may be added as an emulsion mixed and adjusted in advance with water, a surfactant or the like. The polymerization temperature and the polymerization time can be appropriately set within the range where the polymerization reaction occurs.
First, the radically polymerizable monomer that is an essential component of the polymerization is not particularly limited. For example, styrene derivatives such as styrene, α-methylstyrene, p-methylstyrene, p-chlorostyrene, chloromethylstyrene, vinyl esters such as vinyl chloride, vinyl acetate and vinyl propionate, unsaturated nitriles such as acrylonitrile, Methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, (meth) acrylate-2-ethylhexyl, stearyl (meth) acrylate, ethylene glycol (meth) acrylate, trifluoroethyl (Meth) acrylate, pentafluoropropyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) acrylic acid dimethylaminoethyl, (meth) acrylic acid ester derivatives such as diethylaminoethyl, N, N-dimethyl (Meta Acrylamide, N- dimethylaminoethyl (meth) acrylamide, N- dimethylaminopropyl (meth) acrylamide, (meth) acrylamide derivatives, vinyl pyridine derivatives such as 4-vinylpyridine.
Among these, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, N, N-dimethyl (meth) acrylamide, N-dimethylaminoethyl (meth) acrylamide, N-dimethylaminopropyl (meth) ) Monomers having amino groups, such as acrylamide and 4-vinylpyridine, and salts thereof are important as monomers having charge control ability in the production of toner for developing electrostatic charge having positive chargeability. . In addition, the charge control method using the monomer has less influence on the electric resistance of the electrostatic charge developing toner than the charge control method using the charge control agent described later, and is superior in terms of charging stability. Is the method.

Examples of the acidic group that is an essential component applied to the production of the desired particles include a carboxyl group, a phosphoric acid group, a sulfonic acid group, an aromatic hydroxy group, and a methylol group (an acidic group that does not contain an active hydrogen group, for example, A group such as a nitro group, a nitroso group, or an acid anhydride group does not correspond to the “acid group” in the present invention), among which a carboxyl group or a sulfonic acid group is preferable. Examples of these monomers having an acidic group include styrene derivatives such as 4-vinylbenzoic acid, 3-vinylbenzoic acid and 4-styrenesulfonic acid, (meth) acrylic acid, itaconic acid, itaconic acid monobutyl ester, Maleic acid, maleic acid monomethyl ester, maleic acid monobutyl ester, 2-carboxylethyl (meth) acrylate, succinic acid mono (2-acryloyloxyethyl) ester, 2-acrylamido-2-methylpropanesulfonic acid, 2- (methacryloyl) And (meth) acrylic acid derivatives such as oxy) ethylsulfonic acid.
The amount of the monomer having an acidic group is preferably 1 to 30 parts by weight with respect to 100 parts by weight of the total monomers combined with the monomer.
The acid value of the produced particles is preferably in the range of 7 to 200 (mgKOH / g). When the acid value is 7 or less, the reaction is restricted in the chemical modification with the epoxy-modified silicone in the next step, the function of the silicone group on the toner particle surface is not fully exhibited, and good dispersibility and dispersion stability are obtained. If the acid value is 200 or more, the characteristics are hardly improved and the function of the silicone group on the toner particle surface seems to have reached saturation. Furthermore, when the acid value is within the range of 7 to 200 (mgKOH / g), the dispersion stability at the time of particle preparation is improved, and the amount of the dispersant or the dispersion stabilizer can be reduced (self-dispersing). As a result, particles having high monodispersity can be produced, and further, it is advantageous in terms of operation and environment such as reduction in the number of washings. Therefore, the monomer having an acidic group is more preferably blended so that the acid value is in the range of 7 to 200 (mgKOH / g).
These monomers may be used alone or in combination of two or more. Moreover, you may contain the crosslinkable monomer which contains two or more vinyl groups in a monomer as needed. The crosslinkable monomer containing two or more vinyl groups is not particularly limited. For example, divinylbenzene, divinylbiphenyl, divinylnaphthalene, ethylene glycol di (meth) acrylate, butadiene glycol di (meth) acrylate, polyethylene glycol di (Meth) acrylate etc. are mentioned. The said crosslinkable monomer may be used independently and may use 2 or more types together.
A chain transfer agent can be added to the polymerization composition in order to control the degree of polymerization of the resin and adjust physical properties such as the softening point and molecular weight. As the chain transfer agent, a chain transfer agent generally used in radical polymerization reaction can be used, and is not particularly limited. Examples thereof include mercaptans such as octyl mercaptan, dodecyl mercaptan, tert-dodecyl mercaptan, and styrene dimer.

The radical polymerization initiator used for the production of particles having acidic groups on the surface will be described.
A radical polymerization initiator is not specifically limited, A conventionally well-known thing can be applied.
For example, persulfates such as potassium persulfate and ammonium persulfate, benzoyl peroxide, lauroyl peroxide, oxochloroperoxybenzoic acid, t-butylperoxy-2-ethylhexaniate, di-t-butyl peroxide, etc. Oxide, 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2'- Azobis (2,4-dimethylvaleronitrile), 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], dimethyl 2,2′-azobisisobutyrate, 2,2 'Azobis (2-methylpropionamidine) salt, 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionamidine], 4,4'-azo Scan (4-cyanovaleric acid) azo compounds of the like. Among them, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 2,2′-azobis An azo oil-soluble polymerization initiator such as (2,4-dimethylvaleronitrile) is preferably used. The radical polymerization initiator may be used as a redox initiator combined with a reducing agent as necessary. By using a redox initiator, the polymerization activity is increased, the polymerization temperature is lowered, and the polymerization time can be further shortened. Moreover, it is suitable that the compounding quantity of the said radical polymerization initiator shall be 0.1-10 weight part with respect to 100 weight part of polymerizable monomers.

Next, the additive used for preparation of the particle | grains which have the said acidic group is demonstrated.
When producing fine particles having an acidic group, a surfactant may be added as necessary. The surfactant is not particularly limited, but the following ionic and nonionic surfactants are preferably used.
Examples of the ionic surfactant include sodium dodecylbenzenesulfonate, sodium arylalkylpolyethersulfonate, sodium 3,3-disulfonediphenylurea-4,4-diazobis-amino-8-naphthol-6-sulfonate, Sulfates such as sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium dialkylsulfosuccinate, etc., sodium oleate, sodium laurate, sodium caprate, sodium caproate, potassium stearate, etc. Examples include fatty acid salts.
Nonionic surfactants include polyethylene oxide, polypropylene oxide, a combination of polyethylene oxide and polypropylene oxide, higher fatty acid esters of polyethylene glycol, higher fatty acid esters of polypropylene oxide, alkylphenol polyethylene oxide, alkylphenol polypropylene oxide, polyethylene oxide alkyl. Examples include ether, polypropylene oxide alkyl ether glycol, sorbitan ester and the like.
The blending amount of the surfactant is preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the total monomers.

  Furthermore, you may add a dispersion stabilizer as needed. Examples of the dispersion stabilizer include partially saponified polyvinyl alcohol, poly (meth) acrylic acid, poly (meth) acrylic acid-poly (meth) acrylate ester copolymer, polyvinylpyrrolidone, polyvinyl ether, gelatin, methylcellulose, Polymer dispersion stabilizers such as sodium salt of ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, inorganic dispersion stabilizers such as calcium phosphate, magnesium phosphate, aluminum phosphate, calcium carbonate, magnesium carbonate, barium sulfate, magnesium hydroxide, bentonite It is done. The blending amount of the dispersion stabilizer is preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the total monomers.

  Further, these surfactants or dispersion stabilizers can be used after adjusting the pH if necessary. The pH adjustment is preferably a weakly basic or weakly acidic compound. By these treatments, the surfactant or the dispersion stabilizer can be made into a hydrophilic functional group having a salt structure, and the dispersion or dispersion stability function can be effectively extracted.

  In addition to the above, a colorant is added as an essential component. The colorant fine particle dispersion can be adjusted by dispersing the colorant in an aqueous medium or a solvent-based medium. For the dispersion treatment of the colorant, in the case of water, a surfactant or a dispersion stabilizer can be used, and these may be used alone or mixed in an appropriate composition. In the solvent system, a colorant and a solvent that sufficiently wets are selected, and a surfactant or a dispersion stabilizer is also used if necessary. Examples of the solvent used include methanol, ethanol, isopropanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, and tetrahydrofuran. The disperser used for the colorant dispersion treatment is not particularly limited, but is preferably an ultrasonic disperser, a pressure disperser such as a mechanical homogenizer or a pressure homogenizer, a medium type dispersion such as a sand grinder, a diamond fine mill, or a bead mill. Machine.

Examples of the colorant include various pigments and dyes.
Conventionally known pigments can be used as the organic pigment. Although any pigment can be used, suitable organic pigments include, for example, aniline blue, calcoyl blue, chrome yellow, ultramarine blue, duPont oil red, quinoline yellow, methylene blue chloride, copper phthalocyanine, malachite green oxa Rate, lamp black, rose bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 184, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 17, C.I. I. Solvent Yellow 162, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 185, C.I. I. Pigment blue 15: 1, C.I. I. And CI Pigment Blue 15: 3.
A conventionally well-known pigment can be used as an inorganic pigment. Although any pigment can be used, examples of suitable inorganic pigments include carbon black, titanium oxide, bengara, ferrite, and magnetite.
These colorants can be used alone or in combination as desired.

  In addition, so-called processed colorants in which these colorants are previously coated with a resin can be used. Specifically, a color chip (Taihei Chemical Co., Ltd.) in which a colorant and a resin are kneaded under heating with a two-roll roll or the like. Commercially available processing colorants such as those referred to as Taisei Kako Co., Ltd., and Microlith (manufactured by Ciba Specialty Chemicals Co., Ltd.) can be used. The processing colorant should be obtained by any known method such as a coacervation method in which a colorant is dispersed in a resin solution and a poor solvent is added thereto to precipitate the resin on the colorant surface. Can do.

The amount of the colorant used is preferably such that the content with respect to 100 parts by weight of the resin component in the particles having acidic groups on the surface is 2 to 50 parts by weight, preferably 5 to 30 parts by weight.
The volume average particle diameter of the particles having acidic groups on the surface according to the present invention is preferably resin particles having a uniform particle size distribution of 0.3 to 5 μm. The glass transition point (Tg) of the particles according to the present invention is not particularly limited, but is preferably in the range of −10 to 120 ° C. The molecular weight of the resin particles according to the present invention is not particularly limited, but is preferably 2000 to 1000000 in terms of mass average molecular weight.

Next, the method for producing the particles having an acidic group is not particularly limited, and the production conditions include a colorant to be used, a resin to be used (or a polymerizable monomer), and a dispersant to be used (or dispersion stability). It may be set according to the agent). For example, in the dispersion polymerization in an aqueous medium, the above-mentioned colorant and polymerizable monomer are appropriately added to an aqueous medium to which a dispersant or a dispersion stabilizer is added as necessary, and then a homogenizer, a ball mill, a colloid. Dissolve or disperse uniformly with a disperser such as a mill or an ultrasonic disperser, add a polymerization initiator, and perform a temperature rise and polymerization reaction at an appropriate temperature under a nitrogen stream. The polymerization initiator can be added to the polymerizable monomer or before or after dissolution / dispersion in the aqueous medium.
After completion of the polymerization, after cooling to room temperature, the particles having an acidic group can be produced by filtering, washing, and drying the particles having an acidic group by a known method.

Next, a method for producing an electrostatic charge developing toner will be described.
The toner particles for electrostatic development can be obtained by chemically modifying colored particles having acidic groups on the surface as described above using epoxy-modified silicone. The chemical modification is mainly due to a chemical reaction between the acidic group and the epoxy group on the surface of the colored particles. By directly bonding the silicone group to the surface of the colored particle through the ester group, the silicone oil can be used for the colored particles. The toner particles for electrostatic charge development can achieve good dispersibility and long-term dispersion stability without being coated and causing aggregation, fusion or the like between the toner particles for electrostatic charge development.
Toner particles for electrostatic charge development can be produced by treating colored particles having acidic groups on the surface and epoxy-modified silicone in an organic solvent.
Any organic solvent can be used as long as it can dissolve or partially dissolve epoxy-modified silicone oil without dissolving colored particles having acidic groups. A reaction inert organic solvent can be suitably used.
Further, when producing toner particles for liquid development, an electrically insulating liquid is used among reaction inert organic solvents, and after coloring particles having acidic groups on the surface are treated with epoxy-modified silicone, the toner for liquid development is used. It can also be used as This is considered to be because the reaction between the acidic group and the epoxy group results only in the formation of an ester group and an alcoholic OH group, and has very little influence on the electric resistance of the electrostatic charge developing toner. ing.
This electrical insulating liquid is a high-purity petroleum, silicone oil, or the like as a specific commercial product. For the high-purity petroleum, for example, Isopar G, H, L, M (manufactured by Exxon Chemical) or Norper 12 ( In the silicone oil, for example, SH-200 series (manufactured by Toray Dow Corning), KF-96 series (manufactured by Shin-Etsu Chemical), L-45 series (manufactured by Nihon Unicar) And AK series (manufactured by Asahi Kasei Wacker Silicone). Furthermore, silicone oil can be preferably used in these electrically insulating liquids.

  Furthermore, as an epoxy-modified silicone, for example, it has a molecular structure represented by the following formula (2),

（式中、Ｘはエポキシ基、グリシジル基、エポキシシクロヘキサン基等のエポキシ基、ｌは０又は１、Ｙはメチレン、エチレン、プロピレン、ブチレン等の直鎖、或いは分岐のアルキレン連結基、Ｚは直鎖又は分岐シロキシル基を示す。シロキシル基に対して、置換位置としては、片末端、両末端、側鎖、及び側鎖両末端があり、特に制限されないが、中でも片末端（ｍ＝１）が好ましい。Ｚで示されるシロキシル基の好ましい構造は、ジメチルポリシロキサン骨格を有し、末端置換基に炭素数１〜炭素数６の低級アルキル基を有するものが更に好ましく、ジメチルシロキサンの重合度ｎは、１〜５０，より好ましくは１〜１６である。）

(Wherein X is an epoxy group such as an epoxy group, glycidyl group or epoxycyclohexane group, l is 0 or 1, Y is a linear or branched alkylene linking group such as methylene, ethylene, propylene or butylene, and Z is a straight chain. A chain or a branched siloxyl group, with respect to the siloxyl group, the substitution position includes one end, both ends, side chains, and both ends of the side chain, and is not particularly limited, but in particular one end (m = 1) A preferred structure of the siloxyl group represented by Z is more preferably one having a dimethylpolysiloxane skeleton and a terminal alkyl group having a lower alkyl group having 1 to 6 carbon atoms, and the polymerization degree n of dimethylsiloxane is 1 to 50, more preferably 1 to 16.)

  Preferred specific examples of the epoxy-modified silicone include (3-glycidoxypropyl) bis (trimethylsiloxy) methylsilane [manufactured by Amax Co., Ltd.], (3-glycidoxypropyl) pentamethyldisiloxane [Amax ( Low molecular weight epoxy-modified silicone such as MCR-E11 [manufactured by Amax Co., Ltd.], MCR-E21 [manufactured by Amax Co., Ltd.], X-22-173DX [manufactured by Shin-Etsu Chemical Co. ], FZ-3720 [made by Toray Dow Corning Co., Ltd.], BY16-839 [made by Toray Dow Corning Co., Ltd.], SF8411 [made by Toray Dow Corning Co., Ltd.] be able to.

Next, the electrostatic charge developing toner is basically produced by esterification (reaction) of acidic groups by collision between surface acidic groups in colored particles and epoxy groups in epoxy-modified silicone in an organic solvent. In the early stage of the treatment (reaction), the colored particles having acidic groups on the surface are in an agglomerated state. As the treatment (reaction) progresses, the compatibility with the organic solvent increases. It is thought that it progresses to a primary particle dispersion state. Therefore, this treatment is preferably carried out with stirring, more preferably an ultrasonic disperser, a pressure disperser such as a mechanical homogenizer or a pressure homogenizer, a media type disperser such as a sand grinder, a diamond fine mill, a bead mill, Among these, an ultrasonic disperser having excellent dispersion efficiency can be preferably used. Further, this treatment can be carried out by heating if necessary, and is 80 ° C. from room temperature, preferably 50 ° C. from room temperature.
The epoxy-modified silicone is preferably chemically modified by adding 0.01 to 5 equivalents to the acid value of the colored particles having acidic groups on the surface.
Further, when the electrostatic charge developing toner particles of the present invention are used for dry developing toner, after the treatment, the organic solvent is distilled off or filtered by a conventionally known method to separate and dry the toner particles. By doing so, toner particles for dry development can be obtained.

(Application to liquid developing toner)
When the electrostatic charge developing toner particles of the present invention are applied to a liquid developing toner, the toner particle content is preferably 0.5 to 50% by weight, and 1 to 30% by weight with respect to the liquid developing toner. More preferred. When the content of the electrostatic charge developing toner particles is less than 0.5% by weight, the coloring power is poor and a sufficient image density may not be obtained in a printed image. On the other hand, if it exceeds 50% by weight, the viscosity of the liquid developer becomes high and the transportability and stretchability of the liquid developing toner in the printing apparatus are inferior, so that a good printed image may not be obtained.
The average particle size (weight average particle size) of the toner particles is preferably 0.3 to 5 μm. Toner particles larger than 5 μm not only cause a reduction in image quality, but also tend to settle if left standing, and may cause aggregation of toner particles. On the other hand, when the thickness is 0.3 μm or less, the cohesive force increases and handling becomes difficult.
The binder resin for fixing to the transfer agent is controlled by the composition ratio of the polymerizable monomer at the time of producing colored particles having acidic groups on the surface, and is not particularly limited in terms of glass transition temperature, softening temperature, molecular weight, etc. However, it is preferable to design a resin composition capable of suitably fixing an image on a transfer agent during image formation.

Examples of other components contained in the toner particles include a wax and a charge control agent.
The wax is not particularly limited and may be appropriately selected from known ones. Examples thereof include paraffin wax, polyethylene wax, polypropylene wax, polyester wax, alcohol wax, urethane wax and the like. These waxes may be used alone or in combination of two or more.
The charge control agent is not particularly limited and can be appropriately selected from known ones. For example, fluorine-containing surfactants, salicylic acid metal complexes, metal-containing dyes such as azo compounds, quaternary ammonium salts, nigrosine, etc. And azine dyes. These may be used alone or in combination of two or more.

The magnetic material is not particularly limited and can be appropriately selected from known materials. Examples thereof include metals, alloys, metal compounds, and ferrites. Among these, examples of the metal include iron, cobalt, nickel, and the like. Examples of the alloy include alloys of the above metals. Examples of the metal compound include Fe ₃ O ₄ and γ-Fe ₂ O _3. , Cobalt-added oxides, and the like. Examples of the ferrite include MnZn ferrite and NiZn ferrite. These may be used individually by 1 type and may use 2 or more types together.
Further, a known additive may be further added to the electrostatic charge developing toner of the present invention as required. Examples thereof include a dispersant, a heat stabilizer, an antiseptic, a surface tension adjuster, an antioxidant, a near infrared absorber, an ultraviolet absorber, a fluorescent agent, and a fluorescent brightening agent.

(effect)
When the electrostatic charge developing toner according to the present invention is applied to a liquid developing toner, the stability of basic characteristics related to electrophoresis such as mobility is improved by controlling the charge control function at a polymerizable monomer level. Furthermore, the siloxyl group on the colored particle surface provides excellent dispersibility and redispersibility of the toner particles, good fluidity during transportation, high storage stability, and stable and high-quality images over a long period of time. It has characteristics that can be formed.
The electrostatic charge developing toner according to the present invention can be produced by a very simple method. For this reason, the toner characteristics are stable, and a print image with good quality can be manufactured with high reliability.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.
First, a method and an apparatus used for evaluating the electrostatic charge developing toner are shown below.
<The particle size of the colored particles having acidic groups on the surface, and the relative standard deviation (CV value)>
・ Measurement equipment: Particle size analyzer FPAR-1000 (Otsuka Electronics Co., Ltd.)
Sample: Measured with a 1.0 wt% aqueous solution.
<Zeta potential of toner particles for electrostatic charge development>
Measurement device: Measurement was performed at an electric field strength of 500 V / cm using ELS-8000 (manufactured by Otsuka Electronics Co., Ltd.).

Next, in each of the following [Synthesis Examples], colored particles having an acidic group on the surface are prepared.
[Synthesis Example 1]
As a dispersant, polyacrylic acid (5.0 parts by weight) <manufactured by Wako Pure Chemical Industries, Ltd., MW. 5000>, phthalocyanine blue (CI pigment blue 15: 3) (10 parts by weight), 1N-potassium hydroxide (69.38 parts by weight), and 20.6 parts by weight of ion-exchanged water, A 10% by weight phthalocyanine blue dispersion was obtained.
On the other hand, potassium dihydrogen phosphate (0.082 parts by weight), 1N potassium hydroxide (24.74 parts by weight), ethanol (50 parts by weight), and ion-exchanged water (8.26 parts by weight) were mixed with a homogenizer (IKA). Company: Ultratax T25) under high-speed stirring (8000 rpm), methacrylic acid (2.08 parts by weight) as a monomer having a carboxyl group, methyl methacrylate (19.29 parts by weight) as a polymerizable monomer ), 4-vinylpyridine (5.06 parts by weight), which is a monomer having an amino group, is added, and the 10% by weight phthalocyanine blue dispersion (30 parts by weight) is further added and mixed under high-speed stirring for 10 minutes. To obtain a reaction solution.
Subsequently, the above reaction solution and an oil-soluble polymerization initiator (trade name “V-59, manufactured by Wako Pure Chemical Industries, Ltd.) were added to a 500 ml separable flask equipped with a thermometer and a nitrogen inlet tube prepared in advance. ”= 2,2′-azobis (2-methylbutyronitrile)) (0.51 part by weight) in ethanol (10 parts by weight), and the mixture was further stirred at 68 ° C. under a nitrogen stream. The temperature rose. The reaction is further carried out for 6 hours, and then allowed to cool, acidified with 2N-sulfuric acid (pH = 5), filtered, washed twice with water and dried to have a carboxyl group on the surface. As a result, 23.68 parts by weight of colored particles (A) were obtained.
When the particle size distribution of the particles was measured, the average particle size was 0.6 μm, and the relative standard deviation (CV value) was 24%.

[Synthesis Example 2]
Potassium dihydrogen phosphate (0.082 parts by weight), 1N potassium hydroxide (14.25 parts by weight), ethanol (26 parts by weight), and ion-exchanged water (69.75 parts by weight) were homogenizer (manufactured by IKA). : Methacrylic acid (1.07 parts by weight) as a monomer having a carboxyl group, methyl methacrylate (21.23 parts by weight) as a polymerizable monomer under high-speed stirring (8000 rpm) with Ultratax T25), 2- (Dimethylamino) ethyl methacrylate (3.70 parts by weight), which is a monomer having an amino group, was added, and further, Microlith (Ciba Specialty Chemicals, trade name [Blue4G- WA]) (5.0 parts by weight) was added and mixed with stirring at high speed for 30 minutes to obtain a reaction solution.
Subsequently, a 500 ml separable flask equipped with a thermometer and a nitrogen inlet tube prepared in advance was charged with the reaction solution and an oil-soluble polymerization initiator (trade name “V-65” manufactured by Wako Pure Chemical Industries, Ltd.). ”= 2,2′-azobis (2,4-dimethylvaleronitrile)) (0.62 parts by weight) in ethanol (10 parts by weight), and while stirring in a nitrogen stream, 58 ° C. The temperature was raised to. The reaction is further carried out for 6 hours, and then allowed to cool, acidified with 2N-sulfuric acid (pH = 5), filtered, washed twice with water and dried to have a carboxyl group on the surface. As a result, 25.24 parts by weight of colored particles (B) were obtained.
When the particle size distribution of the particles was measured, the average particle size was 1.1 μm, and the relative standard deviation (CV value) was 29%.
Next, epoxy-modified silicone treatment was performed on the colored particles having a carboxyl group on the surface obtained in [Synthesis Example].

[Synthesis Example 3]
Potassium dihydrogen phosphate (0.082 parts by weight), 1N potassium hydroxide (13.57 parts by weight), methanol (72 parts by weight), and ion-exchanged water (74.43 parts by weight) were homogenizer (manufactured by IKA). : 2-acrylamido-2-methylpropanesulfonic acid (2.43 parts by weight), which is a monomer having a sulfonic acid group, is added under high-speed stirring (8000 rpm) with Ultratax T25), and is a processing colorant. Microlith (Ciba Specialty Chemicals, trade name [Blue4G-WA]) (5.0 parts by weight) was added, and methyl methacrylate (20.07 parts by weight) as a polymerizable monomer was added. N- [3- (dimethylamino) propyl] methacrylylamide (3.50 parts by weight), an oil-soluble polymerization initiator (manufactured by Wako Pure Chemical Industries, Ltd.) A solution consisting of product name “V-65” = 2,2′-azobis (2,4-dimethylvaleronitrile)) (0.58 parts by weight) was added and mixed for 30 minutes under high speed stirring to obtain a reaction solution. .
Subsequently, the reaction solution was added to a 500 ml separable flask equipped with a thermometer and a nitrogen inlet tube prepared in advance, and the temperature was raised to 58 ° C. while stirring under a nitrogen stream. The reaction is further carried out for 6 hours, and then allowed to cool, acidified with 2N-sulfuric acid (pH = 5), filtered, washed twice with water and dried to have a carboxyl group on the surface. 26.84 parts by weight of colored particles (C) were obtained.
When the particle size distribution of the particles was measured, the average particle size was 2.2 μm, and the relative standard deviation (CV value) was 15%.

[Example 1]
In a 200 ml beaker, colored particles (B) having a carboxyl group on the surface obtained in Synthesis Example 2 (10 parts by weight), silicone oil [manufactured by Toray Dow Corning Co., Ltd., SH200-2 mm ² / s] (86 .18 parts by weight) and an epoxy-modified silicone oil [X-22-173DX, manufactured by Shin-Etsu Chemical Co., Ltd.] (3.83 parts by weight), an ultrasonic disperser (output: 130 W, frequency: 20 kHz, pulser) System) for 2 hours to obtain a liquid developing toner (I). This colored particle dispersion had an average particle size: 1.3 μm, a relative deviation value (CV value): 25%, and a zeta potential: 46 mV. Further, when this dispersion was subjected to a storage test for 20 days, no aggregation occurred at an average particle diameter of 1.2 μm, and the zeta potential was hardly changed to 43 mV, indicating a very excellent storage stability. .

[Example 2]
In a 200 ml beaker, colored particles (A) (10 parts by weight) having a carboxyl group on the surface obtained in Synthesis Example 1, silicone oil [manufactured by Toray Dow Corning Co., Ltd., SH200-2 mm ² / s] (87 .47 parts by weight) and epoxy-modified silicone oil [manufactured by Amax Co., Ltd., MCR-E11] (2.53 parts by weight), and an ultrasonic disperser (output: 130 W, frequency: 20 kHz, pulser system) Processing was performed for 2 hours to obtain a liquid developing toner (II). This colored particle dispersion had an average particle size: 0.7 μm, a relative deviation value (CV value): 23%, and a zeta potential: +70 mV. Further, when this dispersion was subjected to a storage test for 20 days, no aggregation occurred at an average particle diameter of 0.7 μm, and the zeta potential was hardly changed to 68 mV, indicating an excellent storage stability. .

Example 3
In a 200 ml beaker, colored particles (C) having a sulfonic acid group on the surface obtained in Synthesis Example 3 (10 parts by weight), silicone oil [manufactured by Toray Dow Corning Co., Ltd., SH200-2 mm ² / s] ( 86.18 parts by weight) and an epoxy-modified silicone oil [X-22-173DX, manufactured by Shin-Etsu Chemical Co., Ltd.] (4.35 parts by weight), an ultrasonic disperser (output: 130 W, frequency: 20 kHz, (Pulsar system) for 2 hours to obtain a liquid developing toner (III). This colored particle dispersion had an average particle size of 2.4 μm, a relative deviation value (CV value): 15%, and a zeta potential of +110 mV. Further, when this dispersion was subjected to a storage test for 20 days, the average particle size was 2.4 μm, no aggregation occurred, and the zeta potential was hardly changed to +110 mV, indicating a very excellent storage stability. .

[Comparative Example 1] (Preparation of toner for liquid development by coacervation method)
A vessel equipped with a thermometer and a reflux condenser is charged with branched chain aliphatic hydrocarbon isopar G (Esso Petroleum: 80 parts by weight), toluene (48 parts by weight), ethanol (30 parts by weight), and ethylene. -Partially saponified product of vinyl acetate copolymer Dumiran C-2280 (manufactured by Takeda Pharmaceutical Co., Ltd .: 6.67 parts by weight), phthalocyanine blue (CI Pigment Blue 15: 3) (1.33 parts by weight), and phosphorus Acidic surfactant surfactant Surfsurf AL (Daiichi Kogyo Seiyaku Co., Ltd .: 0.8 parts by weight) was added and stirred at 70 ° C. for 3 hours at high speed to prepare a phthalocyanine blue dispersion. The phthalocyanine blue dispersion is slowly cooled to 30 ° C. under weak stirring, and further, toluene and ethanol are distilled off under reduced pressure to precipitate colored resin particles. Further, zirconium naphthenate is added as a charge control agent. (Solid content concentration: 10% by weight) to obtain a liquid developing toner (IV). This colored particle dispersion had an average particle size of 2.7 μm, a relative deviation value (CV value) of 320%, and a zeta potential of +84 mV. Further, when this dispersion was subjected to a storage test for 20 days, it aggregated and re-dispersed, but the dispersion was poor, and in the particle size measurement, a large peak considered to be an aggregate was observed on the large particle size side, and the zeta potential: It decreased to +27 mV.

[Comparative Example 2]
In Example 1, silicone oil [manufactured by Toray Dow Corning Co., Ltd., SH200-2 mm ^{2 / s} ] (82.35 parts by weight), polyether-modified silicone oil [manufactured by Shin-Etsu Chemical Co., Ltd., KF-945] The ultrasonic treatment was performed in the same manner as in Example 1 except that the amount was changed to (7.66 parts by weight). The polyether-modified silicone oil was hardly dispersed and the particle size could not be measured even though it was twice the weight concentration of the epoxy-modified silicone oil used in Example 1.

[Application Example 1]
Electrophoresis of the colored particle dispersions obtained in Example 1, Example 2, Example 3, and Comparative Example 1 was confirmed using the apparatus shown below.
The electrophoresis apparatus will be described. The evaluation of electrophoresis is performed using the high-speed camera photographing device (9) shown in FIG. First, an ITO film (9c) is deposited on a glass substrate (9d) to a thickness of 100 nm with an interval of 100 μm, and a glass plate (9h) having a thickness of 25 μm is adhered thereon at an interval of 100 μm to provide a liquid reservoir. Next, when the dispersion liquid (9 g) of the surface functional member is injected into the liquid reservoir and a voltage of 1000 V is applied between the ITO electrodes, a state in which droplets migrate is observed from above with a high-speed camera (9a). Observe and evaluate electrophoresis. As a result, in both Example 1, Example 2 and Example 3, fast migration was confirmed, and further, it was confirmed that it also accurately corresponds to electrolysis (polarity). However, in Comparative Example 1, migration having a distribution was observed as a whole, and some electrophoretic particles having a reverse polarity were also observed.

[Application Example 2] <Image evaluation by non-contact type liquid developing device>
For image evaluation, the liquid developing toner III of Example 3 and the liquid developing toner IV of Comparative Example 1 were set in the image forming experimental apparatus having the structure shown in FIG.
In the present invention, the image is visually judged by outputting to PPC paper under the development conditions unified to the transfer bias of −1000 V under the three development bias conditions of 1000 V, 900 V, and 800 V.
The evaluation results are shown in Table 1.

  Surprisingly, it has been found that the liquid developer of the present invention can provide a clear image even under very low development bias conditions. This effect is explained by the synergistic effect that the liquid developer of the present invention is a homogeneous toner particle having a narrow particle size distribution and that the dispersibility and dispersion stability are greatly improved by chemical modification with epoxy-modified silicone. It is thought that it was realized. Furthermore, as an explanation of this great effect, the reason is not clear at the present time, but is presumed as follows. By applying an electric field to uniform toner particles, randomly dispersed particles are arranged in the electric field direction by dielectric polarization, and a chain structure is formed in the electrode direction. This chain structure concentrates the electric field, resulting in low development. It is presumed that a clear image was obtained even under the bias condition. This chain structure formation is considered to involve the homogeneity of toner particles and good dispersibility (fluidity).

It is the figure which showed the electrophoresis apparatus used by the application example of this invention. It is the figure which showed the image formation experiment apparatus used by the image evaluation of the application example of this invention.

Explanation of symbols

9 camera photographing device 9a high speed camera 9b monitor 9c ITO film 9d glass substrate 9f switch 9g dispersion liquid 9h glass plate 9j DC power supply

Claims (6)

A liquid developer containing toner particles in an electrically insulating liquid, wherein the toner particles include at least a binder resin and a colorant, and the colored particles having acidic groups on the surface are chemically treated using epoxy-modified silicone. A liquid developer characterized by being modified and having a relative standard deviation (CV value) of particle size distribution of 30% or less . The liquid developer according to claim 1, wherein the acidic group is a carboxyl group or a sulfonic acid group. The liquid developer according to claim 1, wherein an average particle diameter of the colored particles is 0.3 to 5 μm. A method for producing a liquid developer containing toner particles in an electrically insulating liquid, comprising at least a binder resin and a colorant, wherein a relative standard deviation (CV value) of particle size distribution is 30% or less, and Liquid development characterized by chemically modifying the surface of the colored particles with the epoxy-modified silicone under ultrasonic dispersion in an electrically insulating liquid containing at least colored particles having acidic groups on the surface and epoxy-modified silicone method of manufacturing the agent. The method for producing a liquid developer according to claim 4 , wherein the electrically insulating liquid is a silicone oil having a kinematic viscosity at 25 ° C. in the range of ² to 100 mm ² / s. Colored particles having an acidic group on the surface, the liquid developer producing method according to claim 4 or 5, characterized in that produced by a polymerization method.

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