JP2014232211A - Liquid developer and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the formation of aggregates of toner particles regardless of the elapsed time, even if the toner particles are collected by a blade or the like.SOLUTION: Liquid developer comprises the toner particles, an insulating liquid, and a basic dispersant. The toner particles comprise a resin and a colorant, and the resin comprises a core resin and a shell resin. The basic dispersant includes an alkyl group whose carbon number is at least 8.

Description

  The present invention relates to a liquid developer and a method for producing the same.

  A liquid developer produced by a so-called granulation method is widely used because it is easy to obtain toner particles having a small diameter and a sharp particle size distribution. In addition, toner particles with high meltability and toner particles with high crystallinity are soft even at room temperature, and thus are difficult to obtain by the pulverization method, which is one of the reasons for adopting the granulation method.

  Among such granulation methods, the core resin is dissolved in a good solvent, and a good solvent solution having a SP value different from that of the good solvent is mixed with an interfacial tension adjusting agent to give shear to the poor solvent. A technique is known in which good solvent droplets are formed in a solvent, and then the good solvent is volatilized to form fine particles of a core resin. In this case, as the interfacial tension adjusting agent, a surfactant, a dispersing agent or the like is used.

  Further, in this method, when shell resin fine particles are used as the interfacial tension adjusting agent, the shell resin fine particles cover the surface of the core resin fine particles, and core / shell type toner particles can be obtained. Such a core / shell type toner particle is considered to be excellent as a developer for electrophotography, for example, because it is excellent in stability and has a small particle size and a sharp particle size distribution (Japanese Patent Application Laid-Open No. 2009-96994). Gazette (patent document 1), Unexamined-Japanese-Patent No. 2012-123217 (patent document 2)).

JP 2009-96994 A JP 2012-123217 A

  In a wet development system using a liquid developer, toner particles remaining without being developed on a developing roller or a photoreceptor or toner particles remaining without being transferred are collected using a blade. At that time, if the recovery is continued for a certain period of time, the recovered toner particles may stick and aggregate to form an aggregate.

  Such aggregate formation is considered to be remarkable when the repulsive force between the toner particles in the liquid developer is weak. The core / shell type toner particles as described above were expected to be an effective means for preventing the formation of aggregates because the fine particles of the shell resin between different toner particles have repulsive forces. However, although the formation of the agglomerates is somewhat improved by increasing the amount of the shell resin, there is a limit to the improvement, and no further improvement could be made even if added excessively. This is probably because the amount of the shell resin fine particles existing on the surface of the fine particles of the core resin is limited.

  On the other hand, in the toner particles formed by using various dispersants in place of the fine particles of the shell resin, the formation of aggregates could be reduced to some extent, but the core / shell type toner particles In comparison, since the toner particles themselves tend to have a larger particle size, it has been found that increasing the amount of the dispersant to prevent this results in an adverse effect that the fixability deteriorates and the chargeability deteriorates.

  On the other hand, the liquid developer obtained by adding a dispersant to the toner particles obtained by the pulverization method was able to prevent the formation of aggregates to some extent at the initial stage of recovery by the blade. As the process progressed, the prevention effect decreased significantly. This was presumed to be because the dispersant was detached from the toner particles over a long period of time and the repulsive force between the toner particles was reduced.

  The present invention has been made in view of the current situation as described above, and an object of the present invention is to aggregate toner particles regardless of the passage of time even if the toner particles are collected using a blade or the like. It is an object of the present invention to provide a liquid developer capable of reducing the formation of water.

  The liquid developer according to the present invention includes toner particles, an insulating liquid, and a basic dispersant. The toner particles include a resin and a colorant, and the resin includes a core resin and a shell resin. The basic dispersant has an alkyl group having 8 or more carbon atoms.

  Basic dispersants are amine groups, amino groups, amide groups, pyrrolidone groups, imine groups, imino groups, urethane groups, quaternary ammonium groups, ammonium groups, pyridino groups, pyridium groups, imidazolino groups, and imidazoliums in the molecule. Preferably any of the groups are included.

  The basic dispersant is preferably contained in an amount of 3 parts by mass or less with respect to 100 parts by mass of the toner particles.

  The method for producing a liquid developer according to the present invention preferably includes a first step of producing toner particles and a second step of adding a basic dispersant to the toner particles.

  In the liquid developer according to the present invention, even when toner particles are collected using a blade or the like, the formation of toner particle aggregates can be reduced regardless of the passage of time.

It is a graph which shows the result of having investigated the relationship between the quantity of a basic dispersing agent, and the aggregation degree of a toner particle. 6 is a graph showing the results of examining the relationship between the amount of basic dispersant and the surface potential of toner particles. Is a graph showing the results of examining the relationship between the median diameter D ₅₀ of the amount of the shell resin and the toner particles. It is a graph which shows the result of having investigated the relationship between the quantity of shell resin, and the surface potential of a toner particle. It is a graph which shows the result of having investigated the relationship between the quantity of shell resin, and the aggregation degree of a toner particle. 6 is a graph showing the results of examining the relationship between the amount of basic dispersant and the surface potential of toner particles. 6 is a graph showing the results of examining the relationship between the amount of basic dispersant and the degree of aggregation of toner particles at the initial stage of development. 6 is a graph showing the results of examining the relationship between the amount of a basic dispersant and the degree of aggregation of toner particles during durability (end of development). FIG. 6 is a flowchart illustrating an example of a method for producing a liquid developer according to the present invention in the order of steps. 1 is a schematic conceptual diagram of an electrophotographic image forming apparatus.

  Hereinafter, embodiments according to the present invention will be described in more detail. In the drawings of the present invention, dimensional relationships such as length, width, thickness, and depth are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

<Liquid developer>
The liquid developer according to this embodiment is an electrophotographic liquid developer, paint, and electrostatic recording used in an electrophotographic image forming apparatus (described later) such as a copying machine, a printer, a digital printing machine, or a simple printing machine. It is useful as a liquid developer, an oil-based ink for an ink jet printer, or an ink for electronic paper, and contains toner particles, an insulating liquid, and a basic dispersant. The liquid developer according to the exemplary embodiment preferably includes 10 to 50% by mass of toner particles and 50 to 90% by mass of an insulating liquid, and 3 parts by mass or less of the basic dispersant with respect to 100 parts by mass of the toner particles. It is preferable to include. The liquid developer according to the exemplary embodiment preferably contains 15 to 45% by mass of toner particles, and more preferably contains 20 to 40% by mass of toner particles. The liquid developer according to the exemplary embodiment may include arbitrary components different from the toner particles, the insulating liquid, and the basic dispersant, and the optional components include, for example, a filler, an antistatic agent, and a release agent. , Charge control agent, ultraviolet absorber, antioxidant, anti-blocking agent, heat stabilizer, flame retardant, thickener or dispersant.

<Toner particles>
The toner particles in the present embodiment include a resin and a colorant. The resin includes a shell resin and a core resin made of a resin different from the shell resin. The toner particles in the present embodiment may contain an arbitrary component different from the shell resin, the core resin, and the colorant, and the optional component may be, for example, a wax or a charge control agent.

The median diameter D ₅₀ (hereinafter referred to as “toner particle median diameter D ₅₀ ”) when the particle size distribution of the toner particles in this embodiment is measured on a volume basis may be 0.5 μm or more and 5.0 μm or less. preferable. This particle size is smaller than the particle size of toner particles contained in a conventionally used dry developer, and is one of the features of the present invention. When the median diameter D ₅₀ of the toner particles is less than 0.5 μm, the mobility of the toner particles in an electric field may be deteriorated. Therefore, the developability may be lowered. On the other hand, if the median diameter D ₅₀ of the toner particles exceeds 5.0 μm, the uniformity of the image density may be reduced. Median diameter D ₅₀ of the toner particles, for example (FPIA-3000S manufactured by Sysmex Corporation) flow particle image analyzer can be measured using, for example. In this analyzer, it is possible to use the solvent as a dispersion medium as it is. Therefore, if this analyzer is used, the state of the toner particles in a state closer to the actual dispersion state than the measurement system in the aqueous system can be measured. Can do.

The average circularity of the toner particles is preferably 0.85 or more and 0.96 or more. The circularity of the toner particles is a value obtained by (peripheral length of a circle having an area equal to the projected area of the toner particles) ÷ (peripheral length of the detected toner particles), and measurement of the median diameter D ₅₀ of the toner particles. It is obtained in the same way as the method.

  The mass ratio of the shell particles containing the shell resin and the core particles containing the core resin (shell particles: core particles) is preferably 1:99 to 70:30. From the viewpoint of heat resistance stability of the agent, it is more preferably 2:98 to 50:50, and further preferably 3:97 to 35:65. In other words, the resin is 1 to 70% by mass (more preferably 5 to 50% by mass, more preferably 10 to 35% by mass) of a film-shaped shell and 30 to 99% by mass (more preferably 50%). -95% by mass, more preferably 65-90% by mass). As a result, the toner particles have a core-shell structure (Japanese Patent Laid-Open No. 2009-96994) in which the shell particles containing the shell resin are attached to or coated on the surface of the core particles containing the core resin. On the other hand, if the content (mass ratio) of the shell particles is too low, the blocking resistance of the toner particles may be lowered. On the other hand, if the content (mass ratio) of the core particles is too high, the particle size uniformity of the toner particles may decrease.

<Shell resin>
The shell resin may be a thermoplastic resin or a thermosetting resin. For example, vinyl resin, polyester resin, polyurethane resin, epoxy resin, polyamide resin, polyimide resin, silicon resin, phenol resin, A melamine resin, urea resin, aniline resin, ionomer resin, polycarbonate resin or the like is preferable. Two or more of these may be used in combination as the shell resin. From the viewpoint of ease of production of the liquid developer, it is preferable to use at least one of vinyl resin, polyester resin, polyurethane resin and epoxy resin as the shell resin, and use at least one of polyester resin and polyurethane resin. Is more preferable.

  The vinyl resin may be a homopolymer obtained by homopolymerizing a monomer having a polymerizable double bond, or two or more monomers having a polymerizable double bond may be copolymerized. Copolymers obtained in this way may be used. Examples of the monomer having a polymerizable double bond include the following (1) to (9).

(1) Hydrocarbon having a polymerizable double bond The hydrocarbon having a polymerizable double bond is, for example, an aliphatic hydrocarbon having a polymerizable double bond represented by the following (1-1), or the following (1 -2) is preferably an aromatic hydrocarbon having a polymerizable double bond.

(1-1) Aliphatic hydrocarbon having a polymerizable double bond An aliphatic hydrocarbon having a polymerizable double bond is, for example, a chain having a polymerizable double bond represented by (1-1-1) below. It is preferably a hydrocarbon or a cyclic hydrocarbon having a polymerizable double bond represented by the following (1-1-2).

(1-1-1) Chain hydrocarbon having a polymerizable double bond The chain hydrocarbon having a polymerizable double bond is, for example, an alkene having 2 to 30 carbon atoms (for example, ethylene, propylene, butene, Isobutylene, pentene, heptene, diisobutylene, octene, dodecene, octadecene, etc.); alkadiene having 4 to 30 carbon atoms (for example, butadiene, isoprene, 1,4-pentadiene, 1,5-hexadiene, 1,7-octadiene, etc.) Etc.).

(1-1-2) Cyclic hydrocarbon having a polymerizable double bond A cyclic hydrocarbon having a polymerizable double bond is, for example, a mono- or dicycloalkene having 6 to 30 carbon atoms (for example, cyclohexene, vinylcyclohexene). Or ethylidenebicycloheptene); mono- or dicycloalkadiene having 5 to 30 carbon atoms (for example, monocyclopentadiene or dicyclopentadiene) is preferable.

(1-2) Aromatic hydrocarbon having a polymerizable double bond The aromatic hydrocarbon having a polymerizable double bond is, for example, styrene; hydrocarbyl of styrene (for example, alkyl having 1 to 30 carbon atoms, Cycloalkyl, aralkyl and / or alkenyl) substituted (eg, α-methylstyrene, vinyltoluene, 2,4-dimethylstyrene, ethylstyrene, isopropylstyrene, butylstyrene, phenylstyrene, cyclohexylstyrene, benzylstyrene, crotylbenzene Divinylbenzene, divinyltoluene, divinylxylene or trivinylbenzene); vinylnaphthalene or the like is preferable.

(2) Monomers having a carboxyl group and a polymerizable double bond and their monomers having a carboxyl group and a polymerizable double bond are, for example, unsaturated monocarboxylic acids having 3 to 15 carbon atoms [ For example, (meth) acrylic acid, crotonic acid, isocrotonic acid, cinnamic acid, etc.]; unsaturated dicarboxylic acid having 3 to 30 carbon atoms (anhydride) [for example, (anhydrous) maleic acid, fumaric acid, itaconic acid, ( Anhydrous) citraconic acid or mesaconic acid etc.]; monoalkyl (1-10 carbon atoms) ester of unsaturated dicarboxylic acid having 3 to 10 carbon atoms (for example, maleic acid monomethyl ester, maleic acid monodecyl ester, fumaric acid mono Ethyl ester, itaconic acid monobutyl ester, citraconic acid monodecyl ester and the like). As used herein, “(meth) acrylic acid” means acrylic acid and / or methacrylic acid.

  Examples of the salt of the monomer include alkali metal salts (for example, sodium salt or potassium salt), alkaline earth metal salts (for example, calcium salt or magnesium salt), ammonium salts, amine salts, and quaternary. An ammonium salt or the like is preferable.

  The amine salt is not particularly limited as long as it is an amine compound. For example, primary amine salt (for example, ethylamine salt, butylamine salt or octylamine salt); secondary amine salt (for example, diethylamine salt or dibutylamine salt) A tertiary amine salt (for example, a triethylamine salt or a tributylamine salt) is preferable.

  The quaternary ammonium salt is preferably a tetraethylammonium salt, a triethyllaurylammonium salt, a tetrabutylammonium salt, a tributyllaurylammonium salt, or the like.

  Examples of the salt of a monomer having a carboxyl group and a polymerizable double bond include sodium acrylate, sodium methacrylate, monosodium maleate, disodium maleate, potassium acrylate, potassium methacrylate, monopotassium maleate, Lithium acrylate, cesium acrylate, ammonium acrylate, calcium acrylate, aluminum acrylate, and the like are preferable.

(3) Monomers having a sulfo group and a polymerizable double bond, and salts thereof having a sulfo group and a polymerizable double bond include, for example, vinyl sulfonic acid, α-methylstyrene sulfonic acid, sulfopropyl (Meth) acrylate or 2- (meth) acryloylamino-2,2-dimethylethanesulfonic acid is preferred. Examples of the salt of a monomer having a sulfo group and a polymerizable double bond are listed as “the salt of the monomer” in “(2) Monomer having a carboxyl group and a polymerizable double bond” above. A salt is preferred.

(4) Monomers having a phosphono group and a polymerizable double bond and salts thereof Monomers having a phosphono group and a polymerizable double bond are, for example, 2-hydroxyethyl (meth) acryloyl phosphate or 2-acryloyloxy. Preferred is ethylphosphonic acid or the like. Examples of the salt of a monomer having a phosphono group and a polymerizable double bond are listed as “the salt of the monomer” in “(2) Monomer having a carboxyl group and a polymerizable double bond” above. A salt is preferred.

(5) Monomer having hydroxyl group and polymerizable double bond Monomer having hydroxyl group and polymerizable double bond is, for example, hydroxystyrene, N-methylol (meth) acrylamide or hydroxyethyl (meth) acrylate. And the like.

(6) Nitrogen-containing monomer having a polymerizable double bond As the nitrogen-containing monomer having a polymerizable double bond, for example, the monomers shown in the following (6-1) to (6-4) are: Can be mentioned.

(6-1) A monomer having an amino group and a polymerizable double bond A monomer having an amino group and a polymerizable double bond is, for example, aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, Diethylaminoethyl (meth) acrylate, t-butylaminoethyl methacrylate, N-aminoethyl (meth) acrylamide, (meth) allylamine, morpholinoethyl (meth) acrylate, 4-vinylpyridine, 2-vinylpyridine, crotylamine, N, N -Dimethylaminostyrene, methyl-α-acetaminoacrylate, vinylimidazole, N-vinylpyrrole, N-vinylthiopyrrolidone, N-arylphenylenediamine, aminocarbazole, aminothiazole, aminoindole, aminopyrrole, aminoimidazo It is preferred that in such le or amino mercaptothiazole. The monomer having an amino group and a polymerizable double bond may be a salt of the monomers listed above. The salts of the monomers listed above are preferably, for example, the salts listed as “Salts of the monomers” in “(2) Monomers having a carboxyl group and a polymerizable double bond”.

(6-2) Monomer having an amide group and a polymerizable double bond Monomers having an amide group and a polymerizable double bond are, for example, (meth) acrylamide, N-methyl (meth) acrylamide, N- Butyl acrylamide, diacetone acrylamide, N-methylol (meth) acrylamide, N, N′-methylene-bis (meth) acrylamide, cinnamic amide, N, N-dimethylacrylamide, N, N-dibenzylacrylamide, methacrylformamide, N-methyl-N-vinylacetamide and N-vinylpyrrolidone are preferred.

(6-3) A monomer having 3 to 10 carbon atoms having a nitrile group and a polymerizable double bond and a monomer having 3 to 10 carbon atoms having a polymerizable double bond, for example, ( Preferred are (meth) acrylonitrile, cyanostyrene and cyanoacrylate.

(6-4) A monomer having 8 to 12 carbon atoms having a nitro group and a polymerizable double bond and a monomer having 8 to 12 carbon atoms having a polymerizable double bond include, for example, nitro Styrene or the like is preferable.

(7) A monomer having 6 to 18 carbon atoms having an epoxy group and a polymerizable double bond and a monomer having 6 to 18 carbon atoms having a polymerizable double bond may be, for example, glycidyl (meta ) An acrylate or the like is preferable.

(8) A monomer having 2 to 16 carbon atoms having a halogen element and a polymerizable double bond A monomer having 2 to 16 carbon atoms having a halogen element and a polymerizable double bond includes, for example, vinyl chloride, Preferred are vinyl bromide, vinylidene chloride, allyl chloride, chlorostyrene, bromostyrene, dichlorostyrene, chloromethylstyrene, tetrafluorostyrene and chloroprene.

(9) Ester having 4 to 16 carbon atoms having a polymerizable double bond Ester having 4 to 16 carbon atoms having a polymerizable double bond includes, for example, vinyl acetate; vinyl propionate; vinyl butyrate; diallyl phthalate; Diallyl adipate; isopropenyl acetate; vinyl methacrylate; methyl-4-vinyl benzoate; cyclohexyl methacrylate; benzyl methacrylate; phenyl (meth) acrylate; vinyl methoxyacetate; vinyl benzoate; ethyl-α-ethoxy acrylate; Alkyl (meth) acrylate having an alkyl group [for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate or 2-ethylhexyl (meth) acrylate Dialkyl fumarate (two alkyl groups are straight-chain alkyl groups, branched alkyl groups or alicyclic alkyl groups having 2 to 8 carbon atoms); dialkyl maleates (two alkyl groups) Group is a straight-chain alkyl group having 2 to 8 carbon atoms, a branched alkyl group or an alicyclic alkyl group); poly (meth) allyloxyalkanes (eg, diaryloxyethane, triaryloxyethane) , Tetraallyloxyethane, tetraallyloxypropane, tetraallyloxybutane or tetrametaallyloxyethane; monomers having a polyalkylene glycol chain and a polymerizable double bond [for example, polyethylene glycol (number average molecular weight (hereinafter Will be referred to as “Mn”) = 300) mono (meth) acrylate, polypropylene glycol (Mn = 500) Noacrylate, methyl alcohol ethylene oxide (hereinafter, “ethylene oxide” is abbreviated as “EO”) 10 mol adduct (meth) acrylate or lauryl alcohol EO 30 mol adduct (meth) acrylate, etc.]; poly (meth) acrylates { For example, poly (meth) acrylates of polyhydric alcohols [for example, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate or polyethylene Glycol di (meth) acrylate and the like]} and the like.

  Specific examples of the vinyl resin include, for example, a styrene- (meth) acrylic acid ester copolymer, a styrene-butadiene copolymer, a (meth) acrylic acid- (meth) acrylic acid ester copolymer, and a styrene-acrylonitrile copolymer. Styrene- (maleic anhydride) copolymer, styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic acid-divinylbenzene copolymer or styrene-styrenesulfonic acid- (meth) acrylic acid ester copolymer A polymer or the like is preferable.

  The vinyl resin may be a homopolymer or a copolymer of the monomer having the polymerizable double bond described in (1) to (9) above, or the polymerizable resin described in (1) to (9) above. A polymer obtained by polymerizing a monomer having a heavy bond and a monomer (m) having a polymerizable double bond having a molecular chain (k) may be used. The difference in SP value between the molecular chain (k) in the monomer (m) and the insulating liquid is preferably 2 or less. In the present specification, the “SP value” is a method by Fedors [Polym. Eng. Sci. 14 (2) 152, (1974)].

  Although the monomer (m) having a polymerizable double bond having a molecular chain (k) is not particularly limited, for example, the following monomers (m1) to (m3) are preferable. As the monomer (m), two or more monomers (m1) to (m3) may be used in combination.

  The monomer (m1) having a linear hydrocarbon chain having 12 to 27 carbon atoms (preferably 16 to 25) and a polymerizable double bond is, for example, a mono linear alkyl (unsaturated monocarboxylic acid) ( Preferably, the alkyl is an alkyl having 12 to 27 carbon atoms and an unsaturated dicarboxylic acid mono-linear alkyl (alkyl having 12 to 27 carbon atoms). The unsaturated monocarboxylic acid and unsaturated dicarboxylic acid are, for example, (meth) acrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, citraconic acid, etc. A body or the like is preferable. Specific examples of the monomer (m1) include, for example, dodecyl (meth) acrylate, stearyl (meth) acrylate, behenyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate or (meth) ) Eicosyl acrylate is preferred.

  The monomer (m2) having a branched hydrocarbon chain having 12 to 27 carbon atoms (preferably 16 to 25) and a polymerizable double bond is, for example, a branched alkyl (alkyl carbon of an unsaturated monocarboxylic acid). It is preferably a 12-27) ester or a mono-branched alkyl (alkyl having 12-27 carbon atoms) ester of an unsaturated dicarboxylic acid. The unsaturated monocarboxylic acid and unsaturated dicarboxylic acid are preferably the same as those listed as specific examples of the unsaturated monocarboxylic acid or unsaturated dicarboxylic acid in the monomer (m1), for example. Specific examples of the monomer (m2) are preferably, for example, (meth) acrylic acid 2-decyltetradecyl.

  The monomer (m) having a polymerizable double bond having a molecular chain (k) is a monomer (m3) having a fluoroalkyl chain having 4 to 20 carbon atoms and a polymerizable double bond. preferable.

  The melting point of the shell resin is preferably 0 to 220 ° C, more preferably 30 to 200 ° C, and further preferably 40 to 80 ° C. From the viewpoint of the particle size distribution of the toner particles, the powder flowability of the liquid developer, the heat storage stability and the stress resistance, the melting point of the shell resin is preferably equal to or higher than the temperature at which the liquid developer is produced. . If the melting point of the shell resin is lower than the temperature at which the liquid developer is produced, it may be difficult to prevent the toner particles from being coalesced, and it may be difficult to prevent the toner particles from being split. In addition, the distribution width in the particle size distribution of the toner particles may be difficult to narrow. In other words, there may be a large variation in the particle size of the toner particles. In this specification, melting | fusing point is measured based on the method prescribed | regulated to ASTM D3418-82 using a DSC apparatus (DSC20 by Seiko Instruments Inc.).

The Mn and the mass average molecular weight (hereinafter referred to as “Mw”) of the shell resin are preferably 100 to 5000000, more preferably 200 to 5000000, and further preferably 500 to 500000. The Mn of the resin (excluding the polyurethane resin) was measured using GPC (Gel Permeation Chromatography) under the following conditions with respect to the soluble content in tetrahydrofuran (THF).
Measuring device: “HLC-8120” manufactured by Tosoh Corporation
Column: “TSKgelGMHXL” (2) manufactured by Tosoh Corporation and “TSKgelMultiporeHXL-M” (1) manufactured by Tosoh Corporation
Sample solution: injection amount of sample solution into a 0.25 mass% THF solution column: 100 μl
Flow rate: 1 ml / min Measurement temperature: 40 ° C
Detector: Refractive index detector Reference material: Standard polystyrene (TSK standard POLYSYRENE) manufactured by Tosoh Corporation 12 points (molecular weight: 500, 1050, 2800, 5970, 9100, 18100, 37900, 96400, 190000, 355000, 1090000, 2890000 ).

The Mn and Mw of the polyurethane resin are measured using GPC under the following conditions.
Measuring device: “HLC-8220GPC” manufactured by Tosoh Corporation
Column: “Guardcolum α” (1) and “TSKgel α-M” (1)
Sample solution: Injection amount of dimethylformamide solution into a 0.125% by mass dimethylformamide solution column: 100 μl
Flow rate: 1 ml / min Measurement temperature: 40 ° C
Detector: Refractive index detector Reference material: Standard polystyrene (TSK standard POLYSYRENE) manufactured by Tosoh Corporation 12 points (molecular weight: 500, 1050, 2800, 5970, 9100, 18100, 37900, 96400, 190000, 355000, 1090000, 2890000).

The SP value of the shell resin is preferably 7 to 18 (cal / cm ³ ) ^1/2 , and more preferably 8 to 14 (cal / cm ³ ) ^1/2 .

Shell particles containing a shell resin can be produced, for example, by the method shown in any one of [1] to [7] below. From the viewpoint of ease of production of shell particles, it is preferably produced by the method shown in the following [4], [6] or [7], more preferably produced by the method shown in the following [6] or [7]. It is to be.
[1]: The shell resin is pulverized dry using a known dry pulverizer such as a jet mill.
[2]: The shell resin powder is dispersed in an organic solvent and pulverized wet using a known wet disperser such as a bead mill or a roll mill.
[3]: Spray the shell resin solution using a spray dryer or the like and dry.
[4]: Addition of a poor solvent or cooling to the shell resin solution causes the shell resin to be supersaturated and deposited.
[5]: The shell resin solution is dispersed in water or an organic solvent.
[6]: The shell resin precursor is polymerized in water by an emulsion polymerization method, a soap-free emulsion polymerization method, a seed polymerization method or a suspension polymerization method.
[7]: A shell resin precursor is polymerized in an organic solvent by dispersion polymerization or the like.

  The volume average particle diameter of the shell particles can be appropriately adjusted so as to be a particle diameter suitable for obtaining toner particles having a desired particle diameter. The volume average particle diameter of the shell particles is preferably 0.0005 to 3 μm. The upper limit of the volume average particle size of the shell particles is more preferably 2 μm, and even more preferably 1 μm. The lower limit of the volume average particle diameter of the shell particles is more preferably 0.01 μm, still more preferably 0.02 μm, and most preferably 0.04 μm. For example, when it is desired to obtain toner particles having a volume average particle diameter of 1 μm, the volume average particle diameter of the shell particles is preferably 0.0005 to 0.3 μm, more preferably 0.001 to 0.2 μm. . For example, when it is desired to obtain toner particles having a volume average particle size of 10 μm, the volume average particle size of the shell particles is preferably 0.005 to 3 μm, more preferably 0.05 to 2 μm.

  The volume average particle diameter of the shell particles is determined by a laser particle size distribution measuring device (for example, “LA-920” manufactured by Horiba, Ltd., “Multisizer III” manufactured by Beckman Coulter, Inc.) or “ELS using a laser Doppler method as an optical system” -800 "(manufactured by Otsuka Electronics Co., Ltd.), etc. When the volume average particle diameter of the shell particles is measured with a different measuring device, a difference occurs in the measured value. The measured value at −800 ”is adopted.

<Core resin>
The core resin is preferably a thermoplastic resin, and is preferably a polyester resin, a polyurethane resin, an ethylene resin, a styrene-acrylic resin, an epoxy resin, or the like. As the core resin, two or more of these may be used in combination, but a polyester resin having a high sharp melt property is suitable.

  The polyester resin is preferably a polycondensate of, for example, a polyol and a polycarboxylic acid, a polycarboxylic acid anhydride, or a lower alkyl (alkyl group having 1 to 4 carbon atoms) ester of the polycarboxylic acid. A known polycondensation catalyst or the like can be used for the polycondensation reaction. The ratio of polyol and polycarboxylic acid is not particularly limited. The equivalent ratio of hydroxyl group [OH] to carboxyl group [COOH] ([OH] / [COOH]) is preferably 2/1 to 1/5, more preferably 1.5 / 1 to 1/4. The ratio between the polyol and the polycarboxylic acid may be set so that the ratio is more preferably 1.3 / 1 to 1/3.

  The polyol is preferably, for example, a diol or a polyol having a valence of 3 to 8 or more.

  Examples of the diol include alkylene glycols having 2 to 30 carbon atoms (for example, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, octanediol). , Decanediol, dodecanediol, tetradecanediol, neopentyl glycol or 2,2-diethyl-1,3-propanediol, etc .; alkylene ether glycols with Mn = 106 to 10,000 (for example, diethylene glycol, triethylene glycol, dipropylene glycol, Polyethylene glycol, polypropylene glycol or polytetramethylene ether glycol); alicyclic diols having 6 to 24 carbon atoms (for example, 1,4-cyclohexanedimethanol or Hydrogenated bisphenol A, etc.); an alkylene oxide (hereinafter, “alkylene oxide” is abbreviated as “AO”) adduct (the number of added moles is 2 to 100) of Mn = 100 to 10,000 (for example, 1, 4-cyclohexanedimethanol EO 10 mol adduct, etc.); bisphenols having 15 to 30 carbon atoms (eg bisphenol A, bisphenol F or bisphenol S) AO [eg EO, propylene oxide (hereinafter abbreviated as “PO”) ) Or butylene oxide] The above-mentioned AO adduct (for example, EO of bisphenol A 2 to 4 mol of polyphenol (for example, catechol, hydroquinone, resorcin, etc.) having 12 to 24 carbon atoms or an adduct (number of added moles 2 to 100) Addenda Is a bisphenol A PO 2-4 mol adduct, etc.); weight average molecular weight (hereinafter abbreviated as “Mw”) = 100-5000 polylactone diol (eg, poly-ε-caprolactone diol, etc.); Mw = 1000-20000 Polybutadiene diol or the like is preferable. Among these, as the diol, alkylene glycol or an AO adduct of bisphenols is preferable, and a bisphenol AO adduct alone or a mixture of a bisphenol AO adduct and alkylene glycol is more preferable.

  The polyol having a valence of 3 to 8 or more is, for example, an aliphatic polyhydric alcohol having a valence of 3 to 8 or more and having 3 to 10 carbon atoms (for example, glycerin, trimethylolethane). , Trimethylolpropane, pentaerythritol, sorbitan, sorbitol, etc.); AO (2 to 4 carbon atoms) adduct (2 to 100 carbon atoms) of trisphenol having 25 to 50 carbon atoms (for example, trisphenol EO2 -4 mol adduct or trisphenol polyamide PO 2-4 mol adduct); n = 3-50 novolak resin (eg phenol novolak or cresol novolak) AO (carbon number 2-4) adduct (addition mol) Number 2-100) (eg phenol novolac PO 2 molar adduct or phenol) Lnovolak EO 4 mol adduct, etc.); AO (carbon number 2 to 4) adduct (addition mol number) of polyphenols having 6 to 30 carbon atoms (for example, pyrogallol, phloroglucinol or 1,2,4-benzenetriol) 2 to 100) (for example, pyrogallol EO 4 mole adduct); n = 20 to 2000 acrylic polyol {for example, monomer having hydroxyethyl (meth) acrylate and other polymerizable double bond [for example, styrene , (Meth) acrylic acid or a copolymer with (meth) acrylic acid ester, etc.]. Among these, as the polyol, an aliphatic polyhydric alcohol or an AO adduct of a novolak resin is preferable, and an AO adduct of a novolak resin is more preferable.

  The polycarboxylic acid is preferably, for example, a dicarboxylic acid or a polycarboxylic acid having a valence of 3 to 6 or more.

  The dicarboxylic acid is, for example, an alkanedicarboxylic acid having 4 to 32 carbon atoms (for example, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedicarboxylic acid or octadecanedicarboxylic acid); an alkenedicarboxylic acid having 4 to 32 carbon atoms Acids (eg maleic acid, fumaric acid, citraconic acid or mesaconic acid); branched alkenedicarboxylic acids having 8 to 40 carbon atoms [eg dimer acid or alkenyl succinic acid (eg dodecenyl succinic acid, pentadecenyl succinic acid) Acid or octadecenyl succinic acid etc.]]; branched alkanedicarboxylic acids having 12 to 40 carbon atoms [eg alkyl succinic acid (eg decyl succinic acid, dodecyl succinic acid or octadecyl succinic acid etc.) etc.]; carbon number Is an aromatic dicarbo of 8-20 Acid (e.g., phthalic acid, isophthalic acid, terephthalic acid or naphthalene dicarboxylic acid) is preferably in the like. Among these, as the dicarboxylic acid, alkene dicarboxylic acid or aromatic dicarboxylic acid is preferable, and aromatic dicarboxylic acid is more preferable.

  The polycarboxylic acid having a valence of 3 to 6 or more is preferably, for example, an aromatic polycarboxylic acid having 9 to 20 carbon atoms (for example, trimellitic acid or pyromellitic acid).

  The polycarboxylic acid anhydride may be a dicarboxylic acid anhydride or a polycarboxylic acid anhydride having a valence of 3 to 6 or more. An acid anhydride or pyromellitic acid anhydride is preferable.

  The lower alkyl ester of the polycarboxylic acid may be a lower alkyl ester of a dicarboxylic acid, or may be a lower alkyl ester of a polycarboxylic acid having a valence of 3 to 6 or more. For example, a methyl ester , Ethyl ester or isopropyl ester is preferable.

  The polyester resin preferably has crystallinity. By appropriately selecting a monomer constituting the polyester resin, the polyester resin exhibits crystallinity. The monomer constituting the polyester resin is preferably an aliphatic monomer, more preferably a linear alkyl skeleton having 4 or more carbon atoms, further preferably an aliphatic diol, and an aliphatic dicarboxylic acid. More preferably, the acid anhydride is an aliphatic dicarboxylic acid anhydride or a lower alkyl ester of an aliphatic dicarboxylic acid. Thereby, since the polyester resin tends to be linear, the polyester resin easily exhibits crystallinity. In addition, if the polyester resin expresses crystallinity, the monomer constituting the polyester resin may contain an aromatic dicarboxylic acid or an aromatic diol.

  As the aliphatic diol, ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,9-nonanediol, 1,10-decanediol, or the like is preferably used. Can do. A mixture of two or more of these can also be used.

  As the aliphatic dicarboxylic acid, an alkanedicarboxylic acid having 4 to 20 carbon atoms or an alkanedicarboxylic acid having 4 to 36 carbon atoms can be preferably used. For example, succinic acid, adipic acid, sebacic acid, maleic acid Or fumaric acid etc. can be used more suitably. A mixture of two or more of these can also be used. As the acid anhydride of the aliphatic dicarboxylic acid, for example, an acid anhydride such as succinic acid, adipic acid, sebacic acid, maleic acid or fumaric acid can be preferably used. A mixture of two or more of these can also be used. As the lower alkyl ester of the aliphatic dicarboxylic acid, for example, a lower alkyl ester such as succinic acid, adipic acid, sebacic acid, maleic acid or fumaric acid can be preferably used. A mixture of two or more of these can also be used.

  The compound used for the urethane modification of the polyester resin is preferably a compound containing an isocyanate group, more preferably containing two or more isocyanate groups in one molecule, and may be a chain aliphatic polyisocyanate. It may be a cycloaliphatic polyisocyanate. The chain aliphatic polyisocyanate includes, for example, ethylene diisocyanate; tetramethylene diisocyanate; hexamethylene diisocyanate (hereinafter abbreviated as “HDI”); dodecamethylene diisocyanate; 1,6,11-undecane triisocyanate; Lysine diisocyanate; 2,6-diisocyanatomethyl caproate; bis (2-isocyanatoethyl) fumarate; bis (2-isocyanatoethyl) carbonate; 2-isocyanatoethyl-2,6-di Isocyanatohexanoate; preferably a combination of two or more of these. Cycloaliphatic polyisocyanates include, for example, isophorone diisocyanate (hereinafter abbreviated as “IPDI”); dicyclohexylmethane-4,4′-diisocyanate (hydrogenated MDI); cyclohexylene diisocyanate; methylcyclohexylene diisocyanate (hydrogenated TDI). ); Bis (2-isocyanatoethyl) -4-cyclohexene-1,2-dicarboxylate; 2,5- or 2,6-norbornane diisocyanate; preferably a combination of two or more of these.

  The core resin may contain a urethane-modified polyester resin in which a component derived from a polyester resin is chain-chained with a compound containing an isocyanate group. Thereby, the fixability of the toner particles can be improved. In addition, it is possible to provide a liquid developer that hardly causes high temperature offset or document offset. Here, the component derived from a polyester resin means a portion obtained by removing a portion derived from an isocyanate group from a urethane-modified polyester resin.

  The compound used for urethane modification of the polyester resin preferably contains two or more isocyanate groups in one molecule, and may be a chain aliphatic polyisocyanate or a cyclic aliphatic polyisocyanate. . The chain aliphatic polyisocyanate includes, for example, ethylene diisocyanate; tetramethylene diisocyanate; hexamethylene diisocyanate (hereinafter abbreviated as “HDI”); dodecamethylene diisocyanate; 1,6,11-undecane triisocyanate; Lysine diisocyanate; 2,6-diisocyanatomethyl caproate; bis (2-isocyanatoethyl) fumarate; bis (2-isocyanatoethyl) carbonate; 2-isocyanatoethyl-2,6-di Isocyanatohexanoate; preferably a combination of two or more of these. Cycloaliphatic polyisocyanates include, for example, isophorone diisocyanate (hereinafter abbreviated as “IPDI”); dicyclohexylmethane-4,4′-diisocyanate (hydrogenated MDI); cyclohexylene diisocyanate; methylcyclohexylene diisocyanate (hydrogenated TDI); Bis (2-isocyanatoethyl) -4-cyclohexene-1,2-dicarboxylate; 2,5- or 2,6-norbornane diisocyanate; preferably a combination of two or more of these.

  The Mn of the core resin is preferably 1000 or more and 50000 or less. If the Mn of the core resin is less than 1000, the resin is too soft and may cause high temperature offset. On the other hand, if the Mn of the core resin exceeds 50000, the toner particles are difficult to melt at the time of fixing, which may lead to a decrease in fixing strength.

  It is preferable to appropriately adjust the Mn, melting point, Tg, and SP value of the core resin according to the use of the liquid developer. The Mn of the core resin is preferably 1000 or more and 50000 or less. For example, when the liquid developer according to this embodiment is used as a liquid developer used for electrophotography, electrostatic recording, electrostatic printing, or the like, the number average molecular weight of the core resin is preferably 10,000 to 50,000. The melting point of the core resin is preferably 30 to 80 ° C, and the Tg of the core resin is preferably 40 ° C or higher and more preferably 80 ° C or lower. If the Tg of the core resin is 80 ° C. or lower, fixing at a low temperature is possible.

  The Tg of the resin can be measured by the DSC method, or can be measured using a flow tester. In this specification, Tg of resin (including shell resin) is measured in accordance with a method prescribed in ASTM D3418-82 using a DSC apparatus (DSC20 manufactured by Seiko Instruments Inc.).

  In the present specification, crystallinity means the ratio (Tm / Ta) between the softening point of the resin (hereinafter abbreviated as “Tm”) and the maximum peak temperature of the heat of fusion of the resin (hereinafter abbreviated as “Ta”). It means that it is 0.8 or more and 1.55 or less, and the result of the calorific value change obtained by the DSC (Differential scanning calorimetry) method has a clear endothermic peak instead of showing a stepwise endothermic amount change. means. If the ratio of Tm to Ta (Tm / Ta) is greater than 1.55, it can be said that the resin is not excellent in crystallinity, and the resin is non-crystalline.

  Tm can be measured using a Koka flow tester (for example, CFT-500D manufactured by Shimadzu Corporation). Specifically, while a 1 g sample is heated at a heating rate of 6 ° C./min, a load of 1.96 MPa is applied to the sample by a plunger, and the sample is pushed out from a nozzle having a diameter of 1 mm and a length of 1 mm. Then, the relationship between “plunger descent amount (flow value)” and “temperature” is drawn on a graph. The temperature at which the plunger descending amount is ½ of the maximum value of the descending amount is read from the graph, and the value (temperature when half of the measurement sample is pushed out of the nozzle) is defined as Tm.

  Ta can be measured using a differential scanning calorimeter (for example, “DSC210” manufactured by Seiko Instruments Inc.). Specifically, first, a sample is pretreated. Specifically, after the sample is melted at 130 ° C., the temperature is lowered from 130 ° C. to 70 ° C. at a rate of 1.0 ° C./min, and then from 70 ° C. to 10 ° C. at a rate of 0.5 ° C./min. Let the temperature drop. Thereafter, the sample is heated at a rate of temperature increase of 20 ° C./min by DSC method to measure the endothermic change of the sample, and the relationship between “endothermic amount” and “temperature” is plotted on a graph. At this time, the temperature of the endothermic peak observed at 20 to 100 ° C. is Ta ′. When there are a plurality of endothermic peaks, the temperature of the peak with the largest endothermic amount is defined as Ta '. Then, the sample is stored at (Ta′-10) ° C. for 6 hours, and then stored at (Ta′-15) ° C. for 6 hours.

  When the pretreatment for the sample is completed, the sample subjected to the pretreatment is cooled to 0 ° C. at a temperature drop rate of 10 ° C./min by the DSC method, and then heated at a temperature rise rate of 20 ° C./min. The relationship between the “heat absorption / heat generation amount” and “temperature” is drawn on the graph from the change in heat absorption / exotherm thus measured. The temperature at which the endotherm takes the maximum value is taken as the maximum peak temperature (Ta) of heat of fusion.

  When the core resin contains a urethane-modified polyester resin, the urethane group concentration in the core resin is defined by (mass of urethane groups contained in the core resin) / (mass of the core resin) × 100, and GCMS (gas chromatograph mass) It can be measured using an analyzer. In the present specification, the urethane group concentration in the core resin is a value measured under the following conditions using GCMS after thermally decomposing the core resin under the following conditions. Specifically, the urethane group concentration in the core resin is calculated using the ratio of the ionic strength detected from the thermally decomposed core resin.

(Conditions for thermal decomposition of core resin)
Apparatus: PY-2020iD manufactured by Frontier Laboratories
Sample mass: 0.1 mg
Heating temperature: 550 ° C
Heating time: 0.5 minutes.

(Conditions for measuring urethane group concentration in core resin)
Apparatus: GCMS-QP2010 manufactured by Shimadzu Corporation
Column: UltraALLOY-5 manufactured by Frontier Laboratories (inner diameter: 0.25 mm, length: 30 m, thickness: 0.25 μm)
Temperature rising condition: Temperature rising range: 100 ° C to 320 ° C (held at 320 ° C)
Temperature increase rate: 20 ° C./min.

<Colorant>
The colorant in the present embodiment is preferably dispersed in a resin contained in the toner particles, and the particle size is preferably 0.3 μm or less. When the particle size of the colorant exceeds 0.3 μm, the dispersion of the colorant is deteriorated and the glossiness is lowered. As a result, it may be difficult to achieve a desired hue.

  As the colorant, known pigments and the like can be used without any particular limitation, but the following pigments are preferably used from the viewpoints of cost, light resistance and colorability. In terms of color composition, the following pigments are usually classified into black pigments, yellow pigments, magenta pigments and cyan pigments, and colors other than black (color images) are basically yellow pigments, magenta pigments and cyan pigments. It is toned by subtractive color mixing.

  The black pigment may be carbon black such as furnace black, channel black, acetylene black, thermal black or lamp black, carbon black derived from biomass, or magnetic powder such as magnetite or ferrite. It may be. The azine compound nigrosine which is a purple black dye can be used alone or in combination. Nigrosine includes C.I. I. Solvent Black 7 or C.I. I. One or two materials selected from the group consisting of Solvent Black 5 and the like can be used.

  Examples of magenta pigments or red pigments include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48; 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178 or C.I. I. Pigment Red 222 or the like is preferable.

  Examples of orange pigments or yellow pigments include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 180 or C.I. I. Pigment Yellow 185 or the like is preferable.

  Green pigments or cyan pigments are exemplified by C.I. I. Pigment blue 15, C.I. I. Pigment blue 15; 2, C.I. I. Pigment blue 15; 3, C.I. I. Pigment blue 15; 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. Pigment blue 62, C.I. I. Pigment blue 66 or C.I. I. Pigment Green 7 is preferable.

  The addition amount of the colorant is preferably 10% by mass or more and less than 50% by mass, and more preferably 13% by mass or more and less than 35% by mass with respect to the total solid content of the liquid developer. If the amount of the colorant added relative to the total solid content of the liquid developer is less than 10% by mass, sufficient coloring power may not be obtained. In addition, it may not be possible to prevent liquefaction of the resin by adding a colorant. Specifically, when the degree of crystallinity of the resin contained in the toner particles increases, the resin melts at a low temperature and thus is liable to be liquefied. However, when an appropriate amount of colorant is added, liquefaction is prevented by the filler effect. On the other hand, when the addition amount of the colorant with respect to the total solid content of the liquid developer exceeds 50% by mass, the filler effect becomes too large and it may be difficult to melt the resin. Note that the liquid developer according to the present exemplary embodiment may include only one of the colorants, or may include two or more of the colorants.

<Pigment dispersant>
The pigment dispersant has a function of uniformly dispersing the pigment in the toner particles, and preferably has basicity, for example. Whether or not the pigment dispersant has basicity can be examined according to the following method. 0.5 g of pigment dispersant and 20 ml of distilled water are placed in a glass screw tube, shaken for 30 minutes using a paint shaker, and then filtered to obtain the pH of the filtrate obtained by pH meter (Horiba Co., Ltd.). Measured using D-51) of the Seisakusho. If the measured pH is greater than 7, the pigment dispersant is basic. On the other hand, if the measured pH is less than 7, the pigment dispersant has acidity.

  When the pigment dispersant has basicity, the pigment dispersant preferably has a functional group such as an amino group, an amide group, a pyrrolidone group, an imine group, or a urethane group in the molecule. In addition, the dispersant usually corresponds to a so-called surfactant having a hydrophilic part and a hydrophobic part in the molecule, but various compounds are used as long as it has an action of dispersing the pigment as described above. Can do.

  A commercial product of such a pigment dispersant is, for example, “Ajisper PB-821” (trade name), “Ajisper PB-822” (trade name) or “Ajisper PB-881” (trade name) manufactured by Ajinomoto Fine Techno Co., Ltd. ), “Sol Sparse 28000” (trade name), “Sol Sparse 32000” (trade name), “Sol Sparse 32500” (trade name), “Sol Sparse 35100” (trade name) manufactured by Nippon Lubrizol Co., Ltd. “Solsperse 37500” (trade name) is preferred.

  The pigment dispersant is more preferably one that does not dissolve in the insulating liquid. For example, “Ajisper PB-821” (trade name) and “Ajisper PB-822” (trade name) manufactured by Ajinomoto Fine Techno Co., Ltd. Or “Ajisper PB-881” (trade name) is more preferable. When such a pigment dispersant is used, it is easy to obtain toner particles having a desired shape for unknown reasons.

  Such a pigment dispersant is preferably added in an amount of 1 to 100% by mass, more preferably 1 to 40% by mass, based on the pigment. If the added amount of the pigment dispersant is less than 1% by mass, the dispersibility of the pigment may be insufficient. Therefore, necessary ID (image density) may not be achieved. In addition, the fixability of toner particles may be reduced. On the other hand, when the added amount of the pigment dispersant exceeds 100% by mass, an amount of the pigment dispersant that is larger than the amount of the pigment dispersant necessary for dispersing the pigment is added. For this reason, excess pigment dispersant may be dissolved in the insulating liquid, which may adversely affect the chargeability or fixability of the toner particles. Such a pigment dispersant may be used individually by 1 type, and 2 or more types may be mixed and used for it.

<Insulating liquid>
The insulating liquid preferably has a resistance value that does not disturb the electrostatic latent image (about 10 ¹¹ to 10 ¹⁶ Ω · cm), and is preferably a solvent having low odor and toxicity. . From such a viewpoint, the insulating liquid is preferably an aliphatic hydrocarbon, an alicyclic hydrocarbon, an aromatic hydrocarbon, a halogenated hydrocarbon, or polysiloxane. In particular, from the viewpoints of low odor and toxicity and low cost, the insulating liquid is preferably a normal paraffin solvent or an isoparaffin solvent. For example, Moresco White (manufactured by MORESCO Co., Ltd.), Isopar M (ExxonMobil Corporation), Shellsol (Showa Shell Sekiyu Co., Ltd.), IP Solvent 1620 (Idemitsu Kosan Co., Ltd.), IP Solvent 2028 (Idemitsu Kosan Co., Ltd.) or IP Solvent 2835 (Idemitsu Kosan Co., Ltd.) ) Is preferable. Two or more of these may be mixed and used.

<Basic dispersant>
Unlike the pigment dispersant described above, the basic dispersant mainly has an action of dispersing toner particles in the insulating liquid. For this reason, the above-mentioned pigment dispersant is mainly contained in the toner particles, whereas the basic dispersant is present together with the toner particles mainly in the insulating liquid. Here, the basic dispersant is defined as follows. That is, 0.5 g of a dispersant and 20 ml of distilled water are placed in a glass screw tube, shaken for 30 minutes using a paint shaker, and then filtered to obtain a pH of a filtrate obtained by filtration. Measured using D-51) from Horiba Seisakusho, and the case where the pH is higher than 7 is defined as a basic dispersant. Such a basic dispersant has a basic functional group and an alkyl group having 8 or more carbon atoms. The functional group having basicity has an affinity for toner particles (for example, core resin) and is easily adsorbed on toner particles (for example, core resin). On the other hand, an alkyl group having 8 or more carbon atoms has an affinity for an insulating liquid. As described above, the basic dispersant has, in its molecule, a portion having affinity for the toner particles and a portion having affinity for the insulating liquid. Therefore, in the liquid developer containing such a basic dispersant, the toner particles are uniformly dispersed in the insulating liquid.

  The basic dispersant is a functional group having basicity in the molecule, amino group, amide group, pyrrolidone group, imine group, imino group, urethane group, quaternary ammonium group, ammonium group, pyridino group, pyridium group, It preferably has at least one of an imidazolino group and an imidazolium group. In addition, the basic dispersant may have at least one of an octyl group, a nonyl group, a decyl group, a phenyl group, a naphthyl group, a tetradecyl group, and the like in the molecule as an alkyl group having 8 or more carbon atoms. It may have a skeleton (polymerization degree of 4 or more) obtained by polymerizing alkenyl groups such as vinyl groups or allyl groups. Thus, the alkyl group having 8 or more carbon atoms may be linear, branched, or have a cyclic structure. The basic dispersant is preferably, for example, a polyalkylene polyamine, a modified polyurethane, or a polyester polyamine. As the basic dispersant, Disperbyk-109 (alkylol aminoamide) or Disperbyk-130 (unsaturated polycarboxylic acid polyaminoamide) manufactured by BYK Chemie may be used, or Solsperse manufactured by Nippon Lubrizol Corporation. 13940 (polyesteramine type), Solsperse 17000, Sosulfurase 18000, Solsperse 19000 (fatty acid amine type) or Solsperse 11200 (polyamide type) may be used, or ISP V-216, V-220 or W-660 ( Polyvinylpyrrolidone having a long chain alkyl group) may be used.

  The basic dispersant is preferably contained in an amount of 10 parts by mass or less, more preferably 3 parts by mass or less, and more preferably 0.5 parts by mass to 3 parts by mass with respect to 100 parts by mass of the toner particles. More preferably it is included. Even if the basic dispersant is contained in an amount exceeding 10 parts by mass with respect to 100 parts by mass of the toner particles, it may be difficult to further prevent aggregation of the toner particles. If the basic dispersant is contained in an amount of 3 parts by mass or less with respect to 100 parts by mass of the toner particles, the formation of toner particle aggregates can be reduced over time, and the conductivity of the toner particles can be reduced. Can be prevented. On the other hand, if the basic dispersant is contained in an amount of 0.5 parts by mass or more with respect to 100 parts by mass of the toner particles, the formation of toner particle aggregates can be reduced regardless of the passage of time. This will be described with reference to FIGS.

FIG. 1 is a graph showing the results of examining the relationship between the amount of basic dispersant and the degree of aggregation of toner particles, and FIG. 2 shows the relationship between the amount of basic dispersant and the surface potential of toner particles. It is a graph which shows the result. The horizontal axis “amount of the basic dispersant” in FIGS. 1 and 2 means the amount of the basic dispersant with respect to 100 parts by mass of the toner particles. The same applies to FIGS. 6 to 8 described later. The “degree of aggregation of toner particles” on the vertical axis in FIG. 1 is as shown in Table 1, and shows the result of visual observation of the liquid developer. This also applies to FIGS. 5, 7 and 8 described later. In FIG. 1, L11 indicates the result of the initial development, and L12 indicates the result of the endurance (end of development). In this specification, “initial development” means 3 minutes after the start of development, and “durability” or “end of development” means 3 hours after the start of development. The results shown in FIGS. 1 and 2 are obtained using a liquid developer containing 10 parts by mass of the shell resin with respect to 100 parts by mass of the toner particles and having a median diameter D ₅₀ of the toner particles of 1.2 μm. It was.

  As shown in FIG. 1, when the basic dispersant is contained in an amount of 0.5 parts by mass or more with respect to 100 parts by mass of the toner particles, the formation of toner particle aggregates can be reduced over time. did it. As shown in FIG. 2, when the basic dispersant is contained in an amount of 3 parts by mass or less with respect to 100 parts by mass of the toner particles, the surface potential of the toner particles can be kept high.

  The present inventors have intensively studied in completing the present invention. Below, the matter which the present inventors earnestly examined in completing this invention using FIGS. 3-8 is shown.

First, the present inventors aim to achieve both the prevention of aggregation of toner particles and the securing of chargeability of toner particles by optimizing the content of the shell resin instead of adding a basic dispersant. Thought. Specifically, the amount of the shell resin in 100 parts by mass of the core resin was changed, the median diameter D ₅₀ of the toner particles was measured, the surface potential of the toner particles was measured, and the degree of aggregation of the toner particles was examined. 3 to 5 are graphs showing the results of examining the relationship between the amount of the shell resin, the median diameter D _{50 of} the toner particles, the surface potential of the toner particles, and the degree of aggregation of the toner particles, respectively. The horizontal axis “amount of shell resin” in FIGS. 3 to 5 means the amount of shell resin in 100 parts by mass of toner particles. As shown in FIG. 3, if the shell resin is contained in an amount of 7 parts by mass or more with respect to 100 parts by mass of the core resin, the median diameter D ₅₀ of the toner particles can be made 1.5 μm or less, and the image noise is reduced. A high-quality image was obtained. Further, as shown in FIG. 4, even when the shell resin was contained in an amount of 7 parts by mass or more with respect to 100 parts by mass of the core resin, the surface potential of the toner particles could be kept high. However, as shown in FIG. 5, aggregation of toner particles occurred, and it was difficult to improve even if the content of the shell resin was increased.

  Next, the present inventors added a basic dispersant in place of the shell resin and examined the degree of aggregation of the toner particles. As a result, it was confirmed that the formation of toner particle aggregates was reduced. However, when the surface potential of the toner particles is measured by adding a basic dispersant instead of the shell resin, as shown in FIG. 6, if the amount of the basic dispersant is 5 parts by mass or more, the surface potential of the toner particles Was found to be unable to maintain high. FIG. 6 is a graph showing the results of examining the relationship between the amount of the basic dispersant and the surface potential of the toner particles.

  In addition, the present inventors manufactured a liquid developer by adding a basic dispersant to toner particles obtained by the pulverization method, and examined the degree of aggregation of the toner particles. 7 to 8 are graphs showing the results of examining the relationship between the amount of the basic dispersant and the degree of aggregation of the toner particles at the initial stage of development and at the end of development (late stage of development), respectively. As shown in FIG. 7, at the initial stage of development, the toner particles can be prevented from aggregating by adjusting the amount of the basic dispersant. However, as shown in FIG. 8, at the time of durability, even if the amount of the basic dispersant was adjusted, aggregation of toner particles could not be prevented. The following can be considered as this reason. The adsorbing power of the basic dispersant to the toner particles obtained by the pulverization method is weak. Therefore, even if the basic dispersant is adsorbed on the toner particles at the initial stage of development, it is released from the toner particles over a long period of use. As a result, the dispersibility of the toner particles was reduced, and the toner particles aggregated.

  However, the liquid developer contains toner particles including a core resin and a shell resin, and a basic dispersant, and the basic dispersant has a portion having affinity for the toner particles in the molecule; If it includes a portion having an affinity for the insulating liquid, it is possible to prevent aggregation of the toner particles regardless of the passage of time and to maintain the surface potential of the toner particles high. This is as described above and as shown in FIGS.

The method of measuring the median diameter D ₅₀ of the toner particles, the measuring method of the surface potential of the toner particles, and a method of examining the aggregation degree of toner particles is the same as the method described in Examples below both.

<Method for producing liquid developer>
FIG. 9 is a flowchart illustrating an example of a method for producing a liquid developer according to the present embodiment in the order of steps. The method for producing a liquid developer according to the present embodiment includes a toner particle production step S91 and a basic dispersant addition step S92.

<Toner particle production process>
In the toner particle production step S91, the toner particles are preferably manufactured based on a known method such as a granulation method. Examples of the granulation method include suspension polymerization method, emulsion polymerization method, fine particle aggregation method, method of adding a poor solvent to a resin solution for precipitation, spray drying method or core / shell structure with two different types of resins. The method of forming etc. are mentioned.

  The toner particles in this embodiment can be produced according to the following method. First, the core resin is dissolved in a good solvent to obtain a core resin solution. Next, the above-mentioned core resin solution is mixed with a poor solvent having a SP value different from that of the good solvent together with an interfacial tension adjusting agent to give shear, thereby forming droplets. Thereafter, the good solvent is volatilized to obtain toner particles. In this embodiment, a shell resin is used as the interfacial tension adjusting agent. Thereby, since the shell particles made of the shell resin can be coated on the surface of the core particles made of the core resin, toner particles that can be stably dispersed in the insulating liquid can be formed. If a surfactant or a dispersant is used as the interfacial tension adjusting agent, toner particles having high meltability and crystallinity can be obtained. Further, the particle diameter of toner particles or the shape of toner particles can be controlled by changing the way of applying shear, the difference in interfacial tension, or the interfacial tension adjusting agent (shell resin material).

<Adding step of basic dispersant>
In the basic dispersant addition step S92, a basic dispersant is added to the produced toner particles. As the basic dispersant, it is preferable to use the materials listed in the above <basic dispersant>. Further, as described in the above <basic dispersant>, the basic dispersant is preferably added in an amount of 10 parts by mass or less, more preferably 3 parts by mass or less, with respect to 100 parts by mass of the toner particles. More preferably, 0.5 parts by mass or more and 3 parts by mass or less are added. Thereby, the liquid developer according to the present embodiment can be manufactured.

<Image formation>
The configuration of an apparatus (image forming apparatus) for forming an image made of the liquid developer according to the present embodiment is not particularly limited. The image forming apparatus includes, for example, a single color image forming apparatus (see FIG. 10) in which a single color liquid developer is secondarily transferred to a sheet after primary transfer from the photoreceptor to the intermediate transfer body, and a single color liquid developer is transferred from the photoreceptor to the sheet. It is preferable that the image forming apparatus be directly transferred to the image forming apparatus or a multicolor image forming apparatus that forms a color image by superimposing a plurality of types of liquid developers.

  FIG. 10 is a schematic conceptual diagram of an electrophotographic image forming apparatus. The configuration of the image forming apparatus shown in FIG. 10 is shown below. The liquid developer 21 is pumped up from the developing tank 22 by the anilox roller 23. Excess liquid developer 21 on the anilox roller 23 is scraped off by the anilox regulating blade 24, and the remaining liquid developer 21 is sent to the transport roller 25. On the transport roller 25, the liquid developer 21 is adjusted so that the thickness is uniform and thin.

  The liquid developer 21 on the conveying roller 25 is sent to the developing roller 26. Excess liquid developer on the developing roller 26 is scraped off by the developing cleaning blade 27, and the remaining liquid developer 21 is charged by the developing charger 28 and developed on the photoconductor 29. Specifically, the surface of the photoconductor 29 is uniformly charged by the charging unit 30, and the exposure unit 31 disposed around the photoconductor 29 emits light based on predetermined image information on the surface of the photoconductor 29. Irradiate. As a result, an electrostatic latent image based on predetermined image information is formed on the surface of the photoreceptor 29. By developing the formed electrostatic latent image, a toner image is formed on the photoreceptor 29. The excess liquid developer on the photoconductor 29 is scraped off by the cleaning blade 32.

  The toner image formed on the photoreceptor 29 is primarily transferred to the intermediate transfer member 33 in the primary transfer unit 37, and the liquid developer transferred to the intermediate transfer member 33 is transferred to the recording medium 40 such as paper in the secondary transfer unit 38. Secondary transferred. The liquid developer transferred to the recording medium 40 is fixed by fixing rollers 36a and 36b. The liquid developer remaining on the intermediate transfer member 33 without being subjected to the secondary transfer is scraped off by the intermediate transfer member cleaning unit 34.

For example, development can be performed under the following conditions.
Surface of the photoconductor 29: Positively charged by the charging unit 30 Potential of the intermediate transfer member 33: −400V
Potential of secondary transfer roller 35: -1200V
Recording medium: OK Top Coat Plus (127 g / m ² manufactured by Oji Paper Co., Ltd.)
Amount of toner particles adhering to the recording medium: 2 g / m ²
Speed at which the recording medium passes through the fixing rollers 36a and 36b: 20 m / s
Temperature of fixing rollers 36a and 36b: 80 ° C.
Surface linear velocity (process speed) of the photoreceptor 29: 400 mm / s.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Production Example 1> [Production of dispersion of shell particles (W1)]
In a glass beaker, 100 parts by mass of 2-decyltetradecyl methacrylate, 30 parts by mass of methacrylic acid, 70 parts by mass of an equimolar reaction product of hydroxyethyl methacrylate and phenyl isocyanate, and 0.5% of azobismethoxydimethylvaleronitrile A part by mass was added and mixed by stirring at 20 ° C. Thereby, a monomer solution was obtained.

  Next, a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, a dropping funnel, a solvent removal device, and a nitrogen introduction tube was prepared. 195 parts by mass of THF was put into the reaction vessel, and the monomer solution was put into a dropping funnel provided in the reaction vessel. After the gas phase portion of the reaction vessel was replaced with nitrogen, the monomer solution was added dropwise to THF in the reaction vessel over 1 hour at 70 ° C. in a sealed state. Three hours after the completion of the dropwise addition of the monomer solution, a mixture of 0.05 parts by mass of azobismethoxydimethylvaleronitrile and 5 parts by mass of THF was placed in a reaction vessel, reacted at 70 ° C. for 3 hours, and then cooled to room temperature. . Thereby, a copolymer solution was obtained. THF was removed from the obtained copolymer solution to prepare a shell resin in a dry state. It was 53 degreeC when the glass transition point of shell resin was measured.

  400 parts by mass of the obtained copolymer solution was dropped into 600 parts by mass of IP solvent 2028 (made by Idemitsu Kosan Co., Ltd.) under stirring, and then THF was distilled off at 40 ° C. under a reduced pressure of 0.039 MPa. As a result, a dispersion (W1) of shell particles was obtained. When the volume average particle diameter of the shell particles in the dispersion liquid (W1) was measured using a laser type particle size distribution analyzer (“LA-920” manufactured by Horiba, Ltd.), it was 0.12 μm.

<Production Example 2> [Production of Basic Dispersant Solution]
200 parts by mass of Solsperse 11200 (manufactured by Nippon Lubrizol Corporation) was dissolved in 80 parts by mass of IP solvent 2028. Thereby, a solution for a basic dispersant was obtained.

<Production Example 3> [Production of core resin forming solution (Y1)]
A polyester resin (number average molecular weight: 5400) obtained from sebacic acid, adipic acid and ethylene glycol (molar ratio 0.8: 0.2: 1) in a reaction vessel equipped with a stirrer, a heating / cooling device and a thermometer. ) 970 parts by mass and 300 parts by mass of acetone were added and stirred to dissolve uniformly. To this solution, 30 parts by mass of isophorone diisocyanate (IPDI) was added and reacted at 80 ° C. for 6 hours. When the NCO value became 0, 28 parts by mass of terephthalic acid was added and reacted at 180 ° C. for 1 hour. This obtained core resin (b1). The number average molecular weight of the obtained core resin (b1) was 23000. 1000 parts by mass of the core resin (b1) and 1000 parts by mass of acetone were placed in a beaker and stirred to uniformly dissolve the core resin (b1) in acetone. Thus, a core resin forming solution (Y1) was obtained.

<Production Example 4>
A polyester resin (number average molecular weight: 2500) obtained from terephthalic acid and a bisphenol A propylene oxide adduct (molar ratio 1: 1) was obtained in a reaction vessel equipped with a stirrer, a heating / cooling device, and a thermometer.

<Production Example 5> (Production of Colorant Dispersion Liquid (P1))
In a beaker, 20 parts by mass of acid-treated copper phthalocyanine “FASTGEN Blue FDB-14” manufactured by DIC Corporation, 5 parts by mass of pigment dispersant “Ajisper PB-821” (manufactured by Ajinomoto Fine Techno Co., Ltd.) and 75 parts by mass of acetone The mixture was stirred and dispersed uniformly. Thereafter, copper phthalocyanine was finely dispersed by a bead mill. In this way, a colorant dispersion (P1) was obtained. When the volume average particle diameter of copper phthalocyanine in the colorant dispersion (P1) was measured using a laser type particle size distribution analyzer (“LA-920” manufactured by Horiba, Ltd.), it was 0.2 μm.

<Example 1>
A beaker was charged with 40 parts by mass of the core resin forming solution (Y1) and 20 parts by mass of the colorant dispersion (P1), and the mixture was stirred at 8000 rpm at 25 ° C. using a TK auto homomixer (manufactured by PRIMIX Corporation). . Thereby, a resin solution (Y11) in which the pigment was uniformly dispersed was obtained.

  In another beaker, 67 parts by mass of IP solvent 2028 (manufactured by Idemitsu Kosan Co., Ltd.) and 11 parts by mass of a dispersion of shell particles (W1) were added to uniformly disperse the shell particles. Next, 60 parts by mass of the resin solution (Y11) was added and stirred for 2 minutes while stirring at 10000 rpm using a TK auto homomixer at 25 ° C.

  The mixed solution thus obtained was placed in a reaction vessel equipped with a stirrer, a heating / cooling device, a thermometer, and a solvent removal device, and the temperature was raised to 35 ° C. Acetone was distilled off at 35 ° C. under a reduced pressure of 0.039 MPa until the acetone concentration in the above-mentioned mixed solution became 0.5% by mass or less. Thereafter, IP solvent 2028 was further added to adjust the solid content of the liquid developer to 20% by mass. In this way, a liquid developer was obtained. The solid content of the liquid developer means the solid content of the liquid developer corresponding to a portion obtained by removing the insulating liquid from the liquid developer, and corresponds to toner particles.

  A basic dispersant (“V216” manufactured by ISP (polyvinylpyrrolidone containing a long-chain alkyl group)) was added to the liquid developer. At this time, 0.6 parts by mass of a basic dispersant was added to 20 parts by mass of the solid content of the liquid developer. In this way, the liquid developer of Example 1 was obtained.

<Example 2>
A liquid developer of Example 2 was obtained according to the production method of Example 1 except that 1 part by weight of a basic dispersant was added to 20 parts by weight of the solid content of the liquid developer.

<Example 3>
A liquid developer of Example 3 was obtained according to the production method of Example 1 except that 0.1 part by weight of a basic dispersant was added to 20 parts by weight of the solid content of the liquid developer.

<Example 4>
A liquid developer of Example 4 was obtained according to the production method of Example 1 except that “Solsperse 13940 (solid content: 40%)” manufactured by Nippon Lubrizol Co., Ltd. was used as the basic dispersant. . Therefore, the effective addition amount of the basic dispersant is 1.2 parts by mass with respect to 100 parts by mass of the toner particles.

<Example 5>
A liquid developer of Example 5 was obtained according to the production method of Example 1 except that “V220” manufactured by ISP was used as the basic dispersant.

<Comparative Example 1>
A liquid developer of Comparative Example 1 was obtained according to the production method of Example 1 except that the basic dispersant (“V216” manufactured by ISP) was not added.

<Comparative example 2>
According to the production method of Example 1 except that an acidic dispersant (“Solsperse 3000” manufactured by Nippon Lubrizol Co., Ltd.) was used instead of the basic dispersant (“V216” manufactured by ISP). A liquid developer of Comparative Example 2 was obtained.

<Comparative Example 3>
Comparative example according to the production method of Comparative Example 1 except that 13 parts by mass of the basic dispersant solution of Production Example 2 was added instead of adding 11 parts by mass of the dispersion (W1) of shell particles. 3 liquid developer was obtained. In Comparative Example 3, the basic dispersant solution of Production Example 2 was contained in an amount of 25 parts by mass with respect to 100 parts by mass of the toner particles.

<Comparative example 4>
A comparative example according to the production method of Comparative Example 1 except that 4 parts by mass of the basic dispersant solution of Production Example 2 was added instead of adding 11 parts by mass of the dispersion (W1) of shell particles. 4 liquid developer was obtained. In Comparative Example 4, 7.5 parts by mass of the basic dispersant solution of Production Example 2 was included with respect to 100 parts by mass of the toner particles.

<Comparative Example 5>
100 parts by mass of the polyester resin obtained in Production Example 4 and 20 parts by mass of acid-treated copper phthalocyanine “FASTGEN Blue FDB-14” manufactured by DIC Corporation were mixed using a Henschel mixer (registered trademark). The obtained mixture was melt-mixed with a twin-screw extrusion kneader, cooled, then coarsely pulverized, and then finely pulverized to an average particle size of 6 μm with a jet pulverizer.

34 parts by mass of the obtained toner particles, 1 part by mass of a basic dispersant (“V216” manufactured by ISP), 100 parts by mass of IP solvent 1620 (manufactured by Idemitsu Kosan Co., Ltd.), and 100 parts by mass of zirconia beads Mix and stir in a sand mill for 120 hours. As a result, a liquid developer of Comparative Example 5 was obtained. The obtained toner particles had a median diameter D ₅₀ of 2.3 μm.

<Measurement of median diameter D ₅₀ >
First, 50 mg of each liquid developer of Examples 1 to 5 and Comparative Examples 1 to 5 was added to 20 g of IP solvent 2028 (flow solvent) containing 30 mg of S13940 (manufactured by Nippon Lubrizol Corporation, dispersant). After that, dispersion treatment was performed for about 5 minutes with an ultrasonic disperser “Ultrasonic Cleaner Model VS-150” (manufactured by Wellbo Clear). To obtain a sample for measuring the median diameter D ₅₀ in this way. Using a flow particle image analyzer (FPIA-3000S manufactured by Sysmex Corporation) to measure the median diameter D ₅₀ of the toner particles of the sample. The measurement result is shown as “D ₅₀ ” in Table 2. In Table 2, when D ₅₀ is 1.5 μm or less, it is written as A1, and when D ₅₀ is 2 μm, it is written as C1. If D ₅₀ is small, it can be said that the toner particles are excellent in granulation properties.

<Evaluation of degree of aggregation of toner particles>
The degree of aggregation of toner particles was evaluated using the image forming apparatus shown in FIG. Specifically, the liquid developer 21 was drawn up from the developing tank 22 by the anilox roller 23 and carried on the developing roller 26 via the conveying roller 25. The toner particles of the liquid developer 21 were charged by the development charger 28. At this time, the output of the development charger 28 was 3 μA / cm, and the conveyance speed of the recording medium 40 was 400 mm / s. The bias voltage is applied to +300 V so that the toner particles do not move on the photoconductor 29, and the liquid developer is recovered by the developing cleaning blade 27. The recovered liquid developer is visually observed to remove the toner particles. The degree of aggregation was examined. The result is shown in “Toner particle aggregation degree” in Table 2. In Table 2, “Initial” indicates the result of visual observation of the degree of aggregation of the toner particles in the liquid developer 3 minutes after the start of development. In “Endurance” or “End of development”, development is indicated. The result of visual observation of the degree of aggregation of toner particles in the liquid developer 3 hours after the start is shown. In Table 2, when the aggregation degree of the toner particles is 4 or more, it is indicated as A2, and when the aggregation degree of the toner particles is 3 or less, it is indicated as C2. The degree of aggregation of the toner particles is as shown in Table 1 above.

<Measurement of surface potential>
A surface potential meter was provided between the developing charger 28 and the photoconductor 29 to measure the surface potential of the toner particles on the developing roller 26. The amount of the liquid developer used for measuring the surface potential was 6 g / m ² . The liquid developer used for measuring the surface potential contained 20 parts by mass of toner particles and 80 parts by mass of an insulating liquid. The output of the development charger 28 was 0.5 μA / cm. The results are shown in “Surface potential” in Table 2. In Table 2, when the surface potential is 7.5V or more, it is written as A3, when the surface potential is 5V or more and less than 7.5V, it is written as B3, and when the surface potential is less than 5V, it is shown as C3. It is written. If the surface potential is large, it can be said that the toner particles are excellent in chargeability.

  As shown in Table 2, in Examples 1 to 5, it was found that the toner particles are excellent in granulation property and chargeability and hardly aggregate regardless of the passage of time.

  On the other hand, in Comparative Example 1, the toner particles aggregated even in the initial development stage. The reason is considered that the liquid developer of Comparative Example 1 does not contain a basic dispersant.

  Also in Comparative Example 2, the toner particles aggregated even in the early stage of development. The reason is considered that the liquid developer of Comparative Example 2 contains an acidic dispersant but does not contain a basic dispersant.

  In Comparative Example 3, the toner particles were not excellent in granulation property and chargeability and aggregated at the end of development. The reason for this is considered that the liquid developer of Comparative Example 3 contains a basic dispersant instead of the shell resin.

In Comparative Example 4, since the median diameter D ₅₀ of the toner particles was too large, the evaluation of the degree of aggregation of the toner particles and the measurement of the surface potential were not performed. The reason is the median diameter D ₅₀ of the toner particles was too large, the liquid developer of Comparative Example 4 is considered to be only contain a small amount of a basic dispersant in place of the shell resin.

  In Comparative Example 5, the toner particles were not excellent in granulation properties and aggregated at the end of development. The reason may be that the toner particles of Comparative Example 5 were produced by a pulverization method.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  21 liquid developer, 22 developing tank, 23 anilox roller, 24 anilox regulating blade, 25 transport roller, 26 developing roller, 27 developing cleaning blade, 28 developing charger, 29 photoconductor, 30 charging unit, 31 exposing unit, 32 cleaning blade , 33 Intermediate transfer member, 34 Intermediate transfer member cleaning unit, 35 Secondary transfer roller, 36a, 36b Fixing roller, 37 Primary transfer unit, 38 Secondary transfer unit, 40 Recording medium.

Claims (4)

Including toner particles, an insulating liquid and a basic dispersant;
The toner particles include a resin and a colorant,
The resin includes a core resin and a shell resin,
The basic dispersant is a liquid developer having an alkyl group having 8 or more carbon atoms.   The basic dispersant includes an amine group, an amino group, an amide group, a pyrrolidone group, an imine group, an imino group, a urethane group, a quaternary ammonium group, an ammonium group, a pyridino group, a pyridium group, an imidazolino group, and an imidazo group. The liquid developer according to claim 1, wherein the liquid developer contains any of a lithium group.   The liquid developer according to claim 1, comprising the basic dispersant in an amount of 3 parts by mass or less with respect to 100 parts by mass of the toner particles. A method for producing a liquid developer according to any one of claims 1 to 3,
A first step of producing the toner particles;
And a second step of adding the basic dispersant to the toner particles.

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