JP5867096B2 - Liquid developer, process cartridge, image forming apparatus, and image forming method - Google Patents

Description

  The present invention relates to a liquid developer, a process cartridge, an image forming apparatus, and an image forming method.

Various developers and methods for producing the developers for use in electrophotographic image forming apparatuses have been proposed.
For example, Patent Document 1 discloses a spherical polymer toner having an average particle size of 5 μm or less, and a binder resin containing styrene and alkyl methacrylate (wherein alkyl is within the range of 1 to 4 carbon atoms). There is disclosed an electrophotographic toner comprising a polymer, wherein the molar fraction of styrene in the copolymer is in the range of 0.5 to 0.7.
Patent Document 2 discloses a liquid developer obtained by dispersing toner particles in which particles having an average volume particle diameter of 0.5 μm to 3 μm formed by suspension polymerization are coated with an external additive layer in an insulating liquid. The external additive was formed by stirring and coating in a mixed dispersion containing the toner particle main body and the external additive while maintaining the temperature of the dispersion higher than the glass transition temperature of the toner particle main body. A liquid developer is disclosed.
Patent Document 3 includes a step of preparing an aqueous dispersion in which a dispersoid composed of a material containing a resin material is dispersed in an aqueous dispersion medium composed of an aqueous liquid, and spraying the aqueous dispersion. There is disclosed a method for producing a liquid developer, comprising the step of directly dispersing toner particles obtained by removing the aqueous dispersion medium in the insulating liquid.

JP 7-43941 A Japanese Patent Laid-Open No. 4-16863 JP 2006-195099 A

  An object of the present invention is to provide a liquid developer containing toner particles having a small particle size and a narrow particle size distribution.

In order to achieve the above object, the following invention is provided.
The invention according to claim 1 is a carrier liquid and toner particles dispersed in the carrier liquid and containing a colorant and a binder resin, wherein the binder resin includes a styrene thermoplastic elastomer and styrene- (meta ) Acrylic resin, and the styrene- (meth) acrylic resin includes at least a styrene / butyl acrylate / methyl methacrylate copolymer having a composition ratio derived from methyl methacrylate of 5% by mass or more and 20% by mass or less. And a liquid developer containing toner particles.
The invention according to claim 2 is the liquid developer according to claim 1, wherein the composition ratio derived from styrene in the styrene / butyl acrylate / methyl methacrylate copolymer is 60% by mass or more and 80% by mass or less.
The invention according to claim 3 is the liquid developer according to claim 1 or 2, wherein the content of the styrenic thermoplastic elastomer with respect to the binder resin is 5% by mass or more and 30% by mass or less.
In a fourth aspect of the present invention, the content of the styrene / butyl acrylate / methyl methacrylate copolymer with respect to the binder resin is 40% by mass or more and 80% by mass or less. The liquid developer according to one item.
The invention according to claim 5 is the liquid developer according to any one of claims 1 to 4, wherein the carrier liquid is an insulating liquid mainly composed of an aliphatic hydrocarbon.
The invention of claim 6 contains the liquid developer according to any one of claims 1 to 5 and converts the electrostatic latent image formed on the surface of the electrostatic latent image holding member into the liquid developer. A process cartridge that includes a developing unit that forms a toner image by developing the toner cartridge, and is detachable from the image forming apparatus.
According to a seventh aspect of the present invention, there is provided an electrostatic latent image holding member, a charging unit for charging the surface of the electrostatic latent image holding member, and an electrostatic for forming an electrostatic latent image on the surface of the electrostatic latent image holding member. A latent image forming unit and the liquid developer according to any one of claims 1 to 5 are housed, and the electrostatic latent image formed on the surface of the electrostatic latent image holding member is formed by the liquid developer. An image forming apparatus comprising: a developing unit that develops a toner image; a transfer unit that transfers the toner image to a recording medium; and a fixing unit that fixes the toner image on the recording medium.
The invention of claim 8 includes a charging step of charging the surface of the electrostatic latent image holding member, an electrostatic latent image forming step of forming an electrostatic latent image on the surface of the electrostatic latent image holding member, and the electrostatic A developing step of developing the electrostatic latent image formed on the surface of the latent image holding body with the liquid developer according to any one of claims 1 to 5 to form a toner image; and An image forming method including a transfer step of transferring to a recording medium and a fixing step of fixing the toner image on the recording medium.

According to the first aspect of the present invention, the binder resin for the toner particles includes a styrene-based thermoplastic elastomer and a styrene- (meth) acrylic resin, and the styrene- (meth) acrylic resin is derived from methyl methacrylate. A liquid developer containing toner particles having a small particle size and a narrow particle size distribution compared to a case where the styrene / butyl acrylate / methyl methacrylate copolymer having a ratio of 5% by mass to 20% by mass is not included. Provided.
According to the invention of claim 2, the toner has a small particle size and a narrow particle size distribution compared to the case where the composition ratio derived from styrene in the styrene / butyl acrylate / methyl methacrylate copolymer is outside the above range. A liquid developer containing particles is provided.
According to the invention of claim 3, the liquid development including toner particles having a small particle size and a narrow particle size distribution as compared with the case where the content of the styrenic thermoplastic elastomer with respect to the binder resin is out of the above range. An agent is provided.
According to invention of Claim 4, compared with the case where content of the said styrene / butyl acrylate / methyl methacrylate copolymer with respect to the said binder resin is outside the said range, a particle size is small and particle size distribution is A liquid developer containing narrow toner particles is provided.
According to the invention of claim 5, the carrier liquid contains toner particles having a small particle size and a narrow particle size distribution as compared with the case where the carrier liquid is not an insulating liquid mainly composed of aliphatic hydrocarbons, and has a dispersibility. A good liquid developer is provided.
According to the sixth, seventh, and eighth aspects of the present invention, a styrene-based thermoplastic elastomer and a styrene- (meta) are used as the binder resin for the toner particles on the electrostatic latent image holding member having the electrostatic latent image formed on the surface. ) A liquid which contains an acrylic resin and does not contain a styrene / butyl acrylate / methyl methacrylate copolymer having a composition ratio derived from methyl methacrylate of 5% by mass or more and 20% by mass or less as the styrene- (meth) acrylic resin. A process cartridge, an image forming apparatus, and an image forming method capable of obtaining a high-definition image as compared with the case where a toner image is formed by developing with a developer are provided.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an exemplary embodiment.

  Hereinafter, the present embodiment will be described with reference to the accompanying drawings as appropriate.

<Liquid developer>
The liquid developer according to the exemplary embodiment includes a carrier liquid and toner particles dispersed in the carrier liquid and including a colorant and a binder resin. The binder resin includes a styrene thermoplastic elastomer and a styrene- A styrene / butyl acrylate / methyl methacrylate copolymer containing a (meth) acrylic resin and having a composition ratio derived from methyl methacrylate of 5% by mass or more and 20% by mass or less as the styrene- (meth) acrylic resin. Toner particles.

  Here, “(meth) acryl” means either or both of acrylic and methacrylic. The “styrene / butyl acrylate / methyl methacrylate copolymer” means a copolymer synthesized using styrene, butyl acrylate, and methyl methacrylate. Hereinafter, the styrene- (meth) acrylic resin containing a styrene / butyl acrylate / methyl methacrylate copolymer having a composition ratio derived from methyl methacrylate of 5% by mass or more and 20% by mass or less is referred to as “specific styrene- (meta ) Acrylic resin ”.

The reason for including toner particles having a small particle size and a narrow particle size distribution by the above configuration is not clear, but is presumed as follows.
The method for producing the liquid developer according to the present embodiment is not limited. For example, when toner particles are produced by a kneading and pulverizing method, a styrene thermoplastic elastomer and a styrene- (meth) acrylic resin are kneaded. It is thought that they are not mixed evenly but mixed in stripes. When this kneaded product is pulverized, it is peeled off into a scaly shape to form particles. However, by including the specific styrene / butyl acrylate / methyl methacrylate copolymer as a styrene- (meth) acrylic resin, there is a variation in particle size. It is thought to be suppressed.
Hereinafter, the components of the liquid developer according to this embodiment will be described in detail.

[Toner particles]
The toner particles contained in the liquid developer according to the exemplary embodiment include a colorant and a binder resin, and the binder resin includes a styrene-based thermoplastic elastomer and a styrene- (meth) acrylic resin, and a styrene- (meth) acrylic. The resin contains at least a styrene / butyl acrylate / methyl methacrylate copolymer having a composition ratio derived from methyl methacrylate of 5% by mass or more and 20% by mass or less.

-Styrenic thermoplastic elastomer-
Examples of the styrenic thermoplastic elastomer contained in the toner particles of the present embodiment include block copolymers of styrene and (di) olefins, random copolymers, etc., which have rubber characteristics at room temperature, but at high temperatures. Like thermoplastics, it is a softening material.
For example, polystyrene-polybutadiene-polystyrene, polystyrene-polybutadiene / butylene-polystyrene, polystyrene-polyethylene / butylene-polystyrene, polystyrene-polyisoprene-polystyrene, polystyrene-hydrogenated polybutadiene-polystyrene, polystyrene-hydrogenated polyisoprene-polystyrene, polystyrene- In hydrogenated poly (isoprene / butadiene) -polystyrene and styrene-butadiene block copolymers, double bonds remain in the form of 1-4 and 1-2 bonds, but hydrogenated ones are used. May be. Furthermore, you may use the block copolymer which introduce | transduced the polar group into the soft segment part pinched | interposed between polystyrene. In the examples of the copolymer, before and after being separated by “−” means a block polymer, and before and after being separated by “/”, it may be random or may be a block.
Examples of commercially available products include Asahi Kasei's Tuftec M1911, Tuftec M1943, Tuftec MP10, Asaprene T439, Tufplen A, Tufplen 125, and Kuraray's DYNARON 8630P. In particular, SOE-L611, SOE-L605 (trade name) manufactured by Asahi Kasei Co., Ltd., in which a soft segment portion sandwiched between polystyrenes is introduced with a polar group and hydrogenated, are preferably used.

  The content of the styrenic thermoplastic elastomer in the toner particles is preferably 5% by mass or more and 30% by mass or less, and more preferably 10% by mass or more and 25% by mass or less with respect to the total binder resin. If the content of the styrenic thermoplastic elastomer with respect to the total binder resin is 10% by mass or more and 25% by mass or less, the kneaded product with the styrene- (meth) acrylic resin has good grindability and has a narrow particle size distribution. It is easy to obtain toner particles having.

-Styrene- (meth) acrylic resin-
Examples of the styrene- (meth) acrylic resin contained in the toner particles of the present embodiment include a vinyl copolymer containing a styrene monomer and a (meth) acrylic acid ester monomer as constituent units. At least a styrene / butyl acrylate / methyl methacrylate copolymer having a composition ratio derived from methyl methacrylate of 5% by mass or more and 20% by mass or less is included. If the composition ratio derived from methyl methacrylate in the styrene / butyl acrylate / methyl methacrylate copolymer is 5% by mass or more and 20% by mass or less, preferable pulverization characteristics are exhibited, the particle size is small, and the particle size distribution is narrow. It is easy to obtain toner particles.

  The composition ratio derived from styrene in the styrene / butyl acrylate / methyl methacrylate copolymer is desirably 60% by mass or more and 80% by mass or less. If the composition ratio derived from styrene in the styrene / butyl acrylate / methyl methacrylate copolymer is 60% by mass or more and 80% by mass or less, the toner particles exhibit preferable pulverization characteristics, have a small particle size, and a narrow particle size distribution. It is easy to obtain.

  Examples of the styrene monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, and pn-butyl. Styrene, p-ter-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-dodecyl styrene, p-methoxy styrene, p-phenyl styrene, p-chloro styrene, 3,4-di And chlorostyrene.

  Examples of the (meth) acrylic acid ester monomer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, and (meth) acrylic. In addition to alkyl esters of (meth) acrylic acid such as isobutyl acid, n-octyl (meth) acrylate, dodecyl (meth) acrylate, 2-ethylhexyl acrylate, stearyl (meth) acrylate, 2-chloroethyl acrylate, Phenyl (meth) acrylate, methyl α-chloroacrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, glycidyl (meth) acrylate , Dimethylaminoethyl (meth) acrylate, diethylamino (meth) acrylate Ethyl, bisglycidyl methacrylate, polyethylene glycol di (meth) acrylate, etc. (meth) acryloxyethyl phosphate. Among these, methyl methacrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl acrylate and the like are preferably used.

In addition to the specific styrene- (meth) acrylic resin, as other vinyl monomers, acrylic acid such as acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, and α- or β-alkyl derivatives thereof; Unsaturated dicarboxylic acids such as fumaric acid, maleic acid, citraconic acid, itaconic acid, and monoester derivatives or diester derivatives thereof; use succinic acid mono (meth) acryloyloxyethyl ester, (meth) acrylonitrile, (meth) acrylamide, etc. May be. As the monomer, a crosslinkable monomer having two or more double bonds may be used as necessary.
Examples of the crosslinkable monomer include aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene, ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butanediol diacrylate, and 1,5-pentanediol diester. Acrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyoxyethylene (2) -2,2-bis (4-hydroxyphenyl) ) Diacrylate compounds such as propanediacrylate, polyoxyethylene (4) -2,2-bis (4-hydroxyphenyl) propanediacrylate, and methacrylates thereof Compounds, pentaerythritol triacrylate, trimethylolethane triacrylate, trimethylolpropane triacrylate, polyfunctional crosslinking monomers and their methacrylate compounds such as tetramethylolmethane tetraacrylate, and the like.

The vinyl polymer preferably has a weight average molecular weight (Mw) of 150,000 to 500,000. When the Mw of the vinyl polymer is 150,000 or more, the scratch resistance is surely improved. When the Mw is 500,000 or less, the melt viscosity is kept low and the smoothness of the fixing surface is obtained. Sex is expressed.
The molecular weight distribution (Mw / Mn) of the vinyl polymer is preferably 2 or more and 20 or less. When the molecular weight distribution (Mw / Mn) of the vinyl polymer is 2 or more, the viscosity in the high temperature region is prevented from being reduced and the offset resistance is inhibited, and when it is 20 or less, the fixability is lowered. Is suppressed.
The vinyl polymer may have a plurality of peaks and shoulders in the molecular weight distribution measured by gel permeation chromatography (GPC).

  The content of the styrene / butyl acrylate / methyl methacrylate copolymer in the toner particles is preferably 40% by mass or more and 80% by mass or less with respect to the total binder resin from the viewpoint of grindability. If the content of the styrene / butyl acrylate / methyl methacrylate copolymer is 40% by mass or more and 80% by mass or less, preferable pulverizability is exhibited, and toner particles having a small particle size and a narrow particle size distribution are obtained. easy.

-Colorant-
As the colorant, a known pigment or dye is used. Specifically, the following yellow, magenta, cyan, and black pigments are used.

As yellow pigments, compounds represented by condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complex compounds, methine compounds, and allylamide compounds are used.
As magenta pigments, condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds are used.
As cyan pigments, copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, basic dye lake compounds, and the like are used.
As the black pigment, carbon black, aniline black, acetylene black, iron black and the like are used.

-Other ingredients-
The toner particles of the present embodiment include, in addition to a styrene thermoplastic elastomer, a styrene- (meth) acrylic resin, and a colorant, if necessary, other binder resins, waxes, charge control agents, silica powders, metal oxides It may contain other additives such as products. These additives may be internally added by kneading into a binder resin containing a styrene-based thermoplastic elastomer and a styrene- (meth) acrylic resin, or after being mixed with a toner obtained as particles. And may be externally added.

  As the binder resin other than the styrene-based thermoplastic elastomer and the styrene- (meth) acrylic resin contained in the toner particles, known binder resins can be mentioned. Examples thereof include polyester, polyethylene, polypropylene, polyurethane, epoxy resin, silicone resin, polyamide, and modified rosin.

  The wax is not particularly limited. For example, plant wax such as carnauba wax, wood wax, rice bran wax; animal wax such as beeswax, insect wax, whale wax, wool wax; mineral wax such as montan wax, ozokerite, etc. , Synthetic fatty acid solid ester waxes such as Fischer-Tropsch wax (FT wax) having ester in the side chain, special fatty acid ester, polyhydric alcohol ester; paraffin wax, polyethylene wax, polypropylene wax, polytetrafluoroethylene wax, polyamide wax, and And synthetic waxes such as silicone compounds. Only one type of wax may be used, or two or more types of wax may be used.

  There is no restriction | limiting in particular as a charge control agent, A conventionally well-known charge control agent is used. For example, positively chargeable charge control agents such as nigrosine dye, fatty acid-modified nigrosine dye, carboxyl group-containing fatty acid-modified nigrosine dye, quaternary ammonium salt, amine compound, amide compound, imide compound, organometallic compound; oxycarboxylic acid And a negatively chargeable charge control agent such as a metal complex of an azo compound, a metal complex salt dye, or a salicylic acid derivative. Only one type of charge control agent may be used, or two or more types may be used.

  The metal oxide is not particularly limited, and examples thereof include titanium oxide, aluminum oxide, magnesium oxide, zinc oxide, strontium titanate, barium titanate, magnesium titanate, and calcium titanate. Only one type of metal oxide may be used, or two or more types may be used.

-Toner Particle Manufacturing Method-
The method for producing the toner particles of this embodiment is not particularly limited. For example, the toner particles can be obtained by pulverizing a pulverized toner, a liquid emulsion-dried toner, or a toner produced by a polymerized toner production method in a carrier liquid.
For example, a styrenic thermoplastic elastomer, a binder resin containing a specific styrene- (meth) acrylic resin, a colorant, and if necessary, other additives are added to a mixing device such as a Henschel mixer and mixed. The mixture was melt-kneaded with a twin screw extruder, Banbury mixer, roll mill, kneader, etc., then cooled with a drum flaker, etc., coarsely pulverized with a pulverizer such as a hammer mill, and further pulverized with a pulverizer such as a jet mill Thereafter, pulverized toner is obtained by classification using an air classifier or the like.
In addition, a binder resin containing a styrene-based thermoplastic elastomer and a specific styrene- (meth) acrylic resin, a colorant, and if necessary, other additives are dissolved in a solvent such as ethyl acetate and dispersed like calcium carbonate. After emulsifying / suspending in water to which a stabilizer has been added and removing the solvent, the particles obtained by removing the dispersion stabilizer are filtered and dried to obtain an emulsion-dried toner in liquid.
In addition, a polymerizable monomer, a colorant, and a polymerization initiator (for example, benzoyl peroxide, lauroyl peroxide, isopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, A composition containing methyl ethyl ketone peroxide, etc.) and other additives is added to the aqueous phase under stirring and granulated. After the polymerization reaction, the particles are filtered and dried to obtain a polymerized toner.

  The blending ratio of each material (styrene-based thermoplastic elastomer, specific styrene- (meth) acrylic resin, colorant, other additives, etc.) for obtaining the toner is styrene-based thermoplastic elastomer and styrene- (meth) acrylic. A styrene- (meth) acrylic resin containing a resin, which is at least a styrene / butyl acrylate / methyl methacrylate copolymer having a composition ratio derived from methyl methacrylate of 5% by mass or more and 20% by mass or less, preferably The styrene-based thermoplastic elastomer and the styrene- (meth) acrylic resin with respect to the binder resin are blended so that the respective contents are within the above-described ranges.

  The obtained toner is finely pulverized in a carrier liquid using a known pulverization apparatus such as a ball mill, a bead mill, a high-pressure wet atomization apparatus or the like, whereby the toner particles for liquid developer of the present embodiment are obtained.

The cumulative volume particle diameter D50v of the toner particles is desirably 0.5 μm or more and 5.0 μm or less. By being in the said range, adhesive force is high and developability is improved. In addition, the resolution of the image can be improved. The cumulative volume particle diameter D50v of the toner particles is more preferably 1.0 μm or more and 5.0 μm or less.
The volume average particle size distribution index (GSDv) = (D84v / D16v) ^1/2 of the toner particles is desirably 2.5 or less from the viewpoint of obtaining a high-definition image. From the viewpoint of obtaining a higher definition image, the GSDv of the toner particles is preferably 1.5 or less.

The cumulative volume particle size D50v, number average particle size distribution index (GSDp), volume average particle size distribution index (GSDv), etc. of the toner particles are measured using a laser diffraction / scattering type particle size distribution measuring device, for example, LA920 (manufactured by Horiba, Ltd.). Measured. For the particle size range (channel) divided based on the particle size distribution, a cumulative distribution is drawn from the small diameter side for each volume and number, and the cumulative particle size D16v, the cumulative number particle size D16p, The particle size that is 50% cumulative is defined as cumulative volume particle size D50v and cumulative number particle size D50p, and the particle size that is 84% cumulative is defined as cumulative volume particle size D84v and cumulative number particle size D84p. Using these, the volume average particle size distribution index (GSDv) is calculated as (D84v / D16v) ^1/2 and the number average particle size distribution index (GSDp) is calculated as (D84p / D16p) ^1/2 .

[Carrier liquid]
The carrier liquid is an insulating liquid for dispersing the toner particles, and is not particularly limited. For example, an aliphatic hydrocarbon solvent such as paraffin oil (a commercially available product, Moresco White MT-manufactured by Matsumura Oil Co., Ltd.). 30P, Moresco White P40, Moresco White P70, Exxon Chemical Co. Isopar L, Isopar M, etc., hydrocarbon solvents such as naphthenic oils (exon products are Exxon Chemical Exxol D80, Exol D110, Exol D130) , Nippon Petrochemical Co., Ltd., Naphthezol L, Naphthezol M, Naphthezol H, New Naphthezol 160, New Naphthezol 200, New Naphthezol 220, New Naphthezol MS-20P, etc.), and aromatic compounds such as toluene are included in them. You may make it contain.

Only one type of carrier liquid may be included in the liquid developer of this embodiment, or two or more types may be used. When the carrier liquid is used as a mixed system of two or more kinds, for example, a mixed system of paraffinic solvent and vegetable oil, a mixed system of silicone solvent and vegetable oil, and a mixed system of paraffinic solvent and vegetable oil are used. It is desirable to be.
The carrier liquid used in this embodiment is preferably an insulating liquid mainly composed of aliphatic hydrocarbons, and is desirably composed mainly of paraffin oil. Here, the “main component” is the most abundant component among the components constituting the carrier liquid, and is preferably 50% by volume or more. Paraffin oil has a high affinity with styrene-based thermoplastic elastomer and styrene- (meth) acrylic resin contained in toner particles. By using a carrier liquid containing paraffin oil as a main component, pulverization characteristics and dispersion of toner particles are achieved. Is more reliably improved.

  The carrier liquid is made of various auxiliary materials such as dispersants, emulsifiers, surfactants, stabilizers, wetting agents, thickeners, foaming agents, antifoaming agents, coagulants, gelling agents, anti-settling agents, charging agents. It may contain a control agent, an antistatic agent, an anti-aging agent, a softening agent, a plasticizer, a filler, a flavoring agent, an anti-tacking agent, a release agent and the like.

[Method for producing liquid developer]
The liquid developer according to the exemplary embodiment is prepared by mixing the toner particles and the carrier liquid described above using a dispersing machine such as a ball mill, a sand mill, an attritor, or a bead mill, and pulverizing the toner particles in the carrier liquid. It is obtained by dispersing in
The dispersion of the toner particles in the carrier liquid is not limited to a disperser, and may be dispersed by rotating a special stirring blade at a high speed like a mixer, or by the shearing force of a rotor / stator known as a homogenizer. Alternatively, it may be dispersed by ultrasonic waves.

  The concentration of the toner particles in the carrier liquid may be in the range of 0.5% by mass or more and 40% by mass or less from the viewpoint of controlling the viscosity of the developer appropriately and facilitating the circulation of the developer in the developing machine. Desirably, it is more desirable to set it as the range of 1 to 30 mass%.

  Thereafter, the obtained dispersion liquid may be filtered using, for example, a membrane filter having a pore diameter of 100 μm to remove dust and coarse particles.

By the above method, the binder resin includes a styrene-based thermoplastic elastomer and a styrene- (meth) acrylic resin, and at least the composition ratio derived from methyl methacrylate is 5% by mass or more and 20% by mass as the styrene- (meth) acrylic resin. % Styrene / butyl acrylate / methyl methacrylate copolymer, the average particle diameter D50v is 1.0 μm or more and 5.0 μm or less, and GSDv = (D84v / D16v) ^1/2 is 2.5 or less. A liquid developer in which the toner particles are dispersed in a carrier liquid is obtained.

<Process cartridge, image forming apparatus>
The image forming apparatus according to the present embodiment includes an electrostatic latent image holding member (hereinafter sometimes referred to as “photosensitive member”), a charging unit that charges the surface of the electrostatic latent image holding member, and the electrostatic latent image. The electrostatic latent image forming means for forming an electrostatic latent image on the surface of the holding body and the liquid developer according to the above embodiment are housed, and the electrostatic latent image formed on the surface of the electrostatic latent image holding body is Developing means for developing with a liquid developer to form a toner image, transfer means for transferring the toner image to a recording medium, and fixing means for fixing the toner image to the recording medium.

In the image forming apparatus, for example, the portion including the developing unit may be a cartridge structure (process cartridge) that is detachable from the main body of the image forming apparatus. The process cartridge includes a developing unit that stores the liquid developer according to the above-described embodiment, and develops the electrostatic latent image formed on the surface of the electrostatic latent image holding member with the liquid developer to form a toner image. A process cartridge that is provided and is detachable from the image forming apparatus is preferably used.
Hereinafter, an image forming apparatus using a liquid developer in the present embodiment will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present exemplary embodiment. The image forming apparatus 100 includes a photosensitive member (electrostatic latent image holding member) 10, a charging device (charging unit) 20, an exposure device (electrostatic latent image forming unit) 12, a developing device (developing unit) 14, an intermediate transfer member ( The image forming apparatus includes a transfer unit 16, a cleaner 18, and a transfer fixing roller (transfer unit) 28. The photosensitive member 10 has a cylindrical shape, and a charging device 20, an exposure device 12, a developing device 14, an intermediate transfer member 16, and a cleaner 18 are sequentially provided on the outer periphery of the photosensitive member 10.
The operation of the image forming apparatus 100 will be briefly described below.

The charging device 20 charges the surface of the photoconductor 10 to a predetermined potential, and based on the image signal, the exposure device 12 exposes the charged surface with, for example, a laser beam to form an electrostatic latent image.
The developing device 14 includes a developing roller 14a and a developer storage container 14b. The developing roller 14a is provided such that a part thereof is immersed in the liquid developer 24 stored in the developer storage container 14b. The liquid developer 24 includes an insulating carrier liquid, a styrenic thermoplastic elastomer and a styrene- (meth) acrylic resin as a colorant and a binder resin, and at least methyl methacrylate as the styrene- (meth) acrylic resin. It has toner particles containing a styrene / butyl acrylate / methyl methacrylate copolymer having a composition ratio derived from 5% by mass to 20% by mass.

  In the liquid developer 24, the toner particles are dispersed. For example, the liquid developer 24 is further stirred by a stirring member provided in the developer container 14b. Variation in the position of the density of the toner is reduced. Thus, the liquid developer 24 with reduced toner particle density variation is supplied to the developing roller 14a rotating in the direction of arrow A in the figure.

  The liquid developer 24 supplied to the developing roller 14a is conveyed to the photoconductor 10 in a state where the liquid supply 24 is limited to a constant supply amount by the regulating member, and at a position where the developing roller 14a and the photoconductor 10 are close (or in contact). It is supplied to the electrostatic latent image. As a result, the electrostatic latent image is visualized and becomes a toner image 26.

  The toner image 26 developed on the surface of the photoconductor 10 is conveyed by the photoconductor 10 rotating in the direction of arrow B in the figure and transferred to the paper (recording medium) 30. In this embodiment, the toner image 26 is transferred to the paper 30. Before transfer, the toner image is transferred to the intermediate transfer member 16 in order to improve the transfer efficiency to the recording medium including the separation efficiency of the toner image from the photoconductor 10 and to fix the toner image simultaneously with the transfer to the recording medium. To do. At this time, a peripheral speed difference may be provided between the photosensitive member 10 and the intermediate transfer member 16.

Next, the toner image conveyed in the direction of the arrow C by the intermediate transfer member 16 is transferred and fixed to the paper 30 at the contact position with the transfer fixing roller 28.
The transfer fixing roller 28 sandwiches the paper 30 together with the intermediate transfer member 16, and causes the toner image on the intermediate transfer member 16 to be in close contact with the paper 30. As a result, the toner image is transferred to the paper 30, and the toner image is fixed on the paper to form a fixed image 29. The fixing of the toner image is preferably performed by applying a heating element to the transfer fixing roller 28 and applying pressure and heating. The fixing temperature is usually 120 ° C. or higher and 200 ° C. or lower.

  If the intermediate transfer member 16 has a roller shape as shown in FIG. 1, it forms a roller pair with the transfer fixing roller 28. Therefore, the intermediate transfer member 16 and the transfer fixing roller 28 are respectively used as a fixing roller and a pressure roller in the fixing device. It has a conforming structure and exhibits a fixing function. That is, when the sheet 30 passes through the nip, the toner image is transferred and is heated and pressed against the intermediate transfer member 16 by the transfer fixing roller 28. As a result, the binder resin in the toner particles constituting the toner image is softened, and the toner image is infiltrated into the fibers of the paper 30 to form a fixed image 29 on the paper 30.

  In this embodiment, fixing is performed simultaneously with the transfer to the paper 30. However, the transfer process and the fixing process may be performed separately, and the fixing may be performed after the transfer. In this case, the transfer roller for transferring the toner image from the photoconductor 10 has a function according to the intermediate transfer body 16.

On the other hand, in the photoconductor 10 in which the toner image 26 is transferred to the intermediate transfer body 16, untransferred toner particles remaining on the photoconductor are conveyed to a contact position with the cleaner 18 and collected by the cleaner 18. If the transfer efficiency is close to 100% and residual toner does not cause a problem, the cleaner 18 need not be provided.
Further, the image forming apparatus 100 may further include a static elimination device (not shown) that neutralizes the surface of the photoconductor 10 after the transfer and before the next charging.
The charging device 20, the exposure device 12, the developing device 14, the intermediate transfer member 16, the transfer fixing roller 28, and the cleaner 18 provided in the image forming apparatus 100 are all operated in synchronization with the rotation speed of the photosensitive member 10. Yes.
By forming an image on the recording medium 30 such as paper using the image forming apparatus 100 having such a configuration, a high-definition image can be obtained.

  Hereinafter, although an example is given and it demonstrates more concretely, the following example does not restrict | limit this invention.

[Example 1]
(Synthesis of styrene / butyl acrylate / methyl methacrylate copolymer (I))
Styrene: 70 parts by mass, butyl acrylate: 20 parts by mass, and methyl methacrylate: 10 parts by mass were dissolved in methyl ethyl ketone: 100 parts by mass. After nitrogen substitution, the mixture was heated to 65 ° C., 2 parts by mass of dimethyl 2,2′-azobis (2-methylpropionate) was added, and the mixture was gently stirred at the same temperature for 24 hours.
After completion of the reaction, the solvent and unreacted monomer were distilled off under reduced pressure, and the resulting residue was dissolved in 200 parts by mass of toluene and poured into 1000 parts by mass of methanol while stirring. The obtained insoluble material was filtered off and dried under reduced pressure to obtain the desired styrene / butyl acrylate / methyl methacrylate copolymer (I).

(Preparation of liquid developer (cyan))
A cyan pigment C.I. was added to 60 parts by mass of a styrene-butyl methacrylate copolymer (manufactured by Kao Corporation). I. 40 parts by mass of Pigment Blue 15: 3 (manufactured by Clariant Co., Ltd.) was added and kneaded with a pressure kneader. The kneaded product was coarsely pulverized to prepare a cyan pigment master batch.

Next, a mixture having the following composition was kneaded with a pressure kneader.
Styrene / butyl acrylate / methyl methacrylate copolymer (I): 55 parts by mass Styrene-butadiene block copolymer (Tufprene A manufactured by Asahi Kasei): 20 parts by mass Cyan pigment master batch: 25 parts by mass

After coarsely pulverizing the obtained kneaded material with a sample mill, a mixture of 15 parts by mass of the obtained coarse powder and 85 parts by mass of white oil (Moleco White MT-30P manufactured by Matsumura Oil Co., Ltd.) was mixed with a ball mill. The liquid developer was obtained by grinding for a period of time.
The particle size distribution of the toner particles in the liquid developer was measured by a diffraction / scattering type particle size distribution measuring device (LA-920 manufactured by Horiba, Ltd.). The average particle size (volume-based median diameter D50v) was 3.3 μm, GSDv = (D84v / D16v) ^1/2 : 1.46.

[Example 2]
(Preparation of liquid developer (magenta))
40 parts by mass of magenta pigment PR122 (manufactured by Clariant) was added to 60 parts by mass of a styrene-butyl methacrylate copolymer (manufactured by Kao Corporation), and kneaded with a pressure kneader. The kneaded product was coarsely pulverized to prepare a magenta pigment master batch.

Next, a mixture having the following composition was kneaded with a pressure kneader.
Styrene / butyl acrylate / methyl methacrylate copolymer (I): 42.5 parts by mass Styrene-butadiene block copolymer (Tufprene 125 manufactured by Asahi Kasei): 20 parts by mass The magenta pigment masterbatch: 37.5 parts by mass

After the obtained kneaded material was coarsely pulverized with a sample mill, a mixture of 15 parts by mass of the obtained coarse powder and 85 parts by mass of white oil (Moleco White MT-30P manufactured by Matsumura Oil Co., Ltd.) was mixed with a ball mill. The liquid developer was obtained by grinding for a period of time.
When the particle size distribution of the toner particles in this liquid developer was measured by a diffraction / scattering type particle size distribution measuring device (LA-920 manufactured by Horiba, Ltd.), the average particle size (volume-based median diameter D50v) was 3.5 μm, GSDv = (D84v / D16v) ^1/2 : 1.53.

Example 3
(Preparation of liquid developer (black))
40 parts by mass of carbon black pigment # 25B (manufactured by Mitsubishi Chemical Corporation) was added to 60 parts by mass of a styrene-butyl methacrylate copolymer (manufactured by Kao Corporation), and kneaded with a pressure kneader. The kneaded product was coarsely pulverized to prepare a carbon black pigment master batch.

(Preparation of liquid developer (black))
Next, a mixture having the following composition was kneaded with a pressure kneader.
Styrene / butyl acrylate / methyl methacrylate copolymer (I): 42.5 parts by mass Styrene-butadiene block copolymer (Tufprene 125 manufactured by Asahi Kasei): 20 parts by mass The above carbon black pigment master batch: 37.5 parts by mass Part

After coarsely pulverizing the obtained kneaded material with a sample mill, a mixture of 15 parts by mass of the obtained coarse powder and 85 parts by mass of white oil (Moleco White MT-30P manufactured by Matsumura Oil Co., Ltd.) was mixed with a ball mill. The liquid developer was obtained by grinding for a period of time.
The particle size distribution of the toner particles in the liquid developer was measured by a diffraction / scattering type particle size distribution measuring device (LA-920 manufactured by Horiba, Ltd.). The average particle size (volume-based median diameter D50v) was 2.8 μm, GSDv = (D84v / D16v) ^1/2 : 1.59.

Example 4
(Synthesis of styrene / butyl acrylate / methyl methacrylate copolymer (II))
Styrene: 60 parts by mass, butyl acrylate: 20 parts by mass, and methyl methacrylate: 20 parts by mass were dissolved in methyl ethyl ketone: 100 parts by mass, purged with nitrogen, heated to 65 ° C., and dimethyl 2,2′-azobis ( 2-Methylpropionate): 2 parts by mass were added, and stirring was continued gently at the same temperature for 24 hours.
After completion of the reaction, the solvent and unreacted monomer were distilled off under reduced pressure, and the resulting residue was dissolved in 200 parts by mass of toluene and poured into 1000 parts by mass of methanol while stirring. The obtained insoluble matter was separated by filtration and dried under reduced pressure to obtain the desired styrene-butyl methacrylate copolymer (II).

(Preparation of liquid developer (black))
A mixture having the following composition was kneaded with a pressure kneader.
Styrene / butyl acrylate / methyl methacrylate copolymer (II): 55 parts by mass Styrene-butadiene block copolymer (SOE-L605 manufactured by Asahi Kasei): 20 parts by mass Carbon black pigment master batch (produced in Example 3) Thing): 25 parts by mass

After coarsely pulverizing the obtained kneaded material with a sample mill, a mixture of 15 parts by mass of the obtained coarse powder and 85 parts by mass of white oil (Moleco White MT-30P manufactured by Matsumura Oil Co., Ltd.) was mixed with a ball mill. The liquid developer was obtained by grinding for a period of time.
The particle size distribution of the toner particles in the liquid developer was measured by a diffraction / scattering type particle size distribution measuring device (LA-920 manufactured by Horiba, Ltd.). The average particle size (volume-based median diameter D50v) was 2.8 μm, GSDv = (D84v / D16v) ^1/2 : 1.43.

Example 5
(Preparation of liquid developer (yellow))
40 parts by mass of yellow pigment PY185 (manufactured by Clariant) was added to 60 parts by mass of a styrene-butyl methacrylate copolymer (manufactured by Kao Corporation), and kneaded with a pressure kneader. This kneaded product was coarsely pulverized to produce a yellow pigment master batch.

Next, a mixture having the following composition was kneaded with a pressure kneader.
Styrene / butyl acrylate / methyl methacrylate copolymer (II): 55 parts by mass Styrene-butadiene block copolymer (SOE-L605 manufactured by Asahi Kasei): 20 parts by mass The above-mentioned yellow pigment master batch: 25 parts by mass

After coarsely pulverizing the obtained kneaded material with a sample mill, a mixture of 15 parts by mass of the obtained coarse powder and 85 parts by mass of white oil (Moleco White MT-30P manufactured by Matsumura Oil Co., Ltd.) was mixed with a ball mill. The liquid developer was obtained by grinding for a period of time.
When the particle size distribution of the toner particles in the liquid developer was measured by a diffraction / scattering type particle size distribution measuring apparatus (LA-920 manufactured by Horiba, Ltd.), the average particle diameter (volume-based median diameter D50v) was 4.2 μm, GSDv = (D84v / D16v) ^1/2 : 1.40.

Example 6
(Preparation of liquid developer (cyan))
A mixture having the following composition was kneaded with a pressure kneader.
Styrene / butyl acrylate / methyl methacrylate copolymer (II): 55 parts by mass Styrene-butadiene block copolymer (SOE-L611 manufactured by Asahi Kasei): 20 parts by mass Cyan pigment master batch (produced in Example 1) ): 25 parts by mass

After coarsely pulverizing the obtained kneaded material with a sample mill, a mixture of 15 parts by mass of the obtained coarse powder and 85 parts by mass of white oil (Moleco White MT-30P manufactured by Matsumura Oil Co., Ltd.) was mixed with a ball mill. The liquid developer was obtained by grinding for a period of time.
When the particle size distribution of the toner particles in the liquid developer was measured by a diffraction / scattering type particle size distribution measuring device (LA-920 manufactured by Horiba, Ltd.), the average particle size (volume-based median diameter D50v) was 3.6 μm, GSDv = (D84v / D16v) ^1/2 : 1.50.

Example 7
(Synthesis of styrene / butyl acrylate / methyl methacrylate copolymer (III))
Styrene: 75 parts by mass, butyl acrylate: 20 parts by mass, and methyl methacrylate: 5 parts by mass were dissolved in methyl ethyl ketone: 100 parts by mass, purged with nitrogen, heated to 65 ° C., and dimethyl 2,2′-azobis ( 2-Methylpropionate): 2 parts by mass were added, and stirring was continued gently at the same temperature for 24 hours.
After completion of the reaction, the solvent and unreacted monomer were distilled off under reduced pressure, and the resulting residue was dissolved in 200 parts by mass of toluene and poured into 1000 parts by mass of methanol while stirring. The obtained insoluble material was filtered off and dried under reduced pressure to obtain the desired styrene / butyl acrylate / methyl methacrylate copolymer (III).

(Preparation of liquid developer (cyan))
A mixture having the following composition was kneaded with a pressure kneader.
Styrene / butyl acrylate / methyl methacrylate copolymer (III): 55 parts by mass Styrene-butadiene block copolymer (SOE-L611 manufactured by Asahi Kasei): 20 parts by mass Cyan pigment master batch (produced in Example 1) ): 25 parts by mass

After coarsely pulverizing the obtained kneaded material with a sample mill, a mixture of 15 parts by mass of the obtained coarse powder and 85 parts by mass of white oil (Moleco White MT-30P manufactured by Matsumura Oil Co., Ltd.) was mixed with a ball mill. The liquid developer was obtained by grinding for a period of time.
When the particle size distribution of the toner particles in the liquid developer was measured by a diffraction / scattering type particle size distribution measuring apparatus (LA-920 manufactured by Horiba, Ltd.), the average particle diameter (volume-based median diameter D50v) was 2.4 μm, GSDv = (D84v / D16v) ^1/2 : 1.59.

Example 8
(Preparation of liquid developer (magenta))
A mixture having the following composition was kneaded with a pressure kneader.
Styrene / butyl acrylate / methyl methacrylate copolymer (III): 42.5 parts by mass Styrene-butadiene block copolymer (SOE-L605 manufactured by Asahi Kasei): 20 parts by mass Magenta pigment master batch (produced in Example 2) 37.5 parts by mass

After coarsely pulverizing the obtained kneaded material with a sample mill, a mixture of 15 parts by mass of the obtained coarse powder and 85 parts by mass of white oil (Moleco White MT-30P manufactured by Matsumura Oil Co., Ltd.) was mixed with a ball mill. The liquid developer was obtained by grinding for a period of time.
When the particle size distribution of the toner particles in the liquid developer was measured by a diffraction / scattering type particle size distribution measuring device (LA-920 manufactured by Horiba, Ltd.), the average particle size (volume-based median diameter D50v) was 3.4 μm, GSDv = (D84v / D16v) ^1/2 : 1.55.

[Comparative Example 1]
A mixture having the following composition was kneaded with a pressure kneader.
Styrene-butyl methacrylate copolymer (average molecular weight 320,000, acid value 10 manufactured by Fujikura Kasei Co., Ltd.): 55 parts by mass Styrene-butadiene block copolymer (Tufprene 125 manufactured by Asahi Kasei): 20 parts by mass Cyan pigment master Batch (made in Example 1): 25 parts by mass

After coarsely pulverizing the obtained kneaded material with a sample mill, a mixture of 15 parts by mass of the obtained coarse powder and 85 parts by mass of white oil (Moleco White MT-30P manufactured by Matsumura Oil Co., Ltd.) was mixed with a ball mill. The liquid developer was obtained by grinding for a period of time.
The particle size distribution of the toner particles in the liquid developer was measured by a diffraction / scattering type particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.). The average particle size (volume basis; median diameter D50v) 1.5 μm, GSDv = (D84v / D16v) ^1/2 : 3.0.

[Comparative Example 2]
(Synthesis of styrene / butyl acrylate copolymer (IV))
Styrene: 82 parts by mass, butyl acrylate: 18 parts by mass in methyl ethyl ketone: 100 parts by mass, and after nitrogen substitution, the mixture was heated to 65 ° C. and dimethyl 2,2′-azobis (2-methylpropionate): 2 parts by mass were added and the stirring was continued gently for 24 hours at the same temperature.
After completion of the reaction, the solvent and unreacted monomer were distilled off under reduced pressure, and the resulting residue was dissolved in 200 parts by mass of toluene and poured into 1000 parts by mass of methanol while stirring. The obtained insoluble matter was separated by filtration and dried under reduced pressure to obtain the desired styrene-butyl acrylate copolymer (IV).

(Preparation of liquid developer (cyan))
A mixture having the following composition was kneaded with a pressure kneader.
Styrene-butyl acrylate copolymer (IV): 55 parts by mass Styrene-butadiene block copolymer (Tufprene A manufactured by Asahi Kasei): 20 parts by mass Cyan pigment master batch (prepared in Example 1): 25 parts by mass Part

After coarsely pulverizing the obtained kneaded material with a sample mill, a mixture of 15 parts by mass of the obtained coarse powder and 85 parts by mass of white oil (Moleco White MT-30P manufactured by Matsumura Oil Co., Ltd.) was mixed with a ball mill. The liquid developer was obtained by grinding for a period of time.
When the particle size distribution of the toner particles in the liquid developer was measured by a diffraction / scattering type particle size distribution measuring device (LA-920 manufactured by Horiba, Ltd.), the average particle size (volume basis; median diameter D50v) 20 μm, GSDv = ( D84v / D16v) ^1/2 : 5.0.

[Comparative Example 3]
(Synthesis of styrene / butyl acrylate / methyl methacrylate copolymer (V))
Styrene: 50 parts by mass, butyl acrylate: 20 parts by mass, methyl methacrylate: 30 parts by mass are dissolved in methyl ethyl ketone: 100 parts by mass, and after nitrogen substitution, the mixture is heated to 65 ° C. and dimethyl 2,2′-azobis (2 -Methylpropionate): 2 parts by mass were added, and stirring was continued gently at the same temperature for 24 hours.
After completion of the reaction, the solvent and unreacted monomer were distilled off under reduced pressure, and the resulting residue was dissolved in 200 parts by mass of toluene and poured into 1000 parts by mass of methanol while stirring. The obtained insoluble matter was separated by filtration and dried under reduced pressure to obtain the desired styrene-butyl acrylate-methyl methacrylate copolymer (V).

(Preparation of liquid developer (cyan))
A mixture having the following composition was kneaded with a pressure kneader.
Styrene-butyl acrylate-methyl methacrylate copolymer (V): 55 parts by mass Styrene-butadiene block copolymer (Tufprene A manufactured by Asahi Kasei): 20 parts by mass Cyan pigment master batch (produced in Example 1) : 25 parts by mass

After roughly kneading the obtained kneaded material with a sample mill, a mixture of 15 parts by mass of the obtained coarse powder and 85 parts by mass of white oil (Moleco White P-40 manufactured by Matsumura Oil Co., Ltd.) was mixed with a ball mill. The liquid developer was obtained by grinding for a period of time.
When the particle size distribution of the toner particles in the liquid developer was measured by a diffraction / scattering type particle size distribution measuring apparatus (LA-920 manufactured by Horiba, Ltd.), the average particle size (volume basis; median diameter D50v) 13 μm, GSDv = ( D84v / D16v) ^1/2 : 1.70.

[Comparative Example 4]
(Synthesis of styrene / butyl acrylate / methyl methacrylate copolymer (VI))
Styrene: 80 parts by mass, butyl acrylate: 17 parts by mass, and methyl methacrylate 3 parts by mass were dissolved in methyl ethyl ketone: 100 parts by mass. After nitrogen substitution, the mixture was heated to 65 ° C. and dimethyl 2,2′-azobis (2- Methyl propionate): 2 parts by mass was added and stirring was continued gently at the same temperature for 24 hours.
After completion of the reaction, the solvent and unreacted monomer were distilled off under reduced pressure, and the resulting residue was dissolved in 200 parts by mass of toluene and poured into 1000 parts by mass of methanol while stirring. The obtained insoluble matter was separated by filtration and dried under reduced pressure to obtain the desired styrene-butyl acrylate-methyl methacrylate copolymer (VI).

(Preparation of liquid developer (cyan))
A mixture having the following composition was kneaded with a pressure kneader.
Styrene-butyl acrylate-methyl methacrylate copolymer (VI): 55 parts by mass Styrene-butadiene block copolymer (SOE-L605 manufactured by Asahi Kasei): 20 parts by mass Cyan pigment master batch (produced in Example 1) ): 25 parts by mass

After coarsely pulverizing the obtained kneaded material with a sample mill, a mixture of 15 parts by mass of the obtained coarse powder and 85 parts by mass of white oil (Moleco White MT-30P manufactured by Matsumura Oil Co., Ltd.) was mixed with a ball mill. The liquid developer was obtained by grinding for a period of time.
The particle size distribution of the toner particles in this liquid developer was measured by a diffraction / scattering type particle size distribution measuring device (LA-920, manufactured by Horiba, Ltd.). The average particle size (volume basis; median diameter D50v) 8.5 μm, GSDv = (D84v / D16v) ^1/2 : 3.8.

[Comparative Example 5]
(Synthesis of styrene / butyl acrylate / methyl methacrylate copolymer (VII))
Styrene: 70 parts by mass, butyl acrylate: 5 parts by mass, and methyl methacrylate 25 parts by mass are dissolved in methyl ethyl ketone: 100 parts by mass, and after nitrogen substitution, the mixture is heated to 65 ° C. and dimethyl 2,2′-azobis (2- Methyl propionate): 2 parts by mass was added and stirring was continued gently at the same temperature for 24 hours.
After completion of the reaction, the solvent and unreacted monomer were distilled off under reduced pressure, and the resulting residue was dissolved in 200 parts by mass of toluene and poured into 1000 parts by mass of methanol while stirring. The obtained insoluble matter was separated by filtration and dried under reduced pressure to obtain the desired styrene-butyl acrylate-methyl methacrylate copolymer (VII).

(Preparation of liquid developer (cyan))
A mixture having the following composition was kneaded with a pressure kneader.
Styrene-butyl acrylate-methyl methacrylate copolymer (VII): 55 parts by mass Styrene-butadiene block copolymer (SOE-L605 manufactured by Asahi Kasei): 20 parts by mass Cyan pigment master batch (produced in Example 1) ): 25 parts by mass

After coarsely pulverizing the obtained kneaded material with a sample mill, a mixture of 15 parts by mass of the obtained coarse powder and 85 parts by mass of white oil (Moleco White MT-30P manufactured by Matsumura Oil Co., Ltd.) was mixed with a ball mill. The liquid developer was obtained by grinding for a period of time.
The particle size distribution of the toner particles in the liquid developer was measured by a diffraction / scattering particle size distribution measuring device (LA-920, manufactured by Horiba, Ltd.). The average particle size (volume basis; median diameter D50v) 6.7 μm, GSDv = (D84v / D16v) ^1/2 : 2.0.

Example 9
(Synthesis of styrene / butyl acrylate / methyl methacrylate copolymer (VIII))
Styrene: 85 parts by mass, butyl acrylate: 5 parts by mass, and methyl methacrylate 10 parts by mass are dissolved in methyl ethyl ketone: 100 parts by mass. After nitrogen substitution, the mixture is heated to 65 ° C. and dimethyl 2,2′-azobis (2- Methyl propionate): 2 parts by mass was added and stirring was continued gently at the same temperature for 24 hours.
After completion of the reaction, the solvent and unreacted monomer were distilled off under reduced pressure, and the resulting residue was dissolved in 200 parts by mass of toluene and poured into 1000 parts by mass of methanol while stirring. The obtained insoluble matter was separated by filtration and dried under reduced pressure to obtain the desired styrene-butyl acrylate-methyl methacrylate copolymer (VIII).

(Preparation of liquid developer (cyan))
A mixture having the following composition was kneaded with a pressure kneader.
Styrene-butyl acrylate-methyl methacrylate copolymer (VIII): 55 parts by mass Styrene-butadiene block copolymer (SOE-L605 manufactured by Asahi Kasei): 20 parts by mass Cyan pigment master batch (produced in Example 1) ): 25 parts by mass

After coarsely pulverizing the obtained kneaded material with a sample mill, a mixture of 15 parts by mass of the obtained coarse powder and 85 parts by mass of white oil (Moleco White MT-30P manufactured by Matsumura Oil Co., Ltd.) was mixed with a ball mill. The liquid developer was obtained by grinding for a period of time.
The particle size distribution of the toner particles in the liquid developer was measured with a diffraction / scattering particle size distribution measuring device (LA-920, manufactured by Horiba, Ltd.). The average particle size (volume basis; median diameter D50v) 4.8 μm, GSDv = (D84v / D16v) ^1/2 : 2.2.

Example 10
(Preparation of liquid developer (cyan))
A mixture having the following composition was kneaded with a pressure kneader.
Styrene / butyl acrylate / methyl methacrylate copolymer (I): 30 parts by mass Styrene-butyl methacrylate copolymer (average molecular weight 320,000, acid value 10 manufactured by Fujikura Kasei Co., Ltd.): 25 parts by mass Block copolymer (Tufprene A manufactured by Asahi Kasei): 20 parts by massCyan pigment master batch (prepared in Example 1): 25 parts by mass

After coarsely pulverizing the obtained kneaded material with a sample mill, a mixture of 15 parts by mass of the obtained coarse powder and 85 parts by mass of white oil (Moleco White MT-30P manufactured by Matsumura Oil Co., Ltd.) was mixed with a ball mill. The liquid developer was obtained by grinding for a period of time.
When the particle size distribution of the toner particles in the liquid developer was measured by a diffraction / scattering type particle size distribution measuring apparatus (LA-920 manufactured by Horiba, Ltd.), the average particle diameter (volume-based median diameter D50v) was 2.4 μm, GSDv = (D84v / D16v) ^1/2 : 2.5.

10 Photoconductor (electrostatic latent image holder)
12 Exposure device (electrostatic latent image forming means)
14 Developing device (Developing means)
16 Intermediate transfer body 18 Cleaner 20 Charging device (charging means)
22 Electrostatic latent image 24 Liquid developer 26 Toner image 28 Transfer fixing roller (transfer means)
29 fixed image 30 recording medium 100 image forming apparatus

Claims (8)

Carrier liquid,
Toner particles dispersed in the carrier liquid and containing a colorant and a binder resin, wherein the binder resin contains a styrene-based thermoplastic elastomer and a styrene- (meth) acrylic resin, and the styrene- (meth) As an acrylic resin, at least toner particles containing a styrene / butyl acrylate / methyl methacrylate copolymer having a composition ratio derived from methyl methacrylate of 5% by mass or more and 20% by mass or less;
A liquid developer comprising:   The liquid developer according to claim 1, wherein a composition ratio derived from styrene in the styrene / butyl acrylate / methyl methacrylate copolymer is 60% by mass or more and 80% by mass or less.   3. The liquid developer according to claim 1, wherein a content of the styrenic thermoplastic elastomer with respect to the binder resin is 5% by mass or more and 30% by mass or less.   The liquid developer according to any one of claims 1 to 3, wherein a content of the styrene / butyl acrylate / methyl methacrylate copolymer with respect to the binder resin is 40% by mass or more and 80% by mass or less. .   The liquid developer according to any one of claims 1 to 4, wherein the carrier liquid is an insulating liquid mainly containing an aliphatic hydrocarbon.   A liquid developer according to any one of claims 1 to 5 is stored, and an electrostatic latent image formed on a surface of an electrostatic latent image holding member is developed with the liquid developer to form a toner image. A process cartridge having a developing means for forming and detachable from an image forming apparatus. An electrostatic latent image carrier;
Charging means for charging the surface of the electrostatic latent image holding member;
Electrostatic latent image forming means for forming an electrostatic latent image on the surface of the electrostatic latent image holding member;
A liquid developer according to any one of claims 1 to 5 is stored, and an electrostatic latent image formed on a surface of an electrostatic latent image holding member is developed with the liquid developer to form a toner image. Developing means to form;
Transfer means for transferring the toner image to a recording medium;
Fixing means for fixing the toner image on the recording medium;
An image forming apparatus comprising: A charging step for charging the surface of the electrostatic latent image holding member;
An electrostatic latent image forming step of forming an electrostatic latent image on the surface of the electrostatic latent image holder;
A developing step of developing a toner image by developing the electrostatic latent image formed on the surface of the electrostatic latent image holding member with the liquid developer according to any one of claims 1 to 5;
A transfer step of transferring the toner image to a recording medium;
A fixing step of fixing the toner image on the recording medium;
An image forming method comprising: