JP5636958B2 - Liquid developer, developer cartridge, image forming method, and image forming apparatus - Google Patents

Description

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

  Patent Document 1 discloses a liquid developer in which toner particles mainly composed of a resin material are dispersed in an insulating liquid, and the insulating liquid contains an unsaturated fatty acid monoester. The saturated fatty acid monoester contains an alcohol component having 1 to 8 carbon atoms, the content of the unsaturated fatty acid monoester in the insulating liquid is 10 to 80 wt%, and the insulating liquid A liquid developer having a volume resistivity of 1012 Ωcm or more and a weight average molecular weight Mw of the resin material of 5000 to 15000 is disclosed.

  Patent Document 2 contains an elastomer containing a styrene monomer and a (meth) acrylic acid ester monomer as a main component and a vinyl copolymer as a main component and a styrene block as a constituent unit. A resin composition for a dry toner is disclosed.

  Patent Document 3 discloses a thermoplastic elastomer compound obtained by blending 5 to 50% by weight of a thermoplastic elastomer containing a reactive group represented by a vinyl group with 95 to 50% by weight of a styrene or olefinic thermoplastic elastomer. A printing method is disclosed in which a surface modification is performed by irradiating the molded article with ultraviolet rays and then printing is performed with urethane ink.

  Patent Document 4 discloses that a binder resin solution composed of a low molecular weight vinyl polymer component and a high molecular weight vinyl polymer component has a melting point of 30 Joule / g or more as a toner additive and a melting point of 50 to 100 ° C. A resin composition for dry toner obtained by adding and mixing the low melting point compound in a molten state is disclosed.

  Patent Document 5 discloses a composition containing a colorant, a monomer having a specific structure or a polymer thereof, and a polyfunctional acrylate (methacrylate) monomer or a polymer thereof in an aliphatic hydrocarbon solvent, or a copolymer thereof. There is disclosed a liquid developer for electrophotography in which an ultraviolet fixing toner mainly composed of a polymer is dispersed.

JP 2008-26571 A JP 2002-123040 A JP-A-6-271707 JP-A-7-219269 Japanese Patent Publication No. 6-25875

  An object of the present invention is to provide a liquid developer capable of forming an image having good scratch resistance.

The above problem is solved by the following means. That is,
The invention according to claim 1
Toner particles containing a vinyl resin and a styrene thermoplastic elastomer resin;
A mixture of a radiation curable material and a non-aqueous solvent other than the radiation curable material or a carrier liquid composed of the radiation curable material alone;
A liquid developer containing

The invention according to claim 2
The liquid developer according to claim 1, wherein the thermoplastic elastomer resin is a copolymer of a structural unit derived from a monomer having a styrene skeleton and a structural unit having an unsaturated double bond. .
The invention according to claim 3
The liquid developer according to claim 1, wherein the thermoplastic elastomer resin is a block copolymer of a structural unit derived from a monomer having a styrene skeleton and a structural unit having an unsaturated double bond. is there.
The invention according to claim 4
The content of the vinyl resin with respect to the whole toner particles is 50% by mass or more and 90% by mass or less, and the content of the thermoplastic elastomer resin with respect to the whole toner particles is 5% by mass or more and 50% by mass or less. The liquid developer according to any one of claims 1 to 3.

The invention according to claim 5
The carrier liquid, wherein the radiation curable material is constituted alone is a liquid developer according to any one of claims 1 to 4.

The invention according to claim 6
A developer cartridge containing the liquid developer according to any one of claims 1 to 5 .

The invention according to claim 7 provides:
A latent image forming step of forming a latent image on the surface of the latent image holding member;
The latent image formed on the surface of the latent image holding member is developed with a liquid developer according to any one of claims 1 held on the surface of the developer holding member to claim 5 Toner A development process for forming an image;
A transfer step of transferring the toner image formed on the surface of the latent image holding member onto a recording medium;
A fixing step of fixing the toner image transferred to the recording medium to the recording medium to form a fixed image;
A radiation irradiation step of irradiating the fixed image with radiation;
And an image forming method.

The invention according to claim 8 provides:
The image forming method according to claim 7 , further comprising an initiator addition step of adding an initiator to at least one of the toner image and the fixed image before being irradiated with the radiation in the radiation irradiation step.

The invention according to claim 9 is:
A latent image carrier,
Latent image forming means for forming a latent image on the surface of the latent image holder;
A developing agent holding member, wherein the latent image formed on the surface of the latent image holding member, to any one of claims 1 held on the surface of the developer holding member to claim 5 A developing means for developing with a liquid developer to form a toner image;
Transfer means for transferring the toner image formed on the surface of the latent image holding member onto a recording medium;
Fixing means for fixing the toner image transferred to the recording medium to the recording medium to form a fixed image;
Radiation irradiating means for irradiating the fixed image with radiation;
An image forming apparatus having

The invention according to claim 10 is:
The image forming apparatus according to claim 9 , further comprising an initiator addition unit that adds an initiator to at least one of the toner image and the fixed image before being irradiated with the radiation by the radiation irradiation unit.

  According to the first aspect of the present invention, an image having good scratch resistance is formed as compared with the case where no radiation curable material is contained.

  According to the second aspect of the present invention, an image having good scratch resistance is formed as compared with the case where the thermoplastic elastomer resin does not contain a structural unit having an unsaturated double bond.

According to the fifth aspect of the present invention, an image having good scratch resistance is formed as compared with the case where the carrier liquid is a mixture of a non-aqueous solvent and a radiation curable material.

According to the inventions according to claims 6 to 10 , an image having good scratch resistance can be formed as compared with the case where a liquid developer containing no radiation curable material is used.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus of the present invention.

[Liquid developer]
The liquid developer according to the exemplary embodiment includes a mixture of a toner particle containing a vinyl resin and a styrene thermoplastic elastomer resin, and a radiation curable material and a non-aqueous solvent other than the radiation curable material, or the radiation curable material alone. A liquid developer.
The liquid developer according to the present embodiment has the above characteristics, so that an image having good scratch resistance can be formed as compared with a case where the liquid developer does not have the above characteristics (that is, a case where no radiation curable material is included).

The operation inferred from the configuration of the present embodiment will be described below. The toner particles containing a vinyl resin and a styrene thermoplastic elastomer resin as in this embodiment are considered to have flexibility due to the compatibility of the vinyl resin and the thermoplastic elastomer resin. Therefore, when the liquid developer containing the toner particles is used, the folding resistance is better than when using a liquid developer in which toner particles for dry development using a polyester resin are dispersed as they are in a carrier liquid. Images can be obtained.
In this embodiment, since the carrier liquid containing the radiation curable material is used in addition to the above-described flexible toner particles, the radiation curable material is simply cured by irradiating the image with radiation. It is considered that an image having not only good bending resistance but also good scratch resistance can be obtained.

  In the present embodiment, as the styrene-based thermoplastic elastomer resin, by using a copolymer of a structural unit derived from a monomer having a styrene skeleton and a structural unit having an unsaturated double bond, Furthermore, an image having good scratch resistance can be obtained. The reason for this is not clear, but when the image is irradiated with radiation, the unsaturated double bond contained in the thermoplastic elastomer resin in the toner particles reacts with the radiation curable material in the carrier liquid and is crosslinked, This is presumably because a stronger image can be obtained.

Furthermore, in this embodiment, by using a carrier liquid composed of a radiation curable material alone, it is more scratch resistant than when using a carrier liquid that is a mixture of a radiation curable material and a non-aqueous solvent other than the radiation curable material. A good image can be obtained. The reason for this is not clear, but since all the carrier liquid remaining in the toner image is cured by radiation, particularly when a non-aqueous solvent having a high boiling point (eg, boiling point of 100 ° C. or higher) that tends to remain in the image is used in combination. In comparison, it is considered that a decrease in image intensity due to the non-aqueous solvent remaining in the image without being cured is suppressed. Thereby, for example, it is estimated that an image having better scratch resistance can be obtained.
Hereinafter, the components constituting the liquid developer will be described in more detail.

<Toner particles>
As described above, the toner particles contain at least a vinyl resin and a styrene thermoplastic elastomer resin, and may contain other components such as a colorant and a release agent as necessary.

-Vinyl resin-
The vinyl resin is a resin obtained by polymerizing a vinyl monomer (a monomer having a vinyl group). Examples of vinyl monomers include styrene monomers, (meth) acrylate monomers, and other vinyl monomers. “(Meth) acryl” means either or both of acrylic and methacrylic. The vinyl resin may be a homopolymer obtained by polymerizing one of these monomers, or may be a copolymer using two or more monomers.
Among vinyl resins, examples of the vinyl resin having good compatibility with a styrene-based thermoplastic elastomer resin described later include resins containing a structural unit derived from a styrene monomer. Specific examples of the resin containing a structural unit derived from a styrene monomer include, for example, a styrene monomer homopolymer, a structural unit derived from a styrene monomer, and a (meth) acrylic acid ester system. Examples thereof include a copolymer containing a structural unit derived from a monomer.

  The styrene monomer is a monomer having a styrene skeleton. Specifically, for example, styrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-ter- Examples include butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-dodecyl styrene, p-methoxy styrene, p-phenyl styrene, p-chloro styrene, 3,4-dichlorostyrene, and the like. .

  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 methacrylate, diethylaminoethyl methacrylate, Glycidyl methacrylate, polyethylene glycol dimethacrylate, etc. methacryloxyethyl phosphate.

  Examples of other vinyl monomers include olefin monomers such as ethylene, propylene, butylene, butadiene, and isoprene, and vinyl ester monomers such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl benzoate. Acrylic acid such as acrylic acid, methacrylic acid, α-ethylacrylic acid and crotonic acid and α- or β-alkyl derivatives thereof; unsaturated dicarboxylic acids such as fumaric acid, maleic acid, citraconic acid, itaconic acid and the like Examples include ester derivatives or diester derivatives; succinic acid mono (meth) acryloyloxyethyl ester, (meth) acrylonitrile, acrylamide, and the like.

Examples of the weight average molecular weight (Mw) of the vinyl polymer include a range of 150,000 to 500,000.
Moreover, as a molecular weight distribution (Mw / Mn) of the said vinyl polymer, the range of 2-20 is mentioned, for example.
The vinyl polymer may have a plurality of peaks and shoulders in the molecular weight distribution measured by gel permeation chromatography (GPC).

  The weight average molecular weight (Mw) is measured by gel permeation chromatography (GPC). The molecular weight measurement by GPC is performed with a THF solvent using a Tosoh GPC / HLC-8120 as a measuring device and a Tosoh column / TSKgel Super HM-M (15 cm). The weight average molecular weight is calculated from the measurement result using a molecular weight calibration curve prepared with a monodisperse polystyrene standard sample. The same applies to the measurement of the weight average molecular weight. The number average molecular weight (Mn) is also measured in the same manner as the weight average molecular weight (Mw), and the molecular weight distribution (Mw / Mn) is calculated from these values.

  The content ratio of the vinyl resin in the toner particles is, for example, 50% by mass to 90% by mass, and may be 50% by mass to 70% by mass with respect to the entire toner particles.

-Styrenic thermoplastic elastomer resin-
The styrene-based thermoplastic elastomer resin is a thermoplastic elastomer resin having a structural unit derived from at least a monomer having a styrene skeleton (the styrene-based monomer). Examples of the thermoplastic elastomer resin include those having rubber properties at normal temperature (for example, 25 ° C.) and softening properties similar to thermoplastics at high temperatures.

  Specific examples of the styrene thermoplastic elastomer resin include, for example, a block copolymer of the styrene monomer and the olefin monomer, and more specifically, 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-hydrogenated poly (isoprene). / Butadiene) -polystyrene and the like.

In the above specific examples, for example, “polystyrene-polybutadiene / butylene-polystyrene” is a block copolymer in which a polystyrene block, a polybutadiene block, and a polystyrene block are combined in this order, and the butadiene block is partially Indicates a hydrogenated structure. That is, the above-mentioned “polybutadiene / butylene” means a block in which a butadiene portion and a butylene portion hydrogenated with butadiene are mixed.
In the above specific examples, for example, “hydrogenated polybutadiene” indicates that hydrogen is added to the double bond of polybutadiene.

Moreover, in these block copolymers, you may use the block copolymer which introduce | transduced the polar group into the soft segment part pinched | interposed into polystyrene.
Examples of the polar group include a hydroxyl group, a carboxyl group, an amino group, and an acyl group.

  Among the styrene-based thermoplastic elastomer resins, as a copolymer of a structural unit derived from a monomer having a styrene skeleton (styrene-based monomer) and a structural unit having an unsaturated double bond, for example, Examples thereof include block copolymers of the styrene monomer and an olefin monomer having two or more unsaturated double bonds. Specific examples include polystyrene-polybutadiene-polystyrene, polystyrene-polybutadiene / Examples include butylene-polystyrene and polystyrene-polyisoprene-polystyrene.

Examples of the weight average molecular weight of the styrenic thermoplastic elastomer resin include a range of 30,000 to 300,000.
When the styrenic thermoplastic elastomer resin is a copolymer of a structural unit derived from a styrene monomer and a structural unit having an unsaturated double bond, per structural unit having an unsaturated double bond Examples of the number of unsaturated double bonds in 1 include a range of 1 or more and 3 or less.

  Examples of commercially available styrene-based thermoplastic elastomer resins include Tuftec M1911, Tuftec M1943, Tuftec MP10, Asaprene T439, Tufrene A, Kuraray DYNARON 8630P manufactured by Asahi Kasei Corporation.

  The content ratio of the styrenic thermoplastic elastomer in the toner particles is, for example, from 5% by mass to 50% by mass with respect to the entire toner particles, and may be from 10% by mass to 40% by mass.

-Other components-
In addition to the vinyl resin and the styrene thermoplastic elastomer resin, the toner particles may contain other components such as other resins, colorants, release agents, charge control agents, silica powder, and metal oxides as necessary. You may contain. These other components may be added internally by kneading into the vinyl resin and the styrene thermoplastic elastomer resin, or may be added externally by, for example, mixing after obtaining toner particles. Good. When the toner particles are transparent toner, it is not necessary to include a colorant.

Examples of the other resin include known binder resins such as polyester, polyethylene, polypropylene, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, and paraffin wax. When the toner particles contain the other resin, the content of the other resin with respect to the entire toner particles is, for example, 10% by mass or less.
Further, the toner particles may contain a polyester resin as an additive for controlling the glass transition temperature of the toner particles or as a release agent to be described later. In this case, the content of the polyester resin is, for example, A range of less than 5% by weight is mentioned.

As the colorant, a known pigment or dye is used. Specific examples include yellow, magenta, cyan, and black pigments shown below.
Examples of the yellow pigment include compounds typified by condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complex compounds, methine compounds, and allylamide compounds.
Examples of magenta pigments include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinones, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds.
Examples of cyan pigments include copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, basic dye lake compounds, and the like.
Examples of black pigments include carbon black, aniline black, acetylene black, and iron black.

  The release agent is not particularly limited, and examples thereof include plant waxes such as carnauba wax, sugar wax, and wood wax; animal waxes such as beeswax, insect wax, whale wax, and wool wax; And synthetic hydrocarbon waxes such as Fischer-Tropsch wax (FT wax), polyethylene wax, polypropylene wax, and polyester wax. Only one type of release agent may be used, or two or more types 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 used in the present embodiment is not particularly limited. For example, the toner particles can be obtained by finely pulverizing a toner produced by a pulverized toner, a liquid emulsion dry toner, or a polymerized toner production method in a carrier liquid.
Specifically, for example, a binder resin including a styrene thermoplastic elastomer resin and a vinyl resin, a colorant, and if necessary, other additives are added to a mixing device such as a Henschel mixer and mixed. This mixture is melt-kneaded with a twin screw extruder, etc., cooled with a drum flaker, etc., roughly pulverized with a pulverizer such as a hammer mill, and further finely pulverized with a pulverizer such as a jet mill, and then an air classifier, etc. A classified toner is used to obtain a pulverized toner.
In addition, for example, a binder resin containing a styrene thermoplastic elastomer resin and a vinyl resin, a colorant, and if necessary, other additives are dissolved in a solvent such as ethyl acetate, and a dispersion stabilizer such as calcium carbonate. After emulsifying / suspending in water to which is added, the solvent is removed, and then the particles obtained by removing the dispersion stabilizer are filtered and dried to obtain an emulsified dry toner in liquid.
Further, for example, a polymerizable monomer that forms a binder resin, a colorant, a polymerization initiator (for example, benzoyl peroxide, lauroyl peroxide, isopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichloroylbenzoyl) (Peroxide, methyl ethyl ketone peroxide, etc.) and other additives are added to the aqueous phase under agitation and granulated. After polymerization reaction, the particles are filtered and dried to obtain a polymerized toner. .

  The blending ratio of each material (styrene-based thermoplastic elastomer and styrene-based thermoplastic resin, colorant, other additives, etc.) for obtaining the toner is set in consideration of required characteristics, color, and the like. The obtained toner is finely pulverized in a carrier oil using a known pulverizer such as a ball mill, a bead mill, a high-pressure wet atomizer, or the like, whereby the toner particles for liquid developer of this embodiment are obtained.

  Examples of the volume average particle diameter D50v of the toner particles include a range of 0.5 μm to 5.0 μm, and may be 0.8 μm to 4.0 μm, and may be 1.0 μm to 3.0 μm. May be.

  The volume average particle diameter D50v of the toner particles is measured with a Coulter Multisizer (manufactured by Coulter) for toner particles of 2 μm or more. For toner particles smaller than 2 μm, a dynamic light scattering type particle size distribution measuring device (for example, LB-500 (manufactured by Horiba, Ltd.), Microtrac UPA (manufactured by Nikkiso Co., Ltd.), etc.) or laser diffraction / scattering type It is measured using a particle size distribution measuring device (for example, LS13 320 (manufactured by BECKMAN COULTER) or the like). With respect to the particle size range (channel) divided on the basis of the particle size distribution obtained by the above measurement, a cumulative distribution is drawn from the small diameter side with respect to the volume, and the particle diameter at which 50% is accumulated is defined as volume D50v.

  The toner particle content is, for example, in the range of 0.5% by mass to 40% by mass with respect to the entire liquid developer, and may be 1% by mass to 30% by mass.

<Carrier liquid>
As described above, the carrier liquid is a radiation curable material alone or a mixture of the radiation curable material and a non-aqueous solvent other than the radiation curable material. Each of the radiation curable material and the non-aqueous solvent may be used alone or in combination of two or more.

-Radiation curable material-
The radiation curable material is a compound that is cured by irradiation with radiation, and examples thereof include radical radiation curable materials and cationic radiation curable materials. Examples of radiation include electromagnetic waves such as ultraviolet rays and X-rays; particle beams such as electron beams and neutron rays; among others, practical radiation includes, for example, ultraviolet rays. When the carrier liquid is composed of the radiation curable material alone, the radiation curable material itself serves as a carrier liquid for dispersing the toner particles in the liquid developer.

Among radical radiation curable materials, examples of radical ultraviolet curable materials that are cured by ultraviolet rays include acrylate compounds having a carbon-carbon double bond, and thiol / ene compositions (mixed compositions of polythiol compounds and polyene compounds). Etc.
Specific examples of radical ultraviolet curable materials include polymer compounds such as polyethylene glycol dimethacrylate and polypropylene glycol dimethacrylate; tetrahydrofurfuryl acrylate, 2-hydroxyethyl acrylate, 2-ethylhexyl acrylate, N, N-dimethylacrylamide. 4-hydroxybutyl acrylate, tricyclodecane methacrylate, 2-hydroxyethyl methacrylate, N-vinylpyrrolidone, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, diethylene glycol diacrylate, 1,4-butanediol diacrylate , Monofunctional or bifunctional monomer compounds such as EO-modified bisphenol A diacrylate (manufactured by Toa Gosei Co., Ltd .: M211B) ; Pentaerythritol triacrylate, pentaerythritol tetraacrylate (manufactured by Toagosei Co., Ltd.: M-450), dipentaerythritol hexaacrylate, polyfunctional monomers such as trimethylolpropane triacrylate; and the like.
Among radical radiation curable materials, examples of the radical electron beam curable material that is cured by an electron beam include the same compounds and compositions as the specific examples of the radical ultraviolet curable material.

Among cationic radiation curable materials, examples of cationic ultraviolet curable materials that are cured by ultraviolet rays include 4-hydroxybutyl vinyl ether, isobutyl vinyl ether, cyclohexyl vinyl ether, triethylene glycol divinyl ether, 1,4-butanediol divinyl ether, and the like. Vinyl ether compounds; oxetane compounds such as 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3- (phenoxymethyl) oxetane, 1,3-bis [(3-ethyloxetane-3-yl) methoxy] benzene; (3,4-epoxycyclohexylmethyl) adipate, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, hydrogenated bisphenol A diglycidyl ether, bisphenol Cyclic ether compounds such as Le A diglycidyl ether; epoxy soybean oil, vegetable oil-modified epoxy compounds such as epoxidized linseed oil; and the like.
Among the cationic radiation curable materials, examples of the cationic electron beam curable material that is cured by an electron beam include the same compounds as the specific examples of the cationic ultraviolet curable material.

  As the radiation curable material, either one of the radical radiation curable material and the cationic radiation material may be used, or may be used in combination. For example, a radical radioactive curable material that is not easily affected by moisture, is inexpensive and readily available, and has a fast curing speed, and a cationic radiation material that is not easily affected by oxygen and that cures by a dark reaction after irradiation. It is good also as a liquid developer from which both advantages are acquired by using together.

-Non-aqueous solvent-
The non-aqueous solvent refers to a solvent containing a solvent other than water, and may be a mixture of water and a solvent other than water, but may be a solvent that does not actively contain water.
Non-aqueous solvents include, for example, aliphatic hydrocarbon solvents such as paraffin oil (commercially available products are Moresco White MT-30P, Moresco White P40, Moresco White P70, Made by Matsumura Sekiyu, and Isopar L from Exxon Chemical Co., Ltd.) , Isopar M, etc.), hydrocarbon solvents such as naphthenic oil (commercially available products are Exol D80, Exol D110, Exol D130 manufactured by Exxon Chemical Co., Ltd., Naphthezol L, Naphthezol M, Naphthezol H, New Naphtezol 160 manufactured by Nippon Petrochemical Co., Ltd. , New Naphthezol 200, New Naphthezol 220, New Naphthezol MS-20P, etc.), and an aromatic compound such as toluene may be contained therein.
The non-aqueous solvent may be used alone or in combination of two or more of the above components. When the non-aqueous solvent is used as a mixture of two or more, for example, a paraffin type Examples include a mixed system of a solvent and vegetable oil, and a mixed system of a silicone solvent and vegetable oil.

-Characteristics of carrier liquid-
Examples of the volume resistivity of the carrier liquid include a range of 1.0 × 10 ¹⁰ Ω · cm to 1.0 × 10 ¹⁴ Ω · cm, and 1.0 × 10 ¹⁰ Ω · cm to 1.0 × It may be in a range of 10 ¹³ Ω · cm or less.
In the case where the carrier liquid is composed of the radiation curable material alone, for example, a radiation curable material in which the volume resistivity of the carrier liquid is within the above range may be used. Specifically, for example, a method of using a radiation curable material having a volume resistivity of 1.0 × 10 ¹⁰ Ω · cm or more (for example, polyethylene glycol diacrylate which is a radical radiation curable material) alone may be used. Further, in a form in which the carrier liquid is composed of a radiation curable material alone, a radiation curable material having a volume resistivity of 1.0 × 10 ⁹ Ω · cm or less (for example, cationic radiation curable such as oxetane, epoxy compound, cyclic ether) In the case of using a material etc.), for example, the volume resistivity of the entire carrier liquid is adjusted by adjusting the mixing ratio in combination with a radiation curable material having a volume resistivity of ¹⁰ × 10 ¹⁰ Ω · cm or more. It is good also as a range. Specifically, for example, a carrier liquid of a radiation curable material alone using a combination of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate and 1,4-butanediol divinyl ether, the mixing ratio thereof Examples thereof include a ratio such that the content of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate is 10% by mass or more and 30% by mass or less with respect to the entire radiation curable material.

<Other ingredients>
-Initiator-
In addition to the toner particles and the carrier liquid, the liquid developer may contain an initiator for initiating a curing reaction of the radiation curable material, if necessary. Specifically, for example, when an ultraviolet curable material is used as the radiation curable material, a photopolymerization initiator may be used as the initiator.
When an initiator is used in this embodiment, for example, in the process of forming an image, the initiator is added to the toner image or the fixed image before irradiation with radiation, and the liquid developer does not contain the initiator. Form may be sufficient. In particular, when using an initiator that is difficult to dissolve in the carrier liquid or an initiator that dissolves in the carrier liquid and lowers the volume resistivity, do not add it to the liquid developer, but add it directly to the toner image formed by development. May be.

The initiator is selected depending on the radiation curable material used.
Examples of the initiator in the case of using a radical ultraviolet curable material as the radiation curable material include, for example, benzophenone, benzoin isobutyl ether, benzoin ethyl ether, methyl benzoylbenzoate, benzyl, 4-chlorobenzophenone, 4-phenylbenzophene, 4p-trithiobenzophenone, 2-hydroxy-2,2-dimethylacetophenone, 2,2-diethoxyacetophenone, 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, Lucirin TPO and Lucillin TPO-L from BASF, Ciba Specialty Chemicals' Irgacure 1850, Irgacure 1700, Irgacure 819 and the like.
Among them, an initiator that has a strong function of promoting the curing reaction of the radiation curable material and does not cause yellowing includes, for example, an initiator containing phosphorus in its structure. , 6-trimethylbenzoylphenylethoxyphosphine oxide and the like.

When a hydrogen abstraction type benzophenone photopolymerization initiator is used as an initiator, an amine sensitizer may be used in combination. The added amount of the amine sensitizer is, for example, from 1 part by mass to 15 parts by mass with respect to 100 parts by mass of the benzophenone photopolymerization initiator, and in the range of 3 parts by mass to 8 parts by mass. There may be.
Examples of the amine sensitizer include triethanolamine, triisopropanolamine, 4,4-diethylaminobenzophenone, 2-dimethylaminoethylbenzoic acid, ethyl 4-dimethylaminobenzoate, isoacyl 4-dimethylaminobenzoate, and the like. Is mentioned.

  Examples of the initiator when a cationic ultraviolet curable material is used as the radiation curable material include, for example, Irgacure 250, 2-isopropoxy-4,4,5,5-tetramethyl-1,3 manufactured by Ciba Specialty Chemicals. , 2-dioxaborolane, UVI 6990 manufactured by Union Carbide, UV 9380C manufactured by General Electric, Adeka optomer SP-150 and SP-300 manufactured by Asahi Denka Kogyo Co., Ltd., and the like.

  When an initiator is included in the liquid developer, the amount of the initiator added is, for example, in a range of 0.1 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the radiation curable material, and 0.5 parts by mass. The range may be not less than 8 parts and not more than 8 parts by mass.

  The liquid developer may further contain other components as necessary. Examples of other components include dispersants, charge control agents, emulsifiers, surfactants, antioxidants, wetting agents, thickeners, foaming agents, antifoaming agents, coagulants, gelling agents, and anti-settling agents. , Antistatic agents, anti-aging agents, softeners, plasticizers, fillers, flavoring agents, anti-tacking agents, release agents and the like.

<Method for producing liquid developer>
In the liquid developer, the toner particles, the carrier liquid, and other components as necessary are mixed using a dispersing machine such as a ball mill, a sand mill, an attritor, a roll mill, etc. It is obtained by dispersing in a liquid.
The dispersion of the toner particles in the carrier liquid is not limited to the disperser, and may be dispersed by rotating a special stirring blade like a mixer, or by the shearing force of a rotor / stator known as a homogenizer. Alternatively, it may be dispersed by ultrasonic waves.
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.

[Developer cartridge]
The developer cartridge according to the present embodiment is a developer cartridge in which the liquid developer according to the present embodiment is accommodated. For example, the liquid developer stored in the developer cartridge is supplied to the image forming apparatus through a supply pipe or the like. To the developing device. Since the developer cartridge is replaced when the remaining amount of the liquid developer in the developer cartridge runs out, the developer cartridge may be attached to and detached from the image forming apparatus.

[Image Forming Method and Image Forming Apparatus]
In the image forming method of the present embodiment, a latent image forming step for forming a latent image on the surface of the latent image holding member and the latent image formed on the surface of the latent image holding member are held on the surface of the developer holding member. In addition, the development process for forming the toner image by developing with the liquid developer of the present embodiment, the transfer process for transferring the toner image formed on the surface of the latent image holding member onto the recording medium, and the transfer onto the recording medium. An image forming method comprising: a fixing step of fixing a toner image on a recording medium to form a fixed image; and a radiation irradiation step of irradiating at least one of the toner image and the fixed image with radiation. You may have the initiator addition process which adds an initiator to at least one of the fixed image before irradiating an image and a radiation.

  The image forming apparatus of this embodiment includes a latent image holding member, a latent image forming unit that forms a latent image on the surface of the latent image holding member, and a developer holding member, and is formed on the surface of the latent image holding member. The latent image is developed with the liquid developer of the present embodiment held on the surface of the developer holding member to form a toner image and a toner image formed on the surface of the latent image holding member. Transfer means for transferring onto a recording medium, fixing means for fixing a toner image transferred to the recording medium to the recording medium to form a fixed image, and radiation irradiating means for irradiating at least one of the toner image and the fixed image The image forming apparatus may include an initiator addition unit that adds an initiator to at least one of the toner image and the fixed image before being irradiated with radiation, if necessary.

  In the radiation irradiation step, at least one of the toner image and the fixed image may be irradiated according to the type and amount of the radiation curable material to be used, and both may be irradiated with radiation. Specifically, for example, when a radiation curable material (for example, radical radiation curable material) having a high curing rate is used, the toner image is not irradiated with radiation, and the fixed image is irradiated with radiation. In addition, when using a radiation curable material having a slow curing rate (for example, a cationic radiation curable material), the toner image may be irradiated with radiation, but the toner image is not irradiated with radiation and the fixed image is irradiated with radiation. The form to irradiate may be sufficient. Further, in the image forming step, the number of times of radiation irradiation may be one time or two or more times. For example, the radiation irradiation to the fixed image may be performed twice or more.

The radiation irradiation means may be provided with radiation irradiation means corresponding to the radiation irradiation step. When the radiation irradiation process is performed twice or more, two or more radiation irradiation means corresponding to each radiation irradiation process may be provided, and one radiation irradiation means corresponds to two or more radiation irradiation processes. May be.
Hereinafter, an image forming method and 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 shown in FIG. 1 includes an initiator addition apparatus that adds an initiator to a toner image transferred to an intermediate transfer member, and an ultraviolet irradiation apparatus (radiation irradiation means) that irradiates a fixed image fixed on a recording medium with ultraviolet rays. And an image forming apparatus.

The image forming apparatus 100 includes, for example, a photosensitive member 10 (latent image holding member), a charging device 20, an exposure device 12 (the charging device 20 and the exposure device 12 constitute an electrostatic latent image forming unit), and a developing device 14 (development). Means), an intermediate transfer body 16, a cleaner 18, a transfer fixing roller 28 (the intermediate transfer body 16 and the transfer fixing roller 28 constitute a transfer means, and the transfer fixing roller 28 also serves as a fixing means), an initiator addition device 32, And an ultraviolet irradiation device 34 (radiation irradiation means). 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 (developer holder) and a developer storage container 14b. The developing roller 14a is provided so that a part thereof is immersed in the liquid developer 24 stored in the developer storage container 14b. The developer storage container 14b may be configured such that the liquid developer 24 is supplied from a liquid developer cartridge (not shown). The liquid developer cartridge may be configured to be attached to and detached from the image forming apparatus so that the liquid developer cartridge can be replaced when the remaining amount of the liquid developer 24 runs out.

  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 storage container 14b, so that the toner particles in the liquid developer 24 are maintained. Variations in the position of the concentration of may be 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 developed toner image 26 is conveyed to the photosensitive member 10 that rotates in the direction of arrow B in the figure and transferred to the paper (recording medium) 30. In this embodiment, the photosensitive member 10 is transferred before being transferred to the paper 30. The toner image is temporarily 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 toner and to perform fixing simultaneously with the transfer to the recording medium. At this time, a peripheral speed difference may be provided between the photosensitive member 10 and the intermediate transfer member 16.

An initiator is added to the toner image transferred to the intermediate transfer body 16 by the initiator adding device 32.
As a method of adding an initiator to a toner image, for example, a method in which an initiator is dissolved in a solvent that does not dissolve the toner image is added to the toner image by, for example, coating or spraying, or a liquid or solid (for example, Examples thereof include a method of adding a powdery solid) initiator as it is to a toner image, for example, by spraying or the like, but are not limited to these methods.
Examples of the solvent that does not dissolve the toner image include a mixed solvent of hexane and IPA (isopropyl alcohol) (for example, a hexane / IPA mixing ratio in the range of 10/1 to 5/1).
The amount of the initiator added is, for example, in the range of 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the radiation curable material contained in the toner image ( And the amount of the initiator contained in the solution is within the above range).
In this embodiment, an initiator is added to the toner image transferred to the intermediate transfer body 16, but after the toner image is formed by the developing device 14 and before the ultraviolet ray is irradiated by the ultraviolet ray irradiation device 34. The initiator may be added during the period of time, the initiator may be added to the toner image on the photoreceptor 10, or the initiator may be added to the fixed image 29 fixed on the recording medium.

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 may be performed by applying pressure and heating by providing a heat generating body on the transfer fixing roller 28. Examples of the fixing temperature include 100 ° C. or higher and 180 ° C. or lower.

If the intermediate transfer member 16 has a roller shape as shown in FIG. 1, it constitutes a roller pair with the transfer fixing roller 28. Therefore, the intermediate transfer member 16 and the transfer fixing roller 28 respectively conform to the fixing roller and the pressure roller in the fixing device. It shows a fixing function. That is, when the sheet 30 passes through the contact portion between the transfer fixing roller 28 and the intermediate transfer member 16, for example, a toner image is transferred and is heated and pressed against the intermediate transfer member 16 by the transfer fixing roller 28. Thereby, for example, 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.

Thereafter, the ultraviolet irradiation device 34 irradiates the fixed image 29 fixed on the paper 30 with ultraviolet rays. Thereby, for example, an initiator included in the fixed image 29 starts a curing reaction of the radiation curable material included in the fixed image 29, and the fixed image 29 is cured.
The irradiation energy of ultraviolet rays to be irradiated to the fixed image 29, it may be in the range of fully cured, include, for example, 10 mJ / cm ² or more 5000 mJ / cm ² or less. Examples of the ultraviolet irradiation time include 0.1 seconds to 60 seconds.

  On the other hand, in the photoconductor 10 in which the toner image 26 is transferred to the intermediate transfer body 16, the toner particles that are not transferred and remain on the photoconductor 10 are conveyed to a contact position with the cleaner 18 and are 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.

The image forming apparatus may further include a neutralization device (not shown) that neutralizes the surface of the photoreceptor 10 after the transfer and before the next charging.
For example, all of 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 included in the image forming apparatus 100 are synchronized with the rotational speed of the photosensitive member 10. It may be operated.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, these examples do not limit the present invention. In the text, “parts” and “%” represent “parts by mass” and “mass%”, respectively, unless otherwise specified.

<Adjustment of liquid developer>
-Adjustment of liquid developer 1-
To 60 parts of vinyl resin 1 (styrene acrylic resin, manufactured by Fujikura Kasei Co., Ltd., trade name: FSR-051, weight average molecular weight: 380,000), cyan pigment C.I. I. 40 parts 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 dissolved and dispersed in a ball mill for 24 hours to obtain a mixture 1.
Styrenic thermoplastic elastomer resin 1 (styrene-butadiene-styrene block copolymer composed of structural units derived from styrene and structural units derived from butadiene, manufactured by Asahi Kasei Co., Ltd., trade name: Toughprene A product, unsaturated Number of unsaturated double bonds in the structural unit having double bonds: 1): 20 parts. Vinyl resin 2 (styrene-butyl acrylate resin, manufactured by Fujikura Kasei Co., Ltd., trade name: FSR-053, weight) (Average molecular weight 320,000): 60 parts · Cyan pigment master batch: 20 parts · Ethyl acetate: 100 parts

  On the other hand, 20 parts of calcium carbonate (manufactured by Maruo Calcium Co., Ltd., Luminous) is added as a dispersion stabilizer to an aqueous solution obtained by dissolving 20 parts of sodium chloride (manufactured by Wako Pure Chemical Industries, Ltd.) in 120 parts of ion-exchanged water. And dispersed for 24 hours to obtain a dispersion medium. 100 parts of the mixture 1 is added to 160 parts of this dispersion medium, and emulsified for 1 minute at 8000 rpm 24,000 rpm with an emulsifying apparatus (HIKA-FLEX HOMOGENIZER Ultra Turrax T-25 manufactured by SMT Co., Ltd.), and the suspension is emulsified. Obtained.

  Put the above suspension into a separable flask equipped with a stirrer, thermometer, cooling pipe and nitrogen introduction pipe, and stir at 60 ° C for 3 hours while introducing nitrogen from the nitrogen introduction pipe to remove ethyl acetate. did. Thereafter, the mixture was cooled, a 10% aqueous hydrochloric acid solution was added to the reaction solution to decompose calcium carbonate, and solid-liquid separation was performed by centrifugation. The obtained particles were washed with 1 L of ion exchange water three times, and then the obtained particles were vacuum dried at 40 ° C. to obtain toner particles 1.

Liquid development in which 40 parts of toner particles 1 obtained by drying and a mixture obtained by adding the following components to this are finely pulverized by a ball mill to disperse toner particles 1 having a volume average particle diameter of 1.0 μm in a carrier liquid. Agent 1 was obtained. The volume resistivity of the carrier liquid in the obtained liquid developer was 1.0 × 10 ¹³ Ω · cm.

Nonaqueous solvent 1 (trade name: Isopar L, manufactured by ExxonMobil Chemical Co., Ltd., initial boiling point: 185 ° C.): 40 parts Cationic UV curable material 1 (1,4-butanediol divinyl ether): 30 parts Agent (trade name: Solsperse 20000, manufactured by Nihon Lubrizol): 0.1 part

-Adjustment of liquid developer 2-
As a styrene thermoplastic elastomer resin, Asahi Kasei Co., Ltd. hydrogenated conjugated diene Tuftec H1041 (styrene-ethylene-butylene copolymer, proportion of structural units having unsaturated double bonds: 0 mol%): 20 A liquid developer 2 was obtained in the same manner as the liquid developer 1 except that the parts were used.

-Adjustment of liquid developer 3-
Instead of using the non-aqueous solvent 1 and the cationic ultraviolet curable material 1 as a carrier liquid, a liquid developer is used except that the following radiation curable material is mixed and a non-aqueous solvent other than the radiation curable material is not used. In the same manner as in Example 1, a liquid developer 3 was obtained. The volume resistivity of the carrier liquid in the obtained liquid developer was 2.0 × 10 ¹¹ Ω · cm.

Cationic UV curable material 2 (3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate): 6 parts by weight Cationic UV curable material 1 (1,4-butanediol divinyl ether): 54 parts by weight

-Adjustment of liquid developer 4-
Instead of using the non-aqueous solvent 1 and the cationic ultraviolet curable material 1 as a carrier liquid, the following radiation curable materials are mixed and used, and liquid development is performed except that a non-aqueous solvent other than the radiation curable material is not used. In the same manner as Agent 1, Liquid Developer 4 was obtained. The volume resistivity of the carrier liquid in the obtained liquid developer was 4.0 × 10 ¹¹ Ω · cm.

Cationic ultraviolet curable material 1 (1,4-butanediol divinyl ether): 30 parts Radical ultraviolet curable material 4 (2-ethylhexyl acrylate): 20 parts

-Adjustment of the liquid developer 5-
Instead of using the non-aqueous solvent 1 and the cationic ultraviolet curable material 1 as the carrier liquid, the following radiation curable material was used, and the liquid developer 1 and the liquid developer 1 were used except that a non-aqueous solvent other than the radiation curable material was not used. Similarly, a liquid developer 5 was obtained. The volume resistivity of the carrier liquid in the obtained liquid developer was 3.0 × 10 ¹² Ω · cm.

Radical UV curable material 5 (manufactured by Toa Gosei Co., Ltd., trade name: M-211B, compound name: bifunctional acrylate compound): 30 parts by weight

-Adjustment of liquid developer 6-
Instead of using the non-aqueous solvent 1 and the cationic ultraviolet curable material 1 as a carrier liquid, a liquid developer 6 was obtained in the same manner as the liquid developer 1 except that the following components were mixed and used. . The volume resistivity of the carrier liquid in the obtained liquid developer was 3.7 × 10 ¹² Ω · cm.

· Radical UV curable material 6 (manufactured by Toagosei Co., Ltd., trade name: M-450, compound name: tetrafunctional acrylate compound): 30 parts · non-aqueous solvent 2 (aliphatic hydrocarbon solvent, trade name: Moresco) White P70, manufactured by Matsumura Oil Co., Ltd., initial boiling point: 310 ° C): 40 parts

-Adjustment of liquid developer 7-
Instead of using the non-aqueous solvent 1 and the cationic ultraviolet curable material 1 as the carrier liquid, the following radiation curable material was used, and the liquid developer 1 and the liquid developer 1 were used except that a non-aqueous solvent other than the radiation curable material was not used. Similarly, a liquid developer 7 was obtained. The volume resistivity of the carrier liquid in the obtained liquid developer was 2,0 × 10 ¹⁰ Ω · cm.
Cationic ultraviolet curable material 3 (Oxetane, trade name: OXT-212, manufactured by Toagosei Co., Ltd.): 5 parts

-Adjustment of the liquid developer 8-
Instead of using the non-aqueous solvent 1 and the cationic ultraviolet curable material 1 as the carrier liquid, the following non-aqueous solvent was used, and the liquid curable material was not used. Developer 8 was obtained. The volume resistivity of the carrier liquid in the obtained liquid developer was 5.5 × 10 ¹³ Ω · cm.
Nonaqueous solvent 2 (aliphatic hydrocarbon solvent, trade name: Moresco White P70, manufactured by Matsumura Oil Co., Ltd., initial boiling point: 310 ° C.): 70 parts

-Adjustment of liquid developer 9-
Instead of using the vinyl resin 1 and the vinyl resin 2, a polyester resin (weight average molecular weight: 21000, manufactured by Sanyo Chemical Co., Ltd., trade name: FS-4) is used, and the nonaqueous solvent 1 and the cation are used as a carrier liquid. A liquid developer 9 was obtained in the same manner as the liquid developer 1 except that the following nonaqueous solvent was used instead of the curable ultraviolet curable material 1 and no radiation curable material was used. The volume resistivity of the carrier liquid in the obtained liquid developer was 5.5 × 10 ¹³ Ω · cm.
Nonaqueous solvent 2 (aliphatic hydrocarbon solvent, trade name: Moresco White P70, manufactured by Matsumura Oil Co., Ltd., initial boiling point: 310 ° C.): 70 parts

<Evaluation of liquid developer>
Using the image forming apparatus shown in FIG. 1, the liquid developer obtained was set in the developing device, and a toner image (toner applied amount: 4 g / m ² ) of 3.5 cm × 3.5 cm was formed and evaluated as follows. Went. The fixing temperature is carried out at 160 ° C., UV irradiation intensity was performed at 60 mW / cm ^2, UV irradiation time 1 minute (i.e., ultraviolet irradiation energy 3600mJ / cm ^2). In each example and comparative example, the following cationic initiator solution and radical initiator solution were added at an addition ratio shown in Table 1 so that the total thickness was 3 μm.
As a cationic initiator solution, 2.0 parts of 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (manufactured by Tokyo Chemical Industry Co., Ltd.), which is an initiator, was added to oxetane OXT212. A solution dissolved in 100 parts (manufactured by Toagosei Co., Ltd.) was used.
As a radical initiator solution, 0.5 part of Irgacure 184 (manufactured by Ciba Japan Co., Ltd.) as an initiator was dissolved in 10 parts of hexane / IPA (isopropyl alcohol): 5/1 solution. A solution obtained by adding 5.0 parts of triethanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.) as a polymerization accelerator was used as a radical initiator solution.

−Scratch resistance evaluation−
The scratch resistance was evaluated by visually observing a decrease in image density at the scratched portion after scratching using a scratch tester (pressurizing force 0.5 kg) manufactured by LINAX. The evaluation results are as follows: ◎: almost no decrease in density, ◯: there is a decrease in density but the image remains, △: the background is partially removed, ×: most of the image is peeled off .

-Evaluation of fixability (bending resistance)-
The folding resistance was evaluated by visually observing the degree of destruction of the image after the paper was bent and spread with the image inside, and the folded portion was lightly wiped. The evaluation results were as follows: ：: image peeling was hardly observed, ○: slight and discontinuous image peeling, Δ: discontinuous breakage, ×: continuous breakage.

  As can be seen from the results in Table 1, it can be seen that the scratch resistance of the obtained image is better in the example than in the comparative example.

10 Photoconductor (latent image carrier)
12 Exposure device 14 Developing device (Developing means)
14a Development roller (developer holder)
16 Intermediate transfer body 18 Cleaner 20 Charging device (charging means)
24 Liquid developer 26 Toner image 28 Transfer fixing roller (transfer means, fixing means)
29 Fixed image 30 Paper (recording medium)
32 Initiator addition device 34 UV irradiation device (radiation irradiation means)
100 Image forming apparatus

Claims (10)

Toner particles containing a vinyl resin and a styrene thermoplastic elastomer resin;
A mixture of a radiation curable material and a non-aqueous solvent other than the radiation curable material or a carrier liquid composed of the radiation curable material alone;
A liquid developer comprising:   The liquid developer according to claim 1, wherein the thermoplastic elastomer resin is a copolymer of a structural unit derived from a monomer having a styrene skeleton and a structural unit having an unsaturated double bond.   The liquid developer according to claim 1, wherein the thermoplastic elastomer resin is a block copolymer of a structural unit derived from a monomer having a styrene skeleton and a structural unit having an unsaturated double bond.   The content of the vinyl resin with respect to the whole toner particles is 50% by mass or more and 90% by mass or less, and the content of the thermoplastic elastomer resin with respect to the whole toner particles is 5% by mass or more and 50% by mass or less. The liquid developer according to any one of claims 1 to 3. The liquid developer according to any one of claims 1 to 4 , wherein the carrier liquid is composed of the radiation curable material alone. A developer cartridge containing the liquid developer according to any one of claims 1 to 5 . A latent image forming step of forming a latent image on the surface of the latent image holding member;
The latent image formed on the surface of the latent image holding member is developed with a liquid developer according to any one of claims 1 held on the surface of the developer holding member to claim 5 Toner A development process for forming an image;
A transfer step of transferring the toner image formed on the surface of the latent image holding member onto a recording medium;
A fixing step of fixing the toner image transferred to the recording medium to the recording medium to form a fixed image;
A radiation irradiation step of irradiating the fixed image with radiation;
An image forming method. The image forming method according to claim 7 , further comprising an initiator addition step of adding an initiator to at least one of the toner image and the fixed image before being irradiated with the radiation in the radiation irradiation step. A latent image carrier,
Latent image forming means for forming a latent image on the surface of the latent image holder;
A developing agent holding member, wherein the latent image formed on the surface of the latent image holding member, to any one of claims 1 held on the surface of the developer holding member to claim 5 A developing means for developing with a liquid developer to form a toner image;
Transfer means for transferring the toner image formed on the surface of the latent image holding member onto a recording medium;
Fixing means for fixing the toner image transferred to the recording medium to the recording medium to form a fixed image;
Radiation irradiating means for irradiating the fixed image with radiation;
An image forming apparatus. The image forming apparatus according to claim 9 , further comprising an initiator addition unit that adds an initiator to at least one of the toner image and the fixed image before being irradiated with the radiation by the radiation irradiation unit.