JP5838849B2 - Liquid developer, developer cartridge, process cartridge, image forming apparatus, and image forming method - Google Patents

Description

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

  Patent Document 1 discloses that in an electrostatic image developing color toner containing at least a binder resin, a colorant, and a release agent, 0.01 to 10 wt% α-olefin with respect to the release agent content. There is disclosed a color toner for developing an electrostatic image, characterized by containing a malate copolymer or an α-olefin-maleic anhydride copolymer.

  Patent Document 2 discloses a resin composition for a toner mainly composed of a vinyl copolymer containing a styrene monomer and a (meth) acrylic acid ester monomer as constituent units. There is disclosed a resin composition for toner, wherein the resin composition for use contains a styrene-olefin-styrene ternary block copolymer having a polar group at the terminal.

  Patent Document 3 discloses a toner for developing an electrostatic image characterized by containing a styrene maleic acid copolymer resin as a binder resin, a colorant, and a charge control agent.

JP 05-61240 A Japanese Patent Laid-Open No. 10-239898 Japanese Patent Laid-Open No. 60-108861

  An object of the present invention is to provide a liquid developer capable of charging toner particles with a small amount of charge control agent.

  The invention according to claim 1 includes a carrier liquid, toner particles containing a polymer dispersed in the carrier liquid and containing at least styrene as a polymerization component, and at least a styrene monomer contained in the carrier liquid, and a charge control agent which is a copolymer of an α-olefin and an unsaturated dibasic acid or a modified product thereof.

  The invention according to claim 2 is the liquid developer according to claim 1, wherein the unsaturated dibasic acid is at least one of maleic anhydride and maleic acid.

  The invention according to claim 3 is the liquid developer according to claim 1 or 2, wherein the α-olefin is an α-olefin having 10 to 20 carbon atoms.

  The invention according to claim 4 is a developer cartridge in which the liquid developer according to any one of claims 1 to 3 is accommodated.

  According to a fifth aspect of the present invention, the liquid developer according to any one of the first to third aspects is accommodated, and the electrostatic latent image formed on the surface of the electrostatic latent image holding member is converted into the liquid developer. A process cartridge that includes a developing device that develops toner images to form a toner image and is detachable from the image forming device.

  According to a sixth aspect of the present invention, there is provided an electrostatic latent image holding member, charging means for charging the surface of the electrostatic latent image holding member, and an electrostatic latent image forming an electrostatic latent image on the surface of the electrostatic latent image holding member. An electrostatic latent image forming unit and the liquid developer according to any one of claims 1 to 3 are accommodated, 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.

  According to a seventh aspect of the present invention, there is provided a charging step of charging a 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 static A developing step of 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 3 to form a toner image; and An image forming method comprising: 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, charging of toner particles is realized with a small amount of charge control agent compared to a liquid developer having a charge control agent which is a copolymer of α-olefin and unsaturated dibasic acid. A liquid developer is obtained.
According to the invention of claim 2, a small amount of charge compared to a liquid developer having a charge control agent which is a copolymer using maleic anhydride or an unsaturated dibasic acid other than maleic acid or a modified product thereof. With the control agent, a liquid developer in which charging of toner particles is realized can be obtained.
According to the invention of claim 3, the amount of carbon developer is smaller than that of a liquid developer having a charge control agent that is a copolymer using an α-olefin having a carbon number outside the range of 10 or more and 20 or less, or a modified product thereof. With the charge control agent, a liquid developer in which charging of toner particles is realized can be obtained.
According to the fourth aspect of the present invention, compared with the case where a liquid developer having a charge control agent that is a copolymer of an α-olefin and an unsaturated dibasic acid is stored, a small amount of charge control agent can be used. A developer cartridge containing a liquid developer that can be charged is obtained.

  According to the inventions according to claims 5 to 7, an image in which a decrease in image density is suppressed as compared with a case where a liquid developer having a charge control agent that is a copolymer of an α-olefin and an unsaturated dibasic acid is stored. Process cartridge, image forming apparatus, and image forming method.

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

  Hereinafter, an embodiment which is an example of the present invention will be described in detail.

[Liquid developer]
The liquid developer according to the present embodiment (hereinafter sometimes simply referred to as “developer”) includes a carrier liquid and a polymer dispersed in the carrier liquid and containing at least styrene as a polymerization component (hereinafter referred to as a styrene-based polymer). Toner particles containing a polymer), a charge control agent which is contained in the carrier liquid and is at least a copolymer of styrene monomer, α-olefin and unsaturated dibasic acid, or a modified product thereof, A developer having

The developer according to the present embodiment is a liquid developer that achieves charging of toner particles with a small amount of charge control agent by the above configuration.
The reason for this is not clear, but is thought to be due to the following reasons.

First, toner particles contain at least a styrene polymer and are composed of a polymer having a styrene polymerization site.
On the other hand, the charge control agent is composed of a copolymer having a styrene polymerization site, such as a copolymer of a styrene monomer, an α-olefin and an unsaturated dibasic acid, or a modified product thereof.
Therefore, since both the toner particles and the charge control agent contain a styrene polymerization site, an electrostatic attractive action at the styrene polymerization site acts between the toner particles and the charge control agent. It is thought that it becomes easy to adhere to the surface of the toner particles.
That is, it is considered that the charge control agent is included in the carrier liquid in a state of adhering to the surface of the toner particles, and as a result, the liquid developer according to the present embodiment is a small amount of charge control agent. It is considered that charging of the toner particles is realized.

  From the above, it is considered that the developer according to the present embodiment provides a liquid developer in which toner particles can be charged with a small amount of charge control agent.

In addition, since the charge control agent has an α-olefin as a constituent component of the copolymer, the effect of improving the fluidity of the toner particles and suppressing aggregation of the toner particles during storage is exhibited. it is conceivable that.
Although the reason for the above effect is not clear, the α-olefin alkyl group extends in the lateral direction of the charge control agent, which is a copolymer, so that the affinity with the carrier liquid is increased and the aggregation between the toner particles is increased. It is thought that it is preventing.

In addition, the developer according to this embodiment is a developer having a high solid content of toner particles because the charge control agent is likely to adhere to the surface of the toner particles, and thus the charge control agent is considered to exert a spacer function. However, it is considered that the developer has excellent fluidity.
Further, in the developer according to the present embodiment, since the charge control agent easily adheres to the surface of the toner particles, the amount of the charge control agent present in the carrier liquid is reduced, so that the conductivity of the developer is increased. This is considered to suppress the phenomenon that the image density is lowered.

  Hereinafter, the developer according to the exemplary embodiment will be described in detail.

(Charge control agent)
First, the charge control agent will be described.
As the charge control agent, a charge control agent which is a copolymer of a styrene monomer, an α-olefin and an unsaturated dibasic acid or a modified product thereof is applied.

Examples of the styrene monomer include styrene, styrene-substituted products [alkyl styrene (methyl styrene, t-butyl styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-ethyl styrene, 2,4-dimethyl. Styrene, pn-butyl styrene, p-ter-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-dodecyl styrene), p-methoxy styrene, p-phenyl styrene, 3 , 4-dichlorostyrene, chlorostyrene, dichlorostyrene, bromostyrene, fluorostyrene, nitrostyrene, α-methylstyrene, and the like.
Among these, styrene and alkylstyrene (for example, alkylstyrene having an alkyl group having 1 to 6 carbon atoms) are preferable, and styrene is more preferable.

Examples of the α-olefin include 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, 1-docosene, 1-tetracocene, 1-hexacocene, 1- Examples include octacocene and 1-triacontene.
Among these, α-olefins preferably have 10 to 20 carbon atoms, preferably 12 to 20 carbon atoms, and more preferably 16 to 20 carbon atoms.
Specifically, for example, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene and 1-docosene are desirable, and 1-tetradecene, 1-hexadecene and 1-octadecene are more desirable.
When the number of carbon atoms of the α-olefin is 10 or more, it is considered that the solubility of the charge control agent in the carrier liquid tends to improve, and when it is 20 or less, the decrease in the adhesion force of the charge control agent to the toner particles is suppressed. It seems that there is a tendency.

Examples of the unsaturated dibasic acids include unsaturated dibasic acids, unsaturated dibasic acid anhydrides, and unsaturated dibasic acid monoesters.
Specific examples of the unsaturated dibasic acid include maleic acid, citraconic acid, itaconic acid, alkenyl succinic acid, and fumaric acid.
Examples of the unsaturated dibasic acid anhydride include maleic acid anhydride, citraconic acid anhydride, itaconic acid anhydride, alkenyl succinic acid anhydride, and the like.
Examples of the unsaturated dibasic acid monoester include monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl citraconic acid, and the like.
Among these, unsaturated dibasic maleic acid and unsaturated dibasic anhydride maleic anhydride are desirable, and maleic anhydride is more desirable.

The copolymer constituting the charge control agent may be further composed of other polymerization components.
Examples of other polymerization components include vinyl ether (methyl vinyl ether, butyl vinyl ether, etc.), (meth) acrylic acid, (meth) acrylic acid lower ester [methyl (meth) acrylate, ethyl (meth) acrylate, (meth) Butyl acrylate, etc.) and dienes (butadiene, isoprene, etc.) may be included.

As a desirable ratio (mol ratio) of the polymerization component in the charge control agent, first, the styrenic monomer may be 1 mol% or more and 25 mol% or less, and 3 mol% or more and 24 mol% or less with respect to all copolymer components in the charge control agent. Desirably, 5 mol% or more and 22 mol% or less is more desirable.
The α-olefin is preferably 30 mol% or more and 65 mol% or less, more preferably 30 mol% or more and 60 mol% or less, and more preferably 30 mol% or more and 50 mol% or less with respect to all copolymerization components in the charge control agent.
The unsaturated dibasic acid is preferably 30 mol% or more and 65 mol% or less, more preferably 45 mol% or more and 60 mol% or less, and more preferably 40 mol% or more and 55 mol% or less with respect to all copolymerization components in the charge control agent.
The other components are preferably 0 mol% or more and 10 mol% or less, more preferably 0 mol% or more and 8 mol% or less, and more preferably 0 mol% or more and 5 mol% or less with respect to all copolymerization components in the charge control agent.

The charge control agent may be a modified body of a copolymer constituted by the above polymerization components.
Specific examples include amine-modified products, fluorine-modified products, carboxyl-modified products, epoxy-modified products, and alcohol-modified products. Among these, amine-modified products and alcohol-modified products are desirable, and amine-modified products are preferable. More desirable.
Moreover, the modified body may be partially imidized.

  The weight average molecular weight (Mw) of the charge control agent is preferably from 5,000 to 500,000, preferably from 8,000 to 100,000, and more preferably from 10,000 to 50,000.

  The acid value of the charge control agent is preferably from 0.1 mgKOH / g to 10 mgKOH / g, preferably from 0.2 mgKOH / g to 5 mgKOH / g, more preferably from 0.2 mgKOH / g to 3 mgKOH / g.

The polymerization method of the components constituting the copolymer such as styrene monomer, α-olefin and unsaturated dibasic acids is not particularly limited, and a known method is used.
Examples thereof include a heat self-polymerization method, a method using a radical polymerization initiator, and a method using ultraviolet irradiation.

(Toner particles)
The toner particles will be described.
The toner particles contain at least a styrene polymer.
The toner particles may contain other additives such as other binder resins, colorants, waxes, silica powders, metal oxides and the like in addition to the styrene polymer.
Further, the silica powder and metal oxide additives may be externally added by, for example, performing a mixing process after obtaining toner particles.
Normally, the toner particles include a colorant, but when a transparent toner is used, the colorant may not be included.

  Examples of the styrene polymer include a styrene thermoplastic resin and a styrene thermoplastic elastomer, and it is particularly preferable to use these in combination.

  The styrenic thermoplastic elastomer used in combination contributes mainly to the improvement of the bending resistance by increasing the flexibility of the binder resin constituting the toner particles, and the styrene thermoplastic resin mainly contributes to the improvement of the scratch resistance. To do.

Examples of the styrenic thermoplastic resin include a styrene monomer polymer and a vinyl copolymer containing a styrene monomer and a (meth) acrylic acid ester monomer as constituent units. “(Meth) acryl” means either or both of acrylic and methacrylic.
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 Examples include chlorostyrene, t-butylstyrene, butylstyrene, chlorostyrene, dichlorostyrene, bromostyrene, fluorostyrene, nitrostyrene, 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, and the like methacryloxyethyl 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 styrene monomer and (meth) acrylic acid ester monomer, other vinyl monomers include acrylic acid such as acrylic acid, methacrylic acid, α-ethylacrylic acid, and crotonic acid, and α -Or β-alkyl derivatives; unsaturated dicarboxylic acids such as fumaric acid, maleic acid, citraconic acid, itaconic acid and the like, and monoester derivatives or diester derivatives thereof; succinic acid mono (meth) acryloyloxyethyl ester, (meth) acrylonitrile, Acrylamide or the like may be used. 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. If the weight average molecular weight (Mw) of the vinyl polymer is 150,000 or more, the scratch resistance is surely improved, and if it is 500,000 or less, the melt viscosity is kept low and the smoothness of the fixing surface is obtained. The color development according to the demand 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 styrenic thermoplastic resin is preferably 50% by mass or more and 95% by mass or less, and more preferably 60% by mass or more and 90% by mass or less with respect to the total binder resin, from the viewpoint of grindability.

Examples of the styrenic thermoplastic elastomer include block copolymers of polystyrene and polyolefin, random copolymers, etc., and have rubber characteristics at room temperature (for example, 25 ° C.), 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 Tough Tech M1911, Tuf Tech M 1943, Tuf Tech MP10, Asaprene T439, Tufrene A, and Kuraray DYNARON 8630P manufactured by Asahi Kasei. In particular, SOE-L611, SOE-L611X, SOE-L605 (trade name) manufactured by Asahi Kasei Co., Ltd., in which a soft segment portion sandwiched between polystyrenes has a polar group introduced and hydrogenated, are preferably used.

  The content of the styrenic thermoplastic elastomer is desirably 5% by mass or more with respect to the total binder resin. If the content of the styrenic thermoplastic elastomer is within the above range, the low-temperature fixability is greatly improved in addition to the bending resistance. If the content rate of the styrene-type thermoplastic elastomer with respect to all the binder resin is 5 mass% or more, while bending-proof characteristics will improve reliably, it will be suppressed that the high temperature side offset resistance is impaired. The upper limit of the content of the styrene-based thermoplastic elastomer is not particularly specified, but in consideration of the content of the styrene-based thermoplastic resin, to give a pulverizability of 50% by mass or less with respect to the total binder resin. When the content of the styrene-based thermoplastic resin is increased, it is contained at 40% by mass or less based on the total binder resin.

  As the binder resin other than the styrene polymer, a known binder resin can be mentioned. Examples thereof include polyester, polyethylene, polypropylene, polyurethane, epoxy resin, silicone resin, polyamide, and modified rosin.

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 the magenta pigment, condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinones, 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.

  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.

  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 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-dried toner, or a polymerized toner in a solvent.
For example, styrenic polymer, colorant, and if necessary, add other additives to a mixing device such as a Henschel mixer and mix, and melt this mixture with a twin screw extruder, Banbury mixer, roll mill, kneader, etc. After kneading, cool with a drum flaker, etc., coarsely pulverize with a pulverizer such as a hammer mill, further finely pulverize with a pulverizer such as a jet mill, and then classify with an air classifier etc. Particles are obtained.

Also, styrenic polymers, colorants, and other additives, if necessary, are dissolved in a solvent such as ethyl acetate, and emulsified / suspended in water containing a dispersion stabilizer such as calcium carbonate to remove the solvent. After that, the particles obtained by removing the dispersion stabilizer are filtered and dried to obtain an in-liquid emulsified dry toner.
In addition, a polymerizable monomer, a colorant, and a polymerization initiator (for example, benzoyl peroxide, lauroyl peroxide, isopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichloroylbenzoyl peroxide) that form a binder resin , Methyl ethyl ketone peroxide, etc.) and other additives are added to the aqueous phase under stirring and granulated. After the polymerization reaction, the particles are filtered and dried to obtain polymerized toner particles.

  The volume average particle diameter D50v of the toner particles is desirably 0.5 μm or more and 5.0 μm or less. Within the above range, the developability can be improved. In addition, the resolution of the image can be improved. The volume average particle diameter D50v of the toner particles is more desirably 0.8 μm or more and 4.0 μm or less, and further desirably 1.0 μm or more and 3.0 μm or less.

The volume average particle size D50v, the number average particle size distribution index (GSDp), the volume average particle size distribution index (GSDv) and the like of the toner particles are measured using a laser diffraction / scattering type particle size distribution measuring apparatus, for example, LA920 (manufactured by Horiba, Ltd.). Measured. Draw a cumulative distribution from the smaller diameter side for each particle size range (channel) divided based on the particle size distribution, and particles with a cumulative particle size of 16%, volume D16v, number D16p, and cumulative 50% The diameter is defined as volume D50v, number D50p, and the particle diameter at 84% cumulative is defined as volume D84v, number 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 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.

  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.

  The concentration of toner particles in the carrier liquid (hereinafter sometimes referred to as solid content concentration) is 0.5 mass from the viewpoint of controlling the viscosity of the developer appropriately and smoothing the circulation of the developer in the developing machine. % Or more and 40% by mass or less, and more preferably 1% by mass or more and 30% by mass or less.

[Developer cartridge, process cartridge, image forming apparatus, image forming method]
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. An 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 present embodiment are accommodated, and an electrostatic latent image formed on the surface of the electrostatic latent image holding body is stored. Developing means for developing with the 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.
Note that the liquid developer supplied to the developing device may be supplied from a developer cartridge in which the liquid developer is accommodated.

In the image forming apparatus, for example, the part 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 contains the liquid developer described above. In addition, a process cartridge that includes a developing unit that develops the electrostatic latent image formed on the surface of the electrostatic latent image holding member with a liquid developer to form a toner image, and is detachably attached to 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 has toner particles containing an insulating carrier liquid and an acrylic thermoplastic elastomer and an acrylic thermoplastic resin.

  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 concentration of 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 developed toner image 26 is conveyed to the photosensitive member 10 that rotates in the direction of arrow B in the figure, and is transferred to a paper (recording medium) 30. In this embodiment, the photosensitive member 26 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 10, 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.

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 conform to the fixing roller and the pressing roller in the fixing device, respectively. It shows 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, the photosensitive member 10 having the toner image 26 transferred to the intermediate transfer member 16 is conveyed to a contact position with the untransferred toner particle 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.
The image forming apparatus 100 may further include a neutralization 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, an image having high folding resistance can be obtained.

  Hereinafter, the present embodiment will be specifically described by way of examples. However, the present embodiment is not limited to these examples. In the following description, “part” and “%” all mean “part by mass” and “mass%” unless otherwise specified.

(Measurement methods for various physical properties)
-Measurement of weight average molecular weight of charge control agent-
The developer is sedimented by centrifugation (1000 rpm × 5 minutes), the supernatant is removed by decantation, and the toner is taken out. The extracted toner is washed with a mixed solvent of hexane / ethyl acetate = 1/1 (the mixed solvent is changed depending on the toner resin). The washed liquid was dried under reduced pressure at 150 ° C. to collect the charge control agent. It is measured by gel permeation chromatography (GPC) as a measurement material. The molecular weight measurement by GPC was performed with a THF solvent using a Tosoh column / TSKgel Super HM-M (15 cm) using a Tosoh GPC / HLC-8120 as a measuring device. The weight average molecular weight was calculated from the measurement result using a molecular weight calibration curve prepared with a monodisperse polystyrene standard sample.

-Measurement of acid value of charge control agent-
To measure the acid value, first, the developer is precipitated by centrifugation (1000 rpm × 5 minutes), the supernatant is removed by decantation, and the toner is taken out. The extracted toner is washed with a mixed solvent of hexane / ethyl acetate = 1/1 (the mixed solvent is changed depending on the toner resin). The washed liquid was dried under reduced pressure at 150 ° C. to collect the charge control agent. This was performed according to JIS K0070 as a measurement material, and a measurement method using a neutralization titration method. That is, an appropriate amount of a sample is taken, 100 ml of a solvent (diethyl ether / ethanol mixed solution) and a few drops of an indicator (phenolphthalein solution) are added, and shaken sufficiently until the sample is dissolved on a water bath. This was titrated with a 0.1 mol / l potassium hydroxide ethanol solution, and the end point was when the indicator was light red for 30 seconds. When the acid value is A, the sample amount is S (g), the 0.1 mol / l potassium hydroxide ethanol solution used for the titration is B (ml), and f is the factor of the 0.1 mol / l potassium hydroxide ethanol solution. , A = (B × f × 5.611) / S.

(Production of charge control agent)
-Charge control agent P-1-
In a 200 ml flask equipped with a stirring blade and a cooling pipe, i) 1.2 g of styrene (manufactured by Tokyo Chemical Industry Co., Ltd.) as a styrene monomer, iii) 7.8 g of maleic anhydride as unsaturated dibasic acids (Wako Pure Chemical Industries, Ltd.) 1) 1-octadecene (manufactured by Tokyo Kasei Kogyo Co., Ltd.) and 60 g of toluene were added as α-olefin, followed by nitrogen substitution.
After heating to 70 ° C. to dissolve the contents, a mixed solution of 0.43 g of benzoyl peroxide and 2 g of toluene was added. The oil bath was set to 100 ° C. (internal temperature 90 ° C.) and stirred for 3 hours. Subsequently, a mixed solution of 0.1 g of benzoyl peroxide and 1 g of toluene was added and reacted at 100 ° C. for 1 hour to complete.
The oil bath was removed and the solution was added dropwise to 500 ml of methanol while hot. After stirring at room temperature (25 ° C.) for 5 minutes, the obtained white powder was separated by filtration and vacuum-dried at 40 ° C. for an hour to obtain 20.3 g of a copolymer.
The obtained copolymer was designated as a charge control agent P-1.
When measured by the above-described method, the weight average molecular weight (GPC) was Mw: 15,900, and the acid value was 4.4 mmol / g.

-Charge control agent P-2 to 4-
According to Table 1, a copolymer was prepared in the same manner as the charge control agent P-1, except that i) styrene monomer, ii) α-olefin, and iii) unsaturated dibasic acids were changed. And charge control agents P-2 to P-4.

-Charge control agent P-5
After mixing 2.0 g of charge control agent P-1, 1.53 g of hexadecylamine (manufactured by Tokyo Chemical Industry Co., Ltd.), 10 mg of pyridine (manufactured by Wako Pure Chemical Industries, Ltd.) and 20 ml of xylene, the mixture was stirred at 80 ° C. for 1 hour. The ring closure reaction was carried out at 160 ° C. for 5 hours while removing the generated water.
Reprecipitation was performed with 150 ml of methanol, and vacuum drying was performed at 40 ° C. for an hour, to obtain 3.2 g of charge control agent P-5, which was a partially imidized amine-modified copolymer.
When measured by the method described above, the weight average molecular weight (GPC) was Mw: 20,900, and the acid value was 0.5 mmol / g.

-Charge control agent P-6
According to Table 1, it was partially imidized in the same manner as charge control agent P-5, except that i) styrenic monomer, ii) α-olefin, and iii) unsaturated dibasic acids were changed. In addition, a charge control agent P-6, which is an amine-modified copolymer, was prepared.

-Charge control agent P-7-
According to Table 1, the copolymer was produced similarly to the charge control agent P-1 except having changed the kind and compounding quantity of i) styrene-type monomer, ii) alpha olefin, and iii) unsaturated dibasic acid.
It is generated after 2.0 g of the obtained copolymer, 1.17 g of decylamine (manufactured by Tokyo Chemical Industry Co., Ltd.), 10 mg of pyridine (manufactured by Wako Pure Chemical Industries, Ltd.) and 20 ml of xylene are mixed and stirred at 80 ° C. for 1 hour. The ring closure reaction was carried out at 160 ° C. for 5 hours while removing water out of the system. It reprecipitated with 150 ml of methanol and vacuum-dried at 40 ° C. for an hour to obtain 2.9 g of a charge control agent P-7, which is a partially imidized amine-modified copolymer.

-Charge control agent P-8-
2.0 g of charge control agent P-1, 1.53 g of hexadecylamine (manufactured by Tokyo Chemical Industry Co., Ltd.), 10 mg of pyridine (manufactured by Wako Pure Chemical Industries, Ltd.) and 20 ml of xylene were mixed and stirred at 80 ° C. for 1 hour.
Reprecipitation was performed with 150 ml of methanol and vacuum drying was performed at 40 ° C. for an hour to obtain 3.5 g of a charge control agent P-8, which is an amine-modified copolymer.
When measured by the method described above, the weight average molecular weight (GPC) was Mw: 20,300, and the acid value was 1.6 mmol / g.

-Charge control agent P-9-
According to Table 1, except that the types and blending amounts of i) styrenic monomer, ii) α-olefin, and iii) unsaturated dibasic acid were changed, the copolymer amine was changed in the same manner as charge control agent P-8. The charge control agent P-9 which is a modified body was produced.

-Charge control agent P-10-
Except for changing 1.53 g of decylamine to 1.17 g of decylamine (manufactured by Tokyo Kasei Kogyo Co., Ltd.), it is a partially imidized amine-modified copolymer in the same manner as the charge control agent P-5. 2.9 g of charge control agent P-10 was obtained.
When measured by the above-described method, the weight average molecular weight (GPC) was Mw: 18,300, and the acid value was 0.6 mmol / g.

-Charge control agent P-11
According to Table 1, the type and blending amount of i) styrenic monomer, ii) α-olefin, and iii) unsaturated dibasic acid were changed, and toluene added to the polymerization component was changed from 60 g to 80 g before nitrogen substitution. A copolymer (28.3 g) was produced in the same manner as in the charge control agent P-1.
The obtained copolymer 4.0 g, hexadecylamine 3.6 g, pyridine 50 mg (manufactured by Wako Pure Chemical Industries, Ltd.) and xylene 50 ml were mixed and stirred at 80 ° C. for 1 hour, and then the generated water was removed. The ring closure reaction was performed at 160 ° C. for 5 hours.
7.4 g of charge control agent P-11, which is an amine-modified copolymer and partially imidized, was reprecipitated with 200 ml of methanol and vacuum-dried at 40 ° C. for an hour.
When measured by the method described above, the weight average molecular weight (GPC) was Mw: 22,000, and the acid value was 0.5 mmol / g.

-Charge control agent P-12-
In a 200 ml flask equipped with a stirring blade and a cooling tube, 1.1 g of styrene (manufactured by Tokyo Chemical Industry Co., Ltd.), 13.0 g of itaconic acid (manufactured by Wako Pure Chemical Industries, Ltd.), 1-tetradecene (manufactured by Tokyo Chemical Industry Co., Ltd.) 7 g and 60 g of toluene were added, and nitrogen substitution was performed. After heating to 70 ° C. to dissolve the contents, a mixed solution of 0.43 g of benzoyl peroxide and 2 g of toluene was added. The bath temperature was set to 100 ° C. (internal temperature 90 ° C.), and the mixture was stirred for 3 hours.
Subsequently, a mixed solution of 0.1 g of benzoyl peroxide and 1 g of toluene was added, and the reaction was completed at 100 ° C. for 2 hours. The liquid was brought to 40 ° C., 13.9 g of diisopropylcarbodiimide was added and stirred for 30 minutes, 27 g of octadecylamine was added and stirred for 6 hours. The solution was added dropwise little by little into 1000 ml of methanol. After stirring at room temperature (25 ° C.) for 5 minutes, the obtained white powder was separated by filtration and vacuum-dried at 40 ° C. for an hour to obtain 41 g of a charge control agent P-12.
When measured by the method described above, the weight average molecular weight (GPC) was Mw: 23,900, and the acid value obtained by neutralization titration with KOH / EtOH was 1.8 mmol / g.

-Charge control agent P-13-
According to Table 1, it was partially imidized in the same manner as the charge control agent P-10 except that i) styrenic monomer, ii) α-olefin, and iii) unsaturated dibasic acids were changed. In addition, a charge control agent P-13, which is an amine-modified product of a copolymer, was produced.

-Comparative charge control agent PH-1-
A copolymer of 1-octadecene / maleic anhydride (molar ratio 50/50) was prepared as follows according to the blending amount in Table 1.
To a 200 ml flask equipped with a stirring blade and a condenser tube, 7.8 g of maleic anhydride, 22.2 g of 1-octadecene and 60 g of toluene were added, and nitrogen substitution was performed.
After heating to 70 ° C. to dissolve the contents, a mixed solution of 0.43 g of benzoyl peroxide and 2 g of toluene was added. The oil bath was set to 100 ° C. (internal temperature 90 ° C.) and stirred for 3 hours. Subsequently, a mixed solution of 0.1 g of benzoyl peroxide and 1 g of toluene was added and reacted at 100 ° C. for 1 hour to complete.
The oil bath was removed and the solution was added dropwise to 500 ml of methanol while hot. After stirring at room temperature (25 ° C.) for 5 minutes, the obtained white powder was separated by filtration and vacuum-dried at 40 ° C. for an hour to obtain 22.3 g of a copolymer.
Subsequently, the obtained copolymer was modified with the same number of moles of decylamine as the maleic anhydride moiety in the same manner as the charge control agent P-10, and partially imidized, with the modified amine of the copolymer. There was obtained 2.8 g of charge control agent PH-1.
When measured by the above-described method, the weight average molecular weight (GPC) was Mw: 15,900, and the acid value determined by neutralization titration with KOH / EtOH was 1.1 mmol / g.

-Comparative charge control agent PH-2-
A styrene / maleic anhydride copolymer (molar ratio 50/50) was prepared as follows in accordance with the blending amount shown in Table 1.
To a 200 ml flask equipped with a stirring blade and a condenser tube, 7.8 g of maleic anhydride, 9.4 g of styrene, and 60 g of toluene were added, and nitrogen substitution was performed.
After heating to 70 ° C. to dissolve the contents, a mixed solution of 0.43 g of benzoyl peroxide and 2 g of toluene was added. The oil bath was set to 100 ° C. (internal temperature 90 ° C.) and stirred for 3 hours. Subsequently, a mixed solution of 0.1 g of benzoyl peroxide and 1 g of toluene was added and reacted at 100 ° C. for 1 hour to complete.
The oil bath was removed and the solution was added dropwise to 500 ml of methanol while hot. After stirring at room temperature (25 ° C.) for 5 minutes, the obtained white powder was separated by filtration and vacuum-dried at 40 ° C. for a time to obtain 12.9 g of a copolymer.
Subsequently, the obtained copolymer was modified with the same number of moles of decylamine as the maleic anhydride moiety in the same manner as the charge control agent P-10, and partially imidized, with the modified amine of the copolymer. Some 1.2g of charge control agent PH-2 was obtained.
When measured by the above-described method, the weight average molecular weight (GPC) was Mw: 26,000, and the acid value determined by neutralization titration with KOH / EtOH was 1.9 mmol / g.

(Production of toner particles)
-Toner particles 1-
Thermoplastic resin 1 (styrene-butyl acrylate resin, manufactured by Fujikura Kasei Co., Ltd., trade name: FSR-053, weight average molecular weight: 380,000): 60 parts by mass Cyan pigment C.I. I. Pigment Blue 15: 3 (manufactured by Clariant): 40 parts by mass The above mixture was kneaded with a pressure kneader. The kneaded product was coarsely pulverized to prepare a cyan pigment master batch.

-Cyan pigment master batch: 25 parts by mass-Thermoplastic resin 2 (styrene-butyl acrylate resin, manufactured by Fujikura Kasei Co., Ltd., trade name: FSR-051, weight average molecular weight: 320,000, acid value: 10): 55 parts by mass / thermoplastic elastomer 1 (manufactured by Asahi Kasei Co., Ltd., trade name: SOE-SSL611X, hydrogenated product of styrene-butadiene-styrene block copolymer): 20 parts by mass Next, the above mixture is pressurized again The mixture was kneaded with a kneader.
The obtained mixture was pulverized with a jet mill to obtain cyan particles having a volume average particle diameter of 10 μm.

(Preparation of liquid developer)
-Liquid developer 1
Toner particles 1 (35 parts) are added 100 parts of carrier liquid 1 (manufactured by Matsumura Oil Co., Ltd., trade name: Moresco White MT30P), finely pulverized with a ball mill, and toner particles having a volume average particle diameter of 2.0 μm. A dispersion was obtained.
To this dispersion, carrier liquid 1 and a solution (1.0% by mass) in which charge control agent P-8 is dissolved in carrier liquid 1 are added, the solid content concentration is 18% by mass, and the charge control agent concentration is 0. The liquid developer 1 was obtained by adjusting the content to 15 mass%.

-Liquid developer 2-
A liquid developer 2 was obtained in the same manner as the liquid developer 1 except that the charge control agent P-1 was used instead of the charge control agent P-8.

-Liquid developer 3-
A liquid developer 3 was obtained in the same manner as the liquid developer 1 except that the charge control agent P-5 was used instead of the charge control agent P-8.

-Liquid developer 4-6
Liquid developers 4 to 6 were obtained in the same manner as liquid developer 3 except that the concentration of charge control agent P-5 was changed according to Table 2.

-Liquid developer 7-10-
Liquid developers 7 to 10 were obtained in the same manner as liquid developer 1 except that charge control agent P-8 was changed to a charge control agent according to Table 2.
However, in the liquid developer 10, although the charge control agent P-13 was not completely dissolved in the carrier liquid 1 and was a slightly turbid liquid, the liquid was used as it was.

-Liquid developer 11-
Liquid developer 11 was produced in the same manner as liquid developer 3 except that the carrier liquid was changed to carrier liquid 2 (manufactured by Matsumura Oil Co., Ltd., trade name: Moresco White P40).

-Liquid developer 20-
A liquid developer 20 was obtained in the same manner as the liquid developer 1 except that the charge control agent was not used.

-Liquid developer 21-
A liquid developer 21 was obtained in the same manner as the liquid developer 1 except that PH-1 was used instead of the charge control agent P-8.

-Liquid developer 22-24-
Liquid developers 22 to 24 were obtained in the same manner as liquid developer 1, except that PH-1 was used instead of P-8 and the amount of charge control agent added was changed according to Table 2.

-Liquid developer 25-
The liquid developer 25 was prepared in the same manner as the liquid developer 1 except that the charge control agent PH-2 was used instead of the charge control agent P-8. Since it was not dissolved in the carrier liquid 1 at a ratio of 1.0% by mass, the addition could not be evaluated.

-Adjustment of the liquid developer 30-
A liquid developer 30 was obtained in the same manner as the liquid developer 3 except that the solid content concentration was changed from 18% by mass to 21% by mass.

-Adjustment of liquid developer 31-
A liquid developer 31 was obtained in the same manner as the liquid developer 21 except that the solid content concentration was changed from 18% by mass to 21% by mass.

[Example 1]
The following evaluation was performed using the liquid developer 1.
The results are shown in Table 2.

<Evaluation>
(Charging characteristics)
Two glass substrates with ITO processed by 5cm x 1cm (EHC: 100Ω / □) are used as insulating spacers, and a Naflon sheet (Azwan: 1cm x 1cm x 1.0mm) is sandwiched between the electrode faces inward. It was fixed to become.
1 ml of liquid developer 1 is put in a disposable cell (manufactured by ASONE: 12 × 12 × 45 mm), the above electrode substrate is immersed, a DC voltage of 250 V is applied for 30 seconds, and the electrode is applied with the voltage applied. And the adhesion state of the particles on the ITO electrode surfaces of the positive electrode and the negative electrode was observed to determine the charging characteristics.
The evaluation criteria are + when the toner adhesion amount is larger than the adhesion amount to the positive electrode when the adhesion state is visually judged by the color density of the toner, and it is acceptable even if it is slightly adhered to the positive electrode. And

(conductivity)
The above-mentioned Naflon sheet was sandwiched between the two glass substrates with ITO, the electrode surface was inward, both ends were shifted by 1 cm, and the spacers were fixed so that the distance between them was 2 cm. A developer is put in the gap between the electrodes, a pulse waveform (60 vp-p, frequency 0.1 Hz) is added to measure the charge amount, and the conductivity is calculated.
The evaluation criteria were as follows.
A: Less than 1 × 10 ⁻¹¹ B: 1 × 10 ⁻¹¹ or more, less than 1 × 10 ⁻¹⁰ C: 1 × 10 ⁻¹⁰ or more, less than 1 × 10 ⁻⁹ D: 1 × 10 ⁻⁹ or more If it is C, it is set as an allowable range.

(Image density)
The liquid developer was diluted with the same carrier liquid as used in the preparation of the liquid developer so that the liquid developer would be 2.5%, and the diluted liquid was put into a disposable cell (made of polystyrene). Two transparent electrodes facing each other with a gap of 1 mm were immersed in this, and a voltage of 300 V was applied for 30 seconds. The electrode was pulled up, and the toner deposited on the plus electrode was transferred onto J-coated paper manufactured by Fuji Xerox. The loaded amount of the deposited toner was measured and found to be 3.6 g / m ² .
The transferred image was fixed using an external fixing device at a roller temperature of 100 ° C. and under a nip of 6 mm at 500 mm / sec, and the density of the obtained image was measured.
The evaluation criteria were as follows.
A: 1.0 or more B: 0.8 or more and less than 1.0
C: 0.5 or more and less than 0.8
D: 0.5 or less If the evaluation result is A to C, the allowable range is assumed.

[Examples 2 to 12, Comparative Examples 1 to 7]
Evaluation was performed in the same manner as in Example 1 using a liquid developer according to Table 2.

From the above results, it is clear that the developer of this embodiment can charge the toner particles with a small amount of charge control agent compared to the developer of the comparative example.
Note that the liquid developer 31 used in Comparative Example 7 was poor in toner fluidity, and thus the conductivity and image density could not be evaluated.

10 Photoconductor (electrostatic latent image holder)
12 Exposure device (electrostatic latent image forming device)
14 Developing Device 16 Intermediate Transfer Body 18 Cleaner 20 Charging Device 24 Liquid Developer 26 Toner Image 28 Transfer Fixing Roller (Transfer Device)
29 fixed image 30 recording medium 100 image forming apparatus

Claims (7)

Carrier liquid,
Toner particles dispersed in the carrier liquid and containing a polymer containing at least styrene as a polymerization component;
A charge control agent which is contained in the carrier liquid and is at least a copolymer of a styrene monomer, an α-olefin and an unsaturated dibasic acid, or a modified product thereof;
A liquid developer.   The liquid developer according to claim 1, wherein the unsaturated dibasic acid is at least one of maleic anhydride and maleic acid.   The liquid developer according to claim 1, wherein the α-olefin is an α-olefin having 10 to 20 carbon atoms.   A developer cartridge in which the liquid developer according to claim 1 is stored. Storing the liquid developer according to any one of claims 1 to 3,
A developing device for developing 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 attached to and detached from the 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;
The liquid developer according to claim 1 is stored, and the electrostatic latent image formed on the surface of the electrostatic latent image holding member is developed with the liquid developer to form a toner image. Developing means,
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 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 3 to form a toner image;
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: