JP2013186412A - Liquid developer, image forming apparatus, process cartridge, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide liquid developer that has excellent operability.SOLUTION: A liquid developer contains: an insulating hydrocarbon-based carrier liquid; toner particles that contain colorant, a styrenic thermoplastic elastomer not dissolving in the carrier liquid at 25°C, and a styrenic thermoplastic resin not dissolving in the carrier liquid at 25°C, and are dispersed in the carrier liquid; and a block copolymer that is dissolved in the carrier liquid at 25°C.

Description

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

Regarding the toner used in the dry development system, for example, the following is proposed, but Patent Document 1 discloses a first liquid toner containing a nonpolar solvent system, a thermoplastic synthetic fixing agent, and a dispersant. A non-polar solvent system, and a second liquid toner containing a graft amphiphilic polymer, wherein at least one of the first and second liquid toners contains a dielectric agent. Is disclosed.
In Patent Document 2, in a dispersion composition obtained by dispersing a particulate material in an organic solvent, a range of 0.01 μm to 1 μm that is self-dispersed in the organic solvent on at least a part of the outer surface of the particulate material. A dispersion composition in which a polymer compound having an average particle diameter of the above is adsorbed and the amount of adsorption of the self-dispersing polymer compound is within a range of 20 parts by weight or more and 10,000 parts by weight or less per 100 parts by weight of the particulate material. It is disclosed.

In Patent Document 3, toner particles having pigment particles distributed unevenly on the surface of resin particles insoluble in the electrically insulating carrier liquid are dispersed in the carrier liquid, and mutual contact of the resin particles is suppressed by the pigment particles. The pigment particles are unevenly distributed on the surface of the toner particles so as to cover the surface of the resin particles, and the pigment particles are kneaded in the resin particle dispersion and the colorant particles are pressure-bonded to the resin particle surface. Developers are disclosed.
In Patent Document 4, in a liquid developer containing a pigment, an acrylic thermoplastic resin, an electrical insulating solvent, and a dispersant, the acrylic thermoplastic resin has a swelling degree of less than 0.5 g with respect to the electrical insulating solvent. A liquid developer comprising a modified novolak resin (A) or a graft copolymer (B) having a ring-opening structure of an aromatic ring and an epoxy group by a carboxyl group derived from hydroxycarboxylic acid is disclosed. Yes.

Patent Document 5 discloses a liquid developer comprising at least toner particles, a carrier liquid, and a dispersant, wherein the dispersant is an alkoxytitanium polymer, and a fluorine-containing silane compound is used in combination. Yes.
Patent Document 6 discloses a liquid developer comprising at least toner particles, a carrier liquid, and a dispersant, wherein the dispersant is a polyhydroxytitanium carboxylate compound and a fluorine-containing silane compound. Yes.

Patent Document 7 discloses a resin B comprising a combination of a highly insulating carrier liquid A mainly composed of silicone, a resin b ₁ soluble in the carrier liquid A, and resin particles b ₂ insoluble in the carrier liquid A. In the developer composed of the colorant C and the charge adjusting agent D, the resin b ₁ soluble in the carrier liquid A is made of a resin mainly composed of silicone, and the resin particles b insoluble in the carrier liquid A ₂ comprises at least one resin selected from vinyl polymers and vinyl copolymers including acrylic, vinyl acetate, and styrene resins, and the resin B and the colorant C An electrophotographic liquid developer having a solid content concentration of 10% by weight or more is disclosed.

JP 53-054029 A JP 2001-098206 A JP 2002-278170 A JP 2004-021023 A JP 2011-043650 A JP 2011-053572 A Japanese Patent Application Laid-Open No. 07-261466

  An object of the present invention is to provide a liquid developer having excellent operability.

In order to achieve the above object, the following invention is provided.
The invention according to claim 1
An insulating hydrocarbon carrier liquid;
Toner particles containing a colorant, a styrenic thermoplastic elastomer that does not dissolve in the carrier liquid at 25 ° C., and a styrene thermoplastic resin that does not dissolve in the carrier liquid at 25 ° C., and dispersed in the carrier liquid;
A block copolymer that dissolves in the carrier liquid at 25 ° C .;
A liquid developer containing

The invention according to claim 2
The liquid developer according to claim 1, wherein the block copolymer has at least one repeating unit selected from butylene and ethylene in the structure.

The invention according to claim 3
The liquid developer according to claim 1, wherein the block copolymer is a hydrogenated butadiene rubber.

The invention according to claim 4
4. The liquid developer according to claim 1, wherein a flash point of the carrier liquid is in a range of 70 ° C. or more and 120 ° C. or less. 5.

The invention according to claim 5
The liquid according to any one of claims 1 to 4, wherein the carrier liquid has a content ratio of saturated hydrocarbons having 12 to 15 carbon atoms in all carrier liquids of 90 mass% or more and 100 mass% or less. Developer.

The invention according to claim 6
An electrostatic latent image carrier;
A charging device for charging the surface of the electrostatic latent image holding member;
An electrostatic latent image forming apparatus for forming an electrostatic latent image on the surface of the electrostatic latent image holding member;
A developing device that stores the liquid developer according to claim 1 and that develops the electrostatic latent image formed on the surface of the electrostatic latent image holding member with the liquid developer to form a toner image;
A transfer device for transferring the toner image to a recording medium;
A fixing device for fixing the toner image on the recording medium;
An image forming apparatus.

The invention according to claim 7 provides:
A developing device that stores the liquid developer according to claim 1 and that develops the electrostatic latent image formed on the surface of the electrostatic latent image holding member with the liquid developer to form a toner image,
The process cartridge is detachable from the image forming apparatus.

The invention according to claim 8 provides:
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 claim 1 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;
Is an image forming method.

  According to the first aspect of the present invention, only toner particles containing a styrenic thermoplastic elastomer that does not dissolve in the carrier liquid at 25 ° C. and a styrene thermoplastic resin that does not dissolve in the carrier liquid at 25 ° C. in the carrier liquid. Compared with the case where it contains, the liquid developer excellent in operativity is provided.

  According to the second aspect of the present invention, a liquid developer excellent in operability is provided as compared with the case where the block copolymer does not have at least one repeating unit selected from butylene and ethylene in the structure.

  According to the third aspect of the present invention, a liquid developer excellent in operability is provided as compared with the case where the block copolymer is not hydrogenated butadiene rubber.

  According to the fourth aspect of the present invention, a liquid developer excellent in operability is provided as compared with a case where the flash point of the carrier liquid is not in the range of 70 ° C. or higher and 120 ° C. or lower.

  According to the fifth aspect of the present invention, there is provided a liquid developer having excellent operability as compared with the case where the carrier liquid contains a saturated hydrocarbon having 11 or less carbon atoms or 16 or more carbon atoms in excess of 10% by mass. .

  According to the invention of claim 6, toner particles comprising a carrier liquid, a styrene-based thermoplastic elastomer that does not dissolve in the carrier liquid at 25 ° C., and a styrene-based thermoplastic resin that does not dissolve in the carrier liquid at 25 ° C .; As compared with a case where a liquid developer containing a block copolymer that dissolves in the carrier liquid at 0 ° C. is not used, an image forming apparatus that is superior in liquid feeding property of the liquid developer is provided.

  According to the invention of claim 7, toner particles comprising a carrier liquid, a styrene thermoplastic elastomer that does not dissolve in the carrier liquid at 25 ° C., and a styrene thermoplastic resin that does not dissolve in the carrier liquid at 25 ° C .; A process cartridge excellent in liquid-feeding property of a liquid developer is provided as compared with a case where a liquid developer containing a block copolymer that dissolves in the carrier liquid at 0 ° C. is not used.

  According to the eighth aspect of the present invention, there are provided a carrier liquid, toner particles containing a styrene thermoplastic elastomer that does not dissolve in the carrier liquid at 25 ° C., and a styrene thermoplastic resin that does not dissolve in the carrier liquid at 25 ° C .; An image forming method excellent in liquid feeding property of a liquid developer is provided as compared with a case where a liquid developer containing a block copolymer that dissolves in the carrier liquid at 0 ° C. is not used.

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

  Hereinafter, embodiments of the present invention will be described in detail.

<Liquid developer>
The liquid developer according to this embodiment includes an insulating hydrocarbon carrier liquid, a colorant, a styrene thermoplastic elastomer that does not dissolve in the carrier liquid at 25 ° C., and a styrene system that does not dissolve in the carrier liquid at 25 ° C. Toner particles that contain a thermoplastic resin and are dispersed in the carrier liquid, and a block copolymer that dissolves in the carrier liquid at 25 ° C.

By using toner particles containing a styrenic thermoplastic elastomer and a styrenic thermoplastic resin in a liquid developer, excellent folding resistance, that is, when a recording medium on which an image is formed is folded, An image in which toner dropout is suppressed is obtained. In addition to the above bending resistance, it is excellent in scratch resistance and low temperature fixability.
However, styrene-based thermoplastic elastomers have good compatibility with carrier liquids. Therefore, as the amount of toner particles added to the liquid developer is increased, the liquid viscosity increases and the fluidity decreases, so that the operability of the liquid developer is improved. There was a decline.
In addition, since the carrier liquid is likely to remain in the styrene-based thermoplastic elastomer, the formed image may show back over time.

  In contrast, in the liquid developer according to the exemplary embodiment, the toner particles dispersed in the carrier liquid include a styrene thermoplastic elastomer and a styrene thermoplastic resin, and are dissolved in the carrier liquid at 25 ° C. A block copolymer is contained. As a result, an increase in liquid viscosity of the liquid developer is suppressed, a decrease in fluidity is suppressed, and excellent operability of the liquid developer is obtained. In addition, the occurrence of show-through over time is also suppressed in the formed image.

  The reason why excellent operability can be obtained is not necessarily clear, but is presumed as follows. If the toner particles contain a styrene thermoplastic elastomer and a styrene thermoplastic resin, it is considered that the toner particles contained in the carrier liquid are entangled and aggregated to form an oil gel. On the other hand, by including a block copolymer that dissolves in the carrier liquid at 25 ° C. in the carrier liquid, the block copolymer dissolves in the carrier liquid, and between the toner particles that have absorbed the carrier liquid. This is presumed to prevent entanglement. As a result, entangled toner particles are separated from each other, an increase in liquid viscosity is suppressed, a decrease in fluidity is suppressed, and an excellent operability of the liquid developer can be obtained.

  Hereinafter, the components of the liquid developer according to this embodiment will be described in detail.

[Toner particles]
The toner particles contained in the liquid developer according to the exemplary embodiment include a styrene-based thermoplastic elastomer that does not dissolve in the carrier liquid at 25 ° C. and a styrene-based thermoplastic resin that does not dissolve in the carrier liquid at 25 ° C. . The styrenic thermoplastic elastomer mainly contributes to improving the bending resistance by increasing the flexibility of the binder resin constituting the toner particles, and the styrene thermoplastic resin mainly contributes to improving the scratch resistance.

  Whether or not the styrene thermoplastic elastomer and styrene thermoplastic resin are not dissolved in the carrier liquid is confirmed by the following method. That is, 1 g (1% by mass) of the sample was added to 100 g of the carrier liquid, stirred at 70 ° C., cooled to 25 ° C., and confirmed whether or not it was precipitated as a solid. Is done.

-Styrenic thermoplastic resin-
The styrenic thermoplastic resin contained in the toner particles of the present embodiment represents at least a styrenic thermoplastic resin other than the styrenic thermoplastic elastomer described later.

As the styrenic thermoplastic resin contained in the toner particles of the present embodiment, a polymer of a styrenic monomer, a vinyl type containing a styrene monomer and a (meth) acrylic acid ester monomer as constituent units A copolymer is mentioned. “(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 And chlorostyrene.

Examples of the (meth) acrylic acid ester monomer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, and (meth) acrylic. In addition to alkyl esters of (meth) acrylic acid such as isobutyl acid, n-octyl (meth) acrylate, dodecyl (meth) acrylate, 2-ethylhexyl acrylate, stearyl (meth) acrylate, 2-chloroethyl acrylate, Phenyl (meth) acrylate, methyl α-chloroacrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, glycidyl (meth) acrylate Dimethylaminoethyl 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; mono (meth) acryloyloxyethyl ester of succinic acid, (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 weight average molecular weight (Mw) of the styrenic thermoplastic resin is preferably 150,000 to 500,000. Further, the molecular weight distribution (Mw / Mn) of the styrenic thermoplastic resin is preferably 2 or more and 20 or less.
The styrenic thermoplastic resin 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 in the toner particles is desirably 50% by mass or more and 95% by mass or less, and preferably 60% by mass or more and 90% by mass or less with respect to the total binder resin from the viewpoint of pulverization. Is more desirable.

-Styrenic thermoplastic elastomer-
Examples of the styrene-based thermoplastic elastomer contained in the toner particles of the present embodiment include block copolymers of polystyrene and polyolefin, random copolymers, and the like, which have rubber characteristics at room temperature (25 ° C.). Above this temperature, it is a softening material like thermoplastics.
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 in the toner particles is desirably 5% by mass or more based on the total binder resin. The upper limit of the content of the styrene-based thermoplastic elastomer is not particularly specified, but considering the content of the styrene-based thermoplastic resin, it is preferably 50% by mass or less, and 40% by mass or less with respect to the total binder resin. Is preferred.

The liquid absorption rate of the carrier liquid at 25 ° C. of the styrenic thermoplastic elastomer is preferably 200% or less, more preferably 0% or more and 150% or less, and particularly preferably 5% or more and 100% or less.
The liquid absorption rate is as follows: 2 g of thermoplastic elastomer pellets are placed in a 200 ml beaker containing 100 ml of carrier liquid, left in a thermostatic device at 25 ° C. for 15 hours, filtered through a 200 mesh wire mesh, and separated by filtration. This is a value calculated by the following equation by measuring the increase in weight after absorbing excess oil with filter paper.
Liquid absorption (%) = (weight increase / weight of first dry pellet) × 100

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

As yellow pigments, compounds represented by condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complex compounds, methine compounds, and allylamide compounds are used.
As 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.

-Other additives-
The toner particles of this embodiment contain other additives such as a colorant, a styrene thermoplastic elastomer, and a styrene thermoplastic resin, as well as other binder resins, waxes, charge control agents, silica powder, and metal oxides. You may do it. These additives may be added internally by, for example, kneading into a binder resin containing a styrene thermoplastic elastomer and a styrene thermoplastic resin, or may be mixed after the toner is obtained as particles. You may attach.

  Examples of the binder resin other than the styrene thermoplastic elastomer and the styrene thermoplastic resin contained in the toner particles include known binder resins. Examples thereof include polyester, polyethylene, polypropylene, polyurethane, epoxy resin, silicone resin, polyamide, and modified rosin.

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

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

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

-Toner Particle Manufacturing Method-
The method for producing the toner particles 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-dried toner, or a polymerized toner production method in a carrier liquid.
For example, a binder resin containing styrene-based thermoplastic elastomer and styrene-based thermoplastic resin, a colorant, other additives, and the like are introduced into a mixing device such as a Henschel mixer and mixed, and this mixture is mixed with a twin-screw extruder, Banbury. After melt-kneading with a mixer, roll mill, kneader, etc., cool with a drum flaker, etc., coarsely pulverize with a pulverizer such as a hammer mill, and further finely pulverize with a pulverizer such as a jet mill, then use an air classifier, etc. Thus, a pulverized toner can be obtained.
In addition, binder resins including styrenic thermoplastic elastomers and styrenic thermoplastic resins, colorants, other additives, etc. are dissolved in a solvent such as ethyl acetate, and added to water to which a dispersion stabilizer such as calcium carbonate has been added. After emulsifying / suspending and removing the solvent, the particles obtained by removing the dispersion stabilizer are filtered and dried to obtain an emulsified dry toner in liquid.
In addition, a polymerizable monomer, a colorant, and a polymerization initiator (for example, benzoyl peroxide, lauroyl peroxide, isopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichloroylbenzoyl peroxide) that form a binder resin , Methyl ethyl ketone peroxide, etc.) and other additives are added to the aqueous phase under agitation and granulated. After the polymerization reaction, the particles are filtered and dried to obtain a polymerized toner.

  The blending ratio of each material (styrenic thermoplastic elastomer and styrenic thermoplastic resin, colorant, other additives, etc.) used to obtain the toner is the required bending resistance, scratch resistance, and low temperature fixability. The color may be set in consideration of the color. 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, etc., whereby the toner particles for liquid developer of this embodiment are obtained.

  The volume average particle diameter D50v of the toner particles is desirably 0.5 μm or more and 5.0 μm or less. By being in the said range, adhesive force is high and developability is improved. In addition, the resolution of the image can be improved. The 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.

For the volume average particle size D50v, number average particle size distribution index (GSDp), volume average particle size distribution index (GSDv), etc. of the toner particles, a laser diffraction / scattering type particle size distribution measuring device, for example, LA920 (manufactured by Horiba Ltd.) is used. 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 .

[Block copolymer]
The liquid developer according to this embodiment contains a block copolymer that dissolves in the carrier liquid at 25 ° C. in the carrier liquid.

  Whether the block copolymer is dissolved in the carrier liquid is confirmed by the following method. That is, 1 g (1% by mass) of the sample was added to 100 g of the carrier liquid, stirred at 70 ° C., cooled to 25 ° C., and confirmed whether or not it was precipitated as a solid. Is done.

  The block copolymer (hereinafter referred to as “specific copolymer”) dissolved in the carrier liquid at 25 ° C. in the present embodiment is preferably one having at least one repeating unit selected from butylene and ethylene in the structure. Further, a block copolymer which is a hydrogenated polymer obtained by hydrogenating a copolymer of styrene and an olefin resin as a basic skeleton is preferably used. Preferably, hydrogenated styrene-butadiene rubber, styrene-ethylene-butylene-ethylene block copolymer, ethylene-ethylene-butylene-ethylene block copolymer, styrene-ethylene-butylene-styrene block copolymer, and the like can be mentioned. Of these, hydrogenated butadiene rubber is more preferable.

  Examples of commercially available products include Dynalon 1320P, 1321P, 2324P, 4600P, 6200P, 8601P, and 9901P (trade names) manufactured by JSR, preferably Dynalon 1321P, 2324P, and 4600P, and more preferably Dynalon 2324P. Is mentioned.

  These specific block copolymers are used in a state of being dissolved in a carrier solution. These specific block copolymers are preferably contained in the developer in an amount of 0.5% by mass or more and 20% by mass or less. When the addition amount is 0.5% by mass or more, an increase in the liquid viscosity of the liquid developer is effectively suppressed, and when it is 20% by mass or less, the resin content in the liquid developer becomes too high. Therefore, the thickening of the liquid developer is effectively suppressed.

[Carrier liquid]
The carrier liquid is an insulating liquid for dispersing toner particles, and a hydrocarbon solvent is used. Examples of the volume conductivity of the carrier liquid include a range of 1.0 × 10 ⁻¹⁴ S / m to 1.0 × 10 ⁻¹⁰ S / m.

  The carrier liquid is preferably an insulating hydrocarbon solvent having a flash point of 120 ° C. or less. When the flash point is 120 ° C. or lower, the carrier liquid is effectively removed in the fixing step, and the amount of the carrier liquid remaining in the image can be suppressed. The lower limit is preferably 70 ° C. or higher.

The carrier liquid preferably has a saturated hydrocarbon content of 12 to 17 carbon atoms in the total carrier liquid of 90 to 100 mass%, and more preferably a saturated carbonization of 12 to 15 carbon atoms. The hydrogen content is preferably 90% by mass or more and 100% by mass or less.
Further, the saturated hydrocarbon having 12 carbon atoms preferably has a linear structure, and the saturated hydrocarbon having 16 and 17 carbon atoms preferably has a branched structure.
90% by mass or more of a saturated hydrocarbon having 12 to 17 carbon atoms (particularly, a linear structure for a saturated hydrocarbon having 12 carbons and a branched structure for a saturated hydrocarbon having 16 and 17 carbon atoms) The increase in the low molecular weight flammable compound is suppressed, the electrical conductivity is not excessively increased, and the increase in the viscosity of the liquid developer is effectively suppressed by suppressing the increase in the viscosity of the carrier alone.

Specific examples of the carrier liquid specifically include linear dodecane, tridecane, tetradecane, pentadecane, branched tetradecane, pentadecane, hexadecane, heptadecane and the like. Examples of commercially available products include Cactus normal paraffin NP12, NP13, NP14, SHNP, YHNP, etc. manufactured by JOMO Nisseki.
Also, hydrocarbons such as paraffin oil (in the marketed products, Moresco White MT-30P, Moresco White P40, Moresco White P70, Expar Chemicals Isopar L, Isopar M, etc. manufactured by Matsumura Oil Co., Ltd.), naphthenic oils, etc. Solvent (commercially available products: Exxon Chemical Co., Ltd. Exol D80, Exol D110, Exol D130, Nippon Petrochemical Co., Ltd. Naphthezol L, Naphthezol M, Naphthezol H, New Naphtezol 160, New Naphtezol 200, New Naphthezol 220, New Naphtezol MS-20P Etc.).
In addition, you may contain aromatic compounds, such as toluene, in said carrier liquid.

  Only one type of carrier liquid may be included in the liquid developer of this embodiment, or two or more types may be used.

  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 and pulverizing the above-described toner particles, a specific block copolymer, and a carrier liquid using a dispersing machine such as a ball mill, a sand mill, an attritor, or a bead mill. The block copolymer is dissolved in the carrier liquid and the toner particles are dispersed in the carrier liquid.
Dispersion is not limited to a disperser, and it may be dispersed by rotating a special stirring blade at a high speed like a mixer, or by a rotor / stator shear force known as a homogenizer, or by ultrasonic waves. May be dispersed.

  The concentration of the toner particles in the carrier liquid is preferably in the range of 0.5% by mass to 40% by mass, and more preferably in the range of 1% by mass to 30% by mass.

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

<Process cartridge, image forming apparatus>
The image forming apparatus of the present embodiment includes an electrostatic latent image holding member (hereinafter sometimes referred to as “photosensitive member”), a charging device that charges the surface of the electrostatic latent image holding member, and the electrostatic latent image. An electrostatic latent image forming apparatus for forming an electrostatic latent image on the surface of the holding body, and the electrostatic latent image formed on the surface of the electrostatic latent image holding body while containing the liquid developer according to the present embodiment. A developing device that forms a toner image by developing the toner image with the liquid developer, a transfer device that transfers the toner image to a recording medium, and a fixing device that fixes the toner image on the recording medium.

In the image forming apparatus, for example, the part including the developing device 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. A process cartridge that includes a developing device that develops the electrostatic latent image formed on the latent image holding member with a liquid developer to form a toner image, and is detachable from the image forming device 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 20, an exposure device (electrostatic latent image forming device) 12, a developing device 14, an intermediate transfer member (transfer device) 16, a cleaner 18, A transfer fixing roller (transfer device and fixing device) 28 is included. 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 an insulating hydrocarbon carrier liquid, toner particles containing a styrene thermoplastic elastomer and a styrene thermoplastic resin, and a specific block copolymer.

  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 arrow C by the intermediate transfer body 16 is transferred and fixed to the paper 30 at a position where the toner image is in contact 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. It is desirable to fix the toner image by applying a heating element to the transfer fixing roller 28 and applying pressure and heating. The fixing temperature is usually 120 ° C. or higher and 200 ° C. or lower.

  If the intermediate transfer member 16 has a roller shape as shown in FIG. 1, it forms a roller pair with the transfer fixing roller 28. Therefore, the intermediate transfer member 16 and the transfer fixing roller 28 are respectively used as a fixing roller and a pressure roller in the fixing device. It has a conforming structure and exhibits a fixing function. That is, when the paper 30 passes through the nip, the toner image is transferred and 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, the fixing is performed together 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 included in the image forming apparatus 100 are all operated in synchronization with the rotational speed of the photosensitive member 10. Yes.

  Hereinafter, although an example is given and it demonstrates more concretely, the following example does not restrict | limit this invention. In the text, “part” is based on mass unless otherwise specified.

<Example 1>
-Production of liquid developer-
To 60 parts of styrene acrylic resin (manufactured by Fujikura Kasei Co., Ltd., styrene-butyl acrylate resin, 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 kneaded again with a pressure kneader.
・ Cyan pigment master batch ・ ・ ・ 25 parts ・ Styrene acrylic resin ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・.. 55 parts (Fujikura Kasei Co., Ltd., styrene-butyl acrylate resin / StAc,
Weight average molecular weight 320,000, acid value 10)
・ Styrenic thermoplastic elastomer ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 20 parts ("SOE-L605" manufactured by Asahi Kasei Corporation,
Hydrogenated product of SBS / styrene / butadiene block copolymer)
The kneaded product was pulverized with a jet mill to obtain toner particles (cyan particles) having a volume average particle size of 10 μm.

Next, wet pulverization was performed with a ball mill with the following composition to obtain a liquid developer.
・ Cyan particle ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ 16 parts ・ Paraffin oil (carrier liquid) ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・82 parts (Matsumura Oil Co., Ltd., Moresco White MT-30P, flash point 94 ° C,
(The content of the linear hydrocarbon having 12 to 15 carbon atoms is 98% by mass)
・ Aluminium stearate, di (Wako Pure Chemical Industries, Ltd.) 0.1 part ・ Additive: Hydrogenated styrene butadiene rubber ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ ・・ 2 parts (JSR, Dynalon 2324P)
The volume average particle size of the toner particles (cyan particles) in the liquid developer obtained by the above method was measured with an optical particle size distribution analyzer (LA950, manufactured by Horiba, Ltd.) and found to be 2.0 μm.

-Dissolution test-
Whether or not the styrene acrylic resin (styrene-butyl acrylate resin), styrene thermoplastic elastomer (hydrogenated product of styrene / butadiene block copolymer) is not dissolved in the paraffin oil (carrier liquid), and Whether or not the hydrogenated styrene butadiene rubber was dissolved in the paraffin oil (carrier liquid) was confirmed by the following method.
That is, by adding 1 g (1% by mass) of the sample to 100 g of the carrier liquid, stirring at 70 ° C., and then cooling to 25 ° C., it is confirmed whether or not the sample is precipitated as a solid. It was confirmed that it “dissolves”.

It was confirmed that the hydrogenated products of the styrene-butyl acrylate resin and the styrene / butadiene block copolymer were precipitated as solids and did not dissolve.
Further, it was confirmed that the hydrogenated styrene butadiene rubber was not precipitated as a solid but dissolved.

<Example 2>
A liquid developer was obtained by the method described in Example 1, except that the carrier liquid in Example 1 was changed to “Cactus normal paraffin SHNP (manufactured by JOMO Nisseki Co., Ltd.)”. The volume average particle size of the toner particles in the carrier liquid was 1.8 μm.
In addition, when the above-mentioned dissolution test was performed by changing the carrier liquid to the above-mentioned one, the same result as in Example 1 was obtained.

<Example 3>
A liquid developer was obtained by the method described in Example 1, except that the carrier liquid was changed to “Dodecane (manufactured by Wako Pure Chemical Industries)” in Example 1. The volume average particle size of the toner particles in the carrier liquid was 2.2 μm.
In addition, when the above-mentioned dissolution test was performed by changing the carrier liquid to the above-mentioned one, the same result as in Example 1 was obtained.

<Example 4>
In Example 1, except that the additive: hydrogenated styrene butadiene rubber was changed to “styrene ethylene / butylene ethylene block copolymer (manufactured by JSR, Dynalon 4600P)”, the liquid developer was prepared by the method described in Example 1. Obtained. The volume average particle size of the toner particles in the carrier liquid was 2.0 μm.
When the above-described dissolution test was performed on the styrene ethylene / butylene ethylene block copolymer, the same results as in Example 1 were obtained.

<Example 5>
A liquid developer was obtained by the method described in Example 1 except that the carrier liquid in Example 1 was changed to “n-hexadecane (manufactured by Wako Pure Chemical Industries, Ltd.)”. The volume average particle diameter of the toner particles in the carrier liquid was 4 μm.
In addition, when the above-mentioned dissolution test was performed by changing the carrier liquid to the above-mentioned one, the same result as in Example 1 was obtained.

<Example 6>
A liquid developer was obtained by the method described in Example 1, except that the carrier liquid in Example 1 was changed to “Cactus normal paraffin NP-11 (manufactured by JOMO Nisseki Co., Ltd.)”. The volume average particle size of the toner particles in the carrier liquid was 1.5 μm.
In addition, when the above-mentioned dissolution test was performed by changing the carrier liquid to the above-mentioned one, the same result as in Example 1 was obtained.

<Comparative Example 1>
In Example 1, a liquid developer was obtained by the method described in Example 1 except that the additive: hydrogenated styrene butadiene rubber was not added and an equal amount of carrier liquid was added. The volume average particle size of the toner particles in the carrier liquid was 1.8 μm.

<Comparative example 2>
In Example 1, a liquid developer was obtained by the method described in Example 1 except that an equal amount of styrene acrylic resin (StAc) was added without adding the styrene-based thermoplastic elastomer (SBS). The volume average particle size of the toner particles in the carrier liquid was 0.8 μm.

〔Evaluation test〕
-Measurement of viscosity-
The viscosity at 25 ° C. of the liquid developers obtained in Examples and Comparative Examples was measured with a RE85-L viscometer manufactured by Toki Sangyo Co., Ltd. In addition, the viscosity was measured on condition of shear rate 10S- ¹ and condition of shear rate 2S- ¹ .

-Fixability test-
The liquid developers obtained in the examples and the comparative examples were diluted with the carrier liquid used in each of the examples and the comparative examples so as to have a concentration of 2.5% by mass, and placed in 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 amount of deposited toner was measured and found to be 2 g / m ² . The transferred image was fixed using an external fixing device at a fixing speed of 500 mm / sec under 6 mm Nip.

-Evaluation of bending resistance Folding resistance was evaluated from the degree of destruction of the image after the paper was folded with the transferred image inside, and the folded portion was lightly wiped. The evaluation criteria are as follows.
Good: Image destruction is not visually confirmed. Destruction: Image is broken along the bent line, and toner peeling is confirmed.

-Evaluation of image overlay resistance The image surfaces of two sheets of paper on which images are formed are overlapped and left under conditions of 50 ° C. and 72 hours under a load of 500 g, and then the images are observed to evaluate the following evaluation criteria: It was evaluated by.
No image destruction: Change in the created image is not visually confirmed Image offset: A part of the created image adheres to the superimposed image,
Toner peeling is visually confirmed

-Liquid feedability test-
The liquid developers obtained in Examples and Comparative Examples were set in a liquid feedability evaluation apparatus, the roll was rotated, and the liquid feedability after the start and after 3 hours were confirmed.
In addition, as an evaluation apparatus, the circulation apparatus which passes a developing agent using a liquid feeding pump in the silicon tube with an internal diameter of 6.4 mm and a length of 1 m was used.
Also, good liquid feedability means that the developer is constantly circulating without clogging the tube, while poor liquid feedability means that the developer is clogged in the tube and will not circulate. Refers to the state.

In the initial evaluation after start-up, “good” indicates that the liquid feedability is good even without assistance by stirring, and “liquid feed with additional stirring” indicates that the liquid feedability is good only when assistance is provided by stirring. Evaluated as “Yes”.
In addition, in the evaluation after 3 hours, when the liquid feedability was good and the liquid developer did not gel, it was described as “good”. The case where the improvement was improved was evaluated as “partial gelation”, and the case where the solution was fed in a lump state due to gelation and the carrier liquid was not improved even after additional addition was evaluated as “liquid transfer in lump”.

  As shown in Table 2 above, this example containing a block copolymer that dissolves in a carrier liquid at 25 ° C. as an additive has better fluidity and better image retention after fixing. It can be seen that it is. It can also be seen that the liquid feedability is stable over a long period of time.

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

Claims (8)

An insulating hydrocarbon carrier liquid;
Toner particles containing a colorant, a styrenic thermoplastic elastomer that does not dissolve in the carrier liquid at 25 ° C., and a styrene thermoplastic resin that does not dissolve in the carrier liquid at 25 ° C., and dispersed in the carrier liquid;
A block copolymer that dissolves in the carrier liquid at 25 ° C .;
A liquid developer comprising:   The liquid developer according to claim 1, wherein the block copolymer has at least one repeating unit selected from butylene and ethylene in the structure.   The liquid developer according to claim 1, wherein the block copolymer is a hydrogenated butadiene rubber.   The liquid developer according to claim 1, wherein a flash point of the carrier liquid is in a range of 70 ° C. or higher and 120 ° C. or lower.   The liquid according to any one of claims 1 to 4, wherein the carrier liquid has a content ratio of saturated hydrocarbons having 12 to 15 carbon atoms in all carrier liquids of 90 mass% or more and 100 mass% or less. Developer. An electrostatic latent image carrier;
A charging device for charging the surface of the electrostatic latent image holding member;
An electrostatic latent image forming apparatus for forming an electrostatic latent image on the surface of the electrostatic latent image holding member;
A developing device that stores the liquid developer according to claim 1 and that develops the electrostatic latent image formed on the surface of the electrostatic latent image holding member with the liquid developer to form a toner image;
A transfer device for transferring the toner image to a recording medium;
A fixing device for fixing the toner image on the recording medium;
An image forming apparatus comprising: A developing device that stores the liquid developer according to claim 1 and that develops the electrostatic latent image formed on the surface of the electrostatic latent image holding member with the liquid developer to form a toner image,
A process cartridge that is detachable from the image forming apparatus. 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 claim 1 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: