JP5673184B2 - Liquid developer, process cartridge, image forming apparatus, and image forming method - Google Patents

Description

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

For example, the following toners are proposed for use in the dry development system.
Patent Document 1 discloses a resin composition for toner containing a styrene acrylic resin, a block copolymer of polystyrene and polyolefin, and a wax.
Patent Document 2 discloses a resin composition for toner comprising a styrene acrylic resin having a weight average molecular weight (Mw) of 10,000 to 150,000 and a block copolymer of styrene and olefin.
Patent Document 3 discloses a toner using a thermoplastic elastomer as a binder resin.

On the other hand, the liquid developer is one in which toner particles are dispersed in an insulating carrier liquid, and a type in which toner particles made of a thermoplastic resin are dispersed in a volatile carrier liquid, and a non-volatile carrier. A type in which toner particles made of a thermoplastic resin are dispersed in a liquid is known.
For example, Patent Document 4 discloses a liquid developer containing a polyester resin having a weight average molecular weight of 2000 to 20000 in terms of styrene and a release agent having a melting point of 50 ° C. or more and 100 ° C. or less.

JP 2000-181141 A JP 11-184149 A Japanese Patent Laid-Open No. 2007-079348 JP 2004-205843 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid developer having excellent folding resistance that suppresses toner falling off at a folded portion of a recording medium on which an image is formed.

In order to achieve the above object, the following invention is provided.
The invention according to claim 1 is a block copolymer of an insulating carrier liquid and a methacrylic acid ester having a Tg of 100 ° C. or higher and a methacrylic acid ester or an acrylic ester having a Tg of 0 ° C. or lower. And a toner particle containing an acrylic thermoplastic elastomer and an acrylic thermoplastic resin as a combination.
The invention according to claim 2 is the liquid developer according to claim 1, wherein the content of the acrylic thermoplastic elastomer in the toner particles is 10% by mass or more based on the total binder resin.
According to a third aspect of the present invention, the liquid developer according to the first or second aspect is accommodated, 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. A process cartridge includes a developing unit that forms an image and is detachable from an image forming apparatus.
According to a fourth 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 for forming an electrostatic latent image on the surface of the electrostatic latent image holding member. A latent image forming unit and the liquid developer according to claim 1 or 2 are accommodated, 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. An image forming apparatus comprising: a developing unit that forms an 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 fifth aspect of the present invention, there is provided a charging step for charging the surface of the electrostatic latent image holding member, an electrostatic latent image forming step for forming an electrostatic latent image on the surface of the electrostatic latent image holding member, and the electrostatic A developing process for forming a toner image by developing the electrostatic latent image formed on the surface of the latent image holding body with the liquid developer according to claim 1 or 2, and transferring the toner image to a recording medium. An image forming method including a transfer step and a fixing step of fixing the toner image on the recording medium.

According to the first aspect of the present invention, compared to the case where the toner particles contained in the liquid developer do not contain the acrylic thermoplastic elastomer and the acrylic thermoplastic resin, the portion bent when the recording medium on which the image is formed is folded. Thus, a liquid developer excellent in bending resistance characteristics in which toner is prevented from falling off is provided.
According to the second aspect of the present invention, there is provided a liquid developer having excellent bending resistance as compared with a case where the content of the acrylic thermoplastic elastomer with respect to the total binder resin contained in the toner is less than 10% by mass. Provided.
According to the invention of claim 3, a process cartridge capable of obtaining an image excellent in bending resistance as compared with the case of using a liquid developer in which toner particles containing no acrylic thermoplastic elastomer and acrylic thermoplastic resin are dispersed. Is provided.
According to the fourth aspect of the present invention, an image can be obtained in which an image excellent in bending resistance is obtained as compared with the case of using a liquid developer in which toner particles containing no acrylic thermoplastic elastomer and acrylic thermoplastic resin are dispersed. An apparatus is provided.
According to the invention of claim 5, image formation is obtained in which an image excellent in bending resistance is obtained as compared with the case of using a liquid developer in which toner particles containing no acrylic thermoplastic elastomer and no acrylic thermoplastic resin are used. A method is provided.

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

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

<Liquid developer>
The liquid developer according to the exemplary embodiment includes toner particles including an acrylic thermoplastic elastomer and an acrylic thermoplastic resin, and an insulating carrier liquid for dispersing the toner particles. When an image is formed on a recording medium such as paper using the liquid developer of the present embodiment, an image in which the folding resistance, that is, the toner that has fallen off when the recording medium is folded is suppressed. It is done. The reason why an image having excellent bending resistance can be obtained by using the liquid developer according to this embodiment can be considered as follows.

In the liquid developer of this embodiment, since the acrylic thermoplastic elastomer and the acrylic thermoplastic resin are highly compatible with each other, the acrylic thermoplastic elastomer and the acrylic thermoplastic resin are layered when the toner is melted at the time of fixing. It will solidify in a mixed state without causing a phenomenon such as separation. Acrylic thermoplastic elastomers are more flexible than styrene thermoplastic resins, acrylic thermoplastic resins, and polyester thermoplastic resins that are commonly used in toners. Therefore, it is considered that the bending resistance is improved.
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 of the present embodiment are configured to include an acrylic thermoplastic elastomer and an acrylic thermoplastic resin.

-Acrylic thermoplastic elastomer-
The acrylic thermoplastic elastomer contained in the toner particles of this embodiment is a block copolymer of a methacrylic ester having a Tg of 100 ° C. or higher and a methacrylic ester or an acrylic ester having a Tg of 0 ° C. or lower. Although it has the characteristics of rubber, it is a material that softens at high temperatures like thermoplastics.
Specifically, polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate block copolymer, polymethyl methacrylate-polydodecyl methacrylate-polymethyl methacrylate block copolymer, polymethyl methacrylate-poly Examples thereof include ABA block copolymers such as 2-ethylhexyl methacrylate-polymethyl methacrylate block copolymer and polymethyl methacrylate-polylauryl methacrylate-polymethyl methacrylate block copolymer.
Examples of the products include LA2250, LAB550, LA4285 (above, trade names) manufactured by Kuraray.
In general, the number average molecular weight of the polymer block (A) is in the range of 1,000 to 1,000,000, the number average molecular weight of the polymer block (B) is in the range of 1,000 to 1,000,000, and the total number of block copolymers. The average molecular weight is within the range of 3000 to 3000000 from the viewpoint of moldability, handleability, mechanical properties, compatibility with acrylic resin, fine dispersibility, adhesion, etc. preferable.

  From the viewpoint of further improving the bending resistance, the content of the acrylic thermoplastic elastomer in the toner particles is desirably 10% by mass or more in the total binder resin. When the content of the acrylic thermoplastic elastomer in the total binder resin contained in the toner particles is 10% by mass or more, the bending resistance is further improved. However, if the content of the acrylic thermoplastic elastomer is too high, the scratch resistance tends to decrease. Therefore, the content of the acrylic thermoplastic elastomer in the total binder resin is desirably 50% by mass or less.

-Acrylic thermoplastic resin-
As the acrylic thermoplastic resin contained in the toner particles of this embodiment, a vinyl copolymer containing a polymer of a methacrylic ester monomer and / or a polymer of an acrylate monomer as a structural unit Coalescence is mentioned. Hereinafter, “(meth) acryl” means either or both of acrylic and methacrylic.
Examples of the (meth) acrylic acid ester monomer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, and (meth) acrylic. In addition to alkyl esters of (meth) acrylic acid such as isobutyl acid, n-octyl (meth) acrylate, dodecyl (meth) acrylate, 2-ethylhexyl acrylate, stearyl (meth) acrylate, 2-chloroethyl acrylate, Phenyl (meth) acrylate, methyl α-chloroacrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, glycidyl (meth) acrylate Dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, Glycidyl methacrylate, polyethylene glycol dimethacrylate, etc. methacryloxyethyl phosphate and the like. Among these, methyl methacrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, and the like are desirably used.
The content of the acrylic thermoplastic resin in the toner particles is desirably 50% by mass or more and 95% by mass or less in the total binder resin.

In addition to the above (meth) acrylic acid ester monomers, other vinyl monomers include acrylic acid such as acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, and α- or β-alkyl derivatives thereof. An unsaturated dicarboxylic acid such as fumaric acid, maleic acid, citraconic acid, itaconic acid and the like, and a monoester derivative or a diester derivative thereof; succinic acid mono (meth) acryloyloxyethyl ester, (meth) acrylonitrile, acrylamide, etc. are used Also good.
Moreover, although a copolymer with a styrene-type monomer may be used, it is desirable to use within 10 mass% of the whole resin from a compatible viewpoint with an acrylic thermoplastic elastomer.

The vinyl polymer preferably has a weight average molecular weight (Mw) of 10,000 to 500,000. If the Mw is 10,000 or more, a decrease in the scratch property of the toner resin composition is suppressed, and if it is 500,000 or less, the melt viscosity does not become too high, and the smoothness of the fixing surface is suppressed. Therefore, the color development as desired is expressed in the color image.
The molecular weight distribution (Mw / Mn) is preferably 2 or more and 20 or less. If Mw / Mn is 2 or more, a decrease in viscosity in a high temperature region is suppressed and offset resistance is hardly disturbed, and if it is 20 or less, a decrease in fixability is suppressed.
The vinyl polymer may have a plurality of peaks and shoulders in the molecular weight distribution measured by GPC.

  In addition to acrylic thermoplastic elastomer and acrylic thermoplastic resin, the toner particles of this embodiment include other binder resins, colorants, waxes, charge control agents, silica powder, metal oxides, and the like as necessary. The additive may be contained. These additives may be added internally by, for example, kneading into a binder resin containing an acrylic thermoplastic elastomer and an acrylic thermoplastic resin, or may be externally added by, for example, carrying out a mixing process after obtaining toner as particles. You may attach. In general, a colorant is included, but when a transparent toner is used, the colorant may not be included.

  Examples of the binder resin other than the acrylic thermoplastic elastomer and the acrylic 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.

  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, and examples thereof include plant waxes such as carnauba wax, wood wax and rice bran wax; animal waxes such as bees wax, insect wax, whale wax and wool wax; mineral waxes such as montan wax and ozokerite. , 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.
In addition, it is desirable that components other than the acrylic thermoplastic elastomer and the acrylic thermoplastic resin are 50% by mass or less from the viewpoint of fixability.

-Toner Particle Manufacturing Method-
The method for producing the toner particles of this embodiment is not particularly limited. For example, the toner particles can be obtained by pulverizing a pulverized toner, a liquid emulsion-dried toner, or a toner produced by a polymerized toner production method in a carrier liquid.
For example, a binder resin including an acrylic thermoplastic elastomer and an acrylic thermoplastic resin, a colorant, and, if necessary, other additives are added to a mixing device such as a Henschel mixer and mixed. After melt-kneading with an extruder, Banbury 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 air classification A pulverized toner can be obtained by classification using a machine or the like.

  In addition, binder resins including acrylic thermoplastic elastomers and acrylic thermoplastic resins, colorants, and other additives as required are dissolved in solvents such as ethyl acetate, and dispersion stabilizers such as calcium carbonate are added. After emulsifying / suspending in the produced water and removing the solvent, 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 agitation and granulated. After the polymerization reaction, the particles are filtered and dried to obtain a polymerized toner.

  The blending ratio of each material (acrylic thermoplastic elastomer and acrylic thermoplastic resin, colorant, other additives, etc.) when obtaining toner is the required bending resistance, scratch resistance, low temperature fixability, color It may be set in consideration of the above. 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.

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.

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

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

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

In the image forming apparatus, for example, the 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. A process cartridge that includes a developing unit 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 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, although an example is given and it demonstrates more concretely, the following example does not restrict | limit this invention. In the text, “parts” and “%” represent “parts by mass” and “mass%”, respectively, unless otherwise specified.

Example 1
<Production of developer>
Cyan pigment C.I. in 60 parts by mass of acrylic thermoplastic resin (Fujikura Kasei product: Acrybase MH-105-1) I. 40 parts by mass of Pigment Blue 15: 3 (manufactured by Clariant Co., Ltd.) was added and kneaded with a pressure kneader. The kneaded product was coarsely pulverized to prepare a cyan pigment master batch.
Next, a mixture having the following composition was dissolved and dispersed in a ball mill for 24 hours.
Cyan pigment master batch: 25 parts by mass Acrylic thermoplastic resin (Fujikura Kasei product: Acrybase MM-428): 60 parts by mass (meth) acrylic thermoplastic elastomer (Kuraray product: “LA polymer 4285” MMA / nBA / MMA block copolymer): 10 parts by mass (meth) acrylic thermoplastic elastomer (Kuraray product: “LA polymer 2250” MMA / nBA / MMA block copolymer): 5 parts by mass Ethyl acetate: 200 parts by mass

  On the other hand, 20 parts of sodium carbonate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 135 parts of ion-exchanged water, and 20 parts of calcium carbonate (manufactured by Maruo Calcium Co., Ltd., Luminous) was added as a dispersion stabilizer. The dispersion medium was dispersed by a ball mill for 24 hours. 100 parts of the mixture is added to 170 parts of this dispersion medium, and emulsified for 1 minute at 8000 rpm 24000 rpm in an emulsifying apparatus (HIKA-FLEX HOMOGENIZER Ultra Turrax T-25 manufactured by SMT Co., Ltd.) to obtain a suspension. It was.

Put the above suspension into a separable flask equipped with a stirrer, thermometer, cooling pipe and nitrogen introduction pipe, and stir at 60 ° C for 3 hours while introducing nitrogen from the nitrogen introduction pipe to remove ethyl acetate. did. Thereafter, the mixture was cooled, a 10% aqueous hydrochloric acid solution was added to the reaction solution to decompose calcium carbonate, and solid-liquid separation was performed by centrifugation. The obtained particles were washed with 1 L of ion exchange water three times, and then the obtained particles were vacuum-dried at 40 ° C.
A liquid developer having an average particle diameter of 1.2 μm is obtained by pulverizing a mixture of 103 parts by mass of volatile paraffin oil (Isopar L manufactured by Exxon) and 1.5 parts by mass of Solsperse with a ball mill to 35 parts by mass of dried cyan particles. 1 was obtained.

-Example 2-
<Production of developer>
Cyan pigment C.I. to 60 parts by mass of acrylic thermoplastic resin (Fujikura Kasei product: Acrybase MH-101-5). I. 40 parts by mass of Pigment Blue 15: 3 (manufactured by Clariant Co., Ltd.) was added and kneaded with a pressure kneader. The kneaded product was coarsely pulverized to prepare a cyan pigment master batch.
Next, a mixture having the following composition was kneaded again with a pressure kneader.
Cyan pigment master batch: 25 parts by mass Acrylic thermoplastic resin (Fujikura Kasei product: Acrybase MM-2002-1): 45 parts by mass Acrylic thermoplastic elastomer (Kuraray product: “LA polymer 4285” MMA / nBA / MMA Block copolymer): 20 parts by mass Acrylic thermoplastic elastomer (Kuraray product: “LA polymer 2250” MMA / nBA / MMA block copolymer): 10 parts by mass

The kneaded product was pulverized with a jet mill to obtain cyan particles having an average particle size of 10 μm.
To 35 parts by mass of the cyan particles, a mixture of 103 parts by mass of non-volatile paraffin oil (Moleco White P40 manufactured by Matsumura Oil Co., Ltd.) and 1.5 parts by mass of Solsperse was pulverized with a ball mill to obtain an average particle size of 1. A liquid developer 2 of 1 μm was obtained.

-Example 3-
In Example 2, acrylic thermoplastic resin: 45 parts by mass to 68 parts by mass, acrylic thermoplastic elastomer (Kuraray product: “LA polymer 4285” MMA / nBA / MMA block copolymer): 7 parts by mass of 20 parts by mass Acrylic thermoplastic elastomer (Kuraray product: “LA polymer 2250” MMA / nBA / MMA block copolymer): In addition, the liquid developer 3 was prepared in the same manner except that 10 parts by mass was changed to 0 parts by mass. Obtained. The volume average particle size of the toner particles in the carrier liquid was 0.9 μm.

Example 4
68 parts by weight of an acrylic thermoplastic resin (Fujikura Kasei product: Acrybase MH-101-5) in Example 3 manufactured by Mitsubishi Rayon Co., Ltd., Dianal MB2660 (weight average molecular weight = 65000, Tg = 52 ° C., acid value = 3 mgKOH) / G) 25 parts by weight, acrylic thermoplastic elastomer (Kuraray product: “LA polymer 4285” MMA / nBA / MMA block copolymer) 7 parts by weight was changed to 50 parts by weight in the same manner. 4 was obtained. The volume average particle size of the toner particles in the carrier liquid was 1.0 μm.

-Comparative Example 1-
Other than replacing 30 parts by mass of acrylic thermoplastic elastomer (Kuraray products: “LA polymer 4285” and: “LA polymer 2250”) in Example 2 with acrylic thermoplastic resin (Fujikura Kasei product: Acrybase MM-428) In the same manner, a liquid developer 101 was obtained. The volume average particle size of the toner particles in the carrier liquid was 1.4 μm.

-Comparative Example 2-
The acrylic thermoplastic elastomers (Kuraray products: “LA polymer 4285” and “LA polymer 2250”) in Example 2 were changed to “Asahi Kasei products:“ Asaprene T439 ”styrene-butadiene block copolymer” of styrenic thermoplastic elastomers. A liquid developer 102 was obtained in the same manner. The volume average particle size of the toner particles in the carrier liquid was 0.9 μm.

-Comparative Example 3-
Acrylic thermoplastic resins (Fujikura Kasei products: “Acrybase MH-101-5” and “Acrybase MM-2002-1”) in Example 2 were replaced with styrene thermoplastic resins (FSR053, manufactured by Fujikura Kasei Co., Ltd., weight average). Liquid developer 103 was obtained in the same manner except that the molecular weight was 320,000, Tg was 59 ° C., and the acid value was 10 mg KOH / g. The volume average particle diameter of the toner particles in the carrier liquid was 1.6 μm.

<Evaluation>
-Fixability (MFT evaluation)-
Each prepared liquid developer was diluted with the same oil (Molesco White P-40) so as to be 2.5%, and placed in a disposable (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.

  In the fixing evaluation, in order to evaluate the minimum fixing temperature, the fixing device was remodeled so that the fixing temperature was variable, and the fixing temperature of the fixing roll was increased from 100 ° C. every + 5 ° C. to fix the image. . Make a crease inside the solid part of the solid part of the fixed toner image of the paper on which the image was formed, wipe the part where the fixed toner image was destroyed with tissue paper, measure the white line width, The temperature at which the removed line width was 0.5 mm or less was defined as the minimum fixing temperature (MFT). The results are shown in Table 1. In this evaluation, MFT is evaluated to be good at 130 ° C. or lower.

−Bending resistance−
The folding resistance was evaluated from the degree of destruction of the image after the paper was bent with the image on the inside and the folded portion was lightly wiped. Evaluation was made according to the following criteria.
A: There is slight and discontinuous image peeling.
○: There is discontinuous breakage.
X: There is continuous damage.
The results are shown in Table 1.

-Scratch resistance-
The scratch resistance was evaluated using a 0.5 kg scratching tester manufactured by Linax. The evaluation criteria are as follows.
A: Although the density is lowered, the image remains.
○: The base is left and a part is peeled off.
X: Most of the image is peeled off.
The results are shown in Table 1.

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

Claims (5)

An insulating carrier liquid;
An acrylic thermoplastic elastomer and an acrylic thermoplastic resin, which are dispersed in the carrier liquid and are block copolymers of a methacrylic ester having a Tg of 100 ° C. or higher and a methacrylic ester or an acrylic ester having a Tg of 0 ° C. or lower Toner particles containing,
A liquid developer.   The liquid developer according to claim 1, wherein the content of the acrylic thermoplastic elastomer in the toner particles is 10% by mass or more based on the total binder resin.   A developing means for storing the liquid developer according to claim 1 or 2 and developing a toner image by developing the electrostatic latent image formed on the surface of the electrostatic latent image holding member with the liquid developer. A process cartridge provided and detachable 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;
A developing unit that stores the liquid developer according to claim 1 or 2 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. When,
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 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: