JP2014215603A - Liquid developer, image forming apparatus, image forming method, process cartridge, and liquid developer cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid developer that provides excellent image quality when images are formed through multiple transfer.SOLUTION: There is provided a liquid developer that includes toner particles containing a polyester resin and colorant and having an average circularity of 0.97 or less, and silicone oil.

Description

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

As a developer used for electrophotographic image formation, a liquid developer in which toner particles are dispersed in a carrier liquid is known.
For example, Patent Document 1 includes an insulating liquid, toner particles mainly composed of a polyester resin, and a dispersant represented by a predetermined general formula (I), and the toner particle has a shape factor SF1 of 100 to 130. A liquid developer having a toner particle shape factor SF2 of 110 to 150 is disclosed.
For example, Patent Document 2 discloses a resin having a glass transition point of 50 ° C. or higher, a 50% volume particle diameter Dv (50) of 1 μm to 3 μm, and an average circularity of 0.98 to 0.99. A liquid developer containing particles and a carrier liquid is disclosed.
For example, Patent Document 3 includes one or more shell layers containing a first resin and one core layer containing a second resin, and the weight ratio of the shell layer to the core layer is 1:99. A non-aqueous resin dispersion in which core-shell type resin particles having an average circularity of 0.96 to 1.0 are dispersed in a non-aqueous organic solvent having a relative dielectric constant of 1 to 4 at 20 ° C. Is disclosed.
For example, Patent Document 4 includes an insulating liquid containing a fatty acid monoester and toner particles mainly composed of a styrene-acrylate copolymer, and the toner particles have an average particle size of 0.7 μm to 3 μm. A liquid developer having a toner particle circularity of 0.85 to 0.98 and a toner particle size distribution width S of 1.4 or less is disclosed.

JP 2008-310184 A JP 2011-059478 A JP 2009-096994 A JP 2008-203354 A

  The problem to be solved by the present invention is to provide a liquid developer excellent in image quality when an image is formed by multiple transfer.

The above problem is solved by the following means. That is,
The invention according to claim 1
A liquid developer containing toner particles containing a polyester resin and a colorant and having an average circularity of 0.97 or less, and silicone oil.

The invention according to claim 2
The liquid developer according to claim 1, wherein the toner particles have an average circularity of 0.85 or more.

The invention according to claim 3
A liquid developer cartridge that contains the liquid developer according to claim 1 and is detachable from an image forming apparatus.

The invention according to claim 4
A developing means for containing 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 image carrier with the liquid developer. A process cartridge to be attached to and detached from the image forming apparatus.

The invention according to claim 5
An image carrier,
Charging means for charging the surface of the image carrier;
Latent image forming means for forming an electrostatic latent image on the surface of the charged image carrier;
And a developing unit that stores the liquid developer according to claim 1 and that develops an electrostatic latent image formed on a surface of the image carrier with the liquid developer to form a toner image. ,
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 that performs multiple transfer.

The invention according to claim 6
A charging step for charging the surface of the image carrier;
A latent image forming step of forming an electrostatic latent image on the surface of the charged image carrier;
A developing step of developing a toner image by developing the electrostatic latent image formed on the surface of the image carrier with the liquid developer according to claim 1;
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 for performing multiple transfer.

According to the first aspect of the present invention, there is provided a liquid developer that is superior in image quality when an image is formed by multiple transfer as compared with a case where the average circularity of the toner particles exceeds 0.97.
According to the second aspect of the present invention, there is provided a liquid developer that is superior in image quality when an image is formed by one transfer as compared with the case where the average circularity of the toner particles is less than 0.85.
According to the invention of claim 3, the liquid developer is superior in image quality when an image is formed by multiple transfer, compared to the case where the average circularity of the toner particles contained in the liquid developer is greater than 0.97. A cartridge is provided.
According to the fourth aspect of the present invention, there is provided a process cartridge that is superior in image quality when an image is formed by multiple transfer compared to a case where the average circularity of toner particles contained in the liquid developer is more than 0.97. Provided.
According to the fifth aspect of the present invention, the image forming apparatus is superior in image quality when an image is formed by multiple transfer as compared with the case where the average circularity of the toner particles contained in the liquid developer is more than 0.97. Is provided.
According to the invention of claim 6, the image forming method is superior in image quality when an image is formed by multiple transfer compared to the case where the average circularity of the toner particles contained in the liquid developer is more than 0.97. Is provided.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an exemplary embodiment. It is a schematic block diagram which shows another example of the image forming apparatus which concerns on this embodiment. It is a schematic block diagram which shows another example of the image forming apparatus which concerns on this embodiment.

  Embodiments of the present invention will be described below. In addition, these description and Examples illustrate this invention, and do not restrict | limit the scope of the present invention.

  In the present embodiment, multiple transfer refers to sequentially transferring toner images formed on the surface of an image holding member onto a transfer target and overlapping the toner images on the transfer target. The transfer medium is, for example, an intermediate transfer body in the intermediate transfer system or a recording medium in the direct transfer system.

<Liquid developer>
The liquid developer according to the exemplary embodiment includes toner particles containing a polyester resin and a colorant, and silicone oil, and the average circularity of the toner particles is 0.97 or less.
The liquid developer according to this embodiment is excellent in image quality when an image is formed by multiple transfer by the above configuration. The reason is presumed as follows.

As a liquid developer used for electrophotographic image formation, from the viewpoint of excellent image fastness, a liquid developer in which toner particles containing a polyester resin and silicone oil as a carrier liquid are combined is desirable. Silicone oil has a lower affinity with polyester resin than other oils such as paraffin oil, so it is easily separated from the toner particles in the fixing process. As a result, the image formed with the liquid developer is not retained. There are few carrier liquids and it is thought that it is excellent in fastness.
However, the silicone oil has a low affinity with the polyester resin, so that it easily shifts from the toner particles to the transferred body on the transferred body. Therefore, the amount of carrier liquid between the toner particles is reduced on the transfer target, and the toner particles exhibit a powder behavior. Each time the toner image is superimposed on the transfer target, the toner image is disturbed (for example, , A reduction in the roundness of halftone dots) occurs, and toner image disturbance accumulates.
For the above event, if the average circularity of toner particles containing polyester resin is 0.97 or less, the number of contacts between the toner particles increases, and individual toner particles move on the transfer target, It is considered that the loss from the body is suppressed, and the disturbance of the toner image is suppressed.

In the liquid developer according to the exemplary embodiment, the upper limit of the average circularity of the toner particles is 0.97 or less, and 0.95 or less is more desirable from the viewpoint of better image quality when an image is formed by multiple transfer.
On the other hand, the lower limit of the average circularity of the toner particles is preferably 0.85 or more and more preferably 0.90 or more from the viewpoint of excellent image quality even when an image is formed without multiple transfer (that is, by one transfer). desirable.

In the liquid developer according to the exemplary embodiment, the upper limit of the volume average particle diameter of the toner particles is preferably 5 μm or less from the viewpoint of excellent image quality even when an image is formed without multiple transfer (that is, by one transfer). 4 μm or less is more desirable.
On the other hand, the lower limit of the volume average particle diameter of the toner particles is preferably 1.5 μm or more, and more preferably 2 μm or more. When the volume average particle size is 1.5 μm or more (more desirably 2 μm or more), the viscosity of the liquid developer does not become too high, and the liquid developer is easy to handle.

The average circularity of the toner particles is determined by the following method.
Using the toner particle dispersion as a sample, a toner particle image is image-analyzed by a circularity measuring device, and the circularity of each toner particle is obtained by the following equation.
Circularity = perimeter of a circle having the same area as the projected area (A) of the toner particle image / perimeter of the toner particle image (PM) = [2 × (Aπ) ^1/2 ] / PM
For 5000 or more toner particle images, a cumulative distribution is drawn from the smaller A, and the circularity at an accumulation degree of 50% is defined as the average circularity.

The volume average particle diameter D ₅₀ of the toner particles is determined by the following method.
The toner particles are dispersed in the electrolytic solution, and the particle size distribution is measured using a particle size distribution measuring device. Then, based on the particle size distribution, draw a cumulative distribution of volume from the small diameter side with respect to divided particle size ranges (channels), and the particle diameter at a cumulative 50% volume average particle diameter D _50.

  The average circularity and volume average particle diameter of the toner particles are controlled by adjusting the temperature and holding time of the aggregated particle forming step and the coalescence / union step, for example, when the toner particles are produced by the aggregation coalescence method. Can do.

[Toner particles]
The toner particles include a polyester resin and a colorant. The toner particles may further contain a release agent and various internal and external additives.

The polyester resin is preferably an embodiment in which an amorphous polyester resin and a crystalline polyester resin are used in combination.
In the present embodiment, the “crystalline resin” refers to a resin having a clear endothermic peak instead of a stepwise endothermic amount change in differential scanning calorimetry (DSC). On the other hand, a resin having no clear endothermic peak is an amorphous resin.

The amorphous polyester resin may be obtained by subjecting a polyvalent carboxylic acid and a polyhydric alcohol to a condensation reaction according to a conventional method.
Examples of the polyvalent carboxylic acid include terephthalic acid, isophthalic acid, 1,4-naphthalenedicarboxylic acid, trimellitic anhydride, pyromellitic acid, 2,6-naphthalenedicarboxylic acid and the like; oxalic acid , Aliphatic dicarboxylic acids such as malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, adipic acid, sebacic acid, azelaic acid and dimer acid; alicyclic carboxylic acids such as cyclohexanedicarboxylic acid A trivalent or higher carboxylic acid such as trimellitic acid and pyromellitic acid; anhydrides of these acids; lower alkyl esters of these acids; One type of polyvalent carboxylic acid may be used, or two or more types may be used in combination.
Examples of the polyhydric alcohol include aliphatic diols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, and glycerin; cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, and the like. Alicyclic diols; aromatic diols such as bisphenol A ethylene oxide adducts and bisphenol A propylene oxide adducts; and the like. One type of polyhydric alcohol may be used, or two or more types may be used in combination.

  The glass transition temperature (Tg) of the amorphous polyester resin is preferably 40 ° C. or higher and 80 ° C. or lower, and more preferably 50 ° C. or higher and 70 ° C. or lower. The weight average molecular weight of the amorphous polyester resin is desirably 8000 or more and 30000 or less, and more desirably 8000 or more and 16000 or less.

The crystalline polyester resin may be obtained by subjecting a polyvalent carboxylic acid and a polyhydric alcohol to a condensation reaction according to a conventional method.
Examples of the polyvalent carboxylic acid include oxalic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,12- Aliphatic dicarboxylic acids such as dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid; aromatics such as phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,6-dicarboxylic acid, malonic acid Dicarboxylic acids; trivalent or higher aromatic carboxylic acids such as 1,2,3-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid; anhydrides of these acids; Lower alkyl esters of these acids; and the like. One type of polyvalent carboxylic acid may be used, or two or more types may be used in combination.
Examples of the polyhydric alcohol include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8- Octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18- And aliphatic diols such as octadecanediol and 1,14-eicosandecanediol; trivalent or higher alcohols such as glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol. One type of polyhydric alcohol may be used, or two or more types may be used in combination.

The crystalline polyester resin preferably has a melting temperature in the range of 45 ° C. or higher and 110 ° C. or lower in order to ensure low-temperature fixability and storage stability of the toner particles. A more desirable melting temperature range is 50 ° C. or more and 100 ° C. or less, and a further desirable range is 55 ° C. or more and 90 ° C. or less. The weight average molecular weight of the crystalline polyester resin is desirably 5000 or more and 40000 or less, and more desirably 8000 or more and 30000 or less.
A desirable content of the crystalline polyester resin in the toner particles is 1% by mass or more and 20% by mass or less, and more desirably 3% by mass or more and 15% by mass or less.

The toner particles may contain a binder resin other than the polyester resin. However, the polyester resin preferably accounts for 80% by mass or more of the total amount of the binder resin, more preferably 90% by mass or more, further preferably 95% by mass or more, and 100% by mass. Even more desirable.
Other binder resins other than polyester resins include polystyrene, styrene / acrylic resins, styrene / acrylonitrile copolymers, styrene / butadiene copolymers, styrene / maleic anhydride copolymers, polyethylene, polypropylene, polyurethane, and epoxy resins. , Silicone resin, polyamide, modified rosin, paraffin and waxes.

The colorant contained in the toner particles may be a pigment or a dye, and is preferably a pigment from the viewpoint of light resistance and water resistance.
Examples of the colorant include carbon black, nigrosine, aniline blue, calcoil blue, chrome yellow, ultramarine blue, dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, C. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 12, C.I. I. Pigment blue 15: 1, C.I. I. Pigment blue 15: 3.
The content of the colorant is desirably 1% by mass or more and 30% by mass or less of the toner particles.

The toner particles may contain a release agent for the purpose of preventing offset and the like. Examples of the release agent include paraffin wax and derivatives thereof, montan wax and derivatives thereof, microcrystalline wax and derivatives thereof, Fischer-Tropsch wax and derivatives thereof, polyolefin wax and derivatives thereof, low molecular weight polypropylene, low molecular weight polyethylene, and individual molecules. Alcohols, fatty acids, plant waxes, animal waxes, mineral waxes, ester waxes, acid amides and the like can be mentioned. Derivatives include oxides, polymers with vinyl monomers, and graft modified products.
The content of the release agent is preferably from 0.5% by weight to 40% by weight of the toner particles, more preferably from 1% by weight to 30% by weight, and even more preferably from 3% by weight to 15% by weight.

The toner particles may include inorganic oxide particles. Examples of the inorganic oxide particles include SiO ₂ , TiO ₂ , Al ₂ O ₃ , CuO, ZnO, SnO ₂ , CeO ₂ , Fe ₂ O ₃ , MgO, BaO, CaO, K ₂ O, Na ₂ O, and ZrO. _{2, CaO · SiO 2, K} 2 O · (TiO 2) n, Al 2 O 3 · 2SiO 2, CaCO 3, MgCO 3, BaSO 4, MgSO 4 , and the like. Of these, silica particles and titania particles are preferable. The surface of the inorganic oxide particles may not be previously hydrophobized or may be hydrophobized in advance.

  The proportion of toner particles in the liquid developer is preferably 3% by mass or more and 50% by mass or less, more preferably 5% by mass or more and 40% by mass or less, and further preferably 10% by mass or more and 30% by mass or less.

[Method for producing toner particles]
The toner particles may be produced by any of a dry production method (for example, a kneading pulverization method) and a wet production method (for example, an aggregation coalescence method, a suspension polymerization method, a dissolution suspension method, etc.). There is no restriction | limiting in particular in these manufacturing methods, A well-known manufacturing method is employ | adopted. Among them, it is desirable to obtain toner particles by an aggregation coalescence method.

When the toner particles are produced by the aggregation and coalescence method, for example,
A step of preparing a resin particle dispersion in which resin particles serving as a binder resin are dispersed (resin particle dispersion preparation step);
A step of preparing a colorant dispersion in which colorant particles are dispersed (colorant dispersion preparation step);
Aggregation of resin particles and colorant (and other particles as required) in a dispersion obtained by mixing resin particle dispersion and colorant dispersion (mixing other particle dispersions if necessary) A step of forming aggregated particles (aggregated particle formation step);
Heating agglomerated particle dispersion in which the agglomerated particles are dispersed, fusing and coalescing the agglomerated particles to form toner particles (fusing and fusing step);
Then, toner particles are manufactured.

Hereinafter, the detail of each process of the aggregation coalescence method is demonstrated.
In the following description, a method for obtaining toner particles including a release agent will be described. However, the release agent is used as necessary. Of course, you may use other additives other than a mold release agent.

-Preparation step of resin particle dispersion-
First, a resin particle dispersion in which resin particles to be a binder resin are dispersed is prepared.

  The resin particle dispersion is prepared, for example, by dispersing resin particles in a dispersion medium using a surfactant.

Examples of the dispersion medium used for the resin particle dispersion include an aqueous medium.
Examples of the aqueous medium include water such as distilled water and ion exchange water; alcohols. These may be used individually by 1 type and may use 2 or more types together.

Examples of the surfactant include anionic surfactants such as sulfate ester, sulfonate, phosphate, and soap; cationic surfactants such as amine salt type and quaternary ammonium salt type; polyethylene glycol And nonionic surfactants such as polyphenols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Among these, an anionic surfactant and a cationic surfactant are particularly mentioned. The nonionic surfactant may be used in combination with an anionic surfactant or a cationic surfactant.
Surfactant may be used individually by 1 type and may use 2 or more types together.

As a method for dispersing the resin particles in the dispersion medium, for example, a general dispersion method using a rotary shearing homogenizer, a ball mill having media, a sand mill, a dyno mill, or the like can be given. Depending on the type of the resin particles, the resin particles may be dispersed in the dispersion medium using, for example, a phase inversion emulsification method.
The phase inversion emulsification method is a method in which a resin to be dispersed is dissolved in a hydrophobic organic solvent in which the resin is soluble, neutralized by adding a base to the organic continuous phase (O phase), and then water (W Phase), the phase inversion from W / O to O / W is performed, and the resin is dispersed in the form of particles in the aqueous medium.

The volume average particle size of the resin particles dispersed in the resin particle dispersion is preferably 0.01 μm or more and 1 μm or less, more preferably 0.08 μm or more and 0.8 μm or less, and further preferably 0.1 μm or more and 0.6 μm.
The volume average particle size of the resin particles is a particle size range obtained by measurement with a laser diffraction particle size distribution measuring device (for example, LA-700, manufactured by HORIBA, Ltd.), and for a divided particle size range (channel), A cumulative distribution is drawn from the small particle diameter side with respect to the volume, and the particle diameter that makes the volume 50% of all the particles is defined as the volume average particle diameter. The volume average particle size of particles in other dispersions is also measured in the same manner.

  5 mass% or more and 50 mass% or less are preferable, and, as for content of the resin particle contained in the resin particle dispersion liquid, 10 mass% or more and 40 mass% or less are more preferable.

-Colorant dispersion preparation process-
The colorant dispersion in which the colorant particles are dispersed is prepared by a method similar to the method for preparing the resin particle dispersion. That is, the dispersion medium, surfactant, dispersion method, volume average particle diameter, and particle content of the colorant dispersion are the same as those of the resin particle dispersion.

  In addition, the release agent dispersion in which the release agent particles are dispersed is also prepared by a method similar to the method for preparing the resin particle dispersion. That is, the dispersion medium, surfactant, dispersion method, volume average particle diameter, and particle content of the release agent dispersion are the same as those of the resin particle dispersion.

-Aggregated particle formation process-
Next, the resin particle dispersion, the colorant dispersion, and the release agent dispersion are mixed.
Then, in the mixed dispersion, resin particles, colorant particles, and release agent particles are hetero-aggregated to have resin particles, colorant particles, and release agent particles having a diameter close to the diameter of the target toner particles. Aggregated particles are formed.

Specifically, for example, a flocculant is added to the mixed dispersion, and the pH of the mixed dispersion is adjusted to acidic (for example, pH 2 to 5), and a dispersion stabilizer is added as necessary. The glass dispersion temperature is heated to a temperature close to the glass transition temperature (specifically, for example, the glass transition temperature of the resin particles is −30 ° C. or higher and the glass transition temperature is −10 ° C. or lower). The particles dispersed in are aggregated to form aggregated particles.
The time for holding at the temperature (holding time) may be, for example, not less than 10 minutes and not more than 2 hours.
Usually, the volume average particle diameter of toner particles tends to increase as the temperature is increased and the holding time is increased.

  In the agglomerated particle forming step, for example, the agglomerated agent is added at room temperature (for example, 25 ° C.) while stirring the mixed dispersion with a rotary shearing homogenizer, and the pH of the mixed dispersion is adjusted to be acidic (for example, pH 2 to 5). In addition, heating may be performed after adding a dispersion stabilizer as necessary.

Examples of the flocculant include a surfactant having a polarity opposite to that of the surfactant contained in the mixed dispersion, such as an inorganic metal salt and a bivalent or higher-valent metal complex. When a metal complex is used as the flocculant, the amount of the flocculant used is reduced and the charging characteristics are improved.
An additive that forms a complex or similar bond with the metal ion of the flocculant may be used together with the flocculant. As this additive, a chelating agent is preferably used.

Examples of inorganic metal salts include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate; inorganic metal salts such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide Polymer; and the like.
A water-soluble chelating agent may be used as the chelating agent. Examples of the chelating agent include oxycarboxylic acids such as tartaric acid, citric acid, and gluconic acid; aminocarboxylic acids such as iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA); .
For example, the addition amount of the chelating agent is preferably 0.01 parts by mass or more and 5.0 parts by mass or less, and more preferably 0.1 parts by mass or more and less than 3.0 parts by mass with respect to 100 parts by mass of the resin particles.

-Fusion / unification process-
Next, the aggregated particle dispersion in which the aggregated particles are dispersed is heated to, for example, a glass transition temperature of the resin particles or higher (for example, a temperature of 10 ° C. to 30 ° C. higher than the glass transition temperature of the resin particles), and the temperature And agglomerated particles are fused and united to form toner particles.
The time for maintaining the temperature may be, for example, 30 minutes or more and 5 hours or less. Normally, the longer the holding time is within this range, the average circularity of the toner particles tends to approach 1.

Through the above steps, toner particles are obtained.
In addition, after obtaining the aggregated particle dispersion liquid in which the aggregated particles are dispersed, the aggregated particle dispersion liquid and the resin particle dispersion liquid in which the resin particles are dispersed are further mixed, and resin particles are further added to the surface of the aggregated particles. A process of aggregating to adhere to form second aggregated particles, and heating the second aggregated particle dispersion in which the second aggregated particles are dispersed to fuse and coalesce the second aggregated particles. The toner particles may be manufactured through a step of forming toner particles having a core / shell structure.

After completion of the coalescence / union process, the toner particles formed in the solution are subjected to a known washing process, solid-liquid separation process, and drying process to obtain dried toner particles.
In the washing step, it is preferable to sufficiently perform substitution washing with ion-exchanged water from the viewpoint of chargeability. The solid-liquid separation step is not particularly limited, but suction filtration, pressure filtration, or the like is preferably performed from the viewpoint of productivity. Also, the drying process is not particularly limited, but from the viewpoint of productivity, freeze drying, flash jet drying, fluidized drying, vibration fluidized drying, or the like is preferably performed.

[Silicone oil]
The liquid developer according to the exemplary embodiment includes silicone oil as a carrier liquid for dispersing toner particles. Silicone oil has good dispersibility with respect to toner particles containing a polyester resin, and can be easily separated from the toner particles when the toner particles are heated and melted to obtain a fixed image having excellent fastness. A low-volatile silicone oil having a flash point of 100 ° C. or higher is more preferable as a carrier liquid in terms of reducing the cleaning work of each member in the image forming apparatus and low environmental load.

Examples of the silicone oil include dimethyl silicone oil (for example, KF-96L-5cs, KF-96-10cs, KF-96-20cs, KF-96-50cs, KF-965, and KF-965 manufactured by Shin-Etsu Chemical Co., Ltd.). 968), methyl hydrogen silicone oil (for example, KF-99 manufactured by Shin-Etsu Chemical Co., Ltd.), methylphenyl silicone oil (for example, KF-50 and KF-54 manufactured by Shin-Etsu Chemical Co., Ltd.), and the like.
One type of silicone oil may be used alone, or two or more types may be mixed and used.

  The liquid developer according to this embodiment may contain other insulating liquids (for example, aliphatic hydrocarbons) other than silicone oil as the carrier liquid, but the mass ratio of silicone oil in the carrier liquid is 90%. The content is desirably at least mass%, desirably at least 95 mass%, and more desirably at 100 mass% (that is, no other insulating liquid other than silicone oil is included).

[Other ingredients]
The liquid developer according to the exemplary embodiment may include other components, such as a charge control agent, a dispersant, an emulsifier, a surfactant, a stabilizer, a wetting agent, a thickener, an antifoaming agent, and an anti-settling agent. An agent, an anti-aging agent, an anti-tacking agent, a flavoring agent and the like may be included.

<Image forming apparatus and image forming method>
The image forming apparatus according to the present embodiment includes an image carrier, a charging unit that charges the surface of the image carrier, a latent image forming unit that forms an electrostatic latent image on the charged surface of the image carrier, Developing means for containing a liquid developer and developing the electrostatic latent image formed on the surface of the image carrier with the liquid developer to form a toner image; and transfer means for transferring the toner image to a recording medium And fixing means for fixing the toner image on the recording medium. The liquid developer according to this embodiment is applied as the liquid developer.

  In the image forming apparatus according to the present embodiment, a charging process for charging the surface of the image carrier, a latent image forming process for forming an electrostatic latent image on the charged surface of the image carrier, and a liquid according to the present embodiment. A developing step of developing an electrostatic latent image formed on the surface of the image carrier with a developer to form a toner image; a transferring step of transferring the toner image to a recording medium; and the toner image on the recording medium. And an image forming method (an image forming method according to this embodiment).

  The image forming apparatus according to the present embodiment is a direct transfer type apparatus that directly transfers a toner image formed on the surface of an image carrier to a recording medium; the toner image formed on the surface of the image carrier is transferred to an intermediate transfer member An intermediate transfer type apparatus that primarily transfers the toner image transferred to the surface of the intermediate transfer body and then secondary transfer the toner image to the surface of the recording medium; after the toner image is transferred, the surface of the image carrier before charging is cleaned. A known image forming apparatus such as an apparatus provided with a cleaning unit; an apparatus provided with a charge removing unit that discharges the surface of the image holding member with a discharge light before charging after transferring the toner image;

In the image forming apparatus according to the present embodiment, the portion including the developing unit may be a cartridge structure (process cartridge) that can be attached to and detached from the image forming apparatus.
In the image forming apparatus according to the present embodiment, the portion that stores the liquid developer may have a cartridge structure (liquid developer cartridge) that can be attached to and detached from the image forming apparatus.

  Hereinafter, an image forming apparatus according to the present embodiment will be described with reference to the drawings. The same reference numerals are given to the members having the same configuration, operation, and action throughout the drawings, and redundant description is omitted.

  FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus according to the present embodiment, and is a diagram illustrating a quadruple tandem type and intermediate transfer type image forming apparatus. An image forming apparatus 100 shown in FIG. 1 is configured to superimpose toner images on an intermediate transfer member.

  The image forming apparatus 100 includes an electrophotographic image forming units 101Y, 101M, 101C, and 101K, an intermediate transfer belt 112 (an example of an intermediate transfer member), and a secondary transfer device 114 (an example of a secondary transfer unit). And a fixing device 140 (an example of fixing means). The image forming units 101Y, 101M, 101C, and 101K are juxtaposed at a predetermined distance from each other in the horizontal direction, for example.

Image forming units 101Y, 101M, 101C, and 101K are units that form toner images of yellow (Y), magenta (M), cyan (C), and black (K), respectively, and have the same configuration.
The image forming units 101Y, 101M, 101C, and 101K are wet image forming units, and are respectively a photosensitive member 102 (an example of an image carrier), a charging device 104 (an example of a charging unit), and an exposure device 106 ( An example of a latent image forming unit), a developing device 108 (an example of a developing unit), and a primary transfer device 110 (an example of a primary transfer unit).
Each of the image forming units 101Y, 101M, 101C, and 101K may be a process cartridge that is detachable from the image forming apparatus.

  The photosensitive member 102 functions as an image holding member. Around the photoconductor 102, a charging device 104, an exposure device 106, a developing device 108, and a photoconductor cleaner 131 for removing toner particles and carrier liquid remaining on the surface of the photoconductor 102 after the primary transfer are arranged in this order. ing.

The charging device 104 charges the surface of the photoreceptor 102.
The exposure device 106 forms an electrostatic latent image by exposing the surface of the charged photoreceptor 102 with, for example, a laser beam based on the image signal.

  The developing device 108 is a wet developing device, and includes a developer tank 132, a developer supply roll 134, a supply amount regulating member 136, a developing roll 138, and a developing roll cleaner 139. The developer tank 132, the developer supply roll 134, the supply amount regulating member 136, the development roll 138, and the development roll cleaner 139 may be integrated as a process cartridge that can be attached to and detached from the image forming apparatus.

The developer tank 132 contains the liquid developer G. The developer tank 132 may be provided with a stirring member (not shown) that stirs the liquid developer G.
The developer supply roll 134 is provided so that a part thereof is immersed in the liquid developer G accommodated in the developer tank 132 and is close to or in contact with the development roll 138. The agent G is supplied to the surface of the developing roll 138. The supply amount regulating member 136 controls the supply amount of the liquid developer G by the developer supply roll 134.
The developing roll 138 develops the electrostatic latent image formed on the surface of the photoreceptor 102 as a toner image by the liquid developer G supplied from the developer supply roll 134.
The developing roll cleaner 139 is provided on the downstream side of the photosensitive member 102 in the rotation direction of the developing roll 138, and removes the liquid developer remaining on the surface of the developing roll 138. The removed liquid developer is returned to the developer tank 132 by a circulation means (not shown).

  The primary transfer device 110 is a roll-shaped member, and is provided at a position inside the intermediate transfer belt 112 and facing the photoconductor 102. A bias power supply (not shown) for applying a primary transfer bias is connected to the primary transfer device 110. The primary transfer device 110 transfers the toner image on the photoconductor 102 to the intermediate transfer belt 112 by electrostatic force.

  The intermediate transfer belt 112 is wound around the secondary transfer device 114 and the drive roll 118 and extends through the four image forming units. The intermediate transfer belt 112 travels in a direction from the image forming unit 101Y to the image forming unit 101K. Toner images are transferred from the four image forming units to the intermediate transfer belt 112.

  The secondary transfer device 114 is a roll-shaped member, and is provided inside the intermediate transfer belt 112 and downstream of the four image forming units. The secondary transfer device 114 sandwiches the recording medium P together with the opposing roll 116 and transfers the toner image on the intermediate transfer belt 112 to the recording medium P.

  The fixing device 140 is provided on the downstream side of the secondary transfer device 114 in the traveling direction of the recording medium P. The fixing device 140 pressurizes and heats the toner image on the recording medium P to fix the toner image on the recording medium P. The fixing method in the fixing device 140 may be contact heating fixing using a roll pair or roll / belt pair, or non-contact heating fixing using an oven, a flash lamp, or the like. When an ultraviolet curable liquid developer is used, a non-contact heat fixing fixing method using a UV lamp or the like is used.

Hereinafter, an image forming method by the image forming apparatus 100 will be described.
The charging device 104, the exposure device 106, the developing device 108, the primary transfer device 110, the intermediate transfer belt 112, the secondary transfer device 114, and the fixing device 140 are operated in synchronization with the rotation speed of the photoconductor 102.

First, the charging device 104 charges the surface of the photoconductor 102 rotating in the direction of the arrow to a predetermined potential.
Next, the exposure device 106 exposes the surface of the charged photoconductor 102 based on the image signal to form an electrostatic latent image.

In the developing device 108, the developer supply roll 134 supplies the liquid developer G to the surface of the developing roll 138, and the developing roll 138 conveys the liquid developer G to the photoconductor 102.
The liquid developer G is supplied to the electrostatic latent image on the photosensitive member 102 at a position where the developing roll 138 and the photosensitive member 102 are close to or in contact with each other, and the electrostatic latent image is developed (visualized) to form a toner image. Form.

Next, the primary transfer device 110 transfers the toner image on the photoconductor 102 to the intermediate transfer belt 112 that runs in the direction of the arrow by electrostatic force and pressure. As the intermediate transfer belt 112 passes through the four image forming units in order, the toner images of yellow, magenta, cyan, and black are sequentially superimposed on the intermediate transfer belt 112 to form a superimposed toner image. .
After the toner image is transferred to the intermediate transfer belt 112, the remaining liquid developer is removed by the photoconductor cleaner 131, and the process proceeds to the charging process again.

The intermediate transfer belt 112 to which the toner image of each color has been transferred reaches the secondary transfer device 114.
On the other hand, the recording medium P is fed through a supply device (not shown) to a sandwiched area where the secondary transfer device 114 and the opposing roll 116 are in pressure contact.
Then, the toner image on the intermediate transfer belt 112 is transferred to the recording medium P in the sandwiched area. This transfer is performed, for example, by applying a secondary transfer bias to the secondary transfer device 114 and using electrostatic force and pressure.

  In the fixing device 140, the roll pair included in the fixing device 140 sandwiches the recording medium P on which the toner image is transferred, pressurizes and heats, and fixes the toner image on the surface of the recording medium P. Thereby, a fixed image is formed on the surface of the recording medium P.

  FIG. 2 is a schematic configuration diagram of another example of the image forming apparatus according to the present embodiment, and is a diagram showing a quadruple tandem type and direct transfer type image forming apparatus. The image forming apparatus 200 shown in FIG. 2 is configured to superimpose toner images on a recording medium.

  The image forming apparatus 200 includes electrophotographic image forming units 201Y, 201M, 201C, and 201K, a conveyance belt 220, and a fixing device 140. The image forming units 201Y, 201M, 201C, and 201K are arranged in parallel at a predetermined distance from each other in the horizontal direction, for example.

The image forming units 201Y, 201M, 201C, and 201K are units that form toner images of respective colors of yellow (Y), magenta (M), cyan (C), and black (K), and have the same configuration.
The image forming units 201Y, 201M, 201C, and 201K are wet image forming units, and are respectively a photosensitive member 102, a charging device 104, an exposure device 106, a developing device 108, and a transfer device 210 (transfer means 210). An example).
Each of the image forming units 201Y, 201M, 201C, and 201K may be a process cartridge that can be attached to and detached from the image forming apparatus.

  The photosensitive member 102, the charging device 104, the exposure device 106, the developing device 108, and the fixing device 140 in the image forming apparatus 200 are the photosensitive member 102, the charging device 104, the exposure device 106, the developing device 108, and the fixing device 140 in the image forming apparatus 100. The configuration, operation, and operation of the device 140 are the same.

  The conveyor belt 220 is wound around a drive roll 222 and a support roll 224 and extends through four image forming units. The transport belt 220 travels in the direction from the image forming unit 201K to the image forming unit 201Y, and transports the recording medium P.

  The transfer device 210 is a roll-shaped member, and is provided at a position inside the conveyance belt 220 and facing the photoconductor 102. A bias power supply (not shown) for applying a transfer bias is connected to the transfer device 210.

  In the image forming apparatus 200, the transfer device 210 transfers the toner image on the photoconductor 102 onto the recording medium P conveyed in the direction of the arrow, for example, by electrostatic force and pressure. As the recording medium P sequentially passes through the four image forming units, the toner images of the respective colors of black, cyan, magenta, and yellow are sequentially superimposed on the recording medium P to form a superimposed toner image. The recording medium P on which the superimposed toner image is formed is conveyed to the fixing device 140 and the image is fixed on the surface of the recording medium P.

  FIG. 3 is a schematic configuration diagram of another example of the image forming apparatus according to the present embodiment, and is a diagram illustrating a quadruple tandem type and intermediate transfer type image forming apparatus. An image forming apparatus 300 shown in FIG. 3 is configured to superimpose toner images on a recording medium.

  The image forming apparatus 300 includes electrophotographic image forming units 301Y, 301M, 301C, and 301K, and a fixing device 140. The image forming units 301Y, 301M, 301C, and 301K are arranged in parallel at a predetermined distance from each other in the horizontal direction, for example.

The image forming units 301Y, 301M, 301C, and 301K are units that form toner images of respective colors of yellow (Y), magenta (M), cyan (C), and black (K), and have the same configuration.
The image forming units 301Y, 301M, 301C, and 301K are wet image forming units, and are respectively a photosensitive member 102, a charging device 104, an exposure device 106, a developing device 108, an intermediate transfer member 310, and a transfer member. A roll 320 (an example of a transfer unit).
Each of the image forming units 301Y, 301M, 301C, and 301K may be a process cartridge that can be attached to and detached from the image forming apparatus.

  The photosensitive member 102, the charging device 104, the exposure device 106, the developing device 108, and the fixing device 140 in the image forming apparatus 300 are the photosensitive member 102, the charging device 104, the exposure device 106, the developing device 108, and the fixing device 140 in the image forming apparatus 100. The configuration, operation, and operation of the device 140 are the same.

  The intermediate transfer member 310 is a roll-shaped member and is provided so as to be close to or in contact with the photosensitive member 102. The intermediate transfer member 310 transfers the toner image on the photosensitive member 102 to the intermediate transfer member 310 by, for example, electrostatic force.

  The transfer roll 320 is provided so as to be in contact with the intermediate transfer member 310, and transfers the toner image on the intermediate transfer member 310 to the recording medium P by, for example, electrostatic force and pressure.

In the image forming apparatus 300, the toner image is transferred from the surface of the photoreceptor 102 to the surface of the intermediate transfer member 310. Then, the transfer roll 320 sandwiches the recording medium P conveyed in the direction of the arrow together with the intermediate transfer member 310, and transfers the toner image on the intermediate transfer member 310 to the recording medium P. As the recording medium P sequentially passes through the four image forming units, the toner images of the respective colors of black, cyan, magenta, and yellow are sequentially superimposed on the recording medium P to form a superimposed toner image. The recording medium P on which the superimposed toner image is formed is conveyed to the fixing device 140 and the image is fixed on the surface of the recording medium P.
After the toner image is transferred to the recording medium P, the liquid developer remaining by the intermediate transfer body cleaner 311 is removed from the intermediate transfer body 310, and the process proceeds to the transfer process again.

<Process cartridge, liquid developer cartridge>
The process cartridge according to the present embodiment accommodates the liquid developer according to the present embodiment and develops a toner image by developing the electrostatic latent image formed on the surface of the image holding member with the liquid developer. And a process cartridge that is detachably attached to the image forming apparatus.
For example, in the image forming apparatus shown in FIGS. 1 to 3, the developing device 108 may be a process cartridge according to this embodiment.
The process cartridge according to this embodiment may further include at least one selected from other means such as an image holding member, a charging unit, an electrostatic charge image forming unit, a transfer unit, and a fixing unit. .

The liquid developer cartridge according to the present embodiment is a liquid developer cartridge that accommodates the liquid developer according to the present embodiment and is detachable from the image forming apparatus.
For example, in the image forming apparatus shown in FIGS. 1 to 3, the developer tank 132 may be the liquid developer cartridge according to the present embodiment. When the amount of liquid developer stored in the cartridge is reduced, the cartridge is replaced.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example.
In the following description, “part” is based on mass unless otherwise specified.

<Measurement method of each physical property>
[Weight average molecular weight of polyester resin]
The weight average molecular weight of the polyester resin was calculated from the result of molecular weight measurement by gel permeation chromatography (GPC) using the following measuring apparatus and the molecular weight calibration curve of a monodisperse polystyrene standard sample.
-Measuring device: HLC-8120 (manufactured by Tosoh Corporation)
Column: TSKgel SuperHM-M (manufactured by Tosoh Corporation)
・ Eluent: Tetrahydrofuran

[Acid value of polyester resin]
The acid value of the polyester resin was measured by a neutralization titration method according to JIS K0070-1992.

[Melting temperature and glass transition temperature of polyester resin]
The melting temperature and glass transition temperature of the polyester resin were analyzed by differential scanning calorimetry (DSC). Specifically, using a differential scanning calorimeter (DSC3110 manufactured by Mac Science, thermal analysis system 001), a DSC spectrum was obtained by measuring from 0 ° C. to 150 ° C. at a heating rate of 10 ° C./min.

[Volume average particle diameter of resin particles and toner particles]
The method for measuring the volume average particle diameter of the resin particles and toner particles is as follows.

-When the particle size is 2 µm or more-
Sample for measurement: 0.5 mg or more and 50 mg or less of particles are added to 2 mL of 5% aqueous solution of sodium dodecylbenzenesulfonate (surfactant), and this is added to 100 mL or more and 150 mL or less of the electrolytic solution (Isoton II manufactured by Beckman Coulter) Then, it was prepared by performing a dispersion treatment for 1 minute with an ultrasonic disperser.
Measuring device: Coulter Multisizer II type (manufactured by Beckman-Coulter), aperture diameter 100 μm.
Using the above measurement sample and measurement apparatus, the particle size of 50,000 particles of 2 μm or more and 60 μm or less was measured, and the volume average particle size distribution was determined from the particle size distribution.
Based on the particle size distribution, a cumulative distribution of the volume was drawn from the smaller diameter side with respect to the divided particle size range (channel), and the particle size at which the accumulation was 50% was defined as the volume average particle size.

-When the particle size is less than 2 µm-
Sample for measurement: Ion exchange water was added to the particle dispersion to prepare a solid content of about 10%.
Measuring device: Laser diffraction particle size distribution measuring device (LS13320 manufactured by Beckman-Coulter)
The above measurement sample was put into a cell until an appropriate concentration was reached, and the measurement was performed when the scattering intensity reached a sufficient value. The obtained volume average particle diameter for each channel was accumulated from the smaller volume average particle diameter, and the particle diameter at 50% accumulation was defined as the volume average particle diameter.

[Average circularity of toner particles]
5000 or more toner particles were image-analyzed by a flow-type image analysis method using FPIA-3000 manufactured by Sysmex Corporation, and the circularity was determined according to the above-described calculation formula, and the average circularity was determined from the circularity distribution. The HPF mode (high resolution mode) was used for image analysis. In analyzing the data, the particle size analysis range was set to 0.5 μm to 30.1 μm and the circularity analysis range was set to 0.40 to 1.00 for the purpose of removing measurement noise.

<Synthesis of polyester resin>
[Synthesis of Amorphous Polyester Resin (1)]
A heat-dried two-necked flask is charged with the following raw materials and dibutyltin oxide as a catalyst, introduced with nitrogen gas in a container and heated in an inert atmosphere, and then heated at 150 ° C. to 230 ° C. for about 12 hours. A copolycondensation reaction was performed, and then the pressure was gradually reduced at 210 ° C. to 250 ° C. to obtain an amorphous polyester resin (1).
・ Polyoxypropylene (2,2) -2,2-bis (4-hydroxyphenyl) propane
80 mole parts, polyoxyethylene (2,2) -2,2-bis (4-hydroxyphenyl) propane
20 mol parts ・ Terephthalic acid 50 mol parts ・ Fumaric acid 25 mol parts ・ Dodecenyl succinic acid 25 mol parts

The weight average molecular weight of the amorphous polyester resin (1) was 18,100, and the acid value was 13.9 mgKOH / g.
When the melting temperature of the amorphous polyester resin (1) was analyzed by DSC, no clear peak was shown, and a stepwise endothermic change was observed. The glass transition temperature at the midpoint of the stepwise endothermic change was 62 ° C.

[Synthesis of Amorphous Polyester Resin (2)]
An amorphous polyester resin (2) was obtained in the same manner as the amorphous polyester resin (1) except that the following raw materials were used.
・ Polyoxyethylene (2,0) -2,2-bis (4-hydroxyphenyl) propane
20 mol parts polyoxypropylene (2,2) -2,2-bis (4-hydroxyphenyl) propane
80 mol parts, terephthalic acid 50 mol parts, dodecenyl succinic acid 40 mol parts, 1,2,4-benzenetricarboxylic acid (trimellitic acid) 10 mol parts

The amorphous polyester resin (2) had a weight average molecular weight of 32,600 and an acid value of 16.9 mgKOH / g.
When the melting temperature of the amorphous polyester resin (2) was analyzed by DSC, no clear peak was shown, and a stepwise endothermic change was observed. The glass transition temperature at the midpoint of the stepwise endothermic change was 60 ° C.

[Synthesis of Crystalline Polyester Resin (1)]
The following materials were put into a heat-dried three-necked flask, and the air in the container was replaced with nitrogen gas by a depressurization operation to make an inert atmosphere, followed by mechanical stirring at 180 ° C. for 4 hours. Dimethyl sulfoxide was distilled off under reduced pressure, and then the temperature was gradually raised to 220 ° C. under reduced pressure and stirred for 1.5 hours. When it became a viscous state, it was air-cooled, the reaction was stopped, and the crystallinity A polyester resin (1) was obtained.
-1,10-dodecanedioic acid 43.4 parts-1,9-nonanediol 32.8 parts-Dimethyl sulfoxide 27.0 parts-Dibutyltin oxide 0.03 parts

The weight average molecular weight of the crystalline polyester resin (1) was 23,000.
When the melting temperature of the crystalline polyester resin (1) was analyzed by DSC, it showed a clear peak, and the peak top temperature was 78 ° C.

<Preparation of resin particle dispersion>
[Preparation of Amorphous Polyester Resin Particle Dispersion (1)]
Into a separable flask equipped with a stirrer and a thermometer, 175 parts of methyl ethyl ketone and 70 parts of isopropanol were added to make a mixed solvent, and then 350 parts of amorphous polyester resin (1) was gradually added and stirred with a three-one motor. Then, it was heated to 40 ° C. and dissolved to obtain an oil phase. While stirring the oil phase, 9.6 parts of a 10% by mass NH ₄ OH aqueous solution was added dropwise, and ion-exchanged water was further added to perform phase inversion emulsification. Next, the solvent was removed while reducing the pressure with an evaporator to obtain an amorphous polyester resin particle dispersion (1). The volume average particle diameter of the resin particles was 168 nm. The resin particle concentration was adjusted to 30% by mass with ion exchange water.

[Preparation of Amorphous Polyester Resin Particle Liquid Dispersion (2)]
Except for changing the amorphous polyester resin (1) to the amorphous polyester resin (2), the amorphous polyester resin particle dispersion ( 2) was obtained. The volume average particle diameter of the resin particles in the amorphous polyester resin particle dispersion (2) was 164 nm. The resin particle concentration was adjusted to 30% by mass with ion exchange water.

[Preparation of crystalline polyester resin particle dispersion (1)]
After adding 180 parts of methyl ethyl ketone and 45 parts of isopropanol to a separable flask equipped with a stirrer and a thermometer to make a mixed solvent, 300 parts of crystalline polyester resin (1) is gradually added and stirred with a three-one motor. Then, it was heated to 70 ° C. and dissolved to obtain an oil phase. While stirring the oil phase, 14 parts of a 10% by mass aqueous NH ₄ OH solution was added dropwise, and ion-exchanged water was further added to effect phase inversion emulsification. Next, the solvent was removed while the pressure was reduced with an evaporator to obtain a crystalline polyester resin particle dispersion (1). The volume average particle diameter of the resin particles was 171 nm. The resin particle concentration was adjusted to 25% by mass with ion-exchanged water.

<Preparation of colorant dispersion>
The following materials are mixed, dissolved, and dispersed for 1 hour using a high-pressure impact disperser ultimateizer (HJP30006 manufactured by Sugino Machine Co.) to obtain a colorant dispersion liquid in which a colorant (cyan pigment) is dispersed. It was. The volume average particle diameter of the colorant (cyan pigment) was 160 nm, and the solid content concentration was 25% by mass.
-Cyan pigment (Pigment Blue 15: 3 manufactured by Dainichi Seika Kogyo Co., Ltd.) 1000 parts-Anionic surfactant (Neogen R manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 15 parts-Ion-exchanged water 9000 parts

<Preparation of toner particles (1)>
-Agglomerated particle formation process-
Amorphous polyester resin particle dispersion (1) 190 parts Amorphous polyester resin particle dispersion (2) 190 parts Crystalline polyester resin particle dispersion (1) 62 parts Colorant dispersion 51 parts Anion Surfactant (TeycaPower BN2060, 20% by mass aqueous solution manufactured by Teika) 37 parts The above material is placed in a cylindrical stainless steel container, and a shearing force is applied at a rotational speed of 4,000 rpm using a homogenizer (Ultra Tarax T50 manufactured by IKA). Dispersed and mixed for 10 minutes with addition. Then, after adding a 0.3N nitric acid aqueous solution until the pH of the mixed solution becomes 4.8, 12.5 parts of a 10% by mass nitric acid aqueous solution of aluminum sulfate as an aggregating agent and 12% by mass of ethylenediaminetetraacetic acid (EDTA) 30 parts of the aqueous solution was gradually dropped, and the homogenizer was rotated at 5,000 rpm and dispersed for 15 minutes to obtain a mixed dispersion.
Next, the mixed dispersion was transferred to a polymerization kettle equipped with a stirrer and a thermometer, heated with a mantle heater, and heated to 30 ° C. At this time, the pH of the mixed dispersion was adjusted to a range of 3.2 to 3.8 using 0.3 N nitric acid and 1 N NaOH aqueous solution. The mixed dispersion was kept at the temperature and the pH range for 60 minutes to form aggregated particles.

―Fusion and unity process―
A 1N NaOH aqueous solution was dropped into the mixed dispersion after the formation of aggregated particles to adjust the pH to 7.5, and then the temperature was raised to 85 ° C. The mixed dispersion was held at the temperature for 3 hours to fuse the aggregated particles. After confirming that the aggregated particles were fused with an optical microscope, the mixed dispersion was cooled to 25 ° C. at a temperature decrease rate of 1.0 ° C./min.

-Washing process, drying process-
Under 25 ° C., the pH of the mixed dispersion after coalescence of the aggregated particles was adjusted to pH 9.5 using 0.3N nitric acid and 1N NaOH aqueous solution, and stirred for 20 minutes.
Thereafter, the mixture was sieved with a mesh having a pore diameter of 20 μm, and then the mixed dispersion was filtered to separate into solid and liquid. The solid content was dispersed in 15 times the amount of ion-exchanged water (water temperature: 30 ° C.), stirred for 20 minutes, and then filtered to solid-liquid separate. This process was repeated two more times.
Then, solid content was disperse | distributed in 10 times amount of ion-exchange water (water temperature 30 degreeC), and it stirred with the mechanical stirrer, Then, it filtered by suction and was separated into solid and liquid. This process was repeated two more times.
Thereafter, drying was performed with a vacuum freeze dryer to obtain toner particles (1). Toner particles (1) had a volume average particle size of 2.9 μm and an average circularity of 0.97.

<Preparation of Toner Particles (2) to (8)>
Toner particles in the same manner as in the preparation of toner particles (1), except that the temperature and holding time in the aggregated particle forming step and the temperature and holding time in the coalescence and coalescence step were changed as shown in Table 1. (2) to (8) were prepared. Table 1 shows the volume average particle diameter and average circularity of each toner particle.

<Examples 1 to 7: Production of liquid developers (1) to (7)>
Any one of the toner particles (1) to (7) and dimethyl silicone oil (KF-96-20cs manufactured by Shin-Etsu Chemical Co., Ltd.) are mixed, and a cyan liquid developer (1) to (1) having a solid content concentration of 30% by mass is obtained. 7) was obtained.

<Comparative Example 1: Production of liquid developer (C1)>
Toner particles (8) and dimethyl silicone oil (KF-96-20cs manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed to obtain a cyan liquid developer (C1) having a solid content concentration of 30% by mass.

<Reference Examples 1-2: Production of liquid developers (R1)-(R2)>
Either toner particles (8) or toner particles (1) are mixed with paraffin oil (Moleco White P-70 manufactured by Matsumura Oil Research Co., Ltd.), and a cyan liquid developer (R1) having a solid content concentration of 30% by mass. ) To (R2) were obtained.

<Evaluation>
As an image forming apparatus for evaluation, an image forming apparatus having the configuration shown in FIG. 3 was prepared. Four image forming units provided in this image forming apparatus were loaded with the cyan liquid developer of each of the examples, comparative examples, and reference examples.
Then, image formation using four image forming units (four-time transfer mode) and image formation using only one image forming unit (one-time transfer mode) are performed, and a cyan circular cluster printing chart ( 1200 dpi, 0 degree, 109 lines, coverage 10%).

  The formed image was subjected to image analysis, the circumscribed circle radius and the inscribed circle radius were measured for 50 halftone dots, the roundness (= circumscribed circle radius ÷ inscribed circle radius) was determined, and the arithmetic average was obtained. If the roundness value is 1, the halftone dot shape is a perfect circle, and the larger the roundness value is, the more the halftone dot shape is irregular.

  In Examples 1 to 7 in which the average circularity of the toner particles is 0.97 or less, the roundness of the four-transfer mode is 1 in comparison with Comparative Example 1 in which the average circularity of the toner particles is more than 0.97. It was close to.

  As for Examples 1 to 4 in which the volume average particle diameter of the toner particles is in the range of 2.8 μm to 3.1 μm, Examples 1 to 3 in which the average circularity of the toner particles is 0.85 or more The roundness of the single transfer mode was close to 1 as compared with Example 4 in which the average circularity of was less than 0.85.

  As for Examples 2 and 5 to 7 in which the average circularity of the toner particles is 0.91, the Examples 2, 5 and 6 in which the volume average particle diameter of the toner particles is 5 μm or less are the volume average particles of the toner particles. Compared to Example 7 in which the diameter was more than 5 μm, the roundness of the single transfer mode was close to 1, and the roundness of the four transfer mode was also close to 1.

  In Comparative Example 1 and Reference Example 1 using the same toner particles having an average circularity exceeding 0.97, the difference between the roundness of the single transfer mode and the roundness of the four transfer mode is seen. In Comparative Example 1 in which the carrier liquid is silicone oil, the difference is large, and the roundness of the four-time transfer mode exceeds 2.3, whereas in Reference Example 1 in which the carrier liquid is liquid paraffin, the difference is Was small and similar.

  Comparing Reference Example 1 and Reference Example 2, when the carrier liquid is liquid paraffin, the roundness of the four-time transfer mode does not approach 1 even if the average circularity of the toner particles is 0.97 or less. It was.

100, 200, 300 Image forming apparatus 101Y, 101M, 101C, 101K, 201Y, 201M, 201C, 201K, 301Y, 301M, 301C, 301K Image forming unit 102 Photosensitive member (image carrier)
104 Charging device (charging means)
106 Exposure apparatus (latent image forming means)
108 Developing device (Developing means)
110 Primary transfer device (primary transfer means)
112 Intermediate transfer belt (intermediate transfer member)
114 Secondary transfer device (secondary transfer means)
116 Opposing roll 118 Driving roll 131 Photoconductor cleaner 132 Developer tank 134 Developer supply roll 136 Supply amount regulating member 138 Developing roll 139 Developing roll cleaner 140 Fixing device (fixing means)
210 Transfer device (transfer means)
220 Conveying belt 222 Drive roll 224 Support roll 310 Intermediate transfer body 311 Intermediate transfer body cleaner 320 Transfer roll (transfer means)
G Liquid developer P Recording medium

Claims (6)

  A liquid developer containing toner particles containing a polyester resin and a colorant and having an average circularity of 0.97 or less, and silicone oil.   The liquid developer according to claim 1, wherein the toner particles have an average circularity of 0.85 or more.   A liquid developer cartridge that contains the liquid developer according to claim 1 and is detachable from an image forming apparatus.   A developing means for containing 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 image carrier with the liquid developer. A process cartridge to be attached to and detached from the image forming apparatus. An image carrier,
Charging means for charging the surface of the image carrier;
Latent image forming means for forming an electrostatic latent image on the surface of the charged image carrier;
And a developing unit that stores the liquid developer according to claim 1 and that develops an electrostatic latent image formed on a surface of the image carrier with the liquid developer to form a toner image. ,
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 that performs multiple transfer. A charging step for charging the surface of the image carrier;
A latent image forming step of forming an electrostatic latent image on the surface of the charged image carrier;
A developing step of developing a toner image by developing the electrostatic latent image formed on the surface of the image carrier with the liquid developer according to claim 1;
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 for performing multiple transfer.