JP2008102292A - Method of manufacturing liquid developer, liquid developer, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid developer which excels in charging characteristics and in which toner particles of sufficiently small size are stably dispersed, to provide a method of manufacturing a liquid developer by which such a liquid developer can be efficiently manufactured, and to provide an image forming apparatus capable of forming a high-resolution and high-definition toner image free of blur and unevenness. <P>SOLUTION: The method of manufacturing a liquid developer in which toner particles are dispersed in an insulation liquid includes the steps of associating fine particles mainly containing a resin material so as to obtain associated particles, and disintegrating the associated particles in an insulation liquid so as to obtain toner particles, wherein a dispersant is added to the insulation liquid before disintegrating the associated particles, and the relationship of 0.04≤A/B≤0.3 is satisfied, wherein A represents the electric resistance of the liquid developer in units of Ωcm, and B represents the electric resistance of the insulation liquid in units of Ωcm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

For the developer used for developing the electrostatic latent image formed on the latent image carrier, a dry toner using a toner composed of a material containing a colorant such as a pigment and a binder resin in a dry state; and And a liquid developer in which toner is dispersed in an electrically insulating carrier liquid.
The dry toner is usually produced by a dry pulverization method in which a material containing a colorant and a binder resin is pulverized in a dry state. However, since dry toner handles solid toner, there is an advantage in handling, but there are concerns about adverse effects on the human body due to powder, contamination due to scattering of toner, and uniformity when toner is dispersed There was a problem with sex. Also, with dry toners, particle aggregation tends to occur during storage, etc., and it is difficult to sufficiently reduce the size of toner particles, and it is difficult to form a high-resolution toner image. . In addition, when the size of the toner particles is relatively small, the problem due to the powder as described above becomes more remarkable.

  On the other hand, since the liquid developer uses an insulating liquid as a medium, the problem of aggregation of toner particles in the liquid developer during storage is less likely to occur compared to dry toner, and fine toner particles should be used. it can. As a result, the liquid developer has better fine line image reproducibility, better gradation reproducibility, better color reproducibility, and better image formation at high speed than dry toner. It has the feature of being.

As a method for producing such a liquid developer, a wet pulverization method for producing a liquid developer by pulverizing a material containing a colorant and a resin in an electrically insulating liquid (for example, see Patent Document 1), A polymerization method (for example, see Patent Document 2) is known in which monomer components are polymerized in an electrically insulating liquid to form resin fine particles insoluble in the electrically insulating liquid.
However, the conventional method for producing a liquid developer has the following problems.

  That is, it is difficult to pulverize the toner particles to a sufficiently small size by the wet pulverization method. To make the toner particles sufficiently small, a very large pulverization energy is required for a very long time. In short, the productivity of the liquid developer was extremely low. Further, in the method as described above, the particle size distribution of the toner particles tends to be wide (particle size variation is large). As a result, variation in characteristics (for example, charging characteristics) among the toner particles tends to increase. On the other hand, dry pulverization as described above is also conceivable, but in such a case, it is very difficult to obtain fine particles as required for the toner particles of the liquid developer, and aggregation or the like proceeds, and the comparison It was difficult to obtain small toner particles.

  Also, in the polymerization method, it is difficult to make the conditions for the polymerization reaction suitable, so that a resin material having a suitable molecular weight can be formed, toner particles having a desired size can be formed, It is difficult to reduce the variation sufficiently. As a result, the stability and reliability of the toner quality such as charging characteristics are likely to be low. Further, in the polymerization method, it takes a relatively long time to form toner particles, and the productivity of the liquid developer is poor. In addition, the polymerization method generally requires a large production apparatus and production equipment.

  Further, in the conventional method as described above, it has been difficult to obtain a liquid developer having sufficiently high dispersibility of toner particles. When the dispersibility of the toner particles is poor, there is a problem that when left for a long time, the toner particles settle, and the toner particles aggregate. In addition, once the particles settle and agglomerate, the toner particles are difficult to disperse even if they are stirred again to disperse, and the toner particles can be supplied uniformly during image formation. There was a problem that it was impossible.

JP-A-8-36277 Japanese Patent Publication No.8-7470

  An object of the present invention is to provide a liquid developer having excellent charging characteristics and stably dispersing toner particles having a sufficiently small size, and capable of efficiently producing such a liquid developer. It is an object of the present invention to provide a method for producing a liquid developer, and to provide an image forming apparatus capable of forming a high-definition toner image having high resolution without blurring or unevenness.

Such an object is achieved by the present invention described below.
The method for producing a liquid developer of the present invention is a method for producing a liquid developer in which toner particles are dispersed in an insulating liquid,
A step of associating fine particles mainly composed of a resin material to obtain associated particles;
Crushing the associated particles in the insulating liquid to obtain the toner particles;
At the time of crushing, adding a dispersant to the insulating liquid and crushing,
When the electric resistance of the liquid developer is A [Ωcm] and the electric resistance of the insulating liquid is B [Ωcm], a relationship of 0.04 ≦ A / B ≦ 0.3 is satisfied. .
As a result, it is possible to efficiently produce a liquid developer having excellent charging characteristics and stably dispersing toner particles having a sufficiently small size.

In the method for producing a liquid developer of the present invention, the content of the dispersant in the liquid developer is preferably 0.10 to 3.0 wt%.
Thereby, it is possible to efficiently produce a liquid developer in which charging characteristics are particularly excellent and toner particles having a sufficiently small size are particularly stably dispersed.
In the method for producing a liquid developer according to the present invention, the dispersant is preferably a polymer dispersant.
This makes it possible to efficiently produce a liquid developer in which the associated particles can be crushed particularly efficiently, the charging characteristics are particularly excellent, and sufficiently small toner particles are particularly stably dispersed.

In the method for producing a liquid developer according to the present invention, when the content of the dispersant in the liquid developer is C [wt%] and the content of the toner particles is D [wt%], 0.006 ≦ C It is preferable to satisfy the relationship /D≦0.12.
As a result, a liquid developer having particularly excellent charging characteristics and particularly stable dispersion of sufficiently small toner particles can be produced particularly efficiently.

In the method for producing a liquid developer according to the present invention, the insulating liquid used for crushing is preferably composed of a fatty acid monoester.
Since the fatty acid monoester has a relatively low viscosity, it easily enters between the fine particles constituting the associated particles, and the associated particles can be suitably crushed. In addition, an environmentally friendly liquid developer can be provided.

In the method for producing a liquid developer of the present invention, the viscosity of the insulating liquid used for crushing is preferably 1000 mPa · s or less.
Thereby, the associated particles can be crushed more efficiently.
In the method for producing a liquid developer of the present invention, the interfacial tension of the insulating liquid used for crushing with respect to the resin material is preferably 35 mN / m or less.
Thereby, the dispersibility of the toner particles can be more effectively improved, and the storage stability of the liquid developer can be effectively improved.

In the method for producing a liquid developer according to the present invention, the resin material is preferably a polyester resin.
The polyester resin has high transparency, and when used as a binder resin, the color developability of the obtained image can be increased.
The liquid developer of the present invention is manufactured by the method of the present invention.
As a result, it is possible to provide a liquid developer having excellent charging characteristics and stably dispersing toner particles having a sufficiently small size.

The image forming apparatus of the present invention is an image forming apparatus that forms an image on a recording medium using the liquid developer of the present invention,
A liquid developer reservoir for storing the liquid developer;
A developing unit for developing using the liquid developer supplied from the liquid developer storage unit;
A transfer unit that transfers the image formed by the developing unit onto a recording medium and forms a transfer image;
And a fixing unit that fixes the transfer image formed on the recording medium onto the recording medium.
Accordingly, it is possible to provide an image forming apparatus that can form a high-definition toner image with high resolution without blurring or unevenness.

Hereinafter, a preferred embodiment of a method for producing a liquid developer and a liquid developer according to the present invention will be described in detail.
First, a method for producing a liquid developer according to the present invention will be described.
The method for producing a liquid developer according to the present invention includes a step of forming an associated particle in which resin fine particles mainly composed of a resin material are associated to obtain an associated particle, and a toner particle is obtained by pulverizing the associated particle in an insulating liquid. Process.

<Preparation of associated particles>
First, an example of a method for preparing associated particles in which resin fine particles mainly composed of a resin material are associated will be described.
Any method may be used to prepare the associated particles, but in this embodiment, a dispersoid (mainly composed of a resin material (toner constituent material)) in an aqueous dispersion medium composed of an aqueous liquid. An aqueous emulsion in which (fine particles) are dispersed is obtained, and the dispersoids in the aqueous emulsion are associated to obtain associated particles.

[Aqueous emulsion]
First, the aqueous emulsion used in this embodiment will be described.
The aqueous emulsion obtained in the aqueous emulsion preparation step described below has a structure in which dispersoids (fine particles) are finely dispersed in an aqueous dispersion medium composed of an aqueous liquid.
(Aqueous dispersion medium (aqueous liquid))
The aqueous dispersion medium is composed of an aqueous liquid.
In the present invention, the “aqueous liquid” refers to a liquid that is excellent in water and / or water compatibility (for example, a liquid having a solubility in 100 g of water at 25 ° C. of 30 g or more). As described above, the water-based liquid is composed of water and / or a liquid having excellent compatibility with water, but is preferably composed mainly of water. In particular, the water content is 70 wt%. % Or more is preferable, and 90% by weight or more is more preferable. By using such a material, for example, the dispersibility of the dispersoid in the aqueous dispersion medium can be improved, and the dispersoid in the aqueous emulsion can have a relatively small particle size and a variation in size. It can be less. As a result, the toner particles in the finally obtained liquid developer have a small variation in size and shape between the particles, and have a high degree of circularity.

  Further, the aqueous dispersion medium (aqueous liquid) is preferably one having low compatibility with a high insulating liquid described later (for example, one having a solubility in 100 g of the high insulating liquid at 25 ° C. of 0.01 g or less). . As a result, the shape of the dispersoid can be suitably maintained in the liquid mixture obtained in the liquid mixture preparation step described later, and the shape of the toner particles in the finally obtained liquid developer can be made more uniform. can do.

  Specific examples of the aqueous liquid include, for example, water, alcohol solvents such as methanol, ethanol and propanol, ether solvents such as 1,4-dioxane and tetrahydrofuran (THF), and aromatic heterocycles such as pyridine, pyrazine and pyrrole. Compound solvents, amide solvents such as N, N-dimethylformamide (DMF) and N, N-dimethylacetamide (DMA), nitrile solvents such as acetonitrile, and aldehyde solvents such as acetaldehyde.

(Dispersoid (fine particles))
The dispersoid includes components constituting toner particles in the liquid developer, and includes at least a resin as a main component or a precursor thereof (hereinafter collectively referred to as “resin material”). Consists of materials. Examples of the resin precursor include a monomer, a dimer, and an oligomer of the resin.

Hereinafter, the constituent material of the dispersoid will be described.
1. Resin (resin material)
The dispersoid is made of a material containing a resin (binder resin) as a main component.
In the present invention, the resin (binder resin) is not particularly limited, and for example, polystyrene, poly-α-methylstyrene, chloropolystyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer. Polymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-acrylic acid ester -Styrene resins such as methacrylic acid ester copolymer, styrene-α-chloroacrylic acid methyl copolymer, styrene-acrylonitrile-acrylic acid ester copolymer, styrene-vinyl methyl ether copolymer, etc. A homopolymer or copolymer, Polyester resin, epoxy resin, urethane modified epoxy resin, silicone modified epoxy resin, vinyl chloride resin, rosin modified maleic acid resin, phenyl resin, polyethylene resin, polypropylene, ionomer resin, polyurethane resin, silicone resin, ketone resin, ethylene-ethyl Examples thereof include an acrylate copolymer, a xylene resin, a polyvinyl butyral resin, a terpene resin, a phenol resin, an aliphatic or alicyclic hydrocarbon resin, and one or more of these can be used in combination. Among the above, the polyester resin, for example, has a particularly high affinity with the insulating liquid described in detail later. When the polyester resin is used as a resin material constituting the toner particles, the toner particles in the liquid developer are used. Can be made particularly excellent in dispersibility. Moreover, the polyester resin has high transparency, and when used as a binder resin, the color developability of the obtained image can be made high. In addition, since the polyester resin easily adheres to the dispersant as described later, the dispersant in the liquid developer can be adhered to the surface of the toner particles. For this reason, the dispersing agent released from the toner particles in the insulating liquid can be particularly reduced, and a decrease in the electrical resistance of the liquid developer can be prevented. For this reason, the liquid developer is particularly excellent in charging characteristics.

Although the softening temperature of resin (resin material) is not specifically limited, It is preferable that it is 50-130 degreeC, It is more preferable that it is 50-120 degreeC, It is further more preferable that it is 60-115 degreeC. In the present specification, the softening temperature is a measurement condition in a Koka type flow tester (manufactured by Shimadzu Corporation): temperature increase rate: 5 ° C./min, softening start temperature defined by a die hole diameter of 1.0 mm. Point to.
In addition, the resin mentioned above may contain the hardening | curing agent etc. as needed.

2. Solvent The dispersoid may contain a solvent that dissolves at least a part of the components. Thereby, for example, the fluidity of the dispersoid in the aqueous emulsion can be increased, and the dispersoid in the aqueous emulsion can have a relatively small particle size and small variation in size. it can. As a result, the toner particles in the finally obtained liquid developer have a small variation in size and shape between the particles, and have a high degree of circularity.

Any solvent may be used as long as it dissolves at least a part of the components constituting the dispersoid, but it is preferable to use a solvent having a boiling point lower than that of the aqueous liquid described above. Thereby, a solvent can be removed easily.
Moreover, it is preferable that a solvent is a thing with low compatibility with the aqueous dispersion medium (aqueous liquid) mentioned above (for example, a thing with the solubility with respect to 100 g of aqueous dispersion media at 25 degreeC is 30 g or less). Thereby, the dispersoid can be finely dispersed in a stable state in the aqueous emulsion.
Moreover, the composition of the solvent can be appropriately selected according to, for example, the composition of the resin and the colorant described above, the composition of the aqueous dispersion medium, and the like.

  Examples of the solvent include inorganic solvents such as carbon disulfide and carbon tetrachloride, methyl ethyl ketone (MEK), acetone, diethyl ketone, methyl isobutyl ketone (MIBK), methyl isopropyl ketone (MIPK), cyclohexanone, 3-heptanone, 4 -Ketone solvents such as heptanone, methanol, ethanol, n-propanol, isopropanol, n-butanol, i-butanol, t-butanol, 3-methyl-1-butanol, 1-pentanol, 2-pentanol, n- Alcohol solvents such as hexanol, cyclohexanol, 1-heptanol, 1-octanol, 2-octanol, 2-methoxyethanol, allyl alcohol, furfuryl alcohol, phenol, diethyl ether, dipropyl ether, diisopropyl Ether solvents such as ether, dibutyl ether, 1,2-dimethoxyethane (DME), 1,4-dioxane, tetrahydrofuran (THF), tetrahydropyran (THP), anisole, diethylene glycol dimethyl ether (diglyme), 2-methoxyethanol, Cellosolve solvents such as methyl cellosolve, ethyl cellosolve, phenyl cellosolve, aliphatic hydrocarbon solvents such as hexane, pentane, heptane, cyclohexane, methylcyclohexane, octane, didecane, methylcyclohexene, isoprene, toluene, xylene, benzene, ethylbenzene, Aromatic hydrocarbon solvents such as naphthalene, pyridine, pyrazine, furan, pyrrole, thiophene, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, fluoro Aromatic heterocyclic compound solvents such as furyl alcohol, amide solvents such as N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMA), dichloromethane, chloroform, 1,2-dichloroethane, trichloroethylene, chlorobenzene Halogenated solvents such as acetylacetone, ethyl acetate, methyl acetate, isopropyl acetate, isobutyl acetate, isopentyl acetate, ethyl chloroacetate, butyl chloroacetate, isobutyl chloroacetate, ethyl formate, isobutyl formate, ethyl acrylate, methyl methacrylate, Ester solvents such as ethyl benzoate, amine solvents such as trimethylamine, hexylamine, triethylamine and aniline, nitrile solvents such as acrylonitrile and acetonitrile, nitromethane, nitroethane, etc. Organic solvents such as aldehyde solvents such as nitro solvents, acetaldehyde, propionaldehyde, butyraldehyde, pentanal, and acrylic aldehyde, etc., and a mixture of one or more selected from these may be used. it can.

  The dispersoid usually contains a colorant. Examples of the colorant that can be used include pigments and dyes. Examples of such pigments and dyes include carbon black, spirit black, lamp black (CI No. 77266), magnetite, titanium black, chrome lead, cadmium yellow, mineral fast yellow, navel yellow, and naphthol yellow S. , Hansa Yellow G, Permanent Yellow NCG, Chrome Yellow, Benzidine Yellow, Quinoline Yellow, Tartrazine Lake, Red Mouth Lead, Molybdenum Orange, Permanent Orange GTR, Pyrazolone Orange, Benzidine Orange G, Cadmium Red, Permanent Red 4R, Watching Red Calcium salt, eosin lake, brilliant carmine 3B, manganese purple, fast violet B, methyl violet lake, bitumen, cobalt blue, al Reblue Lake, Victoria Blue Lake, First Sky Blue, Indanthrene Blue BC, Ultramarine, Aniline Blue, Phthalocyanine Blue, Calco Oil Blue, Chrome Green, Chrome Oxide, Pigment Green B, Malachite Green Lake, Phthalocyanine Green, Final Yellow Green G, Rhodamine 6G, quinacridone, rose bengal (C.I. No. 45432), C.I. I. Direct Red 1, C.I. I. Direct Red 4, C.I. I. Acid Red 1, C.I. I. Basic Red 1, C.I. I. Modern Tread 30, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 184, C.I. I. Direct Blue 1, C.I. I. Direct Blue 2, C.I. I. Acid Blue 9, C.I. I. Acid Blue 15, C.I. I. Basic Blue 3, C.I. I. Basic Blue 5, C.I. I. Modern Blue 7, C.I. I. Pigment blue 15: 1, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 5: 1, C.I. I. Direct Green 6, C.I. I. Basic Green 4, C.I. I. Basic Green 6, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 162, nigrosine dye (CI No. 50415B), metal complex dye, silica, aluminum oxide, magnetite, maghemite, various ferrites, cupric oxide, nickel oxide, zinc oxide, zirconium oxide, titanium oxide, Examples thereof include metal oxides such as magnesium oxide and magnetic materials containing magnetic metals such as Fe, Co, and Ni, and one or more of these can be used in combination.

  The content of the colorant in the aqueous emulsion is not particularly limited, but is preferably 0.1 to 15 wt%, and more preferably 0.3 to 10 wt%. If the content of the colorant is less than the lower limit, it may be difficult to form a visible image having a sufficient density depending on the type of the colorant. On the other hand, when the content of the colorant exceeds the upper limit, the fixing characteristics and charging characteristics of the finally obtained toner may be deteriorated.

  The dispersoid may contain a wax. The wax is usually used for the purpose of improving releasability. Examples of such wax include plant waxes such as candelilla wax, carnauba wax, rice wax, cotton wax, and wood wax, animal waxes such as beeswax and lanolin, montan wax, ozokerite, and ceresin. Mineral wax such as mineral wax, wax, paraffin wax, microwax, microcrystalline wax, petroleum wax such as petrolatum, wax, Fischer-Tropsch wax, polyethylene wax (polyethylene resin), polypropylene wax (polypropylene resin) ), Synthetic hydrocarbon waxes such as oxidized polyethylene wax, oxidized polypropylene wax, 12-hydroxystearic acid amide, stearic acid amide, phthalic anhydride imide, chlorinated hydrocarbons Fatty acid amides, esters, ketones, synthetic wax wax such as ether and the like, can be used singly or in combination of two or more of them. Further, as the wax, a crystalline polymer resin having a lower molecular weight may be used. For example, a homopolymer or copolymer of polyacrylate such as poly n-stearyl methacrylate and poly n-lauryl methacrylate (for example, It is also possible to use a crystalline polymer having a long alkyl group in the side chain, such as a copolymer of n-stearyl acrylate-ethyl methacrylate).

The content of the wax in the aqueous emulsion is not particularly limited, but is preferably 1.0 wt% or less, and more preferably 0.5 wt% or less. When the content of the wax is too large, the wax is liberated from the toner particles in the finally obtained liquid developer and becomes coarse and tends to lower the toner transfer efficiency.
The softening temperature of the wax is not particularly limited, but is preferably 50 to 130 ° C, and more preferably 50 to 120 ° C.

  Moreover, components other than these may be contained in the aqueous emulsion. Examples of such components include emulsifying dispersants, charge control agents, magnetic powders, and the like. Among these, when an emulsifying dispersant is used, the dispersibility of the dispersoid is improved, and the dispersion of the shape and size of the dispersoid in the aqueous emulsion is relatively small, and the dispersion The quality shape can be a substantially spherical shape. As a result, the final liquid developer can be obtained as a toner composed of toner particles having a substantially spherical shape, a uniform shape, and a uniform size. Here, examples of the emulsifying dispersant include emulsifiers, dispersants, and dispersion aids.

  Examples of the dispersant include inorganic dispersants such as clay minerals, silica, and tricalcium phosphate, nonionic organic dispersants such as polyvinyl alcohol, carboxymethyl cellulose, polyethylene glycol, and hydroxy stearates, and metal tristearate ( For example, aluminum salts, etc.), distearic acid metal salts (eg, aluminum salts, barium salts, etc.), stearic acid metal salts (eg, calcium salts, lead salts, zinc salts, etc.), linolenic acid metal salts (eg, cobalt salts, Manganese salt, lead salt, zinc salt, etc.), octanoic acid metal salt (eg, aluminum salt, calcium salt, cobalt salt etc.), oleic acid metal salt (eg, calcium salt, cobalt salt etc.), palmitic acid metal salt (eg. , Zinc salts, etc.), naphthenic acid metal salts (eg calcium salts, cobalt salts) Manganese salt, lead salt, zinc salt, etc.), resinate metal salt (eg calcium salt, cobalt salt, manganese lead salt, zinc salt etc.), polyacrylic acid metal salt (eg sodium salt etc.), polymethacrylic acid metal Salt (for example, sodium salt), polymaleic acid metal salt (for example, sodium salt), acrylic acid-maleic acid copolymer metal salt (for example, sodium salt), polystyrene sulfonic acid metal salt (for example, sodium salt) ) And other cationic organic dispersants such as quaternary ammonium salts. Among these, nonionic organic dispersants or anionic organic dispersants are particularly preferable.

The content of the dispersant in the aqueous emulsion is not particularly limited, but is preferably 3.0 wt% or less, and more preferably 0.01 to 1.0 wt%.
Examples of the dispersion aid include anions, cations, and nonionic surfactants.
The dispersing aid may or may not be used in combination with the dispersing agent. When the aqueous emulsion contains a dispersant, the content of the dispersion aid in the aqueous emulsion is not particularly limited, but is preferably 2.0 wt% or less, and is 0.005 to 0.5 wt%. Is more preferable.

Examples of the charge control agent include benzoic acid metal salts, salicylic acid metal salts, alkyl salicylic acid metal salts, catechol metal salts, metal-containing bisazo dyes, nigrosine dyes, tetraphenylborate derivatives, quaternary ammonium salts, Examples thereof include aluminum stearate, alkylpyridinium salts, chlorinated polyester, and nitrohumic acid.
Examples of the magnetic powder include magnetite, maghemite, various ferrites, cupric oxide, nickel oxide, zinc oxide, zirconium oxide, titanium oxide, magnesium oxide, and other metal oxides such as Fe, Co, and Ni. The thing comprised with the magnetic material containing a magnetic metal etc. are mentioned.

In addition to the above materials, for example, zinc stearate, zinc oxide, cerium oxide or the like may be added to the aqueous emulsion.
In the aqueous emulsion, components other than the dispersoid may be dispersed as an insoluble matter. For example, inorganic fine powders such as silica, titanium oxide, and iron oxide, and organic fine powders such as fatty acids and fatty acid metal salts may be dispersed in the aqueous emulsion.

In the aqueous emulsion used in the present invention as described above, since the dispersoid is liquid, the dispersoid tends to have a shape with a high degree of circularity (sphericity) due to its surface tension. Therefore, the finally obtained toner particles in the liquid development have a particularly high degree of circularity, and the variation in shape among the particles is particularly small.
The content of the dispersoid in the aqueous emulsion is not particularly limited, but is preferably 5 to 55 wt%, and more preferably 10 to 50 wt%. Thereby, the productivity of toner particles (liquid developer) can be made particularly excellent while more reliably preventing the dispersoids from binding (aggregating) in the aqueous emulsion.
The average particle size of the dispersoid (liquid dispersoid) in the aqueous emulsion is not particularly limited, but is preferably 0.01 to 3 μm, and more preferably 0.1 to 2 μm. Thereby, the size of the toner particles finally obtained can be optimized. In the present specification, “average particle diameter” refers to an average particle diameter based on volume.

[Aqueous emulsion preparation process]
The aqueous emulsion as described above can be prepared, for example, as follows (aqueous emulsion preparation step).
First, an aqueous solution in which a dispersant is added to the aqueous liquid as necessary is prepared.
On the other hand, a resin liquid containing a resin as a main component of the toner as described above or a precursor thereof (hereinafter collectively referred to as “resin material”) is prepared. For the preparation of the resin liquid, for example, the above-described solvent may be used in addition to the resin material. The resin liquid may be a molten liquid obtained by heating a resin material. Further, for the preparation of the resin liquid, for example, a kneaded product obtained by kneading a toner material such as a resin material and a colorant may be used. By using such a kneaded product, each component in the kneaded product obtained by kneading can be obtained even when the constituent materials of the toner contain components that are hardly dispersed or compatible with each other. It can be in a sufficiently compatible and finely dispersed state. In particular, when a pigment (colorant) having a relatively low dispersibility in the solvent as described above is used, the resin component or the like is effective around the pigment particles by being kneaded in advance before being dispersed in the solvent. Thus, the dispersibility of the pigment in the solvent is improved (particularly fine dispersion in the solvent is possible), and the color developability of the finally obtained toner is also improved. For this reason, in the case where the constituent material of the toner contains a component that is poor in dispersibility in the aqueous dispersion medium of the aqueous emulsion or a component inferior in solubility in the solvent contained in the dispersion medium of the aqueous emulsion. Even so, the dispersibility of the dispersoid in the aqueous emulsion can be made particularly excellent.

Next, an aqueous emulsion in which a dispersoid containing a resin material is dispersed in an aqueous dispersion medium is obtained by gradually adding the resin liquid to the stirred aqueous solution while dropping. By preparing an aqueous emulsion by such a method, the circularity of the dispersoid in the aqueous emulsion can be further increased. As a result, the finally obtained toner particles in liquid development have a particularly high degree of circularity, and the variation in shape among the particles is particularly small. In addition, when dripping a resin liquid, you may heat an aqueous solution and / or a resin liquid. In addition, when a solvent is used for the preparation of the resin liquid, for example, after the dropwise addition as described above, the obtained aqueous emulsion is heated or placed in a reduced-pressure atmosphere to be contained in the dispersoid. At least a part of the solvent may be removed.
Further, the mixing of the resin liquid and the aqueous liquid is performed by phase inversion emulsification by gradually adding (dropping) the aqueous liquid into the colored resin liquid while shearing the resin liquid with a stirrer or the like. A dispersion liquid in which a dispersoid derived from a resin liquid is dispersed in an aqueous liquid may be obtained. Thereby, for example, an aqueous emulsion in which the dispersoid is uniformly and finely dispersed can be easily and reliably obtained.

[Association particle formation process]
Next, an electrolyte is added to the aqueous emulsion obtained as described above, and the dispersoid is associated to form associated particles (associated particle forming step).
Examples of the electrolyte to be added include acidic substances such as hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, and oxalic acid, sodium sulfate, ammonium sulfate, potassium sulfate, magnesium sulfate, sodium phosphate, sodium dihydrogen phosphate, sodium chloride, and chloride. Organic and inorganic water-soluble salts such as potassium, ammonium chloride, calcium chloride, and sodium acetate can be used, and one or more of these can be used in combination. Among these, monovalent cation sulfates such as sodium sulfate and ammonium sulfate can be suitably used for promoting uniform association.

In addition, before adding electrolyte etc., you may add inorganic dispersion stabilizers, such as a hydroxyapatite, and an ionic and nonionic surfactant as a dispersion stabilizer. By adding an electrolyte in the presence of a dispersion stabilizer (emulsifier), non-uniform association can be prevented.
Examples of such a dispersion stabilizer include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene Examples include ethylene sorbitan fatty acid esters, various pluronic nonionic surfactants, alkyl sulfate salt type anionic surfactants, quaternary ammonium salt type cationic surfactants, and the like. Among these, anionic and nonionic surfactants are effective in dispersion stability even when added in a small amount, and can be suitably used. The cloud point of the nonionic surfactant is preferably 40 ° C. or higher.

  The amount of the electrolyte added is preferably 0.5 to 15 parts by weight, more preferably 1 to 12 parts by weight, with respect to 100 parts by weight of the solid content in the aqueous emulsion. More preferably. When the amount of electrolyte added is less than the lower limit, dispersoid association may not proceed sufficiently. Further, when the amount of electrolyte added exceeds the upper limit, dispersoids are not uniformly associated, and coarse particles may be generated, and there is a possibility that the size of toner particles finally obtained may vary. is there.

In addition, this step may be performed immediately after the preparation of the aqueous emulsion, or after adjustment of the aqueous emulsion, the aqueous emulsion may be stored, and then this step may be performed. In the latter case, the storage period is not particularly limited, but if it is within 6 months, the particle size distribution of the associated particles obtained can be made particularly narrow.
Then, after associating, filtration and drying are performed to obtain associated particles.

  The average particle size of the associated particles obtained is preferably 1 to 10 μm, and more preferably 1 to 7 μm. Thereby, the particle diameter of the toner particles finally obtained can be made moderate. In addition, when the average particle size of the associated particles is in such a range, drying is easy during drying, and aggregation particles are prevented from agglomerating and coarsening during drying. can do.

<Crushing process>
Next, the associated particles obtained as described above are pulverized in an insulating liquid constituting the liquid developer (a pulverization step). Thereby, a liquid developer in which toner particles are dispersed in an insulating liquid is obtained.
As described above, the present invention is characterized in that the obtained associated particles are pulverized in an insulating liquid to which a dispersant is added to form toner particles. Thereby, it is possible to provide a liquid developer in which sufficiently small toner particles are stably dispersed.

  More specifically, even if the toner particles are pulverized into relatively small toner particles, the toner particles are crushed in the insulating liquid, so that toner particles coarsened due to aggregation or the like are prevented from being generated. Can do. Further, the insulating liquid can be held on the unevenness of the surface of the toner particles derived from the fine particles (dispersoid), and as a result, the dispersibility of the toner particles can be improved.

Further, in the present invention, toner particles are obtained by crushing the associated particles, so that generation of fine powder (particles extremely smaller than particles of a desired size) is generated as compared with conventional pulverization methods and wet pulverization methods. Can be effectively prevented. As a result, it is possible to effectively prevent deterioration of characteristics such as charging characteristics of the liquid developer finally obtained.
It is also possible to prepare relatively small associated particles and disperse the associated particles as toner particles in an insulating liquid without crushing them to obtain a liquid developer. In this case, the associated particles are dried. At this time, since the particles are small, aggregation or the like is likely to occur, and the size of the toner particles varies.

  In the present invention, at the time of crushing, a dispersing agent is added to the insulating liquid to crush the associated particles. Thereby, the dispersing agent adheres to the surface of the associated particles, the dispersibility of the associated particles is increased, and the viscosity of the mixture of the associated particles and the insulating liquid is lowered. Therefore, the associated particles can be crushed more efficiently, and the dispersibility of the obtained toner particles in the insulating liquid can be increased. Further, by crushing by adding a dispersant, the viscosity of the liquid developer can be maintained in an appropriate range even when the surface area of the associated particles is increased by crushing.

  By the way, usually, when a dispersant is added to the liquid developer, the electrical resistance of the liquid developer is lowered by the dispersant dissolved and dispersed in the insulating liquid. However, by adding a dispersing agent at the time of crushing, the dispersing agent can be attached to the surface of the toner particles. In the obtained liquid developer, the amount of the dispersing agent dissolved and dispersed in the insulating liquid can be reduced. Can be reduced. For this reason, it is possible to prevent the electrical resistance of the liquid developer from being lowered by the dispersant. As a result, the obtained liquid developer has excellent charging characteristics, a narrow particle size distribution, and sufficiently small toner particles are stably dispersed. Further, according to the present invention, such a liquid developer can be efficiently produced.

  On the other hand, for the purpose of adjusting the viscosity, when a dispersant is added to the liquid developer after crushing or without crushing, and simply mixed, the electrical resistance of the liquid developer is increased. I can't. That is, when a dispersant is added to the liquid developer and mixed, the physical force for bringing the toner particles into contact with the dispersant is insufficient, and the dispersant does not suitably adhere to the toner particles.

  In the present invention, the aggregated particles are crushed when the electrical resistance of the liquid developer at room temperature (20 ° C.) is A [Ωcm] and the electrical resistance of the insulating liquid is B [Ωcm], 0.04 ≦ The process is performed so as to satisfy the relationship of A / B ≦ 0.3. Thereby, it is possible to obtain a liquid developer in which sufficiently small toner is stably dispersed while preventing a decrease in the electric resistance of the liquid developer. More specifically, by dispersing the associated particles by applying appropriate energy so that the electrical resistance of the liquid developer and the electrical resistance of the insulating liquid satisfy the above-described relationship, the dispersant is suitably used as a toner particle. In addition, the amount of the dispersant dissolved and dispersed in the insulating liquid can be reduced. In addition, the particle size of the resulting toner particles should be sufficiently small while narrowing the particle size distribution by applying appropriate energy to the associated particles so as to satisfy the above-mentioned relationship and performing crushing. Can do. For this reason, the charging characteristics of the liquid developer can be made excellent, and the occurrence of fading and density unevenness can be prevented during image formation. Further, since the charging characteristics are excellent, the developing property and the transfer property are excellent, and a clear toner image having a high image density can be obtained. Further, since toner particles having a small particle size and a narrow particle size distribution are obtained, the resolution of the toner image can be increased. The electrical resistance of the liquid developer: A [Ωcm] and the electrical resistance of the insulating liquid: B [Ωcm] may satisfy the above relationship, but the relationship of 0.07 ≦ A / B ≦ 0.25 is satisfied. It is preferable to satisfy, and it is more preferable to satisfy the relationship of 0.08 ≦ A / B ≦ 0.2. Thereby, the above-mentioned effect can be acquired more notably.

  The dispersant that can be used for crushing is not particularly limited. For example, polyvinyl alcohol, carboxymethyl cellulose, polyethylene glycol, polycarboxylic acid and its salt, polyacrylic acid metal salt (for example, sodium salt), polymethacrylic acid, and the like. Acid metal salt (for example, sodium salt), polyglycerin fatty acid ester, polyurethane derivative, sorbitan fatty acid ester, polyoxyethylene alkyl ether, alkyl ether type nonionic surfactant, sorbitan derivative nonionic surfactant, polymaleic acid metal salt (For example, sodium salt), acrylic acid-maleic acid copolymer metal salt (for example, sodium salt), polystyrenesulfonic acid metal salt (for example, sodium salt), polyamine aliphatic polycondensate, etc. Agent, viscosity Mineral, silica, tricalcium phosphate, metal tristearate (eg, aluminum salt), metal distearate (eg, aluminum salt, barium salt, etc.), metal stearate (eg, calcium salt, lead salt, zinc) Salt), linolenic acid metal salt (eg, cobalt salt, manganese salt, lead salt, zinc salt, etc.), octanoic acid metal salt (eg, aluminum salt, calcium salt, cobalt salt, etc.), oleic acid metal salt (eg, Calcium salt, cobalt salt, etc.), palmitic acid metal salt (eg, zinc salt), alkylbenzenesulfonic acid metal salt (eg, sodium salt), naphthenic acid metal salt (eg, calcium salt, cobalt salt, manganese salt, lead) Salts, zinc salts, etc.), resinate metal salts (eg calcium salts, cobalt salts, manganese lead salts, zinc salts, etc.), grease And phosphoric fatty acid esters and the like, may be used Among a combination of one or more kinds.

  Among these dispersants, it is preferable to use a polymer dispersant. The polymer dispersing agent particularly preferably adheres to the associated particles at the time of crushing, and the obtained liquid developer can also particularly favorably adhere to the toner particles. For this reason, the dispersibility of the toner particles in the obtained liquid developer is particularly excellent. In the obtained liquid developer, the amount of the dispersant dissolved and dispersed in the insulating liquid can be particularly reduced. For this reason, the liquid developer has particularly excellent charging characteristics. Further, at the time of crushing, the viscosity of the mixture of the associated particles and the insulating liquid can be kept particularly low, and the crushing efficiency can be made particularly excellent.

  In addition, when a compound containing a fatty acid such as vegetable oil or a fatty acid ester as described below is used as the insulating liquid of the liquid developer, a three-branch branch point where a linear side chain comes out is used as a polymer dispersant. It is preferable to use a compound having a structure with many main chains (comb structure). As a result, the polymer dispersant is particularly excellent in affinity with the insulating liquid. For this reason, the toner particles to which the polymer dispersant having a comb structure is attached are particularly excellent in dispersibility in the insulating liquid.

The weight average molecular weight of the polymer dispersant is preferably 1000 to 100,000, more preferably 5000 to 80000. Thereby, the effects as described above can be obtained particularly remarkably.
Moreover, it is preferable that a dispersing agent is a basic dispersing agent. Thereby, the dispersant can adhere to the associated particles and the toner particles particularly preferably.

  Examples of the polymer dispersant that satisfies the above conditions include polyglycerin fatty acid ester and polyamine aliphatic polycondensate. In particular, when a polyamine aliphatic condensate is used, the above-described effects can be obtained particularly remarkably. Examples of the polyamine aliphatic polycondensate include Solsperse (trade name of Nippon Lubrizol).

  The content of the dispersant in the finally obtained liquid developer is preferably 0.10 to 3.0 wt%, more preferably 0.15 to 1.8 wt%, More preferably, it is 1.5 wt%. Thereby, the dispersibility of the toner particles in the liquid developer can be made particularly excellent, the viscosity of the liquid developer can be kept particularly suitable, and the charging characteristics of the liquid developer are particularly excellent. can do. Further, at the time of crushing, the particle size of the toner particles can be made sufficiently small. On the other hand, if the content of the dispersant is less than the lower limit, depending on the insulating liquid used, the viscosity becomes too high during crushing, and the toner particles may not be made sufficiently small. Further, the dispersibility of the toner particles in the obtained liquid developer may not be excellent. Furthermore, the viscosity of the obtained liquid developer may become too high, and in the liquid developing device P1 described later, the liquid developer may not be supplied more uniformly to the application roller P12. On the other hand, when the content of the dispersant exceeds the upper limit, depending on the dispersant used, the electrical resistance of the liquid developer may be too low, and the charging characteristics may not be excellent. For this reason, when image formation is performed, the toner image may be blurred and problems such as density unevenness may occur.

  Examples of the insulating liquid include Isopar E, Isopar G, Isopar H, Isopar L (Isopar; trade name of Exxon Chemical), Cielsol 70, Cielsol 71 (Cielsol; trade name of Ciel Oil), Amsco OMS, Amsco 460 solvents (Amsco; trade name of Spirits), mineral oils such as low and high viscosity liquid paraffin (Wako Pure Chemical Industries), vegetable oils such as linseed oil and soybean oil, fatty acids such as fatty acid monoesters and medium chain fatty acid esters Examples include ester, octane, isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, cyclohexane, cyclooctane, cyclodecane, benzene, toluene, xylene, mesitylene, etc., and one or more of these are used in combination. be able to.

  Among the above-mentioned, when the fatty acid monoester is used as the insulating liquid, the following effects can be obtained. That is, since the fatty acid monoester has a relatively low viscosity, it easily enters between fine particles (dispersoids) constituting the associated particles, and the associated particles can be suitably crushed. In addition, since fatty acid monoester is an environmentally friendly component, it is possible to reduce the environmental load of the insulating liquid due to leakage of the insulating liquid to the outside of the image forming apparatus and disposal of the used liquid developer. . As a result, an environmentally friendly liquid developer can be provided. Further, among the fatty acid monoesters, particularly when an unsaturated fatty acid monoester having an unsaturated bond is used, the unsaturated fatty acid monoester undergoes an oxidative polymerization reaction during fixing, thereby recording toner particles more firmly. It can be fixed on a medium.

  Further, in the obtained liquid developer, when heat or pressure is applied during the fixing process, the fatty acid monoester penetrates into the toner particles (resin material) and plasticizes the toner particles (plasticizer effect). To express. Due to this plasticizer effect, for example, when paper is used as the recording medium, the toner particles can easily enter the gaps between the paper fibers, exhibit an anchor effect, and improve the fixing characteristics between the paper and the toner particles. Further, when the unsaturated fatty acid component is contained in the insulating liquid, the insulating liquid is cured in a state containing the toner particles by heat at the time of fixing, etc., so that the recording medium and the cured liquid developer Due to the anchor effect, the fixing characteristics of the toner particles to the recording medium are excellent. Further, since the toner particles are melted even at a relatively low temperature due to the plasticizer effect and can be fixed on a recording medium, it can be suitably applied to image formation at a low temperature and at a high speed.

  Moreover, when the insulating liquid used for crushing is a fatty acid monoester, the surface of the associated particles is plasticized by the fatty acid monoester, and the dispersant particularly easily adheres to the surface of the associated particles. For this reason, in the obtained liquid developer, the amount of the dispersant dissolved and dispersed in the insulating liquid can be particularly reduced, and the charging characteristics of the liquid developer can be made particularly excellent. Further, since the fatty acid monoester adheres to the toner particles during pulverization and the resin component can be plasticized, the toner particles obtained after pulverization have a particularly high average circularity described later.

Further, when the polymer dispersant is present when pulverizing with the fatty acid monoester, the polymer dispersant can be suitably present (entangled) on the surface of the toner particles. The polymer dispersant has a high affinity with the fatty acid monoester, and therefore, when mixed with a liquid containing other insulating liquid after crushing, the fatty acid monoester is more effective near the surface of the toner particles. Can be held in. For this reason, at the time of crushing, the plasticizer effect of the fatty acid monoester can be more effectively exhibited, and the dispersant can be more effectively adhered to the toner particles. For this reason, the polymer dispersant and the fatty acid monoester act synergistically, and the polymer dispersant and the fatty acid monoester adhere particularly favorably to the toner particle surface. As a result, the dispersibility of the toner particles in the liquid developer is particularly excellent, and the fixing characteristics are particularly excellent. Further, since the plasticizer effect is particularly effectively exhibited, the average circularity of the crushed toner particles becomes particularly high.
In addition, since the polymer dispersant adheres to the surface of the plasticized particles and is not easily released, the storage stability of the liquid developer is particularly excellent.

  Also, the apparatus that can be used for crushing is not particularly limited, for example, ball mill such as vibration ball mill, rotary ball mill, planetary ball mill, universal cutting mill, cutting mill such as rotor speed mill, vertical bead mill, Horizontal bead mills, attritors, SC mills, MSC mills, fine mills and other bead mills, jet mills, classifier mills, disk mills, impact pulverizers, automatic mortars and the like can be used. Among these, it is preferable to use a bead mill or a ball mill. By using these apparatuses, the associated particles can be crushed with a more appropriate shearing force, and the toner particles with a sufficiently small size can be obtained efficiently with a narrow particle size distribution. Further, the fatty acid monoester and the dispersant can be suitably attached to the toner particle surface. For this reason, the obtained liquid developer has a narrow particle size distribution, toner particles having a small particle diameter are particularly stably dispersed, and charging characteristics are particularly excellent.

In the above description, the associated particles are crushed using the whole amount of the insulating liquid constituting the finally obtained liquid developer. However, the aggregated particles are crushed using a part of the insulating liquid. It may be. Thereby, it can disintegrate more efficiently.
Moreover, when crushing using a part of insulating liquid, after crushing, the same liquid as the liquid used for crushing may be added as the insulating liquid, or crushing Later, a liquid different from the liquid used for crushing may be added as an insulating liquid. In the latter case, characteristics such as the viscosity of the finally obtained liquid developer can be easily adjusted.

The electrical resistance of the insulating liquid as described above at room temperature (20 ° C.) is preferably 1 × 10 ⁹ Ωcm or more, more preferably 1 × 10 ¹¹ Ωcm or more, and 1 × 10 ¹² Ωcm or more. More preferably.
The dielectric constant of the insulating liquid is preferably 3.5 or less.
Moreover, it is preferable that the viscosity of the insulating liquid used for crushing is 1000 mPa * s or less, and it is more preferable that it is 1-300 mPa * s. Thereby, the associated particles can be crushed more efficiently. Moreover, in this specification, a viscosity is measured based on JISZ8809 using a vibration viscometer at 25 degreeC.

The interfacial tension of the insulating liquid used for crushing with respect to the resin material constituting the toner particles is preferably 35 mN / m or less, and more preferably 32 mN / m or less. Thereby, the dispersibility of the toner particles can be more effectively improved, and the storage stability of the liquid developer can be effectively improved.
The electrical resistance of the liquid developer at room temperature (20 ° C.) is preferably 1 × 10 ⁹ Ωcm or more, more preferably 1 × 10 ¹¹ Ωcm or more, and 1 × 10 ¹³ Ωcm or more. Is more preferable.

  The average particle size of the toner particles in the finally obtained liquid developer is preferably 0.1 to 5 μm, more preferably 0.1 to 4 μm, and 0.5 to 3 μm. Further preferred. When the average particle diameter of the toner particles is a value within the above range, the variation in characteristics among the toner particles is particularly small, and the reliability of the entire liquid developer is particularly high, while the liquid developer ( The resolution of the image formed by the toner can be made sufficiently high.

The standard deviation of the particle size between toner particles constituting the liquid developer is preferably 1.0 μm or less, more preferably 0.1 to 1.0 μm, and more preferably 0.1 to 0. More preferably, it is 8 μm. As a result, the variation in characteristics among the toner particles becomes particularly small, and the reliability of the entire liquid developer is further improved.
The toner particle content in the liquid developer is preferably 10 to 60 wt%, and more preferably 20 to 50 wt%. Accordingly, it is possible to reliably prevent the toner particles from coming into contact with each other and releasing the dispersant during storage, and the charging characteristics of the liquid developer can be made particularly excellent. Further, the viscosity of the liquid developer can be made appropriate, and conditions such as heating during fixing can be made particularly gentle.

  Further, when the content of the dispersant in the liquid developer is C [wt%] and the content of the toner particles is D [wt%], the relationship of 0.006 ≦ C / D ≦ 0.12 is satisfied. It is preferable to satisfy the relationship of 0.01 ≦ C / D ≦ 0.10. As a result, an appropriate amount of the dispersant can adhere to the toner particles, and the dispersant dispersed and dissolved in the insulating liquid can be particularly reduced while making the dispersibility of the toner particles particularly high. For this reason, it is possible to make the electrical resistance particularly high while making the viscosity of the liquid developer moderate.

  Further, the viscosity of the liquid developer is preferably 20 to 300 mPa · s, and more preferably 30 to 250 mPa · s. When the viscosity of the liquid developer is in such a range, the dispersibility of the toner particles can be increased, and the liquid developer can be applied to the application roller P12 in the liquid developing device P1 as described later. The liquid can be supplied more uniformly, and dripping of the liquid developer from the application roller P12 and the like can be more effectively prevented.

Next, a preferred embodiment of the image forming apparatus of the present invention to which the liquid developer as described above is applied will be described. The image forming apparatus of the present invention includes a liquid developing device that forms a toner image on a recording medium and a fixing device that fixes the formed toner image onto the recording medium.
FIG. 1 shows an example of a contact-type liquid developing device constituting the image forming apparatus of the present invention. The liquid developing device P1 includes a developer container (liquid developer storing unit) P11 that stores a liquid developer, a cylindrical photosensitive member (developing unit) P2 that develops an image (toner image), and a developer container P11. A developing device P10 for supplying a liquid developer to the photosensitive member P2, and an intermediate transfer roller (transfer portion) P18 for transferring an image developed on the photosensitive member P2 to a recording medium to form a transfer image (toner image); ing.

The liquid developing device P1 has a drum of a cylindrical photosensitive member P2, and after the surface is uniformly charged by a charger P3 made of epichlorohydrin rubber or the like, information to be recorded by a laser diode or the like In accordance with the exposure P4, an electrostatic latent image is formed.
The developing device P10 includes a coating roller P12 and a developing roller P13, part of which is immersed in a developer container P11. The application roller P12 is, for example, a metal gravure roller such as stainless steel, and rotates to face the developing roller P13. Further, a liquid developer coating layer P14 is formed on the surface of the coating roller P12, and the thickness thereof is kept constant by the metering blade P15.

  Then, the liquid developer is transferred from the coating roller P12 to the developing roller P13. The developing roller P13 has a low hardness silicone rubber layer on a roller core P16 made of metal such as stainless steel, and a conductive PFA (polytetrafluoroethylene-perfluorovinyl ether copolymer) resin on the surface thereof. A layer is formed, and rotates at the same speed as the photosensitive member P2 to transfer the liquid developer to the latent image portion. The liquid developer remaining on the developing roller P13 after being transferred to the photoreceptor P2 is removed by the developing roller cleaning blade P17 and collected in the developer container P11.

Further, after the transfer of the image (toner image) from the photoreceptor P2 to the intermediate transfer roller P18, the photoreceptor is neutralized by the neutralizing light P21, and the transfer residual toner remaining on the photoreceptor is urethane rubber or the like. It is removed by the cleaning blade P22 constituted by
Similarly, the transfer residual toner remaining on the intermediate transfer roller P18 after being transferred from the intermediate transfer roller P18 to the recording medium F5 such as paper is removed by a cleaning blade P23 made of urethane rubber or the like.
After the image (toner image) formed on the photoreceptor P2 is transferred to the intermediate transfer roller P18, a transfer current is passed through the secondary transfer roller P19, and the recording medium F5 passing between the two is applied to the recording medium F5. The image is transferred, and the toner image (transfer image) on the recording medium F5 is fixed using a fixing device as will be described later.

  FIG. 2 shows an example of a non-contact type liquid developing device constituting the image forming apparatus of the present invention. In the non-contact method, the developing roller P13 is provided with a charging blade P24 made of a phosphor bronze plate having a thickness of 0.5 mm. The charging blade P24 has a function of making frictional charging in contact with the liquid developer layer, and since the application roller P12 is a gravure roll, a developer layer corresponding to the unevenness of the surface of the gravure roll is formed on the development roller P13. Therefore, it functions to uniformly level the unevenness, and the arrangement direction may be either the counter direction or the trail direction with respect to the rotation direction of the developing roller, and may be a roller shape instead of a brate shape.

Further, an interval of 200 μm to 800 μm is provided between the developing roller P13 and the photosensitive member P2, and a frequency of 500 to 3000 Vpp superimposed on a DC voltage of 200 to 800 V and a frequency between the developing roller P13 and the photosensitive member P2. An AC voltage of 50 to 3000 Hz is preferably applied. The rest is the same as the liquid developing apparatus described with reference to FIG.
In FIGS. 1 and 2, the image formation using one color liquid developer has been described. However, when forming an image using a plurality of color toners, each color image is formed using a plurality of color developing devices. Thus, a color image can be formed.

FIG. 3 is a cross-sectional view showing an example of a fixing device constituting the image forming apparatus of the present invention.
As shown in FIG. 3, the fixing device (fixing unit) F40 includes a heat fixing roller F1, a pressure roller F2, a heat-resistant belt F3, a belt stretching member F4, a cleaning member F6, a frame F7, and a spring. F9.
The heat fixing roller (fixing roller) F1 includes a roller base material F1b made of a pipe material, an elastic body F1c covering the outer periphery thereof, and a columnar halogen lamp F1a as a heating source inside the roller base material F1b. It can be rotated counterclockwise as indicated by an arrow in the figure.

Further, the pressure roller F2 has a roller base material F2b made of a pipe material and an elastic body F2c covering the outer periphery thereof, and is rotatable in the clockwise direction indicated by an arrow in the drawing.
A PFA layer is provided on the surface layer of the elastic body F1c of the heat fixing roller F1. As a result, the elastic bodies F1c and 2c have different thicknesses, but the elastic bodies F1c and 2c are substantially uniformly elastically deformed to form a so-called horizontal nip, and with respect to the peripheral speed of the heat fixing roller F1. Since there is no difference in the conveyance speed of the heat-resistant belt F3 or the recording medium F5, which will be described later, extremely stable image fixing is possible.

  In addition, two columnar halogen lamps F1a and F1a constituting a heating source are built in the heat fixing roller F1, and the heating elements of these columnar halogen lamps F1a and F1a are arranged at different positions. Yes. Then, by selectively lighting each columnar halogen lamp F1a, F1a, a fixing nip portion where a heat-resistant belt F3, which will be described later, is wound around the heat-fixing roller F1, and a belt stretching member F4, which will be described later, are attached to the heat-fixing roller F1. The temperature controller is easily performed under different conditions from the sliding contact portion, different conditions between the wide recording medium and the narrow recording medium, or the like.

The pressure roller F2 is disposed so as to face the heat fixing roller F1, and applies pressure to the recording medium F5 on which an unfixed toner image (transfer image) is formed via a heat-resistant belt F3 described later. It is configured to add. By applying pressure, the insulating liquid can be more efficiently penetrated into the recording medium F5. As a result, the toner image F5a can be more firmly fixed on the recording medium F5.
Further, the pressure roller F2 has a roller base material F2b made of a pipe material and an elastic body F2c covering the outer periphery thereof, and is rotatable in the clockwise direction indicated by an arrow in the drawing.

The aforementioned elastic body F1c of the heat fixing roller F1 and the elastic body F2c of the pressure roller F2 are subjected to substantially uniform elastic deformation to form a so-called horizontal nip. Further, since there is no difference in the conveyance speed of the heat-resistant belt F3 or the recording medium F5 described later with respect to the peripheral speed of the heat fixing roller F1, extremely stable image fixing can be performed.
The heat-resistant belt F3 is an endless annular belt that is stretched around the outer periphery of the pressure roller F2 and the belt stretching member F4 and is movable, and is sandwiched between the heat fixing roller F1 and the pressure roller F2. is there.

  The heat-resistant belt F3 has a thickness of 0.03 mm or more, and its front surface (the surface on which the recording medium F5 comes into contact) is formed of PFA, and the rear surface (the pressure roller F2 and the belt stretching member F4 is in contact). The side surface is formed of a seamless tube having a two-layer structure formed of polyimide. The heat-resistant belt F3 is not limited to this, and can be formed of other materials such as a metal tube such as a stainless steel tube or a nickel electroformed tube, or a heat-resistant resin tube such as silicone.

The belt stretching member F4 is disposed upstream of the fixing nip portion between the heat fixing roller F1 and the pressure roller F2 in the conveyance direction of the recording medium F5, and has an arrow P around the rotation axis F2a of the pressure roller F2. It is arranged so that it can swing in the direction.
The belt stretching member F4 is configured to stretch the heat-resistant belt F3 in the tangential direction of the heat fixing roller F1 in a state where the recording medium F5 does not pass through the fixing nip portion. If the fixing pressure is large at the initial position where the recording medium F5 enters the fixing nip portion, the entry may not be smoothly performed and the recording medium F5 may be fixed in a state where the tip of the recording medium F5 is broken. By adopting a configuration in which F3 is stretched in the tangential direction of the heat fixing roller F1, an inlet port of the recording medium F5 through which the recording medium F5 enters smoothly can be formed, and the stable fixing nip portion of the recording medium F5 can be formed. Can enter.

The belt stretching member F4 is inserted into the inner periphery of the heat-resistant belt F3 and cooperates with the pressure roller F2 to apply a tension f to the heat-resistant belt F3 (the heat-resistant belt F3 is a belt). Sliding on the tension member F4). The belt stretching member F4 is disposed at a position where the heat-resistant belt F3 is wound around the heat fixing roller F1 side from the pressing portion tangent L between the heat fixing roller F1 and the pressure roller F2 to form a nip. The protruding wall F4a protrudes from one end or both ends of the belt stretching member F4 in the axial direction. The protruding wall F4a is formed by the heat-resistant belt F3 when the heat-resistant belt F3 approaches one of the axial ends. The contact to the end of the heat-resistant belt F3 is regulated by contacting the wall F4a. A spring F9 is contracted between the end of the protruding wall F4a opposite to the heat fixing roller F1 and the frame, and the protruding wall F4a of the belt stretching member F4 is lightly pressed by the heat fixing roller F1, so that the belt tension is increased. The frame member F4 is positioned in sliding contact with the heat fixing roller F1.
The position where the belt stretching member F4 is lightly pressed against the heat fixing roller F1 is the nip initial position, and the position where the pressure roller F2 is pressed against the heat fixing roller F1 is the nip end position.

  When the liquid developer contains fatty acid monoester, the linear pressure on the recording medium F5 at the nip end position, that is, the linear pressure of the pressure roller F2 on the recording medium F5 is 500 g / cm or less. Preferably, it is 300 g / cm or less. Even with such a relatively low linear pressure, the toner particles can be firmly fixed to the recording medium F5 by applying such a liquid developer. Further, since the linear pressure is relatively low, the driving power of the pressure roller F2 and the heat fixing roller F1 can be reduced, and energy saving can be achieved.

  In the fixing device F40, a recording medium F5 on which an unfixed toner image F5a is formed using an image forming apparatus as will be described later enters the fixing nip portion from the initial nip position and enters the heat resistant belt F3 and the heat fixing roller F1. , And exiting from the nip end position, the unfixed toner image F5a formed on the recording medium F5 is thermally fixed, and then the pressing portion of the pressure roller F2 to the heat fixing roller F1 is pressed. It is discharged in the tangential direction L.

The cleaning member F6 is disposed between the pressure roller F2 and the belt stretching member F4.
The cleaning member F6 is in slidable contact with the inner peripheral surface of the heat-resistant belt F3 and cleans foreign matter, wear powder, and the like on the inner peripheral surface of the heat-resistant belt F3. In this way, by cleaning the foreign matter, wear powder, and the like, the heat-resistant belt F3 is refreshed, and the above-described instability factor of the friction coefficient is removed. Further, the belt stretching member F4 is provided with a recess F4f, and is configured to store foreign matter, abrasion powder, or the like removed from the heat-resistant belt F3.

  In order to stably drive the heat-resistant belt F3 by the pressure roller F2 and the belt stretching member F4 and stably drive the pressure roller F2, the friction coefficient between the pressure roller F2 and the heat-resistant belt F3 is determined by the belt tension. It is good to set larger than the friction coefficient of the frame member F4 and the heat-resistant belt F3. However, the friction coefficient is such that foreign matter enters between the heat-resistant belt F3 and the pressure roller F2 or between the heat-resistant belt F3 and the belt stretching member F4, or the heat-resistant belt F3, the pressure roller F2, and the belt stretching member. It may become unstable due to wear of the contact portion with F4.

  Therefore, the belt tension member F4 and the heat-resistant belt F3 have a winding angle smaller than the winding angle of the pressure roller F2 and the heat-resistant belt F3, and the diameter of the belt stretching member F4 is smaller than the diameter of the pressure roller F2. Set as follows. As a result, the length that the heat-resistant belt F3 slides on the belt stretching member F4 is shortened, which can be avoided from instability factors such as changes with time and disturbances, and the heat-resistant belt F3 is driven stably by the pressure roller F2. Will be able to.

  When the liquid developer contains a fatty acid monoester, the time required for the toner particles to pass through the fixing nip portion (nip time) is preferably 0.02 to 0.2 seconds, 0.03 More preferably, it is -0.1 second. Even if the time required for the toner particles to pass through the fixing nip portion is such a short time, by using such a liquid developer, it can be sufficiently fixed, and the printing speed can be further increased. Can be planned.

The fixing temperature when fixing the unfixed toner image is preferably 80 to 200 ° C, more preferably 80 to 180 ° C. When the fixing temperature is within the above range, when the unsaturated fatty acid component is contained in the liquid developer, the oxidative polymerization reaction (curing reaction) of the unsaturated fatty acid component can proceed more effectively. The toner particles can be fixed particularly firmly on the recording medium.
By using the image forming apparatus of the present invention composed of the liquid developing device and the fixing device as described above, a clear toner image with high resolution without blurring or unevenness can be obtained.

As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to these.
For example, the image forming apparatus of the present invention is not limited to the one constituted by the liquid developing device and the fixing device as described above.
In the above-described embodiment, the aqueous emulsion is obtained, and the association particles are obtained by adding an electrolyte to the aqueous emulsion. However, the present invention is not limited to this. For example, associating particles are prepared by dispersing a colorant, a monomer, a surfactant, and a polymerization initiator in an aqueous liquid, preparing an aqueous emulsion by emulsion polymerization, and adding an electrolyte to the aqueous emulsion and associating. What was prepared using the emulsion polymerization association method may be used, and the associated particle | grains may be obtained by spray-drying the obtained aqueous emulsion.

[1] Production of liquid developer (Example 1)
<Preparation of liquid constituting insulating liquid>
A liquid mainly containing an unsaturated fatty acid glyceride and a liquid mainly containing an unsaturated fatty acid methyl ester used as an insulating liquid were prepared as follows.

First, crude soybean oil was purified as follows to obtain purified soybean oil.
First, crude soybean oil was roughly purified by a low temperature crystallization method using methanol, diethyl ether, petroleum ether, acetone or the like as a solvent.
Next, 300 parts by volume of roughly refined crude soybean oil (first roughly refined oil) was put into the flask, and then 100 parts by volume of boiled water was poured into the flask, and the flask was stoppered.

Next, the flask was shaken, and the above-described crude soybean oil (first crudely refined oil) and boiled water were mixed.
Next, the flask was allowed to stand until the mixed liquid in the flask was separated into three layers.
After complete separation was confirmed, the flask was transferred to a freezer and left for 24 hours.
Thereafter, the components that were not frozen were transferred to another flask.
The same operation as described above was repeated for the unfrozen component, and the obtained non-frozen component was taken out to obtain a crude oil (second crude oil).

Next, in the flask, the crude oil and fat (second crude oil) obtained as described above: 100 parts by volume and active clay mainly composed of hydrous aluminum silicate: 35 parts by volume were mixed. Stir.
Next, the obtained mixture was stored under pressure (0.18 MPa) for 48 hours to completely precipitate the activated clay.
Thereafter, the precipitate was removed to obtain refined soybean oil (hereinafter simply referred to as soybean oil). In addition, the fatty acid glyceride which has linoleic acid as a main component was contained in soybean oil, and the unsaturated fatty acid glyceride in soybean oil was 98 wt%. Moreover, the linoleic acid component was 53 mol% of the total fatty acid components.

  Next, a transesterification reaction between a part of the soybean oil and methanol was performed, and glycerin generated by this reaction was removed to obtain a liquid mainly composed of fatty acid monoesters. Further, by purifying this liquid, soybean oil fatty acid methyl having a fatty acid monoester content of 99.9 wt% or more was obtained. Fatty acid monoesters thus obtained are mainly unsaturated fatty acid monoesters such as methyl oleate, methyl linoleate and methyl α-linolenate, and saturated fatty acid monoesters such as methyl palmitate and methyl stearate. Was mainly composed.

The crude high oleic rapeseed oil was refined in the same manner as soybean oil to obtain a purified high oleic rapeseed oil (hereinafter simply referred to as high oleic rapeseed oil). The high oleic rapeseed oil contained fatty acid glycerides mainly composed of oleic acid, and the unsaturated fatty acid glycerides in the high oleic rapeseed oil was 98 wt%. The oleic acid component and linoleic acid component were 58 mol% and 24 mol%, respectively, of the total fatty acid components.
Next, a transesterification reaction was carried out between a part of this high oleic rapeseed oil and methanol, and the glycerin produced by this reaction was removed to obtain a liquid mainly composed of fatty acid monoesters. Further, by purifying this liquid, rapeseed oil fatty acid methyl having a fatty acid monoester content of 99.9 wt% or more was obtained.

<Preparation of colorant master solution>
First, a mixture of a polyester resin (softening temperature: 125 ° C., Tg: 60.5 ° C., acid value: 7.7) and a cyan pigment as a coloring agent (Pigment Blue 15: 3, manufactured by Dainichi Seika Co., Ltd.) (Mass ratio 50:50) was prepared. These components were mixed using a 20 L type Henschel mixer to obtain a raw material for toner production.

Next, this raw material (mixture) was kneaded using a twin-screw kneading extruder. The kneaded product extruded from the extrusion port of the biaxial kneading extruder was cooled.
The kneaded product cooled as described above was coarsely pulverized to obtain a powder having an average particle size of 1.0 mm or less. A hammer mill was used for coarse pulverization of the kneaded product.
Methyl ethyl ketone was added to the obtained kneaded powder so that the solid content was 30% by mass, and wet dispersion was performed with an Eiger motor mill (manufactured by Eiger, USA: M-1000) to prepare a colorant master solution.

<Preparation of resin solution>
140 parts by weight of methyl ethyl ketone and 60 parts by weight of the polyester resin were added to 133 parts by weight of the colorant master solution, and mixed with an Eiger motor mill (manufactured by Eiger, USA: M-1000) to prepare a resin solution. In this solution, the pigment was uniformly finely dispersed.

<Preparation of aqueous emulsion (aqueous emulsion preparation process)>
500 parts by weight of the above resin liquid and 45.5 parts by weight of methyl ethyl ketone were placed in a cylindrical 2 L separable flask having a Max blend stirring blade, and the solid content of the resin liquid was 55%.
Next, 11.7 ammonia water: 41.7 parts by weight (the molar equivalent ratio with respect to the total amount of carboxyl groups of the polyester resin is 1.1) is added to the resin liquid in the flask, and three-one motor (manufactured by Shinto Kagaku Co., Ltd.) is used. The rotation speed of the stirring blade was set to 210 rpm (peripheral speed of stirring blade: 0.71 m / s), and the mixture was sufficiently stirred, and then 133 parts by weight of deionized water was added while maintaining stirring. While adjusting the temperature of the solution in the flask to 25 ° C. and continuing stirring, 133 parts by weight of deionized water was dropped into the resin liquid to cause phase inversion emulsification, and the dispersoid containing the resin material was dispersed. An aqueous emulsion was obtained.

<Manufacture of associated particles by association (associate particle formation process)>
Next, while continuing stirring in the flask, 285 parts by weight of deionized water was added to the aqueous emulsion so that the total amount of 1N ammonia water and water was 593 parts by weight. Subsequently, 2.6 parts by weight of Emul O (manufactured by Kao Corporation), which is an anionic emulsifier, was diluted to 30 parts by weight of deionized water and added to the aqueous emulsion.
Thereafter, while maintaining the temperature of the aqueous emulsion at 25 ° C., the rotation speed of stirring was 150 rpm (peripheral speed of stirring blade: 0.54 m / s), and 3.5% ammonium sulfate aqueous solution: 300 parts by weight was dropped. The particle size of the dispersoid aggregate was 3.5 μm. After dropping, stirring was continued until the particle size of the dispersoid aggregates grew to 5.2 μm, and the association operation was completed.

  With respect to the obtained aggregate dispersion, the organic solvent was distilled off under reduced pressure, and washing and dehydration were repeated, followed by drying to obtain associated particles. Some of the associated particles are dissolved in methyl ethyl ketone, extracted, and a gas chromatograph with a mass spectrometer (GC-17A + QP-5000, Shimadzu Corporation) equipped with a thermal decomposition apparatus (PYR-4A, Shimadzu Corporation) )). As a result, Emar O (manufactured by Kao Corporation), an anionic emulsifier, was not detected. In addition, the average particle diameter of each particle in each example and comparative example is a volume-based average particle diameter, and the average particle diameter and particle size distribution of these particles are obtained from a Mastersizer 2000 particle analyzer (manufactured by Malvern Instruments Ltd.). And measured.

<Preparation of liquid developer (disintegration process)>
Associative particles obtained by the above method: 40 parts by weight, methyl soybean oil fatty acid: 80 parts by weight, and polyamine aliphatic polycondensation polymer as a dispersant (manufactured by Nippon Lubrizol, trade name “Solsperse 13940”): 1 Part by weight and aluminum stearate (manufactured by Nippon Oil & Fats) as charge control agent: 0.5 part by weight is placed in a zirconia pot (internal volume 500 ml), and further steel beads (bead diameter: 1 mm) are filled to 30% by volume. It put into the pot made from zirconia so that it might become. Crushing was performed for 48 hours at a rotational speed of 210 rpm with a rotary ball mill (manufactured by ANZ51S ASONE). After crushing, 120 parts by weight of high oleic rapeseed oil was added and mixed. Mixing was performed by stirring for 24 hours using a similar ball mill and steel beads (bead diameter: 1 mm) at a volume filling rate of 30% and a rotation speed of 210 rpm. As a result, a liquid developer was obtained.

In the obtained liquid developer, the average particle diameter of the toner particles was 1.3 μm, and the standard deviation of the particle diameter between the toner particles was 0.47 μm. Further, the electric resistance A of the liquid developer is 3.2 × 10 ¹² Ωcm, the electric resistance B of the mixture of the insulating liquid used is 2.6 × 10 ¹³ Ωcm, and B / A is 0.12. there were. In addition, the electrical resistance of the liquid in this specification includes a universal electrometer (MMAII-17B, manufactured by Kawaguchi Electric Mfg.), A liquid electrode (LP-05, manufactured by Kawaguchi Electric Mfg. Co., Ltd.), and a shield box (P-618, Kawaguchi Electric Co., Ltd.). (Manufactured by Seisakusho) was attached and measured at room temperature (20 ° C).

(Examples 2 to 4)
A liquid developer was prepared in the same manner as in Example 1 except that the insulating liquid used for crushing and the insulating liquid added after crushing were used as shown in Table 1.
(Example 5)
Crude high oleic safflower oil was refined in the same manner as soybean oil to obtain a refined high oleic safflower oil (hereinafter simply referred to as high oleic safflower oil). The high oleic safflower oil mainly contained fatty acid glycerides mainly composed of oleic acid, and the unsaturated fatty acid glycerides in the high oleic safflower oil was 98 wt%. The oleic acid component and linoleic acid component were 76 mol% and 16 mol%, respectively, of the total fatty acid components.
Hereinafter, a liquid developer was prepared in the same manner as in Example 1 except that 120 parts by weight of high oleic rapeseed oil was used instead of 120 parts by weight of high oleic rapeseed oil as the insulating liquid added after crushing.

(Example 6)
Crude high oleic sunflower oil was refined in the same manner as soybean oil to obtain a refined high oleic sunflower oil (hereinafter simply referred to as high oleic sunflower oil). The high oleic sunflower oil contained fatty acid glycerides mainly composed of oleic acid, and the unsaturated fatty acid glycerides in the high oleic sunflower oil was 98 wt%. The oleic acid component and linoleic acid component were 80 mol% and 11 mol%, respectively, of the total fatty acid components.
Hereinafter, a liquid developer was prepared in the same manner as in Example 1 except that 120 parts by weight of high oleic rapeseed oil: 120 parts by weight of high oleic rapeseed oil was used as the insulating liquid to be added after crushing.

(Example 7)
A liquid developer was prepared in the same manner as in Example 1 except that 80 parts by weight of soybean oil fatty acid was used instead of 80 parts by weight of soybean oil fatty acid as the insulating liquid used for crushing.
(Examples 8 to 11)
A liquid developer was prepared in the same manner as in Example 1 except that a polyamine aliphatic polymer as a dispersant used for crushing was added as shown in Table 1.

(Example 12)
A liquid developer was produced in the same manner as in Example 1 except that an epoxy resin (softening temperature: 128 ° C.) was used as the resin material.
(Examples 13 to 15)
A liquid developer was prepared in the same manner as in Example 1 except that the dispersant described in Table 1 was used as the dispersant used for crushing.

(Comparative Example 1)
Polyester resin (softening temperature: 125 ° C., Tg: 60.5 ° C., acid value: 7.7): 80 parts by weight, cyan pigment as a colorant (manufactured by Dainichi Seika Co., Ltd., Pigment Blue 15: 3): 20 parts by weight was kneaded at 135 ° C. exceeding the softening point of the resin with two rolls and coarsely pulverized to 1 to 10 mm square to obtain colored chips.

Next, the mixture was pulverized with a pin mill while being cooled with liquid nitrogen, and classified with a mesh having a mesh size of 150 μm to obtain a pulverized product having an average particle diameter of 42 μm.
Next, 40 parts by weight of this pulverized product and 1.0 part by weight of a polyamine aliphatic polymer as a dispersant and 80 parts by weight of soybean oil fatty acid methyl: 80 parts by weight are mixed, and wet pulverization is performed using an attritor (Union Process). went. Next, 121 parts by weight of the obtained pulverized liquid was gradually dropped into 120.5 parts by weight of a liquid mainly containing high oleic rapeseed oil while irradiating an ultrasonic homogenizer to obtain a mixed liquid. In addition, the above-mentioned liquid used what added 0.5 weight part of aluminum stearates as a charge control agent to high oleic rapeseed oil. The average particle size of the toner particles in the obtained liquid developer was 2.0 μm. The standard deviation of the particle diameter between the toner particles was 0.83 μm.

(Comparative Example 2)
By appropriately adjusting the preparation conditions such as the stirring speed in the preparation of the aqueous emulsion and the addition amount and addition conditions of the electrolyte (ammonium sulfate), the average particle diameter of the associated particles in the associated particle dispersion is 1.5 μm. I made it.
Next, the associated particles were separated and dried from the associated particle dispersion in the same manner as in Example 1 described above.

  Next, the associated particles obtained: 40 parts by weight, soybean oil fatty acid methyl: 80 parts by weight, high oleic rapeseed oil: 120 parts by weight, polyamine aliphatic polycondensate as a dispersant: 1.0 part by weight, A liquid developer was obtained by mixing 0.5 parts by weight of aluminum stearate as a charge control agent. The average particle size of the toner particles in the obtained liquid developer was 1.7 μm, and the standard deviation of the particle size between the toner particles was 0.93 μm.

  Table 1 shows the manufacturing conditions of the liquid developer for each of the above Examples and Comparative Examples. In Table 1, the column “Insulating liquid used for crushing” in Comparative Example 1 describes the insulating liquid used for crushing. The column of “insulating liquid added after crushing” in Comparative Example 2 describes the type of insulating liquid used. In Table 1, “HO” indicates “high oleic”. Moreover, all the weight average molecular weights of the dispersing agent used for crushing and grinding described in Table 1 were in the range of 5000 to 80000.

[2] Evaluation Each liquid developer obtained as described above was evaluated as follows.
[2.1] Dispersion stability test 10 mL of the liquid developer obtained in each example and each comparative example was placed in a centrifuge tube, centrifuged at 1100 G for 10 minutes, and then 200 μL of the supernatant was collected. The sample was diluted 100-fold with the insulating liquid used in each example and each comparative example to prepare a sample.
The absorption wavelength of each sample was measured using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, V-570).

Evaluation was performed according to the following four-stage criteria from the absorbance value in the absorption range (685 nm) of the cyan pigment.
A: Absorbance is 1.50 or more (no precipitation is observed).
○: Absorbance is 1.00 or more and less than 1.50 (almost no sedimentation is observed).
Δ: Absorbance of 0.50 or more and less than 1.00 (precipitation is confirmed).
X: Absorbance is less than 0.50 (sedimentation is remarkable and sedimentation starts even when left standing).

[2.2] Preservability The liquid developers obtained in the respective Examples and Comparative Examples were allowed to stand for 8 months in an environment at a temperature of 15 to 25 ° C. Thereafter, the state of the toner in the liquid developer was visually confirmed and evaluated according to the following five criteria.
A: No toner particle floating or coagulation sedimentation is observed.
A: Floating toner particles and coagulation sedimentation are hardly observed.
○: Slight floating or coagulation sedimentation of toner particles is observed, but as a liquid developer
There is no problem.
Δ: Floating or coagulating sedimentation of toner particles is clearly observed.
X: Remarkably floating and coagulating sedimentation of toner particles are observed.

[2.3] Charging Characteristics The charging characteristics were evaluated using a “Laser Zeta Electrometer” ELS-6000 manufactured by Otsuka Electronics Co., Ltd. according to the following four-stage criteria.
A: Potential difference is +100 mV or more.
○: The potential difference is +50 mV or more and less than +100 mV.
Δ: Potential difference is +10 mV or more and less than +50 mV.
X: Potential difference is less than +10 mV.
These results are shown in Table 2 together with the properties of the liquid developer and the electrical resistance of the insulating liquid used.

As is apparent from Table 2, the liquid developer of the present invention was excellent in dispersion stability, storage stability, and charging characteristics. On the other hand, satisfactory results were not obtained with the liquid developers of the comparative examples.
Further, when image formation was performed using the image forming apparatus as shown in FIG. 1, the fixing device as shown in FIG. 3, and the liquid developer of the present invention, the image was clear and free from blurring and unevenness. A high-definition toner image of 2400 dpi was obtained.
In addition, the liquid developer was manufactured and evaluated in the same manner as described above except that Pigment Red 122, Pigment Yellow 180, and Carbon Black (Printex L, manufactured by Degussa) were used as the colorant instead of the cyan pigment. As a result, the same result as above was obtained.

1 is a cross-sectional view illustrating an example of a contact-type liquid developing device that constitutes an image forming apparatus of the present invention. FIG. 2 is a cross-sectional view illustrating an example of a non-contact type liquid developing device constituting the image forming apparatus of the present invention. 1 is a cross-sectional view illustrating an example of a fixing device constituting an image forming apparatus of the present invention.

Explanation of symbols

  P1 ... Liquid developing device P2 ... Photoconductor P3 ... Charger P4 ... Exposure P10 ... Developer P11 ... Developer container P12 ... Application roller P13 ... Development roller P14 ... Liquid developer application layer P15 ... Metering blade P16 ... Roller core P17 ... developing roller cleaning blade P18 ... intermediate transfer roller P19 ... secondary transfer roller P21 ... static light P22 ... cleaning blade P23 ... cleaning blade P24 ... charging blade F40 ... fixing device F1 ... heat fixing roller (fixing roller) F1a ... column-shaped halogen Lamp F1b ... Roller base material F1c ... Elastic body F2 ... Pressure roller F2a ... Rotating shaft F2b ... Roller base material F2c ... Elastic body F3 ... Heat-resistant belt F4 ... Belt stretch member F4a ... Projection wall F4f ... Recess F5 ... Recording medium F5a ... toner image 6 ... cleaning member F7 ... frame F9 ... spring

Claims (10)

A method for producing a liquid developer in which toner particles are dispersed in an insulating liquid,
A step of associating fine particles mainly composed of a resin material to obtain associated particles;
Crushing the associated particles in the insulating liquid to obtain the toner particles;
At the time of crushing, adding a dispersant to the insulating liquid and crushing,
When the electric resistance of the liquid developer is A [Ωcm] and the electric resistance of the insulating liquid is B [Ωcm], a relationship of 0.04 ≦ A / B ≦ 0.3 is satisfied. A method for producing a liquid developer.   The method for producing a liquid developer according to claim 1, wherein the content of the dispersant in the liquid developer is 0.10 to 3.0 wt%.   The method for producing a liquid developer according to claim 1, wherein the dispersant is a polymer dispersant.   When the content of the dispersant in the liquid developer is C [wt%] and the content of the toner particles is D [wt%], the relationship of 0.006 ≦ C / D ≦ 0.12 is satisfied. The method for producing a liquid developer according to claim 1.   5. The method for producing a liquid developer according to claim 1, wherein the insulating liquid used for crushing is composed of a fatty acid monoester.   The method for producing a liquid developer according to claim 1, wherein the insulating liquid used for crushing has a viscosity of 1000 mPa · s or less.   The method for producing a liquid developer according to claim 1, wherein an interfacial tension of the insulating liquid used for crushing with respect to the resin material is 35 mN / m or less.   The method for producing a liquid developer according to claim 1, wherein the resin material is a polyester resin.   A liquid developer produced by the method according to claim 1. An image forming apparatus that forms an image on a recording medium using the liquid developer according to claim 9,
A liquid developer reservoir for storing the liquid developer;
A developing unit for developing using the liquid developer supplied from the liquid developer storage unit;
A transfer unit that transfers the image formed by the developing unit onto a recording medium and forms a transfer image;
An image forming apparatus comprising: a fixing unit that fixes the transfer image formed on the recording medium onto the recording medium.

Images