JP2008203680A - Liquid developer and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid developer excellent in charging characteristics as well as in fixing characteristics of toner particles to a recording medium, and to provide an image forming apparatus using the liquid developer. <P>SOLUTION: The liquid developer contains: an insulating liquid containing a fatty acid monoester, an aliphatic hydrocarbon and/or silicone oil; toner particles dispersed in the insulating liquid; and a polyamine fatty acid condensation polymer as a dispersant. The content of the polyamine fatty acid condensation polymer is preferably 0.5 to 7.5 pts.wt. with respect to 100 pts.wt. of the toner particles. The content X [wt.%] of the aliphatic hydrocarbon and/or silicone oil in the insulating liquid and the content Y [wt.%] of the fatty acid monoester preferably satisfy the relationship of 0.1≤X/Y≤9. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to 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 There is a liquid developer (liquid toner) in which toner is dispersed in an electrically insulating carrier liquid (insulating liquid).
The method using dry toner handles solid-state toner, so there are advantages in handling, but there are concerns about adverse effects on the human body due to powder, as well as contamination due to scattering of toner, and when toner is dispersed There is a problem with uniformity. Further, the dry toner has a problem that the particles are likely to aggregate and it is difficult to sufficiently reduce the size of the toner particles, and it is difficult to form a toner image with high resolution. 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, in the method using a liquid developer, the toner particles are effectively prevented from aggregating in the liquid developer, so that fine toner particles can be used, and a dry toner is used as the binder resin. A resin material having a lower softening point (lower softening temperature) than the resin material used can be used. As a result, in the method using a liquid developer, fine line image reproducibility is good, gradation reproducibility is good, color reproducibility is excellent, and it is also excellent as a high-speed image forming method. It has characteristics.

  However, insulating liquids that have been used in conventional liquid developers are mainly petroleum hydrocarbons. In such a liquid developer, an insulating liquid adheres to the surface of the toner particles during fixing. In the conventional liquid developer, the fixing strength is lowered due to the presence of the insulating liquid adhering to the surface of the toner particles, and a sufficiently satisfactory fixing characteristic cannot be obtained.

In order to solve such problems, attempts have been made to improve the fixing strength by oxidative polymerization reaction of fats and oils at the time of fixing, using naturally derived fats and oils such as vegetable oil as the insulating liquid (for example, Patent Document 1). reference.).
However, the liquid developer using the oils and fats as described above can improve the fixing strength but cannot obtain a sufficient fixing strength.

JP 2006-251252 A

  An object of the present invention is to provide a liquid developer that is excellent in charging characteristics and toner particle dispersion stability and excellent in fixing characteristics of toner particles on a recording medium, and also uses such a liquid developer. An object is to provide an image forming apparatus.

Such an object is achieved by the present invention described below.
The liquid developer of the present invention includes an insulating liquid containing a fatty acid monoester and an aliphatic hydrocarbon and / or silicone oil;
Toner particles dispersed in the insulating liquid;
And a polyamine fatty acid condensation polymer as a dispersant.

In the liquid developer of the present invention, the content of the polyamine fatty acid condensation polymer is preferably 0.5 to 7.5 parts by weight with respect to 100 parts by weight of the toner particles.
In the liquid developer of the present invention, when the content of the aliphatic hydrocarbon and / or the silicone oil in the insulating liquid is X [wt%] and the content of the fatty acid monoester is Y [wt%]. , 0.1 ≦ X / Y ≦ 9 is preferably satisfied.

In the liquid developer of the present invention, the fatty acid monoester is preferably an ester of a fatty acid and a monovalent alcohol having 1 to 4 carbon atoms.
In the liquid developer of the present invention, the viscosity measured according to JIS Z8809 using a vibration viscometer at 25 ° C. is preferably 50 to 1000 mPa · s.
In the liquid developer of the present invention, the resin material constituting the toner particles is preferably a polyester resin.

The image forming apparatus of the present invention includes a plurality of developing units that form a single color image corresponding to each color using a plurality of liquid developers having different colors,
By transporting the recording medium, the plurality of monochrome images formed by the plurality of developing units are sequentially transferred to the recording medium, and an unfixed color image formed by superimposing the transferred plurality of monochrome images is recorded. A transfer portion formed on the medium;
A fixing unit for fixing the unfixed color image on the recording medium,
The liquid developer includes an insulating liquid containing an aliphatic hydrocarbon and / or silicone oil and a fatty acid monoester, toner particles dispersed in the insulating liquid, and a polyamine fatty acid condensation polymer as a dispersant. It is characterized by including.

In the image forming apparatus of the present invention, the plurality of developing units include at least a developing roller that forms the liquid developer layer on a surface thereof, and a compression that causes the toner particles to be unevenly distributed in the vicinity of the surface of the developing roller in the layer. And a photosensitive member that forms the monochrome image by transferring the liquid developer on the developing roller.
In the image forming apparatus according to the aspect of the invention, the compression unit applies an electric field having the same polarity as the toner particles to the layer, thereby causing the toner particles to be unevenly distributed in the vicinity of the surface of the developing roller in the layer. It is preferable.

In the image forming apparatus of the present invention, the developing unit includes at least a developing roller that forms the liquid developer layer on a surface thereof, and a photosensitive that forms the monochromatic image by transferring the liquid developer on the developing roller. And a coating roller for supplying a liquid developer to the developing roller,
Preferably, the application roller is an anilox roller having a groove formed on the surface thereof, and the liquid developer is supplied to the developing roller by carrying the liquid developer in the groove.

  With the above configuration, it is possible to provide a liquid developer that is excellent in charging characteristics and toner particle dispersion stability and excellent in fixing characteristics of toner particles to a recording medium. In addition, an image forming apparatus using such a liquid developer can be provided.

Hereinafter, preferred embodiments of the liquid developer and the image forming apparatus of the present invention will be described in detail.
<Liquid developer>
First, the liquid developer of the present invention will be described.
The liquid developer of the present invention is one in which toner particles are dispersed in an insulating liquid.

<Insulating liquid>
First, the insulating liquid will be described.
In the present invention, the insulating liquid contains a fatty acid monoester and an aliphatic hydrocarbon and / or silicone oil.

[Fatty acid monoester]
In the present invention, the fatty acid monoester in the insulating liquid is a monoester between a fatty acid and an alcohol.
In the conventional liquid developer, the insulating liquid leaks out of the image forming apparatus during use (for example, the volatilization of the insulating liquid during fixing) or the used liquid developer is discarded due to disposal of the used liquid developer. There were concerns about the impact on the environment. Further, the conventional liquid developer has a problem that the fixing property of the toner particles to the recording medium is hindered (fixing strength is reduced) due to the presence of the insulating liquid adhering to the surface of the toner particles.
On the other hand, the fatty acid monoester used in the insulating liquid is an environmentally friendly component. Therefore, it is possible to reduce the load on the environment of the insulating liquid due to the leakage of the insulating liquid to the outside of the image forming apparatus and the disposal of the used liquid developer. As a result, an environmentally friendly liquid developer can be provided.

  The fatty acid monoester has a property of easily penetrating into the toner particles (resin material), and has an effect (plasticizer effect) of suitably plasticizing the toner particles at the time of fixing. Due to this plasticizer effect, for example, when paper is used as the recording medium, the toner particles easily enter the gaps between the paper fibers, so that the fixing characteristics between the paper and the toner particles are excellent. Further, since the toner particles melt at a relatively low temperature and can be fixed on a recording medium due to the plastic effect, it can be suitably applied to image formation at a low temperature and a high speed. In addition, since the toner particles enter the gaps between the fibers of the recording medium in this way, the resulting toner image is smooth without any unevenness, and as a result, the gloss of the formed image is excellent. can do. In particular, in the present invention, as described in detail later, the plasticizer effect as described above can be more effectively exhibited by using it together with a polyamine fatty acid condensation polymer.

  In addition, since the fatty acid monoester is a component that suitably penetrates into the recording medium, the fatty acid monoester adhering to the vicinity of the surface of the toner particles is quickly transferred to the recording medium when the toner particles come into contact with the recording medium during fixing. To penetrate. Along with the permeation of the fatty acid monoester, a part of the toner particles (resin material constituting the toner particles) melted by heat at the time of fixing penetrates into the inside of the recording medium, an anchor effect works, and the paper and toner particles The fixing characteristics of the toner are improved.

Further, when a polyester resin is used as the resin material constituting the toner particles, the affinity with the insulating liquid containing the fatty acid monoester is particularly good as described above. While the dispersibility is very excellent, the fixing property of the toner particles to the recording medium can be made particularly excellent.
Examples of such fatty acid monoesters include oleic acid, palmitoleic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, arachidonic acid, docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and the like. Unsaturated fatty acid alkyl (methyl, ethyl, propyl, butyl, etc.) monoester, butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, etc. And alkyl (methyl, ethyl, propyl, butyl, etc.) monoesters of saturated fatty acids, and the like, and one or more selected from these can be used in combination.

  The fatty acid monoester is a monoester between a fatty acid and an alcohol, and the alcohol is preferably an alkyl alcohol having 1 to 4 carbon atoms. Thereby, the viscosity of the insulating liquid can be made suitable, and the penetration of the liquid developer into the recording medium can be made more suitable. Examples of such alcohol include methanol, ethanol, propanol, butanol, isobutanol and the like.

Moreover, the fatty acid monoester used in the present invention may be produced by a transesterification reaction between a vegetable oil and a monohydric alcohol as described above. That is, the insulating liquid used in the present invention may include a fatty acid monoester obtained by combining one or more selected from fatty acids and alcohols as described above.
Examples of vegetable oils used for transesterification include soybean oil, rapeseed oil, dehydrated castor oil, tung oil, safflower oil, linseed oil, sunflower oil, corn oil, cottonseed oil, sesame oil, corn oil, cannabis oil, evening primrose oil, palm oil (Especially palm kernel oil), coconut oil, coconut oil and the like.

  In addition, the content of the fatty acid monoester in the insulating liquid is preferably 1.0 to 50 wt%, more preferably 10 to 50 wt%, and further preferably 20 to 50 wt%. If the content of the fatty acid monoester in the insulating liquid is less than the lower limit, toner particles may not be sufficiently plasticized by the fatty acid monoester during fixing. On the other hand, when the upper limit is exceeded, the electrical resistance of the liquid developer is lowered, and sufficient charging characteristics may not be obtained. In addition, depending on the constituent material of the member, a member that comes into contact with the liquid developer in the image forming apparatus as described later may swell and the life of the image forming apparatus may be significantly reduced.

[Aliphatic hydrocarbon and silicone oil]
Aliphatic hydrocarbons and silicone oils are generally chemically stable liquids having high electrical resistance. For this reason, a liquid developer using an aliphatic hydrocarbon or silicone oil has good charging characteristics. However, when these components are used as an insulating liquid, there is a problem in that they adhere to the surface of toner particles during fixing and lower the fixing strength. On the other hand, the liquid developer exhibits particularly excellent charging characteristics by using a fatty acid monoester in combination with a polyamine aliphatic polycondensation polymer, which will be described later, as in the present invention, and a toner for a recording medium. Excellent fixing properties of the particles.

  The aliphatic hydrocarbon is not particularly limited, and for example, Isopar E, Isopar G, Isopar H, Isopar L (Exxon Chemical), Cosmo White P-60, Cosmo White P-70, Cosmo White P-120 (Cosmo Petroleum Lubricants Co., Ltd.), Dynafrecia W-8, Daphne Oil CP, Daphne Oil KP, Transformer Oil H, Transformer Oil G, Transformer Oil A, Transformer Oil B, Transformer Oil S (Idemitsu Kosan Co., Ltd.), Cielsol 70, Cielsol 71 ( Ciel Oil Co., Ltd.), Amsco OMS, Amsco 460 Solvent (Spilitz), low viscosity / high viscosity liquid paraffin (Wako Pure Chemical Industries), octane, isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane Cyclohexane, cyclooctane, cyclodecane, and the like, among these, can be used in combination of two or more.

In addition, the aliphatic hydrocarbon preferably has a branched chain of a hydrocarbon group in the molecule. Thereby, the aliphatic hydrocarbon becomes chemically more stable, and the storage stability of the liquid developer using such an aliphatic hydrocarbon becomes particularly excellent. This is considered to be because the structure of the aliphatic hydrocarbon becomes bulky and thus a structure in which a chemical reaction is difficult to occur.
The aliphatic hydrocarbon is preferably a saturated aliphatic hydrocarbon. Thereby, the electrical resistance of the liquid developer can be made particularly high, and the storage stability of the liquid developer can be made particularly excellent.

  The silicone oil is not particularly limited. For example, KF96, KF-4701, KF-965, KS-602A, KS-603, KS-604, KF-41, KF-54, FA-630 (Shin-Etsu Silicone) Manufactured), TSF410, TFS433, TFS434, TFS451, TSF437, (Momentive Performance Materials Japan GK), SH200 (Toray Industries, Inc.), etc., among these, one or a combination of two or more Can be used.

Further, the ratio of the fatty acid monoester to the aliphatic hydrocarbon liquid and / or the silicone oil is not particularly limited, but preferably satisfies the following relationship. That is, when the content of the aliphatic hydrocarbon liquid and the silicone oil in the insulating liquid is X [wt%] and the content of the fatty acid monoester is Y [wt%], 0.1 ≦ X / Y ≦ 9 is preferably satisfied, 0.4 ≦ X / Y ≦ 9 is more preferable, and 0.6 ≦ X / Y ≦ 9 is satisfied. Is more preferable. By satisfying such a relationship, the viscosity of the insulating liquid can be made more appropriate, and the permeability of the insulating liquid into the recording medium can be made higher. As a result, the fixing strength of the toner particles on the recording medium can be made particularly excellent. Further, the plastic effect can be made more prominent, and the gloss (gloss) of the formed image can be made particularly excellent.
The electrical resistance of the insulating liquid as described above at room temperature (20 ° C.) is preferably 1 × 10 ¹² Ωcm or more, and more preferably 8 × 10 ¹² Ωcm or more.
The dielectric constant of the insulating liquid is preferably 3.5 or less.

<Polyamine fatty acid condensation polymer>
Further, the liquid developer (insulating liquid) of the present invention contains a polyamine fatty acid condensation polymer as a dispersant for improving the dispersibility of the toner particles.
As described above, the present invention is characterized in that the polyamine fatty acid condensation polymer as a dispersant and the insulating liquid as described above are used. Thereby, the dispersibility of the toner particles can be made high, and the charging characteristics of the liquid developer can be made excellent. This can be explained as follows.

  Since the polyamine fatty acid polycondensate has a high affinity with the resin material constituting the toner particles, it adheres to the vicinity of the surface of the toner particles, and can effectively prevent aggregation (blocking) of the toner particles. Furthermore, the polyamine fatty acid polycondensate has high affinity with aliphatic hydrocarbons, silicone oils and fatty acid monoesters. As a result, the dispersibility of the toner particles can be made particularly high. In addition, by using the polyamine fatty acid condensation polymer and the insulating liquid as described above, the liquid developer becomes excellent in dispersibility over a long period of time. The change in color of the obtained image can be made small. That is, the liquid developer of the present invention has excellent color reproducibility.

Further, the polyamine aliphatic polycondensation polymer is a component having a positively chargeable characteristic. By attaching such a component near the surface of the toner particles, the charging characteristics of the toner particles can be made higher.
In addition, the polyamine fatty acid condensation polymer can increase the permeability of the fatty acid monoester to the toner particles, and the plastic effect by the fatty acid monoester can be made more remarkable. As a result, the toner particles can be more firmly fixed on the recording medium, and the gloss of the formed image can be made more excellent.

The content of the polyamine fatty acid condensation polymer in the liquid developer is preferably 0.5 to 7.5 parts by weight and more preferably 1 to 5 parts by weight with respect to 100 parts by weight of the toner particles. . Thereby, the effect by including a polyamine fatty acid condensation polymer can be made more remarkable.
In addition to the above components, the liquid developer (insulating liquid) may contain a charge control agent.

  Examples of the charge control agent include metal oxides such as zinc oxide, aluminum oxide, and magnesium oxide, metal salts of benzoic acid, metal salts of salicylic acid, metal salts of alkyl salicylic acid, metal salts of catechol, metal-containing bisazo dyes, nigrosine Examples thereof include dyes, tetraphenylborate derivatives, quaternary ammonium salts, alkylpyridinium salts, chlorinated polyesters, and nitrofunnic acid.

<Toner particles>
Next, toner particles will be described.
[Component material of toner particles (toner material)]
The toner particles (toner) constituting the liquid developer of the present invention include at least a resin material.

1. Resin Material The toner constituting the liquid developer is composed of a material containing a resin material as a main component.
In the present invention, the resin (binder resin) is not particularly limited, and for example, a known resin can be used. Among these, when a polyester resin is used, the dispersibility of the toner particles in the liquid developer can be made particularly excellent. 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.

  By the way, since the polyester resin itself is usually of a negative chargeability or low chargeability (when the acid value is low), it is sufficiently charged when applied to positively chargeable toner particles (liquid developer). It was difficult to obtain characteristics. On the other hand, by using the polyamine aliphatic polycondensation polymer as described above, the negative chargeability of the polyester resin can be canceled and the toner particles can be positively charged reliably. Therefore, even when a negatively chargeable polyester resin is used, stable charging characteristics can be exhibited.

2. Colorant The toner may contain a colorant. The colorant is not particularly limited, and for example, known pigments and dyes can be used.
3. Other Components The toner may contain components other than those described above. Examples of such components include known waxes and magnetic powders.
In addition to the materials described above, for example, zinc stearate, zinc oxide, cerium oxide, silica, titanium oxide, iron oxide, fatty acid, fatty acid metal salt, and the like are used as toner constituent materials (components). Also good.

[Toner particle shape, etc.]
As the toner particles applied to the liquid developer of the present invention, those having fine irregularities on the surface are preferably used. By having such minute irregularities, the above-mentioned fatty acid monoester can be more effectively unevenly distributed (adsorbed) near the surface of the toner particles.
The average particle size of the toner particles composed of the above materials is preferably 0.1 to 5 μm, more preferably 0.1 to 4 μm, and further preferably 0.5 to 3 μm. preferable. When the average particle diameter of the toner particles is a value within the above range, the resolution of an image formed by the liquid developer (toner) can be made sufficiently high.

  The content ratio of the toner particles in the liquid developer is preferably 10 to 60 wt%, and more preferably 20 to 50 wt%. As a result, during storage, the toner particles can be reliably prevented from coming into contact with each other and liberating the fatty acid monoester and the dispersant, and the fixing characteristics and charging characteristics of the liquid developer are made particularly excellent. Can do. Further, the viscosity of the liquid developer can be made appropriate, and conditions such as heating during fixing can be made particularly gentle.

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 in the image forming apparatus as described later, the liquid developer is more evenly distributed on the application roller. In addition, dripping of the liquid developer from the application roller or the like can be more effectively prevented.
Further, the electrical resistance at room temperature (20 ° C.) of the liquid developer composed of the components as described above is preferably 1 × 10 ¹² Ωcm or more, more preferably 2 × 10 ¹² Ωcm or more. preferable.

<< Method for Producing Liquid Developer >>
Next, a preferred embodiment of the method for producing a liquid developer of the present invention will be described.
<First Embodiment>
First, a first embodiment of a method for producing a liquid developer according to the present invention will be described.
In the method for producing a liquid developer according to the present embodiment, in a fatty acid monoester, a toner material mainly composed of a resin material is pulverized to obtain a pulverized dispersion, a pulverized dispersion, and aliphatic carbonization. Mixing with a liquid containing hydrogen and / or silicone oil.

[Crushing process]
In this step, the constituent material (toner material) of the toner particles as described above is wet pulverized in a fatty acid monoester to obtain a pulverized dispersion.
Since the fatty acid monoester has a relatively low viscosity, the degree of freedom of movement of the toner material in the fatty acid monoester is high, and the resistance of the fatty acid monoester is low, the coarsely pulverized product can be efficiently pulverized. Further, since the fatty acid monoester has a high affinity with the above-described resin material and has a relatively low viscosity, the fatty acid monoester can enter a minute crack or the like of the toner material caused by pulverization or the like. As a result, it can be efficiently pulverized and toner particles having a small particle diameter can be formed efficiently. Further, the pulverization rate can be improved. Further, by grinding in a fatty acid monoester having a relatively low viscosity, the energy added for grinding can be used efficiently for grinding the toner material, thus preventing the temperature of the fatty acid monoester from rising. be able to. As a result, even if the resin material constituting the toner material has a low melting point, it can be efficiently pulverized.

  Further, by pulverizing the toner material in the fatty acid monoester, the fatty acid monoester can be unevenly distributed (adsorbed) in the vicinity of the surface of the toner particles in the finally obtained liquid developer. Thus, by making the fatty acid monoester unevenly distributed in the vicinity of the surface of the toner particles, the plastic effect as described above can be made more remarkable. As a result, the toner particles can easily enter through the gaps between the paper fibers (recording medium), so that the fixing strength of the toner particles can be made particularly excellent, and the oxidative polymerization reaction of the soybean oil on the paper surface proceeds. Since solidification is further promoted, the gloss (gloss) of the formed image can be made particularly excellent.

  Further, as the toner material used in this step, it is preferable to use a kneaded product obtained by kneading the toner material such as the resin material and the colorant as described above. By using the kneaded material, even if the material constituting the toner particles contains components that are difficult to disperse or compatible with each other, the components obtained in the kneaded material obtained by kneading are sufficient. It can be in a state of being compatible and finely dispersed. As a result, the variation in characteristics among the toner particles can be made sufficiently small.

Further, as the toner material used in this step, it is preferable to use a coarsely pulverized product obtained by roughly pulverizing the kneaded product as described above. Thus, by using the coarsely pulverized product obtained by roughly pulverizing the kneaded product, the particle size of the toner particles can be reduced more effectively in this step.
The method of wet pulverization is not particularly limited, and can be performed using various pulverizers and crushers such as a ball mill, a vibration mill, a jet mill, and a pin mill.
The wet pulverization step may be performed in multiple steps.

Before mixing the fatty acid monoester and the toner material, it is preferable to add a polyamine fatty acid condensation polymer to the fatty acid monoester. As a result, the polyamine fatty acid polycondensate acts as a pulverization aid, whereby the toner material can be pulverized more efficiently and the dispersibility of the resulting toner particles can be made higher. Further, the polyamine aliphatic polycondensation polymer can be adhered to the surface of the toner particles, and as a result, the charging property of the liquid developer can be further improved. Further, the polyamine aliphatic polycondensate adheres to the surface of the toner particles, so that the fatty acid monoester can be reliably distributed near the surface of the toner particles.
[Mixing process]
Next, the obtained pulverized material dispersion is mixed with aliphatic hydrocarbon and / or silicone oil (mixing step).
As described above, the liquid developer of the present invention is obtained.

Second Embodiment
Next, a second embodiment of the 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 embodiment includes a process for forming an associated particle by associating resin fine particles mainly composed of a resin material to obtain an associated particle, pulverizing the associated particle in a fatty acid monoester, And a dispersion step of dispersing the obtained toner particles in a liquid containing aliphatic hydrocarbon and / or silicone oil.

[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 contains the components constituting the toner particles as described above.
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.

In addition, the composition of the solvent can be appropriately selected according to, for example, the known resin and colorant composition as described above, the composition of the aqueous dispersion medium, and the like.
Such a solvent is not particularly limited, and known organic solvents such as ketone solvents such as MEK and aromatic hydrocarbon solvents such as toluene can be used.
Further, the aqueous emulsified liquid may contain an emulsifying dispersant.

  When an emulsifying dispersant is used, the dispersibility of the dispersoid is improved, and the dispersion of the dispersoid in the aqueous emulsion is relatively easily reduced in size and size. Can be substantially spherical. 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 known emulsifiers and dispersants.

The content of the emulsifier and 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%.
Further, the aqueous emulsion may contain a dispersion aid.
Examples of the dispersion aid include anions, cations, and nonionic surfactants.

The dispersing aid is preferably used in combination with a 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.
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 embodiment 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 10 days, the particle size distribution of the associated particles obtained can be made particularly narrow.
Then, after associating, the associated particles are obtained by filtration, washing, drying and the like.
The average particle size of the obtained associated particles is preferably 0.1 to 7 μm, and more preferably 0.5 to 3 μm. Thereby, the particle diameter of the toner particles finally obtained can be made moderate.

[Crushing process]
Next, the associated particles obtained as described above are crushed in a fatty acid monoester (pulverization step). Thereby, a toner particle dispersion liquid in which toner particles are dispersed in a fatty acid monoester is obtained.
Further, by crushing the associated particles in the fatty acid monoester in this manner, the fatty acid monoester can be unevenly distributed (adsorbed) in the vicinity of the surface of the toner particles in the finally obtained liquid developer. Thus, by making the fatty acid monoester unevenly distributed in the vicinity of the surface of the toner particles, the plastic effect as described above can be made more remarkable. As a result, the toner particles can easily enter through the gaps between the paper fibers (recording medium), so that the fixing strength of the toner particles can be made particularly excellent, and the gloss (gloss) of the formed image is particularly excellent. Can be.

In addition, since it is pulverized in a liquid called fatty acid monoester, it is possible to prevent generation of toner particles coarsened due to aggregation or the like.
Further, the obtained toner particles have irregularities derived from the fine particles (dispersoid) on the surface thereof, so that the fatty acid monoester can be reliably retained on the irregularities.
Further, in the present embodiment, toner particles are obtained by crushing the associated particles, so that fine particles (particles extremely smaller than particles of a target size) are obtained as compared with conventional pulverization methods and wet pulverization methods. Generation | occurrence | production can be prevented effectively. As a result, it is possible to effectively prevent a decrease in charging characteristics of the liquid developer due to fine powder.

In addition, since the fatty acid monoester has a relatively low viscosity, it easily enters between the fine particles (dispersoids) constituting the associated particles, and the associated particles can be suitably crushed.
In addition, before mixing the fatty acid monoester and the associated particles, it is preferable to add a polyamine fatty acid condensation polymer to the fatty acid monoester. As a result, the polyamine fatty acid polycondensate acts as a pulverization aid, and the associated particles can be crushed more efficiently and the dispersibility of the resulting toner particles can be made higher. Further, the polyamine aliphatic polycondensation polymer can be adhered to the surface of the toner particles, and as a result, the charging property of the liquid developer can be further improved. Further, the polyamine aliphatic polycondensate adheres to the surface of the toner particles, so that the fatty acid monoester can be reliably distributed near the surface of the toner particles.

[Dispersing process]
Next, the toner particle dispersion obtained as described above and a liquid containing aliphatic hydrocarbon and / or silicone oil are mixed to disperse the toner particles in the insulating liquid (dispersing step).
As described above, the liquid developer of the present invention in which the polyamine aliphatic polycondensate and the toner particles are dispersed in the insulating liquid containing the fatty acid monoester and the aliphatic hydrocarbon and / or silicone oil is obtained. It is done.

≪Image forming device≫
Next, a preferred embodiment of the image forming apparatus of the present invention will be described.
The image forming apparatus of the present invention forms a color image on a recording medium using the liquid developer of the present invention as described above.
FIG. 1 is a schematic view showing an example of an image forming apparatus to which the liquid developer of the present invention is applied, FIG. 2 is an enlarged view of a part of the image forming apparatus shown in FIG. 1, and FIG. FIG. 4 is an enlarged schematic view of the application roller shown in FIG. 3, and FIG. 5 shows the state of toner particles in the liquid developer layer on the development roller. FIG. 6 is a cross-sectional view showing an example of a fixing device applied to the image forming apparatus shown in FIG.

As shown in FIG. 1, the image forming apparatus 1000 includes four developing units 30Y, 30M, 30C, and 30K, a transfer unit 40, and a fixing unit (fixing device) F40.
The developing units 30Y, 30M, and 30C develop a latent image with a yellow liquid developer (Y), a magenta liquid developer (M), and a cyan liquid developer (C), respectively, and correspond to each color. It has a function of forming a single color image. The developing unit 30K has a function of developing a latent image with a black liquid developer (K) to form a black monochrome image.

Since the developing units 30Y, 30M, 30C, and 30K have the same configuration, the developing unit 30Y will be described below.
As shown in FIG. 2, the developing unit 30Y includes a photoconductor 10Y as an example of an image carrier, a charging roller 11Y, an exposure unit 12Y, a development unit 100Y, and a photoconductor along the rotation direction of the photoconductor 10Y. A body squeeze device 101Y, a transfer backup roller 44Y, a charge removal unit 16Y, a photoreceptor cleaning blade 17Y, and a developer recovery unit 18Y.

The photoreceptor 10Y has a cylindrical base material and a photosensitive layer formed on the outer peripheral surface thereof, and can rotate around a central axis. In this embodiment, as shown by an arrow in FIG. Rotate clockwise.
The photoreceptor 10Y is supplied with a liquid developer by a developing unit 100Y described later, and a layer of the liquid developer is formed on the surface.

The charging roller 11Y is a device for charging the photoconductor 10Y, and the exposure unit 12Y is a device for forming a latent image on the photoconductor 10Y charged by irradiating a laser. The exposure unit 12Y includes a semiconductor laser, a polygon mirror, an F-θ lens, and the like, and charges a modulated laser based on an image signal input from a host computer (not shown) such as a personal computer or a word processor. Irradiate onto the photoconductor 10Y.
The developing unit 100Y is a device for developing the latent image formed on the photoreceptor 10Y using the liquid developer of the present invention. Details of the developing unit 100Y will be described later.

  The photoconductor squeeze device 101Y is disposed on the downstream side of the developing unit 100Y in the rotation direction so as to face the photoconductor 10Y. The photoconductor squeeze roller 13Y and the photoconductor squeeze roller 13Y are pressed and slidably attached to the surface. The cleaning blade 14Y removes the liquid developer and the developer collection unit 15Y that collects the removed liquid developer. The photoreceptor squeeze device 101Y has a function of collecting excess carrier and originally unwanted fog toner from the developer developed on the photoreceptor 10Y, and increasing the toner particle ratio in the visible image.

The neutralization unit 16Y is a device that removes residual charges on the photoreceptor 10Y after the transfer image is transferred onto the recording medium F5 in the transfer unit 40 described later.
The photoconductor cleaning blade 17Y is a rubber member that is in contact with the surface of the photoconductor 10Y, and the liquid development remaining on the photoconductor 10Y after the image is transferred onto the recording medium F5 in the transfer unit 40 described later. It has a function of scraping off and removing the agent.
The developer recovery unit 18Y has a function of recovering the liquid developer removed by the photoconductor cleaning blade 17Y.

Next, the transfer unit 40 will be described.
The transfer unit 40 includes a conveyance belt 41, a belt driving roller 42, a tension roller 43, and transfer backup rollers 44Y, 44M, 44C, and 44K.
The transport belt 41 is an endless elastic belt member and has a function of transporting the recording medium F5.
Further, the conveyor belt 41 is wound around and stretched between a belt driving roller 42 and a tension roller 43, and is rotationally driven by the belt driving roller 42 while being in contact with the photoreceptors 10Y, 10M, 10C, and 10K.

  The transfer backup roller 44Y is provided so that the transfer backup roller 44Y and the transport belt 41 are in contact with each other at a position where the photoconductor 10Y and the transport belt 41 are in contact with each other. Similarly, the transfer backup roller 44M, the transfer backup roller 44C, and the transfer backup roller 44K are in contact with the conveyor belt 41 at positions where the corresponding photoreceptors 10M, 10C, and 10K contact the conveyor belt 41, respectively. It is provided to touch.

In such a configuration, when the recording medium F5 transported by the transport belt 41 passes between each photoconductor and each transfer backup roller by the transport belt 41, a monochrome image formed by each developing unit is formed. And sequentially transferred to the recording medium F5.
As described above, in the image forming apparatus 1000 according to the present embodiment, in the transfer unit 40, the single color images formed by the respective development units are sequentially transferred to the recording medium F5, and the unfixed image formed by superimposing the plurality of single color images. A color image is formed on the recording medium F5.

The transfer unit 40 sequentially transfers the monochrome images formed on the plurality of photoconductors 10Y, 10M, 10C, and 10K to the recording medium F5 such as paper, film, and cloth. Therefore, even if the surface of the recording medium F5 is a sheet material that is not smooth due to fibers or the like, an elastic belt member is employed as a means for improving transfer characteristics following the non-smooth sheet material surface.
The toner image (transfer image) F5a transferred onto the recording medium F5 by the transfer unit 40 is sent to a fixing unit F40, which will be described later, and fixed.

Next, the developing units 100Y, 100M, 100C, and 100K will be described in detail. In the following description, the developing unit 100Y will be typically described.
As shown in FIG. 2, the developing unit 100Y includes a liquid developer storage unit 31Y, a coating roller 32Y, a regulating blade 33Y, a developer stirring roller 34Y, a developing roller 20Y, a developing roller cleaning blade 21Y, and a developing unit. And an agent compression roller (compression means) 22Y.

The liquid developer storage unit 31Y has a function of storing a liquid developer for developing the latent image formed on the photoreceptor 10Y.
The coating roller 32Y has a function of supplying a liquid developer to the developing roller 20Y.
As shown in FIG. 3, the application roller 32Y is a so-called anilox roller in which a groove 32Ya is formed in a uniform and spiral shape on the surface of a metallic roller such as iron and nickel plating is applied. The diameter is about 25 mm. In the present embodiment, as shown in FIG. 3, a plurality of grooves 32Ya are formed obliquely with respect to the rotation direction D2 of the application roller 32Y by so-called cutting or rolling.
The application roller 32Y contacts the liquid developer while rotating clockwise, thereby supporting the liquid developer in the liquid developer storage unit 31Y in the groove 32Ya and supplying the supported liquid developer to the developing roller. Transport to 20Y. Accordingly, the application roller 32Y can apply the liquid developer to the developing roller 20Y with a width in the X direction in which the groove 32Ya is formed.

  Note that the groove pitch (in the X direction in FIG. 4, the period between the crests forming the groove 32 </ b> Ya) is preferably about 55 to 250 μm depending on the required film thickness of the liquid developer. In the present embodiment, the groove pitch P is about 80 μm, the crest width is about 40 μm, the top width PI1 of the groove 32Ya is about 50 μm, the bottom surface width PI2 is about 30 μm, the depth He of the groove 32Ya is about 20 μm, and the crest. The height Hc of 32Yb is configured to be about 30 μm, and an inclined portion SL that is monotonously formed from the center of the peak 32Yb to the bottom of the groove 32Ya is formed. In the present embodiment, the surface roughness Rz of the peak 32Yb is R1a≈1.0 μm, and the surface roughness Rz of the groove 32Ya is R2a≈1.0 μm.

  Since the application roller 32Y has the groove as described above, the liquid developer in the liquid developer reservoir 31Y can be stably supplied to the developing roller 20Y regardless of the viscosity of the liquid developer. For example, even when the image forming apparatus is started for a long period of time and the temperature inside the apparatus increases and the viscosity of the liquid developer decreases, a sufficient amount of liquid developer necessary for development is applied to the developing roller. Stable supply is possible. Therefore, it is possible to reliably prevent or suppress the occurrence of image unevenness in the formed image regardless of the use conditions of the image forming apparatus. By applying the liquid developer of the present invention to the image forming apparatus 1000 having such a coating roller 32Y, the formed toner image is excellent in fixability and clear without image unevenness. Can do.

  The regulating blade 33Y is in contact with the surface of the coating roller 32Y and regulates the amount of the liquid developer D on the coating roller 32Y. That is, the regulation blade 33Y plays a role of scraping off excess liquid developer on the application roller 32Y and measuring the liquid developer D on the application roller 32Y supplied to the development roller 20Y. The restriction blade 33Y is made of urethane rubber as an elastic body, and is supported by a restriction blade support member made of metal such as iron. Further, the regulating blade 33Y is provided on the side where the application roller 32Y rotates and advances from the liquid developer D as viewed from the vertical plane A (that is, the left side in FIG. 2 as viewed from the vertical plane A). . The rubber hardness of the regulation blade 33Y is about 77 degrees according to JIS-A, and the hardness (about 77 degrees) of the contact portion of the regulation blade 33Y with the surface of the coating roller 32Y is about the elasticity of the developing roller 20Y described later. It is lower than the hardness (about 85 degrees) of the pressure contact portion of the body layer to the surface of the application roller 32Y.

The developer stirring roller 34Y has a function of stirring the liquid developer in a uniformly dispersed state.
In the liquid developer storage unit 31Y, the toner particles in the liquid developer have a positive charge, and the liquid developer is agitated by the developer agitation roller 34Y to be in a uniformly dispersed state. By rotating, it is pumped up from the liquid developer reservoir 31Y, the amount of liquid developer is regulated by the regulating blade 33Y, and supplied to the developing roller 20Y.

The developing roller 20Y carries the liquid developer and conveys it to the developing position facing the photoconductor 10Y in order to develop the latent image carried on the photoconductor 10Y with the liquid developer.
The developing roller 20Y forms a liquid developer layer 201Y on the surface thereof by supplying the liquid developer from the coating roller 32Y described above.
The developing roller 20Y includes a conductive elastic layer on the outer peripheral portion of an inner core made of metal such as iron, and has a diameter of about 20 mm. The elastic layer has a two-layer structure. As an inner layer, urethane rubber having a rubber hardness of about 30 degrees and a thickness of about 5 mm is used. As a surface layer (outer layer), the rubber hardness is JIS. -A urethane rubber having a thickness of about 30 μm at about 85 degrees A is provided. The developing roller 20Y is in pressure contact with the application roller 32Y and the photoreceptor 10Y in a state of elastic deformation with the surface layer serving as a pressure contact portion.

  Further, the developing roller 20Y can rotate around its central axis, and the central axis is below the rotational central axis of the photoconductor 10Y. Further, the developing roller 20Y rotates in a direction (counterclockwise in FIG. 2) opposite to the rotation direction of the photoreceptor 10Y (clockwise in FIG. 2). When developing the latent image formed on the photoconductor 10Y, an electric field is formed between the developing roller 20Y and the photoconductor 10Y.

The developer compression roller 22Y is a device having a function of compressing the liquid developer toner carried on the development roller 20Y. In other words, the developer compression roller 22Y applies an electric field having the same polarity as the toner particles 1 to the liquid developer layer 201Y described above, thereby developing the liquid developer layer 201Y in the liquid developer layer 201Y as shown in FIG. This is a device having a function of unevenly distributing the toner particles 1 near the surface of the roller 20Y. By unevenly distributing the toner particles in this way, the development density (development efficiency) can be improved, and as a result, a clear image with high quality can be obtained.
The developer compression roller 22Y is provided with a cleaning blade 23Y.
The cleaning blade 23Y has a function of removing the liquid developer adhering to the developer compression roller 22Y.

  The developing unit 100Y includes a rubber developing roller cleaning blade 21Y that is in contact with the surface of the developing roller 20Y. The developing roller cleaning blade 21Y is a device for scraping off and removing the liquid developer remaining on the developing roller 20Y after development is performed at the developing position. The liquid developer removed by the developing roller cleaning blade 21Y is collected in the liquid developer reservoir 31Y and reused.

In addition, the image forming apparatus 1000 includes a reuse device that reuses the insulating liquid in the liquid developer collected in each developer collection unit (15Y, 18Y).
The recycling apparatus includes a transport path 70 that transports the recovered liquid developer from each developer recovery unit, a filter unit 77 that removes the solid content (toner particles and the like) of the transported liquid developer, And an insulating liquid storage part 74 for storing the insulating liquid from which the solid content has been removed by the filter means 77.

A pump 76 is provided in the conveyance path 70, and the liquid developer collected in each developer collection unit is conveyed to the insulating liquid storage unit 74 by the pump 76.
The insulating liquid stored in the insulating liquid storage unit 74 is appropriately transported to each developing unit and reused by a transport unit (not shown).
The solid content removed by the filter unit 77 is detected by a filter state detection unit (not shown). Then, the filter means 77 is replaced based on the detection result. Thereby, the filtering function of the filter means 77 can be maintained stably.

Next, the fixing unit will be described.
The fixing unit F40 fixes the unfixed toner image F5a formed in the above-described developing unit, transfer unit, and the like on the recording medium F5.
As shown in FIG. 6, the 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. is doing.

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.
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.

  Inside the heat fixing roller F1, two columnar halogen lamps F1a and F1a constituting a heating source are incorporated, 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 arranged to face the heat fixing roller F1, and is configured to apply pressure to the recording medium F5 on which the unfixed toner image F5a is formed via a heat-resistant belt F3 described later. Has been.
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.

  In the fixing portion F40, the recording medium F5 on which the unfixed toner image F5a is formed enters the fixing nip portion from the nip initial position and passes between the heat-resistant belt F3 and the heat fixing roller F1, and the nip end position. As a result, the unfixed toner image F5a formed on the recording medium F5 is fixed, and then discharged in the tangential direction L of the pressing portion of the pressure roller F2 to the heat fixing roller F1.

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.

  The fixing unit F40 has a removing blade (removing means) F12 that removes the insulating liquid adhering (remaining) on the surface of the heat fixing roller F1 after fixing the toner image F5a on the recording medium F5. . The oxidative polymerization accelerator removing blade F12 can remove the insulating liquid and simultaneously remove the toner transferred onto the heat fixing roller F1 at the time of fixing.

  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.
Specifically, the heat (fixing temperature) applied by the heat fixing roller F1 is preferably 80 to 200 ° C, and more preferably 100 to 180 ° C.

As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to these.
For example, the liquid developer of the present invention is not limited to that applied to the image forming apparatus as described above.
Further, the liquid developer of the present invention is not limited to those produced by the production method 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)
First, 80 parts by weight of a polyester resin (softening temperature: 99 ° C.) and 20 parts by weight of a cyan pigment as a coloring agent (Pigment Blue 15: 3, manufactured by Dainichi Seika Co., Ltd.) were 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 (coarse pulverized product) having an average particle size of 1.0 mm or less. A hammer mill was used for coarse pulverization of the kneaded product.
Next, the coarsely pulverized product obtained as described above: 100 parts by weight, soybean oil fatty acid methyl produced by a transesterification reaction between soybean oil and methanol (manufactured by Nisshin Oilio Co., Ltd.): 150 parts by weight, A polyamine fatty acid condensation polymer (manufactured by Nippon Lubrizol Co., Ltd., trade name “Solsperse 13900”): 2.5 parts by weight was prepared as a dispersant. In addition, content of the fatty acid monoester contained in soybean oil fatty acid methyl was 99.9 wt%. Moreover, the fatty acid monoester contained in the soybean oil fatty acid methyl contained linoleic acid, oleic acid, linolenic acid, palmitic acid and the like as the fatty acid component. Moreover, the viscosity of the soybean oil fatty acid methyl measured by using a vibration viscometer at 25 ° C. according to JIS Z8809 was 3.0 mPa · s.
The above components were put into a ball mill and wet pulverized for 200 hours to obtain a pulverized dispersion.
Thereafter, 252.5 parts by weight of the obtained pulverized dispersion liquid and 225 parts by weight of liquid paraffin A (trade name “Cosmo White P-60” manufactured by Cosmo Oil Co., Ltd.) are mixed to obtain a liquid developer. It was.

The average particle size of the toner particles in the obtained liquid developer was 1.5 μm, and the standard deviation of the particle size between the toner particles was 0.85 μm. Moreover, the viscosity of the liquid developer measured in accordance with JIS Z8809 using a vibration viscometer at 25 ° C. was 220 mPa · s.
The same as above except that magenta pigment: pigment red 122, yellow pigment: pigment yellow 180, black pigment: carbon black (Printex L, manufactured by Degussa) was used instead of cyan pigment. Thus, a magenta liquid developer, a yellow liquid developer, and a black liquid developer were produced.

(Examples 2 to 6)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that the liquid used for pulverization, the liquid added after pulverization, and the addition amount of the polyamine aliphatic polycondensation polymer were as shown in Table 1. did.
(Examples 7 to 12)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that the resin material, the liquid used for pulverization, and the liquid added after pulverization were those shown in Table 1. In the table, liquid paraffin B indicates a trade name “Diana Fresia W-8” manufactured by Idemitsu Oil Co., Ltd., and silicone oil indicates a trade name “KF96” manufactured by Shin-Etsu Chemical Co., Ltd. The content of fatty acid monoester contained in the liquid produced by the transesterification reaction between rapeseed oil and methanol was 99.9 wt%. The fatty acid monoester contained in the liquid produced by the transesterification reaction between rapeseed oil and methanol contained linoleic acid, oleic acid, stearic acid, palmitic acid and the like as the fatty acid component.

(Example 13)
First, 80 parts by weight of a polyester resin (softening temperature: 99 ° C.) and 20 parts by weight of a cyan pigment as a coloring agent (Pigment Blue 15: 3, manufactured by Dainichi Seika Co., Ltd.) were 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 (coarse pulverized product) having an average particle size of 1.0 mm or less. A hammer mill was used for coarse pulverization of the kneaded product.

Next, 100 parts by weight of the coarsely pulverized product of the kneaded product was added to 250 parts by weight of toluene, and the polyester resin of the kneaded product was dissolved by treating with an ultrasonic homogenizer (output: 400 μA) for 1 hour. A solution (toner material solution) was obtained. In this solution, the pigment was uniformly finely dispersed.
On the other hand, an aqueous liquid in which sodium dodecylbenzenesulfonate as a dispersant: 1 part by weight and ion-exchanged water: 700 parts by weight were uniformly mixed was prepared.
The aqueous liquid was stirred with a homomixer (made by Tokushu Kika Kogyo Co., Ltd.) while adjusting the stirring rotation speed.
The toner material solution was dropped into the agitated aqueous liquid. As a result, an aqueous emulsion in which the dispersoid having an average particle size of 0.5 μm was uniformly dispersed was obtained.

  Thereafter, the toluene in the aqueous emulsion is removed under the conditions of temperature: 100 ° C. and atmospheric pressure: 80 kPa, and after cooling to room temperature, the concentration of the solid fine particles is adjusted by adding a predetermined amount of water. A dispersed aqueous dispersion was obtained. In the resulting aqueous dispersion, substantially no toluene remained. The obtained aqueous dispersion had a solid content (dispersoid) concentration of 20 wt%. The average particle size of the dispersoid (solid fine particles) dispersed in the suspension was 0.5 μm. The average particle size of the dispersoid was measured using a laser diffraction / scattering particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.).

Next, 0.35 part by weight of a nonionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd., trade name “Epan 450”) is added to 100 parts by weight of the obtained aqueous dispersion while stirring. did.
Next, while adjusting the stirring speed and setting the temperature to 30 ° C., 35 parts by weight of 3% aqueous ammonium sulfate solution was added dropwise to 100 parts by weight of the aqueous dispersion. As a result, an associated particle dispersion in which associated particles are dispersed was obtained.
From the obtained associated particle dispersion, the associated particles were separated by a centrifugal separator, washed, and then dried by a vacuum dryer to obtain associated particles. The average particle diameter of the obtained associated particles was 5.2 μm.

  Next, 4 mm carbon chromium beads are put into a 500 mL container, and then soybean oil fatty acid methyl produced by a transesterification reaction between soybean oil and methanol (Nisshin Oilio Co., Ltd.): 150 parts by weight, a dispersant As a polyamine fatty acid condensation polymer (trade name “Solsperse 13900”, manufactured by Nippon Lubrizol Co., Ltd.): 2.5 parts by weight. In addition, content of the fatty acid monoester contained in soybean oil fatty acid methyl was 99.9 wt%. Moreover, the fatty acid monoester contained in the soybean oil fatty acid methyl contained linoleic acid, oleic acid, linolenic acid, palmitic acid and the like as the fatty acid component. Moreover, the viscosity of the soybean oil fatty acid methyl measured by using a vibration viscometer at 25 ° C. according to JIS Z8809 was 3.0 mPa · s.

Next, 100 parts by weight of the obtained associated particles were added, mixed for 10 minutes with a ball mill, and then crushed with a ball mill for 200 hours to obtain a toner dispersion.
After the pulverization, 225 parts by weight of liquid paraffin A (manufactured by Cosmo Oil, trade name “Cosmo White P-60”) was added to disperse the toner particles. Dispersion was carried out for 24 hours by adding 1 mm beads using a ball mill. 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 0.50 μm. Moreover, the viscosity of the liquid developer measured according to JIS Z8809 using a vibration viscometer at 25 ° C. was 223 mPa · s.
The same as above except that magenta pigment: pigment red 122, yellow pigment: pigment yellow 180, black pigment: carbon black (Printex L, manufactured by Degussa) was used instead of cyan pigment. Thus, a magenta liquid developer, a yellow liquid developer, and a black liquid developer were produced.

(Examples 14 to 18)
Liquid developer corresponding to each color in the same manner as in Example 13 except that the liquid used for crushing, the liquid added after crushing, and the addition amount of the polyamine aliphatic polycondensation polymer are as shown in Table 1. Manufactured.
(Examples 19 to 24)
A liquid developer corresponding to each color was produced in the same manner as in Example 13 except that the resin material, the liquid used for pulverization, and the liquid added after pulverization were those shown in Table 1. In the table, liquid paraffin B indicates a trade name “Diana Fresia W-8” manufactured by Idemitsu Oil Co., Ltd., and silicone oil indicates a trade name “KF96” manufactured by Shin-Etsu Chemical Co., Ltd. The content of fatty acid monoester contained in the liquid produced by the transesterification reaction between rapeseed oil and methanol was 99.9 wt%. The fatty acid monoester contained in the liquid produced by the transesterification reaction between rapeseed oil and methanol contained linoleic acid, oleic acid, stearic acid, palmitic acid and the like as the fatty acid component.

(Comparative Example 1)
A coarsely pulverized product was obtained in the same manner as in Example 1.
Next, the obtained coarsely pulverized product: 100 parts by weight and liquid paraffin A: 150 parts by weight were prepared.
These components were put into a ball mill and wet pulverized for 400 hours to obtain a pulverized dispersion.

Thereafter, 100 parts by weight of the obtained pulverized dispersion liquid and 225 parts by weight of liquid paraffin A were mixed to obtain a liquid developer.
The average particle diameter of the toner particles in the obtained liquid developer was 4.8 μm, and the standard deviation of the particle diameter between the toner particles was 2.86 μm. Moreover, the viscosity of the liquid developer measured according to JIS Z8809 using a vibration viscometer at 25 ° C. was 580 mPa · s.
The same as above except that magenta pigment: pigment red 122, yellow pigment: pigment yellow 180, black pigment: carbon black (Printex L, manufactured by Degussa) was used instead of cyan pigment. Thus, a magenta liquid developer, a yellow liquid developer, and a black liquid developer were produced.

(Comparative Example 2)
A liquid developer corresponding to each color was produced in the same manner as in Comparative Example 1 except that methyl soybean oil was used instead of liquid paraffin A.
(Comparative Example 3)
Associated particles were obtained in the same manner as in Example 12.

Next, 4 mm carbon chrome beads are put into a 500 mL container, and then liquid paraffin A: 150 parts by weight and a polyamine fatty acid polycondensation polymer as a dispersant (trade name “Solsperse 13940” manufactured by Nippon Lubrizol Co., Ltd.) : 2.5 parts by weight were charged.
Next, 100 parts by weight of the obtained associated particles were added, mixed for 10 minutes with a ball mill, and then crushed with a ball mill for 200 hours to obtain a toner dispersion.

After pulverization, 225 parts by weight of liquid paraffin A was added to disperse the toner particles. Dispersion was carried out for 24 hours by adding 1 mm beads using a ball mill. As a result, a liquid developer was obtained.
The average particle size of the toner particles in the obtained liquid developer was 5.3 μm, and the standard deviation of the particle size between the toner particles was 2.41 μm. Moreover, the viscosity of the liquid developer measured according to JIS Z8809 using a vibration viscometer at 25 ° C. was 560 mPa · s.
The same as above except that magenta pigment: pigment red 122, yellow pigment: pigment yellow 180, black pigment: carbon black (Printex L, manufactured by Degussa) was used instead of cyan pigment. Thus, a magenta liquid developer, a yellow liquid developer, and a black liquid developer were produced.

(Comparative Example 4)
Liquid developers corresponding to the respective colors were produced in the same manner as in Comparative Example 3 except that methyl soybean oil was used instead of liquid paraffin A.
(Comparative Example 5)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that the polyamine fatty acid condensation polymer was not added.
For each of the above Examples and Comparative Examples, the type and softening temperature of the resin used, the type and content of the liquid used for pulverization (pulverization) and the liquid added after pulverization (pulverization), and the viscosity of the liquid developer Etc. are shown in Table 1. In Table 1, the polyester resin is shown as PEs, and the epoxy resin is shown as EP.

[2] Evaluation Each liquid developer obtained as described above was evaluated as follows.
[2.1] Fixing Strength Using an image forming apparatus as shown in FIG. 1, an image of a predetermined pattern with a liquid developer obtained in each of the examples and the comparative examples was recorded on a recording paper (manufactured by Seiko Epson Corporation, High quality paper LPCPPA4). Thereafter, heat fixing was performed using a fixing device as shown in FIG. 6 at a set temperature of the heat fixing roller of 100 ° C.
Then, after confirming the non-offset area, the fixed image on the recording paper is erased twice (rubber eraser “LION 261-11” manufactured by Lion Business Machine Co., Ltd.) twice with a pressing load of 1.2 kgf, and the remaining ratio of image density Was measured by “X-Rite model 404” manufactured by X-Rite Inc, and evaluated according to the following five-step criteria.

A: Image density residual ratio is 95% or more (very good).
B: Image density remaining rate is 90% or more and less than 95% (good).
C: Image density remaining rate is 80% or more and less than 90% (normal).
D: Image density residual ratio is 70% or more and less than 80% (slightly bad).
E: Image density residual ratio is less than 70% (very bad).

[2.2] Charging characteristics For the liquid developers obtained in each Example and each Comparative Example, the potential difference was measured using a “microscopic laser zeta electrometer” ZC-2000 manufactured by Microtic Nithion Co., Ltd. Evaluation was made according to the five-stage criteria.
Measurement is performed by diluting the liquid developer with a diluting solvent, placing it in a 10 mm transparent cell, applying a voltage of 300 V at 9 mm between the electrodes, and simultaneously observing the moving speed of the particles in the cell with a microscope. Was obtained by calculating the zeta potential from the calculated value.

A: The potential difference is +100 mV or more (very good).
B: Potential difference is +85 mV or more and less than +100 mV (good).
C: The potential difference is +70 mV or more and less than +85 mV (normal).
D: The potential difference is +50 mV or more and less than +70 mV (somewhat bad).
E: Potential difference is less than +50 mV (very bad).

[2.3] Evaluation of Gloss (Gross) of Formed Toner Image Using an image forming apparatus as shown in FIG. 1, a predetermined pattern of the liquid developer obtained in each of the examples and the comparative examples is used. Images were formed on recording paper (quality paper LPCPPA4, manufactured by Seiko Epson Corporation). Thereafter, heat fixing was performed using a fixing device as shown in FIG. 6 at a set temperature of the heat fixing roller of 100 ° C.

The image on the recording paper thus obtained was measured for gloss (gloss) using a gloss meter (GM-26D manufactured by Murakami Color Research Laboratory), and evaluated according to the following four criteria.
A: Glossiness is 7 or more (very good).
B: Glossiness is 6 or more and less than 7 (good).
C: Glossiness is 5 or more and less than 6 (slightly bad).
D: Glossiness is less than 5 (very bad).

[2.4] Color Reproducibility Using an image forming apparatus as shown in FIG. 1, a toner image of a predetermined pattern by the liquid developer obtained in each of the above examples and each of the comparative examples was recorded on a recording paper (Seiko Epson Corporation). Made on high-quality paper (LPCPPA4), and heat fixing was performed using a fixing device as shown in FIG.

First, a sample of a good dispersion state was prepared, and ΔE was measured with a color difference meter manufactured by X-Rite on the basis of the hue, and evaluated according to the following four-stage criteria.
A: ΔE is less than 4 (very good).
B: ΔE is 4 or more and less than 7 (good).
C: ΔE is 7 or more and less than 10 (somewhat bad).
D: ΔE is 10 or more (very bad).

[2.5] 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 1000 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).
B: Absorbance is 1.00 or more and less than 1.50 (almost no sedimentation is observed).
C: Absorbance is 0.50 or more and less than 1.00 (precipitation is confirmed).
D: Absorbance is less than 0.50 (sedimentation is remarkable and sedimentation starts even when left standing naturally).

[2.6] Peel Strength Using an image forming apparatus as shown in FIG. 1, images of a predetermined pattern with the liquid developer obtained in each of the examples and the comparative examples were recorded on a recording paper (manufactured by Seiko Epson Corporation, It was formed on fine paper LPCPPA4). Thereafter, thermal fixing was performed by using a fixing device as shown in FIG.

After confirming the non-offset area, a Scotch mending tape 10 mm width 810-1-18 was applied to the fixed image on the recording paper, and the tape was peeled off at a speed of 5 cm / s in a direction of 170 ° with respect to the recording paper surface. The residual ratio of image density was measured by “X-Rite model 528” manufactured by X-Rite Inc, and evaluated according to the following five-step criteria.
A: Image density residual ratio is 95% or more (very good).
B: Image density remaining rate is 90% or more and less than 95% (good).
C: Image density remaining rate is 80% or more and less than 90% (normal).
D: Image density residual ratio is 70% or more and less than 80% (slightly bad).
E: Image density residual ratio is less than 70% (very bad).
These results are shown in Table 2.

  As is apparent from Table 2, the liquid developer of the present invention was excellent in fixing strength, charging characteristics, glossiness of formed image, and color reproducibility. Further, the liquid developer of the present invention was excellent in dispersion stability and peel strength. On the other hand, satisfactory results were not obtained with the liquid developers of the comparative examples.

1 is a schematic diagram illustrating an example of an image forming apparatus to which a liquid developer of the present invention is applied. FIG. 2 is an enlarged view of a part of the image forming apparatus shown in FIG. 1. FIG. 2 is a perspective conceptual diagram illustrating a coating roller included in the image forming apparatus illustrated in FIG. 1. It is an expansion schematic diagram of the application | coating roller shown in FIG. FIG. 6 is a schematic diagram illustrating a state of toner particles in a liquid developer layer on a developing roller. FIG. 2 is a cross-sectional view illustrating an example of a fixing device applied to the image forming apparatus illustrated in FIG. 1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Toner particle 1000 ... Image forming apparatus 10Y, 10M, 10C, 10K ... Photoconductor 11Y ... Charging roller 12Y ... Exposure unit 13Y, 13M ... Photoconductor squeeze roller 14Y, 14M ... Cleaning blade 15Y, 15M ... Developer collection part 16Y Destaticizing unit 17Y ... Photoconductor cleaning blade 18Y ... Developer recovery unit 20Y, 20M, 20C, 20K ... Developing roller 201Y ... Liquid developer layer 21Y ... Developing roller cleaning blade 22Y ... Developer compressing roller 23Y ... Developer compressing roller cleaning Blade 30Y, 30M, 30C, 30K ... developing part 31Y ... liquid developer storage part 32Y ... coating roller 32Ya ... groove 32Yb ... mount 33Y ... regulating blade 34Y ... developer stirring roller 40 ... transfer part 41 ... conveying belt DESCRIPTION OF SYMBOLS 42 ... Belt drive roller 43 ... Tension roller 44Y, 44M, 44C, 44K ... Transfer backup roller 70 ... Conveyance path 74 ... Insulating liquid storage part 76 ... Pump 77 ... Filter means 100Y ... Development unit 101Y ... Photoconductor squeeze device F40 ... Fixing part (fixing device) F1 ... heat fixing roller (heating roller) F1a ... column-shaped halogen lamp F1b ... roller base material F1c ... elastic body F11c ... release layer F12 ... removal blade F2 ... pressure roller F2a ... rotary shaft F2b ... roller Substrate F2c ... elastic body F3 ... heat-resistant belt F4 ... belt stretching member F4a ... projection wall F4f ... concave F5 ... recording medium F5a ... toner image F6 ... cleaning member F7 ... frame F9 ... spring

Claims (11)

An insulating liquid comprising a fatty acid monoester and an aliphatic hydrocarbon and / or silicone oil;
Toner particles dispersed in the insulating liquid;
A liquid developer comprising a polyamine fatty acid condensation polymer as a dispersant.   The liquid developer according to claim 1, wherein the content of the polyamine fatty acid condensation polymer is 0.5 to 7.5 parts by weight with respect to 100 parts by weight of the toner particles.   When the content of the aliphatic hydrocarbon and / or the silicone oil in the insulating liquid is X [wt%] and the content of the fatty acid monoester is Y [wt%], 0.1 ≦ X / Y The liquid developer according to claim 1, wherein a relationship of ≦ 9 is satisfied.   The liquid developer according to any one of claims 1 to 3, wherein the fatty acid monoester is an ester of a fatty acid and a monovalent alcohol having 1 to 4 carbon atoms.   5. The liquid developer according to claim 1, wherein the viscosity measured at 25 ° C. using a vibration viscometer in accordance with JIS Z8809 is 50 to 1000 mPa · s.   The liquid developer according to claim 1, wherein the resin material constituting the toner particles is a polyester resin. A plurality of developing units that form a single color image corresponding to each color using a plurality of liquid developers having different colors;
By transporting the recording medium, the plurality of monochrome images formed by the plurality of developing units are sequentially transferred to the recording medium, and an unfixed color image formed by superimposing the transferred plurality of monochrome images is recorded. A transfer portion formed on the medium;
A fixing unit for fixing the unfixed color image on the recording medium,
The liquid developer includes an insulating liquid containing an aliphatic hydrocarbon and / or silicone oil and a fatty acid monoester, toner particles dispersed in the insulating liquid, and a polyamine fatty acid condensation polymer as a dispersant. An image forming apparatus comprising:   The plurality of developing sections include at least a developing roller that forms a layer of the liquid developer on a surface thereof, a compression unit that unevenly distributes the toner particles in the vicinity of the surface of the developing roller in the layer, and a surface on the developing roller. The image forming apparatus according to claim 7, further comprising a photoconductor that forms the single-color image by transferring the liquid developer.   The image forming unit according to claim 8, wherein the compression unit applies the electric field having the same polarity as the toner particles to the layer so that the toner particles are unevenly distributed in the vicinity of the surface of the developing roller in the layer. apparatus. The developing section includes at least a developing roller that forms a layer of the liquid developer on a surface thereof, a photoconductor that forms the monochrome image by transferring the liquid developer on the developing roller, and a liquid that is applied to the developing roller. An application roller for supplying the developer,
The application roller is an anilox roller having a groove formed on a surface thereof, and the liquid developer is supplied to the developing roller by carrying the liquid developer in the groove. Image forming apparatus.   The image forming apparatus according to claim 11, wherein the groove formed in the application roller is provided obliquely with respect to a rotation direction of the application roller.

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