JP2008203371A - Liquid developer and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulating liquid and a liquid developer excellent in preservability and long-term stability as well as fixing characteristics of toner particles to a recording medium, and to provide an image forming apparatus using the above liquid developer. <P>SOLUTION: The liquid developer contains an insulating liquid and toner particles essentially comprising a resin material and is characterized in that: the insulating liquid contains a fatty acid monoester; the resin material has a weight average molecular weight Mw of 5,000 to 15,000; and a component having a molecular weight of at least 100,000 is at most 20 wt.% in the resin material. <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 having excellent storage stability and excellent fixing characteristics of toner particles to a recording medium, and to provide an image forming apparatus using such a liquid developer. It is in.

Such an object is achieved by the present invention described below.
The liquid developer of the present invention has toner particles mainly composed of a resin material, and an insulating liquid.
The insulating liquid contains a fatty acid monoester,
The resin material has a weight average molecular weight Mw of 5000 to 15000, and
In the resin material, a component having a molecular weight of 100,000 or more is 20 wt% or less.

In the liquid developer of the present invention, the insulating liquid preferably contains an aliphatic hydrocarbon liquid and / or silicone oil in addition to the fatty acid monoester.
In the liquid developer of the present invention, the aliphatic hydrocarbon liquid is preferably a saturated hydrocarbon.
In the liquid developer of the present invention, the fatty acid monoester preferably contains a saturated fatty acid having 8 to 16 carbon atoms as a fatty acid component.

In the liquid developer of the present invention, the fatty acid monoester preferably contains an alcohol component having 1 to 4 carbon atoms.
In the liquid developer of the present invention, the content of the fatty acid monoester in the insulating liquid is preferably 25 to 90 wt%.
In the liquid developer of the present invention, the resin material preferably has a glass transition temperature Tg of 15 to 70 ° C. and a softening temperature Tf of 80 to 140 ° C.
In the liquid developer of the present invention, the resin material constituting the toner particles preferably has an ester bond in the chemical structure.

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 has toner particles mainly composed of a resin material, and an insulating liquid. The insulating liquid contains a fatty acid monoester, and the weight average molecular weight Mw of the resin material is: The component having a molecular weight of 10000 to 15000 and having a molecular weight of 100,000 or more in the resin material is 20 wt% or less.

  By satisfying the above configuration, it is possible to provide a liquid developer that is excellent in storage stability and long-term stability and excellent in fixing characteristics of toner particles to a recording medium. Another object of the present invention is to provide an image forming apparatus using the liquid developer.

Hereinafter, preferred embodiments of the present invention will be described in detail.
<Liquid developer>
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.
The insulating liquid used in the present invention contains a fatty acid monoester which is an ester between a fatty acid and a monohydric 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 of the present invention 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 (plastic effect) of suitably plasticizing the toner particles at the time of fixing. Due to this plastic 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 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.

  As described above, the fatty acid monoester penetrates the toner particles (resin material) at the time of fixing and exhibits an effect of plasticizing the toner particles. Furthermore, in a liquid developer containing a fatty acid monoester and toner particles mainly composed of a resin material as described later, the fatty acid monoester suitably penetrates the toner particles during fixing, while the fatty acid monoester during storage. The monoester is reliably prevented from penetrating the toner particles. As a result, aggregation of the toner particles during storage can be reliably prevented, and the storage property of the liquid developer can be improved as well as the fixing characteristics of the toner particles to the recording medium.

  The fatty acid component constituting such a fatty acid monoester is not particularly limited. For example, oleic acid, palmitoleic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, arachidonic acid, docosahexaenoic acid (DHA), Unsaturated fatty acids typified by icosapentaenoic acid (EPA), butyric acid, lauric acid, caproic acid, caprylic acid, capric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, etc. Saturated fatty acid etc. are mentioned, 1 type selected from these, or 2 or more types can be used in combination.

  Among these, when the fatty acid monoester contains a saturated fatty acid as a fatty acid component, the fatty acid monoester is hardly deteriorated (oxidation, decomposition, etc.) and becomes chemically particularly stable. For this reason, the insulating liquid containing such a fatty acid monoester reliably prevents deterioration phenomena such as viscosity increase, discoloration, and decrease in electric resistance over a long period of time, and the storage stability and long-term stability of the liquid developer are prevented. The property is particularly excellent. At the time of fixing, the fatty acid monoester is also transferred to the paper together with the toner particles, and the saturated fatty acid monoester is contained in the formed toner image. As described above, the saturated fatty acid monoester is a component that is not easily deteriorated, and even if the toner image is exposed to the external environment (light, heat, oxygen, etc.), it is reliably prevented from being discolored, and a toner image that is formed. Will be clear for a long time.

  Moreover, when a fatty acid monoester contains a saturated fatty acid as a fatty acid component, it is preferable that a C8-C16 fatty acid is included as a saturated fatty acid. Accordingly, the fatty acid monoester can exhibit a plastic effect particularly effectively at the time of fixing, and the liquid developer has particularly excellent fixing characteristics. In addition, aggregation of toner particles during storage can be reliably prevented.

  Moreover, when the fatty acid monoester (unsaturated fatty acid monoester) which has an unsaturated fatty acid as a fatty acid component among the fatty acid monoesters described above is included in the insulating liquid, the following effects can be obtained. Can do. That is, similarly to the saturated fatty acid monoester, the unsaturated fatty acid monoester penetrates into the toner particles at the time of fixing and develops a plastic effect. In addition, the unsaturated fatty acid monoester undergoes oxidative polymerization by heat applied to the liquid developer at the time of fixing, and is itself cured to further improve the fixing strength between the toner particles and the recording medium. Thereby, the anchor effect mentioned above can be made particularly effective, and particularly excellent fixing strength can be obtained.

  Moreover, although fatty acid monoesters other than such fatty acid monoesters are esters of fatty acids and monohydric alcohols, these alcohols are preferably alkyl alcohols having 1 to 4 carbon atoms. Thereby, the chemical stability of the liquid developer is excellent, and the storage stability and long-term stability of the liquid developer are further improved. Further, the viscosity of the insulating liquid can be made favorable, 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.

  Further, the viscosity of such a fatty acid monoester is preferably 10 mPa · s or less, and more preferably 5 mPa · s or less. Accordingly, it is possible to more suitably infiltrate the recording medium, and to more surely promote the penetration of the toner particles melted by the heat at the time of fixing into the recording medium. In addition, for example, when producing a liquid developer by a method as described later, toner particles having a uniform particle diameter can be suitably obtained. In the present specification, unless otherwise specified, the viscosity is a viscosity measured at 25 ° C. using a vibration viscometer in accordance with JIS Z8809.

Moreover, an aliphatic hydrocarbon liquid may be included as a component constituting the insulating liquid.
An aliphatic hydrocarbon-based liquid is a liquid mainly composed of aliphatic hydrocarbons, and has a high electrical resistance and is a chemically stable liquid. For this reason, the liquid developer using the aliphatic hydrocarbon liquid has particularly excellent developability and transferability, and the obtained toner image has particularly few defects and is particularly clear. In addition, the aliphatic hydrocarbon liquid has a high affinity with the fatty acid monoester and easily penetrates into a recording medium such as paper. For this reason, at the time of fixing, the insulating liquid containing the aliphatic hydrocarbon liquid and the fatty acid monoester can quickly penetrate into the recording medium. Thereby, the amount of the insulating liquid present between the toner particles can be reduced, and the obtained toner image becomes clearer. The aliphatic hydrocarbon liquid is a liquid that absorbs little moisture during storage. For this reason, when the aliphatic hydrocarbon liquid is used as the insulating liquid simultaneously with the fatty acid monoester, the insulating liquid can be suitably prevented from absorbing moisture during storage, and the insulating liquid can be prevented from being denatured (deteriorated). Furthermore, it can prevent suitably. For this reason, the liquid developer is particularly excellent in storage stability and long-term stability.

  The aliphatic hydrocarbon liquid that can be used for the insulating liquid is not particularly limited. For example, Isopar E, Isopar G, Isopar H, Isopar L (Isopar; trade name of Exxon Chemical), Cosmo White P- 60, Cosmo White P-70, Cosmo White P-120 (trade name of Cosmo Oil Lubricants), Dyna Fresia W-8, Daphne Oil CP, Daphne Oil KP, Transformer Oil H, Transformer Oil G, Transformer Oil A, Transformer Oil B, Transformer Oil S (trade name of Idemitsu Kosan Co., Ltd.), Cielsol 70, Cielsol 71 (Cielsol; trade name of Ciel Oil), Amsco OMS, Amsco 460 solvent (Amsco; trade name of Spirits), low viscosity High viscosity Examples include animal paraffin (Wako Pure Chemical Industries), octane, isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, cyclohexane, cyclooctane, and cyclodecane. Among these, one or a combination of two or more is used. can do.

Such an aliphatic hydrocarbon-based liquid is preferably a saturated hydrocarbon. The aliphatic hydrocarbon liquid which is a saturated hydrocarbon becomes a chemically stable liquid, and can maintain the electrical resistance of the liquid developer high over a long period of time.
Further, the aliphatic hydrocarbon liquid preferably has a branched chain of a hydrocarbon group as the constituent aliphatic hydrocarbon. Thereby, the aliphatic hydrocarbon liquid becomes chemically more stable, and the storage stability of the liquid developer using such an aliphatic hydrocarbon liquid is particularly excellent. This is considered to be because the structure of the aliphatic hydrocarbon constituting the aliphatic hydrocarbon-based liquid becomes bulky so that a chemical reaction hardly occurs.

Moreover, a silicone oil may be included as a component which comprises an insulating liquid.
Silicone oil is an organic compound having a siloxane bond as a skeleton. Silicone oil generally has a high electrical resistance. For this reason, when silicone oil is used as the insulating liquid, the liquid developer has a particularly high electric resistance, and the toner image has excellent transferability and developability. Further, the liquid developer contains silicone oil in addition to the fatty acid monoester as an insulating liquid, so that high-speed and low-temperature fixing is possible, and the obtained toner image has excellent fixing strength. This is considered as follows. Silicone oil is compatible with the fatty acid monoester, but has low affinity with the resin constituting the toner particles. For this reason, in liquid developers containing silicone oil and fatty acid monoesters, fatty acid monoesters having high affinity with resin materials selectively permeate near the surface of the toner particles, and exhibit a plastic effect particularly well during fixing. To do. For this reason, it is considered that the toner image can be firmly fixed on the recording medium even when fixing is performed at a relatively low temperature and at a high speed. Moreover, since the silicone oil has various viscosities depending on the type, the viscosity of the liquid developer can be made particularly suitable by selecting the silicone oil. Silicone oil is generally a substance that is chemically stable and has little influence on the human body. For this reason, the liquid developer can suitably prevent deterioration of the insulating liquid during storage, and has excellent storage stability. Even when the insulating liquid leaks out of the image forming apparatus, a safe liquid developer can be obtained.

  Examples of silicone oils that can be used for the insulating liquid include KF96, KF4701, KF965, KS602A, KS603, KS604, KF41, KF54, FA630 (manufactured by Shin-Etsu Silicone), TSF410, TFS433, TFS434, TFS451, TSF437, ( Momentive Performance Materials Japan G.K.), SH200 (Toray Industries, Inc.) and the like can be mentioned, and among these, one type or two or more types can be used in combination.

  In addition, the content of the fatty acid monoester in the insulating liquid is preferably 25 to 90 wt%, more preferably 30 to 75 wt%, and still more preferably 35 to 60 wt%. As a result, the storage stability and long-term stability of the liquid developer are particularly excellent, and at the time of fixing, the plastic effect of the toner particles is suitably expressed, and the fixing properties of the toner particles to the recording medium are particularly excellent. It becomes.

  When the insulating liquid contains an aliphatic hydrocarbon liquid and / or silicone oil in addition to the fatty acid monoester, the ratio of the fatty acid monoester to the aliphatic hydrocarbon liquid and / or silicone oil is particularly Although not limited, it is preferable that the following relationship is satisfied. That is, when the content of the fatty acid monoester in the insulating liquid is X [wt%] and the contents of the aliphatic hydrocarbon liquid and the silicone oil are Z [wt%], 0.3 ≦ X / Z It is preferable that the relationship of ≦ 9.0 is satisfied, and it is more preferable that the relationship of 0.5 ≦ X / Z ≦ 4.0 is satisfied. By satisfying such a relationship, the viscosity of the insulating liquid becomes moderate, and the insulating liquid has sufficiently high electrical insulating properties. As a result, the storage stability and long-term stability of the liquid developer are particularly excellent. Further, at the time of fixing, the fatty acid monoester permeates into the toner particles, and more preferably exhibits a plastic effect, whereby the fixing characteristics of the toner particles to the recording medium are particularly excellent.

The insulating liquid may contain components other than those described above. For example, degradation products of fatty acid glycerides such as fatty acid triglyceride, glycerin and fatty acid, benzene, toluene, xylene, mesitylene and the like can be mentioned, and one or more of these can be used in combination.
Further, the liquid developer (insulating liquid) may contain a dispersant that improves the dispersibility of the toner particles.

  As such a dispersant, for example, polyvinyl alcohol, carboxymethyl cellulose, polyethylene glycol, Solsperse (trade name of Nippon Lubrizol Co., Ltd.), polycarboxylic acid and its salt, polyacrylic acid metal salt (for example, sodium salt), Polymethacrylic acid metal salt (for example, sodium salt), polymaleic acid metal salt (for example, sodium salt), acrylic acid-maleic acid copolymer metal salt (for example, sodium salt), polystyrene sulfonic acid metal salt (for example, , Sodium salts, etc.), polymer dispersants such as polyamine fatty acid condensation polymers, viscosity minerals, silica, tricalcium phosphate, tristearic acid metal salts (for example, aluminum salts), distearic acid metal salts (for example, aluminum salts, Barium salts), metal stearates (e.g. Calcium salt, lead salt, zinc salt, etc.), linolenic acid metal salt (eg, cobalt salt, manganese salt, lead salt, zinc salt, etc.), octanoic acid metal salt (eg, aluminum salt, calcium salt, cobalt salt, etc.), Oleic acid metal salts (for example, calcium salts, cobalt salts, etc.), palmitic acid metal salts (for example, zinc salts), dodecylbenzenesulfonic acid metal salts (for example, sodium salts), naphthenic acid metal salts (for example, calcium salts) , Cobalt salts, manganese salts, lead salts, zinc salts, etc.), resinic acid metal salts (for example, calcium salts, cobalt salts, manganese lead salts, zinc salts, etc.) and the like.

  Among the above-described dispersants, when a polyamine fatty acid condensation polymer is used, the polyamine fatty acid condensation polymer can be attached to the surface of the toner particles, thereby preventing unintentional aggregation of the toner particles. it can. Further, the permeability of the fatty acid monoester to the toner particles can be increased, 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 to the recording medium. Further, the charging characteristics of the toner particles can be made higher.

When the polyamine fatty acid condensation polymer is used, the content of the polyamine fatty acid condensation polymer in the liquid developer is preferably 0.5 to 7.5 parts by weight with respect to 100 parts by weight of the toner particles. More preferably, it is ˜5 parts by weight. Thereby, the effect by using a polyamine fatty acid condensation polymer can be made more remarkable.
The insulating liquid may contain an antioxidant.
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.
The electric resistance of the insulating liquid at room temperature (20 ° C.) is preferably 1.0 × 10 ¹¹ Ωcm or more, more preferably 1.0 × 10 ¹² Ωcm or more, and 1.0 × 10 ^13. More preferably, it is at least Ωcm.
The dielectric constant of the insulating liquid is preferably 3.5 or less.

<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 weight average molecular weight Mw of the resin material constituting the toner particles of the present invention is 5000 to 15000, and the component having a molecular weight of 100,000 or more is 20 wt% or less. By using the resin material satisfying the above conditions together with the insulating liquid described above, the storage of the insulating liquid into the toner particles is reliably suppressed during storage. Thereby, aggregation of toner particles can be reliably prevented, and a liquid developer having excellent storability can be provided. Further, at the time of fixing, the fatty acid monoester contained in the insulating liquid suitably penetrates into the toner particles, and the above-described plastic effect is surely exhibited. Thereby, the fixing characteristics of the toner particles to the recording medium are excellent. In particular, when the toner particles are fixed on the recording medium at a relatively low temperature, the toner formed on the recording medium can be surely prevented from a problem that some of the toner images formed are not fixed. The fixing strength of the image can be made stable and excellent.

As described above, the liquid developer of the present invention includes an insulating liquid containing a fatty acid monoester, a resin material having a weight average molecular weight Mw of 5000 to 15000 and a component having a molecular weight of 100,000 or more and 20 wt% or less. It is characterized by having toner particles as a main component, and an excellent effect can be obtained thereby. On the other hand, the effect of the present invention cannot be obtained with a liquid developer that does not satisfy all the above-described configurations. That is, when the weight average molecular weight Mw of the resin material constituting the toner particles is less than the lower limit of the above range, the fatty acid monoester penetrates into the toner particles even during storage, and the toner particles are completely fused. It can no longer be suppressed. Therefore, the toner particles aggregate in the insulating liquid, and the storage stability of the liquid developer cannot be sufficiently satisfied. Further, the toner particles are fixed in an aggregated state, and it becomes difficult to obtain a clear toner image. Further, since the molecular weight of the resin material is too low, the toner particles fixed on the recording medium are easily peeled off, and it is difficult to form a toner image having a sufficient fixing strength. Further, when a toner containing such a resin material as a main raw material is pulverized or pulverized in a liquid developer manufacturing method as described later, a sufficient shearing force cannot be applied to the toner material. For this reason, the time required for pulverization or pulverization becomes long, and the production cost of toner particles increases. In addition, the toner particles produced in this manner are likely to aggregate and have poor dispersibility, and the storage stability of the produced liquid developer cannot be made excellent. On the other hand, if the weight average molecular weight Mw of the resin material constituting the toner particles is larger than the upper limit of the above range, the above-described plasticity effect of the fatty acid monoester is not sufficiently exhibited, which is great for fixing the toner particles to the recording medium. Heat energy is required, and the fixing temperature becomes high. Further, even if the fixing is performed at a high temperature, it becomes difficult to stably form a toner image having sufficient fixing strength. Further, if the resin material constituting the toner particles contains more than 20 wt% of a component having a molecular weight of 100,000 or more, all the toner particles cannot be uniformly plasticized. As a result, it becomes difficult to make the fixing strength of the toner image formed on the recording medium stable and excellent.
The resin material constituting such toner particles has a weight average molecular weight Mw of 5000 to 15000, preferably 5000 to 13000, and more preferably 5000 to 12000. Thereby, it is possible to further improve the fixing property of the toner particles to the recording medium while further improving the storage stability of the liquid developer.

  Further, in the resin material constituting such toner particles, the component having a molecular weight of 100,000 or more is 20 wt% or less, preferably 18 wt% or less, and more preferably 5 to 15 wt%. Thereby, at the time of fixing, the fatty acid monoester can be more reliably permeated into the individual toner particles, and the fixing strength of the toner image formed on the recording medium can be made more stable and excellent. .

  In the present invention, the resin (binder resin) is not particularly limited as long as it has the above-mentioned properties. For example, a known resin can be used. Examples of such a resin include an ester in the chemical structure. Those having a bond are preferred. A toner composed of a resin that satisfies such conditions has a high affinity with the insulating liquid due to the similarity in chemical structure with the fatty acid monoester described above. Therefore, the dispersibility of the toner particles in the liquid developer can be made particularly excellent, the aggregation of the toner particles during storage can be more effectively prevented, and the storage stability and long-term stability of the liquid developer can be prevented. The property can be made particularly excellent. Further, at the time of fixing, the fatty acid monoester easily penetrates, and the plasticizing effect of the fatty acid monoester on the toner particles can be surely expressed. Thereby, the fixing property of the toner particles to the recording medium can be further improved.

Examples of the resin having an ester bond in the chemical structure include polyester resins, styrene-acrylic acid ester copolymers, and styrene-methacrylic acid ester copolymers. Among these, the polyester resin has high transparency, and when used as a binder resin, the color developability of the obtained image can be increased.
Moreover, it is preferable that the acid value of such resin is 0.1-15 mgKOH / mg, it is more preferable that it is 1-10 mgKOH / mg, and it is further more preferable that it is 3-8 mgKOH / mg. Toner particles made of a resin material that satisfies the above conditions are particularly excellent in affinity with the insulating liquid as described above. Thereby, during storage, the dispersibility of the toner particles in the liquid developer becomes better, and the aggregation of the toner particles can be more efficiently prevented over a long period of time. Further, at the time of fixing, the penetration of the insulating liquid into the toner particles becomes more suitable, the plastic effect is more strongly expressed, and the toner particles can be firmly fixed on the recording medium.

  Further, the resin material constituting the toner particles preferably has a glass transition temperature Tg of 15 to 70 ° C, more preferably 20 to 55 ° C, and further preferably 25 to 50 ° C. By using a resin material that satisfies the above conditions as a constituent material of the toner particles, during storage, the toner particles are more reliably prevented from being fused with each other, and the storage stability of the liquid developer is further improved. Further, at the time of fixing, the penetration of the fatty acid monoester into the toner particles can be made more suitable, and the toner particles can be fixed more firmly on the recording medium at a low temperature.

  Further, the resin material constituting the toner particles preferably has a softening temperature Tf of 80 to 140 ° C., more preferably 85 to 130 ° C., and further preferably 90 to 120 ° C. By using a resin material that satisfies the above conditions as a constituent material of the toner particles, during storage, the toner particles are more reliably prevented from being fused with each other, and the storage stability of the liquid developer is further improved. Further, at the time of fixing, the penetration of the fatty acid monoester into the toner particles can be made more suitable, and the toner particles can be fixed more firmly on the recording medium at a low temperature.

In this specification, the glass transition temperature Tg is a measurement condition in a differential scanning calorimeter DSC-220C (manufactured by SII): sample amount 10 mg, temperature rising rate 10 ° C./min, measurement temperature range 10 to 150 ° C. When measured, it refers to the temperature at the intersection of an extension of the baseline below the glass transition point and a tangent that indicates the maximum slope from the peak rise to the peak apex.
The softening temperature refers to a softening start temperature defined by measurement conditions in a Koka flow tester (manufactured by Shimadzu Corporation): temperature rising rate: 5 ° C./min and die hole diameter 1.0 mm.

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 value (average circularity) of the circularity R represented by the following formula (I) for the toner particles constituting the liquid developer is preferably 0.94 to 0.99, and preferably 0.96 to 0 More preferred is .99.
R = L ₀ / L ₁ (I)
(Where L ₁ [μm] is the circumference of the projected image of the toner particles to be measured, and L ₀ [μm] is the circumference of a perfect circle having an area equal to the area of the projected image of the toner particles to be measured) Represents length)

When the average circularity of the toner particles is in such a range, the insulating liquid can be appropriately contained in the unfixed toner image transferred onto the recording medium, and the fixing strength of the toner particles is higher. Can be.
The average particle size of the toner particles composed of the above materials is preferably 0.7 to 3 μm, more preferably 0.8 to 2.5 μm, and 0.8 to 2 μm. More preferably. When the average particle diameter of the toner particles is within the above range, the variation in characteristics among the toner particles is small, and the liquid developer as a whole is made highly reliable while being formed with the liquid developer. The resolution of the toner image can be made sufficiently high. Further, it is possible to improve the dispersion of the toner particles in the insulating liquid and to improve the storage stability of the liquid developer.

The content ratio of the toner particles in the liquid developer is preferably 10 to 60 wt%, and more preferably 20 to 50 wt%.
In addition, the viscosity (the viscosity measured according to JIS Z8809 using a vibration viscometer at 25 ° C.) of the liquid developer (liquid developer of the present invention) composed of each component as described above is It is preferably 20 to 900 mPa · s, more preferably 30 to 800 mPa · s, and still more preferably 50 to 500 mPa · s. Thereby, since the penetration of the liquid developer into the recording medium becomes more suitable, the fixing characteristics of the toner particles to the recording medium become more excellent. In addition, the image obtained on the recording medium becomes clear with no unevenness, and is particularly suitable as a liquid developer suitable for image formation at high speed.

In addition, the electrical resistance at room temperature (20 ° C.) of the liquid developer composed of the components as described above (the liquid developer of the present invention) is preferably 1.0 × 10 ¹¹ Ωcm or more. More preferably, it is 0.0 × 10 ¹² Ωcm or more.
Moreover, the insulating liquid as described above is, for example, when the insulating liquid contains a fatty acid monoester and the above-described components (aliphatic hydrocarbon, silicone, etc.), these components are mixed. Can be manufactured. A liquid developer can be produced by mixing such an insulating liquid and toner particles, but can also be produced using the following method.

<< Method for Producing Liquid Developer >>
Next, a preferred embodiment of the liquid developer manufacturing method as described above will be described.
In this embodiment, the insulating liquid is described as including a fatty acid monoester and other components.
<First Embodiment>
First, the first embodiment will be described.
In the method for producing a liquid developer of the present embodiment, a toner material preparation step for obtaining a toner material containing a resin material and a colorant, and a toner material mainly composed of a resin material in a fatty acid monoester are pulverized to obtain a pulverized product. A pulverizing step of obtaining a dispersion, a pulverized dispersion, and a mixing step of mixing other components constituting the insulating liquid.

[Toner material preparation process]
First, an example of a method for preparing a toner material mainly composed of a resin material will be described.
Such a toner material may be prepared by any method, but in the present embodiment, a toner material such as a known resin material or a colorant having the above-described properties is kneaded to obtain a toner material. After obtaining the kneaded material constituted by the above, the kneaded material is coarsely pulverized to obtain the coarsely pulverized material constituted by the toner material.

  As described above, by kneading a toner material such as a resin material and a colorant, even in the case where the components constituting the toner particles include components that are not easily dispersed or compatible with each other in the pulverization step described later. In the obtained kneaded product, each component can be sufficiently compatible and finely dispersed. As a result, the variation in characteristics among the toner particles can be made sufficiently small. In addition, by kneading the kneaded material composed of the toner material before the pulverization process described later, the particle diameter of the toner particles can be reduced more effectively in the pulverization process.

[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 and the degree of freedom of movement of the toner material in the fatty acid monoester is high, 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. Further, in the liquid developer manufactured through such a pulverization step, the toner particles can be firmly fixed on the recording medium. This is considered to be due to the following reasons. That is, it is considered that the fatty acid monoester suitably penetrates into the toner particles in the liquid developer finally obtained by crushing the toner material in the fatty acid monoester. Such toner particles exhibit a plastic effect more effectively at the time of fixing. As a result, the toner particles can easily enter through the gaps in the paper fibers (recording medium), so that the fixing strength of the toner particles can be made particularly excellent.

Further, the resin material as described above, which is a component of the toner material, is not easily eroded by the fatty acid monoester in the pulverization step. Therefore, the toner material can be efficiently pulverized and toner particles having a relatively small particle diameter can be easily produced.
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.
Further, before mixing the fatty acid monoester and the toner material, a dispersant as described above may be added to the fatty acid monoester. As a result, the dispersant acts as a pulverization aid, and the toner material can be pulverized more efficiently and the dispersibility of the resulting toner particles can be made higher.

In addition, when the toner material is pulverized in a state where the fatty acid monoester contains the dispersant, it becomes easier for the dispersant to adhere to the surface of the toner particles, thereby improving the charging characteristics of the finally obtained liquid developer. Can be made.
Among the dispersants described above, when a polyamine fatty acid condensation polymer is used, the pulverization efficiency can be effectively increased. Further, when the polyamine fatty acid condensation polymer is present when pulverized with the fatty acid monoester, the polyamine fatty acid condensation polymer can be suitably present on the surface of the toner particles (so as to be entangled). Thereby, the dispersibility of the toner particles in the finally obtained liquid developer can be further improved.

[Mixing process]
Next, the obtained pulverized material dispersion is mixed with other components constituting the insulating liquid (mixing step).
As described above, the liquid developer of the present invention in which toner particles are dispersed in an insulating liquid containing a fatty acid monoester is obtained.

Second Embodiment
Next, a second embodiment will be described.
The method for producing a liquid developer according to the present embodiment is a process for associating resin fine particles mainly composed of a resin material to obtain associated particles, and pulverizing the associated particles in a fatty acid monoester, A step of obtaining a toner particle dispersion in which toner particles are dispersed in a liquid; and a mixing step of mixing the obtained toner particle dispersion and other components constituting the insulating liquid.

[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.
The association particles may be prepared by any method, but in this embodiment, a dispersoid (fine particles) mainly composed of a resin material (toner material) in an aqueous dispersion medium composed of an aqueous liquid. ) Is dispersed, and the dispersoids in the aqueous emulsion are associated to obtain associated particles.

(Preparation of aqueous dispersion)
Hereinafter, the preparation of the aqueous dispersion will be described.
The aqueous dispersion may be prepared by any method, but in this embodiment, first, the toner material as described above is dissolved in a solvent to obtain a toner material solution, and the toner material solution, By mixing with an aqueous dispersion medium composed of an aqueous liquid, an aqueous emulsion in which the dispersoid (liquid dispersoid) containing the toner material is dispersed is obtained, and then at least one of the solvents contained in the aqueous emulsion is obtained. An aqueous dispersion is obtained by removing the part.

The aqueous emulsion can be prepared, for example, as follows (aqueous emulsion preparation step).
First, an aqueous dispersion medium is prepared.
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.

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.
Further, an emulsifying dispersant may be added to the aqueous dispersion medium as necessary. By adding an emulsifying dispersant, an aqueous emulsion can be prepared more easily.
The emulsifying dispersant is not particularly limited, and for example, a known emulsifying dispersant can be used.

On the other hand, the toner material as described above is dissolved in a solvent to prepare a toner material solution.
Any solvent can be used as long as it dissolves at least a part of the toner material, 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 toner material 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 examples thereof include ketone solvents such as MEK and aromatic hydrocarbon solvents such as toluene.
In preparing the toner material solution, for example, a kneaded material obtained by kneading a toner material such as a resin material or 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, the toner material solution is gradually added dropwise to the stirred aqueous dispersion medium to obtain an aqueous emulsion in which the dispersoid containing the toner material is dispersed in the aqueous dispersion medium. It is done. Note that when the toner material solution is dropped, the aqueous dispersion medium and / or the toner material solution may be heated.
Further, instead of the above operation, the aqueous dispersion medium may be added while gradually dropping into the stirred toner material solution. Thus, by adding the aqueous dispersion medium to the toner material solution, the toner material solution undergoes phase inversion emulsification, and the aqueous dispersion medium contains the toner material in the same manner as the aqueous emulsion obtained by the above operation. An aqueous emulsion in which the dispersoid is dispersed can be obtained.

Thereafter, the obtained aqueous emulsion is heated or placed in a reduced-pressure atmosphere to remove at least part of the solvent contained in the dispersoid, and the dispersoid (fine particles) composed of the toner material is dispersed. An aqueous dispersion is obtained.
The content of the dispersoid in the aqueous dispersion 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 surely preventing unintentional aggregation of dispersoids in the aqueous dispersion.
The average particle size of the dispersoid in the aqueous dispersion 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.

(Association particle formation process)
Next, an electrolyte is added to the aqueous dispersion 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 dispersion. 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 with each other and coarse particles may be generated, and there is a possibility that the size of finally obtained toner particles may vary. is there.
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 liquid is obtained.
As described above, the fatty acid monoester is a component having high affinity with the resin material constituting the toner particles. For this reason, when the associated particles are crushed in the fatty acid monoester, the fatty acid monoester is likely to enter between the fine particles (dispersoid) constituting the associated particle, and the associated particles can be efficiently crushed with less energy. Can do. Further, in the liquid developer produced through such a crushing step, the toner particles can be firmly fixed on the recording medium. This is considered to be due to the following reasons. That is, by associating the associated particles obtained as described above in the fatty acid monoester, the fatty acid monoester suitably penetrates into the toner particles in the finally obtained liquid developer. Conceivable. Such toner particles exhibit a plastic effect more effectively at the time of fixing. As a result, the toner particles can easily enter through the gaps in the paper fibers (recording medium), so that the fixing strength of the toner particles can be made particularly excellent.

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.

[Mixing process]
Next, the toner particle dispersion liquid obtained as described above and other components constituting the insulating liquid are mixed to disperse the toner particles in the insulating liquid (mixing step).
As described above, the liquid developer of the present invention in which toner particles are dispersed in an insulating liquid containing a fatty acid monoester is obtained.

≪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 removed liquid developer, and the developer collection unit 15Y 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 this 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.
Further, 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 storage unit 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 fitted 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 (a heat-resistant belt F3 is a belt). Sliding on the tension member F4). This 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 those applied to the liquid developing device and the fixing device 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 second embodiment of the method for producing a liquid developer described above, it has been described that an aqueous dispersion is obtained and an associated particle is obtained by adding an electrolyte to the aqueous emulsion. It is not limited. 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 dispersion by emulsion polymerization, and adding an electrolyte to the aqueous dispersion to be associated. It may be prepared using an emulsion polymerization association method, or may be obtained by spray-drying the obtained aqueous dispersion to obtain associated particles.

Further, in each embodiment (first embodiment, second embodiment) of the method for producing a liquid developer, it has been described that the associated particles are crushed in the fatty acid monoester. However, as the liquid for pulverizing the associated particles, Alternatively, a mixed solution of a fatty acid monoester and other components constituting the insulating liquid may be used. Even if the associated particles are pulverized in such a mixed solution, the above-described effects can be obtained.
In each embodiment (first embodiment, second embodiment) of the method for producing a liquid developer, the insulating liquid has been described as including a fatty acid monoester and other components. However, the insulating liquid is a fatty acid. In the case where the liquid developer is composed only of the monoester, the liquid developer can be produced by omitting the mixing step of each embodiment described above.

(Example 1)
<Preparation of toner material>
(Preparation of colorant masterbatch)
First, polyester resin A (weight average molecular weight Mw: 10200, glass transition temperature Tg: 61 ° C.): 20 parts by weight, cyan pigment as a colorant (Pigment Blue 15: 3, manufactured by Dainichi Seika Co., Ltd.): 20 weights And prepared. These components were mixed using a 20 L type Henschel mixer to obtain a mixture of resin and colorant.
Next, this 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.

(Adjustment of resin components)
Coarse pulverized product obtained as described above: Polyester resin B (weight average molecular weight Mw: 7600, glass transition temperature Tg: 43 ° C.): 80 parts by weight is added to 20 parts by weight, and a 20 L type Henschel mixer is used. And mixed 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.
In addition, the average particle diameter of the coarsely pulverized product thus obtained was measured with a Mastersizer 2000 particle analyzer (manufactured by Malvern Instruments Ltd.). Polyester resin A was prepared from isophthalic acid, n-dodecenyl succinic acid, trimet acid, oleic acid, and polyoxypropylene acid (2,5) -2,2bis (4-hydroxyphenyl) propane. Polyester resin B was prepared from isophthalic acid, neopentyl glycol, and butyl orthotitanate. Further, the resin components (polyester resin A and polyester resin B) constituting the toner material are mixed at the same blending ratio (polyester resin A: polyester resin B = 1: 8) as the resin components constituting the toner material. It knead | mixed using the biaxial kneading extruder. The kneaded product thus obtained had a weight average molecular weight Mw of 7890, a softening temperature Tf of 99 ° C., and a glass transition temperature Tg of 45 ° C. Moreover, the content rate of the component of molecular weight 100000 or more contained in such a resin component was 14 wt%.

<Preparation of liquid developer>
Next, a coarsely pulverized product of the toner material obtained as described above: 40 parts by weight, and a soybean oil transesterification liquid (viscosity 5.1 mPa · s, day) produced by a transesterification reaction between soybean oil and methanol. Kiyoi Rio Co., Ltd., trade name “soybean oil fatty acid methyl”): 60 parts by weight and aliphatic hydrocarbon (viscosity 15 mPa · s, Cosmo Oil Lubricants Cosmo White P-60): 100 g, polyamine fatty acid degenerate Combined (Nippon Lubrizol Corporation, trade name “Solsperse 13940”): 2.0 parts by weight, aluminum stearate (Nippon Yushi Co., Ltd.) is placed in a ceramic pot (internal volume 600 ml), and zirconia balls (ball diameter) : 1 mm) was placed in a ceramic pot so that the volume filling rate was 30%. Crushing was performed for 200 hours at a rotational speed of 220 rpm in a desktop pot mill, and the dispersion in the pot was separated from the zirconia balls and taken out to obtain a liquid developer. In addition, content of the fatty acid monoester in soybean oil transesterification liquid was 99.9 wt% or more.

The average particle diameter of the toner particles in the obtained liquid developer was 1.5 μm, and the standard deviation of the particle diameter between the toner particles was 0.65 μm. Moreover, the viscosity of the liquid developer measured according to JIS Z8809 using a vibration viscometer at 25 ° C. was 227 mPa · s. Further, the electric resistance of the liquid developer was 2.2 × 10 ¹² Ωcm.
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.

(Example 2)
Instead of soybean oil fatty acid methyl, a coconut oil transesterification liquid (viscosity 3.7 mPa · s, “Exepar MC” manufactured by Kao Corporation) produced by transesterification reaction between coconut oil and methanol is used. Liquid developers corresponding to the respective colors were produced in the same manner as in Example 1 except that the content of the transesterification liquid and the aliphatic hydrocarbon in the insulating liquid was changed as shown in Table 1.

(Example 3)
Example 1 except that the polyester resin B to be used is entirely replaced with the polyester resin A, and the components other than the fatty acid monoester and fatty acid monoester to be used are of the types shown in Table 1. In the same manner as described above, liquid developers corresponding to the respective colors were produced.

Example 4
<Preparation of toner material>
(Preparation of colorant masterbatch)
First, polyester resin B (weight average molecular weight Mw: 7600, glass transition temperature Tg: 43 ° C.): 20 parts by weight, cyan pigment as a colorant (manufactured by Dainichi Seika Co., Ltd., Pigment Blue 15: 3): 20 weights And prepared. These components were mixed using a 20 L type Henschel mixer to obtain a mixture of resin and colorant.
Next, this 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.

(Adjustment of resin components)
Coarse pulverized product obtained as described above: Polyester resin C (weight average molecular weight Mw: 4900, glass transition temperature Tg: 38 ° C.): 80 parts by weight is added to 20 parts by weight, and a 20 L type Henschel mixer is used. And mixed 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.
In addition, the average particle diameter of the coarsely pulverized product thus obtained was measured with a Mastersizer 2000 particle analyzer (manufactured by Malvern Instruments Ltd.). Polyester resin C was prepared from isophthalic acid, neopentyl glycol, and butyl orthotitanate. Further, the resin components (polyester resin B, polyester resin C) constituting the toner material are mixed at the same blending ratio (polyester resin A: polyester resin B = 1: 8) as the resin components constituting the toner material. It knead | mixed using the biaxial kneading extruder. The kneaded product thus obtained had a weight average molecular weight Mw of 5200, a softening temperature Tf of 88 ° C., and a glass transition temperature Tg of 39 ° C. Moreover, the content rate of the component of molecular weight 100000 or more contained in such a resin component was 15 wt%.
Using the toner material thus obtained, the above-described implementation was performed except that the types of components other than the fatty acid monoester and fatty acid monoester used and the content in the insulating liquid were as shown in Table 1. In the same manner as in Example 1, liquid developers corresponding to the respective colors were produced.

(Examples 5-7)
Except for the configuration shown in Table 1, liquid developers corresponding to the respective colors were produced in the same manner as in Example 1.
(Example 8)
Polyester resins A and B to be used are all substituted with styrene-acrylic copolymers (weight average molecular weight Mw: 11000, glass transition temperature Tg: 55 ° C.), and other than fatty acid monoesters and fatty acid monoesters to be used Liquid developers corresponding to the respective colors were produced in the same manner as in Example 1 except that the types of components and the contents in the insulating liquid were changed as shown in Table 1.

Example 9
The polyester resins A and B to be used are all replaced with epoxy resins (weight average molecular weight Mw: 14000, glass transition temperature Tg: 60 ° C.), and the fatty acid monoester to be used and the types of components other than the fatty acid monoester, A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that the content in the insulating liquid was changed as shown in Table 1.

(Example 10)
<Preparation of colorant master solution>
First, a mixture (mass ratio 50:50) of the polyester resin A and a cyan pigment (Dainipei Seika Co., Ltd., Pigment Blue 15: 3) as a colorant was prepared. These components were mixed using a 20 L type Henschel mixer to obtain a raw material for toner production.

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

<Preparation of fat liquid>
200 parts by weight of methyl ethyl ketone and 73 parts by weight of polyester resin B were added to 33 parts by weight of the above colorant master solution, and mixed with an Eiger motor mill (manufactured by Eiger, USA: M-1000) to prepare a resin solution. In this solution, the pigment was uniformly finely dispersed.

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

<Production of associated particles by association>
Next, while continuing stirring in the flask, 285 parts by weight of deionized water was added to the aqueous emulsion so that the total amount of 1N ammonia water and water was 593 parts by weight. Subsequently, 2.6 parts by weight of Emul 0 (manufactured by Kao Corporation), which is an anionic emulsifier, was diluted to 30 parts by weight of deionized water and added to the aqueous emulsion.

Thereafter, while maintaining the temperature of the aqueous emulsion at 25 ° C., the rotation speed of stirring was 150 rpm (peripheral speed of stirring blade: 0.54 m / s), and 3.5% ammonium sulfate aqueous solution: 300 parts by weight was dropped. The particle size of the dispersoid aggregate was 3.5 μm. After dropping, stirring was continued until the particle size of the dispersoid aggregates grew to 5.0 μm, and the association operation was completed.
The resulting aggregate dispersion was dried by distilling off the organic solvent under reduced pressure to obtain associated particles.
In addition, the average particle diameter of each particle in each example and comparative example is a volume-based average particle diameter, and the average particle diameter and particle size distribution of these particles are obtained from a Mastersizer 2000 particle analyzer (manufactured by Malvern Instruments Ltd.). And measured.

<Preparation of liquid developer>
Associated particles obtained by the above method: 40 g, coconut oil transesterification liquid (viscosity 3.7 mPa · s, “Exepar MC” manufactured by Kao Corporation) produced by transesterification of coconut oil, which is an oil and fat, and methanol: 60 g, aliphatic hydrocarbon (viscosity 15 mPa · s, “Cosmo White P-60” manufactured by Cosmo Oil Lubricants): 100 g, polyamine aliphatic polycondensate (“Solsperse 11200” manufactured by Nihon Lubrizol): 2 g and stearic acid Aluminum (manufactured by Nippon Oil & Fats): 0.5 g was put in a ceramic pot (internal volume 600 ml), and further zirconia balls (ball diameter: 3 mm) were put in the ceramic pot so that the volume filling rate was 30%. Crushing was performed for 200 hours at a rotational speed of 220 rpm in a desktop pot mill, and the dispersion in the pot was separated from the zirconia balls and taken out to obtain a liquid developer.

The average particle diameter of the toner particles in the obtained liquid developer was 1.5 μm, and the standard deviation of the particle diameter between the toner particles was 0.65 μm. Moreover, the viscosity of the liquid developer measured in accordance with JIS Z8809 using a vibration viscometer at 25 ° C. was 230 mPa · s. Further, the electric resistance of the liquid developer was 2.5 × 10 ¹² Ωcm.
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 11 to 12)
Except for the configuration shown in Table 1, liquid developers corresponding to the respective colors were produced in the same manner as in Example 10.
(Comparative Example 1)
Liquid developers corresponding to the respective colors were produced in the same manner as in Example 1 except that the polyester resins A and B used were all replaced with the polyester resin C.

(Comparative Example 2)
The liquid corresponding to each color was the same as in Example 1 except that the polyester resins A and B used were all replaced with the polyester resin D (weight average molecular weight M _w : 6000, glass transition temperature Tg: 65 ° C.). A developer was produced.
(Comparative Example 3)
The polyester resins A and B to be used are all replaced with the polyester resin E (weight average molecular weight M _w : 17000, glass transition temperature Tg: 75 ° C.), and the types of fatty acid monoesters to be used are as shown in Table 1. Except for the configuration, liquid developers corresponding to the respective colors were produced in the same manner as in Example 1.
(Comparative Example 4)
Each color was changed in the same manner as in Example 1 except that all of the soybean oil fatty acid methyl used was replaced with the aliphatic hydrocarbon used in Example 1 (“Cosmo White P-60” manufactured by Cosmo Oil Lubricants). A liquid developer corresponding to the above was manufactured.

  For each of the above Examples and Comparative Examples, the type of resin used, the weight average molecular weight Mw, the content of components having a molecular weight of 100,000 or more contained in the resin, the softening temperature Tf, the glass transition temperature Tg, the type of fatty acid monoester , Constituting main fatty acid component, alcohol component, content in insulating liquid, types of main components other than fatty acid monoester, content in insulating liquid, viscosity of liquid developer, electric resistance of liquid developer Etc. are shown in Table 1.

  Table 1 shows the configuration of the liquid developer and the evaluation results of the viscosity and the electrical resistance for each of the above Examples and Comparative Examples. Evaluation of the viscosity in Table 1 was performed on the conditions of the measurement temperature of 25 degreeC using the vibration-type viscosity meter (CBC Co., Ltd. product VM-100A) based on JISZ8809. The electrical resistance was evaluated using a universal electrometer (manufactured by Kawaguchi Electric Co., Ltd., MMAII-17B) as a measuring device, and about 2 ml of a sample was placed in a liquid electrode cell, measuring temperature: 20 ° C., applied voltage: 100 V, applied Time: Volume resistivity was measured under the condition of 1 minute.

Table 1 shows the measurement results of the weight average molecular weight Mw, the glass transition temperature Tg, and the softening temperature Tf for the resin materials used in each example and each comparative example.
In Table 1, the weight average molecular weight _Mw of the resin materials of the examples and comparative examples, and the evaluation of the content of components having a molecular weight of 100,000 or more contained in the resin material were evaluated by using a high-speed GPC system manufactured by Tosoh Corporation (HLC- 8220GPC built-in RI / UV-8220), column: TSKgel SuperHZM-M (4.6 mm ID × 15 mmL) × 4, column temperature: 40 ° C., solution: tetrahydrofuran, special grade (manufactured by Kanto Chemical Co., Inc.), flow rate: 0.35 ml / Min, sample concentration: 1 mg / ml, injection amount: 20 μl, standard substance: standard polystyrene (manufactured by Tosoh Corporation), the sample was placed in a column, and the molecular weight was measured. As a sample pretreatment, a resin material was dissolved in tetrahydrofuran, and allowed to stand for a whole day and night, and then filtered through a syringe filter having a pore size of 0.2 μm.

  Moreover, evaluation of the glass transition temperature Tg of the resin material in Table 1 was carried out using DSC (DSC-220C manufactured by SII) as a measuring device, taking about 10 mg of the resin material in an aluminum pan, and the rate of temperature increase: 10 ° C. / min, measurement temperature range: measured at 30 to 150 ° C. In addition, the measurement used the data measured on the same conditions for the 2nd time, raising / lowering temperature (10 degreeC-150 degreeC-10 degreeC).

Moreover, the softening temperature Tf of the resin material in Table 1 was measured using a Koka type flow tester (manufactured by Shimadzu Corporation) as a measuring device under conditions of a temperature rising rate: 5 ° C./min and a die hole diameter of 1.0 mm. .
In Table 1, methyl laurate and ethyl laurate refer to lauric acid monoesters produced by transesterification of lauric acid and methanol or ethanol, respectively, and palm oil fatty acid isobutyl is This refers to a coconut oil transesterification solution produced by a transesterification reaction between coconut oil and isobutanol. Moreover, in Table 1, polyester resin A as a resin material is PEs-A, polyester resin B is PEs-B, polyester resin C is PEs-C, polyester resin D is PEs-D, polyester resin E is PEs-E, St-Ac as styrene-acrylic copolymer, EP as epoxy resin, MeOH as alcohol component of fatty acid monoester, EtOH as ethanol, i-BuOH as isobutanol, and linoleic acid as fatty acid component of fatty acid monoester LN, oleic acid OL, palmitic acid PL, lauric acid LA, myristic acid MR, cosmo white P-60 as aliphatic hydrocarbon a, Dynafrecia W-8 (viscosity 14 mPa · s, Idemitsu Kosan Co., Ltd.) B) KF96 (viscosity 100 mPa · s) as silicone oil Yue Silicone Co., Ltd.) showed c, soybean oil as fat and oil (Nisshin OilliO Group, Ltd.) d. In
In addition, the viscosity and electrical resistance in Table 1 are expressed according to the following four-stage criteria.

<Viscosity>
Very good (A): 50 mPa · s or more and 500 mPa · s or less.
Good (B): 30 mPa · s or more and 800 mPa · s or less. (Except 50mPa · s or more and 500mPa · s or less)
Allowable range (C): 20 mPa · s or more and 900 mPa · s or less. (Except for 80mPa · s or more and 900mPa · s or less)
Poor (D): Less than 20 mPa · s or more than 900 mPa · s.

<Electrical resistance>
Very good (A): 2.0 × 10 ¹² Ωcm or more.
Good (B): 1.5 × 10 ¹² Ωcm or more and less than 2.0 × 10 ¹² Ωcm.
Tolerable range (C): 1.0 × 10 ¹² Ωcm or more and less than 1.5 × 10 ¹² Ωcm.
Poor (D): Less than 1.0 × 10 ¹² Ωcm.

[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 FIGS. 1 to 6, an image of a predetermined pattern with the liquid developer obtained in each of the above examples and each of the comparative examples is recorded on a recording paper (Seiko Epson). It was formed on a high-quality paper LPCPPA4) manufactured by the same company, and the heat fixing was performed with the set temperature of the heat fixing roller being 120 ° 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.) with a pressing load of 1.0 kgf twice, 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.

Very good (A): Image density residual ratio is 95% or more.
Good (B): Image density residual ratio is 90% or more and less than 95%.
Allowable range (C): Image density remaining rate is 80% or more and less than 90%.
Slightly bad (D): Image density remaining ratio is 70% or more and less than 80%.
Poor (E): Image density residual ratio is less than 70%.

[2.2] Low-temperature fixability The toner obtained in each of the above Examples and Comparative Examples was evaluated for a good fixing region and a low-temperature fixability as follows.
First, an image forming apparatus having a configuration as shown in FIGS. 1 to 5 was prepared except that no fixing device was provided. Using this image forming apparatus, an unfixed image sample having a toner image transferred onto a recording medium (high quality plain paper manufactured by Seiko Epson Corporation) was collected. The solid amount of the sample to be collected was adjusted to an adhesion amount of 0.5 mg / cm ² .

  Next, with the surface temperature of the fixing roller of the fixing device constituting the image forming apparatus set to a predetermined temperature, a recording medium on which the above-described unfixed toner image is transferred is used in a fixing device as shown in FIG. By introducing it inside, the toner image was fixed on the recording medium, and the presence or absence of occurrence of offset after fixing was visually confirmed. In this fixing device, the speed at which the toner passes through the nip portion is set to 150 mm / s.

Similarly, the set temperature on the surface of the fixing roller is sequentially changed within a range of 70 to 160 ° C., and the presence or absence of occurrence of offset at each temperature is confirmed, and the maximum temperature at which the low temperature offset occurs is set as the low temperature offset generation temperature. Evaluation was made according to the following four-stage criteria.
A: Low temperature offset generation temperature is less than 90 ° C.
B: Low temperature offset generation temperature is 90 ° C or higher and lower than 100 ° C.
C: Low temperature offset generation temperature is 100 ° C. or higher and lower than 110 ° C.
D: Low temperature offset generation temperature is 110 ° C. or higher.

[2.3] Preservability The liquid developers obtained in the respective Examples and Comparative Examples were allowed to stand for 6 months in an environment at a temperature of 15 to 25 ° C. Thereafter, the state of the toner in the liquid developer was visually confirmed and evaluated according to the following five criteria.
A: No toner particle floating or coagulation sedimentation is observed.
B: Floating and coagulation sedimentation of toner particles are hardly observed.
C: Slight floating or coagulation sedimentation of toner particles is observed, but as a liquid developer
There is no problem.
D: Floating or coagulation sedimentation of toner particles is clearly observed.
E: Suspension and coagulation sedimentation of toner particles are remarkably observed.

[2.4] Environmental stability (long-term stability)
The liquid developers obtained in the respective Examples and Comparative Examples were allowed to stand for 6 months in an environment of 35 ° C. and a relative humidity of 65%. Thereafter, the state of the liquid developer was observed, and changes in the viscosity, color, acid value, and electrical resistance value before and after being allowed to stand were evaluated according to the following five criteria. The acid value was measured according to JIS K2501. The change in color of the liquid developer was evaluated visually. The viscosity was measured according to JIS Z8809 using a vibration viscometer. In addition, the electric resistance value was measured using a universal electrometer MMAII-17B, a liquid electrode LP-05, and a shield box P-618 (manufactured by Kawaguchi Denki Seisakusho).

A: No change in viscosity / color / acid value / electric resistance value of the liquid developer is observed.
B: Almost no change in viscosity / color / acid value / electric resistance value of the liquid developer is observed.
C: A slight change in viscosity / color / acid value / electric resistance value of the liquid developer is observed, but it is in a range where there is no problem as a liquid developer.
D: A change in viscosity / color / acid value / electric resistance value of the liquid developer is clearly recognized.
E: A change in the viscosity / color / acid value / electric resistance value of the liquid developer is noticeable.

[2.5] Evaluation of blocking resistance of fixed printing surface The toner obtained in each of the above Examples and Comparative Examples was evaluated for blocking resistance (blocking resistance) as follows.
First, an image forming apparatus having a configuration as shown in FIGS. 1 to 6 was prepared. Using this image forming apparatus, a predetermined pattern is formed so that the toner weight of the toner image formed on the recording medium is 0.75 mg / cm ² on the recording medium (high quality plain paper manufactured by Seiko Epson Corporation). A single color toner image was transferred and fixed to obtain a fixed toner image.

The two recording media on which image formation was performed were aligned so that the fixed toner images were in close contact with each other, and a weight of 1.0 kgf / cm ² was applied while placing a weight on the recording medium at a temperature of 55 ° C. The fixed toner images on the recording medium were brought into close contact with each other for 24 hours. Thereafter, the weight was removed from the recording medium, and the recording medium was allowed to cool to room temperature (25 ° C.).
After cooling, the two recording media were peeled off to peel off the fixed toner images that were in close contact with each other. The peeled toner image after peeling was visually confirmed, and the presence or absence of adhered powder, uneven gloss, uneven density, etc. was evaluated according to the following four criteria.

A: Adhered powder, uneven gloss, and uneven density are not observed on the fixed toner image.
B: Adhered powder, uneven gloss, and uneven density are hardly observed on the fixed toner image.
C: Slightly adhered powder, uneven gloss, and uneven density are observed on the fixed toner image.
D: Adhered powder, uneven gloss, and uneven density are clearly recognized on the fixed toner image.
These results are shown in Table 2.

As is clear from Table 2, the liquid developer of the present invention was excellent in fixing characteristics, storage stability, and environmental stability (long-term stability). On the other hand, satisfactory results were not obtained with the liquid developers of the comparative examples.
In addition, the liquid developer obtained in each of the above Examples and Comparative Example 1 was sealed and left at 55 ° C. for 12 hours, and the state of the toner particles in the liquid developer after 12 hours was visually confirmed. As a result, in each of the examples, no floating and aggregation / sedimentation of the toner particles were confirmed, but in Comparative Example 1, it was confirmed that the toner particles were aggregated.
Also, image formation was performed using an application roller without grooves instead of the anilox roller provided in the image forming apparatus as shown in FIG. As a result, when an anilox roller was used as the application roller, a clear toner image with less image unevenness could be obtained.

It is sectional drawing which shows an example of the liquid developing device to which the liquid developer of this invention is applied. FIG. 3 is a cross-sectional view illustrating an example of a fixing device to which the liquid developer of the present invention is applied. 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 ... Photoconductor squeeze roller, 14Y ... Cleaning blade, 15Y ... Developer collection part 16Y ... Static elimination unit 17Y ... Photoconductor cleaning blade 18Y ... Developer recovery unit 20Y ... Development roller 201Y ... Liquid developer layer 21Y ... Development roller cleaning blade 22Y ... Developer compression roller 23Y ... Developer compression roller cleaning blades 30Y, 30M, 30C, 30K ... Development Section 31Y ... Liquid developer storage section 32Y ... Application roller 32Ya ... Groove 32Yb ... Mountain 33Y ... Restriction blade 34Y ... Stirring roller 40 ... Transfer section 41 ... Conveying belt 42 ... Belt drive roller 43 ... Tension roller 44 44M, 44C, 44K ... transfer backup roller 70 ... conveying path 74 ... insulating liquid reservoir 76 ... pump 77 ... filter means 100Y ... developing unit 101Y ... photosensitive member squeeze device F40 ... fixing device F1 ... heat fixing roller (heating roller) F1a ... Column-shaped halogen lamp F1b ... Roller base material F1c ... Elastic body F12 ... Removal blade F2 ... Pressure roller F2a ... Rotating shaft F2b ... Roller base material F2c ... Elastic body F3 ... Heat-resistant belt F4 ... Belt stretch member F4a ... Projection Wall F4f ... Recess F5 ... Recording medium F5a ... Toner image F6 ... Cleaning member F7 ... Frame F9 ... Spring

Claims (9)

Having toner particles mainly composed of a resin material and an insulating liquid;
The insulating liquid contains a fatty acid monoester,
The resin material has a weight average molecular weight Mw of 5000 to 15000, and
In the resin material, a component having a molecular weight of 100,000 or more is 20 wt% or less.   The liquid developer according to claim 1, wherein the insulating liquid contains an aliphatic hydrocarbon liquid and / or silicone oil in addition to the fatty acid monoester.   The liquid developer according to claim 2, wherein the aliphatic hydrocarbon liquid is a saturated hydrocarbon.   The liquid developer according to claim 1, wherein the fatty acid monoester contains a saturated fatty acid having 8 to 16 carbon atoms as a fatty acid component.   The liquid developer according to claim 1, wherein the fatty acid monoester contains an alcohol component having 1 to 4 carbon atoms.   The liquid developer according to claim 1, wherein the content of the fatty acid monoester in the insulating liquid is 25 to 90 wt%.   The liquid developer according to any one of claims 1 to 6, wherein the resin material has a glass transition temperature Tg of 15 to 70 ° C and a softening temperature Tf of 80 to 140 ° C.   The liquid developer according to claim 1, wherein the resin material constituting the toner particles has an ester bond in a chemical structure. 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 has toner particles mainly composed of a resin material, and an insulating liquid. The insulating liquid contains a fatty acid monoester, and the weight average molecular weight Mw of the resin material is: An image forming apparatus, wherein a component having a molecular weight of 5,000 to 15000 and having a molecular weight of 100,000 or more is 20 wt% or less.

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