JP2008225442A - Liquid developer and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid developer having superior fixing characteristics of toner particles to a recording medium and superior dispersion stability of the toner particles, and to provide an image forming apparatus using the above liquid developer. <P>SOLUTION: The liquid developer comprises an insulation liquid containing a fatty acid monoester, and toner particles essentially comprising a polyester resin. It is preferred that the average particle size of the toner particles is in the range of 0.7 to 3 μm, the roundness of the toner particles is in the range of 0.85 to 0.98, and the width S of the particle size distribution of the toner particles is 1.4 or less. It is preferred that the insulation liquid contains an aliphatic hydrocarbon and/or silicone oil in addition to the above fatty acid monoester, and that the proportion of the fatty acid monoester included in the insulation liquid is in the range of 5 to 55 wt.%. <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 toner particle fixing properties to a recording medium and excellent dispersion stability of toner particles, and an image forming apparatus using such a liquid developer Is to provide.

Such an object is achieved by the present invention described below.
The liquid developer of the present invention includes an insulating liquid containing a fatty acid monoester;
And toner particles mainly composed of a polyester resin.
In the liquid developer of the present invention, the toner particles have an average particle size of 0.7 to 3 μm,
The circularity of the toner particles represented by the following formula (I) is 0.85 to 0.98,
The width S of the particle size distribution of the toner particles represented by the following formula (II) is preferably 1.4 or less.
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)
S = [D (90) -D (10)] / D (50) (II)
(However, when the particle size distribution of toner particles is measured from a small particle size, the particle size at the point of X% of the total volume in the cumulative volume is D (X).)

In the liquid developer of the present invention, the insulating liquid preferably contains an aliphatic hydrocarbon and / or silicone oil in addition to the fatty acid monoester.
In the liquid developer of the present invention, the fatty acid monoester content in the insulating liquid is preferably 5 to 55 wt%.
In the liquid developer of the present invention, it is preferable that the fatty acid monoester is unevenly distributed near the surface of the toner particles.
In the liquid developer of the present invention, the fatty acid monoester is preferably an ester of a fatty acid and a monovalent alcohol having 1 to 4 carbon atoms.
In the liquid developer of the present invention, the viscosity measured according to JIS Z8809 using a vibration viscometer at 25 ° C. is preferably 50 to 1000 mPa · s.

The image forming apparatus of the present invention includes a plurality of developing units that form a single color image corresponding to each color using a plurality of liquid developers having different colors,
By transporting the recording medium, the plurality of monochrome images formed by the plurality of developing units are sequentially transferred to the recording medium, and an unfixed color image formed by superimposing the transferred plurality of monochrome images is recorded. A transfer portion formed on the medium;
A fixing unit for fixing the unfixed color image on the recording medium,
The liquid developer includes an insulating liquid containing a fatty acid monoester and toner particles mainly composed of a polyester resin.
The image forming apparatus of the present invention includes a plurality of developing units that form a single color image corresponding to each color using a plurality of liquid developers having different colors,
An intermediate transfer unit that sequentially transfers a plurality of the single-color images formed by the plurality of developing units, and forms an intermediate transfer image formed by superimposing the transferred single-color images;
A secondary transfer unit that transfers the intermediate transfer image to the recording medium and forms an unfixed color image on the recording medium;
A fixing unit for fixing the unfixed color image on the recording medium,
The liquid developer includes an insulating liquid containing a fatty acid monoester and toner particles mainly composed of a polyester resin.

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

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

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

Hereinafter, preferred embodiments of the liquid developer and the image forming apparatus of the present invention will be described in detail.
<Liquid developer>
First, the liquid developer of the present invention will be described.
The liquid developer of the present invention is one in which toner particles mainly composed of a polyester resin 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 an effect of plasticizing the polyester resin constituting the toner particles (plasticizer effect) at the time of fixing. Due to this plasticizer effect, for example, when paper is used as the recording medium, the toner particles easily enter the gaps between the paper fibers, so that the fixing characteristics between the paper and the toner particles are excellent. In addition, this plasticizer effect melts the toner particles even at a relatively low temperature and enables fixing to a recording medium, and therefore can be suitably applied to image formation at a low temperature and at 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 transferred to the recording medium when the toner particles come into contact with the recording medium during fixing. Quickly penetrate. Along with the penetration of the fatty acid monoester, some of the toner particles (polyester resin) melted by the heat at the time of fixing penetrate into the inside of the recording medium, the anchor effect works, and the fixing characteristics between paper and toner particles are improved. To do.

  As described above, the fatty acid monoester exhibits an effect of plasticizing the polyester resin constituting the toner particles at the time of fixing. That is, in a liquid developer containing a fatty acid monoester and toner particles containing a polyester resin as a main component, the fatty acid monoester suitably penetrates into the toner particles at the time of fixing and exhibits the plasticizing effect as described above. . On the other hand, during storage, permeation of the fatty acid monoester into the toner particles is suppressed. As a result, aggregation of the toner particles during storage can be reliably prevented, and the storage stability of the liquid developer can be improved as well as the fixing characteristics of the toner particles to the recording medium.

By the way, when forming a full-color image, if there is a large variation in viscosity between the liquid developers corresponding to each color, the color developability of each color will be different in the formed image, and a clear image cannot be obtained. There is a problem.
On the other hand, by including the fatty acid monoester as in the present invention, the dispersion of the viscosity between the liquid developers corresponding to the respective colors can be made relatively small, and a balance is achieved between the respective colors. A clear image can be formed. In other words, since the variation in the viscosity between the liquid developers corresponding to each color is small, the color developability of each color in the formed image can be easily adjusted under the development conditions.

  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 an increase in viscosity, discoloration, and a decrease in electrical resistance over a long period of time, and the storage stability of the liquid developer is particularly high. It will be 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 of the liquid developer is 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 may be included as a component which comprises an insulating liquid.
Aliphatic hydrocarbons are liquids mainly composed of aliphatic hydrocarbons and have high electrical resistance and are chemically stable liquids. For this reason, the liquid developer using the aliphatic hydrocarbon has particularly excellent charging characteristics and storage stability, and the obtained toner image is particularly clear with few defects. In addition, aliphatic hydrocarbons have a high affinity with fatty acid monoesters and easily penetrate into recording media such as paper. Therefore, at the time of fixing, the insulating liquid containing the aliphatic hydrocarbon 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. Aliphatic hydrocarbons are liquids that absorb less moisture during storage. For this reason, when an aliphatic hydrocarbon is used as an insulating liquid simultaneously with a fatty acid monoester, the insulating liquid can be suitably prevented from absorbing moisture during storage, and the insulating liquid is more preferably denatured (deteriorated). Can be prevented. For this reason, the liquid developer is particularly excellent in storage stability.

  The aliphatic hydrocarbon 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 Fluid Fin (Wako Pure Chemical Industries), octane, isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, cyclohexane, cyclooctane, cyclodecane, etc. are used, and among these, one kind or a combination of two or more kinds is used. be able to.

Further, such aliphatic hydrocarbons are preferably saturated hydrocarbons. Aliphatic hydrocarbons, which are saturated hydrocarbons, are particularly chemically stable liquids, and the electric resistance of the liquid developer can be maintained high over a long period of time.
Moreover, it is preferable that the aliphatic hydrocarbon which comprises an aliphatic hydrocarbon has the branched chain of a hydrocarbon group. Thereby, the aliphatic hydrocarbon becomes chemically more stable, and the storage stability of the liquid developer using such an aliphatic hydrocarbon becomes particularly excellent. This is considered to be because the structure of the aliphatic hydrocarbon constituting the aliphatic hydrocarbon 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 polyester resin constituting the toner particles. For this reason, in liquid developers containing silicone oil and fatty acid monoesters, fatty acid monoesters that have a high affinity for polyester resins permeate the surface of the toner particles selectively, and exhibit a particularly favorable plastic effect 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.

  Moreover, it is preferable that content of the fatty acid monoester in an insulating liquid is 5-55 wt%, It is more preferable that it is 10-50 wt%, It is further more preferable that it is 20-50 wt%. When the content of the fatty acid monoester is within the above range, the fatty acid monoester is likely to adhere to the toner particles, and the insulating liquid can be suitably infiltrated into the recording medium, resulting in particularly excellent fixing strength. Is obtained. Furthermore, a fatty acid monoester sufficient to plasticize the toner particles during fixing adheres to the surface of the toner particles, and the toner particles are plasticized and melted. As a result, a particularly excellent glossy image with a desired color tone is more reliably obtained. Is obtained.

  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 charging characteristics 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-mentioned dispersants, polyamine fatty acid polycondensate is a component having a particularly high affinity with the polyester resin constituting the toner particles, and therefore adheres to the vicinity of the toner particle surface and causes aggregation (blocking) between the toner particles. It can be effectively prevented. Furthermore, the polyamine fatty acid polycondensation polymer has high affinity with the fatty acid monoester. As a result, the dispersibility of the toner particles can be made particularly high. In addition, the polyamine fatty acid condensation polymer can increase the permeability of the fatty acid monoester to the toner particles, and the plastic effect by the fatty acid monoester can be made more remarkable. As a result, the toner particles can be more firmly fixed on the recording medium, and the gloss of the formed image can be made more excellent.

Further, the polyamine aliphatic polycondensation polymer is a component having a positively chargeable characteristic. By attaching such a component near the surface of the toner particles, the charging characteristics of the toner particles can be made higher.
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)]
1. Polyester Resin The toner particles (toner) constituting the liquid developer of the present invention are mainly composed of a polyester resin.
The polyester resin has high transparency, and when used as a binder resin, the color developability of the obtained image can be increased.

  In addition, the polyester resin has a very high affinity with the fatty acid monoester as described above due to the similar chemical structure. For this reason, the dispersion stability of the toner particles in the liquid developer can be made excellent. Further, since the polyester resin has high affinity with the fatty acid monoester, the fatty acid monoester as described above can be suitably attached to the surface of the toner particles. As described above, the fatty acid monoester adheres to the surface of the toner particles, so that the plastic effect as described above is more prominent, the toner particles easily penetrate into the recording medium at the time of fixing, and the toner particles melt. It becomes easy. As a result, the color tone is excellent, and the obtained toner image is smooth with no unevenness, and the gloss (gloss) of the formed image can be improved.

A polyester resin is a resin synthesized by dehydration condensation of a polybasic acid and a polyhydric alcohol.
Examples of the polybasic acid include aromatic carboxylic acids such as terephthalic acid, isophthalic acid, phthalic anhydride, trimellitic anhydride, pyromellitic acid, and naphthalenedicarboxylic acid; maleic anhydride, fumaric acid, succinic acid, alkenyl succinic anhydride Examples thereof include aliphatic carboxylic acids such as acid and adipic acid; alicyclic carboxylic acids such as cyclohexanedicarboxylic acid, and the like, and one or more of these can be used in combination. Among these polybasic acids, it is preferable to use an aromatic carboxylic acid. Thus, the toner particles can be easily plasticized with the fatty acid monoester as described above.

  Examples of the polyhydric alcohol include ethylene diol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, glycerin, trimethylolpropane, pentaerythritol and other aliphatic diols, cyclohexanediol, Examples include cyclohexanedimethanol, alicyclic diols such as hydrogenated bisphenol A, aromatic diols such as ethylene oxide adducts of bisphenol A, propylene oxide adducts of bisphenol A, and one or two of these. The above can be used in combination. These polyhydric alcohols can be used alone or in combination of two or more. Of these polyhydric alcohols, aromatic diols and alicyclic diols are preferably used, and aromatic diols are more preferably used. Thus, the toner particles can be easily plasticized with the fatty acid monoester as described above.

The polyester resin preferably has an amino group in the molecule. This facilitates plasticization more easily by the fatty acid monoester and also improves the positive chargeability.
The acid value of the polyester resin can be adjusted by adding a monocarboxylic acid and / or monoalcohol to the resulting polyester resin to esterify the hydroxyl group and / or carboxyl group at the polymerization terminal. it can. Examples of such monocarboxylic acid include acetic acid, acetic anhydride, benzoic acid, trichloroacetic acid, trifluoroacetic acid, and propionic anhydride. Examples of the monoalcohol include methanol, ethanol, propanol, octanol, 2-ethylhexanol, trifluoroethanol, trichloroethanol, hexafluoroisopropanol, and phenol.

The acid value of the polyester resin is preferably 15 KOH mg / g or less, and more preferably 0.5 to 12 KOH mg / g.
The glass transition point of the polyester resin is preferably 15 to 70 ° C, more preferably 20 to 55 ° C. As a result, the fixing property of the liquid developer at a low temperature can be improved, and the gloss of the formed image can be improved.

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

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.]
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 further preferably 0.8 to 2 μm. preferable. 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, the toner particles can be well dispersed in the insulating liquid, and the storage stability of the liquid developer can be increased.

  On the other hand, if the average particle size of the toner particles is less than the lower limit value, the variation in characteristics among the toner particles increases, and the reliability of the liquid developer as a whole cannot be made high. Developability and transferability may not be obtained. In addition, toner particles may aggregate during storage, and the storage stability of the liquid developer may not be sufficient. On the other hand, when the average particle size of the toner particles exceeds the upper limit, the resolution of the formed toner image may not be sufficiently high. In addition, sedimentation tends to occur during storage of the liquid developer, and the storage stability of the liquid developer may not be sufficient. In the present specification, “average particle diameter” refers to an average particle diameter based on volume.

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 0.85 to 0.98, and preferably 0.90. More preferably, it is -0.98, and it is further more preferable that it is 0.92-0.98.
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)

If the toner particles have such an appropriate degree of circularity, an appropriate amount of fatty acid monoester can be held near the surface of the toner particles, so that the plasticizer effect as described above can be more effectively exhibited. Can do. As a result, it is possible to improve the fixing characteristics of the toner particles to the recording medium, and to further improve the gloss of the formed image. In addition, the presence of an appropriate amount of fatty acid monoester near the surface of the toner particles facilitates the dispersion of the toner particles in an insulating liquid during storage, and the dispersion stability of the liquid developer containing the toner particles is particularly excellent. Can be. Further, it is possible to make the toner particle transfer efficiency and mechanical strength particularly excellent while making the particle diameter of the toner particles sufficiently small.
The standard deviation of the average circularity between the toner particles constituting the liquid developer is preferably 0.15 or less, more preferably 0.001 to 0.10, and 0.001 to 0. More preferably, .05. As a result, variations in characteristics such as charging characteristics and fixing strength among the toner particles are particularly reduced, and the reliability of the entire liquid developer is further improved.

Further, the width S of the particle size distribution of the toner particles represented by the following formula (II) is preferably 1.4 or less, more preferably 1.3 or less, and further preferably 1.2 or less.
S = [D (90) -D (10)] / D (50) (II)
(However, when the particle size distribution of toner particles is measured from a small particle size, the particle size at the point of X% of the total volume in the cumulative volume is D (X).)

  When the width S of the particle size distribution of the toner particles is within the above range, the variation in the particle size among the toner particles is reduced, and when the liquid developer is pumped from the developing container to the application roller or the like, Since the gap becomes large, an appropriate amount of insulating liquid adheres to the toner particles, and efficient transfer and development become possible. In addition, since an appropriate insulating liquid (fatty acid monoester) is present between the toner particles at the time of fixing, excellent fixing strength can be obtained. In addition, since there is little variation in particle size among the toner particles, pressure and heat are easily applied to the toner particles at the time of fixing, and the toner particles are melted uniformly, so that an image of a desired color tone can be obtained. Obtainable. Furthermore, since the toner particles are uniformly melted, the smoothness of the toner image becomes excellent, and as a result, the glossiness of the toner image becomes high.

  If the width S of the particle size distribution of the toner particles is larger than the above upper limit value, the variation in the particle size among the toner particles becomes large, and when the liquid developer is pumped from the developing container to the application roller or the like, there is a gap between the toner particles. Therefore, the amount of the insulating liquid adhering to the toner particles is insufficient, and efficient transfer and development become difficult. Further, pressure and heat are not uniformly applied to the toner particles at the time of fixing, and the toner particles cannot be melted uniformly, so that an image having a target color tone cannot be obtained. Further, the smoothness of the toner image is deteriorated, and as a result, the glossiness of the toner image becomes low.

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

  Further, the viscosity of the liquid developer is preferably 20 to 400 mPa · s, and more preferably 30 to 350 mPa · s. When the viscosity of the liquid developer is in such a range, the dispersibility of the toner particles can be increased, and in the image forming apparatus as described later, the liquid developer is more evenly distributed on the application roller. In addition, dripping of the liquid developer from the application roller or the like can be more effectively prevented.

In the case where a plurality of color liquid developers are used, the difference between the viscosity of the liquid developer having the highest viscosity and the viscosity of the liquid developer having the lowest viscosity is preferably 250 mPa · s or less, and 220 mPa · s. The following is more preferable. Thereby, a clear image can be formed.
Further, the electric resistance at room temperature (20 ° C.) of the liquid developer composed of the components as described above is preferably 1 × 10 ¹² Ωcm or more, and more preferably 2 × 10 ¹² Ωcm or more. preferable.

<< Method for Producing Liquid Developer >>
Next, a preferred embodiment of the method for producing a liquid developer of the present invention will be described.
In this embodiment, the insulating liquid is described as including a fatty acid monoester and other components.
The method for producing a liquid developer according to the present embodiment includes a step of associating resin fine particles mainly composed of a polyester resin to obtain an associated particle, and pulverizing the associated particle in a fatty acid monoester, thereby producing toner particles. And a mixing step of mixing the obtained toner particles with 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 polyester resin are associated will be described.
Any method may be used to prepare the associated particles, but in the present embodiment, a dispersoid (mainly composed of a polyester resin (toner constituent material) in an aqueous dispersion medium composed of an aqueous liquid). An aqueous emulsion in which (fine particles) are dispersed is obtained, and the dispersoids in the aqueous emulsion are associated to obtain associated particles.

(Aqueous emulsion)
First, the aqueous emulsion used in this embodiment will be described.
The aqueous emulsion obtained in the aqueous emulsion preparation step described below has a structure in which dispersoids (fine particles) are finely dispersed in an aqueous dispersion medium composed of an aqueous liquid.

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

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

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

-Dispersoid (fine particles)-
The dispersoid contains the components constituting the toner particles as described above.
The dispersoid may contain a solvent that dissolves at least a part of the components. Thereby, for example, the fluidity of the dispersoid in the aqueous emulsion can be increased, and the dispersoid in the aqueous emulsion can have a relatively small particle size and small variation in size. it can. As a result, the toner particles in the finally obtained liquid developer have a small variation in size and shape between the particles, and have a high degree of circularity.

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

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

  When an emulsifying dispersant is used, the dispersibility of the dispersoid is improved, and the dispersion of the dispersoid in the aqueous emulsion is relatively easily reduced in size and size. Can be substantially spherical. As a result, the final liquid developer can be obtained as a toner composed of toner particles having a substantially spherical shape, a uniform shape, and a uniform size. Here, examples of the emulsifying dispersant include known emulsifiers and dispersants.

The content of the emulsifier and the dispersant in the aqueous emulsion is not particularly limited, but is preferably 3.0 wt% or less, and more preferably 0.01 to 1.0 wt%.
Further, the aqueous emulsion may contain a dispersion aid.
Examples of the dispersion aid include anions, cations, and nonionic surfactants.

The dispersing aid is preferably used in combination with a dispersing agent. When the aqueous emulsion contains a dispersant, the content of the dispersion aid in the aqueous emulsion is not particularly limited, but is preferably 2.0 wt% or less, and is 0.005 to 0.5 wt%. Is more preferable.
In the aqueous emulsion, components other than the dispersoid may be dispersed as an insoluble matter. For example, inorganic fine powders such as silica, titanium oxide, and iron oxide, and organic fine powders such as fatty acids and fatty acid metal salts may be dispersed in the aqueous emulsion.

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

(Aqueous emulsion preparation process)
The aqueous emulsion as described above can be prepared, for example, as follows (aqueous emulsion preparation step).
First, an aqueous solution in which a dispersant is added to the aqueous liquid as necessary is prepared.
On the other hand, a resin liquid containing a polyester resin as the main component of the toner as described above is prepared. For the preparation of the resin liquid, for example, the above-described solvent may be used in addition to the polyester resin. The resin liquid may be a molten liquid obtained by heating a polyester resin. For preparing the resin liquid, for example, a kneaded product obtained by kneading a toner material such as a polyester resin 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, a polyester resin or the like is effective around the pigment particles by being kneaded in advance before being dispersed in the solvent. Thus, the dispersibility of the pigment in the solvent is improved (particularly fine dispersion in the solvent is possible), and the color developability of the finally obtained toner is also improved. For this reason, in the case where the constituent material of the toner contains a component that is poor in dispersibility in the aqueous dispersion medium of the aqueous emulsion or a component inferior in solubility in the solvent contained in the dispersion medium of the aqueous emulsion. Even so, the dispersibility of the dispersoid in the aqueous emulsion can be made particularly excellent.

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

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

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

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

In addition, this step may be performed immediately after the preparation of the aqueous emulsion, or after adjustment of the aqueous emulsion, the aqueous emulsion may be stored, and then this step may be performed. In the latter case, the storage period is not particularly limited, but if it is within 10 days, the particle size distribution of the associated particles obtained can be made particularly narrow.
Then, after associating, the associated particles are obtained by filtration, washing, drying and the like.
The average particle size of the obtained associated particles is preferably 0.1 to 7 μm, and more preferably 0.5 to 3 μm. Thereby, the particle diameter of the toner particles finally obtained can be made moderate.

[Crushing process]
Next, the associated particles obtained as described above are crushed in a fatty acid monoester (pulverization step). Thereby, a toner particle dispersion liquid in which toner particles are dispersed in a fatty acid monoester is obtained.
As described above, the fatty acid monoester is a component having high affinity with the polyester resin. 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, by crushing the associated particles in the fatty acid monoester in this manner, the fatty acid monoester can be unevenly distributed (adsorbed) in the vicinity of the surface of the toner particles in the finally obtained liquid developer. Thus, by making the fatty acid monoester unevenly distributed in the vicinity of the surface of the toner particles, the plastic effect as described above can be made more remarkable. As a result, the toner particles can easily enter through the gaps between the paper fibers (recording medium), so that the fixing strength of the toner particles can be made particularly excellent, and the gloss (gloss) of the formed image is particularly excellent. Can be.
In addition, since it is pulverized in a liquid called fatty acid monoester, it is possible to prevent generation of toner particles coarsened due to aggregation or the like.
Further, the obtained toner particles have irregularities derived from the fine particles (dispersoid) on the surface thereof, so that the fatty acid monoester can be reliably retained on the irregularities.

Further, in the present embodiment, toner particles are obtained by crushing the associated particles, so that fine particles (particles extremely smaller than particles of a target size) are obtained as compared with conventional pulverization methods and wet pulverization methods. Generation | occurrence | production can be prevented effectively. As a result, it is possible to effectively prevent a decrease in charging characteristics of the liquid developer due to fine powder.
In addition, since the fatty acid monoester has a relatively low viscosity, it easily enters between the fine particles (dispersoids) constituting the associated particles, and the associated particles can be suitably crushed.

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

[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 is obtained in which toner particles mainly composed of a polyester resin are dispersed in an insulating liquid containing a fatty acid monoester.

In the present embodiment, the association particles are crushed in the fatty acid monoester. However, as the liquid for pulverizing the association particles, a mixed solution of the 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.
Further, in the present embodiment, the insulating liquid has been described as including a fatty acid monoester and other components. However, in the case where the insulating liquid is composed only of a fatty acid monoester, the above-described mixing step. The liquid developer can be manufactured without the above.

<< First Embodiment of Image Forming Apparatus >>
Next, a first 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 a first embodiment 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 a schematic perspective view showing a coating roller included in the image forming apparatus shown in FIG. 1, FIG. 4 is an enlarged schematic view of the coating roller shown in FIG. 3, and FIG. 5 is a diagram of toner particles in the liquid developer layer on the developing roller. FIG. 6 is a 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. Irradiation is performed on 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 the present embodiment, the groove pitch P is about 80 μm, the crest width is about 40 μm, the top width PI1 of the groove 32Ya is about 50 μm, the bottom surface width PI2 is about 30 μm, the depth He of the groove 32Ya is about 20 μm, and the crest. The height Hc of 32Yb is configured to be about 30 μm, and an inclined portion SL that is monotonously formed from the center of the peak 32Yb to the bottom of the groove 32Ya is formed. In the present embodiment, the surface roughness Rz of the peak 32Yb is R1a≈1.0 μm, and the surface roughness Rz of the groove 32Ya is R2a≈1.0 μm.

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

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

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

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

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

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

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

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

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

Next, the fixing unit will be described.
The fixing unit F40 fixes the unfixed toner image F5a formed in the above-described developing unit, transfer unit, and the like on the recording medium F5.
As shown in FIG. 6, the fixing unit F40 includes a heat fixing roller F1, a pressure roller F2, a heat-resistant belt F3, a belt stretching member F4, a cleaning member F6, a frame F7, and a spring F9. is doing.

The heat fixing roller (fixing roller) F1 includes a roller base material F1b made of a pipe material, an elastic body F1c covering the outer periphery thereof, and a columnar halogen lamp F1a as a heating source inside the roller base material F1b. It can be rotated counterclockwise as indicated by an arrow in the figure.
A PFA layer is provided on the surface layer of the elastic body F1c of the heat fixing roller F1. As a result, the elastic bodies F1c and 2c have different thicknesses, but the elastic bodies F1c and 2c are substantially uniformly elastically deformed to form a so-called horizontal nip, and with respect to the peripheral speed of the heat fixing roller F1. Since there is no difference in the conveyance speed of the heat-resistant belt F3 or the recording medium F5, which will be described later, extremely stable image fixing is possible.

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

The pressure roller F2 is arranged to face the heat fixing roller F1, and is configured to apply pressure to the recording medium F5 on which the unfixed toner image F5a is formed via a heat-resistant belt F3 described later. Has been.
Further, the pressure roller F2 has a roller base material F2b made of a pipe material and an elastic body F2c covering the outer periphery thereof, and is rotatable in the clockwise direction indicated by an arrow in the drawing.

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

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

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

  The belt stretching member F4 is 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.

<< Second Embodiment of Image Forming Apparatus >>
Next, a second embodiment of the image forming apparatus of the present invention will be described.
FIG. 7 is a schematic view showing a second embodiment of an image forming apparatus to which the liquid developer of the present invention is applied, and FIG. 8 is an enlarged view of a part of the image forming apparatus shown in FIG.
As shown in FIGS. 7 and 8, the image forming apparatus 1000 ′ includes four developing units 30Y ′, 30M ′, 30C ′, and 30K ′, an intermediate transfer unit 40 ′, a secondary transfer unit (secondary transfer unit). ) 60 ′, a fixing unit (fixing device) F40, and four liquid developer replenishing units 80Y, 80M, 80C, and 80K.
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. 8, the developing unit 30Y ′ includes a photoconductor 10Y ′ as an example of an image carrier, a charging roller 11Y ′, an exposure unit 12Y ′, and a developer along the rotation direction of the photoconductor 10Y ′. It has a unit 100Y ′, a photoreceptor squeeze device 101Y ′, a primary transfer backup roller 51Y ′, a charge removal unit 16Y ′, a photoreceptor cleaning blade 17Y ′, and a developer recovery unit 18Y ′.

The photoconductor 10Y ′ is formed on a cylindrical base material and an outer peripheral surface thereof, and has a photosensitive layer made of a material such as amorphous silicon, and is rotatable about a central axis. Rotates clockwise as indicated by the arrow in FIG.
The photoreceptor 10Y ′ is supplied with a liquid developer by a developing unit 100Y ′, which will be 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 a modulated laser is generated based on an image signal input from a host computer (not shown) such as a personal computer or a word processor. Irradiation is performed on the charged 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 photoreceptor squeeze device 101Y ′ is disposed on the downstream side of the developing unit 100Y ′ in the rotation direction so as to face the photoreceptor 10Y ′, and presses the photoreceptor squeeze roller 13Y ′ and the photoreceptor squeeze roller 13Y ′. The cleaning blade 14Y ′ that removes the liquid developer that comes in contact with the surface and the developer collecting unit 15Y ′ that collects the removed liquid developer are configured. The photoreceptor squeeze device 101Y ′ has a function of collecting excess carrier (insulating liquid) and originally unnecessary fog toner from the developer developed on the photoreceptor 10Y ′, and increasing the ratio of toner particles in the visible image. .

The primary transfer backup roller 51Y ′ is a device for transferring a single color image formed on the photoreceptor 10Y ′ to an intermediate transfer unit 40 ′ described later.
The neutralization unit 16Y ′ is a device that removes residual charges on the photoreceptor 10Y ′ after the intermediate transfer image is transferred onto the intermediate transfer portion 40 ′ by the primary transfer backup roller 51Y ′.

The photoreceptor cleaning blade 17Y ′ is a rubber member in contact with the surface of the photoreceptor 10Y ′, and after the image is transferred onto the intermediate transfer portion 40 ′ by the primary transfer backup roller 51Y ′, the photoreceptor 10Y. 'Has the function of scraping off and removing the liquid developer remaining on the top.
The developer recovery unit 18Y ′ has a function of recovering the liquid developer removed by the photoreceptor cleaning blade 17Y ′.

  The intermediate transfer portion 40 ′ is an endless elastic belt member, and is stretched around a belt driving roller 41 ′ and a pair of driven rollers 42 ′ and 43 ′ to which a driving force of a motor (not shown) is transmitted. Further, the intermediate transfer section 40 ′ is counteracted by the belt drive roller 41 ′ while contacting the photoreceptors 10Y ′, 10M ′, 10C ′, and 10K ′ with the primary transfer backup rollers 51Y ′, 51M ′, 51C ′, and 51K ′. It is driven to rotate clockwise.

Further, the intermediate transfer portion 40 ′ is applied with a predetermined tension by the tension roller 44 ′, and the slack is removed. The tension roller 44 'is downstream of one driven roller 42' in the direction of rotation (movement) of the intermediate transfer unit 40 'and upstream of the other driven roller 43' in the direction of rotation (movement) of the intermediate transfer unit 40 '. It is arranged.
Single-color images corresponding to the respective colors formed by the developing units 30Y ′, 30M ′, 30C ′, and 30K ′ by the primary transfer backup rollers 51Y ′, 51M ′, 51C ′, and 51K ′ are formed on the intermediate transfer unit 40 ′. The images are sequentially transferred, and single color images corresponding to the respective colors are superimposed. As a result, a full-color developer image (intermediate transfer image) is formed on the intermediate transfer portion 40 ′.

  In the intermediate transfer unit 40 ′, the single-color images formed on the plurality of photoconductors 10Y ′, 10M ′, 10C ′, and 10K ′ are sequentially secondarily transferred and overlapped and carried, and a secondary transfer unit described later. At 60 ', the images are collectively transferred to a recording medium F5 such as paper, film, cloth or the like. Therefore, when the toner image is transferred to the recording medium F5 in the secondary transfer process, even if the surface of the recording medium F5 is a sheet material that is not smooth due to fiber or the like, the secondary transfer characteristics follow the surface of the non-smooth sheet material. An elastic belt member is employed as means for improving the above.

The intermediate transfer unit 40 ′ is provided with a cleaning device including an intermediate transfer unit cleaning blade 46 ′, a developer recovery unit 47 ′, and a non-contact type bias applying member 48 ′.
The intermediate transfer portion cleaning blade 46 ′ and the developer recovery portion 47 ′ are arranged on the driven roller 43 ′ side.
The intermediate transfer unit cleaning blade 46 ′ scrapes off the liquid developer adhering to the intermediate transfer unit 40 ′ after the image is transferred onto the recording medium F5 by the secondary transfer unit (secondary transfer unit) 60 ′. It has a function to remove.
The developer recovery unit 47 ′ has a function of recovering the liquid developer removed by the intermediate transfer unit cleaning blade 46 ′.

  The non-contact type bias applying member 48 ′ is disposed away from the intermediate transfer portion 40 ′ at a position facing the tension roller 44 ′. The non-contact type bias applying member 48 ′ applies a bias voltage having a polarity opposite to that of the toner to the liquid developer toner (solid content) remaining on the intermediate transfer portion 40 ′ after the secondary transfer. As a result, the toner is discharged, and the electrostatic adhesion force of the toner to the intermediate transfer portion 40 ′ is reduced. In this example, a corona charger is used as the non-contact type bias applying member 48 '.

  Note that the non-contact type bias applying member 48 ′ is not necessarily disposed at a position facing the tension roller 44 ′. For example, the position between the driven roller 42 ′ and the tension roller 44 ′, the driven roller 42 ′. Further, it can be disposed at an arbitrary position on the downstream side in the moving direction of the intermediate transfer portion and on the upstream side of the driven roller 43 ′ in the moving direction of the intermediate transfer portion. As the non-contact type bias applying member 48 ′, a known non-contact type charger other than the corona charger can be used.

Further, an intermediate transfer unit squeeze device 52Y ′ is arranged downstream of the primary transfer backup roller 51Y ′ in the moving direction of the intermediate transfer unit 40 ′.
This intermediate transfer portion squeeze device 52Y ′ is a means for removing excess insulating liquid from the transferred liquid developer when the liquid developer transferred onto the intermediate transfer portion 40 ′ has not reached the desired dispersion state. Is provided.

The intermediate transfer unit squeeze device 52Y ′ includes an intermediate transfer unit squeeze roller 53Y ′, an intermediate transfer unit squeeze cleaning blade 55Y ′ that presses and slides against the intermediate transfer unit squeeze roller 53Y ′, and an intermediate transfer unit squeeze cleaning blade. The developer collecting unit 56Y ′ collects the liquid developer removed at 55Y ′.
The intermediate transfer unit squeeze device 52Y ′ has a function of recovering excess carrier from the developer primarily transferred to the intermediate transfer unit 40 ′, increasing the toner particle ratio in the visible image, and recovering originally unnecessary fog toner. Have

  The secondary transfer unit 60 ′ includes a pair of secondary transfer rollers arranged at a predetermined interval along the transfer material moving direction. Of the pair of secondary transfer rollers, the secondary transfer roller disposed on the upstream side in the moving direction of the intermediate transfer portion 40 ′ is the upstream secondary transfer roller 61 ′. The upstream secondary transfer roller 61 'can be brought into pressure contact with the belt driving roller 41' via the intermediate transfer portion 40 '.

Of the pair of secondary transfer rollers, the secondary transfer roller disposed downstream in the moving direction of the transfer material is the downstream secondary transfer roller 62 ′. The downstream secondary transfer roller 62 ′ can be brought into pressure contact with the driven roller 42 ′ via the intermediate transfer portion 40 ′.
That is, the upstream side secondary transfer roller 61 ′ and the downstream side secondary transfer roller 62 ′ bring the recording medium F5 into contact with the intermediate transfer portion 40 ′ hung on the belt driving roller 41 ′ and the driven roller 42 ′, respectively. Then, the intermediate transfer image formed on the intermediate transfer portion 40 ′ by color overlap is secondarily transferred to the recording medium F5.

  In this case, the belt driving roller 41 ′ and the driven roller 42 ′ also function as backup rollers for the upstream side secondary transfer roller 61 ′ and the downstream side secondary transfer roller 62 ′, respectively. That is, the belt driving roller 41 'is also used as an upstream backup roller disposed upstream of the driven roller 42' in the moving direction of the recording medium F5 in the secondary transfer unit 60 '. The driven roller 42 ′ is also used as a downstream backup roller disposed downstream of the belt driving roller 41 ′ in the moving direction of the recording medium F 5 in the secondary transfer unit 60 ′.

  Accordingly, the recording medium F5 conveyed to the secondary transfer unit 60 ′ is moved from the pressure contact start position (nip start position) between the upstream secondary transfer roller 61 ′ and the belt driving roller 41 ′ to the downstream secondary transfer roller 62. It is in close contact with the intermediate transfer belt in a predetermined movement region of the transfer material up to the pressure contact end position (nip end position) between 'and the driven roller 42'. As a result, the full-color intermediate transfer image on the intermediate transfer portion 40 ′ is secondarily transferred to the recording medium F 5 in close contact with the intermediate transfer portion 40 ′ over a predetermined time, so that good secondary transfer is performed.

Further, the secondary transfer unit 60 ′ includes a secondary transfer roller cleaning blade 63 ′ and a developer recovery unit 64 ′ with respect to the secondary transfer roller 61 ′. Further, the secondary transfer unit 60 ′ includes a secondary transfer roller cleaning blade 65 ′ and a developer recovery unit 66 ′ with respect to the secondary transfer roller 62 ′. The secondary transfer roller cleaning blades 63 ′ and 65 ′ are in contact with the secondary transfer rollers 61 ′ and 62 ′, respectively, and the liquid development remaining on the surfaces of the secondary transfer rollers 61 ′ and 62 ′ after the secondary transfer. Scrape off the agent. Further, each developer collecting section 64 ′, 66 ′ collects the liquid developer scraped off from each secondary transfer roller 61 ′, 62 ′ by each secondary transfer roller cleaning blade 63 ′, 65 ′. Store.
The toner image (transfer image) F5a transferred onto the recording medium F5 by the secondary transfer unit 60 ′ is sent to the fixing unit (fixing device) F40 as described above to be 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. 8, the developing unit 100Y ′ includes a liquid developer reservoir 31Y ′, a coating roller 32Y ′, a regulating blade 33Y ′, a developer stirring roller 34Y ′, a developing roller 20Y ′, and a developing roller. It has a cleaning blade 21Y ′ and a corona discharger (compression means) 23Y ′.

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 application roller 32Y ′ has a function of supplying a liquid developer to the development roller 20Y ′.
The application roller 32Y ′ is called a so-called anilox roller in which grooves are uniformly and spirally formed on the surface of a metallic roller such as iron and nickel-plated, and its diameter is about 25 mm. is there. In the present embodiment, as in the above-described embodiment, a plurality of grooves are formed obliquely with respect to the rotation direction of the application roller 32Y ′ by so-called cutting or rolling. The application roller 32Y ′ contacts the liquid developer while rotating counterclockwise, thereby supporting the liquid developer in the liquid developer storage unit 31Y ′ in the groove, and The toner is conveyed to the developing roller 20Y ′.

  The regulating blade 33Y 'contacts the surface of the coating roller 32Y' and regulates the amount of liquid developer on the coating roller 32Y '. In other words, the regulation blade 33Y 'plays a role of scraping off excess liquid developer on the application roller 32Y' and measuring the liquid developer on the application roller 32Y 'supplied to the development roller 20Y'. The regulation blade 33Y 'is made of urethane rubber as an elastic body, and is supported by a regulation blade support member made of metal such as iron. The regulation blade 33Y 'is provided on the side where the application roller 32Y' rotates and advances from the liquid developer (that is, the right side in FIG. 8). 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 application roller 32Y ′ (about 77 degrees) is described later. It is lower than the hardness (about 85 degrees) of the pressure contact portion of the 20Y ′ elastic body layer to the surface of the application roller 32Y ′. Further, the excess liquid developer thus scraped off is collected in the liquid developer storage unit 31Y ′ and reused.

The developer stirring roller 34Y ′ has a function of stirring the liquid developer in a uniformly dispersed state. Thus, even when a plurality of toner particles 1 are aggregated, the toner particles 1 can be suitably dispersed. In particular, the toner particles 1 can be suitably dispersed even when the liquid developer once used is reused.
In the liquid developer storage unit 31Y ′, the toner particles 1 in the liquid developer have a positive charge, and the liquid developer is stirred by the developer stirring roller 34Y ′ to be in a uniformly dispersed state. As the roller 32Y ′ rotates, it is pumped up from the liquid developer reservoir 31Y, and 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 transports it to the developing position facing the photoreceptor 10Y ′ in order to develop the latent image carried on the photoreceptor 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 periphery 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 each of the application roller 32Y ′ and the photoreceptor 10Y ′ in a state of being elastically deformed 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. 8) opposite to the rotation direction of the photoconductor 10Y ′ (clockwise in FIG. 8). 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 corona discharger (compression unit) 23Y 'is a device having a function of compressing the toner of the liquid developer carried on the developing roller 20Y'. In other words, the corona discharger 23Y ′ applies the electric field having the same polarity as that of 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 in the vicinity of 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.

In the developing unit 100Y ′, the application roller 32Y ′ and the developing roller 20Y ′ are separately driven by different power sources (not shown). The amount of liquid developer supplied onto the developing roller 20Y ′ can be adjusted by changing the rotation speed (linear speed) ratio between the coating roller 32Y ′ and the developing roller 20Y ′.
Further, the developing unit 100Y ′ includes a rubber developing roller cleaning blade 21Y ′ in contact with the surface of the developing roller 20Y ′ and a developer recovery unit 22Y ′. The developing roller cleaning blade 21Y ′ is a device for scraping off and removing the liquid developer remaining on the developing roller 20Y ′ after the development is performed at the developing position. The liquid developer removed by the developing roller cleaning blade 21Y ′ is collected in the developer collecting unit 22Y ′.

  As shown in FIGS. 7 and 8, the image forming apparatus 1000 ′ includes liquid developer replenishing units 80Y, 80M, 80C that replenish liquid developer to the developing units 30Y ′, 30M ′, 30C ′, and 30K ′. It has 80K. These liquid developer replenishers 80Y, 80M, 80C, and 80K are respectively provided with liquid developer tanks 81Y, 81M, 81C, and 81K, insulating liquid tanks 82Y, 82M, 82C, and 82K, and stirring devices 83Y, 83M, 83C and 83K.

  The liquid developer replenishing sections 80Y, 80M, 80C, and 80K contain high-density liquid developers corresponding to the respective colors. Insulating liquid tanks 82Y, 82M, 82C, and 82K contain insulating liquids, respectively. Furthermore, each stirring device 83Y, 83M, 83C, 83K includes a predetermined amount of each high-concentration liquid developer from each liquid developer supply unit 80Y, 80M, 80C, 80K, and each insulating liquid tank 82Y, 82M, A predetermined amount of each insulating liquid from 82C and 82K is supplied.

  The stirrers 83Y, 83M, 83C, and 83K mix and stir the supplied high-concentration liquid developer and the insulating liquid, respectively, and respectively store the liquid developer reservoirs 31Y ′, 31M ′, and 31C. A liquid developer corresponding to each color used in “, 31K” is prepared. The liquid developers produced by the stirring devices 83Y, 83M, 83C, and 83K are supplied to the liquid developer reservoirs 31Y ', 31M', 31C ', and 31K', respectively.

Further, as shown in FIGS. 7 and 8, the liquid developer replenishing units 80Y, 80M, 80C, and 80K have the liquids collected by the developer collecting units 15Y ′, 15M ′, 15C ′, and 15K ′, respectively. The developer and each liquid developer collected by each developer collection unit 22Y ′, 22M ′, 22C ′, 22K ′ are collected and reused.
Since the fixing unit F40 is the same as that of the above-described embodiment, the description thereof is omitted.

As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to these.
For example, the liquid developer of the present invention is not limited to that applied to the image forming apparatus as described above.
Further, the liquid developer of the present invention is not limited to those produced by the production method as described above.

  In the above-described embodiment, the aqueous emulsion is obtained, and the association particles are obtained by adding an electrolyte to the aqueous emulsion. However, the present invention is not limited to this. For example, associating particles are prepared by dispersing a colorant, a monomer, a surfactant, and a polymerization initiator in an aqueous liquid, preparing an aqueous emulsion by emulsion polymerization, and adding an electrolyte to the aqueous emulsion and associating. What was prepared using the emulsion polymerization association method may be used, and the associated particle | grains may be obtained by spray-drying the obtained aqueous emulsion.

[1] Production of liquid developer (Example 1)
<Preparation of liquid containing fatty acid monoester>
A liquid containing a fatty acid monoester constituting the insulating liquid was prepared as follows.
First, crude soybean oil was purified as follows to obtain purified soybean oil.
First, crude soybean oil was roughly purified by a low temperature crystallization method using methanol, diethyl ether, petroleum ether, acetone or the like as a solvent.

Next, 300 parts by volume of roughly refined crude soybean oil (first roughly refined oil) was put into the flask, and then 100 parts by volume of boiled water was poured into the flask, and the flask was stoppered.
Next, the flask was shaken, and the above-described crude soybean oil (first crudely refined oil) and boiled water were mixed.
Next, the flask was allowed to stand until the mixed liquid in the flask was separated into three layers.
After complete separation was confirmed, the flask was transferred to a freezer and left for 24 hours.
Thereafter, the components that were not frozen were transferred to another flask.
The same operation as described above was repeated for the unfrozen component, and the obtained non-frozen component was taken out to obtain a crude oil (second crude oil).

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

  Next, a transesterification reaction between the obtained soybean oil and methanol was performed, and glycerin generated by this reaction was removed to obtain a liquid mainly composed of fatty acid monoesters. Further, by purifying this liquid, soybean oil fatty acid methyl having a fatty acid monoester content of 99.9 wt% or more was obtained. Fatty acid monoesters thus obtained are mainly unsaturated fatty acid monoesters such as methyl oleate, methyl linoleate and methyl α-linolenate, and saturated fatty acid monoesters such as methyl palmitate and methyl stearate. Of which unsaturated fatty acid monoesters accounted for 84%. Moreover, the viscosity of the soybean oil fatty acid methyl measured by using a vibration viscometer at 25 ° C. according to JIS Z8809 was 3.0 mPa · s.

<Preparation of colorant master solution>
First, a mixture (mass ratio 50:50) of a polyester resin (softening temperature: 99 ° C.) and a cyan pigment as a colorant (manufactured by Dainichi Seika Co., Ltd., Pigment Blue 15: 3) 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 powder of the kneaded material so that the solid content was 30 wt%, and wet-dispersed with an Eiger motor mill (manufactured by Eiger, USA: M-1000) to prepare a colorant master solution.

<Preparation of resin solution>
200 parts by weight of methyl ethyl ketone and 73 parts by weight of the polyester resin were added to 33 parts by weight of the colorant master solution, and the mixture was 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 wt%.
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 polyester resin 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 parts by weight, soybean oil fatty acid methyl: 60 parts by weight, polyamine aliphatic polycondensate (manufactured by Nippon Lubrizol, trade name “Solsperse 11200”): 1 part by weight and stearic acid Aluminum (made by Japanese fats and oils): 0.5 part by weight was put in a ceramic pot, and 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 to obtain a toner dispersion.

After the crushing, 100 parts by weight of liquid paraffin (trade name “COSMO White P-60” manufactured by Cosmo Oil Co., Ltd.) as an aliphatic hydrocarbon was added to disperse the toner particles. Dispersion was performed for 24 hours by putting zirconia balls having a ball diameter of 1 mm. As a result, a liquid developer was obtained.
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.

In addition, what was prepared as follows was used as a polyester resin (softening temperature: 99 degreeC) of a present Example.
Raw materials such as an acid, an alcohol component, and a catalyst having the following composition were put into a 50 liter reaction kettle and reacted at 210 ° C. for 12 hours under a normal pressure nitrogen stream. Thereafter, the pressure was reduced successively and the reaction was continued at 10 mmHg. The reaction was followed by the softening point based on ASTM E28-517, and the reaction was terminated when the softening point reached 88 ° C.

Terephthalic acid 79.7 parts by weight Isophthalic acid 53.1 parts by weight Ethylene glycol 28.6 parts by weight Neopentyl glycol 48.0 parts by weight Tetrabutyl titanate 1.0 part by weight

The obtained polymer was a colorless solid having an acid value of 10.0, a glass transition point (Tg) of 53 ° C., and a softening temperature (T1 / 2) of 99 ° C.
Further, the weight average molecular weight was measured by using a GPC measuring apparatus (HLC-8120GPC manufactured by Tosoh Corporation) as a separation column in combination with TSK-GEL G5000HXL / G4000HXL / G3000HXL / G2000HXL manufactured by Tosoh Corporation, column temperature: 40 ° C., solvent: tetrahydrofuran, solvent It was a weight average molecular weight of 7400 when it was measured at a concentration of 0.5% by mass, a filter: 0.2 μm, a flow rate: 1 ml / min and converted using standard polystyrene to obtain a molecular weight.

(Example 2)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that methyl rapeseed oil fatty acid prepared as follows was used in place of soybean oil fatty acid methyl.
Crude rapeseed oil was refined in the same manner as the soybean oil of Example 1 to obtain a refined rapeseed oil (hereinafter simply referred to as rapeseed oil). The rapeseed oil contained fatty acid glycerides mainly composed of oleic acid, and the unsaturated fatty acid glycerides in the rapeseed oil was 98 wt%. The oleic acid component and linoleic acid component were 52 mol% and 24 mol%, respectively, of the total fatty acid components.

  Next, a transesterification reaction between this rapeseed oil and methanol was performed, and glycerin produced by this reaction was removed to obtain a liquid mainly composed of fatty acid monoesters. Further, by purifying the liquid, rapeseed oil fatty acid methyl having a fatty acid monoester content of 99.9 wt% or more was obtained. In addition, the viscosity of the rapeseed oil fatty acid methyl measured according to JIS Z8809 using a vibration viscometer at 25 ° C. was 3.0 mPa · s.

(Example 3)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that the alcohol used in the transesterification reaction was changed to ethanol. In addition, the obtained soybean oil fatty acid ethyl ester had a fatty acid monoester content of 99.9 wt% or more.
Example 4
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that the alcohol used in the transesterification reaction was changed to butanol. The obtained soybean oil fatty acid butyl ester had a fatty acid monoester content of 99.9 wt% or more.

(Example 5)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., trade name “KF96”) was used instead of liquid paraffin.
(Example 6)
Instead of liquid paraffin, liquid paraffin (Cosmo Oil Co., Ltd., trade name “Cosmo White P-60”) and silicone oil (Shin-Etsu Chemical Co., Ltd., trade name “KF96”) are mixed in a one-to-one mix. A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that the liquid was used.
(Example 7)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that soybean oil purified in the same manner as in Example 1 was used instead of liquid paraffin.

(Example 8)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that the polyester resin shown in Table 1 was used.
In addition, as polyester resin, what was prepared as follows was used.
Raw materials such as an acid, an alcohol component, and a catalyst having the following composition were put into a 50 liter reaction kettle and reacted at 210 ° C. for 12 hours under a normal pressure nitrogen stream. Thereafter, the pressure was reduced successively and the reaction was continued at 10 mmHg. The reaction was followed by the softening point based on ASTM E28-517, and the reaction was terminated when the softening point reached 115 ° C.

Terephthalic acid 79.7 parts by weight Isophthalic acid 53.1 parts by weight Ethylene glycol 28.6 parts by weight Neopentyl glycol 48.0 parts by weight Tetrabutyl titanate 1.0 part by weight

The obtained polymer was a colorless solid having an acid value of 10.0, a glass transition point (Tg) of 65 ° C., and a softening temperature (T1 / 2) of 125 ° C.
Further, the weight average molecular weight was measured by using a GPC measuring apparatus (HLC-8120GPC manufactured by Tosoh Corporation) as a separation column in combination with TSK-GEL G5000HXL / G4000HXL / G3000HXL / G2000HXL manufactured by Tosoh Corporation, column temperature: 40 ° C., solvent: tetrahydrofuran, solvent It was measured at a concentration of 0.5% by mass, a filter: 0.2 μm, a flow rate: 1 ml / min, converted using standard polystyrene, and a molecular weight was determined. The weight average molecular weight was 9000.

(Examples 9 to 11)
Liquid developers corresponding to the respective colors were produced in the same manner as in Example 1 except that the contents of fatty acid monoesters and aliphatic hydrocarbons in the insulating liquid were adjusted as shown in Table 1.
(Example 12)
In the crushing step, liquid developers corresponding to the respective colors were produced in the same manner as in Example 1 except that zirconia balls having a diameter of 4 mm were used and crushing was performed at a rotational speed of 330 rpm for 240 hours.
(Example 13)
In the crushing step, liquid developers corresponding to the respective colors were produced in the same manner as in Example 1 except that zirconia balls having a diameter of 0.8 mm were used and crushing was performed at a rotation speed of 150 rpm for 110 hours.

(Comparative Example 1)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that the polyester resin was changed to an epoxy resin (Epicoat 1004, softening temperature: 128 ° C.).
(Comparative Example 2)
In the crushing step, each color corresponds to each color in the same manner as in Example 1 except that liquid paraffin (manufactured by Cosmo Oil Co., Ltd., trade name “Cosmo White P-60”) was used instead of soybean oil fatty acid methyl. A liquid developer was produced.

(Comparative Example 3)
In the crushing process, a liquid developer corresponding to each color was used in the same manner as in Example 1 except that silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., trade name “KF96”) was used instead of soybean oil fatty acid methyl. Manufactured.
Table 1 shows the production conditions and physical properties of the liquid developer for the above Examples and Comparative Examples.

[2] Evaluation Each liquid developer obtained as described above was evaluated as follows.
[2.1] Fixing Strength Using an image forming apparatus as shown in FIG. 1, an image of a predetermined pattern with a liquid developer obtained in each of the examples and the comparative examples was recorded on a recording paper (manufactured by Seiko Epson Corporation, High quality paper LPCPPA4). Thereafter, heat fixing was performed using a fixing device as shown in FIG. 6 at a set temperature of the heat fixing roller of 100 ° C.

Then, after confirming the non-offset area, the fixed image on the recording paper is erased twice (rubber eraser “LION 261-11” manufactured by Lion Business Machine Co., Ltd.) twice with a pressing load of 1.2 kgf, and the remaining ratio of image density Was measured by “X-Rite model 404” manufactured by X-Rite Inc, and evaluated according to the following five-step criteria.
A: Image density residual ratio is 95% or more (very good).
B: Image density remaining rate is 90% or more and less than 95% (good).
C: Image density remaining rate is 80% or more and less than 90% (normal).
D: Image density residual ratio is 70% or more and less than 80% (slightly bad).
E: Image density residual ratio is less than 70% (very bad).

[2.2] Dispersion stability test 10 mL of the cyan liquid developer obtained in each example and each comparative example was placed in a centrifuge tube, centrifuged at 1000 G for 10 minutes, and then 200 μL of the supernatant was added. The sample was collected and diluted 100 times with the insulating liquid used in each example and each comparative example to prepare a sample.
The absorption wavelength of each sample was measured using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, V-570).

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

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

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

[2.4] Storage Stability The liquid developers obtained in the above 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 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 / electric resistance value of liquid developer is observed.
B: Almost no change in viscosity / color / electric resistance value of liquid developer is observed.
C: A slight change in viscosity / color / electric resistance value of the liquid developer is observed, but liquid development
There is no problem as an agent.
D: A change in viscosity / color / electric resistance value of the liquid developer is clearly recognized.
E: A change in viscosity / color / electric resistance value of the liquid developer is remarkably recognized.

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

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

[2.6] Resolving power Using an image forming apparatus as shown in FIG. 1, a color image of a predetermined pattern is formed on a recording paper by using the liquid developer obtained in each of the examples and the comparative examples. The resolution was examined.
These results are shown in Table 2.

As is apparent from Table 2, the liquid developer of the present invention was excellent in fixing strength and dispersion stability. Further, the liquid developer of the present invention was excellent in storage stability, charging characteristics, resolving power, and glossiness of the formed image. On the other hand, satisfactory results were not obtained with the liquid developers of the comparative examples.
[3] Resin synthesis (Linear polyester resin PES1)
Raw materials such as an acid, an alcohol component, and a catalyst having the following composition were put into a 50 liter reaction kettle and reacted at 210 ° C. for 12 hours under a normal pressure nitrogen stream. Thereafter, the pressure was reduced successively and the reaction was continued at 10 mmHg. The reaction was followed by the softening point based on ASTM E28-517, and the reaction was terminated when the softening point reached 95 ° C.

Terephthalic acid 79.7 parts by weight Isophthalic acid 53.1 parts by weight Ethylene glycol 28.6 parts by weight Neopentyl glycol 48.0 parts by weight Tetrabutyl titanate 1.0 part by weight

The obtained polymer (PES1) was a colorless solid and had an acid value of 10.0, a glass transition point (Tg) of 55 ° C., and a softening point (T1 / 2) of 107 ° C.
In addition, the weight average molecular weight was measured using a GPC measuring apparatus (HLC-8120GPC manufactured by Tosoh Corporation), and Tosoh TSK-GEL G5000HXL / G4000HXL / G3000HXL / G2000HXL was used in combination as a separation column. Column temperature: 40 ° C./solvent: tetrahydrofuran -Solvent concentration of 0.5 mass%, filter: 0.2 μm, flow rate: 1 ml / min, converted using standard polystyrene, and the molecular weight was determined. The weight average molecular weight was 7740.

(Linear polyester resin PES2)
Raw materials such as an acid, an alcohol component, and a catalyst having the following composition were put into a 50 liter reaction kettle and reacted at 210 ° C. for 11 hours under a normal pressure nitrogen stream. Thereafter, the pressure was reduced successively and the reaction was continued at 10 mmHg. The reaction was followed by the softening point according to ASTM E28-517 and terminated when the softening point reached 87 ° C.

Terephthalic acid 53.1 parts by weight Isophthalic acid 79.7 parts by weight Ethylene glycol 26.0 parts by weight Neopentyl glycol 43.7 parts by weight Tetrabutyl titanate 1.0 part by weight The resulting polymer (PES2) is a colorless solid. The acid value was 10.0, the glass transition point (Tg) was 46 ° C., and the softening point (T1 / 2) was 95 ° C. Moreover, it was the weight average molecular weight 5200.

(Branched polyester resin PES3)
Raw materials such as an acid, an alcohol component, and a catalyst having the following composition were put into a 50 liter reaction kettle and reacted at 240 ° C. for 12 hours under a normal pressure nitrogen stream. Thereafter, the pressure was reduced successively and the reaction was continued at 10 mmHg. The reaction was followed by the softening point based on ASTM E28-517 and terminated when the softening point reached 159 ° C.

Terephthalic acid 19.4 parts by weight Isophthalic acid 90.7 parts by weight Adipic acid 17.1 parts by weight Ethylene glycol 25.4 parts by weight Neopentyl glycol 42.6 parts by weight Tetrabutyl titanate 1.0 part by weight Epiclone 830 3.0 parts by weight (Dai Nippon Ink Chemical Co., Ltd. bisphenol F type epoxy resin epoxy equivalent 170 (g / eq)
Cardura E 1.0 part by weight (Alkyl glycidyl ester manufactured by Shell Japan) Epoxy equivalent 250 (g / eq)
The obtained polymer (PES3) was a colorless solid having an acid value of 9.8, a glass transition point (Tg) of 40 ° C., and a softening point (T1 / 2) of 176 ° C. Moreover, it was the weight average molecular weight 176000.

[4] Production of liquid developer (Example 14)
<Preparation of liquid containing fatty acid monoester>
A liquid containing a fatty acid monoester constituting the insulating liquid was prepared as follows.
First, crude soybean oil was purified as follows to obtain purified soybean oil.
First, crude soybean oil was roughly purified by a low temperature crystallization method using methanol, diethyl ether, petroleum ether, acetone or the like as a solvent.

Next, 300 parts by volume of roughly refined crude soybean oil (first roughly refined oil) was put into the flask, and then 100 parts by volume of boiled water was poured into the flask, and the flask was stoppered.
Next, the flask was shaken, and the above-described crude soybean oil (first crudely refined oil) and boiled water were mixed.
Next, the flask was allowed to stand until the mixed liquid in the flask was separated into three layers.
After complete separation was confirmed, the flask was transferred to a freezer and left for 24 hours.

Thereafter, the components that were not frozen were transferred to another flask.
The same operation as described above was repeated for the unfrozen component, and the obtained non-frozen component was taken out to obtain a crude oil (second crude oil).
Next, in the flask, the crude oil and fat (second crude oil) obtained as described above: 100 parts by volume and active clay mainly composed of hydrous aluminum silicate: 35 parts by volume were mixed. Stir.

Next, the obtained mixture was stored under pressure (0.18 MPa) for 48 hours to completely precipitate the activated clay.
Thereafter, the precipitate was removed to obtain refined soybean oil (hereinafter simply referred to as soybean oil). In addition, the fatty acid glyceride which has linoleic acid as a main component was contained in soybean oil, and the unsaturated fatty acid glyceride in soybean oil was 98 wt%. Moreover, the linoleic acid component was 53 mol% of the total fatty acid components.

  Next, a transesterification reaction between the obtained soybean oil and methanol was performed, and glycerin generated by this reaction was removed to obtain a liquid mainly composed of fatty acid monoesters. Further, by purifying this liquid, soybean oil fatty acid methyl having a fatty acid monoester content of 99.9 wt% or more was obtained. Fatty acid monoesters thus obtained are mainly unsaturated fatty acid monoesters such as methyl oleate, methyl linoleate and methyl α-linolenate, and saturated fatty acid monoesters such as methyl palmitate and methyl stearate. Of which unsaturated fatty acid monoesters accounted for 84%. Moreover, the viscosity of the soybean oil fatty acid methyl measured by using a vibration viscometer at 25 ° C. according to JIS Z8809 was 3.0 mPa · s.

<Preparation of colorant master solution>
First, a mixture (mass ratio 50:50) of the polyester resin PES1 and a cyan pigment (manufactured by Dainichi 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 powder of the kneaded material so that the solid content was 30 wt%, and wet-dispersed with an Eiger motor mill (manufactured by Eiger, USA: M-1000) to prepare a colorant master solution.

<Preparation of resin solution>
200 parts by weight of methyl ethyl ketone and 73 parts by weight of the polyester resin were added to 33 parts by weight of the colorant master solution, and the mixture was 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 wt%.
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 polyester resin 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 parts by weight, soybean oil fatty acid methyl: 60 parts by weight, polyamine aliphatic polycondensate (manufactured by Nippon Lubrizol, trade name “Solsperse 11200”): 1 part by weight and stearic acid Aluminum (made by Japanese fats and oils): 0.5 part by weight was put in a ceramic pot, and 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 to obtain a toner dispersion.

After crushing, 100 parts by weight of rapeseed oil (manufactured by Nisshin Oilio Co., Ltd., trade name “High Oleic Rapeseed Oil”) was added to disperse the toner particles. Dispersion was performed for 24 hours by putting zirconia balls having a ball diameter of 1 mm. As a result, a liquid developer was obtained.
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 15)
A liquid developer was produced in the same manner as in Example 14 except that PES2 synthesized as described above was used as the polyester resin.
(Example 16)
A liquid developer was produced in the same manner as in Example 14 except that the polyester resin used was a mixture of PES1 and PES2 at a weight ratio of 1: 4.
(Example 17)
A liquid developer was produced in the same manner as in Example 14 except that a polyester resin in which PES2 and PES3 were mixed at a weight ratio of 1: 6 was used.

(Example 18)
Crude rapeseed oil was refined in the same manner as the soybean oil of Example 14 to obtain a refined rapeseed oil (hereinafter simply referred to as rapeseed oil). The rapeseed oil contained fatty acid glycerides mainly composed of oleic acid, and the unsaturated fatty acid glycerides in the rapeseed oil was 98 wt%. The oleic acid component and linoleic acid component were 52 mol% and 24 mol%, respectively, of the total fatty acid components.

Next, a transesterification reaction between a part of the rapeseed oil and methanol was carried out, and glycerin produced by this reaction was removed to obtain a liquid mainly composed of fatty acid monoesters. Further, by purifying this liquid, rapeseed oil fatty acid methyl having a fatty acid monoester content of 99.9 wt% or more was obtained.
Hereinafter, as the insulating liquid, rapeseed oil fatty acid methyl was used instead of soybean oil fatty acid methyl, and liquid developer corresponding to each color was prepared in the same manner as in Example 14 except that soybean oil was used instead of rapeseed oil. Manufactured.

(Example 19)
In the synthesis of the polyester resin PES1, a polyester resin PES4 having an amino group was synthesized by using one obtained by substituting the hydrogen of the ethylene group of ethylene glycol with an amino group. The polyester resin PES4 was a colorless solid having an acid value of 10.0, a glass transition point (Tg) of 56 ° C., and a softening point (T1 / 2) of 108 ° C.

In addition, the weight average molecular weight was measured using a GPC measuring apparatus (HLC-8120GPC manufactured by Tosoh Corporation), and Tosoh TSK-GEL G5000HXL / G4000HXL / G3000HXL / G2000HXL was used in combination as a separation column. Column temperature: 40 ° C./solvent: tetrahydrofuran -The solvent concentration was 0.5 mass%, the filter was 0.2 µm, the flow rate was 1 ml / min, and the molecular weight was calculated using standard polystyrene.
Using this polyester resin PES4, liquid developers corresponding to the respective colors were produced in the same manner as in Example 14.

(Comparative Example 4)
In the crushing step, each color was treated in the same manner as in Example 14 except that liquid paraffin (trade name “Cosmo White P-60” manufactured by Cosmo Oil Co., Ltd.) was used instead of soybean oil fatty acid methyl and rapeseed oil. A corresponding liquid developer was prepared.
(Comparative Example 5)
In the crushing step, liquid corresponding to each color was obtained in the same manner as in Example 14 except that silicone oil (trade name “KF96”, manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of soybean oil fatty acid methyl and rapeseed oil. A developer was produced.
Tables 3 and 4 show the production conditions and physical properties of the liquid developer for each of the above examples.

[5] Evaluation The following evaluations were performed on the liquid developers obtained in Examples 14 to 19 and Comparative Examples 1 to 3.
[5.1] Fixing Strength Using an image forming apparatus as shown in FIGS. 7 and 8, images of a predetermined pattern with the liquid developer obtained in each of the examples and the comparative examples are recorded on a recording paper (Seiko Epson). It was formed on a high-quality paper LPCPPA4) manufactured by the company. Thereafter, heat fixing was performed using a fixing device as shown in FIG. 6 at a set temperature of the heat fixing roller of 100 ° C.
Then, after confirming the non-offset area, the fixed image on the recording paper is erased twice (rubber eraser “LION 261-11” manufactured by Lion Business Machine Co., Ltd.) with a pressing load of 1.5 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.
A: Image density residual ratio is 95% or more (very good).
B: Image density remaining rate is 90% or more and less than 95% (good).
C: Image density remaining rate is 80% or more and less than 90% (normal).
D: Image density residual ratio is 70% or more and less than 80% (slightly bad).
E: Image density residual ratio is less than 70% (very bad).

[5.2] Dispersion stability test 10 mL of the cyan liquid developer obtained in each example and each comparative example was placed in a centrifuge tube, centrifuged at 1000 G for 10 minutes, and then 200 μL of the supernatant was added. The sample was collected and diluted 100 times with the insulating liquid used in each example and each comparative example to prepare a sample.
The absorption wavelength of each sample was measured using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, V-570).

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

[5.3] Evaluation of Gloss (Gross) of Formed Toner Image Using an image forming apparatus as shown in FIGS. 7 and 8, the liquid developer obtained in each of the examples and comparative examples was used. An image of a predetermined pattern was formed on a recording paper (quality paper LPCPPA4 manufactured by Seiko Epson Corporation). Thereafter, heat fixing was performed using a fixing device as shown in FIG. 6 at a set temperature of the heat fixing roller of 100 ° C.

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

[5.4] Storage stability The liquid developers obtained in the above 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 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 / electric resistance value of liquid developer is observed.
B: Almost no change in viscosity / color / electric resistance value of liquid developer is observed.
C: A slight change in viscosity / color / electric resistance value of the liquid developer is observed, but liquid development
There is no problem as an agent.
D: A change in viscosity / color / electric resistance value of the liquid developer is clearly recognized.
E: A change in viscosity / color / electric resistance value of the liquid developer is remarkably recognized.

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

A: The potential difference is +120 mV or more (very good).
B: Potential difference is +100 mV or more and less than +120 mV (good).
C: Potential difference is +70 mV or more and less than +100 mV (normal).
D: The potential difference is +50 mV or more and less than +70 mV (somewhat bad).
E: Potential difference is less than +50 mV (very bad).

[5.6] Resolution The image forming apparatus as shown in FIGS. 7 and 8 is used to form a color image of a predetermined pattern on the recording paper using the liquid developer obtained in each of the examples and the comparative examples. The resolving power was examined visually.
These results are shown in Table 5.

  As is apparent from Table 5, the liquid developer of the present invention was excellent in fixing strength and dispersion stability. Further, the liquid developer of the present invention was excellent in storage stability, charging characteristics, resolving power, and glossiness of the formed image. In addition, the image formed using the liquid developer obtained in the examples was clear with no color unevenness. On the other hand, satisfactory results were not obtained with the liquid developers of the comparative examples.

1 is a schematic diagram illustrating a first embodiment of an image forming apparatus to which a liquid developer of the present invention is applied. FIG. 2 is an enlarged view of a part of the image forming apparatus shown in FIG. 1. FIG. 2 is a perspective conceptual diagram illustrating a coating roller included in the image forming apparatus illustrated in FIG. 1. It is an expansion schematic diagram of the application | coating roller shown in FIG. FIG. 6 is a schematic diagram illustrating a state of toner particles in a liquid developer layer on a developing roller. FIG. 2 is a cross-sectional view illustrating an example of a fixing device applied to the image forming apparatus illustrated in FIG. 1. It is a schematic diagram showing a second embodiment of an image forming apparatus to which the liquid developer of the present invention is applied. FIG. 8 is an enlarged view of a part of the image forming apparatus shown in FIG. 7.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Toner particle 1000 ... Image forming apparatus 10Y, 10M, 10C, 10K ... Photoconductor 11Y ... Charging roller 12Y ... Exposure unit 13Y, 13M ... Photoconductor squeeze roller 14Y, 14M ... Cleaning blade 15Y, 15M ... Developer collection part 16Y Destaticizing unit 17Y ... Photoconductor cleaning blade 18Y ... Developer recovery unit 20Y, 20M, 20C, 20K ... Developing roller 201Y ... Liquid developer layer 21Y ... Developing roller cleaning blade 22Y ... Developer compressing roller 23Y ... Developer compressing roller cleaning Blade 30Y, 30M, 30C, 30K ... developing part 31Y ... liquid developer storage part 32Y ... coating roller 32Ya ... groove 32Yb ... mount 33Y ... regulating blade 34Y ... developer stirring roller 40 ... transfer part 41 ... conveying belt DESCRIPTION OF SYMBOLS 42 ... Belt drive roller 43 ... Tension roller 44Y, 44M, 44C, 44K ... Transfer backup roller 70 ... Conveyance path 74 ... Insulating liquid storage part 76 ... Pump 77 ... Filter means 100Y ... Development unit 101Y ... Photoconductor squeeze device F40 ... Fixing section (fixing device) F1 ... heat fixing roller (heating roller) F1a ... column-shaped halogen lamp F1b ... roller base material F1c ... elastic body F11c ... release layer F12 ... removal blade F2 ... pressure roller F2a ... rotary shaft F2b ... roller Substrate F2c ... elastic body F3 ... heat-resistant belt F4 ... belt stretching member F4a ... projection wall F4f ... concave F5 ... recording medium F5a ... toner image F6 ... cleaning member F7 ... frame F9 ... spring 1000 '... image forming apparatus 10Y', 10M ', 10C', 10K '... photosensitive member 11Y' ... charge roller 12Y '... exposure unit 13M', 13Y '... photosensitive member squeeze rollers 14Y', 14M '... cleaning blades 15M', 15Y ', 15C', 15K '... developer recovery unit 16Y '... static elimination unit 17Y' ... photosensitive member cleaning blade 18Y '... developer recovery unit 20Y', 20M ', 20C', 20K '... developing roller 201Y' ... liquid developer layer 21Y '... developing roller cleaning blade 23Y' ... corona Discharger (compression means) 30Y ', 30M', 30C ', 30K' ... developing unit 31Y '... liquid developer storage unit 32Y' ... application roller 33Y ... regulating blade 34Y ... stirring roller 40 '... intermediate transfer unit 41' ... Belt drive roller 42 ', 43' ... driven roller 44 '... tension roller La 46 '... Intermediate transfer part cleaning blade 47' ... Developer recovery part 48 '... Non-contact type bias applying member 51Y', 51M ', 51C', 51K '... Primary transfer backup roller 52Y', 52M ', 52C' , 52K '... intermediate transfer unit squeeze device 53Y' ... intermediate transfer unit squeeze roller 55Y '... intermediate transfer unit squeeze cleaning blade 56Y' ... developer recovery unit 60 '... secondary transfer unit 61' ... upstream side secondary transfer roller 62 '... downstream side secondary transfer rollers 63', 65 '... secondary transfer roller cleaning blades 64', 66 '... developer recovery unit 70Y ... transport path 80Y, 80M, 80C, 80K ... liquid developer replenishment unit 81Y, 81M 81C, 81K ... Liquid developer tanks 82Y, 82M, 82C, 82K ... Insulating liquid tanks Click 83Y, 83M, 83C, 83K ... stirrer 100Y '... developing unit 101Y' ... photoreceptor squeeze device

Claims (13)

An insulating liquid containing a fatty acid monoester;
A liquid developer comprising toner particles mainly composed of a polyester resin. The toner particles have an average particle size of 0.7 to 3 μm;
The circularity of the toner particles represented by the following formula (I) is 0.85 to 0.98,
The liquid developer according to claim 1, wherein a width S of a particle size distribution of the toner particles represented by the following formula (II) is 1.4 or less.
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)
S = [D (90) -D (10)] / D (50) (II)
(However, when the particle size distribution of toner particles is measured from a small particle size, the particle size at the point of X% of the total volume in the cumulative volume is D (X).)   The liquid developer according to claim 1, wherein the insulating liquid contains an aliphatic hydrocarbon and / or a silicone oil in addition to the fatty acid monoester.   The liquid developer according to any one of claims 1 to 3, wherein a content of the fatty acid monoester in the insulating liquid is 5 to 55 wt%.   The liquid developer according to claim 1, wherein the fatty acid monoester is unevenly distributed near the surface of the toner particles.   The liquid developer according to claim 1, wherein the fatty acid monoester is an ester of a fatty acid and a monovalent alcohol having 1 to 4 carbon atoms.   The liquid developer according to any one of claims 1 to 6, wherein a viscosity measured in accordance with JIS Z8809 using a vibration viscometer at 25 ° C is 50 to 1000 mPa · s. 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,
An image forming apparatus, wherein the liquid developer contains an insulating liquid containing a fatty acid monoester and toner particles mainly composed of a polyester resin. A plurality of developing units that form a single color image corresponding to each color using a plurality of liquid developers having different colors;
An intermediate transfer unit that sequentially transfers a plurality of the single-color images formed by the plurality of developing units, and forms an intermediate transfer image formed by superimposing the transferred single-color images;
A secondary transfer unit that transfers the intermediate transfer image to the recording medium and forms an unfixed color image on the recording medium;
A fixing unit for fixing the unfixed color image on the recording medium,
An image forming apparatus, wherein the liquid developer contains an insulating liquid containing a fatty acid monoester and toner particles mainly composed of a polyester resin.   The plurality of developing sections include at least a developing roller that forms a layer of the liquid developer on a surface thereof, a compression unit that unevenly distributes the toner particles in the vicinity of the surface of the developing roller in the layer, and a surface on the developing roller. The image forming apparatus according to claim 8, further comprising a photoconductor that forms the single-color image by transferring the liquid developer.   The image forming apparatus according to claim 10, wherein the compression unit applies the electric field having the same polarity as the toner particles to the layer, thereby causing the toner particles to be unevenly distributed in the vicinity of the surface of the developing roller in the layer. apparatus. The developing section includes at least a developing roller that forms a layer of the liquid developer on a surface thereof, a photoconductor that forms the monochrome image by transferring the liquid developer on the developing roller, and a liquid that is applied to the developing roller. An application roller for supplying the developer,
The application roller is an anilox roller having a groove formed on a surface thereof, and the liquid developer is supplied to the developing roller by carrying the liquid developer in the groove. The image forming apparatus described in 1.   The image forming apparatus according to claim 12, wherein the groove formed in the application roller is provided obliquely with respect to a rotation direction of the application roller.

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