JP2009015244A - Liquid developer and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid developer excellent in low temperature fixability and storage stability and to provide an image forming apparatus using the developer. <P>SOLUTION: The liquid developer includes an insulating liquid containing a fatty acid monoester and toner particles composed of a material containing a resin material and an ester-based wax, wherein the ester-based wax included in the toner particles is plasticized by the fatty acid monoester. When the melting point of the ester-based wax not plasticized and the melting point of the ester-based wax after plasticized by the fatty acid monoester are denoted by Tm<SB>1</SB>[°C] and Tm<SB>2</SB>[°C], respectively, they are preferably controlled to satisfy a relation of 2≤Tm<SB>1</SB>-Tm<SB>2</SB>≤20. The melting point of the ester-based wax not plasticized by the fatty acid monoester is preferably 65 to 100°C. <P>COPYRIGHT: (C)2009,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 has not been sufficiently fixed at a low temperature, although the fixing strength is improved. Further, in the conventional liquid developer, toner particles aggregate over time, and the storage stability is not sufficient.

JP 2006-251252 A

  An object of the present invention is to provide a liquid developer having excellent low-temperature fixability and excellent storage stability, and an image forming apparatus using the same.

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;
Toner particles composed of a material containing a resin material and an ester wax,
The ester wax contained in the toner particles is plasticized with the fatty acid monoester.

In the liquid developer of the present invention, the melting point of the ester wax in an unplasticized state is Tm ₁ [° C.], and the melting point of the ester wax in a state plasticized with the fatty acid monoester is Tm ₂ [ [° C.], it is preferable that the relationship 2 ≦ Tm ₁ −Tm ₂ ≦ 20 is satisfied.
In the liquid developer of the present invention, the melting point of the ester wax that is not plasticized with the fatty acid monoester is preferably 65 to 100 ° C.

In the liquid developer of the present invention, it is preferable that the ester wax contains carnauba wax.
In the liquid developer of the present invention, the content of the fatty acid monoester in the insulating liquid is preferably 1.0 to 50 wt%.
In the liquid developer of the present invention, the resin material preferably contains a polyester resin.
In the liquid developer of the present invention, a step of associating fine particles composed of a material containing the resin material and the ester wax to obtain associated particles;
The fatty acid monoester constituting the insulating liquid is preferably produced using a method comprising a step of pulverizing the associated particles to obtain toner particles.

The image forming apparatus of the present invention includes a plurality of developing units that form the 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;
Toner particles including a resin material and an ester wax,
The ester wax contained in the toner particles is plasticized with the fatty acid monoester.
By satisfying the above configuration, it is possible to provide a liquid developer excellent in low-temperature fixability and excellent in storage stability, and an image forming apparatus using such a liquid developer.

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

<Insulating liquid>
First, the insulating liquid will be described.
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.
In contrast, the fatty acid monoester used in the liquid developer 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 leakage of the insulating liquid to the outside of the image forming apparatus and disposal of the used liquid developer. As a result, an environmentally friendly liquid developer can be provided.

  The fatty acid monoester has an effect of plasticizing the resin material constituting the toner particles (plasticizer effect). 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 toner particles even at a relatively low temperature and enables fixing on a recording medium, and thus can be suitably applied to image formation at low temperature and 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 will be 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 (resin material) melted by the heat at the time of fixing penetrate into the inside of the recording medium, and the anchor effect works, improving the fixing characteristics between paper and toner particles. To do.

The fatty acid monoester also has an effect of plasticizing an ester wax, which will be described later, which is a material constituting the toner particles. The plasticized ester wax will be described in detail later.
Examples of such fatty acid monoesters include oleic acid, palmitoleic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, arachidonic acid, docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and the like. Unsaturated fatty acid alkyl (methyl, ethyl, propyl, butyl, etc.) monoester, butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, etc. And alkyl (methyl, ethyl, propyl, butyl, etc.) monoesters of saturated fatty acids, and the like, and one or more selected from these can be used in combination.

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

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

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

  In addition to the fatty acid monoester, for example, Isopar E, Isopar G, Isopar H, Isopar L (Isopar; trade name of Exxon Chemical), Cielsol 70, Cielsol 71 (Cielsol; Ciel Oil) Company name), Amsco OMS, Amsco 460 solvent (Amsco; product name of Spirits), mineral oil such as low viscosity / high viscosity liquid paraffin (Wako Pure Chemical Industries), vegetable oil such as rapeseed oil, soybean oil, silicone oil , Octane, isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, cyclohexane, cyclooctane, cyclodecane, benzene, toluene, xylene, mesitylene and the like.

Among the above-mentioned, when vegetable oil is contained in the insulating liquid, the following effects can be obtained.
Vegetable oil is an environmentally friendly component like the fatty acid monoester described above. Therefore, it is possible to reduce the load on the environment of the insulating liquid due to leakage of the insulating liquid to the outside of the image forming apparatus and disposal of the used liquid developer. As a result, an environmentally friendly liquid developer can be provided.
The vegetable oil contains unsaturated fatty acid glycerides. An unsaturated fatty acid glyceride is an ester (glyceride) of a fatty acid and glycerin, and contains an unsaturated fatty acid as a fatty acid component.

  Unsaturated fatty acid glycerides are components that can contribute to improving the long-term storage stability of the resulting toner image. This will be described in detail below. An unsaturated fatty acid component is a component that itself can be cured by being oxidized. Therefore, when a toner image is formed and fixed on a recording medium using a liquid developer containing an unsaturated fatty acid glyceride, the unsaturated fatty acid glyceride remaining together with the toner particles on the toner image is oxidized by oxygen in the air or the like. The toner particles can be polymerized, and the toner particles can be firmly bonded to each other or to the recording medium. Further, since the unsaturated fatty acid glyceride can be oxidatively polymerized while covering the surface of the toner image, a protective film of the unsaturated fatty acid glyceride cured on the surface of the toner image can be formed. As described above, the toner image can be reduced in deterioration due to physical external force such as friction, air, light, etc. over a long period of time, and has excellent long-term storage stability.

  Unsaturated fatty acids constituting glycerides are not particularly limited, but monounsaturated fatty acids such as crotonic acid, myristoleic acid, palmitoleic acid, oleic acid, elaidic acid, vaccenic acid, gadoleic acid, erucic acid, and nervonic acid, linol Of polyunsaturated fatty acids such as acids, α-linolenic acid, γ-linolenic acid, arachidonic acid, eleostearic acid, stearidonic acid, arachidonic acid, succinic acid, docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), etc. Examples thereof include unsaturated fatty acids and derivatives thereof, and one or more selected from these can be used in combination.

  When vegetable oil is contained in the insulating liquid, the content of vegetable oil in the insulating liquid is preferably 20 to 90 wt%, more preferably 30 to 80 wt%, and 40 to 70 wt%. More preferably it is. When the content of vegetable oil in the insulating liquid is within the above range, the unsaturated fatty acid glyceride remaining in the formed toner image becomes appropriate, and the obtained toner image has a protective film as described above on the surface. It is suitably formed and has particularly excellent long-term storage stability.

Moreover, the saturated fatty acid glyceride may contain a saturated fatty acid component. By including the saturated fatty acid component, it is possible to keep the chemical stability of the liquid developer and the electrical insulation of the insulating liquid even higher.
Examples of saturated fatty acids constituting such saturated fatty acid components include butyric acid (C4), caproic acid (C6), caprylic acid (C8), capric acid (C10), lauric acid (C12), and myristylic acid (C14). , Palmitic acid (C16), stearic acid (C18), arachidic acid (C20), behenic acid (C22), lignoceric acid (C24) and the like, and one or more selected from these are used in combination. be able to. Among the saturated fatty acids as described above, the number of carbon atoms in the molecule is preferably 6-22, more preferably 8-20, and even more preferably 10-18. . By including a saturated fatty acid component composed of such a saturated fatty acid, the effects as described above are exhibited more significantly.

  Further, the liquid developer (insulating liquid) may contain an antioxidant having a function of preventing / suppressing oxidation of naturally derived components such as fatty acid monoesters and vegetable oils. Thereby, the unintentional oxidation of the naturally derived component in the liquid developer can be prevented. As a result, it is possible to prevent deterioration of the liquid developer (insulating liquid) over time, and the dispersibility of the toner particles, the fixing strength to the recording medium, the charging characteristics, etc. are particularly excellent over a long period of time. can do.

Further, the liquid developer (insulating liquid) may contain a dispersant that improves the dispersibility of the toner particles.
Examples of such a dispersant include polyvinyl alcohol, carboxymethyl cellulose, polyethylene glycol, Ajisper PB821 (trade name of Ajinomoto Co., Inc.), Solsperse (trade name of Nippon Lubrizol Co., Ltd.), polycarboxylic acid and salts thereof, and 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) Etc.), polystyrenesulfonic acid metal salts (for example, sodium salts), polymer dispersants such as polyamine fatty acid condensation polymers, viscosity minerals, silica, tricalcium phosphate, metal salts of tristearic acid (for example, aluminum salts), Distearic acid metal salts (for example, aluminum salts, Lithium salts, etc.), stearic acid metal salts (eg calcium salts, lead salts, zinc salts etc.), linolenic acid metal salts (eg cobalt salts, manganese salts, lead salts, zinc salts etc.), octanoic acid metal salts (eg , Aluminum salts, calcium salts, cobalt salts, etc.), oleic acid metal salts (eg, calcium salts, cobalt salts, etc.), palmitic acid metal salts (eg, zinc salts, etc.), dodecylbenzenesulfonic acid metal salts (eg, sodium salts) Etc.), 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.), etc. Can be mentioned.

Among the above-described dispersants, when a polymer dispersant is used, the polymer dispersant can be attached to the surface of the toner particles, and thus, unintentional aggregation between the toner particles can be prevented.
When the polymer dispersant is used, the content of the polymer dispersant 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, and 1 to 5 parts. More preferred are parts by weight. Thereby, the effect by using a polymer dispersing agent can be made more remarkable.

Although the viscosity of an insulating liquid is not specifically limited, It is preferable that it is 5-1000 mPa * s, It is more preferable that it is 50-800 mPa * s, It is further more preferable that it is 100-500 mPa * s. When the viscosity of the insulating liquid is within the above range, when the liquid developer is squeezed out from the developer container onto the application roller, an appropriate amount of the insulating liquid adheres to the toner particles, and the developability of the toner image. , Transferability can be made particularly excellent. Further, the toner particles can be made more highly dispersible, and in an image forming apparatus as described later, the liquid developer can be supplied more uniformly to the application roller. It is possible to more effectively prevent the liquid developer from dripping. In addition, aggregation and sedimentation of the toner particles can be prevented, and the dispersibility of the toner particles in the insulating liquid can be made higher. On the other hand, when the viscosity of the insulating liquid is less than the lower limit value, there is a possibility that problems such as dripping of the liquid developer from the application roller or the like may occur in the image forming apparatus described later. On the other hand, if the viscosity of the insulating liquid exceeds the upper limit, the dispersibility of the toner particles cannot be sufficiently increased, and the liquid developer cannot be more uniformly supplied to the application roller in an image forming apparatus as described later. There is a case. However, the viscosity in this specification refers to a value measured at 25 ° C.
The electrical resistance of the insulating liquid as described above at room temperature (20 ° C.) is preferably 1 × 10 ⁹ Ωcm or more, more preferably 1 × 10 ¹¹ Ωcm or more, and 1 × 10 ¹³ Ωcm or more. More preferably.
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]
The toner particles include at least an ester wax plasticized with the above-described fatty acid monoester and a binder resin (resin material).

1. Ester wax First, the ester wax will be described.
In the present invention, the ester wax contained in the toner particles is plasticized with the fatty acid monoester contained in the insulating liquid described above.
Further, such an ester wax is present in a state where at least a part thereof is exposed on the surface of the toner particles.

By the way, as described above, when an insulating liquid containing a fatty acid monoester is used, the resin material constituting the toner particles is plasticized and the low-temperature fixability is improved, but the surface of the toner particles becomes soft due to plasticization. Therefore, in the liquid developer, the toner particles tend to aggregate with time and there is a problem that storage stability is lowered.
On the other hand, the liquid developer of the present invention can improve the storage stability of the liquid developer by including in the toner particles an ester wax plasticized with a fatty acid monoester. This is considered to be due to the following reasons.

  That is, ester wax is a component that can maintain a relatively hard state even in a plasticized state. Therefore, since a part of the ester wax is exposed on the surface of the toner particles, when the toner particles are in contact with each other, the plasticized resin materials on the surfaces of the toner particles are effectively in contact with each other. Can be prevented. As a result, aggregation of toner particles can be prevented, and the storage stability of the liquid developer can be improved.

Further, the ester wax plasticized with the fatty acid monoester has a lower melting point than the same ester wax not plasticized with the fatty acid monoester. Therefore, the toner particles can be dissolved at a relatively low temperature without applying a very high temperature, and the toner particles can be fixed at a low temperature.
Furthermore, ester wax is a component having sharp melt properties. For this reason, during storage (when there is not much change in heat), the toner particles are prevented from agglomerating, thereby contributing to the storage stability of the liquid developer. Melts and contributes to low temperature fixability.

An ester wax plasticized with a fatty acid monoester has a lower melting point than the same ester wax not plasticized with a fatty acid monoester. When the melting point of the same ester wax not plasticized by Tm ₁ is Tm ₁ and the melting point of the ester wax plasticized by the fatty acid monoester is Tm ₂ , the relationship 2 ≦ Tm ₁ −Tm ₂ ≦ 20 is satisfied. It is preferable to satisfy the relationship of 2 ≦ Tm ₁ −Tm ₂ ≦ 15. Thereby, the effect of this invention can be made more remarkable. In the present specification, the melting point of the plasticized ester wax refers to the absorption start value (inflection point) at 2ndrun measured by differential scanning calorimetry (DSC) using toner particles as a sample.

  The ester wax as described above is preferably present in the toner particles so as to cover at least a part of the surface of the toner particles. Thereby, when the toner particles come into contact with each other, it is possible to more effectively prevent the plasticized resin materials on the surfaces of the toner particles from coming into contact with each other. As a result, the storage stability of the liquid developer can be further improved.

The melting point of the ester wax not plasticized with the fatty acid monoester is preferably 65 to 100 ° C, more preferably 65 to 90 ° C, and further preferably 65 to 85 ° C. Thereby, the storage stability and low-temperature fixability of the liquid developer can be further improved.
Examples of ester waxes include carnauba wax, rice wax, methyl laurate, methyl myristate, methyl palmitate, methyl stearate, butyl stearate, candelilla wax, cotton wax, wood wax, beeswax, lanolin, and montan wax. Etc., and one or more of these can be used in combination. Among the above, carnauba wax has a high sharp melt property, and therefore can be suitably used for the liquid developer of the present invention.
The content of the ester wax is preferably 1 to 20 parts by weight and more preferably 3 to 15 parts by weight with respect to 100 parts by weight of the resin material. Thereby, the storage stability and low-temperature fixability of the liquid developer can be further improved.

2. Resin material (binder resin)
The toner particles are made of a material containing a resin material as a main component.
In the present invention, the resin (binder resin) is not particularly limited, and for example, a known resin can be used. Among these, the polyester resin has high affinity with the above-described fatty acid monoester due to the similarity of its molecular structure. Therefore, when the polyester resin is used as the resin material, the dispersibility of the toner particles in the liquid developer is improved. It can be made particularly excellent. Moreover, the polyester resin has high transparency, and when used as a binder resin, the color developability of the obtained image can be made high. Further, since the polyester resin has high affinity with the ester wax described above, it is possible to effectively prevent the wax from being detached from the toner particles into the insulating liquid. As a result, the storage stability of the liquid developer can be further increased.
Although the glass transition point of the resin material used by this invention is not specifically limited, It is preferable that it is 15-70 degreeC, It is more preferable that it is 20-55 degreeC, It is further more preferable that it is 25-50 degreeC. Thereby, the low temperature fixability of the liquid developer can be further improved. Further, the liquid developer is more suitable for image formation at high speed.

3. Colorant The toner may contain a colorant. The colorant is not particularly limited, and for example, known pigments and dyes can be used.
4). 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 above materials, for example, zinc stearate, zinc oxide, cerium oxide, silica, titanium oxide, iron oxide, fatty acid, fatty acid metal salt, etc. are used as the constituent material (component) of the toner particles. May be.

[Toner particle shape]
The average particle size of the toner particles in the present invention composed of the above materials is preferably 0.7 to 3 μm, more preferably 0.8 to 2.5 μm, and 0.8 to More preferably, it is 2.0 μm. When the average particle diameter of the toner particles is within the above range, the variation in characteristics among the toner particles is small, and the liquid developer as a whole is made highly reliable while being formed with the liquid developer. The resolution of the toner image can be made sufficiently high. Further, it is possible to improve the dispersion of the toner particles in the insulating liquid and to improve the storage stability of the liquid developer. In the present specification, “average particle diameter” refers to an average particle diameter based on volume.

≪Liquid developer manufacturing method≫
As an example of the method for producing the liquid developer of the present invention, a case where associated disintegrated particles are used as toner particles will be described. The production method to be described mainly includes an associating particle forming step of associating fine particles composed of a material (toner constituent material) containing a resin material and an ester-based wax to obtain associating particles, and associating particles in the fatty acid monoester. And crushing to obtain toner particles, and mixing step of mixing the obtained toner particles and other components constituting the insulating liquid.

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

[Aqueous emulsion]
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 aqueous 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 small variations in size and shape among the particles.

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

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

(Dispersoid (fine particles))
The dispersoid includes a component constituting the toner particles in the liquid developer, and is composed of a material including at least a resin material and an ester wax.
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 small variations in size and shape among the particles.

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

Moreover, the composition of the solvent can be appropriately selected according to, for example, the composition of the resin and the colorant described above, the composition of the aqueous dispersion medium, and the like.
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. 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.
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 the toner constituent material 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 resin material. The resin liquid may be a molten liquid obtained by heating a resin material. Further, for the preparation of the resin liquid, for example, a kneaded product obtained by kneading a toner constituent material such as a resin material, an ester wax, or a colorant may be used. By using such a kneaded product, each component in the kneaded product obtained by kneading can be obtained even when the constituent materials of the toner contain components that are hardly dispersed or compatible with each other. It can be in a sufficiently compatible and finely dispersed state. In particular, when a pigment (colorant) having a relatively low dispersibility in the solvent as described above is used, the resin component or the like is effective around the pigment particles by being kneaded in advance before being dispersed in the solvent. Thus, the dispersibility of the pigment in the solvent is improved (particularly fine dispersion in the solvent is possible), and the color developability of the finally obtained toner is also improved. For this reason, in the case where the constituent material of the toner contains a component that is poor in dispersibility in the aqueous dispersion medium of the aqueous emulsion or a component inferior in solubility in the solvent contained in the dispersion medium of the aqueous emulsion. Even so, the dispersibility of the dispersoid in the aqueous emulsion can be made particularly excellent.

Next, an aqueous emulsion in which a dispersoid containing a resin material is dispersed in an aqueous dispersion medium is obtained by gradually adding the resin liquid to the stirred aqueous solution while dropping. By preparing an aqueous emulsion by such a method, the circularity of the dispersoid in the aqueous emulsion can be further increased. As a result, the finally obtained toner particles 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.
Further, instead of the above operation, a water-soluble solution may be gradually added dropwise to the stirred resin liquid. By adding an aqueous solution, the resin liquid undergoes phase inversion emulsification, and an aqueous emulsion in which a dispersoid containing a resin material is dispersed in an aqueous dispersion medium, similar to the aqueous emulsion obtained by the above operation, is obtained. It is done.

[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 preferably 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. If 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.

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

<Crushing process>
Next, the associated particles obtained as described above are 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.
Thus, by crushing in the fatty acid monoester, the resin material and the ester wax can be efficiently plasticized during crushing. Further, the plasticized ester wax exposed on the surface of the pulverized particles (toner particles) formed by pulverization spreads along the surface of the pulverized particles by the energy of pulverization. Accordingly, the ester wax covers at least a part of the surface of the toner particles, and the storage stability of the liquid developer can be further improved.

Moreover, since the fatty acid monoester has a relatively low viscosity, the associated particles can be efficiently crushed.
In addition, since the toner particles are obtained by crushing the associated particles, the generation of fine powder (particles that are extremely smaller than the target size particles) is more effective than conventional pulverization methods and wet pulverization methods. Can be prevented. As a result, it is possible to effectively prevent deterioration of characteristics such as charging characteristics of the liquid developer finally obtained.
It is also possible to prepare relatively small associated particles and disperse the associated particles as toner particles in an insulating liquid without crushing them to obtain a liquid developer. In this case, the associated particles are dried. At this time, since the particles are small, aggregation or the like is likely to occur, and the size of the toner particles varies.

Although the time required for crushing depends on the type of equipment used for crushing, for example, when crushing with a ball mill using a ball having a diameter of about 1 to 10 mm, it is preferably about 10 to 300 hours, More preferably, it is about 100 to 200 hours. Thereby, generation of fine powder can be prevented, and a liquid developer having a uniform toner particle diameter can be produced.
After pulverization, if necessary, the remaining insulating liquid component is added to obtain the liquid developer of the present invention.
In addition, it is preferable to add a polymer dispersant to the fatty acid monoester before mixing the fatty acid monoester and the associated particles. As a result, the polymer dispersant acts as a grinding aid, and the associated particles can be crushed more efficiently and the dispersibility of the resulting toner particles can be made higher.

<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 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.

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

As shown in FIGS. 1 and 2, 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, and a fixing unit. (Fixing device) F40 and four liquid developer supply portions 80Y, 80M, 80C, and 80K are provided.
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 single color 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. The image forming apparatus includes a body 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 photoreceptor 10Y has a cylindrical base material and a photosensitive layer formed on the outer peripheral surface thereof, and can rotate around a central axis. In this embodiment, as shown by an arrow in FIG. Rotate clockwise.
The photoreceptor 10Y is supplied with a liquid developer by a developing unit 100Y described later, and a layer of the liquid developer is formed on the surface.

  The charging roller 11Y is a device for charging the photoconductor 10Y, and the exposure unit 12Y is a device for forming a latent image on the photoconductor 10Y charged by irradiating a laser. The exposure unit 12Y includes a semiconductor laser, a polygon mirror, an F-θ lens, and the like, and charges a modulated laser based on an image signal input from a host computer (not shown) such as a personal computer or a word processor. Irradiate onto the photoconductor 10Y.

The developing unit 100Y is a device for developing the latent image formed on the photoreceptor 10Y using the liquid developer of the present invention. Details of the developing unit 100Y will be described later.
The photoconductor squeeze device 101Y is disposed on the downstream side of the developing unit 100Y in the rotation direction so as to face the photoconductor 10Y. The photoconductor squeeze roller 13Y and the photoconductor squeeze roller 13Y are pressed and slidably attached to the surface. The cleaning blade 14Y removes the liquid developer and the developer collection unit 15Y that collects the removed liquid developer. The photoreceptor squeeze device 101Y has a function of collecting excess carrier (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 unit 40 by the primary transfer backup roller 51Y.
The photoconductor cleaning blade 17Y is a rubber member that is in contact with the surface of the photoconductor 10Y, and remains on the photoconductor 10Y after the image is transferred onto the intermediate transfer portion 40 by the primary transfer backup roller 51Y. It has a function of scraping off and removing the liquid developer.
The developer recovery unit 18Y has a function of recovering the liquid developer removed by the photoconductor cleaning blade 17Y.

The intermediate transfer unit 40 is an endless elastic belt member, is wound around a belt driving roller 41 and a tension roller 42, and is stretched by the primary transfer backup rollers 51Y, 51M, 51C, and 51K. It is rotationally driven by the driving roller 41 while contacting with 10M, 10C, 10K.
A single color image corresponding to each color formed by the developing units 30Y, 30M, 30C, and 30K is sequentially transferred to the intermediate transfer unit 40 by the primary transfer backup rollers 51Y, 51M, 51C, and 51K, and a single color corresponding to each color is transferred. The images 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 secondarily transferred and superposed one after another, and recorded on paper, film, cloth, and the like in a lump. Secondary transfer is performed on the medium F5. Therefore, in transferring the toner image 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 the 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.

A cleaning device including an intermediate transfer unit cleaning blade 46 and a developer recovery unit 47 is disposed on the tension roller 42 side that stretches the intermediate transfer unit 40 together with the belt drive roller 41.
The intermediate transfer portion cleaning blade 46 has a function of scraping and removing the liquid developer adhering to the intermediate transfer portion 40 after the image is transferred onto the recording medium F5 by the secondary transfer roller 61.

The developer recovery unit 47 has a function of recovering the liquid developer removed by the intermediate transfer unit cleaning blade 46.
An intermediate transfer unit squeeze device 52Y is disposed downstream of the primary transfer backup roller 51Y in the moving direction of the intermediate transfer unit 40.
The intermediate transfer unit squeeze device 52Y is provided as a means for removing excess insulating liquid from the transferred liquid developer when the liquid developer transferred onto the intermediate transfer unit 40 has not reached the desired dispersion state. ing.

  The intermediate transfer unit squeeze device 52Y includes an intermediate transfer unit squeeze roller 53Y, an intermediate transfer unit squeeze backup roller 54Y disposed opposite to the intermediate transfer unit squeeze roller 53Y with the intermediate transfer unit 40 interposed therebetween, and an intermediate transfer unit squeeze roller 53Y. It comprises an intermediate transfer unit squeeze cleaning blade 55Y that cleans the surface by pressing and sliding, and a developer recovery unit 15M.

  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 unwanted toner. . The developer recovery unit 15M uses a mechanism for recovering the carrier recovered by the cleaning blade 14M of the magenta photosensitive member squeeze roller disposed downstream in the moving direction of the intermediate transfer unit 40. The developer transfer unit squeeze the intermediate transfer unit squeeze roller 53Y. This is also used for the cleaning blade 55Y. In this way, in the developer collection units 15M, 15C, and 15K (developer collection units 15C and 15K are not shown) of the image carrier squeeze device for the second and subsequent colors, the primary transfer backup roller 51 of the previous color ( Y, M, C) is used as a developer recovery unit of the intermediate transfer unit squeeze device 52 (Y, M, C) disposed downstream of the intermediate transfer unit 40 in the moving direction, so that the interval between them is constant. It can be regulated, and the structure can be simplified and the size can be reduced.

The secondary transfer unit 60 includes a cleaning device including a secondary transfer roller 61 facing the belt driving roller 41 with the intermediate transfer unit 40 interposed therebetween, and a cleaning device including a cleaning blade 62 and a developer recovery unit 63 of the secondary transfer roller 61. Be placed.
In the secondary transfer unit 60, the recording medium F5 is conveyed and supplied in accordance with the timing at which the intermediate transfer image formed on the intermediate transfer unit 40 by overlapping colors reaches the transfer position of the secondary transfer unit 60. The intermediate transfer image is secondarily transferred to the recording medium F5.
The toner image (transfer image) F5a transferred onto the recording medium F5 by the secondary transfer unit 60 is sent to a fixing unit F40, which will be described later, and fixed.

The cleaning blade 62 has a function of scraping and removing the liquid developer adhering to the secondary transfer roller 61 after the image is transferred onto the recording medium F5 by the secondary transfer roller 61.
The developer recovery unit 63 has a function of recovering the liquid developer removed by the cleaning blade 62.

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.
The application roller 32Y is 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 has a diameter of about 25 mm. . In the present 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 clockwise, thereby supporting the liquid developer in the liquid developer storage section 31Y in the groove, and the supported liquid developer is transferred to the developing roller 20Y. Transport to.

  The regulating blade 33Y is in contact with the surface of the coating roller 32Y and regulates the amount of liquid developer on the coating roller 32Y. That is, the regulation blade 33Y plays a role of scraping off the 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 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 coating roller 32Y rotates and advances from the liquid developer as viewed from the vertical surface A (that is, the left side in FIG. 2 as viewed from the vertical surface 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. Further, the excess liquid developer 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, and the coating roller 32Y. , The liquid developer is stored in 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 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 body layer has a two-layer structure. As the inner layer, urethane rubber having a rubber hardness of about 30 degrees JIS-A and a thickness of about 5 mm is used, and as the surface layer (outer layer), the rubber hardness is JIS. A urethane rubber having a thickness of about 30 μm at about 85 ° A is provided. The developing roller 20Y is in pressure contact with the coating 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. 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 liquid developer removed by the cleaning blade 23Y is collected in the liquid developer reservoir 31Y and reused.

  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.

As shown in FIGS. 1 and 2, the image forming apparatus 1000 includes liquid developer replenishing sections 80Y, 80M, 80C, and 80K that replenish liquid developer to the developing section 30Y. Since the configurations of the liquid developer supply portions 80Y, 80M, 80C, and 80K are the same, the liquid developer supply portion 80Y will be described below.
The liquid developer supply unit 80Y includes a recovered liquid developer storage unit 81Y, a supply liquid developer storage unit 82Y, transport means 83Y and 84Y, a pump 85Y, and a filter 86Y.

  The recovered liquid developer storage unit 81Y mainly stores the recovered liquid developer recovered by the developer recovery unit 18Y, and supplies the recovered liquid developer to the liquid developer storage unit 31Y of the developing unit 30Y by the transport unit 83Y. . In addition, the liquid developer is stored in the replenishment liquid developer storage portion 82Y, and the liquid developer is supplied to the liquid developer storage portion 31Y by the transport means 84Y. The composition of the liquid developer stored in the replenishment liquid developer storage portion 82Y and the composition of the recovered liquid developer stored in the recovered liquid developer storage portion 81Y are the same as the liquid developer stored in the liquid developer storage portion 31Y. It may be different or different.

Further, the liquid developer collected in the developer collecting unit 18Y is supplied to the liquid developer replenishing unit 80Y through the conveyance path 70Y.
The transport path 70Y is provided with a pump 85Y. The pump 85Y transports the liquid developer recovered by each developer recovery section to the recovered liquid developer storage section 81Y.
Further, a filter 86Y is provided in the conveyance path 70Y, and coarse particles, foreign matter, and the like can be removed from the collected liquid developer. Solid content such as coarse particles and foreign matter removed by the filter 86Y is detected by a filter state detection means (not shown). Then, the filter 86Y is replaced based on the detection result. Thereby, the filtering function of the filter 86Y can be stably maintained.

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. 4, 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.
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.
The pressure roller F2 includes a roller base material F2b made of a pipe material and an elastic body F2c covering the outer periphery thereof, and is rotatable in the clockwise direction indicated by an arrow in the drawing.

  A PFA layer is provided on the surface layer of the elastic body F1c of the heat fixing roller F1. As a result, the elastic bodies F1c and 2c have different thicknesses, but the elastic bodies F1c and 2c are substantially uniformly elastically deformed to form a so-called horizontal nip, and with respect to the peripheral speed of the heat fixing roller F1. Since there is no difference in the conveyance speed of the heat-resistant belt F3 or the recording medium F5, which will be described later, extremely stable image fixing is possible.

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 sliding contact with the inner peripheral surface of the heat-resistant belt F3 to clean foreign matter, abrasion powder, and the like on the inner peripheral surface of the heat-resistant belt F3. By cleaning the foreign matter, wear powder, and the like in this way, the heat-resistant belt F3 is refreshed, and the above-described factor of instability 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, and 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) to the surface of the heat fixing roller F1 after fixing the toner image F5a on the recording medium F5. . The removing blade F12 can remove the insulating liquid and simultaneously remove the toner and the like that have moved onto the heat fixing roller F1 during 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 160 ° C, more preferably 100 to 150 ° C, and further preferably 100 to 140 ° C.

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

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

[1] Production of liquid developer (Example 1)
<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 (glass transition point: 47 ° 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>
6. Colorant master solution: 33 parts by weight, methyl ethyl ketone: 200 parts by weight, polyester resin: 73 parts by weight, water-based carnauba wax emulsion (melting point Tm _{1 of} unplasticized carnauba wax: 71.5 ° C.): Eight parts by weight (parts by weight as pure carnauba wax) were added and mixed with an Eiger motor mill (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) 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: 100 parts by weight, soybean oil fatty acid methyl: 150 parts by weight, polymer dispersant (trade name “Solsperse 13900” manufactured by Nippon Lubrizol Co., Ltd.): 2.5 parts by weight and stearic acid Aluminum (made by Japanese fats and oils): 1.25 parts 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 completion of the crushing, 250 parts by weight of rapeseed oil (manufactured by Nisshin Oilio Co., Ltd., trade name “High Oleic Rapeseed Oil”) was added to disperse 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.

(Examples 2 to 5)
Liquid developers corresponding to the respective colors were produced in the same manner as in Example 1 except that the ester wax content was adjusted to the values shown in Table 1.
(Examples 6 to 8)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that an ester wax having a melting point as shown in Table 1 was used.

(Examples 9 to 11)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that a polyester resin having a glass transition point as shown in Table 1 was used as the resin material.
(Examples 12 to 14)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that the content of soybean oil fatty acid methyl contained in the insulating liquid was adjusted as shown in Table 1.

(Example 15)
Liquid developers corresponding to the respective colors were produced in the same manner as in Example 1 except that soybean oil (Nisshin Oilio Co., Ltd.) was used instead of rapeseed oil.
(Example 16)
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 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 is used instead of soybean oil fatty acid methyl, and liquid paraffin (trade name “Cosmo White P-60” manufactured by Cosmo Oil Co., Ltd.) is used instead of rapeseed oil, In the same manner as in Example 1, liquid developers corresponding to the respective colors were produced.

(Example 17)
Liquid development corresponding to each color was carried out in the same manner as in Example 1 except that a styrene-acrylic acid ester copolymer having a glass transition point of 20 ° C. and a softening temperature of 81 ° C. was used as the resin material constituting the toner particles. An agent was produced.

(Comparative Example 1)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that the aqueous carnauba wax emulsion was not added.
(Comparative Example 2)
Liquid developers corresponding to the respective colors were produced in the same manner as in Example 1 except that Isopar H (trade name of Exxon Chemical Co., Ltd.) was used instead of soybean oil fatty acid methyl.

(Comparative Example 3)
Liquid development corresponding to each color in the same manner as in Example 1 except that low molecular weight propylene wax (manufactured by Sanyo Chemical Industries, trade name “Sunwax 131P”, melting point: 108 ° C.) was used instead of the water-based carnauba wax emulsion. An agent was produced.
Table 1 shows materials constituting the liquid developer for each of the above Examples and Comparative Examples. The polyester resin is indicated as PES, and the styrene-acrylic acid ester copolymer is indicated as ST-AC. The low molecular weight propylene wax is denoted as PP. Further, the melting point Tm ₂ of the plasticized ester wax contained in the toner particles in the obtained liquid developer was measured according to the following procedure and is shown in Table 1.

<Measurement of melting point of plasticized ester wax>
First, 10 g of the liquid developer obtained in each of the above examples and comparative examples is placed on a filter paper to separate the oil component (insulating liquid).
Next, the solid content obtained by separating the oily component is put into a 10 mL sample container, and about 10 mL of Isopar H (petroleum saturated hydrocarbon manufactured by ExxonMobil Co., Ltd.) is added and shaken sufficiently.
Next, the mixed liquid is further solid-liquid separated with a filter paper. The solid content remaining on the filter paper was dried under room temperature conditions (20 ° C., 40% RH) for 24 hours to obtain a DSC measurement sample.
The obtained sample was measured by differential scanning calorimetry (DSC), and the absorption start value (inflection point) at 2ndrun was defined as the melting point Tm ₂ of the plasticized ester wax.

[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 using the liquid developer obtained in each of the above examples and comparative examples was recorded on a recording paper (quality paper manufactured by Seiko Epson Corporation). LPCPPA4). Thereafter, thermal fixing was performed using a fixing device as shown in FIG. 4 at a set temperature of the heat fixing roller of 130 ° C. and a printing speed of 30 sheets / minute.

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] Low-temperature fixability Using an image forming apparatus as shown in FIG. 1, images of a predetermined pattern with the liquid developer obtained in each of the examples and comparative examples were recorded on a recording paper (manufactured by Seiko Epson Corporation). , High quality paper LPCPPA4). Thereafter, using a fixing device as shown in FIG. 4, heat fixing was performed at three set temperatures of 110 ° C., 130 ° C., and 150 ° C. for the heat fixing roller.

  Thereafter, after confirming the non-offset area, a Scotch mending tape 10 mm width 810-1-18 was pasted on the fixed image on the recording paper obtained at each level, and 5 cm / s in a direction of 170 ° with respect to the recording paper surface. The tape was peeled off at a speed of 5 mm, and the residual density of the image density was measured by “X-Rite model 528” manufactured by X-Rite Inc. The evaluation was made according to the following five 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).

[2.3] Storage Stability The liquid developers obtained in the above Examples and Comparative Examples were allowed to stand for 12 hours in an environment of temperature: 55 ° C. and humidity: 30% RH. Thereafter, the state of the toner in the liquid developer was visually confirmed and evaluated according to the following five-step criteria.
A: No toner particle floating or coagulation sedimentation is observed.
B: Floating and coagulation sedimentation of toner particles are hardly observed.
C: Slight floating or coagulation sedimentation of toner particles is observed, but as a liquid developer
There is no problem.
D: Floating or coagulation sedimentation of toner particles is clearly observed.
E: Suspension and coagulation sedimentation of toner particles are remarkably observed.
These results are shown in Table 2.

As is apparent from Table 2, the liquid developer of the present invention was excellent in low-temperature fixability and storage stability. On the other hand, satisfactory results were not obtained with the liquid developers of the comparative examples.
In the evaluation of the fixing strength, when the printing speed was increased from 30 sheets / minute to 40 sheets / minute, 50 sheets / minute, and 60 sheets / minute and evaluated in the same manner as described above, the same result was obtained. It was. This shows that the liquid developer of the present invention is suitable for high-speed printing.
Further, when the toner particles in the liquid developer obtained in each Example were separated and the surface of the toner particles was analyzed by TOF-SIMS, at least a part of the surface of the toner particles was covered with ester wax. It was confirmed that

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

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Toner particle 1000 ... Image forming apparatus 10Y, 10M, 10C, 10K ... Photoconductor 11Y ... Charging roller 12Y ... Exposure unit 13M, 13Y ... Photoconductor squeeze roller 14M, 14Y ... Cleaning blade 15M, 15Y ... 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 Blades 30Y, 30M, 30C, 30K ... developing unit 31Y ... liquid developer storage unit 32Y ... application roller 33Y ... regulator blade 34Y ... developer stirring roller 40 ... intermediate transfer unit 41 ... belt drive roller 42 ... tension Roller 46 ... Intermediate transfer part cleaning blade 47 ... Developer recovery part 51Y, 51M, 51C, 51K ... Primary transfer backup roller 52Y, 52M, 52C, 52K ... Intermediate transfer part squeeze device 53Y ... Intermediate transfer part squeeze roller 54Y ... Intermediate Transfer unit squeeze backup roller 55Y ... Intermediate transfer unit squeeze cleaning blade 60 ... Secondary transfer unit 61 ... Secondary transfer roller 62 ... Cleaning blade 63 ... Developer recovery unit 70Y ... Conveyance path 80Y, 80M, 80C, 80K ... Liquid developer Replenishment unit 81Y ... recovered liquid developer storage unit 82Y ... replenishment liquid developer storage unit 83Y, 84Y ... conveying means 85Y ... pump 86Y ... filter 100Y ... development unit 101Y ... photoconductor squeeze device F40 ... fixing unit (fixing device) F1 ... heat fixing roller (heating roller) F1a ... column halogen lamp F1b ... roller base material F1c ... elastic body F12 ... removal blade F2 ... pressure roller F2a ... rotary shaft F2b ... roller base material F2c ... elastic body F3 ... heat-resistant belt F4 ... belt tension member F4a ... protruding wall F4f ... recess F5 ... recording medium F5a ... toner image F6 ... cleaning member F7 ... frame F9 ... spring

Claims (8)

An insulating liquid containing a fatty acid monoester;
Toner particles composed of a material containing a resin material and an ester wax,
A liquid developer, wherein the ester wax contained in the toner particles is plasticized with the fatty acid monoester. When the melting point of the ester wax in an unplasticized state is Tm ₁ [° C.] and the melting point of the ester wax in a state plasticized with the fatty acid monoester is Tm ₂ [° C.], 2 ≦ The liquid developer according to claim 1, wherein a relationship of Tm ₁ −Tm ₂ ≦ 20 is satisfied.   3. The liquid developer according to claim 1, wherein a melting point of the ester wax in a state not plasticized with the fatty acid monoester is 65 to 100 ° C. 4.   The liquid developer according to claim 1, wherein the ester wax includes carnauba wax.   5. The liquid developer according to claim 1, wherein the content of the fatty acid monoester in the insulating liquid is 1.0 to 50 wt%.   The liquid developer according to claim 1, wherein the resin material includes a polyester resin. Associating fine particles composed of a material containing the resin material and the ester wax to obtain associated particles;
The liquid developer according to any one of claims 1 to 6, wherein the liquid developer is produced using a method comprising: pulverizing the associated particles in a fatty acid monoester constituting the insulating liquid to obtain toner particles. . Using a plurality of liquid developers having different colors, a plurality of developing units that form the monochromatic image corresponding to each color;
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;
Toner particles including a resin material and an ester wax,
An image forming apparatus, wherein the ester wax contained in the toner particles is plasticized with the fatty acid monoester.

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