JP2008299141A - Liquid developer, method for manufacturing liquid developer and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid developer not harmful to the environment, excellent in low-temperature fixability and capable of firmly fixing toner particles on a recording medium, to provide a method for manufacturing a liquid developer by which such a liquid developer can be efficiently manufactured, and to provide an image forming apparatus using such a liquid developer. <P>SOLUTION: The liquid developer has toner particles consisting mainly of a resin material and an insulating liquid, wherein the toner particles contain a fatty acid monoester and the resin material contained in the toner particles are swollen with the fatty acid monoester. The insulating liquid preferably contains a fatty acid triglyceride. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid developer, a method for producing 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, toner particles are effectively prevented from agglomerating in the liquid developer, so that fine toner particles can be used, and the binder resin has a low melting point. Things 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, the conventional liquid developer has the following problems. Insulating liquids that have been used in conventional liquid developers are generally mainly petroleum-based hydrocarbons. In such a liquid developer, an insulating liquid adheres to the surface of the toner particles during fixing. In the conventional liquid developer, the fixing strength is lowered due to the presence of the insulating liquid adhering to the surface of the toner particles, and a sufficiently satisfactory fixing characteristic cannot be obtained.

  In order to solve such problems, attempts have been made to improve the fixing strength by oxidative polymerization reaction of fats and oils at the time of fixing, using naturally derived fats and oils such as vegetable oil as the insulating liquid (for example, Patent Document 1). reference.). However, the liquid developer using the oils and fats as described above can improve the fixing strength but cannot obtain a sufficient fixing strength. In addition, there has been a problem that offset or the like frequently occurs in fixing at a low temperature accompanying energy saving in recent years.

JP 2006-251252 A

  An object of the present invention is to provide a liquid developer that is environmentally friendly, has excellent low-temperature fixability, and can firmly fix toner particles on a recording medium, and can efficiently manufacture such a liquid developer. Another object of the present invention is to provide a method for producing a liquid developer, and to provide an image forming apparatus using such a liquid developer.

Such an object is achieved by the present invention described below.
The liquid developer of the present invention has toner particles mainly composed of a resin material and a non-volatile insulating liquid,
The toner particles contain a fatty acid monoester,
The resin material contained in the toner particles is swollen by the fatty acid monoester.

In the liquid developer of the present invention, the fatty acid monoester preferably contains a fatty acid having 8 to 22 carbon atoms as a fatty acid component.
In the liquid developer of the present invention, the fatty acid monoester preferably contains an alcohol component having 1 to 4 carbon atoms.
In the liquid developer of the present invention, the insulating liquid preferably contains a fatty acid triglyceride.
In the liquid developer according to the aspect of the invention, it is preferable that the resin material includes an ethylene copolymer.
In the liquid developer of the present invention, the resin material preferably contains a polyester resin.

The method for producing a liquid developer of the present invention includes a resin solution preparation step of preparing a resin solution in which a resin material is dissolved in a first liquid containing a fatty acid monoester.
Adding a second liquid having a lower solubility of the resin material than the first liquid to the resin solution, and precipitating the resin material in the resin solution to form resin fine particles; It is characterized by having.
In the method for producing a liquid developer according to the present invention, the second liquid preferably contains a fatty acid triglyceride.

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 has toner particles mainly composed of a resin material and an insulating liquid, the toner particles contain a fatty acid monoester, and the resin material contained in the toner particles includes: It is swollen by the fatty acid monoester.

  By satisfying the above configuration, it is environmentally friendly, has excellent low-temperature fixability, and provides a liquid developer capable of firmly fixing toner particles on a recording medium, and efficiently produces such a liquid developer. It is possible to provide a method for producing a liquid developer that can be used, and to provide an image forming apparatus using such a liquid developer.

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

[Component material of toner particles (toner material)]
The toner particles (toner) constituting the liquid developer of the present invention contain at least a resin material and a fatty acid monoester. The resin material in the toner particles is swollen by the fatty acid monoester.
The fatty acid monoester has an effect of plasticizing the resin material contained in the toner particles (plastic effect). The toner particles contain a fatty acid monoester, and the resin material is swollen with the fatty acid monoester, so that the resin material in the toner particles is effectively plasticized and has a low melting point. Therefore, when the toner particles are heated at the time of fixing, the resin material in the toner particles can be easily melted and fixed to the recording medium even at a relatively low temperature. Therefore, the toner particles can be fixed in close contact with the recording medium, and the fixing strength of the obtained toner image is excellent. For example, when paper is used as the recording medium, the toner particles can easily enter the gaps between the paper fibers. Then, a part of the toner particles (resin material constituting the toner particles) melted by the heat at the time of fixing penetrates the inside of the recording medium, and in this state, the toner particles are allowed to cool and harden, whereby the anchor effect is obtained. This improves the fixing characteristics between paper and toner particles. For this reason, the liquid developer containing such toner particles is excellent in high-speed and low-temperature fixability and excellent in fixing strength of the formed toner image.

  On the other hand, when the fatty acid monoester is not contained in the toner particles, the excellent low-temperature fixability and fixing characteristics as described above cannot be obtained. That is, at the time of low-temperature fixing, toner particles that do not contain a fatty acid monoester cannot be suitably melted by heat and cannot be fixed in close contact with a recording medium. For this reason, the fixing strength of the fixed toner image is inferior. Further, low temperature offset is likely to occur.

  In addition, the resin material swollen with the fatty acid monoester is plasticized and has a lower melting point than the same resin material not swollen with the fatty acid monoester. Therefore, the swelling of the resin material in the toner particles by the fatty acid monoester can be confirmed by comparing the melting point of the toner particles with the melting point of the resin material constituting the toner particles. That is, when the melting point of the toner particles is lower than the melting point of the resin material constituting the toner particles, the resin material in the toner particles can be regarded as swollen.

Hereinafter, each component constituting the toner particles will be described in detail.
1. Resin Material The toner constituting the liquid developer is composed of a material including a resin material (hereinafter also simply referred to as resin) as a main component.
In the present invention, the resin (resin material) is not particularly limited, and for example, a known resin can be used.

  In particular, when the resin material contains an ethylene copolymer, the following effects can be obtained. Ethylene copolymers have high affinity with fatty acid monoesters. For this reason, the ethylene-based copolymer swollen with the fatty acid monoester can reliably retain the fatty acid monoester, and can prevent the fatty acid monoester from flowing out into the insulating liquid. For this reason, the characteristics of the liquid developer can be stabilized over a long period of time. Further, the ethylene copolymer is suitably plasticized and has a low melting point by swelling with a fatty acid monoester as described later. Therefore, at the time of fixing, even when fixing is performed at a relatively low temperature, the toner particles can be securely fixed to the recording medium, and the obtained toner image is particularly excellent in fixing strength. It will be a thing. In addition, toner particles containing an ethylene-based copolymer can reliably prevent deformation, aggregation, and the like of toner particles even when a liquid developer is stored in a relatively high temperature environment. Examples of such an ethylene copolymer include an ethylene- (meth) acrylic acid copolymer, ethylene vinyl acetate, a partially saponified product of ethylene vinyl acetate, and an ethylene- (meth) acrylic acid ester copolymer. It is done. Among these, when the resin contains an ethylene- (meth) acrylic acid copolymer, the above-described effects can be obtained particularly remarkably.

  The resin may include a material having an ester bond in the chemical structure. When the resin contains such a material, the resin in the toner particles can swell particularly easily, and is plasticized and has a low melting point. In particular, when a liquid developer is produced using a method as described later, the resin material of the toner particles is easily swollen by the fatty acid monoester. For this reason, even when the liquid developer is fixed at a relatively low temperature, the toner particles can be reliably fixed on the recording medium, and the obtained toner image has particularly excellent fixing strength. Further, when fatty acid triglyceride as described later is included as the insulating liquid, the toner particles composed of a resin that satisfies such conditions are in the insulating liquid due to the similarity in chemical structure with the fatty acid triglyceride. Dispersibility is particularly excellent, aggregation of toner particles during storage can be prevented more efficiently, and storage stability of the liquid developer can be particularly excellent. Examples of the resin having an ester bond in such a chemical structure include a polyester resin, a styrene-acrylic acid ester copolymer, and a styrene-methacrylic acid ester copolymer. Among these, the polyester resin has high transparency, and when used as a binder resin, the color developability of the obtained image can be increased.

  Moreover, although melting | fusing point Tm [degreeC] of resin (resin material) is not specifically limited, It is preferable that it is 80-140 degreeC, It is more preferable that it is 85-120 degreeC, It is further that it is 85-115 degreeC. preferable. Thus, the toner particles can be reliably fixed on the recording medium at the time of fixing. Even when the fixing temperature at the time of fixing is relatively low, the toner particles can be suitably fixed on the recording medium. In addition, unintentional deformation and aggregation of toner particles can be prevented more reliably during storage. In the present specification, the melting point can be measured, for example, according to JIS K 7121: 1987.

  Further, when the resin (resin material) contains an ethylene copolymer, the Vicat softening point Tv [° C.] of the resin is not limited to 40 ° C., preferably 45 ° C. to 95 ° C. Is more preferable, and it is still more preferable that it is 50-90 degreeC. Thereby, aggregation of the toner particles during storage and deformation of the toner particles can be prevented more reliably. In addition, in this specification, the Vicat softening point can use what is measured based on JISK7206: 1999, for example.

  Moreover, it is preferable that the acid value of such resin is 0.1-15 mgKOH / mg, it is more preferable that it is 1-10 mgKOH / mg, and it is further more preferable that it is 3-8 mgKOH / mg. Toner particles made of a resin material that satisfies the above conditions are particularly excellent in affinity with the insulating liquid as described above. Thereby, during storage, the dispersibility of the toner particles in the liquid developer becomes better, and the aggregation of the toner particles can be more efficiently prevented over a long period of time.

2. Fatty Acid Monoester As described above, the toner particles contain a fatty acid monoester. The fatty acid monoester is an ester of a fatty acid and a monohydric alcohol.
As described above, the fatty acid monoester is capable of plasticizing the resin material and lowering the melting point by swelling the resin material contained in the toner particles. In particular, in the present invention, the resin material in the toner particles is swollen by the fatty acid monoester. For this reason, at the time of low-temperature fixing, the toner particles of the liquid developer of the present invention can be easily melted and have excellent low-temperature fixability as compared with toner particles not containing a fatty acid monoester. Further, the fixing strength of a toner image formed using this liquid developer can be made excellent. The fatty acid monoester is an environmentally friendly component. Accordingly, it is possible to reduce an environmental load due to leakage of the liquid developer outside 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 component constituting such a fatty acid monoester is not particularly limited. For example, oleic acid, palmitoleic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, arachidonic acid, docosahexaenoic acid (DHA), Unsaturated fatty acids typified by icosapentaenoic acid (EPA), butyric acid, lauric acid, caproic acid, caprylic acid, capric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, etc. Saturated fatty acid etc. are mentioned, 1 type selected from these, or 2 or more types can be used in combination.

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

  Moreover, it is preferable that a fatty acid monoester contains a C8-C22 fatty acid as a fatty acid component. As a result, the fatty acid monoester is particularly easy to swell the resin material of the toner particles, and the resin material swollen by the fatty acid monoester is particularly easily plasticized and has a low melting point. Therefore, the liquid developer has particularly excellent fixing characteristics, and the toner particles can be firmly fixed to the recording medium even when the fixing temperature is low.

  The fatty acid monoester is an ester of a fatty acid and a monovalent alcohol, and the alcohol is preferably an alkyl alcohol having 1 to 4 carbon atoms. As a result, the fatty acid monoester is particularly easy to swell the resin material of the toner particles, and the resin material swollen by the fatty acid monoester is particularly easily plasticized and has a low melting point. Therefore, the toner particles can be firmly fixed on the recording medium. In addition, the chemical stability of the liquid developer is excellent, and the storage stability and long-term stability of the liquid developer are further improved. Examples of such alcohol include methanol, ethanol, propanol, butanol, isobutanol and the like.

3. Colorant The toner particles 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 particles 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 size, etc.]
The average particle size of the toner particles composed of the above materials is preferably 0.7 to 3 μm, more preferably 0.8 to 2.5 μm, and 0.8 to 2 μm. Is more preferable. When the average particle diameter of the toner particles is within the above range, the variation in characteristics among the toner particles is small, and the liquid developer as a whole is made highly reliable while being formed with the liquid developer. The resolution of the toner image can be made sufficiently high. Further, it is possible to reliably prevent the toner particles from being excessively swollen, plasticized, aggregated and deformed by the fatty acid monoester during storage. Further, at the time of fixing, the toner particles are particularly easily melted and can be firmly fixed to the recording medium even at a relatively low temperature. 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, the “average particle size” means a volume-based average particle size unless otherwise specified.
The content ratio of the toner particles in the liquid developer is preferably 10 to 60 wt%, and more preferably 20 to 50 wt%.

<Insulating liquid>
Next, the insulating liquid will be described. The insulating liquid functions as a medium for dispersing the toner particles, and usually has high electrical insulation and non-volatility.
The insulating liquid constituting the liquid developer of the present invention may be anything, but preferably contains a fatty acid triglyceride.

Hereinafter, the fatty acid triglyceride will be described.
The fatty acid triglyceride is a triglyceride of glycerin and a fatty acid.
When the insulating liquid contains a fatty acid triglyceride, the dispersibility of the toner particles is particularly excellent, and the storage stability of the liquid developer is particularly excellent. This is considered as follows. Fatty acid triglycerides have high affinity for fatty acid monoesters. For this reason, the toner particles containing the fatty acid monoester can be preferably dispersed in the insulating liquid containing the fatty acid triglyceride. In addition, the fatty acid triglyceride contained in the insulating liquid can elute the fatty acid monoester adhering to the toner particle surface and reduce the content of the fatty acid monoester on the toner particle surface. The surface of the particles can be made hard. For this reason, it is possible to reliably prevent the toner particles from being aggregated and deformed during storage. In addition, fatty acid triglycerides are relatively large molecules, and it is difficult to swell the resin material by entering the toner particles during storage. For this reason, the fatty acid monoester inside the toner particles is unlikely to come into contact with the fatty acid triglyceride in the insulating liquid outside the toner particles, and is not easily eluted into the insulating liquid. For this reason, the resin material inside the toner particles is kept swollen by the fatty acid monoester. For this reason, even when the surface of the toner particles becomes hard as described above, the liquid developer has excellent low-temperature fixability and can firmly fix the toner particles to the recording medium.

Further, since fatty acid triglyceride is an environmentally friendly component, 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 component contained in the fatty acid triglyceride is not particularly limited. For example, butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristylic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoserine. Saturated fatty acids such as acids, crotonic acid, myristoleic acid, palmitoleic acid, oleic acid, elaidic acid, vaccenic acid, gadoleic acid, erucic acid, nervonic acid and other monounsaturated fatty acids, linoleic acid, α-linolenic acid, γ -Unsaturated fatty acids of polyunsaturated fatty acids such as linolenic acid, arachidonic acid, eleostearic acid, stearidonic acid, arachidonic acid, sardine acid, docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and derivatives thereof 1 or a combination of two or more selected from these Can be used together.

  Among these, when the fatty acid triglyceride contains a saturated fatty acid component, it becomes possible to keep the chemical stability of the liquid developer and the electrical insulation of the insulating liquid even higher. Moreover, among the saturated fatty acids as described above, the number of carbon atoms in the molecule of the saturated fatty acid component is preferably 6-22, more preferably 8-20, and 10-18. More preferably. By including such a saturated fatty acid component, the effects as described above are further prominent.

  Further, when the fatty acid triglyceride contains an unsaturated fatty acid component, the fatty acid triglyceride can contribute to an improvement in long-term storage stability of a toner image obtained after image formation. This is considered as follows. An unsaturated fatty acid component is a component that itself can be cured by being oxidized. For this reason, when a toner image is formed and fixed on a recording medium using a liquid developer containing a fatty acid triglyceride containing an unsaturated fatty acid, the fatty acid triglyceride remaining together with the toner particles in the toner image is oxygen in the air. The toner particles can be oxidatively polymerized, and the toner particles or the toner particles and the recording medium can be particularly firmly bonded. Further, since the unsaturated fatty acid component of the fatty acid triglyceride can be oxidatively polymerized while covering the surface of the toner image, a protective film of the fatty acid triglyceride cured on the surface of the toner image can be formed. As described above, the toner image can be made less deteriorated by a physical external force such as friction, air, light, etc. over a long period of time, and has a particularly excellent long-term storage stability.

Fatty acid triglycerides as described above are, for example, palm oil, palm oil, palm kernel oil, sunflower oil, safflower oil, rice oil, rice bran oil, rapeseed oil, olive oil, sesame oil, canola oil, soybean oil, linseed oil, castor oil, etc. It can be efficiently obtained from naturally-derived oils and fats such as oils and fats derived from plants and oils and fats derived from various animals such as cow oil.
The content of fatty acid triglyceride in the insulating liquid is preferably 20 to 90 wt%, more preferably 30 to 80 wt%, and further preferably 40 to 70 wt%. Thereby, the dispersibility of the toner particles in the liquid developer can be made particularly excellent, and the chemical stability of the liquid developer can be made particularly excellent.

  In addition, other liquids may be used as the insulating liquid. Such a liquid is not particularly limited, and for example, KF96, KF4701, KF965, KS602A, KS603, KS604, KF41, KF54, FA630 (manufactured by Shin-Etsu Silicone), TSF410, TSF433, TSF434, TSF451, TSF437, (momentive)・ Performance Materials Japan GK), SH200 (manufactured by Toray Industries, Inc.) and other silicone oils, Isopar E, Isopar G, Isopar H, Isopar L (Exxon Chemical), Cosmo SP-10, Cosmo White P- 60, Cosmo White P-70, Cosmo White P-120 (manufactured by Cosmo Oil Lubricants), Dyna Fresia W-8, Daphne Oil CP, Daphne Oil KP, Transformer Oil H, Transformer Oil , Transformer oil A, Transformer oil B, Transformer oil S (manufactured by Idemitsu Kosan Co., Ltd.), Cielsol 70, Cielsol 71 (manufactured by Ciel Oil), Amsco OMS, Amsco 460 solvent (manufactured by Spirits), low viscosity / high viscosity liquid paraffin (Wako Pure Chemical Industries), aliphatic hydrocarbons such as octane, isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, cyclohexane, cyclooctane and cyclodecane, fatty acid monoglycerides, fatty acid triglycerides, fatty acid triglycerides such as fatty acids Decomposition products, benzene, toluene, xylene, mesitylene, fatty acid monoesters, and the like. Among these, one kind or two or more kinds can be used in combination.

  Among the above, when the insulating liquid contains an aliphatic hydrocarbon, the following effects can be obtained. Aliphatic hydrocarbons generally have high electrical resistance and are chemically stable. For this reason, the liquid developer using the aliphatic hydrocarbon has particularly excellent developability and transferability, and the resulting toner image is clear with few defects and the like. In addition, aliphatic hydrocarbons tend to penetrate into recording media such as paper. For this reason, at the time of fixing, the insulating liquid containing the aliphatic hydrocarbon system can quickly penetrate into the recording medium. In addition, the aliphatic hydrocarbon has a high affinity with the fatty acid monoester. Therefore, the toner particles swollen, plasticized, and melted by the fatty acid monoester are suitably used as a recording medium together with the aliphatic hydrocarbon. By penetrating and exhibiting an anchor effect in this state, it can be fixed particularly firmly on the recording medium. For this reason, when such a liquid developer is used, even when fixing at high speed and low temperature, the toner particles can be particularly easily contacted, melted, and firmly bonded during fixing. The fixing strength of the obtained toner image is particularly excellent. In addition, the aliphatic hydrocarbon liquid is a liquid that absorbs less moisture. For this reason, when an aliphatic hydrocarbon is contained in an insulating liquid, it can prevent suitably that an insulating liquid absorbs moisture at the time of a preservation | save, and can prevent suitably that an insulating liquid denatures (deteriorates). That is, an aliphatic hydrocarbon having low hygroscopicity and high affinity with the fatty acid monoester surrounds the periphery of the fatty acid monoester, thereby suitably preventing the fatty acid component from being released by contact with the fatty acid monoester and moisture. can do. Further, as described above, the aliphatic hydrocarbon itself is chemically stable and has little modification (deterioration) during storage. For this reason, the liquid developer is particularly excellent in long-term stability.

  Moreover, when the insulating liquid contains silicone oil, the following effects can be obtained. Silicone oil is an organic compound having a siloxane bond as a skeleton. Silicone oil generally has a high electrical resistance. For this reason, when silicone oil is used as the insulating liquid, the liquid developer has particularly high electrical resistance, and toner image transferability and developability are particularly excellent. Further, when the liquid developer contains silicone oil as the insulating liquid, high-speed and low-temperature fixing can be performed particularly easily, and the fixing strength of the obtained toner image is particularly excellent. This is considered as follows. Silicone oil has a low affinity for the fatty acid monoester and the resin constituting the toner particles. For this reason, in the liquid developer containing silicone oil as the insulating liquid, the fatty acid monoester having high affinity with the resin material is selectively held in the toner particles, and the resin material is particularly suitably swollen and plasticized. Lower melting point. For this reason, it is considered that the toner image can be firmly fixed on the recording medium even when fixing is performed at a relatively low temperature and at a high speed. Further, since silicone oil has various viscosities depending on the type, the viscosity of the liquid developer can be made particularly suitable by selecting the silicone oil. Silicone oil is generally a substance that is chemically stable and has little influence on the human body. For this reason, the liquid developer can suitably prevent deterioration of the insulating liquid during storage, and has excellent storage stability. Even when the insulating liquid leaks out of the image forming apparatus, a safe liquid developer can be obtained.

The insulating liquid may be a mixture of fatty acid triglyceride and the liquid described above.
In the liquid developer of the present invention, the insulating liquid is a non-volatile liquid. Thereby, it is possible to reliably prevent the insulating liquid from volatilizing at the time of fixing, and it is possible to reliably prevent the generation of a volatile organic compound (VOC). As a result, the liquid developer is particularly harmless to the human body and living organisms. Moreover, it can be set as an environmentally friendly liquid developer.

  The initial boiling point of the insulating liquid is preferably 105 ° C. or higher, and more preferably 140 ° C. or higher. Thereby, volatilization of the insulating liquid can be prevented more reliably. As a result, the liquid developer is particularly harmless to the human body and living organisms. Further, it can be a liquid developer that is particularly environmentally friendly. The initial boiling point refers to the temperature at which the first drop of the flocculated effluent has fallen under certain conditions and, in particular, obtained by conducting a distillation test based on JIS K 2254. it can. For a liquid composed of one component, for example, a temperature close to the boiling point tends to be the initial boiling point. Also, a liquid composed of two or more components tends to be close to the boiling point of the component having the lowest boiling point when there is no azeotropy.

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, Solsperse (trade name of Nippon Lubrizol), Azisper PB821 (trade name of Ajinomoto Co., Inc.), polycarboxylic acid and salts thereof, 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 polyamine fatty acid condensation polymer is used, the polyamine fatty acid condensation polymer can be attached to the surface of the toner particles, thereby preventing unintentional aggregation of the toner particles. it can.
When the polyamine fatty acid condensation polymer is used, the content of the polyamine fatty acid condensation polymer in the liquid developer is preferably 0.5 to 7.5 parts by weight with respect to 100 parts by weight of the toner particles. More preferably, it is ˜5 parts by weight. Thereby, the effect by using a polyamine fatty acid condensation polymer can be made more remarkable.

The insulating liquid may contain an antioxidant.
The liquid developer (insulating liquid) may contain a charge control agent.
Examples of the charge control agent include metal oxides such as zinc oxide, aluminum oxide, and magnesium oxide, metal salts of benzoic acid, metal salts of salicylic acid, metal salts of alkyl salicylic acid, metal salts of catechol, metal-containing bisazo dyes, nigrosine Examples thereof include dyes, tetraphenylborate derivatives, quaternary ammonium salts, alkylpyridinium salts, chlorinated polyesters, and nitrofunnic acid.
The electric resistance of the insulating liquid at room temperature (20 ° C.) is preferably 1.0 × 10 ¹¹ Ωcm or more, more preferably 1.0 × 10 ¹² Ωcm or more, and 2.0 × 10 ^12. More preferably, it is at least Ωcm.
The dielectric constant of the insulating liquid is preferably 3.5 or less.

In addition, the viscosity (the viscosity measured according to JIS Z8809 using a vibration viscometer at 25 ° C.) of the liquid developer (liquid developer of the present invention) composed of each component as described above is 50 to 1000 mPa · s, more preferably 100 to 1000 mPa · s, and still more preferably 100 to 900 mPa · s. Thereby, since the penetration of the liquid developer into the recording medium becomes more suitable, the fixing characteristics of the toner particles to the recording medium become more excellent. In addition, the image obtained on the recording medium becomes clear with no unevenness, and is particularly suitable as a liquid developer suitable for image formation at high speed.
In addition, the electrical resistance at room temperature (20 ° C.) of the liquid developer composed of the components as described above (the liquid developer of the present invention) is preferably 1.0 × 10 ¹¹ Ωcm or more. More preferably, it is 0.0 × 10 ¹² Ωcm or more.

<< Method for Producing Liquid Developer >>
Next, an example of a method for producing the liquid developer as described above will be described.
The method for producing a liquid developer of the present invention mainly comprises a resin solution adjusting step of preparing a resin solution in which a resin material is dissolved in a first liquid containing a fatty acid monoester, and the first liquid is added to the resin solution. A resin deposition step of adding a second liquid having a lower solubility of the resin material and depositing the resin material in the resin solution to form resin fine particles (toner particles). Further, in the liquid developer manufacturing method of the present embodiment, before the resin solution preparation step, a kneading step of kneading the resin and the colorant to obtain a kneaded product, and crushing the kneaded product to obtain a pulverized product And crushing step. Thereby, the liquid developer as described above can be obtained easily and reliably, and the toner particles easily and reliably contain the fatty acid monoester, and the resin material is swollen by the fatty acid monoester. Further, by depositing the resin material using the insulating liquid and forming the toner particles as described above, it is not necessary to pulverize the constituent material of the toner particles, and the production method of the energy-saving liquid developer is obtained. Further, the first liquid and the second liquid used for the deposition of the resin material are nonvolatile liquids in the present embodiment. For this reason, the first liquid and the second liquid can be used as components of the liquid developer, and it is not necessary to remove unnecessary liquid such as distillation. For this reason, it becomes the manufacturing method of the liquid developer which is excellent in productivity and using resources effectively.

[Kneading process]
First, a resin material and a colorant are kneaded to obtain a kneaded product.
The raw material used for kneading includes the resin material and the colorant as described above. In particular, since the raw material contains a colorant, the air contained in the raw material in this step (especially the air embraced by the colorant) can be efficiently removed, and bubbles are mixed (residual) inside the toner particles. Can be effectively prevented. In addition, by uniformly kneading the resin material and the colorant in this way, the dispersibility and solubility of the colorant in the resin solution described later can be made particularly excellent. The colorant is particularly uniformly distributed. The raw material used for kneading is preferably a mixture of these components in advance.

For the kneading of the raw materials, for example, various kneaders such as a continuous biaxial kneading extruder, a kneader or a batch triaxial roll, a continuous biaxial roll, a wheel mixer, and a blade mixer can be used. Among these, it is preferable to use a twin-screw kneading extruder as the kneading machine. Thereby, while being able to knead | mix a raw material efficiently, the air contained in a raw material can be removed.
Moreover, the raw material used for kneading | mixing may contain the dispersing agent as mentioned above. As a result, the dispersibility and solubility of the colorant in the resin solution to be described later can be made particularly excellent, and thus the toner particles obtained have a particularly uniformly distributed colorant.

[Crushing process]
Next, the kneaded product as described above is pulverized to obtain a pulverized product. Thus, by pulverizing the kneaded product, a resin solution described later can be obtained relatively easily and more uniformly. As a result, the liquid developer finally obtained can also have a smaller toner particle size and can be suitably used for high-resolution image formation.

The pulverization method is not particularly limited, and for example, it can be performed using various pulverizers such as a ball mill, a vibration mill, a jet mill, and a pin mill, and a crusher.
The pulverization process may be performed in multiple steps (for example, two stages of a coarse pulverization process and a fine pulverization process). In addition, after such a pulverization step, a classification process or the like may be performed as necessary. For the classification treatment, for example, a sieve, an airflow classifier or the like can be used.

[Resin solution preparation process]
Next, a resin solution in which the resin material is dissolved in the first liquid containing the fatty acid monoester is prepared. Thus, the resin material can be swollen by the fatty acid monoester by dissolving the resin material in the first liquid containing the fatty acid monoester. For this reason, the obtained toner particles surely contain the fatty acid monoester contained in the first liquid and become swollen.

The resin solution may be prepared by any method. For example, the resin solution can be obtained by mixing the pulverized product as described above and the first liquid containing the fatty acid monoester with a stirrer such as a high-speed stirrer. . Thereby, the resin material contained in the pulverized product can be reliably dissolved in the first liquid, and the colorant can be reliably dispersed and dissolved in the first liquid.
The stirrer that can be used for preparing the resin solution may be any one, and examples thereof include an attritor, a ball mill, a planetary ball mill, a bead mill, a sand mill, a high-speed mixer, and a homogenizer.

Moreover, in this process, in addition to the pulverized material described above, a resin material may be added and mixed. Accordingly, the concentration of the colorant in the toner particles can be easily adjusted in the obtained liquid developer.
In this step, these materials may be heated when the pulverized product and the first liquid are mixed. Thereby, the resin material can be reliably dissolved in the first liquid. In such a case, the material temperature of the material constituting the resin solution is preferably 80 to 160 ° C, and more preferably 90 to 140 ° C. Thereby, the resin material can be easily and reliably dissolved in the first liquid. Moreover, if it is material temperature as above-mentioned, a quality change, volatilization, etc. of the component contained in a resin solution can be prevented reliably.

The first liquid may contain any fatty acid monoester as described above and can dissolve the resin material, and may contain other components. For example, a part of the insulating liquid constituting the liquid developer as described above may be included. Further, for example, a dispersant or the like may be included.
Although the content rate of solid content in a resin solution is not specifically limited, It is preferable that it is 30-70 wt%, and it is more preferable that it is 40-60 wt%. When the solid content is within the above range, the viscosity characteristic of the resin solution can be made particularly suitable while the resin material is reliably dissolved in the first liquid. Further, the concentration of toner particles in the obtained liquid developer can be made sufficiently high.

[Resin deposition process]
Next, a second liquid having a lower solubility of the resin material than the first liquid is added, and the resin material is precipitated in the resin solution to form resin fine particles (toner particles). Thereby, a liquid developer in which toner particles are dispersed in an insulating liquid is obtained. Such a second liquid usually constitutes mainly the insulating liquid of the liquid developer. Moreover, the resin fine particles obtained in this way contain a fatty acid monoester, and the resin material is swollen by the fatty acid monoester. More specifically, when the second liquid is added and the resin material is precipitated as resin fine particles, the resin material takes in and deposits a part of the first liquid having higher affinity (solubility). As described above, since the resin fine particles are precipitated after the resin material is once dissolved in the fatty acid monoester, the resin fine particles contain the fatty acid monoester contained in the first liquid. Further, the fatty acid monoester is uniformly contained in the resin fine particles. In addition, by depositing resin fine particles in this way, resin fine particles (toner particles) having a desired particle size and a narrow particle size distribution can be obtained.

  The second liquid only needs to have a lower solubility of the resin material than the first liquid. For example, the constituent component of the insulating liquid of the liquid developer described above can be used, but includes fatty acid triglyceride. It is preferable. Thereby, resin fine particles (toner particles) having a desired particle size and a uniform size can be obtained easily and reliably. This is considered as follows. Fatty acid triglycerides have low solubility of the resin material and are particularly excellent in affinity with fatty acid monoesters. For this reason, when fatty acid triglyceride is added to the resin solution, the fatty acid triglyceride diffuses quickly into the resin solution, and it is possible to reliably prevent the occurrence of uneven concentration of the fatty acid triglyceride in the resin solution. For this reason, it is considered that resin fine particles having a uniform size are likely to precipitate and grow in the resin solution.

  The addition of the second liquid to the resin solution may be performed by any method, but a method of dropping the second liquid while stirring the resin solution is preferable. As a result, it is possible to reliably prevent the occurrence of uneven concentration of the second liquid in the resin solution, and in particular, resin fine particles having a uniform size can be obtained.

  Any apparatus may be used for stirring the resin solution, but an apparatus capable of applying a shearing force at high speed is preferable. For example, a homogenizer, a homomixer, a planetary mixer, or the like can be used. As a result, the added second liquid can be quickly and uniformly dispersed and dissolved, and the occurrence of uneven concentration of the second liquid can be reliably prevented. Further, the resin fine particles once formed can be more reliably prevented from collapsing while efficiently depositing the resin fine particles. As a result, resin fine particles having a small variation in shape and particle size among the particles can be obtained efficiently.

Moreover, it is preferable that the material temperature in this process is 5-160 degreeC, and it is more preferable that it is 10-150 degreeC. As a result, it is possible to obtain a liquid developer easily and reliably while preventing the material from being altered or decomposed.
In this step, the temperature of the resin solution may not be constant. For example, the resin solution may be one that gradually decreases the temperature. Thereby, the solubility of the resin material of the resin solution can be lowered, and the resin fine particles are easily precipitated. For this reason, the manufacturing method of the liquid developer is particularly excellent in productivity. In this case, the temperature of the resin solution may be lowered when the second liquid is added, or the temperature of the resin solution may be lowered after the addition of the second liquid.

In this step, a charge control agent, a dispersant and the like may be added. These additions may be after the second liquid is added, or may be before the addition. Further, it may be added simultaneously with the second liquid.
Moreover, after adding a 2nd liquid, you may add a liquid further. Thereby, the concentration of the insulating liquid and the toner particles in the liquid developer can be easily adjusted. In this case, the liquid to be added may have the same composition as the first liquid and the second liquid, or may have a different composition.
Alternatively, after adding the second liquid and adding the resin fine particles, the liquid in which the resin fine particles are dispersed may be replaced with another liquid to prepare a liquid developer. In this case, part of the liquid to be dispersed may be replaced, or all of the liquid may be replaced.

≪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 monochrome image.

Since the developing units 30Y, 30M, 30C, and 30K have the same configuration, the developing unit 30Y will be described below.
As shown in FIG. 2, the developing unit 30Y includes a photoconductor 10Y as an example of an image carrier, a charging roller 11Y, an exposure unit 12Y, a development unit 100Y, and a photoconductor along the rotation direction of the photoconductor 10Y. 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. Irradiation is performed on the photoconductor 10Y.

The developing unit 100Y is a device for developing the latent image formed on the photoreceptor 10Y using the liquid developer of the present invention. Details of the developing unit 100Y will be described later.
The photoconductor squeeze device 101Y is disposed on the downstream side of the developing unit 100Y in the rotation direction so as to face the photoconductor 10Y. The photoconductor squeeze roller 13Y and the photoconductor squeeze roller 13Y are pressed and slidably attached to the surface. The cleaning blade 14Y removes the removed liquid developer, and the developer collection unit 15Y collects the removed liquid developer. The photoreceptor squeeze device 101Y has a function of collecting excess carrier (insulating liquid) and originally unnecessary fog toner from the developer developed on the photoreceptor 10Y, and increasing the toner particle ratio 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, wound around a belt driving roller 41 and a tension roller 42, and stretched between primary transfer backup rollers 51Y, 51M, 51C, and 51K. It is rotationally driven by the drive 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 are collectively recorded on paper, film, cloth, and the like. Secondary transfer is performed on the medium F5. Therefore, when the toner image is transferred to the recording medium F5 in the secondary transfer process, even if the surface of the recording medium F5 is a sheet material that is not smooth due to fiber or the like, the secondary transfer characteristics follow the surface of the non-smooth sheet material. An elastic belt member is employed as means for improving the above.

  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 to 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 plane A (that is, the left side in FIG. 2 as viewed from the vertical plane A). The rubber hardness of the regulation blade 33Y is about 77 degrees according to JIS-A, and the hardness (about 77 degrees) of the contact portion of the regulation blade 33Y with the surface of the coating roller 32Y is about the elasticity of the developing roller 20Y described later. It is lower than the hardness (about 85 degrees) of the pressure contact portion of the body layer to the surface of the application roller 32Y. 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 layer has a two-layer structure. As an inner layer, urethane rubber having a rubber hardness of about 30 degrees and a thickness of about 5 mm is used. As a surface layer (outer layer), the rubber hardness is JIS. -A urethane rubber having a thickness of about 30 μm at about 85 degrees A is provided. The developing roller 20Y is in pressure contact with the application roller 32Y and the photoreceptor 10Y in a state of elastic deformation with the surface layer serving as a pressure contact portion.

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

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

The developer compression roller 22Y is provided with a cleaning blade 23Y.
The cleaning blade 23Y has a function of removing the liquid developer adhering to the developer compression roller 22Y. The liquid developer removed by the cleaning blade 23Y is collected in the liquid developer reservoir 31Y and reused.
Further, the developing unit 100Y includes a rubber developing roller cleaning blade 21Y that is in contact with the surface of the developing roller 20Y. The developing roller cleaning blade 21Y is a device for scraping off and removing the liquid developer remaining on the developing roller 20Y after development is performed at the developing position. The liquid developer removed by the developing roller cleaning blade 21Y is collected in the liquid developer storage unit 31Y and reused.

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

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

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 with it). The side surface is formed of a seamless tube having a two-layer structure formed of polyimide. The heat-resistant belt F3 is not limited to this, and can be formed of other materials such as a metal tube such as a stainless steel tube or a nickel electroformed tube, or a heat-resistant resin tube such as silicone.

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

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

The position where the belt stretching member F4 is lightly pressed against the heat fixing roller F1 is the nip initial position, and the position where the pressure roller F2 is pressed against the heat fixing roller F1 is the nip end position.
In the fixing portion F40, the recording medium F5 on which the unfixed toner image F5a is formed enters the fixing nip portion from the nip initial position and passes between the heat-resistant belt F3 and the heat fixing roller F1, and the nip end position. As a result, the unfixed toner image F5a formed on the recording medium F5 is fixed, and then discharged in the tangential direction L of the pressing portion of the pressure roller F2 to the heat fixing roller F1.

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

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

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

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

  Specifically, the heat (fixing temperature) applied by the heat fixing roller F1 is preferably 80 to 160 ° C, more preferably 100 to 150 ° C, and further preferably 100 to 140 ° C. Since the liquid developer of the present invention is excellent in fixability at a low temperature, the toner image can be firmly fixed on the recording medium even when the fixing temperature is such a relatively low temperature. Further, since the fixing can be performed at such a relatively low fixing temperature, the volatilization of the insulating liquid in the liquid developer is particularly small. For this reason, it becomes an environment-friendly liquid developer that is not particularly harmful to living organisms and human bodies.

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. For example, in the above-described embodiment, the resin solution is prepared using a pulverized product obtained by kneading and pulverizing a colorant and a resin material. However, the resin solution may be prepared without using such a pulverized product. For example, a resin solution may be obtained by directly mixing the first liquid, the colorant, and the resin material.

[1] Production of liquid developer (Example 1)
<Preparation of colorant master (kneading process, grinding process)>
First, ethylene- (meth) acrylic acid copolymer as a resin material (melting point: 98 ° C., Vicat softening point: 78 ° C., manufactured by Mitsui DuPont Polychemical Co., Ltd., trade name: Nucrel N410): 40 parts by weight A mixture of 50 parts by weight of a cyan pigment (manufactured by Dainichi Seika Co., Ltd., Pigment Blue 15: 3) as a colorant and 10 parts by weight of a dispersant (manufactured by Ajinomoto Co., Inc., trade name: Ajisper PB821). Prepared. These components were mixed using a 20 L type Henschel mixer to obtain a raw material for a colorant master.
Next, this raw material was kneaded using a biaxial kneading extruder heated to 120 ° C. to obtain a kneaded product. Next, the kneaded product extruded from the extrusion port of the biaxial kneading extruder was cooled (kneading step).
The kneaded product cooled as described above was coarsely pulverized to obtain a powder having an average particle size of 2.0 mm or less to obtain a colorant master (pulverized product). A hammer mill was used for coarse pulverization of the kneaded product (pulverization step).

<Resin solution preparation process>
Next, the obtained colorant master (ground product): 50 parts by weight and an ethylene- (meth) acrylic acid copolymer (melting point: 98 ° C., Vicat softening point: 78 ° C., Mitsui DuPont as an additional resin material) Made by Polychemical Co., Ltd., trade name: Nucrel N410: 50 parts by weight, methyl laurate as a first liquid (fatty acid monoester, manufactured by Lion Corporation, carbon number of fatty acid: 12, trade name: pastel M-12): Stirring and mixing were performed at a rotational speed of 8000 rpm with a homogenizer (manufactured by Microtech Nichion) while heating 100 parts by weight in a stainless steel container until the material temperature became 120 ° C. .
When the material temperature reached 120 ° C., the mixture was stirred with a homogenizer at a rotation speed of 8000 rpm for 30 minutes while keeping the temperature constant to obtain a resin solution. In this resin solution, the pigment was uniformly finely dispersed.

<Resin deposition process>
Next, with respect to the obtained resin solution, heating is stopped and stirring is performed under the same conditions, while resin fine particles (toner particles) are precipitated, and a resin fine particle dispersion in which colored resin fine particles (toner particles) are dispersed is obtained. Obtained. As the second liquid, 300 parts by weight of high oleic rapeseed oil (manufactured by Nisshin Oilio Co., Ltd., trade name: canola oil) was used. The resin fine particles were precipitated by stirring while dropping high temperature oleic rapeseed oil and gradually cooling the resin solution to room temperature.

Next, in the obtained resin fine particle dispersion, zirconium octate (Hope Pharmaceutical Co., Ltd., Octop Zr) as a charge control agent: 5 parts by weight, polyamine aliphatic polymer (Nippon Lubrizol Co., Ltd.) as a dispersant, Product name: Solsperse 11200): 2 parts by weight were added with stirring to obtain a cyan liquid developer. Further, when the volume-based average particle size of the resin fine particles was measured with a Mastersizer 2000 particle analyzer (manufactured by Malvern Instruments Ltd.), the average particle size was 2.3 μm, and coarse particles of 5 μm or more were less than 1 vol%. there were.
(Examples 2 to 10)
A liquid developer was produced in the same manner as in Example 1 except that the resin material, the first liquid, the type of the second liquid, and the content were changed as shown in Table 1.

(Comparative Example 1)
First, polyester resin as a resin material (melting point: 125 ° C., glass transition temperature: 60 ° C.): 40 parts by weight, cyan pigment as a colorant (Pigment Blue 15: 3 manufactured by Dainichi Seika Co., Ltd.): 50 wt. Part and a dispersant (manufactured by Ajinomoto Co., Inc., trade name: Ajisper PB821): 10 parts by weight. These components were mixed using a 20 L type Henschel mixer to obtain a raw material for a colorant master.

Next, this raw material was kneaded using a biaxial kneading extruder heated to 120 ° C. to obtain a kneaded product. Next, 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 2.0 mm or less to obtain a colorant master (pulverized product). A hammer mill was used for coarse pulverization of the kneaded product.
Next, a biaxial kneading extruder in which 50 parts by weight of the pulverized product thus obtained and 50 parts by weight of a polyester resin (melting point: 125 ° C., glass transition temperature: 60 ° C.) were heated to 120 ° C. The resulting mixture was kneaded and coarsely pulverized after cooling to obtain a powdered colored raw material having an average particle size of 1.0 mm or less.

  Next, coloring raw material: 20 parts by weight, aliphatic hydrocarbon as an insulating liquid (Cosmo Oil Lubricants, Cosmo SP-10): 80 parts by weight, zirconium octate as a charge control agent (manufactured by Hope Pharmaceutical Co., Ltd., Octope) Zr): 1 part by weight, polyamine aliphatic polymer as a dispersant (manufactured by Nippon Lubrizol Corporation, trade name: Solsperse 11200): 2 parts by weight are put in a pot of a planetary ball mill (Gokin Planetaring, Planet H), Further, zirconia balls having a diameter of 1 mm were added, and the coloring material was pulverized and dispersed for 24 hours. As a result, a liquid developer was obtained.

(Comparative Example 2)
As insulating liquid, aliphatic hydrocarbon (Cosmo Oil Lubricants Cosmo SP-10): 60 parts by weight, methyl laurate: 20 parts by weight, ethylene- (meth) acrylic acid copolymer (melting point) as resin material A liquid developer was produced in the same manner as in Comparative Example 1 except that 98 ° C., Vicat softening point: 78 ° C., Mitsui DuPont Polychemical Co., Ltd., trade name: Nucrel N410) was used.
(Comparative Example 3)
A liquid developer was produced in the same manner as in Example 1 except that toluene was used instead of methyl laurate as the first liquid.

(Comparative Example 4)
First, the adjustment of the colorant master and the resin solution preparation step were performed in the same manner as in Example 1.
<Resin deposition process>
Next, resin fine particles were deposited in the same manner as in Example 1 except that toluene was used instead of methyl laurate as the first liquid.
Next, toluene was distilled off under reduced pressure from the obtained resin fine particle dispersion.
Next, methyl laurate: 20 parts by weight, zirconium octate as a charge control agent (Octope Zr): 5 parts by weight, polyamine aliphatic polymer as a dispersant (based on the resin fine particle dispersion) Nippon Lubrizol Corporation, trade name: Solsperse 11200): 2 parts by weight were added with stirring to obtain a cyan liquid developer.

Table 1 shows the configurations of the resin material, the first liquid, the second liquid, and the toner particles used in the production of the liquid developer for each of the above Examples and Comparative Examples.
In Table 1, the polyester resin as the resin material is shown as PEs, and the ethylene- (meth) acrylic acid copolymer is shown as EMAA. Moreover, in the table | surface, high oleic rapeseed oil was shown as HO rapeseed oil. Moreover, in each Example and each comparative example, in addition to the liquid as described above, the second liquid is KF96 (viscosity: 100 mPa · s, manufactured by Shin-Etsu Silicone), soybean oil (Nisshin) As shown in Table 1, they were appropriately selected and used. In addition, in each of Examples and Comparative Examples, other fatty acid monoesters used as the first liquid other than those described above are those obtained by transesterifying each fatty acid with an alcohol component. It was. In the column of the content of each constituent material of the liquid developer, the content in the liquid developer is shown.

  Moreover, in Table 1, the melting point measured based on JISK7121: 1987 of the resin material was shown by Tm [degreeC]. Further, in the table, in the columns of Vicat softening point and glass transition temperature, for ethylene- (meth) acrylic acid copolymer, the Vicat softening point measured in accordance with JIS K7026: 1999 is Tv [° C.]. Moreover, about the polyester resin, the glass transition temperature measured based on JISK7121 was shown by Tg [degreeC]. Further, the melting point of the toner particles was measured in accordance with JIS K7121: 1987 for the toner particles filtered from the obtained liquid developer.

  The toner particles of Examples and Comparative Examples obtained by filtration in the same manner were subjected to fatty acid monoester extraction operation, and the fatty acid monoester contained in the toner particles was detected by gas chromatography. As a result, in each example, it was confirmed that the toner particles contained a fatty acid monoester, but in each comparative example, it was not confirmed that the toner particles contained a fatty acid monoester. In the toner particles of Examples and Comparative Examples in which the toner particles contain fatty acid monoesters and the melting point of the toner particles is lower than that of the resin material, the resin material is considered to be swollen with the fatty acid monoester. It was shown to.

[2] Evaluation Each liquid developer obtained as described above was evaluated as follows.
[2.1] Fixing Strength Using an image forming apparatus as shown in FIGS. 1 to 4, a single-color image of a predetermined pattern using the liquid developer obtained in each of the examples and the comparative examples is recorded on a recording paper ( It was formed on high-quality paper LPCPPA4) manufactured by Seiko Epson, and the heat fixing roller was set at 110 ° C., and heat fixing was performed at a fixing speed of 50 sheets per 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.) with a pressing load of 1.0 kgf twice, and the remaining ratio of image density Was measured by “X-Rite model 404” manufactured by X-Rite Inc, and evaluated according to the following five-step criteria.
Very good (A): Image density residual ratio is 95% or more.
Good (B): Image density residual ratio is 90% or more and less than 95%.
Allowable range (C): Image density remaining rate is 80% or more and less than 90%.
Slightly bad (D): Image density remaining ratio is 70% or more and less than 80%.
Poor (E): Image density residual ratio is less than 70%.
Further, it was not possible to confirm how the insulating liquid volatilized (generation of odor and vapor) when fixing was performed using the liquid developer of each example.

[2.2] Low-temperature fixability The toner obtained in each of the above Examples and Comparative Examples was evaluated for a good fixing region and a low-temperature fixability as follows.
First, an image forming apparatus having a configuration as shown in FIGS. 1 to 3 was prepared except that the fixing apparatus was not provided. Using this image forming apparatus, an unfixed image sample in which a single color toner image was transferred onto a recording medium (high quality plain paper LPCPPA4 manufactured by Seiko Epson Corporation) was collected. The solid amount of the sample to be collected was adjusted to an adhesion amount of 0.5 mg / cm ² .

Next, the recording medium on which the unfixed toner image is transferred in a state where the surface temperature of the fixing roller of the fixing device constituting the image forming apparatus is set to a predetermined temperature is shown in FIG. By introducing it inside, the toner image was fixed on the recording medium, and the presence or absence of occurrence of offset after fixing was visually confirmed. In this fixing device, the fixing was set to 50 sheets per minute (the number of sheets passing through the nip portion of A4 paper). The set temperature of the surface of the fixing roller is sequentially changed in the range of 60 to 160 ° C., and the presence or absence of occurrence of offset at each temperature is confirmed. The maximum temperature at which low temperature offset occurs is defined as the low temperature offset generation temperature. Evaluation was carried out according to a four-stage standard.
A: Low temperature offset generation temperature is less than 95 ° C.
B: Low temperature offset generation temperature is 95 ° C or higher and lower than 110 ° C.
C: Low temperature offset generation temperature is 110 ° C. or higher and lower than 120 ° C.
D: Low temperature offset generation temperature is 120 ° C. or higher.

[2.3] Long-term stability of toner image (stable period)
Using the image forming apparatus as shown in FIGS. 1 to 4, a single-color image of a predetermined pattern using the liquid developer obtained in each of the examples and the comparative examples is recorded on a recording paper (quality paper manufactured by Seiko Epson Corporation). LPCPPA4) was formed and heat fixing was performed at a set temperature of the heat fixing roller of 130 ° C. Immediately after fixing, the image density of the toner image was measured by “X-Rite model 404” manufactured by X-Rite Inc. Then, it was left standing under an atmosphere of 15 to 35 ° C. temperature, 50 to 70% humidity, and sunlight. After confirming the non-offset area of the toner image every month, erase the fixed image on the recording paper by rubbing twice with an eraser (LION 261-11, manufactured by Lion Secretariat) with a pressing load of 1.0 kgf. The image density was measured by “X-Rite model 404” manufactured by X-Rite Inc. Compared with the image density after special image formation, a period in which the residual ratio of the toner image is 60% or more was defined as a stable period of the toner image, and evaluation was performed according to the following five criteria.

A: The toner image has a stable period of 24 months or more.
B: The toner image has a stable period of 18 months or more and less than 24 months.
C: The stable period of the toner image is 12 months or more and less than 18 months.
D: The stable period of the toner image is 6 months or more and less than 12 months.
E: The toner image has a stable period of less than 6 months.

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

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

A: No change in viscosity / color / acid value / electric resistance value of the liquid developer is observed.
B: Almost no change in viscosity / color / acid value / electric resistance value of the liquid developer is observed.
C: A slight change in viscosity / color / acid value / electric resistance value of the liquid developer is observed, but it is in a range where there is no problem as a liquid developer.
D: A change in viscosity / color / acid value / electric resistance value of the liquid developer is clearly recognized.
E: A change in the viscosity / color / acid value / electric resistance value of the liquid developer is noticeable.
These results are shown in Table 2. In the table, in the columns of evaluation of fixing strength, low temperature fixability, and toner image stability period, specific image density residual ratio [%], low temperature offset occurrence temperature [° C.], toner image are shown in parentheses. The stable period [month] is shown respectively.

  As is apparent from Table 2, the liquid developer of the present invention is suitable for low-temperature fixing, and the formed toner image is firmly fixed on the recording medium even when fixing is performed at a relatively low temperature. Was. Further, even when the liquid developer of the present invention is stored for a long period of time, the toner particles are less dispersible and the liquid developer is less deteriorated, and is excellent in storage stability and environmental stability. On the other hand, satisfactory results were not obtained with the liquid developers of the comparative examples.

Further, as shown in Table 1, in each example, the melting point of the toner particles is lower than the melting point of the resin material used. Therefore, the fatty acid monoester causes the resin material in the toner particles to swell. It was confirmed that On the other hand, in each comparative example, it could not be confirmed that the resin material in the toner particles was swollen by the fatty acid monoester.
Further, in the examples using HO rapeseed oil and soybean oil mainly containing fatty acid triglyceride as the second liquid, the coarse particles in the liquid developer were particularly few. This is considered to be because the fatty acid, ligselide, and fatty acid monoester have high affinity, and the concentration unevenness of the fatty acid triglyceride in the resin solution at the time of dropping the second liquid is reduced.

In addition, toner images formed with a liquid developer using soybean oil fatty acid methyl, high rapeseed rapeseed oil, or soybean oil as the first liquid and the second liquid showed excellent fixing strength over a long period of time. . It is considered that the unsaturated fatty acid component is contained in these liquids, so that the toner image is stable even when stored for a long time.
In addition, the first distillation point of the first liquid, the second liquid, and the insulating liquid of the obtained liquid developer used in each example were used with an automatic distillation tester (ADM-1E, manufactured by Meitec). When obtained in accordance with JIS K 2254, the initial boiling point of the insulating liquids of all Examples was 108 ° C. or higher.
In addition, the liquid developer was manufactured and evaluated in the same manner as described above except that Pigment Red 122, Pigment Yellow 180, and Carbon Black (Printex L, manufactured by Degussa) were used as the colorant instead of the cyan pigment. As a result, the same result as above was obtained.

1 is a 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 ... coating roller 33Y ... regulating blade 34Y ... stirring roller 40 ... intermediate transfer unit 41 ... belt drive roller 42 ... tension roller 46 ... Intermediate transfer unit cleaning blade 47 ... Developer recovery unit 51Y, 51M, 51C, 51K ... Primary transfer backup roller 52Y, 52M, 52C, 52K ... Intermediate transfer unit squeeze device 53Y ... Intermediate transfer unit squeeze roller 54Y ... Intermediate transfer Part squeeze backup roller 55Y ... intermediate transfer part squeeze cleaning blade 60 ... secondary transfer unit 61 ... secondary transfer roller 62 ... secondary transfer roller cleaning blade 63 ... developer recovery part 70Y ... conveying path 80Y, 80M, 80C, 80K ... Liquid developer replenishment section 81Y ... recovered liquid developer storage section 82Y ... replenishment liquid developer storage section 83Y, 84Y ... transport means 85Y ... pump 86Y ... filter 100Y ... development unit 101Y ... photoconductor squeeze device F40 ... fixing section (fixed) F1 ... Heat fixing roller (heating roller) F1a ... Column halogen lamp F1b ... Roller base material F1c ... Elastic body F12 ... Removal blade F2 ... Pressure roller F2a ... Rotating shaft F2b ... Roller base material F2c ... Elastic body F3 ... Heat resistance Belt F4 ... Belt tension member F4a ... Projection wall F4f ... Recess F5 ... Recording medium F5a ... Toner image F6 ... Cleaning member F7 ... Frame F9 ... Spring

Claims (9)

Toner particles mainly composed of a resin material and a non-volatile insulating liquid,
The toner particles contain a fatty acid monoester,
The liquid developer, wherein the resin material contained in the toner particles is swollen by the fatty acid monoester.   The liquid developer according to claim 1, wherein the fatty acid monoester contains a fatty acid having 8 to 22 carbon atoms as a fatty acid component.   The liquid developer according to claim 1, wherein the fatty acid monoester includes an alcohol component having 1 to 4 carbon atoms.   The liquid developer according to claim 1, wherein the insulating liquid contains a fatty acid triglyceride.   The liquid developer according to claim 1, wherein the resin material contains an ethylene copolymer.   The liquid developer according to claim 1, wherein the resin material includes a polyester resin. A resin solution preparing step of preparing a resin solution in which a resin material is dissolved in a first liquid containing a fatty acid monoester;
Adding a second liquid having a lower solubility of the resin material than the first liquid to the resin solution, and precipitating the resin material in the resin solution to form resin fine particles; A method for producing a liquid developer, comprising:   The method for producing a liquid developer according to claim 7, wherein the second liquid contains a fatty acid triglyceride. 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 has toner particles mainly composed of a resin material and an insulating liquid, the toner particles contain a fatty acid monoester, and the resin material contained in the toner particles includes: An image forming apparatus swelled by the fatty acid monoester.

Images