JP2010175780A - Liquid developer and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid developer which is highly dependent on thermophysical property of a resin and which excels in low temperature fixing property, and to provide an image forming apparatus using the liquid developer. <P>SOLUTION: As a rosin resin 3 can change its molecular structure according to surrounding conditions, it is possible to effectively introduce esters in resin molecules. The esters in carrier solution 10 penetrate in the resin molecules in a toner particle 1. The esters penetrating in the molecules expand a distance between the molecules of the resin and can reduce energy required for changing a state of the resin from a solid state to a liquid state. Therefore, it is possible to reduce thermal energy required for fixing and obtain the liquid developer 100 which excels in low temperature fixing property. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid developer used for developing an electrostatic latent image in an electrophotographic process, and an image forming apparatus using the liquid developer.

In an electrophotographic process, as a developer used to develop an electrostatic latent image formed on a latent image carrier, toner particles containing a colorant such as a pigment and a binder resin are dispersed in an electrically insulating carrier liquid. Liquid developers are known.
As the resin contained in the toner particles, a polyester resin, a styrene-acrylate copolymer, an epoxy resin, or the like is used. Such a resin has the characteristics that it is easy to handle and the color developability of the resulting image is good.
In addition, when a rosin resin is used as the resin contained in the toner particles, it is characterized by excellent chargeability, excellent dispersion stability, and long-term storage stability.
However, since the affinity between the recording medium paper and the electrically insulating carrier liquid is not good, the carrier liquid does not penetrate into the paper and it is difficult to fix the toner particles.
In order to improve the fixing property of toner particles, it is known to use vegetable oil having affinity for paper as a carrier liquid (see, for example, Patent Document 1).

JP 2008-209655 A (page 6)

In the liquid developer described in Patent Document 1, the use of vegetable oil having a high affinity for paper as a carrier liquid improves the penetration into paper and improves the fixability at high temperature, but the fixability at low temperature is improved. It was difficult to secure.
Here, the low-temperature fixability means a fixability in fixing when the fixing method is not particularly limited, but the member heated during fixing is 120 ° C. or less.

  The present invention has been made to solve the above-described problems, and can be realized as the following forms or application examples.

[Application Example 1]
A liquid developer comprising: toner particles containing a rosin resin oriented in an outer shell; and an electrically insulating carrier liquid containing esters that disperse the toner particles.

According to this application example, the rosin resin oriented in the outer shell changes its molecular structure according to the surrounding conditions, and effectively incorporates the esters in the electrically insulating carrier liquid into the resin molecule. Esters that have penetrated between molecules increase the intermolecular distance of the resin and reduce the energy required to change the state of the resin from a solid state to a liquid state (hereinafter, this effect is referred to as a plasticizer effect). Accordingly, the thermal energy required for fixing is reduced, and a liquid developer having excellent low-temperature fixability of toner particles can be obtained.
Here, the state of the resin used for the toner particles is a very important factor for improving the fixability. If it is in a liquid state, it becomes more compatible with the recording medium and the fixability is improved.

[Application Example 2]
The liquid developer, wherein the rosin resin has a molecular weight of 1000 to 20000.
In this application example, the molecular weight of the rosin resin out of the resins used for toner particle formation is relatively low, 1000 to 20000, so that the number of molecules in the fixed amount is increased. The rosin-based resin has the highest acid value among the resins constituting the toner particles and has hydrophilicity, so that it is oriented to the outermost shell of the toner particles. Therefore, the plasticizer effect of the outer shell resin is great, the penetration of the ester into the resin is promoted, and a liquid developer having better low-temperature fixability of the toner particles can be obtained.

[Application Example 3]
Using a plurality of liquid developers having different colors, a plurality of developing units that form single color images corresponding to the plurality of liquid developers, and a plurality of the single color images formed by the plurality of developing units are sequentially transferred. An intermediate transfer unit that forms an intermediate transfer image formed by superimposing a plurality of transferred single color images; and a secondary that transfers the intermediate transfer image to a recording medium and forms an unfixed color image on the recording medium. An electrically insulating material comprising: a transfer portion; a fixing portion for fixing the unfixed color image on the recording medium; wherein the liquid developer includes toner particles containing a rosin resin oriented in an outer shell; and esters. An image forming apparatus comprising: a functional carrier liquid.

  According to this application example, by using a plurality of developing units having different colors, different colors are mixed at the time of developing to form a single color image, and the image quality is not disturbed. Further, in the intermediate transfer portion, it is possible to accurately transfer a monochrome image without color misregistration when forming a color image. In addition, in the secondary transfer portion that transfers onto the recording medium, the intermediate transfer image can be efficiently transferred onto the recording medium. Furthermore, in the fixing unit, an image forming apparatus that efficiently infiltrates an electrically insulating carrier liquid containing esters into the recording medium and reliably fixes the toner particles with a resin, particularly a rosin resin, contained in the toner particles. Is obtained.

[Application Example 4]
In the image forming apparatus, the developing unit includes a supply unit that supplies the liquid developer for forming the monochromatic image, a recovery unit that recovers excess liquid developer in the supply unit, An image having a partition provided between the supply unit and the recovery unit, and excess liquid developer in the supply unit is recovered by the recovery unit through the partition. Forming equipment.
In this application example, the supply unit that supplies the liquid developer can efficiently supply the liquid developer to the development unit. In addition, the recovery unit that recovers the excess liquid developer collects the excess liquid developer, and an image forming apparatus that sends the liquid developer to the developing unit again is obtained.

Hereinafter, preferred embodiments of the liquid developer will be described in detail.
FIG. 1 shows a schematic diagram of a liquid developer 100 in the embodiment.
The liquid developer 100 is obtained by dispersing toner particles 1 in an electrically insulating carrier liquid 10. Hereinafter, each component of the liquid developer 100 will be described in detail.

(Carrier liquid)
The carrier liquid 10 contains at least one of fatty acid monoester or phthalic acid ester and fatty acid triglyceride.

(Fatty acid monoester)
A fatty acid monoester is a monoester between a fatty acid and a monohydric alcohol, and contains an unsaturated fatty acid as a fatty acid component.
Here, what has a C8-C18 linear alkyl group as a fatty-acid component is preferable.
In the case where only fatty acid components composed of linear alkyl groups having less than 8 carbon atoms are included, the fatty acid component is hydrolyzed by moisture present in the air or slightly contained moisture in the carrier liquid 10, It is decomposed into fatty acid and alcohol, and excessive free fatty acid is generated. For this reason, the free fatty acid penetrates into the toner particles 1 during storage. As a result, aggregation of the toner particles 1 is caused, and as the liquid developer 100, sufficiently satisfactory storage stability and long-term stability cannot be obtained. In addition, the carrier liquid 10 containing excessive free fatty acid has poor electrical insulation, and the toner particles 1 are not sufficiently adhered to the electrostatic latent image, thereby obtaining a high-definition, high-quality toner image. I can't.
On the other hand, when the fatty acid component contains only a linear alkyl group having a carbon number greater than 18, the molecular weight of the fatty acid component becomes too large, and the fatty acid monoester toner particles at the time of fixing Penetration into 1 becomes difficult to occur. Therefore, the plasticizer effect of the carrier liquid 10 on the toner particles 1 is not sufficiently exhibited, and the fixing characteristics of the liquid developer 100 cannot be improved.

On the other hand, the fatty acid monoester having a linear alkyl group having 8 to 18 carbon atoms as the fatty acid component surely exhibits the plasticizer effect as described above at the time of fixing, and has a linear alkyl group. It becomes a steric hindrance, and water molecules are unlikely to approach the ester bond portion of the fatty acid monoester, and hydrolysis of the fatty acid monoester is suppressed. Thereby, the generation amount of the free fatty acid in the carrier liquid 10 can be suitably suppressed over a long period of time.
Further, at the time of fixing, such a fatty acid monoester permeates the toner particles 1, thereby suitably exhibiting a plasticizer effect. Thereby, the fixing characteristics of the toner particles 1 to the recording medium can be made excellent.
Further, the penetration of the carrier liquid 10 into the recording medium becomes suitable, and the liquid developer 100 is more suitably cured by the oxidative polymerization reaction. Due to these effects, the fixing characteristics of the toner particles 1 to the recording medium become more excellent.
By using a combination of such a fatty acid monoester and a fatty acid triglyceride as the carrier liquid 10 that constitutes the liquid developer 100, the toner liquid 1 is excellent in fixability to a recording medium, and liquid. The storage stability and long-term stability of the developer 100 can be improved.

  Examples of such fatty acid components include unsaturated fatty acids such as monovalent unsaturated fatty acids such as oleic acid and palmitoleic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, arachidonic acid, docosahexaenoic acid (DHA). ), Eicosapentaenoic acid (EPA) and the like, polyunsaturated fatty acids having a plurality of double bonds in the molecule, and conjugated unsaturated fatty acids thereof. Examples of saturated fatty acids include butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, and lignoceric acid.

  The alcohol component of the fatty acid monoester may be an alcohol that becomes a linear alkyl group or an alcohol that becomes a branched alkyl group. Examples of the alcohol that becomes a linear alkyl group include propanol (C3), butanol (C4), and pentanol. (C5) Hexanol (C6), heptanol (C7), octanol (C8), nonanol (C9), decanol (C10) dodecanol (C12) and the like can be mentioned. Moreover, as alcohol used as a branched alkyl group, isopropanol (C3), 2-butanol (C4), isobutanol (C4), tert-butanol (C4), 2-pentanol (C5), 3-pentanol (C5) ), 2,2-dimethyl-1-propanol (C5), 2-hexanol (C6), 3-methyl-3-pentanol (C6), 2,3-dimethyl-2-butanol (C6), 2-heptanol ( C7), 2,4-dimethyl-3-pentanol (C7), 2-octanol (C8), 2-ethyl-1-hexanol (C8), 1,1-diethyl-3-methyl-1-propanol (C8) Etc.

(Phthalic ester)
Phthalates are esters between phthalic acid and monohydric alcohols. As an alcohol component, what has a C9-C11 linear alkyl group is preferable.
In the case where only an alcohol component composed of a linear alkyl group having a carbon number of less than 9 is included, the alcohol component is hydrolyzed by moisture present in the air or slightly contained in the carrier liquid 10, It is decomposed into phthalic acid and alcohol, and excessive free phthalic acid is generated. For this reason, free phthalic acid penetrates into the toner particles 1 during storage. As a result, aggregation of the toner particles 1 is caused, and as the liquid developer 100, sufficiently satisfactory storage stability and long-term stability cannot be obtained. In addition, the carrier liquid 10 containing excessively free phthalic acid has a poor electrical insulating property, and the toner particles 1 are insufficiently attached to the electrostatic latent image, so that a high-definition, high-quality toner image can be obtained. Can't get.
On the other hand, if the alcohol component contains only a linear alkyl group having 11 or more carbon atoms, the molecular weight of the alcohol component becomes too large, and the phthalate ester toner particles during fixing It becomes difficult to penetrate into. Therefore, the plasticizer effect of the carrier liquid 10 on the toner particles 1 is not sufficiently exhibited, and the fixing characteristics of the liquid developer 100 cannot be improved.

On the other hand, the phthalate ester having a linear alkyl group having 9 to 11 carbon atoms as an alcohol component surely exhibits the plasticizer effect as described above at the time of fixing, and has a linear alkyl group. This is a steric hindrance, making it difficult for water molecules to approach the ester bond portion of the phthalate ester, thus inhibiting hydrolysis of the phthalate ester. Thereby, the generation amount of free phthalic acid in the carrier liquid 10 can be suitably suppressed over a long period of time.
By using a combination of such a phthalate ester and a fatty acid triglyceride as the carrier liquid 10 constituting the liquid developer 100, the toner liquid 1 has excellent fixability to a recording medium, and a liquid. The storage stability and long-term stability of the developer 100 can be improved.

  Examples of alcohol components include propanol (C3), butanol (C4), pentanol (C5) hexanol (C6), heptanol (C7), octanol (C8), nonanol (C9), decanol (C10) dodecanol (C12), and the like. Can be mentioned. In addition, the alcohol of the phthalate ester may have a branched alkyl group, and examples of the alcohol that becomes the branched alkyl group include isopropanol (C3), 2-butanol (C4), isobutanol (C4), and tert-butanol (C4). 2-pentanol (C5), 3-pentanol (C5), 2,2-dimethyl-1-propanol (C5), 2-hexanol (C6), 3-methyl-3-pentanol (C6), 2, 3-dimethyl-2-butanol (C6), 2-heptanol (C7), 2,4-dimethyl-3-pentanol (C7), 2-octanol (C8), 2-ethyl-1-hexanol (C8), 1 , 1-diethyl-3-methyl-1-propanol (C8) and the like.

(Fatty acid triglyceride)
A fatty acid triglyceride is a triester (triglyceride) between a fatty acid and glycerin, and contains an unsaturated fatty acid as a fatty acid component.
When the fatty acid triglyceride in the carrier liquid 10 contains an unsaturated fatty acid as a fatty acid component, the toner particles 1 are firmly fixed on the recording medium while the liquid developer 100 has excellent storage stability and long-term stability. Can do. Examples of such unsaturated fatty acid components include monovalent unsaturated fatty acids such as oleic acid and palmitoleic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, arachidonic acid, docosahexaenoic acid (DHA), Examples thereof include polyunsaturated fatty acids having a plurality of double bonds in the molecule, such as icosapentaenoic acid (EPA), and conjugated unsaturated fatty acids thereof.

Among the unsaturated fatty acid components described above, monovalent unsaturated fatty acids have particularly excellent chemical stability. Therefore, when the fatty acid triglyceride in the carrier liquid 10 contains a monovalent unsaturated fatty acid as a fatty acid component, the storage stability and long-term stability of the liquid developer 100 are particularly excellent. On the other hand, polyunsaturated fatty acids are components having higher reactivity (oxidation reactivity) than monovalent unsaturated fatty acids. Therefore, when the fatty acid triglyceride in the carrier liquid 10 contains a polyunsaturated fatty acid as a fatty acid component, the oxidative polymerization reaction of the carrier liquid 10 at the time of fixing suitably proceeds, and the toner particles 1 are recorded on the recording medium. Can be firmly fixed.
In addition, when the fatty acid triglyceride contains a saturated fatty acid in addition to the unsaturated fatty acid as the fatty acid component, the chemical stability and electrical insulation of the liquid developer 100 can be kept high, so that The change can be prevented, the electrical resistance can be kept high, and the storage stability and long-term stability of the liquid developer 100 can be improved. Examples of such saturated fatty acids include butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, and lignoceric acid.

  The fatty acid triglycerides as described above are, for example, plant-derived oils such as soybean oil, rapeseed oil, safflower oil, sunflower oil, linseed oil, olive oil, corn oil, coconut oil, cottonseed oil, dehydrated castor oil, palm kernel oil, coconut oil and the like. It can be efficiently obtained by purifying naturally-derived fats and oils such as animal-derived fats and oils such as herring oil and sardine oil. Examples of the purification method include a method in which unrefined fats and oils are mixed with boiled water, and after the mixed solution is completely separated into three layers, components to be frozen in the freezer are removed. Moreover, fatty acid triglyceride with higher purity can be obtained by repeating this method.

  When the carrier liquid 10 does not contain fatty acid triglycerides, the low molecular weight and low viscosity fatty acid monoesters and phthalic acid esters can easily penetrate into the toner particles 1 even during storage, and the plasticizer effect can be obtained. growing. As a result, aggregation of the toner particles 1 tends to occur, and the storage stability and long-term stability of the liquid developer 100 cannot be sufficiently satisfied.

Below, content of fatty acid monoester or phthalic acid ester and fatty acid triglyceride will be described.
(Fatty acid monoester and fatty acid triglyceride)
If the content of fatty acid triglyceride is low, the fixability can be secured without problems, and if the content of fatty acid triglyceride is large, long-term storage properties can be secured without problems.
When the content of the fatty acid triglyceride in the carrier liquid 10 containing the fatty acid monoester is 40 to 90 wt%, either the fixing property or the long-term storage property can be secured without any problem, and the other property is slightly Stay in the improvement.
The content of 60 to 70 wt% is more preferable because the fixability and long-term storage stability can be secured without problems.

Further, when the content of the fatty acid monoester is small, long-term storage stability can be secured without problems, and when the content of the fatty acid monoester is large, fixing properties can be secured without problems.
If the carrier liquid 10 is composed of only fatty acid triglyceride and fatty acid monoester, the fixing property or long-term storage stability is 10 to 60 wt% of the fatty acid monoester content in the carrier liquid 10. One of the characteristics can be secured without any problem, and the other characteristic is only slightly improved.
A content of 30 to 40 wt% is more preferable because fixing properties and long-term storage can be secured without problems.

That is, the fatty acid triglyceride / fatty acid monoester has a fatty acid triglyceride / fatty acid monoester of preferably 4/6 to 9/1, more preferably 7/3 to 6/4.
By setting more preferable conditions, a well-balanced liquid developer 100 that can achieve both long-term storage stability, charging characteristics, and fixability can be obtained.
As a result, while maintaining sufficient dispersion stability and charging characteristics, the penetration of the fatty acid monoester into the toner particles 1 at the time of fixing becomes more suitable, and the plasticizer effect is surely exhibited. Thereby, the low temperature fixability of the toner particles 1 to the recording medium can be made particularly excellent.

The excellent effects as described above are manifested by including in the carrier liquid 10 a fatty acid triglyceride and a fatty acid monoester having a linear alkyl group having 8 to 18 carbon atoms as the fatty acid component.
On the other hand, even if any of these is missing in the carrier liquid 10, the effect of the present invention cannot be obtained. That is, when the carrier liquid 10 does not contain a fatty acid triglyceride, the low-molecular weight and low-viscosity fatty acid monoester easily permeates into the toner particles 1 even during storage. A plasticizer effect is exhibited. As a result, aggregation of the toner particles 1 tends to occur, and the storage stability and long-term stability of the liquid developer 100 cannot be sufficiently satisfied. Further, when the fatty acid monoester having the above-described characteristics is not included, the plasticizer effect on the toner particles 1 of the carrier liquid 10 is not expressed and the penetration of the liquid developer 100 into the recording medium is difficult to occur. As a result, the fixing characteristics of the toner particles 1 to the recording medium cannot be made sufficient.

The fatty acid triglyceride and the fatty acid monoester preferably contain an unsaturated fatty acid component.
The unsaturated fatty acid triglyceride means a fatty acid triglyceride having at least one unsaturated fatty acid in the molecular structure as a fatty acid component.
This unsaturated fatty acid component is a component that can contribute to improving the fixability of the toner particles 1 to the recording medium. More specifically, since the unsaturated fatty acid component is oxidized at the time of fixing, a polymerization reaction proceeds, and itself is cured. Therefore, the toner particles 1 are caused by an anchor effect between the recording medium and the cured liquid developer 100. The fixing property can be improved. Thereby, the fixing characteristics of the toner particles 1 to the recording medium can be made excellent. In addition, since the unsaturated fatty acid component is cured, it is possible to easily and reliably add the recorded toner image with an aqueous ballpoint pen.
As a result, while maintaining sufficient dispersion stability and charging characteristics, the penetration of the fatty acid monoester into the toner particles 1 at the time of fixing becomes more suitable, and the plasticizer effect is surely exhibited. Thereby, the low temperature fixability of the toner particles 1 to the recording medium can be made particularly excellent.

(Phthalate esters and fatty acid triglycerides)
If the content of fatty acid triglyceride is low, the fixability can be secured without problems, and if the content of fatty acid triglyceride is large, long-term storage properties can be secured without problems.
The content of the fatty acid triglyceride in the carrier liquid containing the phthalic acid ester is preferably 40 to 90 wt%, more preferably 50 to 90 wt%, and even more preferably 70 to 80 wt%.
If the content of the fatty acid triglyceride is 40 to 90 wt%, either the fixing property or the long-term storage property can be secured without any problem, and the other property is only slightly improved.
A content of 70 to 80 wt% is more preferred because it can ensure the fixability and long-term storage stability without problems.

If the phthalate content is low, long-term storage can be ensured without problems, and if there is a large amount of phthalate, fixability can be ensured without problems.
If the carrier liquid 10 is composed of only fatty acid triglyceride and phthalic acid ester, the content of the phthalic acid ester in the carrier liquid 10 is 10 to 60 wt%, more preferably 10 to 50 wt%. Either the fixing property or the long-term storage property can be secured without any problem, and the other property is only slightly improved.
A content of 20 to 30 wt% is more preferable because fixing properties and long-term storage stability can be secured without problems.

That is, the fatty acid triglyceride / phthalic acid ester ratio in fatty acid triglyceride / phthalic acid ester is preferably 4/6 to 9/1, more preferably 5/5 to 9/1, and further 7 It is preferably / 3 to 6/4.
By setting the above-described more preferable conditions, it is possible to obtain a well-balanced liquid developer 100 that can achieve both long-term storage stability, charging characteristics, and fixability.

  Accordingly, the penetration of the phthalate ester into the toner particles 1 at the time of fixing is further improved while maintaining sufficient dispersion stability and charging characteristics, and the plasticizer effect is surely exhibited. Thereby, the low temperature fixability of the toner particles 1 to the recording medium can be made particularly excellent.

  The excellent effect as described above is manifested by including in the carrier liquid 10 a fatty acid triglyceride and a phthalic acid ester having a linear alkyl group having 9 to 11 carbon atoms as an alcohol component. On the other hand, even if any of these is missing in the carrier liquid 10, the effect of the present invention cannot be obtained. Further, when the fatty acid monoester having the above-described characteristics is not included, the plasticizer effect on the toner particles 1 of the carrier liquid 10 is not expressed and the penetration of the liquid developer 100 into the recording medium is difficult to occur. As a result, the fixing characteristics of the toner particles 1 to the recording medium cannot be made sufficient.

The carrier liquid 10 may contain a dispersant that improves the dispersibility of the toner particles 1.
Examples of such a dispersant include polyvinyl alcohol, carboxymethyl cellulose, polyethylene glycol, Solsperse (registered trademark) (trade name of Nippon Lubrizol), polycarboxylic acid and salts thereof, and polyacrylic acid metal salts (for example, sodium Salt), polymethacrylic acid metal salt (for example, sodium salt), polymaleic acid metal salt (for example, sodium salt), acrylic acid-maleic acid copolymer metal salt (for example, sodium salt), polystyrene sulfonic acid Metal salt (for example, sodium salt), polymer dispersant such as fatty acid amine, polyamine fatty acid condensation polymer, viscosity mineral, silica, tricalcium phosphate, metal tristearate (for example, aluminum salt), metal distearate Salt (eg, aluminum salt, barium salt, etc.), Metal salts of thearic acid (for example, calcium salts, lead salts, zinc salts), metal salts of linolenic acid (for example, cobalt salts, manganese salts, lead salts, zinc salts, etc.), metal salts of octanoic acid (for example, aluminum salts, calcium salts) Salt, cobalt salt, etc.), oleic acid metal salt (eg, calcium salt, cobalt salt, etc.), palmitic acid metal salt (eg, zinc salt), dodecylbenzenesulfonic acid metal salt (eg, sodium salt), naphthenic acid Metal salts (for example, calcium salt, cobalt salt, manganese salt, lead salt, zinc salt and the like), resinate metal salts (for example, calcium salt, cobalt salt, manganese lead salt, zinc salt and the like) and the like can be mentioned.

  Among the dispersants, when a fatty acid amine is used, the fatty acid amine can be adhered to the surface of the toner particles 1, thereby preventing unintentional aggregation between the toner particles 1. Further, when a fatty acid monoester is used as the ester, the permeability of the fatty acid monoester to the toner particles 1 can be increased, and the plasticizer effect by the fatty acid monoester can be made more remarkable. As a result, the toner particles 1 can be more firmly fixed to the recording medium. Further, the charging characteristics of the toner particles 1 can be made higher.

  When the polyamine fatty acid condensation polymer is used, it is sufficient that the content of the polyamine fatty acid condensation polymer in the liquid developer 100 is 0.5 to 7.5 parts by weight with respect to 100 parts by weight of the toner particles 1. 2 to 4 parts by weight is preferable because high chargeability can be obtained in addition to sufficient dispersion stability. Thereby, the effect by using a polyamine fatty acid condensation polymer can be made more remarkable.

Further, the carrier liquid 10 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.

When zinc oxide is used as the charge control agent, the charge amount of the toner particles 1 in the electric field can be increased as compared with the case of the dispersant alone. As a result, the charging property of the liquid developer 100 can be further improved.
The content of zinc oxide in the liquid developer 100 is preferably 0.5 to 4.0 parts by weight with respect to 100 parts by weight of the toner particles 1 because high chargeability is obtained. 0.0 part by weight is more preferable because the carrier liquid 10 can maintain high insulation in addition to high chargeability. Thereby, the above-mentioned effect can be made more remarkable.

The electric resistance at room temperature (for example, 20 ° C.) of the carrier liquid 10 as described above is preferably 1 × 10 ¹² Ωcm or more because a high electric field sufficient to move the toner particles 1 can be maintained, and preferably 7 × 10 ¹² Ωcm or more. It is more preferable because an electric field higher than the electric field for moving the toner particles 1 can be formed.

(Toner particles)
The toner particles 1 include at least a binder resin (resin material) and a colorant.
1. Resin Material FIG. 1 shows a schematic cross-sectional view of the toner particles 1. The toner particles 1 contain a rosin resin 3 as a resin material.
The toner particles 1 include a rosin resin 3 oriented in the outer shell 2. The rosin resin 3 may be oriented to a part of the outer shell 2 or may be oriented to the entire outer shell 2.
The rosin resin 3 is a component having high affinity (compatibility) with the paper as the fixing substrate. Therefore, the toner particles 1 having such a rosin resin 3 have a particularly high fixability to paper.

The rosin resin 3 has many carboxylic acid groups in its chemical structure. The rosin resin 3 has a bulky steric structure, and the carboxylic acid in the chemical structure is easily exposed on the surface of the molecule. Therefore, an amine dispersant as will be described later is firmly attached to the surface of the toner particle 1 containing the rosin resin 3 so that the amine group of the amine dispersant and the carboxylic acid group of the rosin resin 3 are attracted to each other. Adhere to. As a result, the dispersibility of the toner particles 1 can be improved over a long period of time, and the positive charging characteristics of the liquid developer 100 can be improved.
The rosin resin 3 may be any resin that exists on at least a part of the surface of the toner particle 1, may be unevenly distributed on the surface of the toner particle 1, and covers the surface of the toner particle 1. May exist. In the latter case, it exhibits the most affinity for paper and has a particularly high fixability.

Examples of such rosin-based resin 3 include rosin-modified phenolic resin, rosin-modified maleic resin, rosin-modified polyester resin, fumaric acid-modified rosin-based resin, ester gum, and the like. Can be used in combination.
The softening point of the rosin-based resin 3 is preferably 80 to 190 ° C. because fixing can be performed at a low temperature, and 80 to 130 ° C. is more preferable because low-temperature fixing can be performed at a higher speed. As a result, it is possible to achieve both the fixing characteristics and the heat-resistant storage stability of the toner particles 1 at a higher level while improving the long-term dispersion stability and charging characteristics of the toner particles 1.
In the present specification, the softening point is a measurement condition in a Koka type flow tester (manufactured by Shimadzu Corporation): temperature increase rate: 5 ° C./min, softening start temperature defined by a die hole diameter of 1.0 mm. Point to.

  In addition, the weight average molecular weight of the rosin resin 3 is preferably 1000 to 20000 because plasticization occurs without any problem. Furthermore, when it is 3000-5000, since plasticization occurs while maintaining the state excellent in long-term storage stability, it is more preferable. Thereby, it can plasticize efficiently with the carrier liquid 10, and can also make long-term dispersion stability and the charging characteristic excellent.

  In addition, the content of the rosin resin 3 in the resin material constituting the toner particles 1 is preferably 1 to 50 wt% in order to improve fixability while maintaining long-term storage. Further, it is more preferable that the content is 10 to 30 wt% because sufficient long-term storage stability is obtained and higher low-temperature fixability is obtained. As a result, the rosin resin 3 can be more reliably present on the surface of the toner particles 1, and the low-temperature fixability of the toner particles 1 can be more effectively improved.

The toner particles 1 may contain a known resin other than the rosin resin 3 as described above.
In particular, it is preferable to use the rosin resin 3 as described above in combination with a resin material having an ester bond. Since the resin material having such a bond has low compatibility with the rosin resin 3, the rosin resin 3 can be surely present on the surface of the toner particles 1.

  Examples of the resin material having an ester bond include polyester resins, styrene-acrylic acid ester copolymers, and methacrylic resins. Among these, it is particularly preferable to use a polyester resin. The polyester resin has high transparency, and when used as a binder resin, the color developability of the obtained image can be increased. Further, since the polyester resin has a particularly low compatibility with the rosin-based resin 3, the polyester resin more reliably phase-separates with the rosin-based resin 3 in the toner particles 1, and the rosin-based resin 3 is more effectively separated from the surface of the toner particles 1. Can exist.

  The softening point of the resin material other than the rosin resin 3 contained in the toner particles 1 is preferably 50 to 130 ° C. because fixing is possible at a low temperature. The softening point is 60 to 115 ° C. at a low temperature and at a higher speed. Since fixing becomes possible, it is more preferable. Thereby, the low-temperature fixing characteristics of the toner particles 1 can be made particularly excellent.

  Further, when the toner particles 1 include a resin having an ester bond, it is preferable that the resin having an ester bond includes two or more resin components having different weight average molecular weights. Specifically, the toner particles include, as a resin having an ester bond, a first resin component having a relatively low weight average molecular weight and a second resin component having a weight molecular weight larger than that of the first resin component. Is preferred. Thus, the following effects are acquired by including multiple types of resin components.

The first resin component having a relatively small weight average molecular weight can be easily melted even at a relatively low temperature. Therefore, the toner particles 1 contain such a first resin component, so that when the toner image is heated at the time of fixing, even if the fixing temperature is relatively low (for example, 100 to 140 ° C.) The first resin component can be melted together with the rosin resin 3, and the toner particles 1 can be easily softened and firmly fixed on the recording medium. In addition, since the toner particles 1 are relatively easily melted as described above, the toner particles 1 having a plurality of different colorants are easily melted and mixed at the time of fixing, and the color developability of the obtained toner image is excellent. It will be a thing.
On the other hand, the second resin component having a relatively large weight average molecular weight is unlikely to melt and soften even under a relatively high temperature environment. For this reason, when the toner particles 1 contain such a second resin component, when the liquid developer 100 is stored in an unused state in the image forming apparatus or the like, the liquid developer 100 is relatively Even when the temperature is high (for example, 40 to 80 ° C.), the toner particles 1 are prevented from melting or the toner particles 1 from being deformed. In particular, even when the first resin component or the rosin resin 3 starts to soften in such an environment, such a second resin component acts as a skeleton of the toner particles 1. As a result, the plurality of toner particles 1 in the liquid developer 100 are more reliably prevented from adhering to each other and aggregating or deforming in the high temperature environment as described above.
As described above, since the toner particles 1 contain the first resin component and the second resin component as described above in addition to the rosin resin 3, the liquid developer 100 has high low-temperature fixing characteristics, and the toner particles 1 have a long-term stability. It is possible to achieve both dispersion stability.

  In such a case, if the weight average molecular weight of the first resin component is 3000 to 12000, the fixing property by the rosin resin 3 is not inhibited, and the first resin component itself is plasticized to the esters in the carrier liquid 10. It is preferable because the low-temperature fixability is improved, and it is more preferably 4000 to 10000, in addition to the improvement of the fixability, the long-term storage stability can be maintained higher, and more preferably 5000 to 7000. It is more preferable because higher fixability and higher long-term storage stability can be obtained. The weight average molecular weight of the second resin component is preferably 20000 to 400000 because long-term storage stability is obtained, and if it is 10000 to 250,000, the long-term storage stability and the second resin component itself are the carrier liquid 10. Since it is plasticized by the esters therein, the low-temperature fixability is improved, which is more preferable.

  Further, the content of the first resin component in the resin material constituting the toner particles 1 is preferably 30 to 80 wt% because sufficient low-temperature fixability can be obtained, and if it is 40 to 75 wt%, the low-temperature fixing is performed. This is more preferable because it can be compatible in a dimension with high stability and long term storage stability. The content of the second resin component in the resin material constituting the toner particles 1 is preferably 5 to 40 wt% in order to obtain long-term storage stability, and if it is 10 to 30 wt%, low-temperature fixability and long-term storage stability are obtained. It is more preferable because it is compatible with a high storage stability.

2. Colorant The toner particles 1 may contain a colorant. The colorant is not particularly limited, and for example, known pigments and dyes can be used.

3. Other Components The toner particles 1 may contain components other than those described above. Examples of such components include known waxes and magnetic powders.
As the constituent material (component) of the toner particles 1, 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. It may be used.

(Toner particle shape)
The average particle diameter of the toner particles 1 composed of the above materials is preferably 0.5 to 3 μm, more preferably 1 to 2.5 μm, and further preferably 1 to 2 μm. . When the average particle diameter of the toner particles 1 is a value within the above range, the variation in characteristics among the toner particles 1 is small, and the reliability of the liquid developer 100 as a whole is high, while the liquid developer is high. The resolution of the toner image formed by 100 can be made sufficiently high. Further, the toner particles 1 can be well dispersed in the carrier liquid 10 and the storage stability of the liquid developer 100 can be improved. In the present specification, “average particle diameter” refers to an average particle diameter based on volume.
The content of the toner particles 1 in the liquid developer 100 is preferably 10 to 60 wt%, and more preferably 20 to 50 wt%.

Next, a preferred embodiment of a method for manufacturing the liquid developer 100 will be described.
The manufacturing method of the liquid developer 100 includes a dispersion preparation step for preparing a dispersion in which a resin material and a colorant as described above are dispersed in an aqueous dispersion medium, and a plurality of dispersoids are combined to form a combined particle. A coalescing step, an organic solvent contained in the coalesced particles is removed, a solvent removal step for obtaining toner particles 1 containing a resin material and a colorant, an amine cyclic dispersant is added to the carrier liquid 10, and a toner A dispersion step of dispersing the particles 1 in the carrier liquid 10.

Hereinafter, each process of the manufacturing method of the liquid developer 100 is demonstrated in detail.
1. Dispersion Preparation Step First, an aqueous dispersion is prepared.
The aqueous dispersion may be prepared by any method, for example, the following method.
A resin liquid preparation process for obtaining a resin liquid by dissolving and dispersing the constituent materials of the toner particles 1 such as a resin and a colorant in an organic solvent, and adding an aqueous dispersion medium composed of the aqueous liquid to the resin liquid, A liquid dispersoid containing a toner material is formed in an aqueous liquid and adjusted by a dispersoid forming process for obtaining an aqueous dispersion in which the dispersoid is dispersed.

(Resin liquid preparation process)
In the resin liquid preparation process, a resin liquid in which a resin material (rosin resin 3 and other resin materials) is dissolved or dispersed in an organic solvent is prepared.
First, a resin liquid in which a resin material and a hydrolysis inhibitor are dissolved or dispersed in an organic solvent is prepared.
The prepared resin liquid contains a constituent material of the toner particles 1 and an organic solvent as described below.
The organic solvent may be any as long as it dissolves at least a part of the resin material, but it is preferable to use an organic solvent having a boiling point lower than that of the aqueous liquid described later. Thereby, the organic solvent can be easily removed.
Moreover, it is preferable that an organic solvent is a thing with low compatibility with the aqueous dispersion medium mentioned later. For example, the thing whose solubility with respect to 100 g of aqueous dispersion media in 25 degreeC is 30 g or less is mentioned. Thereby, the toner material can be finely dispersed in a stable state in the aqueous emulsion.
Further, the composition of the organic solvent can be appropriately selected according to, for example, the resin material, the composition of the colorant, the composition of the aqueous dispersion medium, and the like as described above.
Such an organic solvent is not particularly limited, and examples thereof include ketone solvents such as MEK and aromatic hydrocarbon solvents such as toluene.

The resin liquid can be obtained, for example, by mixing a resin material, a colorant, an organic solvent, etc. with a stirrer or the like. Examples of the stirrer that can be used for preparing the resin liquid include DESPA (manufactured by Asada Tekko Co., Ltd.), T.C. K. Robotics / T. K. Examples thereof include a high-speed stirrer such as a homodisper 2.5-type blade (manufactured by Primex).
Moreover, it is preferable that the material temperature at the time of stirring is 20-60 degreeC, and it is more preferable that it is 30-50 degreeC.

Although the content rate of solid content in a resin liquid is not specifically limited, It is preferable that it is 40-75 wt%, it is more preferable that it is 50-73 wt%, and it is further more preferable that it is 50-70 wt%.
When the solid content is within the above range, the dispersoid constituting the dispersion (emulsion suspension) described later may have a higher sphericity (a shape close to a true sphere). The shape of the toner particles 1 finally obtained can be made more surely suitable.
In the preparation of the resin liquid, all the components of the resin liquid to be prepared may be mixed at the same time, or a part of the components of the resin liquid to be prepared may be mixed in advance to prepare a mixture (master). After that, the mixture (master) may be mixed with other components.

(Dispersoid formation processing)
In the dispersoid formation process, an aqueous dispersion medium is added to the resin liquid to form a dispersoid containing the toner material (liquid dispersoid) in the aqueous liquid and the dispersoid is dispersed (aqueous dispersion). )
The aqueous dispersion medium is composed of an aqueous liquid. As the aqueous liquid, a liquid mainly composed of water can be used.
The aqueous liquid may contain, for example, a solvent having excellent compatibility with water (for example, a solvent having a solubility in 100 parts by weight of water at 25 ° C. of 50 parts by weight or more).

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

In preparing the aqueous dispersion, for example, a neutralizing agent may be used. Thereby, for example, the functional group (for example, carboxyl group) of the resin material can be neutralized, and the shape, size uniformity, and dispersibility of the dispersoid in the prepared aqueous dispersion liquid. Can be particularly excellent. For this reason, the obtained toner particles 1 have a particularly narrow particle size distribution.
For example, the neutralizing agent may be added to the resin liquid or may be added to the aqueous liquid.
Further, the neutralizing agent may be added in a plurality of times in the preparation of the aqueous dispersion.

As the neutralizing agent, a basic compound can be used. More specifically, for example, inorganic bases such as sodium hydroxide, potassium hydroxide and ammonia, and organic bases such as diethylamine, triethylamine and isopropylamine can be used. 1 type selected from these, or 2 or more types can be used in combination. The neutralizing agent may be an aqueous solution containing the above compound.
Moreover, the usage-amount of a basic compound has the preferable amount (1-3 equivalent) equivalent to 1-3 times the amount required in order to neutralize all the carboxyl groups which a resin material has, and is equivalent to 1-2 times The amount to be (1-2 equivalent) is more preferred.
Thereby, it is possible to effectively prevent the formation of irregular dispersoids, and it is possible to make the particle size distribution of the particles obtained in the coalescence step described in detail later sharper.

  The aqueous dispersion medium may be added to the resin liquid by any method, but it is preferable to add an aqueous liquid containing water to the resin liquid while stirring the resin liquid. That is, it is performed by gradually adding (dropping) an aqueous liquid into the resin liquid while applying shear to the resin liquid with a stirrer or the like, and phase-inverting from a W / O type emulsion to an O / W type emulsion. Finally, it is preferable to obtain an aqueous dispersion in which the dispersoid derived from the resin liquid is dispersed in the aqueous liquid.

Examples of the stirrer that can be used for the preparation of the aqueous dispersion include DESPA (manufactured by Asada Tekko Co., Ltd.), K. Robotics / T. K. Examples thereof include a high-speed stirrer such as a homodisper 2.5-type blade (manufactured by Primics), a slasher (manufactured by Mitsui Mining Co., Ltd.), a Cavitron (manufactured by Eurotech), or a high-speed disperser.
Further, at the time of adding the aqueous liquid to the resin liquid, stirring is preferably performed so that the blade tip speed is 10 to 20 m / sec, and more preferably 12 to 18 m / sec.
When the blade tip speed is a value within the above range, an aqueous dispersion can be obtained efficiently, and the dispersion of the shape and size of the dispersoid in the aqueous dispersion can be made particularly small. In particular, the uniform dispersibility of the dispersoid can be made excellent while preventing the generation of fine dispersoids and coarse particles.

The solid content in the aqueous dispersion is not particularly limited, but is preferably 5 to 55 wt%, and more preferably 10 to 50 wt%.
Thereby, the productivity of toner particles can be made particularly excellent while preventing unintentional aggregation of the dispersoids in the aqueous dispersion more reliably.
Moreover, it is preferable that the material temperature in this process is 20-60 degreeC, and it is more preferable that it is 20-50 degreeC.

2. Combined Step Next, a plurality of dispersoids are combined to obtain combined particles. The coalescence of dispersoids usually proceeds as a result of collision of dispersoids containing an organic solvent so that they are integrated.
In the process of uniting in this way, the rosin resin 3 and other resin materials have low compatibility, and therefore, layer separation is likely to occur. In addition, since the rosin resin 3 contains a large amount of carboxylic acid, the rosin resin 3 has a high affinity with an aqueous liquid and tends to be present on the surface of the dispersoid or coalesced particles. For this reason, the rosin-based resin 3 can surely exist (is unevenly distributed) on the surface of the finally obtained toner particles 1.
The coalescence of a plurality of dispersoids is performed by adding an electrolyte to the dispersion while stirring the dispersion. Thereby, coalesced particles can be obtained easily and reliably. Moreover, the particle diameter and particle size distribution of the coalesced particles can be controlled easily and reliably by adjusting the amount of electrolyte added.

It does not specifically limit as electrolyte, Well-known organic and inorganic water-soluble salt etc. can be used 1 type or in combination of 2 or more types.
The electrolyte is preferably a monovalent cation salt. Thereby, the particle size distribution of the obtained coalesced particles can be narrowed. In addition, by using a monovalent cation salt, it is possible to reliably prevent generation of coarse particles in this step.
Moreover, among the above-mentioned, it is preferable that electrolyte is a sulfate (for example, sodium sulfate, ammonium sulfate) or carbonate, and it is especially preferable that it is a sulfate. Thereby, the particle diameter of the coalesced particles can be controlled particularly easily.

The amount of the electrolyte added in this step is preferably 0.5 to 3 parts by weight, preferably 1 to 2 parts by weight, based on 100 parts by weight of the solid content in the dispersion to which the electrolyte is added. Is more preferable. As a result, the particle diameter of the coalesced particles can be controlled particularly easily and reliably, and the generation of coarse particles can be reliably prevented.
The electrolyte is preferably added in the form of an aqueous solution. As a result, the electrolyte can be quickly diffused throughout the dispersion, and the amount of electrolyte added can be easily and reliably controlled. As a result, coalesced particles having a desired particle size and a particularly narrow particle size distribution can be obtained.

Moreover, when adding electrolyte in the state of aqueous solution, it is preferable that the density | concentration of the electrolyte in aqueous solution is 2-10 wt%, and it is more preferable that it is 2.5-6 wt%.
As a result, the electrolyte can be diffused through the entire dispersion particularly quickly, and the amount of electrolyte added can be easily and reliably controlled. Further, by adding such an aqueous solution, the content of water in the dispersion when the addition of the electrolyte is completed becomes suitable. For this reason, the growth rate of the coalesced particles after the addition of the electrolyte can be made moderately slow to the extent that productivity does not decrease. As a result, the particle size can be controlled more reliably. In addition, unintentional coalescence of coalesced particles can be reliably prevented.

When the electrolyte is added as an aqueous solution, the rate of addition of the aqueous electrolyte solution is 0.5 to 10 parts by weight / minute with respect to 100 parts by weight of the solid content in the dispersion to which the aqueous electrolyte solution is added. Is preferable, and it is more preferable that it is 1.5-5 weight part / min.
As a result, it is possible to prevent the uneven concentration of the electrolyte from occurring in the dispersion, and reliably prevent the generation of coarse particles. Further, the particle size distribution of the coalesced particles is particularly narrow. Further, by adding the electrolyte at such a rate, the coalescing rate can be controlled particularly easily, and it becomes particularly easy to control the average particle size of the coalesced particles, and the productivity of the toner particles 1 can be increased. It can be particularly excellent.

The addition of the electrolyte may be performed in a plurality of times. As a result, coalescent particles having a desired size can be obtained easily and reliably, and the circularity of the obtained coalescent particles can be surely made sufficiently large.
Moreover, this process is performed in the state which stirred the dispersion liquid. Thereby, coalesced particles with particularly small variations in shape and size among the particles can be obtained.

For stirring the dispersion, for example, an agitation blade such as an anchor blade, a turbine blade, a fiddler blade, a full zone blade, a max blend blade, or a half moon blade may be used, and among these, a max blend blade or a full zone blade is preferable. As a result, the added electrolyte can be quickly and uniformly dispersed and dissolved to reliably prevent the uneven concentration of the electrolyte from occurring. Moreover, it is possible to more reliably prevent the coalesced particles once formed from collapsing while efficiently coalescing the dispersoid. As a result, coalesced particles with small variations in shape and particle size among the particles can be obtained efficiently.
The blade tip speed of the stirring blade is preferably from 0.1 to 10 m / second, more preferably from 0.2 to 8 m / second, and even more preferably from 0.2 to 6 m / second. When the blade tip speed is a value within the above range, the added electrolyte can be uniformly dispersed and dissolved, and the occurrence of uneven concentration of the electrolyte can be reliably prevented. In addition, it is possible to more reliably prevent the coalesced particles once formed from collapsing while more efficiently coalescing the dispersoid.

  The average particle diameter of the obtained coalesced particles is preferably 0.5 to 5 μm, and more preferably 1.5 to 3 μm. Thereby, the particle diameter of the toner particle 1 finally obtained can be made moderate.

3. Solvent removal (solvation removal) process Then, the organic solvent contained in a dispersion liquid is removed. Thereby, resin fine particles (toner particles 1) dispersed in the dispersion are obtained.
The removal of the organic solvent may be performed by any method, but can be performed, for example, under reduced pressure. Thereby, the organic solvent can be efficiently removed while sufficiently preventing the modification of the constituent material such as the resin material.
Moreover, it is preferable that the process temperature in this process is temperature lower than the glass transition point (Tg) of the resin material which comprises coalesced particle.

Moreover, you may perform this process in the state which added the antifoamer to the dispersion liquid. Thereby, an organic solvent can be removed efficiently.
Antifoaming agents include, for example, mineral oil-based antifoaming agents, polyether-based antifoaming agents, silicone-based antifoaming agents, lower alcohols, higher alcohols, fats and oils, fatty acids, fatty acid esters, phosphoric acid Esters can be used.
Although the usage-amount of an antifoamer is not specifically limited, It is preferable that it is 20-300 ppm by weight ratio with respect to the solid content contained in a dispersion liquid, and it is more preferable that it is 30-100 ppm.

In this step, at least a part of the aqueous liquid may be removed together with the organic solvent.
In this step, it is not always necessary to remove all of the organic solvent (the total amount of the organic solvent contained in the dispersion). Even in such a case, the remaining organic solvent can be sufficiently removed in other steps described later.

4). Cleaning Step Next, the resin fine particles (toner particles 1) obtained as described above are cleaned.
By performing this step, even if an organic solvent or the like is contained as an impurity, these can be efficiently removed. As a result, the amount of volatile organic compound (TVOC) in the resin fine particles finally obtained can be made particularly small.
In this step, for example, resin fine particles are separated by solid-liquid separation (separation from an aqueous liquid), and then solid dispersion (resin fine particles) is redispersed in water and solid-liquid separation (resin fine particles from an aqueous liquid is separated). Separation). The redispersion of solids in water and solid-liquid separation may be repeated a plurality of times.

5). Drying Step Thereafter, the toner particles 1 can be obtained by performing a drying process.
The drying step can be performed using, for example, a vacuum dryer (for example, ribocorn (manufactured by Okawara Seisakusho), nauter (manufactured by Hosokawa Micron) etc.), fluidized bed dryer (manufactured by Okawara Seisakusho), etc.

6). Dispersing Step Next, an amine-based dispersant is added to the carrier liquid 10 and the toner particles 1 obtained as described above are dispersed in the carrier liquid 10. Thereby, the liquid developer 100 is obtained.
Any method may be used for dispersing the toner particles 1 and the respective dispersants in the carrier liquid 10, for example, by mixing the carrier liquid 10, the toner particles 1, and the amine cyclic dispersant with a bead mill, a ball mill, or the like. It can be carried out. By mixing by such a method, the plasticizer in the carrier liquid 10 can surely permeate the toner particles 1.

Further, at the time of dispersion, a component other than the carrier liquid 10, the toner particles 1 and the respective dispersants may be mixed.
Further, the dispersion of the toner particles 1 and the respective dispersants in the carrier liquid 10 may be performed using the entire amount of the carrier liquid 10 constituting the liquid developer 100 finally obtained. It may be performed using a part of.
Further, when the toner particles 1 and the dispersant are dispersed using a part of the carrier liquid 10, the same liquid as the liquid used for dispersion may be added as the carrier liquid 10 after the dispersion. Alternatively, after dispersion, a liquid different from the liquid used for dispersion may be added as the carrier liquid 10. In the latter case, characteristics such as viscosity of the liquid developer 100 finally obtained can be easily adjusted.

  When the liquid developer 100 is manufactured by the method as described above, the toner particles 1 contained include the rosin resin 3 on at least a part of the surface thereof, and the shape between the toner particles 1 The variation is small. Thereby, the surface area of the particle surface does not vary between particles, and the amount of penetration of the plasticizer does not vary between particles. As a result, the toner particles 1 have excellent low-temperature fixability, excellent long-term dispersion stability, can effectively suppress variation in charging characteristics among the toner particles 1, and can be used in development and transfer processes. In addition, the configuration of the apparatus used for development and transfer can be simplified.

Next, a preferred embodiment of the image forming apparatus 1000 will be described. The image forming apparatus 1000 forms a color image on a recording medium using the liquid developers 100Y, 100M, 100C, and 100K that are the liquid developers 100 of the respective colors.
FIG. 2 is a schematic diagram showing an image forming apparatus 1000 to which the liquid developers 100Y, 100M, 100C, and 100K are applied, and FIG. 3 is an enlarged view of a part of the image forming apparatus 1000 shown in FIG.

  In FIG. 2, an image forming apparatus 1000 includes four developing units 30Y, 30M, 30C, and 30K, an intermediate transfer unit 40, a secondary transfer unit 60 as a secondary transfer unit, and a fixing unit (fixing device) F40. There are four liquid developer supply sections 90Y, 90M, 90C, and 90K.

The developing units 30Y, 30M, and 30C develop the latent image with a yellow liquid developer 100Y (Y), a magenta liquid developer 100M (M), and a cyan liquid developer 100C (C), respectively. Has a function of forming a single color image corresponding to the above. Further, the developing unit 30K has a function of developing a latent image with the black liquid developer 100K (K) to form a black (black) single color image.
Since the developing units 30Y, 30M, 30C, and 30K have the same configuration, the developing unit 30Y will be described below.

  In FIG. 3, a developing unit 30Y includes a photoconductor 10Y as an example of a latent image carrier, a charging roller 11Y, an exposure unit 12Y, a development unit 200Y, and a photoconductor squeeze along the rotation direction of the photoconductor 10Y. The apparatus 101Y includes a primary transfer backup roller 51Y, a charge removal unit 16Y, a photoreceptor cleaning blade 17Y, and a developer recovery unit 18Y.

Photoreceptor 10Y has a cylindrical base material and a photosensitive layer formed of a material such as amorphous silicon formed on the outer peripheral surface thereof, and is rotatable around a central axis. Rotates clockwise as indicated by the arrow in FIG.
The photoreceptor 10Y is supplied with a liquid developer 100Y by a developing unit 200Y described later, and a layer of the liquid developer 100Y 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 laser light indicated by an arrow in the drawing. is there. The exposure unit 12Y includes a semiconductor laser, a polygon mirror, an F-θ lens, and the like, and charges the modulated laser light based on an image signal input from a host computer (not shown) such as a personal computer or a word processor. Irradiate onto the photoconductor 10Y.

  The developing unit 200Y is a device for developing the latent image formed on the photoreceptor 10Y using the liquid developer 100Y. Details of the developing unit 200Y will be described later.

The photoconductor squeeze device 101Y is disposed on the downstream side in the rotation direction from the developing unit 200Y so as to face the photoconductor 10Y. The cleaning blade 14Y removes the liquid developer 100Y, and the developer collection unit 15Y collects the removed liquid developer 100Y.
The photosensitive member squeeze device 101Y has a function of recovering excess carrier liquid 10 and originally unnecessary fog toner from the liquid developer 100Y used for development on the photosensitive member 10Y, and increasing the ratio of the toner particles 1 in the visible image. Have.

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 photoconductor 10Y after the monochrome 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. After the monochrome image is transferred onto the intermediate transfer unit 40 by the primary transfer backup roller 51Y, the photoconductor cleaning blade 17Y remains on the photoconductor 10Y. The liquid developer 100Y to be scraped off is removed and removed.
The developer recovery unit 18Y has a function of recovering the liquid developer 100Y removed by the photoconductor cleaning blade 17Y.

In FIG. 2, the intermediate transfer unit 40 is an endless elastic belt member, and is stretched around a belt driving roller 41 and a pair of driven rollers 44 and 45 to which a driving force of a motor (not shown) is transmitted.
The intermediate transfer unit 40 is driven to rotate counterclockwise by the belt driving roller 41 while contacting the photoreceptors 10Y, 10M, 10C, and 10K by the primary transfer backup rollers 51Y, 51M, 51C, and 51K.
Further, the intermediate transfer unit 40 is applied with a predetermined tension by a tension roller 49 so that slack is removed. The tension roller 49 is disposed downstream of the one driven roller 44 in the rotation (movement) direction of the intermediate transfer unit 40 and upstream of the other driven roller 45 in the rotation (movement) direction of the intermediate transfer unit 40. .

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 sequentially primary-transferred and superposed on each other. Secondary transfer is performed on a recording medium F5 such as paper, film, or cloth. Therefore, when the toner image (intermediate transfer 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 surface of the non-smooth sheet material is copied. As a means for improving the secondary transfer characteristics, an elastic belt member is employed.

The intermediate transfer unit 40 is provided with a cleaning device including an intermediate transfer unit cleaning blade 46, a developer recovery unit 47, and a non-contact type bias applying member 48.
The intermediate transfer portion cleaning blade 46 and the developer recovery portion 47 are arranged on the driven roller 45 side.
The intermediate transfer portion cleaning blade 46 scrapes off the liquid developer 100 adhering to the intermediate transfer portion 40 after the intermediate transfer image is secondarily transferred onto the recording medium F5 by the secondary transfer unit (secondary transfer portion) 60. It has the function of dropping and removing.
The developer recovery unit 47 has a function of recovering the liquid developer 100 removed by the intermediate transfer unit cleaning blade 46.

The non-contact type bias applying member 48 is disposed away from the intermediate transfer unit 40 at a position facing the tension roller 49. The non-contact type bias applying member 48 applies a bias voltage having a polarity opposite to that of the toner particles 1 to the toner particles 1 of the liquid developer 100 remaining on the intermediate transfer portion 40 after the secondary transfer.
Thereby, the toner particles 1 are neutralized, and the electrostatic adhesion force of the toner particles 1 to the intermediate transfer portion 40 is reduced. In this example, a corona charger is used as the non-contact type bias applying member 48.
Note that the non-contact type bias applying member 48 is not necessarily disposed at a position facing the tension roller 49, and the intermediate transfer unit 40 from the driven roller 44 such as a position between the driven roller 44 and the tension roller 49, for example. The intermediate transfer unit 40 can be disposed at an arbitrary position downstream of the driven roller 45 and upstream of the driven roller 45 in the moving direction. The non-contact type bias applying member 48 may be a known non-contact type charger other than the corona charger.

In FIG. 3, an intermediate transfer unit squeeze device 52Y is arranged downstream of the primary transfer backup roller 51Y in the moving direction of the intermediate transfer unit 40.
The intermediate transfer unit squeeze device 52Y serves as a means for removing excess carrier liquid 10 from the transferred liquid developer 100Y when the liquid developer 100Y transferred onto the intermediate transfer unit 40 has not reached the desired dispersion state. Is provided.
The intermediate transfer unit squeeze device 52Y is removed by the intermediate transfer unit squeeze roller 53Y, the intermediate transfer unit squeeze cleaning blade 55Y that presses and slides against the intermediate transfer unit squeeze roller 53Y, and the intermediate transfer unit squeeze cleaning blade 55Y. The developer collecting unit 56Y collects the liquid developer 100Y.
The intermediate transfer unit squeeze device 52Y collects excess carrier liquid 10 from the liquid developer 100Y primarily transferred to the intermediate transfer unit 40, increases the ratio of toner particles 1 in the image, and removes originally unwanted fog toner. Has the function of collecting.

In FIG. 2, the secondary transfer unit 60 includes a pair of secondary transfer rollers that are spaced apart from each other by a predetermined distance along the moving direction of the recording medium F <b> 5. Of these pair of secondary transfer rollers, the secondary transfer roller disposed on the upstream side in the moving direction of the intermediate transfer unit 40 is the upstream secondary transfer roller 64. The upstream secondary transfer roller 64 can be pressed against the belt drive roller 41 via the intermediate transfer unit 40.
Of the pair of secondary transfer rollers, the secondary transfer roller disposed on the downstream side in the moving direction of the intermediate transfer unit 40 is the downstream secondary transfer roller 65. The downstream secondary transfer roller 65 can be brought into pressure contact with the driven roller 44 via the intermediate transfer unit 40.
That is, the upstream side secondary transfer roller 64 and the downstream side secondary transfer roller 65 bring the recording medium F5 into contact with the intermediate transfer unit 40 that is hung on the belt driving roller 41 and the driven roller 44, respectively. The intermediate transfer image formed by superimposing colors on 40 is secondarily transferred to the recording medium F5.

In this case, the belt driving roller 41 and the driven roller 44 also function as backup rollers for the upstream side secondary transfer roller 64 and the downstream side secondary transfer roller 65, respectively. In other words, the belt drive roller 41 is also used as an upstream backup roller disposed in the secondary transfer unit 60 on the upstream side of the driven roller 44 in the moving direction of the recording medium F5. The driven roller 44 is also used as a downstream backup roller disposed in the secondary transfer unit 60 on the downstream side in the moving direction of the recording medium F5 from the belt driving roller 41.
Accordingly, the recording medium F5 conveyed to the secondary transfer unit 60 is moved from the pressure contact start position (nip start position) between the upstream side secondary transfer roller 64 and the belt drive roller 41 to the downstream side secondary transfer roller 65 and the driven roller. 44 is in close contact with the intermediate transfer portion 40 in a predetermined movement region of the recording medium F5 up to the press-contact end position (nip end position) with 44. As a result, the full-color intermediate transfer image on the intermediate transfer unit 40 is secondarily transferred to the recording medium F5 in close contact with the intermediate transfer unit 40 for a predetermined time, so that good secondary transfer is performed.

The secondary transfer unit 60 includes a secondary transfer roller cleaning blade 66 and a developer recovery unit 67 with respect to the upstream side secondary transfer roller 64. Further, the secondary transfer unit 60 includes a secondary transfer roller cleaning blade 68 and a developer recovery unit 69 with respect to the downstream side secondary transfer roller 65.
The secondary transfer roller cleaning blades 66 and 68 are in contact with the upstream secondary transfer roller 64 and the downstream secondary transfer roller 65, respectively, and after the secondary transfer, the upstream secondary transfer roller 64 and the downstream secondary. The liquid developer 100 remaining on the surface of the transfer roller 65 is scraped off and removed. Further, the developer recovery units 67 and 69 are respectively provided with the liquid developer 100Y scraped off from the secondary transfer roller 64 and the downstream secondary transfer roller 65 by the upstream secondary transfer roller cleaning blades 66 and 68, respectively. 100M, 100C, and 100K are collected and stored.

The toner image (intermediate transfer image) transferred onto the recording medium F5 by the secondary transfer unit 60 is sent to a fixing unit (fixing device) F40, and is heated and pressurized to be fixed on the recording medium F5.
Specifically, the fixing temperature is preferably 80 to 160 ° C., more preferably 100 to 150 ° C., and further preferably 100 to 140 ° C.

Next, the developing units 200Y, 200M, 200C, and 200K will be described in detail. In the following description, the developing unit 200Y will be typically described.
In FIG. 3, the developing unit 200Y includes a liquid developer storage unit 31Y, a coating roller 32Y, a regulating blade 33Y, a developer stirring roller 34Y, a communication unit 35Y, a recovery screw 36Y, a developing roller 20Y, and a developing roller. It has a cleaning blade 21Y, a developer recovery unit 24Y, and a corona discharger (compression unit) 25Y.

  The liquid developer storage unit 31Y has a function of storing the liquid developer 100Y for developing the latent image formed on the photoreceptor 10Y, and includes a supply unit 31aY that supplies the liquid developer 100Y to the development unit 30Y. A recovery unit 31bY that recovers excess liquid developer 100Y generated in the supply unit 31aY and the like, and a partition 31cY that partitions the supply unit 31aY and the recovery unit 31bY.

The supply unit 31aY has a function of supplying the liquid developer 100Y to the application roller 32Y, and has a concave portion in which the developer stirring roller 34Y is installed. Further, the liquid developer 100Y is supplied to the supply unit 31aY from the liquid developer mixing tank 93Y through the communication unit 35Y.
The collection unit 31bY collects the excess liquid developer 100Y collected in the liquid developer 100Y and the developer collection units 15Y and 24Y supplied excessively to the supply unit 31aY. The collected liquid developer 100Y is conveyed to a liquid developer mixing tank 93Y described later and reused. The recovery unit 31bY has a concave portion, and a recovery screw 36Y is installed near the bottom.

A wall-shaped partition 31cY is provided at the boundary between the supply unit 31aY and the recovery unit 31bY. The partition 31cY partitions the supply unit 31aY and the recovery unit 31bY and can prevent the recovered liquid developer 100Y from being mixed into the fresh liquid developer 100Y. Further, when the excess liquid developer 100Y is supplied to the supply unit 31aY, the excess liquid developer 100Y can overflow from the supply unit 31aY to the recovery unit 31bY beyond the partition 31cY. For this reason, the amount of the liquid developer 100Y in the supply unit 31aY can be kept constant, and the amount of the liquid developer 100Y supplied to the application roller 32Y can be kept constant. For this reason, the image quality of the finally formed image becomes stable.
Further, the partition 31cY is provided with a notch, and the liquid developer 100Y can overflow from the supply part 31aY to the recovery part 31bY through the notch.

The coating roller 32Y has a function of supplying the liquid developer 100Y 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 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 coating roller 32Y contacts the liquid developer 100Y while rotating counterclockwise, thereby supporting the liquid developer 100Y in the supply unit 31aY in the groove, and the supported liquid developer 100Y is transferred to the developing roller. Transport to 20Y.

The regulating blade 33Y contacts the surface of the coating roller 32Y and regulates the amount of the liquid developer 100Y on the coating roller 32Y. That is, the regulation blade 33Y plays a role of scraping off the excess liquid developer 100Y on the application roller 32Y and measuring the liquid developer 100Y 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.
The regulating blade 33Y is provided on the side where the application roller 32Y rotates and advances from the liquid developer 100Y (that is, the right side in FIG. 3). 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 (about 77 degrees) is provided in the developing roller 20Y described later. It is lower than the hardness (about 85 degrees) of the pressure-contact part to the surface of the coating roller 32Y of the obtained elastic body layer. Further, the excess liquid developer 100Y that has been scraped off is collected in the supply unit 31aY and reused.

The developer stirring roller 34Y has a function of stirring the liquid developer 100Y 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 the supply unit 31aY, the toner particles 1 in the liquid developer 100Y have a positive charge, and the liquid developer 100Y is agitated by the developer agitation roller 34Y to be in a uniformly dispersed state. By rotating, it is pumped up from the liquid developer reservoir 31Y, and the amount of the liquid developer 100Y is regulated by the regulating blade 33Y and supplied to the developing roller 20Y. Further, by being stirred by the developer stirring roller 34Y, the liquid developer 100Y can be stably overflowed to the collection unit 31bY side beyond the partition 31cY, and the liquid developer 100Y is prevented from staying and being compressed. be able to.
Furthermore, the developer stirring roller 34Y is provided in the vicinity of the communication portion 35Y. For this reason, the liquid developer 100Y supplied from the communication unit 35Y can quickly diffuse, and the liquid level of the supply unit 31aY is stabilized even when the liquid developer 100Y is supplied to the supply unit 31aY. Can be. By providing such a developer agitation roller 34Y in the vicinity of the communication portion 35Y, the communication portion 35Y has a negative pressure, and the liquid developer 100Y can be sucked up naturally.

The communication unit 35Y is a portion that is provided vertically below the developer stirring roller 34Y, communicates with the liquid developer mixing tank 93Y, and sucks the liquid developer 100Y from the liquid developer mixing tank 93Y to the supply unit 31aY.
By providing the communication portion 35Y below the developer stirring roller 34Y, the liquid developer 100Y supplied from the communication portion 35Y is stopped by the developer stirring roller 34Y, and the liquid top surface does not rise due to blowing, The upper surface of the liquid is held almost constant, and the liquid developer 100Y can be stably supplied to the coating roller 32Y.

  The recovery screw 36Y provided near the bottom of the recovery unit 31bY is made of a cylindrical member, has a spiral rib on the outer periphery, and has a function of maintaining the fluidity of the recovered liquid developer 100Y. The liquid developer 100Y has a function of promoting conveyance of the liquid developer 100Y to the liquid developer mixing tank 93Y.

The developing roller 20Y carries the liquid developer 100Y and conveys the latent image carried on the photoconductor 10Y to a developing position facing the photoconductor 10Y in order to develop the latent image carried on the photoconductor 10Y by the liquid developer 100Y.
The developing roller 20Y forms a layer of the liquid developer 100Y on the surface thereof by supplying the liquid developer 100Y from the coating roller 32Y described above.
The developing roller 20Y includes a conductive elastic layer on the outer peripheral portion of an inner core made of metal such as iron, and has a diameter of about 20 mm. The elastic body layer has a two-layer structure. As the inner layer, urethane rubber having a rubber hardness of about 30 degrees JIS-A and a thickness of about 5 mm is used, and as the surface layer (outer layer), the rubber hardness is JIS. A urethane rubber having a thickness of about 30 μm at about 85 ° A is provided. The developing roller 20Y is in pressure contact with the photoreceptor 10Y in an elastically deformed state 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. 3) opposite to the rotation direction (clockwise in FIG. 3) of the photoconductor 10Y. When developing the latent image formed on the photoconductor 10Y, an electric field is formed between the developing roller 20Y and the photoconductor 10Y.

  The corona discharger (compression unit) 25Y is an apparatus having a function of compressing the toner particles 1 of the liquid developer 100Y carried on the developing roller 20Y. In other words, the corona discharger 25Y applies an electric field having the same polarity as that of the toner particles 1 to the liquid developer 100Y described above, thereby causing toner particles near the surface of the developing roller 20Y in the layer of the liquid developer 100Y. 1 is a device having a function of unevenly distributing 1. By unevenly distributing the toner particles 1 in this manner, the development density (development efficiency) can be improved, and as a result, a clear image with high quality can be obtained.

In the developing unit 200Y, the coating roller 32Y and the developing roller 20Y are separately driven by different power sources (not shown). The amount of the liquid developer 100Y supplied onto the developing roller 20Y can be adjusted by changing the rotation speed (linear speed) ratio between the coating roller 32Y and the developing roller 20Y.
The developing unit 200Y includes a rubber developing roller cleaning blade 21Y that is in contact with the surface of the developing roller 20Y, and a developer recovery unit 24Y. The developing roller cleaning blade 21Y is an apparatus for scraping off and removing the liquid developer 100Y remaining on the developing roller 20Y after development is performed at the developing position. The liquid developer 100Y removed by the developing roller cleaning blade 21Y is collected in the developer collecting unit 24Y.

  As shown in FIGS. 2 and 3, the image forming apparatus 1000 includes liquid developer supply units 90Y, 90M, and 90D that supply liquid developers 100Y, 100M, 100C, and 100K to the development units 30Y, 30M, 30C, and 30K. 90C and 90K are provided. These liquid developer replenishers 90Y, 90M, 90C, and 90K are respectively provided with liquid developer tanks 91Y, 91M, 91C, and 91K, carrier liquid tanks 92Y, 92M, 92C, and 92K, and a liquid developer mixing tank 93Y, 93M, 93C, 93K.

The liquid developer tanks 91Y, 91M, 91C, and 91K store high-density liquid developers 100Y, 100M, 100C, and 100K corresponding to the respective colors. Further, the carrier liquid 10 is stored in each of the carrier liquid tanks 92Y, 92M, 92C, and 92K. Further, each liquid developer mixing tank 93Y, 93M, 93C, 93K includes a predetermined amount of high-concentration liquid developers 100Y, 100M, 100C, 100K from each liquid developer tank 91Y, 91M, 91C, 91K. A predetermined amount of each carrier liquid 10 is supplied from each carrier liquid tank 92Y, 92M, 92C, 92K.
Each of the liquid developer mixing tanks 93Y, 93M, 93C, and 93K is mixed by a stirrer equipped with each of the supplied high-concentration liquid developers 100Y, 100M, 100C, and 100K, and each carrier liquid 10, respectively. The liquid developers 100Y, 100M, 100C, and 100K corresponding to the colors used in the supply units 31aY, 31aM, 31aC, and 31aK are prepared by stirring. The liquid developers 100Y, 100M, 100C, and 100K prepared in the liquid developer mixing tanks 93Y, 93M, 93C, and 93K are supplied to the supply units 31aY, 31aM, 31aC, and 31aK, respectively. Yes.

In FIG. 3, the liquid developer 100Y recovered by the recovery unit 31bY is recovered and reused in the liquid developer mixed layer 93Y. The same applies to the liquid developer mixing tanks 93M, 93C, and 93K.
Here, in the toner particles 1, the amine cyclic dispersant is firmly attached to the surface of the toner particles 1 containing the rosin resin 3 as described above. For this reason, even if the toner particles 1 are subjected to stress accompanying recovery (for example, stress due to a cleaning blade), the amine cyclic dispersant is reliably prevented from detaching and dropping from the toner particles 1. The toner particles 1 as described above have high redispersibility in the carrier liquid 10. Therefore, the collected toner particles 1 can be suitably reused for image formation.
In the above-described embodiment, the configuration having the corona discharger 25Y as the image forming apparatus 1000 has been described. However, the corona discharger may not be provided.

According to such an embodiment, there are the following effects.
(1) Since the molecular structure of the rosin resin 3 can be changed according to the surrounding conditions, esters can be effectively incorporated into the resin molecule. Esters in the carrier liquid 10 penetrate between the resin molecules in the toner particles 1. Esters that have penetrated between molecules can increase the intermolecular distance of the resin and reduce the energy required to change the state of the resin from solid to liquid. Therefore, it is possible to reduce the heat energy necessary for fixing, and it is possible to obtain the liquid developer 100 having excellent low-temperature fixability.

  (2) Further, by including the rosin resin 3 oriented in the outer shell 2, the toner particles 1 are three-dimensional due to the bulky structure of the rosin resin 3 oriented in the outer shell 2 when dispersed in the carrier liquid 10. A repulsive effect is produced, and dispersion stability can be obtained as an effect. Furthermore, since the rosin resin 3 has a high polarity, high chargeability can also be obtained.

  (3) When the liquid developer 100 is manufactured by the method as described in the embodiment, the toner particles 1 included include the rosin-based resin 3 on at least a part of the surface thereof, and the toner particles 1 The variation in shape between the two is small. As a result, the surface area of the toner particles 1 does not vary between the toner particles 1, and the amount of plasticizer permeation does not vary between the toner particles 1. As a result, the toner particles 1 have excellent low-temperature fixability, excellent long-term dispersion stability, can effectively suppress variation in charging characteristics among the toner particles 1, and can be used in development and transfer processes. In addition, the configuration of the apparatus used for development and transfer can be simplified.

  (4) In addition, fatty acid monoesters and phthalic acid esters, which are esters contained in the carrier liquid 10, permeate the toner particles 1 during the fixing process and develop a plasticizer effect. Due to this plasticizer effect, the toner particles 1 can be changed in state with lower energy. For example, when paper is used as the recording medium F5, the state change is possible with low energy, and the toner particles 1 whose state has changed from a solid state to a liquid state can easily enter the gaps between the paper fibers. The fixing strength can be made higher. Therefore, due to the plasticizer effect, the toner particles 1 can be changed in state even at low energy (low temperature), and the low-temperature fixability can be improved.

  (5) By making the molecular weight of the rosin resin 3 out of the resins used for forming the toner particles 1 relatively low, 1000 to 20000, the number of molecules in the fixed amount increases. The rosin resin 3 has the highest acid value among the resins constituting the toner particles 1 and has hydrophilicity, so that it can be oriented to the outermost side of the toner particles 1. Therefore, penetration of the ester into the resin can be promoted, and the liquid developer 100 excellent in low-temperature fixability can be obtained.

(6) Further, the carrier liquid 10 contains both fatty acid triglyceride and fatty acid monoester or phthalic acid ester, so that the toner particles 1 are prevented from aggregating with each other during storage. Excellent in properties. On the other hand, at the time of fixing, the fixing strength of the toner particles 1 on the recording medium F5 can be made excellent. This can be explained as follows.
That is, the fatty acid triglyceride, fatty acid monoester, and phthalic acid ester contained in the carrier liquid 10 are a resin material that is a main component of the toner particles 1 as described later, particularly a polyester resin, and a rosin resin 3 having an ester bond. Excellent affinity.
The fatty acid triglyceride having a fatty acid skeleton and the fatty acid monoester have an ester structure in the structure. In addition, an ester bond is also present in the rosin resin 3 having a polyester resin or an ester bond. Among those having the same structure, the energy difference due to the difference in structure becomes small, so that the affinity is improved. Therefore, the dispersibility of the toner particles 1 in the carrier liquid 10 is good, and aggregation (blocking) between the toner particles 1 is effectively prevented during storage, and the storage stability of the liquid developer 100 can be improved. Stability is excellent.
On the other hand, at the time of fixing, heat is applied to the liquid developer 100, so that the fatty acid monoester and the phthalic acid ester penetrate into the toner particles 1 and develop the plasticizer effect as described above. As a result, the toner particles 1 can be firmly fixed to the recording medium F5 even in fixing at a low temperature, so that the low-temperature fixability is improved.

(7) By using the carrier liquid 10 containing a fatty acid triglyceride and a fatty acid monoester or phthalic acid ester, the low-temperature fixability of the toner particles 1 with respect to the recording medium F5 such as paper can be improved and particularly excellent. It shows the fixing strength.
This can be explained as follows. In general, fatty acid monoesters and phthalic acid esters have a lower viscosity than fatty acid triglycerides. Further, by including one or both of fatty acid triglyceride and fatty acid monoester or phthalic acid ester in the carrier liquid 10, both the carrier liquid 10 and the liquid developer 100 can have an appropriate viscosity, and liquid development can be achieved. The penetration of the agent 100 into the recording medium F5 can be made suitable. Furthermore, since the carrier liquid 10 is cured in a state containing the toner particles 1 by the oxidative polymerization reaction of the unsaturated fatty acid component in the carrier liquid 10, the anchor effect between the cured liquid developer 100 and the recording medium F5 The toner particles 1 can be firmly fixed to the recording medium F5.

  (8) By using a plurality of developing units 30Y, 30M, 30C, and 30K having different colors, different colors are mixed during development to form a single color image, and the image quality is not disturbed. In addition, in the intermediate transfer unit 40, it is possible to accurately perform primary transfer of a single-color image accurately without color deviation when forming a color image. Further, the secondary transfer unit 60 that transfers onto the recording medium F5 can efficiently secondary transfer the intermediate transfer image onto the recording medium F5. Further, in the fixing unit F40, the carrier liquid 10 containing esters can efficiently penetrate into the recording medium F5, and the resin contained in the toner particles 1, particularly the rosin resin 3, can be fixed reliably. Therefore, the image forming apparatus 1000 using such liquid developers 100Y, 100M, 100C, and 100K can be obtained.

  (9) The supply units 31aY, 31aM, 31aC, and 31aK that supply the liquid developers 100Y, 100M, 100C, and 100K efficiently transfer the liquid developers 100Y, 100M, 100C, and 100K to the developing units 30Y, 30M, 30C, and 30K. Can be supplied. Further, the respective recovery units 15Y and 24Y for recovering the excess liquid developer 100Y, 100M, 100C, and 100K collect the excess liquid developer 100Y, 100M, 100C, and 100K, and develop the development units 30Y, 30M, 30C, and The liquid developers 100Y, 100M, 100C, and 100K can be sent again to 30K. Therefore, the image forming apparatus 1000 using such liquid developers 100Y, 100M, 100C, and 100K can be obtained.

Hereinafter, the liquid developer 100 will be described in detail based on examples.
Example 1
First, toner particles 1 were manufactured. In addition, about the process in which temperature is not described, it performed at room temperature (25 degreeC).
1. Dispersion adjustment process (Preparation of colorant master solution)
First, as a resin material, polyester resin L (weight average molecular weight Mw: 5,200, glass transition temperature: 46 ° C., softening temperature: 95 ° C., acid value: 10.0 mgKOH / g): 100 parts by weight was prepared.
Next, a mixture (mass ratio 50:50) with a cyan pigment (manufactured by Dainichi Seika Co., Ltd., Pigment Blue 15: 3) as a colorant was prepared. The resin material and the colorant were mixed using a 20 L type Henschel mixer to obtain a raw material for toner production.
Next, this raw material (mixture) was kneaded using a twin-screw kneading extruder. The kneaded product extruded from the extrusion port of the biaxial kneading extruder was cooled.
The kneaded material cooled as described above was coarsely pulverized to obtain a colorant master batch having an average particle size of 1.0 mm or less. A hammer mill was used for coarse pulverization of the kneaded product.

(Resin liquid preparation process)
Colorant masterbatch: 97.5 parts by weight methyl ethyl ketone: 175 parts by weight, polyester resin: 172.3 parts by weight, rosin modified phenolic resin (Arakawa Chemical Industries, acid value: 22 mgKOH / g or less, softening point: 172-2 182, weight average molecular weight: 100,000): 55.3 parts by weight were mixed with a high-speed disperser (manufactured by Primics, TK Robotics / TK homodisper type 2.5 blade), and neogen as an emulsifier ( Registered trademark) SC-F (Daiichi Kogyo Seiyaku Co., Ltd.): 1.38 parts by weight were added to prepare a resin solution. In this solution, the pigment was uniformly finely dispersed.

(Dispersoid formation processing)
Next, 50 parts by weight of 1N ammonia water was added to the resin liquid in the vessel, and the stirring blade was mixed with a high-speed disperser (Primics Co., Ltd., TK Robotics / TK homodisper type 2.5 blade). 170 parts by weight while stirring with a blade tip speed of 7.5 m / s, adjusting the temperature of the solution in the flask to 25 ° C., and then stirring with a blade tip speed of 14.7 m / s Of deionized water was added dropwise to cause phase inversion emulsification. While continuing stirring, 70 parts by weight of deionized water was further added to the resin solution. As a result, an aqueous dispersion in which the dispersoid containing the resin material was dispersed was obtained.

2. Unification Step Next, the aqueous dispersion was transferred to a stirring vessel having a Max Blend blade, and the temperature of the aqueous dispersion was adjusted to 25 ° C. while stirring at a blade tip speed of 1.0 m / s.
Next, while maintaining the same temperature and stirring conditions, a 5.0% sodium sulfate aqueous solution: 300 parts by weight was dropped, and the dispersoids were coalesced to form coalesced particles. After the dropping, the stirring was continued until the 50% volume particle diameter Dv (50) [μm] of the coalesced toner particles grew to 3 μm. When Dv (50) of the coalesced particles reached 2.5 μm, 120.6 parts by weight of deionized water was added to complete the coalescence.

3. Solvent Removal Step The organic solvent was distilled off under reduced pressure until the solid content was 23 wt%, to obtain a resin fine particle slurry.

4). Washing Step Next, the slurry was subjected to a washing treatment by performing solid-liquid separation, further redispersing in water (reslurry), and repeating solid-liquid separation. Thereafter, a wet cake (resin fine particle cake) of colored resin fine particles was obtained by suction filtration. The moisture content of the wet cake was 35 wt%.

5). Thereafter, toner particles 1 were obtained by drying the obtained wet cake using a vacuum dryer.

6). Dispersing Step Toner particles obtained by the above-mentioned method: 17.5 parts by weight, as amine dispersant, Nimine (registered trademark) DT-208, rapeseed oil (manufactured by Nisshin Oilio Co., Ltd., trade name “HIOLEIC rapeseed oil”): 90 parts by weight, fatty acid ester (made by Lion Chemical Co., Ltd., trade name “Pastel (registered trademark) M-14”: 45 parts by weight, aluminum stearate as a charge control agent (manufactured by NOF Corporation): 0.5 parts by weight of ceramic The mixture was placed in a pot (internal volume: 600 ml), and zirconia balls (ball diameter: 1 mm) were further placed in a ceramic pot so that the volume filling rate was 85%, and dispersed in a tabletop pot mill at a rotational speed of 230 rpm for 24 hours. As a result, a liquid developer 100C was obtained.

Dv (50) of the toner particles in the obtained liquid developer 100C was 2.00 μm. The 50% volume particle diameter Dv (50) [μm] of the obtained toner particles 1 was measured with a Mastersizer 2000 particle analyzer (manufactured by Malvern Instruments Ltd.). Further, the particle diameters of toner particles 1 obtained in each of Examples and Comparative Examples described below were similarly determined.
Further, the viscosity of the obtained liquid developer 100C at 25 ° C. was 80 mPa · s.

  Further, instead of cyan pigment, magenta pigment: Pigment Red 238 (manufactured by Sanyo Dye), yellow pigment: Pigment Yellow 180 (manufactured by Clariant), black pigment: carbon black (printex L, manufactured by Degussa) In addition, a magenta liquid developer 100M, a yellow liquid developer 100Y, and a black liquid developer 100K were manufactured in the same manner as described above except that the respective changes were made.

(Example 2 to Example 16)
The liquid developers 100Y, 100M, 100C, and 100K corresponding to the respective colors were changed in the same manner as in Example 1 except that the rosin resin 3 material, the material and composition of the carrier liquid 10, and the blending amount were changed as shown in Table 1. Manufactured.

Examples 1 to 6 are examples in which the type of fatty acid monoester or phthalic acid ester is changed.
Examples 7 to 10 are examples when the type of the rosin resin 3 is changed.
Examples 11 and 12 are examples in which the quantitative ratio between the fatty acid triglyceride and the fatty acid monoester was changed.
Examples 13 and 14 are examples in which the quantitative ratio between the fatty acid triglyceride and the phthalate ester is changed.
Examples 15 and 16 are examples in which the amount of the rosin resin 3 is changed.

(Comparative Example 1)
Liquid developers 100Y, 100M, 100C, and 100K corresponding to the respective colors were produced in the same manner as in Example 1 except that only rapeseed oil was used as the carrier liquid 10.

(Comparative Example 2)
Liquid developers 100Y, 100M, 100C, and 100K corresponding to the respective colors were produced in the same manner as in Example 1 except that the rosin resin 3 was not used as the resin for the toner particles 1.

(Comparative Example 3)
Liquid developers 100Y, 100M, 100C, and 100K corresponding to the respective colors were used in the same manner as in Example 1 except that only rapeseed oil was used as the carrier liquid 10 and no rosin resin 3 was used as the resin for the toner particles 1. Manufactured.

(Comparative Example 4)
Liquid developers 100Y, 100M, 100C, and 100K corresponding to the respective colors were manufactured in the same manner as in Example 1 except that polymer rosin was used as the rosin resin 3.

(Comparative Example 5)
As the rosin resin 3, liquid developers 100Y, 100M, 100C, and 100K corresponding to the respective colors were manufactured in the same manner as in Example 1 except that low molecular rosin was used.

Table 1 shows the composition, physical properties, physical properties, content, and the like of the liquid developer 100 for each of the above Examples and Comparative Examples.
The symbols in the table indicate the following materials.
R1: Rosin-modified polyester resin (Arakawa Chemical Industries, trade name “Marquide (registered trademark) No. 1”)
R2: Rosin-modified phenolic resin (Arakawa Chemical Industries, trade name “Tamanol (registered trademark) 361”, acid value: 5 to 20 mg KOH / g, softening point: 140 ° C. or higher, weight average molecular weight: 10,000 to 20000)
R3: rosin modified phenolic resin (manufactured by Arakawa Chemical Industries, trade name “Tamanol (registered trademark) 145”, acid value: 18 mgKOH / g or less, softening point: 140 to 155, weight average molecular weight: 20000)
R4: urethane-modified rosin resin (amine value: 6 mgKOH / g, acid value: 30 mgKOH / g, softening point: 120 to 130, weight average molecular weight: 20000)
R5: Rosin-modified phenol resin (Arakawa Chemical Industries, acid value: 6-22 mg KOH / g, softening point: 172-182, weight average molecular weight: 100,000)
R6: rosin modified phenolic resin, acid value: 4-16 mg KOH / g, softening point: 83-95, weight average molecular weight: 800)
L: Polyester resin L
H: Polyester resin H
D1: Naimin (registered trademark) DT-208 (manufactured by NOF Corporation)
L1: Fatty acid triglyceride (manufactured by Nisshin Oilio Co., Ltd., trade name “High Oleic Rapeseed Oil”)
P1: Fatty acid methyl ester (product name “Pastel (registered trademark) M-14” manufactured by Lion Chemical Co., Ltd.)
P2: fatty acid methyl ester (product name “Pastel (registered trademark) M-8” manufactured by Lion Chemical Co., Ltd.)
P3: fatty acid methyl ester (product name “Pastel (registered trademark) M-12” manufactured by Lion Chemical Co., Ltd.)
P4: Soybean oil fatty acid methyl (viscosity 5.1 mPa · s, manufactured by Nisshin Oilio Co., Ltd., trade name “soybean oil fatty acid methyl”)
P5: Phthalate ester (trade name “DINP”, manufactured by J-Plus Co., Ltd.)
P6: Phthalate ester (trade name “DIDP”, manufactured by JPLUS
P7: Phthalate ester (trade name “D-10”, manufactured by J-Plus Co., Ltd.)

Each liquid developer 100Y, 100M, 100C, and 100K obtained as described above was evaluated as follows.
1. Evaluation of Low Temperature Fixability Using an image forming apparatus as shown in FIGS. 2 and 3, an image of a predetermined pattern by the liquid developers 100Y, 100M, 100C, and 100K obtained in each of the examples and the comparative examples is recorded on a recording medium F5. Recording paper (manufactured by Seiko Epson Corporation, high-quality paper LPCPPA4). Thereafter, heat fixing was performed using the fixing device F40 with the set temperature of the heat fixing roller being 100 ° C.
Then, after confirming the non-offset area, the fixed image on the recording paper is erased twice (rubber eraser “LION 261-11” manufactured by Lion Business Machine Co., Ltd.) twice with a pressing load of 1.2 kgf, and the remaining ratio of image density Was measured by “X-Rite model 404” manufactured by X-Rite Inc, and evaluated according to the following five-step criteria.
A: Image density residual ratio is 95% or more (very good).
B: Image density residual ratio is 90% or more and less than 95% (good).
C: Image density remaining rate is 80% or more and less than 90% (normal).
D: Image density residual ratio is 70% or more and less than 80% (slightly bad).
E: Image density residual ratio is less than 70% (very bad).

2. Evaluation of chargeability The following evaluations were performed on the liquid developers 100Y, 100M, 100C, and 100K obtained as described above.
2-1. Development Efficiency Using the image forming apparatus 1000 as shown in FIGS. 2 and 3, the liquid developer 100Y obtained in each of the examples and comparative examples on the developing rollers 20Y, 20M, 20C, and 20K of the image forming apparatus 1000. , 100M, 100C, 100K liquid developer layers 100Y, 100M, 100C, 100K were formed. Next, the surface potentials of the developing rollers 20Y, 20M, 20C, and 20K are set to 300V, and the surface potentials of the photoconductors 10Y, 10M, 10C, and 10K are uniformly charged at 500V to expose the photoconductors 10Y, 10M, 10C, and 10K. The surface charge of the photoreceptors 10Y, 10M, 10C, and 10K was attenuated, and the surface potential was set to 50V. The developing rollers 20Y, 20M, 20C, and 20K after the layers of the liquid developers 100Y, 100M, 100C, and 100K pass between the photoreceptors 10Y, 10M, 10C, and 10K and the developing rollers 20Y, 20M, 20C, and 20K. The toner particles 1 above and the toner particles 1 on the photoreceptors 10Y, 10M, 10C, and 10K were collected with a tape. Each tape used for sampling was affixed on a recording paper, and the concentration of each toner particle 1 was measured. After the measurement, the concentration of the toner particles 1 collected on the photoconductors 10Y, 10M, 10C, and 10K is set to the concentration of the toner particles 1 collected on the photoconductors 10Y, 10M, 10C, and 10K, and the developing rollers 20Y, 20M, A value obtained by multiplying the numerical value obtained by dividing the sum of the toner particle 1 collected at 20C and 20K by the sum of 100 was obtained as development efficiency, and evaluated according to the following four criteria. It can be said that the higher the development efficiency, the better the toner particles 1 have charging characteristics.
A: The development efficiency is 95% or more, and the development efficiency is particularly excellent.
B: The development efficiency is 90% or more and less than 95%, and the development efficiency is excellent.
C: Development efficiency is 80% or more and less than 90%, and there is no practical problem.
D: The development efficiency is less than 80% and the development efficiency is inferior.

3. Evaluation of dispersion stability Liquid developer 100Y, 100M, 100C, 100K obtained in each example and each comparative example: 10 mL was put into a test tube (12 mm in diameter, 120 mm in length), and the sedimented depth after standing for 1 week. The thickness was measured and evaluated according to the following four-stage criteria.
A: Settling depth is 0 mm.
B: The settled depth is greater than 0 mm and 2 mm or less.
C: The settled depth is larger than 2 mm and 5 mm or less.
D: The settled depth is larger than 5 mm.

4). Evaluation of high-temperature storage stability The liquid developers 100Y, 100M, 100C, and 100K: 6 g obtained in each Example and each Comparative Example were placed in a glass sample bottle (20 ml) and sealed tightly. This was stored still for 24 hours in an environment of 55 ° C. and 30% RH. In each sample bottle, the volume average particle diameter Db before storage and the volume average diameter Da after storage are measured with a particle size distribution meter (Mastersizer 3000), and the rate of change (%) = (Db−Da) × 100 / Db was determined and evaluated according to the following four-stage criteria.
A: Change rate was 2% or less.
B: The rate of change was greater than 2% and 10% or less.
C: The rate of change was greater than 10% and 50% or less.
D: The rate of change was greater than 50%.

  Table 2 summarizes the evaluation results. The liquid developers 100Y, 100M, 100C, and 100K in each example are excellent in low-temperature fixability, charging characteristics (positive charging characteristics), dispersion stability, and high-temperature storage stability, and low temperature without impairing other characteristics. The effect of improving the fixing property was confirmed. On the other hand, satisfactory results were not obtained with the liquid developers 100Y, 100M, 100C, and 100K of the comparative examples.

Various changes can be made in addition to the above-described embodiments and modifications.
For example, the liquid developer 100 is not limited to that applied to the image forming apparatus 1000 as described above.
Further, the liquid developer 100 is not limited to the one manufactured by the manufacturing method as described above.
In the embodiment, the water-based emulsion is obtained and the coalescent particles are obtained by adding an electrolyte to the water-based emulsion, but the present invention is not limited thereto. For example, the coalesced particles are prepared by dispersing a colorant, a monomer, a surfactant, and a polymerization initiator in an aqueous liquid, preparing an aqueous emulsion by emulsion polymerization, and adding an electrolyte to the aqueous emulsion to associate. The emulsion may be prepared using an emulsion polymerization association method, or may be obtained by spray-drying the obtained aqueous emulsion to obtain coalesced particles.

Schematic of a liquid developer. 1 is a schematic diagram illustrating an image forming apparatus. FIG. 3 is an enlarged view of a part of the image forming apparatus.

  DESCRIPTION OF SYMBOLS 1 ... Toner particle, 2 ... Outer shell, 3 ... Rosin resin, 10 ... Carrier liquid, 15Y ... Developer collection part, 18Y ... Developer collection part, 30Y, 30M, 30C, 30K ... Development part, 31aY ... Supply part , 31bY ... recovery unit, 31cY ... partition, 40 ... intermediate transfer unit, 47 ... developer recovery unit, 56Y ... developer recovery unit, 60 ... secondary transfer unit, 90Y, 90M, 90C, 90K ... liquid developer supply unit , 100, 100Y, 100M, 100C, 100K, liquid developer, 1000, image forming apparatus, F5, recording medium, F40, fixing unit (fixing apparatus).

Claims (4)

Toner particles containing a rosin resin oriented in the outer shell;
A liquid developer comprising: an electrically insulating carrier liquid containing esters that disperse the toner particles. The liquid developer according to claim 1,
The liquid developer according to claim 1, wherein the rosin resin has a molecular weight of 1000 to 20000. A plurality of developing units that form a single color image corresponding to the plurality of liquid developers 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 a 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 image forming apparatus, wherein the liquid developer includes toner particles containing a rosin resin oriented in an outer shell and an electrically insulating carrier liquid containing esters. The image forming apparatus according to claim 3.
The developing unit includes a supply unit that supplies the liquid developer for forming the monochrome image, a recovery unit that recovers excess liquid developer in the supply unit, the supply unit, and the recovery unit. And a partition provided between
An excess of the liquid developer in the supply unit is collected in the collection unit through the partition.

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