JPH1124324A - Water-base liquid developer for electrophotography - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high stability, excellent dispersion stability, redispersibility, light fastness and water resistance by dispersing toner particles in which colorant is included in a coated state in carrier liquid principally composed of water. SOLUTION: The toner particles made of the colorant insoluble the water and resin are dispersed in the carrier liquid principally composed of the water. The colorant is insoluble in the carrier liquid and included in the coating film formed of thermoplastic resin having hydrophilic radical. The colorant is pigment or oil dye. Furthermore, the toner particles are dispersed in organic solvent which is insoluble in the colorant and the carrier liquid and dissolves the coating film formed of thermoplastic resin having the hydrophilic radical and simultaneously the resin is made insoluble in the carrier liquid principally composed of the water, whereby the developer is obtained. The toner particles are formed in a state where the colorant is firmly included in the coated state with the resin insoluble in the carrier liquid and having the hydrophilic radical and are dispersed in the carrier liquid in a particulate state, so that the developer shows the excellent dispersion stability and the good redispersibility.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner used when an image corresponding to an electrostatic latent image is wet-developed with an aqueous liquid developer in an electrophotographic process or the like. The present invention relates to an aqueous liquid developer for electrophotography having improved properties and redispersibility.

[0002]

2. Description of the Related Art A developing method using a liquid developer requires no fixing, is excellent in halftone reproducibility, and can provide a high-resolution image as compared with a dry developing method using a powder toner. Despite its features, it uses a low dielectric constant and highly insulating liquid, such as aliphatic hydrocarbons, as a carrier liquid, so it has a petroleum odor and belongs to a flammable liquid and may be flammable. However, there are problems in safety and hygiene, such as slight toxicity as an organic solvent. For this reason, at present, the use of liquid developers in very limited applications is currently limited.

In order to solve such problems of the conventional liquid developer, a method of developing an electrostatic latent image formed by electrophotography using a liquid developer containing water as a main component has been proposed. Some have been proposed. For example, as disclosed in JP-B-39-4299, a method in which a corona charge is added to the photoconductive material layer in advance from the outside and charged, and an electrostatic latent image formed by exposure is developed with an aqueous developer. Positioning the exposed photoconductive material layer on the surface of the aqueous coloring developer as in JP-A-39-29135 and 40-18992 so as not to come in contact with the solution,
A method in which a voltage is applied from outside to develop the photoconductive material layer by contacting only the unexposed portion of the photoconductive material layer. A method of forming a latent image according to the above and developing with charged colorant particles, as in JP-B-56-3545, applying an insulating layer on an electrostatic image formed on a photoconductor, and applying an aqueous liquid A method of developing with a developer, a method of developing an electrostatic latent image formed on electrostatic recording paper by an aqueous developer using an aqueous developer as in JP-B-56-35870, and JP-B-56-782. In this way, a mist of the aqueous liquid developer is supplied to the electrostatic latent image surface,
A method of developing an electrostatic latent image, as in JP-A-8-286432,
A method of developing an electrostatic latent image formed on a photoconductor by a backside exposure method using an aqueous developer can be used.

On the other hand, the fact is that little has been studied about the developers used in these aqueous developing methods.
Most of the conventionally proposed ones have a dye dissolved in water or a colloid colored with a dye.
A developer using such a dye has a light resistance of a recorded image,
Water resistance often becomes a problem. That is, when the recording image is exposed to water such as rain or drinking water, the recording image may bleed or disappear.

In order to solve the above-mentioned problems of light resistance and water resistance, use of a pigment as a coloring agent has been considered.
Actually, the description can be seen in the example of JP-B-54-13785, which is a dispersion of the pigment in water with a nonionic surfactant. There was a problem with sex.

Further, Japanese Patent Application Laid-Open No. 8-286432 proposes a liquid developer containing a pigment and a partially crosslinkable resin as an aqueous developer suitable for the backside exposure method. Since the use of the resin described above, aggregation of toner particles is easily promoted, and there are problems in storage stability and re-dispersibility of settled toner.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the conventional aqueous liquid developer for electrophotography. That is, to provide a good electrophotographic aqueous liquid developer having good light fastness and water fastness, and having little sedimentation and aggregation, excellent storage stability and excellent redispersibility. is there.

Another object of the present invention is to provide a color electrophotographic aqueous liquid developer having good dispersion stability. Another object of the present invention is to provide a highly safe electrophotographic liquid developer.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that at least a water-insoluble colorant is substantially insoluble in a carrier liquid and has a hydrophilic group-containing film. The present invention has been found to solve the above-mentioned problems by using an aqueous liquid developer in which toner particles covered by a forming thermoplastic resin are dispersed in a carrier liquid containing water as a main component. Reached.

That is, the present invention provides an aqueous liquid developer for electrophotography wherein toner particles comprising at least a water-insoluble colorant and a resin are dispersed in a carrier liquid containing water as a main component. The present invention provides an aqueous liquid developer for electrophotography, wherein the colorant is substantially insoluble in a carrier liquid and is covered by a film-forming thermoplastic resin having a hydrophilic group. Further, the present invention provides the aqueous liquid developer, wherein the colorant is a pigment or an oil-based dye.

Further, according to the present invention, the toner particles comprise a film-forming thermoplastic resin having a hydrophilic group and being substantially insoluble in the colorant and the carrier liquid, at least partially dissolving the resin. An aqueous liquid developer for electrophotography, wherein the aqueous liquid developer for electrophotography is obtained by dispersing the resin in an organic solvent and simultaneously or subsequently insolubilizing the resin in a carrier liquid containing water as a main component. provide. It is also substantially insoluble in the carrier liquid,
The liquid developer for electrophotography, wherein the film-forming thermoplastic resin having a hydrophilic group is a resin having an acid value of 50 or more and 280 or less and having at least a part of the acid group neutralized.

The aqueous liquid developer of the present invention exhibits excellent dispersion stability and good redispersibility because the resin substantially insoluble in the carrier liquid and having a hydrophilic group can strongly fix the colorant. This is considered to be because toner particles are formed in a state of being encapsulated in the coating liquid and are dispersed in the carrier liquid.

Hereinafter, the present invention will be described in more detail. As the colorant in the present invention, a water-insoluble colorant such as a conventionally known pigment and oil-soluble dye is used alone or in combination. Specifically, pigments that are generally commercially available can be used without particular limitation. For example, carbon black, phthalocyanine blue, phthalocyanine green, brilliant carmine 3
B, Brilliant Carmine 6B, Barium Red 2B,
Calcium Red 2B, Strontium Red 2B, Calcium Red, Lake Red C, Quinacridone Magenta, Disazo Yellow AAA, Disazo Yellow AAM
X, disazo yellow AAOT, disazo yellow AA
OT, isoindolinone yellow and the like can be used.

The oil-soluble dyes include, for example, CI Solvent Yellow 1, 2, 3, 13, 19, 22, 29, 3
6, 37, 38, 39, 40, 43, 44, 45, 4
7, 62, 63, 71, 76, 81, 85, 86; CI
Solvent Red 8, 27, 35, 36, 37, 38,
39, 40, 58, 60, 65, 67, 69, 81, 8
6, 89, 91, 92, 97, 99, 100, 109,
118, 119, 122; CI Solvent Blue 14,
24, 26, 34, 37, 38, 39, 42, 43, 4
5, 48, 52, 53, 55, 59, 67; CI Solvent Black 3, 5, 7, 8, 14, 17, 19, 2
0, 22, 24, 26, 27, 28, 29, 43, 45
And the like.

As the carrier liquid used in the present invention, water is mainly used, but if necessary, various water-soluble organic solvents can be appropriately mixed. Examples of such a water-soluble organic solvent include, for example, methyl alcohol, ethyl alcohol, n-butyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, sec-butyl alcohol, carbon number such as tert-butyl alcohol Amides of dimethylformamide and dimethylacetamide; ketones such as acetone and diacetone alcohol; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol, propylene glycol, butylene glycol; Triethylene glycol,
Alkylene glycols having an alkylene group containing 2 to 6 carbon atoms, such as hexylene glycol and diethylene glycol; glycerin; ethylene glycol methyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or Lower alkyl ethers of polyhydric alcohols such as ethyl) ether; N-methyl-2-pyrrolidone;
Pyrrolidones such as 2-pyrrolidone; dimethylsulfoxide, imidazolidinone and the like.

The aqueous liquid developer of the present invention may contain various known dispersants as necessary to enhance the dispersibility of the colorant and toner particles. Such dispersants include:
For example, fatty acid soap, alkyl ether carboxylate, alkyl benzene sulfonate (ABS, LA)
S), alkyl naphthalene sulfonate, dialkyl sulfosuccinate, alkyl sulfoacetate, α-
Olefin sulfonate, N-acylmethyltaurine,
Anionic surfactants such as higher alcohol sulfates, alkyl ether sulfates, polyoxyethylene alkylphenyl sulfates, alkyl ether phosphates and alkyl phosphates; aliphatic amine salts, benzalkonium salts, chlorides Benzethonium, pyridinium salt,
Cationic surfactants such as imidazolium salts; amphoteric surfactants such as carboxybetainic acid, aminocarboxylate, imidazolinium betaine, lecithin; polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene lanolin Derivatives,
Ethylene oxide derivative of alkylphenol formalin condensate, polyoxyethylene polyoxypropylene block polymer, polyoxyethylene glycerin fatty acid ester, polyoxyethylene sorbitan fatty acid ester,
Examples include nonionic surfactants such as polyethylene glycol fatty acid esters, fatty acid monoglycerides, polyglycerin fatty acid esters, sorbitan fatty acid esters, and propylene glycol fatty acid esters.

The aqueous liquid developer of the present invention may contain, as required, additives such as an antioxidant, a preservative, a plasticizer, and a defoamer, in addition to the above-mentioned dispersant. The hydrophilic group of the film-forming thermoplastic resin having a hydrophilic group, which is substantially insoluble in the carrier liquid in the present invention, includes a carboxyl group, a hydroxyl group, an amino group, a ketone group, a sulfo group, and the like, oxygen, nitrogen, sulfur, and the like. And the like. In the present invention, the film-forming thermoplastic resin having a hydrophilic group can be used without any particular limitation as long as it is substantially insoluble in the carrier liquid. Since the foaming property of the resin is suppressed low, preferably a self-water dispersible resin having a hydrophilic group, more preferably a carboxylic acid group, a sulfonic acid group, a self-water dispersible resin having an acid group such as a sulfinic acid group It is desirable to use More preferably, a self-water-dispersible resin having an acid value of 50 or more and 280 or less, at least a part of which is neutralized with a base, is mentioned. The resin having the specific acid value is most generally a styrene- (meth) acrylic acid-based resin, for example, styrene or α-
Substituted styrenes such as methylstyrene, acrylic acid methyl ester, acrylic acid ethyl ester, acrylic acid butyl ester, acrylic acid ester such as 2-ethylhexyl acrylate, methacrylic acid methyl ester, methacrylic acid ethyl ester, methacrylic acid butyl ester, It is a copolymer containing at least one or more monomer units selected from methacrylic esters such as 2-ethylhexyl methacrylate and at least one or more monomer units selected from acrylic acid and methacrylic acid.

Here, the acid value refers to the number of mg of potassium hydroxide required to neutralize 1 g of the resin. When the resin having an acid group of the present invention is used as a self-water-dispersible resin, it is necessary to neutralize at least a part of the acid group with a base, if necessary. Neutralization with a base, that is, an alkaline neutralizing agent may be performed by neutralizing the obtained self-water-dispersible resin so that the resin does not dissolve in water.

The neutralization rate of the synthetic resin is not necessarily limited. As a basic alkaline neutralizing agent,
For example, hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide and lithium hydroxide; basic substances such as ammonia, triethylamine and morpholine; and alcohol amines such as triethanolamine, diethanolamine and N-methyldiethanolamine. .

The method of adding the neutralizing agent to the resin having the specific acid value used in the present invention to neutralize the resin includes adding a neutralizing agent to a solution of the resin in an organic solvent in advance.
When mixing the organic solvent solution of the resin with the aqueous medium, a method of adding the resin to the aqueous medium may be selected, but the former is more preferable because the particle diameter can be easily controlled.

When the acid value of the resin is less than 50, the obtained toner particles have insufficient water dispersion stability, and when the acid value exceeds 280, the water dispersibility dissolved in an organic solvent is low. Aggregation is likely to occur when the resin is neutralized with a base.

The resin may be at least partially covalently crosslinked or ionically crosslinked by a polyvalent metal. In the present invention, a conventionally known microencapsulation technique is applied in order to obtain toner particles in which the colorant is substantially insoluble in the carrier liquid and is encapsulated by a film-forming thermoplastic resin having a hydrophilic group. Gained by things. The term "microencapsulation technology" used here refers to the adjustment of concentration, temperature, pH, solubility, etc., or a chemical reaction such as a polymerization reaction or a curing reaction. Material) is deposited or polymerized to cover the new substance with resin etc.
The method itself and the obtained effect are different from the conventional method of coating the colorant with a resin mainly by physical adsorption.

In the present invention, a specific method for obtaining toner particles in which a colorant is substantially insoluble in the carrier liquid and is encapsulated by a film-forming thermoplastic resin having a hydrophilic group includes an organic phase. An interfacial polymerization method in which the wall-forming material is present separately in both the aqueous phase and the aqueous phase, and the polymerization reaction proceeds at the interface between the organic phase and the aqueous phase to form microcapsules.The material that forms the wall only in the organic phase is present. In-Situ polymerization method to form microcapsules by dispersing the substance to be microencapsulated in a polymer solution in advance, forming this film into the desired shape and curing the polymer to form a film In-liquid curing coating method,
The substance to be microencapsulated is dispersed in a polymer solution in advance, and water is added to the solution or the solution is added to water in the presence of an emulsifier and / or a dispersion stabilizer. There is a phase inversion emulsification method in which a film is formed by causing a phase phenomenon.

Still further, the polymer is dissolved in an aqueous phase,
There is also a coacervation method in which pH, temperature, concentration, etc. are phase-separated to form microcapsules, and any of these can be used.

When the temperature of a solution of a polymer dissolved in a good solvent is lowered, a poor solvent is added, or another polymer is added, fine droplets of a concentrated solution of the polymer are separated from the solution. This is a phenomenon called coacervation, which is a kind of phase separation. The fine droplets of the concentrated solution gather on the surface of the core substance particles to form a capsule wall film, and the resin used at this time is called a wall forming resin. Such a microencapsulation method is called a coacervation method, and in the present invention, of the above methods, the phase inversion emulsification method included in the interfacial deposition method, or the above-mentioned method, for reasons such as easy production. It is preferable to apply the coacervation method. Coacervation method and phase inversion emulsification using a film-forming thermoplastic resin which can be self-dispersed in water with a base and a base in an amount sufficient to disperse the resin in water without using an emulsifier or a dispersion stabilizer. The method is particularly preferable because the adverse effects of the emulsifier and the dispersion stabilizer hardly occur, and a separate step of removing the same is not required.

Hereinafter, a method for obtaining toner particles in the present invention will be specifically described. That is, in order to obtain the resin-coated toner particles of the present invention, the colorant and the film-forming thermoplastic resin having a hydrophilic group which is substantially insoluble in the carrier liquid are dissolved in an organic solvent which dissolves at least a part of the resin. It can be obtained by dispersing with a solvent and simultaneously or subsequently insolubilizing the resin substantially in a water-based carrier liquid.

Hereinafter, the production method will be described in more detail. The first stage (mill base production). The resin is dissolved in an organic solvent, a colorant is dispersed therein, and a mill base is prepared using a ball mill, a bead mill or the like (mill base manufacturing method 1). Colorant / resin ratio is 1 /
0.5 to 1/20 is desirable. At this time, in order to effectively adsorb the resin to the colorant, an aqueous medium mainly composed of water used as the carrier liquid is added to the resin in advance in addition to the organic solvent that dissolves the resin. And the resin
A mill base may be prepared by partially insolubilizing the mixed solvent and dispersing with a colorant in a resin dispersion state (mill base manufacturing method 2). Further, in the method of preparing a resin dispersion before the preparation of the mill base as described above, if a self-water dispersible resin having an acid group such as a carboxylic acid group, a sulfonic acid group, and a sulfinic acid group is used as the resin, hand,
By adding the neutralizing agent within a range in which the resin does not completely dissolve in the mixed solvent, a good resin dispersion can be obtained.

Second Step (Resin Coating, Preparation of Colored Resin Particle Dispersion) The mill base obtained in the first step is mixed with an aqueous medium, preferably twice or more the amount of the ketone solvent in the mill base. Thus, a resin coating step of obtaining water-dispersible toner particles in which the colorant is encapsulated by the resin is performed. When the resin having the specific acid group is used as the resin for the mill base produced via the mill base manufacturing method 1, the resin coating can be improved by adding a neutralizing agent as necessary. Done.

Third step (implementation of desolvation) In order to make the adsorption and coating of the resin on the colorant more reliable, and to enhance the dispersion stability and redispersibility of the toner particles, the first step is a mill-based process. It is preferable to perform a desolvation step of removing the used organic solvent. Furthermore, after the completion of the second or third step, it is preferable to carry out a step of removing coarse particles by filtration or centrifugation.

In the above, the production method via the mill base production method 1 is a production method by the phase inversion emulsification method, while the production method via the mill base production method 2 is a production method by the coacervation method.

In the aqueous liquid developer of the present invention, the color resin particle dispersion containing the toner particles thus obtained is prepared by using a carrier liquid at a predetermined concentration, and the colorant content is 0.1 to 10%.
It can be obtained by diluting such that

The aqueous medium as a carrier liquid mixed with the mill base is a liquid medium containing water as a main component,
In addition to water, the above-mentioned various water-soluble organic solvents can be added as necessary.

In the present invention, examples of the organic solvent which is substantially insoluble in the carrier liquid and dissolves the film-forming thermoplastic resin having a hydrophilic group include ketone solvents such as acetone, dimethyl ketone and methyl ethyl ketone, and methanol. Alcohol solvents such as ethanol and isopropyl alcohol; chlorine solvents such as chloroform and methylene chloride; aromatic solvents such as benzene and toluene; ester solvents such as ethyl acetate; ethylene glycol monomethyl ether; ethylene glycol dimethyl ether; If the resin component is an acrylic resin, at least one combination selected from a ketone-based solvent and an alcohol-based solvent can be used as long as the resin dissolves a resin such as a glycol ether-based solvent or an amide. Is good. The amount of the organic solvent used is not particularly limited as long as the effects of the present invention are achieved, but the weight ratio of the film-forming thermoplastic resin having a hydrophilic group to the organic solvent is 1 /
An amount that becomes 1 to 1/20 is preferable.

In the above-mentioned mill base, a dispersant, a plasticizer, an antioxidant, an antifoaming agent, a preservative, and the like may be used as necessary together with the solvent, the resin, and the coloring agent.

In order to develop an image corresponding to an electrostatic latent image using the aqueous liquid developer of the present invention, the electrostatic latent image on the support formed by charging and image exposure is applied to the aqueous liquid developer. And can be visualized.

That is, in order to develop an image corresponding to an electrostatic latent image using the aqueous liquid developer of the present invention, a photosensitive substrate comprising a conventionally known organic photoconductor or inorganic photoconductor is applied to a photosensitive substrate. After forming the charge image, the liquid developer of the present invention is brought into contact with the developer, and the excess developer is removed to obtain an image corresponding to the electrostatic latent image.

As described above, although the mechanism of developing an electrostatic latent image using an aqueous developer is not clear, the wettability of the latent image portion is changed to hydrophilic by the presence of electric charge, and the lipophilic non-image It is considered that a wettability contrast occurs between the toner image and the developer, and the developer adheres to the hydrophilic portion, that is, the portion where the electrostatic latent image is present, thereby obtaining a visible image.

Examples of the organic photoconductor include well-known organic photoconductors. Examples thereof include a poly-N-vinylcarbazole-based electrophotographic photosensitive substrate, and an electrophotographic photosensitive substrate containing an organic pigment as a main component. Illustrative examples of the inorganic photoconductor include:
Zinc oxide, titanium oxide, selenium, etc. are mentioned, but in order to obtain a high-quality image, it is not necessary to transfer a developed image, and the photosensitive substrate itself can be used as a recording medium. It is preferable to use titanium or the like.

Further, the aqueous liquid developer of the present invention can be prepared by using means other than the photoreceptor, for example, electrostatic recording paper, ion flow recording paper, plastic The present invention can also be applied when developing an electrostatic latent image formed on a dielectric such as a film. The development in this case can be performed in the same manner as in the case of the photoreceptor, but in order to neutralize the electrostatic latent image due to contact with water and to avoid background fouling, electrostatically record a highly insulating liquid in advance. It is preferable to apply the highly insulating liquid after coating on paper or ion flow paper or to form an electrostatic latent image, and then develop using the aqueous liquid developer of the present invention. As such a highly insulating liquid, for example, dimethyl silicone,
Various silicone oils such as methylphenyl silicone, methyl hydrogen silicone, cyclic polydimethylsiloxane, and fluorosilicone, and various modified silicone oils obtained by modifying silicone oils such as acryl-modified, alkyl-modified, fatty acid-modified, and epoxy-modified, hexane, and pentane , Octane, Nonane, Decane, Undecane, Dodecane, and Isopar G, H, L,
Branched aliphatic hydrocarbons sold under trade names such as M and V, linear aliphatic hydrocarbons such as Norper 14, 15, 16 (manufactured by Exxon Chemical Co.), and fluorocarbons thereof. And halogenated hydrocarbons.

The image thus obtained can be fixed by removing excess developer and drying the carrier liquid in the image area. However, it is necessary to heat the developed image to a temperature higher than the glass transition temperature of the resin. Can be further strongly fixed.

[0041]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention includes the following embodiments. 1. In an electrophotographic aqueous liquid developer in which toner particles comprising at least a water-insoluble colorant and a resin are dispersed in a carrier liquid containing water as a main component, the toner particles are such that the colorant is a carrier liquid. An aqueous liquid developer for electrophotography, wherein the aqueous liquid developer for electrophotography is encapsulated by a film-forming thermoplastic resin having a hydrophilic group and substantially insoluble in water. 2. The colorant is a pigment or an oil-soluble dye. An aqueous liquid developer as described in the above. 3. The resin-coated toner particles are made to disperse the colorant and the film-forming thermoplastic resin having a hydrophilic group substantially insoluble in the carrier liquid using an organic solvent that dissolves at least a part of the resin. At the same time or successively, the resin is substantially insolubilized in a carrier liquid containing water as a main component. The aqueous liquid developer for electrophotography according to the above. 4. The film-forming thermoplastic resin substantially insoluble in the carrier liquid and having a hydrophilic group is a resin having an oxidation of 50 to 280 and at least partially neutralizing an acid group. . The aqueous liquid developer for electrophotography according to the above.

Hereinafter, a preferred embodiment of the present invention will be described. As the resin, an acid value obtained by copolymerizing at least one monomer selected from the group consisting of styrene, substituted styrene, and (meth) acrylic acid ester with (meth) acrylic acid is 50 to 280 and a molecular weight of 1000. More than 100,000 or less of the vinyl copolymer, a mixture of a synthetic resin and a pigment dissolved in a mixed organic solvent of a ketone-based solvent and an alcohol-based solvent, and a pigment mill mixed with a ball mill or a bead mill to obtain a colored mill base. . Further, in order to enhance the dispersibility of the colorant, the dispersant may be appropriately added. The weight ratio of the vinyl resin to the mixed organic solvent is preferably 1/1 to 1/20, more preferably 1/2 to 1/10, of the vinyl resin / mixed organic solvent. The weight ratio of the pigment to the vinyl resin is preferably from 1 / 0.5 to 1/20 for pigment / vinyl resin, and more preferably from 1 / 0.7 to 1/10.

A base such as an alcoholamine capable of neutralizing the acid group of the resin is added to the colored mill base, and the mixture is stirred and mixed. Further, an aqueous medium containing water is twice mixed with a ketone solvent in the mill base while stirring. By performing the above-described drop-mixing, an aqueous colored dispersion in which toner particles having a colorant encapsulated in the self-water dispersible resin are dispersed in an aqueous medium is obtained. The amount of the base to be added is not particularly limited.
It is desirable to add an amount that becomes 0 to 100%.

The above method is one of the microencapsulation methods called the phase inversion emulsification method. In addition, an aqueous colored dispersion is obtained by using one of the following coacervation methods. May be. That is, when making a colored mill base by milling using a ball mill, a bead mill, etc., in order to make the adsorption of the resin to the pigment effective, in advance, the resin is mainly composed of water together with an organic solvent that dissolves the resin. A water-soluble organic solvent and a neutralizing agent such as alcoholamine are added to form a resin dispersion, which is used and dispersed together with a colorant to form a mill base. Also,
In order to enhance the dispersibility of the colorant, the dispersant may be appropriately added. The amount of the aqueous medium is from 2 to 8 of the ketone solvent.
Double is preferred. Further, the amount of the base as a neutralizing agent to be added is not particularly limited, but it is desirable to add a base amount such that the neutralization ratio is 50 to 100%. By drop-mixing the aqueous medium containing water into the colored mill base thus formed, an aqueous colored dispersion can be obtained in the same manner as in the phase inversion emulsification method.

From the aqueous colored dispersion obtained by both methods, the organic solvent used for dissolving the synthetic resin is removed by distillation under reduced pressure, and coarse particles are removed by a method such as filter filtration to obtain a concentrated toner. . Thereafter, the concentrated toner is diluted with a carrier liquid so that the concentration of the pigment becomes 1 to 5%, a necessary additive is added, and the mixture is stirred to obtain an aqueous liquid developer for electrophotography.

The development of an image corresponding to an electrostatic latent image using the aqueous liquid developer of the present invention can be suitably performed by performing the following steps. First step: An electrostatic latent image is formed on an electrostatic recording paper by an electrostatic recording method or an ion flow method.

Second step: A highly insulating liquid such as silicone oil is applied on the electrostatic recording paper. Third step: before the highly insulating liquid is completely dried, it is brought into contact with the aqueous developer.

Fourth step: A clear toner image corresponding to an electrostatic latent image without fog is obtained by squeezing with a roller having a mesh.

[0049]

Next, the present invention will be described more specifically with reference to examples and comparative examples. In the following examples, “parts” represents “% by mass”.

(Mill Base Production Example 1) Copper phthalocyanine pigment 20 parts Styrene- (meth) acrylic acid resin 20 parts (styrene / acrylic acid / methacrylic acid = 65/10)
/ 25; molecular weight 45000; acid value 241; glass transition temperature 116 ° C) A mixture of 50 parts of methyl ethyl ketone and 150 parts of glass beads is kneaded with a paint shaker for 4 hours, and 40 parts of methyl ethyl ketone and 40 parts of isopropyl alcohol are added to take out the contents. And 170 parts of a mill base. (Millbase Production Example 2) Copper phthalocyanine pigment 20 parts Styrene- (meth) acrylic acid resin 20 parts (styrene / methyl methacrylate / methacrylic acid /
2-ethylhexyl acrylate = 59/15/15/1
1: molecular weight 40000; acid value 100; glass transition temperature 60
C.) A mixture of 60 parts of methyl ethyl ketone and 150 parts of glass beads was kneaded with a paint shaker for 4 hours, and 30 parts of methyl ethyl ketone and 40 parts of isopropyl alcohol were added to take out the contents to obtain 170 parts of a mill base solution. (Mill Base Production Example 3) A mill base was produced in the same manner as in Production Example 2 except that a quinacridone magenta pigment was used instead of the copper phthalocyanine pigment, to obtain 170 parts of a magenta mill base. (Mill base production example 4) Styrene- (meth) acrylic acid resin (styrene / methacrylic acid / acrylic acid = 75/15 /) in a mixed solvent of methyl ethyl ketone 180 parts isopropyl alcohol 80 parts ion exchange water 460 parts triethanolamine 20 parts 1
0; molecular weight: 45,000; acid value: 160) and mixed and stirred to obtain a resin dispersion.

[0051] 150 parts of the above resin dispersion liquid and 12 parts of carbon black RAVEN1080 (manufactured by Columbian Carbon Co., Ltd.) were dispersed with zirconia beads in a batch type small bead mill for 2 hours, and the mill base was taken out. Example 1 Millbase 170 parts of triethanolamine (equivalent to a resin neutralization rate of 82%) was added to 170 parts of the millbase of Production Example 1, and a mixture of 200 parts of glycerin and 450 parts of ion-exchanged water was added with stirring. Dripping at a rate of 5 ml per minute,
A colored resin particle dispersion was obtained. Methyl ethyl ketone and isopropyl alcohol were distilled off from the obtained dispersion using a rotary evaporator to obtain a concentrated toner in which resin-coated toner particles were dispersed. Further, the obtained concentrated toner was filtered using a 1.2 μm filter, and 150 parts of ion-exchanged water was added to obtain a cyan aqueous liquid developer.

The resulting aqueous liquid developer had an average particle size of 0.23 μm and a zeta potential of −60 mV. After leaving the aqueous developer at room temperature for 3 months, there was almost no sedimentation toner, and even toner particles which settled slightly were redispersed by light shaking, and no aggregated toner was observed.

In order to perform development using this developer, first, an electrostatic recording paper (K-530M-3 manufactured by Shin-Oji Paper Co., Ltd.) and a monochrome electrostatic plotter (EP-101 manufactured by Matsushita Electric Transmission Co., Ltd.) are used. Thus, an electrostatic latent image was formed on the electrostatic recording paper.

Next, silicone oil (DC-34 manufactured by Shin-Etsu Silicone Co., Ltd.) was applied to the electrostatic recording paper on which the electrostatic latent image was formed.
5) was applied thinly. The electrostatic latent image forming surface of the electrostatic recording paper coated with the silicone oil was brought into contact with the surface of the developer of Example 1 to perform development. Thereafter, when squeezing was performed using a metal roller with a metal mesh, a clear cyan image corresponding to an electrostatic latent image having no background stain was obtained.

The cyan image was dried at 120 ° C. for 1 minute and fixed, and the fixability of the image was evaluated by peeling off the cellophane tape. As a result, the toner hardly adhered to the cellophane tape, showing good fixability.

Example 2 Millbase 170 parts of N-methyl-diethanolamine were added to 170 parts of the millbase of Production Example 2.
Of a mixture of 200 parts of glycerin and 600 parts of ion-exchanged water was dropped at a rate of 5 ml / min to obtain a colored resin particle dispersion. Methyl ethyl ketone and isopropyl alcohol were distilled off from the obtained colored resin particle dispersion using a rotary evaporator to obtain a cyan aqueous colored dispersion in which resin-coated toner particles were dispersed. After stirring the obtained colored dispersion, 3 μm
Filtration was performed using an m filter to obtain a concentrated toner. Further, 150 parts by weight of ion-exchanged water was added to the obtained concentrated toner to obtain a cyan aqueous liquid developer. The obtained developer had a particle size of 0.22 μm and a zeta potential of −50 mV. This developer had good storage stability, redispersibility and fixability, similarly to the developer of Example 1. After forming an electrostatic latent image on electrostatic recording paper in the same manner as in Example 1, isoparaffin (Isopor M manufactured by Exxon Chemical Co., Ltd.) was applied, and development was performed in the same manner as in Example 1. A clear cyan image with no image was obtained. (Example 3) In the same manner as in Example 2, an aqueous magenta colored dispersion was obtained. After stirring the obtained colored dispersion, 3 μm
To obtain a concentrated toner. Further, 150 parts by weight of ion-exchanged water was added to obtain a magenta color aqueous liquid developer. The resulting developer has a particle size of 0.3.
At 1 μm, the zeta potential was -45 mV. When the storage stability, redispersibility, and fixability were evaluated in the same manner as in Example 1, all were good.

When development was carried out in the same manner as in Example 2, a clear magenta image without background smear was obtained. (Example 4) 120 parts of ion-exchanged water was added at a rate of 5 parts per minute to 150 parts of the mill base obtained in Production Example 4 of the mill base.
It was dropped at a speed of ml to obtain a black resin particle dispersion. Methyl ethyl ketone and isopropyl alcohol were distilled off from the obtained dispersion using a rotary evaporator to obtain a black aqueous colored dispersion in which resin-coated toner particles were dispersed. After stirring the obtained colored dispersion, it was filtered using a 3 μm filter to obtain a concentrated toner. Further, 150 parts of ion-exchanged water was added to 150 parts of the obtained concentrated toner to obtain a black aqueous liquid developer. After forming an electrostatic latent image on the electrostatic recording paper in the same manner as in Example 1, a thin coating of silicone oil (DC-345 manufactured by Shin-Etsu Silicone Co., Ltd.) is performed, and development is performed using this black aqueous liquid developer. Then, when squeezed by a metal roller with a metal mesh, a clear black image corresponding to an electrostatic latent image without background contamination was obtained. The obtained developer had a particle size of 0.18 μm and a zeta potential of −55 mV. This developer had good storage stability, redispersibility and fixability, similarly to the developer of Example 1. (Comparative Example) 30 parts of a copper phthalocyanine pigment and 70 parts of polystyrene were melt-kneaded using a kneader and then dry-pulverized to obtain a cyan colorant coated with polystyrene.

9 parts of the above-mentioned cyan colorant J-7001 (aqueous emulsion resin manufactured by Shonson Polymer Co., Ltd.) 17 parts 20 parts of ion-exchanged water were wet-dispersed using a ball mill to obtain a concentrated toner. Further, 15 parts of water was added to 10 parts of the concentrated toner, followed by filtration using a 1.2 μm filter to obtain a comparative aqueous developer.

Using the obtained comparative aqueous developer, development was carried out in the same manner as in Example 1, but the image density was low. In addition, dispersion stability is poor compared to the examples,
The sedimented toner which had been left at room temperature for three months hardly re-dispersed under slight shaking, and had poor storage stability and re-dispersibility.

[0060]

The aqueous liquid developer for electrophotography according to the present invention comprises:
The toner particles, which are substantially insoluble in the carrier liquid and in which the colorant is coated and covered by a resin having a hydrophilic group, are dispersed in a carrier liquid containing water as a main component. And exhibit excellent dispersion stability and re-dispersibility as well as excellent light fastness and water fastness, thereby enabling electrophotographic aqueous color liquid development.

Claims (4)

[Claims] 1. An electrophotographic aqueous liquid developer in which toner particles comprising at least a water-insoluble colorant and a resin are dispersed in a carrier liquid containing water as a main component. An aqueous liquid developer for electrophotography, characterized in that the agent is encapsulated by a film-forming thermoplastic resin having a hydrophilic group and substantially insoluble in a carrier liquid. 2. The aqueous liquid developer according to claim 1, wherein the colorant is a pigment or an oil-soluble dye. 3. The resin-coated toner particles comprise a colorant and a film-forming thermoplastic resin substantially insoluble in the carrier liquid and having a hydrophilic group, and an organic solvent dissolving at least a part of the resin. 2. The aqueous liquid developer for electrophotography according to claim 1, wherein the resin is obtained by dispersing the resin and then simultaneously or successively insolubilizing the resin in a carrier liquid containing water as a main component. Agent. 4. The film-forming thermoplastic resin substantially insoluble in the carrier liquid and having a hydrophilic group is a resin having an acid value of 50 or more and 280 or less and at least partially neutralized acid groups. The aqueous liquid developer for electrophotography according to claim 1, wherein: