JPH1124410A - Wet type developing method for electrostatic charge image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image excellent in light resistance and water resistance and to obtain a full-color image without fogging by superposing by using an electrostatic recording body forming a high insulating material layer and a specified water liquid developer. SOLUTION: An electrostatic charge image is directly formed on an electrostatic recording body by directly actuating an electric field and a high insulating material layer is formed on the electrostatic recording body on which the electrostatic charge image is formed. Then, the electrostatic charge image is developed by a water liquid developer obtained by dispersing toner grains consisting of at least a colorant being insoluble in water and a resin in a carrier liquid whose the main component is water. As a high insulating material used here, a liquid material is preferable and silicone oil such as dimethylsilicone and aliphatic hydrocarbon such as hexan or pentane are cited, for example. The content ratio of the colorant being insoluble in water is preferably made to 0.1 to 10 wt.%, preferably 1 to 5 wt.% in the water liquid developer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for developing an electrostatic image with an aqueous liquid developer.

[0002]

2. Description of the Related Art A wet developing method using a liquid developer does not require fixing, is excellent in halftone reproducibility, and provides a high-resolution image, as compared with a dry developing method using a powder toner. On the other hand, it has low dielectric constant and high insulating liquid such as aliphatic hydrocarbons as the carrier liquid, so it has petroleum odor and belongs to flammable liquid, and there is danger of ignition There were problems in safety and hygiene, such as that the organic solvent had some toxicity. 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,
Examples include a method in which an electrostatic latent image formed on a photoconductor by a backside exposure method is developed using an aqueous developer and transferred to paper or the like.

[0004] 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.

By the way, in order to obtain a high quality image by utilizing the features of the wet development, in the above-mentioned conventional aqueous developing method, an electrostatic image on a recording medium is transferred by a developer in which fine particle toner is dispersed. A method of directly developing a final image without a process is effective. When including a transfer step, for example, JP-A 8-286432, when performed only by electrostatic method and pressure as described in JP-A-8-339091,
Since the carrier liquid remains in the toner layer, there is a disadvantage that transfer crushing is likely to occur, and it has been difficult to obtain a high quality image.

As an image forming method for obtaining a final image by directly developing without a transfer step, an electrostatic charge image is formed by applying an electric field directly on an electrostatic recording medium such as an electrostatic recording method or an ion flow method. After that, a method of obtaining an image by wet toner development,
There is a method of forming an electrostatic charge image using a photosensitive paper obtained by applying a photoconductive substance such as zinc oxide or titanium oxide to a paper as a recording medium, and then developing the image by wet toner development to obtain an image.

However, in the method of forming and developing an electrostatic image using photosensitive paper as described in JP-B-56-3545, a colored substance soluble in water such as a dye is used as a coloring substance of an aqueous developer. Is used, the water resistance of the developed image is poor, therefore, it is difficult to perform full-color development by over-development, it is difficult for the dye to disturb the electrostatic latent image and obtain a high-quality image, There are also problems such as weather resistance and water resistance of the recorded image.

Further, as described in JP-B-56-35870, the method of performing wet development with an aqueous developer using an electrostatic recording paper having a specific composition by using an electrostatic recording method, In addition, the developer used is of a type in which a dye is dissolved, and there is a problem caused by the developer described above. Further, there is a problem that fogging cannot be avoided if a high-concentration developer is used.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the conventional wet developing method of an electrostatic image using an aqueous liquid developer. That is, an object of the present invention is to provide an aqueous wet developing method which gives an image having good light fastness and water fastness, has no fog even when a high concentration aqueous developer is used, and can obtain a full-color image by superposition.

Another object of the present invention is to provide a highly safe, aqueous wet developing method for an electrostatic image.

[0011]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, have found that an electrostatic recording medium having a high insulating material layer formed thereon, a water-insoluble coloring agent and a resin. By using an aqueous liquid developer in which toner particles consisting of are dispersed in a carrier liquid containing water as a main component,
The inventors have found that the above-mentioned problems can be solved, and have reached the present invention.

That is, the present invention provides a process of directly forming an electrostatic image by applying an electric field directly to an electrostatic recording medium, and forming a highly insulating material layer on the electrostatic recording medium on which the electrostatic image has been formed. And developing the electrostatic charge image with an 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. Provided is a wet developing method for an electrostatic charge image.

Hereinafter, the present invention will be described in more detail. The electrostatic recording medium used in the present invention is not particularly limited, and any known electrostatic recording medium can be used. A metal plate or a metal-deposited film may be used, but among the electrostatic recording media, electrostatic recording paper generally used for electrostatic recording, recording paper for ion flow, plastic film, etc., is used to hold an electrostatic charge. A dielectric material that can be used or a material obtained by applying such a dielectric material on a support such as paper or plastic is preferably used.

In the present invention, a step of directly forming an electrostatic charge image by directly applying an electric field to the electrostatic recording medium, and a step of forming a highly insulating material layer on the electrostatic recording medium on which the electrostatic charge image is formed However, any of these steps may be performed first. That is, a step of directly applying an electric field to an electrostatic recording medium on which an electrostatic image is not formed to directly form a required electrostatic image is performed, and then the electrostatic recording on which the electrostatic image is formed is performed. A step of forming a high insulating material layer on the body may be performed, and conversely, a step of forming a high insulating material layer on an electrostatic recording medium on which an electrostatic image is not formed may be performed. Thereafter, a step of directly forming an electrostatic image by applying an electric field directly to the electrostatic recording medium may be performed.

The step of forming an electrostatic image directly on the electrostatic recording medium by directly applying an electric field to the electrostatic recording medium includes:
For example, there are an electrostatic recording method in which charging is performed by a printing signal using a large number of needle electrodes, a method of controlling an ion flow from an ion generating source based on a printing signal, a so-called ion flow method, a method by corona discharge, and the like.

In the ion flow method, there are a method using a corona discharge in an ion generating portion and a method in which a discharge is generated in a pulsed manner between electrodes to generate ions. In both cases, the ion flow is controlled by the direction of an electric field between the electrodes. This is done by changing By controlling the ion flow rate, it is possible to freely control the density of each recording pixel forming an image, and it is possible to perform natural halftone expression without using a pseudo method such as dither method, so that it is particularly suitable for color reproduction. Because it ’s so good
preferable. In addition, since the ion flow method forms an electrostatic image in a non-contact manner, it is possible to form an electrostatic image in a non-contact manner after forming a layer of a highly insulating material on an electrostatic recording medium,
It is particularly preferably used in the present invention. Regarding the polarity of the electrostatic image, development can be performed in either positive or negative direction, but negative charging is preferable because image density can be easily obtained.

As the highly insulating substance used in the step of forming a highly insulating substance layer on the electrostatic recording medium on which an electrostatic charge image is formed, a liquid substance is preferable, for example, dimethyl silicone, Methylphenyl silicone,
Methyl hydrogen silicone, cyclic polydimethylsiloxane,
Various silicone oils such as fluorosilicone, and various modified silicone oils obtained by modifying silicone oils such as acryl-modified, alkyl-modified, fatty acid-modified, and epoxy-modified, hexane, pentane, octane, nonane, decane,
In addition to undecane and dodecane, branched-chain aliphatic hydrocarbons sold under the trade names such as Isopar G, H, L, M, and V by Exxon Chemical Company, Norper 14, 15, 15, 1
6 (manufactured by Exxon Chemical Co., Ltd.) and halogenated hydrocarbons such as fluorocarbons.

In order to form the high insulating material layer on the electrostatic recording medium, for example, a method of forming a high insulating material layer on a roll and applying the layer to the electrostatic recording medium, Immersed in a highly insulating material, a method of impregnating a sponge or the like with a highly insulating material and applying it to an electrostatic recording medium, and a method of spraying and applying a highly insulating material.
In any case, in order to form a highly insulating material on the electrostatic recording medium in a thin film and uniformly, after performing the developing process,
It is preferable to provide a step of removing excess aqueous liquid developer in the non-image area and the image area. For this purpose, it is desirable to squeeze (press) with, for example, a roll.

The aqueous liquid developer used in the present invention is one in which toner particles comprising a water-insoluble colorant and a resin are dispersed in a carrier liquid containing water as a main component. In the present invention, any one in which the colorant and the resin coexist in one toner particle can be used, but the durability, dispersion stability, and reproducibility of the image formed on the electrostatic recording medium can be used. From the viewpoint of dispersibility and the like, the toner particles are preferably an aqueous liquid developer in which the colorant is substantially insoluble in the carrier liquid and is covered by a film-forming thermoplastic resin having a hydrophilic group. It is preferable that the resin in the toner particles does not substantially have a crosslinked portion from the viewpoint of film formation.

As the colorant of the aqueous liquid developer used 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 3B, brilliant carmine 6B, barium red 2B, calcium red 2
B, strontium red 2B, calcium red, lake red C, quinacridone magenta, disazo yellow AAA, disazo yellow AMX, disazo yellow AAOT, disazo yellow AAOT, isoindolinone yellow and the like can be used.

Examples of oil-soluble dyes include 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, 3
6, 37, 38, 39, 40, 58, 60, 65, 6
7, 69, 81, 86, 89, 91, 92, 97, 9
9, 100, 109, 118, 119, 122;

CI Solvent Blue 14, 24, 26,
34, 37, 38, 39, 42, 43, 45, 48, 5
2, 53, 55, 59, 67;

CI Solvent Black 3, 5, 7, 8,
14, 17, 19, 20, 22, 24, 26, 27, 2
8, 29, 43, 45 and the like.

As the water-insoluble colorant, it is preferable to use a pigment rather than an oil-soluble dye, since the image has better water resistance and light resistance.

As the carrier liquid used in the liquid developer used in the present invention, water is mainly used, but if necessary, various water-soluble organic solvents can be appropriately mixed.

Examples of such water-soluble organic solvents include methyl alcohol, ethyl alcohol, n-butyl alcohol, isopropyl alcohol, n-propyl alcohol, n-butyl alcohol, sec-butyl alcohol,
Alkyl alcohols having 1 to 4 carbon atoms such as tert-butyl alcohol; amides such as 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,
Alkylene glycols having an alkylene group containing 2 to 6 carbon atoms, such as triethylene glycol, hexylene glycol, diethylene glycol and the like; glycerin;
Lower alkyl ethers of polyhydric alcohols such as ethylene glycol methyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, and triethylene glycol monomethyl (or ethyl) ether;
Pyrrolidones such as methyl-2-pyrrolidone and 2-pyrrolidone; dimethylsulfoxide, imidazolidinone and the like.

As the resin of the aqueous liquid developer used in the present invention, conventionally known water-soluble resins or water-dispersible resins can be used without any particular limitation.

In the aqueous liquid developer used in the present invention,
The content of the colorant insoluble in water is 0.1 to 10% by weight,
Preferably, the content is 1 to 5% by weight. The weight ratio of the colorant / resin insoluble in water is not limited, but is usually 2/1 to 1/20, preferably 1 / 0.7 to 1/10.

The aqueous liquid developer used in the present invention contains a coloring agent and toner particles in order to enhance dispersibility.
If necessary, various known dispersants may be contained. Further, if necessary, as an additive, for example, an antioxidant, a preservative,
A plasticizer, an antifoaming agent and the like can be contained.

In the present invention, the aqueous liquid developer is developed by using a film-forming resin having a hydrophilic group, which is substantially insoluble in a carrier liquid, and using a toner particle coated with a colorant. Is preferred. The reason is that the aqueous liquid developer in which such toner particles are dispersed is easy to obtain a uniform image without unevenness, and has better dispersion stability and redispersibility. This is because it is possible to stably output an image having good water resistance.

As the film-forming thermoplastic resin which is substantially insoluble in the carrier liquid and has a hydrophilic group in the present invention, known and commonly used resins can be used. For example, styrene resins, (meth) acrylic resins, Polyester resin,
Polyurethane-based resins and the like can be mentioned. Examples of the hydrophilic group of these resins include groups containing atoms such as oxygen, nitrogen, and sulfur, such as carboxylic acid groups, hydroxyl groups, amino groups, ketone groups, and sulfo groups.

According to the present invention, it is substantially insoluble in a carrier liquid,
As the film-forming thermoplastic resin having a hydrophilic group, a water-dispersible resin having an acid group of a carboxylic acid group, a sulfonic acid group and a sulfine group is preferably used.

The self-water-dispersible resin which is substantially insoluble in the carrier liquid and is preferable as the film-forming thermoplastic resin having a hydrophilic group is a synthetic resin having an acid value of 50 to 280, at least a part of which is a synthetic resin. Examples include those obtained by neutralization with a base. The acid value refers to the number of mg of potassium hydroxide used to neutralize 1 g of the resin. Most commonly, the synthetic resin having the specific acid value is styrene- (meth)
Acrylic resin, for example, styrene or α
-Substituted styrenes such as methylstyrene, acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate And a copolymer containing at least one monomer unit selected from methacrylic acid esters such as 2-ethylhexyl methacrylate and at least one monomer unit selected from acrylic acid and methacrylic acid.

Examples of the alkaline neutralizing agent as a base include hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide and lithium hydroxide, basic substances such as ammonia, triethylamine and morpholine; triethanolamine and diethanolamine And alcohol amines such as N-methyldiethanolamine. As the neutralizing agent, those which easily volatilize after the development image is formed are preferable.

In the present invention, as a specific method for obtaining toner particles in which a colorant is substantially insoluble in the carrier liquid and is covered by a film-forming thermoplastic resin having a hydrophilic group, a conventionally known microparticle is used. What is necessary is just to apply encapsulation technology.

Specifically, for example, an interfacial polymerization method in which a wall forming material is separately present in both the organic phase and the aqueous phase, and a polymerization reaction proceeds at the interface between the organic phase and the aqueous phase to form microcapsules, In-Situ polymerization method, in which a material that forms walls only in the organic phase is present to form microcapsules, the polymer is dissolved in the aqueous phase, and the phase is separated by changing the pH, temperature, concentration, etc. In the coacervation method to be formed, a substance to be microencapsulated is dispersed in a polymer solution in advance, and water is added to the solution in the presence of an emulsifier and / or a dispersion stabilizer, or the solution is added to water. A phase inversion emulsification method in which a film is formed by adding a solution or causing a phase inversion phenomenon.The substance to be microencapsulated is dispersed in a polymer solution in advance. Leave the solution include a submerged curing coating method or the like to form a film by curing the polymer with trimmed to a desired shape, and either can be used.

In the aqueous liquid developer used in the present invention, the coacervation method and the coacervation method, which are included in the interface deposition method, which is a general concept, out of the above microencapsulation methods, for reasons such as ease of production. Phase inversion emulsification is preferred.

The steps of the coacervation method will be specifically described, for example, as follows. First, as a first step, a mill base is prepared by dissolving a wall-forming resin insoluble in a carrier liquid containing water as a main component in an organic solvent and dispersing a colorant therein. As a second step, an encapsulation step is performed in which the mill base obtained in the first step is mixed with an excess amount of an aqueous medium to obtain water-dispersible toner particles containing a colorant. As a third step, in order to enhance the dispersion stability and redispersibility of the toner particles, a desolvation step of removing the organic solvent used in the first step of the mill-based step is provided.

The steps of the phase inversion emulsification method are specifically described, for example, as follows. First, as a first step, a mill base is prepared by dissolving a wall-forming resin insoluble in a carrier liquid containing water as a main component in an organic solvent and dispersing a colorant therein.
In the second stage, the mill base obtained in the first stage is mixed with an aqueous medium in the presence of an emulsifier and / or a dispersion stabilizer to exhibit a phase inversion emulsification phenomenon and disperse an aqueous dispersion containing a colorant therein. An encapsulation step is performed to obtain a toner particle having a high quality. The third step is the same as above.

If necessary, the above-mentioned additives and the like may be used in the above-mentioned mill base together with the above-mentioned solvent, the above-mentioned wall-forming resin and the coloring agent.

In the above, the method using an emulsifier and / or a dispersion stabilizer has been described. However, in the coacervation method and the phase inversion emulsification method, the base is self-watered without using an emulsifier or a dispersion stabilizer. The coacervation method and the phase inversion emulsification method, which use a dispersible film-forming thermoplastic resin and a base in an amount sufficient to disperse the resin in water, are less likely to cause adverse effects due to emulsifiers and dispersion stabilizers. This is particularly preferred in that a separate step of removing is not required.

The aqueous liquid developer of the present invention includes a water-insoluble colorant obtained by the coacervation method and the phase inversion emulsification method, wherein the water-insoluble colorant is substantially insoluble in a water-based carrier liquid and has a hydrophilic group. The aqueous dispersion of the toner particles encapsulated by the film-forming resin having the above formula (I) can be obtained by adjusting the concentration of the aqueous dispersion with the carrier liquid so as to have a predetermined concentration. Usually, an aqueous dispersion of more concentrated toner particles is prepared, and this is diluted with a carrier liquid containing water as a main component.

In the preferred aqueous liquid developer described above, the content of the water-insoluble colorant and the weight ratio of the water-insoluble colorant / resin are the same as described above.

In the present invention, in order to develop an electrostatic charge image using an aqueous liquid developer, for example, as described above, the electrostatic charge image is formed by directly applying an electric field to the electrostatic recording medium by the means described above. After the formation, the highly insulating material layer is formed on the surface of the electrostatic recording medium on which the electrostatic image has been formed, and then the aqueous liquid developer is brought into contact with the surface of the highly insulating material layer. As a result, an image corresponding to an electrostatic charge image can be obtained by removing the excess developer and the excess high insulating material.

At this time, if the high insulating material layer is thin or evaporates and does not sufficiently cover the surface of the electrostatic recording medium, fogging may occur, so care must be taken. Further, as described above, after forming and coating a high insulating material layer on the electrostatic recording medium, an electrostatic charge image may be formed and then developed as described above.

As described above, although the mechanism of developing an electrostatic image using an aqueous liquid developer is not clear, the wettability of the latent image portion changes to hydrophilicity due to the presence of the 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 image exists, thereby obtaining a visible image.

The specific method in the step of developing with an aqueous liquid developer is not particularly limited. For example, a roller developing method in which a liquid film of the developer is formed on a roll and brought into contact with an electrostatic recording medium to perform development, Spray method for developing by spraying the developer onto the electrostatic recording medium, developing method by supplying the developer from a shower or slit, etc., dipping method for immersing the electrostatic recording medium in the developer, developing to sponge, etc. And a method in which a developer is impregnated and brought into contact with an electrostatic recording medium to develop the same, and the like.

As described above, it is preferable to add a squeezing step after development to remove excess developer and excess high insulating material. However, in the case where squeezing can be performed simultaneously with development as in the roller developing method, Is not necessary. Examples of the squeezing method include a method of squeezing the developer with a pair of rolls, a method of squeezing with a single roll in the case of rear development, and an air knife method of squeezing the liquid by blowing air strongly.

The image developed according to the present invention is obtained when an electrostatic recording medium is coated with a fixing agent or when an electrostatic recording medium coated with a dielectric layer having a fixing function is used. Does not require a fixing step, but if a film-forming thermoplastic resin is used as the resin,
In order to firmly fix the developed image, it is also possible to fix the developed image by heating the resin to a temperature higher than the softening point of the resin by a known fixing method.

Examples of such a fixing method include a non-contact heating fixing method using an infrared heater, a flash lamp, a high frequency wave, a hot air or the like, a contact heating fixing method using a hot plate or a heat roll, or a non-heating method using only a fan or the like. A fixing method, a pressure fixing method using a pressure roller, a solvent fixing method using a solvent, and the like are known. In the present invention, a squeeze method,
The fixing method is not particularly limited. However, it is preferable that after squeezing in order to efficiently remove water contained in the image, the developed image is heated to a temperature higher than the softening point of the resin to perform fixing.

[0052]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention includes the following embodiments. 1. Forming an electrostatic image directly by applying an electric field directly to the electrostatic recording medium, forming a highly insulating material layer on the electrostatic recording medium on which the electrostatic image has been formed, and Developing the toner particles comprising at least a water-insoluble colorant and a resin with an aqueous liquid developer in which the toner particles are dispersed in a carrier liquid containing water as a main component.

2. After performing the step of forming a highly insulating material layer on an electrostatic recording medium on which an electrostatic image has not been formed, implementing the step of directly forming an electrostatic image by directly applying an electric field to the electrostatic recording medium 2. A method for wet development of an electrostatic image as described in 1 above.

3. 2. The electrostatic charge according to the above item 1, wherein a step of directly forming an electrostatic image by applying an electric field directly to the electrostatic recording medium is performed, and then a step of forming a highly insulating material layer on the electrostatic recording medium is performed. Wet development of images.

4. 4. The method according to any one of claims 1 to 3, wherein the method of directly forming an electrostatic charge image by applying an electric field directly to the electrostatic recording medium is a method of controlling an ion flow from an ion source based on a print signal. Wet development method of the electrostatic image of the above.

5. 5. The method for developing an electrostatic image according to any one of the above 1, 2, 3 and 4, further comprising a step of removing excess developer in the non-image area and the image area after the development step.

6. A toner in which the toner particles comprising at least a water-insoluble colorant and a resin are coated and encapsulated with a film-forming resin having a hydrophilic group, wherein the colorant is substantially insoluble in a carrier liquid containing water as a main component. The wet development method for an electrostatic image according to any one of the above items 1, 2, 3, 4 and 5, wherein the particles are particles.

Hereinafter, a preferred embodiment of the present invention will be described with reference to a case where an aqueous liquid developer is obtained by a phase inversion emulsification method as an example of an interfacial deposition method.

An organic solvent solution of a film-forming thermoplastic synthetic resin obtained by copolymerizing styrene and (meth) acrylic acid as essential components, having an acid value of 50 to 280 and a molecular weight of 1,000 to 100,000. An organic solvent solution of the styrene- (meth) acrylic acid copolymer is obtained. This is mixed with a pigment, and the mixture is ground to obtain a colored mill base. As the organic solvent, a ketone-based hydrophobic organic solvent is mainly used.

To the colored mill base, a base capable of neutralizing the acid group of the synthetic resin is added in an amount sufficient to disperse the copolymer in an aqueous medium even without an emulsifier or a dispersion stabilizer, followed by stirring and mixing. Further, by adding an aqueous medium containing water dropwise thereto with stirring, a phase inversion emulsification phenomenon is exhibited, and a hydrophilic group is contained, and the colorant is coated and encapsulated by the copolymer having self-water dispersibility. To obtain an aqueous colored dispersion in which the toner particles are dispersed in an aqueous medium. The phase inversion phenomenon is smoothly performed by including the alcohol-based hydrophilic solvent in the colored mill base.

Further, 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 filtration with a filter to obtain a concentrated toner. Thereafter, the concentrated toner is diluted with a carrier liquid so as to have a predetermined concentration, a necessary additive is added, and the mixture is stirred to obtain an aqueous liquid developer.

The development of an image corresponding to an electrostatic latent image using the aqueous liquid developer of the present invention can be suitably carried out 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, development is carried out by bringing it into contact with the aqueous developer. Fourth step: A toner image corresponding to the electrostatic latent image is obtained by squeezing using a roller with a mesh.

Further, in order to obtain a firmly fixed image, the image is heated above the softening point of the resin.

[0066]

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

(Production Example 1 of aqueous liquid developer) Copper phthalocyanine pigment 20 parts Styrene- (meth) acrylic acid resin 20 parts (styrene / acrylic acid / methacrylic acid = 75/10)
/ 15; molecular weight 45000; acid value 160; glass transition temperature 116 ° C) A mixture of 50 parts of methyl ethyl ketone and 150 parts of glass beads is ground for 4 hours using a paint shaker, 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.

A mixture of 50 parts of glycerin and 400 parts of ion-exchanged water was dropped at a rate of 5 ml / min while stirring and adding 6.8 parts of triethanolamine to 170 parts of the mill base to obtain a resin resin particle dispersion. Was. 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 100 parts of ion-exchanged water was added to obtain a cyan aqueous liquid developer.

(Production Example 2 of aqueous liquid developer) Quinacridone magenta 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 1
(16 ° C.) A mixture of 50 parts of methyl ethyl ketone and 150 parts of glass beads was kneaded with a paint shaker for 4 hours, and 40 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.

A mixed solution of 50 parts of glycerin and 400 parts of ion-exchanged water was added dropwise to 170 parts of the mill base at a rate of 5 ml / min with stirring, and colored microcapsules were obtained. Methyl ethyl ketone and isopropyl alcohol were distilled off from the obtained capsule liquid using a rotary evaporator to obtain a concentrated toner in which microencapsulated toner particles were dispersed.
Further, the obtained concentrated toner was filtered using a 1.2 μm filter, and 100 parts of ion-exchanged water was added to obtain a magenta aqueous liquid developer.

(Production Example 3 of Aqueous Liquid Developer) Copper phthalocyanine pigment 12 parts J-7001 (aqueous emulsion resin manufactured by Shonson Polymer) 28 parts Deionized water 80 parts was wet-dispersed using a ball mill to obtain a concentrated toner. .
Further, 300 parts of ion-exchanged water was added to the obtained concentrated toner to obtain a cyan aqueous liquid developer.

When the basic characteristics of the aqueous liquid developer of each Production Example were compared and compared, the redispersibility of Production Examples 1 and 2 was superior to that of Production Example 3.

(Example 1) Electrostatic recording paper (K manufactured by Shin-Oji Paper Co., Ltd.)
-530M-3) and monochrome electrostatic plotter (EP-1 manufactured by Matsushita Electric Transmission Co., Ltd.)
01) to form an electrostatic latent image on electrostatic recording paper. Next, a thin layer of silicone oil (DC-345, manufactured by Shin-Etsu Silicone Co., Ltd.) was applied to the electrostatic recording paper on which the electrostatic latent image was formed.

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 obtained in Production Example 1 of the aqueous liquid developer to perform development. After that, when squeezed by a metal roller with a metal mesh,
A clear cyan image corresponding to an electrostatic latent image without background smear was obtained. The obtained developed image had no development unevenness and was excellent in uniformity.

The cyan image was dried at 125 ° 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. Further, water was sprinkled on the image after fixing, but there was no bleeding of the image, and an image having good water resistance was obtained. When this image was rubbed with a cloth, the developer did not transfer to the cloth at all.

(Example 2) Development was carried out in the same manner as in Example 1 except that the developer of Production Example 2 of the aqueous liquid developer was used. As a result, a clear magenta image without background stain was obtained.
As in Example 1, the image after fixing showed good fixability and water resistance. The obtained developed image had no development unevenness and was excellent in uniformity. When the image sprinkled with water was rubbed with a cloth in the same manner as in Example 1, the developer did not transfer to the cloth at all.

(Example 3) Development was carried out in the same manner as in Example 1 except that Production Example 3 of the aqueous liquid developer was used. As a result, a clear cyan image without background smear was obtained. As in Example 1, the image after fixing showed good fixability and water resistance.
When an image sprinkled with water was rubbed with a cloth in the same manner as in Example 1, the developer slightly transferred to the cloth.

Example 4 Electrostatic recording paper (K-Shin Oji Paper Co., Ltd.)
530M-3) is coated with Isopar L (Exxon Chemical Co., Ltd.) thinly, masked with an image pattern and charged with corona.
An electrostatic latent image was formed. Next, the electrostatic recording paper on which the electrostatic latent image was formed was brought into contact with the surface of the developer obtained in Production Example 1 of the aqueous liquid developer 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 obtained developed image had no development unevenness and was excellent in uniformity.

The above cyan image was converted into 1
The image was dried at 25 ° C. for 1 minute and fixed, and the fixing property 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. Although water was sprinkled on the image after fixing, there was no bleeding of the image, and an image having good water resistance was obtained. The obtained developed image had no development unevenness and was excellent in uniformity. When this image was rubbed with a cloth, the developer did not transfer to the cloth at all.

Comparative Example A cyan aqueous liquid developer was obtained in the same manner as in Production Example 3 except that the same amount of methylene blue was used instead of the copper phthalocyanine pigment.
The development was performed in the same manner as described above. In the obtained developed image, the developer hardly leveled and remained in the form of droplets, and the uniformity was poor. When an image sprinkled with water was rubbed with a cloth in the same manner as in Example 1, the developer was considerably transferred to the cloth.

[0081]

According to the developing method of the present invention, a step of directly forming an electrostatic image by directly applying an electric field to an electrostatic recording medium, and a step of forming a highly insulating material on the electrostatic recording medium having the electrostatic image formed thereon. Since it includes a step of forming a layer and a step of developing the electrostatic charge image with an aqueous liquid developer in which toner particles composed of at least a water-insoluble colorant and a resin are dispersed in a carrier liquid containing water as a main component, Aqueous wet developing method for an electrostatic image, which has good light fastness and water fastness of a developed image and has no fog even when a so-called high-concentration aqueous developer having a high colorant concentration is used and a color image is obtained. Can be provided.

Further, the present invention provides a highly safe aqueous electrostatic wet image developing method for an electrostatic image because an aqueous liquid developer in which toner particles are dispersed in a carrier liquid containing water as a main component is used. be able to.

Claims (6)

[Claims] A step of directly forming an electrostatic image by directly applying an electric field to the electrostatic recording medium; and a step of forming a highly insulating material layer on the electrostatic recording medium on which the electrostatic image has been formed. Developing the electrostatic image with an 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. Wet development method. 2. A method according to claim 1, wherein a step of forming a highly insulating material layer on the electrostatic recording medium on which no electrostatic image is formed is performed, and then an electric field is directly applied to the electrostatic recording medium to directly form the electrostatic image. 2. The method of claim 1, wherein the step of forming is performed. 3. The method according to claim 1, wherein a step of directly forming an electrostatic image by applying an electric field directly to the electrostatic recording medium is performed, and then a step of forming a highly insulating material layer on the electrostatic recording medium is performed. Item 1
The wet development method of the electrostatic image described in the above. 4. A method for directly forming an electrostatic image by directly applying an electric field to an electrostatic recording medium is a method of controlling an ion flow from an ion generating source based on a print signal. 4. The wet development method for an electrostatic image according to 1, 2, or 3. 5. The method according to claim 1, further comprising the step of removing excess developer in the non-image area and the image area after the developing step.
5. The wet development method for an electrostatic image according to 2, 3, or 4. 6. The toner particles comprising at least a water-insoluble colorant and a resin, wherein the colorant is a film-forming resin having a hydrophilic group and substantially insoluble in a carrier liquid containing water as a main component. 6. The method of claim 1, 2, 3, 4 or 5, wherein the toner particles are coated and encapsulated.