JPH0243178B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an electrophotographic lithographic printing material.

Generally, an electrophotographic light-sensitive material has a photoconductive layer made of a photoconductive substance and a binder provided on the surface of a support that has been subjected to conductive treatment. Forming an image on the photoconductive layer through the process and using it as a plate for offset printing is widely used in the field of light printing because the plate-making operation is simple, quick, and inexpensive. .

An electrophotographic lithographic printing material is required to have properties as a lithographic printing material in addition to properties as a general electrophotographic copying material. That is, after image formation, the non-image area becomes oil-insensitive.
Because the photoconductive surface must be wetted with a special aqueous surface treatment solution, the so-called etchant, and because large amounts of dampening water are used during lithographic printing, lithographic printing materials require excellent water resistance. It is also required that the photoconductive layer does not peel off during printing.

In view of these demands, many proposals have been made to date to provide a precoat layer on a conductive support before forming a photoconductive layer on the support, and to form a photoconductive layer on this precoat layer. . In addition to the requirements for the above-mentioned properties such as water resistance, this precoat layer is made of an aromatic hydrocarbon solvent so that the coating liquid for forming the photoconductive layer has a photoconductive substance dispersed in a binder resin. It is also required to have excellent resistance to organic solvents since images are formed by a liquid development method in which toner is dispersed in a hydrocarbon-based organic solvent.

It is desirable for both water resistance and organic solvent resistance to be at a high level, but in general, water resistance and organic solvent resistance are mutually contradictory properties, so the precoating methods proposed so far As yet, there is no layer that completely satisfies these requirements, and due to the insufficient level of their properties and the imbalance of their properties, only electrophotographic lithographic materials with various drawbacks can be obtained. This has become one of the most difficult techniques for those skilled in the art. Special Public Service 1977-
18708, the water resistance and organic solvent resistance of the precoat layer is improved by using film-forming resins with reactive hydroxyl or carboxyl groups, such as copolymers of styrene, hexyl acrylate, acrylonitrile, methacrylic acid, polyvinyl alcohol, and carboxylated resins. copolymers of styrene and maleic anhydride, carboxylated ethylene and maleic anhydride copolymers, hydroxyethylcellulose, crotonic acid and vinyl acetate copolymers, etc., such as dimethylolmelamine, dimethyltrimethylolmelamine, It has been proposed to solve this problem by crosslinking with an aminoplastic initial condensate such as urea formaldehyde to make it water-insoluble, and several crosslinking methods have since been reported.

However, the present inventors have confirmed that even though the precoat layer obtained in this manner has water resistance in the sense that it does not dissolve in water, it cannot completely prevent water from penetrating.

Good water resistance is also required for the backcoat layer, usually the conductive layer. Conductive backcoat layers are more difficult to prevent penetration of etchant and dampening solution due to the relatively large amount of conductive agent used.
Therefore, in order to reduce the amount of the conductive agent in the conductive layer as much as possible, it is possible to impregnate the paper support with inorganic salts or to include the conductive agent in the precoat layer in view of electrophotographic properties. If it contains, the water resistance will be poor.

The object of the present invention is to have good electrophotographic properties,
It is an object of the present invention to provide a method for producing an electrophotographic lithographic printing plate having a precoat layer and a conductive backcoat layer, which does not suffer from drawbacks due to water resistance and organic solvent resistance.

Further objects and advantages of the present invention can be understood from the following description of the specification.

The above-mentioned objects of the present invention are to provide a method for producing an electrophotographic printing plate in which a photoconductive layer is formed on the surface of a conductive support via a precoat layer, in which the precoat layer and/or the back coat layer is coated with a group containing active hydrogen. It consists essentially of a water-soluble polymer compound, an insolubilizing agent for the water-soluble polymer compound, a water-dispersible resin, an inorganic pigment, and a conductive agent, in which the water-soluble polymer compound accounts for at most Ten
% by weight, the content of the water-dispersible resin relative to the water-soluble polymer compound is at least 5 times by weight, and the inorganic pigment accounts for at most 60% by weight, and the water absorption is 60% or less. It has been found that this can be achieved by applying, drying, and forming a coating liquid characterized by the following properties:

The present invention will be explained in more detail below.

The water-soluble compound having a group containing active hydrogen used in the present invention is a water-soluble polymer compound having a carboxyl group, a hydroxyl group, an amino group, an imino group, etc.
Examples include starch or its derivatives, cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, casein, polyvinyl alcohol, and styrene-maleic anhydride copolymers.

The insolubilizing agent for the water-soluble polymer compound is one that can react with the active hydrogen-containing group to make it insoluble in water. Known compounds include aldehyde compounds such as glyoxal and dimethylurea, dialdehyde starch and polyamide disclosed in Japanese Patent Publication No. 43-28405, epoxidized polyamide disclosed in Japanese Patent Publication No. 48-9803, and epoxy compounds disclosed in Japanese Patent Publication No. 47-23594.

The proportion of the water-soluble polymeric compound relative to the total solids content should be at most 10% by weight, preferably from 2 to 8% by weight. When the amount exceeds 10% by weight, not only complete water resistance cannot be obtained, but also the reaction with the insolubilizing agent progresses during the aging of the coating solution, which tends to cause problems that impede the coating process.

The water-dispersible resin used in the present invention includes polyethylene, polystyrene powder dispersed in water, vinyl synthetic resin emulsion (latex),
For example, water-dispersible emulsions made by emulsion polymerization or emulsion copolymerization of vinyl group-containing monomers such as acrylic acid or its esters, methacrylic acid or its esters, vinyl chloride, vinylidene chloride, vinyl acetate, acrylonitrile, butadiene, styrene, etc. can be used.

JP-A-48-9803 discloses a proposal to improve the printing durability by using a vinyl synthetic resin emulsion in the precoat layer to improve adhesion to the photoconductive layer. One of the characteristics of the method of the present invention is that the proportion of these vinyl synthetic resin emulsions used is extremely large, and as a result, it is extremely water resistant despite containing the conductive agent described below. disadvantages based on,
In other words, it was possible to obtain a lithographic printing plate with high printing durability without defects such as plate wrinkles.

The water-dispersible resin is used in an amount of at least 5 times, preferably 8 times or more, relative to the water-soluble polymer compound, and accounts for 20 to 70% by weight of the total solid content.
The range shall be .

The inorganic pigments used in the present invention include calcium,
Barium, lead carbonates, titanium, silicon, lead oxides, aluminum, zinc hydroxides, zinc, calcium, barium, lead sulfates, silicon, aluminum silicates, barium, calcium, zinc sulfides Selected from known inorganic pigments such as.

The inorganic pigment used in the present invention has a water absorption of 60%
Below, it should preferably be 50% or less. As you can easily imagine, inorganic pigments with a water absorption of 60% or more will absorb a large amount of etch solution and immersion water, causing plate wrinkles and layer peeling, even if the coating liquid satisfies all other conditions.

Even inorganic pigments of the same type generally have different water absorptions, and even inorganic pigments of different types have different water absorptions.

The water absorption as defined herein can be measured according to the oil absorption amount (oil absorption) in the pigment test method of JIS K5101. In other words, by performing the same procedure as in the JIS K5101 oil absorption test method except for replacing the boiled oil with regular water, water will adhere to the surface of the pigment particles, and when you touch it with your hand, you will notice that the water The end point is when the adhesion reaches a level where it can be detected.
The amount of water used up to that point is determined, and the amount of water absorbed (water absorption) is calculated using the following formula.

H/P×100 (%) H: Amount of water used (ml), P: Amount of pigment used (g) The proportion of the inorganic pigment used in the present invention in the total solid content is 60% by weight or less. . If the amount used is more than that, even if the inorganic pigment has a water absorption of 60% or less, the purpose of the present invention cannot be fully satisfied. When the photoconductive layer is applied, there are no defects such as surface cracks or pinholes.
In order to obtain a smooth surface quality, the proportion of the inorganic pigment in the total solid content is in the range of 20 to 60% by weight.

Known conductive agents can be used in the present invention. For example, polyvinyltrimethylammonium chloride, polyvinylbenzyltrimethylammonium chloride, poly-4-vinylpyridine, poly-2-vinylpyridine polymethacrylic acid diethylaminoethyl hydrochloride, di-2-ethylhexylsulfosuccinate, sodium cetyl phosphate, polystyrene sulfonic acid Mention may be made of polyelectrolytes such as sodium or ammonium salts, polyacrylates, methyl vinyl ether maleic anhydride copolymer sodium salt, or inorganic salts such as chlorides.

The amount of conductive agent used in the precoat layer is 20°C.
10 ¹⁰ to 10 ¹¹ Ω・cm at 60% relative humidity, preferably 5
It is preferable to set the surface resistivity to be in the range of ×10 ¹⁰ to 10 ¹¹ Ω·cm.

Even with the pre-coat layer produced by the method of the present invention, if the surface resistivity is made smaller than that range, it is possible to obtain a good image without fogging, especially at low humidity, but on the other hand, the printing durability decreases. .

Due to the precoat layer components of the method of the present invention, even if a small amount of conductive agent is used, the printing durability does not decrease at all, and a good image can be obtained.

The amount of the conductive agent to form the conductive back coat layer can be arbitrary, and when the same compound as the conductive agent used in the precoat layer is used, it is about 5 to about 100% of the amount of the conductive agent used in the precoat layer. It can be in the double range.

By using a conductive agent in the precoat layer and, if necessary, using a conductive paper support impregnated with an inorganic salt, the amount of conductive agent used in the conductive backcoat layer can be relatively reduced. Therefore, it has the advantage of being able to alleviate the drawbacks due to the water resistance of the back coat layer.

The coating liquid for the precoat layer or backcoat layer in the method of the present invention consists essentially of the above-mentioned components. Substantive meaning refers to the extent to which these components account for approximately 80% by weight of the total solids, especially approximately 90% by weight or more, and excludes the use of other components such as pigment dispersants and antifoaming agents. isn't it.

The precoat layer or backcoat layer in the present invention is applied by a conventional method at a dry coating amount of 3 to 30 g/m ² , preferably 5 to 20 g/m ² .
Formed by drying.

The support used in the present invention is made of ordinary papermaking pulp or a pulp suspension containing a small amount of synthetic fiber, synthetic resin, etc., and a moisture strengthening agent such as a thermosetting condensation resin, polyamide resin, starch, or polyvinyl alcohol. A wet reinforced paper internally added with a sizing agent, a filler, etc. or siped pressed can be used, and it can also be impregnated with a moisture-absorbing liquid inorganic salt to impart conductivity.

The present invention will be explained below using examples.

Example 1 A coating solution for forming a conductive layer having the following composition was applied on the back side of a paper base mainly made of N pulp at a dry coating amount of 13 g/m ²
Apply and dry.

[Coating liquid for forming conductive layer]

Kaolin clay (50% water dispersion, water absorption 35.5
%) 600 parts by weight polyvinyl alcohol (10% aqueous solution)
200 〃 SBR latex (solid content 50%) 450 〃 Polyvinylpenzyltrimethylammonium chloride (solid content 30%) 200 〃 Melamine-formaldehyde initial condensate (solid content 80%, violet resin - 613 Sumitomo Chemical Co., Ltd. ) made)
15 parts by weight On the other hand, a coating solution for forming a precoat layer having the following composition was applied to the front side of the paper base so that the dry coating amount was 9 g/m ² , dried (100°C), and the surface of the precoat layer (surface resistivity 7 ×10 ¹⁰ Ω・cm, 20℃60%RH)
After supercalendering, a photoconductive layer was formed on the surface.

[Coating liquid for forming pre-coat layer]

Kaolin clay (50% water dispersion, water absorption 35.5
%) 200 parts by weight finely divided polystyrene (average particle size 0.5μ, 48.5% aqueous dispersion) 150 parts by weight polyvinyl alcohol (10% aqueous solution)
200 〃 SBR latex (solid content 50%) 150 〃 Violet resin-613 15 〃 Ammonium polystyrene sulfonate (30% aqueous solution) 6 〃 The photoconductive layer forming coating liquid has the following formulation, dry coating amount is approximately 20g / ^m2 , and heated to 100℃.
It was dried.

[Coating liquid for forming photoconductive layer]

Zinc oxide 200 parts by weight Acrylic resin (50% liquid) 80 Rose Bengal (2% methanol solution)
15 〃 Xylene 250 〃 The surface coated with the photoconductive layer had a uniform surface quality with no surface cracks or pinholes.

This plate was heated to 60% RH and 20% RH at 20°C.
After seasoning under the following conditions, each plate was made using an electrophotographic plate making machine Diafax EP-11 (manufactured by Mitsubishi Paper Industries Co., Ltd., a plate making machine for liquid development), and an etch liquid for electrophotographic mastering, Diafax LOM-OH (Mitsubishi Paper Mills Co., Ltd.). (manufactured by Paper Industries Co., Ltd.) to make it desensitized, and the printing press Toko
Printed using Mode 1810 (manufactured by Tokyo Aircraft Instruments Co., Ltd.).

There was no fogging under either 60%RH or 20%RH conditions, and high-density, clear images were obtained. Even after treatment with etchant, no curling occurs, and installation into the printing machine is possible with smooth operation. Even when printing with dampening water or printing more than 5,000 sheets, there are no wrinkles or layer peeling. It was confirmed that the printing plate obtained by the method of the present invention was extremely excellent.

Comparative Examples 1 to 5 Comparative precoats were prepared in the same manner as in Example 1 except that the precoat liquid was changed as follows, and tested in the same manner.

Comparison 1: Pre-coat layer polyvinyl alcohol
400 parts by weight (13.2% by weight) Comparison 2: Pre-coat layer with polystyrene removed Comparison 3: Pre-coat layer with polyvinyl alcohol
150 parts by weight and 400 parts by weight of kaolin clay and polystyrene removed Comparison 4: Water absorption of kaolin clay in pre-coat layer
Comparison 5: Substituted with 69% calcium carbonate: Pre-coat layer excluding polyvinyl alcohol and violet resin-613. In both cases, background staining due to plate wrinkles etc. occurred after printing up to 4000 sheets, and in Comparisons 3 and 4, the layer peeled off. In Comparison 5, surface cracking occurred, confirming the superiority of the plate of Example 1.

Example 2 A printing plate was prepared in exactly the same manner as in Example 1 except that the same amount of calcium carbonate (water absorption 41.5%) was used instead of kaolin clay, and the same results as in Example 1 were obtained.

Example 3 A printing plate was prepared in exactly the same manner as in Example 1 except that the same amount of polyamide or epoxidized polyamide (both manufactured by Deutsche Hercules) was used for the violet resin-613 in the precoat layer and backcoat layer. Exactly the same results were obtained.

Example 4 Example 1 was repeated except that the following precoat and backcoat solutions were used.

[Coating liquid for forming pre-coat layer]

Part by weight Kaolin clay (50% water dispersion, water absorption 35.5
%) 200 Acrylic acid ester emulsion (45% solids) 230 Polyvinyl alcohol (10% aqueous solution) 100 Glyoxal 5 Ammonium polystyrene sulfonate (30% aqueous solution) 5 [Coating liquid for back coat layer formation] Part by weight Kaolin clay (50%) Water dispersion, water absorption 35.5
%) 600 Polyvinyl acetate emulsion (solid content 50%)
500 Hydroxyethylcellulose (10% aqueous solution)
200 Polyamide (manufactured by Deitsku Hercules, 30%
Liquid) 70 Polyvinylbenzyltrimethylammonium chloride (solid content 30%) 200 As in Example 1, an electrophotographic lithographic printing plate with excellent electrophotographic properties and high printing durability without defects due to water resistance and organic solvent resistance was produced. I was able to get it.

Claims (1)

[Claims] 1. In a method for producing an electrophotographic lithographic printing plate in which a photoconductive layer is formed on the surface of a conductive support via a precoat layer, the precoat layer and/or backcoat layer is formed of a water-soluble polymer compound having a group containing active hydrogen, consisting essentially of an insolubilizing agent, a water-dispersible resin, an inorganic pigment, and a conductive agent for the water-soluble polymer compound, in which the water-soluble polymer compound accounts for at most 10% by weight; The content of the water-dispersible resin relative to the water-soluble polymer compound is at least 5 times by weight, and the inorganic pigment accounts for at most 60% by weight and has a water absorption of 60% or less. The above method of applying, drying, and forming a coating liquid characterized by: