JPH04363295A - Planographic printing plate - Google Patents

Abstract

PURPOSE:To eliminate the generation of a stain on the peripheral part of printed matter such as a newspaper by subjecting the photosensitive layer provided on an aluminum support to image forming exposure and development before subjecting the end part of the support to desensitizing treatment. CONSTITUTION:A PG plate wherein a photosensitive layer is provided on an aluminum support being a material of a planographic printing plate is obtained by applying surface roughening treatment, anodic oxidation treatment and hydrophilic treatment to the aluminum support and subsequently providing the photosensitive layer to the treated support and, at the time of use, a required original picture film is placed on the photosensitive layer to be irradiated with ultraviolet rays or active light and the irradiated photosensitive layer is subjected to developing treatment to form a printing plate. In the manufacturing process of this printing plate, the end part of the support is subjected to desensitizing treatment after the photosensitive layer is subjected to image forming exposure and development. As a desensitizing agent used in this desensitizing treatment, for example, an aqueous solution containing a hydrophilic org. high- molecular compound and an acidic compound is used.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new lithographic printing plate, and more particularly to a lithographic printing plate that does not cause stains around printed matter and is particularly suitable for use in newspaper printing.

0002

BACKGROUND OF THE INVENTION As lithographic printing plate materials, PS plates in which a photosensitive layer is provided on an aluminum support are predominant. This PS plate material has a photosensitive layer provided on an aluminum support after roughening, anodizing and hydrophilic treatment, and when used, a required original film is placed on the photosensitive layer. After irradiation with actinic light such as ultraviolet rays, the plate can be used as a printing plate by performing a development process.

However, in conventional lithographic printing plates made in this way, when printing continuously on a roll of paper using a rotary press such as newspaper printing, the width of the paper is Due to the small width of the printing plate, printing ink adhering to the edges of the printing plate is transferred to the paper, which appears as linear smears on the edges of the newspaper.

As a method for preventing such staining, a method has been proposed in which, for example, in a PS plate material in which a photosensitive layer is provided on an aluminum support having a hydrophilic surface, the end face of the aluminum support is desensitized. (Tokuko Showa 6)
2-61946). However, in this method, if the desensitizing treatment is performed manually for each plate material, the desensitizing agent will get around to the photosensitive layer and the back side of the aluminum support, and when stacked and packaged, the printing plate This has the disadvantage that the material cannot be peeled off. In order to prevent this, it is possible to apply a desensitizing agent after stacking the packaging units, but even in this case, the disadvantage is that the desensitizing agent seeps between the plates and prevents them from peeling. , has not yet been put into practical use.

[0005]

[Problems to be Solved by the Invention] Under these circumstances, an object of the present invention is to provide a lithographic printing plate that does not cause stains around printed matter and is particularly suitable for newspaper printing. This was done as a.

[0006]

[Means for Solving the Problem] As a result of intensive research to develop a lithographic printing plate that does not cause stains around printed matter, the present inventors have discovered that the photosensitive layer is subject to the necessary image-forming exposure and development treatments. The inventors have discovered that the above object can be achieved by desensitizing the ends of the aluminum support after the above-described process, and have completed the present invention based on this knowledge.

That is, the present invention provides a lithographic printing method characterized in that after a photosensitive layer provided on an aluminum support is subjected to image-forming exposure and development treatment, the edges of the support are desensitized. The version is provided.

As the aluminum support used in the lithographic printing plate of the present invention, any one can be selected from among those conventionally used for PS plate materials. Such a product is made by, for example, mechanically roughening one side of an aluminum plate with a thickness of about 0.3 mm, then anodizing it in a sulfuric acid bath, and then subjecting it to hydrophilic treatment. Preferred examples include aluminum supports.

On the other hand, there are no particular restrictions on the photosensitive layer.
Photosensitive layers conventionally used in PS plate materials, such as those made of diazo resin and hydrophobic resin,
- A compound consisting of a quinonediazide compound and a novolak resin can be used.

In the present invention, the photosensitive layer provided on the aluminum support is first subjected to image-forming exposure and then developed. In the image forming exposure, a desired original film is brought into close contact with the photosensitive layer using a means such as a vacuum adhesion method, and active light such as ultraviolet rays is irradiated onto the film, and active light irradiated areas and non-irradiated areas are separated. This is a process that causes a difference in solubility in the developer.

On the other hand, in the development process, a developer is applied to the photosensitive layer in which a difference in solubility has occurred in this way. , is a step of forming an image by selectively dissolving and removing only the areas not irradiated with active light using a developer such as an alkaline aqueous solution.

[0012] The printing plate obtained in this manner can be directly applied to a printing press, but in this case, the periphery of the printed matter becomes dirty, so in the present invention, the edges of the aluminum support are treated with a desensitizing agent. Desensitization treatment is required. Further, when performing this desensitization treatment, it is desirable that the corners of the aluminum support on the photosensitive layer side be rounded. When it has such a shape, the effect of the desensitization treatment is significantly exhibited.

There are no particular restrictions on the desensitizing agent used in this desensitizing treatment, and those conventionally used as desensitizing agents for lithographic printing plates can be used. Examples of such a desensitizing agent include an aqueous solution containing a hydrophilic organic polymer compound and an acidic compound.

Examples of the hydrophilic organic polymer compound include gum arabic, dextrin, alginate, carboxymethyl cellulose, hydroxyethyl cellulose,
Hydroxypropyl methylcellulose, polyvinyl alcohol, polyvinylpyrrolidone, polyacrylamide,
Copolymers containing acrylamide units, polymethacrylic acid, copolymers containing methacrylic acid units, copolymers of vinyl methyl ether and maleic anhydride, copolymers of vinyl acetate and maleic anhydride, phosphoric acid modified starch Among them, gum arabic is preferred. These hydrophilic organic polymer compounds may be used alone or in combination of two or more, and the blending amount is usually 1 to 40% by weight based on the total weight of the desensitizing agent. , preferably in the range of 5 to 30% by weight.

On the other hand, the acidic compound may be either an organic acid or an inorganic acid, such as mineral acids such as phosphoric acid, sulfuric acid, and nitric acid, citric acid, tannic acid, malic acid, glacial acetic acid, lactic acid, and sulfuric acid. Among these, phosphoric acid and phosphonic acid are particularly preferred. These acidic compounds also have the effect of enhancing the desensitizing effect. In the present invention, these acidic compounds may be used alone or in combination of two or more,
The blending amount is usually 0.0 based on the total weight of the desensitizing agent.
It is selected in the range of 1 to 8% by weight, preferably 0.1 to 5% by weight.

The desensitizing agent may further contain a metal salt of a strong acid. Such metal salts include, for example, sodium, potassium, magnesium, calcium and zinc salts of nitric acid, sodium salts of sulfuric acid,
Examples include potassium salts, magnesium salts, calcium salts, and zinc salts, sodium salts, potassium salts, magnesium salts, calcium salts, and zinc salts of chromic acid, and sodium and potassium salts of hydrofluoric acid. These metal salts can be used alone or in combination of two or more. The blending amount is usually selected within the range of 0.01 to 5% by weight based on the total weight of the desensitizing agent.

[0017] The desensitizing agent may also contain a wetting agent or a surfactant. As wetting agents, lower polyhydric alcohols are preferred, such as ethylene glycol,
Examples include diethylene glycol, triethylene glycol, propylene glycol, butylene glycol, pentanediol, hexylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, tripropylene glycol, glycerin, sorbitol, pentaerythritol, and the like. Examples of the surfactant include nonionic surfactants such as polyoxyethylene alkyl phenyl ether and polyoxyethylene polyoxypropylene block copolymer, fatty acid salts, alkyl sulfate ester salts, alkylbenzenesulfonates, alkylnaphthalenesulfonates, Anionic surfactants such as dialkyl sulfosuccinate salts, alkyl phosphate salts, naphthalene sulfonic acid formalin condensate, betaine type,
Glycine type, alanine type, sulfobetaine type amphoteric surfactants, etc. can be used.

These wetting agents and surfactants can be contained preferably in an amount of 0.5 to 10% by weight, more preferably 1 to 5% by weight, based on the total weight of the desensitizing agent.

The desensitizing agent thus obtained is applied to the edges of the printing plate surface which has been subjected to image forming exposure and development processing, but it may also be applied after applying a gum solution after the development processing. A gum solution and a desensitizing agent may be used in combination. Note that when storing for a long period of time, care must be taken as even the image area becomes desensitized.

[0020] The desensitizing agent has a coating film weight of 0.
It is effective to apply it in a range of 1 to 50 g/m2. Application methods include, for example, brush, sponge,
A method using a roller or the like or a method of applying by spraying can be used, but it is also possible to use a developing device commercially available as a PS plate processor, or an application in which a desensitizing agent is applied downstream of the gum processing process. This method is advantageous because it allows for consistent processing. The edge to be coated differs depending on the printing format, but if only one edge of the printing plate will be the printing surface, it is sufficient to apply the desensitizing agent to only that edge, but there are various usage patterns. With this in mind, it is advantageous to apply it preferably to two opposing ends, more preferably to the outer peripheral end.

Next, one of the preferred plate-making methods for the printing plate of the present invention will be described.
To explain an example, first, the required original film is vacuum-adhered to the photosensitive layer surface of the PS plate material, then it is selectively irradiated with active light such as ultraviolet rays, and a developer is applied to the irradiated and non-irradiated areas. A solubility difference is generated in the original film, and then development is performed to form a relief image corresponding to the original film. Next, the lithographic printing plate of the present invention can be obtained by applying a desensitizing agent to the edges of the printing plate after performing a gum treatment if necessary.

[0022]

[Effects of the Invention] The lithographic printing plate of the present invention is one in which the edges of the plate are desensitized after forming an image, and it is easy to make the plate, and it also prevents stains from forming on the periphery of printed matter. It is especially suitable for printing on large paper such as newspapers.

[0023]

EXAMPLES Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples in any way.

Production example Production of PS plate material 0.3mm thick,
A roll of aluminum plate with a width of 1200 mm was degreased with an aqueous sodium phosphate solution, and then heated at 3 A/d in a hydrochloric acid bath.
After electropolishing at a current density of 2, it was anodized in a sulfuric acid bath. Furthermore, it was immersed for 30 seconds in a 5% by weight aqueous solution of JIS No. 3 sodium silicate at 80°C, followed by thorough washing with water and drying. N-(4-
5 g of a copolymer with a molar ratio of hydroxyphenyl) methacrylamide units/2-hydroxyethyl methacrylate units/acrylonitrile units/methyl methacrylate units/methacrylic acid units 15/15/25/35/10, p
- 0.5 g of 2-methoxy-4-hydroxy-5-benzoylbenzenesulfonate, a condensate of diazodiphenylamine and formaldehyde, 0.1 g of Victoria Piure Blue BOH [manufactured by Hodogaya Chemical Co., Ltd.], methyl alcohol 30g and 2-methoxyethyl alcohol 30g
A photosensitive solution consisting of 1.5 g was applied using a roll coater to a dry weight of 1.7 g/m 2 and dried at 100° C. for 2 minutes to prepare a negative PS plate material.

[0025] After 50 plates of the PS plate material obtained in this manner were stacked with interleaf paper in between, they were cut into a size of 1099 mm x 400 mm using a down cut shear.

Comparative Example 10 PS plates obtained in the manufacturing example were stacked, and 3
A desensitizing agent consisting of 60 g of 0% by weight aqueous gum arabic solution, 1 g of sodium hexametaphosphate, 1 g of magnesium sulfate, 24 g of 85% phosphoric acid and 30 g of water was applied with a sponge and dried at room temperature to prepare a printing plate material.

The printing plate material thus obtained had no value as a printing plate material because the desensitizing agent had penetrated between the plates.

Example 1 After the photosensitive layer of the PS plate material obtained in Production Example was subjected to the required image forming exposure, 30 g of benzyl alcohol, 2 g of sodium metasilicate, 5 g of sodium hydrogen sulfate, 10 g of sodium dodecylbenzenesulfonate, and 1000g water
The film was developed with a developer consisting of the following: and then gummy with an aqueous solution of gum arabic at 14° Baumé.

Next, the desensitizing agent used in the comparative example was applied to the edge of the plate with a sponge and dried at room temperature. When printed on paper, no linear stains were observed on the periphery of the newspaper.

Example 2 The same procedure as in Example 1 was carried out except that instead of the desensitizing agent in Example 1, a compound consisting of 2 g of polyacrylamide, 10 g of 85% phosphoric acid, 70 g of water and 25 g of isopropyl alcohol was used. When the test was carried out, no linear stains were found around the newspaper.

Example 3 The same procedure as in Example 1 was carried out except that 3 g of polyvinyl alcohol, 3 g of aminotrimethylenephosphonic acid and 94 g of water were used instead of the desensitizing agent in Example 1. , no linear stains were observed on the periphery of the newspaper.

Example 4 Instead of the desensitizing agent in Example 1, 60 g of a 30% by weight aqueous gum arabic solution, 10 g of 85% phosphoric acid, 1 g of magnesium sulfate, 1 g of polyoxyethylene polyoxypropylene block copolymer and 27 g of water were used. The experiment was carried out in the same manner as in Example 1, except that a material consisting of .

Example 5 The same procedure as in Example 3 was carried out except that the 14° Baume aqueous solution of gum arabic was not used, and no linear stains were observed on the periphery of the newspaper. Ta.

Example 6 The same procedure as in Example 4 was carried out except that the 14° Baume aqueous solution of gum arabic was not used, and no linear stains were observed on the periphery of the newspaper. Ta.

Example 7 A roll of aluminum plate with a thickness of 0.3 mm and a width of 1200 mm was polished with a nylon brush using 400 mesh permiston, washed well with water, and heated at 70°C for 10 minutes.
It was immersed for 10 seconds in an aqueous sodium hydroxide solution of % by weight. Subsequently, after electrolytic polishing at 200 C/dm2 in a 1 wt% nitric acid bath, desmutting was performed for 2 minutes in a 30 wt% sulfuric acid aqueous solution, and then the oxide film weight was reduced to 2 in a 4 wt% sulfuric acid aqueous solution.
．． The aluminum support was anodized to 0 g/m2, then thoroughly washed with water and dried to prepare an aluminum support.

Next, on this aluminum support, 2.5% of the esterified product of naphthoquinone-1,2-diazide-5-sulfonyl chloride and pyrogallol acetone resin was placed.
g, cresol/formaldehyde resin 5g, t-butylphenol/formaldehyde resin 0.5g, Oil Blue #603 [manufactured by Orient Chemical Industry Co., Ltd.] 0.0
5 g of methyl ethyl ketone and 50 g of methoxyethyl acetate, the film weight after drying was 2.
Coat using a roll coater so that it is g/m2,
A positive PS plate material was prepared by drying at 100° C. for 2 minutes.

Next, 50 PS plates obtained in this way were stacked with interleaf paper in between, and then down cut and
It was cut into a size of 1003 mm x 800 mm using a shear.

This plate material was set in a vacuum printing frame, and after being irradiated with ultraviolet rays from a metal halide lamp for 30 seconds from a distance of 1 m through a positive film, 50 g of JIS No. 3 sodium silicate and 30 g of a 40% by weight potassium hydroxide aqueous solution were added.
The film was developed with a developer consisting of g and 1000 g of water, then thoroughly washed with water, and then gummy treated with an aqueous solution of gum arabic at 14° Baumé.

Next, a desensitizing agent consisting of 5 g of carboxymethylcellulose, 5 g of hydroxyethylidene-1,1-disulfonic acid and 90 g of water was applied to the edges of this plate using a sponge and dried at room temperature. When printed on a rotary offset printing press, no linear stains were observed on the periphery of the newspaper.

Furthermore, when printing was carried out in the same manner without applying the desensitizing agent, linear stains were observed on the periphery of the newspaper.

Claims (1)

[Claims] 1. A lithographic printing plate characterized in that a photosensitive layer provided on an aluminum support is subjected to image-forming exposure and development, and then the edges of the support are desensitized.