JPS5952079B2 - Processing liquid for lithographic printing plates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a processing liquid used for a lithographic printing plate whose surface layer has a zinc oxide-resin dispersion system.

After forming an image on an electrophotographic material having a photoconductive layer in which photoconductive zinc oxide is dispersed in an insulating resin such as silicone resin or acrylic resin by a conventional method, non-image areas are desensitized and lithographic printing is performed. It is known to be used as a plate master.

Desensitizing liquids used in such treatments are often
The main components are ferrocyanide or ferrocyanide and water-soluble phosphate. When ferrocyanide dissociates in this desensitizing solution, it becomes Fe(CN)O”- and Fe(CN)
) creates an equilibrium between each ion of O°-. When the desensitizing liquid in such a state comes into contact with the exposed non-image area of zinc oxide, it reacts with the exposed zinc oxide and desensitizes the non-image area. However, in conventional desensitizing liquids, the deterioration of ferrocyanide, especially due to light, is remarkable.This not only deteriorates the quality of the liquid, such as deterioration and precipitation, but also causes so-called gear stains in the non-image areas of the lithographic printing plate. This was causing soiling. The present invention eliminates the above-mentioned drawbacks, and provides a processing liquid for lithographic printing plates that does not cause deterioration in the quality of the liquid and does not cause gear stains or background stains.

That is, the treatment liquid of the present invention contains a hydrophilic copolymer composed of a basic polymerizable monomer and a polymerizable carboxylic acid metal salt as an active ingredient.

Specific examples of such hydrophilic copolymers include basic polymerizable monomers such as acrylamide, vinylpyridine, N-N'-dimethylaminoethyl methacrylate, N-methylolacrylamide, acrylmorpholine, and vinylhydroxam, and acrylic acid. Copolymers with polymerizable carboxylic acid metal salts such as manganese, cobalt vinylbenzoate, zinc crotonate, nickel itaconate, cobalt methacrylate, zinc methacrylate, more specifically acrylamide-manganese acrylate copolymers, Vinyl pyridine - cobalt vinyl benzoate copolymer, N/N'-dimethylaminoethyl methacrylate - zinc crotonate copolymer, N
- Methyloacrylamide - nickel itaconate copolymer, acrylic morpholine - cobalt methacrylate copolymer, vinylhydroxam - nickel methacrylate copolymer and the like.

To make these hydrophilic copolymers, a basic polymerizable monomer, a polymerizable carboxylic acid, a polymerization initiator, and water are placed in a reaction vessel and reacted with stirring, and an aqueous metal acetate solution is mixed with the reactant. , the reaction may be carried out by heating at 70 to 80°C.

A manufacturing example thereof is shown below. Production Example Acrylamide 70g Acrylic acid 213g Potassium persulfate 4g Water 2657g The above ingredients were mixed and reacted at a reaction temperature of 70 to 80°C for 6 hours.

Next, 1000 g of the obtained hydrophilic copolymer was mixed with 500 g of a 1% manganese acetate solution at a reaction temperature of 80 to 9.
The reaction is carried out at 0° C. for 8 hours to obtain a hydrophilic copolymer metal salt consisting of acrylamide and manganese acrylate.

The hydrophilic copolymer thus obtained is usually used at a concentration of 0.1 to 5% by weight, and the hydrophilic coating can easily desensitize non-image areas.

In addition, the processing solution of the present invention includes various additives used in general desensitizing solutions, such as PH buffers such as ammonium phosphate, sodium phosphate, and phosphoric acid; citric acid, malonic acid, lactic acid, and tartaric acid. , amino acids, various inorganic acids, or salts thereof; wetting agents such as glycerin, glycol, CMC, vinylpyrrolidone, etc. can be added.

The treatment liquid of the present invention can also be used as a dampening solution to be applied before inking a lithographic printing plate after desensitization treatment.

In this case, the treatment liquid is diluted approximately 6 to 7 times before use.
Examples and comparative examples are shown below.

Example 1 100 g of a 10% aqueous solution of a copolymer consisting of acrylamide/manganese acrylate = 50/50 (molar ratio) was added to 1 part of water.
Dilute with 0.00ml to obtain a treatment solution.

Example 2 50 g of a 10% aqueous solution of a copolymer consisting of vinylpyridine/cobalt crotonate = 30/70 (mole ratio) was mixed with 10 g of water.
Dilute with 0ml and use as a treatment solution.

Example 3 N-methylol acrylamide/nickel itaconate =
50 g of a 10% aqueous solution of a copolymer having a molar ratio of 70/30 is diluted with 100 ml of water to obtain a treatment liquid.

Example 4 Add 10 g of ammonium phosphate to the treatment solution of Example 1.

Example 5 10 g of citric acid and 1 portion of sodium phosphate were added to the treatment solution of Example 2.
Add 0g.

Comparative Example 1 Dilute with 100 ml of a 10% aqueous solution of a copolymer consisting of acrylamide/acrylic acid = 50/50 (molar ratio) to obtain a treatment liquid.

Comparative Example 2 A 10% aqueous solution of a copolymer consisting of vinylpyridine/crotonic acid = 30/70 (mole ratio) is diluted with 100 ml of water, and then 10 g of citric acid and 10 g of ammonium citrate are added to prepare a treatment liquid.

Comparative example 3 Sodium ferocyanate 30g Trisodium phosphate 10g citric acid 10g Water 1000m1 Prepare a processing solution consisting of:

Next, after forming an image on a commercially available zinc oxide/resin dispersion electrophotographic light-sensitive material, it is desensitized using each of the processing solutions mentioned above to prepare a lithographic printing master, and printing is performed using tap water as a dampening solution. Ta.

Claims (1)

[Claims] 1. A lithographic printing plate processing liquid containing as an active ingredient a hydrophilic copolymer consisting of a basic polymerizable monomer and a polymerizable carboxylic acid metal salt.