JPS61230990A - Desensitizer for offset printing - Google Patents

Abstract

PURPOSE:To enable printing without containing any cyanide compound, and provided with instantaneous desensitizing ability, and without surface contamination with one treatment by going through a processor, by making this solution contain oganic compound which has two or more phosphonic radical in one molecule. CONSTITUTION:A desensitizing treatment solution is made to contain organic compound which has two or more phosphonic radicals in one molecule and a desensitizing treatment is performed with the above solution. Organic compounds with a phosphoric radical in one molecule may be used singularly with an anticipation of sufficient desensitizing effect, and these compounds have a remarkable water retention characteristics, therefore, once desenstitizing treatment is carried out, even if printing is performed after a block surface has been dried, ink is separated in a few seconds and a printing matter without contamination may be obtained. In connection with the use of subject desensitizing liquid, a desirable ranges of pH of the solution would be in the ranges of 3.5-5.0. The treatment solution may be diluted with water for use as dampening water.

Description

Detailed Description of the Invention (2) Field of Industrial Application The present invention relates to a desensitizing treatment liquid for offset printing, and more specifically, it relates to a desensitizing treatment liquid for offset printing, and more specifically, for processing an electrophotographic copying material on which an image has been formed by electrophotography as an original plate for offset printing. This invention relates to a desensitizing solution that does not contain any cyanide compounds.

CB) Conventional technology The electrophotographic offset master consists of sensitizing a photoconductive fine powder such as zinc oxide and a resin binder such as acrylic resin or silicone resin on a conductive support such as metal, plastic, or coated paper. It has a photosensitive layer consisting of a photosensitive agent, and is subjected to seven photographic operations of charging, exposure, development, and fixing to form an image, and then treated with a desensitizing treatment liquid and used for printing.

Generally, in offset printing, a plate having an oleophilic image area and a hydrophilic non-image area is used for printing, but since the offset master photosensitive surface is originally oil-based, it can be printed without any desensitizing treatment. If this happens, ink will also adhere to non-image areas, making it impossible to obtain clean printed matter. Therefore, before printing, it is necessary to desensitize the non-image area of the master to make it hydrophilic. Therefore,
The characteristics that a desensitizing treatment liquid should have are that it exhibits a desensitizing effect on all masters made using different development methods and developers, there is no performance deterioration during long-term storage, and it has the ability to desensitize during printing. In addition to not exhibiting any decrease in viscosity, the desensitization treatment can be carried out easily and in an extremely short period of time.

Desensitizing treatment liquids conventionally used for this purpose include cyanide treatment liquids containing iron hexacyanosalt as a main component, inosit hexaphosphoric acid, tannic acid, and their derivatives or amine cobalt complex salts. There are known non-cyanide processing liquids whose main components are Among these, cyanide salts have been used for a long time and have a strong desensitizing ability and are effective in a short period of time, but iron hexacyano salts are decomposed by heat and light and cyanide is liberated, so they are harmful to pollution. I can't get rid of the problem. In this respect, although the latter does not cause pollution problems or performance deterioration due to light or heat, it has been difficult to provide a practical desensitizing effect in a short period of time.

(C) Purpose of the Invention Accordingly, the present invention provides a process that does not contain any cyanide compounds that pose a pollution problem, has an instant desensitizing ability, and enables printing without background smearing in one pass through a processor. It provides liquid.

(Di Structure of the Invention The present inventors have attempted to solve the above problems. As a result of intensive studies, the desensitizing treatment solution contains an organic compound having two or more phosphonic groups in one molecule, and The inventors have discovered that an offset printing plate that provides printed matter without background smudge can be obtained by performing a desensitization treatment using the above-mentioned method. Based on this knowledge, the present invention has been completed.

The organic compounds having a phosphonic group in one molecule as used in the present invention include l-acetomidopropane-1゜1-diphosphonic acid, 1-propionamidoethane-1,1-diphosphonic acid, l-hydroxyethane-1, 1-diphosphonic acid, 1
-aminoethane-1゜1-diphosphonic acid, 4-aminobutane-1,1-diphosphonic acid, (4-chlorophenyl)
Hydroxymethane diphosphonic acid, cyclohexyliminobis(methanephosphonic acid), dichloromethane diphosphonic acid, N,N-dimethylaminomethane diphosphonic acid, 1-
Hydroxyethane-1,1-diphosphonic acid M, 2-N-methylaminoethane-1,1-diphosphonic acid, phenylaminomethane diphosphonic acid, vinylidene diphosphonic acid, 2
-(1-piperidinyl)ethane-1,1-diphosphonic acid, 2-pyrimidinylthiomethane diphosphonic acid, 2-ethylthiomethane diphosphonic acid, nitrilotris (methylenephosphonic acid), ethylenediaminetetrakis (methylenephosphonic acid) guanidine- N,N-diphosphonic acid, etc. and their salts can be expected to have a sufficient desensitizing effect even when used alone, and since they have extremely high water retention properties, they can be treated with a desensitizing effect. Even if the printing plate is used for printing after it has dried, the ink separates within a few seconds, making it possible to obtain printed matter without background stains. Therefore, the treatment liquid of the present invention has the above-mentioned phosphonic acid as its main component, but in addition to these, it also contains inosit hexaphosphoric acid, tannic acid, amine cobalt complex, amino acid, etc. as a desensitizing agent, and organic as a regulator. - Inorganic acids, hydroxides, basic substances such as amines, etc. Wetting agents such as glycerin, sorbitol polyacrylic M[, CMC, gum arabic, etc., rust preventives such as nitrite, amines, etc., preservatives such as dehydrocarbon It can be used by adding appropriate amounts of sodium acetate, tridicanetetramine hexaacetate, and the like.

When implementing this treatment solution, the voice of the solution is 3.5 to 5.
A range of 0 is preferred. Furthermore, this treatment liquid can be diluted with water and used as a dampening solution.

Next, the present invention will be explained with reference to Examples and Comparative Examples.

Example 1 Example 2 Example 3 Comparative Example An image was formed on an electrophotographic light-sensitive material containing a zinc oxide-resin dispersion system according to a conventional method, and then subjected to degreasing treatment with the above treatment liquid to obtain an original plate for offset printing. Each treatment solution was diluted 8 times with water and used as a dampening solution for printing, and the results are shown in the table.

As shown in the table, Examples 1 to 3 all have 5,000 units from the first sheet.
Good prints with no background smear and no decrease in ink density were obtained for more than 30 pages, but in the comparative example, the desensitization was weak and the ink covered the non-image areas, making it impossible to print more than 30 pages. .

As described above, if an organic compound having two or more phosphonic groups in one molecule is used in the processing solution, the processing ability will not change against heat or light, and the deposition rate of the desensitized film will be increased. A processing solution that is significantly improved compared to conventional cyanide-free processing solutions can be produced.

Claims (1)

[Claims] A desensitizing liquid for offset printing, characterized in that it contains an organic compound having two or more phosphonic groups in one molecule.