JPS6012958B2 - Desensitizing liquid for lithographic printing plates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an unfattening liquid for use in lithographic printing plates whose surface layer has a zinc oxide/resin dispersion system.

An electrophotographic light-sensitive material having a photoconductive layer in which photoconductive zinc oxide is dispersed in an insulating resin such as a silicone resin or an acrylic resin is subjected to image formation by a conventional method, and then subjected to a desensitization treatment on the non-image area and lithographic printing. It is known to be used as a master.

The unfattening liquid used for this kind of treatment is often
p such as ferrocyanide or its water-soluble phosphate
The main component is H buffering agent. And this ferrocyanide becomes Fe(CN) and Fe(CN) in the liquid.
) The reed is dissociated into each ion, and these ions exist in equilibrium. When the non-lipidizing liquid in such a state comes into contact with the zinc oxide-resin dispersion photoconductive layer, each ion in the non-lipidizing liquid reacts with the originally fat-sensitive zinc oxide exposed in the non-image area. Make this fat. In this way, the degreasing process (etching) is carried out.
In conventional fat-free liquids, the ferrocyanide deteriorates significantly, which not only causes a drop in quality and discoloration of the liquid, but also tends to cause so-called gear stains and background stains in non-image areas of planographic printing plates. That is, ferrocyanide undergoes oxidation and/or dissociation, especially when exposed to light, resulting in equilibrium between Fe(CN) and Fe(CN) poison ions, and a small amount of FeH and FeH We found that they coexist.
The ions combine to form a deep blue color, which discolors the solution, and precipitates to promote dissociation with equilibrium retention, thereby lowering the value of the corresponding active ingredient and spreading the precipitation. To go. Other discolorations and precipitation result from the oxidation of ferrocyanide to ferrocyanide and/or the formation of brown rust compounds of ferric ferrocyanide. The effectiveness of the conversion solution, ie, its ability to react with zinc oxide and render non-image areas hydrophilic, is thus progressively compromised. The present invention has developed a desensitizing liquid for lithographic printing plates that prevents the deterioration of ferrocyanide over time through the addition of amino acids and makes it difficult for graze stains and background stains to occur in the non-image areas of lithographic printing.In other words, it has improved rigidity. This is what we provide.

The main components of such a nonfatting liquid are ferrocyanide, water-soluble phosphate, and amino acids or water-soluble salts thereof.

Huh.

Cyanide, as mentioned above, is a substance that converts zinc oxide into a fumakuban, examples of which are sodium ferrocyanide and ferrocyanide. Potassium cyanide, sodium ferrocyanide, potassium ferrocyanide, etc. The appropriate amount to be used is about 3 to 3% by weight based on the total solid content. Examples of water-soluble phosphates include primary ammonium phosphate, secondary ammonium phosphate, tertiary ammonium phosphate, primary sodium phosphate, and secondary sodium phosphate.

These phosphates are used as pH buffers. The amount used is preferably about 20 to 5% by weight based on the total solid content.
Examples of amino acids or water-soluble salts thereof include L-glutamic acid, L-aspartic acid, L-arani. Examples include L-glycine, L-glutamine, L-proline, y-aminolactic acid, lysine, leucine, cysteine, histidine, methionine, and their alkali metal salts.

These can prevent the deterioration of ferrocyanide as described above. The amount used is 10 to 10% of the total solid content.
It is about 5% by weight. In addition to the above components, in the present invention, p
Various organic or inorganic acids can be used as H regulators.

For example, these acids are phosphoric acid, tartaric acid, malic acid, malonic acid, acetic acid, pyrophosphoric acid, oxalic acid, and the like. The unfattening liquid of the present invention can be used not only for desensitizing a zinc oxide/resin dispersion photoconductive layer, but also as a dampening solution during lithographic printing.

When used as a fat-free treatment liquid, the concentration is 80-100.
%, and when using it as dampening water, dilute the above treatment liquid about 6 to 9 times and use it as dampening water. Examples and comparative examples are shown below. Example 1 Potassium ferrocyanide 52 L-glutamic acid 10 primary ammonium talate 10 secondary ammonium talate 10 tera water 500 After mixing and dissolving the ingredients, the pH was adjusted to 5 with citric acid.

Absorbent cotton was impregnated with the obtained desensitizing solution, and the photoconductive layer surface of a commercially available zinc oxide/resin dispersion electrophotographic photosensitive material having an image was treated to prepare a lithographic printing plate (hereinafter referred to as a master). When this was set in a lithographic printing machine and 300 forks were printed using the desensitizing liquid as dampening water, both the master and the resulting printed matter were clear and free of any stains. On the other hand, as Comparative Example 1, potassium ferrocyanide 5
evening, primary ammonium phosphate 10 evenings, secondary ammonium phosphate 20 evenings, ethylenediaminetetraacetic acid 0.5 evening,
A nonfatting liquid consisting of 10 parts citric acid and 500 parts water,
Comparative Example 2 was Fukameito Hijiri liquid consisting of 10 parts of potassium ferrocyanide, 10 parts of polyvinylsulfonic acid and 500 parts of water, and Comparative Example 3 was 10 parts of potassium ferrocyanide, 20 parts of sodium sulfite, 5 parts of citric acid and 500 parts of water.
An unfattening solution was prepared, and the unfattening treatment and printing were carried out in the same manner.

The above results are shown in the table below.

*Example 2 of soiling during printing on the 300 printer A nonfatting solution was prepared according to Example 1 using the same amount of L-aspartic acid in place of L-glutamic acid, and was subjected to nonfatting and printing, but the same amount The results were obtained.

Example 3 An insensitive oil was prepared according to Example 1 except that the same amount of L-alanine was used in place of L-glutamic acid, and the same result was obtained when it was subjected to insensitizing and printing.

Example 4 A desensitizing solution was prepared according to Example 1 except that the same amount of L-glycine was used in place of L-glutamic acid, and it was subjected to desensitization and printing, and similar results were obtained.

Example 5 A desensitizing solution was prepared in accordance with Example 1 except that the same amount of L-glutamine was used instead of L-glutamic acid, and the same result was obtained when the desensitizing solution was subjected to desensitizing and printing.

Example 6 A desensitizing liquid was prepared according to Example 1 except that L-proline was used instead of L-glutamic acid, and after desensitization, it was subjected to printing, and similar results were obtained.

Example 7 A desensitizing solution was prepared by using the same amount of L-glutamic acid monosodium salt in place of L-glutamic acid in Example 1, and after being subjected to the desensitizing treatment, it was used for printing, and similar results were obtained. It was done.

Example 8 A desensitizing liquid was prepared by using the same amount of y-aminolactic acid in place of L-glutamic acid in Example 1, and after desensitization treatment, it was subjected to printing, and similar results were obtained.

Claims (1)

[Claims] 1. A desensitizing liquid for lithographic printing whose main components are ferrocyanide, water-soluble phosphate, and amino acids or water-soluble salts thereof.