JPS61181695A - Desensitizing treatment liquid for lithographic printing plate - Google Patents

Abstract

PURPOSE:To permit printing free of ground staining by one-time passage of processor as well as to obtain quick and complete desensitizing effect with good compatibility with lithographic printing plate by adding a water-swelling inorganic compound fine particles to a desensitizing treatment liquid. CONSTITUTION:A water-swelling inorganic compound, selected from natural ores (e.g., smectite group of montmorillonite, etc., vermiculite, etc.), and water- swelling synthetic fluoro-mica group including inorganic compounds, wherein OH groups of crystals are partly substituted with fluorine, water-swelling synthetic fluoro-vermiculite group, water-swelling synthetic fluoro-smectite group, etc., where the water-swelling synthetic fluoro-mica group is particularly recommendable, having an average grain size of 1mum or less on dry basis, is added to a desensitizing treatment liquid in a range of 0.5-50g/l preferably. The treatment liquid may contain various desensitizing components or additives, such as inorganic or organic acids or their salts, basic compounds, metal salts, chelating agents, wetting agents, etc. By using the desensitizing treatment liquid, printing free of ground staining can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Application Field The present invention relates to a processing liquid used for desensitizing various lithographic printing plates.

(J3) Prior art The plate conventionally used as a lithographic printing original plate has a photocurable photosensitive rtII film on a metal support such as aluminum.
A PS plate is provided, which forms an image by dissolving and removing the resin in the unexposed areas, and has a photosensitive layer dispersed in a photoconductive fine-particle resin binder such as zinc oxide on a conductive support. An electrophotographic plate in which an image is formed using an electrophotographic method, an image-receiving layer provided on a base paper, and a direct drawing plate in which an image is formed by xerography or υ type printing written with lipophilic ink on the base paper, and a support. A silver salt photographic plate having a silver halide emulsion layer provided thereon is mentioned. Among these, plates other than silver salt photographic plates are desensitized to make the non-image areas hydrophilic, but since the chemical properties of the non-image areas are different, a desensitizing agent suitable for each is used. As a result, a plate-specific process 71 must be used, and no satisfactory desensitizing liquid and dampening liquid that can be shared with each plate material has been found.

In addition, regarding the desensitizing effect of the processing liquid, in hand etching, which is performed by soaking the processing liquid in absorbent cotton or sponge and applying it to the surface of the plate by hand, the processing liquid is sufficiently applied to the plate surface, so the desensitization effect is reduced. The difference in processing capacity was not so noticeable, but the desensitization effect was greater when the plate was immersed in a processing solution and was squeezed with a roll using automated desensitization processing equipment (e.g. Mitsubishi Paper Etching Converter 0H-11). Differences were observed in the print quality, and in some cases, printing stains were caused.

(Q. Purpose of the Invention The present invention was made in order to eliminate the above-mentioned drawbacks. It has good compatibility with lithographic printing plates, can quickly and completely desensitize it, and can be passed through a processor once. Desensitization treatment for lithographic printing plates that enables printing without background smearingg,
It's all about providing.

(To) Structure of the Invention As a result of intensive studies in order to solve these problems, the present inventor has included water-swellable inorganic compound fine particles in the desensitization treatment liquid, and if the desensitization treatment is performed using this, It was discovered that a lithographic printing plate that gives printed matter without background smearing can be obtained, and based on this detailed study, the present invention was completed.

The water-swellable inorganic compounds referred to in the present invention include hectorite,
Natural ores such as smectite group and vermiculite group such as montmorillonite, water-swellable synthetic fluorinated mica group containing inorganic compounds in which some of the OH groups in the crystals of these ores are replaced with fluorine, water-swellable synthetic fluorinated vermiculite group, It refers to synthetic inorganic compounds such as water-swellable synthetic fluorosmetite group, and water-warmable synthetic fluoromica group is particularly preferred.

Further, the average particle diameter of these water-swellable inorganic compounds in a dry state is preferably 1 μm or less.

The desensitizing solution for lithographic printing plates of the present invention can contain various desensitizing components or additives in addition to the water-swellable inorganic compound fine particles described above, examples of which include ferricyan salt, Hexacyanoiron salt of ferrocyanate, phosphoric acid, boric acid, hydrochloric acid, inosit hexaphosphoric acid, tannins, gluconic acid, succinic acid, citric acid and other inorganic and organic acids and their salts, sodium hydroxide, hydroxide Basic compounds such as potassium, triethanolamine and ammonia, metal salts such as alum, ferric chloride and ferric chloride, chelating agents such as ethylenediaminetetraacetic acid, nitrilotriacetic acid, diaminoglobanoltetraacetic acid and its salts. , 2-/' lovanol, ethanediol, sodium alginate, carboxymethyl cellulose, polyvinyl alcohol, polyvinylpyrrolidone, gum arabic, and the like, but are not limited thereto.

The amount of water-swellable inorganic compound fine particles contained in the treatment material of the present invention is preferably in the range of 0.5 t/l to 50 ηl.

Water-swellable inorganic compound fine particles less than 0.5 f/l°
In this case, a sufficient hydrophilic film is not formed and there is no scumming prevention effect. On the other hand, if it exceeds 50 f/, the desensitization becomes strong, printing start-up is poor, ink receptivity is deteriorated, and the image becomes blurred, which is not preferable.

When using this treatment solution, the pH of the solution should be 4.0 to 5.
A range of 0 is desirable. Further, this treatment liquid can be diluted 4 to 10 times with water and used as a humidifying liquid.

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

Example 1 The mixture was thoroughly stirred and the pH was adjusted to 4.0 with potassium hydroxide.

Example 2 was sufficiently dissolved and the pH was adjusted to 4.0 with potassium hydroxide.

Comparative example 1 The mixture was thoroughly stirred and the pH was adjusted to 4.0 with potassium hydroxide.

Comparative example 2 The mixture was thoroughly stirred and the pH was adjusted to 4.0 with potassium hydroxide.

On the other hand, an image was formed using a commercially available electrophotographic offset master according to a conventional method, and then desensitization treatment was performed once using an etching converter 0H-11 (manufactured by Mitsubishi Paper Industries) using each treatment solution. In addition, the hot water used was diluted in a volume ratio of 1 part of the same treatment solution to 9 parts of tap water.

The table shows the results of printing with a small offset printing machine (Toupe Model 810, manufactured by Tokyo Aircraft Instruments).

As mentioned above, in both Examples 1 and 2, from the first printed page to the
After printing more than 1,000 copies, prints were obtained that were free of background stains and had good visibility of halftone dots. On the other hand, the comparative example has a weak desensitizing effect of 10
It was impossible to print more than one sheet.

Claims (1)

[Claims] A desensitizing liquid for lithographic printing plates, characterized by containing fine particles of a water-swellable inorganic compound.