JPH07257060A - Desensitized processing liquid for offset printing - Google Patents

Abstract

PURPOSE:To prepare desensitized processing liquid for offset printing which generates no surface stain just only in one processing of an automatic desensitized processing device and produces good ink spread by improving the desensitized film manufacturing speed causing problems in the cyanogen-free type processing liquid. CONSTITUTION:Processing liquid is composed of phytic acid or its salt, alkaline colloid silicic acid of particle diameter less than 10nm and cyclodextrin as main components. No problems of public pollution are caused in the processing liquid, and the liquid is of superior desensitized processing capability and can be used as the desensitized processing liquid and wetting water for offset printing of good ink spread at the starting time of printing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a desensitizing treatment liquid for offset printing, and more particularly, the present invention relates to a desensitizing treatment liquid for printing an offset printing plate by an electrophotographic method or an offset printing plate by a direct drawing method. Regarding Furthermore, the present invention relates to a cyan-free desensitizing treatment liquid for offset printing, which does not contain any cyanide compound.

[0002]

2. Description of the Related Art Generally, in offset printing, a plate having an oleophilic image portion and a hydrophilic non-image portion is used. However, the non-image portion as it is has insufficient hydrophilicity and is not subjected to desensitizing treatment. If you print, ink will adhere to the non-image area,
It is not possible to obtain a printed product without stains. Therefore,
Before printing, it is necessary to desensitize (etch) the non-image area of the master in advance.

For this purpose, the processing liquid used for the electrophotographic offset printing plate and the direct drawing offset printing plate has been a cyan type having a hexacyanoiron salt such as a ferrocyan salt or a ferricyan salt as a main component. It was In particular, the treatment liquid containing a hexacyanoiron salt as a main component has a wide latitude depending on the treatment conditions. For example, even if the treatment liquid is passed through once or twice with an automatic desensitizing treatment device (etching device), the treatment liquid can be handled manually. Even when applied to the plate material (hand etching), a good printed matter could be obtained. However, the hexacyano iron salt may be decomposed by heat or light to generate free cyan, and the desensitizing solution mainly composed of the hexacyano iron salt has a problem in pollution.

On the other hand, as a method for solving such a problem, a cyan-free type desensitizing solution containing phytic acid (inosit hexaphosphate) or its salt as a main component has been proposed, but it is still insufficient. At present, satisfactory quality has not been completed.

A disadvantage of using phytic acid or a salt thereof as a main desensitizing agent is that the desensitizing film formation rate is slow. Specifically, in hand etching performed by mixing the desensitizing treatment liquid with absorbent cotton or sponge and applying it by hand on the surface of the plate, the desensitizing treatment liquid is sufficiently applied to the plate surface. The difference in the oil processing capacity is not so noticeable, but an automated desensitizing processing device (for example, Mitsubishi Papermaking Etching Converter OH-1
In the processing by 1) etc., there was a case where a difference in the performance of the desensitizing treatment from that of the cyan type was observed, and the printed matter was sometimes stained.

As a method for solving the above problems, JP-A-59-207290, JP-A-61-215089,
JP-A-61-230991 discloses a combination of phytic acid or a salt thereof with acidic colloidal silicic acid having a particle size of 40 nm or less. The film formation speed of these is similar to that of the cyan type, and the background of the printed matter does not get smeared by the processing of the automated desensitizing processing device, but when the processing liquid is applied to the plate surface by hand or the automated desensitization In the case where the oiling processing device performs the processing twice to completely eliminate the background stain of the printed matter, the desensitization processing is performed even on the image portion,
Ink has difficulty in adhering to the image area, and there is a drawback that the ink does not easily get on at the beginning of printing.

[0007]

DISCLOSURE OF THE INVENTION The present invention is intended to improve the slow film-forming rate of desensitization which is contained in a cyan-free type processing solution such as phytic acid or a salt thereof, and is easy to manufacture. An object of the present invention is to provide a desensitizing treatment liquid for offset printing, which is stable in quality, has no stain on the printed matter in one pass of an automated desensitizing treatment device, and has good ink coverage.

[0008]

As a result of intensive studies to solve the above problems, the present inventors have found the following method and completed the present invention.

That is, the present invention is a combination of three components of phytic acid or a salt thereof, an alkaline colloidal silicic acid having a particle size of less than 10 nm, and cyclodextrin in a desensitizing solution, which is excellent due to the synergistic effect of these components. It is also possible to provide desensitizing ability and good ink adhesion in the image area.

The phytic acid or salt thereof used in the present invention means inositol hexaphosphate ester or salt thereof, and the salt means silver salt of sodium, potassium, calcium, magnesium or the like, or mixed binding salt thereof. These phytic acids or salts thereof have a strong chelating action with a metal and form a desensitizing product with a metal salt on the surface of an offset printing plate, and are therefore used as a main agent of a desensitizing treatment liquid.

The alkaline colloidal silicic acid having a particle size of less than 10 nm as used in the present invention means a colloidal solution in which ultrafine particles of silicic acid anhydride are dispersed in water with water as a dispersion medium, and the hydrogen ion concentration (pH) of the solution is 9 or more. It refers to the range of 11. When the particle size is larger than 10 nm, the desensitizing film formation rate is increased and the desensitizing ability is increased, but on the other hand, the phenomenon that the ink is hard to adhere to the image area occurs. Generally, colloidal silicic acid is in a stable state when the pH is alkaline, and when the pH is out of the range of 9 to 11, colloidal particles are likely to be unstable such as precipitation. This alkaline colloidal silicic acid having a particle size of less than 10 nm is used together with phytic acid or its salt as the main ingredient, and has a function as an auxiliary agent for imparting a desensitizing ability.

Cyclodextrin is a non-reducing maltooligosaccharide in which 6 to 12 glucose molecules are cyclically linked by α-1,4-glucoside bonds, and it was made to act on starch by the oxygen of microorganisms. It came to be produced on an industrial scale. The main products from starch are α, β, γ consisting of 6, 7 and 8 glucose
Each has a cyclodextrin. Since cyclodextrin has a unique molecular structure called a molecular cavity, various substances are taken into the molecular cavity. Therefore, functions and applications utilizing this characteristic are being developed. It is considered that when cyclodextrin is used in the desensitizing solution for offset printing, it has a function of incorporating phytic acid or its salt and alkaline colloidal silicic acid having a particle size of less than 10 nm to enhance the desensitizing ability. Furthermore, since it has solubility in water, it is considered that it has a wetting action on the offset printing plate.

When the amount of the above-mentioned substance constituting the treatment liquid of the present invention is small, the desensitizing ability becomes insufficient, and when it is too large, ink-carrying failure occurs. Therefore, phytic acid or its content in 1000 parts by weight of the treatment liquid is insufficient. 5 to 100 parts by weight of salt, more preferably 10 to 50 parts by weight, 0.01 to 5 parts by weight of alkaline colloidal silicic acid having a particle size of less than 10 nm, more preferably 0.03.
~ 1 part by weight, cyclodextrin 1-100 parts by weight,
It is more preferably 5 to 50 parts by weight.

The treatment solution of the present invention is not particularly limited in the order of dissolution, but preferably, cyclodextrin is completely dissolved after adding phytic acid or a salt thereof to water,
After that, it is better to add alkaline colloidal silicic acid.

In the treatment liquid of the present invention, in addition to the above components, p
Basic substances such as organic and inorganic acids, sodium hydroxide, and ammonia water are used as H regulators, ethylene glycol, glycerin, carboxymethyl cellulose, alginate, gum arabic, etc. are used as wetting agents, and E is used as an anticorrosive agent.
DTA, amines and phosphoric acids can be used by adding an appropriate amount of salicylic acid, bromonitroalcohol, triethylenetetramine hexaacetate or the like as a preservative.

When printing is carried out using the treatment liquid of the present invention, the treatment liquid can be diluted 5 to 20 times with water and used as fountain solution.

[0017]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited thereto.

Example 1 Phytic acid 30 g Alkaline colloidal silicic acid (pH 10.1, particle size 7 to 9 nm, solidity ratio 30%) 2 g α-Cyclodextrin 30 g Water was added to 1000 g, and these were well stirred to dissolve insensitive oil. It was used as a chemical treatment liquid.

Example 2 Phytic acid 10 g Alkaline colloidal silicic acid (pH 10.1, particle size 7 to 9 nm, solidity ratio 30%) 3 g β-cyclodextrin 50 g Glycerin 30 g Water was added to 1000 g, and these were well stirred to dissolve.

Example 3 Phytic acid 50 g Alkaline colloidal silicic acid (pH 9.2, particle size 4 to 6 nm, solidity rate 20%) 0.2 g γ-Cyclodextrin 5 g Ethylene glycol 30 g Water was added to 1000 g

Comparative Example 1 The same as Example 1 except for the alkaline colloidal silica was used.

Comparative Example 2 The same as Example 1 except that α-cyclodextrin was omitted was used.

An image was formed on an electrophotographic offset master (ZM-5 made by Mitsubishi Paper Mills) by a plate making machine (ZM-33S made by Mitsubishi Paper Mills) to obtain an offset printing plate. An automatic desensitizing treatment device (etching converter OH-1 manufactured by Mitsubishi Paper Mills) was prepared using the treatment liquids of Examples 1 to 3 and Comparative Examples 1 and 2 described above.
Desensitizing treatment was carried out using 1). The dampening water used was the same treatment solution diluted with water 15 times. These are small offset printing machines (Toko Model 8 manufactured by Tokyo Airlines Keiki Co., Ltd.)
The results of printing in 10) are shown in Table 1.

[0024]

[Table 1]

(Note) ^{* 1} Good without scumming and plate skipping ^{* 2} Good with prints of 5 or less on which ink is completely applied from the start of printing, and bad with 10 or more

As described above, in Examples 1 to 3, 4000 to
Even after printing 5,000 sheets, there was no stain or print skip, and the ink coverage at the beginning of printing was good, but in Comparative Examples 1 and 2, the occurrence of stains and the ink coverage at the beginning of printing were observed. It was

[0027]

INDUSTRIAL APPLICABILITY The present invention provides a desensitizing treatment liquid for offset printing and a fountain solution which does not contain a cyanide compound which is a problem in terms of pollution, has an excellent desensitizing treatment ability, and has good ink transfer at the beginning of printing. can do.

Claims (1)

[Claims] 1. A desensitizing treatment liquid for offset printing, comprising phytic acid or a salt thereof, alkaline colloidal silicic acid having a particle size of less than 10 nm, and cyclodextrin.