JPH07257061A - Desensitized processing liquid for offset printing - Google Patents

Abstract

PURPOSE:To prepare desensitized processing liquid for offset printing of good ink spread at the starting time of printing in which no printing stain is generated when an automatic desensitized processing device is used or processing liquid is applied by hand by improving the desensitized film forming speed making 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 a metallic nickel salt as main components. A cyanogen compound causing a public pollution is not contained in the liquid, and the liquid is provided with the 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, hand-etching by hand-coating the desensitizing solution with cotton wool or sponge on the surface of the plate, the desensitizing solution 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 stains of printed materials do not occur due to the processing of the automated desensitizing processing device, but when the processing liquid is applied to the plate surface by hand or the automated desensitizing processing is performed. If the decolorization device is used twice to completely eliminate the background stains on the printed matter, the desensitizing process is applied to the image area, making it difficult for ink to adhere to the image area. It had a drawback that it caused the phenomenon that it was difficult to ride.

[0007]

DISCLOSURE OF THE INVENTION The present invention is to improve the slow film-forming rate of desensitization in a cyan-free type processing solution such as phytic acid or a salt thereof, and is easy to manufacture and 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 a metal nickel salt in a desensitizing solution.
Due to these synergistic effects, excellent desensitizing ability and good ink adhesion to the image area can be provided.

The phytic acid or salt thereof used in the present invention means inositol hexaphosphate ester or salt thereof, and the salt means metal 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 thus are used as a main agent of a desensitizing treatment liquid.

The alkaline colloidal silicic acid having a particle size of less than 10 nm is 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 to 11. Refers to a range. 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. Therefore, the particle size is preferably less than 10 nm. Colloidal silicic acid is generally p
When H is alkaline, it is in a stable state and the pH is 9
If it deviates from the range of 11 to 11, the colloidal particles are likely to be in an unstable state such as being precipitated. 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.

The metal nickel salt is a metal compound having a positive divalent valence and is required to be water-soluble. Specifically, nickel sulfate, nickel chloride, nickel carbonate, nickel acetate, nickel bromide, Examples include nickel iodide.
Of these, nickel sulfate is particularly preferable.
It is considered that these metallic nickel salts have a function of promoting the reaction of phytic acid or a salt thereof with zinc oxide to form a chelate compound.

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.
To 1 part by weight, the metallic nickel salt is 1 to 100 parts by weight, and 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 it is preferable to add phytic acid or a salt thereof to water and then completely dissolve the metal nickel salt, and then add the alkaline colloidal silicic acid. Good to do.

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 Alkali colloidal silicic acid (pH 10.1, particle size 7-9 nm, solidity ratio 30%) 3 g Nickel sulfate 20 g Water was added 1000 g, and these were well stirred and dissolved to desensitize them. It was a liquid.

Example 2 Phytic acid 50 g Alkaline colloidal silicic acid (pH 9.2, particle size 4 to 6 nm, solidity ratio 20%) 0.2 g Nickel sulfate 5 g Glycerin 10 g Water was added to 1000 g, and these were well stirred and dissolved. To obtain a desensitizing treatment liquid.

Example 3 Phytic acid 10 g Alkaline colloidal silicic acid (pH 9.5, particle size 7-9 nm, solidity ratio 30%) 1 g Nickel chloride 50 g Water was added 1000 g Stir well to dissolve and desensitize It was used as a treatment liquid.

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 for nickel sulfate was used.

An image was formed on an electrophotographic offset master (LOM-IIB manufactured by Mitsubishi Paper Mills) using a plate making machine (EP-31V manufactured by Mitsubishi Paper Mills) to obtain an offset printing plate. An automatic desensitization processing apparatus (etching converter OH- manufactured by Mitsubishi Paper Mills) was prepared using the processing solutions of Examples 1 to 3 and Comparative Examples 1 and 2 above.
11) was used to perform desensitizing treatment. The dampening water used was the same treatment solution diluted with water 15 times. Table 1 shows the results of printing these with a small offset printing machine (Toko Model 810 manufactured by Tokyo Airlines Keiki Co., Ltd.).

[0024]

[Table 1]

^{* 1} good for those with no background stains and plate jumps ^{* 2} good for those with 5 or less printed sheets on which ink is completely applied from the start of printing, and good for 10 or more

As described above, in Examples 1 to 3, even when 4000 to 5000 sheets were printed, stains and print skips did not occur.
Also, the ink coverage at the beginning of printing was good, but Comparative Example 1
In Nos. 2 and 3, the occurrence of stains and skipped printing was observed, and there were also cases in which the ink transfer at the beginning of printing was defective.

[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 (2)

[Claims] 1. A desensitizing treatment liquid for offset printing, comprising phytic acid or a salt thereof, an alkaline colloidal silicic acid having a particle size of less than 10 nm, and a metal nickel salt. 2. The desensitizing treatment liquid according to claim 1, wherein the metal nickel salt is nickel sulfate.