JPH0527558B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a dampening solution used for printing electrophotographic offset masters, silver salt printing plates, and PS plates.

[Conventional technology]

In an electrophotographic offset master, a lipophilic image is first obtained by an electrophotographic method on a photosensitive layer formed by coating a photoconductive fine powder such as zinc oxide on a support together with an electrically insulating resin. Next, the non-image area is converted from lipophilic to hydrophilic by etching treatment to form a printing plate. In order to maintain the initial hydrophilicity in the printing plate, the etching solution is usually diluted several times and used as a dampening solution.

There is also a method of directly writing on a master using a lipophilic writing instrument or type to create a printing plate, and a method of using electrophotographic copying. In this case, use the same dampening water.

Many dampening solution formulations have been proposed so far. If they are classified according to their main components, they can be divided into yellow blood salt type and non-yellow blood salt type. Yellow blood salt systems have traditionally been used. Although it is unstable to heat and light and has drawbacks such as a decrease in etching power, generation of precipitation, and pollution over natural aging, it can be said that the overall printing characteristics are stable.

[Problem that the invention seeks to solve]

However, there are cases where it is impossible to print with the yellow blood salt type. That is, when printing with quick-drying colored inks conventionally used for PS plates, the printed matter tends to become smudged, roller striped, emulsified, etc., and is not practical. Furthermore, acid-free paper has been increasingly used for printing paper recently. Acid-free paper is very similar in appearance and feel to conventional acid-based paper and is therefore difficult to distinguish. For this reason, there are cases where printing without realizing it causes stains that cannot be removed, which can be confusing.
It is well known that increasing the number of times of etching or lowering the pH of the dampening water does not provide a fundamental solution.

On the other hand, a typical example of a non-yellow blood salt type is a phytate type. However, phytate alone has a weak hydrophilicity and is problematic for use as an etching solution. However, if this is diluted and used as dampening water, printing may be possible to some extent despite some problems. The problems are that the printing condition is unstable, and if the amount of water and ink is not constantly adjusted, stains and water loss are likely to occur, and printing durability is likely to occur.
They tend to cause roller stripping, rust the printing press, etc.

[Means to solve the problem]

However, as a result of detailed and rigorous research and logical considerations, the present inventors have discovered that in each case, the cause of the above-mentioned troubles is calcium carbonate contained in the ink and neutral paper. In other words, calcium carbonate dissolves into dampening water during printing,
A hydrophilic reaction product of calcium ions and dampening water components is generated, and if it accumulates on the roller surface of the printing plate, it will become a roller strip, and if it adheres to the toner image area of the master, it will result in poor printing durability. .
Therefore, the present inventors investigated methods to prevent calcium carbonate from eluting, methods to prevent calcium carbonate from reacting with dampening solution components even if eluted, or methods to prevent hydrophilic reactants from being generated even if calcium carbonate reacts, and finally found that phytate When used together with hexametaphosphate,
It was discovered that a dampening solution that can be stably used can be obtained in any case, and the present invention was achieved.

Although the reaction mechanism of hexametaphosphate with calcium ions has not been completely clarified, it is thought that hexametaphosphate reacts quickly with the eluted calcium ions and prevents them from binding with dampening solution components. The addition of hexametaphosphate did not impair the inherent properties of the fountain solution.

That is, the present invention is a printing plate dampening solution containing at least phytate and hexametaphosphate. Phytate can be used at a concentration of 1 to 50 g/1, and hexametaphosphate can be used at a concentration of 0.05 to 20 g/1.

Materials that can be used in the present invention will be explained below.

Examples of the phytic acid salts used in the present invention include alkali metal salts, ammonium salts, and amine salts of phytic acid, and examples of hexametaphosphates include alkali metal salts, ammonium salts, and the like of hexametaphosphoric acid.

Furthermore, the dampening solution of the present invention can also contain a PH regulator and a PH buffer. They use well-known inorganic acids, organic acids, and their salts alone or in combination. Inorganic acids include phosphoric acid, sulfuric acid, hydrochloric acid, and nitric acid, and organic acids include formic acid, acetic acid, butyric acid, valeric acid, lactic acid, tartaric acid, propionic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, and maleic acid. , phthalic acid, citraconic acid, itaconic acid, fumaric acid, tricarballylic acid, glycolic acid, propionic acid, thioglycolic acid, malic acid, citric acid, gluconic acid, pyruvic acid, glucolic acid, salicylic acid, adipic acid,
These include hydroacrylic acid, glyceric acid, and p-toluenesulfonic acid. These salts include alkali metal salts, ammonium salts, amine salts, and the like.

It is also preferable to add a chelating agent such as EDTA-2Na to control the reaction with calcium ions.

Furthermore, in the present invention, it is also desirable to add a water-soluble cationic polymer and a low molecular electrolyte compound as disclosed in JP-A-60-23099, since this makes it difficult to cause stains.

In addition, as wetting agents and wetting agents, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin,
Gum arabic, carboxymethylcellulose, acrylic polymers, methanol, ethanol, iso and normal propyl alcohol, triethanolamine, etc. can be added.

Furthermore, salicylic acid, phenol, butyl phenol-parabenzoate, sodium dehydroacetate, 4-isothiazolone-3-one compound, etc. can be added as preservatives. In addition, sodium nitrite, dicyclohexylammonium nitrite, etc. can also be added as a rust preventive agent.

Examples of the present invention are shown below. However, the present invention is not limited by this.

Example 1 Sodium phytate 8.0g Sodium hexametaphosphate 4.0g Water 1000.0g Fujifilm
The master, which was plate-made and etched using the ELP system, was printed on acid-free paper. From the beginning of printing to 10,000 sheets, clear printing was possible without any stains or poor printing durability. When I continued printing while replenishing this dampening water, I was able to print a total of 60,000 sheets. There were no occurrences of stains, poor printing durability, roller strips, water damage, poor inking, etc. during printing. Furthermore, there was no problem in printing on ordinary acidic paper. I was also able to print on colored paper, art paper, and book paper without any problems. When this liquid was diluted 20 times, it could also be used for printing PS plates.

Comparative Example 1 Yellow Blood Salt 4.0g Monosodium Phosphate 12.0g Water 1000.0g When printing was carried out under the same conditions as in Example 1, scumming occurred after 500 sheets. So, when I changed to a new master and printed again, scumming occurred from the beginning of printing.

Comparative Example 2 Sodium phytate 10.0g Water 1000.0g When printing was carried out under the same conditions as in Example 1, printing durability failure occurred after 7000 sheets. So when I changed to a new master and printed again,
After printing 5,000 copies, the printing became defective.

Example 2 Phytic acid 8.0 g Sodium hexametaphosphate 10.0 g Gluconic acid 5.0 g Water 1000.0 g Printing was carried out under the same conditions as in Example 1 except that the ink was replaced with DICF gloss ultramarine, and more than 30,000 sheets were printed. There was no occurrence of background stains or poor printing durability.

Example 3 Potassium phytate 12.0g Sodium hexametaphosphate 20.0g Malic acid 6.0g EDTA-2Na 0.4g Glycerin 8.0g Polyamide-epichlorohydrin resin 0.1g Ethanol 3.0g 4-thiazolone-3-one compound 0.02g Water 1000.0g Example 1 When printing was carried out under the same conditions, more than 50,000 copies were printed without any background smudges or poor printing durability. In addition, the halftone gradation was well reproduced and water/ink adjustment was extremely easy. During one month of continuous use, there were no stains, poor printing durability, roller strips, water damage, mold, rust, etc. There was no problem with using colored ink and PS version.

〔Effect of the invention〕

When using the printing fountain solution of the present invention, a large number of printed matter can be obtained without staining or poor printing durability.

Claims (1)

[Claims] 1. A printing fountain solution containing at least phytate and hexametaphosphate.