JPS627597A - Damping water for printing - Google Patents

Abstract

PURPOSE:To enable damping water to be stably used for printing, by adding a phytic acid salt and a hexametaphosphoric acid salt to damping water. CONSTITUTION:The damping water comprises at least a phytic acid salt, preferably in a concentration of 1-50g/l, and a hexametaphosphoric acid salt, preferably in a concentration of 0.05-20g/l. The phytic acid salt may be an alkali metal salt, ammonium salt, an amine salt or the like of phytic acid, whereas the hexametaphosphoric acid salt is an alkali metal salt, ammonium salt or the like of hexametaphosphoric acid. Further, a pH adjustor, a buffering agent or the like may be added to the damping water. The hexametaphosphoric acid salt rapidly eacts with calcium ions to prevent the latter from combining with other constituents of the damping water, thereby preventing contamination, emulsification and degradation of durability in repeated printing.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to electrophotographic offset masters, silver salt printing plates, 2
Concerning dampening water used for printing 8th edition.

[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, an etching process converts the non-image areas from lipophilic to hydrophilic 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 writing directly on a master using a lipophilic writing instrument or a type to create a printing plate, and a method of using an electrophotographic transfer method. 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 been used conventionally. Although it is unstable to heat and light and has drawbacks such as a decrease in etching power, generation of precipitation, and pollution properties even with natural aging, it can be said that the overall printing characteristics are stable.

[Problem that the invention seeks to solve]

However, in some cases, it may not be possible to print both colors with the yellow blood salt type. That is, when printing with the quick-drying color ink conventionally used in the 28th plate, staining, roller stripping, emulsification, etc. of the printed matter are likely to occur, making it impractical. Furthermore, acid-free paper has recently been increasingly used for printing paper. Acid-free paper is very similar in appearance and feel to conventional acid-based paper and is therefore easily distinguishable. As a result, there are some confusing cases where you unknowingly print and have to clean up the stains.

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 spots are likely to occur, printing durability is likely to be poor, roller stripping is likely to occur, and printing This can cause the machine to rust, etc.

[Means for Solving the Problem] However, as a result of detailed and rigorous research and logical considerations, the inventors of the present invention have determined that in each case, the cause of the above trouble is calcium carbonate contained in the ink and neutral paper. I came to find out something. In other words, calcium carbonate is dissolved into dampening water during printing, and a hydrophilic reaction product of calcium ions and dampening water components is produced. When this is deposited on the roller surface of the printing plate, it becomes a roller strip and the master If it adheres to the toner image area, printing durability will be poor.

Therefore, the present inventors investigated methods to prevent calcilum carbonate from eluting, methods to prevent it from reacting with dampening water components even if it elutes, methods to prevent hydrophilic reactants from being generated even if the calcium carbonate reacts, and finally found that phytate The present invention was achieved by discovering that a dampening solution that can be stably used in any case can be obtained when a hexametaphosphate is used in combination with a hexametaphosphate.

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 the dampening solution components. The addition of hexametaphosphate did not impair the inherent properties of the fountain solution at all.

That is, the present invention is a printing plate dampening solution containing at least phytate and hexametaphosphate. Phytate is 1-50 s/l, hexametaphosphate is (LO
It can be used at a concentration of 5 to 20 s/l.

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

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

Furthermore, the dampening solution of the present invention can also contain a pH adjusting agent and a pH buffering agent. 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, propio/acid, oxalic acid, malonic acid, succinic acid, curtaric acid, and maleic acid. Acids, phthalic acid, citraconic acid, itaconic acid, fumaric acid, tricarnolylic acid, glycolic acid, propio/acid, thioglycolic acid, linnoic acid, citric acid, gluconic acid, pyruvic acid, gelcholic acid, salicylic acid, adipic acid , hydroacrylic acid, glyceric acid, I)-)luenesulfonic acid, and the like. These salts include alkali metal salts, ammonium salts,
There are amine salts, etc.

It is also preferred for controlling the reaction of a chelating agent such as EDTA-2Na with the added m4 calcium ion.

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 No. 60-23099, since this makes it difficult to cause stains.

In addition, as wetting agents and wetting agents, ethylene glycol, carbon glycol, triethylene glycol, I-lyethylene glycol, glycerin, gum arabic, calxexymethyl cellulose, acrylic polymer, methanol, ethanol, isopropyl alcohol, triethylene glycol, Ethanolamine etc. can be added.

Furthermore, as preservatives, salicylic acid, phenol, butyl phenoloxybenzoate, sodium dehydroacetate, 4-
Isothiazolone-3-one compounds and the like can be added. 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 aOg Sodium hexametaphosphate 4.0g water
100 (10°) Using dampening water with this prescription,
The master, which was plate-made and etched using the Fu±Film ELP system, was printed on neutral paper. It was possible to print clearly from the beginning of printing to 10,000 sheets 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 was no occurrence of stains, poor printing durability, roller stripping, water loss, 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 be used for printing 23 plates.

Comparative Example 1 Yellow Blood Salt 4.09 Monosodium Phosphate 12.0° Water
100α09 When printing was carried out under exactly 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 1α09 water
100α09 When printing was carried out under exactly the same conditions as in Example 1, printing durability failure occurred after 7000 sheets. So I replaced it with a new master and printed it again, but after 5,000 copies, it became a failed print.

Example 2 Phytic acid aOg sodium hexametaphosphate 1αOg gluconic acid
5.0g water
When printing was carried out under exactly the same conditions as in Example 1 except that the 100αOg ink was replaced with DICli'' gloss ultramarine blue, there was no occurrence of background smudge or printing durability defects for more than 30,000 copies.

Example 6 Potassium phytate 12.0.

Sodium hexametaphosphate 20.0゜phosphoric acid
6. OgEDTA-2Na
α49 Glycerin aOg? Riamido-epichlorohydrin P phosphorus resin 0.1g Ethanol 5.0g 4-thiazolone-6-one compound 0.02° Water 100αoz When printing was carried out under exactly the same conditions as in Example 1, more than 50,000 sheets were completely blank. There was no occurrence of stains or poor printing durability. In addition, the halftone gradation was well reproduced, and water/ink adjustment was extremely easy. -During continuous use for several months, stains, poor printing durability, etc.
There were no roller strips, water damage, mold, or rust. There was no problem in using colored ink and 23rd edition.

〔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.

Representative Patent Attorney (8107) Kiyoshi Sasaki (and 2 others)
given name)

Claims (1)

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