JPH043918B2 - - Google Patents

Description

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

[Prior Art] An electrophotographic offset master first obtains a lipophilic image 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 area 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 are also methods of writing directly on the master using a lipophilic writing instrument or type to create a printing plate, and methods of using electrophotography. 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.

[Problems to be Solved by the Invention] However, there are cases where it is impossible to print with the yellow blood salt system. That is, when printing with quick-drying color 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 become roller strips, etc.

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, and a hydrophilic reaction product of calcium ions and dampening water components is produced. If this deposits on the roller surface of the printing press, it becomes a roller strip, and the master's If it adheres to the toner image area, printing durability will be poor. Furthermore, the eluted calcium carbonate increases the pH of the dampening solution,
It inhibits the hydrophilic reaction and causes stains.

[Means for Solving the Problems] Therefore, the present inventors proposed a method in which calcium carbonate is not eluted, a method in which calcium carbonate is not reacted with the dampening water component even if it is eluted, or a method in which a hydrophilic reactant is not generated even if it is reacted. As a result of searching for a method that would not increase the pH, they discovered that when yellow blood salt and phytate were used together in a specific amount, a dampening solution that could be stably used in any case was obtained. I reached it. Although the effects of each have not yet been fully elucidated, the main hydrophilic reaction is carried out by the yellow blood salt, and a small amount of phytate causes a mild inking reaction, making the entire surface of the master less likely to get dirty. It is thought that the For this reason, stains that occur when yellow blood salts are used alone do not occur, and it is thought that the problems that occur when phytate salts are used alone do not occur.

In the present invention, inorganic or organic acids or their salts as described later can be added as PH regulators or PH buffers, but these are also considered to act to efficiently promote the reaction. .

The proposal to use yellow blood salt and phytate together was made by Tokkosho.
45-24609 and JP-A No. 54-10003, these were made to improve the performance as an etching solution. It seems that the two were used together to compensate for their inferiority due to their inferior strength. Within the range of the addition amount of yellow blood salt of the present invention, printing can be performed without any problem under normal printing conditions such as acidic paper and black ink (of course, background smear occurs with color ink and neutral paper). However, if phytic acid is used alone within the range of addition amount, background smear will occur even under normal printing conditions. The reason for this is presumed to be that the hydrophilization reaction cannot occur within this addition amount range. Only when yellow blood salt and phytic acid are used in combination, it becomes possible to print colored inks or neutral paper using the mechanism described above.

That is, the present invention uses at least 1 to 10 yellow blood salts.
g/, phytic acid or its salt 0.1 to 2 g/
It is a printing dampening water containing PH of 3 to 7.

In the present invention, it is possible to further add a PH regulator, a PH buffer, a wetting agent, a wetting agent, a rust preventive, a rust preventive, and the like.

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

Yellow blood salt is represented by the general formula M ₄ [Fe(CN) ₆ ] (where M is Li, Na, K, NH ₄ , Rb, Cs). In particular, Na and K are extremely preferable in terms of performance and cost.

Phytate is an alkali metal salt of phytic acid,
There are ammonium salts, amine salts, etc.

Inorganic or organic acids or salts thereof can be used as PH regulators and PH buffers, and they can be used alone or in combination. For example, inorganic acids include phosphoric acid, sulfuric acid, hydrochloric acid, and nitric acid; organic acids include formic acid, acetic acid, butyric acid, valeric acid, lactic acid, tartaric acid, and propionic acid; oxalic acid, malonic acid, succinic acid, glutaric acid, Maleic acid, phthalic acid, citraconic acid, itaconic acid, fumaric acid, tricarballylic acid, glycolic acid, propionic acid, thioglycolic acid, malic acid, citric acid, gleconic acid, pyrupic acid, glucolic acid, salicylic acid, adipic acid, Hydroacrylic acid, glyceric acid, p-toluenesulfonic acid,
Examples include polyacrylic acid. Examples of the salts include alkali metal salts, ammonium salts, and amine salts. Acids or salts having an acid dissociation constant of 10 ^-2 to ^{10 -13} are preferred. More preferably, the organic acid or its salt is contained in an amount of 0.1 to 50 g/, especially 0.5 to 30 g/. Furthermore, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, glycerin, gum arabic, carboxymethyl cellulose, acrylic polymer, methanol, ethanol, iso and normal propyl alcohol, triethanolamine, etc. can be added as wetting agents and wetting agents. and to prevent precipitation of Prussian blue and tumble blue due to the decomposition of yellow blood salts.
It is desirable to add a chelating agent such as EDTA-2Na.

In the present invention, in order to fully exhibit the desensitizing effect of the yellow blood salt, it is preferable to add a phosphate, and the phosphates include orthophosphoric acid, primary phosphoric acid, and secondary phosphoric acid.
These include alkali metal salts and ammonium salts of phosphoric acid.

Furthermore, salicylic acid, phenol, butyl phenol-parabenzoate, sodium dehydroacetate, 4-isothiazolone-3-one compound, etc. can be added as preservatives.

Aspects of the present invention are shown below.

Embodiment 1 A dampening solution according to the claims, further containing a PH regulator, a PH buffer, a wetting agent, a wetting agent, a preservative, a rust preventive, and the like.

Embodiment 2 The dampening water according to the claims, further containing 0.1 to 50 g/of an organic acid or a salt thereof.

Examples of the present invention are shown below. However, this does not limit the present invention.

Example 1 Yellow Blood Ammonium 4.0g Monosodium Phosphate 15.0g Phytic Acid 2.0g Water 1000.0g Fujifilm
The master, which was plate-made and etched using the ELP system, was printed on neutral paper using DIC F gloss black ink. I was able to print 10,000 sheets clearly and without any smudges from the beginning of printing. When I continued printing while replenishing this dampening water, I was able to print a total of 50,000 sheets with No. 5. There were no problems such as stains, roller strips, or water damage during printing.

Comparative Example 1 Sodium yellow blood 4.0g Monosodium phosphate 15.0g Water 1000.0g When printing was carried out under the same conditions as in Example 1, scumming occurred after 3000 sheets. So, when I changed to a new master and printed again, scumming occurred from the beginning of printing.

Comparative Example 2 Sodium phytate 12.0g Water 1000.0g When printing was carried out under the same conditions as in Example 1, printing durability failure occurred after 5000 sheets. So I replaced it with a new master and printed it again, but it still didn't work.
After 5,000 sheets, the print life became defective.

Example 2 Sodium yellow blood 5.0g Monosodium phosphate 15.0g Sodium phytate 1.0g Gluconic acid 15.0g Water 1000.0g Printing was carried out under exactly the same conditions as in Example 1 except that the ink was replaced with DIC F gloss ultramarine. As a result, over 30,000 copies were printed without any background stains or poor printing durability.

Example 3 Yellow Blood Potassium 4.0g Monosodium Phosphate 10.0g Phytic Acid 0.5g Glycolic Acid 6.0g Water 1000.0g When printing was carried out under the same conditions as in Example 1, more than 50,000 sheets were smudged. There was no occurrence of

Example 4 Yellow blood potassium 4.0g Monopotassium phosphate 20.0g Potassium phytate 2.0g Malic acid 6.0g EDTA-2Na 0.4g Glycerin 8.0g 4-thiazolone-3-one compound 0.02g Water 1000.0g Example 1 and eyelash When printing was carried out under the same conditions, over 50,000 copies were printed without any background smearing. After continuous use for one month with continued replenishment, there was no occurrence of scumming, roller strips, water damage, mold, sludge, sediment, rust, etc., and stable and clear prints were always obtained.

Comparative Example 3 In the formulation shown in Example 3, 5 phytic acid
A dampening solution was prepared with a change in g. When printing was carried out using this dampening water under exactly the same conditions as in Example 1, defective inking occurred after 1000 sheets.

[Effects of the Invention] As described above, when using the dampening solution of the present invention, a large number of printed matter can be obtained without causing problems such as scumming.

Claims (1)

[Claims] 1 Contains at least 1 to 10 g of yellow blood salt, 0.1 to 2 g of phytic acid or its salt, and has a pH of 3 to 3.
7 dampening water for printing.