JPS63207645A - Correction fluid for printing plates - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (A> Industrial Application Field The present invention is directed to an offset printing plate that eliminates ink receptivity by converting unnecessary portions of an image formed on the printing plate into hydrophilic ones. It relates to image correction fluid for
More specifically, unnecessary parts of the image on the offset printing plate formed by a photographic or physical method can be treated with a specific treatment agent at any stage in the printing process to improve printing characteristics, in particular. It is related to making the base material completely hydrophilic without causing any trouble, and eliminating ink receptivity. Since such processing is usually called "correction" in the printing field, the Ministry of the Invention and others will follow this term hereinafter.

Furthermore, the processing agent used in the correction operation will be referred to as a "correction agent."

(B) Prior art and its problems In general, areas that require correction that occur in printing master plates manufactured by photolithography include those that already exist in the copy original, those that occur during exposure, and other irregularities. - There are some that occur during the development process.

This means, for example, if there are unwanted images in the reproduced original, if there are dust and dirt particles, fingerprints or other stains, or if the original is made by gluing together different originals, Shadows may appear during exposure.

In order to obtain good printed matter, all of these points must be corrected during the plate-making and printing stages.

Generally speaking, correction operations are essential, and it is desirable to be able to perform necessary corrections at any stage of the plate-making and printing processes.

Many attempts have been made to correct unwanted images in offset printing plates that utilize images as ink receptive.

For example, Japanese Patent Publication No. 48-92101, same town 51-21901
Compounds having a mercapto or thione group and a hydrophilic group, such as those described in Japanese Patent No. 54-53002, No. 59-9661, etc., can reliably and almost instantaneously make silver images hydrophilic. .

In addition, Japanese Patent Application Laid-Open No. 48-41808 describes red blood salt and EDTA.
Modifiers consisting of silver oxidizing agents such as metal salts and thiocyanates have been described.

Roughly, right by the inventors! F! ! Acid ferric complex salts and halides (e.g. potassium bromide, ammonium bromide,
Other modifiers have also been proposed, such as potassium iodide (potassium iodide, etc.).

Further, as a correcting agent for zinc oxide master, for example, metal salts described in Japanese Patent Publication No. 48-5681 are known.

However, with conventional correction agents, when corrections are made by lightly rubbing the image area, such as with a method commonly known as ``pine stick correction'' or a method using a correction pen, the corrected edges often become ink receptive and become smudged. There are drawbacks that arise.

Furthermore, when using the correction pen method, there is a drawback that the correction liquid at the pen tip easily evaporates and dries, making it impossible to make corrections.

(C) Object of the Invention The first object of the present invention is to provide a correction solution for offset printing plates that allows for reliable correction and has excellent storage stability of the correction agent solution.

Another object of the present invention is that the drying time at the pen tip is extremely slow;
It is an object of the present invention to provide a correction liquid for an offset printing plate that dries quickly after correction and is suitable for a correction pen method that allows correction to be performed reliably.

(D) Structure of the Invention The above object of the present invention is to provide an offset printing plate correction fluid that:
This was achieved by the above-mentioned correction fluid characterized in that it contains low molecular weight gelatin.

As is well known, gelatin is used as a photographic material and as food.

Piratin includes alkali-treated gelatin, M-treated gelatin, and gelatin derivatives treated and modified by various methods, and usually has an average molecular weight of tens of thousands or hundreds of thousands.

Measuring molecular weight involves analysis of terminal groups, analysis of amino acid composition,
Methods such as light scattering, gel filtration, ultracentrifugation, and surface pressure are known.

As is well known, the gelatin-containing photographic layer is coated by applying a gelatin coating solution and then gelatin (referred to as setting).

Gelatin gelation is said to be observed from an average molecular weight of about 30,000, but the gelatin commonly used for photography is gelatin with an average molecular weight of about 100,000. It has an average molecular weight of about 70,000 to about 150,000. Gelatin with an average molecular weight of about 30,000 or less has no setting phenomenon, or even if it does, it is very weak, and it is difficult to form a good photographic layer with a coating liquid of gelatin alone, so it is not normally used for photography. do not have.

As used herein, the term low molecular weight gelatin refers to gelatin having the properties described above.

The typical average molecular weight of low molecular weight pyratine is approximately 3.00.
0 to 30,000, preferably about 5,000 to 20,000.

Low molecular weight hylatin is produced by, for example, enzymatically decomposing ordinary photographic gelatin.

The low molecular weight IL'Latin is about 1 to about 10 per 111 parts of correction fluid.
09, preferably in the range of about 5 to about 50 g.

The correction fluid of the present invention containing low-molecular-weight gelatin is particularly useful for use in so-called correction pen systems such as felt-tip pens. That is, it not only improves the stability of the corrected edge over time as described above, but also functions as a drying inhibitor to prevent the corrected pen from overdrying.

The correction fluid of the present invention containing low molecular weight gelatin contains the above-mentioned correction agent, but the type of correction agent is not limited.

The correction fluid of the present invention preferably uses water, various alcohols, or a mixed solvent thereof as a solvent.

It can also contain elements to make the liquid viscous, such as carboxymethylcellulose, polyvinyl alcohol, and glycerin, and elements to color the liquid, such as pigments and organic or inorganic pigments, but these are essential. is not an element of

Furthermore, fine particle powder as described in JP-A-51-21901 may also be included.

The correction fluid of the present invention is stable. In addition, it can be corrected quickly and completely, and even if it is rubbed strongly after correction, ink will not get on the correction area. Therefore, a larger number of sheets can be printed.

Examples of the offset printing plate used in the present invention include Japanese Patent Publication No. 30562/1970, Japanese Patent Application Laid-open No. 21602/1983, U.S. Pat. No. 3,454.398, Japanese Unexamined Patent Publication No. 1973
Included are offset printing plates that are ink receptive to silver halide images, such as No. 3-9603.

Further, a zinc oxide master, PS plate, etc. may be used.

(E) Examples Example 1 Other than having hydroquinone 1.Otj/Tde in the physical development nucleus layer of the offset printing plate (plate Nα3) described in Example 1 of JP-A-53-2''1602. A lithographic printing material was prepared in the same manner.

After image-wise exposure of the lithographic printing material, the transfer Is!
Transfer development was performed by immersion in a stop solution for 30 seconds at 30°C, followed by immersion in a stop solution for 30 seconds (25°C), excess liquid was removed by squeezing, and the material was dried under atmospheric conditions.

A correction fluid was prepared using the compounds and amounts shown in Table 1 below and filled into felt correction pens. The areas to be corrected on the above planographic printing plate were corrected by rubbing them with these correction pens.

(Margin below) Table 1 (g/water 100IIJR) * Gelatin with an average molecular weight of approximately 1,800,000
D product name), Silver Master (manufactured by Mitsubishi Paper Mills,
Product name) 10.0 using special etching liquid and moisturizing liquid
00 copies were printed.

In the areas corrected with correction fluid A'''C, the ink caused scuffing on the edges, and this scumming increased as the number of prints increased.On the other hand, the areas corrected with correction fluid B had 10,0
Even when printing 00 sheets, no scumming occurred at all.

Furthermore, the caps of the correction pens containing correction fluids A and B were removed, and the pens were left in the atmosphere at a room temperature of 25 DEG C. and a humidity of 1f40% R1-1, and then the pens were corrected to examine their dryness. The pen containing correction fluid dried the pen tip in just one hour and was unable to make stable corrections, whereas the pen containing correction &B was able to make corrections without any problems even after being left for 30 days. .゛Example 2 N-methylethanolamine was added to the correction fluid B of Example 1.
The correction fluid containing II11 gave similar results.

Example 3 Modification of Example 1 Low molecular weight gelatin binding at 8kB
(Similar results were obtained using a correction fluid with an average molecular weight of approximately 10,000.

Example 4 A test was conducted according to Example 1 using a correction pen filled with the following correction liquid. One similar result was obtained.

(F) Effects of the Invention The correction liquid of the present invention does not cause scumming on the correction area and can maintain the correction effect stably. Also, when using the correction pen method, the correction liquid does not cause drying of the pen tip. Work efficiency can also be improved due to the suppressing effect.

Claims (1)

[Claims] (1) A correction fluid for printing plates characterized by containing low molecular weight gelatin.