JPH04147150A - Correcting agent for printing plater - Google Patents

Abstract

PURPOSE:To realize a correcting agent for an offset printing plate without exerting adverse influence on human body and the environment, being capable of correcting rapidly and surely and being superior to the preservation stability of the correcting agent solution by incorporating a specified compound in the correcting agent. CONSTITUTION:In the offset printing plate using a silver image by allowing it to an ink accepting property, the offset printing plate image correcting agent is one canceling the unnecessary part on the silver image formed on the printing plate and the compound represented with formula I is used by incorporating it in the correcting agent. In formula I, R1 is an alkylen group, R2 is a group having a water soluble group, preferably represents a hydroxyalkyl group (for example, hydroxyethyl group, hydroxypropyl group), a carboxyalkyl group (for example caboxyethyl group, carboxypropyl group), an aminoalkyl group (for example aminoethylgroup, aminopropylgroup), a sulfoalkyl group (for example sulfoethyl group, sulfopropyl group), X is 0 or S atom, m is 2 or 4 and n is 1-4. Thus the correcting agent which is safe and can correct promptly and surely and the durability of the effect is long and the stability of the solution is superior, is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Field of Application The present invention relates to an offset printing plate in which a silver image is made ink receptive, and in which unnecessary portions of the silver image formed on the printing plate are removed. It relates to an image correcting agent for offset printing plates that erases unnecessary parts of a silver image on an offset printing plate formed by a photographic or physical method, as appropriate at any stage in the printing process. In particular, printing properties can be improved by treating the surface with a specific treatment agent.
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 present inventors 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.

- Correction operations are essential in boat fishing, and it is desirable to be able to make 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 silver images for ink receptivity.

For example, JP-A-48-921.01, JP-A-51-2190
1. Compounds having a mercapto or thione group and a hydrophilic group described in 1982-53002 and 1988-9661 can reliably and almost instantaneously make a silver image hydrophilic. Although it is possible, it has drawbacks such as having a strong odor, having an adverse effect on the human body due to its strong acidity, and lacking in storage stability, so improvements are desired.

In addition, the correction agent containing red blood salt or EDTA metal salt and thiocyanate described in JP-A No. 48-41808 has problems with pollution and gradually loses ink acceptance after printing after correction. It has drawbacks such as smudging after the recovery of its properties and lack of storage stability.

(C) Purpose of the Invention The purpose of the present invention is to have no adverse effect on the human body or the environment, to be able to perform quick and reliable modification, to maintain hydrophilicity for a long period of time after modification, and to improve the storage stability of the modification agent solution. It is an object of the present invention to provide a correcting agent for offset printing plates that is also excellent.

(D) Structure of the Invention The above object of the present invention was achieved by using a compound represented by the following general formula (1) as a modifier.

General formula (I) H H In the formula, R3 represents an alkylene group, and R2 is a group having a water-soluble group, preferably a hydroxyalkyl group (e.g., hydroxyethyl group, hydroxypropyl group), a carboxyalkyl group (e.g., carboxyethyl group, carboxypropyl group), aminoalkyl group (e.g. aminoethyl group, aminopropyl group), sulfoalkyl group (
For example, sulfoethyl group, sulfopropyl group), X is 0 or S atom, m is 2 or 4, n
is 1 to 4.

Typical thioether compounds used in the present invention are described below, but the invention is not limited thereto.

The synthesis of the compound of general formula (I) of the present invention basically consists of:
This was done by reacting the corresponding dithiols with bisepoxide compounds. Further, dithiols serving as starting materials can be easily synthesized by the method disclosed in JP-A-59-147350. The details of the synthesis method will be described below using synthesis examples.

Synthesis Example 1 (Synthesis of Exemplified Compound 1) 10°5 g of ethylene glycol diglydicyl ether and 21.9 g of 3.6-cythia 1.8-octanediol
and sodium methoxide (28% in methanol) Ig
The mixture was heated at a bath temperature of 105° for 24 hours. The reaction mixture was distilled off at 160°C (3 mml 1 g), and 27.6 g
A brown oil was obtained.

The correction agent of the present invention can be used as a correction fluid using water, various alcohols, or a mixed solvent thereof.

It is also possible to use a so-called correction pen method.

A concentration range of the correcting agent from 0.1 to 20 g/V is sufficient, preferably from 1.0 to 10 g/I.

In addition, elements that make the liquid viscous, such as carboxymethyl cellulose, polyvinyl alcohol, and glycerin, and elements that color the liquid, such as dyes and organic or inorganic pigments, can be included, but these are essential elements. isn't it.

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

The correction agent of the present invention does not cause staining around the correction area, which is a drawback of conventional correction agents. Moreover, it is not a type that chemically removes silver images, but a new type that increases the water retention of the repaired area and prevents ink from being deposited on it, so if the compound of the present invention is removed with a solvent or the like, the image will be regenerated.

Therefore, unlike the conventional method, re-correction is possible.

The modifier of the present invention is stable and odorless. 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.

Offset printing plates that use the silver image of the present invention as ink receptivity include Japanese Patent Publication No. 30562/1982, Japanese Patent Application Laid-open No. 21602/1983, and U.S. Pat. No. 3.721.559.
In addition to U.S. Patent No. 3,490,905, etc., U.S. Patent No. 3,4
54.398, JP-A-53-9603, and other offset printing plates having silver halide images that are ink receptive are included.

Examples will be described below.

(E) Example Same procedure as described in Example 1 of JP-A-53-21602 except that 1.0 g/rrr of hydroquinone was added to the physical development nucleus layer of the offset printing plate (Plate Nu 3 ). A lithographic printing material was prepared.

After the lithographic printing material was imagewise exposed, it was immersed in a transfer developer having the following formulation at 30°C for 30 seconds to perform transfer development, and subsequently immersed in a stop solution having the following formulation for 30 seconds (25°C). The excess liquid was removed by squeezing and the material was dried under atmospheric conditions.

A correction liquid was prepared using the compound and amount shown in the following correction liquid as a correction agent, and the portion of the lithographic printing plate to be corrected was wiped with the correction liquid soaked in absorbent cotton.

[Transfer developer]

[Stopping liquid] The printing plate thus obtained was processed using an offset printing machine N.B. Dick 350CD (A, B, Dick 350C).
D (trade name) was attached, and printing was performed after wiping the plate surface with a liquid called Prescription (E). The printing room was at 22° C. and 60% humidity.

[E) 20th photo, 2゜ 000th sheet and 5゜ 000 pieces Ink receptivity of corrected areas in own printing (background stains) ) evaluate, The results are shown in Table 1.

〔Correction fluid〕 The following compounds were used as comparison compounds. (a) It was used.

(Margin below) (a) H Table 1 revised evaluation ○...Ink is not accepted at all.

△... Slight ink receptivity.

×...Perfect ink receptivity.

As can be seen from the results in Table 1, the exemplified compounds of the present invention are effective when used alone, but are also effective when used in combination with EDTA-2Na and sodium iodide.

Example 2 Example 1 was followed except that the correction fluid of Example 1 was filled into a felt-tip pen. Similar to Example 1, the results were excellent.

(F) Effects of the Invention The correction agent of the present invention is safe, allows quick and reliable correction, has a long-lasting effect, and has excellent liquid stability.

Claims (1)

[Claims] (1) In a correcting agent for offset printing plates that uses a silver image as ink receptivity, the correcting agent has the following general formula (I).
A printing plate correction agent characterized by containing a compound represented by: General formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R_1 represents an alkylene group, R_2 represents a group having a water-soluble group, X is an O or S atom, and m is 2 or 4, and n is 1 to 4.)