JPH04146439A - Agent for correcting printing plate - Google Patents

Abstract

PURPOSE:To provide the agent for correcting an offset printing plate capable of rapid and secure correction without adversely affecting human bodies and environments, capable of maintaining hydrophilicness for a long time after the correction, and superior in storage stability the correcting solution by incorporating a specified thioether compound as the correcting agent. CONSTITUTION:The thioether compound to be used for the agent for erasing unnecessary parts of a silver image formed on the offset printing plate to correct it is a compound represented by general formula (I) and this agent is used as the correcting solution by using water, various kinds of alcohols, or a mixture of some of them. A preferably concentration of this correcting solution is 0.1 - 20g/l, and it may contain a thickener for raising its viscosity, such as carboxymethyl cellulose, polyvinyl alcohol, or glycerin, and further, dyes, organic or inorganic pigments, or the like. This correcting solution is stable and odorless, and it can correct rapidly and perfectly, and no ink attaches to the corrected part even strongly rubbed after the correction, thus permitting a large number of prints to be made by using this offset printing plate corrected by this correcting agent.

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. Generally, in the printing field, such processing is called "correction", and the present inventors will hereinafter follow it.

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 silver images for ink receptivity.

For example, JP-A-48-92101, JP-A-51-21901
Compounds having a mercapto or thione group and a hydrophilic group, such as those described in JP-A No. 5.4-53002 and JP-A No. 59-9661, 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 disadvantages 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) -N In the formula, n represents 0.1 or 2, and R is a group having one or more water-soluble groups, preferably a hydroxyalkyl group (
For example, hydroxyethyl group, hydroxypropyl group)
, carboxyalkyl group (eg, carboxyethyl group, hydroxypropyl group), aminoalkyl group (eg, aminoethyl group, aminopropyl group), sulfoalkyl group (eg, sulfoethyl group, sulfobutyl group).

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

-N -N N-N -N The synthesis of the thioethers of the present invention was basically carried out by alkylation of the corresponding thiols.

Alkylating agents can be used, for example, in Journal on Organic Chemistry (J, 0.C,) 26.4987 (
It can be easily synthesized by the method of (1961). The details of the synthesis method will be described below using synthesis examples.

Synthesis Example 1 (Synthesis of Compound 5) 2.5-dimercapto-1,3,4-thiadiazole 1
, 5g was dissolved in 30ml of ethyl alcohol, 1.1g of triethylamine was added, and then 2chloro-2'-
Add 1.4 g of hydroxydiethyl sulfide. After 3 hours of reflux, the reaction mixture was poured into water, extracted with ethyl acetate, and the ethyl acetate layer was washed with water and dried over anhydrous sodium sulfate. After distillation under reduced pressure, the residue was separated by column chromatography (chloroform/methanol = 3/I). The desired fraction was distilled off under reduced pressure, and the precipitate was recrystallized from a mixed solvent of ethyl acetate/n-hexane to obtain a white powder.

mp 83-84.5℃ Yield 2.11gCMR (
DMSO) δ187.0.157.0.60, 9.
33.9.33.4.31.0 The modifier of the present invention comprises water,
Various alcohols or a mixed solvent thereof can be used as a correction fluid. It is also possible to use a so-called correction pen method.

A concentration range of the correcting agent of 0.1 to 20 g/I is sufficient, preferably 1.0 to Log/j! It is.

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. In addition, the silver image is not of the type that is chemically removed, but is of the 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.
3.490.905, etc., as well as U.S. Patent Nos. 3 and 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 A lithographic plate was prepared in the same manner as described in Example 1 of JP-A-53-21602, except that 1.0 g/nf of hydroquinone was added to the physical development nucleus layer of the offset printing plate (plate Nα3). A printing material was produced.

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 a transfer image, and subsequently, it was immersed in a stop solution having the following formulation for 30 seconds (at 25°C). After soaking and squeezing to remove excess liquid, 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]

[Stop liquid] The printing plate thus obtained was processed using an offset printing machine N.B. Dick 350CD (A, B, Dick 3
50CD (trade name), and printing was performed after wiping the plate surface with a liquid called Prescription (E). The printing room is 22℃ and humidity 60%.
Met.

(E) The ink receptivity (background smudge) of the corrected portions printed on the 20th, 2,000th, and 5,000th sheets was evaluated, and the results are shown in Table 1.

〔Correction fluid〕

The following compounds were used as comparison compounds. (a) (b) use did.

(a) -N (b) (Margin below) 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 also 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, n represents 0, 1, or 2, and R is a group having one or more water-soluble groups.)