JPH03293358A - Improved retouching agent for printing plate - Google Patents

Abstract

PURPOSE:To stabilize the dispersion of fine powder in the retouching liquid by using a specific water-soluble polymer as a dispersant. CONSTITUTION:This retouching liquid is compounded with an org. compd. (A) having >=1 mercapto groups or thion groups and >=1 hydrophilic groups within the same molecule, the fine powder (B) having >=1mum grain size and the water-soluble polymer having <=20,000 number average mol. wt. A alpha- thioglycerol, etc., are usable as the component A, silica, etc., of a desired grain size as the component B and a copolymer of formula, etc., as the component C, respectively. The component B is stably dispersed when this component C is used and, therefore, the rapid and sure retouching is executed in arbitrary stages.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is an offset printing plate in which a silver image is made ink receptive, and unnecessary portions of the silver image formed on the offset printing plate are made hydrophilic. By converting to
The invention relates to an image correction liquid for offset printing plates that eliminates ink receptivity, and more specifically, it is used to remove unnecessary portions of a silver image on an offset printing plate formed by a photographic or physical method at any time during the printing process. It is concerned with making the surface completely hydrophilic and eliminating ink receptivity without causing any trouble to printing properties, substrates, etc., by appropriately wiping the entire surface with a specific treatment liquid at a step.

Since such processing is usually called "correction" in the printing field, the present inventors will follow this term hereinafter. Furthermore, the processing liquid used in the correction operation will be referred to as a "correction liquid."

(Prior art) In general, the areas that require correction that occur in printing original plates manufactured by photolithography include those that already exist in the copy original, those that occur during exposure, and those that occur during other uneven development processes. There are some things that occur due to

This means, for example, that there are unnecessary images in the reproduced original, that there are dust and dirt, particulates, fingerprints or other contamination, or that a manuscript made by pasting together various manuscripts is used as the original. In some cases, 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 utilizing silver images as full ink receptive.

For example, hydrophilic metal salts, rubber, latex,
A method of precipitating gelatin or other hydrophilic polymers or pigments, or a method of mechanically removing the silver image using an eraser, knife, etc., or a method of removing a silver image by mechanically removing a silver image using a dichromium powder, red blood salt, etc., and sulfurous acid. This method involves removing metallic silver from the image area by treatment with a so-called silver image bleach-fixing composition containing salt and thiosulfate. However, with the above methods, it is difficult to completely correct, the lipophilic image is exposed again during printing, it causes other problems such as staining, and the processing takes time, reducing work efficiency. Alternatively, not only does the correction fluid itself have drawbacks such as insufficient stability and a decline in performance during storage, but also after printing has begun, that is, after an ink film has been formed on the silver image. It was difficult to erase or modify the image.

Therefore, as a correction liquid for erasing the image after printing has started, that is, after forming an ink film on the silver image, at least one mercapto group or thione group and at least one thione group in the same molecule are used. JP-A-51-21901 proposes a processing liquid containing an organic compound having two hydrophilic groups and fine powder having a particle size of 1 μm or more.

Using this processing liquid, it is possible to correct the image after printing has started, but if the processing liquid is left for a while, fine powder particles with a particle size of 1 μm or more will gradually settle out, so it is possible to correct the image immediately before use. Unless carefully re-dispersed during the process, there is a drawback that the erasability after printing starts becomes uneven, and an improvement is desired.

(Objective of the Invention) The object of the present invention is to provide an off-sensor in which fine particle powder with a particle size of lμ or more is stably dispersed so that image correction can be performed quickly and reliably, and it can be applied at any stage during the printing process. An object of the present invention is to provide a correction agent for printing plates.

(Structure of the Invention) The above object of the present invention is to provide (I) an organic compound having at least one mercapto group or thione group and at least one hydrophilic group in the same molecule; and (II) a fine particle powder with a particle size of 1 μ or more. This was achieved by using a modifier consisting of (III) a water-soluble polymer having a carboxyl group and a number average molecular weight of about 20,000 or less as a dispersant.

Specific examples of compounds that fall under (1) include the following compounds.

Hydroxymercaptans such as 2-mercaptoethanol, α-thioglycerin, thioglycolic acid, a-mercaptopropionic acid, β-mercaptopropionic acid, α
- Mercaptoalkyl carbons and derivatives thereof such as mercaptobutyric acid, β-mercaptobutyric acid, γ-mercaptobutyric acid, bis(mercaptomethyl) dilute acid, a-mercaptocaproic acid, cysteine, 2-mercaptoedyl sulfone, Mercaptoalkylsulfonic acids such as mercaptopropylsulfonic acid and 2,3-dimercaptopropenesulfonic acid, as well as compounds containing aromatic or heterocyclic rings, are also effective, such as P-mercaptobenzoic acid, P-mercaptobenzenesulfonic acid, 2-mercaptobenzimidazole-5-sulfonic acid, 2-mercaptobenzthiazole-5-sulfonic acid-1-methylbenzthiazole-5-sulfonic acid-2-thione, 2-mercaptobenzoxazole-5-sulfonic acid, etc. There is. Salts of the above compounds are also effective. Particularly useful practical concentration ranges for these compounds are generally 0.1% of the correction fluid.
and 15% by weight. (Things that fall under the element Ill include silica powder, clay, calcium carbonate, etc., and those with a particle size of 1 μ or more are particularly effective.

The function of the element (If) is to mechanically etch the surface of the silver image, that is, it is sufficient that it has the function of so-called polishing sand, and is not necessarily limited to this. do not have. What is important is to properly correct the image without causing printing stains due to development that is inconvenient to printing, that is, scratches on the plate surface.

As a result of intensive studies by the present inventors, in the case of an offset printing plate having a gelatin layer or a gelatin-silver halide emulsion layer on the substrate, by rubbing the image area with a hydrophilic liquid containing particles of 1 μ to 15 μ. Favorable results were obtained. Considering the dispersion stability of the particles, the practically preferred particle size was in the range of 3 to 10 μm.

Also, a substantially effective amount of the particulate bed in the correction fluid of the present invention is between 2 and 50%, preferably 10 and 40%, by weight of the moisture in the correction fluid.

The water-soluble polymer corresponding to element (to) has a carboxyl group and has a low molecular weight, that is, a number average molecular weight of about 20,000 or less.

Such water-soluble polymers include olefinically unsaturated compounds containing carboxyl groups as heptadmer units, such as acrylic acid, methacrylic acid, sorbic acid, maleic acid,
It can be a homopolymer of fumaric acid, itaconic acid, citraconic acid, etc., or a copolymer of an olefinically unsaturated compound containing a carboxyl group as a heptamer unit and a vinyl monomer copolymerizable therewith.

Examples of the vinyl monomer for obtaining the copolymer used in the present invention include styrene, styrene substituted with alkyl such as methyl and ethyl, styrene substituted with alkoxy such as methoxy and ethoxy, styrene derivatives such as styrene substituted with halogen such as chlor, Ethylene, propylene, butylene, ethylenically unsaturated monoolefins such as imbutylene, vinyl chloride, vinylidene chloride, vinyl bromide, etc.
Vinyl rhodanide, vinyl acetate, vinyl propionate,
Vinyl esters such as vinyl benzoate and vinyl butyrate, alkyl esters of acrylic acid or methacrylic acid such as methyl, ethyl, propinopeisoptinopene n-butyl, n-octyl, and 2-ethylhexyl, acrylonitrile, methacrylonitrile , derivatives of acrylic acid or methacrylic acid such as acrylamide, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, vinyls such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopronyl ketone, N-vinyl pyrrole, N - Examples include N-vinyl compounds such as vinylcarbazole and N-vinylpyrrolidone, and vinylnaphthalenes, and copolymer components may include different types of olefinically unsaturated compounds containing carboxyl groups. .

The amount of olefinically unsaturated compounds containing carboxyl groups in the copolymer is about 10% by weight or more, preferably about 20% by weight or more. This carboxyl group is sodium,
It may be a salt of potassium, ammonium, etc., or an acid anhydride (for example, maleic anhydride).

The water-soluble polymer used in the present invention has a number average molecular weight (M
n) is about 20,000 or less, especially about 1.0
A range of 0.00 to about 15,000 is preferred.

The water-soluble polymer used in the present invention can be easily produced by known production methods such as solution polymerization, and can also be obtained as a commercially available product.

A specific example is shown below.

In addition, Polymerization ratio is weight% It is shown in

(1) (3) H5 +cH2cMnnia500 0OH (4) H3 +CH2C+ OONH4 Mn:6000 (5) Mn:4500 (13) 0ONa 0OK CON(Ut-192 0ONa 0ONa 0OCH3 (22) CH3 Mn:1000 (2 4 ) (-CH2-CH2 volume CH-CH pile Mn: 3000 o=c cooθ・NHa NH2 (25) (26) [27] [28] The water-soluble polymer used in the correction fluid of the present invention is mainly water-soluble. It is preferable to include it in the range of 0.5 to 20% by weight, preferably 1 to 10% by weight in the solvent consisting of 2.
More than one species may be used in combination, or other polymeric substances may be used in small amounts as necessary.

Furthermore, the correction fluid of the present invention may contain the following elements as other elements. For example, suitable organic solvents for promoting dissolution and removal of the ink film are those that are miscible with water, such as alcohols such as methanol, ethanol, and propatool, acetone, and dimethylformamide.

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

The correction agent of the present invention is a stable fine powder with a particle size of 1μ or more,
Good dispersion allows quick and reliable corrections before printing and at any stage during the printing process.

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.
No. 3,490,905, etc., as well as U.S. Patent Department 3, 4
54,398 and Japanese Patent Application Laid-Open No. 53-9603, offset printing plates having silver halide images that are ink receptive are included.

(Example) Example 1 Hydroquinone 1. (A lithographic printing material was produced in the same manner except that it contained 1/yr?).

After exposing the lithographic part (IJ) material according to the image, it was immersed in a transfer developer having the following formulation at 30°C for 30 seconds to perform transfer development, and subsequently, it was immersed in a stop solution having the following formulation for 30 seconds.
Dip for seconds (25° C.), squeeze to remove excess liquid, and dry the material under atmospheric conditions.

A correction solution was prepared using the compounds and amounts shown in Table 1 below as a correction agent, and the portions of the lithographic printing plate to be corrected were wiped with the correction solution soaked in absorbent cotton.

[Transfer developer]

[Stopping liquid] The printing plate thus obtained was run on an offset printing machine N.B. Dick 350CD (A, B, Dick350CD
(trade name), and printed after wiping the plate surface with a prescribed liquid. The printing room was at 22° C. and 60% humidity.

[E]

The ink receptivity of the corrected area on the 1,000th page that was corrected before printing and printed, and the 1,000th page that was corrected after printing and printed and treated with processing liquid (G), and the correction liquid was applied for 2 months. The dispersibility and redispersibility of the fine particles were evaluated after being allowed to stand naturally, and are shown in Table 2.

Table 1 (Unit 2) Table 2 revised evaluation ○...Ink is not accepted at all.

M... Slight ink receptivity.

×...Perfect ink receptivity.

Example 2 When a-thioglycerol in Example 1 was replaced with thiomalic acid and the same evaluation as in Example 1 was performed, good results similar to those in Example 1 were obtained.

(Effects of the Invention) Since the correcting agent of the present invention has fine powder with a particle size of 1 μm or more dispersed stably and well, correction can be performed quickly and reliably before printing and at any stage during the printing process.

Claims (1)

[Claims] 1. In an image correction liquid for an offset printing plate that uses a silver image as ink receptivity, the correction liquid contains an organic compound having at least one mercapto group or thione group and at least one hydrophilic group in the same molecule. An improved corrector for offset printing plates, characterized in that it contains a fine particle powder having a particle size of 1 μm or more, and a water-soluble polymer having a carboxyl group and a number average molecular weight of about 20,000 or less.