JPH03282476A - Agent for correcting printing plate - Google Patents

Abstract

PURPOSE:To maintain correction ability and hydrophilicness for a long time after correction, and to enable storage of a corrected plate by using a correcting agent comprising an organic compound having at least one mercapto or thione group and at least one hydrophilic group in one molecule and a soluble bromide and/or iodide. CONSTITUTION:The correcting agent to be used comprises the organic compound having at least one mercapto or thione group and at least one hydrophilic group in one molecule, e.g., hydroxymercaptan, such as 2-mercaptoethanol or alpha-thioglycerin, and the soluble bromide and/or iodide in a concentration of >=0.3 mol/l. This correcting agent is prepared by adding them into water, one of many kinds of alcohols, or their mixture, thus permitting the rapid and assured correction ability not to be impaired in the case of >=3.0 in pH small in influence to human bodies, hydrophilicness to be maintained for a long time after the correction, and stable printing to be carried out even after storage of printed plate.

Description

Detailed Description of the Invention (A) Industrial Application Field The present invention is directed to an offset printing plate in which a silver image is made ink receptive and unnecessary portions of the silver image formed on the printing plate are made hydrophilic. The present invention relates to an image modifying agent for offset printing plates that eliminates ink receptivity by converting the ink receptivity to color, and more specifically, it eliminates unnecessary silver images on offset printing plates formed photographically or physically. This process involves treating the surface of a part with a specific treatment agent at any stage in the printing process to completely make it hydrophilic and eliminate ink receptivity without causing any problems to the printing properties or base material. be.

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-48-92101, JP-A-51-21901
Compounds having a mercapto or thione group and a hydrophilic group described in ``Sho 54-53002, ``Sho 59-9661, etc.'' can reliably and almost instantaneously make silver images hydrophilic. However, stable images cannot be erased unless under strong acidic conditions with a pH of 2.0 or less, which has a negative impact on the human body.Due to dirt around the erased area, it is not possible to maintain the image after processing, and it is difficult to store the image after printing. There are drawbacks such as the erased portion of the image being restored by the printing plate, and improvements are desired.

(C) Object of the invention The object of the invention is to impair the ability of an organic compound to quickly and reliably modify an organic compound having at least one mercapto or thionic group and at least one hydrophilic group in the same molecule. It is an object of the present invention to provide a correcting agent for an offset printing plate that can maintain hydrophilicity for a long period of time after correction and can be used for plate placement after correction.

(D) Structure of the Invention The above object of the present invention is to combine an organic compound having at least one mercapto group or thione group and at least one hydrophilic group in the same molecule, a soluble bromide of 0.3 moles or more per liter, and/or Or achieved by modifiers consisting of soluble iodides.

Examples of organic compounds having at least one mercapto group or thione group and at least one hydrophilic group in the same molecule include the following compounds.

2-Mercaptoethanol, hydroxymercaptans such as α-thioglycerin, thioglycolic acid, α-mercaptopropionic acid, β-mercaptopropionic acid, α
-Mercaptoalkyl carboxylic acids and their derivatives such as mercaptobutyric acid, β-mercaptobutyric acid, γ-mercaptobutyric acid, bis(murcaptomethyl)butyric acid, α-mercaptocaproic acid, distein, 2-mercaptoethylsulfonic acid, mercaptopropylsulfonic acid , 2.3-dimercaptopropenesulfonic acid and other mercaptoalkylsulfonic acids, as well as aromatic rings or heterocyclic rings, are also effective. For example, p-mercaptobenzoic acid, p-mercaptobenzenesulfonic acid, 2-mercapto Benz imidazole-5-sulfonic acid, 2-mercaptobenzthiazole-5-sulfonic acid, 1-methylbenzthiazole-5
-sulfonic acid-2-thione, 2-mercaptobenzoxazole-5-sulfonic acid, and the like. Salts of the above compounds are also effective. A particularly useful practical concentration range for these compounds is generally between 0.1% and 15% by weight of the correction fluid.

Soluble bromide and soluble iodide mean bromide and iodide that are soluble in the solvent of the correction fluid solution.

Usually, water is used as part or all of the solvent, so
Water-soluble bromides or iodides, such as potassium bromide,
Specific examples include sodium bromide, ammonium bromide, potassium iodide, sodium iodide, and ammonium iodide.

It is thought that these bromides and iodides act on silver ions and silver complexes present in the vicinity of the silver image, converting them into silver halide in an aqueous solution.

However, the effect of the present invention is not observed with water-soluble chlorides (eg, sodium chloride). Particularly preferred are water-soluble bromides.

The amount of soluble bromide or soluble iodide is required to be 0.3 mol or more per liter of corrector solution, preferably 0.3 mol or more.
The amount is up to 5 mol or more and can be dissolved. Two or more types may be combined.

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

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

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 modifying agent of the present invention does not impair the ability to quickly and reliably modify organic compounds that have at least one mercapto group or thione group and at least one hydrophilic group in the same molecule even at pH 3° or higher, which has little effect on the human body. , it can maintain hydrophilicity for a long time after correction, and there is no recovery of the image even after printing.

Therefore, printing can be performed more stably.

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 No. 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.

(E) Examples Example 1 The same as described in Example 1 of JP-A-53-21602 except that 1.0 g/rr1 of hydroquinone was added to the physical development nucleus layer of the offset printing plate (plate Na5). A lithographic printing material was prepared. After image-wise exposure of the lithographic printing material, it is treated with a transfer developer having the following formulation:
Transfer development is performed by immersion at 0°C for 30 seconds, followed by immersion in a stop solution having the following formulation for 30 seconds (25°C), squeezing to remove excess liquid, and drying the material under atmospheric conditions. did.

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]

[Stop liquid] After printing the 20th, 2,000th, and 5,000th sheet, leave it set in the printing machine and print it for 2 hours, then wipe the printing surface with the processing liquid called prescription (E). After printing the 1000th sheet, the ink receptivity (background smudge) of the corrected area was evaluated, and the results are shown in Table 2.

Ni B Dick 350CD (A, B, Dick
350CD (trade name), and after wiping the plate surface with a liquid called Prescription (E), printing was performed. The printing room is 22℃ and humidity is 60℃.
%Met.

(E) revised evaluation ○...Ink is not accepted at all.

△... Slight ink receptivity.

X: Perfect ink receptivity.

Example 2 Example 1 was followed except that the correction fluid of Example 1 was filled into a felt-tip pen. The results were the same as in Example 1.

Example 3 Example 1 was followed except that 5 g of silica powder having an average particle size of 3 to 7 μm was added as a fine powder described in JP-A-51-21901 to the correction fluid of Example 1. Example 1
got the same result.

Example 4 α-thioglycerol of Example 1 was replaced with thioglycolic acid, p
- Example 1 was followed except that mercaptobenzoic acid was substituted. The results were the same as in Example 1.

(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 correction agent for offset printing plates 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. A printing plate correction agent comprising 0.3 mol or more of soluble bromide and/or soluble iodide.