JPH027455B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is an offset printing plate that utilizes a silver image as ink receptivity, and eliminates ink receptivity by converting unnecessary portions of the silver image formed on the offset printing plate into hydrophilicity. It relates to an image modifying agent for plates, and more specifically, it can be used to remove unnecessary portions of a silver image on an offset printing plate formed by a photographic or physical method using a specific processing agent as appropriate at any stage of the printing process. The present invention relates to completely making the surface hydrophilic and eliminating ink receptivity by treating the surface with the following methods, without causing any problems to the printing properties, base material, etc. 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." In general, the areas that need to be corrected in printing master plates manufactured by photolithography include those that already exist in the copy original, those that occur during exposure,
and others caused by non-uniform development processing. This means, for example, the presence of unwanted images in the reproduced original, the presence of dust and dirt particles, etc.
If fingerprints or other smudges are present, or if originals are made by gluing together various originals, shadows may appear upon 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 make necessary corrections at any stage of the plate-making and printing processes. A number of attempts have been made to correct unwanted images in offset printing plates by utilizing the silver image as an ink receptivity. For example, by precipitating a hydrophilic metal salt, rubber, latex, gelatin, or other hydrophilic polymer or pigment on the silver image, or by mechanically removing the silver image using an eraser, knife, etc.; This method involves removing metallic silver from the image area by treating with a so-called silver image bleach-fixing composition containing an oxidizing agent such as dichromate or red blood salt, and sulfite or thiosulfate.
However, it is difficult to completely correct the problem using the above methods. The lipophilic image may be exposed again during printing or cause other problems such as staining.
In addition, processing takes time and reduces 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 the start of one-shot printing, that is, after an ink film is formed on the silver image. image deletion,
In other words, it was practically difficult to make corrections. A modifying agent consisting of a compound having a mercapto or thione group and a hydrophilic group (for example, a hydroxyl group, a carboxyl group, a sulfonic acid group, etc.) in the same molecule, which is described in JP-A No. 48-92101, and an improved version thereof. The modifiers disclosed in JP-A-51-21901 and JP-A-54-53002 are both excellent products that have considerably solved the drawbacks of the prior art described above, and have reliable and almost instantaneous reactions. It was possible to make the silver image hydrophilic. However, despite their excellent modifying ability, these modifiers still have drawbacks. This is because mercapto compounds have a characteristic bad odor, and like cysteine, they are easily oxidized and are unstable when used as a correction solution.Furthermore, because they are made into a strongly acidic solution, they can have an adverse effect on the human body. , ease of handling and workability, etc. Therefore, there is a strong demand for the development of an odorless correction agent that satisfies the conditions required for a correction agent as described above. Therefore, an object of the present invention is to avoid the above-mentioned drawbacks, to be able to quickly and completely correct images, to prevent the corrected area from being exposed again even when printing a large number of sheets, and to be able to be stored for a long period of time. It is an object of the present invention to provide an odorless and harmless correction agent that does not reduce its correction ability. The above object of the present invention was achieved by using an S-triazine compound represented by the following general formula as a modifier. general formula In the formula, R represents a hydrogen atom or a -R'-COOH group, and R' represents an alkylene group or an arylene group. Typical S-triazine compounds used in the present invention are described below, but the invention is not limited thereto. Synthesis examples of these compounds are described below. Synthesis Example 1 Synthesis of Compound 1 1.65 g of 2-amino-4,6-dichloro-S-triazine obtained by the method described in Chem. Ber. 32 695 (1899). was dissolved in 10 ml of DMF, and 1.6 g of 70% sodium bisulfide was added while keeping the internal temperature at 0 to 5° C. by cooling with ice from the outside. After stirring for 3 hours, 10 ml of water was added and the mixture was acidified with 1N hydrochloric acid to remove the precipitated crystals, followed by recrystallization from water to obtain 0.27 g of Compound 1. Melting point is 316
~318°C, and M ⁺ was 160 by mass spectrometry. Synthesis Example 2 Synthesis of Compound 2 1.84 g of cyanuric chloride dissolved in 50 m of acetone was added to 10 g of ice water, and 1.68 g of sodium bicarbonate and 1.40 g of glycine ethyl hydrochloride were added while stirring while keeping the internal temperature at 0 to 5°C. Stir for 30 minutes. The reaction product was extracted with ethyl acetate, dried over sodium sulfate, the ethyl acetate was distilled off, and the precipitated crystals were recrystallized from cyclohexane to give 1.3 g of 4,6-di-chloro-
2-ethoxycarbonylmethylamino-S-triazide was obtained. The melting point was 89-90.5°C. 1.11 g of the obtained 4,6-di-chloro-2-ethoxycarbonylmethylamino-S-triazine
70% Sodium Hydrosulfide 0.8% dissolved in 5ml DMF
g was added thereto, and the mixture was stirred at room temperature for 1 hour. Add 5ml of water
Acidify with 1N hydrochloric acid, remove the precipitate, wash with water in a funnel, and dissolve in 20ml of 1N caustic soda for 10 minutes at 120°C.
After hydrolysis at °C, the mixture was neutralized with 1N hydrochloric acid, and the precipitate was collected and recrystallized from water. Melting point 238℃
(Decomposition) 0.62 g of the above compound 2 was obtained. M ⁺ was 218 by mass spectrometry. Synthesis Example 3 Synthesis of Exemplified Compound 4 Compound 4 was obtained in the same manner as in Synthesis Example 2 using ethyl p-aminobenzoate instead of glycine hydrochloride ethyl ester. The melting point was 320°C or higher, and M ⁺ was 280 by mass spectrometry. The correction agent of the present invention can be used as a correction fluid using an organic solvent, water, or a mixed solvent thereof. A concentration range of modifier from 0.1 to 20% by weight is sufficient, preferably from 1.0 to 10% by weight. In addition, elements for making the liquid viscous, such as carboxymethyl cellulose, polyvinyl alcohol, and glycerin, and elements for coloring the liquid, such as pigments and organic or inorganic pigments, can be included.
These are not required elements. Furthermore, fine particle powder as described in JP-A-51-21901 may also be included. The modifier of the present invention is nonvolatile, stable, and odorless. In addition, it can be corrected quickly and completely, and ink will not get on the correction area even if it is rubbed strongly after correction. Therefore, a larger number of sheets can be printed. The modifier of the present invention can also be used in combination with the S-triazine compound of the following general formula described in Japanese Patent Application No. 56-203595 (see Japanese Patent Application Laid-Open No. 58-105231). general formula (In the formula, R ₁ and R ₂ each represent a mercapto group or a hydroxyl group.) A compound in which R ₁ and R ₂ are both mercapto groups, at least one of R ₁ and R ₂
Compounds in which one is a hydroxyl group are included. Examples of these compounds are trithiocyanuric acid,
These are dithiocyanuric acid and monothiocyanuric acid. As an offset printing plate that utilizes the silver image of the present invention for ink receptivity, Japanese Patent Publication No. 48-30562,
Japanese Patent Application Publication No. 53-21602, U.S. Patent No. 3721559, U.S. Patent No.
In addition to No. 3,490,905, offset printing plates having silver halide images that are ink receptive are included, such as US Pat. Examples will be described below. Example 1 Polyethylene terephthalate film (100μ)
After subbing the base with a known aqueous solution containing gelatin, nitrocellulose and parachlorphenol as main components, a top coating solution prepared with the following composition was applied thereon and dried to obtain an offset printing plate. 0.2% silver nitrate aqueous solution 10c.c. 1% potassium bromide aqueous solution 1c.c. 2% formalin solution 10c.c. 0.03N sodium hydroxide aqueous solution 100c.c. Bring the total volume to 200c.c. with water. This was previously subjected to contact treatment with an alkaline reducing agent solution (transfer developer) together with the negative image on the photosensitive negative sheet using the principle of silver complex diffusion transfer using a known method to obtain a positive image on an offset printing plate. Then, as a correction agent, a correction solution was prepared using the compounds and amounts shown in Table 1 below, each with 80 mmol of caustic soda and water to make a total volume of 100 ml, and the image area of the offset printing plate to be corrected was coated with absorbent cotton. The area was wiped with the correction fluid soaked in the area.

[Transfer developer]

Water 700ml Potassium hydroxide 20g Anhydrous sodium sulfite 60g Potassium bromide 0.5g 2-Mercaptobenzoic acid 1g 3-Mercapto-4-acetamide-5-n
-heptyl 1,2,4-triazole 0.15g 2-methyl-2-amino-1-propanol
Add 10g water to make 1. [Stop solution] Water 2 Citric acid 10g Sodium citrate 35g Then, using the compounds and amounts shown in Table 2 below as a correcting agent, each was made up to a total volume of 100ml with 80mmol of caustic soda and water, and further fine-particle silica (average particle size 7μm ) was added to prepare a correction liquid, and the image area of the offset printing plate to be corrected was wiped with the correction liquid soaked in absorbent cotton.

[Table] The printing plate thus obtained was mounted on an offset printing machine, and after wiping the plate surface with the silver image lipophilic liquid used in Example 1, the printing plate was injected with offset black ink, ABC 3-1012. (A.B. Dick3-1012 product name) was used for printing. The temperature in the printing room was 22°C and 60% humidity. After printing more than 5,000 sheets and observing the correction effect, it was found that the correction effect was sufficient in both cases, but in Comparison A and Comparison B, after 2,000 to 3,000 sheets, stains appeared around the edges, and the spread was visible, making it impossible to reach the required image. had been deleted. On the contrary, Compounds 2, 3, and 4 of the present invention showed no such adverse effects and showed good results. Example 3 Compound 2 as a correction agent in the correction fluid of Example 2
(20m mol) and dithiocyanuric acid (20m mol)
Example 2 was repeated except for combining. Similar to compounds 2, 3, and 4, good results were obtained.

Claims (1)

[Scope of Claims] 1. A printing plate correction agent that utilizes a silver image as printing ink receptivity, characterized in that the correction agent contains an S-triazine compound represented by the following general formula. Correcting agent. general formula (In the formula, R represents a hydrogen atom or a -R'-COOH group, and R' represents an alkylene group or an arylene group.