JP3130138B2 - Plate surface treatment liquid for lithographic printing plates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate surface treating solution for improving the ink receptivity of an image portion at the start of printing in a lithographic printing plate utilizing image silver as ink receptivity.

[0002]

2. Description of the Related Art Printing plates using silver halide emulsions having high sensitivity and spectral sensitization have already been put into practical use in several forms. Among them, US Pat. No. 3,721,559, US Pat. No. 3,490,905, and Japanese Patent Publication No. Sho.
Nos. 8-30562, U.S. Pat. Nos. 3,385,701 and 3,814,603, JP-B-44-27242, JP-A-53-21602, U.S. Pat. 5
No. 3-9603.

Although these are roughly classified into several types of printing plate manufacturing methods, they are common in that image silver is made ink receptive. A lithographic printing plate is composed of an image portion that receives a new oil-based ink and a non-image portion that is hydrophilic and receives water. Therefore, in normal lithographic printing, both water and ink are supplied to the printing plate, the image portion selectively receives color ink, the non-image portion selectively receives water, and the ink on the image line is, for example, paper. This is done by transferring it to a substrate.

[0004] In order to obtain good printed matter, it is required that the difference between the lipophilicity and the hydrophilicity of the surface of the image portion and the non-image portion is sufficiently large.

The plate making method using the above-mentioned silver halide emulsion is simple, reliable and quick, can be automated, and has the features of high sensitivity, high resolution and high image reproducibility. However, the difference between the lipophilicity and the hydrophilicity between the image portion and the non-image portion was not sufficiently large as compared with a printing plate (PS plate) or the like realized from an organic colloid such as a diazo photosensitive material.

In order to overcome such a disadvantage, Japanese Patent Publication No. Sho 48
JP-A-29723 and JP-A-58-127928 show that a compound having a mercapto group or a thione group acts on a silver image to improve ink receptivity.
Also, JP-A-48-45305 and JP-A-54-83502.
No. 57-29046 and others show that inorganic fine particles such as colloidal silica and colloidal alumina are adsorbed on the surface of a lithographic printing plate to form a hydrophilic layer on the surface of the printing plate, thereby improving the hydrophilicity. Have been. That is, the mercapto group or the like of the compound having a mercapto group or the like is adsorbed on image silver, the hydrophobic portion of the compound covers the image silver, inorganic fine particles such as colloidal silica cover the non-image portion, and the image portion and It is considered that the difference between the lipophilicity and the hydrophilicity from the non-image area increases.

However, the above-mentioned inorganic fine particles such as colloidal silica improve the hydrophilicity of the non-image area, but act even on the image area and inhibit the action of the compound having a mercapto group or the like on image silver, This deteriorated the ink acceptability and caused density unevenness in printed matter.

[0008]

In the lithographic printing plate, colloidal silica or the like which does not impair the hydrophilicity of the non-image portion and does not inhibit the action of the compound having a mercapto group or the like on the image silver of the image portion. Investigations have been made on a desensitizing agent to be replaced with inorganic fine particles. For example, there are water-soluble synthetic polymers such as polyvinyl alcohol and polyacrylic acid, which do not inhibit the action of the compound having a mercapto group or the like, but have a higher hydrophilicity in the non-image area than colloidal silica. It had the disadvantage of dropping.

An object of the present invention is to provide a lithographic printing plate surface treatment containing a desensitizing agent which improves the hydrophilicity of a non-image area and does not inhibit the action of a compound having a mercapto group or the like on image silver. Providing a liquid.

[0010]

SUMMARY OF THE INVENTION The above objects of the present invention are as follows.
This has been achieved by using a plate surface treating solution for a lithographic printing plate utilizing image silver as ink acceptability, which contains at least one compound having at least one mercapto group or thione group and pullulan.

The pullulan related to the present invention is represented by the following chemical formula 1.
And has a structure represented by Black Yeast
Is a kind of polysaccharide produced outside the cells when a bacterium is cultured, and sucrose and glucose sugar are used as carbon sources for the cultivation.

[0012]

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The pullulan of the present invention having a molecular weight of from 1 to 2,000,000 can be easily produced. The production and properties of pullulan are described in Polymer 26, p. 93 (1977). Also, pullulan is an industrial product from Hayashibara Co., Ltd., which has pullulan PF-20 and PI-20 and triglucose.
It is sold under the trademark A. The molecular weight of pullulan used in the present invention is not particularly limited, but is preferably 1 to 10
A range of about 100,000 is preferred.

The compounds having a mercapto group or a thione group used in the present invention are described in JP-B-48-29723 and JP-A-58-127728. Basically, it has a structure consisting of a mercapto group or a thione group and a lipophilic group.

The compound having a mercapto group or a thione group of the present invention has the general formula shown in the following chemical formula 2.

[0016]

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(Wherein R is hydrogen, an alkyl group having 12 or less carbon atoms, allyl group, aralkyl group, and Z is N, C
And the remaining atomic groups of the bond necessary to form a 5- or 6-membered ring with the above. )

Specific examples of the 5- or 6-membered ring include imidazole, imidazoline, thiazole, thiazoline,
Oxazole, oxazoline, pyrazoline, triazole, thiadiazole, oxadiazole, tetrazole, pyridine, pyrimidine, pyridazine, pyrazine, triazine, etc., and these rings may be two or more condensed rings; And those condensed with a naphthalene ring.

Specific examples of such compounds include 2-mercapto-4-phenylimidazole and 2-mercapto-1
-Benzylimidazole, 2-mercapto-benzimidazole, 1-ethyl-2-mercapto-benzimidazole, 2-mercapto-1-butyl-benzimidazole, 1,3-diethyl-benzimidazoline-2-thione, 1,3- Dibenzyl-imidazolidin-2-thione, 2,2'-dimercapto-1,1'-decamethylene-diimidazoline, 2-mercapto-4-phenylthiazole, 2-mercapto-benzothiazole, 2-mercaptonaphthothiazole, 3- Ethyl-benzothiazoline-2-thione, 3-dodecyl-benzothiazoline-2
-Thione, 2-mercapto-4,5-diphenyloxazole, 2-mercaptobenzoxazole, 3-pentyl-benzoxazoline-2-thione, 1-phenyl-3-methylpyrazolin-5-thione, 3-mercapto-4-allyl -5-pentadecyl-1,2,4-triazole, 3-mercapto-5-nonyl-1,2,4-triazole, 3-mercapto-4-acetamido-5-heptyl-1,2,4-triazole, -Mercapto-
4-amino-5-heptadecyl-1,2,4-triazole, 2-mercapto-5-phenyl-1,3,4-thiadiazole, 2-mercapto-5-phenyl-1,
3,4-thiadiazole, 2-mercapto-5-n-heptyl-oxathiazole, 2-mercapto-5-phenyl-1,3,4-oxadiazole, 2-heptadecyl-5-phenyl-1,3,4 -Oxadiazole, 5
-Mercapto-1-phenyl-tetrazole, 2-mercapto-5-nitropyridine, 1-methyl-quinoline-
2 (1H) -thione, 2-mercapto-4-hydroxy-6-pentadecylpyridine, 3-mercapto-4-methyl-6-phenyl-pyridazine, 2-mercapto-
5,6-diphenyl-pyrazine, 2-mercapto-4,
6-diphenyl-1,3,5-triazine, 2-amino-4-mercapto-6-benzyl-1,3,5-triazine, 1,5-dimercapto-3,7-diphenyl-S
-Triazolino [1,2-a] -S-triazoline and the like, but are not limited thereto.

The amount of the mercapto compound used in the present invention is from 0.1 to 10 g per liter of the working solution, but is preferably added in the range of from 0.5 to 5 g.

The amount of pullulan used in the present invention is as follows:
2: 1 to 3 by weight relative to the mercapto compound
0: 1, preferably in the ratio of 5: 1 to 20: 1. Thereafter, the mixture is prepared by adding other compounds and the like to the mixed solution as needed.

As described above, the present invention relates to a plate surface treatment solution for improving the ink receptivity at the start of printing on a lithographic printing plate using the image silver as ink receptivity, and from the development process to the start of printing. Is a plate surface treatment liquid to be applied to the printing plate surface. In addition to the above compounds, commonly used buffers, preservatives, preservatives, wetting agents, surfactants and the like can be mixed in the plate surface treatment liquid.
Examples thereof include inorganic acids such as phosphoric acid and sulfuric acid, organic acids such as succinic acid and propionic acid, and complexing agents such as iminodiacetic acid and ethylenediaminetetraacetic acid. Also, inorganic fine particles such as colloidal silica can be mixed in a range that does not inhibit the action of the compound having a mercapto group or the like.

With regard to a lithographic printing plate utilizing image silver as ink receptivity, a silver halide emulsion can be contained in the printing plate itself or as a silver source for a printing plate having an image receiving layer by a silver diffusion transfer method. It may be on another negative sheet.

The silver halide emulsion includes silver chloride, silver bromide,
Any of silver chlorobromide and those containing iodide may be used.The binder is preferably gelatin, but a part or all of the gelatin may be replaced with another colloidal substance, for example, casein, albumin, a cellulose derivative or the like. Good. Silver halide is 0.5-7 g / m in terms of silver nitrate
² , The binder can be used usually in the range of 0.5-10 g / m ² .

The method for producing a silver halide emulsion can be produced by a method known in the ordinary photographic industry. Particularly, a production method for use in a printing plate is disclosed in the above-mentioned known patent documents. Can be helpful.

The lithographic printing plate used in the present invention is generally treated with an alkali developing solution after image exposure. As such a developer, any one of an ordinary photographic developer containing a developing agent such as hydroquinone, a developer of a silver diffusion transfer method containing hypo and the like, or a high alkali developer obtained by converting them into an activator can be used.

[0027]

EXAMPLES The present invention will be described below with reference to examples, but is of course not limited thereto.

Example 1 A matted layer containing silica particles having an average particle size of 5 μm was provided on one side of a polyester film support having been subjected to a subbing treatment, and the opposite side was provided with carbon black in such an amount that the light reflectance was 3%. An anti-halation undercoat layer (adjusted to pH 4) containing 20% by weight of silica powder having an average particle diameter of 7 μ with respect to photographic gelatin, and a silica powder having an average particle diameter of 7 μ after chemical sensitization. 5% by weight based on gelatin
And a high-sensitivity silver chloride emulsion (adjusted to pH 4) spectrally sensitized to the green sensitive region containing the above-mentioned ratio.

The undercoat layer was coated at 3.5 g / m ² , the emulsion layer at 0.8 g / m ² , and silver halide in terms of silver nitrate at 1.0 g / m ² . The undercoat layer and the emulsion layer contain formalin as a hardening agent in an amount of 5.0 mg / g gelatin based on gelatin. After drying and heating at 40 ° C. for 14 days, the plate No. 2 of JP-A-54-103104 Example 2 was placed on this emulsion layer. A lithographic printing plate is manufactured by applying and drying the core coating solution described in No. 31. The silver halide emulsion was obtained by adding 4 × 10 ⁻⁶ mol of rhodium chloride per mol of silver halide at the time of physical ripening, and had an average grain size of 0.4 μm.

The lithographic printing plate precursor thus obtained is image-exposed with a plate making camera having an image reversing mechanism, and is developed with the following developing solution (used solution) at 30 ° C. for 30 seconds. Treated with stabilizing solution. <Developer> Sodium hydroxide 24 g Potassium hydroxide 8 g Anhydrous sodium sulfite 50 g 2-Methyl-2-amino-1-fluoroethanol 30 g Make up to 1 liter with water. <Stabilizing solution> Phosphoric acid 1.2 g Sodium diphosphate 25 g Anhydrous sodium sulfite 2.5 g Ethylene glycol 5 g Colloidal silica (20% aqueous solution) 1 g Make up to 1 l with water. (Adjusted to pH 6)

The printing plate prepared by the above operation is set in an offset printing press, and a plate surface treatment liquid as shown below is applied to the printing plate, and the printing machine is supplied with an AB Dick 1250 (AB)
-Dick's trademark offset printing press), the ink is
AB-Dick 3-1012 at the time of the ink receptivity test
Black gloss, F gloss 68 for hydrophilicity (ground stain) test
Purple S ink (Dainippon Ink), OD30 for humidifier
(Moisturizing liquid manufactured by Mitsubishi Paper Mills) was used for printing.

Citric acid 1 g Sodium citrate 2 g Denatured alcohol 350 g Mercapto compound 1 g Desensitizer 10 g Make up to 1 l with water. Table 1 shows the combinations of the mercapto compound and the desensitizing agent.

[0033]

[Table 1]

Compound A in Table 1 is 2-mercapto-5-
n-Heptyl-oxadiazole, B is 2-mercapto-4-phenylimidazole.

The evaluation of ink acceptability was evaluated as the number of prints until a print was started at the same time that the ink was brought into contact with the plate surface and the paper was started to be fed, and a good image density and no density unevenness were obtained. The evaluation of the water retention (ground stain) of the non-image area was evaluated according to the following evaluation criteria, based on the number of printed sheets when the background stain was generated and could not be used for printing. ２０００ 2000 sheets or more △ 500 to 2000 sheets × 1 to 500 sheets The printing results are shown in Table 2.

[0036]

[Table 2]

From the results, it was confirmed that the present invention improves the hydrophilicity of the non-image area, and quickly obtains a good print without density unevenness without inhibiting the ink receptivity of the image area.

[0038]

According to the embodiments of the present invention, in a lithographic printing plate utilizing image silver as ink receptivity, the hydrophilicity of the non-image area is improved, and the effect of the mercapto compound on the image silver of the image area is improved. A good print without density unevenness can be obtained without obstructing the printing.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-254454 (JP, A) JP-A-57-125938 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03F 7/07 B41N 3/08 G03F 7/00 503

Claims (1)

(57) [Claims] A plate surface treating solution for a lithographic printing plate utilizing image silver as ink receptivity, comprising a compound having at least one kind of mercapto group or thione group and pullulan.