JP3329595B2 - Lithographic printing plate processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing method for improving the ink receptivity and printing durability of an image area in a lithographic printing plate placing 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. No. 3,454,398, U.S. Pat. 5
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 lipophilic 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 before printing to improve ink receptivity. That is, the mercapto group or the like of the compound is adsorbed on image silver, the hydrophobic region of the compound covers the image silver, and the difference in lipophilicity and hydrophilicity between the image portion and the non-image portion becomes relatively large. It is considered.

Most of the above compounds having a mercapto group or a thione group are insoluble in water, but are soluble in an alkaline solution or an organic solvent. At present, it is used for a developer which is an alkaline solution and an etchant which uses an organic solvent.

However, even in such a method, if a lithographic printing plate utilizing the above-mentioned image silver as ink acceptability is left on a plate, the ink acceptability and printing durability are deteriorated. That is, the cause of this is that when the plate is kept, the silver portion of the image that receives ink is oxidized, the lipophilicity of the image portion is deteriorated, and the ink receptivity and printing durability are deteriorated. Conceivable.

At present, sulfites, which are inorganic antioxidants, are added to neutralizing solutions (stabilizing solutions) used.
There was no effect in preventing oxidation of the image area, and the ink acceptability and printing durability of the image area were deteriorated.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lithographic printing plate utilizing image silver as ink receptivity.
An object of the present invention is to improve the ink receptivity and printing durability of an image area in a placing plate.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a lithographic printing plate utilizing image silver as ink receptivity, containing at least one or more organic antioxidants .
This was achieved by treating with a neutralizing solution (stabilizing solution) having a pH of 4 to 7 .

The organic antioxidants used in the present invention include aromatic amines such as phenyl-α-naphthylamine,
Phenols such as 2,6-di-t-butyl-p-cresol (BHT), natural antioxidants such as ascorbic acid, tocopherol, aminomethanesulfonic acid, hydroxymethanesulfonic acid, hydroquinone, propyl gallate, gallic Examples thereof include, but are not limited to, isoamyl acid.

The amount of the compound of the present invention used in the neutralizing solution (stabilizing solution) is 1 to 30 g / l, preferably 2 to 2 g / l.
0 g / l. The compounds can be used in combination of two or more. Thereafter, the mixture is prepared by adding other compounds and the like to the mixed solution as needed.

In addition to the above compounds, commonly used buffers, preservatives, preservatives, wetting agents, surfactants and the like can be mixed with the neutralizing solution. For example, in the case of a neutralizing solution, the pH is kept at 4 to 7 by using an inorganic acid such as phosphoric acid or sulfuric acid, or an organic acid such as succinic acid or propionic acid as a buffer. Further, complexing agents such as iminodiacetic acid and ethylenediaminetetraacetic acid can be mixed. Also, inorganic fine particles such as colloidal silica can be mixed as long as the action of the compound is not inhibited.

Further, a compound having a mercapto group or a thione group can be mixed as long as it can be dissolved.

Specific examples of the compound having a mercapto group or a thione group include 2-mercapto-4-phenylimidazole, 1,3-dibenzyl-imidazolidin-2-thione, 2-mercapto-4-phenylthiazole and 2-mercapto-4,5- Diphenyloxazole, 3-mercapto-4-acetamido-5-heptyl-1,2,4-triazole, 2-mercapto-5-n-
Heptyl-oxadiazole, 5-mercapto-1-phenyl-tetrazole, 2-mercapto-5-nitropyridine, 2-mercapto-4,6-diphenyl-1,
Examples thereof include 3,5-triazine and 1,5-dimercapto-3,7-diphenyl-S-triazolino [1,2-a] -S-triazoline, but are not limited thereto.

With regard to a lithographic printing plate utilizing image silver as an 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, and the binder is preferably gelatin. 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 .

A 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.

[0021]

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 surface of a polyester film support having been subjected to a subbing treatment, and the opposite surface 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 gelatin of the undercoat layer was applied at a rate of 3.5 g / m ² , the gelatin of the emulsion layer was applied at a rate of 0.8 g / m ² , and the silver halide was converted to silver nitrate at a rate of 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 Example 2 of JP-A-54-103104 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 was image-exposed with a plate making camera having an image reversing mechanism, and developed with the following developer (used solution) at 30 ° C. for 30 seconds. <Developer> Sodium hydroxide 24 g Potassium hydroxide 8 g Anhydrous sodium sulfite 50 g 2-Methyl-2-amino-1-fluoroethanol 30 g 2-Mercapto-5-n-hexyl-oxasitol 0.2 g Make up to 1 liter with water.

After the above-mentioned development processing, processing was carried out with a neutralizing solution (stabilizing solution) as shown below. <Stabilizing solution> Phosphoric acid 1.2 g Sodium monophosphate 25 g Ethylene glycol 5 g Compound A 3 g Make up to 1 l with water. (Adjusted to pH 6) Compound A is as shown in Table 1.

The printing plate (before placing) prepared by the above operation and the printing plate (after placing) stored in a cool and dark place for one month are then set in an offset printing machine, and the RYOBI3200CD (Ryobi) is placed in the printing machine. Trademark of Offset Printing Press, Inc.), ink is AB-Dick3-1012
SLM-OD30 (humidifying solution manufactured by Mitsubishi Paper Mills) was used as black ink and a moisturizing solution, and etching was performed with this moisturizing solution to perform printing.

[0027]

[Table 1]

The ink acceptability was evaluated as the number of prints until a print was started at the same time when the ink was brought into contact with the plate surface and a paper was started to be fed, and a good image density and no density unevenness were obtained. The printing durability was evaluated according to the following criteria based on the number of printed sheets at the time of the ink jump of the silver image portion. 1: 5000 sheets or less 2: 20000 sheets or less 3: 30000 sheets or less 4: 30000 or more Printing results are shown in Table 2.

[0029]

[Table 2]

From the results, it was confirmed that the ink receptivity and printing durability can be improved even after the plate is placed.

[0031]

According to the embodiment of the present invention, in a planographic printing plate utilizing image silver as ink receptivity, it is possible to improve the ink receptivity and printing durability of an image portion in a stationary plate.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-54-135002 (JP, A) JP-A-2-259643 (JP, A) JP-A-2-284146 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G03F 7/07 B41N 3/08

Claims (1)

(57) [Claims] 1. A lithographic plate comprising at least one organic antioxidant and being treated with a neutralizing solution (stabilizing solution) having a pH of 4 to 7 using image silver as ink receptivity. Processing method of printing plate.