JPH05278363A - Stabilizer for planographic printing plates - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a neutralizing solution for a lithographic printing plate which uses a photosensitive silver halide emulsion and improves the ink releasing ability of the lithographic printing plate. [Structure] A neutralizing solution for a lithographic printing plate to which a photosensitive silver halide emulsion is applied contains at least one amino acid-based surfactant which is one type of zwitterionic surfactant. [Effect] The ink releasing ability of the planographic printing plate could be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stabilizing solution for a lithographic printing plate to which a photosensitive silver halide emulsion is applied.

2. Description of the Related Art A lithographic printing plate comprises an oleophilic portion that receives ink and a hydrophilic non-printing portion that does not receive ink, and the non-printing portion generally receives water. Therefore, in normal lithographic printing, both ink and water are supplied to the plate surface, and the image area selectively receives the colored ink and the non-image area receives water to transfer the ink on the image to the paper. Done by

Therefore, in order to obtain a good printed matter, the difference in the lipophilicity and hydrophilicity of the surface between the image area and the non-image area is sufficiently large, and when the water-ink in the emulsified state comes, It is necessary that the line portions receive sufficient ink and the non-printed portions receive sufficient water, and it is desirable that the effect lasts up to as much printed matter as possible.

In a lithographic printing plate to which a photosensitive silver halide emulsion is applied, the silver image portion becomes lipophilic and the ink receptivity is obtained, and the non-silver image portion becomes hydrophilic and the water receptivity is obtained. Due to this selectivity, the ink attached to the silver image portion is transferred to the paper, and a printed matter is obtained. However, the non-silver image portion is hydrophilic but poor in water retention, and the repulsion of the printing ink is extremely poor, so that ink stains are noticeable on the non-silver image portion due to printing. In order to improve the hydrophilicity of the non-silver image portion, a method of adsorbing a cellulose derivative or arabic rubber on the plate surface is known, but the hydrophilicity obtained by these methods is still insufficient, and ink and water When the ink is supplied to perform printing, ink stains occur on the non-silver image portion of the printed matter.

The response of the in-key water is important for printing, and it is preferable that the response is fast when ink and water feeds are changed to set appropriate printing conditions. In particular, in the field of offset rotary presses, in order to prevent paper breakage, often the etching with dampening water is omitted at the start of printing,
Ink adheres to the non-silver image area. Therefore, the desorption speed of the ink is important at the time of rising, and the desorption speed of the ink is required. This is called the ink detachment ability.

The term "ink releasing ability" as used herein means that the ink is applied to the entire surface of the lithographic printing plate without supplying the dampening liquid and printing is started, and then the ink is supplied after the dampening liquid is supplied to perform normal printing. Refers to the speed at which the image can be removed from the non-silver image portion of the plate surface, and the faster the speed, the better the ink desorption ability.

[0006]

A lithographic printing plate to which a photosensitive silver halide emulsion is applied is a printing plate (PS) which has been realized and is essentially composed of, for example, a diazonium salt photosensitive material or a p-diazoquinone photosensitive material. It has a drawback that it is extremely inferior to the ink releasing ability in comparison with the plate).

Conventionally, in order to prevent ink stains on the non-image area of a lithographic printing plate, a cellulose derivative or colloidal silica is used in a developing solution, a neutralizing solution, an etching solution, a moistening solution, etc. (Japanese Patent Laid-Open No. 54-83502). It is known to add hydrophilic polymers such as polyvinyl alcohol and the like.
However, these techniques take into consideration the ink stain prevention property of the non-image area at the time of printing a large number of prints, and are different from the ink removal ability related to the inkey water responsiveness at the start of printing, which is different from the ink removal performance. It was not a technique that could achieve a sufficient effect in terms of releasability. An object of the present invention is to provide a neutralizing solution for a lithographic printing plate to which a photosensitive silver halide emulsion capable of imparting an ink releasing ability to a plate surface is applied.

[0008]

The above-mentioned object is to provide at least an amino acid-based surfactant, which is one type of zwitterionic surfactant, in a neutralizing solution for a lithographic printing plate to which a photosensitive silver halide emulsion is applied. It was achieved by containing one or more kinds.

[0009] The amino acid-based surfactants are those which are derivatized from various generally known amino acids (eg, glycine, glutamic acid, histidine, etc.), and N-acyl amino acids having a long-chain acyl group introduced and That salt. These synthetic methods are described in Yoshinosuke Yoshida: “Organic Synthetic Chemistry” 33, 672 (1975) and the like.
For example, fatty acid residues such as coconut oil fatty acid, stearic acid, lauric acid, and palmitic acid are used in the long-chain acyl group portion. The amino acid-based surfactant is commercially available, for example, from Ajinomoto Co., Inc. as “Amisoft” and from Lion Co., Ltd. as “Lipomin”.

The amino acid-based surfactant used in the present invention is 0.4-4.0% by weight, preferably 1.5-% by weight in a neutralizing solution for a lithographic printing plate to which a photosensitive silver halide emulsion is applied.
It is desirable to contain 3.5% by weight.

The neutralizing solution of the present invention is applied to a lithographic printing plate to which a silver halide emulsion is applied as described above,
In the plate-making process, it means a solution used for neutralizing the pH of the plate surface after development processing within the range of 5-8. The silver halide emulsion may be any of silver chloride, silver bromide, silver chlorobromide and those containing iodide, and gelatin is preferable as the binder, but part or all of gelatin is another colloidal substance, For example, casein, albumin, polyvinyl alcohol / maleic anhydride,
It may be substituted with a cellulose derivative, an acrylamide / vinylimidazole copolymer, or the like. The amino acid-based surfactant of the present invention is considered to specifically adsorb to these binders and improve the ink releasing ability, but the details are unknown.

The neutralizing solution of the present invention contains, in addition to an amino acid-based surfactant, a desensitizing accelerator (eg, cellulose derivative, polyacrylic acid, gum arabic, colloidal silica, etc.), a buffering agent (eg, potassium phosphate, citric acid). Sodium acid salt, sodium propionate, etc.) complexing agent (for example, iminodiacetic acid, ethylenediaminetetraacetic acid, ethanolamine, etc.),
And wetting agents (eg ethylene glycol, polyethylene glycol, etc.) can be admixed. In addition, antiseptics, fungicides, and rust preventives may be added as necessary.

[0013]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. 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 which had been subjected to an undercoating treatment, and the opposite surface thereof contained carbon black in an amount such that the light reflectance was 3%. , A halation-preventing subbing layer (adjusted to pH 4) containing 20% by weight of silica powder having an average particle size of 7 μm, and silica powder having an average particle size of 7 μm after being chemically sensitized to photographic gelatin On the other hand, a high-sensitivity silver chloride emulsion layer (adjusted to pH 4) spectrally sensitized in the green region was provided in a proportion of 5% by weight.

The gelatin of the undercoat layer was 3.5 g / m ² , the gelatin of the emulsion layer was 0.8 g / m ² , and the silver halide equivalent to silver nitrate was 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 with respect to gelatin. 14 after drying at 40 ℃
After heating for a day, the emulsion layer was overlaid on the surface of JP-A-54-103.
104 The core coating solution described in Plate No. 31 of Example 2 is applied and dried to produce a lithographic printing plate. The silver halide emulsion contains 4 × 10 − per mol of silver halide during physical ripening.
6 mol of rhodium chloride was added, and the average particle size was 0.40 μm.

The lithographic printing plate precursor thus obtained is image-exposed with a plate-making camera having an image reversal mechanism, and developed with the following developer (working solution) at 30 ° C. for 30 seconds, and then the following: The solution was treated with the neutralizing solution shown in the table. <Developer> Sodium hydroxide 7.5 g Potassium hydroxide 17 g Anhydrous sodium sulfite 35 g Triethanolamine 10 g 2-Mercaptobenzoic acid 0.25 g 3-Mercapto 4-acetamido 5-a-0.2 g Heptyl-1,2 , 4-triazole Uracil 1 g Make up to 1 liter with water.

[0016]

[Table 1] Surfactants A and B in the table are the amino acid-based surfactants of the present invention, respectively, and are “Amisoft CT-12 and HS-21” commercially available from Ajinomoto Co., Inc., respectively.
HEC, CMC and PVA represent hydroxyethyl cellulose, carboxymethyl cellulose and polyvinyl alcohol, respectively. Colloidal silica is the amount of 20% solution added. Suwanol AM is a zwitterionic surfactant marketed by Nikko Chemical Company.

The printing plate produced by the above operation was set in an offset printing machine (Ryobi 560 offset printing machine with a Dahlgren device), and printing was performed using a dampening liquid having the following composition. Ink is made by Dainippon Ink and Co., Ltd.
World-RFb ink was used.

<Moisturizing liquid> (use liquid is diluted 10 times with water) Water 800 ml Ethylenediaminetetraacetic acid 0.5 g Colloidal silica (20% solution) 33 g Sodium dihydrogen phosphate 10 g Ethylene glycol 60 g

The determination of the ink releasing ability is carried out after 100 sheets of normal printing are stopped by stopping the water supply of the dampening liquid, the ink is placed on the entire plate surface, and after the normal printing is restarted until a good image is reproduced. This was done by recording the number of sheets. The judgment results are shown in the table.

[0020]

[Table 2] As is clear from the results, the lithographic printing plate treated with the neutralizing solution containing the amino acid-based surfactant of the present invention, compared with the conventional desensitizing agent, cellulose derivative, hydrophilic polymer, etc. It was found that it would be a lithographic plate with excellent separation ability.

[0021]

According to the embodiments of the present invention, it is possible to improve the ink releasing ability at the start of printing for a lithographic printing plate to which a photosensitive silver halide is applied.

Claims (1)

[Claims] 1. A neutralizing solution for a lithographic printing plate to which a photosensitive silver halide emulsion is applied, which contains at least one amino acid type surfactant which is one kind of zwitterionic surfactant.