JPH06344680A - Plate cleaning agent for planographic printing plates - Google Patents

Abstract

(57) [Summary] [Purpose] In a lithographic printing plate that uses image silver as an ink acceptor, it is excellent in both the cleaning effect of non-image areas and the effect of improving desensitization. The purpose is to provide a cleaning agent. Composition: Achieved by a solution containing glycol ethers. [Effect] The cleaning effect of the non-image area and the desensitizing property were improved, and a stable printed matter could be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plate surface cleaning agent for a lithographic printing plate which utilizes image silver as an ink receptivity.

[0002]

2. Description of the Related Art A printing plate using a silver halide emulsion having high sensitivity and capable of spectral sensitization has already been put into practical use in several forms. Among them, offset printing plates that utilize a silver image as an ink-receptive material include U.S. Pat. Nos. 3,721,559, 3,490,905, and JP-B-4.
No. 8-30562, U.S. Pat. 5
3-9603, etc.

Although these are roughly classified into several types as a method for producing a printing plate, they are common in that the image silver is made ink-receptive. The lithographic printing plate is composed of an image-forming portion that receives lipophilic ink and a non-image-forming portion that is hydrophilic and receives water. Therefore, if the balance is lost and the hydrophilic non-image area is deteriorated for some reason, the lipophilic ink adheres to the area to cause scumming.

It has been customary to remove this adhered ink and treat it with a cleaning agent (also called a plate cleaner) that restores the hydrophilicity of the area. As this cleaning agent, an O / W type emulsion in which an aqueous solution of gum arabic and a petroleum distillate are mixed has been conventionally used, but this cleaning agent is mainly an offset PS plate (pre).
It is designed to be compatible with an offset printing plate using a metal substrate such as a sensitized plate.

In fact, when this cleaning agent is used for cleaning and desensitizing the plate surface of a lithographic printing plate which uses image silver as an ink receptivity, there are disadvantages. For example, there are problems such as a decrease in the hydrophilicity of the non-image area due to a petroleum fraction and an emulsification of the ink. At present, no cleaning agent suitable for a lithographic printing plate that utilizes image silver as an ink acceptor has been developed.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to provide an image silver ink which is excellent in both the cleaning effect and the desensitization improving effect without the drawbacks found in the prior art. The purpose of the present invention is to provide a plate surface cleaning agent for a lithographic printing plate which is used as an acceptability.

[0007]

The above objects of the present invention are as follows.
Achieved by a plate cleaning agent characterized by containing glycol ethers.

The glycol ethers relating to the present invention are described below, but the invention is not limited thereto.

Ethylene glycol monoethyl ether,
Examples thereof include ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, diethylene glycol monobutyl ether, diethylene glycol diethyl ether, and dipropylene glycol monomethyl ether.

The content of the glycol ether used in the present invention is 5 to 100% by weight, preferably 2
It is 0 to 100% by weight.

Further, the plate surface cleaning agent may be mixed with commonly used buffering agents, preservatives, preservatives, wetting agents, surfactants and the like, if necessary. 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.

Regarding a lithographic printing plate utilizing image silver as an ink-receptive material, a silver halide emulsion may be contained in the printing original plate itself, or as a silver supply source for a printing original plate having an image receiving layer by a silver diffusion transfer method, It may be provided on another negative sheet.

The silver halide emulsion comprises silver chloride, silver bromide,
Any of silver chlorobromide and those containing iodide may be used, and the binder is preferably gelatin, but gelatin may be partially or wholly replaced with other colloidal substances such as casein, albumin and cellulose derivatives. Good. Silver halide is 0.5-7 g / m in terms of silver nitrate
² and the binder can be usually used in the range of 0.5-10 g / m ² .

The method for producing a silver halide emulsion can be carried out by a method known in the ordinary photographic industry, and a method particularly for use in a printing plate is also disclosed in the above-mentioned known patent documents. Can be used as a reference.

The lithographic printing plate used in the present invention is generally treated with an alkali developing solution after imagewise exposure. As the developer, any developer such as a normal photographic developer containing a developing agent such as hydroquinone, a developer for silver diffusion transfer method containing hypo, etc., or a highly alkaline developer obtained by activating them can be used.

[0016]

The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1 A matting layer containing silica particles having an average particle size of 5 μ was provided on one surface of a polyester film support which had been subjected to an undercoating treatment, and the opposite surface thereof had a light reflectance of 3% of carbon black. A halation-preventing subbing layer (adjusted to pH 4) containing 20% by weight of silica powder having an average particle size of 7μ with respect to photographic gelatin, and a silica powder having an average particle size of 7μ after being chemically sensitized. 5% by weight to gelatin
And a high-sensitivity silver chloride emulsion spectrally sensitized (adjusted to pH 4) in the green range.

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 contained formalin as a hardening agent in an amount of 5.0 mg / g gelatin with respect to gelatin. After drying and heating at 40 ° C. for 14 days, the plate No. 1 of Example 2 of JP-A-54-103104 was placed on the emulsion layer. The core coating solution described in 31 is applied and dried to produce a lithographic printing plate. The silver halide emulsion was prepared by adding 4 × 10 ⁻⁶ mol of rhodium chloride per mol of silver halide during 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 reversal mechanism, and developed with the following developer (use liquid) at 30 ° C. for 30 seconds, and then the following: Treated with stabilizer. <Developer> Sodium hydroxide 24 g Potassium hydroxide 8 g Anhydrous sodium sulfite 50 g 2-Methyl-2-amino-1-propanol 30 g Water to make 1 liter. <Stabilizing solution> Phosphoric acid 1.2 g Dibasic sodium phosphate 25 g Anhydrous sodium sulfite 2.5 g Ethylene glycol 5 g Colloidal silica (20% aqueous solution) 1 g Water to make 1 liter. (Adjusted to pH 6)

Using the printing plate prepared by the above operation,
Ryobi 2800CD (trademark of offset printing machine made by RYOBI) in the printing machine, AB-Dick3-1 in the ink
When OD30 (a humidifying liquid manufactured by Mitsubishi Paper Mills Co., Ltd.) was used as the black ink and the dampening liquid, printing was performed. After printing about 10,000 sheets, scumming occurred on the non-image area of the printing plate.

Therefore, a plate surface cleaning agent having the composition shown in the following table was prepared, and this was included in a sponge to wash the non-image area.

[0022]

[Table 1]

As the PS plate cleaning agent in Table 1, CU-3 manufactured by Fuji Photo Film Co., Ltd. was used.

After the plate surface was washed, about 2000 sheets were printed again, and it was examined whether or not background stain was generated on the non-image area of the printing plate. The printing results are shown in Table 2.

[0025]

[Table 2]

From the results, it can be seen that the present invention is excellent in recoverability of detergency and desensitization of non-image areas.

[0027]

According to the embodiments of the present invention, in a lithographic printing plate that uses image silver as an ink-receptive property, it is possible to improve the detergency and desensitization of non-image areas and obtain a stable printed matter. I can.

Claims (1)

[Claims] 1. A plate surface cleaning agent for a lithographic printing plate, which uses image silver as an ink receptive agent, which contains glycol ethers.