JPH0132795B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a lithographic printing plate support made of an aluminum plate or an aluminum alloy plate. Specifically, a support for a lithographic printing plate that has a surface with excellent hydrophilicity and water retention, has good adhesion to the photosensitive layer provided on the aluminum plate or aluminum alloy plate, and has excellent printing durability. This relates to a manufacturing method. Conventionally, aluminum plates, which have been used as supports for lithographic printing plates, are often used to improve their hydrophilicity and water retention for dampening water during printing, as well as their adhesion to the photosensitive layer provided thereon. It is used after being roughened (grained) by mechanical polishing, chemical etching, electrolytic etching, etc. The surface shape (grain shape) of a grained aluminum plate greatly contributes to the plate-making performance and printing performance of a printing plate, and it is extremely important to control the shape. For example, as a printing plate support for a proofing machine that requires good image reproducibility and resolution, a grained support in which relatively fine and shallow pits are densely present is suitable. On the other hand, the printing plate support for this machine, which requires excellent water retention and high printing durability, has pits with uniform diameters (microscopically uniform).
Moreover, a deep grain shape is suitable. As a graining method, the electrolytic etching method in particular is more effective than mechanical polishing methods (ball polishing, brush polishing, etc.) or chemical etching methods, in that it can produce anything from a relatively fine and shallow grain shape to a deep and uniform grain shape. It has attracted attention in recent years because it is possible. Generally, in the electrolytic etching method, an aluminum plate is immersed in a suitable electrolyte solution and subjected to electrolysis with alternating current or direct current to perform graining. Hydrochloric acid is the most well-known electrolyte. However, when electrolytically etching is performed using hydrochloric acid as an electrolyte, it is possible to obtain deep grains and uniform microscopic grains (for example, the shape when observed with a microscope, etc., at a magnification of 100 to 1200 times). Therefore, when used as a printing plate support for this machine, it has excellent water retention and release properties of the photosensitive layer in areas that should be non-image areas during development, but it is difficult to remove the photosensitive layer in image areas. It is not always possible to obtain satisfactory adhesiveness and printing durability. The inventors of the present invention have carried out extensive research with these points in mind, and have found that by using an aqueous solution containing hydrochloric acid and phenols as the electrolyte, the bit diameter is uniform and deep, which improves water retention and printing durability. The present inventors have discovered that excellent grain can be obtained, and have completed the present invention. That is, the gist of the present invention resides in a method for producing a support for a lithographic printing plate, which comprises electrolytically etching an aluminum plate or an aluminum alloy plate in an electrolytic solution containing hydrochloric acid and phenols. Hereinafter, the present invention will be described in detail. As the aluminum plate applied to the method of the present invention, a pure aluminum plate or an alloy plate mainly composed of aluminum, such as silicon, magnesium, iron, copper, zinc, manganese, An aluminum alloy plate containing chromium or the like is used. The surface of aluminum plates or aluminum alloy plates (hereinafter simply referred to as aluminum plates) is contaminated with oil, rust, dirt, etc.
Prior to electrolytic etching, it is desirable to degrease and wash the aluminum plate in a conventional manner. For example, solvent degreasing with Triclean, thinner, etc., emulsion degreasing with kerosene and triethanolamine, etc., immersion in a caustic soda aqueous solution with a concentration of 1 to 10% at 20 to 70°C for 5 seconds to 10 minutes, and stains that cannot be removed by degreasing alone. Examples include a method in which the oxide film is removed, and then immersed in an aqueous solution of nitric acid or sulfuric acid with a concentration of 10 to 20% at 10 to 50°C for 5 seconds to 5 minutes to neutralize and remove smut after alkali etching. In the present invention, electrolytic etching of an aluminum plate is carried out in an electrolytic solution containing hydrochloric acid and phenols. By adding phenols, grains with uniform pit diameters can be obtained. Examples of such phenols include phenol, monovalent phenols such as cresol, catechol, resorcinol,
Examples include divalent phenols such as hydroquinone and orcine, and trivalent phenols such as pyrogallol, phloroglucin, and hydroxyhydroquinone. Particularly preferred are divalent and trivalent phenols such as catechol, resorcinol, and pyrogallol. The electrolytic solution of the present invention usually contains 3.5 to 35 g of hydrochloric acid/
, preferably 7 to 20 g/and phenols
It contains 0.01-20g/, preferably 0.1-15g/. If the hydrochloric acid concentration is too high, smuts are likely to form and grains with an uneven macroscopic shape (shape when observed with the naked eye) are likely to be formed.
g/or less is preferable. On the other hand, if the hydrochloric acid concentration is too low, the pits formed by electrolytic etching will become microscopically non-uniform, so it is preferably 3.5 g/or more. In addition, if the concentration of phenols is too high, the edge effect during electrolysis will become large, and the shape of grains in the center and edges of the treated aluminum plate will become uneven, and moreover, a lot of smut will occur, so phenols The concentration of these substances is preferably 20g/or less. On the other hand, if the concentration of phenols is too low, the effect of addition cannot be obtained sufficiently, so the concentration of phenols is preferably 0.01 g/or more. The temperature of the electrolytic solution is usually about 10°C to 40°C. The current density is appropriately selected depending on the desired grain depth, but is usually 20 to 200 A/dm2, preferably 50 to 200 A/ ^dm2 .
It is ^about 150A/dm2. If an aluminum plate is electrolytically etched under such conditions, the diameter of the pits will be uniform, the pits will be close enough to each other, and there will be very few flat plateau-like parts, making it a good printing plate. A grain of sand is obtained. The electrolytic etching method according to the present invention is a batch method,
Any continuous method can be used. A continuous method is carried out, for example, by passing an aluminum strip continuously through an electrolytic cell. The aluminum plate electrolytically etched in this way is desmatted by immersing it in an aqueous alkali or acid solution at room temperature to 80°C for 1 to 5 minutes according to a conventional method as required, and then neutralized. Used as a support for It goes without saying that the aluminum plate may be anodized in a conventional manner when used as a support for a printing plate. Specifically, electrolysis is carried out using an aqueous solution of sulfuric acid or phosphoric acid with a concentration of 10 to 50% at a current density of 1 to 10 A/dm ² . After the anodic oxidation, sealing or hydrophilic treatment may be performed using hot water, silicate, dichromate, acetate, hydrophilic polymer compound, etc., if necessary. The photosensitive material applied to the aluminum plate of the present invention obtained by the treatment as described above is not particularly limited, and various known materials can be used. For example, compositions consisting of a hydrophilic polymer and a diazonium salt, diazo compounds such as diazodiphenylamine, compositions of a quinone diazide compound and an alkali-soluble resin, unsaturated carboxylic acids that dimerize upon irradiation with actinic rays, such as cinnamon Examples thereof include acids, polymers whose constituent components are phenylene diacrylic acid, compositions of a binder polymer and a compound that causes a polymerization reaction upon irradiation with actinic rays, and azide compounds. A photosensitive lithographic printing plate can be produced by dissolving the above photosensitive substance together with various known additives in a suitable solvent, applying the solution to the aluminum plate of the present invention, and drying it. If the photosensitive lithographic printing plate is overlaid with copies, exposed and developed according to the conventional method, it will have excellent hydrophilicity and water retention, and will also have good adhesion between the image area made of photosensitive material and the aluminum plate. It is possible to obtain a printing plate that is extremely strong and has excellent printing durability. Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Examples 1 to 8 and Comparative Example 1 0.3 mm thick aluminum plate (material 1050, tempered
H16) was immersed in a 3% caustic soda aqueous solution at 50°C for 1 minute to perform alkali etching.
Washed with water. Further, it was immersed in 10% nitric acid at 25° C. for 1 minute to neutralize and desaturate, and then washed with water. When this aluminum plate was electrolytically etched under the conditions shown in Table 1, grained plates with uniform pit diameters were obtained in all cases compared to the comparative example.

【table】

[Table] Example 9 Electrolytically etched grained plates according to Example 8 and Comparative Example 1 were subsequently heated at 60°C in a 5% caustic soda solution.
After desmatting for seconds, it was neutralized and washed with water. After further anodic oxidation in a 20% sulfuric acid solution at 20° C. and 3 A/dm ² for 1 minute, an o-quinonediazide based photosensitive solution was applied to prepare a photosensitive lithographic printing plate. This photosensitive printing plate was exposed and developed using a positive film to obtain a printing plate, which was used for offset printing. As a result, the printing plate made using the aluminum plate of Example 8 had excellent hydrophilicity and water retention, was resistant to staining, and was still in a printable state even after printing 150,000 copies. On the other hand, the printing plate made using the aluminum plate of Comparative Example 1 showed poor ink adhesion in the image area after 100,000 copies were printed. Examples 9 and 10 and Comparative Example 2 During the manufacturing process of the photosensitive lithographic printing plate obtained in Example 8, 0.05 mole of pyrogallol was added in place of 5 g of pyrogallol used in the electrolytic solution for electrolytic etching.
A total of three types of photosensitive lithographic printing plates obtained in exactly the same manner except that 0.05 mol/mol of catechol and 0.1 mol/mol/tartaric acid were used, respectively, were imaged with a positive film and developed. Obtained a printed version of. Using a friction fastness tester (manufactured by Daiei Kagaku Seiki Seisakusho), the abrasion resistance of the remaining photosensitive layer was measured by rubbing 500 times at a load of 200g (the original state is 100%).The results are shown in Table 2. It was hot on the street.

[Table] From the results, it can be seen that the present invention is significantly superior to the case where other additive components are used in the electrolytic solution, at least in terms of adhesion between the photosensitive layer and the support.

Claims (1)

[Scope of Claims] 1. A method for producing a support for a lithographic printing plate, which comprises electrolytically etching an aluminum plate or an aluminum alloy plate in an electrolytic solution containing hydrochloric acid and phenols. 2 Claim 1 in which the electrolytic solution contains 3.5 to 35 g of hydrochloric acid and 0.1 to 15 g of phenols
The method described in section. 3. The method according to claim 1, wherein the phenol is catechol, resorcinol, or pyrogallol.