JPH0132078B2 - - 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. The present invention relates to a method of manufacturing a body. Conventionally, the aluminum plate used as a support for lithographic printing plates is often coated with water to improve its hydrophilicity and water retention for dampening water during printing, as well as its adhesion to the photosensitive layer provided thereon. It is used after its surface has been 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 printing plate supports for proofing machines that require good image reproducibility and resolution, relatively fine and shallow pits (pits) are used.
A grain shape with dense grains is suitable. on the other hand,
As a printing plate support for this machine that requires excellent water retention and high printing durability, it is suitable to have pits with uniform diameters (microscopically uniform) and a deep grained shape. ing. Among the graining methods, electrolytic etching is more effective than mechanical polishing methods (ball polishing, brush polishing, etc.) and chemical etching methods in producing 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 to do so. 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 electrolytic etching is performed using hydrochloric acid as an electrolyte,
It is difficult to obtain grains with uniform pit diameters and deep pits with a uniform microscopic shape (shape when observed under 100 to 1000 times magnification with a microscope, etc.). When used as a printing plate support, it has excellent water retention and release properties of the photosensitive layer in areas that should become non-image areas during development, but it has poor adhesion and printing durability of the photosensitive layer in image areas. You can't always get what you're satisfied with. The inventors of the present invention have carried out extensive research with these points in mind, and have found that when an aqueous solution containing hydrochloric acid and an unsaturated carboxylic acid or its salt is used as the electrolyte, the pit diameters are fine and uniform, and the pits are dense and compact. In addition, the present inventors have discovered that a grain having deep pits can be obtained, and as a result, a printing plate support with excellent water retention and printing durability can be obtained, and the present invention has been completed. That is, the gist of the present invention is to produce a support for a lithographic printing plate, which comprises electrolytically etching an aluminum plate or an aluminum alloy plate in an electrolytic aqueous solution containing hydrochloric acid and an unsaturated carboxylic acid or a salt thereof. It lies in the method. To explain the present invention in detail below, the aluminum plate applied to the method of the present invention includes a pure aluminum plate or an alloy plate mainly composed of aluminum, such as silicon, magnesium, iron, copper, zinc, manganese, chromium. Aluminum alloy plates containing aluminum alloys and the like are 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, 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, stains that cannot be removed by degreasing alone, and natural oxidation. remove the film,
Then, in an aqueous solution of nitric acid or sulfuric acid with a concentration of 10-20%.
Examples include a method of immersing 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 aqueous solution containing hydrochloric acid and an unsaturated carboxylic acid or a salt thereof. The electrolytic aqueous solution of the present invention usually contains 0.1 to 1 mol of hydrochloric acid and 0.01 to 1 mol of unsaturated carboxylic acid or a salt thereof.
It contains 1 mol/, preferably 0.05 to 0.5 mol/. If the hydrochloric acid concentration in the electrolytic aqueous solution is too high, smuts are likely to be formed, resulting in uneven grains with poor grain appearance.On the other hand, if the hydrochloric acid concentration is too low, the pits formed will be microscopically non-uniform. Therefore, a concentration within the above range is preferable. In addition, if the concentration of unsaturated carboxylic acid or its salt is too high, the pitching suppressing effect will be strong, and the current density will have to be extremely high to obtain the desired grain. A concentration within the above range is preferable since it becomes impossible to obtain a grain having a small pit diameter and dense and deep pits. The unsaturated carboxylic acid or its salt used in the present invention is not particularly limited, but has 3 carbon atoms.
-5 unsaturated carboxylic acids or salts thereof are preferred. Specific examples include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, and alkali metal salts thereof. Particularly preferred are acrylic acid, crotonic acid, maleic acid, and itaconic acid. In the present invention, electrolytic etching is usually carried out at a bath temperature of 10 to 70°C and a current density of 20 to 200 A/dm ² , preferably 50 to 150 A/dm ² for 5 to 120 seconds.
In particular, the present invention has the advantage that a good grain can be obtained even by electrolytic etching at a bath temperature of 40° C. or higher, which is generally considered undesirable. That is, since high-temperature electrolytic etching is possible, the electrolytic voltage can be lowered, and as a result, power costs can be reduced. Furthermore, the cooling cost for suppressing the rise in bath temperature due to heat generated during electrolytic etching can be significantly reduced. These advantages are
This is even more noticeable in high-speed electrolytic etching using a continuous method. If an aluminum plate is electrolytically etched under the above conditions, it is possible to obtain a grain-grained aluminum plate with pits that are sufficiently close to each other, with few flat plateau-like parts, and with dense and deep pits. It can be done. The aluminum plate electrolytically etched in this way is desmatted according to a conventional method by immersing it in an aqueous alkali or acid solution at room temperature to 80°C for 1 to 5 minutes, and then the printing plate is neutralized. Used as a support for At this time, the aluminum plate may be further subjected to anodizing treatment. For example, 10 to 50
% in an aqueous solution such as sulfuric acid or phosphoric acid, with a current density of 1
This is done by electrolyzing at ~10 A/dm ² .
After the anodizing treatment, pore sealing or hydrophilic treatment may be performed with hot water, silicate, dichromate, acetate, hydrophilic polymer compound, etc. as appropriate. 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 hydrophilic polymers and diazonium salts, diazo compounds such as diazodiphenylamine, compositions of quinone diazide compounds and alkali-soluble resins, 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-mentioned photosensitive substance together with various known additives in a suitable solvent, applying the solution to the aluminum plate of the present invention, and drying the solution. If an object is placed on this photosensitive lithographic printing plate and exposed and developed according to a 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. A printing plate that is extremely strong and has excellent printing durability can be obtained. 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 the gist thereof is exceeded. Examples 1 to 6 and Comparative Examples 1 to 2 0.3 mm thick aluminum plate (material 1050, tempered
H18) was immersed in a 1% aqueous sodium hydroxide solution at 50°C for 1 minute to carry out alkali etching, and then washed with water. Next, it was immersed in 10% nitric acid at 25°C for 1 minute to neutralize and desmat, and then washed with water. This aluminum plate was subjected to electrolytic etching under the conditions shown in Table 1. The results are shown in Table 1.

[Table] Example 7 and Comparative Example 3 The grained aluminum plates obtained in Example 1 and Comparative Example 1 were subsequently desmatted in a 5% caustic soda solution at 60°C for 10 seconds, and then
% sulfuric acid solution at 25° C., 6 A/dm ² and 30 seconds. Next, a photosensitive lithographic printing plate was prepared by applying an 0-quinonediazide photosensitive solution. This photosensitive lithographic printing plate was exposed to light using a positive film and developed to obtain a printing plate. Next, when used for offset printing, the printing plate made using the aluminum plate of Example 1 had good hydrophilicity and water retention, and was very easy to print, with no peeling of the image area even after printing 200,000 copies. I couldn't help it. On the other hand, in the printing plate made using the aluminum plate of Comparative Example 1, part of the image area peeled off after 80,000 copies were printed, resulting in poor ink adhesion. Examples 8, 9 and Comparative Example 4 During the photosensitive lithographic printing plate obtained in Example 7 and the printing plate manufacturing process, crotonic acid and tartaric acid were used at the same concentration in place of acrylic acid used in the electrolyte for electrolytic etching. A total of three types of photosensitive lithographic printing plates obtained in exactly the same manner except for the above were used, and after image exposure with a positive type film, development was performed to obtain three types of printing plates. 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 these results, it can be seen that the present invention is significantly superior to the best method in which 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 aqueous solution containing hydrochloric acid and an unsaturated carboxylic acid or a salt thereof. 2. The method according to claim 1, wherein the unsaturated carboxylic acid is an unsaturated carboxylic acid having 3 to 5 carbon atoms. 3. The method according to claim 1, wherein the unsaturated carboxylic acid is acrylic acid, crotonic acid, maleic acid or itaconic acid. 4. The method according to claim 1, wherein the electrolytic aqueous solution contains 0.1 to 1 mole of hydrochloric acid and 0.01 to 1 mole of unsaturated carboxylic acid.