JPH03253600A - Production of base for printing plate - Google Patents

Abstract

PURPOSE:To produce the base for printing plates having uniform grain of a large bit diameter by subjecting an aluminum sheet to an electrochemical surface roughening treatment by using an AC in an electrolyte essentially composed of nitric acid to which sodium ions are added. CONSTITUTION:The aluminum sheet is subjected to the electrochemical surface roughening treatment by using the AC in the electrolyte essentially composed of the nitric acid. The sodium ions are added into the electrolyte essentially composed of the nitric acid in the process for production of the above-mentioned aluminum base for printing plates. The sodium ions are added in the form of a salt, such as sodium nitrate, and the concn, thereof is about <=1.5g/l, more preferably 0.5 to 1.0g/l. The concn. of the nitric acid is preferably about 5 to 25g/l. The treatment by this electrolyte is adequately executed at about 20 to 60 deg.C, about 20 to 100A/dm<2> current density and about 5 to 90sec treating time. The surface of the grain having the uniform pit diameter is formed in this way and the aluminum base for printing plates having the excellent hydrophilic property, water holdability and printing resistance is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing an aluminum support for printing plates. The present invention relates to a method of chemical treatment, and in particular to a method of producing an aluminum support for a printing plate comprising an aluminum plate roughened into a uniform honeycomb structure suitable for use in offset printing plates.

(Prior Art) Aluminum has conventionally been used as a support for offset printing plates, but its surface has been designed to provide good adhesion to the photosensitive layer provided thereon, as well as to protect against moisture used during printing. The surface is usually roughened for purposes such as retaining water.

Mechanical surface roughening methods such as pole grain, wire grain, and brush grain are known as such surface roughening methods, but in recent years, methods have been developed in which alternating current is passed through an aluminum plate in an acidic electrolyte such as hydrochloric acid or nitric acid. For this reason, an electrolytic surface roughening method that electrochemically roughens the surface of an aluminum plate is attracting attention.

According to this electrolytic surface roughening method, an aluminum plate having a uniformly roughened surface with a smaller average roughness distribution can be obtained compared to the conventional mechanical roughening method, but the conditions for obtaining such a roughened surface are is extremely narrow, and if conditions such as electrolyte composition, temperature, and electrolytic conditions are kept constant, it is possible to easily obtain products with uniform performance with very little variation, resulting in stable products. Suitable for industrial production. By electrochemical roughening method, the pits are large and deep compared to their diameter, suitable as aluminum supports for printing plates.
A number of methods have been proposed to obtain a uniform and dense grain.

The methods include a surface roughening treatment method using a special electrolytic power supply waveform (Japanese Patent Application Laid-Open No. 1983-67507), a ratio of the amount of electricity at the anode and the cathode during electrolytic surface roughening treatment using alternating current (special The power waveform (Japanese Patent Application Laid-Open No. 55-25381), the combination of the amount of current per unit area (Japanese Patent Application Laid-Open No. 56-29699), etc. are known.

[Problems to be Solved by the Invention] As a method for roughening the surface of a support for a printing plate, it is a conventional method to roughen the surface electrochemically using alternating current in an aqueous solution mainly composed of nitric acid or hydrochloric acid. In particular, a method of electrochemically roughening the surface using alternating current with an aqueous solution containing nitric acid as a main ingredient is often used because it is easy to obtain a product with a long printing life with a relatively low amount of electricity. However, at this time, 1 piece 1
However, in order to improve the printing performance of the negative layer, it was necessary to keep the surface roughness low while increasing the pit diameter. To achieve this, the temperature of the electrolytic solution may be set low, but setting the temperature of the electrolytic solution low has the drawback of increasing the load on the refrigerator. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing an aluminum support for a printing plate, which eliminates the conventional drawbacks and allows a large grain size with a uniform pit diameter to be obtained.

[Means for Solving the Problems] The present inventors have discovered that when sodium ions are added to an electrolytic solution mainly composed of nitric acid, the pit diameter increases. That is, the present invention relates to a method for manufacturing an aluminum support for a printing plate in which surface roughening treatment is carried out electrochemically using alternating current in an electrolytic solution mainly composed of nitric acid, which is characterized in that sodium ions are added thereto. This is a method for manufacturing an aluminum support for use.

As the electrochemical surface roughening treatment in the present invention, a well-known electrochemical surface roughening treatment can be applied, and a surface roughening method using alternating current can be used.

The alternating current waveform used for electrochemical surface roughening in the present invention is a current with a waveform obtained by alternating positive and negative polarities, such as a rectangular wave, trapezoidal wave, sine wave, and triangular wave, and is limited. A rectangular wave is particularly preferable, although it is not limited to that.

As the electrolytic bath, any bath used for electrochemical surface roughening using ordinary alternating current can be used, but a particularly suitable one is an aqueous solution containing 5 to 25 g/f of nitric acid, and the liquid temperature is 20 ° C. ~60°C is preferred. Also, the current density is 2 O
It is preferably in the range of A/dm2 to 100 A/dm'. If the electrolytic treatment time is too long or too short, an optimum roughened surface will not be obtained, so it is preferably within a range of 5 to 90 seconds.

Electrochemical surface roughening by the method of the present invention can be carried out by a batch method, a semi-continuous method, or a continuous method.

Before electrolytic surface roughening treatment, immersion treatment in caustic soda or acid, or cathodic electrolysis treatment in a neutral salt aqueous solution as described in JP-A-59-11295 may be performed according to a conventional method. Further, mechanical surface roughening treatment may be performed.

As an aluminum support for electrolytic surface roughening, JIS
1050 material, JIS 1100 material, jIs 3
0[)3 material or an aluminum alloy plate containing 0.3% or more of Mn can be used.

Sodium ions in the nitric acid electrolyte are sodium nitrate,
It is added in the form of sodium salts such as sodium sulfate and sodium chloride, but sodium nitrate is particularly suitable. In addition, sodium ions that adhere to the aluminum plate and enter from the previous process are also brought into the nitric acid electrolyte.

The concentration of sodium ions is not preferable if it is too high or too low, and is preferably 1.5 g/42 or less, especially 0.5 to L, Og
A range of /l is preferred.

Of course, the electrolytic solution mainly composed of nitric acid in the present invention may contain ammonium ions and aluminum ions. Ammonium ions and aluminum ions may be added to the nitric acid electrolyte in the form of ammonium salts and aluminum salts. Ammonium ions and aluminum ions increase in the electrolyte through electrolytic roughening treatment in the nitric acid electrolyte. In order to keep the concentration constant, the electrolytic solution is drained and nitric acid, water, etc. are replenished. Along with this, sodium ions are also discarded. In addition, sodium ions are attached to the aluminum support and brought in or taken out. Therefore, in order to keep the concentration of sodium ions in the electrolytic solution mainly composed of nitric acid constant, it is necessary to control these quantitative relationships. The aluminum support that has been electrochemically roughened in this way is immersed in an aqueous solution containing acid or alkali to remove and lighten the smut that is mainly composed of aluminum hydroxide that was generated during the electrochemical roughening treatment. By performing this etching, an even better aluminum support for printing plates can be obtained. For mild etching, electropolishing treatment in a phosphoric acid or sulfuric acid electrolyte may be performed.

In addition, by anodizing the rough plate obtained in the above manner in an electrolytic solution containing sulfuric acid or phosphoric acid according to a conventional method, a printing plate with excellent hydrophilicity, water retention, and printing durability can be obtained. It is possible to manufacture a support for Of course, after the anodizing treatment, it may be immersed in an aqueous solution containing sodium silicate or the like to perform a hydrophilic treatment.

The electrochemical surface roughening treatment referred to in the present invention also includes a combination of nitric acid bath and hydrochloric acid bath, and different frequencies. In combination with an electrolytic cell,
What can be applied in combination with known electrochemical surface roughening treatments, such as surface roughening treatment with smut removal treatment in between, and electrochemical surface roughening treatment in separate treatment tanks? Needless to say.

[Example] Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples.

[Example 1] 5% JIS 1050-H14 aluminum rolled plate
It was immersed in a caustic soda aqueous solution at 60° C. for 30 seconds to perform degreasing and cleaning treatment, and after washing with water, it was immersed in an aqueous solution containing 1% nitric acid for 10 seconds and then washed with water. This aluminum plate was heated at 45°C in an electrolytic solution with a nitric acid concentration of 12.5 g/f and an aluminum ion concentration of 4.5 g/strain at a current density of 4.
Electrolytic surface roughening treatment was performed for 5 seconds using square wave alternating current of OA/cm2. (at this time) in the nitric acid electrolyte
The IJium ion concentration was adjusted to Og/ by adding sodium nitrate.
C0,2g/f, 0.5g/R,0,8g/C1,0
g/R12,0g/1. The results were as shown in Table 1.

Table 1 In this case, the electrolytic conditions are as follows: Hydrochloric acid concentration ■ 2.5 g/n
, aluminum ion concentration 4.5g/A, liquid temperature 45℃,
Common conditions were a current density of 40A7/cm2 and an electrolysis time of 5 seconds.

As is clear from Table 1, sodium ion is 0.5
~1.0g/I! With a quality grade of Palanc, a uniform rough surface with an average pit diameter of 2 μm was obtained.
The average pit diameter of Examples 1-1 and 1-2 was 1 μm, and giant pits of about 1011 m were partially present. Further, in the comparative example, unetched portions were formed, and the aluminum plate exhibited metallic luster. The roughened surface shape was observed using a scanning electron microscope JSM-T22OA manufactured by JEOL. For observation, the aluminum plate after electrolytic roughening was immersed in an aqueous sulfuric acid solution of 300 g/V at 60° C. for 120 seconds and then washed with water to remove aluminum hydroxide produced by electrolytic roughening.

[Effects of the Invention] As described in the detailed explanation of the present invention, a method for producing an aluminum support for a printing plate, which performs electrochemical surface roughening treatment using alternating current in an electrolytic solution mainly containing nitric acid. By adding IJium ions (in an electrolytic solution), it is possible to produce an aluminum plate with a large pit diameter and a uniformly rough surface. It became possible to produce lithographic printing plates that could produce good quality prints.

Claims (1)

[Claims] In a method for producing an aluminum support for a printing plate in which surface roughening treatment is carried out electrochemically using alternating current in an electrolytic solution mainly composed of nitric acid, sodium ions are added to the electrolytic solution mainly composed of nitric acid. A method for producing an aluminum support for printing plates, characterized by: