JPH03260100A - Production of base for printing plate - Google Patents

Abstract

PURPOSE:To obtain a long-sized base for printing plates having high stability by regulating the concn. of Na ions brought into an electrolytic soln. to a specified range when the surface of an Al sheet is electrochemically roughened in the electrolytic soln. based on hydrochloric acid. CONSTITUTION:When the surface of an Al sheet is electrochemically roughened with AC in an electrolytic soln. based on hydrochloric acid, the concn. of Na ions brought into the electrolytic soln. is regulated to 0-1g/l. Since Na ions sticking on the Al sheet are brought into the electrolytic soln., the concns. of Na ions, Al ions and hydrochloric acid in the soln. are kept constant by replenishing hydrochloric acid and water and discharging the electrolytic soln. by an amt. corresponding to the total amt. of the replenishers. Uniform quality is ensured and a long-sized base for printing plates with slight variation is obtd.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing an aluminum support for printing plates, and more specifically, the present invention relates to a method for producing an aluminum support for printing plates, and more specifically, the present invention relates to a method for producing an aluminum support for printing plates. The present invention relates to a method for chemical treatment, and in particular to a method for manufacturing an aluminium support for printing plates, which is made of an aluminum plate roughened into a uniform honeycomb structure suitable for use in offset printing plates.

[Prior Art] Aluminum has traditionally 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 and to protect against moisture used during printing. The surface is usually roughened for purposes such as retaining water.

Mechanical surface roughening methods such as ball grain, wire grain, and brush grain are known as such surface roughening methods, but in recent years, methods have been developed in which an alternating current is passed through an aluminum plate in an acidic electrolyte such as hydrochloric acid or nitric acid. As a result, an electrolytic surface roughening method in which the surface of an aluminum plate is subjected to electrochemical [il] treatment 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 various conditions such as electrolyte composition, temperature, and electrolytic conditions are kept constant, products with very little variation and uniform performance can be easily obtained.

[Problem to be solved by the invention] It is a conventional method to remove rolling oil and natural oxide film from the surface of an aluminum plate before electrolytic surface roughening treatment, and there is a method in which electrolytic surface roughening is performed after alkali etching. (Japanese Unexamined Patent Publication No. 5165607) and a method in which an aluminum plate is cathodic electrolytically treated in a neutral salt aqueous solution and then electrolytically roughened (Japanese Patent Application No. 1265287) are known. However, between the electrolytic surface roughening treatment process and the pretreatment method for electrolytic surface roughening treatment (hereinafter referred to as etching treatment), a water washing process is normally provided, but it is necessary to prevent the treatment solution from the previous process from being brought in. I can't do that. Furthermore, there was a problem in that the shape of the pits obtained in the electrolytic surface roughening treatment step was significantly distorted due to the liquid from the previous step brought in.

[Means and effects for solving the problem] As a result of our efforts to improve the long-length stability of electrolytic surface roughening treatment, we found that one of the factors was the It was discovered that the instability of the roughened state due to the increase in ammonium ions was the cause. However, the instability of the roughened state could not be resolved solely by the increase in ammonium ions. As a result of extensive research, the present inventors have discovered that the graining properties become unstable due to the introduction of an aqueous solution used in the pretreatment step of electrolytic surface roughening, and have thus arrived at the present invention. -Pre-treatment of aluminum plate for electrolytic surface roughening of Aldanium or Aluminum alloy plate in electrolytic solution mainly composed of hydrochloric acid or nitric acid for boat fishing, i.e. removing rolling oil and natural oxide film on the surface of aluminum plate. It is common practice to use caustic soda for this treatment. Another disadvantage is that the sodium ions brought into the acidic electrolyte used here have a negative effect on electrolytic surface roughening. That is, the graining properties become unstable due to the sodium ions brought into the acidic aqueous solution, and if the surface roughening treatment process lacks long-length stability, it becomes difficult to obtain constant quality over a long length.

An object of the present invention is to solve the above-mentioned problems and provide a method for producing an aluminum support for a printing plate which has a constant quality over a long length and has good long-length stability.

The above object of the present invention is to perform a surface roughening treatment of an aluminum support for a printing plate by electrochemically roughening an aluminum plate using alternating current or direct current in an electrolytic solution mainly containing hydrochloric acid. An aluminum support for printing plates, which is characterized in that the surface roughening method of the aluminum support for printing plates adjusts the concentration of sodium ions carried into an electrolytic solution mainly consisting of hydrochloric acid to a range of 10-1 g/f. The problem is solved by the manufacturing method.

The method of the present invention uses an electrolyte mainly composed of hydrochloric acid, and the sodium ion concentration in the electrolyte is controlled within a certain concentration range by adding sodium salt additives or bringing in sodium ions from a pretreatment process. It is characterized by being adjusted to.

As the sodium ion concentration in this electrolyte increases, the bit shape obtained by electrolytic roughening changes, so the roughened surface in the length direction of the aluminum plate that is continuously electrolytically roughened changes. The shape becomes irregular,
Its performance as a printing plate support varies along its length. Therefore, by controlling the sodium ion concentration in this electrolytic solution within a certain range in conjunction with the electrolytic graining conditions, electrolytic graining can be stably performed along the length of the aluminum support for printing plates. becomes possible. The sodium ion concentration can be adjusted within a certain range by, for example, changing the amount of electrolyte solution.

Specifically, sodium ions adhere to the aluminum plate and are brought in, so sodium ions, aluminum ions, and hydrochloric acid are removed by replenishing hydrochloric acid and water and discarding the electrolyte equivalent to the replenished amount. The concentration can be kept constant.

Particularly advantageous electrolysis conditions for the aluminum support for printing plates in the present invention are as follows.

Salt flI concentration is 5-15g/j! , iron, copper, manganese, magnesium, etc. may be contained in the aluminum plate. Alternatively, as disclosed in Japanese Patent Application No. 1-56377, an electrolytic solution containing ammonium ions may be used.

In the present invention, electrochemical roughening in an acidic electrolyte using alternating current means that alternating current is supplied between the aluminum plate and the counter electrode in an acidic electrolyte containing metal ions. The acidic electrolyte referred to in the present invention can be any one used for electrochemical surface roughening using ordinary alternating current, but a particularly preferred one is one in which hydrochloric acid is It is a liquid containing ~15 g/l. Salts containing NOi- or C such as aluminum nitrate, aluminum chloride, ammonium nitrate, ammonium chloride, manganese nitrate, manganese chloride, iron nitrate, and iron chloride may be added to these solutions. Of course, it is possible to add metal ions that dissolve from the aluminum plate as a trace component to more stably roughen the surface.The electrolytic treatment time can be either too long or too short. A current density of 20 to 100 A/dm is preferable, since a rough surface cannot be obtained, and the current density is preferably 5 to 90 seconds. The liquid temperature is 3
The temperature is preferably 0 to 60° C. The power source used for surface roughening may be alternating current or direct current, but when roughening treatment is performed continuously using direct current, it is preferable to alternately arrange anodes and cathodes.

When roughening the surface using alternating current, the frequency of the power source used for surface roughening is 0, 1 to 4 depending on the type of electrolyte.
You can select from a wide range up to 00Hz. Frequency 100-140
Hz is preferable, and the duty ratio is 1:1 for the NB waveform.
It is desirable for the equipment to use a rectangular wave. When expressed as a time constant, waveform distortion is preferably 2 m5ec or less. In the present invention, carbon is preferable as the counter electrode for supplying alternating current to the aluminum plate.

The present invention relates to electrolytic surface roughening.
Needless to say, it is also applicable to a method that combines mechanical surface roughening and electrolytic surface roughening as described in Japanese Patent No. 16918.

[Example 11] A JI51050 aluminum plate was washed with a caustic soda aqueous solution and then with water. Add this aluminum plate to 174 degrees hydrochloric acid.
2.5 g/j! , 11.5 at a current density of 35 A/dm'' at 35°C in an electrolyte with an aluminum ion concentration of 5 g/l.
Second electrolytic surface roughening treatment was performed. At this time, the sodium ion concentration in the hydrochloric acid electrolyte is Og/j2, Ig/
/! and 2 g/1. The results were as shown in Table 1.

In this case, the electrolytic conditions are salt #! Concentration 12.5g/
l, aluminum ion concentration 5g/j! , 1ffl temperature 3
5"c, ft current density 5 A/dm",
Electrolysis time of 11.5 seconds was a common condition.

As is clear from Table 1, sodium ions are 2g/f
If the increase exceeds fi, the quality grade becomes C rank,
Unfinished: Ching will occur, and not only will the surface be roughened, but the appearance will also be poor. Observation of the Ki surface shape was performed using a scanning electron microscope JSM-T22OA manufactured by JEOL. In addition, during observation, the quality of the first surface after electrolytic roughening was graded A: Very good B: Fairly good C: Poor The aluminum plate was dissolved in sulfuric acid at 300 g/1. ．． After immersing at 60℃ for 120 seconds, washing with water and electrolytically roughening the surface.7
The aluminum hydroxide was removed.

[Effect of the Invention 1 As described in the present invention, when electrolytically roughening an aluminum plate or aluminum J1 alloy using alternating current in an electrolyte containing hydrochloric acid as a living body, if-ifium ions in the electrolyte are Concentration from O to Ig/I! By limiting the surface area to 100 nm, it has become possible to perform stable electrolytic surface roughening that provides constant quality over a long length. Further, if the sodium ion concentration in the electrolytic solution is controlled to 0 to 1 g/l, the water washing process provided between the previous process and the previous process becomes unnecessary.

(3 others)

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 hydrochloric acid, the concentration of sodium ions contained in the electrolytic solution mainly composed of hydrochloric acid is determined. 1. A method for producing an aluminum support for printing plates, which comprises adjusting the amount of aluminum to a range of 0 to 1 g/l.