JPH03126899A - Production of support for printing plate - Google Patents

Abstract

PURPOSE:To simplify stages for producing a support for a printing plate by electrolyzing an Al sheet as the cathode in an electrolytic soln. of a neutral salt and electrochemically roughening the surface of the sheet in an acidic aq. soln. CONSTITUTION:An Al or Al alloy sheet is electrolyzed as the cathode in an electrolytic soln. of a neutral salt such as NaCl. After washing, the surface of the sheet is electrochemically roughened in an acidic aq. soln. of nitric acid, etc., contg. metal ions. Since a surface modifying effect due to the cathodic electrolysis enables satisfactory degreasing and the dissolution of the surface layer of the Al sheet, chemical cleaning for electrolytic surface roughening can be omitted. A support for a printing plate having a uniformly roughened surface 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, it involves electrochemically roughening an aluminum plate (including an aluminum alloy). The present invention relates to a method of carrying out an electrochemical modification treatment, and in particular to a method of manufacturing an aluminum support for a printing plate made of a uniformly roughened aluminum plate suitable for use in offset printing plates.

[Conventional technology]

Conventionally, an aluminum plate has been used as a support for offset printing plates, and its surface is used to improve adhesion to the photosensitive layer provided on it and to retain dampening water used during printing. The surface is usually roughened for various purposes. Mechanical surface roughening methods such as boulder raining and brush graining are known as such surface roughening methods, but in recent years, the surface of the aluminum trinium plate has been electrochemically roughened in an acidic electrolyte such as hydrochloric acid or nitric acid. Electrolytic surface roughening methods that perform surface roughening treatment are attracting attention. According to this electrolytic surface roughening method, an aluminum plate having a uniformly roughened surface with a small average roughness distribution can be obtained compared to the conventional mechanical roughening method, but the conditions for obtaining such a roughened surface are If conditions such as electrolyte composition, temperature, and electrolysis conditions are kept very narrow, it is possible to easily obtain products with uniform performance with very little variation.

Oxides, smut, and the like exist unevenly on the surface of an aluminum plate because processing oil, oxygen in the air, moisture, etc. are intricately intertwined with aluminum during rolling and processing. If electrolytic surface roughening treatment is immediately performed on the aluminum ram surface in such a state, uniform surface roughening treatment may not be performed and uneven treatment may occur. This treatment unevenness is unfavorable in terms of appearance, and also causes deterioration in the adhesion of the paint film when a paint film or the like is placed on the aluminum surface.

Therefore, conventionally, before electrolytic surface roughening treatment, the aluminum material is immersed in an acidic or alkaline aqueous solution to remove machining oil, oxides, smut, etc., and dissolve the machining-affected layer to clean and homogenize the surface. I am doing it.

It is known from JP-A-54-65607 that rolling oil and natural oxide film existing on the surface of an aluminum plate are removed in an alkaline aqueous solution such as caustic soda prior to electrolytic surface roughening.

[Problem to be solved by the invention]

As a conventional method, before electrolytic surface roughening treatment, cleaning treatment with caustic soda is performed for the purpose of degreasing and removing natural oxide film, but since it is a chemical dissolution reaction with caustic soda, the amount of dissolution is suppressed. was difficult. Since the etching process is performed using a strong alkali, there is a drawback that holes are easily formed in the aluminum plate. In addition, waste liquid treatment costs were high because dialysis membranes and the like were used to remove aluminum eluted from the caustic soda.

[Means and effects for solving the problems] The purpose of the present invention is to solve the conventional drawbacks, and to give a role to the reaction at the auxiliary electrode, which did not directly contribute to the electrolytic surface roughening reaction, and to improve the printing plate support. An object of the present invention is to provide a manufacturing method that further simplifies the manufacturing process and is advantageous in terms of cost.

The above object of the present invention is achieved by electrolytically treating an aluminum plate (including an aluminum alloy plate) in a neutral salt electrolyte as a cathode, and then electrochemically roughening the plate in an acidic aqueous solution.

The neutral salt aqueous solution referred to in the present invention is JP-A No. 52-26904.
and JP-A No. 59-11295, alkali metal halides or alkali metal nitrates, and sodium chloride and sodium nitrate are particularly preferred.

The pH is preferably 6-8. The concentration is O, preferably 1 to 10%. Platinum, ferrite, iridium oxide, etc. can be used as the electrode facing the aluminum plate used for cathode electrolysis in the present invention.

In the present invention, continuously cathodic electrolytically treating an aluminum plate in a neutral salt electrolyte means electrolytically treating the aluminum plate by applying a DC voltage between the aluminum plate and the electrode facing it. Direct current voltage refers to a voltage whose polarity does not change, and includes continuous direct current, comb waveform, and alternating current rectified by semiconductor elements.

In the present invention, the voltage to be supplied for cathode electrolysis may be determined by providing a DC power source as shown in Figure 2, or by continuously electrifying an aluminum plate in an acidic electrolyte using AC as shown in Figure 1. In the method of chemically roughening the surface, a part of the current used for surface roughening may be diverted through a rectifier, and the diverted current may be used for cathode electrolysis in a neutral salt aqueous solution.

That is, as shown in FIG. 2, the pretreatment of the aluminum plate is performed in the cathodic electrolysis step (C) by placing the aluminum plate facing the anode (5) of the DC power source (3) in a neutral salt aqueous solution (9). This is done by cathodic electrolysis, in which case the aluminum plate is powered by a power supply roll (8).

FIG. 1 is a schematic diagram showing another embodiment of the present invention, in which the pretreatment (cleaning) of the aluminum plate is performed in the cathodic electrolysis step (C) by rectifying the AC power source (2) with the ) A portion of the current is supplied to the anode (5), and the surface of the aluminum plate (1) facing the anode (5) is subjected to cathodic electrolysis in a neutral salt aqueous solution (9). In the washing step (W), water is sprayed from a spray nozzle for washing, and then in the anodizing step (A), the material is anodized in an acidic electrolyte (10) using an alternating current from an alternating current power source (2).

In the present invention, roughening the surface electrochemically in an acidic electrolyte means performing electrochemical roughening treatment by applying a voltage between the aluminum plate and the counter electrode in an acidic electrolyte containing metal ions. It means to give.

The voltage at this time may be either alternating current or direct current, and it goes without saying that all known electrochemical surface roughening methods can be applied.

The acidic electrolyte used in the present invention can be any one used for electrochemical surface roughening using ordinary alternating current, but a particularly preferred one contains 5 to 15 (g/I!) of nitric acid. It is a liquid that These solutions contain Nos., such as aluminum nitrate, aluminum chloride, ammonium nitrate, ammonium chloride, manganese nitrate, manganese chloride, iron nitrate, iron chloride, etc.
Salts containing or may be added.

The current density of the direct current used for cathode electrolysis in the present invention is 1 to 1
00A/dnf is preferred. Electrolytic treatment time is 0.1 to 9
Preferably, it is in the range of 0 seconds. In aqueous salt solutions with a pH of 6 to 8, which are particularly advantageous conditions, dissolved aluminium ions precipitate in the form of aluminum hydroxide or aluminum oxide hydrates, so that by filtration or centrifugation, the neutral salts can be removed. It is possible to remove it continuously from the aqueous solution.

In the present invention, caustic soda, sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, hydrofluoric acid, chromic acid, etc. are used to chemically clean the surface of an aluminum plate before or after cathodic electrolytic treatment in a neutral salt electrolyte. A dipping treatment may also be performed. However, the chemical cleaning treatment for electrolytic surface roughening can be omitted because sufficient degreasing and dissolution of the aluminum plate surface layer are achieved due to the surface modification effect of the cathodic electrolytic treatment in the present invention.

〔Example〕

Examples of the present invention are shown below, but the embodiments of the present invention are not limited thereto.

Example 1 A JIS1050-H1B aluminum plate was subjected to continuous electrolytic surface roughening treatment in the apparatus shown in FIG. The conditions for the neutral salt electrolyte at this time were a 5% aqueous sodium chloride solution and a temperature of 50'C.

The conditions for the acidic electrolyte were a 1% aqueous solution of hydrochloric acid and a temperature of 35°C. The area ratio of the electrodes used for cathodic electrolysis and electrolytic surface roughening in an acidic aqueous solution was 2:8, and the materials of the electrodes were carbon and iridium oxide, respectively. Cyrisk was used as a rectifier to divert the current used for surface roughening. The current density is 50 A/d for electrolytic surface roughening and 25 A for cathodic electrolytic treatment.
/dbo was. Moreover, the surface of the aluminum plate before electrolytic roughening after cathodic electrolysis and water washing treatment was oxidized silver, and the presence of rolling oil etc. was not observed. When the surface of the aluminum plate after electrolytic roughening was observed, no unevenness was observed on the surface, which tends to occur when the etching treatment in an alkaline aqueous solution is omitted. When the surface of the aluminum plate was observed with a scanning electron microscope, it was found to be uniformly roughened and suitable as a support for printing plates.

〔Effect of the invention〕

Advantageous manufacturing of printing plate supports is achieved by electrolytically treating an aluminum plate (including aluminum alloy plate) as a cathode in a neutral salt electrolyte and then electrochemically roughening the surface in an acidic aqueous solution. It became possible to do so.

[Brief explanation of the drawing]

FIGS. 1 and 2 show a processing procedure showing an embodiment of the present invention. Continued Supplementary Positive book 1999/January 77th

Claims (1)

[Claims] 1. A method for producing a printing plate support, which comprises electrolytically treating an aluminum plate as a cathode in a neutral salt electrolyte and then electrochemically roughening the surface in an acidic aqueous solution.