JPH021390A - Production of aluminum support for printing plate - Google Patents

Abstract

PURPOSE:To provide a shallower grain and a deeper grain simultaneously in a surface of an aluminum support by a method wherein an AC current is passed directly to electrodes in one circuit, whereas electrodes in the other circuit are provided as small electrodes comprising at least one pair of an anode and a cathode arranged alternately, and an AC power is applied by using diodes provided respectively between the small electrodes and a power supply. CONSTITUTION:At the time of graining an aluminum support 5 for a printing plate in an acidic electrolytic liquid 8 in an electrolyzer 6, a AC power supply 1 with a frequency of at least 14Hz is used to pass an AC current directly to electrodes 9 in one circuit, thereby a surface of the support 5 is shallowly etched to have a uniform grain. Electrodes in the other circuit are provided as small electrodes comprising at least one pair of an anode 4 and a cathode 3 arranged alternately, and diodes 2a, 2b or rectifying mechanisms are provided respectively between the electrodes 3, 4 and a power supply 1. A phenomenon arising from application of a DC power is caused to occur at the electrode parts, whereby the surface of the support 5 is provided with a uniform grain large in the diameter and depth of pits constituting the grain.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a printing plate support, and in particular to a method for manufacturing a printing plate support made of a roughened aluminum plate suitable for offset printing plates. It is something.

[Conventional technology]

Aluminum plates are used as printing plate supports, especially lithographic printing plate supports. Due to the diversification of users, aluminum plates are becoming more diverse, ranging from those close to pure aluminum to those with manganese added to increase strength.・It has become η.

In order to use such an aluminum plate as a lithographic printing plate support, it is necessary to have appropriate adhesion and water retention properties for photosensitive materials.

For this purpose, the surface of the aluminum plate must be roughened to have uniform and dense grains. This surface roughening treatment has a significant effect on the printing performance such as staining performance of the plate material when printing is actually performed, so its quality is an important factor in the production of the plate material.

As a method for roughening an aluminum support for a printing plate, an alternating current electrolytic roughening method is generally employed. among them,
Japanese Patent Application Laid-open No. 58-207400 describes frequencies of 0.3 to
It has been disclosed that surfacing at a low frequency of 15 Hz is good for obtaining a uniform surface.

However, the above method has a drawback in that when the aluminum plate is continuously roughened, processing unevenness in the form of horizontal stripes occurs at right angles to the direction in which the aluminum plate travels.

Therefore, in order to solve the above problems, the applicant first
We have applied for a method of electrochemically roughening the surface at a frequency of 0 Hz or higher (Japanese Patent Application No. 12568/1983), and we also applied a method in which an anode and a cathode are arranged alternately and a direct current is applied to these electrodes. filed a patent application (Japanese Patent Application No. 62297835) in which an aluminum support is passed through these electrodes.

Furthermore, Japanese Patent Publication No. 61-48596 discloses a method of preventing electrode deterioration by providing an auxiliary counter electrode with a diode or a mechanism acting like a diode for controlling the flow of anode current in the main counter electrode. ing.

[Problem to be solved by the invention]

However, although the surface roughening method using a frequency of 10 Hz or higher is an excellent method for obtaining a uniform surface, it has the disadvantage of shallow grains, whereas the method of applying direct current to alternating anodes and cathodes is an excellent method for obtaining a uniform surface. This is an excellent method for obtaining deep grains, but it has the drawbacks of large grain diameters and depths, and poor staining performance.Furthermore, when anodes and cathodes are arranged alternately in the same tank, the electrode A bypass current flows between them, and when actually converting an aluminum plate into an I11 plane, the current efficiency is poor.
In order to avoid this, if the electrodes are placed in separate tanks, there will be a large number of processing tanks, which has the disadvantage of extremely high initial costs and maintenance costs.

In addition, the method described in Japanese Patent Publication No. 61-4859 is anode.
-ys flow only, and this auxiliary counter electrode had the problem that it did not contribute to grain formation.

The object of the present invention is to solve the conventional drawbacks and to simultaneously and efficiently form shallow grains obtained by alternating current high frequency and deep grains obtained by a tank in which an anode and a cathode are alternately combined. The object of the present invention is to propose a method for manufacturing a lithographic printing plate support using an electrolytic treatment method that can reduce the aforementioned bypass current and increase efficiency.

[Means to solve the problem]

The above-mentioned object of the present invention is to provide a method for roughening an aluminum support in an acidic electrolyte, in which an AC power source of 14 Hz or higher is used, and the current is applied to the electrodes of one circuit, while the electrodes of the other circuit are It consists of at least one or more pairs of small electrodes in which anodes and cathodes are arranged alternately, and a diode or diode-like conductor is connected between these four poles and a power source.
This is achieved by a method for producing an aluminum support for a printing plate, characterized in that an alternating current is applied using a fiL mechanism and the aluminum support is passed facing these electrodes. The present invention will be explained in detail below. The aluminum support used in the present invention includes pure aluminum plate,
Alternatively, alloy plates containing aluminum as a main component may be mentioned, but aluminum containing 0.3% or more of manganese is particularly effective.

The aluminum support is first alkali-etched. Preferred alkaline agents include caustic soda, caustic potash, sodium metasilicate, soda carbonate, sodium aluminate, and sodium gluconate. Concentration 0°01~20%, temperature 20
The 2 hours at ~90°C is appropriately selected from the range of 5 seconds to 5 minutes, and the preferable etching amount is 0.
01-5g/r+(.

In particular, in the case of an aluminum support containing many impurities such as manganese, the appropriate etching amount is 0.01 to 1 g/rr.

Subsequently, since alkali-intolerant substances (smut) remain on the surface of the alkali-etched aluminum plate, desmutting may be performed as necessary.

The treatment No. 11 is as described above, but is followed by electrolytic etching using the electrochemical surface roughening method of the present invention.

The present invention will be explained using figures.

(2) is an AC power source and has a frequency of I 4 If z or more. 40Hz-120H from the viewpoint of grain formation
z is more preferable, and as in US Pat. No. 4,087,341, a special waveform, a rectangular wave, etc. may be selected as appropriate depending on the desired quality. An alternating current is passed directly through the electrodes 9 of one circuit, and the electrodes of the other circuit are composed of electrodes in which at least one set of anodes and cathodes are arranged alternately.In this example, two sets of anodes 4 and cathodes 3 are arranged alternately. 2 is a diode, which is attached to the circuit of each electrode 3, 4, and the diodes 2a, 2b are arranged so as to correspond to the polarity for an anode current and a cathode current, respectively. The ratio of current controlled by these electrodes and the number of pairs of anodes 4 and cathodes 3 are appropriately selected depending on the desired grain size.

As the electrode used in the present invention, any of those used in known electrochemical processing can be used.As the anode 4, a valve metal such as titanium, tankle, or niobium is plated or clad with a platinum-based metal. Valve metals coated or sintered with platinum-based metal oxides, aluminum, stainless steel, etc. can be used. Particularly preferred for use as an anode is a valve metal clad with platinum, and the life of the anode can be further extended by cooling the electrode with water by passing water inside it.

As the cathode 3, a metal that does not dissolve when the electrode potential is negative can be selected from the Poolhey diagram, but carbon is particularly preferred.

5 is an aluminum plate, 6 is an electrolytic cell, and 7 is a liquid supply nozzle. 8 is an electrolytic solution, preferably 5 to 50 g/I! mainly composed of nitric acid or hydrochloric acid! The aluminum concentration in the electrolytic bath is 50g/j! The following is suitable, more preferably 2 to 20 g/l.Additives may be added to this nitric acid if necessary, but when producing nitric acid, it becomes difficult to control the liquid concentration.

The current density varies depending on the desired grain shape, electrolyte conditions, etc., but is preferably in the range of 10 to 500 A/drrr (7), and the electrolyte bath temperature is preferably 15°C to 7°C. 30°C to 60°C is good.

The electrolysis time varies depending on the desired grain shape, current density, etc., but is preferably in the range of 2 to 100 seconds.

Reference numeral 9 denotes an electrode, and any common electrode used in AC power supplies can be used, but carbon is better from the viewpoint of cost and longevity.

Preferably, the surface-treated aluminum is subsequently treated with M or an alkaline solution. Specifically, in addition to sulfuric acid described in Japanese Patent Publication No. 56-11316,
Phosphoric acid or a mixture of phosphoric acid and chromic acid is used. Further, smut adhering to the surface is removed by lightly etching with an alkaline solution such as caustic soda as described in Japanese Patent Publication No. 4B-28123.

When removing attached smut with an alkaline solution, the aluminum surface is etched, so alkali-insoluble components remain. Therefore, it is necessary to desmut again with an acidic solution (sulfuric acid, phosphoric acid, chromic acid, etc.).

The anodic oxide film is preferably formed on the back surface in a thickness of 0.1 to log/n (more preferably 0.3 to 5 g/nr).

It is preferable to perform alkali etching and desmutting treatment before anodizing.

The processing conditions for anodic oxidation vary depending on the electrolyte used, so it cannot be determined unconditionally, but in general, the concentration of the electrolyte is 1 to 80% by weight, the temperature of the solution is 5 to 70°C, and the current density is Appropriate ranges are 0.5 to 60 A/dm2, voltage 1 to 100 V, and electrolysis time 1 second to 5 minutes.

The grained aluminum plate with the anodic oxide film obtained in this way is itself stable and has excellent hydrophilic properties, so a photosensitive coating can be immediately applied on top, but if necessary, the surface can be further coated. Can be processed. For example, the coating amount of the silicate layer made of the alkali metal silicate described above or the highly hydrophilic undercoat layer is preferably 5 to 150 mg/po.

Next, a photosensitive coating film is provided on the aluminum support treated in this way, imagewise exposed, developed and plate-made, and then set in a printing machine to start printing.

[Function] In the method of roughening the surface of an aluminum support in an acidic electrolyte, the present invention uses AC 7ittX of 14 Hz or higher, so that the alternating current flows as it is in the electrode 9 of one circuit. It is possible to create shallow etchings with fine grains. The electrodes of the other circuit are composed of small electrodes in which at least one set of anodes 4 and cathodes 3 are arranged alternately,
By using a rectifying mechanism that acts like a diode or a diode between these electrodes and the power source, the sand H has a uniform grain size with a large diameter and depth in order to cause a phenomenon caused by direct current application at the electrode part. Made.

Further, since the adjacent anode and cathode small electrodes in this part do not act simultaneously, a bypass current does not flow and the current efficiency is not deteriorated, so that the bypass current is effectively utilized.

Moreover, since the cathode 3 of this small electrode effectively contributes to grain formation, the efficiency current can be further increased.

[Example] Example-1 Manganese 1. A JIS 3003 aluminum support containing 1% porosity was heated with 2% caustic soda aqueous solution at 45°C. 8? In the middle of the night, it was washed for 7 minutes and etched so that the aluminum content was 0.1 g/n, then the smut was removed and washed with water.

Thereafter, 4.5 g/l of aluminum ions were mixed in a 15 g/R nitric acid aqueous solution, and the first
The surface was roughened using the method shown in the figure. The power source used was 80 Hz alternating current. The current density was set to 40 A/dn+, and the amount of electricity at the cathode was set to 400 coulombs/dnr. When the surface smut of this sample was removed and the surface was observed, it was found that uniform pits were formed over the entire surface, with deep pits and shallow pits forming at the same time. Thereafter, an anodized film of 2.4 g/+rf was applied in 20% sulfuric acid, washed with water, and dried. This is referred to as substrate [A].

Comparative Example-1 A board similar to that of the example was pretreated in the same manner as the first
In the tank shown in the figure, a diode was installed to control only the anode current, and the diode on the cathode side was removed. In a tank like this,
When the surface was roughened under the same conditions as in Example 1, smut was removed, and the surface was observed, it was found that many shallow bits were generated using conventional high-frequency waves. Thereafter, an anodized film of 2.58/rrr was applied in 20% sulfuric acid, washed with water, and dried.

Based on this) anti-CB).

A photosensitive layer was provided on the substrates (A) to [B] thus prepared by applying the following composition so that the weight of the coating needle after drying was 2.5 g/rd.

Photosensitive liquid composition: Ester compound of naphthoquinone-12-diazide-5-sulfonyl chloride, pyrogallol, and acetone resin (Recited in Example 1 of U.S. Patent No. 3.635.709) 0.75 g Talesol Novolank resin 2. OOg
Oil Flu #603 (Orient Chemical Co., Ltd.) 0.0/Ig ethylene dichloride... 16g 2-methoxyethyl acetate The photosensitive lithographic printing plate thus prepared was heated in a vacuum printing frame to a transparent positive film. Through 1!N's distance Yu 11
After exposure for 50 seconds using a 3 kW metal halide lamp, the molar ratio of 52':h/~ago was 1.
5.26% aqueous solution of thorium silicate (PH-12)
．． After developing in step 7), printing was carried out in the usual manner.

The printing machine used was Spring 1-25 (manufactured by Kurumae Printing Co., Ltd.).

Table 1 shows all the evaluation results.

Table 1 [Effects of the Invention] The method for producing an aluminum support for printing plates of the present invention allows shallow grains to be obtained at alternating current frequencies and deep grains to be obtained in a tank in which an anode and a cathode are alternately combined, while also being efficient. Since it is possible to form the substrate as much as possible, and also to minimize bypass current and increase efficiency, the substrate made using this method was able to exhibit excellent printing performance as shown in Table 1.

[Brief explanation of the drawing]

FIG. 1 is a side view of an electrolytic treatment apparatus according to an embodiment of the method for producing an aluminum support for printing plates according to the present invention. ■... AC power supply 2a, 2b... Diode cathode 4 - Aluminum support, electric waste tank 7... Liquid supply nozzle, electrolyte solution 9... Electrode, anode (3 others)

Claims (1)

[Claims] (1) In a method of roughening an aluminum support in an acidic electrolyte, an AC power source of 14 Hz or higher is used to directly apply AC to the electrodes of one circuit, and at least one electrode of the other circuit is roughened. It consists of small electrodes in which more than one set of anodes and cathodes are arranged alternately, and an alternating current is applied between these electrodes and a power source using a diode or a rectifying mechanism that acts like a diode, and the aluminum support is connected to these electrodes. A method for producing an aluminum support for a printing plate, characterized by passing the aluminum support facing the plate.