JPH01259993A - Manufacture of aluminum support for printing plate - Google Patents

Abstract

PURPOSE:To scarcely affect the influence of variations in manufacturing conditions and to stably manufacture in a state that necessary electric amount is small by specifying an interval between anode and cathode through which a support is passed. CONSTITUTION:Anodes 1a, 1b, and cathode 2a, 2b are alternately disposed oppositely to an aluminum support 4 in an acidic electrolyte 3, a DC voltage is applied between both electrode plates, and the support 4 is passed at an arbitrary interval to the electrodes, thereby continuously electrochemically roughing it. In this case, the interval between adjacent anode and cathode is set to 15mm or more. Thus, the aluminum plate 4 becomes a mesh structure in which pits each having a deeper depth than its diameter are uniformly and densely provided. No irregular process of lateral fringe occurs in an offset printing plate or the like and printing performance and printability are stabilized. It can be manufactured stably with less electric amount.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an aluminum support for printing plates, and in particular, an aluminum support for printing plates made of a roughened aluminum plate suitable for offset printing plates. The present invention relates to a manufacturing method.

[Conventional technology]

An aluminum plate (including an aluminum alloy plate) is used as a printing plate support and an offset printing plate support.

Generally, in order to use an aluminum plate as a plate material (support) for offset printing, it is necessary to have appropriate adhesion to a photosensitive material and water retention.

To achieve this, the surface of the aluminum plate must be roughened so that it has a uniform and dense grain.This roughening process affects the printing performance and durability of the plate material when actually performing offset printing after plate making. Since it has a significant effect on printing force, its quality is an important factor in the production of plate materials.

The alternating current electrolytic etching method is generally used to roughen the surface of aluminum supports for printing plates, and the current used is a special alternating waveform current such as an ordinary sine wave alternating current or a square wave. . Then, the surface of the aluminum plate is roughened using an alternating current using a suitable electrode such as graphite as the counter electrode, and the process is usually performed in two cycles, but the resulting pit depth is generally shallow. , the printing durability was poor. For this reason, a number of methods have been proposed in order to obtain an aluminum plate suitable as a support for a printing plate, which has a grain that is uniformly and densely populated with pits that are deep compared to its diameter. The methods include the ratio of the amount of electricity at the anode and cathode during electrolytic surface roughening using alternating current (Japanese Patent Application Laid-Open No. 1983-65607), the power supply waveform (
Japanese Patent Application Laid-Open No. 55-25381), a combination of energization amount per unit area (Japanese Patent Application Laid-Open No. 56-29699), etc. are known.

However, the pits obtained by the method of manufacturing an aluminum plate for printing plates as described above are not deep enough, lack uniformity, and have a complicated uneven shape. However, when offset printing plates were formed, the printing performance and printing durability were insufficient, and it was extremely difficult to obtain a satisfactory plate. As a way to solve this problem, Japanese Patent Application Laid-Open No. 58-2074
As proposed in Publication No. 00, 0.3-15Hz
A method of electrochemical surface roughening using low frequency alternating current is known.

However, the method proposed in Japanese Patent Application Laid-Open No. 58-207400 has the disadvantage that the printing plate using this method produces uneven processing of horizontal stripes at right angles to the direction of travel of the aluminum plate, and this disadvantage has been solved. The present applicant previously filed Japanese Patent Application No. 62-297835 as a method for obtaining printing performance and rigidity without producing horizontal stripe-like processing unevenness.

In Japanese Patent Application No. 62-297835, an anode and a cathode are arranged alternately facing an aluminum plate, and a DC voltage is applied between the two plates to continuously roughen the surface electrochemically. This is the way to do it.

[Problem to be solved by the invention]

However, in the method proposed in Japanese Patent Application No. 62-297835, when the distance between the anode and the cathode is small, it is susceptible to variations in manufacturing conditions such as the flow of electrolyte, and the photosensitive layer is coated on the support. There was a drawback that the performance of the resulting printing plate was unstable. Additionally, if the distance between the anode and cathode is small, a large amount of current flows directly from the anode to the cathode without passing through the support, and the amount of electricity is more than twice the amount of electricity actually required to roughen the surface of the support. was required to obtain a printing plate with the desired performance.

[Means and effects for solving the problem] As a result of various studies, the present inventors have discovered that the method is less susceptible to changes in manufacturing conditions;
We have discovered a method for stably producing aluminum supports for printing plates in an industrially advantageous manner while requiring a small amount of electricity.

That is, the object of the present invention is to alternately arrange an anode and a cathode in electrodes facing an aluminum support in an acidic electrolytic solution, apply a DC voltage between these two plates, and move the aluminum support between these electrodes. A method for continuous electrochemical roughening of the surface of a printing plate by passing it through the electrode while maintaining an arbitrary distance between the anode and the cathode, characterized in that the distance between the anode and the cathode is 15 or more. This is achieved by a method of manufacturing an aluminum support.

In the present invention, setting the distance between the anode and the cathode to be 15 m or more means that the anode 1 and the cathode 2 are installed alternately in the same tank as shown in FIG.
For example, this means that the distance d+ between the anode and the cathode, for example, the distance dt between the cathode and the anode, is each 15W or more. In this case, the surface can be roughened either by arranging the electrodes with the anode at the top or the cathode at the top.

By changing the length of the anode and cathode aluminum plates in the advancing direction, changing the passing speed of the aluminum plates, and changing the flow rate, liquid temperature, liquid composition, and current density, it is possible to obtain an arbitrary rough surface on the aluminum plate. can.

The acidic electrolyte used in the present invention is preferably an aqueous solution containing mainly nitric acid or hydrochloric acid;
Mixture of nitric acid and hydrochloric acid, nitric acid or hydrochloric acid with organic acid, sulfuric acid,
An aqueous solution containing phosphoric acid, hydrofluoric acid, hydrobromic acid, etc. may also be used.

Examples of the aluminum support applicable to the present invention include a pure aluminum plate or an alloy plate containing aluminum as a main component.

In the present invention, prior to electrochemical roughening, the aluminum support may be subjected to the following well-known treatment. For example, the aluminum support is immersed in a caustic soda aqueous solution,
Pretreatment involves performing alkali etching to remove surface stains and natural oxide films, and then immersing the material in a nitric acid or sulfuric acid aqueous solution for neutralization and smut removal treatment after the alkali etching. Further, for example, the surface of the aluminum support may be cleaned by electrolytic polishing in an electrolytic solution mainly containing sulfuric acid or phosphoric acid.

These processes can be selected and used as needed.

Of course it doesn't have to be done.

The DC current waveform used for electrochemical surface roughening in the present invention is a current waveform whose polarity does not change, and any of the following can be used: a comb-shaped waveform, continuous DC, and full-wave rectification of commercial AC using Cyrisk. In particular, it is preferable to use a smoothed continuous DC current as shown in FIG.

As the electrolytic bath, any one used for electrochemical surface roughening using ordinary alternating current can be used, but particularly suitable ones are an aqueous solution containing 5 to 20 g/l of hydrochloric acid, or an aqueous solution containing 5 to 20 g/l of nitric acid. g/j! It is an aqueous solution containing, and the liquid temperature is preferably 20°C to 60°C.

In addition, the current density is 2OA/dr4~20OA/drrl
It is preferable that it is in the range of . If the electrolytic treatment time is too long or too short, an optimal rough surface will not be obtained;
Preferably, it is in the range of seconds. Electrochemical surface roughening according to the method of the present invention can be carried out by a batch method, a semi-continuous method, or a continuous method, but it is most preferable to use a continuous method.

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.

As the electrode used in the present invention, any electrode used in known electrochemical processing can be used.

Examples of anodes include pulp metals such as titanium, tantalum, and niobium plated or clad with white metals, pulp metals coated with or sintered with white metal oxides, aluminum, stainless steel, etc. Available for use. Particularly preferred for use as an anode is a pulp metal clad with platinum, and the life of the anode can be further extended by cooling the electrode by passing water through it.

As the cathode, it is possible to use a metal that does not dissolve when the electrode potential is made negative from the Pool Bay diagram, but carbon is particularly preferred.

In addition, by anodizing the roughened 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 rigidity can be obtained. Supports can be manufactured. 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 a nitric acid bath and a hydrochloric acid bath, a combination with an electrolytic bath that uses alternating current to roughen the surface electrochemically, and a roughening treatment that includes smut removal treatment in between. Needless to say, the present invention can be applied in combination with known electrochemical surface roughening treatments, such as a method in which surface roughening treatment and electrochemical surface roughening are carried out in divided treatment tanks.

〔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 A JIS3003-H14 aluminum rolled plate was immersed in a 10% caustic soda aqueous solution for 30 seconds, followed by a cleaning treatment and washed with water. This aluminum plate is placed in an electrolytic cell 5 as shown in FIG. 1, with the anode 1 made of platinum and the cathode 2 made of carbon. Eighteen tubes of 20 mm and 1 L were alternately placed in the electrolytic solution 3, and passed through the aluminum plate 4 continuously with a distance of 10 m above the electrode 1.2.

The electrodes were arranged with the anode 1 at the top, the current density per electrode was 60 A/drrf, and a smoothed continuous direct current as shown in FIG. 2 was used. The length of the aluminum plate of the electrode in the advancing direction was 20 mm for both the anode 1 and the cathode 2. The threading speed of aluminum plate 4 is 18 m/sin
Met.

The electrolyte solution 3 used was 15g/j of nitric acid! The aqueous solution contained therein had a liquid temperature of 45°C. The aluminum temporary 4 that came out of the electrolytic cell 5 was then washed with water and treated with 300 g/j of sulfuric acid! The sample was immersed in an aqueous solution containing the sample at 60° C. for 60 seconds to remove the smut component mainly composed of aluminum hydroxide produced by electrochemical surface roughening treatment, and then washed with water.

The roughened plate thus obtained has an average surface roughness of 0.2
It had uniform honeycomb-shaped pits with a diameter of 1 μm.

In addition, 100 g of sulfuric acid was added to the aluminum plate obtained as above so that the amount of oxide film was 2.0 g/rrr.
/j! Anodization treatment was carried out at 35°C in an aqueous solution containing the above. After washing with water, it was immersed in an aqueous solution containing 2.5% No. 3 sodium silicate at 70° C. for 20 seconds to make it hydrophilic.

A photosensitive layer was coated on the thus obtained aluminum plate to produce a printing plate, and the resulting printing plate had good plate-making properties, rigidity resistance of 100,000 sheets, and stain resistance. .

Comparative Example 1 An aluminum roughened plate was prepared in the same manner as in Example 1, except that the electrodes were arranged with a distance of 10 degrees between the anode 1 and the cathode 2.

The roughened plate thus obtained has an average surface roughness of 0.1
In 2IIm, there were no dense pits.

Further, the aluminum obtained as described above was subjected to anodizing treatment and hydrophilization treatment in the same manner as in Example-1.

A photosensitive layer was coated on the aluminum plate thus obtained to produce a printing plate, and the resulting printing plate had a rigidity resistance of 40,000 sheets, compared to the printing plate obtained in Example-1. It was extremely small. In addition, there were large variations in both staining performance and plate inspection performance, and the desired performance could not be obtained.

Comparative Example 2 An aluminum roughened plate was prepared in the same manner as Comparative Example 1 except that the current density per electrode was 150 A/dnl.

The roughened plate thus obtained has an average surface roughness of 0.2
Although the diameter was 0 μm, pits were not uniformly present.

Further, the aluminum obtained as described above was subjected to anodizing treatment and hydrophilic treatment in the same manner as in Example-1.

A photosensitive layer was coated on the aluminum plate obtained in this way and a printing plate was manufactured. The printing plate obtained had a printing durability of 80,000 sheets, and there were wide variations in both staining performance and plate inspection performance. (The desired performance could not be obtained.

〔Effect of the invention〕

In the acidic electrolyte of the present invention, an anode and a cathode are arranged alternately as electrodes facing the aluminum support, a DC voltage is applied between these two plates, and the aluminum support is placed at an arbitrary distance from these electrodes. A method for producing an aluminum support for a printing plate, characterized in that the distance between the anode and the cathode is 15III11 or more, in a method of continuously performing electrochemical roughening by passing the aluminum support while maintaining As a result, the aluminum plate has a grain structure in which pits with a deep depth compared to its diameter exist uniformly and densely, and there is no horizontal stripe-like processing unevenness in offset printing plates, etc., which is satisfactory. We were able to stably obtain printing performance and stiffness resistance. In addition, it has become possible to stably and industrially advantageously produce a rough aluminum plate suitable as an aluminum support for printing plates using as little electricity as possible.

In addition, since surface roughening is performed using direct current, there is no need for a special power supply, compared to conventional roughening using alternating current, and the routing of busbars from the power supply to the electrolytic cell is easier. It has become simpler and can be manufactured advantageously in terms of equipment cost.

[Brief explanation of the drawing]

FIG. 1 is an embodiment of an apparatus used in the manufacturing method of the present invention, and FIG. 2 is a voltage waveform diagram of a direct current waveform according to the present invention. 1, la, lb...anode 2.2a, 2b...cathode 3...electrolyte 4...aluminum plate (support) 5...electrolytic cell 6°...liquid supply nozzle d, ...
Distance d between anode and cathode! ... Distance agent between the cathode and other adjacent anodes
Patent attorney (8107) Kiyotaka Sasaki (and 3 others) Figure 1

Claims (1)

[Claims] (1) Alternately arrange the anode and cathode electrodes facing the aluminum support in an acidic electrolyte, apply a DC voltage between these two plates, and set the aluminum support at an arbitrary distance from these electrodes. A method for manufacturing an aluminum support for a printing plate, characterized in that the distance between the anode and the cathode is set to 15 mm or more, in a method of continuously performing electrochemical roughening by passing the aluminum support while maintaining the .