JPH0798427B2 - Method for producing aluminum support for printing plate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing an aluminum support for printing plates, and particularly to a printing support comprising a roughened aluminum plate suitable for offset printing plates. The present invention relates to a method for manufacturing a body.

[Conventional technology]

An aluminum plate (including an aluminum alloy plate) is used as a printing plate support, particularly 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 adhesiveness to a photosensitive material and water retention.

For this purpose, the surface of the aluminum plate must be roughened so as to have uniform and fine grain. This roughening treatment has a significant influence on the printing performance and printing durability of the plate material when offset printing is actually carried out after plate making, and therefore its quality is an important factor in plate material manufacture.

An AC electrolytic etching method as shown in FIG. 5 is generally adopted as a roughening method for an aluminum support for a printing plate, and as a current, a normal sine wave AC current, a special alternating wave such as a rectangular wave is used. Waveform current is used. Roughening treatment of the aluminum plate is performed by alternating current with an appropriate electrode such as graphite as a counter electrode, which is usually performed in one treatment, but the hit depth obtained there is generally shallow. The printing durability was inferior. Therefore, various methods have been proposed in order to obtain an aluminum plate suitable as a printing plate support having a grain in which pits having a depth deeper than its diameter are present uniformly and densely. As a method thereof, the ratio of the amount of electricity at the time of anode and cathode at the time of electrolytic surface roughening using alternating current (JP-A-54-65607), power waveform (JP-A-55-25381), unit Combination of energization amount per area (JP-A-56-29699)
Etc. are known.

However, the pits obtained by the method for manufacturing an aluminum plate for a printing plate as described above are not sufficiently deep and lack uniformity, and have a complicated uneven shape. When an offset printing plate was formed, the printing performance and printing durability were insufficient, and it was extremely difficult to obtain a satisfactory product. As a method for solving this, as proposed in Japanese Patent Laid-Open No. 207400/1983, there is known a method of performing electrochemical surface roughening using an alternating current having a low frequency of 0.3 to 15 Hz.

However, even with the method described above, it is difficult to obtain an aluminum plate having a double pit structure excellent in printing performance and a good grain shape having an appropriate depth, and Japanese Patent Laid-Open No. 54-85802 discloses an alternating voltage. By using the smut removal treatment between the first and second stage electrochemical graining treatment,
A relatively deep pit is obtained by the first roughening treatment, and a fine pit is generated by the second roughening treatment, which has a double pit structure with excellent printing performance and an appropriate depth. It proposes a method to obtain the grain shape.

[Problems to be Solved by the Invention]

However, according to the method disclosed in JP-A-54-85802, a grain shape having excellent printing performance can be easily obtained, but a large amount of electricity is required for the electrochemical graining treatment in the first stage. Generally, a large-capacity AC power supply with low power conversion efficiency must be used, and there is a drawback that equipment cost and running cost are large.

In addition, since a large alternating current is used, it is difficult to handle the bus bar, and there are many design restrictions.

However, when an aluminum plate is continuously subjected to electrochemical surface roughening by using an alternating current of low frequency as proposed in JP-A-58-207400, a printing plate using the aluminum plate becomes aluminum. There is a drawback that horizontal stripe-shaped uneven processing occurs at right angles to the traveling direction of the plate.

Further, when a low frequency alternating current is used, the carbon used for the conventional electrochemical graining is remarkably dissolved, which makes it difficult to put it into practical use industrially.

The object of the present invention is to solve the above-mentioned problems, reduce equipment costs, running costs, and offset printing plates without design restrictions, and to obtain satisfactory printing performance and durability without causing horizontal stripe-shaped uneven processing. Printing power can be obtained.
It is another object of the present invention to provide a method for producing an aluminum support for a printing plate, which is made of an aluminum plate having a grain in which pits having a depth deeper than its diameter are present uniformly and densely.

[Means and Actions for Solving the Problems]

As a result of various studies, the inventors of the present invention, in a method of continuously electrochemically roughening in an aqueous solution mainly containing nitric acid or hydrochloric acid, the electrodes facing the aluminum plate were used as an anode and a cathode. Are alternately arranged, a DC voltage is applied between these bipolar plates, and the aluminum plate is electrochemically roughened by passing through the aluminum support with these electrodes at an arbitrary interval. Compared to diameter
It has been found that deep pits are created.

At this time, when the moving speed of the aluminum plate is constant, the pit diameter of the grain changes by adjusting the length of the electrode with respect to the traveling direction of the aluminum plate. When the electrode length is increased, the pit diameter tends to be large and deep, and when the electrode length is shortened, the pit diameter tends to be small.

Therefore, it was decided to utilize this phenomenon to perform the electrochemical surface roughening treatment in two stages. In the electrochemical graining treatment of the first step, an electrode facing the aluminum plate and an anode and a cathode are alternately arranged, and a DC voltage is applied between these both electrodes to fix the aluminum support. Roughening treatment is performed by passing these electrodes at an arbitrary interval. Next, the smut component composed mainly of aluminum hydroxide, which is generated by the electrochemical graining treatment in the first stage, is removed.

After that, as the second-stage electrochemical surface-roughening treatment, similarly to the first-stage electrochemical surface-roughening treatment, the electrodes facing the aluminum plate were used as anodes and cathodes, which were alternately arranged. Then, a DC voltage is applied between the two electrode plates, and a roughening treatment is performed by passing the aluminum support and these electrodes at an arbitrary interval.

At this time, it is more preferable to change the length per electrode used for the first surface roughening treatment and the length per electrode used for the second step.

By doing so, a deep grain is produced in the first stage electrochemical graining treatment, and a second grain is obtained in the second stage electrochemical graining treatment. It is possible to easily obtain a double-structured pit including fine pits on the hit surface.

The smut removal treatment provided between the electrochemical roughening treatments of the first and second stages is necessary for superimposing the sand grains of the first and second stages. If the removal process is not performed, the grain will not overlap well.

That is, the object of the present invention is to arrange the electrodes facing the aluminum plate in an acidic electrolyte alternately with the anode and the cathode, and to apply a DC voltage between these two electrode plates so that the aluminum plate and these electrodes can be arbitrarily arranged. It is the first method to pass with a space of
Electrochemical surface roughening treatment of the second and second steps,
This is accomplished by a method for producing an aluminum support for a printing plate, which comprises performing a smut removing treatment between the first and second electrochemical roughening treatments.

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a process drawing of the manufacturing method of the present invention. This is a manufacturing method in which direct current electrolytic etching is performed, smut removal processing is performed, and then current electrolytic etching processing is performed.

In the direct current electrolytic etching process according to the present invention, the anode 1 and the cathode 2 may be alternately installed in the same tank as shown in FIG. Alternatively, as shown in FIG. 4, the anode 1 and the cathode 2 may be provided as separate tanks, and the tanks in which the anodes and the cathodes are installed may be alternately arranged.

The acidic electrolytic solution used in the present invention is preferably an aqueous solution containing nitric acid or hydrochloric acid as a main component. of course,
Mixture of nitric acid and hydrochloric acid, nitric acid or hydrochloric acid with organic acid, sulfuric acid,
You may use the aqueous solution which mixed phosphoric acid, hydrofluoric acid, hydrobromic acid, etc.

Examples of the aluminum support applied 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 the electrochemical roughening, the aluminum support may be subjected to the following well-known treatment. For example, immersing an aluminum support in a caustic soda solution,
This is a pretreatment such as alkali etching for removing surface dirt and natural oxide film, and then dipping in an aqueous nitric acid or sulfuric acid solution for neutralization and smut removal treatment after alkali etching. Further, for example, the surface of the aluminum support is washed by electrolytic polishing in an electrolytic solution containing sulfuric acid or phosphoric acid as a main component. These treatments can be selected and used as needed. Of course, it may not be performed.

The direct current waveform used for electrochemical surface roughening in the present invention is a current waveform whose polarity does not change, and any of comb-shaped waveform, continuous direct current, commercial alternating current full-wave rectified by a thyristor, etc. can be used. In particular, it is preferable to use a smoothed continuous direct current.

As the electrolytic bath, any of those used for electrochemical surface roughening using an ordinary alternating current can be used, but a particularly preferable one is an aqueous solution containing 5 to 20 g of hydrochloric acid or nitric acid of 5
It is an aqueous solution containing ~ 20 g /, and the liquid temperature is preferably 20 ° C to 60 ° C. Further, the current density is preferably in the range of 20 A / dm ^{2 to} 200 A / dm ² . If the electrolytic treatment time is too long or too short, an optimal rough surface cannot be obtained, and it is preferably in the range of 5 to 90 seconds. The electrochemical surface roughening by the method of the present invention can be carried out by any of the batch method, the semi-continuous method and the continuous method, but the continuous method is most preferable.

The electrochemically roughened aluminum support is immersed in an aqueous solution containing an acid or an alkali to remove the smut mainly composed of aluminum hydroxide produced by the electrochemical roughening treatment and to remove it mildly. By carrying out the above etching, a more excellent aluminum support for a printing plate can be obtained. The mild etching may be performed by electrolytic polishing treatment in a phosphoric acid or sulfuric acid electrolytic solution.

As the electrode used in the present invention, any of those used in Kochi's electrochemical treatment can be used. As the anode, a valve metal such as titanium, tantalum, or niobium plated or clad with a white metal-based metal, a valve metal coated or sintered with an oxide of a white metal-based metal, aluminum, stainless steel, or the like is used. It can be used. Particularly preferred for use as an anode is a valve metal,
Platinum is clad, and the life of the anode can be further extended by passing water inside the electrode to cool the electrode.

As the cathode, a metal that does not dissolve when the electrode potential is made negative can be selected from the pool bay diagram, but carbon is particularly preferable.

The arrangement of electrodes may be either anode or cathode,
Both can roughen the surface. When the anode is at the head, a relatively rough surface with a relatively low amount of electricity is obtained, and when the cathode is at the head, relatively deep pits are easily obtained.

The arrangement of the electrodes can be arbitrarily selected according to the target rough surface.

Further, an arbitrary rough surface can be obtained by changing the lengths of the anode and the cathode in the traveling direction of the aluminum plate, the passing speed of the aluminum plate, the flow velocity, the liquid temperature, the liquid composition, and the electric density. . Further, when the anode and the cathode are divided into different baths as shown in FIG. 4, the electrolysis conditions of each treatment bath may be changed.

Further, by subjecting the roughened plate obtained as described above to anodizing treatment in an electrolytic solution containing sulfuric acid or phosphoric acid according to a usual method, a printing plate excellent in hydrophilicity, water retention and printing durability is obtained. A support can be manufactured. Of course, after anodizing, soak in an aqueous solution containing sodium silicate,
You may perform hydrophilic treatment.

The desmutting treatment performed between the first stage and the second stage only needs to be able to almost completely remove the smut mainly composed of aluminum hydroxide generated in the electrolytic surface roughening treatment, and may be a caustic soda solution, a high temperature sulfuric acid solution, or a high temperature nitric acid solution. It is enough to dissolve and remove the smut by immersing it in a solution, phosphoric acid or chromic acid solution. Further, it is desirable to perform sufficient water washing before and after the desmut treatment so that the electrolytic bath and the desmut bath are not mixed with each other.

In addition, in order to increase the efficiency of removing smut, electrolytic treatment may be applied in the above aqueous solution.

〔Example〕

Next, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

Example-1 A JIS 3003-H14 rolled aluminum plate was immersed in a 10% aqueous sodium hydroxide solution for 30 seconds, washed, and washed with water.
This aluminum plate is subjected to the steps shown in FIG. 1,
The direct current electrolytic etching treatment 10 is used as the first-stage electrochemical graining treatment. DC electrolytic etching process is the second
As shown in the figure, the anode 1 of the electrolytic cell 5 is platinum, the cathode is carbon, and the distance between the anode 1 and the cathode 2 is 100 mm.
Fourteen electrodes were installed alternately inside the aluminum plate 4 and the electrodes 1 and 2 were continuously passed through the aluminum plate 4 with a space of 10 mm. The electrodes were arranged with the anode first. At that time, the current density per electrode was 80 A / dm ² , and a smoothed continuous direct current was used as shown in FIG. The length of the electrode in the aluminum plate advancing direction was 100 mm for both anode 1 and cathode 2. The passing speed of the aluminum plate 4 was 12 m / min. The electrolyte 3 used was an aqueous solution containing 15 g of nitric acid at a liquid temperature of 45 ° C.
Met.

The aluminum plate 4 which has finished the electrochemical graining treatment (DC electrolytic etching treatment) in the first stage and has exited the electrolytic bath 5 is then washed with water and treated with 300 g of sulfuric acid as a smut removal treatment 11 shown in FIG. The sample was immersed in an aqueous solution containing 60 ° C. for 60 seconds to remove the smut component mainly composed of aluminum hydroxide produced by the electrochemical graining treatment and washed with water.

After that, a direct current electrolytic etching treatment 12 shown in FIG. 1 is performed as the second-stage electrochemical graining treatment, and eight anodes and eight cathodes are used by using an electrolysis apparatus as shown in FIG. The electrode was installed, and the length of the electrode in the aluminum plate advancing direction was set to 50 mm. Otherwise, the treatment was carried out in exactly the same manner as the electrochemical graining treatment of the first stage.

The aluminum plate that came out of the electrolytic cell was washed with water and 300 g of sulfuric acid was added.
It was immersed in an aqueous solution containing 60 ° C. for 60 seconds to remove the smut component composed mainly of aluminum hydroxide produced by the electrochemical graining treatment and washed with water.

The rough plate thus obtained has an average surface roughness of 0.21.
It had a double-structured grain in which honeycomb-shaped pits having an average pit diameter of 1.5 μm were overlapped on honeycomb-shaped pits having an average pit diameter of 3 μm.

The aluminum plate obtained as described above was anodized at 35 ° C. in an aqueous solution containing 100 g / sulfuric acid so that the amount of the oxide film was 2.0 g / m ² . After washing with water, it was immersed in an aqueous solution containing 2.5% of No. 3 sodium silicate at 70 ° C. for 20 seconds for hydrophilic treatment.

A photosensitive bath was applied on the aluminum plate thus obtained to produce a printing plate. The printing plate obtained had a printing durability of 130,000 sheets and had good stain performance and plate-making properties. Met.

Comparative Example-1 A JIS 3003-H14 rolled aluminum plate was dipped in a 10% aqueous solution of caustic soda for 30 seconds, washed, and washed with water.
This aluminum plate was subjected to electrochemical graining treatment under the same equipment and conditions as in the first stage of Example-1. Further, the same smut treatment as in Example-1 was performed.

The rough plate thus obtained has an average surface roughness of 0.21μ.
m had uniform honeycomb-shaped pits. The pit diameter was 3 μm on average.

Further, the aluminum plate obtained as described above was anodized at 35 ° C. in an aqueous solution containing 100 g / sulfuric acid so that the amount of oxide film was 2.0 g / m ² . After washing with water, it was immersed in an aqueous solution containing 2.5% of No. 3 sodium silicate at 70 ° C. for 20 seconds for hydrophilic treatment.

A photosensitive layer was applied on the aluminum plate thus obtained to produce a printing plate. The printing plate obtained had a printing durability of 100,000 sheets, and had good stain performance and plate making property. there were.

However, the printing durability was inferior to that of Example-1.

〔The invention's effect〕

In the present invention, electrodes facing an aluminum plate are alternately arranged in an acidic electrolyte, and a direct current voltage is applied between these electrodes to keep the aluminum plate at an arbitrary distance from these electrodes. The first and second stages of electrochemical graining treatment are performed by
According to the method for manufacturing an aluminum support for a printing plate, which is characterized by performing a smut removal treatment between the electrochemical graining treatments of the second step, the aluminum plate has a pit with a depth deeper than its diameter. Printing that has a double-structured grain structure in which evenly and densely exists, and that satisfactory printing performance and printing durability can be obtained without causing horizontal stripe-shaped processing unevenness in offset printing plates and the like. It has become possible to industrially and stably produce an aluminum rough surface plate suitable as an aluminum support for plates.

In addition, since roughening is performed using a direct current, it is not necessary to use a special power supply device compared to conventional roughening using alternating current, and the bus bar from the power supply device to the electrolytic cell can be easily handled. Therefore, it has become possible to manufacture with an advantage in terms of equipment cost and running cost.

[Brief description of drawings]

FIG. 1 is a process diagram of the present invention, FIGS. 2 and 4 are side sectional views of an embodiment of the apparatus used in the present invention, and FIG. 3 is a voltage waveform diagram of a direct current waveform according to the present invention. FIG. 1 is a side sectional view of an example of a conventional AC electrolytic etching apparatus. 1 …… Anode, 2 …… Cathode 3 …… Electrolyte solution, 4 …… Aluminum plate 5 …… Electrolyzer 10,12 …… DC electrolytic etching treatment 11 …… Smut treatment

Claims (1)

[Claims] 1. An anode and a cathode are alternately arranged in an acidic electrolytic solution so as to face an aluminum plate, and a DC voltage is applied between the both electrodes so that the aluminum plate is separated from these electrodes at an arbitrary distance. The first stage and the second stage
An aluminum support for a printing plate, characterized by performing an electrochemical graining treatment of the first step and performing a smut removal treatment between the electrochemical graining treatments of the first step and the second step. Manufacturing method.