JPH0798428B2 - 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 a printing plate, and particularly for a printing plate comprising a roughened aluminum plate suitable for offset printing plates. The present invention relates to a method for manufacturing a support.

[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. The aluminum plate is roughened by an alternating current using an appropriate electrode such as graphite as a counter electrode, which is usually performed in a single treatment, but the pit 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 A combination of energization amounts per area (Japanese Patent Laid-Open No. 56-29699) is known.

However, even with the above method, 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. In Japanese Patent Laid-Open No. 54-85802, an alternating voltage is used. Then, the smut removal treatment is sandwiched between the electrochemical roughening treatments of the first and second stages,
Sand with relatively deep pits obtained by the roughening treatment of the second stage and fine pits generated by the roughening treatment of the second stage, having a double pit structure with excellent printing performance and an appropriate depth A method for obtaining the eye shape is proposed.

[Problems to be Solved by the Invention]

However, according to the method disclosed in Japanese Patent Laid-Open No. 54-85802, while a grain shape having excellent printing performance can be easily obtained, a large amount of electricity is required for the first-step electrochemical graining treatment.
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.

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,
Another object of the present invention is to provide a method for producing an aluminum support for a printing plate, which comprises 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]

The above-mentioned object of the present invention is that the electrochemical graining treatment in the first step is carried out by alternately arranging the electrodes facing the aluminum plate in the acidic electrolytic solution as anodes and cathodes, and by applying a DC voltage between these bipolar plates. Is applied and the aluminum plate is allowed to pass through these electrodes at an arbitrary interval, and the electrochemical graining treatment in the second step is an alternating current electrolytic etching method in an acidic electrolytic solution. This is achieved by a method for producing an aluminum support for a printing plate, which comprises performing a smut removing treatment between the electrochemical roughening treatments of the second and second stages.

As a result of various studies, the present inventors have found that in the method of continuously electrochemically roughening a surface in an aqueous solution containing nitric acid or hydrochloric acid, the electrodes facing the aluminum plate are used as anodes and cathodes, which are alternated. The aluminum plate is electrochemically roughened by applying a DC voltage between these two electrode plates and passing the aluminum support at an arbitrary distance from these electrodes. In comparison, it was found that deep pits were created.

The present invention is characterized in that the direct current electrolytic etching treatment and the alternating current electrolytic etching treatment are combined and a smut treatment is sandwiched therebetween.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a process chart of the present invention in which a DC electrolytic etching process 10 is first performed, a smut process 11 is then performed, and an AC electrolytic etching process is performed.

As shown in FIG. 2, the direct current electrolytic etching treatment 10 according to the present invention is such that the first electrochemical roughening treatment is carried out by alternately arranging the electrodes facing the aluminum plate in the same electrolytic bath in the same electrolyte as the anode 1 And the cathode 2 may be arranged, or as shown in FIG. 4, the anode 1 and the cathode 2 may be arranged separately as separate tanks.

Roughening treatment by applying a DC voltage between these electrodes and passing the aluminum plate 4 with these electrodes (anode 1 and cathode 2) at an arbitrary interval is deeper than the diameter. This is to generate a deep pit.

Next, as shown in FIG. 1, smut processing 11 is performed. A smut component composed mainly of aluminum hydroxide, which is generated by the electrochemical graining treatment (DC electrolytic etching treatment 10), is removed. After that, an alternating current electrolytic etching process 12 is performed as a second-stage electrochemical graining process. An aluminum plate 4 and an electrode 6 facing the aluminum plate 4 are placed in an acidic electrolyte solution 3 containing nitric acid or hydrochloric acid as a main component by an apparatus as shown in FIG.
An alternating voltage is applied between the and via the power supply roll 7 to roughen the surface and generate fine pits.

By doing this, deep grain is generated in the first stage electrochemical graining treatment, and the pit surface of the deep grain obtained previously in the second stage electrochemical graining treatment It is possible to easily obtain a double-structured pit including fine pits.

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

Next, the requirements for the present invention will be described in order.

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 stains and natural oxide film, and then dipping in nitric acid or an aqueous nitric 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 doesn't have to be done.

In the present invention, the DC current waveform used for the first-stage electrochemical surface roughening is a current waveform whose polarity does not change, and can be a comb-shaped waveform, continuous DC, or commercial AC that is full-wave rectified by a thyristor. However, it is preferable to use a smoothed continuous direct current as shown in FIG.

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 / hydrochloric acid, or 5 nitric acid.
It is an aqueous solution containing ~ 20 g /, and the liquid temperature is preferably 20 ° C to 60 ° C. The current density is preferably in the range of ² 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 graining 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.

As the electrode used in the present invention, any of known electrodes used for 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.

The desmutting treatment performed between the first step and the second step only needs to be able to almost completely remove the smut mainly composed of aluminum hydroxide generated in the electrolytic surface roughening treatment, and the caustic soda solution, high temperature sulfuric acid solution, high temperature nitric acid 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.

In the surface roughening treatment performed in the second step, an alternating voltage is applied between an aluminum plate and an electrode facing the aluminum plate in an acidic aqueous solution to perform electrochemical surface roughening. The alternating voltage is commercial alternating current, commercial alternating current with phase angle control by thyristor,
A rectangular wave or the like can be used, but the rectangular wave is most preferable. The electrode facing the aluminum plate can be made of carbon or the like, and the electrolytic treatment method and apparatus as described in JP-A-60-33398 and JP-A-62-127500 can be applied. it can.

In the present invention, the electrolytic solution used for the first and second-step electrochemical graining treatments is preferably an aqueous solution containing nitric acid or hydrochloric acid as a main component.

Of course, a mixed solution of nitric acid and hydrochloric acid, or an aqueous solution of nitric acid or hydrochloric acid mixed with organic acid, sulfuric acid, phosphoric acid, hydrofluoric acid, hydrobromic acid or the like may be used.

The most suitable electrolyte used in the second-stage electrochemical graining treatment is an aqueous solution containing 5 to 20 g / hydrochloric acid or 5 to 20 g / nitric acid, and the liquid temperature is 20 ° C.
-60 ° C is preferred. The current density is 20A / dm ² ~ 200A / dm
It is preferably in the range of ² . The electrolytic treatment time is preferably in the range of 5 to 90 seconds because an optimum rough surface cannot be obtained if it is too long or too short. 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 it is preferable to use the continuous method.
Most preferred.

The frequency of the alternating current waveform includes aluminum material, liquid composition,
The optimum value varies depending on the electrolysis conditions such as current density.
It can be used over a wide range up to 0 Hz and is not particularly limited. When roughening using high-purity aluminum such as JIS 1050 materials and 1100 materials
A relatively high frequency region of 15 to 60 Hz is suitable, and 40 to 60 Hz is particularly preferable. When performing surface roughening using JIS 3003 material, a relatively high frequency range of 0.1 to 15 Hz is suitable, and 0.2 to 1.2 Hz is particularly preferable. For aluminum alloys, the optimum frequency range varies depending on the composition and heat treatment conditions.

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

The rough plate obtained as described above is anodized in an electrolytic solution containing sulfuric acid or phosphoric acid according to a usual method to obtain a printing plate excellent in hydrophilicity, water retention and printing durability. Can be manufactured. Of course, after the anodizing treatment, it may be immersed in an aqueous solution containing sodium silicate or the like to carry out the hydrophilic treatment.

〔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 officially approved as shown in Fig. 1,
A direct current electrolytic etching process is used as the first-stage electrochemical graining process. As the DC electrolytic etching treatment,
In the electrolytic cell 5 as shown in FIG. 2, the anode 1 is platinum and the cathode is carbon, and the anode 1 and the cathode 2 are separated by 100 mm, and 14 electrodes are alternately placed in the electrolytic solution 3 to form electrodes 1 and 2. The aluminum plate 4 was continuously passed with an interval of 10 mm above. 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 electrolytic solution 3 used is an aqueous solution containing 15 g / nitric acid, and the solution temperature is 45
It was ℃. The aluminum plate which has finished the first-stage electrochemical graining treatment (DC electrolytic etching treatment) and has exited the electrolytic cell 5 is then washed with water and contains 300 g / nitric acid as the smut removal treatment 11 shown in FIG. Immerse the solution in 60 ℃ for 60 seconds,
The smut component mainly composed of aluminum hydroxide produced by the electrochemical graining treatment was removed and washed with water.

After that, the first electrochemical graining treatment of the second step was performed.
After performing the AC electrolytic etching treatment 12 shown in the figure, a square wave AC 80 A / d having a frequency of 1.0 Hz was produced using the apparatus shown in FIG.
The surface was roughened at m ² for 5 seconds.

The electrode 6 was made of carbon, and the feeding roll 7 was made of aluminum. The aluminum plate 4 was passed over the carbon electrode 6 with a space of 10 mm. Electrolyte 3 used
Was an aqueous solution containing 15 g / nitric acid. Liquid temperature is 45 ° C
Met.

The aluminum plate that came out of the electrolytic cell 3 was washed with water and then washed with sulfuric acid 30
It was immersed in an aqueous solution containing 0 g / 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 0.30 μm.
At m, it had a double-structured grain structure having dense honeycomb-shaped pits on the large-wave-structured grain.

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 plate was applied onto the aluminum plate thus obtained to produce a printing plate.The printing plate obtained had good plate making properties, printing durability of 150,000 sheets, and good stain resistance. It was

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 (DC electrolytic etching 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 roughening 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〕

According to the present invention, in the electrochemical graining treatment of the first step, the electrodes facing the aluminum plate are alternately arranged in the acidic electrolytic solution, and the anode and the cathode are arranged, and a DC voltage is applied between the both electrodes. Then, the aluminum plate is allowed to pass through these electrodes at an arbitrary interval, and the electrochemical graining treatment in the second step is an alternating current electrolytic etching method in an acidic electrolytic solution. By the method for manufacturing the aluminum support for printing plates, which is characterized by performing the smut removal treatment between the second and the electrochemical roughening treatment of the second step, the equipment cost and running cost are reduced, and there are also design restrictions. Not only decrease,
It is possible to easily obtain a double-structured grain in which dense honeycomb-shaped pits are superposed on a large-wave-shaped grain in terms of quality, and horizontal stripe-shaped processing unevenness occurs in offset printing plates. It has become possible to obtain satisfactory printing durability and printing performance without any occurrence.

[Brief description of drawings]

FIG. 1 is a process diagram of the present invention, FIGS. 2, 4, and 5 are side sectional views of an embodiment of the apparatus used in the present invention, and FIG. 3 is a voltage waveform of a direct current waveform according to the present invention. It is a figure. 1 ... Anode, 2 ... Cathode 3 ... Electrolyte solution, 4 ... Aluminum plate 5 ... Electrolyte tank, 6 ... Electrode 7 ... Power supply roll, 8 ... Liquid supply nozzle 10 ... DC electrolytic etching treatment 11 …… Smut removal treatment 12 …… AC electrolytic etching treatment

Claims (1)

[Claims] 1. The electrochemical graining treatment in the first step comprises alternately arranging an anode and a cathode facing an aluminum plate in an acidic electrolytic solution, and applying a DC voltage between these electrodes. Is applied and the aluminum plate is allowed to pass through these electrodes at an arbitrary interval, and the electrochemical graining treatment in the second step is an alternating current electrolytic etching method in an acidic electrolytic solution. A method for producing an aluminum support for a printing plate, which comprises performing a smut removal treatment between the second and second electrochemical graining treatments.