JP2945502B2 - Continuous electrolytic surface roughening method of aluminum support for offset printing plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aluminum support for an offset printing plate,
The present invention relates to a method for continuous electrolytic surface roughening of an aluminum support for an offset printing plate, wherein the electrolytic surface roughening is performed by controlling the impedance of a plurality of electrolytic cells to be substantially constant.

[0002]

2. Description of the Related Art Conventionally, an aluminum plate has been widely used as a support for an offset printing plate, and a so-called PS plate in which a photosensitive layer composition is applied thereon in a thin layer has been put to practical use. The aluminum plate is generally subjected to a surface treatment to increase the adhesiveness of the photosensitive layer, the water retention of the non-image area or the abrasion resistance. In such a surface treatment,
After being degreased to clean the surface, it is roughened (also called graining) to make the surface uneven, and then anodized to increase the surface hardness, and then hydrophilic if necessary. After that, a support for an offset printing plate is obtained.

[0003] Among these treatments, various methods have been put to practical use for the surface roughening treatment in order to satisfy the above requirements of the printing plate. That is, brush graining, ball graining,
Mechanical surface roughening method such as liquid honing, chemical surface roughening method by chemical etching with hydrochloric acid or nitric acid, or electrolytic surface roughening method by electrochemical etching with these acids, or a combination of these A method for roughening the surface is known. Among these methods, the electrolytic surface roughening method can finely adjust the grain shape and surface roughness depending on the electrolytic solution composition and electrolytic conditions as compared with other methods. At the heart of the method. For example, brush graining and electrolytic surface roughening (JP-A-53-123204), chemical etching and electrolytic surface roughening (JP-A-60-208294),
Liquid honing and electrolytic surface roughening (JP-A-60-18390)
Are known. In the electrolytic surface roughening method, pits are formed on the aluminum surface, and the pit size, depth, and pit distribution can be changed depending on current density, liquid concentration, liquid composition, liquid temperature, and the like during electrolysis. It is widely known that the shape of the surface produced in this way greatly affects the properties of the offset printing plate support,
Generally, the center line surface roughness; Ra is adjusted to 0.3 to 1.0 μm. However, in practice, a composite grain that cannot be expressed only by the value of Ra is more preferable, and a method of performing electrolytic surface roughening in two stages by changing the current density in order to obtain a more complicated rough surface has been devised. (Japanese Patent Publication No. 56-51119).

In general, in the electrolytic surface roughening method, an electrolytic solution mainly containing hydrochloric acid or nitric acid is used, and electrolysis is performed by flowing a direct current or an alternating current (single phase or three phases). In the electrolytic surface roughening treatment, it is necessary to supply a large current to a continuously moving aluminum plate strip, so the power supply method has been devised, and without directly contacting the power supply terminal to the aluminum plate, for example, a single-phase AC current In the case of (1), the processing tank is divided into two, and a power supply is connected between both electrodes. In the case of three-phase AC, each terminal of the three phases is divided into three tanks and connected (metal surface). Technology Vol30, N
o. 10, 1979, P541 to P546) A so-called indirect power supply method in which an electrolytic solution is supplied and energized is adopted.

[0005] In the electrolytic treatment tank by the indirect power supply method, the same electrolytic solution is generally supplied to two or three tanks and subjected to electrolytic treatment in order to obtain impedance matching between the electrode of each treatment tank and the aluminum plate to be treated. You. In this case, since the electrolytic solution is the same, the current value and the temperature are fixed, and the process is performed while changing only the process time. If different electrolytes are supplied to each tank, the impedance will be different, electrolysis will be limited to the higher impedance, and the proper treatment effect of the electrolyte with the lower impedance cannot be obtained, and a composite grain will be obtained. I can't do that. In addition, in order to obtain fine grain, generally the current density must be lowered, but in this case, a uniform grain cannot be obtained in a short time treatment, and the treatment speed is reduced or the treatment tank is lengthened. It is necessary to
At present, productivity is poor. Furthermore, in continuous processing,
Once the apparatus is constructed, the size of the electrolytic cell is determined, and the size is limited, and the degree of freedom in improving the electrolytic solution is reduced.

[0006]

SUMMARY OF THE INVENTION According to the present invention, in an electrolytic graining treatment in which the same power source is connected to the electrodes of two or three electrolytic cells by an indirect power supply method, different electrolytic solutions are supplied to each of the electrolytic cells. Accordingly, the present invention provides a continuous electrolytic treatment method for stably obtaining a composite grain of an aluminum support for an offset printing plate.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method for continuously electrolyzing an aluminum plate strip by an indirect power supply method by passing it through two or three electrolytic baths. Electrodes connected to the same power supply are arranged in the tank, and different electrolytic solutions are supplied to the respective electrolytic cells, and the impedance between the electrodes and the aluminum plate to be treated is determined by the concentration, composition, temperature, or distance between the electrodes of the electrolytic solution. A continuous electrolytic surface roughening method for an aluminum support for an offset printing plate, characterized in that the aluminum support for an offset printing plate is controlled and subjected to electrolytic treatment under substantially constant impedance.

As the aluminum plate used in the present invention, pure aluminum and various metals, for example, an aluminum alloy containing a small amount of silicon, magnesium, iron, copper, zinc, manganese, chromium, titanium and the like are suitable. A trace amount of impurity metal contained in aluminum or a small amount of metal added arbitrarily has a large effect on the size, shape and distribution of pits obtained by electrolysis, and also on the strength of the aluminum plate A number of patents have been filed to provide In the continuous treatment method of the present invention, each treatment of degreasing, surface roughening, desmutting and anodic oxidation is performed, and washing is appropriately performed between each treatment.

In the degreasing treatment, the rolling oil on the aluminum surface is removed to expose a clean aluminum plate surface. Examples of the degreasing method include solvent degreasing with, for example, trichloroethylene, perchlorethylene, etc., alkali degreasing with sodium hydroxide, sodium carbonate, sodium metasilicate, trisodium phosphate, tetrasodium pyrophosphate, soap, or a mixture thereof. Emulsion degreasing using a combination of a surfactant, kerosene, triethanolamine, sodium hydroxide, etc .; and electrolytic degreasing called finishing degreasing, which removes contamination that cannot be removed by the above chemical degreasing. Also, ultrasonic cleaning is effective.

Next, in the present invention, as the surface roughening treatment, electrolytic surface roughening treatment is suitable for obtaining a pit-like grain, but additional mechanical or chemical surface roughening treatment is carried out. It may be added before, after or before or after roughening. The current used in the electrolytic surface roughening treatment was a single-phase or three-phase commercial AC or a part of the AC waveform cut by a sine wave, thyristor, etc. in the range of 10 to 100 Hz including these. Asymmetric current, symmetric sine wave, non-sinusoidal wave, non-sinusoidal wave, symmetrical non-sinusoidal wave, etc. in which the current of the waveform and the positive / negative current ratio are not equal can be used.

In the electrolytic surface roughening treatment of the present invention, indirect power supply is preferable. That is, in the indirect power supply, a power source is connected to each electrode of two or three electrolytic cells, and a current flows to the aluminum plate to be processed through the electrolytic solution. Therefore, it is possible to supply different electrolytic solutions to the two or three electrolytic cells for one power supply to perform different processing. That is, composite roughening processing can be performed with one power supply. However, conventionally, the same electrolytic solution has been supplied to obtain impedance matching. In general, the electrolytic solution has a different impedance depending on the chemical composition, for example, hydrochloric acid and nitric acid, and the impedance decreases (or increases) as the solution concentration or the temperature increases (or decreases) even with the same chemical composition. In the present invention, in the electrolytic treatment by indirect power supply, a different electrolytic solution is supplied to each treatment tank and circulated, so that the impedance of each tank is equal,
The electrolytic solution is adjusted by changing the composition, the solution concentration, the temperature, or the distance between the electrodes of the electrolytic solution, and the composite surface roughening process is continuously performed by one power supply.

In the indirect power supply, the height of the treated surface is changed to a two- or three-tank type in which an aluminum plate band is once lifted by an upper roll outside the liquid and passed to the next tank. There is a slit type that separates the tanks with narrow gaps, minimizes leakage of the electrolyte, and squeezes the electrolyte with a squeegee roll to straighten the electrolytic treatment. Either can be used as long as it can be separated. In order to prevent mixing of different electrolyte solutions before and after, washing between the tanks may be added as necessary. The power supplied to the aluminum plate varies depending on the composition of the electrolytic solution, the temperature, the distance between the electrodes, and the like. However, in order to obtain an appropriate grain for the printing plate, generally, the voltage is 1 to 60 V and the current density is 5 to 60 V. It is used in the range of 50-4000 coulombs in terms of electricity at 60 A / dm ² . The temperature of the electrolytic solution is preferably 0 to 60 ° C., and the distance between the electrode and the aluminum plate is preferably 1 to 10 cm.

As the electrolyte, an aqueous solution of nitric acid or a salt thereof, hydrochloric acid or a salt thereof, or one or a mixture of two or more thereof can be used. If necessary, sulfuric acid, phosphoric acid, chromic acid, boric acid, organic acids or their salts, nitrates, chlorides, ammonium salts, amines, surfactants, other corrosion promoters, corrosion inhibitors, stabilization An agent or the like may be added for use. As the concentration of the electrolytic solution, the concentration of the above-mentioned acids was set at 0.1.
Preferably, the concentration is 1 to 10% by weight, and the concentration of aluminum ions in the electrolyte is maintained in the range of 0 to 10 g / liter. In the electrolytic surface roughening treatment, aluminum is melted and acids are consumed by the progress of electrolysis, so that a part of the electrolyte is discarded while removing a part of the electrolyte so that the composition of the electrolyte does not deviate from a predetermined set range. It is preferable to provide a replenishing device for replenishing the electrolyte solution.

The aluminum plate strip which has been subjected to the electrolytic surface roughening treatment as described above is sufficiently washed with water. However, smut usually adheres to the surface of the strip, and the pits cannot be removed only by washing with water, but are closed. In order to remove the smut, a desmutting process is performed. For the desmutting treatment, an alkali agent usually used for a degreasing treatment can be used. In the desmut treatment, the smut dissolves and a pit surface appears. The amount of the dissolution varies depending on the treatment conditions with the electrolytic solution,
0.1 to 1 g / m ² is appropriate. The desmutted roughened aluminum strip is then usually anodized. In the anodizing treatment, an aluminum oxide film is formed on the aluminum surface, not only preventing the surface from being denatured, but also significantly improving the surface hardness and improving the printing durability during printing. Since an oxide film is formed only on the anode, a direct current is usually used as the current. As the electrolyte, an acid having low solubility of the formed oxide film, such as sulfuric acid, oxalic acid, chromic acid, or phosphoric acid, is used. The conditions of the anodic oxidation were as follows: solution concentration 1 to 40%, current density 0.1 to 0.1%.
Used in the range of 10 A / dm ² and anodized until the required film thickness is obtained. The temperature affects the hardness of the oxide film, and the lower the temperature, the higher the hardness. The thickness of the anodic oxide film is appropriately adjusted depending on the printing durability of the printing plate.
μm is sufficient.

The support for offset printing plate thus obtained is provided with a conventionally known photosensitive layer,
It is used as an offset printing plate or a photosensitive lithographic printing plate for practical use. As the photosensitive layer, for example, polyvinyl alcohol and dichromates, diazo resin and acrylates, o-quinonediazide compound and novolak-type phenol or cresol resin, phenylenediacrylic acid-type photocrosslinkable polymer, and addition-polymerizable ethylene compound There is a photopolymerizable photopolymer composed of an alkali-soluble resin, and the like. Further, as the photoconductive photosensitive layer, a photosensitive layer composed of an inorganic or organic photoconductive substance and an alkali-soluble resin can be provided. Further, a silver halide photosensitive layer may be provided. The lithographic printing plate thus obtained is subjected to close exposure of a positive or negative film original or image formation by image exposure with a laser, and the non-image portion is eluted with an eluate such as an alkali or alcohol to make a plate. And supplied to the printing press. Hereinafter, the continuous electrolytic surface roughening method of the present invention will be described in more detail with reference to examples.

[0016]

【Example】

Example 1 An A1050 type aluminum plate strip having a width of 300 mm and a thickness of 0.3 mm was moved at a processing speed of 2 m / min.
Immersion in 30% caustic soda for 30 seconds, rinsed with water, passed through a two-cell type liquid indirect power supply type electrolytic cell under the following conditions, roughened with an 675 A, 50 Hz single-phase AC current for 45 seconds, and rinsed with water. And then immersed in 4% caustic soda for 30 seconds at 25 ° C., desmutted, washed with water,
Anodized with a direct current of 135 A through a 45 ° C., 15% sulfuric acid for 45 seconds, washed with water, and then dried to obtain an aluminum support for offset printing plates. First tank Electrolyte: 1.5% hydrochloric acid Temperature: 25 ° C Aluminum-electrode 5cm Second tank Electrolyte: 2.0% Nitric acid Temperature: 20 ° C Aluminum-electrode 5cm

In order to separately control the impedance of each tank during electrolysis, a monitor electrode was installed and monitored, and the impedance of both tanks always showed the same value. An electrophotographic photosensitive layer composed of phthalocyanine and an alkali-soluble acrylic resin was applied to the support thus obtained, and a toner image was formed by an electrophotographic method. The printing plate suitability was shown. For comparison, each of the first and second tanks was filled with the same electrolyte and subjected to electrolytic surface-roughening treatment. A fine uniform rough surface as in Example 1 was not obtained.

Example 2 An A1100 type aluminum plate strip having a width of 300 mm and a thickness of 0.3 mm was moved at a processing speed of 2 m / min.
After immersing in 4% caustic soda for 30 seconds, wash with water,
Under the following conditions, the solution is passed through a two-cell type liquid indirect power supply type electrolytic cell for 45 seconds, subjected to AC electrolytic surface roughening with a single-phase AC current of 400 A, washed with water, and then washed at 25 ° C with 4% caustic soda for 30 minutes.
Immersed for 2 seconds, desmutted, washed with water, then 25 ° C, 1
The solution was passed through 5% sulfuric acid, anodized with a direct current of 135 A, washed with water, and then dried to obtain a support for an aluminum lithographic printing plate. First tank Electrolyte: 1.4% Hydrochloric acid Temperature: 35 ° C 5cm between aluminum and electrodes Second tank Electrolyte: 2.0% Hydrochloric acid temperature: 5 ° C 5cm between aluminum and electrodes Impedance of each tank during electrolysis is always the same value showed that. The support thus obtained showed good suitability for a lithographic printing plate as in Example 1.

Example 3 While moving an A1050 type aluminum plate strip having a width of 300 mm and a thickness of 0.3 mm at a processing speed of 2 m / min, a 50
After immersing in 4% caustic soda for 30 seconds, wash with water,
Under the following conditions, the solution is passed through a two-cell type liquid indirect power supply type electrolytic cell for 30 seconds to roughen the AC electrolytic surface with a single-phase AC current of 525 A, rinse with water, and then wash at 25 ° C. with 4% caustic soda.
Desmut by immersing for 0 seconds, washing with water, then 25 ° C,
It was passed through 15% sulfuric acid, anodized with a direct current of 135 A, washed with water, and then dried to obtain an aluminum support for offset printing plates. 1st tank Electrolyte: 1.4% hydrochloric acid Temperature: 10 ° C Aluminum-electrode 3cm 2nd tank Electrolyte: 2.0% hydrochloric acid Temperature: 10 ° C Aluminum-electrode 4.5cm

During the electrolysis, the impedance of each tank always showed the same value. The support thus obtained showed good suitability for a lithographic printing plate as in Example 1. For comparison, each of the first and second tanks was filled with the same electrolyte, and the surface between the electrodes was roughened with the same distance between the electrodes. An appropriate rough surface could not be obtained even when the current density and temperature were changed. At 2.0%, smut adhered much, local pits were generated, and a good rough surface could not be obtained.

Example 4 While moving an A1050 type aluminum sheet strip having a width of 300 mm and a thickness of 0.3 mm at a processing speed of 2 m / min,
Immersed in 4% caustic soda for 30 seconds, washed with water, and placed in a three-cell type indirect liquid supply type electrolytic cell under the following conditions.
After passing through for 5 seconds, AC electrolytic surface roughening was performed with a three-phase AC current of 450 A, washed with water, then immersed in 25% C. 4% caustic soda for 30 seconds, desmutted, washed with water, and then washed with 25 ° C., 15%
% Sulfuric acid and anodized with 135 A direct current,
After washing with water and drying, a support for an aluminum lithographic printing plate was obtained. First tank Electrolyte: 1.4% hydrochloric acid Temperature: 10 ° C Aluminum-electrode 3cm 2nd tank Electrolyte: 2.0% Hydrochloric acid temperature: 10 ° C Aluminum-electrode 4.5cm Third tank Electrolyte: 2. 2% nitric acid Temperature: 15 ° C Aluminum-electrode 5 cm During electrolysis, the impedance of each tank always showed the same value. The support thus obtained showed good suitability for a lithographic printing plate as in Example 1.

[0022]

According to the electrolytic graining treatment method of the present invention, the degree of freedom of the electrolytic graining treatment condition is increased, and a single power supply can stably remove fine composite grain without local pits in a short time. Can be obtained.

Claims (1)

(57) [Claims] 1. A method in which an aluminum plate strip is passed through two or three electrolytic baths to perform continuous electrolytic treatment by an indirect power supply method, wherein the same power supply is connected to the two or three electrolytic baths. Electrodes are arranged, different electrolytic solutions are supplied to each electrolytic cell, and the impedance between the electrodes and the aluminum strip to be treated is controlled by the concentration, composition, temperature or distance between the electrodes of the electrolytic solution, and a substantially constant impedance is obtained. A method for continuous electrolytic surface roughening of an aluminum support for offset printing plates, wherein the electrolytic treatment is performed under the following conditions.