JPH04314595A - Method for continuously electrolytically roughening aluminum substrate for offset printing plate - Google Patents

Abstract

PURPOSE:To stably obtain uniform complex grains by an electrolytic roughening treatment by an indirect power supply method in the production of an aluminum substrate for an offset printing plate. CONSTITUTION:In an electrolytic roughening treatment by an indirect power supply method, different electrolyte is supplied to each electrolytic bath, and an impedance between an electrode and an aluminum plate to be treated in each bath is controlled by the density, composition, and temperature of the electrolyte or a distance between electrodes. In this manner, a continuous electrolytic roughening treatment is conducted under a substantially constant impedance.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for producing an aluminum support for offset printing plates, and in particular,
The present invention relates to a continuous electrolytic surface roughening method for an aluminum support for an offset printing plate, characterized in that electrolytic surface roughening is carried out by controlling the impedance of a plurality of electrolytic cells to be substantially constant.

0002

BACKGROUND OF THE INVENTION Hitherto, aluminum plates have been widely used as supports for offset printing plates, and so-called PS plates, in which a photosensitive layer composition is coated in a thin layer thereon, have been put into practical use. The above-mentioned aluminum plate is generally surface-treated to increase the adhesion of the photosensitive layer, water retention or abrasion resistance of the non-image area. In this kind of surface treatment,
After being degreased to clean the surface, it is roughened (also called graining) to make the surface uneven, then anodized to increase surface hardness, and then hydrophilized if necessary. It is processed into a support for offset printing plates.

Among these treatments, various methods of surface roughening treatment have been put into practical use in order to meet the above-mentioned requirements for printing plates. That is, mechanical surface roughening methods such as brush graining, ball graining, liquid honing, etc., chemical surface roughening methods using chemical etching using hydrochloric acid or nitric acid, or electrolytic surface roughening methods using electrochemical etching using these acids. Surface roughening methods or a combination of these methods are known. Among these methods, the electrolytic surface roughening method allows fine adjustment of the grain shape and surface roughness by changing the electrolyte composition and electrolytic conditions compared to other methods, and in recent years, surface roughening The method is central. For example, brush graining and electrolytic roughening (Japanese Patent Application Laid-Open No. 123204/1983)
, chemical etching and electrolytic surface roughening (JP-A-60-2082)
No. 94), liquid honing and electrolytic surface roughening (Japanese Unexamined Patent Publication No. 6
0-18390) and other combinations are known. In the electrolytic surface roughening method, pits are formed on the aluminum surface, and the size, depth, and distribution of the pits can be changed depending on the current density, liquid concentration, liquid composition, liquid temperature, etc. during electrolysis. It is widely known that the shape of the surface created in this way has a great effect on the properties of the support for offset printing plates, and generally the centerline surface roughness; Ra value is 0.3 to 1. Adjusted to 0μ. However, in practice R
A method of electrolytic surface roughening in two stages by changing the current density has been devised in order to obtain a more preferable composite grain surface that cannot be expressed by the value of a alone, and a more complex surface roughness. 56-51119).

Generally, in the electrolytic surface roughening method, an electrolytic solution containing hydrochloric acid or nitric acid as a main ingredient is used, and electrolysis is carried out by flowing a direct current or an alternating current (single-phase or three-phase). In electrolytic surface roughening treatment, it is necessary to supply a large current to a continuously moving aluminum plate band, so the power supply method has been devised. In this case, divide the processing tank into two and connect the power supply between both electrodes, and in the case of three-phase AC, connect each terminal of the three phases to the three tanks (metal surface Technology Vol3
0, No. 10, 1979, P541-P546) A so-called indirect power supply method is adopted in which an electrolytic solution is supplied and electricity is supplied.

[0005] In electrolytic treatment tanks using the indirect power supply method, in order to obtain impedance matching between the electrodes of each treatment tank and the aluminum plate to be treated, the same electrolytic solution is generally supplied to two or three tanks for electrolytic treatment. Ru. In this case, since the electrolyte is the same, the current value and temperature are kept constant, and only the treatment time is changed. If different electrolytes are supplied to each tank, the impedance will be different, and electrolysis will be limited to the one with higher impedance, making it impossible to obtain a proper treatment effect with the electrolyte with lower impedance, resulting in composite grain. I can't do that. Furthermore, in order to obtain a fine grain, it is generally necessary to lower the current density, but in this case, it is not possible to obtain a uniform grain with a short treatment time, and the treatment speed must be lowered or the treatment bath lengthened. It becomes necessary to
The current situation is that productivity is poor. Furthermore, in continuous processing,
Once the equipment is constructed, the size of the electrolytic cell is determined, and this size limits the degree of freedom in improving the electrolyte.

[0006]

[Problems to be Solved by the Invention] The present invention is an electrolytic surface roughening treatment in which the same power source is connected to the electrodes of two or three electrolytic cells using an indirect power supply method, and a different electrolyte is supplied to each treatment tank. 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]

[Means for Solving the Problems] The present invention is a method for continuously electrolyzing an aluminum plate strip by passing it through two or three electrolytic cells by an indirect power supply method, and in which Electrodes connected to the same power supply are arranged in the tanks, and different electrolytes are supplied to each electrolytic tank, and the impedance between the electrodes and the aluminum plate strip to be treated is adjusted depending on the concentration, composition, temperature, or distance between the electrodes of the electrolyte. This is a continuous electrolytic surface roughening method for an aluminum support for an offset printing plate, which is characterized in that the electrolytic treatment is carried out under controlled and substantially constant impedance.

As the aluminum plate used in the present invention, pure aluminum and aluminum alloys containing small amounts of various metals such as silicon, magnesium, iron, copper, zinc, manganese, chromium, titanium, etc. are suitable. A small amount of impurity metal contained in aluminum or a small amount of arbitrarily added metal has a large effect on the size, shape, and distribution of grain pits obtained by electrolysis, and also has a large effect on the strength of the aluminum plate. A large number of patent applications have been filed to provide this. In the continuous treatment method of the present invention, degreasing, surface roughening, desmutting, and anodic oxidation treatments are performed, and water washing is performed as appropriate between each treatment.

In the degreasing treatment, the rolling oil on the aluminum surface is removed to expose the clean surface of the aluminum plate. Examples of degreasing methods include solvent degreasing using trichlorethylene, perchlorethylene, etc., alkaline degreasing using sodium hydroxide, sodium carbonate, sodium metasilicate, trisodium phosphate, tetrasodium pyrophosphate, soap, etc., or a mixture thereof. There are methods such as emulsion degreasing using a combination of surfactants, kerosene, triethanolamine, sodium hydroxide, etc., and electrolytic degreasing called finish degreasing, which removes contamination that cannot be removed by the above-mentioned chemical degreasing. Ultrasonic cleaning is also effective.

[0010] Next, as the surface roughening treatment in the present invention, electrolytic surface roughening treatment is suitable for obtaining pit-like grains, but mechanical or chemical surface roughening treatment may be additionally performed as an auxiliary surface roughening treatment. It may be added before or after roughening, or before or after roughening. The current used for electrolytic surface roughening treatment is single-phase or three-phase commercial alternating current, or a sine wave including these in the range of 10 to 100 Hz.
Currents with a waveform in which a part of the alternating current waveform is cut by a thyristor or the like, an asymmetrical type in which the positive and negative current ratios are not equal, a symmetrical sine wave, a non-sine wave, a symmetrical non-sine wave, etc. can be used.

[0011] Indirect power supply is preferable for the electrolytic surface roughening treatment of the present invention. That is, in indirect power supply, a power source is connected to each electrode of two or three electrolytic cells, and a current flows through the electrolytic solution to the aluminum plate to be processed. Therefore, it is possible to supply different electrolytes to two or three electrolytic cells for this one power source to perform different treatments. That is, a single power source can perform complex surface roughening processing. However, conventionally, the same electrolyte solution has been supplied in order to obtain impedance matching. In general, the impedance of an electrolytic solution differs depending on its chemical composition, for example, hydrochloric acid and nitric acid, and even if the chemical composition is the same, the impedance decreases (or increases) as the concentration or temperature of the electrolyte increases (or decreases). In the present invention, a different electrolyte is supplied to each treatment tank in electrolytic treatment using indirect power supply, and circulated through each tank, and the composition, concentration, temperature, or distance between the electrodes of the electrolyte is changed so that the impedance of each tank is equal. It is characterized in that it is adjusted and subjected to electrolytic treatment, and the composite surface roughening treatment is performed continuously using one power source.

[0012] In indirect power supply, the electrolyzer is of a two- or three-tank type, in which the aluminum plate strip is once lifted onto a roll above the liquid between the tanks and passed to the next tank, and the height of the processing surface can be changed. There is a slit type that partitions the tanks with narrow slits to minimize electrolyte leakage, and furthermore, uses a squeegee roll to squeeze out the electrolyte and process it straight. If it is possible to separate them, either can be used. In order to prevent different electrolytes from mixing before and after, washing with water may be added between the tanks as necessary. The power supplied to the aluminum plate varies depending on the composition of the electrolyte, temperature, distance between electrodes, etc., but in general, in order to obtain an appropriate grain for a printing plate, the voltage is generally 1 to 60 V, and the current density is 5 to 60 V. It is used at 60A/dm2, and the amount of electricity is in the range of 50 to 4000 coulombs. Also, the temperature of the electrolyte is 0 to 60℃
The distance between the electrode and the aluminum plate is preferably in the range of 1 to 10 cm.

As the electrolyte, an aqueous solution of nitric acid or its salt, hydrochloric acid or its salt, or a mixture of one or more thereof can be used. Furthermore, 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, and stabilizers are added. It may also be used with the addition of agents. The concentration of the electrolyte is 0.
It is preferable that the aluminum ion concentration in the electrolytic solution is maintained in the range of 0 to 10 g/liter. In the electrolysis treatment, as the electrolysis progresses, aluminum dissolves and acids are consumed, so some of the electrolyte is discarded while the acids are removed so that the composition of the electrolyte does not deviate from the predetermined range. It is preferable to install a replenishment device for replenishing and managing the electrolyte solution.

[0014]Although the aluminum plate strip subjected to the electrolytic surface roughening treatment as described above is thoroughly washed with water, smut usually adheres to the surface and cannot be removed by washing alone, blocking the pits. In order to remove the smut, a desmutting process is performed. For the desmutting treatment, an alkaline agent that is normally used for degreasing treatment can be used. In the desmutting process, the smut is dissolved and a pit surface appears. The amount dissolved varies depending on the treatment conditions with the electrolyte, but 0
．． 1 to 1 g/m2 is suitable. The desmutted roughened aluminum strip is usually then anodized. Anodizing produces an aluminum oxide film on the aluminum surface, which not only prevents surface deterioration but also significantly improves surface hardness and improves printing durability. Since the oxide film is formed only on the anode, direct current is usually used. As the electrolytic solution, acids such as sulfuric acid, oxalic acid, chromic acid, and phosphoric acid, which have low solubility in the formed oxide film, are used. The conditions for anodic oxidation are a liquid concentration of 1 to 40% and a current density of 0.1.
~10 A/dm2 and anodized until the required film thickness is obtained. Temperature affects the hardness of the oxide film, and although it becomes harder at lower temperatures, it also becomes brittle, so it is usually anodized at a temperature around room temperature. The thickness of the anodic oxide film is adjusted appropriately depending on the printing durability grade of the printing plate, but it is 0.
1 to 2 μm is sufficient.

The offset printing plate support thus obtained was provided with a conventionally known photosensitive layer.
It is used as an offset printing plate or a photosensitive planographic printing plate for practical use. As a photosensitive layer, for example, polyvinyl alcohol and dichromates, diazo resin and acrylic esters, o-quinone diazide compound and novolak type phenol or cresol resin, phenylene diacrylic acid type photocrosslinkable polymer, addition polymerizable ethylene compound, etc. There are photopolymerizable photopolymers made of alkali-soluble resins, etc. Further, as a photoconductive photosensitive layer, a photosensitive layer consisting of an inorganic or organic photoconductive substance and an alkali-soluble resin can be provided. Furthermore, a silver halide photosensitive layer can also be provided. The lithographic printing plate obtained in this way is image-formed by contact exposure of a positive or negative film original or by image exposure with a laser, and the non-image areas are eluted with an eluent such as alkali or alcohol to form a plate. and fed to the printing press. Hereinafter, the continuous electrolytic surface roughening method of the present invention will be explained 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.
After immersing it in 4% caustic soda for 30 seconds at 50°C, it was washed with water, and was heated with a single-phase alternating current of 675 A and 50 Hz while passing it through a two-tank type liquid indirect power supply electrolytic bath under the following conditions.
The surface was roughened by alternating current electrolysis for 5 seconds, washed with water, and then heated to 4% at 25°C.
Desmat by immersing in caustic soda for 30 seconds, washing with water,
After that, it was passed for 45 seconds in 15% sulfuric acid at 25°C to 135A.
The aluminum support for an offset printing plate was obtained by anodic oxidation with a direct current of 200 mL, washed with water, and then dried. 1st tank electrolyte: 1.5% hydrochloric acid Temperature: 25°C between aluminum and electrodes 5cm 2nd tank electrolyte: 2.0% nitric acid Temperature: 20°C between aluminum and electrodes 5cm

In order to separately manage the impedance of each tank during electrolysis, monitor electrodes were installed and monitored, and the impedance of both tanks always showed the same value. An electrophotographic photosensitive layer made of phthalocyanine and an alkali-soluble acrylic resin was coated on the support thus obtained, a toner image was formed by electrophotography, and the non-image area was eluted and removed. Showed suitability for printing plate. For comparison, when both the first and second tanks were filled with the same electrolyte and electrolytically roughened, the surfaces were rough and uneven, and even when the current density and temperature were changed, A fine and uniformly roughened surface as in Example 1 could not be obtained.

Example 2 An A1100 type aluminum plate strip having a width of 300 mm and a thickness of 0.3 mm was immersed in 4% caustic soda at 50° C. for 30 seconds while moving at a processing speed of 2 m/min, and then washed with water and subjected to the following conditions. The material was passed through a two-tank indirect liquid power supply type electrolytic bath for 45 seconds, subjected to alternating current electrolytic roughening with a single-phase alternating current of 400 A, washed with water, and then desmutted by immersion in 4% caustic soda at 25° C. for 30 seconds. It was washed with water, passed through 15% sulfuric acid at 25° C., anodized with a direct current of 135 A, washed with water, and then dried to obtain a support for an aluminum lithographic printing plate. 1st tank electrolyte: 1.4% hydrochloric acid Temperature: 35°C between aluminum and electrode 5cm 2nd tank electrolyte: 2.0% hydrochloric acid Temperature: 5°C between aluminum and electrode 5cm During electrolysis, the impedance of each tank is always the same value showed that. The support thus obtained exhibited good lithographic printing plate suitability as in Example 1.

Example 3 An A1050 type aluminum plate strip having a width of 300 mm and a thickness of 0.3 mm was immersed in 4% caustic soda at 50° C. for 30 seconds while moving at a processing speed of 2 m/min, and then washed with water and processed under the following conditions. The material was passed through a two-tank indirect liquid power supply type electrolytic bath for 30 seconds, subjected to alternating current electrolytic roughening with a single-phase alternating current of 525 A, washed with water, and then desmutted by immersion in 4% caustic soda at 25°C for 30 seconds. , washed with water, passed through 15% sulfuric acid at 25° C., anodized with a direct current of 135 A, washed with water, and then dried to obtain an aluminum support for an offset printing plate. 1st tank electrolyte: 1.4% hydrochloric acid Temperature: 10°C between aluminum and electrodes 3cm 2nd tank electrolyte: 2.0% hydrochloric acid Temperature: 10°C between aluminum and electrodes 4.5cm

During electrolysis, the impedance of each tank always showed the same value. The support thus obtained exhibited good lithographic printing plate suitability as in Example 1. For comparison, both the first tank and the second tank were filled with the same electrolyte solution, the distance between the electrodes was the same, and electrolytic surface roughening treatment was performed.
At 1.4%, the surface was rough and uneven, and even if the current density and temperature were changed, an appropriately rough surface could not be obtained. Further, at 2.0%, there was a lot of smut adhesion, localized pits were generated, and a good rough surface could not be obtained.

Example 4 An A1050 type aluminum plate strip having a width of 300 mm and a thickness of 0.3 mm was immersed in 4% caustic soda at 50° C. for 30 seconds while moving at a processing speed of 2 m/min.
Rinse with water, pass through a 3-bath type indirect liquid power supply electrolyzer for 45 seconds under the following conditions, roughen the surface with AC electrolysis using a 450A three-phase alternating current, rinse with water, then immerse in 4% caustic soda at 25°C for 30 seconds. Soak, desmat, wash with water, then 2
It was passed through 15% sulfuric acid at 5° C., anodized with a direct current of 135 A, washed with water, and then dried to obtain a support for an aluminum lithographic printing plate. 1st tank electrolyte: 1.4% hydrochloric acid Temperature: 10°C between aluminum and electrode 3cm 2nd tank electrolyte: 2.0% hydrochloric acid Temperature: 10°C between aluminum and electrode 4.5cm 3rd tank electrolyte: 2. 2% nitric acid Temperature: 15°C 5cm between aluminum and electrode During electrolysis, the impedance of each tank always showed the same value. The support thus obtained exhibited good lithographic printing plate suitability as in Example 1.

[0022]

[Effects of the Invention] The electrolytic surface roughening treatment method of the present invention increases the degree of freedom in electrolytic surface roughening treatment conditions, and can stably process fine composite grains without local pits in a short time using a single power source. You can get it.

Claims (1)

[Claims] [Claim 1] A method of continuously electrolyzing an aluminum plate strip by passing it through two or three electrolytic cells by an indirect power supply method, wherein the same power source is connected to the two or three electrolytic cells. Arranging electrodes and supplying different electrolytes to each electrolytic cell,
An aluminum support for an offset printing plate, characterized in that the impedance between the electrode and the aluminum plate strip to be treated is controlled by the concentration, composition, temperature, or distance between the electrodes of an electrolytic solution, and the electrolytic treatment is performed under a substantially constant impedance. Continuous electrolytic surface roughening method.