JPH054468A - Continuous electrolytic surface roughening method for aluminum support body for offset printing plate - Google Patents

Abstract

PURPOSE:To obtain uniform composite grain stably by an electrolytic surface roughening treatment for the manufacture of an aluminum support body for offset printing plate. CONSTITUTION:For an electrolytic surface roughening treatment for an aluminum band plate, a rotational body with a flat plate shaped or spiral shaped insulating plate, which is provided between an electrode and the aluminum band plate to be treated, and the electrode area of which is variable, is rotated in the following direction of opposite direction to the carrying direction, and a continuous electrolytic surface roughening treatment is performed while current density during the electrolytic treatment is being changed.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing an aluminum support for offset printing plates, and
A continuous aluminum support for offset printing plates characterized by performing electrolytic surface roughening while changing the current density by an insulating rotary plate provided between a counter electrode and an aluminum plate strip to be treated in electrolytic surface roughening. The present invention relates to an electrolytic surface roughening method.

[0002]

2. Description of the Related Art Conventionally, an aluminum plate has been widely used as a support for offset printing plates, and a so-called PS plate in which a photosensitive layer composition is applied in a thin layer is practically used. The aluminum plate is generally surface-treated in order to increase the adhesiveness of the photosensitive layer and the water retention or abrasion resistance of the non-image area. With such surface treatment,
After degreasing to clean the surface, roughening (also called graining) to make the surface uneven, and then anodizing to increase surface hardness, and then hydrophilic if necessary It is processed into a support for offset printing plate.

Among these treatments, various methods have been put into practical use for the surface roughening treatment in order to satisfy the above-mentioned requirements of the printing plate. That is, brush graining, ball graining,
Liquid honing, mechanical surface roughening method, 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 them, the electrolytic surface roughening method is capable of finely adjusting the shape and surface roughness of the grain depending on the electrolytic solution composition and electrolysis conditions as compared with other methods. Has become the center 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)
And the like are known. In the electrolytic surface-roughening method, pits are formed on the aluminum surface, and the pit size, depth, and pit distribution state can be changed depending on the current density, liquid concentration, liquid composition, liquid temperature during electrolysis. It is widely known that the shape of the surface thus produced has a great influence on the characteristics of the offset printing plate support,
Generally, the center line average roughness; Ra value is adjusted to 0.3 to 1.0 μ. However, in practice, it is more preferable to use a composite grain that cannot be expressed only by the value of Ra, and in order to obtain a more complicated rough surface, the current density is changed and electrolytic roughening is performed in two steps to perform electrolytic roughening. (Japanese Patent Publication No. 56-51119)
Has also been devised. Generally, in the electrolytic surface-roughening method, an electrolytic solution containing hydrochloric acid or nitric acid as a main component is used and electrolysis is performed by applying 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 the continuously moving aluminum strip, so the feeding method has been devised, and the direct feeding method in which the feeding terminal is directly contacted with the aluminum plate, or the direct aluminum feeding method is used. Connect the power supply between both electrodes by dividing the processing tank into two, for example, in the case of single-phase alternating current, through the electrolytic solution between the counter electrode and the plate without contacting the power supply terminal. However, in the case of three-phase alternating current, the terminals of the three phases are divided into three tanks and connected, and an electrolytic solution is supplied to energize (metal surface technology Vol30, No.10,1979, P541 to P546), so-called indirect. The power feeding method is also adopted.

In continuous surface roughening by electrolysis, once the apparatus is constructed, the size of the processing tank is generally determined, and the processing time is regulated by the processing speed, and even if the processing liquid is improved, it matches the appropriate conditions. It is difficult to do so, and there is little freedom. Even in the case of indirect power supply, the same electrolytic solution is supplied to two or three tanks for electrolytic treatment. In this case, however, since the electrolytic solution is the same, the current value and temperature are constant in each tank. , Only the processing time is changed. Also,
If necessary, different treatment liquids are supplied to the respective tanks in order to obtain a composite grain, but in order to obtain a fine grain, the current density must generally be lowered. In this case, it is not possible to obtain a uniform grain in the short-time treatment, and coarse pits are generated locally, so either reduce the treatment speed or
At present, it is necessary to lengthen the processing tank, and the productivity is poor.

[0005]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention In the electrolytic graining treatment, the present invention keeps the set current constant, electrolyzes while continuously changing the current density between the counter electrode and the aluminum strip to be treated, and performs offset printing. It is intended to provide a continuous electrolytic treatment method for stably obtaining a composite grain of an aluminum support for a plate.

[0006]

According to the present invention, in the electrolytic roughening treatment of an aluminum strip, a rotary body having a flat or spiral insulating plate attached between the electrode and the aluminum strip to be treated is provided and conveyed. Direction and forward direction or reverse direction to change the electrode area, while changing the current density during the electrolytic treatment, electrolytic roughening treatment is characterized by continuous electrolytic roughening of the aluminum support for offset printing plates. This is a surface treatment method. That is, by utilizing the fact that the area covering the treated aluminum plate strip of the insulating plate changes depending on the rotation angle of the rotating body in which the flat or spiral insulating plate is attached between the counter electrode and the treated aluminum plate strip, The electrolytic graining treatment is performed while changing the current density of the current flowing into the aluminum strip to be treated during treatment.

As the aluminum plate used in the present invention, pure aluminum and various metals such as aluminum alloys 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 arbitrarily added metal has a great influence on the size, shape and distribution of the pits of the grain obtained by electrolysis, and also on the strength of the aluminum plate. give.

In the continuous processing method of the present invention, degreasing, roughening,
Each treatment of desmutting and anodic oxidation is performed, and water is appropriately washed between each treatment.

In the degreasing treatment, rolling oil on the aluminum surface is removed to expose the clean surface of the aluminum plate. Examples of the degreasing method include solvent degreasing with trichloroethylene, perchlorethylene, etc., alkali degreasing with sodium hydroxide, sodium carbonate, sodium metasilicate, trisodium phosphate, tetrasodium pyrophosphate, soap, etc., or a mixture thereof. , A surfactant, kerosene, triethanolamine, sodium hydroxide, etc. are combined for emulsion degreasing, and electrolytic degreasing called finish degreasing for removing contamination that cannot be removed by the above chemical degreasing. Fork ultrasonic cleaning is also effective.

In the present invention, as the surface roughening treatment, electrolytic surface roughening treatment is suitable for obtaining pit-shaped grain, but additionally, mechanical or chemical surface roughening treatment may be used for electrolytic surface roughening treatment. It may be added before, after, or before or after chemical conversion. In the electrolytic graining treatment, if Faraday's law is generally established and the product of the current density and the treatment time is equal, the amount of aluminum dissolved by the treatment is constant. However, the change in surface roughness due to electrolytic treatment is not constant, and the surface roughness differs between low current density / long time treatment and high current density / short time treatment.

In the present invention, when carrying out the electrolytic treatment, an insulating plate whose axis is set to be orthogonal to the carrying direction or not parallel to the carrying direction is installed between the counter electrode and the aluminum plate band to be treated, and the angle is set by rotation. By changing the range of 0 to 360 degrees, the area of the surface of the aluminum to be exposed which is exposed to the counter electrode is changed, whereby the electrolytic surface roughening treatment is continuously performed while changing the current density. That is, the angle at which the insulating plate is parallel to the direction between the electrodes is 0 °, 180 ° or 1 rotation
In the case of 0 degree, the area covering the treated aluminum surface is the largest, and as a result, the area exposed to the counter electrode is small and the current density of the treated aluminum surface is increased. When the angle of the insulating plate is 90 degrees or 270 degrees, the area covering the aluminum surface to be treated is the smallest, and as a result, the area exposed to the counter electrode is large and the current density on the aluminum surface to be treated decreases. However, it is almost the set value. Although the insulating plate of the present invention can achieve the purpose of changing the current density only by changing the angle, the current density of the aluminum surface to be treated can be continuously changed by further rotating during the treatment.
Further, when rotating the insulating plate of the present invention, the insulating plate does not need to be a flat plate having a constant width in the width direction of the aluminum to be treated, may be a plate that is divided and attached at different angles in the middle, Further, it may be a plate spirally wound around one axis. In the case of such a spiral plate, the angle continuously changes periodically when viewed in the width direction, but when rotated, it changes periodically and becomes uniform. The installation of the rotating insulating plate of the present invention has further side effects. That is, by rotating, the effect of stirring the electrolytic solution also occurs, the retention of generated gas is reduced, and uniform treatment can be achieved.

The diameter of the rotating body to which the insulating plate of the present invention is attached is limited by the distance between the electrode and the aluminum plate to be treated, and is naturally made smaller than the distance. Further, in order to prevent the generated gas from accumulating in the electrode, when a plurality of electrodes are installed at short intervals with respect to the processing length of the aluminum to be processed, the shaft of the rotating body to which the insulating plate of the present invention is attached is installed. May be installed between the electrodes, and it is effective if the portion protruding from the axis is in a position covering the area of the aluminum to be treated facing the electrodes. In this case, even if it is larger than the distance, You can reach the public. When rotating the rotating body to which the insulator of the present invention is attached, the number of rotations is not particularly limited, but is preferably selected within a range that does not synchronize with the conveying speed and the power supply frequency. Further, the drive for rotation is not always necessary, and may be omitted as long as the drive that gives the set rotation speed can be obtained by the liquid flow of the electrolytic solution circulation. Further, in order to positively obtain the rotational driving force by the electrolytic solution flow, a driving propeller can be provided at the end of the insulating plate rotating shaft in the width direction or at the non-treated portion of the aluminum plate band.

The electric current used for the electrolytic surface roughening treatment is single-phase or three-phase commercial alternating current or ^{10 to} 100 Hz including them.
, Sine wave within the range, waveform current in which a part of AC waveform is cut by thyristor, asymmetric type with unequal positive / negative current ratio, symmetric sine wave, and non-sine wave, symmetric non-sine wave, etc. Can be used. Further, in the present invention, since the current density is changed by the insulating plate during the electrolytic treatment, it is possible to use a lower frequency or direct current as described above.

Both direct power feeding and indirect power feeding can be applied to the electrolytic graining treatment of the present invention. 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 treated. Therefore, the same electrolytic solution may be supplied to the two or three electrolytic cells for this one power source, or different electrolytic solutions may be supplied to perform different treatments. Further, in the electrolytic treatment of the present invention, the counter electrode may have an arbitrary size and may be divided in the carrying direction, and the insulating plate of the present invention is provided at least at one place for any one of the counter electrodes in each tank. You can

For the electrolytic cell in the indirect power supply, the aluminum plate strip is once lifted outside the liquid between the tanks and is passed through the next tank to a two or three tank type, and the height of the treated surface is changed. There is a slit type that divides the tanks with narrow slits and straightly electrolytically treats it, or a slit type that minimizes leakage of electrolyte solution and further straightens electrolytic treatment while squeezing electrolyte solution with a squeegee roll. As long as it is possible to separate the front and rear electrolytes between the tanks, either one can be used.
When different electrolytic solutions are supplied to the front and rear tanks, water may be added between the tanks as needed to prevent the different electrolytic solutions before and after mixing. The power supplied to the aluminum plate varies depending on the composition of the electrolytic solution, the temperature, the distance between the electrodes, etc., but generally, in order to obtain a suitable grain as a printing plate, the voltage is 1 to 60 V and the current density is 5 to 60 A. / d
It is used in the range of m ² and 50-4000 coulombs of electricity. The temperature of the electrolytic solution is preferably 0 to 60 ° C., and the distance between the electrode and the aluminum plate is preferably in the range of 1 to 10 cm.

As the electrolytic solution, nitric acid or a salt thereof, hydrochloric acid or a salt thereof, or an aqueous solution of one kind or a mixture of two or more kinds thereof can be used. Further, if necessary, sulfuric acid, phosphoric acid, chromic acid, boric acid, organic acid, or their salts, nitrates, chlorides, ammonium salts, amines, surfactants, other corrosion accelerators, corrosion inhibitors, stabilization You may add and use an agent. Regarding the concentration of the electrolyte, the concentration of the above acids is 0.1.
It is preferably 1 to 10% by weight and the concentration of aluminum ions in the electrolytic solution is preferably maintained in the range of 0 to 10 g / l. In electrolytic surface roughening treatment, as the electrolysis progresses, aluminum melts and acids are consumed.Therefore, while discarding a part of the electrolytic solution, the acids are removed so that the composition of the electrolytic solution does not deviate from the predetermined setting range. It is preferable to install a replenishing device for replenishing the electrolytic solution.

The aluminum plate strip electrolytically surface-roughened as described above is sufficiently washed with water, but smut usually adheres to the surface and cannot be removed by only washing with water, and blocks the pits. Desmutting is applied to remove the smut. For the desmutting treatment, an alkaline agent usually used for degreasing treatment can be used. Desmutting dissolves the smut and reveals the pit surface. The amount of dissolution varies depending on the treatment conditions with the electrolytic solution, but is 0.
1 to 1 g / m ² is suitable.

The desmutted roughened aluminum strip is usually then anodized. Anodizing treatment produces an aluminum oxide film on the aluminum surface, which not only prevents surface denaturation but also significantly improves the surface hardness.
The printing durability during printing is improved. Since an oxide film is formed only on the anode, a direct current is usually used. As the electrolytic solution, an acid such as sulfuric acid, oxalic acid, chromic acid, phosphoric acid, etc., which has a low solubility in the produced oxide film is used. The conditions for anodic oxidation are:
It is used at a liquid concentration of 1 to 40% and a current density of 0.1 to 10 A / dm ² , and anodized until the required film thickness is obtained. The temperature influences the hardness of the oxide film, and the hardness becomes higher at low temperature, but it becomes brittle, so that it is usually anodized at a temperature near room temperature. The thickness of the anodic oxide film is appropriately adjusted depending on the printing durability grade of the printing plate, but 0.1 to 2 μm is sufficient.

The thus obtained support for offset printing plates is provided with a conventionally known photosensitive layer,
It can be put to practical use as an offset printing plate or a photosensitive planographic printing plate. Examples of the photosensitive layer include polyvinyl alcohol and dichromates, diazo resins and acrylic esters, o-quinonediazide compounds and novolac type phenol or cresol resins, phenylenediacrylic acid type photocrosslinkable polymers, and addition polymerizable ethylene compounds. There is a photopolymerizable photopolymer made of an alkali-soluble resin. 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 can be provided. The lithographic printing plate thus obtained is image-formed by contact exposure of a positive or negative film original or image exposure by a laser, and the non-image area is eluted with an eluent of alkali, alcohol, etc. And supplied to the printing machine.

[0020]

EXAMPLES The continuous electrolytic surface roughening method of the present invention will be described in more detail by way of examples.

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 1.3 m / min to obtain 50
After immersing in 4% caustic soda for 30 seconds at 4 ° C, it was washed with water and filled with 2.0% hydrochloric acid into a direct power supply type electrolytic cell in which a counter electrode and a rotor having the following sizes are arranged, and 600A, 5A
A single-phase alternating current of 0 Hz is applied to each electrode terminal to roughen the AC electrolytic surface, rinse with water, and then at 25 ° C. in 4% caustic soda.
Soak for 0 seconds to desmut, wash with water, and then at 25 ℃,
It was passed through 15% sulfuric acid for 45 seconds, anodized at a direct current of 90 A, washed with water, and then dried to obtain an aluminum support for offset printing plates.

Distance between electrode and aluminum to be treated: 10 cm Electrode: width 300 mm, length 250 mm 4 sheets Rotating body: width 5 cm, length 300 mm insulating plate Rotation radius 2.5 cm Rotation axis is below each electrode Center aluminum surface to be treated Installed at a height of 3 cm, rotation speed 45 rpm The condition of electrolytic surface roughening is calculated from the area blocked by the rotating body, the rotating body angle is 90 degrees, 270 degrees: when it is in the direction perpendicular to the aluminum to be treated, it is almost 20 A / dm ² . Set value Rotating body angle 0 °, 180 °: Increased to 25 A / dm ² when parallel to the aluminum to be treated

An electrophotographic photosensitive layer composed of phthalocyanine and an alkali-soluble acrylic resin was applied to the support thus obtained, and a plate was prepared by an electrophotographic method, showing good suitability for lithographic printing plate. For comparison, when the insulating plate was removed and electrolytic surface roughening treatment was performed, coarse pits remained on the surface and the surface was non-uniform, and a fine and uniform rough surface as in Example 1 could not be obtained.

Example 2 In Example 1, the insulating plate was moved from the flat plate to the same width for 2 rotations / 30.
An aluminum support for an offset printing plate was obtained in the same manner as in Example 1 by replacing with a 0 mm spiral plate. The support thus obtained showed good lithographic printing plate suitability as in Example 1.

Example 3 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 4 m / min at 50 ° C. for 4 hours.
After soaking in 30% caustic soda for 30 seconds, it was rinsed with water, and a slit type liquid indirect power supply type electrolytic cell, in which a counter electrode and a rotating body having the following sizes were arranged, was filled with 2.0% hydrochloric acid to 900 A, 50 Hz. A single-phase alternating current is applied to each electrode terminal to roughen the AC electrolytic surface and rinse with water, then 25 ° C, 4%
Soak in caustic soda for 30 seconds, desmut, wash with water,
Then, pass it through 15% sulfuric acid at 25 ° C for 30 seconds to 120 A.
Was anodized with a direct current of, washed with water, and then dried to obtain an aluminum support for offset printing plates.

First tank: Distance between electrode and non-treated aluminum: 7 cm Electrode: Width 300 mm, length 500 mm 2 sheets Rotating body: Width 3 cm, length 300 mm insulating plate Rotation radius 1.5 cm Rotation shaft is covered under each electrode The height is set to 2 cm above the surface of the treated aluminum and three pieces are installed at equal intervals of 100 mm between the axes and synchronized so that the three pieces have the same angle. Rotation speed 70 rpm Second tank The same counter electrode and insulating plate as in the first tank are arranged. The electrolytic roughening condition in each tank is calculated from the area blocked by the rotating body. The rotating body angle is 90 degrees, 270 degrees: When set in the direction perpendicular to the treated aluminum, at approximately 30A / dm ² , the set value was set. Rotor angle 0 °, 180 °: When set in the direction parallel to the treated aluminum, increased to 43A / dm ² , and the support thus obtained was treated with phthalocyanine. When an electrophotographic photosensitive layer made of an alkali-soluble acrylic resin was applied and a plate was prepared by an electrophotographic method, good lithographic printing plate suitability was exhibited.

Example 4 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 1.2 m / min,
After soaking in 50 ° C., 4% caustic soda for 30 seconds, washing with water, and filling a 3-tank type liquid indirect power supply type electrolytic cell having a counter electrode and a rotating body of the following sizes with 1.8% hydrochloric acid, A 180A three-phase alternating current is applied to each electrode terminal, and the electrolytic electrolytic surface is roughened, washed with water, then immersed in 4% caustic soda at 25 ° C for 30 seconds to desmut, and washed with water, and then 2
It was passed through 5% sulfuric acid at 15% sulfuric acid, anodized at a direct current of 135 A, washed with water, and then dried to obtain a support for an aluminum lithographic printing plate.

First tank: Distance between electrode and aluminum to be treated: 7 cm Electrode: Width 300 mm, length 200 mm 2 pieces Rotating body: Width 3 cm, length 300 mm insulating plate Rotation radius 1.5 cm Rotation shaft is covered under each electrode Installed at a height of 2 cm from the treated aluminum surface, and synchronize so that a total of four under each electrode have the same angle. Rotation speed 73 rpm Second tank Electrode-treated aluminum distance: 7 cm Electrode: width 300 mm, length 200 mm 2 sheets Rotating body: width 3 cm, length 300 mm insulating plate Rotation radius 1.5 cm Rotation shaft under each electrode Installed at a height of 2 cm from the treated aluminum surface, installed two pieces at equal intervals of 70 mm between axes, and synchronize so that a total of four pieces under each electrode have the same angle. Rotation speed 45 rpm Third tank The same counter electrode as in the first tank is arranged and no rotating body is attached.

The conditions for electrolytic surface roughening in each tank are calculated from the area blocked by the rotating body. The first and second tanks have a rotating body angle of 90 °, 270 °: a direction perpendicular to the aluminum to be treated 15A / Dm ² almost set value Rotating body angle 0 degree, 180 degree: Increased to 21 A / dm ² when parallel to the aluminum to be treated Set value at 15 A / dm ² in the third tank The support thus obtained is Similar to Example 1, it showed good lithographic printing plate suitability.

[0030]

According to the electrolytic surface-roughening treatment method of the present invention, the current density in the same tank can be changed independently of the set current of the power source, and a uniform fine composite grain without local pits can be formed. It can be stably obtained.

[Procedure amendment]

[Submission date] July 29, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

The diameter of the rotating body to which the insulating plate of the present invention is attached is limited by the distance between the electrode and the aluminum plate to be treated, and is naturally made smaller than the distance. Further, in order to prevent the generated gas from accumulating in the electrode, when a plurality of electrodes are installed at short intervals with respect to the processing length of the aluminum to be processed, the shaft of the rotating body to which the insulating plate of the present invention is attached is installed. May be installed between the electrodes, and it is effective if the portion protruding from the axis is in a position covering the area of the aluminum to be treated facing the electrodes. In this case, even if it is larger than the distance, The effect can be reached. When rotating the rotating body to which the insulator of the present invention is attached, the number of rotations is not particularly limited, but is preferably selected within a range that does not synchronize with the conveying speed and the power supply frequency. Further, the drive for rotation is not always necessary, and may be omitted as long as the drive that gives the set rotation speed can be obtained by the liquid flow of the electrolytic solution circulation. Further, in order to positively obtain the rotational driving force by the electrolytic solution flow, a driving propeller can be provided at the end of the insulating plate rotating shaft in the width direction or at the non-treated portion of the aluminum plate band.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

The current used for the electrolytic surface roughening treatment is a single-phase or three-phase commercial alternating current or 10 to 10 including these.
A sine wave within the range of 0 Hz, a waveform current in which part of the AC waveform is cut by a thyristor, etc., an asymmetric type with unequal positive / negative current ratios, a symmetric sine wave, and a non-sine wave, a symmetric non-sine wave Etc. can be used. Further, in the present invention, since the current density is changed by the insulating plate during the electrolytic treatment, it is possible to use a lower frequency or direct current as described above.

Claims (1)

Claim: What is claimed is: 1. In electrolytic surface roughening treatment of an aluminum strip, a rotor provided between the electrode and the aluminum strip to be treated and having a flat or spiral insulating plate attached thereto is provided. An aluminum for offset printing plate characterized by performing electrolytic surface-roughening treatment while changing the electrode area by rotating the rotating body in the forward direction or the reverse direction to the conveying direction and changing the current density during the electrolytic treatment. Method for continuous electrolytic surface roughening treatment of a support.