JPH02165995A - Manufacture of aluminum supporter for lithographic printing plate - Google Patents

Abstract

PURPOSE:To manufacture an aluminum supporter having a sand-grain surface having excellent performance by arranging two electrodes into the electrolytic cell, connecting residual one electrode to an aluminum plate and electrolyzing the aluminum plate by three-phase ACs. CONSTITUTION:One end of a web-shaped aluminum plate 1 is held by a feeding roll 2 and a guide roll 31, the central section 10 of the aluminum plate 1 is guided by guide rolls 32, 33 and dipped into an electrolytic cell 8 into which an electrolyte 7 is introduced, and the other end of the aluminum plate 1 is conducted by a guide roll 33. The aluminum plate 1 is carried in the direction A by the feeding roll 2 and the guide rolls 31, 32, 33. One pole of three phase ACs is connected to the feeding roll 2, and residual two electrodes 51, 52 are disposed into the electrolytic cell 8. When electrolytic treatment is performed by using the device, electrolysis is executed among the aluminum plate 1 and the electrodes 51, 52 and sand-grain surfaces having a large number of pits are acquired, and a supporter for a printing plate excellent in water retentivity and adhesive properties with a photosensitive layer can be obtained.

Description

Detailed Description of the Invention: a. Industrial Application Field The present invention relates to a method for producing an aluminum support for a lithographic printing plate, and more specifically to a lithographic plate in which an aluminum plate is electrolytically polished (grained) using three electrodes. The present invention relates to a method for producing an aluminum support for printing plates.

b. Prior art Conventionally, aluminum plates have been widely used as supports for lithographic printing plates, and in order to improve the adhesion of photosensitive films and provide water retention to non-image areas, aluminum plates have been widely used as supports for lithographic printing plates. It was common to roughen the surface (also called graining or polishing).

Methods for roughening an aluminum plate include mechanical polishing methods such as ball polishing or brush polishing, and electrolytic roughening methods by electrochemically etching the aluminum plate in hydrochloric acid, nitric acid, or an electrolytic solution containing these as main ingredients. There are various methods such as chemical etching using chemicals, dry or wet honing methods, and methods that combine these methods.

Among these methods, electrolytic surface roughening methods have attracted attention in recent years, and most of them involve performing electrolytic treatment using alternating current in an electrolytic solution containing mainly hydrochloric acid or nitric acid.

The shape and surface roughness of the grains created by electrolysis can be adjusted by changing electrolysis conditions such as the electrolyte composition and the amount of electricity. Also, in the case of electrolytic polishing, unlike mechanical polishing, pits (holes) are formed on the aluminum surface.
It is possible to make pits of various sizes and depths.

It is well known that the size, depth, and distribution of the pits greatly affect the properties of the support for planographic printing plates. The average roughness Ra is 0.4 to 1
．． A large amount of electricity was required to create a grain of 0μ. This was a big problem in manufacturing printing plates.

In order to eliminate these drawbacks, a surface roughening treatment method that combines surface roughening by brush polishing and surface roughening by electrolytic polishing in an acidic electrolytic solution (Japanese Unexamined Patent Publication No. 123204/1982); current density is varied. (Japanese Patent Publication No. 56-51119); A method in which electrolytic polishing is performed by applying an alternating waveform current after mechanical polishing (Japanese Patent Publication No. 55-137993; No. 142,695/1982) have been published, but all of them consume a large amount of power and are not fully satisfactory in terms of rigidity resistance, water retention, or oil insensitivity.

Therefore, there has been a strong demand for the development of a method for producing an aluminum support with a grained surface that has low running costs and has excellent performance as a lithographic printing plate.

By the way, the conventional electrolytic surface roughening method is as shown in Figures 1 and 2.
As shown in the figure, electrolytic treatment was performed using alternating current with a single-phase single pole or single-phase double pole.

In Figures 1 and 2, 1 is a web-shaped aluminum plate, 2 is a power supply roll, 3 is a guide roll, 5 is an electrode plate, 6 is a power source, 7 is an electrolytic solution, 8 is an electrolytic cell, 9 is a wiring cable It is.

The method shown in FIG. 1 is a direct power supply method to the aluminum plate 1, in which the aluminum plate 1 is supplied with power from a power supply roll 2 and passes through an electrolyte 7 while being guided by a guide roll 3. Electrolysis occurs between the aluminum plate 1 and the surface of the aluminum plate 1 to be electrolytically polished.

Further, the method shown in FIG. 2 is an indirect power supply method in which power is supplied indirectly by the aluminum plate 1 and the electrode plate 5, and electrolysis occurs between the two electrode plates 5, 5 and the aluminum plate 1. The surface of the aluminum plate I is electrolytically polished.

In order to obtain a grain with favorable performance as a lithographic printing plate support using these methods, from past examples, uniform bits (holes) cannot be obtained unless electrolysis is performed at high current and high power. do not have. Therefore, the disadvantage is that the running cost is high. Furthermore, regarding the composition of the electrolytic solution, a bit with a uniform diameter cannot be obtained unless the electrolyte is mixed in a solution with a low acidic concentration and the concentration of aluminum ions is low. To do this, the electrolyte must be constantly replaced, and if it is discarded as waste, it will cause environmental problems, and the acid neck contained in the waste must be replenished, which ultimately increases running costs. Connect. Furthermore, the indirect power supply method shown in Figure 2 requires about twice as much voltage as the method shown in Figure 1, which increases power consumption and costs. I can't get a good grain.

Problems to be Solved by the C0 Invention The present invention has been made in view of the above-mentioned problems, and uses three-phase alternating current to electrolytically polish an aluminum plate with low power consumption, thereby polishing the aluminum plate as a support for lithographic printing plates. It is an object of the present invention to provide a method for producing an aluminum support with a grained surface with excellent performance.

69 Means for Solving the Problems The present invention provides continuous electrolytic treatment of an aluminum plate by arranging two electrodes in the same electrolytic layer and connecting the remaining electrode to the aluminum plate to electrolyze aluminum using three-phase alternating current. The present invention provides a method for producing an aluminum support for a lithographic printing plate, which comprises electrolyzing the plate.

The aluminum plate includes pure aluminum and aluminum alloy.

In the method of the present invention, first, the surface of the aluminum plate is pretreated in order to remove rolling oil from the surface of the aluminum plate and expose a clean aluminum surface. Examples of pretreatment methods include solvents.

There are methods such as cleaning with a surfactant or etching cleaning with an alkaline agent.

This is followed by electrolytic treatment, but before that, mechanical polishing may be performed to save power consumption during electrolysis and to make the grain more complex. Although this mechanical polishing method is not particularly limited, a brush polishing method is preferable in consideration of manufacturing convenience or the case of polishing a coiled aluminum plate. The mechanical polishing is preferably carried out so that the resulting center line average roughness (Ra) is 0.3 to 0.7 μ.

When such mechanical polishing is performed, it is better to chemically alkali-etch the surface of the aluminum plate for the purpose of removing the abrasive and aluminum polishing residue. Examples of alkaline agents include sodium hydroxide, potassium hydroxide, sodium triphosphate, potassium triphosphate, sodium aluminate, sodium carbonate, sodium metasilicate, and sodium orthosilicate, which can be used alone or in combination of two or more. A liquid mixture can be used.

The alkaline concentration of the alkaline etching solution is preferably 1 to 60% by weight, and at a liquid temperature of 30 to 100°C, 2 to 6% by weight.
Treat for 0 seconds and etch 2-13 g/m. Etching methods include immersing the aluminum plate in an etching bath, applying alkaline etching solution with a spray or nozzle, and etching the aluminum plate by pouring it through the armpit through a slit-like opening. After the above alkaline etching, nitric acid and phosphoric acid.

Smut is removed by desmutting with sulfuric acid, chromic acid, or a mixed acid containing two or more of these acids, or by simply washing with water, or in some cases, washing with high pressure water (3 kg/cd or more).

Following these treatments, the electrolytic treatment of the present invention is performed.

The electricity used for electrolytic treatment is 107~3-phase AC.
A sine wave within the 200Hz range, a waveform with part of the alternating current cut off by a thyristor, etc., with a (+) (-) ratio of 30
% or less, a symmetrical sine wave, a non-sinusoidal wave of 10 Hz or more, a symmetrical non-sinusoidal wave, etc. can mainly be used.

As a result of numerous experiments conducted by the present inventors, the power applied to the aluminum plate was determined based on the grain shape and from an economic standpoint.
The voltage is about 1-50V, more preferably 5-35V, and the current density is about 5-50 A/d, more preferably 10-35V.
40 A/drd, and the amount of electricity is about 50 to 4000 coulombs, more preferably 100 to 3000 coulombs. Further, the temperature of the electrolytic bath is about 10 to 60° C., preferably 20 to 50° C., and the distance between the electrode and the aluminum plate is 1 to 10 cm+, more preferably 2 to 5 cm.

Further, as the electrolytic solution, one or a mixture of two or more of nitric acid or its salt, hydrochloric acid or its salt, etc. can be used. Furthermore, if necessary, sulfuric acid, phosphoric acid, chromic acid, boric acid, nitrates, chlorides, ammonium salts, amines, other corrosion promoters, 1gJ of corrosion inhibitors, stabilizers, etc. may be added to the electrolyte. do not have.

The electrolyte concentration is O01~10% of the above acids.
It is desirable that the aluminum ion concentration in the electrolytic solution is kept constant in the range of 0 to 10 g/l, more preferably 2 to 8 g/2.

As electrolysis progresses, aluminum ions dissolve into the electrolyte (so if the electrolyte deviates from the predetermined concentration range, some of the electrolyte should be discarded and a new acid solution added. We will replenish the electrolyte that has been discarded.
It can be used again by removing aluminum ions from the liquid by contacting it with an ion exchange resin membrane or using a diaphragm method, and at the same time regenerating the acids.

The aluminum plate electrolyzed in the above manner is thoroughly washed with water, and then alkaline etched with a small amount of solution of about 1 to 8 g/nf depending on the case to open up the diameter of the electrolyzed bit. The alkaline agent used at this time can be approximately the same as the alkaline etching solution used after the mechanical polishing described above.

When such alkali etching is performed, it is desirable to wash the smut generated by the alkali etching with high-pressure washing water or desmut with the various acids mentioned above.

Next, the aluminum plate may be subjected to treatments such as anodic oxidation treatment and subsequent chemical conversion treatment in order to prevent scratches on the surface and to more firmly adhere the photosensitive layer.

As the anodizing treatment method, conventionally known methods can be used. For example, using an aqueous solution of sulfuric acid, phosphoric acid, chromic acid, oxalic acid, etc., or a combination of two or more of these as a bath, direct current or alternating current is applied to the aluminum plate to form an anodized film on the surface of the aluminum plate. Can be done.

The anodized aluminum plate may be further subjected to silicate treatment using sodium silicate, potassium silicate, or the like, if necessary.

A lithographic printing plate or a photosensitive lithographic printing plate (PS plate) can be produced by providing a conventionally known photosensitive layer on the thus obtained support for a lithographic printing plate of the present invention. For example, aluminum flat intaglio plates made of polyvinyl alcohol and dichromates or water-soluble diazo resin;
Alternatively, it can be used for aluminum albumen plates, and even aluminum white plates made of water-soluble diazo resin and lacquer.

The photosensitive layer for a photosensitive lithographic printing plate (PS plate) includes a negative photosensitive layer made of a mixture of a solvent-soluble diazo resin and an acrylic acid ester, and a mixture of an 0-quinonediazide compound and a novolak-type phenol or cresol resin. A positive photosensitive layer, a photosensitive layer using a photocrosslinkable photopolymer such as phenylene diacrylic acid, a photosensitive layer made of a photopolymerizable photopolymer composition consisting of an addition polymerizable ethylene compound and an alkali-soluble resin, and an azide photosensitive layer. A photosensitive layer made of a novolak type phenolic resin or the like can be used. It can also be used as a support for a lithographic printing plate used in an electrophotographic method in which a zinc oxide material or an organic photoconductor is used as a photosensitive material to perform flash exposure or laser scanning exposure.

FIGS. 3 and 4 are conceptual diagrams of an apparatus for carrying out electrolytic treatment in the method for producing an aluminum support for lithographic printing plates of the present invention.

In the apparatus shown in FIGS. 3 and 4, one end of a web-shaped aluminum plate 1 is connected to a power supply roll 2 and a guide roll 3. The central part 1 of the aluminum plate 1
0 is guide roll 3□, 3. guided by the electrolyte 7
The other end of the aluminum plate 1 is guided by a guide roll 33.

The aluminum plate 1 is connected to a power supply roll 2 and guide rolls 3゜3□, 3. It is configured so that it can be transported in the direction indicated by arrow A in the figure.

In the above device, one pole of the three-phase AC is connected to the power supply roll 2, and the remaining two electrodes 5. ,5. is arranged in the electrolytic cell 8. In the device shown in FIG.
A shielding plate (insulator) 4 is provided between the squares.

In addition, in FIGS. 3 and 4, 6 is a three-phase AC power source, and 9 is a wiring cable.

When electrolytic treatment is carried out using the apparatus shown in FIGS. 3 and 4, electrolysis is carried out between the aluminum plate 1 and the electrodes 51, 5□.

When electrolysis is performed using these methods, compared to single-phase alternating current methods as shown in Figures 1 and 2 above, when the same amount of electricity is applied, electrolysis is performed in smaller and more numerous forms than in a single phase. Many and uniform bits (holes) are formed. The present inventors discovered that this is not only due to the efficiency of the three-phase system, but also that the number of bits is at least twice as high.

In single-phase electrolysis, bits are formed locally and intensively, whereas in the case of the present invention, bits (holes) are formed under one electrode, and bits are formed under the other electrodes, although it is not theoretically clear. Furthermore, it is thought that the number of bits more than doubles, probably because bits are formed at other locations on the aluminum surface.

Therefore, when the same amount of electricity is applied as before, a grained surface with a larger number of pits can be obtained compared to conventional printing plate supports, which means that the water retention and adhesion with the photosensitive layer are better. An excellent support for printing plates will be obtained.

The present inventors also discovered that when electrolysis is carried out by the method of the present invention, uniform and fine bits can be obtained even if the concentration of aluminum ions contained in the electrolytic layer is higher than conventionally. This means that the electrolyte needs to be replaced less than before, which is an advantage in that running costs can be kept low.

Electrolysis using the apparatus shown in Figures 3 and 4 looks like a negative point, but in the apparatus shown in Figure 3, if the distance between the electrodes is set at least 5 times the depth of the electrolyte, leakage current can be reduced. It has been found through experiments by the inventors that this can be ignored.

In the device shown in Figure 4, there is a shielding plate (seamless material) in the middle.
Put 4. This allows the leakage current between each electrode to be reduced to an almost negligible level.

Hereinafter, the present invention will be described in more detail based on examples with reference to the drawings, but the present invention is not limited to these examples unless the gist thereof is exceeded. In addition, % in an example shows weight %.

Example 1; Comparative Example 1.2 An aluminum plate (material 1050) with a thickness of 0.24 days and a width of 1000 mm was degreased with alkali and then thoroughly washed with water. then 7
After etching the surface by pouring a 20% caustic soda solution at 0°C for 5 seconds, the surface was washed with running water, and electrolysis was carried out in various electrolytic cells under the conditions shown in Table 1 by applying approximately the same amount of electricity. Next, after washing with water, the surface was etched by pouring a 70°C Cl2O% caustic soda solution over it, further washing with water, and then anodizing in a 10% sulfuric acid aqueous solution at 30°C to form a 2.5g/rrt. An oxide film was formed. Table 1 shows the evaluation results of the surface grain shape and surface roughness of the obtained aluminum plate. Furthermore, electron micrographs of the surface are shown in FIG. 5 (Example 1) and FIG. 6 (Comparative Example 1).

Table ◎ Good as a printing plate × Unsuitable as a printing plate Example 1 was electrolyzed by the method of the present invention, and Comparative Example 1 was electrolyzed by the conventional direct power feeding method for comparison. The amount was the same as in Example 1. As is clear from FIGS. 5 and 6, uniform pores are uniformly formed over the entire surface of the aluminum plate (FIG. 5) obtained by the method of the present invention.

On the other hand, in Comparative Example 1 (Figure 6), the pores were non-uniform;
Because the holes are extremely large or deep, there is a risk that ink will get stuck in the large holes and cause stains, making them undesirable as printing plates. Also, in the case of Comparative Example 2 in which the voltage and current were increased using the method shown in Figure 1,
I couldn't get a good grain.

In order to create a grain suitable as a printing plate support using the method shown in Figure 1, it was necessary to reduce the concentration of aluminum ions to less than 2g72 and apply a voltage of approximately 2B or more compared to the method of the present invention. . This requires a lot of power and
This means that the electrolyte must be replaced frequently, leading to an increase in running costs compared to Example 1.2.

Examples 2 and 3; Comparative Example 3.4 An aluminum plate with a thickness of 0.24 mm and a width of 1000 mm (
After degreasing the material (Material 1050) with an alkali, the surface was roughened with a nylon brush while applying a permiston aqueous suspension, and then thoroughly washed with water. Next, a 70°C 520% caustic soda solution was poured over the surface for 5 seconds to etch the surface, and then the surface was washed with running water, and electrolysis was carried out in various electrolytic cells under the conditions shown in Table 2 by applying the same amount of electricity. Next, after washing with water, the surface was etched by pouring a 70°C Cl2O% caustic soda solution over it, further washing with water, and then anodizing in a 10% sulfuric acid aqueous solution at 30°C.
．． An oxide film of 5 g/rrf was formed. The evaluation results of the obtained surface grain shape and surface roughness are shown in Table 2.

Table ◎ Good as a printing plate Δ Not very good as a printing plate × Unsuitable as a printing plate Electron micrographs of the surfaces of the aluminum plates obtained in Example 2 and Comparative Example 4 are shown in FIGS. 7 and 8. As is clear from these comparisons, the aluminum plate of Example 2 has more holes (bits) formed on its surface than the aluminum plate of Comparative Example 4.

In Comparative Examples 3 and 4, in order to form a grain shape suitable for a printing plate on the surface of an aluminum plate, the aluminum ion concentration was adjusted to 2 g in the method shown in FIG. 1 or 2. and the voltage is about 2 of Examples 2 and 3.
I had to spend more than twice as much.

This leads to an increase in running costs.

By applying the following composition liquid to the aluminum plates obtained in Examples 1 to 3 and Comparative Examples 1 to 4 above, a positive PS plate having a photosensitive layer with a dry weight of 2.0 g/rrf was prepared. Lfs,.

The obtained 15th plate was exposed under a positive film using a 3KW high pressure mercury lamp from a distance of 111 for 60 seconds. Next, it was immersed for 20 seconds in a developer having the following composition at 25°C to form an image.

In this case, the larger the number of sheets, the better the water retention in the non-image area.

Furthermore, the printing durability of the image area was also examined at the same time. These results are shown in Table 3.

Table 3 After washing with water and desensitizing with gum arabic solution, each aluminum plate was placed in a printing machine, and the ink roller was dropped without adding water to the plate surface, allowing ink to adhere to the entire surface of the image area and non-image area. . Thereafter, a water rod was dropped on the paper, and the number of sheets (hereinafter referred to as the number of waste sheets) until the non-image ink was completely removed and a clean print was obtained was determined. In this case, the plate with the least number of wasted sheets is the best one. In addition, on the other hand, raise the water rod while printing normally, and check the number of sheets until ink starts to stick to the non-image area and the printed matter starts to become smeared (hereinafter referred to as the number of smeared sheets) without applying water. Ta.

As is clear from the results shown in Table 3, the printing plates obtained by the methods of Examples 1 to 3 are plates with excellent water retention and printing durability.

f8 Effects of the Invention According to the present invention, a support with good water retention and stiffness resistance can be obtained with a low amount of electric power.

[Brief explanation of the drawing]

Figures 1 and 2 are conceptual diagrams of a conventional electrolytic treatment apparatus, Figures 3 and 4 are conceptual diagrams of an electrolytic treatment apparatus in the method of the present invention, and Figure 5 is a surface of an aluminum plate obtained in Example 1. Fig. 6 is a photomicrograph of the surface of the aluminum plate obtained in Comparative Example 1, Fig. 7 is a photomicrograph of the surface of the aluminum plate obtained in Example 2, and Fig. 8 is a photomicrograph of the surface of the aluminum plate obtained in Comparative Example 4. This is a micrograph of the surface of an aluminum plate. ...Web-like aluminum plate ...Power supply roll ...Shielding plate (insulator) ...Power supply ...Electrolytic cell ...Guide roll ...Electrode plate ...Electrolyte ...Wiring cable Procedural Dispute Letter (Voluntary)

Claims (1)

[Claims] Planographic printing characterized in that, in carrying out continuous electrolytic treatment of an aluminum plate, two electrodes are placed in the same electrolytic layer, the remaining one electrode is connected to the aluminum plate, and the aluminum plate is electrolyzed by three-phase alternating current. A method for manufacturing an aluminum support for plates.