JPH0714673B2 - Method for producing support for lithographic printing plate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a lithographic printing plate support, and in particular, after roughening the surface of an aluminum plate, it is anodized in a molten salt electrolyte. The present invention relates to a method for producing a lithographic printing plate support.

[Conventional technology]

Conventionally, an aluminum plate is widely used as a support for lithographic printing plates, but the surface of the support is roughened in order to improve the adhesion between the support and the photosensitive layer and to impart water retention to the non-image area. A so-called graining process, which is a chemical conversion process, is performed.

As a concrete means of this graining, sandblasting,
There are ball grain, wire grain, brush grain with nylon brush and abrasive / water slurry, mechanical graining method by spraying abrasive / water slurry on the surface with high pressure, and also from alkali or acid or their mixture. There is a chemical graining method in which the surface is roughened with another etching agent. In addition, JP-A-54-14
Electrochemical graining method described in JP 6234 and JP-B-48-28123, for example, mechanical graining method and electrochemical graining method described in JP-A-53-123204 There is also known a method in which the mechanical graining method described in JP-A-56-55291 is combined with the chemical graining method using a saturated aqueous solution of an aluminum salt of a mineral acid.

The aluminum plate surface-roughened by the above method can be used immediately or after further chemical conversion treatment as a lithographic printing plate support, but when a lithographic printing plate with high printing durability is desired. In order to improve the adhesion of the image area to the support and improve the mechanical strength of the surface of the non-image area, further anodization treatment is performed.

In the field of producing a support for this printing plate, conventionally, anodizing treatment has been carried out by using sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfamic acid,
It is carried out by applying a direct current or an alternating current to an aluminum plate in boric acid, benzenesulfonic acid or the like or an aqueous solution in which two or more kinds thereof are combined.

As described above, anodizing treatment with various electrolytic solutions is performed, but sulfuric acid, phosphoric acid, etc. are widely used.

By the way, the photosensitive lithographic printing plate is attached to a printing machine through a plate making process based on exposure, development and gumming.
Printing is performed, but scratches occur on the surface during transportation of the plate, during plate making, or during removal of dust on the plate surface during printing, and during printing, the surface is abraded by paper dust, ink particles, etc. Resulting in. In particular, when the surface is a non-image area surface, the ink adheres to the scratched and worn portions and becomes a stain, which appears on the printed matter.

When the surface of the non-image area is anodized as described above and the alumina film is present, the surface becomes hard, is not easily scratched, and is not easily worn, so that the generation of dirt can be suppressed. By increasing the amount of the anodic oxide film, this effect is further strengthened, but in order to increase the amount of the anodic oxide film, a large amount of electric power is required, and there is a drawback that the manufacturing cost is increased.

[Problems to be solved by the invention]

Therefore, in view of the problems of the prior art as described above, an object of the present invention is to provide a relatively small amount of anodized film, with which scratches and stains on printed matter are less likely to occur in the non-image area, and moreover, excellent abrasion resistance Another object of the present invention is to provide a method for producing a lithographic printing plate support including an anodizing treatment for providing an anodized film.

[Means for solving problems]

The present invention, after roughening the surface of the aluminum plate,
When anodizing in a molten salt electrolyte, the hardness of the oxide film rises, scratches on non-image areas and stains on printed materials do not easily occur even with a small amount of film, and at the same time an anodized film with excellent abrasion resistance is obtained. It was made based on this finding by finding out what can be obtained.

That is, the present invention provides a method for producing a lithographic printing plate support, which comprises subjecting at least one surface of an aluminum plate to a surface roughening treatment and then anodizing in a molten salt electrolyte.

Hereinafter, the present invention will be described in detail.

Aluminum plates used in the present invention include pure aluminum and aluminum alloy plates. Various aluminum-containing alloys can be used, for example, silicon, copper, manganese, magnesium, chromium, zinc,
An alloy of aluminum with a metal such as lead, bismuth, or nickel is used. These alloys may contain some iron and titanium as well as other negligible amounts of impurities.

As the surface-roughening treatment of the present invention, it is preferable to grain the aluminum plate. Before that, a cleaning treatment may be carried out, if necessary, for the purpose of removing oil, fat, rust, dust, etc. adhering to the surface of the aluminum plate.
This cleaning treatment includes, for example, solvent degreasing with trichlene, alkali etching degreasing with caustic soda, and the like. When alkaline etching degreasing such as caustic soda occurs, smut occurs, so
Desmutting to remove this (eg 10-30%
It is customary to further perform a treatment of dipping in nitric acid).

The surface-roughening treatment can be carried out by the various treatment methods described above, but as the mechanical graining method, sand blasting, wire grain, brush grain using nylon brush and abrasive / water slurry, abrasive / water slurry There is a method of spraying the surface with high pressure, for example,
Printing Bulletin "Basics of lithographic printing" (author Kenichi Sugiyama,
Issued December 1, 1965) Based on the mechanical roughening treatment described on pages 35-37. As the chemical roughening treatment,
The method of treating with a saturated solution of an aluminum salt of a mineral acid described in JP-A-55-31187 may be used. As an electrochemical graining method, for example, Japanese Patent Application Laid-Open No. 52-152302
The method disclosed in JP-B No. 48-28123 and Japanese Patent Publication No. 48-28123 are used, and the method disclosed in JP-A-56-55291 is a combination of mechanical surface roughening treatment and chemical surface roughening treatment. The method described in U.S. Pat.No. 2,344,510, JP-B-57-16918, and JP-A-56-28893 disclose mechanical roughening treatment and electrochemical roughening treatment. A combined method or the like is used. In addition, JP-A-60-
A method in which a chemical surface-roughening treatment and an electrochemical surface-roughening treatment as described in Japanese Patent No. 208294 are combined may be used. In particular, as the roughening treatment in which the effect of the present invention is remarkably exhibited, a chemical roughening treatment or a combination of a mechanical roughening treatment and a chemical roughening treatment, or a chemical roughening treatment and an electrical treatment. A treatment in combination with a chemical surface roughening treatment can be mentioned.

It is preferable that the aluminum plate that has been roughened as described above is then chemically cleaned. This chemical treatment has a function of removing abrasives, aluminum debris, etc. that have eroded on the surface after the mechanical roughening treatment, and the chemical or electrochemical roughening treatment after the roughening treatment. In this case, it has a function of removing so-called smut, which is a surface residue, from the surface. The details of such chemical treatment are described in US Pat. No. 3,834,998 for the former and in JP-B-48-28123 and JP-A-53-12739 for the latter.

The aluminum plate that has been roughened and cleaned as described above is then anodized in a molten salt electrolyte.

The electrolytic solution of anodizing treatment in the molten salt electrolytic solution used in the present invention is a solid salt melted at a temperature lower than 660 ° C. (aluminum melting point), that is, a melting point of 660 ° C.
Is a molten salt having a melting point of less than 350 ° C. Specifically, sulfates (eg ammonium hydrogensulfate, sodium hydrogensulfate), nitrates (eg ammonium nitrate, sodium nitrate), formates (eg ammonium formate, sodium formate), chlorates (eg sodium chlorate), perchlorine. Acid salts (nickel perchlorate) and the like are included alone or as a mixture. Of these, the sulfates alone or as a mixture are preferable because they are relatively inexpensive and relatively easy in terms of temperature control. In addition, 0.1 wt% to 5 wt% of chloride, silicate, or oxide of alkali metal or alkamidic earth metal may be added to the electrolyte solution.

The treatment temperature is sufficient if it is equal to or higher than the melting point of the substance to be used, but it is preferably 300 ° C. or lower because aluminum is subjected to the rounding treatment. The current density can be any current density, but considering the film formation efficiency, it is 1A / d.
m ^{2 to} 40 A / dm ² is preferable. The weight of aluminum oxide thus obtained is 0.3 to 5.0 g / m ² , and preferably
It is 0.5 to 3.0 g / m ² . The power source may be direct current or alternating current, but in the case of continuous processing, it is better to be able to perform processing in a short time, and it is preferable to perform processing with direct current.

The aluminum plate anodized in the molten salt electrolyte as described above is further treated by a method such as immersion in an aqueous solution of an alkali metal silicate, for example, sodium silicate, as described in U.S. Pat.No. 3,181,461. Or
Treated with polyvinyl sulfonic acid as described in U.S. Pat.No. 4,153,461 or U.S. Pat.
As described in No. 6, hydrophilic cellulose containing a water-soluble metal salt (such as zinc acetate) (for example,
An undercoat layer (such as carboxymethyl cellulose) may be provided.

On the lithographic printing plate support thus obtained,
As a photosensitive layer of a PS plate (abbreviation of Pre-Sensitized Plate), a photosensitive layer that has been conventionally known can be provided to obtain a photosensitive lithographic printing plate. , Has excellent performance.

The composition of the photosensitive layer includes (a) a diazo resin and a binder, (b) an o-naphthoquinonediazide compound, (c) an azide compound and a binder, and (d) an ethylenically unsaturated compound. A photopolymerizable composition composed of a monomer, a photopolymerization initiator and a polymer binder, and (e) a polymer composed of a photocrosslinkable polymer having a —CH═CH—CO— group in its main chain or side chain are included. These details are described in detail in US Pat. No. 4,238,560. Such a photosensitive layer is added to the support produced according to the present invention in an amount of about 0.1 to about 7 g / m ² , more preferably 0.5 to 4 g / m ² .
It is provided so that the coating amount is m ² .

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples. In addition, "%" indicates "wt%" unless otherwise specified.

Example 1 An aluminum plate having a thickness of 0.24 mm was first roughened in a 400 mesh pumicetone-water suspension by using a rotating nylon brush. The centerline surface roughness was 0.6μ.
After washing with water, dip it in a 10% sodium hydroxide aqueous solution at 50 ° C for 60 seconds to remove abrasives and aluminum debris that are difficult to stick to the aluminum plate to balance the surface, then wash with water and then with 20% nitric acid. It was neutralized and washed. After washing with water, in a 0.7% aqueous nitric acid solution, a rectangular wave alternating waveform with a voltage of 13 volts at the anode and a voltage of 6 volts at the cathode (power waveform described in the example of JP-A-52-77702) was used for 20 seconds. Electrochemically grained. Then, add 10% sodium hydroxide solution at 40 ℃ for 10
After dipping treatment for 2 seconds to remove smut generated by electrochemical graining, the substrate was washed with 20% nitric acid for neutralization and then with water to obtain a substrate [A].

Next, the amount of oxide film in the molten salt electrolytic solution of the electrolytic solution composition of ammonium hydrogen sulfate and sodium hydrogen sulfate (equal molar ratio)
Anodization was carried out at a temperature of 170 ° C. and a current density of 1.5 A / dm ^{2 so} as to obtain 1.4 g / m ² , followed by washing with water and drying to obtain a support [a]. The support [ii] thus obtained was coated with a photosensitive solution having the following composition and dried to form a photosensitive layer. The dry coating amount of the photosensitive layer was 2.5 g / m ² .

Photosensitive liquid The photosensitive lithographic printing plate thus prepared was placed as a light source of a 2 KW metal halide lamp at a position separated by 1 m and exposed through a positive transparent surface for 60 seconds. 25 ° C.) and further gummed.

Developer The surface of the non-image area of the lithographic printing plate thus prepared was scratched at a constant speed by applying a load (5 g to 600 g) to the needle using a sapphire needle having a tip diameter of 0.4 mm. Then, the portion of the load on the plate where the scratches started to be scratched was visually determined, and the results are shown in Table 1.

Also, a 1 μAl ₂ O ₃ abrasive paper was attached to the wear wheel, and the degree of wear when the non-image area surface of the lithographic printing plate made with a load of 500 gr was reciprocated 700 times was measured by a gloss meter [Nippon Denshoku Industries Co., Ltd. Made, Σ8
0, COLOR MEASURING SYSTEM] ΔGs value (gloss value before abrasion-gloss value after abrasion: incident angle of optical part, light receiving angle of 60 °) for comparative evaluation. The results are shown in Table 2.

Furthermore, a comparative evaluation was performed on the stains on the printed matter and the degree of contamination of the non-image area when the plate was printed by a conventional method. The results are shown in Table 2 above.

Comparative Example 1 The substrate [A] of Example 1 was placed in an 18% sulfuric acid aqueous solution at a temperature of 25 ° C. and a current density of 1. so that the oxide film amounts were 1.4 g / m ² and 3.0 g / m ² .
It was anodized at 5 A / dm ² , washed with water and dried to obtain a support [B]. From the coating of the photosensitive layer to the evaluation of printing and the measurement of the degree of wear, the same procedure as in Example 1 was performed. The result is first
The results are shown in Tables and Tables 2.

Example 2 The substrate [A] of Example 1 was heated at a temperature of 170 so that the amount of oxide film was 1.4 g / m ² in a molten salt electrolytic solution having an electrolytic solution composition of sodium hydrogensulfate and ammonium hydrogensulfate (equal molar ratio). After anodizing at a temperature of 1.5 A / dm ² at a temperature of 1.5 ° C., washing with water, dipping in a 2% sodium silicate aqueous solution at 70 ° C. for 1 minute, washing with water and drying, a support [C] was obtained.

The support thus obtained was coated with a photosensitive solution having the following composition and dried to form a photosensitive layer. The dry coating amount of the photosensitive layer was 2.5 g / m ² .

Photosensitive liquid The photosensitive lithographic printing plate made in this way is 3K from a distance of 1m through a transparent negative film in a vacuum baking frame.
After exposure for 50 seconds using a W metal halide lamp, development was performed with a developing solution having the following composition, and gumming was performed with an aqueous solution of gum arabic to obtain a lithographic printing plate.

Developer After that, the process from scratching of the non-image area to printing evaluation and abrasion measurement was performed in the same manner as in Example 1. The results are shown in Table 1 and Table 2.
Shown in the table.

Comparative Example 2 The substrate [A] of Example 1 was anodized in an aqueous sulfuric acid solution in the same manner as in Comparative Example 1, washed with water and then changed to a 2% aqueous sodium silicate solution.
It was immersed at 70 ° C. for 1 minute, washed with water and dried to obtain a support [d]. After that, the processes from coating of the photosensitive layer to evaluation of printing and measurement of wear were performed in the same manner as in Example 2. The results are shown in Tables 1 and 2.

In the above examples, the roughening treatment in which the mechanical roughening treatment and the electrochemical roughening treatment are combined, and the molten salt in the bath of ammonium hydrogensulfate and sodium hydrogensulfate [equal molar ratio] is used. Although the case of anodizing in the electrolytic solution is shown, similar results were obtained for any other roughening treatment and also for the anodizing treatment with another molten salt electrolytic solution.

Similar results were obtained for a combination of anodizing treatment with an aqueous sulfuric acid solution and anodizing treatment with a molten salt electrolyte.

〔The invention's effect〕

When printing with a lithographic printing plate using the lithographic printing plate support of the present invention, even in a small amount of anodized film, scratches are less likely to occur in the non-image area, the abrasion resistance is excellent, and stains are generated on the printed matter. A print was obtained that was difficult and had a reduced degree of contamination in the non-image areas.

Claims (1)

[Claims] 1. A method for producing a lithographic printing plate support, which comprises subjecting at least one surface of an aluminum plate to a surface roughening treatment and then anodizing in a molten salt electrolyte.