JPH0542783A - Manufacture of support for lithographic printing form plate - Google Patents

Abstract

PURPOSE:To provide a method for manufacture of an aluminum support which is likely to be capable of being manufactured economically at a low cost by a method wherein the support for the lithographic printing plate form with which contamination and greasing of a non-image area are not caused even through additional treatment for making hydrophilicity is not carried out since friction and a scratch have a resistant property is stabilized in offset printing. CONSTITUTION:After roughening a surface of an aluminum support, anodizing process is carried out in oxialic acid aqueous solution or firstly in the oxalic acid aqueous solution and then in sulfuric acid aqueous solution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a support for printing plates, and more particularly to a method for anodizing a support made of aluminum or an aluminum alloy, which is particularly suitable for offset printing plates. The present invention relates to a method for efficiently forming an anodized film.

[0002]

2. Description of the Related Art Lithographic printing is a printing method that utilizes the fact that water and oil do not mix in terms of physical properties. It is a plate surface consisting of a water-receptive non-image area and an ink-receptive image area on one plane. Is formed, and when water is supplied to the plate surface and water is retained in the non-image portion, and ink is further supplied to the plate surface, the ink is retained only in the image portion. Is a printing method of printing on paper after transferring to a blanket.

Conventionally, as a photosensitive material for preparing a lithographic printing plate used for lithographic printing, there is a so-called "PS plate", which is a plate-like support made of aluminum or aluminum alloy (hereinafter, especially Unless otherwise specified, it is abbreviated as an aluminum support) which is coated with a photosensitive composition.
The photosensitive plate surface of the S plate is exposed in a desired image shape, and a positive PS
In the plate, the exposed portion is dissolved with water or an organic solvent or a mixture thereof to form a non-image portion, and the non-exposed portion maintains the property of not being dissolved in the above solution to form an image portion. Is to dissolve the non-exposed portion with the above solution to form a non-image portion, and to maintain the property of the exposed portion not to be dissolved in the above solution to form an image portion to form a printing plate surface.

As described above, the non-image portion of the printing plate surface is
It is the aluminum surface itself of the support because it is the part where the layer of the photosensitive composition is removed. Therefore, when the surface of the aluminum support constitutes a non-image portion, it is necessary to have a property of retaining water, so that the property of retaining water (water retention) is generally improved by roughening or the like. Further, aluminum is a relatively soft material, which is inferior in abrasion resistance and corrosion resistance, so when it is used as a support for a lithographic printing plate, it is usually subjected to the above-mentioned surface roughening treatment and, if necessary, a solution of acid or alkali etc. And then anodized to form a hard film.

As a method of roughening the surface of the aluminum support, for example, a wire roughening method, a brush graining method, a sand blasting method, and a ball graining method are used as a mechanical roughening method. As a chemical method, an alkali etching method is used, and as an electrochemical surface roughening method, a method of roughening by direct current or alternating current in a dilute aqueous solution of nitric acid, hydrochloric acid or a salt thereof is used. Further, the method disclosed in JP-A-54-63902, in which both direct current and alternating current are combined for roughening, can also be used.

After the surface of the aluminum support is roughened, it is anodized in order to improve the wear resistance and corrosion resistance of the surface as described above. This anodizing treatment has been conventionally performed by anodizing in an aqueous solution of sulfuric acid or phosphoric acid using an aluminum support as an anode and using an alternating or direct current.

For example, US Pat. No. 4,211,619 describes an example of forming an anodized film of 0.5 to 10 g / m ^{2 on} the surface of a roughened aluminum support using sulfuric acid as an electrolytic solution. There is. The anodic oxide film formed by using this sulfuric acid as an electrolytic solution is generally an amorphous film, and a relatively thick film can be obtained, but the resistance to alkaline solution is low and the film is eroded when plate making an alkaline solution as a developer. As a result, the abrasion resistance of the surface of the aluminum support is deteriorated, and scumming during printing is likely to occur.

Further, US Pat. No. 3,511,661 describes an example of anodic oxidation in a 42-85% strength phosphoric acid aqueous solution. The oxide layer obtained by anodizing in a phosphoric acid aqueous solution has a denser oxide film than the oxide layer obtained by anodizing in a sulfuric acid aqueous solution, has excellent resistance to alkali, and is under development. However, since the oxide film is thin, it has poor scratch resistance. A thick oxide film cannot be easily obtained, and an anodizing treatment at a high voltage for a long time is required to obtain a relatively thick film.

In order to remedy these drawbacks of the prior art, US Pat. No. 4,229,440 discloses phosphoric acid 10-50.
g / liter, sulfuric acid 25-150 g / liter, and current density 4-25 A / dm ² in an electrolyte aqueous solution containing aluminum salt 5-25 g / liter, temperature 25-65 ° C.
An example of performing anodizing treatment is described. However, when the mixed electrolyte aqueous solution is used as an electrolytic medium for anodizing treatment, it is difficult to control the concentration of the components of the electrolytic aqueous solution, which is a problem in production control.

As another improvement step, an anodic oxidation treatment performed in two steps is known. 1 out of 2 process anodizing
The process is often anodizing in a sulfuric acid solution. For example, a treatment method in which the first anodic oxidation is performed in an aqueous sulfuric acid solution is described in, for example, British Patent GB-A 14
No. 10768 discloses a method of first anodizing in a sulfuric acid aqueous solution and then electrolessly treating with phosphoric acid, and US Pat. No. 3,940,321 discloses a method of first anodizing in a sulfuric acid aqueous solution. As the second step, a method of performing anodic oxidation in a phosphoric acid aqueous solution is described. However, the oxide layer obtained by anodizing in a sulfuric acid aqueous solution is not desirable because it is redissolved when treated in a phosphoric acid aqueous solution.

West German Patent DE-A 3206470 firstly anodizes in an aqueous solution of sulfuric acid, and then as a second step anodizing in an aqueous solution containing phosphoroxo, phosphorfluor and / or phosphoroxofluor anions. Is described.

It is known that one of the two-step anodizing treatment is performed in a phosphoric acid aqueous solution. European Patents EP-B 0007233 and 000723
In No. 4, the anodizing treatment is first performed in a 45% phosphoric acid aqueous solution, and then the anodizing treatment is performed in a 15% sulfuric acid aqueous solution.

In US Pat. No. 4,396,470, the first step is an aqueous solution containing 328 to 380 g / l phosphoric acid, and the second step is a mixture of 20 to 150 g / l sulfuric acid and 250 to 380 g / l phosphoric acid. Anodizing treatment is performed in an aqueous solution.

As described above, the oxide film formed by the anodizing treatment performed in the phosphoric acid aqueous solution is dense, and it is necessary to perform the anodizing treatment at a high voltage in order to form the anodizing film on it. In the process under the high and high voltage, a non-uniform portion is often formed on the oxide film, and a print stain is generated on the portion.

In particular, anodizing treatment in a mixed electrolyte aqueous solution is not preferable because the process control becomes complicated and the process is expensive. Japanese Unexamined Patent Publication No. 60-56093 describes an anodizing treatment in which an anodizing treatment is carried out in an electrolyte aqueous solution having a phosphorus-containing anion and the second step is anodizing treatment in a sulfuric acid aqueous solution. This treatment method cannot be said to be a stable process because the voltage varies during the treatment in the first process.

As described above, the surface of the roughened aluminum support for a printing plate is subjected to an anodic oxidation treatment, which comprises one or more steps using sulfuric acid or phosphoric acid, for example, and the surface thereof is subjected to an anodic oxidation layer. Various methods of anode participation treatment have been proposed to provide a surface that does not stain or stain the non-image area and has a surface with further improved abrasion resistance and corrosion resistance, but with a treatment method that is still satisfactory. However, it is desired to realize a treatment method that is particularly stable and economically inexpensive.

Further, in order to prevent the non-image area from being contaminated and scummed when the offset printing is performed, conventionally, it is necessary to further perform a hydrophilic treatment after the anodizing treatment. For this hydrophilic treatment, a method of immersing the surface of the roughened aluminum support having an anodized layer in an aqueous solution of an alkali metal silicate or 5
It was usual to carry out hydrophilic treatment by a method such as "sealing treatment" in a steam atmosphere of 0 to 300 ° C and 90 Torr or more. Surface treatment of the lithographic printing plate support which does not require such additional post-treatment is a preferred treatment method.

As described above, a method of anodizing treatment which is easy to manage, stable, and economical without contamination and background stain of the non-image area without additional hydrophilic treatment has not yet been realized.

Although this anodizing method is an excellent anodizing method which can be performed in one step and stably, it needs to be anodized at a higher voltage than the anodizing method in a sulfuric acid aqueous solution. Therefore, low voltage processing was desired.

[0020]

SUMMARY OF THE INVENTION The object of the present invention is to provide a roughened aluminum support surface with phosphoric acid as an electrolyte solution in order to obtain a support which does not stain or stain the non-image area in offset printing. The development of an anodizing method that does not require high running cost as in the case of forming an anodizing layer that does not require additional hydrophilic treatment such as sealing after anodizing. To do.

At the same time, the surface of the roughened aluminum support having an anodized layer excellent in water retention has a sufficiently thick oxide film, and thus an anodizing treatment method having abrasion resistance and scratch resistance is developed. To do.

A further object of the present invention is to develop an anodizing method which can further reduce the running cost required for the anodizing step.

[0023]

As a result of working on the problem of developing an anodizing treatment capable of forming an anodized film having the above characteristics, the present inventors have succeeded in developing a sheet-shaped or web-shaped material made of aluminum or an aluminum alloy. Is mechanically, chemically and / or electrochemically roughened,
A method for producing a lithographic printing plate support, which comprises performing anodizing treatment in an aqueous oxalic acid solution.

Preferably, a sheet-shaped or web-shaped material made of aluminum or an aluminum alloy is mechanically, chemically and / or electrochemically roughened, and then,
This object can be achieved by a method for producing a lithographic printing plate support, which is characterized in that (1) an oxalic acid aqueous solution and then (2) a sulfuric acid aqueous solution are anodized in two steps. ..

As conditions particularly advantageous for the anodizing treatment of the aluminum support for printing plates in the present invention, industrially, oxalic acid is 1 to 180 g / liter and aluminum ion is 0.1 to 10 g / liter. desirable. The liquid temperature is preferably 5 to 70 ° C. Current density is 2-10
0 A / dm ² is preferable, and a commercial alternating current rectified by a thyristor is generally used. Processing time is 3 to 50
0 seconds is preferred.

As an especially advantageous condition for the two-step anodizing treatment of the aluminum support for a printing plate in the present invention, industrially, the oxalic acid in the treatment liquid in the first stage is 1-18.
0 g / liter, 0.1-10 g aluminum ion
It is desirable that the amount of sulfuric acid in the second stage treatment liquid is 5 to 400 g / liter, and the amount of aluminum ion is 0.1 to 10 g / liter.

In order to keep the concentration of the electrolyte component such as oxalic acid, sulfuric acid and aluminum ion used for the anodizing treatment of the present invention at an optimum concentration, it may be monitored regularly and may be continuous or discontinuous. It is desirable to circulate the electrolyte solution in the treatment tank and, if necessary, to an external electrolyte solution stock tank to maintain the concentration of the electrolyte component at an optimum concentration.

The thickness of the anodized film obtained by the method of the present invention can be determined by the anodizing method in an oxalic acid electrolyte solution.
Even in the two-step anodic oxidation method in an oxalic acid electrolyte solution and then in a sulfuric acid electrolyte solution, a layer as thick as that obtained when sulfuric acid is used as the electrolyte solution is obtained. Moreover, this anodic oxide film has a strong resistance to an alkaline solution, and also has a high wear resistance and a scratch resistance. In addition, these resistances increase up to a certain value as the thickness of the anodic oxide film increases.

A high voltage and a relatively long treatment time were required for anodic oxidation in the oxalic acid electrolyte solution, but in the two-step method, even when the same amount of anodized film was obtained, in the oxalic acid electrolyte solution, a high voltage was required. The anodizing time can be shortened, the subsequent anodizing in the sulfuric acid electrolyte solution can be anodizing at a low voltage, and the total processing time of the two steps can be shortened, which is energy-efficient and is a desirable method. ..

With the support having an oxide film obtained by the anodic oxidation method according to the present invention, a printing plate that does not stain or stain the non-image area in offset printing can be obtained without additional hydrophilic treatment. ..

The aluminum plate used in the present invention includes pure aluminum and aluminum alloy plate. Various aluminum alloys can be used, and for example, aluminum alloys with metals such as silicon, iron, copper, manganese, magnesium, chromium, zinc, bismuth, and nickel are used. The aluminum plate may be in the form of a sheet or a web, and it is also possible to use a laminate of paper, plastic, or another metal with the surface of the aluminum having aluminum as a material. The aluminum plate should not cause dimensional changes when it is mounted on a printing machine as a printing plate. For example, a plate made of aluminum alone generally has a thickness of 0.1 to 0.5 mm. What is used.

The surface of the aluminum plate may be subjected to a degreasing treatment for removing the rolling oil on the surface, if necessary, prior to the roughening treatment. The surface of the aluminum plate is roughened in order to improve water retention and adhesion with a layer of a photosensitive material coated thereon. As the roughening method, the above-mentioned method, that is, the mechanical roughening method, the chemical roughening method, the electrochemical roughening method, or a method combining them can be used.

The aluminum plate thus roughened is subjected to alkali etching treatment and neutralization treatment, if necessary. When the electrochemical surface roughening method is used, it is usual to carry out desmutting treatment with phosphoric acid, sulfuric acid, chromic acid, etc., if necessary.

The surface-roughened and alkali-etched aluminum plate is anodized in order to improve the wear resistance and corrosion resistance of the surface. The anodizing step is usually followed by a step of additionally hydrophilizing the surface, but in the step of the present invention, this additional hydrophilizing treatment is unnecessary. However, of course, such hydrophilic treatment may be performed. This additional hydrophilization treatment includes U.S. Pat. Nos. 2,714,066 and 3,1.
No. 81,461, by treatment with an alkali metal silicate, for example, by dipping in an aqueous solution of sodium silicate, as described in US Pat.
An undercoat layer of hydrophilic cellulose (eg, carboxymethyl cellulose, etc.) containing a water-soluble metal salt (eg, zinc acetate, etc.) can also be provided, as described in the specification of No. 0,426.

On the lithographic printing plate support thus obtained, a photosensitive layer conventionally known as a photosensitive layer of a PS plate (abbreviation of Pre-sensitized Plate) is provided to provide a photosensitive lithographic printing plate. Can be obtained.

The photosensitive composition for these photosensitive layers includes
For example, (1) a diazo compound represented by a condensate of p-diazophenylamine and paraformaldehyde, which is soluble in a water-soluble or water-insoluble organic solvent, preferably a water-insoluble organic solvent is used. Examples of preferable diazo compounds include fluorocapric acid salts of condensates of p-diazodiphenylamine and paraformaldehyde and 5-nitroorthotoluenesulfonic acid salts. Such a diazo compound is used alone to prepare a resist, but is also used with a binder such as a shellac or a copolymer compound containing hydroxyethyl acrylate. (2)
o-quinonediazide compounds, especially preferred are o-
Naphthoquinone diazide sulfonic acid ester, o-naphthoquinone diazide carboxylic acid ester, o-naphthoquinone diazide sulfonic acid amide and the like are used. Such o
The quinonediazide compound is used alone in the preparation of a resist, but it is used as a mixture with an alkali-soluble resin such as a novolac type phenol resin. (3) A photosensitive azide compound, for example, an aromatic azide compound in which an azido group is bonded to an aromatic ring directly or through a carbonyl group or a sulfonyl group. Preferred aromatic azide compounds are compounds containing one or more groups such as azidophenyl, azidostyryl, azidobenzal and azidocinnamoyl. These photosensitive azide compounds are also used together with the binder. A preferred binder is an alkali-soluble resin (for example, a novolac type phenol resin or a vinyl copolymer containing polyacrylic acid).
(4) Polymer compounds containing a cinnamic acid group, for example, thinner as described in US Pat. Nos. 3,030,208, 3,707,373 and 3,453,237. Suitable photosensitive compositions include, for example, a photosensitive resin containing a photosensitive resin composed of a (2-propylidene) malonic acid compound such as millidenmalonic acid and a bifunctional glycol compound as a main component.

These photosensitive compositions are applied, optionally together with a thermal polymerization inhibitor, a plasticizer and a pigment, on the roughened aluminum support having an anodized layer of the present invention which is excellent in water retention. An excellent lithographic printing plate can be prepared, and the lithographic printing plate obtained by plate-making treatment thereof has excellent properties such as non-image area contamination and background stain resistance, and good printing durability. There is.

[0038]

【Example】

[Example 1] The surface of a JIS 1050 aluminum sheet was grained with a rotating nylon brush using a pumice-water suspension as an abrasive. The surface roughness (center line average roughness) at this time was 0.5 μm. After washing with water, a 10% caustic soda aqueous solution was immersed in a solution warmed to 70 ° C., and etching was performed so that the dissolution amount of the aluminum surface was 5 g / m ² . After washing with water, immerse in 30% nitric acid aqueous solution for 1 minute, and
Voltage in anode aqueous solution of 23% at anode and voltage at cathode at 12V
The rectangular wave alternating waveform of Japanese Patent Application Laid-Open No. 52-77702
(Current waveforms described in the examples of the publication), electrolytic etching is carried out at an anode-time electric quantity of 160 coulomb / dm ² .
It was immersed in a solution of 30% sulfuric acid at 50 ° C. for desmutting and then washed with water.

Next, under the conditions shown in Table 1, the temperature was adjusted so that the weight of the anodic oxide film would be 2.5 g / m ² respectively.
The aluminum substrate (A), the aluminum substrate (B), the aluminum substrate (C), and the aluminum substrate (D) were obtained by anodizing using a direct current of ² ° C. and a current density of 2 A / dm ² .

[0040]

[Table 1]

Next, the coating amount after drying the following photosensitive solution was 2.5.
It was coated on each of the aluminum substrates (A), (B), (C), and (D) so as to have g / m ^2, and a photosensitive layer was provided.

Photosensitive Solution Esterification product of naphthoquinone-1,2-diazido-5-sulfonyl chloride and pyrogallol-acetone resin (described in Example 1 in the specification of US Pat. No. 3,635,709). 0.90 g cresol novolac resin 2.00 g phthalic anhydride 0.20 g 2- (p-butoxyphenyl) -4,6-bis (tricolorolmethyl) -S-triazine 0.02 g oil-soluble dye ( CI 42595) 0.03 g ethylene chloride 15 g methyl cellosolve 12 g The PS plate thus prepared was exposed through a transparent positive film in a vacuum frame at a distance of 1 m from a metal halide lamp of 3 kw for 50 seconds, and then exposed to SiO 2.
Development was carried out with a 5.26% aqueous solution of sodium silicate (pH = 12.7) having a molar ratio of ₂ / Na ₂ O of 1.74.

After developing in this way, the contamination degree of the non-image area was examined by the following method, and the results shown in Table 2 were obtained. In addition, the results of examining scratch resistance with an offset printing machine are also shown.

(1) Evaluation Method for Contamination of Non-Image Area Judgment was made by the difference between the reflection optical density of the non-image area and the reflection optical density of the surface of the support immediately before coating the photosensitive layer.

(2) Method of evaluating scratch resistance Judgment was made by the degree of the surface of the non-image area after 350 cycles of the non-image area with alumina abrasive paper using an abrasion tester (NUS-ISO-1 type) manufactured by Suga Test Instruments Co., Ltd. ..

[0046]

[Table 2]

[0047]

(1) A lithographic printing plate support having improved scratch resistance can be obtained. (2) A lithographic printing plate support having improved non-image area contamination and background stain is obtained.

(3) The electrolysis voltage is lower than that in the case of using phosphoric acid as the electrolyte solution, and especially in the case of oxalic acid (two-step method),
Since the electrolysis voltage of the process may be lower, a small-scale power supply is sufficient.

(4) When using oxalic acid as the electrolyte solution 1
Since neither the step method nor the two-step method requires additional hydrophilic treatment such as sealing treatment after the anodizing treatment, the facility cost can be reduced.

(5) When using oxalic acid as the electrolyte solution 1
In both the two-step method and the two-step method, the efficiency of forming the anodized film is very good as compared with the case of using phosphoric acid as the electrolyte solution.

Claims (2)

[Claims] 1. A sheet-like or web-like material made of aluminum or aluminum alloy is mechanically, chemically and / or electrochemically roughened, and then anodized in an oxalic acid aqueous solution. A method for producing a characteristic lithographic printing plate support. 2. A sheet-shaped or web-shaped material made of aluminum or an aluminum alloy is subjected to a mechanical, chemical and / or electrochemical surface roughening treatment, and then (1) in an aqueous oxalic acid solution, followed by ( 2) A method for producing a lithographic printing plate support, which comprises performing anodizing treatment in two steps in a sulfuric acid aqueous solution.