JPH06301212A - Production of silver salt offset printing master plate and silver salt offset printing master plate - Google Patents

Abstract

PURPOSE:To improve printing durability and reproducibility of picture images by subjecting an aluminum supporting body to anodic oxidation, bringing the supporting body into contact with a soln. containing metal ions and then with a reducing agent soln. to reduce the metal ions into physical development nucleus metal or metal alloy. CONSTITUTION:An aluminum supporting body is subjected to anodic oxidation and brought into contact with a soln. containing metal ions of physical developing nucleus. Then the ion adsorbing to the anodic oxidation film is reduced to physical development nucleus metal or metal alloy. Namely, at least the anodic oxidation film side of the aluminum supporting body having an anodic oxidation film is brought into contact with a soln. containing metal ions which constitute the physical development nucleus and then into contact with a reducing agent-contg. soln. to form the physical development nucleus. Then a silver halide photosensitive layer is formed thereon. In this process the aluminum plate used for the supporting body is preferably pure aluminum or aluminum alloy containing a small amt. of various metals such as silicon, magnesium, iron, copper, zinc, manganese, chromium, and titanium.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an offset printing plate, and more particularly to a silver salt offset printing plate by a silver salt diffusion transfer method.

[0002]

2. Description of the Related Art Conventionally, in the general printing field, an aluminum plate was used as a support, and a diazo photosensitive composition, an azide photosensitive composition or a photopolymer photosensitive composition was applied in a thin layer on the so-called PS. Plates are widely used as offset printing plates. After exposure, the PS plate elutes and removes the non-image area, and uses the anodized surface of aluminum for the non-image area, and has excellent printing performance such as water retention and printing durability.
There is a problem that the light sensitivity is low, a large output light source is required for laser direct plate making, etc., and the sharpness of the image is poor, so that only contact baking using a film can be used. Recently, an electrophotographic OPC printing plate in which an electrophotographic photosensitive layer is provided on an aluminum support, a toner image is developed, and then a non-image portion is dissolved and removed by using a toner as a resist has come into practical use. This printing plate has high photosensitivity, uses the anodized surface of aluminum in the non-image area, and has excellent printing performance such as water retention and printing durability, and it is beginning to be put to practical use in laser direct plate making for newspapers. Since this method requires corona charging, not only is it difficult to put it into practical use in contact baking, but also the holding time of the charge is limited, making laser direct plate making difficult in high-quality printing such as general printing. Further, there is a problem that the plate making apparatus is complicated and expensive because it requires steps such as corona charging and toner development.

On the other hand, in the field of light printing, it has excellent photosensitivity,
Electrophotographic zinc oxide printing plates and silver salt printing plates using the silver salt diffusion transfer method have been put to practical use, but a paper or film is used for the support, and the photosensitive layer is directly hydrophilized in the non-image area. However, the water retention was poor and the printing durability was limited.

The silver salt lithographic printing plate using the silver salt diffusion transfer method (DTR method) is described in "Photographic Silver" by Andre Lot and Edith Weide, published by Focal Press, London New York (1972). Halide Diffusion Processes ", pages 101-130, for some examples.

As described therein, in a lithographic printing plate using the DTR method, a two-sheet type in which a transfer material and an image receiving material are separately provided, or they are provided on a single support. Two types of mono-sheet type are known. For a two-sheet type lithographic printing plate, see JP-A-57-1
It is described in detail in Japanese Patent No. 58844. For mono-sheet type, Japanese Patent Publication No. 48-30562,
51-15765, JP-A-51-111103,
It is described in detail in each of the publications such as No. 52-150105. All were developed for light printing and had limited printing durability.

The silver salt type lithographic printing plates using aluminum as a support are disclosed in JP-A-57-118244 and 57-57.
-158844, 63-260491, JP-A-3
It is described in detail in each publication such as No. -116151.
For example, in JP-A-63-260491, a physical development nucleus solution in which silver sol prepared by the curry method is dispersed in gelatin is applied on a roughened and anodized aluminum support to form a physical development nucleus layer. A silver salt printing plate is described which is formed and provided with a silver halide photosensitive layer thereon.
In this printing plate, unexposed silver halide is converted into a soluble silver complex by development in the presence of a developing agent and a silver halide solvent, diffuses into a physical development nucleus layer below to form a silver image, and the exposed silver halide is It is chemically developed and remains on the photosensitive layer, and then the entire photosensitive layer is dissolved and removed to leave a silver image, thereby obtaining a printing plate. Therefore, although the anodized surface of aluminum can be used and is excellent in water retention, the physical development nuclei are in the form of particles and are wrapped in a hydrophilic polymer, and even if a silver image is deposited, it does not adhere to the aluminum surface. There was a problem that the adhesiveness was poor and sufficient printing durability could not be obtained. In addition, when the photosensitive layer is eluted after development, the image peels off together with the physical development nucleus layer, and there is a problem of lack of stability.

[0007]

DISCLOSURE OF THE INVENTION The present invention aims to improve the method of physical development nucleation in a silver salt offset printing plate using aluminum as a support to improve printing durability and image reproducibility. To aim.

[0008]

Means for Solving the Problems The present inventors have diligently studied the above problems. As a result, after the aluminum support was anodized, the aluminum support was brought into contact with an aqueous solution containing physical development nucleus metal ions, and then the ions adsorbed on the anodized film were reduced to physical development nucleus metals or metal alloys. It was found that a printing plate having excellent properties and image reproducibility can be obtained.

That is, according to the present invention, after at least the anodic oxide film side of the aluminum support having the anodic oxide film on its surface is contacted with the metal ion-containing solution constituting the physical development nuclei,
A method for producing a silver salt offset printing original plate, which comprises contacting with a reducing agent-containing solution to form physical development nuclei, and providing a silver halide photosensitive layer thereon.

Next, the silver salt offset printing original plate of the present invention and the method for producing the same will be described in detail.

The aluminum plate used for the support of the present invention includes pure aluminum and various metals such as silicon, magnesium, iron, copper, zinc, manganese, chromium,
An aluminum alloy plate containing a small amount of titanium or the like is 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 order to use the above aluminum plate as a support for an offset printing plate, it is generally subjected to a surface treatment before coating the photosensitive layer. Surface treatment generally involves degreasing, roughening,
Desmutting and anodic oxidation are performed, and the treatment is continuously performed using an aluminum coil. Rinsing is added as needed between each treatment. Next, a method of manufacturing the support will be described in the order of processing steps.

The degreasing treatment removes an oxide film or the like formed by contact with oil or air during rolling of the aluminum surface to expose a clean aluminum plate surface so that the subsequent steps can be uniformly processed. Is given. Examples of the degreasing method include solvent degreasing with trichloroethylene, perchlorethylene, etc., alkaline degreasing with sodium hydroxide, sodium carbonate, sodium metasilicate, trisodium phosphate, tetrasodium pyrophosphate, soap, etc., or a mixture thereof. There are methods such as emulsion degreasing in which a surfactant, kerosene, triethanolamine, sodium hydroxide and the like are combined, and electrolytic degreasing called finish degreasing that removes contamination that cannot be removed by the above chemical degreasing. Fork ultrasonic cleaning is also effective.

Next, a roughening process is performed. The roughening treatment gives unevenness to the surface and directly contributes to the improvement of the adhesiveness of the photosensitive layer by the anchor effect.However, in the offset printing plate, printing such as printing durability and water retention printing image quality is performed. Since it affects the basic performance of, various methods are now in practical use for improving these performances.
That is, mechanical graining methods such as brush graining, ball graining and liquid honing, chemical graining methods by chemical etching with hydrochloric acid or nitric acid, or electrolysis by electrochemical etching with these acids. A roughening method, or a method of roughening it by combining them is known.

Among them, the electrolytic surface roughening method can finely adjust the shape and surface roughness of the grain depending on the composition of the electrolytic solution and the electrolysis conditions as compared with other methods. It is the center of the roughening method. For example, brush graining and electrolytic surface roughening (described in JP-A-53-123204), chemical etching and electrolytic surface roughening (JP-A-60-208294).
Liquid honing and electrolytic surface roughening (JP-A-60).
-18390 gazette)) and the like are known. The electrolytic surface-roughening method is a preferred method for surface-roughening the silver salt offset printing plate support of the present invention. In the electrolytic surface-roughening method, pits are formed on the aluminum surface, and the size, depth, and distribution of pits can be changed depending on the current density, liquid concentration, liquid composition, liquid temperature during electrolysis.
The shape of the surface is generally represented by a roughness meter, and its size is suitably center line average roughness; Ra value of 0.3 to 1.0 μ.

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 carried out by applying a direct current or an alternating current (single phase or three phases). In electrolytic surface roughening treatment, it is necessary to supply a large current to a continuously moving aluminum plate strip, so the power feeding method has been devised, and the direct power feeding method in which the power feeding terminal is directly contacted with the aluminum plate, or direct aluminum Connect the power supply between both electrodes, without contacting the power supply terminal with the plate, via the electrolytic solution between the counter electrode, for example, in the case of single-phase alternating current, divide the processing tank into two However, in the case of three-phase alternating current, each of the three-phase terminals is divided into three tanks and connected, and an electrolytic solution is supplied to energize the so-called indirect power supply method (Metal surface technology Vol. 30, No. 10, 1979, P541
~ P546) can also be adopted.

The electric current used for electrolytic surface roughening treatment is single-phase or three-phase commercial alternating current, or 10 to 300 Hz including them.
, Sine wave within the range, waveform current with a part of AC waveform 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.

The power supplied to the aluminum plate varies depending on the composition of the electrolytic solution, the temperature, the distance between the electrodes and the like, but in order to obtain a suitable grain as a printing plate, the voltage is generally 1 to
60 V, 5-60 A / dm ² at the current density on the treated surface,
It is used in the range of 50 to 4000 coulombs in terms 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, stabilizing agents. You may use it, adding an agent and the like.

Regarding the concentration of the electrolytic solution, it is preferable that the concentration of the above-mentioned acids is 0.1 to 10% by weight and the concentration of aluminum ions in the electrolytic solution is maintained in the range of 0 to 10 g / liter. In the electrolytic surface roughening treatment, as the electrolysis proceeds, aluminum melts and the 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 replenisher for replenishing the electrolyte 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 which is usually used for degreasing treatment can be used. Desmutting dissolves the smut and reveals the pit surface. The amount of dissolution depends on the treatment conditions with the electrolytic solution,
0.1 to 1 g / m ² is suitable.

The desmutted roughened aluminum strip is then anodized. In the anodizing treatment, an aluminum oxide film is formed on the aluminum surface, which not only prevents the surface from being denatured, but also significantly improves the surface hardness and improves the printing durability during printing. Particularly in the present invention, the micropores of the porous oxide film are positively used as the anodic oxide film. As an electrolytic solution for forming such a porous oxide film, sulfuric acid, oxalic acid, chromic acid, phosphoric acid, or the like or a mixture thereof is preferable, and an acid having low solubility of the generated oxide film is preferable.
The size of the micropores of the anodic oxide film generated by these acids changes depending on the type of acid and also changes according to the voltage applied during anodic oxidation. The size of the micropores is usually 0.01 to 0.1 μm, but it can be enlarged by a pore widening technique of immersing in a low concentration of phosphoric acid, sulfuric acid or the like after anodizing treatment.

Since the anodic oxide film is formed only on the anode, a direct current is usually used. The conditions of anodization are as follows: liquid concentration 1-40%, current density 0.1-10 A / dm
^2. Used in the voltage range of 10 to 100V. The thickness of the anodic oxide film varies depending on the current density and time, and is appropriately adjusted depending on the printing durability grade of the printing plate.
Is enough. The temperature affects the hardness of the anodic oxide film,
Although the hardness becomes higher at lower temperatures, it is inferior in flexibility, so that it is usually anodized at a temperature near room temperature.

Next, in the present invention, after anodic oxidation, a physical development nucleus forming treatment is carried out in which the solution is brought into contact with a metal ion-containing solution constituting physical development nuclei and then brought into contact with a reducing agent-containing solution. In general, the surface of the inside of the micropores is hydrated and loses its activity as time goes by after the treatment of the porous anodic oxide film, and the adsorbability of metal ions decreases in the physical development nucleation treatment. Also, in a high humidity atmosphere, the micropores themselves are sealed by hydration, and the adsorptivity is significantly reduced. Therefore, it is preferable to perform the physical development nucleation treatment immediately after anodizing, washing with water and drying, but the time until the physical development nucleation treatment differs depending on the storage atmosphere. In the atmosphere, it is preferable to stay for 2 to 3 days.
Such a change in the porous anodic oxide film can be detected, for example, as a change in the measured value of the dye adsorbing property or the surface tension.

Examples of physical development nuclei generally used in the DTR method include heavy metals such as silver, gold, platinum, palladium, copper, cadmium, lead, cobalt and nickel, or their sulfides and selenides. Since the reproducibility changes depending on the type of physical development nuclei, the optimum physical development nuclei are selected depending on the type, configuration, application, etc. of the DTR material.

These physical development nuclei are described in the above patent publication by reducing the corresponding metal ions to form a metal colloidal dispersion, or by mixing a metal ion solution with a soluble sulfide or selenide solution to form a water-insoluble metal. It can be obtained by making a colloidal dispersion of sulfide or metal selenide, and is used in the form of so-called colloidal particles. Since it is in a particle state, it is not possible to put nuclei in the micropores of the porous anodic oxide film, and for stability of dispersion, poly-N-vinylpyrrolidone, gelatin as a protective colloid or as a binder is used. , Carboxymethyl cellulose, hydroxymethyl cellulose, polyvinyl alcohol, polyacrylamide, acrylamide-vinyl imidazole copolymer, etc. are added and applied.

On the other hand, in the present invention, the physical development nuclei are obtained by first contacting an aluminum support having an anodized film on the surface with a solution containing a metal ion by a method such as dipping, and then dipping in a solution containing a reducing agent. Then, the physical development nuclei are deposited. That is, in the present invention, it is adsorbed in the form of metal ions in the micropores of the porous anodic oxide film in advance, and then reduced to form physical development nuclei of metal or metal sulfide or selenide. Normally, in the dipping treatment, the ions do not penetrate to the bottom of the micropores, but they are adsorbed relatively near the entrance. In the present invention, the silver ions supplied from the silver halide photosensitive layer by development are deposited on the physical development nuclei to form a silver image, so that the physical development nuclei are preferably present near the entrance rather than at the bottom of the pores. More preferable. The amount of adsorption is extremely small, and it is not necessary to increase the amount so that the pores are blocked. Silver is deposited from the physical development nuclei existing in the pores, and the image becomes as if rooting in the pores, and a silver image with excellent adhesiveness is obtained.

As a metal ion source for forming physical development nuclei, an aqueous solution of the above-mentioned corresponding metal sulfate, nitrate, halide, cyanide or the like, or an aqueous solution obtained by dissolving these in a small amount of acid or alkali, or Can be used as alcohol or a mixed solution of alcohol and water. In the present invention, the concentration of the metal ion source compound in the aqueous solution is 0.0
01-0.2 g / l is sufficient.

The reducing agent is appropriately selected depending on the physical development nuclei to be used, but for example, hydrated hydrazine, hydrazine hydrochloride, hydrazine sulfate, methylhydrazine, 1,2-
Hydrazine compounds such as dimethylhydrazine, acetohydrazine, phenylhydrazine, sodium hypophosphite, sodium borohydride, potassium borohydride, Rochelle salt, dimethylamine borane, diethylamine borane, formalin, hydroquinone, glucose, ferrous chloride, chloride Reducing agents such as stannous tin, sodium thiosulfate, ascorbic acid and thiourea can be used alone or in combination. In the present invention, the concentration of the reducing agent in the solution is
The range of 0.001 to 0.5 g / l is preferable.

In the physical development nucleation treatment of the metal ion-containing solution and the reducing agent-containing solution of the present invention, the treatment liquid contains no particulate metal colloid, and no polymer is added to the treatment liquid. It can be effectively deposited in the micropores of the film, and a strong physical development nucleus can be formed. Further, since only dipping is sufficient for the treatment, it is also possible to carry out a physical development nucleation treatment continuously by anodizing after anodizing at the stage of surface treatment of the aluminum coil. Even if physical development nuclei are formed on the surface of the anodic oxide film outside the micropores, the effect of the present invention is not hindered, but if a large amount is formed, stains may occur during printing. It is preferable to remove the excess liquid by washing with water after.

The support subjected to the physical development nucleation treatment is then provided with a silver halide photosensitive layer. The photosensitive silver halide used in the present invention is selected from commonly used silver chloride, silver bromide, silver iodide, silver chlorobromide, silver chloroiodide, silver iodobromide, silver chlorobromoiodide and the like. To be selected. The emulsion type may be either a negative type or a positive type, and a special type described in JP-A-54-48544 using a non-photosensitive silver halide emulsion which is hardly soluble with a photosensitive silver halide. May be These silver halide emulsions can be chemically or spectrally sensitized if necessary. If desired, an overlayer may be provided for the purpose of improving image sharpness such as halation prevention.

The photosensitive halogenated emulsion provided on the physical development nucleus-containing anodic oxide film layer is a silver chloride, silver bromide, silver iodide, silver chlorobromide, silver chloroiodide, or iodine prepared by a conventional method. Any of silver bromide, silver chlorobromoiodide emulsion and the like may be used. The silver halide emulsion can be subjected to various chemical sensitizations such as noble metal sensitization, sulfur sensitization, reduction sensitization, and sensitization combining these sensitizations, and if necessary, a sensitizing dye such as cyanine. Spectral sensitization can be performed by using a dye such as merocyanine or merocyanine. Further, additives such as antifoggants, stabilizers and surfactants may be contained by known methods. For details of the photosensitive silver halide emulsion and a method for producing the same, reference can be made to the description in JP-A-49-55402.

As the protective colloid of the photosensitive silver halide emulsion, various gelatin such as acid-treated gelatin, alkali-treated gelatin, gelatin derivative and grafted gelatin can be used, and polyvinylpyrrolidone, various starches, albumin, polyvinyl alcohol, A hydrophilic polymer compound such as gum arabic or hydroxyethyl cellulose may be contained.

In the DTR type aluminum lithographic printing plate, a silver image is formed by the following procedure. In the imagewise exposed light-sensitive silver halide emulsion layer, unexposed silver halide is converted into a soluble silver complex in the presence of a developing agent and a silver halide solvent, and exposed silver halide is chemically developed. The unexposed portion of the soluble silver complex diffuses into the physical development nuclei layer and forms a silver image in the presence of physical development nuclei. After forming a silver image, the silver halide photosensitive layer is removed and used as a lithographic printing plate.

The developer used in the present invention contains an alkaline substance such as sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium triphosphate or an amine compound, a preservative such as sodium sulfite and a viscous agent. For example, additives such as carboxymethyl cellulose, antifoggants such as potassium bromide, toning agents such as 1-phenyl-5-mercaptotetrazole, development modifiers such as polyoxyalkylene compounds can be included. As the developing agent used in the present invention, polyhydroxybenzenes and 3-pyrazolidinone are preferable, and these developing agents may be used in a so-called main agent built-in type contained in the plate material constituting layer.

Wash-off for removing the silver halide photosensitive layer can be carried out by washing with running water at a temperature of about 20 to 40 ° C. Further, after wash-off, a plate surface protective agent such as gum arabic may be applied as necessary to protect the plate surface.

[0037]

EXAMPLES The silver salt offset printing plate of the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

Example 1 An A1050 type aluminum plate strip having a width of 300 mm and a thickness of 0.2 mm was moved at a processing speed of 1.3 m / min to obtain 50
After immersing in 4% caustic soda aqueous solution for 30 seconds at 40 ° C, rinse with water, fill the electrolytic cell of the direct power feeding system with 2.0% hydrochloric acid at 5 ° C, and apply a single-phase alternating current of 20 A / dm ² and 50 Hz from the power source to 45%. Flowing to each electrode terminal for a second, AC electrolytic surface roughening,
Rinse with water, then dipped in 4% caustic soda aqueous solution at 25 ° C for 30 seconds to desmut, rinse with water, then 25 ° C, 15
% Sulfuric acid for 45 seconds to anodize at a direct current of 5 A / dm ² , washed with water, and then dried to obtain an aluminum support for offset printing plates.

Immediately thereafter, it was immersed in a 0.5% silver nitrate aqueous solution for 1 minute, washed with water, then immersed in a 0.2% thiourea aqueous solution for 1 minute, and reduced to form physical development nuclei. The physical development nuclei at this time are silver sulfide.

An ortho-sensitized silver chloride gelatin emulsion was added to the thus-obtained physical development nucleation-treated support at a silver content of 1.5 g / m ² and a gelatin content of 1.0 g / m ² . A silver halide photosensitive layer was formed by applying the above-mentioned coating solution and drying to obtain a silver salt offset printing original plate.

Comparative Example For comparison, a gelatin coating solution containing silver colloid (silver: gelatin = 1: 1 weight ratio) prepared by the curry method was applied to the anodized aluminum support of Example 1 to give a coating composition of 0.
A 05 g / m ² physical development nucleus layer was formed, and Example 1 was formed thereon.
Was coated with silver halide emulsion and dried to obtain a silver salt offset printing original plate.

Next, the printing plate precursors of Example 1 and Comparative Example were contact-exposed to a standard resolution test chart (USAF) using a tungsten lamp as a light source, and developed with the following developer (1) at 20 ° C. for 30 seconds. After development, the film was washed in warm water to remove the residual film, and a silver salt offset printing plate was obtained.

Developer (1) Sodium sulfite 50 g / l Hydroquinone 12 g / l Phenidone B 6 g / l Sodium hydroxide 12 g / l Sodium thiosulfate 10 g / l Potassium bromide 1.0 g / l pH 13.0 Phenidone B = 4- Methyl-1-phenyl-3-pyrazolidone

When the image reproducibility of the printing plates thus obtained was compared on the plate surface, it was 80 to 100 in Example 1.
The number of lines / mm, and in the comparative example, 30 to 50 lines / mm, the present invention was found to be excellent. Further, when both plates were simultaneously loaded on an offset printing machine and the printing durability was compared, the present invention was possible up to 50,000 sheets without causing scumming. It was found that the printing plate was missing and the present invention was a printing plate excellent in printing durability.

Example 2 An aluminum support prepared in the same manner as in Example 1 was immersed in a metal ion-containing aqueous solution containing 0.01% palladium chloride and 0.05% phosphoric acid for 1 minute and then washed with water, and then 0. It was immersed in a 0.5% aqueous solution of boron hydride for 1 minute and reduced to form physical development nuclei.

A silver halide emulsion similar to that used in Example 1 was coated on the thus-obtained physical development nucleation-treated support and dried to obtain a silver salt offset printing original plate. Further, the printing plate precursor thus prepared was imagewise exposed, developed with the following developer at 20 ° C. for 30 seconds, washed after development with warm water to remove the residual film, and a silver salt offset printing plate was obtained.
When the printing plate thus obtained was placed on an offset printing machine and printed, 50,000 sheets could be printed without causing scumming.

Developer (2) Sodium sulfite 50 g / l Hydroquinone 12 g / l Phenidone B 12 g / l Sodium hydroxide 2 g / l Sodium thiosulfate 10 g / l 2-Methylaminoethanol 40 cc / l Potassium bromide 0.5 g / l pH 11.4

Example 3 An A1050 type aluminum plate strip having a width of 300 mm and a thickness of 0.24 mm was moved at a processing speed of 1.3 m / min to obtain 50
After immersing in 4% caustic soda aqueous solution for 30 seconds at 40 ° C., rinse with water, fill the indirect power supply type electrolytic cell with 2.0% nitric acid at 20 ° C., and supply a single phase alternating current of 40 A / dm ² and 50 Hz from the power supply to 45 Flowing to each electrode terminal for 2 seconds, AC electrolytic surface roughening, washing with water, then 3% in 4% caustic soda aqueous solution at 25 ° C.
Soak for 0 seconds to desmut, wash with water, then at 25 ℃,
An aluminum support for an offset printing plate was obtained by passing it through 15% phosphoric acid for 10 minutes, anodizing at a direct current of 1 A / dm ² , washing with water, and then drying.

A silver salt offset printing original plate was obtained in the same manner as in Example 2, and when the plate was made and printed, 50,000 sheets could be printed without causing scumming.

Example 4 A silver salt offset printing plate was obtained in the same manner as in Example 3 except that the anodic oxidation treatment was carried out in a 4% oxalic acid solution for 5 minutes.

When the printing plates of Examples 2 to 4 were evaluated in the same manner as in Example 1, all showed an image reproducibility of 100 lines / mm or more and printing durability of 50,000 sheets or more, which was excellent. It turned out to be a silver salt printing plate.

[0052]

INDUSTRIAL APPLICABILITY In the DTR type silver salt printing original plate using anodized aluminum as a support, after the aluminum support is anodized, it is brought into contact with an aqueous solution containing metal ions as in the present invention, and then an aqueous solution of a reducing agent. By contacting with the above to reduce the ions to the physical development nucleus metal or metal alloy, a silver salt offset printing plate excellent in printing durability and image reproducibility can be obtained.

Claims (2)

[Claims] 1. A physical development nucleus is prepared by contacting at least the anodic oxide film side of an aluminum support having an anodic oxide film on its surface with a metal ion-containing solution constituting physical development nuclei and then with a reducing agent-containing solution. And a silver halide photosensitive layer is provided on it to prepare a silver salt offset printing original plate. 2. The silver salt offset printing plate according to claim 1, wherein physical development nuclei are formed in pores of the anodic oxide film.