JPH04306660A - Processing for lithographic form plate - Google Patents

Abstract

PURPOSE:To obtain the lithographic printing press which permits the superior adhesiveness with ink and high printing resistance by carrying out development by a treating liquid in which the content of sodium thiosulfate does not exceed a certain value. CONSTITUTION:As for a lithographic printing press, a supporting body is made of the anode-oxized aluminium, and a physical development nucleus layer or a photosensitive silver halide photograph emulsion layer is formed on the supporting body, and development is carried out by using a treating liquid containing a content of sodium thiosulfate per l of 2 grams or less. The aluminium supporting body used in this case improves the close adhesion performance with the photosensitive layer formed on the supporting body and improves the water retentivity, and the surface is roughened, and after the surface roughening treatment, the anode oxidation treatment is carried out. As the physical development nucleus, is listed the compound used in the silver complex salt diffusion print, and the colloid of gold, silver, etc., the metal sulfide through the mixing of sulfide and the water-soluble salt of palladium, zinc, etc., can be used. As the main chemical for development, are preferable polyhydroxy benzene, 3-pyrazolidinone, etc.

Description

Description: TECHNICAL FIELD The present invention relates to a method for processing lithographic printing plates with improved printability. [0002] Lithographic printing plates using the silver complex diffusion transfer method (DTR method) are described in "Photo" by Andre Lott and Edith Weide, published by Focal Press, London and New York (1972). Some examples are described in "Graphic Silver Halide Diffusion Processes", pages 101-130. As stated therein, lithographic printing plates using the DTR method include a two-sheet type in which the transfer material and image-receiving material are separate, or a two-sheet type in which the transfer material and image-receiving material are separate, or a plate in which they are provided on a single support. Two sheet types are known. Regarding the two-sheet type lithographic printing plate, JP-A-57
It is described in detail in the specification of No.-158844. or,
For the mono sheet type, please refer to Special Publication No. 48-30562.
No. 51-15765, JP-A-51-111103
No. 52-150105 and other specifications. [0004] With lithographic printing plates using paper as a support, it is difficult to print with high quality, including printing durability, due to plate elongation and water penetration during printing. Film supports are used to overcome these problems and improve printing performance. For example, cellulose acetate film, polyvinyl acetal film, polystyrene film, polypropylene film, polyethylene terephthalate film, or a composite film in which polyester, polypropylene, or polystyrene film is coated with polyethylene film, etc. can be used as the support. However, although lithographic printing plates using film as a support have been improved in terms of plate elongation and moisture absorption compared to paper-based printing plates, printing durability, water retention, and even printing Problems remain in terms of ease of applying the plate to the machine, etc. In order to solve the various problems of the above-mentioned lithographic printing plates using paper or film as a support, a silver salt type lithographic printing plate using a metal, especially aluminum, as a support is known. JP-A No. 57-118244, No. 5
It is described in detail in various specifications such as No. 7-158844 and No. 63-260491. [0007] In the specification of JP-A-63-260491,
A monosheet-type lithographic printing plate using the DTR method is described in detail, in which aluminum is used as a support, a physical development nucleus layer is provided thereon, and a photosensitive silver halide emulsion layer is further provided thereon. According to this, after the lithographic printing plate is imagewise exposed and subjected to diffusion transfer development, the residual emulsion coating is removed by washing in warm water to produce a printing plate. Problems to be Solved by the Invention The present inventors have studied various processing methods for the mono-sheet type DTR type lithographic printing plate using aluminum as a support described in the above patent. I found a problem with this. That is, the lithographic printing plate is used as
It has been found that even if development is carried out using a developer such as that described in the Examples of Specification No. 0491, there is a problem that ink coverage is slow and sufficient printing durability cannot be obtained. An object of the present invention is to solve the above problems and provide a lithographic printing plate with improved ink loading and printing durability. Means for Solving the Problems The above object of the present invention is to provide a lithographic printing method using anodized aluminum as a support and having a physical development nucleus layer and a light-sensitive silver halide photographic emulsion layer thereon. This was achieved by developing the plate with a processing solution in which the content of sodium thiosulfate per liter did not exceed 2 g. [0011] The surface of the aluminum support used in the lithographic printing plate of the present invention may be roughened in order to improve adhesion with the photosensitive layer provided thereon and to improve water retention. be exposed. This surface roughening treatment (so-called graining) is performed by mechanical roughening treatment such as ball graining, wire graining, brush graining, etc., or by chemically dissolving aluminum with chloride, fluoride, etc. There are chemical surface roughening treatments and electrolytic surface roughening treatments performed by electrochemically dissolving aluminum. [0012] After the surface roughening treatment, it is necessary to perform an anodic oxidation treatment. Although conventionally well-known methods can be used for the anodizing treatment, sulfuric acid is used as the most useful electrolyte. Next, phosphoric acid, nitric acid, etc. are also useful electrolytes. Furthermore, JP-A-55-28
Also useful are the sulfuric and phosphoric acid mixtures disclosed in '400. [0013] In the sulfuric acid method, treatment is usually performed using direct current, but alternating current can also be used. The concentration of sulfuric acid is 5~
Used at 30% and 5-25 in the temperature range of 20-60℃
Electrolytic treatment is performed for 0 seconds to provide an oxide film of 1 to 10 g/m2 on the surface. Furthermore, the current density at this time is 1 to 2
0 A/dm2 is preferred. In the case of phosphoric acid method, 5 to 5
It is treated with a current density of 1-15 A/dm2 for 10-300 seconds at a concentration of 0% and a temperature of 30-60°C. [0014] It is preferable to perform a desmut treatment prior to the anodic oxidation treatment. That is, a roughened aluminum substrate was heated with 10-50% hot sulfuric acid (40-60%
℃) or dilute alkali (sodium hydroxide, etc.) to remove the smut attached to the surface. Further, after the anodic oxidation treatment, post-treatment can be performed if necessary. For example, a method of immersion treatment in an aqueous solution of polyvinylphosphonic acid disclosed in British Patent No. 1,230,447 is used. Also,
If necessary, it is possible to provide a hydrophilic polymer undercoat layer, but the choice is made depending on the properties of the photosensitive layer provided thereon. The physical development nuclei of the physical development nucleus layer used in the present invention may be those used in the known silver complex diffusion transfer method, such as colloids such as gold and silver, water-soluble salts such as palladium and zinc, and sulfides. Metal sulfides mixed with can be used. For details and manufacturing methods, see, for example, Focal Press, London and New York (1972), by Andre Lott and Edith Weide.
Photographic Silver Halide Diffusion Processes. Various hydrophilic colloids can be used as protective colloids in the photosensitive silver halide emulsion layer of the printing plate of the present invention. That is, various gelatins such as acid-treated gelatin, alkali-treated gelatin, gelatin derivatives, and grafted gelatin can be used, as well as polyvinylpyrrolidone, various starches, albumin, polyvinyl alcohol,
Hydrophilic polymer compounds such as gum arabic and hydroxyethyl cellulose can be contained. Hydrophilic colloids used include gelatin, gelatin derivatives,
Examples include polyvinyl alcohol, polyvinylpyrrolidone, etc., but it is preferable to use a hydrophilic colloid layer that does not substantially contain a hardening agent in order to facilitate the peelability of the hydrophilic colloid layer after physical development. The types of photosensitive silver halide emulsions used in the present invention include commonly used silver chloride, silver bromide,
It is selected from silver iodide, silver chlorobromide, silver chloroiodobromide, silver iodobromide, and the like. The type of emulsion may be either negative or positive type.
The special type described in No. 4 may also be used. These silver halide emulsions can be chemically or spectrally sensitized as required. As the developing agent used in the present invention, polyhydroxybenzenes and 3-pyrazolidinones are preferred, and these agents may be used in the form of a so-called agent-containing type, which is contained in the constituent layers of the plate material. The developing solution used in the present invention contains alkaline substances such as potassium hydroxide, sodium hydroxide, lithium hydroxide, tertiary sodium phosphate, or amine compounds, preservatives such as sodium sulfite, thickening agents,
For example carboxymethylcessulose, antifoggants such as potassium bromide, toning agents such as 1-phenyl-5-
Additives such as mercaptotetrazole, developer modifying agents, and polyoxyalkylene compounds can be included. The pH of the developer is usually about 10 to 14, preferably about 12 to 14, but the pretreatment (for example, anodization) conditions of the aluminum support of the lithographic printing plate used,
It varies depending on the photographic element, the desired image, the type and amount of various compounds in the developer, development conditions, etc. Wash-off for removing the gelatin layer can be carried out by rinsing with running water at a temperature of about 20 to 30°C. [0023] Example 1 An aluminum plate with a thickness of 0.30 mm was degreased with a 4% aqueous sodium hydroxide solution, and then a 10V alternating current was applied for about 20 minutes in an approximately 1% hydrochloric acid solution. After flowing for a minute, the aluminum plate was immediately anodized with 20% by weight sulfuric acid at a current density of 1 A/dm2 for 5 minutes, and then washed with water and dried to prepare an aluminum plate with an anodized surface. The following physical development nuclear solution was coated onto this support at a coating amount of 10 mg/m2 in terms of silver weight. The physical development nucleus is Carey L.
A gelatin solution was added to the silver sol prepared by method ea) to adjust the weight ratio of silver to gelatin to 1. The coating amount is 50mg/m2. After drying, a photosensitive silver halide emulsion layer having the following composition was coated and dried to prepare a photosensitive lithographic printing plate. Ortho-sensitized silver chloride emulsion (containing 1 mol% silver iodide, average grain size 0.3 μ), silver halide coverage expressed in silver nitrate 2 g/m2, gelatin coverage 0.4 g/m
2. After imagewise exposing the thus obtained lithographic printing plate from a negative film using a contact exposure meter,
After developing at 20° C. for 10 seconds with a developer substantially free of sodium thiosulfate according to the present invention and a developer containing sodium thiosulfate as a comparative developer as shown in Table 1, immediately rinse with running water for 30 seconds. The gelatin layer was washed off. The density of the image area of the photosensitive printing plate thus obtained was measured using a reflection densitometer. [0027] As can be seen from Table 1, the density of image silver obtained using the developing solution of the present invention in which the content of sodium thiosulfate does not exceed 2 g per liter is as follows: The amount of transferred silver decreased significantly when the content of sodium thiosulfate exceeded 2 g/l, and when the amount of sodium thiosulfate added in the developer was 8 g/l, It can be seen that it is almost impossible to obtain a transferred silver image. Example 2 After the lithographic printing plate of the present invention developed by the method of Example 1 was subjected to wash-off treatment, the following Table 2 was prepared before the plate surface was dry.
Apply the plate surface protection liquid with absorbent cotton, etc. and let it dry. The lithographic printing plates prepared in this way were run on a printing machine A.B. Dick 350CD (trademark of an offset printing machine manufactured by A.B. Dick), and the ink receptivity and printing durability were evaluated using the following methods. are shown in Table 3. [Table 2] [Table 3] [0032] Ink receptivity is evaluated by the number of prints until a print with good image density is obtained by simultaneously starting paper feed while bringing the ink roller into contact with the plate surface. did. The printing durability was evaluated by the number of sheets printed when printing became impossible due to either poor ink coverage in the image area or line skipping. As can be seen from the results in Table 3, 1 of the present invention
Lithographic printing plates treated with a developer containing no more than 2 g of sodium thiosulfate per liter have good ink transfer and extremely high printing durability; It can be seen that the ink coverage of the lithographic printing plates treated with a developer containing no more than 2 g of sodium thiosulfate was significantly reduced, and the printing durability was also significantly reduced as the amount of sodium thiosulfate added increased. [0034] As described above, it is possible to obtain a lithographic printing plate having good ink coverage and extremely high printing durability.

Claims (1)

[Claims] Claim 1: A lithographic printing plate using anodized aluminum as a support and having a physical development nucleus layer and a light-sensitive silver halide photographic emulsion layer thereon, the content of sodium thiosulfate per liter being 2 g. A method for processing a lithographic printing plate using a silver complex diffusion transfer method, which is characterized by developing with a processing solution that does not exceed .