JPH09244198A - Processing method for planographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain stabilization at the time of running processing by a dip developing system, to improve printing performance in a coating developing system and to stably develop a planographic printing plate by using a developer of a specified pH contg. ions of at least one kind of weak acid. SOLUTION: At the time of processing a planographic printing plate utilizing a silver salt diffusion transfer process, a developer of >=pH12 contg. ions of at least one kind of weak acid or its salt is used. The weak acid is an inorg. weak acid such as phosphoric or pyrophosphoric acid or an org. weak acid such as ascorbic acid or iminodiacetic acid. The counter ion of the salt is preferably Li, Na or K. The weak acid ion content of the developer is >=5mmol/l, preferably 20-100mmol/l.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a lithographic printing plate using a silver complex salt diffusion transfer method, and more particularly to a method for improving the printability in a dip development method and a coating and development method. .

[0002]

2. Description of the Related Art A lithographic printing plate utilizing a silver salt diffusion transfer method (DTR method), particularly a lithographic printing plate having a silver halide emulsion layer, is disclosed, for example, in U.S. Pat. Nos. 3,728,114 and 4,134,769.
No. 4, No. 4,160,670, No. 4,336,321, No. 4,501,81
1, No. 4,510,228, and No. 4,621,041.

The exposed silver halide crystal undergoes chemical development in the emulsion layer by development processing to become blackened silver, forming a hydrophilic non-image area. On the other hand, the unexposed silver halide crystals are solubilized by the silver complex salt forming agent in the developer, diffused to the physical development nucleus layer on the surface, and are reduced as an image-accepting image silver by the reducing action of the developing agent on the physical development nuclei. To deposit.

The DTR method has a mechanism in which chemical development and dissolution physical development simultaneously proceed in a single developing solution. Therefore, in order to obtain a good printed matter, it is important to balance the speed between the area where the chemical development which becomes the non-image area occurs and the area where the dissolution physical development becomes the image area.

[0007] For example, if the physical development by dissolution is prioritized over the chemical development, it may cause background smearing due to softening of the image and defective printing durability. On the contrary, if the chemical development is prioritized over the dissolution physical development, the printing durability becomes poor.

By the way, an automatic plate-making camera with a built-in developing tank is generally used as a plate-making processing method that has been realized for DTR lithographic printing plates. That is, after exposure with a plate making camera, the printing plate passes through the developer stored in the developing tank,
After passing, the developing solution remaining on the plate surface is removed by a mechanical method, for example, by passing it between squeezing rollers having a contact pressure, and then passed through a neutralizing solution tank to adjust the pH of the plate surface, Like the developing solution, the neutralizing solution remaining on the plate surface is removed by a mechanical method and dried to prepare a printing plate.

In the plate-making processing method as described above, when the number of processed sheets increases due to the running processing, there is a gap between the planographic printing plate processed in the initial stage and the planographic printing plate processed after a large number of sheets. , There was a difference in the printing performance of the lithographic printing plate.
It is considered that the characteristics of the processing solution are changed due to causes such as air oxidation of the processing solution and contamination with components eluted from the photosensitive material.

On the other hand, in recent years, there is a concern that the waste liquid of photographic light-sensitive material processing may adversely affect the global environment, and a developing system for reducing the amount of waste liquid of photographic processing is required, and a coating and developing system is proposed as a processing method therefor. ing. For example, JP-A-48-76603, JP-A-57-115549, JP-A-6-27680, JP-A-6-27682, and Japanese Patent Application No.
No. 334028 is disclosed.

Compared with the conventional immersion development method, the above-mentioned coating and development method can be processed with a small amount of the developing solution, so that it is possible to always develop with a new solution, and the problems due to the running processing as described above are less likely to occur. . On the other hand, since the amount of the developing solution used for development is limited, there is a problem that it is difficult to perform sufficient development. In particular, to reduce the amount of waste liquid,
The problem becomes remarkable when the coating amount of the developing solution is reduced.

That is, in the developing system having a coating mechanism, a new developing solution component is not supplied to the plate surface after coating and supplying, and the developing solution coating amount is reduced in order to reduce the waste liquid amount of the developing solution. However, due to slight fluctuations in developer characteristics, the balance between chemical development and physical development is likely to be lost, resulting in problems such as background stains and printing plates having poor printing durability.

Further, in the development processing apparatus having a coating mechanism, when the supplied coating liquid is non-uniform, or when the temperature changes during coating, the portion on the lithographic printing plate surface that has been treated is treated. There was a defect that the printing plate had different printing characteristics in some parts.

[0012]

SUMMARY OF THE INVENTION The object of the present invention is to provide DT
It is intended to provide a method for stably developing a lithographic printing plate utilizing the R method, and particularly to stabilize during running processing in a dip development method and improve printing performance in a coating and developing method. Another object of the present invention is to provide a coating and developing method which can obtain high printing performance even when treated with a small amount of developing solution in order to reduce the amount of waste liquid.

[0013]

SUMMARY OF THE INVENTION The above objects of the present invention are as follows.
A method for treating a lithographic printing plate utilizing a silver salt diffusion transfer method, which comprises at least one weak acid ion and p
A method for treating a lithographic printing plate, which comprises using a developer having H of 12 or more. And a method of processing a lithographic printing plate utilizing a silver salt diffusion transfer method using a development processing system having a coating mechanism, the developer containing at least one weak acid ion and having a pH of 12 or more. It was achieved by a method for treating a lithographic printing plate characterized by using

The developing device used in the processing method of the present invention is not particularly limited, but if roughly classified, it has an immersion developing device which has been generally used conventionally, and an application mechanism for applying a developing solution onto the photosensitive surface. It is a developing device. In the immersion developing apparatus, the photosensitive material is generally conveyed by a pair of conveying rollers that are driven, carried into a processing tank filled with a processing liquid, and then carried out of the post-processing tank for a certain period of time.

The volume of the processing tank is several liters to several tens of liters, although it depends on the size of the photosensitive material to be processed. The immersion time of the light-sensitive material is in the range of 5 seconds to 60 seconds, but is about 3 seconds in the processing method in which the processing tank described below is downsized. Preferably 7 seconds to 30
Seconds.

In the processing method in which the processing tank is miniaturized as described in JP-A-4-158360, the photosensitive material carried into the processing solution tank is carried out in a relatively short time, and the necessary developing time is required. Is designed to maintain the development reaction in the space even after being discharged from the processing liquid tank.

In the present invention, the development processing system having a coating mechanism is generally a method of coating and supplying a developing solution to the photosensitive surface coated with a silver halide emulsion layer.
For example, there are a liquid coating method, a dropping roller coating method, a dropping knife coating method, a spray coating method, a brush coating method and the like described in 8-76603. Further, a bar coating method using a bar coder (manufactured by ETO CHEMICAL APPARATUS Co.) and the above-mentioned Japanese Patent Application No. 5-334028.
Coating method described in Japanese Patent Publication No. 6-276
No. 80, No. 6-27682, a method of forming a developer pool between the nip of a pair of non-rotating rod-shaped members, passing a photosensitive material between the nip, and applying the developer is known. is there.

The coating amount of the developing solution on the lithographic printing plate is generally in the range of 10 to 80 ml, preferably 20 to 60 ml per square meter of the printing plate, and the developing time (from the coating of the developing solution to the developing solution Time until the development effect is stopped) is 3 seconds or more, preferably 3 to 10 seconds.

The developer used in the present invention has a pH of 12
That is all. In order to activate the developing agent and the silver halide solvent, a pH of 10 or more is possible, but in the DTR lithographic printing plate which requires mechanical strength for printing in the image part,
The pH is 12 or higher, preferably 13 or higher.

As described above, hydroxides such as potassium hydroxide and sodium hydroxide have been used as alkali agents in order to prepare a high pH developer. However, when a DTR lithographic printing plate is subjected to a multi-plate treatment by a dipping method or a coating and developing treatment, it is not possible to obtain a lithographic printing plate having good printing performance only with the above alkaline agent, and Even if the pH of the developer was further increased, a lithographic printing plate having sufficient printing performance and high printing durability could not be obtained.

In the case of the immersion developing method, when a large number of sheets are processed by running processing, the developing solution is contaminated and fatigued, and the printing performance is significantly reduced. On the other hand, in the developing method having a coating mechanism, the amount of the developing solution is limited, and thus the activity of the developing solution applied on the photosensitive surface is lowered in the developing process, and the printing performance is lowered.

As described above, each of the two developing methods has its own problems, and as a result of various studies by the present inventors, it was found that treatment with a developer containing a weak acid ion suppresses the deterioration of printing characteristics. It was

That is, the weak acid ion exhibits its function as a weak alkali only when the existing environment is in a neutral or acidic atmosphere. Therefore, the effect is exhibited only when applied to a high pH developer having a pH of 12 or more, such as a developer for a DTR lithographic printing plate. In particular, when only a small amount of developing solution is supplied onto the photosensitive surface, as in the coating and developing method, the development activity in the film during the progress of the development reaction is specifically reduced after it penetrates into the emulsion layer of the photosensitive material. It is thought to be suppressed and maintained.

By adding weak acid ions to the developing solution, a planographic printing plate having high printing durability which could not be obtained by simply increasing the pH of the developing solution or increasing the concentration of potassium hydroxide, sodium hydroxide or the like. I discovered that a print version would be realized.

Examples of the source of weak acid ions used in the present invention include weak acid and weak acid salt compounds. For example, phosphoric acid and its salts, pyrophosphoric acid and its salts,
Inorganic weak acid ions such as tripolyphosphoric acid and its salts, boric acid and its salts, carbonic acid and its salts, silicic acid and its salts, arsenic acid and its salts, vanadic acid and its salts, ascorbic acid and its salts, iminodiacetic acid and Organic weak acid ions such as salts thereof, glutamic acid and salts thereof, nitrilotriacetic acid and salts thereof, citric acid and salts thereof, propionic acid and salts thereof, and can be used alone or in combination of two or more. However, compounds that become silver halide solvents such as sulfites and thiosulfates are not included in the weak acid ions of the present invention.

The counter ion of the weak acid salt is not particularly limited, but lithium, sodium and potassium are preferable.

The content of weak acid ions in the developer used in the present invention is 5 mmol or more per liter, preferably 20 mmol to 100 mmol. The weak acid ion is added to the developer by adding a weak acid and a weak acid salt compound, which are ion generating sources, to the developer and then adjusting the pH to 12 or more with potassium hydroxide or sodium hydroxide. There is a method of adding a weak acid and a weak acid salt compound to a developer whose pH is adjusted to 12 or more with sodium hydroxide or potassium hydroxide. In the latter case, the pH is readjusted to 12 or higher if necessary after adding the weak acid and weak acid salt compounds.

The developing solution used in the present invention includes thickeners such as hydroxymethyl cellulose, carboxymethyl cellulose, polyethylene glycol, antifoggants such as potassium bromide, compounds described in JP-A-47-262201, hydroquinone, A developer such as methol or phenidone can be contained.

In carrying out the DTR method, for example, British Patent Nos. 1,000,115, 1,012,476 and 1,017,
No. 273, No. 1,042,477, etc., it is possible to incorporate a developer into a silver halide emulsion layer and / or an image receiving layer or another water-permeable hydrophilic colloid layer adjacent thereto. Has been done. Therefore, in such a material, the processing solution used in the developing step may be a so-called "alkali activating solution" containing no developer.

The silver halide emulsion of the lithographic printing plate used in the practice of the present invention may be silver chloride, silver bromide, silver chlorobromide, silver chloroiodide, silver chlorobromoiodide, etc. Silver is silver halide having 70 mol% or more. These silver halides are spectral sensitizers (spectral sensitizing dyes according to the light source and application, for example, camera type, laser light type, panchromatic type for color separation, etc.), gelatin hardener, coating aid, antifoggant , A plasticizer, a developer, a matting agent, and the like.

Binders for silver halide emulsions are the natural and / or synthetic binders commonly used for this purpose.
For example, gelatin, colloidal albumin, cellulose derivative and the like can be used.

An undercoat layer for improving adhesion and / or an undercoat layer for the purpose of preventing halation may be included on the lower side (support surface) of the silver halide emulsion layer.
Matting agents can also be included.

The support on which the silver halide emulsion layer is coated is
Paper, various films, plastic, paper coated with a substance for resin, metal, and the like can be used.

Physical Development The physical development nuclei used in each layer are
Metals such as antimony, bismuth, cadmium, cobalt, palladium, nickel, silver, lead and zinc, and their sulfides are well known as examples of this type of chemical. The physical development nucleus described in JP-A-5-265264 can also be used. Each layer of physical development may contain a developer,
It may contain a water-soluble binder.

The lithographic printing plate prepared according to the present invention can be converted or enhanced to be ink receptive by a compound as described in the specifications such as JP-B-48-29723 and US Pat. No. 3,721,539.

The printing method or the desensitizing liquid, the dampening liquid and the like to be used can be based on a commonly known method.

[0037]

EXAMPLES The present invention will be described below with reference to examples, but is of course not limited thereto.

Example 1 In a lithographic printing plate utilizing the DTR method, an antihalation layer containing silica particles, an ortho-sensitized silver chloride emulsion layer and a physical development nucleus layer were sequentially coated on an undercoated polyester film support. Using a width of 404 mm and a length of 500 mm,
A fine line image was exposed on the planographic printing plate with a plate making camera having an image reversing mechanism.

As the plate-making treatment liquid, the following developer A and neutralizing liquid were used. The processing temperature of the developing solution and the neutralizing solution is 30 each.
It adjusted so that it might be set to 25 degreeC and 25 degreeC.

Developer A Potassium hydroxide 15 g Sodium hydroxide 10 g Sodium sulfite 35 g N-aminoethylethanolamine 10 g Weak acid ions 60 mmol Water is added to make 1 liter. The liquid pH is 13.4.

Neutralizing solution 1 potassium phosphate 36 g sodium sulfite 2 g EDTA-Na 6.25 g Water is added to make 1 liter.

A commercially available DTR lithographic printing plate camera processor CP-414S (Mitsubishi Paper Mills Co., Ltd.) is used as an automatic developing device.
/ Dainippon Screen Mfg. Co., Ltd.). The developing solution (7 liters) was filled with the above developer, and the neutralizing solution (6 liters) was filled with the above neutralizing solution, and 100 plates were processed.

The planographic printing plate prepared by the above operation, 1
The plate and 100th plate were mounted on a Heidenberg TOK offset printing machine, the etching liquid was applied all over the plate surface, and printing was carried out using a dampening liquid for a DTR lithographic printing plate.

The printing evaluation was performed according to the following criteria. A: 100 micron fine lines are not missing even with 20000 sheets or more. B: 15,000 sheets lack 100 micron fine lines. C: 10000 sheets have 100 micron thin lines missing. D: 100 micron fine line missing on 7,000 sheets or less.

[0045]

[Table 1]

As is clear from Table 1, by adding weak acid ions to the developing solution in the immersion developing process, a lithographic printing plate excellent in printing characteristics (printing durability) can be obtained even in the multi-plate processing. It was

Example 2 A coating and developing treatment apparatus described in JP-A-6-27680 was prepared, the coating amount was adjusted to 40 ml per square meter, and the planographic printing plate and the treatment liquid shown in Example 1 were used. Processed. The obtained printing plate was printed according to Example 1 and evaluated. Table 2 shows the results.

[0048]

[Table 2]

From the above results, in the coating and developing method, when a small amount of developing solution is applied and supplied for development, by adding weak acid ions to the developing solution, high printing performance unpredictable from conventional developing solutions can be obtained. can get. Incidentally, the coating and developing system is different from the dipping system of Example 1, and from the standpoint of always treating with a new solution, a stable one can be obtained regardless of the number of treated sheets.

[0050]

INDUSTRIAL APPLICABILITY According to the present invention, a lithographic printing plate using a silver salt diffusion transfer method can be obtained which is more stable and has better printing characteristics than ever before. In particular, it is possible to stabilize the running process in the immersion development system and improve the printing performance in the coating and development system. Further, in the coating and developing system, high printing performance can be obtained even if a small amount of developing solution is used, so that the amount of waste liquid can be reduced.

Claims (2)

[Claims] 1. A method for treating a lithographic printing plate using a silver salt diffusion transfer method, which comprises using a developing solution containing at least one weak acid ion and having a pH of 12 or more. How to process printing plates. 2. A method for treating a lithographic printing plate using a silver salt diffusion transfer method by using a development treatment system having a coating mechanism, which comprises at least one kind of weak acid ion and has a pH of 12 or more. A method for treating a lithographic printing plate, which comprises using a certain developing solution.