JPH049295B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a lithographic printing plate using a silver complex diffusion transfer method for high-intensity, short-time exposure using a scanning exposure method. A lithographic printing plate in which a transferred silver image obtained by the silver complex diffusion transfer method can be immediately used for ink receptivity has already been developed in Japanese Patent Publication No. 48-30562 and Japanese Patent Application Laid-Open No.
53-21602, 1983-103104, 1984-9750, etc., and are well known. According to a typical implementation method of a silver complex diffusion transfer method suitable for manufacturing such a lithographic printing plate, a support is provided, and a subbing layer for preventing halation, a silver halide emulsion layer, and a physical development nucleus layer are formed on the support. When a photosensitive material consisting of the above is imagewise exposed and developed, the silver halide on which the latent image has been formed becomes blackened silver in the emulsion layer. At the same time, silver halide on which no latent image has been formed is dissolved by the action of a silver halide complexing agent contained in the processing solution and diffused onto the surface of the photosensitive material. The dissolved and diffused silver complex salt is deposited as a silver image on the physical development nuclei of the surface layer by the reducing action of the developing agent. The resulting silver image is subjected to development and, if necessary, a sensitization treatment to enhance its ink receptivity, and then placed in an offset printing press.
The ink image is transferred to the printed material. In conventional methods, the silver halide emulsion layer is
By merocyanine dye, cyanine dye, etc.
It was spectrally sensitized to have a maximum sensitivity in the green region around 550 nm, and exposed for several seconds to several tens of seconds using a plate-making camera using a normal light source such as a tungsten light source. However, in the above conventional method,
Even though the above-mentioned lithographic printing plate originally had excellent sharpness and resolution, it had a limit of about 133 lines/inch. Moreover, if one tries to obtain color printed matter from a color original, there are still problems in that not only the resolution is insufficient, but also the production of printing plates and plate-making operations are complicated. Today, as a method to solve the above-mentioned problems, various types of laser light such as neon-helium lasers, light emitting diodes (LEDs), cathode ray tubes (CRTs), etc. are used to provide extremely high illuminance and short periods of time (10 ^-5 seconds or less). A possible method is to apply flash exposure using a scanning exposure method and perform direct plate making. It is known that this type of exposure method causes so-called high-intensity reciprocity failure, resulting in a decrease in sensitivity, gradation, etc., and may also worsen printing characteristics such as background smearing and silver image scattering. many. In particular, in the lithographic printing plates as described above, the above-mentioned drawbacks become more noticeable because the amount of silver per unit area is smaller than that in ordinary light-sensitive materials using a scanning exposure method. For the above-mentioned exposure light source, it is important to use a sensitizing dye that matches the wavelength of light emitted by the light source. JP-A-53-21601 describes the use of betaine or anionic cyanine sensitizing dyes as offset printing plates with high sensitivity and improved printing characteristics; It is also stated that silver or silver iodobromide emulsions are preferred. However, even when the lithographic printing plate described in this patent was made and printed by scanning short-time exposure, it was not possible to obtain satisfactory results as described below. An object of the present invention is to provide a lithographic printing plate using a silver complex diffusion transfer method that is highly sensitive to flash exposure using a scanning exposure method and has good printing characteristics. The object of the present invention is to provide a lithographic printing plate having a silver halide emulsion layer on a support and a physical development nucleus layer thereon, wherein the silver halide emulsion layer comprises two
Silver chloride, which may contain up to mol % silver iodide, comprises at least 80 mol % silver halide, and the underside of the emulsifier is such that the reflectance of the exposed light is not more than 10%. This was achieved by a lithographic printing plate using a silver complex diffusion transfer method for a flash exposure light source using a scanning exposure method, which is characterized by anti-halation. The present invention will be explained in detail below. In low-light long exposure like conventional camera exposure, as described in the above-mentioned Japanese Patent Application Laid-Open No. 53-21601,
Generally, as the content of silver bromide and silver iodide increases, the sensitivity increases. However, printing plates made by scanning flash exposure have the drawbacks of background smearing and the tendency for fine line silver images to be removed. Emulsions containing at least 80 mol %, preferably 90 mol % of silver chloride with less silver iodide provide higher sensitivity in scanning flash exposure, and the above-mentioned printing defects can be improved to some extent. , it was still not satisfactory. This drawback was overcome by the discovery that printing properties in scanning flash exposure could be improved by antihalation layers. As is well known, the antihalation layer improves resolution,
The silver halide emulsion layer that contains cyanine sensitizing dye until sufficient sensitivity can be obtained improves sharpness, but the sensitizing dye improves resolution,
Since the sharpness is considerably improved, the antihalation layer, which normally causes a decrease in sensitivity, can be set to the minimum necessary density. However, with such a low-density antihalation layer, the silver chloride-based emulsion described above can reduce the sacrifice in sensitivity, but has the drawback of insufficient printing properties. It was hot. The silver halide emulsion of the lithographic printing plate of the present invention preferably contains 80 mol% or more of silver chloride, such as silver chloride, silver chlorobromide, silver chloroiodide, silver chlorobromoiodide, etc. containing 0.1 to 2 mol of silver iodide. is 90 mol% or more silver halide. The average grain size of these silver halide grains is preferably
The range is from 0.2 to 0.6 microns, but ranges other than this can also be used. Furthermore, more than 90% of all silver halide grains are within ± the average grain size.
Preferably, it is a monodispersed emulsion having a grain size within 30%. Although silver halide grains are preferably substantially cubic or tetradecahedral, silver halide having other crystal habits may also be used. The binder used in the silver halide emulsion of the lithographic printing plate of the present invention is usually gelatin.
One or more hydrophilic polymer binders such as gum arabic, polyvinyl alcohol, polyvinylpyrrolidone, carboxymethyl cellulose, polyacrylamide, styrene-maleic anhydride copolymer, polyvinyl methyl ether-maleic anhydride copolymer, etc. It can also be replaced. Furthermore, an aqueous vinyl polymer dispersion (latex) can also be used. Salts of iridium, cobalt, nickel, rhodium, palladium, platinum, etc. can be used at any point in the preparation of the silver halide emulsion. The silver halide emulsion uses a spectral sensitizing dye depending on the wavelength of the light source. Preferred sensitizing dyes are the betaine or anionic cyanine sensitizing dyes described in JP-A-53-21601, and typical ones are those represented by the following general formula (). General formula () In formula (), R ₁ to _{R 2} are each an alkyl group (e.g., methyl group, ethyl group, propyl group, butyl group, β-sulfoethyl group, γ-sulfopropyl group, γ-sulfobutyl group, vinylmethyl group, β
-carboxyethyl group, γ-carboxypropyl group, δ-carboxybutyl group, etc.), alkenyl group,
Represents an aryl group, an aralkyl group, and R ₁ and
At least one of R ₂ is a substituted alkyl group having a sulfo group or a carboxyl group. _R3 ～ _R6
each represents a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a hydroxyl group, an alkoxycarbonyl group, or a halogen atom, and R ₃ and R ₄ or R ₅ and R ₆ may form a benzene ring. R ₇
represents an alkyl group, an aryl group, or an aralkyl group. Y ₁ and Y ₂ each represent an O atom, an S atom, a Se atom, or N-R ₈ (R ₈ is a lower alkyl group). X
represents a cation such as hydrogen, alkali metal, ammonium, etc. Represents m or 1 or 0. Next, typical sensitizing dyes used in the present invention are illustrated. The sensitizing dye used in the present invention can be synthesized by methods known to those skilled in the art. It can be added to the silver halide emulsion at any time before the emulsion is coated. The amount added can vary within a wide range, but good results are in the range from 5.times.10.sup. ^-5 to 1.times.10.sup. ^-2 mol per mole of silver halide. The optimum amount to be added varies depending on the conditions of the silver halide emulsion, such as the halogen composition, the average grain size of the silver halide grains, and the crystal habit. The silver halide emulsion layer can contain other conventional additives such as coating aids, antifoggants, hardeners, matting agents (water retention agents), and developing agents. It is necessary to provide the underside of the silver halide emulsion layer with measures to prevent halation so that the reflectance of the scanning flash exposure light as described above is 10% or less. Such a means may be an undercoat layer which also serves as an antihalation layer, and the support may be colored. As the colorant, known colorants such as dyes and pigments can be used, and carbon black is particularly preferred. The antihalation undercoat layer can also contain a matte increaser, a developing agent, and the like. The lithographic printing plate of the present invention has an image-receiving layer containing physical development nuclei on its surface. As physical development nuclei, known ones such as metals such as antimony, bismuth, cadmium, cobalt, palladium, nickel, silver, lead, zinc, and their sulfides can be used. The image-receiving layer does not need to contain hydrophilic colloids, and may include gelatin, carboxymethylcellulose, gum arabic, sodium alginate, hydroxyethyl starch, dextrin, hydroxyethylcellulose, polystyrene sulfonic acid, a copolymer of vinylimidazole and acrylamide, Hydrophilic colloids such as polyvinyl alcohol can be included, preferably in amounts of up to 0.1 grams per square meter. Hygroscopic substances, such as wetting agents such as sorbitol, glycerol, etc., may be present in the image-receiving layer. Furthermore, the image-receiving layer may also contain pigments for preventing scumming such as barium sulfate, titanium dioxide, china clay and silver, developing agents such as hydroquinone, and hardening agents such as formaldehyde. The support may be, for example, paper, film, such as 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, metal, or metallized paper. Or it can be a support for a metal/paper laminate. Paper supports coated on one or both sides with an alpha-olefin polymer, such as polyethylene, are also useful. The DTR processing solution used in the present invention includes alkaline substances such as sodium hydroxide, potassium hydroxide, lithium hydroxide, trisodium phosphate, etc., sulfites as preservatives, silver halide solvents such as thiosulfate, etc. , thiocyanates, cyclic imides, thiosalicylic acid, amines, etc., thickening agents such as hydroxyethyl cellulose, carboxymethyl cellulose, antifoggants such as potassium bromide, 1-
Phenyl-5-mercabutotetrazole, JP-A-Sho
47-26201, developers such as hydroquinone, 1-phenyl-3-pyrazolidone,
Development modifiers such as polyoxyalkylene compounds,
It can contain onium compounds and the like. In carrying out the silver complex diffusion transfer method, for example, British Patent No. 1000115, British Patent No. 1012476, British Patent No.
As described in specifications such as No. 1017273 and No. 1042477, a developer is mixed into the silver halide emulsion layer and/or the image receiving layer or other water permeable layer adjacent thereto. . Therefore, for such materials, the processing solution used in the development step may be a so-called "alkaline activating solution" that does not contain a developer. The ink receptivity of the lithographic printing plates produced according to the present invention can be changed or enhanced with compounds such as those described in Japanese Patent Publication No. 48-29723 and US Pat. No. 3,721,539. The printing method, the desensitizing liquid, the dampening liquid, etc. used can be any commonly known method. The present invention will be explained below with reference to examples, but of course it is not limited thereto. Example 1 A matting layer containing silica particles with an average particle size of 5 μm was provided on one side of a subbed-treated polyester film support, and carbon black was applied on the other side in an amount that gave a light reflectance of 3% at 633 nm. including,
20% by weight of photographic gelatin average particle size 7μ
An antihalation undercoat layer containing m silica powder (adjusted to pH 4.0) and an average particle size after being chemically sensitized.
77μm silica powder to photographic gelatin
A spectrally sensitized high-sensitivity silver halide emulsion layer (adjusted to pH 4.0) containing % by weight was provided. Gelatin for the undercoat layer was coated at a rate of 3.5 g/m ² , gelatin for the emulsion layer was coated at a rate of 0.8 g/m ² , and silver halide was coated at a rate of 1.0 g/m ² in terms of silver nitrate. The undercoat layer and emulsion layer contain formalin as a hardening agent in an amount of 5.0 mg/g gelatin. After drying and heating at 40℃ for 14 days, on top of this emulsion layer,
The core coating liquid described in Example 2 of JP-A-53-21602 (polymer is No. 3 copolymer of acrylamide and imidazole, hydroquinone is 0.8 g/m ²
) is coated and dried to produce a lithographic printing plate. The silver halide emulsion had 4 x 10 ^-6 mol of rhodium chloride added per mol of silver halide during physical thermal formation, and had an average grain size of 0.40 microns. Chemical sensitization is 3×10 ^-5 per mole of silver halide.
moles of sodium thiosulfate, 4 x 10 ^-5 moles
The experiment was carried out using HAucl ₄ , and the spectral sensitizing dye used was Exemplified Dye (2) in an amount of 3×10 ⁻⁴ mol per mol of silver halide. In this way, the halogen composition of the silver halide emulsion was changed as follows, and the lithographic printing plates A to
D was produced. Values represent mol%.

[Table] Using a neon-helium laser oscillator (Direct Scanagraph SG-606 manufactured by Dainippon Screen), these samples were applied to the above lithographic printing plate using a contact screen (manufactured by Dainippon Screen) using a neutral gray wedge. was exposed to light for 10 ^-5 seconds. After exposure, development was performed using the following diffusion transfer developer. <Transfer developer> Water 700ml Potassium hydroxide 20g Anhydrous sodium sulfite 50g 2-mercaptobenzoic acid 1.5g 2-methylaminoethanol 15g Make 1 with water. After the development process, the original plate was passed between two squeezing rollers to remove excess developer, and immediately treated with a neutralizing solution having the following composition at 25°C for 20 seconds, and the excess liquid was removed using a squeezing roller. , dried at room temperature. <Neutralizing solution> Water 600ml Citric acid 10g Sodium citrate 35g Colloidal silica (20% liquid) 5ml Ethylene glycol 5ml Add water to bring the total volume to 1. Table 1 shows the sensitivity, sharpness, and resolution of each lithographic printing plate. Sensitivity is the amount of exposure required to prevent the formation of transfer deposits, and is expressed as a relative value with Sample A set as 100. Also, the resolution is 100, 133, for gray contact screen.
Use 150, 175 and 200 lines/inch,
The fine halftone dots (5% dots) could be reproduced firmly and clearly, and were given a rating of 1 (100 lines/inch) to 5 (200 lines/inch) based on the number of screen lines. <Degreasing liquid> Water 600ml Isopropyl alcohol 400ml Ethylene glycol 50g 3-Mercapto-4-acetamide-5-n-
Heptyl-1,2,4,-triazole 1g <Moisturizing liquid> O-phosphoric acid 10g Nickel nitrate 5g Sodium sulfite 5g Ethylene glycol 100g Colloidal silica (20% liquid) 28g Add water to make 2. The printing machine is AB Deitsku 350CD (A.
A trademark of an offset printing machine manufactured by B.DicK was used. The printing durability was evaluated based on the number of sheets that could not be printed due to occurrence of scumming or silver flying, and is shown in the right column of Table 1 based on the following criteria.

[Table] Each lithographic printing plate made with the contact screen showing the resolution evaluation shown in Table 1 was mounted on an offset printing machine, the following desensitizing liquid was applied all over the plate surface, and the following dampening liquid was used to print. I did this. 1 4,000 sheets or more 2 4,000 to 6,000 sheets 3 6,000 to 8,000 sheets 4 8,000 to 10,000 sheets 5 10,000 sheets or more The lithographic printing plate D of the present invention has sufficiently high sensitivity to neon-helium laser light compared to B and C. Example 2 In Sample D of Example 1, the amount of carbon black in the undercoat layer was adjusted to have a light reflectance of 8%, 21%, and 633 nm, respectively.
Lithographic printing plates prepared at 37% or 52% were similarly tested. The results of resolution and printing durability are shown in Table 2.

[Table] For reference, Table 3 shows the results when printing plates E to H were exposed to light for 30 seconds using a normal plate making camera.

[Table] Example 3 A light-emitting diode exposure device (10 ^-7 seconds) was applied to a lithographic printing plate prepared in the same manner as in Example 1 except that sensitizing dye (1) in Example 1 was replaced with sensitizing dye (6). When exposure was performed using the same method and evaluation was performed using the method of Example 1, similar results were obtained. Example 4 Lithographic printing plate 4 prepared in the same manner as in Example 1 except that the sensitizing dye (2) in Example 1 was replaced with the dye below.
The seeds were exposed to light using an argon laser oscillation device (10 ^-5 seconds) and tested using the method of Example 1.
Similar results were obtained.

Claims (1)

[Claims] 1 A lithographic printing plate having a silver halide emulsion layer on a support and a physical development nucleus layer thereon, wherein the silver halide emulsion layer is a chloride emulsion layer which may contain up to 2 mol% of silver iodide. At least 80 mol% silver
A flash exposure light source using a scanning exposure method, characterized in that the underside of the emulsion layer is provided with antihalation so that the reflectance of exposed light is 10% or less. A lithographic printing plate that utilizes the silver complex diffusion transfer method.