JPH0447302B2 - - Google Patents

Description

[Detailed description of the invention]

(A) Industrial Application Field The present invention relates to a lithographic printing plate using a silver complex diffusion transfer method suitable for using laser light, particularly semiconductor laser light, as a light source. (B) Prior art and its problems A lithographic printing plate in which a transferred silver image obtained by the silver complex diffusion transfer method can be immediately used as ink receptivity has already been published in Japanese Patent Publication No. 48-30562 and Japanese Patent Application Laid-Open No.
53-21602, 1982-103104, 1982-9750, etc., and are well known. According to a typical implementation method of the silver complex diffusion transfer method suitable for the plate making method of 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 is imagewise exposed and developed, the silver halide on which a 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 with a normal light source such as a tungsten light source. However, the above-mentioned conventional method has limitations even though the lithographic printing plate originally has excellent sharpness and resolution. 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 one method for solving the above-mentioned problems, plate making using laser light has been proposed. For example, US Pat. No. 4,501,811,
Unexamined Japanese Patent Applications 1986-71055, 1983-75838, 1983-
100148 and the like disclose a lithographic printing plate for use with a helium-neon laser or a light emitting diode. As described in these patent specifications, in these lithographic printing plates using the silver complex diffusion transfer method, the surface physical development nucleus layer affects the spectral sensitization, resulting in the sensitivity to the target laser light being reduced. or deteriorate storage stability,
In addition, as a result of forming a soft transferred deposited silver image by silver complex salt diffusion transfer development, sharpness and resolution decrease, and furthermore, background stains occur and the silver image comes off during printing, resulting in insufficient printing durability. Because of the lack of strength and sluggishness, it is difficult to produce a lithographic printing plate of the desired high quality. Therefore, a sensitizing dye that meets these requirements must not only have sufficiently high sensitivity at the wavelength of laser light, but also have good storage stability and the ability to form a high-contrast transferred deposited silver image. It must completely satisfy the following requirements, including the absence of adverse effects such as scumming, and the ability to form strong transferred deposited silver that cannot be removed during printing even with minute amounts of silver. Various types of lasers are known, but
A method using a helium-neon, argon, or other laser light source as a scanner type light source provides high output, but has disadvantages such as large and expensive equipment and low power consumption efficiency. On the other hand, semiconductor lasers have advantages such as being small, inexpensive, easy to modulate, and have a long life. Semiconductor lasers include Ga/As/P; Ga/Al/As; Ga/As;
Semiconductors of systems such as In/P; In/As are used,
The wavelength of this laser light is generally longer than 700 nm, and in particular there are many wavelengths longer than 750 nm. Photosensitive planographic printing plates that use such long-wavelength semiconductor laser light as a light source for image exposure are disclosed, for example, in Japanese Patent Application No. 60-244880, Japanese Patent Application No. 60-245059-245062, Japanese Patent Application No. 60-254202, Japanese Patent Application No. 60-254202, No. 1986-280426, No. 1983-
It is described in the specification of No. 284046, etc. However, silver halide photographic materials containing sensitizing dyes with maximum spectral sensitivity at wavelengths longer than 700 nm are generally known to have poor storage stability, especially those containing a physical development nucleus layer adjacent to the emulsion layer. In the case of lithographic printing plates, this drawback is significant, and moreover, they may exhibit low sensitivity or low printing durability immediately after production. One of the reasons for this is thought to be that the sensitizing dye is desorbed and decomposed by other substances in the silver halide emulsion layer. According to the research of the present inventors, these drawbacks are:
For example, it was found that the larger the ratio of binder (mainly gelatin) to silver halide in the silver halide emulsion layer, the better the problem. There is naturally a limit because it causes Therefore, a solution is needed that does not adversely affect such printability. Furthermore, it is also necessary to obtain even higher sensitivity to semiconductor laser light. (C) Purpose of the Invention The purpose of the present invention is to provide a lithographic printing plate using a silver complex diffusion transfer method that has high sensitivity to low-output semiconductor laser light, high printing durability, and excellent storage stability. That's true. (D) Structure of the Invention The above object of the present invention is to provide a lithographic printing plate having on a support at least a silver halide emulsion layer containing a sensitizing dye having maximum spectral sensitivity in a wavelength range longer than 700 nm and a physical development nucleus layer. In the emulsion layer,
This was achieved using a lithographic printing plate characterized by containing a water-soluble polymer having a carboxyl group and an average molecular weight of 20,000 or less. The present invention will be further explained in detail below. The polymer used in the present invention is characterized by being a water-soluble polymer containing a carboxyl group (including its salt or acid anhydride) and having a low molecular weight, that is, a number average molecular weight of 20,000 or less. Such water-soluble polymers are olefinically unsaturated compounds containing carboxyl groups as monomer units, such as acrylic acid, methacrylic acid, sorbic acid, maleic acid, fumaric acid, itaconic acid,
It can be a homopolymer of citraconic acid or the like, or a copolymer of an olefinic unsaturated compound containing a carboxyl group as a monomer unit and a vinyl monomer copolymerizable therewith. Examples of the vinyl monomer for obtaining the copolymer used in the present invention include styrene, styrene substituted with alkyl such as methyl and ethyl, styrene substituted with alkoxy such as methoxy and ethoxy, styrene derivatives such as styrene substituted with halogen such as chlor, Ethylenically unsaturated monoolefins such as ethylene, propylene, butylene, isobutylene,
Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate, methyl, ethyl, propyl, isobutyl, n-butyl, n-octyl , alkyl esters of acrylic acid or methacrylic acid such as 2-ethylhexyl, derivatives of acrylic acid or methacrylic acid such as acrylonitrile, methacrylonitrile, acrylamide, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, vinyl Examples include vinyl compounds such as methyl ketone, vinylhexyl ketone, and methyl isopronyl ketone, N-vinyl compounds such as N-vinylpyrrole, N-vinylcarbazole, and N-vinylpyrrolidone, and vinylnaphthalenes. The copolymer component may include different types of olefinic unsaturated compounds. The amount of olefinically unsaturated compounds containing carboxyl groups in the copolymer is about 10% by weight or more, preferably about 20% by weight or more. This carboxyl group may be a salt of sodium, potassium, ammonium, etc., or an acid anhydride (for example, maleic anhydride). The water-soluble polymer used in the present invention has a number average molecular weight ( _o ) of 20,000 or less, especially about
A range of 1000 to about 10000 is preferred. The water-soluble polymer used in the present invention can be easily produced by a known production method such as solution polymerization, and can also be obtained as a commercially available product. A specific example is shown below. In addition, the polymerization ratio is weight%
It is shown in

【table】

[Table] ｜ ｜

COOH COOCH ₂ CH ₃

[Table] The water-soluble polymer used in the present invention is about 0.2 to about 100 g, preferably about 1 g, per mole of silver halide.
It is best to add in the range of ~50g. The addition time may be any time up to the coating of the silver halide emulsion. Since the water-soluble polymer inhibits diffusion transfer development seen in high molecular weight polymers such as gelatin, it is not necessary to reduce the amount of gelatin in the silver halide emulsion. You may reduce the amount. The sensitizing dyes having maximum spectral sensitivity in the wavelength region longer than 700 nm used in the present invention are disclosed in, for example, U.S. Pat.
Same No. 3482978, Same No. 3552974, Same No. 3573921,
It can be described in the specifications of the same No. 3582344, the same No. 3623881, etc. Preferably, for example, the following general formulas () to ()
A dye represented by is used. In general formulas () to (), Z ₁ and Z ₂ are
Each may be the same or different, and each represents an atomic group necessary to form a 5- or 6-membered nitrogen-containing heterocycle. R ₁ and R ₂ may be the same or different, and each represents an alkyl group or an alkenyl group. R ₃ represents an alkyl group, an alkenyl group, or an aryl group. R ₄ to _{R 10} may be the same or different, and each represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group, or an alkoxy group. However, R ₆ and R ₇ or R ₈ and R ₉ can also be linked to each other to form a 5- or 6-membered ring. R ₁₁ and R ₁₂ may be the same or different and each represents an alkyl group or an aryl group, and R ₁₁ and R ₁₂ are connected to each other to form a 5- or 6-membered group.
It is also possible to form a membered ring. Y is a sulfur atom,
Represents an oxygen atom, N-R ₁₃ (R ₁₃ is an alkyl group). X represents an acid anion. l, m, n, p and q each represent 1 or 2. Specific examples of Z ₁ and Z ₂ include thiazole, benzithiazole, naphtho[1,2-d]thiazole, naphtho[2,1-d]thiazole, naphtho[2,3-d]thiazole, selenazole, and benzoselenium. sol, naphtho[2,1-d]selenazole, naphtho[1,2-d]selenazole, oxazole, benzoxazole, naphtho[1,2
-d]oxazole, naphtho[2,1-d]oxazole, naphtho[2,3-d]oxazole,
Examples include nitrogen-containing heterocycles such as 2-quinoline, 4-quinoline, 3,3-dialkylindolenine, imidazole, benzimidazole, naphtho(1,2-d]imidazole, and pyridine.
These heterocycles include alkyl groups (e.g., methyl, ethyl, butyl, trifluoromethyl, etc.),
Aryl groups (e.g., phenyl, tolyl, etc.), hydroxy groups, alkoxy groups (e.g., methoxy,
ethoxy, butoxy, etc.), carboxy groups, alkoxycarbonyl groups (e.g., methoxycarbonyl, ethoxycarbonyl, etc.), halogen atoms (e.g., fluorine, chlorine, bromine, iodine), aralkyl groups (e.g., benzyl, phenethyl, etc.), cyano It may have one or more substituents such as a group or an alkenyl group (eg, allyl). In R ₁ and R ₂ , the alkyl group is methyl,
Lower alkyl groups such as ethyl, propyl, butyl,
Hydroxyalkyl groups such as β-hydroxyethyl and γ-hydroxypropyl, alkoxyalkyl groups such as β-methoxyethyl and γ-methoxypropyl, and acyloxyalkyl groups such as β-acetoxyethyl, γ-acetoxypropyl and β-benzoyloxyethyl. , carboxyalkyl groups such as carboxymethyl, β-carboxyethyl, alkoxycarbonylalkyl groups such as methoxycarbonylmethyl, ethoxycarbonylmethyl, β-ethoxycarbonylethyl, β-sulfoethyl, γ
Examples of the alkenyl group include sulfoalkyl groups such as -sulfopropyl and -sulfobutyl, aralkyl groups such as benzyl, phenethyl and sulfobenzyl, and allyl. Examples of R ₃ include alkyl groups and alkenyl groups as described above for R ₁ and R ₂ , as well as aryl groups such as phenyl, tolyl, methoxyphenyl, chlorophenyl, and naphthol. R ₄ to _{R 10} are a hydrogen atom, a halogen atom (e.g. chlorine, bromine, iodine, fluorine), an alkyl group as described for R ₁ and R ₂ , an aryl group as described for R ₁ and R ₂ It is an alkoxy group having alkyl (ie, OR ₁ group), and the 5- or 6-membered ring formed by R ₆ and R ₇ or R ₈ and R ₉ may be substituted with a lower alkyl group or the like. R ₁₁ and R ₁₂ are
R ₁ and R ₂ represent an alkyl group or an aryl group as described above, and R ₁₁ and R ₁₂ can be linked to each other to form a 5- or 6-membered ring. Examples of R ₁₃ include the alkyl groups described for R ₁ and R ₂ . Examples of the acid anion of It does not exist if . Specific examples of the sensitizing dye used in the present invention are illustrated below. 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 coating the emulsion. The amount added can vary within a wide range, but good results are in the range 1.times.10.sup. ^-6 to 1.times.10.sup. ^-3 mol per mol 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 of the lithographic printing plate of the present invention can be silver chloride, silver bromide, silver chlorobromide, silver chloroiodide, silver chlorobromoiodide, etc., and preferably silver chloride is a halogen containing 50 mol% or more. It is chemical silver. The average particle size of these silver halide grains is preferably in the range of 0.2 to 0.8 microns, but ranges other than this can also be used. Furthermore, silver halide accounts for 90 of the total number of grains.
A monodispersed emulsion having a grain size within ±30% of the average grain size is preferred. 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, and gelatin is partially composed of starch, hydroxyethylcellulose, gum arabic, polyvinyl alcohol, polyvinylpyrrolidone, carboxymethylcellulose, and polyacrylamide. , styrene-maleic anhydride copolymer, polyvinyl methyl ether-maleic anhydride copolymer, and the like can also be substituted with one or more hydrophilic polymer binders. Furthermore, an aqueous vinyl polymer dispersion (latex) can also be used. These binders are at most twice the amount of silver halide, preferably
Up to 1.5 times (weight ratio) is desirable. Silver halide emulsions can be sensitized in a variety of ways when they are manufactured or coated. Chemically sensitized by methods well known in the art, for example with sodium thiosulfate, alkylthioureas, or with gold compounds such as gold rhodan, gold chloride, or a combination of both. is preferred. In addition, by using compounds of metals belonging to groups of the periodic table, such as salts of cobalt, nickel, rhodium, palladium, iridium, platinum, etc., at any stage in the production of silver halide emulsions, particularly high It is possible to obtain characteristics favorable for printing plates for direct plate making, such as sensitivity, high sharpness, and high resolution. The amount added is 10 ^-8 to 1 mole of silver halide.
It is in the range of 10 ⁻³ mol. The silver halide emulsion layer may contain other additives such as coating aids, hardeners,
It can contain conventional additives such as antifoggants, matting agents (water retention agents), and developing agents. Below the silver halide emulsion layer (on the support side), an undercoat layer is provided to improve adhesion, or an undercoat layer that may contain a coloring agent such as carbon black or a compound that absorbs light of 700 nm or more is provided. This layer can also contain a developing agent, a matting agent, and the like. The image-receiving layer is provided above the silver halide emulsion layer, that is, as the outermost surface layer. Physical development nuclei include antimony, bismuth,
cadmium, cobalt, palladium, nickel,
Known metals such as silver, lead, and zinc and their sulfides can be used. The image receiving layer contains gelatin, carboxymethyl cellulose, gum arabic, sodium alginate, hydroxyethyl starch, dialdehyde starch, dextrin, hydroxyethyl cellulose, polystyrene sulfonic acid,
It may contain one or more hydrophilic colloids such as a copolymer of vinylimidazole and acrylamide and polyvinyl alcohol. The hydrophilic colloid contained in the image-receiving layer is preferably 0.5 g/m ² or less. Hygroscopic substances such as humectants such as sorbitol, glycerol, etc. may be present in the image-receiving layer. Furthermore, the image-receiving layer contains pigments for preventing scumming such as barium sulfate, titanium dioxide, china clay, and silver, developing agents such as hydroquinone, and formaldehyde and dichloro-S-
Curing agents such as triazines may also be included. The support may be, for example, paper, film such as cellulose acetate film, polyvinyl acetal film, polystyrene film, polypropylene film, polyethylene terephthalate, or a composite film such as polyester, polypropylene or polystyrene film coated with polyethylene film, metal, 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. These supports may contain a compound capable of preventing halation. The developing solution used in the present invention includes alkaline substances such as sodium hydroxide, potassium hydroxide, lithium hydroxide, trisodium phosphate, etc., sulfite as a preservative, and silver halide solvents such as thiosulfate. , thiocyanates, cyclic imides, thiosalicylic acid, amines, etc., thickening agents such as hydroxyethyl cellulose, carboxymethyl cellulose, antifoggants such as potassium bromide, 1-
Phenyl-5-mercaptotetrazole, JP-A-Sho
Compounds and developers described in 47-26201, such as hydrodoquinone, 1-phenyl-3-pyrazolidone,
Development modifiers such as polyoxyalkylene compounds, onium compounds, etc. can be included. In carrying out the silver complex diffusion transfer method, for example, British Patent No. 1000115, British Patent No. 1012476, British Patent No.
1017273, No. 1042377, etc., it has been practiced to incorporate a developer 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 liquid used in the development step may be a so-called "alkaline activating liquid" which 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. (E) Examples The present invention will be explained below using examples, but it is of course 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 polyester film support, and a matting layer containing silica particles with an average particle size of 5 μm was provided on the other side, and carbon black was provided on the opposite side, and 20% by weight of photographic gelatin was added to the support. An undercoat layer (adjusted to pH 4.5) containing silica powder with an average grain size of 7 μm and a silver halide emulsion layer (adjusted to pH 4.5) chemically sensitized with a gold compound and hypo are provided. The silver halide emulsion contains 5 x 10 ^-6 mol of rhodium chloride per mol of silver halide during physical ripening, and has an average grain size of 0.4 microns, with all grains within ±30% of the average grain size. More than 90% of the particles were distributed as substantially cubic silver chloride crystals. Gelatin for the undercoat layer was coated at a rate of 3.0 g/m ² , gelatin for the emulsion layer was coated at a rate of 1.0 g/m ² , and silver halide was coated at a rate of 1.2 g/m ² in terms of silver nitrate. The undercoat layer and emulsion layer contained formalin as a hardening agent in an amount of 5.1 mg/g gelatin. After drying and heating at 40°C for 14 days, the core coating liquid for plate No. 11 in Example 1 of JP-A-54-103104 was similarly prepared on top of this emulsion layer. , apply. The silver halide emulsion layer contains the above-mentioned sensitizing dye (25) in an amount of 1×10 ^-4 mole per mole of silver halide. This is designated as blank sample A. Samples B to H were prepared by adding polymers shown in Table 1 to the silver halide emulsion of blank sample A. The amount of polymer added was 1 silver halide in each case.
The amount was 10 g per mole. For these samples, immediately after production (however, at 35℃)
After being stored at 50° C. and 80% relative humidity for 4 days, it was exposed to light as follows. A dark red filter (Fuji Photo Film SC-70) that transmits light with wavelengths longer than approximately 700 nm was attached to the light source, and each sample was exposed to flash light for 10 ^-5 seconds through a light wedge to prepare samples for sensitometry. . On the other hand, for these samples, a laser diode scanner that emits at 780 nm, Ultra
Images were exposed using a Setter (manufactured by Ultre, USA) to prepare samples for printing. Each image-exposed sample was developed with the following DTR developer at 25°C for 30 seconds. 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 squeezing rollers. , dried at room temperature. <Transfer developer> Water 700ml Sodium hydroxide 18g Potassium hydroxide 7g Sodium hydrosulfite 50g 2-mercaptobenzoic acid 2g Uracil 2g 2-methylaminoethanol 30ml 5-phenyl-2-mercapto-1,3,4
-Oxadiazole 0.1g Adjust to 1 with water. <Neutralizing solution> Water 600ml Citric acid 10g Sodium citrate 35g Coloridal silica (20% liquid) 5ml Ethylene glycol 5ml Add water to bring the total volume to 1. The printing durability was determined by pasting each sample onto a single sheet, attaching this sheet to an offset printing machine, applying the following desensitizing liquid all over the plate surface, and printing using the following dampening liquid. Ivy. The printing machine used was A.B. Dick 350CD (trademark of an offset printing machine manufactured by A.B. Dick). The printing durability based on the number of sheets that could not be printed was evaluated using the following criteria, and the first
Shown in the table. Evaluation 1 1000 sheets or less 2 1000-3000 sheets 3 3000-5000 sheets 4 5000-7000 sheets 5 7000 sheets or more <Desensitizing 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 sensitivity is expressed as a relative value with the sensitivity of Sample A immediately after production as 100, which is the amount of exposure required to stop the formation of transferred deposited silver.

【table】

[Table] Example 2 Other than adding 2×10 ^-4 mol of sensitizing dye (17) per 1 mol of silver halide to a silver chloroiodobromide emulsion containing 20 mol % of silver bromide and 1 mol % of silver iodide. A lithographic printing plate was prepared according to Example 1. A lithographic printing plate was prepared in the same manner by adding 20 g of the polymer shown in Table 2 per mole of silver halide to the silver halide emulsion. A test was conducted in accordance with the method of Example 1, except that a transfer developer having the following formulation was used. <Transfer developer> Water 700ml Sodium hydroxide 30g Anhydrous sodium sulfite 60g Sodium thiosulfate (pentahydrate) 15g Potassium thiocyanate 10g Hydroquinone 15g Phenidone 2g Potassium bromide 1g 1-phenyl-5-mercaptotetrazole
Make 1 with 0.1g water. The results are shown in Table 2. Note that the sensitivity is expressed as a relative sensitivity with the sample immediately after production as 100.

[Table] (F) Effects of the Invention According to the present invention, a sensitizing dye having maximum spectral sensitivity at 700 nm or more is used, which has high sensitivity to semiconductor laser light, high printing durability, and excellent storage stability. A lithographic printing plate using the silver complex diffusion transfer method can be obtained.

Claims (1)

[Claims] 1. In a lithographic printing plate having at least a silver halide emulsion layer containing a sensitizing dye having maximum spectral sensitivity in a wavelength range longer than 700 nm and a physical development nucleus layer on a support, the emulsion layer has an average carboxyl group. A lithographic printing plate characterized by containing a water-soluble polymer having a molecular weight of 20,000 or less.