JP2002283758A - Original film for planographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an original film for planographic printing plate having excellent on-press developability as well as high sensibility and good printing durability. SOLUTION: The original film has a heat sensitive layer containing polymer particles having block isocianate groups, a hydrophilic resin and a photothermal converting substance on a hydrophilic supporting body. The polymer particulates having the block isocianate groups preferably contains the photothermal converting substance, furthermore it is more preferable that the hydrophilic resin has the groups to react with isocianate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lithographic printing plate precursor having a hydrophilic heat-sensitive layer on a support. More specifically, the present invention relates to a lithographic printing plate precursor capable of performing plate making by scanning exposure and on-press development based on digital signals and having excellent printing durability.

[0002]

2. Description of the Related Art Numerous studies have been made on printing plates for computer-to-plate systems, which have been remarkably advanced in recent years. Among them, with the aim of further streamlining the process and solving the problem of waste liquid treatment, lithographic printing plate precursors that can be directly mounted on a printing machine and printed without being developed after exposure have been studied, and various methods have been studied. Proposed.

[0003] One of the methods for eliminating the processing step is to mount an exposed lithographic printing plate precursor on a cylinder of a printing press, and supply a dampening solution and ink while rotating the cylinder. There is a method called on-press development for removing a non-image portion. That is, after exposing the printing master,
It is a system that is mounted on a printing machine as it is and the processing is completed in the normal printing process. A lithographic printing plate precursor suitable for such on-press development has a photosensitive layer (thermosensitive layer) that is soluble or dispersible in a fountain solution or an ink component, and is also placed on a printing machine placed in a bright room. It is required to have a light-room handling property suitable for being developed by the above method.

[0004] For example, Japanese Patent No. 2938397 discloses a lithographic printing plate precursor in which a photosensitive layer in which fine particles of a thermoplastic hydrophobic polymer are dispersed in a hydrophilic binder polymer is provided on a hydrophilic support. ing. According to this publication, in the lithographic printing plate precursor, after forming an image by exposing the particles of the thermoplastic hydrophobic polymer by heat with infrared laser exposure, mounting the plate on a printing press cylinder, dampening water and And / or on-press development with ink. Further, since the lithographic printing plate precursor has a photosensitive region in the infrared region, it is also suitable for handling in a bright room.

Further, Japanese Patent Application Laid-Open No. 9-127683 and WO 9
Japanese Patent Application Laid-Open No. 9-10186 also describes that a printing plate is produced by on-press development after combining thermoplastic fine particles by heat. However, although the above-described method of forming an image by the simple coalescence of fine particles by heat shows good on-press developability, there is a problem that the printing strength is insufficient due to low image strength.

On the other hand, JP-A-62-164049 and JP-A-6-140649
JP-1088 discloses a photosensitive material in which a blocked isocyanate is combined with a light-to-heat conversion material. However, these materials have a problem that sensitivity and printing durability are insufficient due to the use of a low-molecular-weight blocked isocyanate. Was. JP 2000
No. 275834 discloses a photosensitive composition containing an aqueous resin having a blocked isocyanate group and an infrared absorber, but after exposing the photosensitive composition to a printing press without treatment. When mounting and printing are started, there is a problem that the on-press developability of the non-image area is poor and a large amount of waste paper is required.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems, that is, a lithographic plate having good on-press developability, high sensitivity and good printing durability. The purpose is to provide an original plate for printing plates.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and as a result, the polymer in the fine particles has a blocked isocyanate group and the heat-sensitive layer contains a hydrophilic resin. As a result, it has been found that the above disadvantages of the prior art can be overcome, and the lithographic printing plate precursor having excellent on-press developability and image strength can be obtained. That is, the present invention is as follows. (1) A lithographic printing plate precursor comprising a hydrophilic support and a heat-sensitive layer containing a polymer particle having a blocked isocyanate group, a hydrophilic resin and a photothermal conversion substance. (2) The lithographic printing plate precursor as described in (1) above, wherein the polymer particles having a blocked isocyanate group contain a photothermal conversion substance. (3) The lithographic printing plate precursor as described in (1) above, wherein the hydrophilic resin has a group that reacts with isocyanate. (4) The lithographic printing plate precursor as described in (1) above, wherein the thermosensitive layer contains a compound having two or more groups that react with isocyanate in the molecule.

The lithographic printing plate precursor according to the present invention can form an image by scanning laser exposure based on digital exposure. By the heat generated by the irradiation of laser exposure,
The hydrophobic polymer fine particles contained in the heat-sensitive layer are at least partially thermally fused, and at the same time, the blocking agent of the blocked isocyanate contained in the polymer molecule is dissociated. The polymer having a free isocyanate group undergoes a self-crosslinking reaction or a crosslinking reaction with a hydrophilic resin, and the image area strength is improved. From the above results, it is possible to provide a lithographic printing plate precursor that maintains good on-press developability and has excellent printing durability.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The lithographic printing plate precursor according to the present invention will be described in detail below. As described above, the lithographic printing plate precursor of the present invention contains a polymer particle having a blocked isocyanate group, a hydrophilic resin, and a photothermal conversion substance on a substrate having a hydrophilic surface (abbreviated as a hydrophilic support). It has a heat-sensitive layer formed by applying a coating solution of the composition. First, each component of the heat-sensitive layer, which is a characteristic part of the lithographic printing plate precursor according to the invention, will be described.

(Polymer Particle Having Blocked Isocyanate Group) As a method for preparing a polymer particle having a blocked isocyanate group used in the present invention, for example, an emulsion polymerization method, a suspension polymerization method, and a soap-free emulsion polymerization method can be used. A method of preparing particles while polymerizing the monomer to, dispersing in water, dissolving a polymer prepared in advance in a water-immiscible organic solvent, mixing and emulsifying this with an aqueous solution containing a dispersion, There is a solvent evaporation method or the like in which heat is applied to make the organic solvent fly into fine particles while flying. However, it is not limited to these methods.

As a monomer used for synthesizing a polymer containing a blocked isocyanate group, for example, as described in JP-A-9-43845,
2-methacryloyloxyethyl isocyanate, 4-vinylphenyl isocyanate, as well as a (meth) acrylate monomer in which a group capable of decomposing by heat and generating an isocyanate group, such as a phenoxyloxycarbonylaminophenyl group, is previously introduced into the molecule. And a monomer having an isocyanate group such as a diisocyanate condensate with 2-hydroxyethyl (meth) acrylate with various blocking agents.

The polymer having a blocked isocyanate group can be synthesized by polymerizing a monomer containing a blocked isocyanate as described above. However, after polymerizing the isocyanate monomer, the polymer is blocked with various blocking agents by a polymer reaction. Can also be obtained.

In the blocking reaction, for example, the blocking agent is a hydroxyl group such as alcohol, phenol or oxime (general formula R-OH) and an isocyanate compound (general formula R'-N = C = O). In this case, a urethane bond is formed by the addition reaction as in RO-CO-NH-R '. When reacting with an active hydrogen compound (—CH ₂ —) such as acetylacetone, an amide bond is formed, and when the blocking agent is an amino group, a urea bond is formed.

Utilizing this fact, the above-mentioned bond uses urethane resin, amide resin and urea resin existing in the main chain as a blocked isocyanate polymer, and at least partially decomposes the main chain by heat to generate isocyanate. Can be done.

As the blocking agent for blocking the isocyanate group, known ones can be used. For example, phenol, cresol, xylenol, naphthol, p
Phenols such as nitrophenol, p-chlorophenol, guaiacol, catechol and resorcinol; lactams such as ε-caprolactam; oximes such as methylethylketoxime, acetoxime, butanone oxime and cyclohexanone oxime; ) Formyloxys such as acrylate and 2-formyloxyethyl propionate, alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol, benzyl alcohol, propylene glycol monomethyl ether and isopropanol, acetylacetone, ethyl acetoacetate and malonic acid Active methylenes such as diethyl, diethylamine, diphenylamine, dibutylamine, aniline, N, N-dimethylhydrazine, Enylnaphthylamine, amines such as carbazole, imidazole, 2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole, 2,4-diamino-6 ｛2′-methylimidazole (1 ′)｝ ethyl-s-triazine, Examples include heterocyclic compounds such as benzotriazole, basic nitrogen-containing compounds such as N, N-diethylhydroxylamine and hydroxypyridine, and hydrophilic blocking agents such as sodium acid sulfite. Regardless of the method by which the blocked isocyanate group is introduced, it is preferable that the blocked isocyanate is dissociated at a temperature of 80C to 200C to generate isocyanate.

The weight average molecular weight of the polymer having a blocked isocyanate group is preferably in the range of 5,000 to 400,000. Further, from the viewpoint of photosensitive material performance such as heat sealability, ink receptivity, and printing durability, a copolymer with a monomer having a polymerizable vinyl group containing no blocked isocyanate group can be used.

Examples of the polymerizable monomer include styrenes such as styrene, hydroxystyrene and methylstyrene, (meth) acrylic acid, methyl (meth) acrylate, butyl (meth) acrylate, and t- (meth) acrylate.
-(Butyl), (meth) acrylate acids and (meth) acrylates such as cyclohexyl (meth) acrylate, 2-hydroxyethyl acrylate, (meth) acrylamide, acrylonitrile, maleate such as diethyl maleate and dimethyl maleate. Acid esters and the like. In particular, a functional group capable of reacting with an isocyanate group,
Hydroxy groups such as 2-hydroxyethyl acrylate,. It is preferable from the viewpoint of image strength to copolymerize with a monomer having a carboxyl group such as (meth) acrylic acid and an amide group such as (meth) acrylamide.

The average particle size of the polymer particles is 0.01 to 3
μm is preferable, and among them, 0.05 to 1.0 μm is more preferable, and 0.02 to 0.4 μm is particularly preferable. Within this range, good resolution and stability over time can be obtained.

The amount of the polymer particles added is preferably at least 40% by weight, more preferably at least 60% by weight, based on the solid content of the heat-sensitive layer. Within this range, good sensitivity and printing durability can be obtained simultaneously with good on-press developability.

(Hydrophilic resin) The hydrophilic resin preferably contains a group that reacts with isocyanate, for example, a hydroxy group, an amino group, a carboxy group, an amide group, and a mercapto group.

Specific examples of the hydrophilic resin include gum arabic, casein, gelatin, starch derivatives, soya gum, hydroxypropylcellulose, methylcellulose, carboxymethylcellulose and its sodium salt, cellulose acetate, sodium alginate, vinyl acetate-
Maleic acid copolymers, styrene-maleic acid copolymers, polyacrylic acids and their salts, polymethacrylic acids and their salts, homopolymers and copolymers of hydroxyethyl methacrylate, homopolymers and copolymers of hydroxyethyl acrylate, homopolymers of hydroxypropyl methacrylate Polymers and copolymers, hydroxypropyl acrylate homopolymers and copolymers, hydroxybutyl methacrylate homopolymers and copolymers, hydroxybutyl acrylate homopolymers and copolymers, polyethylene glycols, hydroxypropylene polymers, polyvinyl alcohols, and at least a hydrolysis degree 60% by weight, preferably at least 80% by weight
Of polyvinyl acetate, polyvinyl formal, polyvinyl pyrrolidone, acrylamide homopolymers and copolymers, methacrylamide homopolymers and copolymers, N-methylol acrylamide homopolymers and copolymers, 2-acrylamide-
Examples thereof include homopolymers and copolymers of 2-methyl-1-propanesulfonic acid, homopolymers and copolymers of 2-methacryloyloxyethylphosphonic acid, polyallylamine, and polyethyleneimine.

The amount of the hydrophilic resin added to the heat-sensitive layer is preferably 5 to 70%, more preferably 5 to 40% of the solid content of the heat-sensitive layer. Within this range, good on-press developability and film strength are obtained, which is preferable.

(Light-to-heat conversion material) The heat-sensitive layer of the present invention contains a light-to-heat conversion material that absorbs infrared rays and generates heat in order to improve sensitivity. As such a photothermal conversion material, 700
Any pigment may be used as long as it is a light-absorbing substance having an absorption band in at least a part of the wavelength range of 1200 to 1200 nm. In particular, when an image is formed by laser light exposure, a light absorbing substance having light absorption at a laser light wavelength is preferable.

Examples of pigments include commercially available pigment and color index (CI) handbook, "Latest Pigment Handbook" (edited by Japan Pigment Technical Association, 1977), and "Latest Pigment Application Technology" (CMC Publishing, 1986). And "printing ink technology" (CMC Publishing, 1984) can be used.

These pigments can be used after being subjected to a known surface treatment, if necessary, in order to improve the dispersibility in the layer to which the pigment is added. Surface treatment methods include a method of surface-coating a hydrophilic resin or a lipophilic resin, a method of attaching a surfactant, and a reactive substance (for example, silica sol, alumina sol, a silane coupling agent or an epoxy compound,
A method of bonding an isocyanate compound) to the surface of the pigment. Pigment to be added to the hydrophilic layer is easy to disperse with the water-soluble resin, and so as not to impair the hydrophilicity,
It is desirable that the surface is coated with a hydrophilic resin or silica sol. The particle size of the pigment is preferably in the range of 0.01 μm to 1 μm, and more preferably in the range of 0.01 μm to 0.5 μm. As a method for dispersing the pigment, a known dispersion technique used in the production of ink or toner can be used. Particularly preferred pigments include carbon black.

Examples of the dye include commercially available dyes and literatures (eg, “Dye Handbook” edited by The Society of Synthetic Organic Chemistry, 1975, “Chemical Industry”, May 1986, “Near-infrared absorbing dyes”, May 1986, pp. 45-51). , "Development and Market Trend of Functional Dyes in the 90's", Chapter 2, Section 2.3 (1990), CM) or patents can be used.
Specifically, azo dyes, metal complex salt azo dyes, pyrazolone azo dyes, anthraquinone dyes, phthalocyanine dyes,
Infrared absorbing dyes such as carbonium dyes, quinone imine dyes, polymethine dyes and cyanine dyes are preferred.

Further, for example, see JP-A-58-12524.
No. 6, JP-A-59-84356, JP-A-60-787
No. 87, etc .;
173696, JP-A-58-181690, methine dyes described in JP-A-58-194595, and the like;
JP-A-58-112793, JP-A-58-22479
No. 3, JP-A-59-48187, JP-A-59-739
No. 96, JP-A-60-52940, JP-A-60-63
744, etc .; squarylium dyes described in JP-A-58-112792; cyanine dyes described in British Patent 434,875; and dyes described in U.S. Pat. No. 4,756,993. And cyanine dyes described in U.S. Pat. No. 4,973,572, dyes described in JP-A-10-268512, JP-A-11-23.
No. 5,883, phthalocyanine compounds.

Further, US Pat.
No. 938 is also preferably used, and substituted arylbenzo (thio) pyrylium salts described in U.S. Pat. No. 3,881,924;
No. 42645, JP-A-58-181051, JP-A-58-220143, JP-A-59-41363, JP-A-59-84248, and JP-A-59-84248.
No. 84249, No. 59-146063, No. 59-14
No. 6061, pyranium compounds described in JP-A-59-216146, cyanine dyes described in US Pat. No. 4,283,475, pentamethine thiopyrylium salts described in U.S. Pat. 5-70
No. 2, a pyrylium compound, Eporin III-178, Epolite III-130, manufactured by Eporin Co., Ltd.
Epolite III-125 and the like are also preferably used. Among these, a preferred dye to be added to a hydrophilic matrix such as a hydrophilic resin of the heat-sensitive layer is a water-soluble dye, and specific examples are shown below. However, the present invention is not limited to these.

[0030]

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[0031]

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It is preferable to include a photothermal conversion agent in the polymer fine particles used in the heat-sensitive layer from the viewpoint of sensitivity and image strength. The photothermal conversion agent contained in the polymer fine particles may be the above-mentioned infrared absorbing dye, but is more preferably a lipophilic dye. Specific examples include the following dyes.

[0033]

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[0034]

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[0035]

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The above-mentioned organic photothermal conversion agent can be added up to 30% by weight in the thermosensitive layer. Preferably 5
The content is 25% by weight, particularly preferably 7 to 20% by weight. Within this range, good sensitivity is obtained.

In the heat-sensitive layer of the present invention, metal fine particles can be used as a light-to-heat conversion agent. Many of the metal fine particles are light-heat converting and also self-heating. Preferred metal fine particles include Si, Al, Ti, V, and C.
r, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr,
Mo, Ag, Au, Pt, Pd, Rh, In, Sn,
A simple substance or an alloy of W, Te, Pb, Ge, Re, and Sb, or fine particles of oxides and sulfides thereof are exemplified.
Among the metals constituting these metal fine particles, preferred metals have a melting point of about 100, which is easily fused by light irradiation.
Metals having an absorption in the infrared, visible or ultraviolet region below 0 ° C., such as Re, Sb, Te, Au, Ag, Cu, G
e, Pb and Sn. Particularly preferred are metal fine particles having a relatively low melting point and a relatively high absorbance to heat rays, for example, Ag, Au, Cu, Sb, Ge.
And Pb, particularly preferred elements are Ag, Au and Cu.

Further, for example, Re, Sb, Te, Au, A
g, Cu, Ge, Pb, Sn or other low-melting metal particles and self-heating metal particles such as Ti, Cr, Fe, Co, Ni, W, Ge, etc. It may be composed of a substance. Ag, Pt, Pd
It is preferable to use a combination of a metal-type micro-piece and a metal-type micro-piece having particularly large light absorption when made into the same micro-piece.

The effects of the present invention can be further exerted by subjecting the surfaces of the above-described fine particles of a metal simple substance and an alloy to hydrophilic treatment. Means of surface hydrophilicity is a compound that is hydrophilic and has an adsorptivity to particles, such as a surface treatment with a surfactant, or a surface treatment with a substance having a hydrophilic group that reacts with the constituent substances of the particles, A method such as providing a protective colloid hydrophilic polymer film can be used. Particularly preferred is a surface silicate treatment. For example, in the case of fine iron particles, the surface can be made sufficiently hydrophilic by a method of immersing in an aqueous solution of sodium silicate (3%) at 70 ° C. for 30 seconds. Other metal fine particles can be subjected to a surface silicate treatment in the same manner.

The size of these particles is preferably 10 μm.
m, more preferably 0.003 to 5 μm, particularly preferably 0.01 to 3 μm. Within this range, good sensitivity and resolving power can be obtained, which is preferable.

In the present invention, when these metal fine particles are used as a light-to-heat conversion agent, the amount added is preferably at least 10% by weight, more preferably at least 20% by weight, particularly preferably at least 30% by weight of the solid of the heat-sensitive layer. Used in weight percent or more. High sensitivity is obtained within this range, which is preferable.

Further, various compounds other than those described above may be added to the heat-sensitive layer of the present invention. For example, in order to further improve the printing durability, a compound having two or more functional groups that react with isocyanate in the molecule, for example, 1,4-
Diols such as butanediol and polyamine compounds such as diethylenetriamine can be added.

In the present invention, a known catalyst is used to promote the dissociation of the blocked isocyanate group of the polymer in the particles during heating or to promote the reaction between the isocyanate and the functional group such as a hydrophilic resin or an additive. Can be contained in Specific examples include dibutyltin dilaurate, dimethylstannic chloride, trimethyltin hydroxide, stannic chloride, tetra-n-butyltin, stannous chloride, tin octoate, bismuth nitrate, zinc naphthenate, cobalt naphthenate, Antimony trioxide, titanic acid, tetramethylbutanediamine, 1,4-diazabicyclo [2,2,
2] Octane, triethylamine and the like. These may be used in combination. These can be contained in the particles.

Further, after the image is formed, the heat-sensitive layer of the present invention may
In order to make it easy to distinguish between the image area and the non-image area, a dye having a large absorption in the visible light region can be used as a colorant for the image. Specifically, Oil Yellow # 10
1, oil yellow # 103, oil pink # 312,
Oil Green BG, Oil Blue BOS, Oil Blue # 603, Oil Black BY, Oil Black B
S, Oil Black T-505 (all manufactured by Orient Chemical Industries, Ltd.), Victoria Pure Blue, Crystal Violet (CI42555), Methyl Violet (CI42535), Ethyl Violet, Rhodamine B (CI145170B), Malachite Green (CI
42000), methylene blue (CI52015) and the like.
And dyes described in JP-A-62-293247. Also, pigments such as phthalocyanine pigments, azo pigments, and titanium oxide can be suitably used. The addition amount is preferably 0.01 to 10% by weight based on the total solid content of the heat-sensitive layer coating solution.

Further, a plasticizer can be added to the heat-sensitive layer of the present invention, if necessary, to impart flexibility and the like to the coating film. For example, polyethylene glycol, tributyl citrate, diethyl phthalate, dibutyl phthalate,
Dihexyl phthalate, dioctyl phthalate, tricresyl phosphate, tributyl phosphate, trioctyl phosphate, tetrahydrofurfuryl oleate, and the like are used.

The heat-sensitive layer of the present invention is prepared by dissolving or dispersing the above-mentioned necessary components in a solvent to prepare a coating solution and coating the same.
As the solvent used here, ethylene dichloride,
Cyclohexanone, methyl ethyl ketone, methanol,
Ethanol, propanol, ethylene glycol monomethyl ether, 1-methoxy-2-propanol, 2-
Methoxyethyl acetate, 1-methoxy-2-propyl acetate, dimethoxyethane, methyl lactate, ethyl lactate, N, N-dimethylacetamide, N, N-dimethylformamide, tetramethylurea, N-methylpyrrolidone, dimethylsulfoxide, sulfolane, γ-butyl lactone, toluene, water and the like,
It is not limited to this. These solvents are used alone or as a mixture. The solid content concentration of the coating solution is preferably 1 to 50% by weight.

The coating amount (solid content) of the heat-sensitive layer on the support obtained after coating and drying varies depending on the application, but is generally preferably 0.5 to 5.0 g / m ² . Various methods can be used as a method of applying. For example,
Examples include bar coater coating, spin coating, spray coating, curtain coating, dip coating, air knife coating, blade coating, and roll coating.

The coating solution for the heat-sensitive layer according to the present invention may contain a surfactant for improving coating properties, for example, JP-A-62-1987.
A fluorinated surfactant as described in JP 170950 can be added. The preferred addition amount is 0.01 to 1% by weight, more preferably 0.05 to 0.5% by weight of the total solids of the heat-sensitive layer.

The lithographic printing plate precursor of the present invention is provided on the image forming layer to protect the surface of the hydrophilic image forming layer from contamination by lipophilic substances during storage and contamination (fingerprints) due to finger contact during handling. May be provided with a hydrophilic overcoat layer.

The hydrophilic overcoat layer used in the present invention can be easily removed on a printing press, and is selected from a water-soluble resin or a water-swellable resin obtained by partially crosslinking a water-soluble resin. It contains.

The water-soluble resin is selected from water-soluble natural polymers and synthetic polymers, and can be used to form a film when applied and dried using the water-soluble resin alone or together with a crosslinking agent. Specific examples of the water-soluble resin preferably used in the present invention include, as natural polymers, gum arabic, water-soluble soybean polysaccharide, and cellulose derivatives (eg, carboxymethyl cellulose, carboxyethyl cellulose,
Methylcellulose), its denatured forms, white dextrin, pullulan, enzymatically degraded etherified dextrin, etc.
For synthetic polymers, polyvinyl alcohol (having a hydrolysis rate of polyvinyl acetate of 65% or more), polyacrylic acid,
Its alkali metal salt or amine salt, polyacrylic acid copolymer, its alkali metal salt or amine salt, polymethacrylic acid, its alkali metal salt or amine salt,
Vinyl alcohol / acrylic acid copolymer and its alkali metal salt or amine salt, polyacrylamide, its copolymer, polyhydroxyethyl acrylate, polyvinylpyrrolidone, its copolymer, polyvinyl methyl ether, vinyl methyl ether / maleic anhydride copolymer Polymer, poly-2-acrylamido-2-methyl-1-propanesulfonic acid, alkali metal salt or amine salt thereof, poly-2-acrylamido-2-methyl-1-propanesulfonic acid copolymer, alkali metal salt thereof Alternatively, amine salts and the like can be mentioned. Further, according to the purpose, two or more of these resins can be used in combination. However, the invention is not limited to these examples.

When at least one or more of the water-soluble resins is partially crosslinked to form an overcoat layer on the hydrophilic layer, the crosslinking is carried out by a crosslinking reaction using a reactive functional group of the water-soluble resin. . The cross-linking reaction may be covalent cross-linking or ionic cross-linking.

The crosslinking reduces the tackiness of the surface of the overcoat layer and improves the handleability of the lithographic printing plate. However, if the crosslinking proceeds excessively, the overcoat layer changes to lipophilic, and the Moderate partial cross-linking is preferred because it makes removal of the layer difficult. The preferable degree of partial cross-linking is as follows: when the printing plate is immersed in water at 25 ° C., the hydrophilic overcoat layer remains without eluting in 30 seconds to 10 minutes, but elution is observed in 10 minutes or more. It is about.

Examples of the compound (crosslinking agent) used in the crosslinking reaction include known polyfunctional compounds having crosslinking properties, such as polyepoxy compounds, polyamine compounds, polyisocyanate compounds, polyalkoxysilyl compounds, titanate compounds, and the like. Aldehyde compounds, polyvalent metal salt compounds,
Hydrazine and the like.

The crosslinking agents can be used alone or as a mixture of two or more. Among the crosslinking agents, a particularly preferred crosslinking agent is a water-soluble crosslinking agent, but a water-insoluble one can be used by dispersing it in water with a dispersant.

Particularly preferred combinations of the water-soluble resin and the crosslinking agent include carboxylic acid-containing water-soluble resin / polyvalent metal compound, carboxylic acid-containing water-soluble resin / water-soluble epoxy resin, and hydroxyl group-containing resin / dialdehydes. .

A suitable amount of the crosslinking agent is 2 to 2 of the water-soluble resin.
-10% by weight. Within this range, good water resistance can be obtained without impairing the removability of the overcoat layer on a printing press.

In addition, a nonionic surfactant can be mainly added to the overcoat layer in the case of application of an aqueous solution for the purpose of ensuring uniformity of application. Specific examples of such a nonionic surfactant include sorbitan tristearate, sorbitan monopalmitate, sorbitan triolate, stearic acid monoglyceride, polyoxyethylene nonyl phenyl ether, polyoxyethylene dodecyl ether, and the like. . The proportion of the nonionic surfactant in the total solid content of the overcoat layer is preferably 0.05 to 5% by weight, and more preferably 1 to 3% by weight.

When the water-soluble resin is not crosslinked, the thickness of the overcoat layer of the present invention is from 0.1 μm to 4.
0 μm is preferred, and a more preferred range is from 0.1 μm to 1.0 μm. When the water-soluble resin is partially crosslinked, the range is preferably 0.1 to 0.5 μm, and 0.1 to 0.3 μm.
μm is more preferred. Within this range, contamination of the hydrophilic layer by the lipophilic substance can be prevented without impairing the removability of the overcoat layer on the printing press.

In the lithographic printing plate precursor of the present invention, the support to which the heat-sensitive layer can be applied is a dimensionally stable plate-like material such as paper or plastic (eg, polyethylene, polypropylene, polystyrene, etc.). ) Laminated paper, metal plate (eg, aluminum, zinc, copper, etc.), plastic film (eg, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, Polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, etc.), and paper or plastic film on which the above-mentioned metal is laminated or vapor-deposited. Preferred supports include a polyester film or an aluminum plate.

The aluminum plate is a pure aluminum plate or an alloy plate containing aluminum as a main component and containing a trace amount of a different element. Further, a plastic is laminated on a thin film of aluminum or an aluminum alloy. The foreign elements contained in aluminum alloys include silicon, iron, manganese, copper, magnesium, chromium, zinc,
There are bismuth, nickel, titanium and the like. The content of the foreign element in the alloy is at most 10% by weight or less. However, as the aluminum plate applied to the present invention, an aluminum plate of a conventionally known material can be appropriately used.

The thickness of the substrate used in the present invention is 0.05 mm to 0.6 mm, preferably 0.1 mm to 0.6 mm.
0.4 mm, particularly preferably 0.15 mm to 0.3 mm
It is.

Prior to using the aluminum plate, it is preferable to perform a surface treatment such as surface roughening and anodic oxidation. The surface treatment makes it easy to improve hydrophilicity and ensure adhesion to the heat-sensitive layer.

The surface roughening treatment of the aluminum plate surface is carried out by various methods, for example, a method of mechanically roughening the surface, a method of electrochemically dissolving and roughening the surface, and a method of chemically roughening the surface. It is performed by a method of selective dissolution. Known mechanical methods such as a ball polishing method, a brush polishing method, a blast polishing method, and a buff polishing method can be used as the mechanical method. As a chemical method, a method of immersing in a saturated aqueous solution of an aluminum salt of a mineral acid as described in JP-A-54-31187 is suitable. Further, as an electrochemical surface roughening method, there is a method of performing an alternating or direct current in an electrolytic solution containing an acid such as hydrochloric acid or nitric acid. Also, an electrolytic surface roughening method using a mixed acid as disclosed in JP-A-54-63902 can be used.

The surface roughening by the above-mentioned method is performed when the center line average roughness (Ra) of the surface of the aluminum plate is 0.2-1.
It is preferable that the coating be performed within a range of 0 μm. The roughened aluminum plate is subjected to an alkali etching treatment using an aqueous solution of potassium hydroxide or sodium hydroxide as necessary, and further neutralized, and then, if necessary, anodized to enhance abrasion resistance. Processing is performed. As the electrolyte used for the anodic oxidation treatment of the aluminum plate, various electrolytes that form a porous oxide film can be used, and generally, sulfuric acid, hydrochloric acid, oxalic acid, chromic acid, or a mixed acid thereof is used. The concentration of these electrolytes is appropriately determined depending on the type of the electrolyte. Anodizing treatment conditions vary depending on the electrolyte to be used and cannot be specified unconditionally. However, in general, the concentration of the electrolyte is 1 to 80% by weight, the solution temperature is 5 to 70 ° C., and the current density is 5 to 60 A / dm ² , a voltage of 1 to 100 V, and an electrolysis time of 10 seconds to 5 minutes are appropriate. The amount of the formed oxide film is 1.0 to 5.0.
g / m ^2, it is particularly preferably 1.5 to 4.0 g / m ^2.

As the support used in the present invention, a substrate having the above-mentioned surface treatment and having an anodized film may be used as it is.
For further improvement of heat insulation, etc., if necessary,
A process for enlarging micropores of an anodized film, a process for sealing micropores, and a process for hydrophilizing a surface immersed in an aqueous solution containing a hydrophilic compound, which are described in JP-A-00-65219 and Japanese Patent Application No. 2000-14387, are appropriately performed. You can choose to do it. Suitable hydrophilic compounds for the above-mentioned hydrophilic treatment include polyvinylphosphonic acid, compounds having a sulfonic acid group, saccharide compounds, citric acid, alkali metal silicates, potassium zirconium fluoride, phosphates / inorganic fluorine compounds, and the like. Can be mentioned.

When a support having insufficient surface hydrophilicity such as a polyester film is used as the support of the present invention, it is desirable to apply a hydrophilic layer to make the surface hydrophilic. As the hydrophilic layer, described in Japanese Patent Application No. 2000-10810,
Applying a coating solution containing a colloid of an oxide or hydroxide of at least one element selected from beryllium, magnesium, aluminum, silicon, titanium, boron, germanium, tin, zirconium, iron, vanadium, antimony and transition metals. The hydrophilic layer formed is preferred. Among them, a hydrophilic layer formed by applying a coating solution containing a colloid of silicon oxide or hydroxide is preferable.

In the present invention, before coating the heat-sensitive layer, if necessary, an inorganic undercoat layer such as a water-soluble metal salt such as zinc borate described in Japanese Patent Application No. 2000-143487, or For example, an organic undercoat layer containing carboxymethyl cellulose, dextrin, polyacrylic acid, or the like can be provided. The undercoat layer may contain the photothermal conversion agent.

The lithographic printing plate precursor of the present invention forms an image by heat. Specifically, direct image-like recording with a thermal recording head or the like, scanning exposure with an infrared laser, high illuminance flash exposure such as a xenon discharge lamp, infrared lamp exposure, or the like is used. Semiconductors that emit infrared light with a wavelength of 700 to 1200 nm are used. Exposure with a solid-state high-output infrared laser such as a laser or a YAG laser is preferable.

The lithographic printing plate precursor of the present invention, which has been image-exposed, can be mounted on a printing press without any further treatment, and can be printed by an ordinary procedure using ink and fountain solution.

The lithographic printing plate precursor of the present invention, which has been subjected to image exposure, can be prepared by a simple lithographic printing method using no dampening solution, for example, as disclosed in Japanese Patent Publication Nos.
9-27124, JP-B-49-27125, JP-A-53-36307, and JP-A-53-36.
No. 308, JP-B-61-52867, JP-A-58-2114844, and JP-A-53-27803.
JP, JP-A-53-29807, JP-A-54-29807
146110, JP-A-57-212274, JP-A-58-37069, JP-A-54-10
Lithographic printing using the emulsion ink described in JP-A-6305 is also possible.

As described in Japanese Patent No. 2938398, these lithographic printing plate precursors are mounted on a cylinder of a printing press, exposed to a laser mounted on the printing press, and then exposed on a press. It is also possible to develop. These lithographic printing plate precursors can be used for printing after development using water or an appropriate aqueous solution as a developing solution.

[0073]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which, of course, are not intended to limit the scope of the present invention.

[Synthesis Example] (Synthesis of Monomer, M-1) Sulfanilamide 86
g, pyridine 79 g, N, N-dimethylacetamide 2
75 g of phenyl chlorocarbonate was added dropwise to the 00 ml of the mixture while cooling with ice. After completion of the dropwise addition, the mixture was stirred at room temperature overnight, poured into acidic hydrochloric acid water, and the precipitated crystals were filtered.
By recrystallizing from ethyl acetate, p-phenoxyloxycarbonylaminophenylsulfonamide was obtained as white crystals. Yield 132 g.

To a mixture of 54.4 g of the above-obtained p-phenoxyloxycarbonylaminophenylsulfonamide, 40 g of triethylamine, 2 g of N, N-dimethylaminopyridine and 150 ml of N, N-dimethylacetamide, 22.8 g of methacrylic acid chloride. Was added dropwise while cooling with ice. After the addition, the mixture was stirred for 2 hours, poured into water, and the precipitated crystals were filtered. By recrystallizing from toluene-ethyl acetate (3/7), N- (p-phenoxycarbonylaminophenylsulfonyl) methacrylamide (M-1) was obtained as white crystals. Yield 40
g. mp 190-193 ° C.

(Synthesis of Polymer P-1) Condenser,
In a 300 ml three-necked round bottom flask equipped with a stirrer, 5.2 g of styrene and 2- (O- [1'-methylpropylideneamino] carboxylamino) ethyl methacrylate (MOI-BM; manufactured by Showa Denko KK) 12.1 g was dissolved in 35.2 g of methyl ethyl ketone, and 70 g
After heating to ° C, 0.4 g of V-60 was added as an initiator, and a polymerization reaction was carried out at 70 ° C for 8 hours. After the completion of the reaction, the reaction solution was cooled to room temperature, 50 g of methyl ethyl ketone was further added to dilute the reaction solution, and the reaction solution was added to 1500 ml of n-hexane with stirring to precipitate a white polymer. The polymer was identified, washed with n-hexane, and dried under vacuum to obtain 14 g of a white polymer. The weight average molecular weight was 26,000.

(Synthesis of Polymer P-2) 14.6 g of the above monomer (M-1) and 16.3 g of methyl methacrylate
g was dissolved in 93 g of dimethylacetamide, and heated to 65 ° C. while stirring under a nitrogen stream. 45 mg of 2,2'-azobis (2,4-dimethylpareronitrile) was added. Two hours later, 45 mg of 2,2'-azobis (2,4-dimethylpareronitrile) was added, and two hours later,
Further, 99 mg of 2,2'-azobis (2,4-dimethylpareronitrile) was added. After stirring at 65 ° C. for 2 hours, the mixture was cooled to room temperature. After adding 50 ml of acetone to the reaction solution, the mixture was poured into 2 L of water, and the precipitated solid was collected by filtration, washed with water, and dried. The weight average molecular weight was 20,000.

(Preparation of Polymer Particle Dispersion (1)) 30
In a 00 ml three-necked flask, 9.2 g of sodium dodecyl sulfate and 1350 ml of distilled water were weighed, and the mixture was stirred at 75 ° C. under a stream of room air for 10 minutes. A solution obtained by mixing 0.462 g of potassium persulfate, 11.3 ml of distilled water, and 3.42 ml of a 1M aqueous solution of sodium hydrogen carbonate was added to this solution, and then 52 g of styrene and 2- (O-methacrylic acid) were added.
[1'-Methylpropylideneamino] carboxyamino) ethyl (MOI-BM; manufactured by Showa Denko KK): 1
21 g of the mixed solution was added dropwise over 3 hours. After the addition, 0.462 g of potassium persulfate and 14.2 of distilled water were further added.
ml, and 3.42 ml of a 1 M aqueous sodium hydrogen carbonate solution
Was added, and stirring was continued for 3 hours. The obtained reaction mixture was cooled to room temperature, and filtered through a glass filter to obtain an aqueous latex solution. The solids concentration of the aqueous latex solution thus obtained was 11.3% by weight, and the average particle size of the latex was 40 nm.

(Preparation of Polymer Particle Dispersion Liquid (2)) 20
In a 00 ml three-necked flask, 9.2 g of sodium dodecyl sulfate and 1200 ml of distilled water were weighed and stirred at 75 ° C. for 10 minutes in a room air flow. After adding a solution obtained by mixing 0.462 g of potassium persulfate, 11.3 ml of distilled water, and 3.42 ml of a 1M aqueous solution of sodium hydrogen carbonate, 104 g of styrene was added dropwise over 3 hours.
After the addition, 0.462 g of potassium persulfate, 14.2 ml of distilled water, and a 1M aqueous solution of sodium hydrogencarbonate were further added.
A solution mixed with 42 ml was added, and stirring was continued for 3 hours. The obtained reaction mixture was cooled to room temperature, and filtered through a glass filter to obtain an aqueous latex solution. The solid content concentration of the aqueous latex solution thus obtained was 11% by weight.
The average particle size of the latex was 40 nm.

(Preparation of Polymer Particle Dispersion (3)) In a mixture of 6 g of methyl ethyl ketone and 12 g of ethyl acetate, 2.32 g of polymer P-1 and anionic surfactant Pionin A-41C (manufactured by Takemoto Yushi Co., Ltd.) 0.07 g was dissolved to produce an oil phase. To this, an aqueous phase of 8.07 g of a 4% aqueous solution of polyvinyl alcohol (PVA205 manufactured by Kuraray Co., Ltd.) was added, and a homogenizer was used at 10 rpm at 15,000 rpm.
Emulsified for minutes. After adding 39.78 g of water, the liquid was heated at 40 ° C. for 3 hours while removing the organic solvent. The measured solid content was 5.4% by weight. The average particle size was 0.3 μm.

(Preparation of Polymer Particle Dispersion Liquid (4)) A mixture of 6 g of methyl ethyl ketone and 12 g of ethyl acetate was added with 1.84 g of polymer P-1 and 0.48 g of a photothermal conversion agent (IR-31 described in this specification). 0.07 g of anionic surfactant Pionin A-41C (manufactured by Takemoto Yushi Co., Ltd.) was dissolved to prepare an oil phase. To this, an aqueous phase of 8.07 g of a 4% aqueous solution of polyvinyl alcohol (PVA205 manufactured by Kuraray Co., Ltd.) was added, and a homogenizer was used at 10 rpm at 15,000 rpm.
Emulsified for minutes. After adding 39.78 g of water, the liquid was heated at 40 ° C. for 3 hours while removing the organic solvent. The measured solid content was 5.4% by weight. The average particle size was 0.33 μm.

(Preparation of Polymer Particle Dispersion (5)) A mixture of 6 g of methyl ethyl ketone and 12 g of ethyl acetate was added with 1.84 g of polymer P-2, 0.48 g of a photothermal conversion agent (IR-27 described in this specification), 0.07 g of anionic surfactant Pionin A-41C (manufactured by Takemoto Yushi Co., Ltd.) was dissolved to prepare an oil phase. To this, an aqueous phase of 8.07 g of a 4% aqueous solution of polyvinyl alcohol (PVA205 manufactured by Kuraray Co., Ltd.) was added, and a homogenizer was used at 10 rpm at 15,000 rpm.
Emulsified for minutes. After adding 39.78 g of water, the liquid was heated at 40 ° C. for 3 hours while removing the organic solvent. The measured solid content was 5.4% by weight. The average particle size was 0.33 μm.

(Preparation of Polymer Particle Dispersion (6)) A mixture of 6 g of methyl ethyl ketone and 12 g of ethyl acetate was added with 2.32 g of polystyrene having a weight average molecular weight of 25000 and pionin A-41C anionic surfactant (Takemoto Yushi Co., Ltd.)
(0.07 g) was dissolved to produce an oil phase. 4% for this
Polyvinyl alcohol (PVA20 manufactured by Kuraray Co., Ltd.)
5) The aqueous phase of 8.07 g of the aqueous solution was added, and the mixture was emulsified with a homogenizer at 15000 rpm for 10 minutes. Water 39.78
After the addition of g, the solution was heated at 40 ° C. for 3 hours while removing the organic solvent. The measured solid content was 5.4% by weight. The average particle size was 0.33 μm.

(Preparation of Polymer Particle Dispersion (7)) A mixture of 6 g of methyl ethyl ketone and 12 g of ethyl acetate was mixed with 1.84 g of polystyrene (weight average molecular weight: 25,000) and a photothermal conversion agent (IR-31 described in the present specification). 48 g and 0.07 g of anionic surfactant Pionin A-41C (manufactured by Takemoto Yushi Co., Ltd.) were dissolved to prepare an oil phase. 4% polyvinyl alcohol (PVA manufactured by Kuraray Co., Ltd.)
205) The aqueous phase of 8.07 g of the aqueous solution was added and emulsified with a homogenizer at 15000 rpm for 10 minutes. 3 water
After adding 9.78 g, the solution was heated at 40 ° C. for 3 hours while removing the organic solvent. The measured solid content was 5.4% by weight. The average particle size is 0.33
μm.

(Example of Production of Support) Thickness 0.3 mm, Material
JIS A 1050 aluminum plate and No. 8 nylon brush and 8
Using a 00 mesh aqueous suspension of pamistone, the surface was grained and washed thoroughly with water. 10% of this board
After being immersed in an aqueous sodium hydroxide solution at 70 ° C. for 60 seconds to perform etching, the substrate was washed with running water, further neutralized and washed with 20% nitric acid, and then washed with water. This was subjected to electrolytic surface roughening treatment in an aqueous 1% nitric acid solution at an anode electricity of 300 C / dm ² using a sinusoidal alternating current under the condition of Va = 12.7 V. When the surface roughness of the aluminum plate was measured, it was 0.45 μm (Ra display). Followed by 30
After immersion in a 55% sulfuric acid aqueous solution and desmutting at 55 ° C. for 2 minutes, direct current electrolysis was performed at 33 ° C. and 15% sulfuric acid at a current density of 5 A / dm ² for 45 seconds to form an anodized film. 60 ° C to enlarge the micropores of the generated anodized film
Was immersed in 50 g / l sulfuric acid for 1 minute, treated with a 2.5% by weight aqueous solution of sodium silicate at 70 ° C. for 12 seconds, washed with water and dried to obtain a support.

[Example 1] The following thermosensitive layer coating solution (1) was prepared on the support obtained in the above Production Example, and then coated with a bar and dried in an oven at 60 ° C for 120 seconds. A lithographic printing plate precursor having a layer dry coating amount of 0.8 g / m ² was prepared.

(Thermal Layer Coating Solution (1)) Polymer Particle Dispersion (1) 20 g PVA 205 (manufactured by Kuraray Co., Ltd.) 4% aqueous solution 7.75 g Light-to-heat converting agent (IR-10 described in this specification) 0.34 g 26.5 g of distilled water

The lithographic printing plate precursor obtained as described above was used as a Gr plate equipped with a water-cooled 40 W infrared semiconductor laser.
EO Trendsetter 3244VFS
After exposure under the conditions of an output of 9 W, an outer drum rotation speed of 210 rpm, a plate surface energy of 100 mj / cm ² , and a resolution of 2400 dpi, the film was mounted on a cylinder of a printing machine SOR-M manufactured by Heidelberg without supplying a developing solution, and dampening water was supplied. Thereafter, printing was performed by supplying ink and further supplying paper. As a result, on-press development can be performed without any problems.
It was possible to print up to 6,000 sheets.

Example 2 A 4% aqueous solution of PVA205 (manufactured by Kuraray Co., Ltd.) of the heat-sensitive layer coating solution (1) of Example 1 was changed to a 4% aqueous solution of polyacrylic acid (weight average molecular weight: 25,000). Similarly, a heat-sensitive layer coating solution (2) was prepared to prepare a lithographic printing plate precursor, and exposure and printing were performed under the same conditions. As a result, on-press development was possible without any problem, and up to 4,000 sheets could be printed.

Example 3 The following heat-sensitive layer coating solution (3) was prepared on a support prepared by the same method as in Example 1, and then coated with a bar, followed by oven heating at 60 ° C. for 120 seconds. After drying, a lithographic printing plate precursor having a dry coating amount of the heat-sensitive layer of 0.8 g / m ² was prepared and exposed and printed under the same conditions as in Example 1.

(Thermal Layer Coating Solution (3)) Polymer Particle Dispersion Solution (3) 20 g Light-to-heat converting agent (IR-10 described in this specification) 0.34 g

As a result, on-press development was possible without any problem, and printing was possible up to 5,000 sheets.

Example 4 A polymer particle dispersion liquid (4) was used as a heat-sensitive layer coating liquid (4) on a support prepared by the same method as in Example 1, coated with a bar, and heated in an oven at 60 ° C. After drying for 120 seconds, a lithographic printing plate precursor having a dry coating amount of the heat-sensitive layer of 0.8 g / m ² was prepared. Exposure and printing were performed under the same conditions as in Example 1. As a result, on-press development could be performed without any problem, and up to 12,000 sheets could be printed.

Example 5 The polymer particle dispersion (4) in the heat-sensitive layer coating solution of Example 4 was replaced with the polymer particle dispersion (5).
In the same manner as above, except that the coating solution (5) was prepared, a lithographic printing plate precursor was prepared, and exposed and printed under the same conditions. As a result, on-press development was possible without any problem, and up to 10,000 sheets could be printed.

Example 6 The following heat-sensitive layer coating solution (6) was prepared on a support prepared by the same manufacturing method as in Example 1, then coated with a bar, and dried in an oven at 60 ° C. for 120 seconds. Then, a lithographic printing plate precursor having a dry coating amount of the heat-sensitive layer of 0.8 g / m ² was prepared, and exposed and printed under the same conditions as in Example 1. As a result, on-press development was possible without any problem, and up to 20,000 sheets could be printed.

(Thermal Layer Coating Solution (6)) Polymer Particle Dispersion (4) 20 g Diethylenetriamine (5.4% aqueous solution) 1.17 g

COMPARATIVE EXAMPLE 1 Except that the polymer particle dispersion liquid (1) in the heat-sensitive layer coating liquid (1) of Example 1 was changed to the polymer particle dispersion liquid (2), the heat-sensitive layer coating liquid ( 7) was prepared and a lithographic printing plate precursor was prepared, and exposed and printed under the same conditions. As a result, on-press development could be performed without any problem, but the number of printable sheets was 1,000 sheets, which was insufficient.

[Comparative Example 2] Except that the polymer particle dispersion liquid (3) in the heat-sensitive layer coating liquid (3) of Example 3 was changed to the polymer particle dispersion liquid (6), the same procedure was repeated. 8) was prepared and a lithographic printing plate precursor was prepared, and exposed and printed under the same conditions. As a result, on-press development was possible without any problem, but the number of printable sheets was insufficient at 1,500.

[Comparative Example 3] The same procedure as in Example 4 was repeated except that the polymer particle dispersion (4) in the thermosensitive layer coating liquid (4) was changed to the polymer particle dispersion (7). 9) was prepared and a lithographic printing plate precursor was prepared, and exposed and printed under the same conditions. As a result, on-press development was possible without any problem, but the number of printable sheets was 2,000, which was insufficient.

[Comparative Example 4] The following heat-sensitive layer coating solution (10) was prepared on a support obtained by the same production method as in Example 1, then coated with a bar, and dried in an oven at 60 ° C for 120 seconds. Then, a lithographic printing plate precursor having a dry coating amount of the heat-sensitive layer of 0.8 g / m ² was prepared. Exposure and printing were carried out under the same conditions as in Example 1. However, poor on-press developability occurred and no good printed matter was obtained.

(Coating solution for thermosensitive layer (10)) Polymer particle dispersion (1) 20 g Photothermal conversion agent (IR-10 described in this specification) 0.34 g Distilled water 28.4 g

As is clear from the above results, the lithographic printing plate precursors of Examples 1 to 6 of the present invention had good on-press developability and excellent printing durability and obtained satisfactory results. Examples 1-4
Each of the lithographic printing plate precursors was unsatisfactory in some properties.

[0103]

As described above, the lithographic printing plate precursor of the present invention can be subjected to plate making by scanning laser exposure and on-press development based on digital exposure. The polymer fine particles contained in the thermosensitive layer are at least partially thermally fused, and at the same time, the blocking agent of the blocked isocyanate contained in the polymer molecule is dissociated. The polymer having a free isocyanate group undergoes a self-crosslinking reaction or a crosslinking reaction with a hydrophilic resin, and the image area strength is improved. As a result, an unexposed portion can maintain good on-press developability, and an image portion can provide a lithographic printing plate precursor having excellent printing durability.

 ──────────────────────────────────────────────────続 き Continuing on the front page F-term (reference) 2H025 AA01 AA12 AB03 AC08 AD01 BH02 BJ03 CB41 CB51 CC11 CC20 FA10 2H096 AA06 BA20 EA04 EA23 2H114 AA04 AA24 BA01 BA10 DA03 DA04 DA08 DA11 DA21 DA34 DA41 DA42 DA46 DA46 DA46 DA46 DA50 EA01 EA03 EA08

Claims (4)

[Claims] 1. A lithographic printing plate precursor comprising a hydrophilic support and a heat-sensitive layer containing a polymer particle having a blocked isocyanate group, a hydrophilic resin and a photothermal conversion substance. 2. The lithographic printing plate precursor according to claim 1, wherein the polymer particles having a blocked isocyanate group contain a photothermal conversion substance. 3. The lithographic printing plate precursor according to claim 1, wherein the hydrophilic resin has a group that reacts with isocyanate. 4. The lithographic printing plate precursor according to claim 1, wherein the heat-sensitive layer contains a compound having two or more groups that react with isocyanate in the molecule.