JP2002086946A - Original plate for heat sensitive lithographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an original plate for a heat sensitive lithographic printing plate capable of printing by mounting in a printer as it is without treating after scanning exposure based on a digital signal, suppressing scattering of a scum due to an ablation and improving surface adhesive problem of adhering a fingerprint mark at a handling time. SOLUTION: The original plate for the heat sensitive lithographic printing plate comprises (1) an ink acceptive layer, (2) a hydrophilic layer containing a colloidal particle-like oxide or a hydroxide of at least one element selected from the group consisting of beryllium, magnesium, aluminum, silicon, titanium, boron, germanium, tin, zirconium, iron, vanadium, antimony and transition metals, and (3) a hydrophilic overcoating layer on a support. In this case, at least one layer of the acceptive layer, the hydrophilic layer and the overcoating layer contains a photothermal conversion agent. The overcoating layer contains a water swelling resin obtained by partly crosslinking a water soluble resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive lithographic printing plate not requiring development. More specifically, an image can be recorded by infrared laser beam scanning exposure based on a digital signal, and the recorded image can be directly mounted on a printing machine and printed without going through a conventional developing process. The present invention relates to a lithographic printing plate that is capable of being excellent in sensitivity, printing start inking property, and printing durability.

[0002]

2. Description of the Related Art Various methods have been proposed for a lithographic printing plate precursor that can be mounted on a printing machine without any processing after exposure and printing can be performed. One of the promising methods is a method using ablation in which a solid-state high-power infrared laser such as a semiconductor laser or a YAG laser is used for exposure, and the exposed portion is heated with a photothermal conversion agent that converts light into heat, thereby causing decomposition and evaporation. It is. That is, a hydrophilic layer is provided on a substrate having a lipophilic ink-receiving surface or a lipophilic ink-receiving layer, and the hydrophilic layer is ablated and removed.

[0003] WO 94/18005 discloses a hydrophilic layer in which polyvinyl alcohol is crosslinked with a hydrolyzate of tetraethoxysilicon and further contains titanium dioxide particles on a lipophilic laser light absorbing layer. There is disclosed a lithographic printing plate which can be mounted on a printing press without development by ablation of a lithographic printing plate.

[0004] WO98 / 40212, WO99 / 19
No. 143 and WO 99/19144, on a substrate coated with an ink receiving layer, a hydrophilic layer mainly composed of a colloid such as silica crosslinked with a crosslinking agent such as aminopropyltriethoxysilane is provided. A lithographic printing plate ablating layers is disclosed.

[0005]

However, a conventional heat-sensitive lithographic printing plate utilizing ablation causes a laser exposure device or an optical system to be contaminated by scattering of ablation debris to reduce the resolution, There was a problem of scattering.

As a result of various studies, it has been found that a three-dimensionally cross-linked hydrophilic layer whose heating part is easily removed by a fountain solution or ink at the time of printing is formed on a substrate having an ink-receiving surface or coated with an ink-receiving layer. It has been found that the above problem can be solved by using a heat-sensitive lithographic printing plate precursor in which a water-soluble overcoat layer is sequentially provided (Japanese Patent Application No. 11-24).
No. 7764). However, even in such a heat-sensitive lithographic printing plate, since the overcoat layer is water-soluble, the surface is sticky when touched by wet hands,
There was a problem of fingerprint marks.

[0007] Accordingly, an object of the present invention is to further solve the above-mentioned new problem, and it is possible to print directly after being exposed to a printing machine without performing processing,
An object of the present invention is to provide a heat-sensitive lithographic printing original plate that suppresses scattering of scum due to ablation and that has improved the problem of surface stickiness such as the adhesion of fingerprints during handling.

[0008]

Means for Solving the Problems As a result of intensive studies, the present inventor has found that the above object can be achieved by adding a water-swellable resin obtained by partially crosslinking a water-soluble resin to an overcoat layer. I found it. That is, the present invention is as follows.

On a support, (1) an ink receiving layer, (2)
Beryllium, magnesium, aluminum, silicon, titanium, boron, germanium, tin, zirconium, iron, vanadium, antimony and a hydrophilic layer containing a colloidal particulate oxide or hydroxide of at least one element selected from transition metals, And (3) a heat-sensitive lithographic printing plate having a hydrophilic overcoat layer, wherein at least one of an ink receiving layer, a hydrophilic layer and a hydrophilic overcoat layer contains a photothermal conversion agent, A heat-sensitive lithographic printing plate, wherein the water-soluble overcoat layer contains a water-swellable resin obtained by partially crosslinking a water-soluble resin.

[0010]

Embodiments of the present invention will be described below in detail.

[0011] The hydrophilic overcoat layer of the present invention contains a water-swellable resin obtained by partially crosslinking a water-soluble resin. By partially crosslinking the water-soluble resin to improve water resistance,
The object of the present invention is to suppress the surface tackiness, prevent the adhesion of fingerprint marks, and improve the handleability of a lithographic printing original plate. In addition, this hydrophilic overcoat layer swells with fountain solution, transfers to a blanket at the start of printing, and is further transferred to paper and removed, as in conventional on-press development, There is no problem that the overcoat layer dissolves in the dampening solution and adversely affects printing.

However, if the crosslinking proceeds too much, the overcoat layer changes to lipophilicity, making it difficult to remove the overcoat layer on a printing press and deteriorating the inking property at the start of printing. Therefore, the degree of partial cross-linking suitable for the present invention is the water resistance in which the hydrophilic overcoat layer does not elute and remains for 30 seconds to 10 minutes when the printing plate is immersed in water at 25 ° C. If the elution time is less than 30 seconds, the crosslinking is insufficient, and if the elution time is 10 minutes or more, the crosslinking is excessively advanced.

The water-soluble resin of the hydrophilic overcoat layer comprises:
It is selected from a water-soluble natural polymer and a synthetic polymer and used together with a cross-linking agent, and the coated and dried film has a film-forming ability. 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,
Polymethacrylic acid copolymer, 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 Polymer, polyvinyl methyl ether, vinyl methyl ether / maleic anhydride copolymer, poly-2-acrylamido-2-methyl-1-propanesulfonic acid, an alkali metal salt or amine salt thereof, poly-2-acrylamide-2- Methyl-
Examples thereof include a 1-propanesulfonic acid copolymer, an alkali metal salt or an amine salt thereof, and the like. 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.

Next, a method of crosslinking a water-soluble resin will be described. The overcoat layer is formed on the hydrophilic layer by partially crosslinking at least one of the above-mentioned water-soluble resins. Crosslinking is performed by performing 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.

Examples of the compound used in the crosslinking reaction include known polyfunctional compounds having crosslinking properties, such as polyepoxy compounds, polyisocyanate compounds, polyalkoxysilyl compounds, polyvalent metal salt compounds, polyamine compounds, and aldehyde compounds. And hydrazine. The crosslinking reaction can be accelerated by adding a known catalyst.

Specific examples of known polyfunctional compounds having crosslinkability include the following compounds.

Specific examples of the polyepoxy compound include glycerin polyglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, trimethylolpropane polyglycidyl ether, trimethylolpropane polyglycidyl ether, sorbitol polyglycidyl ether,
And polycondensates of bisphenols or hydrogenated products thereof with epihalohydrin.

Specific examples of the polyamine include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, hexamethylenediamine, propylenediamine, polyethyleneimine, and polyamidoamine.

Specific examples of the polyisocyanate compound include tolylene diisocyanate, diphenylmethane isocyanate, liquid diphenylmethane diisocyanate,
Aromatic isocyanates such as polymethylene polyphenyl isocyanate, xylylene diisocyanate, naphthalene-1,5-diisocyanate, cyclohexanephenylene diisocyanate, isopropylbenzene-2,4-diisocyanate; aliphatic isocyanates such as hexamethylene diisocyanate and decamethylene diisocyanate; Cyclohexyl diisocyanate, alicyclic diisocyanate such as isophorone diisocyanate,
Further, a polypropylene glycol / tolylene diisocyanate addition reaction product may, for example, be mentioned.

Examples of the silane compound include methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, phenyltriethoxysilane, vinyltriethoxysilane, γ-aminopropyltriethoxysilane, N- (β-aminoethyl)- γ-aminopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane,
β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldiethoxysilane, 3-chloropropylmethyldimethoxysilane, vinyltris (methylethylketoxime) silane, methyltris (methylethylketoxime) silane , Vinyltriacetoxysilane, etc.

Examples of the titanate compound include tetraethyl orthosilicate, bis (dioctyl pyrophosphate) ethylene titanate, isopropyl triactanoyl titanate, isopropyl dimethacryl isostearyl titanate, isopropyl isostearoyl diacryl titanate, isopropyl (dioctyl phosphate) titanate), isopropyl Tricumylphenyl titanate, isopropyl tri (N-aminoethylaminoethyl) titanate, dicumylphenyloxyacetate titanate, diisostearoylethylene titanate, isopropyltriinstearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl tris (dioctyl phosphate) titanate , Tetraiso Ropyl bis (dioctyl phosphite) titanate, tetraoctyl bis (ditrisyl phosphite) titanate, tetra (2,2 diallyloxymethyl-1-butyl) bis (ditridecyl phosphite titanate, bis (dioctyl pyrophosphate) oxyacetate Titanates, bis (dioctyl pyrophosphate) oxyacetate titanates, and the like.

Examples of the aldehyde compound include formaldehyde, acetaldehyde, propylaldehyde, butyraldehyde, glyoxal, glutaraldehyde, terephthalaldehyde and the like.

Examples of the polyvalent metal salt compound include water-soluble salts of metals such as zinc, calcium, magnesium, barium, strontium, cobalt, manganese and nickel.

These crosslinking agents can be used alone or in combination of two or more. Among these 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 a water-soluble resin and a 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. .

The preferred 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 aqueous solution application 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 nonylphenyl 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.

The thickness of the overcoat layer used in the present invention is preferably 0.1 to 0.5 μm, and more preferably 0.1 to 0.3 μm. Within this range, good scattering of ablation scum can be obtained without impairing the removability of the overcoat layer on the printing press.

The hydrophilic layer used in the present invention is a layer which is insoluble in a fountain solution by lithographic printing using a fountain solution and ink, and is a layer of beryllium, magnesium, aluminum, silicon,
Titanium, boron, germanium, tin, zirconium,
It is formed by applying a solution containing colloidal particulate oxide or hydroxide of at least one element selected from iron, vanadium, antimony and transition metal, and polyacrylic acid. Aluminum, silicon, titanium and zirconium are particularly preferred among the elements constituting the colloidal particulate oxide or hydroxide used in the present invention.

The size of the colloid used in the present invention is as follows.
Spherical silica having a particle size of 5 to 100 nm is preferable. Spherical particles having a particle size of 10 to 50 nm are 50 to 400 nm
Can be used. Feathers such as 100 nm × 10 nm like aluminum oxide or hydroxide colloids are also effective.

These colloids can be prepared by various known methods such as hydrolysis of halides or alkoxy compounds of the above elements or condensation of hydroxides. For example,
A sol can also be prepared by applying a hydrolysis / condensation reaction directly from di, tri and / or tetraalkoxysilane under an acid catalyst to apply. When this sol is applied, a stronger hydrophilic three-dimensional crosslinked film can be obtained. In addition, a commercially available product such as Nissan Chemical Industries, Ltd. may be selected and used as the colloid dispersion liquid.

The hydrophilic layer of the present invention may contain a hydrophilic resin. As the hydrophilic resin, those having a hydrophilic group such as hydroxyl, carboxyl, hydroxyethyl, hydroxypropyl, amino, aminoethyl, aminopropyl, carboxymethyl and the like are preferable.

Specific hydrophilic resins include gum arabic, casein, gelatin, starch derivatives, carboxymethylcellulose and their Na salts, cellulose acetate, sodium alginate, vinyl acetate-maleic acid copolymers, styrene-maleic acid copolymers, Polyacrylic acids and their salts, polymethacrylic acids and their salts, hydroxyethyl methacrylate homopolymers and copolymers, hydroxyethyl acrylate homopolymers and copolymers, hydroxypropyl methacrylate homopolymers and copolymers, hydroxypropyl acrylate homopolymers and Copolymers, hydroxybutyl methacrylate homopolymers and copolymers, hydroxybutyl acrylate homopolymers and copolymers, Lithylene glycols, hydroxypropylene polymers, polyvinyl alcohols, and homopolymers and copolymers of hydrolyzed polyvinyl acetate, polyvinyl formal, polyvinyl butyral, polyvinyl pyrrolidone, and acrylamide having a degree of hydrolysis of at least 60% by weight, preferably at least 80% by weight , Methacrylamide homopolymers and polymers, N-methylolacrylamide homopolymers and copolymers, and the like.

These hydrophilic resins are used together with a colloid, and the proportion of the hydrophilic resin is determined when the hydrophilic resin is water-soluble.
The total solid content of the hydrophilic layer is preferably 40% by weight or less, and in the case of a non-water-soluble hydrophilic resin, the total solid content is preferably 20% by weight or less.

The hydrophilic layer of the present invention may contain, in addition to the above-mentioned colloid and hydrophilic resin, a crosslinking agent for accelerating the crosslinking of the colloid. As such a colloid crosslinking agent, an initial hydrolysis condensate of tetraalkoxysilane, trialkoxysilylpropyl-N, N, N-trialkylammonium halide or aminopropyltrialkoxysilane is preferable. It is preferable that the addition ratio is 5% by weight or less of the total solid content of the hydrophilic layer.

Although the hydrophilic resin can be used as it is, it may be used together with a crosslinking agent for the hydrophilic resin other than the colloid, if necessary, in order to increase the printing durability. Examples of such a crosslinking agent include initial hydrolysis and condensate of formaldehyde, glyoxal, polyisocyanate and tetraalkoxysilane, dimethylol urea and hexamethylol melamine.

The hydrophilic layer containing each component described above is provided by preparing a solution in which each component is dissolved or dispersed in a solvent, and coating the solution. As the main solvent of the hydrophilic layer coating solution, water and low-boiling alcohols such as methanol, ethanol and propanol are used alone or as a mixture.

The hydrophilic layer of the present invention may further include a well-known fluorine-based surfactant for improving the surface condition of the coating.
A silicon-based surfactant, a polyoxyethylene-based surfactant, or the like may be added.

The coating thickness of the hydrophilic layer of the present invention is preferably from 0.1 μm to 3 μm. Within this range, ablation is good and printing durability is good.

The ink receiving layer of the present invention contains a lipophilic organic polymer soluble in a solvent capable of forming a film. Useful organic polymers include polyester, polyurethane, polyurea, polyimide, polysiloxane, polycarbonate, phenoxy resin, epoxy resin, phenol / formaldehyde resin, alkylphenol / formaldehyde resin, polyvinyl acetate, acrylic resin and copolymers thereof, and polyvinylphenol. , Polyvinyl halogenated phenol, methacrylic resin and its copolymer, acrylamide copolymer, methacrylamide copolymer, polyvinyl formal, polyamide, polyvinyl butyral, polystyrene, cellulose ester resin,
Examples thereof include polyvinyl chloride and polyvinylidene chloride.

Among these, as a more preferred compound, a resin having a hydroxyl group, a carboxyl group, a sulfonamide group or a trialkoxysilyl group in a side chain is excellent in adhesion to a substrate or an upper hydrophilic layer, and in some cases, It is desirable because it is easily cured with a crosslinking agent. In addition, an acrylonitrile copolymer, a polyurethane, a copolymer having a sulfonamide group in a side chain or a copolymer having a hydroxyl group in a side chain, which is photocured with a diazo resin, is preferable.

Other phenol, cresol (m-cresol, p-cresol, m / p mixed cresol), phenol / cresol (m-cresol, p-cresol, m / p mixed cresol), phenol-modified xylene, t-butylphenol, Octylphenol, resorcinol, pyrogallol, catechol, chlorophenol (m-Cl, p-Cl), bromophenol (m-
Novolak resins and resole resins for condensation with formaldehyde such as Br, p-Br), salicylic acid and phloroglucinol, as well as condensation resins for the above phenolic compounds and acetone are useful.

As other suitable high molecular compounds, copolymers having a molecular weight of usually 10,000 to 200,000, which includes monomers represented by the following (1) to (12) as constituent units, can be mentioned. (1) Acrylamides, methacrylamides, acrylates, methacrylates and hydroxystyrenes having an aromatic hydroxyl group, for example, N- (4-hydroxyphenyl) acrylamide or N- (4-hydroxyphenyl) methacryl Amide, o
-, M- and p-hydroxystyrene, o-, m- and p-hydroxyphenyl acrylate or methacrylate, (2) acrylates and methacrylates having an aliphatic hydroxyl group, for example, 2-
Hydroxyethyl acrylate or 2-hydroxyethyl methacrylate,

(3) Methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, amyl acrylate, hexyl acrylate, cyclohexyl acrylate, octyl acrylate, phenyl acrylate, benzyl acrylate, acrylic acid-2 (Substituted) acrylates such as -chloroethyl, 4-hydroxybutyl acrylate, glycidyl acrylate, N-dimethylaminoethyl acrylate, (4) methyl methacrylate,
Ethyl methacrylate, propyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, octyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-chloroethyl methacrylate, 4-hydroxybutyl methacrylate, (Substituted) methacrylates such as glycidyl methacrylate and N-dimethylaminoethyl methacrylate;

(5) Acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-ethylacrylamide, N-ethylmethacrylamide, N-hexylacrylamide, N
-Hexyl methacrylamide, N-cyclohexyl acrylamide, N-cyclohexyl methacrylamide, N
-Hydroxyethylacrylamide, N-hydroxyethylacrylamide, N-phenylacrylamide, N
-Phenylmethacrylamide, N-benzylacrylamide, N-benzylmethacrylamide, N-nitrophenylacrylamide, N-nitrophenylmethacrylamide, N-ethyl-N-phenylacrylamide and N
Acrylamide or methacrylamide such as -ethyl-N-phenylmethacrylamide,

(6) Ethyl vinyl ether, 2-chloroethyl vinyl ether, hydroxyethyl vinyl ether, propyl vinyl ether, butyl vinyl ether,
Vinyl ethers such as octyl vinyl ether and phenyl vinyl ether; (7) vinyl esters such as vinyl acetate, vinyl chloroacetate, vinyl butyrate and vinyl benzoate; (8) styrenes such as styrene, methyl styrene and chloromethyl styrene; 9)
Vinyl ketones such as methyl vinyl ketone, ethyl vinyl ketone, propyl vinyl ketone, and phenyl vinyl ketone; (10) olefins such as ethylene, propylene, isobutylene, butadiene, and isoprene; (11) N
-Vinylpyrrolidone, N-vinylcarbazole, 4-vinylpyridine, acrylonitrile, methacrylonitrile, etc.

(12) N- (o-aminosulfonylphenyl) acrylamide, N- (m-aminosulfonylphenyl) acrylamide, N- (p-aminosulfonylphenyl) acrylamide, N- [1- (3-aminosulfonyl) Naphthyl] acrylamide, acrylamides such as N- (2-aminosulfonylethyl) acrylamide, N- (o-aminosulfonylphenyl) methacrylamide, N- (m-aminosulfonylphenyl) methacrylamide, N- (p-aminosulfonyl) Methacrylamides such as phenyl) methacrylamide, N- [1- (3-aminosulfonyl) naphthyl] methacrylamide, N- (2-aminosulfonylethyl) methacrylamide, and o-aminosulfonylphenyl acrylate, m-amino Sulfo sulfonyl phenyl acrylate,
p-aminosulfonylphenyl acrylate, 1- (3
-Aminosulfonylphenylnaphthyl) unsaturated sulfonamides such as acrylates such as acrylate, o-aminosulfonylphenylmethacrylate, m
Unsaturated sulfonamides such as methacrylic esters such as -aminosulfonylphenyl methacrylate, p-aminosulfonylphenyl methacrylate and 1- (3-aminosulfonylphenylnaphthyl) methacrylate;

The ink receiving layer of the present invention further comprises a crosslinking agent,
An adhesion aid, a colorant, inorganic or organic fine particles, a coating surface condition improving agent, and a plasticizer can be added as necessary. In addition, the ink receiving layer may contain a light-to-heat conversion agent for increasing the sensitivity or a heat coloring or decoloring additive for forming a printed image after exposure.

Specific crosslinking agents for crosslinking organic polymers include diazo resins, aromatic azide compounds, epoxy resins, isocyanate compounds, blocked isocyanate compounds, initial hydrolyzed condensates of tetraalkoxy silicon, glyoxal, aldehyde compounds and methylol. Compounds can be mentioned.

As the adhesion aid, the above diazo resin is excellent in adhesion to the substrate and the hydrophilic layer. In addition, a silane coupling agent, an isocyanate compound and a titanium coupling agent are also useful.

As the coloring agent, ordinary dyes and pigments are used. In particular, rhodamine 6G chloride, rhodamine B chloride, crystal violet, malachite green oxalate, oxazine 4 perchlorate, quinizarin,
2- (α-naphthyl) -5-phenyloxazole and coumarin-4. Specifically, as other dyes,
Oil Yellow # 101, Oil Yellow # 103, Oil Pink # 312, Oil Green BG, Oil Blue BOS, Oil Blue # 603, Oil Black B
Y, oil black BS, oil black T-505
(The above are manufactured by Orient Chemical Industry Co., Ltd.), Victoria Pure Blue, Crystal Violet (CI4255)
5), methyl violet (CI42535), ethyl violet, methylene blue (CI52015), patent pure blue (manufactured by Sumitomo Sangoku Chemical Co., Ltd.), brilliant blue, methyl green, erythricin B, basic fuchsin, m-cresol purple, auramine, 4
Triphenylmethane-based, diphenylmethane-based, oxazine-based, xanthene-based, iminonaphthoquinone-based, azomethine-based or anthraquinone-based dyes such as -p-diethylaminophenyliminaphthoquinone and cyano-p-diethylaminophenylacetanilide; -293247, Japanese Patent Application No. 7-3351.
No. 45 can be mentioned. When the dye is added to the ink receiving layer, it is usually about 0.02 to 10% by weight based on the total solid content of the receiving layer.
More preferably, the proportion is from about 0.1 to 5% by weight.

Further, fluorine-based surfactants and silicon-based surfactants, which are well-known compounds as coating surface condition improvers, can also be used. Specifically, a surfactant having a perfluoroalkyl group or a dimethylsiloxane group is useful for preparing the coated surface.

Examples of the inorganic or organic fine particles usable in the present invention include colloidal silica and colloidal aluminum having a diameter of 10 nm to 100 nm, and inactive particles having a particle diameter larger than those of colloids, for example, silica particles, surface hydrophobization. Silica particles, alumina particles, titanium dioxide particles, other heavy metal particles, clay and talc. The addition of these inorganic or organic fine particles to the ink receiving layer has the effect of improving the adhesion to the upper hydrophilic layer and increasing the printing durability in printing. The addition ratio of these fine particles in the ink receiving layer is 80% by weight or less of the total amount, preferably 40% by weight or less.

Further, a plasticizer may be added to the ink receiving layer of the present invention, if necessary, to impart flexibility 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, oligomers of acrylic acid or methacrylic acid And polymers.

Further, it is preferable to add a coloring or decoloring compound to the ink receiving layer of the present invention in order to sharpen the image area and the non-image area when exposed. For example,
Leuco dyes (leucomalachite green, leucomalachite green, etc.) along with thermal acid generators such as diazo compounds and diphenyliodonium salts
Leuco crystal violet, lactone of crystal violet, etc.) and PH discoloration dye (eg, dye such as ethyl violet, Victoria Poor Blue BOH)
Is used. In addition, a combination of an acid coloring dye and an acidic binder as described in EP 897134 is also effective. In this case, the bond in the associated state forming the dye is broken by heating, and a lactone is formed to change from colored to colorless. The addition ratio of these coloring or decoloring systems is 10% by weight based on the total solids in the receiving layer.
It is preferably at most 5% by weight.

As a solvent for coating the ink receiving layer, alcohols (methanol, ethanol, propyl alcohol, ethylene glycol, diethylene glycol,
Propylene glycol, dipropylene glycol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, ethylene glycol monoethyl ether, etc.), ethers (tetrahydrofuran, ethylene glycol dimethyl ether, propylene glycol dimethyl ether, tetrahydropyran, etc.), ketones (acetone, methyl ethyl ketone, Acetylacetone, etc.), esters (methyl acetate, ethylene glycol monomethyl monoacetate, methyl lactate, ethyl lactate,
Gamma-butyrolactone), amides (formamide, N-methylformamide, pyrrolidone, N-methylpyrrolidone, etc.) and the like can be used. These solvents are used alone or in a mixed state. When preparing a coating solution, the concentration of the components of the ink receiving layer (total solids including additives) in the solvent is preferably 1 to 50% by weight. In addition, a film can be formed not only from the above-mentioned application from an organic solvent but also from an aqueous emulsion. In this case, the concentration is preferably 5% by weight to 50% by weight.

The thickness of the ink-receiving layer in the present invention after coating and drying is not particularly limited, but is preferably 0.1 μm or more since it functions as a heat insulating layer when provided on a metal plate. It is more preferably at least 0.2 μm. When a lipophilic plastic film is used as the substrate, the ink receiving layer only needs to be able to function as an adhesive layer with the upper layer. It is preferably at least 05 μm.

In the present invention, a photothermal conversion agent having a function of absorbing infrared rays and generating heat is added to at least one of the ink receiving layer, the hydrophilic layer and the overcoat layer in order to increase the sensitivity to infrared rays. .

The photothermal conversion agent may be any substance that absorbs light of 700 nm or more, and various pigments and dyes can be used. Examples of pigments include commercially available pigment and color index (CI) handbook, “Latest Pigment Handbook” (edited by The Japan Pigment Technical Association, 1977), “Latest Pigment Application Technology” (CMC Publishing, 1986), “printing”. Pigments described in "Ink Technology" (CMC Publishing, 1984) can be used.

Examples of the kind of the pigment include a black pigment, a brown pigment, a red pigment, a violet pigment, a blue pigment, a green pigment, a fluorescent pigment, a metal powder pigment, and a polymer-bound pigment. Specifically, insoluble azo pigments, azo lake pigments, condensed azo pigments, chelated azo pigments, phthalocyanine pigments, anthraquinone pigments, perylene and perinone pigments, thioindigo pigments, quinacridone pigments, dioxazine pigments, isoindolinone pigments And quinophthalone pigments, dyed lake pigments, azine pigments, nitroso pigments, nitro pigments, natural pigments, fluorescent pigments, inorganic pigments, carbon black, and the like.

These pigments may be used without being subjected to a surface treatment, or may be used after being subjected to a surface treatment. The method of surface treatment is a method of surface coating a hydrophilic resin or lipophilic resin,
A method of attaching a surfactant, a method of bonding a reactive substance (for example, silica sol, alumina sol, a silane coupling agent, an epoxy compound, an isocyanate compound, and the like) to the surface of the pigment are considered. The above surface treatment method,
It is described in "Properties and Applications of Metallic Soaps" (Koshobo), "Printing Ink Technology" (CMC Publishing, 1984) and "Latest Pigment Application Technology" (CMC Publishing, 1986). Among these pigments, those that absorb infrared rays are preferred because they are suitable for use in lasers that emit infrared rays. As such a pigment that absorbs infrared rays, carbon black is particularly preferred.

As the pigment to be added to the hydrophilic layer and the overcoat layer of the present invention, particularly, the surface is coated with a hydrophilic resin or silica sol so as to be easily dispersed in a water-soluble or hydrophilic resin and not to impair the hydrophilicity. Carbon black is useful.

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. As the disperser, an ultrasonic disperser,
Sand mills, attritors, pearl mills, super mills, ball mills, impellers, dispersers, KD mills, colloid mills, dynatrons, three-roll mills, pressure kneaders and the like can be mentioned. Details are described in “Latest Pigment Application Technology” (CMC Publishing, 1986).

As the dye, commercially available dyes and literatures (for example, “Dye Handbook” edited by The Society of Synthetic Organic Chemistry, published in 1970)
"Chemical Industry", May 1986, p. 45-51 "Near-infrared absorbing dyes", "Development and market trends of functional dyes in the 1990s", Chapter 2, Section 2.3 (1990), or known dyes described in patents can be used. . Specifically, infrared absorbing dyes such as azo dyes, metal complex salt azo dyes, pyrazolone azo dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinone imine dyes, polymethine dyes, and cyanine dyes are preferred.

Further, examples of the infrared absorbing dye include, for example, JP-A-58-125246 and JP-A-59-84356.
Cyanine dyes described in JP-A-60-78787, JP-A-58-173696, JP-A-58-173696
181690, methine dyes described in JP-A-58-194595 and the like, JP-A-58-112793,
JP-A-58-224793, JP-A-59-48187
JP-A-59-73996, JP-A-60-5294
No. 0, naphthoquinone dyes described in JP-A-60-63744 and the like, squalilium dyes described in JP-A-58-112792 and the like, British Patent 434,8
No. 75, and US Pat. No. 4,756,9.
No. 93, a cyanine dye described in U.S. Pat. No. 4,973,572, a dye described in JP-A-10-268512, and a phthalocyanine compound described in JP-A-11-235883.

As a dye, 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 (US Pat. No. 4,327,169)
Described in JP-A-58-18.
No. 1051, No. 58-220143, No. 59-413
No. 63, No. 59-84248, No. 59-84249
Pyrylium compounds described in JP-A-59-146063 and JP-A-59-146061;
Cyanine dyes described in U.S. Pat. No. 2,216,146, pentamethine thiopyrylium salts described in U.S. Pat. No. 4,283,475, and Japanese Patent Publication Nos. 5-135514 and 5-19702.
Nos. 4,059,098, 4,098,098, 4,098,097, and 3,087,098. Also preferred are pyrylium compounds described in Japanese Patent Application Publication No. JP-A-2002-209, Epolite III-178, Epolite III-130, Epolite III-125 and the like. Among these, a particularly preferred dye to be added to the overcoat layer and the hydrophilic layer is a water-soluble dye, and specific examples are listed below by structural formulas.

[0067]

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[0068]

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The dye used in the ink receiving layer of the present invention may be the above-mentioned infrared absorbing dye, but is preferably a more lipophilic dye. More preferred dyes include the dyes exemplified below.

[0070]

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[0071]

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The proportion of the light-to-heat converting agent is 1 to 50% by weight, preferably 2 to 20% by weight of the solid content in the hydrophilic layer. In the overcoat layer, 1 to 70% by weight of solids,
Preferably 2 to 50% by weight, when the photothermal conversion agent is a dye,
The proportion is particularly preferably 2 to 30% by weight, and when the photothermal conversion agent is a pigment, the proportion is particularly preferably 20 to 50% by weight. The addition ratio of the photothermal conversion agent to the ink receiving layer is preferably 20% by weight or less of the total solids of the ink receiving layer, and particularly preferably 15% by weight or less. Within these ranges, good sensitivity can be obtained without impairing the film strength of each layer.

As the support used in the present invention, a dimensionally stable plate is used. Paper, lipophilic plastic (eg, polyethylene, polypropylene, polystyrene, etc.) laminated paper, metal plate (eg, aluminum, zinc, copper, nickel, stainless steel plate, etc.),
Plastic films (eg, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, etc.), and the above metals are laminated or deposited Paper or plastic film etc. are included.

Preferred substrates are polyethylene terephthalate film, polycarbonate film, aluminum or steel plate, or aluminum or steel plate laminated with a lipophilic plastic film.

The aluminum plate used in the present invention is a pure aluminum plate or an alloy plate containing aluminum as a main component and containing a trace amount of a different element, and furthermore, a plastic in which a thin film of aluminum or aluminum alloy is laminated with plastic. It is. The foreign elements contained in aluminum alloys include silicon, iron, manganese, copper, magnesium,
There are chromium, zinc, bismuth, nickel, titanium and the like. The content of the foreign element in the alloy is at most 10% by weight or less. Further, an aluminum plate from an aluminum ingot using the DC casting method or an aluminum plate from an ingot using the continuous casting method may be used. However, as the aluminum plate applied to the present invention, an aluminum plate of a conventionally known and used 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 facilitates the adhesion to the ink receiving layer.

The surface roughening treatment of the aluminum plate surface is performed 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 carried out by a method of selective dissolution. As a mechanical method, a known method such as a ball polishing method, a brush polishing method, a blast polishing method, and a buff polishing method can be used. 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 carrying out an alternating current or a 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 also 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 required, and further neutralized, and then anodized to enhance abrasion resistance if desired. Processing is performed.
As an electrolyte used for anodizing the aluminum plate, various electrolytes forming 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. The anodizing treatment conditions vary depending on the electrolyte used and cannot be specified unconditionally, but generally the concentration of the electrolyte is 1 to 80% by weight.
Solution, liquid temperature is 5 to 70 ° C, 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 1.0-5.
0 g / m ^2, it is particularly preferably 1.5 to 4.0 g / m ^2.

The substrate used in the present invention may be a substrate having the above-mentioned surface treatment and having an anodized film as it is. However, in order to further improve the adhesiveness to the upper layer and the heat insulating property, it is necessary. Accordingly, Japanese Patent Application No. 2000-65219
And anodic oxide coating described in Japanese Patent Application No. 2000-14387, enlarging the micropores, sealing the micropores, and immersing the surface in an aqueous solution containing a hydrophilic compound. Can be done. Suitable hydrophilic compounds for the above-mentioned hydrophilization treatment include polyvinyl phosphonic 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.

The heat-sensitive lithographic printing plate of the present invention forms an image by heat. Specifically, direct image-like recording using a thermal recording head or the like, scanning exposure using an infrared laser, high-intensity flash exposure such as a xenon discharge lamp, or infrared lamp exposure is used. Semiconductors that emit infrared light having 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 image-exposed printing plate of the present invention can be mounted on a printing press without further processing. Alternatively, it is also possible to attach a printing original plate to a printing press, perform laser exposure on the printing press, and then perform printing as it is.

[0082]

The present invention will be described below in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 [Production of Aluminum Substrate] Aluminum 99.5 weight
%, 0.01% by weight of copper, 0.03% by weight of titanium,
JI containing 0.3% by weight of iron and 0.1% by weight of silicon
SA1050 rolled 0.24mm aluminum plate
Of a 400 mesh pamistone (manufactured by Kyoritsu Ceramics)
Weight percent aqueous suspension using a rotating nylon brush
After graining the surface, it was thoroughly washed with water. This is 15
Wt% sodium hydroxide aqueous solution (aluminum 4.5
% Of aluminum) and the dissolution amount of aluminum is 5 g / m^Two
And then washed with running water. Change
Neutralized with a 1% by weight aqueous nitric acid solution, then 0.7% by weight nitric acid
Anode in acid aqueous solution (containing 0.5% by weight of aluminum)
Square wave alternating wave with hour voltage 10.5V, cathode hour voltage 9.3V
Voltage (current ratio r = 0.90, Japanese Patent Publication No. 58-5796)
160 using the current waveform described in the publication example)
C / dm^TwoThe electrolytic surface roughening treatment was performed with the amount of electricity at the time of anode.
After washing with water, in a 10% by weight aqueous sodium hydroxide solution at 35 ° C
Immersion in aluminum, the amount of aluminum dissolved is 1 g / m ^TwoWill be
After the etching, the substrate was washed with water. Next, at 50 ° C., 30
Immersed in an aqueous solution of sulfuric acid by weight and desmutted.
I washed. Furthermore, a 20% by weight aqueous solution of sulfuric acid at 35 ° C. (Al
0.8% by weight) and using direct current
A porous anodic oxide film forming treatment was performed. That is, current density
Degree 13A / dm^TwoAnd adjust the electrolysis time
Anodic oxide film weight 2.7 g / m^TwoMake a support
Was. After washing the support with water, 70 ° C. sodium silicate
It was immersed in a 0.2% by weight aqueous solution, washed with water and dried. Adhesion
The amount is 5 mg / m as Si^TwoMet. As above
The obtained support was measured with a Macbeth RD920 reflection densitometer.
The measured reflection density is 0.30 and the center line average roughness Ra is
It was 0.58 μm.

[Application of Ink Receiving Layer] On the above support,
An ink receiving layer coating solution having the following composition was applied to a coating solution amount of 11.2.
Coating was performed with a bar coater so as to be 5 ml / m ² . Then, it is dried by heating at 100 ° C. for 1 minute, and the dried coating amount is about 0.1%.
An ink receiving layer of 45 g / m ² was obtained.

(Coating solution of ink receiving layer) Epicoat 1100L (manufactured by Yuka Shell Epoxy Co., Ltd.) 0.8 g Epicoat 1001 (manufactured by Yuka Shell Epoxy Co., Ltd.) 0.2 g Photothermal conversion agent (IR described in this specification) -24) 0.2 g Methyl ethyl ketone 13 g Propylene glycol monomethyl ether 12 g

[Coating of hydrophilic layer] On the ink receiving layer thus provided, the following hydrophilic layer coating solution (I) was applied by a bar, dried at 100 ° C for 1 minute, and dried at a dry coating amount of 0.1 µm. 39
g / m ² of the hydrophilic layer was obtained.

(Hydrophilic Layer Coating Solution (I)) Methanol Silica (manufactured by Nissan Chemical Industries, Ltd .: silica particle diameter: 10 to 20 nm, colloid composed of a methanol solution containing 30% by weight) 3 g Polyacrylic acid (weight average molecular weight: 2. 50,000) 5% by weight methanol solution 2 g Methyl lactate 1 g Methanol 17.53 g

On the hydrophilic layer, an overcoat layer coating solution OC-1 having the following composition was coated with a bar and dried at 100 ° C. for 90 seconds to form a thermosensitive layer having an overcoat layer having a dry coating weight of 0.22 g / m ^2. A lithographic printing original plate (1) was produced.

(Overcoat Layer Coating Solution OC-1) Gum Arabic (28% by weight aqueous solution) 1.5 g Photothermal conversion agent (Dye IR-10 described in this specification) 0.042 g Polyoxyethylene nonylphenyl ether (10 Wt% aqueous solution) 0.168 g Calcium acetate (10 wt% aqueous solution) 0.3 g Deionized water 22 g

The heat-sensitive lithographic printing plate (1) thus obtained was used as a Trendsetter (40W) manufactured by Creo.
(A plate setter equipped with a 830 nm semiconductor laser) at an energy of 200 mJ / cm ² . The exposed base plate was attached to Komori Corporation's Lithrone printing machine without further processing.
Plate etchant EU-3 (Fuji Photo Film Co., Ltd.)
/ Water / isopropyl alcohol (volume ratio 1/99 /
10) a fountain solution and Dainippon Ink and Chemicals, Inc.
When the dampening solution and the ink were simultaneously operated using Geos G black ink and the art-coated paper was supplied and printing was started, the ink was completely deposited on the fifth sheet, and then the ink was applied.
Many thousands of good prints without stains were obtained.

The heat-sensitive lithographic printing original plate (1) showed no fingerprint mark even when touching the plate surface with bare hands. On the other hand, in the heat-sensitive lithographic printing original plate prepared by removing calcium acetate from the overcoat layer, fingerprint marks slightly adhered. The on-press developability did not differ between the presence and absence of calcium acetate. 25 ° C
Immersed in water for 1 minute to examine the removability of the overcoat layer. With calcium acetate, the overcoat layer remained almost completely, but without calcium acetate,
Nearly half of them dissolved out. When immersed in water at 25 ° C. for 11 minutes, the overcoat layer flowed out even with calcium acetate. From this result, it can be seen that the water resistance of the plate surface was improved by partially crosslinking the overcoat layer.

Example 2 A heat-sensitive lithographic printing plate (2) was prepared in the same manner as in Example 1 except that the overcoat layer coating solution OC-2 of Example 1 was replaced with the overcoat layer coating solution OC-2 having the following composition. ) Was prepared. Dry coating weight of overcoat layer 0.24 g / m ²
Met.

(Overcoat Layer Coating Solution OC-2) Soya Gum K-31 (28% aqueous solution) 1.5 g Photothermal conversion agent (Dye IR-10 described in this specification) 0.042 g Polyoxyethylene nonylphenyl ether (10% by weight aqueous solution) 0.168 g Magnesium acetate (10% by weight aqueous solution) 0.4 g Deionized water 22 g Here, soya gum K-31 is a water-soluble soybean polysaccharide manufactured by Fuji Oil Co., Ltd.

The heat-sensitive lithographic printing original plate (2) was exposed and printed in the same manner as in Example 1. As a result, the ink was completely deposited on the fifth sheet, and 20,000 sheets of good printed matter free of stains thereafter was gotten.

The heat-sensitive lithographic printing original plate (2) did not show any fingerprint mark even when touching the plate surface with bare hands. On the other hand, Example 2
The one prepared by removing magnesium acetate from the overcoat layer of No. 1 had fingerprint traces clearly adhered. The on-press developability did not differ between the presence and absence of magnesium acetate. 25 ° C
The removal of the overcoat layer when immersed in water for 1 minute showed that the overcoat layer remained almost completely in the presence of magnesium acetate, but almost 1 in the absence of magnesium acetate.
00% dissolved out. When immersed in water at 25 ° C. for 11 minutes, outflow of the overcoat layer occurred even with magnesium acetate. From this result, it can be seen that the water resistance of the printing plate was improved.

Example 3 A heat-sensitive lithographic printing plate (3) was prepared in the same manner as in Example 1 except that the overcoat layer coating solution OC-3 of Example 1 was replaced with the overcoat layer coating solution OC-3 having the following composition. ) Was prepared. Dry coating weight of overcoat layer 0.26 g / m ²
Met.

(Overcoat Layer Coating Solution OC-3) Polyacrylic acid (weight-average molecular weight: 25,000, 28% by weight aqueous solution) 1.5 g Photothermal conversion agent (dye IR-10 described in this specification) 0.042 g Polyoxyethylene nonylphenyl ether (10% by weight aqueous solution) 0.168 g Magnesium acetate (10% by weight aqueous solution) 0.8 g Deionized water 22 g

When the heat-sensitive lithographic printing original plate (3) was exposed and printed in the same manner as in Example 1, the ink was completely deposited on the fifth printing start, and 20,000 sheets of good printed matter free of stains thereafter was gotten.

The heat-sensitive lithographic printing original plate (3) showed no fingerprint mark even when touching the plate surface with bare hands. On the other hand, Example 3
The one prepared by removing magnesium acetate from the overcoat layer of No. 1 had fingerprint traces clearly adhered. The on-press developability did not differ between the presence and absence of magnesium acetate. 25 ° C
Of the overcoat layer when immersed in water for 1 minute, the overcoat layer remained almost completely in the presence of magnesium acetate, but was 100% in the absence of magnesium acetate.
% Dissolved completely. When immersed in water at 25 ° C. for 11 minutes, outflow of the overcoat layer occurred even with magnesium acetate. From this result, it can be seen that the water resistance of the printing plate was improved.

[0100]

According to the present invention, it is possible to print by directly mounting on a printing machine without performing post-exposure processing.
A heat-sensitive lithographic printing plate can be provided in which scattering of scum due to ablation is suppressed, and the problem of surface stickiness, that is, adhesion of fingerprints during handling is improved.

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Claims (1)

[Claims] 1. An ink receiving layer comprising: (1) an ink receiving layer,
(2) It contains a colloidal particulate 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. A heat-sensitive lithographic printing plate precursor having a hydrophilic layer, and (3) a hydrophilic overcoat layer, wherein at least one of the ink receiving layer, the hydrophilic layer and the hydrophilic overcoat layer contains a photothermal conversion agent. A heat-sensitive lithographic printing plate, wherein the hydrophilic overcoat layer contains a water-swellable resin obtained by partially crosslinking a water-soluble resin.