JP2002214780A - Photosensitive planographic printing plate and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the adhesiveness of a photosensitive layer to a substrate in a planographic printing plate with the photosensitive layer on the surface of the substrate, to improve the developability and printing resistance of the planographic printing plate and to particularly provide a planographic printing plate in which satisfactory image strength and printing resistance are imparted to an image obtained by scanning exposure with laser light. SOLUTION: In the photosensitive planographic printing plate with a photopolymerizable photosensitive layer containing an ethylenically unsaturated compound, a photopolymerization initiating system and a polymer binder on a substrate obtained by surface-roughening and anodically oxidizing an aluminum plate, the acid value of the photopolymerizable photosensitive layer is adjusted to 25-34.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a photosensitive lithographic printing plate. More specifically, the present invention relates to a photosensitive lithographic printing plate having a photopolymerizable photosensitive layer containing an ethylenically unsaturated compound, a photopolymerization initiation system and a polymer binder on an aluminum support. Regarding improvement.

[0002]

2. Description of the Related Art Conventionally, as a method of forming an image by exposing a photopolymerizable composition, a photosensitive composition comprising a photopolymerizable composition comprising an ethylenically unsaturated compound and a photopolymerization initiator, or further comprising a polymer binder, etc. After forming a layer on the surface of the support, exposing and polymerizing and curing the ethylenically unsaturated compound in the photopolymerizable composition in the exposed portion, a cured relief image is formed by dissolving and removing the non-exposed portion. The method is universal.
In recent years, as an exposure method, an argon ion laser, an FD-YAG laser, which can greatly improve productivity,
Attention has been paid to scanning exposure with laser light such as a semiconductor laser and a YAG laser, and in particular, light of a wavelength of 488 nm of an argon ion laser as a visible light laser, FD-YA
Light with a wavelength of 532 nm of a G laser is promising.

[0003] Higher sensitivity of the photopolymerizable composition corresponding to the laser scanning exposure has been actively studied, but the high-speed scanning exposure by the laser beam still has insufficient sensitivity.
It was difficult to form an image having sufficient strength. on the other hand,
Studies have been made to improve the image intensity by processing after laser scanning exposure. For example, a method of performing heat treatment after laser scanning exposure and before development processing, and a method of further post-exposure after development processing have been proposed. For example, Japanese Patent Application Laid-Open No. 6-1
The inventions described in JP-A-48885 and JP-A-6-289611 are characterized by the composition of the photosensitive layer. In the examples, post-exposure after development is described.

The high-sensitivity photosensitive layer suitable for such laser scanning exposure has a different composition from that of a photosensitive layer such as a carbon arc lamp, a mercury lamp, or a metallohalide lamp which is exposed to an ordinary light through an original image, and is based on aluminum. It was found that there was a problem in the adhesion to the support. As a countermeasure, methods such as heat treatment and post-exposure are known, but in such a case, a dedicated heat treatment device or post-exposure device is required, which leaves problems in cost, installation place, workability, and the like. .

As an attempt to improve the adhesion between the photosensitive layer and the support, the support is roughened by a mechanical, chemical, or electrochemical method, and subsequently, a chemical etching treatment, an anodic oxidation treatment, a chemical conversion treatment, and a hydrophilic treatment are performed. Various methods have been proposed for controlling the surface state of the support by combining various kinds of treatments such as a chemical conversion treatment, a sealing treatment, and a primer coating treatment. On the other hand, many proposals have been made on the improvement of the photosensitive layer side with regard to the structure, properties, compounding amount and the like of the ethylenically unsaturated compound, the photopolymerization initiation system and the polymer binder constituting the main ingredient of the photosensitive layer. Also, various additives for the photosensitive layer such as a thermal polymerization inhibitor, an antifoaming agent, a coloring agent, a plasticizer, a pH adjuster, a surfactant, a development accelerator, and a storage stabilizer have been proposed. For example, JP
-10719, JP-A-2000-275830, JP-A-20
JP-A-00-122279 describes improved inventions such as polymer binders, surfactants, and accelerators. However, there is no known technique which focuses on the acid value of the entire photosensitive layer and mentions its relationship with the developing property and printing durability.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a lithographic printing plate having a photosensitive layer on the surface of a support, in which the adhesion between the support and the photosensitive layer is increased and the printing durability of the lithographic printing plate is improved. With the goal. In particular, an object of the present invention is to provide a lithographic printing plate that provides an image obtained by scanning exposure with a laser beam with sufficient image strength and printing durability.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, specified the acid value of the photosensitive layer containing an ethylenically unsaturated compound, a photopolymerization initiation system and a polymer binder. The present inventors have found that the above object can be achieved by controlling the range, and completed the present invention. That is, the present invention relates to a photosensitive lithographic printing plate having a photopolymerizable photosensitive layer containing an ethylenically unsaturated compound, a photopolymerization initiation system, and a polymer binder on a support; Is a photosensitive lithographic printing plate characterized by having an acid value of 25 to 34.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The photosensitive lithographic printing plate of the present invention comprises the following components on a support: (A) an ethylenically unsaturated compound, (B) a photopolymerization initiation system, and (C) a polymer binder. A photosensitive layer comprising a photopolymerizable composition is formed.

Here, the ethylenically unsaturated compound as the component (A) of the photopolymerizable composition constituting the photosensitive layer is defined as:
When the photopolymerizable composition is irradiated with actinic rays,
(B) A monomer having an ethylenically unsaturated bond that undergoes addition polymerization by the action of a photopolymerization initiation system as a component, and in some cases, crosslinks and cures. In addition, the meaning of the monomer here is a concept corresponding to a so-called polymer, and in addition to the monomer in a narrow sense, includes a dimer, a trimer, and other oligomers. I do. In addition, the photopolymerization initiation system means a combination of a radical generator (photopolymerization initiator) and a sensitizer.

In the present invention, as the ethylenically unsaturated compound as the component (A), a compound having one ethylenically unsaturated bond in one molecule, specifically, for example, (meth)
Acrylic acid [In the present invention, “(meth) acryl” means acryl and methacryl. Unsaturated carboxylic acids such as crotonic acid, isocrotonic acid, maleic acid, itaconic acid, and citraconic acid, and alkyl esters thereof, (meth) acrylonitrile, (meth) acrylamide, and styrene; Compounds having two or more saturated bonds in one molecule are preferred.

Typical examples of the polyfunctional ethylenically unsaturated compound include esters of a polyhydroxy compound and an unsaturated carboxylic acid, and urethane (meth) acrylate of a polyisocyanate compound and a hydroxyalkyl (meth) acrylate compound. (Meth) acrylates of polyepoxy compounds and (meth) acrylic acid or hydroxyalkyl (meth) acrylate compounds, phosphates having (meth) acryloyloxy group, and carboxylic acids having (meth) acryloyloxy group And the like. In the present invention, it is preferable to adjust the acid value by using phosphates or carboxylic acids for a part of these ethylenically unsaturated compounds.

Specific examples of the esters include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, tripropylene glycol, trimethylene glycol, tetramethylene glycol, neopentyl glycol, and hexamethylene. Glycol, nonamethylene glycol, trimethylolethane, tetramethylolethane, trimethylolpropane, glycerol, pentaerythritol, dipentaerythritol,
Sorbitol and its reaction products of aliphatic polyhydroxy compounds such as ethylene oxide adducts, propylene oxide adducts, diethanolamine, triethanolamine and the like with unsaturated carboxylic acids as described above, for example, ethylene glycol (Meth) acrylate, diethylene glycol di (meth) acrylate,
Triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, tetramethylene glycol di (meth) acrylate, neopentyl glycol di (meth) ) Acrylate, hexamethylene glycol di (meth) acrylate, nonamethylene glycol di (meth) acrylate, trimethylolethanetri (meth) acrylate, tetramethylolethanetri (meth) acrylate, trimethylolpropanedi (meth) acrylate, trimethylol Propane tri (meth) acrylate, trimethylolpropane ethylene oxide added tri (meth) acrylate, glycerol di (meth) acrylate Glycerol tri (meth) acrylate, glycerol propylene oxide addition tri (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth)
Acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol di (meth) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (Meth) acrylate, sorbitol tri (meth) acrylate, sorbitol tetra (meth) acrylate, sorbitol penta (meth) acrylate, sorbitol hexa (meth)
Acrylates and the like, and similar crotonates, isocrotonates, maleates, itaconates, citraconates and the like can be mentioned.

Further, as the esters, a reaction product of an aromatic polyhydroxy compound such as hydroquinone, resorcinol, pyrogallol and an unsaturated carboxylic acid, specifically,
For example, a reaction product of a heterocyclic polyhydroxy compound such as hydroquinone di (meth) acrylate, resorcinol di (meth) acrylate, pyrogallol tri (meth) acrylate, and tris (2-hydroxyethyl) isocyanurate with an unsaturated carboxylic acid Specifically, for example, di (meth) acrylate and tri (meth) acrylate of tris (2-hydroxyethyl) isocyanurate, and a reaction product of a polyhydroxy compound, an unsaturated carboxylic acid, and a polycarboxylic acid Specifically, for example, a condensate of ethylene glycol with (meth) acrylic acid and phthalic acid, a condensate of diethylene glycol with (meth) acrylic acid and maleic acid, pentaerythritol, (meth) acrylic acid and terephthalic acid With butanediol, glycerin and (meth) Condensates of acrylic acid and adipic acid.

Examples of the urethane (meth) acrylates include, for example, hexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine methyl ester diisocyanate, lysine methyl ester triisocyanate, dimer acid Aliphatic polyisocyanates such as diisocyanate, 1,6,11-undecatriisocyanate, 1,3,6-hexamethylene triisocyanate, 1,8-diisocyanate-4-isocyanatomethyloctane, cyclohexane diisocyanate, dimethylcyclohexane diisocyanate, 4, Alicyclic polyisocyanates such as 4'-methylenebis (cyclohexyl isocyanate), isophorone diisocyanate, and bicycloheptane triisocyanate; p-phenylene diisocyanate,
2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, tetramethyl xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, tolidine diisocyanate, 1,5-naphthalene diisocyanate, tris (isocyanate phenyl methane) , Aromatic polyisocyanates such as tris (isocyanatephenyl) thiophosphate, polyisocyanate compounds such as heterocyclic polyisocyanates such as isocyanurate, hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, glycerol di (meth) acrylate , Pentaerythritol tri (meth) acrylate,
Reaction products with a hydroxyalkyl (meth) acrylate compound such as tetramethylolethane tri (meth) acrylate are exemplified.

The epoxy (meth) acrylates include, for example, (poly) ethylene glycol polyglycidyl ether, (poly) propylene glycol polyglycidyl ether, (poly) tetramethylene glycol polyglycidyl ether, (Poly) pentamethylene glycol polyglycidyl ether, (poly) neopentyl glycol polyglycidyl ether,
Aliphatic polyepoxy compounds such as (poly) hexamethylene glycol polyglycidyl ether, (poly) trimethylolpropane polyglycidyl ether, (poly) glycerol polyglycidyl ether, (poly) sorbitol polyglycidyl ether, sorbitan polyglycidyl ether, triglycidyl Heterocyclic polyepoxy compounds such as isocyanurate, triglycidyl tris (2-hydroxyethyl) isocyanurate, phenol novolak polyepoxy compound, brominated phenol novolak polyepoxy compound, (o-, m-, p-) cresol novolak polyepoxy Compounds, bisphenol A polyepoxy compounds, bisphenol F polyepoxy compounds and other aromatic polyepoxy compounds such as polyepoxy compounds, and (meth) a Reaction products of acrylic acid or hydroxyalkyl (meth) acrylate compounds.

As the phosphates having a (meth) acryloyloxy group, specifically, those represented by the following general formula (Ia) or (Ib) are preferable.

[0017]

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[In the formulas (Ia) and (Ib), R ¹ represents a hydrogen atom or a methyl group, n is an integer of 1 to 25, and m is 1, 2, or 3. Here, n is preferably from 1 to 10, particularly preferably from 1 to 4. Specific examples thereof include, for example, (meth) acryloyloxyethyl phosphate, bis [(meth) acryloyloxyethyl] phosphate, (meth) ) Acryloyloxyethylene glycol phosphate and the like, which may be used alone or as a mixture.

Other polyfunctional ethylenically unsaturated compounds other than the above include, for example, ethylene bis (meth)
Examples thereof include (meth) acrylamides such as acrylamide, allyl esters such as diallyl phthalate, and vinyl group-containing compounds such as divinyl phthalate.

In the present invention, the (meth) acryloyloxy group described above is used as the ethylenically unsaturated compound as the component (A) from the viewpoints of exposure sensitivity, printing durability, and developability as a photosensitive layer. It is preferable to contain phosphates, and the content of the phosphates in the whole ethylenically unsaturated compound is 1 to 60% by weight, particularly 5 to 5% by weight.
It is preferably 0% by weight.

In the present invention, the photopolymerization initiation system as the component (B) of the photopolymerizable composition constituting the photosensitive layer generally comprises a radical generator (photopolymerization initiator) and a sensitizer, and in some cases, Further, it contains a polymerization accelerator. The radical generator is a compound that generates an active radical when the photopolymerizable composition is irradiated with an actinic ray and causes the ethylenically unsaturated compound as the component (A) to polymerize, Those having sensitivity in the ultraviolet to near-infrared light region can be mentioned. In particular, those sensitive to the visible light region are preferable, and examples thereof include titanocenes, hexaarylbiimidazoles, halogenated hydrocarbon derivatives, diaryliodonium salts, and organic peroxides.
Among them, titanocenes and hexaarylbiimidazoles are preferable, and titanocenes are particularly preferable, in view of sensitivity as a photopolymerizable composition, adhesion to a support, and storage stability.

Examples of the titanocenes include compounds described in JP-A-59-152396 and JP-A-61-151197, for example, dicyclopentadienyltitanium dichloride, dicyclopentadienyl Titanium bisphenyl, dicyclopentadienyl titanium bis (2,4-difluorophenyl), dicyclopentadienyl titanium bis (2,6-difluorophenyl), dicyclopentadienyl titanium bis (2,4,6- Trifluorophenyl), dicyclopentadienyl titanium bis (2,3,5,6-tetrafluorophenyl), dicyclopentadienyl titanium bis (2,3,4,5,6-pentafluorophenyl), (Methylcyclopentadienyl) titanium bis (2,6-difluoro Phenyl), di (methylcyclopentadienyl) titanium bis (2,3,4,5,6
-Pentafluorophenyl), dicyclopentadienyltitanium bis [2,6-difluoro-3- (1-pyrrolyl) phenyl] and the like.

The hexaarylbiimidazoles include, for example, 2,2'-bis (o-chlorophenyl)-
4,4 ′, 5,5′-tetra (p-chlorophenyl) biimidazole, 2,2′-bis (o-chlorophenyl)
-4,4 ', 5,5'-tetra (o, p-dichlorophenyl) biimidazole, 2,2'-bis (o-chlorophenyl) -4,4', 5,5'-tetra (p-fluorophenyl) ) Biimidazole, 2,2'-bis (o-chlorophenyl) -4,4 ', 5,5'-tetra (o, p-
Dibromophenyl) biimidazole, 2,2'-bis (o, p-dichlorophenyl) -4,4 ', 5,5'-
Tetra (o, p-dichlorophenyl) biimidazole,
2,2′-bis (o-bromophenyl) -4,4 ′,
5,5'-tetra (o, p-dichlorophenyl) biimidazole, 2,2'-bis (o-bromophenyl)-
4,4 ′, 5,5′-tetra (p-iodophenyl) biimidazole, 2,2′-bis (o-bromophenyl)
-4,4 ', 5,5'-tetra (o-chloro-p-methoxyphenyl) biimidazole, 2,2'-bis (o-
(Chlorophenyl) -4,4 ', 5,5'-tetra (p-
Hexaarylbiimidazole compounds having a halogen-substituted aromatic ring such as chloronaphthyl) biimidazole. These hexaarylbiimidazole compounds include, for example, Bull.Chem.Soc.Japan; 33,565 (1960), J.Or
g. Chem .; 36, 2262 (1971) and the like.

As a sensitizer for activating the radical generator upon irradiation with actinic rays to effectively generate an active radical, a sensitizer particularly sensitive to the visible light region is preferable. No. 3479185, triphenylmethane-based leuco dyes such as leuco crystal violet and leucomalachite green, photoreducing dyes such as erythrosin and eosin Y,
Aminophenyl ketones such as Michler's ketone and aminostyryl ketone disclosed in U.S. Pat. Nos. 3,549,367 and 3,652,275;
Β-diketones disclosed in US Pat. No. 4,790,464, indanones disclosed in US Pat. No. 4,162,162, JP-A-6-301208, JP-A-8-12925.
No. 8, JP-A-8-129259, JP-A-8-1466
Coumarin-based pigments disclosed in JP-A Nos. 05-111605 and 8-221605, ketocoumarin-based pigments disclosed in JP-A-52-112681, and JP-A-59-564.
Aminostyrene derivatives and aminophenylbutadiene derivatives disclosed in U.S. Pat.
No. 10, aminophenyl heterocycles disclosed in U.S. Pat. No. 4,966,830; julolidine heterocycles disclosed in U.S. Pat. No. 4,966,830;
Compounds such as pyromethene dyes disclosed in JP-A-5885 and JP-A-11-271969. Among them, coumarin pigments and pyromethene pigments are preferred.

Examples of the polymerization accelerator for enhancing the photopolymerization initiation ability include 2-mercaptobenzothiazole,
Mercapto group-containing compounds such as 2-mercaptobenzimidazole, 2-mercaptobenzoxazole, and 3-mercapto-1,2,4-triazole; N, N-dialkylaminobenzoic acid ester; N-phenylglycine; N-aryl-α-amino acids or derivatives thereof such as salts such as sodium salts, derivatives such as esters thereof, N-phenylalanine, or salts thereof such as ammonium and sodium salts, derivatives thereof such as esters, and the following general formula: And hydrogen-donating compounds such as the compounds represented by (II).

[0026]

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[In the formula (II), R ² represents a hydrogen atom or an alkyl group which may have a substituent; R ³ represents a hydrogen atom, an alkyl group which may have a substituent; A vinyl group which may have a group, an allyl group which may have a substituent, an (meth) acryloyloxy group which may have a substituent, an aryl group which may have a substituent Or an aromatic heterocyclic group which may have a substituent, wherein the benzene ring may have a substituent, and p is an integer of 2 to 10. ]

Here, examples of the substituent on the benzene ring include an alkyl group which may have a substituent, an alkoxy group which may have a substituent, and an acyl group which may have a substituent. Group, an alkoxycarbonyl group which may have a substituent, a vinyl group which may have a substituent, an allyl group which may have a substituent, and a group which may have a substituent (meth A) an acryloyloxy group, an aryl group which may have a substituent, or an aromatic heterocyclic group which may have a substituent.

In the present invention, as the polymer binder as the component (C) of the photopolymerizable composition constituting the photosensitive layer, for example, (meth) acrylic acid, (meth) acrylic acid ester, (meth) acrylate Homopolymers or copolymers such as acrylonitrile, (meth) acrylamide, maleic acid, styrene, vinyl acetate, vinylidene chloride, and maleimide, as well as polyamide, polyester, polyether, polyurethane, polyvinyl butyral, polyvinyl pyrrolidone, polyethylene oxide, and acetyl Cellulose and the like can be mentioned, and among them, a carboxyl group-containing polymer is preferred from the viewpoint of alkali developability, and specifically, (meth) acrylic acid and alkyl (meth) acrylate (having 1 to 10 carbon atoms). ) Copolymers containing ester or styrene as a copolymer component Preferably, the acid value of the carboxyl group-containing polymer is 10 to 250, weight average molecular weight is preferably 0.5 to 100 to 250,000. In addition, JP
Those having a carboxyl group and an unsaturated bond described in JP-A-312055 are also preferable. In the present invention, it is preferable to adjust the acid value of the photosensitive layer using these carboxyl group-containing polymers.

The acid value of the polymer binder containing a carboxyl group is calculated as follows. For example, in a copolymer of monomers A, B and C, when one carboxyl group is present in monomer C, the acid value of the polymer binder is c / ([A] × a + [B] × b + [ C] × c) × 56.
Calculated as 1 × 1000. Here, [A], [B], and [C] represent the molecular weights of monomers A, B, and C, and a, b, and c represent the copolymerization rates of monomers A, B, and C.

As the polymer binder, those having an ethylenically unsaturated bond in the side chain are preferable, and as the ethylenically unsaturated bond, the following general formulas (IIIa), (IIIb),
Or those represented by (IIIc) are preferred.

[0032]

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[In the formulas (IIIa), (IIIb) and (IIIc), R^Four
Represents a hydrogen atom or a methyl group; ^Five, R⁶, R⁷, R
⁸, And R⁹Are each independently a hydrogen atom, a halogen atom
Child, amino group, dialkylamino group, carboxyl group,
Alkoxycarbonyl group, sulfo group, nitro group, cyano
Group, an alkyl group which may have a substituent,
Optionally having an alkoxy group or a substituent
Alkylamino groups and optionally substituted alkyl
Rusulfonyl group, aryl which may have a substituent
Group, aryloxy group which may have a substituent, substitution
An arylamino group which may have a group or a substituent
Represents an arylsulfonyl group which may have
Oxygen atom, sulfur atom, imino group, or alkylimino
Represents a group. ]

Here, an alkyl group for R ^{5 to} R ⁹ ,
Examples of the substituent of the alkoxy group, the alkylamino group, the alkylsulfonyl group, the aryl group, the aryloxy group, the arylamino group, and the arylsulfonyl group include, for example,
Examples thereof include an alkyl group, an alkoxy group, an alkylthio group, an amino group, a dialkylamino group, a nitro group, a cyano group, a phenyl meaning, and a halogen atom.

The polymer binder having an ethylenically unsaturated bond in the side chain represented by the formula (IIIa) is prepared by adding a carboxyl group-containing polymer to allyl glycidyl ether, glycidyl (meth) acrylate, α-ethyl glycidyl ( Meta)
Acrylate, glycidyl crotonate, glycidyl isocrotonate, crotonyl glycidyl ether, monoalkyl monoglycidyl itaconate, monoalkyl monoglycidyl fumarate, monoalkyl monoglycidyl maleate and other unsaturated compounds containing an aliphatic epoxy group, Alternatively, an alicyclic epoxy group-containing unsaturated compound such as 3,4-epoxycyclohexylmethyl (meth) acrylate may be used at a temperature of about 80 to 120 ° C.,
In about 50 to 50 hours, 5 to 90 mol%, preferably 3 to 90 mol% of the carboxyl groups of the carboxyl group-containing polymer.
It is obtained by reacting about 0 to 70 mol%.

Polymer binders having an ethylenically unsaturated bond represented by the formula (IIIb) in the side chain include allyl (meth) acrylate, 3-allyloxy-2-hydroxypropyl (meth) acrylate, cinnamyl (meth) A) a compound having two or more unsaturated groups such as acrylate, crotonyl (meth) acrylate, methallyl (meth) acrylate, N, N-diallyl (meth) acrylamide, and an unsaturated carboxylic acid such as (meth) acrylic acid; Alternatively, it can be obtained by copolymerizing with an unsaturated carboxylic acid ester such that the ratio of the former compound having an unsaturated group to the whole is 10 to 90 mol%, preferably about 30 to 80 mol%. Similarly, polymer binders having an ethylenically unsaturated bond represented by the formula (IIIc) in the side chain include vinyl (meth) acrylate, 1-chlorovinyl (meth) acrylate, and 2-phenylvinyl (meth) Acrylate,
Compounds having two or more types of unsaturated groups such as 1-propenyl (meth) acrylate, vinyl crotonate, vinyl (meth) acrylamide, and unsaturated carboxylic acids such as (meth) acrylic acid or further unsaturated carboxylic acid esters Are copolymerized so that the ratio of the former compound having an unsaturated group to the whole is 10 to 90 mol%, preferably about 30 to 80 mol%.

In the present invention, the contents of the ethylenically unsaturated compound (A), the photopolymerization initiation system (B), and the polymer binder (C) constituting the photosensitive layer are as follows: The radical generator in the photopolymerization initiation system of the component (B) is usually 0.1 to 80 parts by weight, preferably 0.5 to 100 parts by weight of the ethylenically unsaturated compound of the component A).
６０60 parts by weight, the sensitizer is usually 0.01-20 parts by weight,
Preferably 0.05 to 10 parts by weight, the polymerization accelerator is usually 0.1 to 80 parts by weight, preferably 0.5 to 60 parts by weight, and the polymer binder of the component (C) is usually 10-4
00 parts by weight, preferably 20 to 200 parts by weight.

Further, as the photopolymerizable composition in the present invention, various additives, for example, a thermal polymerization inhibitor such as hydroquinone, p-methoxyphenol and 2,6-di-tert-butyl-p-cresol may be used. 20 parts by weight or less of a colorant comprising an organic or inorganic dye / pigment, 40 parts by weight or less of a plasticizer such as dioctyl phthalate, didodecyl phthalate, and tricresyl phosphate, and sensitivity characteristics such as tertiary amine and thiol. An improver, a coating improver such as a fluorine-based surfactant or the like, and a development accelerator may be contained in a proportion of 10 parts by weight or less and a dye precursor in a proportion of 30 parts by weight or less.

The important recognition in the present invention is to control the acid value of the entire photosensitive layer containing the above-mentioned main agent and auxiliary agent (various additives) in the range of 25 to 34. The origin of the compound having an acid value is not particularly limited, but the ethylenically unsaturated compound as the component (A) and the polymer binder as the component (C) constituting the photosensitive layer may have an acid group. preferable. For example, as the component (A), phosphates having a (meth) acryloyloxy group and carboxylic acids having a (meth) acryloyloxy group, and as the component (C), (meth) acrylic acid and (meth) acrylic acid are used. The acid value can be adjusted by using an alkyl (1 to 10 carbon atoms) ester or a carboxyl group-containing polymer containing styrene as a copolymer component and changing the amount of the acid component used. . Select to represent the acid value of the photopolymerizable photosensitive layer in another indicator, as the sum number of the photosensitive layer 10 ⁶ g acid groups per (a phosphate group and / or carboxyl group), preferably from 450 to 600 amino range Is done. Further, the acidic group preferably has both a phosphate group and a carboxyl group, and the ratio of the phosphate group to the carboxyl group is usually 10:90 to 90:10, preferably 15:85 to 85:15. . The number of the acidic groups can be quantified by an NMR method, an FT-IR method, a MASS method, or the like.

In order to impart sufficient strength to the photopolymerizable photosensitive layer for laser exposure, it is considered advantageous to use an alkali or a component which is hardly soluble in various chemicals. In order to have it, a somewhat higher acid value was required. However, the strength of the photosensitive layer
It has been found that, in addition to the properties of the components constituting the photosensitive layer, damage during development has a significant effect. That is, those having a relatively low acid value which are not easily damaged by the alkaline developer are advantageous. However, it has been found that a certain degree of polarity is essential in terms of compatibility with a hydrophilic support and imparting developability, and an acid value of 25 to 34 is an appropriate region. On the other hand, since the developing solution is not easily damaged during development, the developing solution used is less than pH 13, especially pH 9-1.
Two are preferred.

In producing the lithographic printing plate of the present invention, the photopolymerizable composition is usually applied to the surface of a support as a solution in which the above components are dissolved in an appropriate solvent, and then heated and dried. To form a photosensitive layer comprising the photopolymerizable composition on the surface of a support.

The support is a plate made of aluminum or an alloy containing aluminum as a main component and containing silicon, copper, manganese, magnesium, chromium, zinc, lead, bismuth, nickel, and the like. 0.01-10
mm, preferably 0.05 to 1 mm.

Prior to the formation of the photosensitive layer made of the photopolymerizable composition on the surface of the aluminum plate support, usually, a degreasing treatment, a roughening treatment (graining treatment), a desmutting treatment, an anodic oxidation treatment, What has been subjected to a sealing treatment, an undercoating treatment and the like is used.

Here, the degreasing treatment includes a method of wiping with a solvent, immersing or steam-cleaning, a method of immersing or spraying with an alkaline aqueous solution, and then neutralizing with an aqueous acid solution.
It is performed according to a conventional method such as a method of dipping or spraying using a surfactant.

The surface roughening treatment (graining treatment) includes mechanical treatment methods such as a ball polishing method, a brush polishing method, a blast polishing method, a honing polishing method and a buff polishing method, and electrochemical etching using hydrochloric acid, nitric acid or the like. Method (electrolytic etching method), chemical etching method using an acid or alkali etching agent,
Alternatively, they are performed by appropriately combining them. Among them, brush polishing, ball polishing, liquid honing polishing, electrolytic etching, chemical etching, and the like are preferable, and in particular, electrolytic etching in which hydrochloric acid or nitric acid is used to perform electrolysis with alternating current or direct current. In this case, an acid concentration of about 0.5 to 5% by weight,
The treatment is preferably performed at a current density of about 200 A / dm ^{2 and} a voltage of about 10 to 40 V at a temperature of about 20 to 50 ° C. When sulfuric acid, oxalic acid, or the like is appropriately added during the electrolytic etching method, an oxide film can be formed simultaneously with etching.

The acid etching agents include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and oxalic acid. The alkaline etching agents include sodium hydroxide, sodium carbonate, sodium aluminate, sodium metasilicate, sodium phosphate, and the like. Potassium hydroxide, lithium hydroxide and the like are used. These acid or alkali etching agents are usually 0.5
It is used as an aqueous solution of ５０50% by weight, preferably 1-30% by weight, and the treatment is usually carried out at a temperature of 20-100 ° C., preferably 30-80 ° C. On the high temperature and high concentration side, the etching rate is high, which is advantageous for industrial production. However, since there is a problem in control of the surface state and stability, it is usually selected from the above range. Mild etching at a low temperature and low concentration is preferable in terms of uniformity of the surface state of the support. By such a roughening treatment, the surface of the support becomes JIS
The average roughness (Ra) specified in B0601 is 0.1 to
The thickness is about 1.5 μm, preferably about 0.2 to 1.0 μm.

On the surface of the roughened aluminum,
Mechanical polishing scum, by-products during etching, such as aluminum oxide, oxide hydrate, hydroxide, as well as oxides of impurities such as iron, hydroxide, and other substances called smut There is accumulation. The smut formed by electrolytic etching is often in the form of a spud and porous.
The smut is considered to cause dust and dirt in a later step, or has an adverse effect on the adhesiveness to the photosensitive layer, and a step called “desmut” for removing the smut is added.

The desmut treatment may be performed by using an acid such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, or chromic acid, or sodium hydroxide, potassium hydroxide, sodium metasilicate, sodium phosphate, sodium pyrophosphate, potassium phosphate, sodium aluminate, or the like. This is performed according to a conventional method such as immersion or spraying using an aqueous alkali solution.

For example, at a concentration of 1 to 4% by weight and a liquid temperature of 0 to 40
Conditions such as immersion in an aqueous solution of sodium hydroxide at about 1 ° C. for about 1 to 10 seconds can be given. Preferably, 0.3 to 3% by weight of sodium hydroxide aqueous solution having a liquid temperature of 5 to 30 ° C is 1 to 5%.
A second immersion method can be used.

Next, an oxide film is formed to chemically stabilize the desmutted aluminum surface.
Usually, an electrochemical method is used. Anodizing treatment is
Generally, an aqueous solution of sulfuric acid, phosphoric acid, boric acid or the like is used as an electrolytic solution. In particular, an aqueous solution containing mainly sulfuric acid or sulfuric acid and an aqueous solution containing oxalic acid, phosphoric acid, chromic acid, malonic acid, or the like is used. It is preferable from the viewpoint of printability. At that time, the acid concentration is 5
５０50% by weight, preferably 15-30% by weight, current density is 1-60 A / dm ² , preferably 2-50 A / d
The treatment is preferably performed at m ² , voltage of 1 to 150 V, electrolytic bath temperature of 5 to 50 ° C., preferably 15 to 35 ° C., and electrolysis time of about 5 to 60 seconds. The amount of the oxide film formed on the aluminum plate by using these is preferably 1 to 100 mg / dm ² , and particularly preferably 10 to 50 mg / dm ² .

The support subjected to the anodizing treatment is subjected to a sealing treatment as required. This treatment involves boiling water, steam,
This is performed according to a conventional method such as immersion or spraying using an aqueous solution of sodium silicate, an aqueous solution of dichromate, or the like.

The underlining process performed as needed is
A resin containing an acid group or an onium group, a resin having a cationic quaternary ammonium salt group, polyvinylphosphonic acid, starch, a water-soluble polymer such as cellulose, or an aqueous solution of a metal salt such as fluorinated zirconic acid, Or, it is performed according to a conventional method such as spraying.

Further, if necessary, a treatment with an alkali silicate such as sodium silicate or hot water, a dipping treatment of a resin having a cationic quaternary ammonium base or a water-soluble polymer compound such as polyvinyl sulfonic acid in an aqueous solution, etc. Can be applied.

The solvent used for applying the photopolymerizable composition solution to the surface of the support is not particularly limited as long as it has sufficient solubility for the components used and gives good coating properties. For example, methyl cellosolve, ethyl cellosolve,
Cellosolve solvents such as methyl cellosolve acetate and ethyl cellosolve acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monobutyl ether acetate, dipropylene Propylene glycol solvents such as glycol dimethyl ether, butyl acetate, amyl acetate, ethyl butyrate, butyl butyrate, diethyl oxalate, ethyl pyruvate, ethyl-2-hydroxybutyrate, ethyl acetoacetate, methyl lactate, ethyl lactate, 3-methoxy Ester solvents such as methyl propionate, heptanol, hexanol, Seton alcohol, alcohol-based solvents such as furfuryl alcohol, cyclohexanone,
Examples thereof include ketone solvents such as methyl amyl ketone, highly polar solvents such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone, and mixed solvents thereof, and those in which an aromatic hydrocarbon is added thereto. The usage ratio of the solvent is usually in the range of about 1 to 20 times by weight based on the total amount of the photopolymerizable composition.

The coating method is, for example, dip coating, spinner coating, spray coating, roll coating,
A coating rod or the like can be used. The coating amount varies depending on the application, but is usually 0.1 to 1 as a dry film thickness.
0 g / m ^2, preferably in the range of 0.5 to 5 g / m ^2.

The photopolymerizable image-forming material of the present invention is used for preventing the photopolymerizable composition from inhibiting polymerization by oxygen on the photosensitive layer of the photopolymerizable composition formed on the surface of the support. It is preferable that an oxygen barrier layer is formed.

The constituents of the oxygen barrier layer are water,
Or, with water, methanol, ethanol, propanol,
A polymer soluble in a mixed solvent with an alcohol such as isononyl alcohol or a water-miscible organic solvent such as tetrahydrofuran, for example, polyvinyl alcohol, and a partially acetalized product thereof, and a cation-modified product thereof such as a quaternary ammonium salt; Derivatives such as anion-modified products thereof with sodium sulfonate, polypinylpyrrolidone, polyethylene oxide, methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, gelatin, gum arabic, methylvinylether-maleic anhydride copolymer, polyacryl Partially saponified acid esters, carboxyl group-containing compounds such as unsaturated carboxylic acids such as vinylpyrrolidone, (meth) acrylic acid, and itaconic acid and derivatives thereof, hydroxyethyl ( Data) copolymers of copolymerizable components a hydroxyl group-containing compounds such as acrylamide and the like.

Among them, polyvinyl alcohol and its derivatives are preferable from the viewpoint of oxygen barrier property and the like, and the degree of saponification is 70 to 99 mol%, more preferably 85 to 95 mol%.
Preferably, the weight average molecular weight is 0.2 to 500,000, more preferably 0.4 to 100,000.

Further, from the viewpoint of adhesiveness to the photosensitive layer, vinylpyrrolidone-based polymers such as polyvinylpyrrolidone and vinylpyrrolidone-vinyl acetate copolymer, acrylic polymer emulsions, diisocyanate compounds, p-toluenesulfonic acid, It is preferable to contain hydroxyacetic acid and the like, and it is preferable to contain these in an amount of 0.1 to 60 parts by weight, more preferably 1 to 50 parts by weight, based on 100 parts by weight of the polyvinyl alcohol and its derivative.

Further, from the viewpoint of imparting preservability, it is preferable to contain an organic acid such as succinic acid or an organic acid salt such as ethylenediaminetetraacetic acid. Nonionics such as phenyl ether, anionics such as sodium dodecylbenzenesulfonate, cationic surfactants such as alkyltrimethylammonium chloride, and other defoaming agents, dyes, plasticizers, pH adjusters, etc. It may be contained in a proportion of 10 parts by weight or less based on 100 parts by weight of the alcohol and its derivative.

The oxygen barrier layer is formed as a solution of water or a mixed solvent of water and a water-miscible organic solvent by the same coating method as that for the photosensitive layer described above. Usually 1 to 10 g / m ² , preferably 1.5 to
The range is 7 g / m ² .

In the image forming method of the present invention, the photopolymerizable image forming material is exposed, developed, and, if necessary, further heated or post-exposed. As the exposure, there is a method of irradiating a carbon arc lamp, a mercury lamp, a metallohalide lamp, a xenon lamp, a tungsten lamp, or the like through the original image. In the present invention, scanning exposure using laser light is preferable.

As the laser exposure light source, for example,
Helium cadmium laser, argon ion laser, FD-YAG laser, helium neon laser,
A semiconductor laser, a YAG laser, a ruby laser, or the like is used. Specifically, a semiconductor laser in a blue-violet region with a wavelength of about 390 to 430 nm, an argon ion laser at about 488 nm, an FD-YAG laser at about 532 nm, and a 700 to 1300 nm Semiconductor laser and YAG
Laser and the like. The appropriate amount of laser exposure varies depending on the type of laser light source or plotter used. For example, in the case of a semiconductor laser in the blue-violet region of 390 to 430 nm, 0.5 to 100 μJ / cm ² , an argon ion laser near 488 nm and an argon ion laser near 532 nm are used. FD-
5 ~ 500μJ / cm ² , 700 ~
0.5-200mJ for 1300nm semiconductor laser
/ Cm ² is preferred. Conventionally, after laser exposure, 40
In many cases, a step of stabilizing the latent image by performing a heat treatment in a temperature range of from about 300 ° C. to about 100 ° C. is often adopted. However, in the present invention, the adhesion between the support and the photosensitive layer is good. Therefore, it is possible to directly enter the next development step without performing such heat treatment. One of the features of the present invention is that the process is simplified and contributes to productivity.

In the processing method of the present invention, after the photosensitive lithographic printing plate has been subjected to image exposure with such a laser exposure machine, the protective layer is washed with water before development to remove all or most of the protective layer. Good. The method of washing with water is not particularly limited, but specifically, a method of dissolving by immersing in water, a method of dissolving and removing by spraying water in a shower, and a method of removing a brush in a state of being immersed or sprayed with water. And the like. The washing temperature is usually 4 to 70
° C, preferably 10 to 50 ° C, more preferably 15 to 3 ° C.
0 ° C., and the washing time is about 1 second to 5 minutes, depending on the washing method. The washing water may contain a surfactant and a water-miscible organic solvent, if necessary.

Examples of the developing solution include, for example, sodium silicate, potassium silicate, lithium silicate, ammonium silicate, sodium metasilicate, potassium metasilicate, sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, Inorganic alkali salts such as sodium bicarbonate, potassium carbonate, sodium diphosphate, sodium tertiary phosphate, ammonium diphosphate, ammonium tertiary phosphate, sodium borate, potassium borate, ammonium borate, or monomethylamine, dimethylamine, trimethylamine , Monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, monobutylamine, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diethylamine Alkali developer comprising an aqueous solution of about 0.1 to about 10% by weight of an organic amine compounds such as propanolamine is used.

For the purpose of improving the image quality, shortening the development time, etc., the developing solution may contain, for example, polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers, polyoxyethylene alkyl ester. , Sorbitan alkyl esters, monoglyceride alkyl esters, etc., nonionic, alkyl benzene sulfonates, alkyl naphthalene sulfonates, alkyl sulfates, alkyl sulfonates, sulfosuccinate salts, etc., alkyl betaines, amino acids Amphoteric surfactants such as isopropyl alcohol, benzyl alcohol, ethyl cellosolve, butyl cellosolve, phenyl cellosolve, propylene glycol, diacetone alcohol, etc. It is possible. The photosensitive layer of the present invention is characterized by having an acid value of 25 to 34, which is lower than that of the prior art.
Is preferably less than 13, especially 9 to 12.

The development is usually performed by a known development method such as immersion development, spray development, brush development, or ultrasonic development.
Preferably about 10 to 60 ° C, more preferably 15 to 4 ° C.
This is performed at a temperature of about 5 ° C. for a time of about 5 seconds to about 10 minutes. At this time, the oxygen barrier layer may be removed in advance with water or the like, or may be removed during development.

[0068]

EXAMPLES Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples unless it exceeds the gist. In the following examples, the acid value was measured according to the following. Lithographic printing plate (sample)
The photosensitive layer (about 0.1 to 0.5 g) was eluted with methyl cellosolve, and the obtained photosensitive layer solution was determined by titration with 0.1 N sodium hydroxide using phenolphthalein as an indicator. The weight of the photosensitive layer was calculated as the weight difference between the lithographic printing plates before and after the dissolution treatment of the photosensitive layer. The photosensitive layer Xg is
If neutralized with 0.1 ml of 0.1N NaOH aqueous solution,
The acid value is determined by the following equation. Acid value = Y × 0.1 × 56.1 / X

Example 1 The following ethylenically unsaturated component (A) was coated on the surface of the following aluminum plate support:
A coating solution of a photopolymerizable composition comprising a radical generator as a polymerization initiator as a component (B), a sensitizer, a polymerization accelerator, a polymer binder as a component (C), and other components, and a solvent is used. dry film thickness using. the coating is 2.0 g / m ^2, to form a photosensitive layer comprising a photopolymerizable composition was dried for 2 minutes at 70 ° C.. Further, a mixed aqueous solution of polyvinyl alcohol and polyvinylpyrrolidone (polyvinyl alcohol: polyvinylpyrrolidone = 70% by weight: 30% by weight) was further dried thereon by using a bar coater to have a dry film thickness of 3%.
g / m ² and dried at 70 ° C. for 4 minutes to form an oxygen barrier layer, thereby producing a photosensitive lithographic printing plate as a photopolymerizable image forming material. The acid value of the photosensitive layer is 30, as the acidic group of the photosensitive layer 10 in ⁶ g, a phosphate group in the ethylenically unsaturated compound [(A) component]: 202
And 351 carboxyl groups in the polymer binder [component (C)], for a total of 553.

Production of Support A raw aluminum sheet having a thickness of 0.24 mm was degreased with a 3% by weight aqueous solution of sodium hydroxide and then washed with water. Then, in a 18.0 g / liter nitric acid bath, at 25 ° C. and 87 A
A surface roughening treatment by electrolytic etching was performed at a current density of / dm ² for 11 seconds. After washing with water, it was immersed in a 4.5% by weight aqueous solution of sodium hydroxide at 30 ° C. for 2 seconds to perform a desmut treatment. After desmut treatment, wash with water
The solution was neutralized with a 10% by weight aqueous solution of nitric acid at 5 ° C. for 5 seconds and washed with water. Then, in a 30% by weight sulfuric acid bath, 30 ° C., 10 A /
Anodize at current density of dm ² for 16 seconds, wash with water,
After drying, an aluminum plate support was obtained. The surface average roughness (Ra) of the support was measured according to JIS B0601, and was 0.6 μm.

(A) Ethylenically unsaturated compound Mixture of methacryloyloxyethyl phosphate and bis (methacryloyloxyethyl) phosphate of the following A (acid value 171); 8 parts by weight of hexamethylene bis [tris (acryloyloxymethyl) of the following B ) Ethyl urethane] (zero acid value); 22 parts by weight 2,2-bis (4-acryloyloxydiethyleneoxyphenyl) propane of the following C (zero acid value); 22 parts by weight

[0072]

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(B) Photopolymerization initiator (B-1) Radical generator dicyclopentadienyltitanium bis [2,6-difluoro-3- (1-pyrrolyl) phenyl]; 5 parts by weight

(B-2) Sensitizer Compound of the following D; 0.5 parts by weight Compound of the following E; 0.5 parts by weight

[0075]

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(B-3) Polymerization accelerator 2-mercaptobenzothiazole; 5 parts by weight N-phenylglycine benzyl ester; 5 parts by weight

(C) Polymer binder Methyl methacrylate (80 mol%) / methacrylic acid (20 mol%) copolymer (weight average molecular weight: 50,000)
Reaction product obtained by reacting 3,4-epoxycyclohexylmethyl acrylate (acid value 53, 50 mol% of carboxyl groups of methacrylic acid component react); 45 parts by weight

Other component pigment (P.B. 15: 6); 4 parts by weight dispersant ("Disperbyk 161" manufactured by BYK-Chemie);
2 parts by weight surfactant (“Emulgen 104P” manufactured by Kao Corporation); 2
Parts by weight surfactant ("S-381" manufactured by Asahi Glass Co., Ltd.); 0.3 parts by weight

Solvent propylene glycol monomethyl ether acetate; 600 parts by weight cyclohexanone; 545 parts by weight

The obtained photosensitive lithographic printing plate was subjected to FD-YA
Using a G laser exposure machine (“Platejet” manufactured by Cybolic Science International), 2000 dpi, 6.8 m
Under a condition of W (exposure amount: 120 μJ / cm ² ), 2% flat knitting was exposed. Then, potassium silicate 3% by volume, sodium alkylnaphthalenesulfonate-based surfactant (concentration 3
5% by weight, Kao Corporation "Perex NBL") 5% by volume,
Using a developing solution (pH 11.2) consisting of 92% by volume of water, an automatic developing machine (Diamond manufactured by Western Litho Tech) was used.
(Developer) at a developer temperature of 30 ° C. and a transport speed of 4 FPM. The results are shown in Table 1.

The planographic printing plate obtained by making a plate in this manner was set on a printing machine (RP-1 manufactured by Roland) to perform a printing durability test. The printing durability was determined by a reproduction state of 2% of the image area after printing 30,000 sheets. The results are shown in Table 1. ；: Reproducibility of 90% or more △: Reproducibility of 50% or more, less than 90% ×: Reproducibility of less than 50%

Example 2 In Example 1, as shown in Table 1, the amount of (A) the ethylenically unsaturated compound used was changed from 8 parts by weight to 3 parts by weight, and (C) The use amount of the agent was changed from 45 parts by weight to 35 parts by weight,
Instead, 10 parts by weight of a polymer binder was used, and the acid value of the entire photosensitive layer was set to 29. The (C) polymer binder is a methyl methacrylate (70 mol%) / methacrylic acid (30 mol%) copolymer (weight average molecular weight 50,000)
And a reaction product obtained by reacting 3,4-epoxycyclohexylmethyl acrylate (acid value: 107, 33 mol% of carboxyl groups of the methacrylic acid component react). A photosensitive lithographic printing plate was prepared in the same manner as in Example 1 except for the above changes. Hereinafter, exposure and development were performed in synchronization with each other, and a printing durability test was performed. The results are shown in Table 1.

[Comparative Examples 1 to 4] The acid value of the entire photosensitive layer was changed as shown in Table 1 by changing the compounding amount of (A) an ethylenically unsaturated compound or (C) a polymer binder. A photosensitive lithographic printing plate was prepared in the same manner as in Example 1 except for the above. Hereinafter, exposure and development were performed in synchronization with each other, and a printing durability test was performed. The results are shown in Table 1. It can be seen that good printing durability cannot be obtained when the acid value of the photosensitive layer is out of the range of the present invention.

[0084]

[Table 1]

[0085]

According to the present invention, a photosensitive lithographic printing plate having excellent adhesion between the support and the photosensitive layer and excellent developability and printing durability can be obtained. In particular, a sufficient image intensity can be given to an image obtained by scanning exposure with a laser beam.

Claims (9)

[Claims] A photosensitive lithographic printing plate having a photopolymerizable photosensitive layer containing an ethylenically unsaturated compound, a photopolymerization initiation system, and a polymer binder on a support, wherein the photopolymerizable photosensitive layer is A photosensitive lithographic printing plate having an acid value of 25 to 34. 2. The photosensitive lithographic printing plate according to claim 1, wherein the number of acidic groups in 10 ⁶ g of the photopolymerizable photosensitive layer is from 450 to 600. 3. The photosensitive lithographic printing plate according to claim 1, wherein the ethylenically unsaturated compound contains a phosphate having a (meth) acryloyloxy group. 4. The photosensitive lithographic printing plate according to claim 1, wherein the polymer binder has a carboxyl group. 5. A polymer binder comprising (meth) acrylic acid.
The photosensitive lithographic printing plate according to any one of claims 1 to 4, wherein the photosensitive lithographic printing plate is a (meth) acrylate copolymer or a derivative thereof. 6. An image forming method comprising subjecting the photosensitive lithographic printing plate according to claim 1 to laser exposure. 7. An image forming method, wherein the photosensitive lithographic printing plate according to claim 1 is exposed to a laser and then developed with an alkali developing solution containing an anionic surfactant. 8. An image forming method, wherein the photosensitive lithographic printing plate according to claim 1 is developed with an alkali developing solution having a pH of 12 or less after laser exposure. 9. An image forming method, wherein the photosensitive lithographic printing plate according to claim 1 is exposed to a laser, and then developed with a developer containing an alkali alkylnaphthalenesulfonate and an alkali silicate.