JP2007125835A - Original lithographic printing plate and lithographic printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithographic printing original plate which is free from the deterioration of exposure sensitivity and has improved plate strength as an original printing plate which does not require post-exposure development, and a lithographic printing plate to be obtained from the lithographic printing original plate. <P>SOLUTION: This lithographic printing original plate includes a photosensitive layer formed through a primary coat or directly on a support, wherein the a photosensitive resin composition forming the photosensitive layer contains at least an organic fine particle with from 1 or above to less than 80 of a hydroxyl group value (KOHmg/g) and a hydrophilic resin. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a printing original plate, in particular, a lithographic printing original plate using a fountain solution, and more specifically, a lithographic printing original plate that is sensitive to light in the near-infrared region and can be directly drawn on the plate with a laser beam, and The present invention relates to a planographic printing plate obtained by irradiating the original with light.

  With the spread of computers, there is a so-called computer-to-plate (CTP) type printing plate in which data on a computer is directly printed on a plate material with a laser beam, thermal head, or ink jet without using a plate-making film. It has begun to spread. Of these, plates using laser light are classified into two types: a photon mode type by photoreaction and a heat mode type in which photothermal conversion is performed to cause a thermal reaction. Among them, the heat mode type CTP plate has an advantage that it can be handled in a bright room, and is said to become mainstream in the future. Also, in photon mode, post-processes such as deactivation and development are essential so that unexposed parts do not react after exposure, whereas in heat mode these post-processes can be omitted. The mode type printing plate is expected to be a so-called development-less plate that does not use a developer.

  There are three types of development-less plates. Ablation type that burns off the surface layer by laser exposure, development type on printer that removes non-image area or image area with dampening water or ink on the printing press, hydrophilicity (or ink repellency) of laser exposure area There are three types of polarity conversion that change, and are proposed by various companies.

  Among these, the ablation type is recommended to be wiped off or washed after exposure because the burned-out surface layer becomes dust and adheres to the plate surface. Further, the development type on the printing press has a problem that the removed material is easily contaminated by mixing with dampening water, and the color of the printed material is clouded by mixing with ink. On the other hand, the polarity conversion type does not require any post-process such as wiping, and does not generate a removed material that adversely affects printing, and thus a complete process-less version is possible and is expected in the future.

  Therefore, the present applicants have developed and proposed a polarity conversion type development-less plate comprising a hydrophilic resin photosensitive layer obtained by crosslinking a photosensitive resin composition, and the surface changes from hydrophilic to ink-philicity by light irradiation. It was. For example, JP 2001-180144 A (Patent Document 1), JP 2002-362052 A (Patent Document 2), JP 2002-370467 A (Patent Document 3), JP 2004-122599 A (Patent Document 2). Document 4), International Publication No. 01/083234 (Patent Document 5), etc. have hydrophobic resin fine particles dispersed in a hydrophilic polymer matrix as a photosensitive layer, and the light absorber present in the photosensitive layer is irradiated with light. In this way, light is converted into heat, and the generated heat causes the hydrophobic polymer to foam or heat-seal, so that the hydrophilicity of the photosensitive layer in the light-irradiated portion is lost and changes to ink affinity. It is something that uses that.

  These lithographic printing plates are completely processless plates that do not require development or wiping operations. However, only the surface of the laser light irradiated area changes to ink-philic properties, so that the surface layer is scraped or peeled off if the plate surface is not strong enough. May occur, and the image line may deteriorate accordingly. Therefore, it has been desired to provide a plate with improved strength so that it can cope with printed matter having a large number of printed copies. However, in this case, if the sensitivity is lowered, the exposure time for plate making becomes long and plate making efficiency is lowered. Therefore, it has been desired to supply a plate with improved plate strength and no reduction in exposure sensitivity.

On the other hand, in a laser-sensitive lithographic printing original plate, a layer mainly composed of a thermoplastic polymer fine particle containing a hydroxyl group, an amine compound and a solvent-soluble binder polymer is used as a heat-sensitive layer for the purpose of improving image reproducibility and printing durability. A laser-sensitive lithographic printing original plate is also known (see Patent Document 6, etc.). However, the heat-sensitive layer in the method described in this publication is an oleophilic layer and requires development for obtaining a printing plate.
JP 2001-180144 A Japanese Patent Laid-Open No. 2002-362052 JP 2002-370467 A JP 2004-122599 A International Publication No. 01/083234 JP-A-11-334238

  An object of the present invention is to provide a lithographic printing plate and a lithographic printing plate which are sensitive to laser light in the near-infrared region, require no development or wiping operation, and have improved plate strength without reducing exposure sensitivity. Is to provide.

  As a result of intensive studies, the present inventors have improved the strength of the printing plate without reducing the exposure sensitivity by using organic fine particles having a hydroxyl value of 1 or more and less than 80 as the organic fine particles forming the image area. As a result, the present invention has been completed.

That is, the present invention has the following configuration.
(1) In a lithographic printing plate precursor having a photosensitive layer formed directly on the support via an underlayer or directly, at least the hydroxyl value (KOHmg / g) is 1 or more in the photosensitive resin composition forming the photosensitive layer A lithographic printing original plate comprising organic fine particles and a hydrophilic resin of less than 80.
(2) The hydrophilic resin in the photosensitive layer is an N-alkyl or N-alkylene-substituted (meth) acrylamide compound represented by the following general formula (1) (Chemical Formula 1) and / or (2) (Chemical Formula 2). The lithographic printing plate precursor as described in (1), which comprises a hydrophilic resin obtained by reaction using the lithographic printing plate.

(Wherein R ₁ represents a hydrogen atom or a methyl group, and R ₂ and R ₃ represent a hydrogen atom, a lower alkyl or a lower alkoxy group.)

(Wherein R ₁ represents a hydrogen atom or a methyl group, A represents (CH ₂ ) n (where n is 4 to 6) or (CH ₂ ) ₂ O (CH ₂ ) ₂ ).
(3) The hydrophilic resin is obtained from one or more compounds selected from compounds represented by the following general formula (3) (Chemical Formula 3) and / or salts thereof: (1) to (2) The lithographic printing original plate described.

(In the formula, R represents a hydrogen atom or a lower alkyl group, and n represents an integer of 1 to 8.)
(4) The lithographic printing plate precursor as described in (1) to (3), wherein the photosensitive resin composition forming the photosensitive layer contains a crosslinking agent capable of reacting with a hydroxyl group.
(5) The lithographic printing plate precursor according to (1) to (4), wherein the photosensitive layer is hydrophilic, and the surface of the photosensitive layer has a property of changing from hydrophilic to oleophilic upon irradiation with laser light.
(6) The lithographic printing original plate as described in (1) to (5), wherein the photosensitive resin composition forming the photosensitive layer further contains a light absorber and a surfactant.
(7) A lithographic printing plate obtained by irradiating light to the lithographic printing original plate described in (1) to (6).

  By using the lithographic printing original plate of the present invention, it is possible to provide a lithographic printing original plate that has excellent printing durability and can eliminate the need for steps such as development and wiping after exposure.

  Hereinafter, the lithographic printing original plate of the present invention, the lithographic printing plate obtained therefrom and the production method thereof will be described in detail.

  The lithographic printing original plate and lithographic printing plate of the present invention have a photosensitive layer formed directly or via an underlayer on a support, and at least in the photosensitive resin composition forming the photosensitive layer. It contains organic fine particles having a hydroxyl value (KOHmg / g) of 1 or more and less than 80 and a hydrophilic resin.

  In general, fine particles formed from a resin having a hydrophilic substituent tend to concentrate the hydrophilic substituent near the interface in contact with water. In the organic fine particles used in the present invention, the hydroxyl group is considered to be a hydrophilic substituent, and the surface of the fine particle is considered to have a partial hydroxyl group structure. Therefore, a part of the hydroxyl groups present on the particle surface react with the crosslinking agent, so that the organic fine particles can improve the strength of the plate without deteriorating the function of causing thermal fusion during light irradiation and forming the image area. It is considered a thing.

[Photosensitive layer]
Next, the photosensitive layer that can be used in the lithographic printing original plate of the present invention will be described. The lithographic printing original plate of the present invention is preferably a development-less plate for offset printing using a fountain solution, and is preferably hydrophilic and non-image portions other than the light-irradiated portion of the photosensitive layer. Therefore, in the present invention, the photosensitive layer is preferably hydrophilic and insoluble in water. In the printing original plate of the present invention, the photosensitive layer in the portion irradiated with light such as laser light is not removed by ablation, and the hydrophilicity of the photosensitive layer has a property of changing to ink-philicity. Is preferred. Therefore, the lithographic printing original plate of the present invention can eliminate the need for development or wiping after light irradiation. In order to embody the above-described change in characteristics, the photosensitive layer used in the lithographic printing original plate of the present invention comprises a photosensitive resin composition containing organic fine particles, a hydrophilic resin, a crosslinking agent, and a light absorber. It is preferable to crosslink. Among them, in the present invention, it is particularly important to use organic fine particles having a hydroxyl value (KOHmg / g) of 1 or more and less than 80 as the organic fine particles and to contain a hydrophilic resin.

  Details of the organic fine particles will be described. In the lithographic printing original plate of the present invention, the hydroxyl value (KOHmg / g) of the organic fine particles contained in the photosensitive resin composition forming the photosensitive layer is 1 or more and less than 80, preferably 5 or more and 75 or less. is there. By using a material in this range, the photosensitive layer does not significantly reduce the fluidity when the organic fine particles form the image line portion by heat fusion, that is, without decreasing the image line forming ability during light irradiation. It becomes possible to improve the intensity | strength of. This is because the organic fine particles dispersed in the photosensitive layer react with a cross-linking agent described later, so that the organic fine particles are partially involved in the crosslinking in the photosensitive layer. The strength of the photosensitive layer can be improved without reducing the forming ability. Further, it is considered that the hydrophilicity of the surface of the organic fine particles is improved by the effect of the hydroxyl group remaining on the surface of the particle without reacting, and printing can be performed without causing scumming even in an unexposed portion.

  In addition, the hydroxyl value said here points out mg number of potassium hydroxide required in order to neutralize the acid anhydride required in order to esterify OH group in 1 g of resin. The hydroxyl value is measured by back titration with a known acid anhydride. In particular, a method using phthalic anhydride as the acid anhydride and imidazole as the catalyst is desirable, and a solvent for dissolving these acid anhydrides and catalysts is preferable. Use pyridine as the reaction reagent. As a solvent for diluting these after reacting the reaction reagent with the resin, a solvent having excellent resin solubility such as pyridine or tetrahydrofuran is used. In the present invention, it is particularly preferable to use a hydroxyl value determined by the method described in the Examples section.

  Next, the average particle diameter of the organic fine particles will be described. The range of the preferable average particle diameter of the organic fine particles is 5 nm or more and 150 nm or less, and particularly preferably 5 nm or more and 100 nm or less. By being in this range, it is considered that the interfacial energy with water is small and the surface is highly hydrophilic. In addition, particles having a small particle diameter in this range have high fluidity in the photosensitive resin composition and are expected to be more uniformly dispersed in the photosensitive layer. The average particle size of the fine particles is generally measured with a particle size measuring device (for example, “laser particle size analysis system based on the dynamic light scattering method” or “Microtrack”) after thinning with water. Is possible. In addition, fine particles can be sliced after freezing and measured with a transmission electron microscope, and this method is particularly preferably used when the average particle size is 10 nm or less.

  Next, details of the resin forming the organic fine particles will be described. The organic fine particles used in the present invention have a hydroxyl value (KOHmg / g) of 1 or more and less than 80, but there is no particular limitation as long as the resin can form particles satisfying this condition. Examples of resins capable of forming organic fine particles used in the present invention include polyester, polyvinyl alcohol, ethylene vinyl alcohol copolymer, polystyrene resin, polyacrylic resin, styrene-acrylic copolymer, polyether polyol, etc. However, a resin having a hydroxyl group only at the resin terminal is preferable for the following reasons.

  In the present invention, it is preferable to use a resin having a hydroxyl group at the resin terminal as a raw material resin for forming organic fine particles. When the resin is made into particles, it is considered that a hydrophilic hydroxyl group is present in the vicinity of the particle surface and a hydrophobic resin skeleton is present as a block inside the particle. Therefore, the hydrophilic / hydrophobic contrast between the particle surface and the inside of the particle is increased as compared with particles made from a resin in which hydroxyl groups are uniformly dispersed in the resin skeleton. Therefore, in the unexposed area, a non-image area with high hydrophilicity is formed due to the effect of the hydroxyl group on the surface, and in the light irradiated area, the hydrophobic area inside the particle is exposed on the plate surface due to the fusion of the particle, and the image is highly ink-adhesive. It is thought that a line part is formed. A polyester resin can be mentioned as a suitable example of the resin having a hydroxyl group at the resin terminal as described above. Although there is no particular limitation on the monomer that forms the polyester, it is desirable to use an aromatic alcohol monomer so as to improve the hydrophobicity of the resin skeleton and to improve the ink receiving property.

  Examples of aromatic alcohol monomers include compounds having a bisphenol A skeleton, such as bisphenol A, bisphenol A-2 propylene oxide adduct, bisphenol A-3 propylene oxide adduct, bisphenol A-polypropylene oxide adduct, bisphenol A- 2 ethylene oxide adduct, bisphenol A-3 ethylene oxide adduct, bisphenol A-polyethylene oxide adduct, and the like. Among the above monomers, it is particularly preferable to use a bisphenol A-2 propylene oxide adduct or a bisphenol A-3 propylene oxide adduct, and the amount is preferably 5 mol% or more and 100 mol% or less.

  In addition, a trihydric or higher polyhydric alcohol can be used for the purpose of adjusting the molecular weight, and specifically, 1,2,3,6-hexanetetrol, 1,4-sorbitol, pentaerythritol, dipentaerythritol. , Tripentaerythritol, 1,2,4-butanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-tri A hydroxymethylbenzene etc. can be illustrated. When these trihydric or higher polyhydric alcohols are used, if the proportion of polyhydric alcohol in all alcohol monomers exceeds 20 mol%, gelation tends to occur and polycondensation becomes difficult. It is preferable to use in the range of 2-20 mol%.

  Although there is no limitation in particular also about an acid monomer, It is preferable to use an aromatic acid monomer for the same reason as an alcohol monomer. The amount of the aromatic acid monomer is preferably 10% by mole or more and 100% or less in the total acid monomers. As specific examples of the aromatic acid monomer, aromatic dibasic acids such as phthalic anhydride, phthalic acid, terephthalic acid, and isophthalic acid are preferably used. In addition to the above, usable dicarboxylic acids include malonic acid, succinic acid, glutamic acid, adipic acid, azelaic acid, sebacic acid, azelaic acid and other aliphatic dicarboxylic acids, maleic acid, fumaric acid, citraconic acid, itaconic acid, etc. Examples thereof include unsaturated dicarboxylic acids and lower alkyl esters thereof. In addition, for the purpose of adjusting the molecular weight, monocarboxylic acid, trivalent or higher polycarboxylic acid, and the like can be used. Specifically, as monocarboxylic acid, aliphatic carboxylic acid such as propionic acid, butyric acid, caproic acid, caprylic acid, pelargonic acid, stearic acid, benzoic acid, toluic acid, α-naphthoic acid, β-naphthoic acid, phenylacetic acid An aromatic ring-containing monovalent carboxylic acid such as trimellitic acid, pyromellitic acid, and acid anhydrides thereof can be illustrated as polycarboxylic acids. When using monocarboxylic acid, if the proportion of monocarboxylic acid in all acid monomers exceeds 30 mol%, the oxidation and hydroxyl value in the resin will decrease, so use within the range of 0.5-30 mol%. It is preferable to use it in an amount of 2 to 20 mol%. Moreover, when using polyvalent carboxylic acid, since it will become easy to raise | generate gelatinization when the ratio of monocarboxylic acid exceeds 20 mol% in all the acid monomers, it uses in the range of 0.5-20 mol%. It is particularly preferable to use it in an amount of 2 to 20 mol%.

  For the purpose of promoting emulsification, the resin that forms the organic fine particles described above reacts with a part of the hydroxyl group in the resin with a divalent or higher acid monomer such as maleic acid or phthalic acid to convert a part thereof to an acid terminal. Or as a metal salt or amine salt thereof. When a part is converted into an acid terminal or a salt thereof as described above, the remaining hydroxyl value (KOHmg / g) may be within the range specified in the present invention.

  The method for producing the organic fine particles is not particularly limited, and a method for obtaining the organic fine particles is, for example, a method in which an unsaturated monomer can be polymerized in water with or without using an emulsifier or a dispersant as appropriate. Specifically, emulsion polymerization, soap-free emulsion polymerization, precipitation polymerization, dispersion polymerization, a method obtained by suspension polymerization of unsaturated monomers, self-emulsification by directly introducing hydrophilic components into the resin skeleton using hydrophilic raw materials Mold or ionomer type, a resin obtained by adding a dispersion aid or a surfactant as necessary, and mechanically emulsified, and after the resin is dissolved in a soluble organic solvent in advance, Known methods such as a so-called solution suspension method for dispersing in water or a method in which these can be appropriately combined can be exemplified. Even those obtained can be used as long as for the production of a range defined by the present invention. In the present invention, the organic fine particles contained in the photosensitive resin composition forming the photosensitive layer may be used singly or in combination of two or more.

  The photosensitive layer of the present invention is composed mainly of an organic compound and is preferably insoluble in water. In order to make it insoluble in water, the photosensitive layer preferably contains a crosslinking agent capable of causing a crosslinking reaction upon receiving heat or light in the presence or absence of a catalyst. The cross-linking reaction of the cross-linking agent may be performed with a compound other than the cross-linking agent having an appropriate functional group, or a cross-linking agent having a self-cross-linking property may be used, but more preferably has a self-cross-linking property. It is a crosslinking agent. Here, the crosslinking agent having the property of self-crosslinking refers to a compound capable of reacting with and binding to the same functional group of the compound or another functional group of the compound. Furthermore, the crosslinking agent in the present invention is preferably one that can react with the hydroxyl group on the surface of the organic fine particles to improve the strength of the photosensitive layer, and preferably contains a crosslinking agent that can react with the hydroxyl group. Specific examples of these include compounds containing an epoxy group, methylol groups, and compounds containing an imino group. By using these compounds, a strong cross-linked product can be produced while maintaining the hydrophilicity of the photosensitive layer.

Compounds containing epoxy groups are known to crosslink between epoxy groups, and the remaining epoxy groups are consumed by self-condensation without reacting with the crosslinkable functional groups of the hydrophilic polymer. It is preferable because it becomes finer and strength increases. Examples of the compound containing an epoxy group include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, and diglycol having 3 or more carbon atoms. Diglycidyl ether such as glycidyl ether, hydrogenated bisphenol A diglycidyl ether, sorbitol polyglycidyl ether, polyglycol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, triethylolpropylene polyglycidyl ether Aliphatic, such as resorcinol diglycidyl ether, bisph Can Knoll A type glycidyl ether, such as those containing an aromatic ring or a cyclic compound such as triglycidyl isocyanurate include. Examples of commercially available compounds include epoxy compounds manufactured by Nagase ChemteX Corporation, “Denacol ^™ ” series, and the like.

Examples of the compound having a methylol group and an imino group include a melamine resin and a phenol resin. A melamine resin is used from the viewpoint of the balance between hydrophilicity and printing durability and reactivity with hydroxyl groups of organic fine particles. It is preferable. In the melamine resin, a methylol alkyl type in which the crosslinkable substituent part is completely alkylated has a slow reaction rate and hardly progresses self-condensation. Therefore, it is preferable to use a melamine resin of a type containing an imino group and a methylol group. . The self-condensation of the melamine resin makes the network structure in the photosensitive layer dense and increases the mechanical strength. Examples of commercially available products that can be used include melamine resin “Cymel ^™ ” series manufactured by Nippon Cytec Industries, Ltd.

  The content of the crosslinking agent in the photosensitive layer resin composition is preferably 10 to 40% by mass, and particularly preferably 10 to 30% by mass, as a solid content. When the content of the crosslinking agent is in the above range, the photosensitive layer can exhibit good hydrophilicity, and can provide a photosensitive layer that does not dissolve in water even during printing.

  Furthermore, the photosensitive resin composition forming the photosensitive layer of the present invention preferably contains a hydrophilic resin. Here, the hydrophilic resin refers to a hydrophilic group such as a hydroxyl group, an amide group, a sulfonamide group, an oxymethylene group, an oxyethylene group, an acidic group such as a carboxyl group, a sulfonic acid group, or a phosphonic acid group, or these acidic groups. It is a resin having a basic alkali metal salt, amine salt or the like, and is a resin having solubility in water. Specifically, the solubility in water is preferably 20% by mass or more, more preferably 50% by mass or more, and still more preferably 80% by mass or more in water at 25 ° C. The hydrophilic resins can be used alone or in combination of two or more.

  More specific examples of the hydrophilic resin of the present invention include the following resins. That is, polymerization and copolymerization of saponified products of polyvinyl acetate, celluloses, gelatin, unsaturated monomers having the above-mentioned hydrophilic groups, N-vinylacetamide, N-vinylformamide, vinyl acetate, vinyl ether, etc. And a hydrolyzed resin thereof.

  Among these, the hydrophilic resin preferably used in the present invention uses N-alkyl or N-alkylene-substituted (meth) acrylamide including (meth) acrylamide represented by at least the following general formula (1) and / or (2). Acrylamide resin obtained by reaction.

(Wherein R ₁ represents a hydrogen atom or a methyl group, and R ₂ and R ₃ represent a hydrogen atom, a lower alkyl or a lower alkoxy group.)

(Wherein R ₁ represents a hydrogen atom or a methyl group, A represents (CH ₂ ) n (where n is 4 to 6) or (CH ₂ ) ₂ O (CH ₂ ) ₂ ).
In general formulas (1) and (2), specific examples of the lower alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group, and the lower alkoxy group includes a methoxy group, an ethoxy group, and a propoxy group. Can be mentioned. More preferably, R _{2 in the} compound (1) is a methyl group or an ethyl group, and R ₃ is a hydrogen atom, a methyl group, an ethyl group, or a propyl group.

  Specific examples of the N-alkyl or N-alkylene-substituted (meth) acrylamide represented by the compounds (1) and (2) include (meth) acrylamide, N-methyl (meth) acrylamide, and N-ethyl (meth). Acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-methyl-N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, Nn-propyl (meth) Examples include acrylamide, N- (meth) acryloylpyrrolidine, N- (meth) acryloylpiperidine, N-acryloylhexahydroazepine, N-acryloylmorpholine, methoxymethyl (meth) acrylamide, and butoxymethyl (meth) acrylamide. In the description of the present invention, (meth) acrylamide and the like mean both acrylamide and methacrylamide. Among these monomers, those obtained by polymerization using acrylamide as a monomer are even more preferable. Of course, two or more of the above compounds can be used. Furthermore, the amount used when the compounds (1) and (2) are used as the monomer of the hydrophilic resin is preferably 60% by mass or more, more preferably 60 to 99.9% by mass in the hydrophilic resin. More preferably, it is 70-99.5 mass%. By using the above compound, the lithographic printing original plate of the present invention can exhibit good hydrophilicity.

  The hydrophilic resin obtained from the compound described in the general formula (1) and / or (2) is further selected from compounds represented by the following general formula (3) (Chemical Formula 3) and / or salts thereof. It is preferred to add more than one species of compound.

Specific examples of the compound represented by the general formula (3) and / or salts thereof include allyl sulfonic acid, sodium allyl sulfonate, potassium allyl sulfonate, methallyl sulfonic acid, sodium methallyl sulfonate, and methallyl sulfonic acid. Potassium, ammonium methallyl sulfonate and the like can be mentioned, and a hydrophilic resin obtained by using one or more compounds selected from these as monomers is preferable. In particular, methallyl sulfonic acid, sodium methallyl sulfonate, It is preferable to use potassium methallylsulfonate. The amount of these monomers used is preferably 0.01 to 10% by mass, more preferably 0.1 to 5% by mass, and still more preferably 0.2 to 3%, based on the total amount of the hydrophilic resin used. % By mass. By using the above compound, the hydrophilicity of the hydrophilic resin can be further improved.

In addition, as monomers that can constitute other hydrophilic resins, monobasic unsaturated acids such as (meth) acrylic acid, dibasic unsaturated acids such as itaconic acid, fumaric acid, maleic acid and anhydrides thereof, etc. Monomers having a carboxyl group, sulfoethyl (meth) acrylate, (meth) acrylamidomethylpropanesulfonic acid, vinylsulfonic acid, vinylmethylsulfonic acid, isopropenylmethylsulfonic acid, (meth) acrylic acid and sulfonic acid groups such as ethylene oxide Monomers, hydroxyethyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, hydroxypropyl (meth) acrylate, polypropylene glycol mono (meth) acrylate, hydroxybutyl (meth) acrylate, methylol (meth) acrylate Monomers having a hydroxyl group such as amide, unsubstituted or substituted itaconic acid amide, unsubstituted or substituted fumaric acid amide, unsubstituted or substituted phthalic acid amide, N-vinylacetamide, N-vinylformamide, diacetone (meth) acrylamide, In addition to N-substituted (meth) acrylamide derivatives including (meth) acrylamide shown in the above (1) and (2), such as propyl (meth) acrylamide, methoxymethyl (meth) acrylamide, butoxymethyl (meth) acrylamide, etc. Monomers having an amide group, monomers having a glycidyl group such as glycidyl (meth) acrylate, paravinylphenyl glycidyl ether, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl ( Acrylate), dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, isopronyl (meth) acrylate, adamantyl (meth) acrylate, cyclohexyl (meth) acrylate, Monomers having hydrophobic properties such as styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, vinyl acetate, methylene bisacrylamide, methylene bisacrylamide, ethylene bisacrylamide, ethylene bismethacrylamide, ethylene glycol diacrylate, ethylene glycol Dimethacrylate, diethylene glycol acrylate, diethylene glycol methacrylate, divinylbenzene, Examples of conventionally known various monomers including polyfunctional monomers such as allyl acrylamide, triallyl isocyanurate, pentaerythritol triacrylate, and the like, as long as the hydrophilicity of the hydrophilic resin is not impaired, These can be used as needed. Examples of commercially available hydrophilic resins include polyacrylamide “Hopron ^™ ” series manufactured by Mitsui Chemicals, Inc.

In the present invention, the photosensitive resin composition forming the photosensitive layer preferably further contains a light absorber. This light absorber is preferably one that absorbs light and generates heat, and appropriately uses light in a wavelength region that is absorbed by the light absorber when irradiated with light. Specific examples of light absorbers include cyanine dyes, polymethine dyes, phthalocyanine dyes, naphthalocyanine dyes, anthracocyanine dyes, porphyrin dyes, azo dyes, benzoquinone dyes, naphthoquinone dyes, dithiol metal complexes , Metal complexes of diamine, various pigments such as nigrosine, and carbon black. Among these dyes, dyes that absorb light in the region of 750 to 1100 nm are preferable from the viewpoints of handling in a bright room, output of a light source used in an exposure machine, and ease of use. A dye having an absorption wavelength λmax of 750 to 900 nm is preferred. The absorption wavelength range of the dye can be changed depending on the length of the substituent or the conjugated system of π electrons. In order to effectively perform photothermal conversion, the extinction coefficient εmax at the maximum absorption wavelength is preferably 1 × 10 ⁵ L mol ⁻¹ cm ⁻¹ or more, more preferably 2 × 10 ⁵ L mol ⁻¹ cm ^{−. 1} or more. These light absorbers may be dissolved or dispersed in an aqueous solution containing the photosensitive resin composition, but the light absorber is contained in the photosensitive layer, so that the plate has sufficient hydrophilicity. In order to give, in the present invention, among the above-mentioned light absorbers, hydrophilic light absorbers are preferable. Specifically, a light absorber having a solubility in water of 1% by mass or more is preferable.

  In the present invention, various surfactants may be added to the photosensitive resin composition in order to increase the stability to printing conditions. Examples of the surfactant include an anionic surfactant, a cationic surfactant, a nonionic surfactant, and an amphoteric surfactant. Moreover, in order to improve the applicability | paintability of photosensitive resin composition aqueous solution, you may add additives, such as a repellency inhibitor and a leveling agent. The addition amount of these surfactants is not particularly limited, but is preferably 0.001 to 5 parts by weight with respect to 100 parts by weight as a total of the hydrophilic resin, the crosslinking agent and the organic fine particles.

  In the present invention, the photosensitive layer is formed by crosslinking the above-described photosensitive resin composition. The composition ratio of the photosensitive resin composition is preferably in the following range to provide a good printing plate. be able to. The blending amount of the hydrophilic resin in the photosensitive resin composition is preferably 20 parts by weight or more with respect to 100 parts by weight in total of the hydrophilic resin, the crosslinking agent, the organic fine particles, and the light absorber. More preferably, it is 20 parts by weight or more and 60 parts by weight or less.

  The amount of the crosslinking agent in the photosensitive resin composition in the present invention is in the range of 3 to 60 parts by weight with respect to 100 parts by weight in total of the hydrophilic resin, the crosslinking agent, the organic fine particles and the light absorber. Is more preferable, and 5 to 50 parts by weight is more preferable. When the amount of the crosslinking agent is within the above range, good hydrophilicity and good printing durability can be exhibited in the planographic printing plate of the present invention.

  The amount of organic fine particles in the photosensitive resin composition is preferably large from the viewpoint of making the light irradiated portion ink-philic. However, if the amount is too large, the hydrophilicity of the plate is lowered, and there is a possibility of causing background staining in printing. Come out. From these viewpoints, the amount of the organic fine particles in the photosensitive resin composition in the present invention is preferably 15 to 15 in terms of solid content with respect to a total of 100 parts by weight of the hydrophilic resin, the crosslinking agent, the organic fine particles and the light absorbent. It is preferably 80 parts by weight, more preferably 25 to 70 parts by weight. The mixing ratio of the light absorber in the photosensitive resin composition of the present invention is 2 to 40 parts by weight of the light absorber with respect to 100 parts by weight of the total of the hydrophilic resin, the crosslinking agent, the organic fine particles, and the light absorber. Is more preferable, and it is more preferable that it is 2-30 weight part. By being in the above range, the printing durability and hydrophilicity of the plate are hardly adversely affected, and the effect can be sufficiently expected.

[Underlayer]
In the lithographic printing original plate according to the present invention, in addition to providing the photosensitive layer directly on the support, it is also possible to provide an underlayer for improving the adhesion between the support and the photosensitive layer. The composition of the undercoat layer used at this time is not particularly limited, but it is preferable to use a hydrophobic polymer such as polyester, urethane, acrylic, vinyl acetate, synthetic rubber, or ethylene.

  The hydrophobic polymer used in these underlayers can be in the form of a uniform solution or emulsion dissolved in an aqueous solution or an organic solvent, and these can be formed into a base layer by forming a film. Particularly preferred is a polymer emulsion type. This hydrophobic polymer emulsion may be a forced emulsification type or a self-emulsification type. When an emulsion is used, the average particle size of the polymer is preferably about 5 to 500 nm, more preferably 10 to 300 nm in order to prevent surface irregularities of the underlayer.

  This emulsion preferably has a property of forming a film by fusion when the dispersion solvent evaporates after coating. If there is no problem in production, the film forming temperature is not particularly limited and may be any temperature. One or two or more kinds of the hydrophobic polymers can be mixed and used for the underlayer. Furthermore, a tough film can be formed by adding a crosslinking agent.

  When this underlayer is applied, for example, a bar coater, roll coater, blade coater, gravure coater, curtain flow coater, die coater, dip coater, spray method or the like may be used. Although there is no restriction | limiting in particular in the film thickness of a base layer, Usually, about 0.1-10 micrometers, Preferably it is 0.2-5 micrometers.

  After application of the underlayer, the photosensitive resin composition may be applied as it is, or may be used after being heated or blown and dried. The base layer thus provided improves the adhesion between the support / underlying layer interface and the underlayer / photosensitive layer interface, so that the printing durability is good, and even when dampening water is supplied, peeling at the interface does not occur.

[Support]
The lithographic printing original plate and the lithographic printing plate of the present invention are those in which a photosensitive layer is directly provided on a support via an underlayer, but the support used in this case is not particularly limited, and is publicly known. Things can be used. Specific examples of the support include metal plates such as aluminum plates, steel plates, stainless steel plates, and copper plates, plastic films and papers such as polyester, nylon, polyethylene, polypropylene, polycarbonate, and ABS resin, and plastic film laminated paper. The thickness of these supports is not particularly limited, but is usually about 100 to 400 μm. Further, these supports may be subjected to surface treatment such as oxidation treatment, chromate treatment, sand blast treatment, corona discharge treatment, etc. in order to improve adhesion to the underlayer.

  In the present invention, the photosensitive layer may be formed by applying a solution containing a photosensitive resin composition containing a hydrophilic resin, a crosslinking agent, organic fine particles, and a light absorber to a substrate, and drying and curing. The application method varies depending on the viscosity of the solution to be applied, the application speed, and the like. Usually, for example, a roll coater, a blade coater, a gravure coater, a curtain flow coater, a die coater, or a spray method may be used. After coating the coating solution, it is heated to dry and crosslink the hydrophilic resin. The heating temperature is usually about 50 to 200 ° C. The film thickness of the photosensitive layer is not particularly limited, but is usually preferably about 0.5 to 10 μm.

  In the printing original plate of the present invention, after forming a photosensitive layer made of a hydrophilic resin, calendering may be performed, or a film may be laminated on the photosensitive layer in order to protect the photosensitive layer.

  When the lithographic printing original plate of the present invention is irradiated with light in the absorption wavelength region of the light absorber, for example, light in the region of 750 to 1100 nm, the light absorber absorbs the light and generates heat. Due to this heat generation, the organic fine particles are thermally fused in the light irradiation part of the photosensitive layer, and the hydrophilicity is lost and the ink becomes an ink-philic ink. What is obtained in this way is a planographic printing plate. At this time, if the amount of light irradiation is excessively increased or a light absorber is added in a large amount, the photosensitive layer is removed and ablated by decomposition, combustion, etc., and the decomposed material is scattered around the irradiated portion. So this must be avoided.

  As described above, in the lithographic printing original plate according to the present invention, the hydrophilicity of the photosensitive layer in the portion irradiated with light changes to the ink-philic property, and the ink adheres to the light irradiated portion without performing development or wiping operation. And printing becomes possible.

  The wavelength of the light used for light irradiation of the lithographic printing original plate in the present invention is not particularly limited, and light that matches the absorption wavelength region of the light absorbent may be used. At the time of irradiation, it is preferable to scan the convergent light at a high speed from the point of irradiation speed, and it is easy to use and suitable for a high-output light source. Laser light having an oscillation wavelength in the range is preferable, and for example, a high-power semiconductor laser of 830 nm or a YAG laser of 1064 nm is used. Exposure machines equipped with these lasers are already on the market as so-called thermal plate setters (exposure machines).

The present invention will be specifically described below with reference to examples and comparative examples. Moreover, the measurement method and determination method of the data in each table are as follows.
(Measurement of hydroxyl value)
The hydroxyl value of the organic fine particles in the present invention was measured by back titration with the following acid anhydride. To 2 g of resin, 5 cc of a separately prepared phthalating reagent (prepared at a ratio of 500 cc of pyridine / 70 g of phthalic acid / 10 g of imidazole) is added and dissolved, and then allowed to stand at 100 ° C. for 1 hour. Thereafter, 1 cc of water, 70 cc of tetrahydrofuran and several drops of phenolphthalein / ethanol solution were added to the resin solution, and titration was performed with a 0.4 N NaOH aqueous solution. The point at which the color of the sample solution colored from colorless to purple was used as the end point, and the hydroxyl value (KOHmg / g) was calculated from the titration amount and the sample mass at this time.

(Particle size of organic fine particles)
In the present invention, an average particle diameter value (g (GAMMA)) obtained from a scattering intensity distribution (g (GAMMA)) in a laser particle size analysis system (LPA-3000 / 3100: manufactured by Otsuka Electronics Co., Ltd.) based on the dynamic light scattering method. φ) was defined as the average particle size.

(Plate strength measurement)
In the present invention, the strength of the plate is 500 g on a Gakushin friction tester type II (manufactured by Tester Sangyo Co., Ltd.), and 6 sheets of BEMCOT ^(R) M-3 (manufactured by Asahi Kasei Co., Ltd.) are layered on pure water. The surface of the plate was abraded at 30 times / minute with a wet one, and the number of times the plate surface began to be scratched or scraped was visually counted. In the present invention, the number of times the plate surface starts to be scratched or scraped is defined as the plate strength standard. Therefore, the stronger the number of wear resistance, the stronger the plate. In this measurement, the upper limit of the number of wear was set to 4000 times, and a plate that was not scratched or scraped on the plate surface even after being worn 4000 times was accepted.

(Print evaluation)
This drawn plate is set on an offset printing machine (SPRINT21 manufactured by Komori Corporation), 2% aqueous solution of H liquid astromark 3 of Nikken Chemical Research Co., Ltd. as dampening water, and manufactured by Toyo Ink Mfg. Co., Ltd. as ink. Printing was carried out using HiEcho ^TM SOY. In this patent, printing evaluation was performed using a printing plate exposed at 270 mJ / cm ² , and a film with 2% halftone dots reproduced after printing 1000 sheets was regarded as a passing sensitivity. Further, after printing 20,000 sheets, a 50% halftone dot density was measured, and a dot gain of 10% or more was regarded as passing printing durability. These halftone dot concentrations were measured using an X-Rite ^(R) 528 spectrophotometer (manufactured by X-Rite).

(Synthesis of hydrophobic resin (P-1))
A 3 liter four-necked flask is equipped with a reflux condenser, a water separator, a nitrogen gas inlet tube, a thermometer, and a stirrer, and a bisphenol A / propylene oxide adduct (polyol ^TM KB300, manufactured by Mitsui Chemicals, Inc.) 40. 6 parts, 10.2 parts of trimethylolpropane, 44.4 parts of isophthalic acid, and 4.8 parts of stearic acid were charged, and dehydration condensation was performed at 180 to 240 ° C. while introducing nitrogen into the flask. When the acid value of the reaction product reached a predetermined value, the reaction product was extracted from the flask, cooled and pulverized to obtain a hydrophobic resin (P-1). The obtained hydrophobic resin had a hydroxyl value of 55.3.

(Preparation of organic fine particles (E-1))
Hydrophobic resin (P-1) 50 g synthesized in the above-mentioned method in a four-necked separable flask equipped with a thermometer, stirring blade, condenser, and dropping funnel, sodium lauryl sulfate (Emar ^TM 10 manufactured by Kao Corporation) ) 2.5 g, methyl ethyl ketone 25 g and tetrahydrofuran 12.5 g were charged and dissolved at 75 ° C., and further mixed and dispersed with a homomixer. Then, 1N ammonia aqueous solution was added so as to be equivalent to the acid value of the polyester resin. After stirring for 30 minutes, 200 g of ion exchange water at 70 ° C. was added to emulsify and disperse. Furthermore, it distilled until the fraction temperature became 100 degreeC with the flask for distillation, and obtained organic fine particles (E-1). The average particle size of the obtained organic fine particles was 80 nm.

(Synthesis of hydrophobic resin (P-2))
Attach a reflux condenser, water separator, nitrogen gas inlet tube, thermometer, and stirrer to a 3 liter 4-neck flask, and 29 parts of bisphenol A / propylene oxide adduct (manufactured by Mitsui Chemicals, Inc., Polyol ^TM KB300) Then, 23 parts of diethylene glycol, 2 parts of trimethylolpropane and 42.5 parts of isophthalic acid were charged, and dehydration condensation was performed at 180 to 240 ° C. while introducing nitrogen into the flask. When the acid value of the reaction product reached a predetermined value, the reaction product was extracted from the flask, cooled and pulverized to obtain a hydrophobic resin (P-2). The obtained hydrophobic resin had a hydroxyl value of 76.5.

(Preparation of organic fine particles (E-2))
Organic fine particles (E-2) were prepared by the same operation as the preparation of E-1, except that the hydrophobic resin was changed to P-2. The average particle size of E-2 was 120 nm.

(Synthesis of hydrophobic resin (P-3))
Attach a reflux condenser, water separator, nitrogen gas inlet tube, thermometer, and stirrer to a 3 liter 4-neck flask, and 70 parts of flake-shaped recycled PET (weight average molecular weight 55000) in units of ethylene glycol units in the PET. Then, 30.0 parts of neopentyl glycol, 23.8 parts of isophthalic acid, and 8.0 parts of benzoic acid were charged, and dehydration condensation polymerization was performed at 240 ° C. while introducing nitrogen into the flask. When the acid value of the reaction product reached a predetermined value, it was extracted from the flask, cooled and pulverized to obtain a hydrophobic resin (P-3). The obtained hydrophobic resin had a hydroxyl value of 4.8 (KOH mg / g).

(Preparation of organic fine particles (E-3))
Organic fine particles (E-3) were prepared in the same manner as in E-1, except that the hydrophobic resin was changed to P-3. The average particle size of E-3 was 142 nm.

(Synthesis of hydrophobic resin (P-4))
A reflux condenser, a water separator, a nitrogen gas inlet tube, a thermometer and a stirrer were attached to a 3 liter four-necked flask, and 100 parts of bisphenol A / propylene oxide adduct (manufactured by Mitsui Chemicals, Inc., Polyol ^TM KB300) Then, 120 parts of isophthalic acid was charged, and dehydration condensation was performed at 180 to 240 ° C. while introducing nitrogen into the flask. When the acid value of the reaction product reached a predetermined value, the reaction product was extracted from the flask, cooled and pulverized to obtain a hydrophobic resin (P-6). The resulting hydrophobic resin had a hydroxyl value of 0.4.

(Preparation of organic fine particles (E-4))
Organic fine particles (E-4) were prepared in the same manner as in E-1, except that the hydrophobic resin was changed to P-4. The average particle size of E-4 was 40 nm.

(Synthesis of hydrophobic resin (P-5))
A reflux condenser, a water separator, a nitrogen gas inlet tube, a thermometer and a stirrer were attached to a 3 liter four-necked flask, and flaky recycled PET (weight average molecular weight 55000) was measured in units of ethylene glycol units in the PET. 4 parts, 27.6 parts of neopentyl glycol, 8 parts of trimethylolpropane, 15 parts of terephthalic acid and 6 parts of adipic acid were charged and dehydration condensation polymerization was performed at 240 ° C. while introducing nitrogen into the flask. When the acid value of the reaction product reached a predetermined value, it was extracted from the flask, cooled and pulverized to obtain a hydrophobic resin (P-5). The obtained hydrophobic resin had a hydroxyl value of 82.7.

(Preparation of organic fine particles (E-5))
Organic fine particles (E-5) were prepared in the same manner as in E-1, except that the hydrophobic resin was changed to P-5. The average particle size of E-5 was 110 nm.

Example 1
After applying a resin solution for the underlayer (Orestar ^TM UD350, manufactured by Mitsui Chemicals Co., Ltd., 40 wt% solid content) to a 0.3 mm thick aluminum plate using a wire bar, it was dried at 150 ° C. for 1 minute, A 5 μm underlayer was formed. An aqueous solution of a photosensitive resin composition having the following composition was applied onto the underlayer prepared by the above method using a wire bar, and then dried at 150 ° C. for 20 minutes to form a photosensitive layer having a thickness of 2 μm. A master for lithographic printing was prepared. In addition, "part" shown below shows the weight part about solid content of each resin or compound.

Hydrophilic resin: Polyacrylamide resin (Hopron ^TM H520B, manufactured by Mitsui Chemicals, Inc.) 40 parts Hydrophobic fine particles: Organic fine particles (E-1) 35 parts Crosslinker: Methylated melamine resin (Nippon Cytec Industries, Inc., Cymel ^TM 385) 25 parts Light absorber: Cyanine dye (λmax 784 nm in methanol solution, εmax 2.43 × 10 ⁵ Lmol ⁻¹ cm ⁻¹ ) 15 parts Surfactant: Anionic surfactant (Daiichi Kogyo Seiyaku ( Co., Ltd. Neocor ^TM YSK) 5 parts This plate is irradiated with scanning laser light while condensing a semiconductor laser beam having a wavelength of 830 nm to an irradiation energy density of 270 mJ / cm ² to draw image information of 200 lines / inch. A printing plate was prepared. When the strength was measured with a friction tester, scratches and scrapes were not detected on the plate surface even after abrasion 4000 times. In addition, 2% halftone dots were reproduced on the printed material after printing 1000 sheets, and the dot gain at the 50% halftone area after printing 20,000 sheets was 14%.

Example 2
A photosensitive resin composition aqueous solution was prepared with the same composition as in Example 1 except that the organic fine particles of Example 1 were changed to E-2, and a printing original plate was prepared, drawn, and the printing plate was prepared. Produced. When the strength was measured with a friction tester, scratches and scrapes were not detected on the plate surface even after abrasion 4000 times. In addition, 2% halftone dots were reproduced after printing 1000 sheets, and the dot gain in the 50% halftone area after printing 20,000 sheets was 11%.

Example 3
A photosensitive resin composition aqueous solution was prepared with the same composition as in Example 1 except that the organic fine particles of Example 1 were changed to E-3, and a printing original plate was prepared, drawn, and the printing plate was prepared. Produced. When the strength was measured with a friction tester, scratches and scrapes were not detected on the plate surface even after abrasion 4000 times. Further, 2% halftone dots were reproduced after printing 1000 sheets, and the dot gain at the 50% halftone portions after printing 20,000 sheets was 12%.

Example 4
A photosensitive resin having the same composition as that of Example 1 except that the organic fine particles of Example 1 were changed to Mistpearl ^(R) A-203 (Arakawa Chemical Industries, Ltd .; hydroxyl value 34.8). A composition aqueous solution was prepared, a printing original plate was prepared, drawn, and a printing plate was prepared. When the strength was measured with a friction tester, scratches and scrapes were not detected on the plate surface even after abrasion 4000 times. Further, 2% halftone dots were reproduced after printing 1000 sheets, and the dot gain at the 50% halftone portions after printing 20,000 sheets was 10%.

Comparative Example 1
A photosensitive resin composition aqueous solution is prepared with the same composition as in Example 1 except that the organic fine particles of Example 1 are changed to E-4, and a printing original plate is prepared, drawn, and the printing plate is prepared. Produced. When the strength was measured with a friction tester, the plate surface started to be scraped when it was worn about 100 times. Further, although the 2% halftone dot was reproduced after printing 1000 sheets, the dot gain at the 50% halftone portion after printing 20,000 sheets was 3%, and the printing durability was insufficient.

Comparative Example 2
A photosensitive resin composition aqueous solution was prepared with the same composition as in Example 1 except that the organic fine particles of Example 1 were changed to E-5, and a printing original plate was prepared, drawn, and a printing plate was prepared. Produced. When the strength was measured with a friction tester, scratches and scrapes were not detected on the plate surface even after abrasion 4000 times. In the printing evaluation, 2% halftone dots were not reproduced after printing 1000 sheets due to insufficient sensitivity. Then, when the same printing evaluation was performed by increasing the energy of the irradiated laser, 2% halftone dots were finally reproduced when the irradiation energy was increased to 400 mJ / cm ⁻² . Further, the dot gain was less than 10% from the beginning of printing, and the dot gain at the 50% halftone portion after printing 20,000 sheets was -8%, and the printing durability was insufficient.

  A lithographic printing plate that is sensitive to light in the near-infrared region, can be directly drawn on the plate with a laser beam, does not require development or wiping operations, and has excellent printing durability, and a lithographic printing plate obtained from the original plate provide.

Claims (7)

In a lithographic printing plate precursor having a photosensitive layer formed directly on the support through an undercoat layer, the photosensitive resin composition forming the photosensitive layer has at least a hydroxyl value (KOHmg / g) of 1 or more and less than 80. A lithographic printing plate precursor comprising certain organic fine particles and a hydrophilic resin. The hydrophilic resin in the photosensitive layer reacts with an N-alkyl or N-alkylene-substituted (meth) acrylamide compound represented by the following general formula (1) (Chemical Formula 1) and / or (2) (Chemical Formula 2) The lithographic printing original plate according to claim 1, which comprises a hydrophilic resin obtained in this manner.

(Wherein R ₁ represents a hydrogen atom or a methyl group, and R ₂ and R ₃ represent a hydrogen atom, a lower alkyl or a lower alkoxy group.)

(Wherein R ₁ represents a hydrogen atom or a methyl group, A represents (CH ₂ ) n (where n is 4 to 6) or (CH ₂ ) ₂ O (CH ₂ ) ₂ ). The lithographic printing material according to claim 1 or 2, wherein the hydrophilic resin is obtained from one or more compounds selected from compounds represented by the following general formula (3) (chemical formula 3) and / or salts thereof: Original edition.

(In the formula, R represents a hydrogen atom or a lower alkyl group, and n represents an integer of 1 to 8.) 4. The lithographic printing plate precursor according to claim 1, wherein the photosensitive resin composition forming the photosensitive layer contains a crosslinking agent capable of reacting with a hydroxyl group. 5. The lithographic printing plate precursor according to claim 1, wherein the photosensitive layer is hydrophilic and the surface of the photosensitive layer has a property of changing from hydrophilic to oleophilic upon irradiation with laser light. The lithographic printing plate precursor according to any one of claims 1 to 5, wherein the photosensitive resin composition forming the photosensitive layer further contains a light absorber and a surfactant. A lithographic printing plate obtained by irradiating light to the lithographic printing original plate according to claim 1.