JP2016151613A - Photosensitive lithographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photosensitive lithographic printing plate having high sensitivity and excellent scratch resistance.SOLUTION: A photosensitive lithographic printing plate has at least a photocurable photosensitive layer and a protective layer in the stated order on a base material, with the photocurable photosensitive layer closer to the base material than the protective layer. The protective layer consists of at least two layers of a layer comprising no wax particles and a layer comprising wax particles thereon.SELECTED DRAWING: None

Description

  The present invention relates to a photosensitive lithographic printing plate having at least a photocurable photosensitive layer on a substrate. More specifically, the present invention relates to a photosensitive lithographic printing plate that can be developed with a chemical-less developer containing substantially no alkali agent.

  2. Description of the Related Art In recent years, plate making systems using the CTP (Computer To Plate) system have been fully digitized by the expansion of JDF (Job Definition Format), and work efficiency has been greatly improved. In addition, in terms of hardware, such as output machines and printing plates, the creation of products that take into consideration human health and the environment as well as increasing efficiency through the development of process-less and chemical-less products has become widespread. However, for thermal and photopolymer type CTP printing plates (planographic printing plates capable of making plates by the CTP method) which are currently mainstream, a developer containing a strong alkali agent is used after laser exposure of the printing plate. The non-image area is eluted and removed, followed by washing with water and gumming, and is used for printing. It was an issue.

  There has been proposed a photosensitive composition that avoids the use of such an alkaline developer and can be developed with water or the like. For example, in Japanese Patent Laid-Open No. 5-27437 (Patent Document 1), an aqueous photosensitive composition containing a carboxyl group-containing resin, an amine compound, a photocurable unsaturated compound, a photopolymerization initiator and water is used for the production of printed circuits. Use is disclosed. JP-A 2003-215801 (Patent Document 2) uses a photosensitive composition using an anionic water-soluble polymer having a polymerizable double bond group in the side chain as a binder polymer for a photosensitive lithographic printing plate. Is disclosed. However, when used as a lithographic printing plate using the above-described photosensitive composition, there is a problem that scratches are likely to occur during handling.

  Conventionally, on a photocurable photosensitive layer made of a photosensitive composition, in order to protect the photocurable photosensitive layer and improve scratch resistance, the sensitivity of the polymerizable radicals reacts with oxygen in the air to reduce the sensitivity. In general, a protective layer containing a water-soluble resin or the like is provided as an oxygen blocking layer for preventing the above.

  Japanese Patent Application Laid-Open No. 2004-125876 (Patent Document 3) shows that scratch resistance is improved by forming the protective layer in a two-layer structure, but there are cases where sufficient effects cannot be obtained.

  On the other hand, scratch resistance is improved by adding wax particles to the protective layer in JP 2007-245690 (Patent Document 4) and lubricant in JP 2002-365413 (Patent Document 5). However, if the amount of the wax particles added is increased until a sufficient effect is obtained, the effect as an oxygen barrier layer is lowered and the sensitivity is lowered.

JP-A-5-27437 JP 2003-215801 A Japanese Patent Application Laid-Open No. 2004-125876 JP 2007-245690 A Japanese Patent Laid-Open No. 2002-365813

  An object of the present invention is to provide a photosensitive lithographic printing plate excellent in scratch resistance without deteriorating sensitivity.

  The present invention relates to a photosensitive lithographic printing plate having at least a photocurable photosensitive layer and a protective layer in this order on the base material from the side close to the base material, wherein the protective layer contains no wax particles and a wax in the upper layer. It was achieved by a photosensitive lithographic printing plate characterized in that it is at least two layers comprising particles.

  According to the present invention, it is possible to provide a photosensitive lithographic printing plate having high sensitivity and excellent scratch resistance.

  Hereinafter, the present invention will be described in detail.

  As the substrate that the photosensitive lithographic printing plate of the present invention has, a substrate subjected to hydrophilic treatment is suitable, and examples include a hydrophilicized aluminum plate, various plastic films, and paper laminated with various plastics. . Among them, a plastic film which is flexible and is a material with little deformation due to tension is preferably used. Preferred examples of the plastic film include polyethylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, polystyrene, polyvinyl acetal, polycarbonate, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, and cellulose nitrate. Polyethylene terephthalate and polyethylene naphthalate are preferably used.

  In hydrophilizing the substrate of the photosensitive lithographic printing plate of the present invention, it is preferable to provide a hydrophilic layer described later between the substrate and the photocurable photosensitive layer, and the surface of the substrate is In order to improve adhesion to the hydrophilic layer and a layer such as a backing layer provided as necessary, surface treatment may be performed. Examples of such surface treatment include corona discharge treatment, flame treatment, plasma treatment, and ultraviolet irradiation treatment. An undercoat layer may be provided on the substrate as a further surface treatment.

  The photosensitive lithographic printing plate of the present invention has at least a photocurable photosensitive layer and a protective layer in this order on the substrate.

  In the present invention, the photocurable photosensitive layer preferably contains a photopolymerization initiator. Conventionally known compounds can be used as the photopolymerization initiator. For example, trihaloalkyl-substituted compounds (for example, s-triazine compounds and oxadiazole derivatives as trihaloalkyl-substituted nitrogen-containing heterocyclic compounds, trihaloalkylsulfonyl compounds), organic boron salts, hexaarylbiimidazoles, titanocene compounds, thios Examples thereof include compounds and organic peroxides. Among these photopolymerization initiators, organic boron salts are preferably used. More preferably, a combination of a trihaloalkyl-substituted compound and an organic boron salt is used. A combination of a trihaloalkyl-substituted compound and an organic boron salt is preferable because the sensitivity can be further improved.

  The trihaloalkyl-substituted compound that is a photopolymerization initiator is specifically a compound having at least one trihaloalkyl group such as a trichloromethyl group or a tribromomethyl group in the molecule. Preferred examples include the trihaloalkyl group. S-triazine derivatives and oxadiazole derivatives may be mentioned as compounds in which is bonded to a nitrogen-containing heterocyclic group, or trihaloalkylsulfonyl in which the trihaloalkyl group is bonded to an aromatic ring or a nitrogen-containing heterocyclic ring via a sulfonyl group Compounds.

  Particularly preferred examples of compounds in which a trihaloalkyl group is bonded to a nitrogen-containing heterocyclic group and trihaloalkylsulfonyl compounds are shown below.

  The organoboron anion constituting the organoboron salt is represented by the following general formula 1.

In the formula, each of R ₁ , R ₂ , R ₃ and R ₄ may be the same or different, and represents an alkyl group, aryl group, aralkyl group, alkenyl group, alkynyl group, cycloalkyl group or heterocyclic group. Represent. Of these, it is particularly preferred that one of R ₁ , R ₂ , R ₃ and R ₄ is an alkyl group and the other substituent is an aryl group.

  Examples of the cation constituting the organic boron salt include alkali metal ions and onium compounds, but onium salts are preferred, for example, ammonium salts such as tetraalkylammonium salts, sulfonium salts such as triarylsulfonium salts, and triarylalkyls. Examples thereof include phosphonium salts such as phosphonium salts. Examples of particularly preferred organic boron salts are shown below.

  The content of the photopolymerization initiator as described above is preferably used in the range of 0.1 to 30 parts by mass with respect to 100 parts by mass of the total solid content of the photocurable photosensitive layer, and more preferably 1 to 15 parts. It is preferably included in the range of parts by mass.

  The photocurable photosensitive layer preferably contains a compound having a polymerizable double bond group. The compound having a polymerizable double bond group is a polymer compound having a polymerizable double bond group or a low molecular compound having a polymerizable double bond group. From the viewpoint of photopolymerization efficiency, it is preferable to contain a low molecular weight compound having a polymerizable double bond group.

  The polymer compound having a polymerizable double bond group will be described. The polymer compound having a polymerizable double bond group is a polymer compound formed by an arbitrary repeating unit, and a polymer compound in which a polymerizable double bond group is bonded to a side chain through an arbitrary linking group. It is. Among them, a polymer compound having a vinyl group as a reactive double bond group is preferably used, and a polymer compound in which a phenyl group substituted with a vinyl group is bonded to the main chain directly or via an arbitrary linking group is particularly preferably used. It is done. In addition, in order to enable development with substantially no alkali agent (chemicalless developer), it is possible to introduce a sulfo group, a quaternary ammonium group, or the like linked to the main chain via an arbitrary linking group. Among them, a polymer compound having a sulfo group can be preferably used because of its high developability. The sulfo group may form a salt (for example, sodium salt, potassium salt, lithium salt, amine salt, etc.). These linking groups are not particularly limited, and include any group, atom, or a combination thereof. The phenyl group and sulfo group substituted with a vinyl group may be independently bonded to the main chain, or the phenyl group substituted with a vinyl group and the sulfo group share part or all of the linking group. You may combine with.

  In the phenyl group substituted by the vinyl group, the phenyl group may be substituted, and the vinyl group is a halogen atom, carboxyl group, sulfo group, nitro group, cyano group, amide group, amino group, alkyl group. , An aryl group, an alkoxy group, an aryloxy group and the like may be substituted.

  The polymer compound in which the phenyl group substituted with the vinyl group of the present invention is bonded to the main chain directly or through an arbitrary linking group has, in detail, one having a group represented by the following general formula 2 in the side chain. preferable.

In the formula, R ₅ , R ₆ and R ₇ may be the same or different and are each a hydrogen atom, halogen atom, carboxyl group, sulfo group, nitro group, cyano group, amide group, amino group, alkyl group. Group, aryl group, alkoxy group, aryloxy group, alkylsulfanyl group, arylsulfanyl group, alkylamino group, arylamino group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, alkylsulfonyl group, arylsulfonyl group An alkyl group and an aryl group constituting these groups are a halogen atom, a carboxyl group, a sulfo group, a nitro group, a cyano group, an amide group, an amino group, an alkyl group, an aryl group, an alkenyl group, a hydroxy group, Alkoxy group, aryloxy group, alkylsulfanyl group , Arylsulfanyl group, alkylamino group, arylamino group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, alkylsulfonyl group, arylsulfonyl group and the like. Among these groups, those in which R ₅ and R ₆ are hydrogen atoms and R ₇ is a hydrogen atom or a lower alkyl group having 4 or less carbon atoms (for example, a methyl group, an ethyl group, etc.) are particularly preferable.

In the formula, R ₈ is hydrogen atom, halogen atom, carboxyl group, nitro group, cyano group, amide group, amino group, alkyl group, aryl group, alkoxy group, aryloxy group, alkylsulfanyl group, arylsulfanyl group, alkylamino. And a group selected from a group, an arylamino group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an alkylsulfonyl group, and an arylsulfonyl group. The alkyl group and aryl group constituting these groups are halogen atom, carboxyl group, sulfo group, nitro group, cyano group, amide group, amino group, alkyl group, aryl group, alkenyl group, alkynyl group, hydroxy group. , Alkoxy groups, aryloxy groups, alkylsulfanyl groups, arylsulfanyl groups, alkylamino groups, arylamino groups, acyl groups, alkoxycarbonyl groups, aryloxycarbonyl groups, alkylsulfonyl groups, arylsulfonyl groups, etc. good.

In the formula, L ₁ represents an atom selected from a carbon atom, a nitrogen atom, an oxygen atom and a sulfur atom, or a polyvalent linking group consisting of an atom group selected from a hydrogen atom, a carbon atom, a nitrogen atom, an oxygen atom and a sulfur atom. Represent. Specific examples include groups composed of the structural units exemplified below and the heterocyclic groups shown below. These groups may be used alone or in any combination of two or more.

The linking group L ₁ preferably includes a heterocyclic ring. Examples of the heterocyclic ring constituting L ₁ include pyrrole ring, pyrazole ring, imidazole ring, triazole ring, tetrazole ring, isoxazole ring, oxazole ring, oxadiazole ring, isothiazole ring, thiazole ring, thiadiazole ring, thiazole Triazole ring, indole ring, indazole ring, benzimidazole ring, benzotriazole ring, benzoxazole ring, benzthiazole ring, benzselenazole ring, benzothiadiazole ring, pyridine ring, pyridazine ring, pyrimidine ring, pyrazine ring, triazine ring, quinoline And a nitrogen-containing heterocycle such as a ring and a quinoxaline ring, a furan ring, a thiophene ring, and the like. These heterocycles may have a substituent.

  When the polyvalent linking group described above has a substituent, examples of the substituent include a halogen atom, a carboxyl group, a sulfo group, a nitro group, a cyano group, an amide group, an amino group, an alkyl group, an aryl group, an alkenyl group, and an alkynyl group. Group, hydroxy group, alkoxy group, aryloxy group, alkylsulfanyl group, arylsulfanyl group, alkylamino group, arylamino group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, alkylsulfonyl group, arylsulfonyl group, etc. It is done.

In the formula, m ₁ represents an integer of 0 to 4, p ₁ represents an integer of 0 or 1, and q ₁ represents an integer of ₁ to 4.

  The polymer compound having a polymerizable double bond group is a polymer composed only of a repeating unit having a phenyl group substituted with a vinyl group on the side chain and a repeating unit having a sulfo group or a quaternary ammonium group. Alternatively, a polymer into which another repeating unit is introduced may be used as long as the effects of the present invention are not hindered. Further, it may be a copolymer with another monomer, and such a monomer may be used alone or two or more of them may be used.

  Moreover, the high molecular compound which has a polymerizable double bond group of this invention can introduce | transduce arbitrary substituents into the terminal of a polymer principal chain by using a chain transfer agent. Specifically, linear alkane thiols, particularly linear alkane thiols substituted with silicon atoms bonded to alkoxy groups or halogen atoms, are preferably used because they can be used at the time of polymerization as a chain transfer agent. Can do. Examples of such chain transfer agents include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyldimethoxymethylsilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltrichlorosilane, 3-mercaptopropyldichloromethylsilane, 4 -Mercaptobutyltrimethoxysilane, 4-mercaptobutyldimethoxymethylsilane, 4-mercaptobutyltriethoxysilane, 4-mercaptobutyltrichlorosilane, 4-mercaptobutyldichloromethylsilane, and the like. May be bonded via an oxygen atom by hydrolytic condensation to form a siloxane bond.

  Preferred examples of the polymer compound having a polymerizable double bond group are shown below, but the present invention is not limited to these examples. The numbers in the exemplified structural formulas represent the mass% of each repeating unit in the copolymer total composition of 100 mass%.

  The weight average molecular weight of the polymer compound having a polymerizable double bond group is preferably in the range of 1,000 to 1,000,000, and more preferably in the range of 50,000 to 600,000. The high molecular compound which has a polymerizable double bond group may be used individually by 1 type, and may mix and use arbitrary 2 or more types. The content of the polymer compound having a polymerizable double bond group is preferably in the range of 20 to 80 parts by mass with respect to 100 parts by mass of the total solid content of the photocurable photosensitive layer.

  Next, a low molecular compound having a polymerizable double bond group will be described. In this case, any low molecular compound having a polymerizable double bond group can be preferably used as long as it is a compound that undergoes polymerization by radicals generated by photolysis of the photopolymerization initiator. Furthermore, when a compound having two or more polymerizable double bond groups in the molecule is used, a crosslinked product is formed as a result of polymerization by radicals. Therefore, a negative photosensitive lithographic printing plate material is used. When constituted, it forms a cross-linked hard image part film, so that it can be used very preferably to give a printing plate excellent in printing durability and ink transferability. Examples of compounds having a polymerizable double bond group that can be used for such purposes include bis [2-di (propenoyloxymethyl) butyl] ether, bis [2,2,2-tri (propenoyloxymethyl). )] Ether, [2,2,2-tri (propenoyloxymethyl) ethyl] [2-hydroxy-2,2-bis (propenoyloxymethyl) ethyl] ether, bis [2-di (propenoyloxymethyl) ) Propyl] ether, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, tetraethylene glycol diacrylate, trisacryloyloxyethyl isocyanurate, tripropylene glycol diacrylate, trimethylol Propane triac relay Polyfunctional acrylic monomers such as pentaerythritol triacrylate and pentaerythritol tetraacrylate, etc. Polyester (meth) acrylate, urethane (meth) acrylate, epoxy (meth) acrylate etc. of various oligomers introduced with acryloyl group and methacryloyl group Can be mentioned. The content of the polymerizable compound described above is preferably in the range of 1 to 30 parts by mass with respect to 100 parts by mass of the total solid content of the photocurable photosensitive layer.

  The photocurable photosensitive layer preferably contains a compound for sensitizing the above-described photopolymerization initiator so as to be compatible with various light sources from ultraviolet light to near infrared light. Such compounds include cyanine dyes, cyanine, phthalocyanine, merocyanine, porphyrin, spiro compounds, ferrocene, fluorene, fulgide, imidazole, perylene, phenazine, phenothiazine, polyene, azo compounds, diphenylmethane, triphenylmethane, trimethine acridine, ketocoumarin. Quinacridone, indigo, squarylium compound, coumarin compound, carbazole compound, carbomerocyanine dye, aminobenzylidene ketone dye, pyromethine dye, styryl dye, or (thio) pyrylium compound. Of these, cyanine dyes, coumarin compounds or (thio) pyrylium compounds are preferred. The content of the dye is preferably in the range of 0.01 to 3% by mass and more preferably in the range of 0.5 to 1.5% by mass with respect to the photopolymerization initiator. The example of the compound which sensitizes a photoinitiator is shown below.

  As other elements constituting the photocurable photosensitive layer, various colorants are preferably added for the purpose of improving visibility. As a colorant added for such purposes, an aqueous dispersion of a color pigment can be most preferably used. As an example of an aqueous dispersion of such a pigment, any material in which various colored pigments such as black, blue, red, green and yellow are dispersed in water in the presence of various water-soluble dispersants can be used. . In particular, carbon black, phthalocyanine blue, phthalocyanine green, and the like as pigments are particularly preferred because they are readily available and relatively easy to disperse in water. Examples of dispersants that can be used to disperse these pigments in water include water-soluble nonionic surfactants having an oxyethylene group such as polyethylene glycol and polypropylene glycol, polyacrylic acid, and polyvinylpyrrolidone. , Polystyrene-maleic acid half ester copolymer, polystyrene-maleic acid copolymer, and other various water-soluble polymers. Such a dispersant is preferably contained in a range of 5 to 50 parts by mass with respect to 100 parts by mass of the color pigment. Furthermore, when using a color pigment, it is preferable that it is contained in the range of 0.1-20 mass parts with respect to 100 mass parts of total solid content of a photocurable photosensitive layer.

  The photocurable photosensitive layer preferably contains a silane coupling agent. When the photocurable photosensitive layer contains a silane coupling agent, excellent printing durability can be obtained.

  The silane coupling agent is not particularly limited as long as the purpose is achieved, and any silane coupling agent can be used. For example, epoxycyclohexylethyltrimethoxysilane, glycidoxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, methacryloxypropyltrimethoxysilane, mercaptopropyltrimethoxysilane, mercaptopropyltriethoxysilane, methyltrimethoxysilane, dimethyldimethoxy Silane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, styryltrimethoxysilane, styryltriethoxysilane, hexyltrimethoxysilane, decyltrimethoxysilane , Vinyltris (3-methoxyethoxy) silane, vinyltriethoxysilane, vinyltrimeth Sisilane, 3-methacryloyloxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-methacryloyl Oxypropylmethyldiethoxysilane, N-β (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β (aminoethyl) -aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-γ -Aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane and the like. Among them, epoxycyclohexylethyltrimethoxysilane, glycidoxypropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, acryloxypropyltrimethoxysilane, methacryloxypropyltrimethoxysilane, mercaptopropyltrimethoxysilane, mercaptopropyltri Particularly preferred are trialkoxysilanes such as ethoxysilane. In addition, a silane coupling agent may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

  As a quantity of the silane coupling agent which a photocurable photosensitive layer contains, the range of 0.01-20 mass parts is preferable with respect to 100 mass parts of total solid content of a photocurable photosensitive layer.

  The photocurable photosensitive layer preferably contains an antioxidant. Examples of the antioxidant include antioxidants described in pages 12 to 16 of "Antioxidant Handbook" (October 25, 1951) published by Taiseisha Co., Ltd., mercapto group-containing compounds, and thioethers. Sulfur-containing compounds such as group-containing compounds; phosphorus-containing compounds such as phosphites; amines; phenols; hydroquinones; ascorbic acids. Of these, amines, phenols, and ascorbic acids are preferably used. As addition amount of antioxidant, it is preferable to use in 0.01-10 mass parts with respect to 100 mass parts of total solid content of a photocurable photosensitive layer.

  As amines, hindered amine compounds are preferably used. As such hindered amine compounds, LA52, LA57, LA62 (manufactured by Adeka), TINUVIN 144, 765, 770DF (manufactured by Ciba Japan), Siasorb UV-3346, UV-3529, UV-3853 ( Sun Chemical Co., Ltd.).

  As commercial products of phenols, NOCRACK NS-5, NS-6, NS-30 (manufactured by Ouchi Shinsei Chemical Co., Ltd.), Sianox CY1790, CY2777, CY-XS4 (manufactured by Sun Chemical Co., Ltd.) A hindered phenol compound such as GA80, GM, GS, WXR, MDP (manufactured by Sumitomo Chemical Co., Ltd.) can be used in the present invention.

  Ascorbic acids include ascorbic acid, sodium ascorbate, sodium erythorbate and the like.

  The photocurable photosensitive layer of the present invention is formed by preparing an emulsion in water containing a photopolymerization initiator and other hydrophobic components as a dispersed phase, and applying an aqueous dispersion containing this onto a substrate. It is preferable.

  In preparing the emulsion in water, it is preferable to emulsify and disperse the components of the dispersed phase in water in the presence of an anionic surfactant, thereby providing an emulsion in water that can maintain a stable emulsion dispersion state even when exposed to a certain high temperature. can get. Examples of such anionic surfactants include higher fatty acid salts such as sodium laurate, sodium stearate, and sodium oleate, alkyl sulfates such as sodium dialkylsulfosuccinate, sodium lauryl sulfate, and sodium stearyl sulfate, and octyl alcohol sulfate. Higher alcohol sulfates such as sodium, sodium lauryl alcohol sulfate, ammonium lauryl alcohol sulfate, aliphatic alcohol sulfates such as sodium acetyl alcohol sulfate, alkyl benzene sulfonates such as sodium dodecylbenzene sulfonate, butyl naphthalene sulfone Alkyl naphthalene sulfonates such as sodium acid and sodium isopropyl naphthalene sulfonate Alkyl diphenyl ether disulfonates such as sodium didiphenyl ether disulfonate, alkyl phosphate esters such as sodium lauryl phosphate and sodium stearyl phosphate, polyethylene oxide adducts of sodium lauryl ether sulfate, polyethylene oxide adducts of ammonium lauryl ether sulfate, trilauryl ether sulfate Polyethylene oxide adducts of alkyl ether sulfates such as polyethylene oxide adduct of ethanolamine, polyethylene oxide adducts of alkyl phenyl ether sulfates such as polyethylene oxide adduct of sodium nonylphenyl ether sulfate, polyethylene of sodium lauryl ether phosphate Polyethylene oxide of alkyl ether phosphates such as oxide adducts De adducts, and polyethylene oxide adducts of alkyl phenyl ether phosphate salts of polyethylene oxide adducts of nonyl phenyl ether sodium phosphate and the like. Of these, sodium dialkyl sulfosuccinate, alkyl naphthalene sulfonates and polyethylene oxide adducts of alkyl ether sulfates are particularly preferred because they form the most stable emulsions in water.

  Further, by adding the above-described polymer compound having a polymerizable double bond group and a sulfo group to this system, the emulsion dispersion stability is further improved. The polymer compound may be added at the time of emulsification and dispersion, or may be added after the emulsification and dispersion. However, by adding at the time of emulsification and dispersion, the dispersed particle diameter of the emulsion in water is remarkably reduced, so that it is extremely fine. Since it is dispersed in the form of simple droplets and fine particles, problems such as sedimentation or levitation over time can be suppressed, which is more preferable. Furthermore, it is also possible to preferably perform a part of the polymer compound at the time of dispersion to prepare an emulsion in water and then add the polymer compound after a stable emulsion is prepared.

  When emulsifying and dispersing hydrophobic components such as photopolymerization initiators in water, a mixed solution is prepared using an organic solvent that can dissolve or disperse these components and mixed with water. It is preferable to emulsify and disperse using an activator or a polymer compound having a polymerizable double bond group and a sulfo group. However, if the other additive used is a liquid and the other hydrophobic components are dissolved in this and the mixture of both is liquid, the mixture of both is emulsified in water without using an organic solvent. It is also possible to disperse. It is possible to prepare an underwater emulsion in which both are mixed in advance, but the underwater emulsion may be prepared separately. Regarding the method of emulsifying and dispersing, any dispersing machine such as a rotary dispersing machine, a media mill, an ultrasonic dispersing machine or a kneading machine can be used, and a commercially available apparatus such as a homomixer, a homogenizer, or a sand grinder. Can be preferably used.

  The organic solvent that can be used for emulsification dispersion means an organic solvent that is liquid at room temperature and can dissolve or disperse the components of the dispersed phase. Examples of organic solvents that can be used in the present invention include volatile organic solvents and non-volatile organic solvents. When a volatile organic solvent is used, it is preferable to remove the volatile organic solvent from the produced emulsion in water by heating or leaving it. In the case of using a non-volatile organic solvent, the non-volatile organic solvent exhibits a flash point higher than 50 ° C., and the countermeasure as a dangerous substance may be reduced in normal handling, which is preferable.

  Examples of the solvent that can be preferably used in the present invention as the volatile organic solvent include lower alkanol acetates such as ethyl acetate, propyl acetate, and butyl acetate, ethylene glycol monomethyl ether acetate, and ethylene glycol monoethyl ether acetate. Ethylene glycol acetates such as methyl ethyl ketone, methyl isobutyl ketone, ketones such as cyclohexanone, hydrocarbons such as hexane, cyclohexane and heptane, aromatics such as benzene, toluene and xylene, etc. Of these, ethyl acetate is most preferably used for various reasons described later.

  Nonvolatile organic solvents that can be used in the present invention include phosphoric acid esters, phthalic acid esters, acrylic acid esters, methacrylic acid esters and other carboxylic acid esters, fatty acid amides, alkylated biphenyls, alkylated terphenyls, alkylated naphthalenes, Examples include diarylethane, chlorinated paraffin, alcohol solvent, phenol solvent, ether solvent, monoolefin solvent, epoxy solvent and the like. Specific examples include tricresyl phosphate, trioctyl phosphate, octyl diphenyl phosphate, tricyclohexyl phosphate, dibutyl phthalate, dioctyl phthalate, dilaurate phthalate, dicyclohexyl phthalate, butyl olefinate, diethylene glycol benzoate, dioctyl sebacate, Dibutyl sebacate, dioctyl adipate, trioctyl trimellitate, acetyl triethyl citrate, octyl maleate, dibutyl maleate, isoamylbiphenyl, chlorinated paraffin, diisopropylnaphthalene, 1,1'-ditolylethane, monoisopropylbiphenyl, diisopropylbiphenyl, 2,4-ditertiaryamylphenol, N, N-dibutyl-2-butoxy-5-tertiaryoctylaniline, hydroxy Ikikosan ethylhexyl esters, high boiling point solvent such as polyethylene glycol.

  In the present invention, the organic solvent used for emulsification dispersion is more preferably a volatile organic solvent. In this case, the emulsion in water can be most stably produced, and it is preferable because the emulsified dispersion state is kept stable even when exposed to a temperature higher than room temperature. As the volatile organic solvent, ethyl acetate is particularly preferable. Since ethyl acetate is highly volatile, it can be easily removed from the emulsion in water simply by placing it under heating or reduced pressure. The emulsion in water after the distillation of ethyl acetate is in a solid dispersion state, such as ethyl acetate. This is extremely preferable because it forms a coating solution that is more stable than a state containing a solvent.

  Next, the production method for producing an underwater emulsion will be described more specifically.

  Using the organic solvent such as ethyl acetate described above, a solution in which the hydrophobic component is dissolved or dispersed is prepared. When adding this to water containing an anionic surfactant, a polymer compound having a polymerizable double bond group and a sulfo group, etc., a known stirring device capable of high-speed shearing such as a homomixer or a homogenizer is used. An emulsified solution in water can be prepared by emulsifying and dispersing by using. The organic solvent may contain other water-insoluble compounds contained in the coating solution for coating the photocurable photosensitive layer of the present invention, and the water used as the dispersion medium may be contained in the coating solution. Other water soluble compounds may be added. Moreover, the emulsification dispersion method can be carried out in a batch manner, or can be carried out continuously in a state of flowing through the piping system in a continuous manner, and in that case, the emulsification dispersion is carried out in a temperature range of 0 to 70 ° C. Is preferred.

  Regarding the dry solid content coating amount of the photocurable photosensitive layer itself, it is preferably formed with a dry solid content coating amount in the range of 0.3 to 10 g per square meter by dry mass, and further in the range of 0.5 to 3 g. It is extremely preferable to exhibit good resolution and to ensure the printing durability of fine line images and fine dot images, and at the same time to greatly improve the ink transportability.

<Protective layer>
The photosensitive lithographic printing plate of the present invention has a protective layer on the photocurable photosensitive layer. The protective layer of the present invention comprises at least two layers: a layer not containing wax particles and a layer containing wax particles on the upper layer.

  The wax particles contained in the protective layer are not particularly limited as long as they can be uniformly dispersed in the protective layer, but the melting point may be 50 ° C. or higher for the purpose of preventing fusion during production or storage. preferable.

  The wax particles of the present invention include carnauba wax, beeswax, spermaceti, wood wax, jojoba oil, lanolin, ozokerite, paraffin wax, montan wax, candelilla wax, ceresin wax, microcrystalline wax, rice wax and other natural waxes, polyethylene Examples thereof include wax, Fischer-Tropsch wax, montan wax derivative, paraffin wax derivative, and microcrystalline wax derivative.

  Particularly preferred wax particles are carnauba wax, microcrystalline wax, polyethylene wax, polypropylene wax, candelilla wax and paraffin wax. Wax particles may be used alone or in combination of two or more. In order to facilitate emulsification, these wax particles may be oxidized to introduce polar groups such as hydroxyl groups, ester groups, carboxyl groups, aldehyde groups, and peroxide groups. Commercially available wax particles can be used. Examples of commercially available wax particles include AQUACER 497, AQUACER 501, AQUACER 531, AQUACER 533, AQUACER 537, AQUACER 539, AQUACER 593, AQUACER 2500, and AQUACER 2500 from Big Chemie Japan Co., Ltd. Etc. The added amount of wax particles is preferably 20 to 200 parts by mass with respect to 100 parts by mass of the total solid content of the layer containing the wax particles.

  Devices related to the protective layer have been conventionally used and are described in detail in US Pat. No. 3,458,311 and JP-A-55-49729. As a material that can be used for the protective layer, for example, a water-soluble polymer compound having relatively excellent crystallinity is preferably used. Specifically, polyvinyl alcohol, polyvinyl pyrrolidone, acidic celluloses, gelatin, gum arabic, and polyacrylic are used. Water-soluble polymers such as acids are known, but among these, using polyvinyl alcohol as the main component provides the best results in terms of basic properties such as oxygen barrier properties and development removability of the protective layer. give. The polyvinyl alcohol used for the protective layer may be partially substituted with an ester, an ether and an acetal as long as it contains an unsubstituted vinyl alcohol unit for having necessary oxygen barrier properties and water solubility. Similarly, some of them may have other copolymer components. Any of these techniques can be used in the present invention. There is a preferred range for the amount of dry solids applied when applying such a protective layer, and both the layer containing no wax particles and the layer containing wax particles have a dry mass of 0 per square meter on the photocurable photosensitive layer. It is preferably formed with a dry solid content coating amount in the range of 1 to 10 g, and more preferably in the range of 0.2 to 2 g per square meter.

<Hydrophilic layer>
The photosensitive lithographic printing plate preferably has a hydrophilic layer on the substrate. The hydrophilic layer is preferably a hydrophilic layer containing an inorganic filler, and the hydrophilic layer preferably contains gelatin.

  The gelatin will be described in more detail. For example, lime-processed gelatin is manufactured as follows. First, ossein consisting only of collagen from which calcium phosphate has been removed is immersed in lime saturated water for 2 to 3 months, then washed with water, neutralized, and extracted with hot water at about 60 ° C (No. 1 extraction). Do. Next, the second extraction is performed at about 70 ° C., the third extraction is performed at about 85 ° C., and the fourth extraction is further performed at 95 ° C. Each extract is filtered, concentrated under reduced pressure, cooled and solidified at about 10 ° C., and then dried to obtain gelatin.

  In the above example, ossein is pretreated with lime water (alkaline treatment), but as other pretreatment, acid treatment by soaking in a dilute acid solution such as hydrochloric acid or sulfuric acid for a short time (10 to 48 hours), pronase And enzyme treatment using pepsin and the like. In the example described above, the extraction is performed from 60 ° C. to the fourth extraction at 95 ° C. starting from the first extraction, but the first extraction can be started at a temperature of generally 45 ° C. or higher. In the above example, the number of extractions is four, but by reducing the difference from the previous extraction temperature, for example, seven extractions are possible. In general, commercially available gelatin is appropriately mixed after drying the gelatin extracted several times according to the required physical properties and chemical properties.

  In order to obtain gelatin, bone gelatin made from ossein extracted from bovine bone is preferred. The pretreatment is preferably gelatin that has been subjected to alkali treatment or enzyme treatment. Further, gelatin obtained by the first and second extractions is preferable in that a particularly high jelly strength can be obtained.

The preferred amount of gelatin is preferably in the range of 0.5 to 2.0 g / ^{m 2,} the range of 0.8 to 1.5 g / ^{m 2} is more preferable.

  In the hydrophilic layer, in addition to the above-described gelatin, other hydrophilic binders can be used in combination. The amount of the other hydrophilic binder is preferably 0 to 10% by mass, more preferably 0 to 5% by mass, based on the total amount of gelatin contained in the hydrophilic layer.

  Examples of other hydrophilic binders include proteins such as gelatin derivatives or cellulose derivatives, gum arabic, starch and derivatives thereof, cellulose derivatives (for example, hydroxypropylmethylcellulose), glycogen, agarose, pectin, dextran, pullulan and other polysaccharides, Examples thereof include synthetic polymer compounds such as polyvinyl alcohol, modified polyvinyl alcohol, polyvinyl pyrrolidone, styrene / maleic acid copolymer salt, styrene / acrylic acid copolymer salt, and acrylamide polymer.

  Examples of the inorganic filler contained in the hydrophilic layer include calcium carbonate, magnesium carbonate, zinc oxide, titanium dioxide, barium sulfate, aluminum hydroxide, zinc hydroxide, colloidal silica, pore silica, and kaolin. Of these, titanium dioxide, barium sulfate, aluminum hydroxide, and colloidal silica are preferable.

  Titanium dioxide may be either a rutile type or an anatase type, and the production method is not limited to either the sulfuric acid method or the chlorine method. You may use them individually or in mixture. Furthermore, from the viewpoint of dispersion stability and other functionality, it is possible to selectively use those subjected to various surface treatments. Examples of commercially available titanium dioxide include SR-1, R-650, R-5N, R-7E, R-3L, A-110, and A-190 from Sakai Chemical Industry Co., Ltd. Typek R-580, R-930, A-100, A-220, CR-58 from Titanium Industry Co., Ltd. Kronos KR-310, KR-380, KA-10 from Titanium Industry Co., Ltd. KA-20, etc., Titanics JR-301, Takeda Co., Ltd., JR-600A, JR-800, JR-701, etc., Taipure R-900, R-931 from DuPont Co., Ltd. Etc.

  As barium sulfate, it is preferable to use precipitated barium sulfate produced by adding a sulfate aqueous solution to a barium chlorine solution and chemically precipitating. Precipitated barium sulfate is commercially available, for example, as “Variace” from Sakai Chemical Industry Co., Ltd., having various particle diameters or surface-treated ones, any of which can be used.

  Aluminum hydroxide mixes bauxite, which is an ore containing alumina, with caustic soda or sodium aluminate solution, extracts the alumina component under high temperature and high pressure conditions, separates and removes red mud as a dissolution residue from the extract, A clarified sodium aluminate solution is obtained, and then seeds are added to the solution to crystallize aluminum hydroxide, and the obtained aluminum hydroxide can be pulverized. Various grades of aluminum hydroxide are commercially available from Showa Denko Co., Ltd. as “Hijilite”, and any of them can be used.

  Colloidal silica is obtained by heating and aging a silica sol obtained by metathesis of sodium silicate with an acid or the like or through an ion exchange resin layer. Alternatively, it can also be produced by a liquid phase synthesis method such as hydrolysis of an alkoxide. For example, manufactured by Nissan Chemical Industries, Ltd. Snowtex XS, Snowtex S, Snowtex 20, MP-2040, MP-1040, Snowtex ZL, Snowtex O, Snowtex OL, Snowtex UP, Snowtex PS-S , Snowtex PS-M and the like are commercially available, and any of them can be used.

  In addition, it is desirable that the content of the silicon-containing compound is small in the entire inorganic filler having the above particle size distribution. The silicon-containing compound is colloidal silica, pore silica, kaolin, or the like, and is preferably used at 5% by mass or less, more preferably 3% by mass or less, particularly 1% by mass with respect to the total inorganic filler. It is desirable to use in the following. As a result, a hydrophilic layer superior in developability can be obtained.

  The hydrophilic layer preferably contains a crosslinking agent for the purpose of improving the film strength and adhesive strength of the hydrophilic layer. As examples of the crosslinking agent, melamine resin, epoxy resin, polyisocyanate compound, aldehyde compound, silane compound, chromium alum, divinyl sulfone, and the like can be suitably used. A particularly preferred crosslinking agent is divinyl sulfone. The amount of the crosslinking agent is preferably 1.0 to 30% by mass with respect to the solid content of the hydrophilic binder contained in the hydrophilic layer.

  In order to sufficiently crosslink the hydrophilic layer, for example, after the hydrophilic layer is formed, a heating treatment for 0.5 to 10 days may be performed at a temperature of 30 to 60 ° C., preferably 40 to 50 ° C. preferable. Even if the hydrophilic layer is subjected to printing as a non-image part at the time of printing by such a heating treatment, it is natural that printability is sufficient, but sufficient performance can be expressed in terms of scratch resistance.

  The hydrophilic layer preferably contains a surfactant. In consideration of the applicability of a coating liquid containing a high concentration of the inorganic filler in the hydrophilic layer, and also the printability, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, etc. It is preferable to contain a nonionic surfactant. In addition, anionic surfactants such as polyoxyethylene alkyl ether acetate, polyoxyethylene alkyl ether phosphate, polyoxyethylene alkyl ether sulfate, polyoxyethylene alkylphenyl ether sulfate, and the like are also preferably used. Fatty acid alkylbetaine type amphoteric surfactants such as coconut oil fatty acid amidopropyl betaine, lauric acid amidopropyl betaine, myristic acid amidopropyl betaine, octanoic acid amidopropyl betaine / alkyl betaine type amphoteric Surfactant / sulfobetaine-type amphoteric surfactants such as dodecylaminomethyldimethylsulfopropylbetaine and octadecylaminomethyldimethylsulfopropylbetaine / amino acid-type amphoteric surfactants such as sodium lauroylglutamate, potassium lauroylglutamate, lauroylmethyl-β-alanine / Amine oxide type amphoteric surfactants such as lauryl dimethylamine N-oxide and oleyldimethylamine N-oxide can be used. That. The addition amount of the above-described surfactant is preferably 0.2 to 15% by mass, more preferably 1.5 to 10% by mass in terms of solid content with respect to the hydrophilic binder of the hydrophilic layer. Regarding the dry solid content coating amount of the hydrophilic layer itself, it is preferable to form the dry solid content in the range of 1 to 20 g per square meter in terms of dry mass.

  When applying the hydrophilic layer of the photosensitive lithographic printing plate, the photocurable photosensitive layer provided on the upper layer, the protective layer, or the like, a coating solution of the composition comprising the above-described elements on the substrate Is applied and dried. As the coating method, various known methods can be used, and examples thereof include bar coater coating, slide hopper coating coating, curtain coating, blade coating, air knife coating, roll coating, spin coating, and dip coating. it can.

  Light sources used for exposure to form image patterns on photosensitive lithographic printing plates include carbon arc, high pressure mercury lamp, ultra high pressure mercury lamp, low pressure mercury lamp, deep UV lamp, xenon lamp, metal halide lamp, tungsten lamp, halogen lamp, excimer A UV lamp, LED lamp, various fluorescent lamps (white fluorescent lamp, black light, chemical light, etc.) can be used, but scanning exposure with a laser is very preferable in terms of plate making efficiency. Examples of the laser light source include a blue-violet semiconductor laser (violet laser), an argon laser, a helium / neon laser, a red LED, a near infrared laser, and an infrared laser. The scanning method may be any of an internal drum system, an external drum system, a planar scanning system, etc., but an internal drum system is preferred.

<Development processing>
The processing solution in the development processing may contain a surfactant or an alkali agent as necessary for the purpose of improving the image quality and shortening the processing time. The polymer compound having a polymerizable double bond group has an acidic group such as a carboxyl group or a sulfo group, and the acidic group is in the form of a metal salt or an ammonium salt in the photocurable photosensitive layer. In some cases, it is possible to process with a chemical-less developer substantially free of an alkali agent, that is, a neutral developer having a pH of less than 9. In particular, when the compound having a polymerizable double bond group has a neutralized salt of a sulfo group, good developability can be obtained, and processing is possible with pure water. In the case where sufficient developability cannot be obtained even with a neutralized sulfo group salt, a surfactant can be added to the neutral developer for the purpose of improving developability.

  Nonionic properties such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl aryl ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, monoglyceride alkyl esters as surfactants, alkylbenzene sulfonates, alkylnaphthalene sulfonic acids Anionic surfactants such as salts, alkyl sulfates, alkyl sulfonates, sulfosuccinate esters, amphoteric surfactants such as alkyl betaines, amino acids, isopropyl alcohol, benzyl alcohol, ethyl cellosolve, butyl cellosolve, phenyl cellosolve, propylene glycol And water-soluble organic solvents such as diacetone alcohol.

  The development is usually carried out by a known development method such as immersion development, spray development, brush development, ultrasonic development, etc., preferably at a temperature of about 10 to 60 ° C., more preferably about 15 to 45 ° C. for 5 seconds to It takes about 10 minutes. At that time, the protective layer provided as necessary on the photocurable photosensitive layer may be removed in advance with water or the like, or may be removed during development.

  EXAMPLES Hereinafter, although this invention is demonstrated using an Example, this invention is not limited by this description. In the following description, “%” and “part” are based on mass unless otherwise specified.

Example 1
<Hydrophilic layer>
A hydrophilic layer coating solution 1 having the following composition was applied on a polyethylene terephthalate substrate having a thickness of about 200 μm by a slide hopper coating method. At that time, the moisture application amount was set in advance to be 35 g / m ² . Immediately after coating, the coating film was gelled with cold air of 1 to 5 ° C., and then dried using a dry air set at 50 ° C. After drying, the hydrophilic layer was completed by putting it in a thermo-hygrostat adjusted to 40 ° C. and 40% RH and heating for 7 days.

<Hydrophilic layer coating solution 1>
Gelatin: GEL Type I 1.2 parts (Alkaline-treated gelatin made from beef bone ossein, 1st and 2nd extracted gelatin mixture)
Inorganic filler 1: Titanium dioxide 4.0 parts (SR-1, Sakai Chemical Industry Co., Ltd., average diameter ≈ 0.3 μm, refractive index = 2.04)
Inorganic filler 2: 1.6 parts of barium sulfate (B35, manufactured by Sakai Chemical Industry Co., Ltd., average diameter≈0.3 μm, refractive index = 1.23)
Inorganic filler 3: 0.4 parts of aluminum hydroxide (H42, manufactured by Showa Denko KK, average diameter≈1.0 μm, refractive index = 1.24)
Inorganic filler dispersant (acrylic acid copolymerized metal salt, 10% solution) 1.0 part POE nonylphenyl ether sulfate Na (10% solution) 0.4 part divinyl sulfone (5% solution) 4.0 parts Total amount with water 35 parts.

<Photocurable photosensitive layer>
On the hydrophilic layer obtained above, the photocurable photosensitive layer coating solution (aqueous dispersion) obtained as follows was applied so that the dry solid content was 1.5 g / m ² . After application, the film was dried for 10 minutes in a 75 ° C. drier.

<Photocurable photosensitive layer coating solution>
An aqueous phase having the following composition was prepared.
<Water phase>
Polymer compound having polymerizable double bond group and sulfo group
(SP-2) Average molecular weight 80,000 20 parts Perex OTP (sodium dialkylsulfosuccinate: manufactured by Kao Corporation) 5 parts Ion-exchanged water 300 parts

A dispersed phase having the following composition was prepared.
<Dispersed phase>
AD-TMP
(Bis [2-di (propenoyloxymethyl) butyl] ether, Shin-Nakamura Chemical Co., Ltd.) 6 parts Organoboron salt (BC-7) 2 parts Trihaloalkyl-substituted compound (T-8) 1.5 parts Increase Dye-sensitive dye (VS-1) 0.05 part Acryloxypropyltrimethoxysilane 0.08 part Antioxidant (2,2'-methylenebis (4-ethyl-6-tert-butylphenol))
0.01 parts ethyl acetate 200 parts

  The aqueous dispersion is prepared using a Mizuho Kogyo Co., Ltd. tabletop vacuum emulsifier PVQ-1D, in which a homomixer is placed in a sealed container and the solvent can be distilled off while heating under reduced pressure. Went. The rotation speed of the homomixer was set to 5000 rpm. The aqueous phase and the dispersed phase prepared above were introduced into a vacuum emulsification apparatus, and emulsified and dispersed by high-speed stirring with a homomixer for 20 minutes at room temperature. Thereafter, 0.2 parts of Pigment Blue 15 as a colorant was added and stirred, and the inside of the vacuum emulsifier was depressurized with an aspirator, and the temperature was raised to 50 ° C. under a depressurization condition of 20% of atmospheric pressure, and ethyl acetate was added. Distilled under reduced pressure. From the amount of ethyl acetate collected in the cooler, it was confirmed that all the ethyl acetate used was distilled off from the emulsion in water. Thus, a photocurable photosensitive layer coating solution was prepared.

<Protective layer>
A protective layer coating solution A and a protective layer coating solution B were prepared according to the following protective layer formulation, and a protective layer was applied according to Table 1. In applying the protective layer, the lower layer coating solution is applied onto the photocurable photosensitive layer so that the dry solid content is 1.0 g / m ^2, and after application, in a 75 ° C. drier for 10 minutes. Drying was performed. Thereafter, the upper layer coating solution was applied so that the dry solid content was 1.0 g / m ^2, and after application, drying was performed in a dryer at 75 ° C. for 10 minutes to obtain a photosensitive lithographic printing plate.

<Protective layer coating liquid A>
Polyvinyl alcohol PVA-205 (manufactured by Kuraray Co., Ltd.) 1 part Ion-exchanged water 9 parts

<Protective layer coating solution B>
Polyvinyl alcohol PVA-205 (manufactured by Kuraray Co., Ltd.) 1 part Wax particles (described in Table 1) 0.5 part Ion-exchanged water 9 parts

<Scratch resistance>
The scratch resistance of the photosensitive lithographic printing plate obtained above was determined by applying a load of 200 g to a diamond needle having a diameter of 0.05 mm using a HEIDON 18 type continuous load type scratch tester (manufactured by Shinto Kagaku Co., Ltd.). The photosensitive lithographic printing plate was scratched from above, and the degree of damage to the protective layer at that time was evaluated according to the following evaluation criteria. The obtained results are shown in Table 1.
(Evaluation criteria)
1: The protective layer is completely peeled 2: The peeling of the protective layer is remarkable 3: The protective layer is slightly peeled 4: The surface of the protective layer is scratched but not peeled 5: The protective layer surface is not damaged at all can not see

<Sensitivity>
The sensitivity of the photosensitive lithographic printing plate obtained above was evaluated as follows. The exposure amount on the printing plate was set to 600 μJ / cm ² , and the solid image was exposed with light having a wavelength of 405 nm through a gray scale. Thereafter, the sample was immersed in ion exchange water at 18 ° C. for 15 seconds, rubbed with the cellulose sponge on the surface having the photocurable photosensitive layer / protective layer, and then dried to prepare a sample. Sensitivity was judged from the exposure amount at which the density of the image area was constant. A smaller value indicates higher sensitivity. The obtained results are shown in Table 1.

  As can be seen from Table 1, according to the present invention, it is understood that a lithographic printing plate having high sensitivity and excellent scratch resistance can be obtained.

Claims (1)

  A photosensitive lithographic printing plate having at least a photocurable photosensitive layer and a protective layer in this order on the base material from the side closer to the base material, wherein the protective layer does not contain wax particles and a layer containing wax particles as an upper layer thereof A photosensitive lithographic printing plate comprising at least two layers.