JP2014174360A - Method for producing lithographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a lithographic printing plate having excellent printing dirt and plate durability even after long term preservation.SOLUTION: Provided is a method for producing a lithographic printing plate characterized in that, in a method for producing a lithographic printing plate having at least a photocurable photosensitive layer on a base material, both a water phase and a dispersion phase including a photoinitiator are coated with an aqueous dispersion including an oxidation inhibitor to form the photocurable photosensitive layer.

Description

  The present invention relates to a method for producing a lithographic printing plate having at least a photocurable photosensitive layer on a substrate. More specifically, the present invention relates to a method for producing a lithographic printing plate suitable for a lithographic printing plate that can be developed with a chemical-less developer substantially free of an alkali agent.

  In recent years, CTP (abbreviation of Computer To Plate) has been fully digitized due to the expansion of JDF (abbreviation of 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, in thermal type and photopolymer type CTP printing plates which are currently mainstream, after the printing plate is laser-exposed, non-image areas are eluted and removed using a developer containing a strong alkali agent, and then washed with water and gum. Since it becomes what is used for printing through a drawing process, it has become a big subject from the viewpoint of the cost of a strong alkali agent-containing developer and the cost of waste liquid and from the viewpoint of environmental burden.

  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 the photosensitive composition described above is developed with water or the like using an automatic developing machine, the generation of sludge that accumulates in the water developer becomes significant, and the sludge adheres to the surface of the photosensitive composition film, resulting in image defects. In some cases, improvements were required.

  As a method for solving the above-mentioned problem, for example, JP 2011-209354 A (Patent Document 3) discloses a photopolymerization initiator and a compound having a polymerizable double bond group as a water-soluble polymer having a sulfonate group. And a method using an underwater emulsion emulsified and dispersed in the presence of an anionic surfactant, in which the photopolymerization initiator is contained in the dispersed phase. In such a system, the above-mentioned image defect problem is solved and good storage stability can be obtained, but further improvement has been demanded for storage stability.

  On the other hand, Japanese Patent Application Laid-Open No. 2005-84302 (Patent Document 4) describes that the addition of an antioxidant to the protective layer can improve the decrease in sensitivity associated with long-term storage, and Japanese Patent Application Laid-Open No. 2002-333707 ( Patent Document 5) describes that a printing plate having excellent storage stability can be obtained by adding an antioxidant to the photosensitive layer.

JP-A-5-27437 JP 2003-215801 A JP 2011-209354 A JP 2005-84302 A JP 2002-333707 A

  An object of the present invention is to provide a method for producing a lithographic printing plate having excellent printing stains and printing durability even after long-term storage.

  The present invention relates to a method for producing a lithographic printing plate having at least a photocurable photosensitive layer on a substrate, and an aqueous dispersion containing an antioxidant is applied to both an aqueous phase and a dispersed phase containing a photopolymerization initiator. This is achieved by a method for producing a lithographic printing plate, characterized in that the photocurable photosensitive layer is formed.

  According to the present invention, it is possible to provide a lithographic printing plate excellent in printing stain and printing durability even after long-term storage.

  Hereinafter, the present invention will be described in detail.

<Base material>
Examples of the substrate of the present invention include aluminum plates, various plastic films, paper laminated with various plastics, and the like. 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 substrate include polyethylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, polystyrene, polyvinyl acetal, polycarbonate, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, and cellulose nitrate. In particular, polyethylene terephthalate and polyethylene naphthalate are preferably used.

  The surface of these base materials may be surface-treated in order to improve adhesion with a hydrophilic layer or a backing layer provided as necessary. Examples of such surface treatment include corona discharge treatment, flame treatment, plasma treatment, and ultraviolet irradiation treatment. As a further surface treatment, an undercoat layer may be provided on the base material in order to enhance the adhesiveness with the hydrophilic layer provided on the base material.

<Photocurable photosensitive layer>
The lithographic printing plate of the present invention has at least a photocurable photosensitive layer on the substrate. Such a photocurable photosensitive layer contains at least a photopolymerization initiator.

<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, trihaloalkyl-substituted compounds and organic boron salts are particularly 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 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, more preferably 1 to 15 parts by mass with respect to 100 parts by mass of the total solid content of the photocurable photosensitive layer. It is preferably included in the range of parts.

  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 use a low molecular weight compound having a polymerizable double bond group in combination.

  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, thia 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.

  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 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, and tetraethylene glycol diacrylate. Polyfunctional acrylic monomers such as trisacryloyloxyethyl isocyanurate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, etc., or acryloyl group, methacryloyl group Polyester (meth) acrylate, urethane (meth) acrylate, epoxy (meth) acrylate, etc. are also used in the same way as various oligomers introduced with That.

  The photocurable photosensitive layer of the lithographic printing plate of the present invention preferably contains a compound for sensitizing the above-mentioned photopolymerization initiator. As compounds that sensitize the sensitivity in the wavelength range of 400 to 430 nm, cyanine dyes, coumarin compounds described in JP-A-7-271284, JP-A-8-29973, etc., JP-A-9-230913, Carbazole compounds described in JP-A No. 2001-42524 and the like, carbomerocyanine dyes described in JP-A-8-262715, JP-A-8-272096, JP-A-9-328505, and the like, JP-A-4-194857, JP-A-6-295061, JP-A-7-84863, JP-A-8-220755, JP-A-9-80750, JP-A-9-236913, etc. Aminobenzylidene ketone dyes, JP-A-4-184344, JP-A-6-301208, Pyrromethine dyes described in JP-A-7-225474, JP-A-7-5585, JP-A-7-281434, JP-A-8-6245, etc., and JP-A-9-80751 Styryl dyes or (thio) pyrylium compounds. 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 of a lithographic printing plate, it is preferable to add various colorants 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 of the lithographic printing plate 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-methacryloyloxypropyltrimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyl Trimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, N-β (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β (aminoethyl) -amino Propylmethyldimethoxysilane, 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.

  As the antioxidant used in the aqueous phase and the dispersed phase in the production of the lithographic printing plate of the present invention, from the "Antioxidant Handbook" (October 25, 1977, first edition) published by Taiseisha Co., Ltd. Antioxidants described on page 16, sulfur-containing compounds such as mercapto group-containing compounds and thioether group-containing compounds; phosphorus-containing compounds such as phosphites; amines; phenols; hydroquinones; Examples include acids. Of these, amines, phenols, and ascorbic acids are preferably used. The total addition amount of the antioxidant to the aqueous phase and the dispersed phase may be 0.01 to 10 parts by mass with respect to 100 parts by mass of the total solid content of the photocurable photosensitive layer of the present invention. preferable.

  As amines, hindered amine compounds are preferably used. As such hindered amine compounds, LA52, LA57, LA62 (manufactured by Adeka Co., Ltd.), TINUVIN 144, 765, 770DF (manufactured by Ciba Japan Co., Ltd.), 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.

  In the present invention, a photocurable photosensitive layer is formed by forming an emulsion in water containing the above-described photopolymerization initiator as a dispersed phase and applying an aqueous dispersion containing the emulsion to a substrate as a coating liquid. In particular, an aqueous dispersion containing an underwater emulsion of a low-molecular compound having a photopolymerization initiator and a polymerizable double bond group is more preferably a coating liquid.

  In preparation of an emulsion in water of a photopolymerization initiator, the photopolymerization initiator is emulsified and dispersed in water in the presence of an anionic surfactant, so that the emulsion dispersion in water can be stably maintained even when exposed to a certain high temperature. A thing is obtained. 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 dispersion of the photopolymerization initiator or may be added after the emulsification dispersion, but by adding at the time of emulsification dispersion, the dispersed particle size of the underwater emulsion in water is remarkably increased. It is more preferable because it decreases and disperses in the form of extremely fine droplets and fine particles, and thus the occurrence of problems such as sedimentation or levitation over time can be suppressed. 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 the photopolymerization initiator in water, prepare a solution using an organic solvent that can dissolve or disperse the photopolymerization initiator and antioxidant, and mix it with water in which the antioxidant is dissolved. A method of emulsifying and dispersing the aforesaid anionic surfactant or a polymer compound having a polymerizable double bond group and a sulfo group is preferred. However, if the other additive used is a liquid, and the photopolymerization initiator and the antioxidant are dissolved in this solution and the mixture of both is liquid, the mixture of both must be prepared without using an organic solvent. It is also possible to emulsify and disperse in water. It is possible to prepare a water-in-water emulsion in which a photopolymerization initiator, an antioxidant, and other additives are mixed in advance, and both of them are mixed. 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 photopolymerization initiator and the antioxidant. 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 emulsifying and dispersing the photopolymerization initiator 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 in which a photopolymerization initiator is dispersed will be described more specifically.

  Using the above-mentioned organic solvent such as ethyl acetate, a solution in which the photopolymerization initiator and the antioxidant are dissolved or dispersed is prepared. Known to be capable of high-speed shearing such as a homomixer or a homogenizer when added to water containing an antioxidant, an anionic surfactant, a polymer compound having a polymerizable double bond group and a sulfo group, etc. An emulsified solution in water can be prepared by emulsifying and dispersing using the above stirring device. The organic solvent may contain other water-insoluble compounds contained in the coating solution for coating the photopolymerizable 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.

<Hydrophilic layer>
The lithographic printing plate can have 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 (washed with lime), 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 other hydrophilic binder is preferably 0 to 10% by mass, more preferably 0 to 5% by mass, based on the total amount of hydrophilic binder contained in the hydrophilic layer.

  Examples of other hydrophilic binders include gelatins other than the gelatin of the present invention, proteins such as gelatin derivatives, or cellulose derivatives, gum arabic, starch and derivatives thereof, cellulose derivatives (eg, hydroxypropylmethylcellulose), glycogen, agarose, pectin, Examples thereof include polysaccharides such as dextran and pullulan, 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.

<Inorganic filler>
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. Thereby, a lithographic printing plate substrate excellent in developability can be obtained.

<Crosslinking agent>
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 forming the hydrophilic layer, it is 0.5 to 10 days, preferably 1 to 7 days at a temperature of 30 to 60 ° C., preferably 40 to 50 ° C. It is preferable to perform a heating process. 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.

<Surfactant>
The hydrophilic layer preferably contains a surfactant. In consideration of applicability of a coating liquid containing a high concentration of inorganic filler in the hydrophilic layer, and also printability, polyoxyethylene alkyl ether acetate, polyoxyethylene alkyl ether phosphate, polyoxyethylene alkyl ether An anionic surfactant such as sulfate and polyoxyethylene alkylphenyl ether sulfate is preferably contained. As described above, when the membrane surface pH of the hydrophilic layer is 7.0 or less, the surfactant is preferably an amphoteric surfactant. Thereby, good coating stability can be obtained. Such amphoteric surfactants include coconut oil fatty acid amidopropyl betaine, lauric acid amidopropyl betaine, myristic acid amidopropyl betaine, fatty acid alkyl betaine type amphoteric surfactant / lauryldimethylaminoacetic acid, Alkylbetaine-type amphoteric surfactants such as stearyldimethylaminoacetic acid / sulfobetaine-type amphoteric surfactants such as dodecylaminomethyldimethylsulfopropylbetaine and octadecylaminomethyldimethylsulfopropylbetaine / sodium lauroylglutamate, potassium lauroylglutamate, lauroylmethyl- Amino acid type amphoteric surfactants such as β-alanine / amine oxides such as lauryldimethylamine N-oxide and oleyldimethylamine N-oxide It includes amphoteric surfactants. Of these, fatty acid alkyl betaine surfactants and alkyl betaine surfactants are preferred, and fatty acid alkyl betaine surfactants are particularly preferred. These amphoteric surfactants are sold under the product name of Amorgen from NIKKOL AM of Nikko Chemicals Co., Ltd., Softazolin of Kawaken Fine Chemical Co., Ltd., and Daiichi Kogyo Seiyaku Co., Ltd. . 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.

<Protective layer>
In the planographic printing plate, it is also preferable to further provide a protective layer on the photocurable photosensitive layer. The protective layer prevents the entry of low molecular weight compounds such as oxygen and basic substances present in the atmosphere that inhibit the image formation reaction caused by exposure in the photocurable photosensitive layer into the photocurable photosensitive layer. It has a preferable effect of further improving the exposure sensitivity. Furthermore, the effect which prevents the surface in a photocurable photosensitive layer from a damage | wound is also anticipated. Therefore, the properties desired for such a protective layer are low permeability of low molecular weight compounds such as oxygen and excellent mechanical strength, and further, transmission of light used for exposure is not substantially inhibited. It is desirable that it has excellent adhesiveness and can be easily removed in the development step after exposure.

  Such a device relating to the protective layer has been conventionally devised, and is 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, and among these, using polyvinyl alcohol as a main component gives the best results in terms of basic properties such as oxygen barrier properties and development removability. 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. There is a preferred range for the amount of dry solids applied when applying such a protective layer, and it is formed on the photocurable photosensitive layer with a dry solid content of 0.1 to 10 g per square meter in dry mass. In particular, the range of 0.2 to 2 g is preferable. The protective layer is coated and dried on the photocurable photosensitive layer using various known coating methods.

  When applying a hydrophilic layer of a planographic printing plate, a photocurable photosensitive layer provided on the upper layer, a protective layer, or the like, a coating solution of a composition composed of the above-described elements is applied on a substrate. , Produced by drying. 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.

<Development processing>
The processing liquid 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. When the 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. Can be processed with a chemical-less developer substantially free of an alkali agent described later, 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, an activator 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 (TISR1, manufactured by 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 following photocurable photosensitive layer coating solution is applied so that the solid content is 1.5 g / m ^2, and dried for 10 minutes in a 75 ° C. drier after coating. did.

<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 Antioxidant (described in Table 1)
300 parts of ion exchange water

A dispersed phase having the following composition was prepared.
<Dispersed phase>
Pentaerythritol tetraacrylate 6 parts Organoboron salt (BC-7) 2 parts Trihaloalkyl-substituted compound (T-8) 1.5 parts Sensitizing dye (VS-1) 0.05 parts 3-Acryloxypropyltrimethoxysilane 0 .08 parts antioxidant (described in Table 1)
200 parts of ethyl acetate

  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 coating solution is prepared according to the following protective layer formulation, coated on the photocurable photosensitive layer so that the solid content is 1.5 g / m ^2, and dried for 10 minutes in a 75 ° C. drier after coating. A lithographic printing plate was obtained.

<Protective layer coating solution>
Polyvinyl alcohol PVA-102 (manufactured by Kuraray Co., Ltd.) 1 part Ion-exchanged water 9 parts

<Exposure / Development>
A test chart for the lithographic printing plate obtained above using a blue-violet semiconductor laser (output 60 mW) that emits light at 405 nm as an exposure light source immediately after production and after storage at 35 ° C. for 1 month, and setting the plate surface exposure energy to 200 μJ / cm ² The image was exposed. Thereafter, the plate was immersed in ion exchange water at 18 ° C. for 15 seconds, rubbed with the cellulose sponge on the surface having the photopolymerizable photosensitive layer / protective layer, and then dried to prepare a printing plate. Using this printing press plate, printing durability and printing stain were evaluated by the following methods.

<Print durability>
The printing press uses the Heidelberg QM46 offset sheet-fed printing press, the new champion F gloss ink H manufactured by DIC Corporation is used for the printing ink, and the 3% dilution of SLM-OD50 manufactured by Mitsubishi Paper Industries Co., Ltd. is used as the dampening liquid. Printing. In the plate finishing, a gauge film was used, and the standard 200 μm was set to 300 μm (+100 μm). As an evaluation, the printing paper surface at the start and the printing paper surface at the time of printing 10,000 sheets were compared, and the 50% halftone dot attenuation rate and the fine defects in the solid portion were carefully observed with a 25x magnifier. The determination was made using the following evaluation criteria. The results are shown in Table 1.
A: Almost no change is observed in the halftone dot portion and the solid portion.
○: Slight attenuation (attenuation rate of less than 10%) is observed at the halftone dot portion.
However, no defects are observed in the solid part.
Δ: A clear attenuation (attenuation rate of 10% or more) is observed at the halftone dots.
However, no defects are observed in the solid part.
X: Halftone dot part is attenuated by 50% or more,
Or abnormalities such as defects are observed in the solid portion.

<Print stain>
The printing press uses the Heidelberg QM46 offset sheet-fed press as well as the printing durability. The printing ink is New Champion F Gloss Purple S. The dampening solution is a 0.5% dilution of Toho H manufactured by Toho Seiki Co., Ltd. Printing was performed using Note that the standard plate finishing was 200 μm. As the print stain evaluation, the print paper surface at the start and the print paper surface at the time of printing 5,000 sheets were compared, and the determination was made using the following evaluation criteria. The results are shown in Table 1.
A: No soiling is observed up to the 5,000th sheet.
○: Soil is recognized between 3,000 and less than 5,000.
Δ: Soil is recognized between 1,000 and less than 3,000.
X: Stain is observed between 1 sheet and less than 1,000 sheets.

  As can be seen from Table 1, according to the present invention, a lithographic printing plate having excellent printing durability and printing stain can be obtained even after long-term storage.

Claims (1)

  In a method for producing a lithographic printing plate having at least a photocurable photosensitive layer on a substrate, the light is obtained by applying an aqueous dispersion containing an antioxidant to both an aqueous phase and a dispersed phase containing a photopolymerization initiator. A method for producing a lithographic printing plate, comprising forming a curable photosensitive layer.