JP2014172265A - Heat-sensitive lithographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sensitive lithographic printing plate which combines good printing resistance and fouling resistance and especially suppresses occurrence of blanket stains.SOLUTION: A heat-sensitive lithographic printing plate has, on a support, an image formation layer comprising a thermoplastic resin, a heat-meltable substance and a hydrophilic binder and uses heated parts of the image formation layer as image parts and the non-heated parts of the image formation layer as non-image parts. The image formation layer contains a polymer compound which has a polymerizable double bond group and a hydrophilic group.

Description

  The present invention relates to a heat-sensitive lithographic printing plate, and more particularly to a heat-sensitive lithographic printing plate that does not require so-called debris processing such as layer removal processing in a conventional ablation method or on-machine development method.

  In recent years, various plate making methods of planographic printing plates using various digital printers have been proposed with the development of computers and peripheral devices. For example, Japanese Patent Application Laid-Open Nos. 6-138719 and 6-250424 disclose plate making using a dry electrophotographic laser printer, and Japanese Patent Application Laid-Open No. 9-58144 includes on-demand using hot-melt ink. A plate making by an ink jet printer, and a plate making by a thermal printer using a thermal transfer ink ribbon are known from JP-A 63-166590.

  The plate making method using the printer as described above is largely divided from the conventional optical mode type using a visible light laser or the like, and is not subject to safety light restrictions in handling, and thus has a great advantage in this respect. . In addition, printing plates made by these plate making methods are collectively referred to as processless printing plates because they do not require any post-exposure development processing that is normally used in conventional optical mode types.

  However, all of the above processless printing plates form a printing plate by transferring and imparting a grease-sensitive (that is, lithographic printing ink inking property) recorded image to a support surface provided with a water retention layer. Therefore, there were the following problems.

1) Since a layer for forming an image is hydrophilic, adhesion of toner, ink or the like is not sufficient. For example, a transfer toner image density is insufficient, or white spots are generated in a transfer image.
2) A problem that the transfer image is not sufficiently fixed, the printing durability is lowered, and in particular, a part of a small point character or a halftone image in a highlight portion is lost.
3) A problem that a small background is generated due to irregular transfer of a small amount of toner to the non-image area or rubbing of the thermal transfer ink ribbon.

  On the other hand, a thermosensitive lithographic printing plate or the like in which an image forming layer containing a thermoplastic resin or heat-meltable particles is provided on a support, and an oleophilic image portion is obtained by thermal printing with a thermal head or an infrared laser Has also been proposed.

  For example, Japanese Patent Application Laid-Open No. 58-199153 (Patent Document 1) or Japanese Patent Application Laid-Open No. 59-174395 (Patent Document 2) directly draws heat on an image forming layer with a thermal head or the like without using a thermal transfer ribbon or the like. A heat-sensitive lithographic printing plate from which an oleophilic image area can be obtained is described. In JP 2000-190649 A (Patent Document 3) and JP 2000-301846 A (Patent Document 4), thermal lithographic printing in which an oleophilic image portion is obtained by direct heat drawing with an infrared laser or the like. A version is also listed. Each of these is a phase change type printing plate, and the part that was originally hydrophilic causes phase change and changes to hydrophobic (lipophilic). In normal lithographic printing, both water and ink are simultaneously supplied to the oleophilic image area obtained as described above, the image area accepts colored ink, and the other non-image areas are hydrophilic. Accept water selectively and not accept ink. Printing is performed by transferring the ink received on the image portion onto a printing medium such as paper.

  However, the above-described heat-sensitive lithographic printing plate using phase conversion uses the heated portion of the image forming layer as the image portion and the non-heated portion of the image forming layer as the non-image portion. And also serves as a non-image part. For this reason, even with the same heat-sensitive lithographic printing plate, a printing plate that forms an image portion and a non-image portion by so-called debris processing such as a conventional ablation method or on-machine development method (for example, developing with water or a fountain solution) Unlike heat-sensitive lithographic printing plates, which remove the non-heated image-forming layer by processing and expose the hydrophilic layer provided between the image-forming layer and the support) Contains plastic resin and hot-melt material. That is, since the debris treatment is not performed at all, the coated film is used for printing as it is regardless of whether it is a heating part or a non-heating part. For this reason, increasing the oil sensitivity (lipophilicity) of the heated part has the contradictory tendency of sacrificing hydrophilicity on the other hand, and it is extremely difficult to improve printing durability and stain resistance in a balanced manner. Met.

  In order to improve the problems as described above, in JP-A-11-95417 (Patent Document 5), printing durability and water retention can be achieved by using a crosslinked hydrophilic resin such as polyvinyl alcohol or carboxymethyl cellulose in the image forming layer. However, the level of oleophilicity in the image area is low and the difference between lipophilicity / hydrophilicity is not sufficient. . JP-A-2000-75471 (Patent Document 6) uses a thermoplastic resin, a wax dispersion, a water repellent or the like as a hydrophobic substance, and uses gelatin, polyvinyl alcohol or the like as a hydrophilic substance. However, the difference in lipophilicity / hydrophilicity was not sufficient. Further, JP-A No. 2001-96710 (Patent Document 7) discloses a lithographic printing plate on which an image is formed by heat-meltable particles in which a hydrophilic material is physically coated and fixed. JP-A No. 2010-234724 (Patent Document 8) discloses a heat-sensitive lithographic printing plate having an image forming layer containing a specific thermoplastic resin and a water-soluble polymer compound. However, the balance between printing durability and stain resistance is further improved. On the other hand, there has been a problem such as blanket stains in which ink is deposited on non-image areas on the blanket.

JP 58-199153 A JP 59-174395 A JP 2000-190649 A Japanese Patent Laid-Open No. 2000-301846 JP-A-11-95417 JP 2000-75471 A JP 2001-96710 A JP 2010-234724 A

  An object of the present invention is to provide a heat-sensitive lithographic printing plate that has both good printing durability and stain resistance, and is particularly unlikely to cause blanket stains.

  The object of the present invention is to have an image forming layer containing a thermoplastic resin, a heat-meltable substance, and a hydrophilic binder on a support, the heated portion of the image forming layer as an image portion, and the image forming layer. A heat-sensitive lithographic printing plate using the non-heated part of the heat-sensitive part as a non-image part, wherein the image-forming layer contains a polymer compound having a polymerizable double bond group and a hydrophilic group Achieved by lithographic printing plate.

  According to the present invention, it is possible to provide a heat-sensitive lithographic printing plate that has both good printing durability and stain resistance, and is particularly resistant to blanket stains.

  The heat-sensitive lithographic printing plate of the present invention comprises an image forming layer containing a thermoplastic compound, a heat-meltable substance, a hydrophilic binder, and further containing a polymer compound having a polymerizable double bond group and a hydrophilic group. . When the image-forming layer is heated and drawn with a thermal head or an infrared laser, the thermoplastic resin buried in the hydrophilic binder melts in the heated part and elutes in a form that partially oozes out to the extreme surface of the layer. Expresses hydrophobicity. Furthermore, at the portion where heat is applied, the polymerizable double bond group of the polymer compound having a polymerizable double bond group and a hydrophilic group is thermally polymerized to form a stronger image. On the other hand, the thermoplastic resin in the part where heat is not applied remains buried in the hydrophilic binder and does not exhibit hydrophobicity, and in addition to the hydrophilicity originally possessed by the image forming layer, the polymer having the above-described polymerizable double bond group Since the compound further has a hydrophilic group, a higher hydrophilicity is maintained, thereby obtaining a heat-sensitive lithographic printing plate having excellent printing durability and stain resistance, particularly excellent in blanket stain resistance. be able to.

  The polymer compound having a polymerizable double bond group and a hydrophilic group contained in the image forming layer in the heat-sensitive lithographic printing plate of the present invention will be described. The polymer compound having a polymerizable double bond group and a hydrophilic group is a polymer compound formed by an arbitrary repeating unit, and the polymerizable double bond group is bonded to a side chain through an arbitrary linking group. In addition, it is preferably a polymer compound in which a hydrophilic group is bonded to the main chain directly or through an arbitrary linking group. Examples of the hydrophilic group include a carboxyl group and a sulfo group, and these may form a salt (for example, sodium salt, potassium salt, lithium salt, ammonium salt, etc.). Among them, a polymer compound having a vinyl group as a polymerizable double bond group is preferably used. For example, various compounds described in JP-B-49-34041, JP-A-6-105353, JP-A-2000-187322, and the like are used. These polymer compounds can be used. Examples of the polymer compound preferably used in the present invention are shown below. In the formula, the numbers indicate the mass% of each repeating unit in the copolymer total composition of 100 mass%.

  As a more preferable example of the polymer compound having a polymerizable double bond group and a hydrophilic group in the side chain as described above, a phenyl group substituted with a vinyl group is bonded to the main chain directly or via any linking group. A polymer compound is particularly preferably used. Moreover, in order to improve the hydrophilic property of a non-image part and to obtain favorable stain resistance, a polymer compound having a sulfo group as an hydrophilic group via an arbitrary linking group can be preferably used. The sulfo group may form a salt as described above. These linking groups are not particularly limited, and include any group, atom, or a combination thereof. The phenyl group and the sulfo group substituted with the vinyl group may be independently bonded to the main chain, or the phenyl group substituted with the 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 by the vinyl group contained in the image forming layer of the present invention is bonded to the main chain directly or through an arbitrary linking group is represented by the following general formula (1). Those having a group in the side chain are preferred.

In the formula, R ₁ , R ₂ and R ₃ may be the same or different, and each is 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, It may be substituted with a reelsulfanyl group, an alkylamino group, an arylamino group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an alkylsulfonyl group, an arylsulfonyl group, or the like. Among these groups, those in which R ₁ and R ₂ are hydrogen atoms and R ₃ 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 ₄ is a 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 and a hydrophilic group contained in the image forming layer of the present invention includes the above repeating unit having a polymerizable double bond group, a carboxyl group, a sulfo group, and a quaternary ammonium group. The polymer may be composed only of repeating units having the same, or may be a polymer into which other repeating units are further introduced as long as the effects of the present invention are not impaired. Further, it may be a copolymer with other monomers, and such monomers may be used alone or two or more of them may be used.

  In addition, the polymer compound having a polymerizable double bond group and a hydrophilic group contained in the image forming layer of the present invention can introduce an arbitrary substituent at the end of the polymer main chain by using a chain transfer agent. Can do. 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 and a hydrophilic group contained in the image forming layer 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%.

  In the present invention, the weight average molecular weight of the polymer compound having a polymerizable double bond group and a hydrophilic group contained in the image forming layer is preferably in the range of 1,000 to 1,000,000, and more preferably in the range of 10,000 to 500,000. It is particularly preferable that In the present invention, the polymer compound having a polymerizable double bond group and a hydrophilic group may be used alone or in a combination of two or more.

  In the present invention, the preferable amount of the polymer compound having a polymerizable double bond group and a hydrophilic group contained in the image forming layer is 0.01 to 20% by mass with respect to the total solid content of the image forming layer. Preferably, 0.1-10 mass% is more preferable.

  In the present invention, the thermoplastic resin contained in the image forming layer is a solid water-insoluble organic polymer compound that is made of a chain polymer and exhibits plasticity upon heating, and is a water-based coating liquid as a coating liquid for the image forming layer. In the case of using an aqueous dispersion, an aqueous dispersion (emulsion, latex) is preferable. Typical examples are synthetic rubber latex including modified products such as styrene butadiene copolymer, acrylonitrile butadiene copolymer, methyl methacrylate butadiene copolymer, styrene acrylonitrile butadiene copolymer, styrene methyl methacrylate butadiene copolymer. Styrene maleic anhydride copolymer, methyl vinyl ether maleic anhydride copolymer, polyacrylic acid copolymer, polystyrene, styrene / acrylic acid ester copolymer, polyacrylic acid ester, polymethacrylic acid ester, acrylic acid ester An aqueous dispersion such as a / methacrylic acid ester copolymer and a low melting point polyamide resin can also be used. These thermoplastic resins can be used alone or in combination of two or more. Synthetic rubber latex is preferably used as the thermoplastic resin because of its affinity with the printing ink vehicle (binder component). Such synthetic rubber latex is preferably of a type that self-crosslinks by heat from the viewpoint of printing durability. The self-crosslinking type means that it is possible to form a three-dimensional network by heat without the presence of a crosslinking agent. When producing such a synthetic rubber latex, a carboxyl group, a hydroxyl group, or a methylol is used as a copolymerization component. It can be obtained by the presence of a reactive functional group such as an amide group, an epoxy group, a carbonyl group, or an amino group. Moreover, as a reactive functional group, a carboxyl group, a hydroxyl group, and an amino group are preferable, and especially the synthetic rubber latex which has a carboxyl group as a reactive functional group is preferable. As a result, the image area is self-crosslinked to obtain good printing durability, and at the same time, the non-image area that is not heated is preferable because excellent water retention is obtained. A particularly preferred synthetic rubber latex is a carboxy-modified styrene butadiene copolymer. A preferable blending amount of the thermoplastic resin is preferably 5 to 50% by mass, and more preferably 20 to 40% by mass with respect to the total solid content of the image forming layer.

  Moreover, in order to make it easy to express the effect of melting and fusing by heat, it is preferable to use a thermoplastic resin having a glass transition temperature of 50 to 150 ° C, more preferably 55 to 120 ° C. If the glass transition temperature is less than 50 ° C., a phase change occurs in a liquid state during the production process, and oleophilicity appears in the non-image area, which may cause printing stains. When the temperature exceeds 150 ° C., the polymer is hardly melted by heat, and it may be difficult to form a strong image with a relatively small output laser or a small thermal printer.

  Examples of the heat-meltable substance contained in the image forming layer in the present invention include, for example, waxes such as carnauba wax, microcrystalline wax, paraffin wax, polyethylene wax, lauric acid, stearic acid, oleic acid, palmitic acid, behenic acid, In addition to metal salts of higher fatty acids such as montanic acid, esters and amides, naphthol derivatives such as 2-benzyloxynaphthalene, biphenyl derivatives such as p-benzylbiphenyl, 4-allyloxybiphenyl, m-terphenyl, Polyether compounds such as 2-bis (3-methylphenoxy) ethane, 2,2'-bis (4-methoxyphenoxy) diethyl ether, bis (4-methoxyphenyl) ether, diphenyl carbonate, dibenzyl oxalate, dioxalate (P-Chlorobenzyl) S Carbonate or oxalate diester derivatives such as Le, and the like. These can be used alone or in admixture of two or more, and a hot-melt material having a melting point of 50 to 150 ° C. is preferably used. If the melting point is less than 50 ° C., it will melt during the production process, which may cause soiling of the printed matter. On the other hand, when it exceeds 150 ° C., it is difficult to melt by applying heat from a thermal head or the like, and the lipophilicity may be poor. The amount of the heat-meltable substance used in the image forming layer is preferably 1 to 50% by mass, more preferably 5 to 30% by mass, based on the total solid content of the image forming layer.

  Of the above hot-melt materials, compounds other than waxes, fatty acids and esters thereof, and amides are preferably used after being subjected to a fine dispersion treatment in order to increase reactivity by heat. As a fine dispersion treatment method, a bead mill such as a roll mill, a colloid mill, a ball mill, an attritor or a sand mill, which is a wet dispersion method generally used at the time of producing a paint, can be used. In the bead mill, ceramic beads such as zirconia, titania and alumina, metal beads such as chrome and steel, glass beads and the like can be used. The dispersed particle diameter is preferably from 0.1 to 1.2 μm in median diameter, particularly preferably from 0.3 to 0.8 μm. The median diameter is the particle diameter (cumulative average diameter) at which the cumulative curve becomes 50% when the total curve of one population of particles is 100%, and the particle size distribution is evaluated. As one of the parameters to be measured, it can be measured using a laser diffraction / scattering particle size distribution measuring apparatus LA920 (manufactured by Horiba, Ltd.) or the like.

  The image forming layer of the present invention contains a hydrophilic binder. Examples of the hydrophilic binder include cellulose derivatives such as hydroxyethyl cellulose and carboxymethyl cellulose, starch and derivatives thereof, polysaccharides such as glycogen, agarose, pectin, dextran, and pullulan, gelatin, casein, sodium alginate, polyvinyl alcohol, polyvinyl pyrrolidone, Examples thereof include styrene / maleic acid copolymer salts and styrene / acrylic acid copolymer salts. These hydrophilic binders can be used alone or in combination of two or more, but gelatin can be particularly preferably used. The amount of the hydrophilic binder used in the image forming layer of the present invention is preferably 5 to 55% by mass based on the total solid content of the image forming layer.

  The image forming layer of the heat-sensitive lithographic printing plate of the present invention preferably contains a crosslinking agent in order to improve the film strength, adhesive strength, etc. of the image forming 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. In addition, the necessary water resistance and mechanical strength can be obtained, and the amount of the crosslinking agent is 1 with respect to the solid content of the hydrophilic binder contained in the image-forming layer in order to avoid fluctuations in characteristics over time when stored. -30 mass% is preferable, and as a more preferable usage-amount, it is the range of 2-20 mass%.

  In the heat-sensitive lithographic printing plate of the present invention, a developer or a color former (electron donating property) such as a phenol derivative or an aromatic carboxylic acid derivative used for general heat-sensitive recording paper and pressure-sensitive recording paper for ensuring visibility. Dye precursor).

  Specific examples of the developer include 4-cumylphenol, hydroquinone monobenzyl ether, 4,4'-isopropylidenediphenol, 1,1-bis (4-hydroxyphenyl) cyclohexane, 4,4'- Dihydroxydiphenyl-2,2-butane, 4,4′-dihydroxydiphenylmethane, 2,2-bis (4-hydroxyphenyl) -4-methylpentane, 2,2-bis (4-hydroxyphenyl) heptane, bis (4 -Hydroxyphenylthioethoxy) methane, 1,5-di (4-hydroxyphenylthio) -3-oxapentane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, 1,4-bis [α -Methyl-α- (4'-hydroxyphenyl) ethyl] benzene, 1,3-bis [α-methyl-α- (4'-hydro Cyphenyl) ethyl] benzene, 4,4'-dihydroxydiphenyl sulfide, di (4-hydroxy-3-methylphenyl) sulfine, 4-hydroxy-4'-methyldiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone 2,4'-dihydroxydiphenylsulfone, 4,4'-dihydroxydiphenylsulfone, bis (3-allyl-4-hydroxyphenyl) sulfone, 4-hydroxyphenyl-4'-benzyloxyphenylsulfone, 4-hydroxy-3 ', 4'-tetramethylenebiphenylsulfone, 3,4-dihydroxyphenyl-p-tolylsulfone, 4,4'-dihydroxybenzophenone, benzyl 4-hydroxybenzoate, N, N'-di-m-chlorophenylthiourea, N- (phenoxy Phenolic compounds such as (ciethyl) -4-hydroxyphenylsulfonamide, zinc 4- [3- (p-tolylsulfonyl) propyloxy] salicylate, 4- [2- (p-methoxyphenoxy) ethyloxy] zinc salicylate, 5- [P- (2-p-methoxyphenoxyethoxy) cumyl] Zinc salts of aromatic carboxylic acids such as zinc salicylate and zinc p-chlorobenzoate, and organic acidic substances such as antipyrine complexes of zinc thiocyanate The

  Specific examples of color formers (electron-donating dye precursors) include (1) 3,3′-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (1) as a triarylmethane compound ( Crystal violet lactone), 3,3′-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,2-dimethylindol-3-yl) phthalide, 3- (P-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3,3- Bis (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethyl Ruaminophthalide, 3,3-bis (9-ethylcarbazol-3-yl) -5-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -5-dimethylaminophthalide, 3- p-dimethylaminophenyl-3- (1-methylpyrrol-2-yl) -6-dimethylaminophthalide and the like: (2) 4,4'-bis-dimethylaminobenzhydrin benzyl ether, N -Halophenyl leucooramine, N-2,4,5-trichlorophenyl leucooramine, etc .: (3) As xanthene compounds, rhodamine B-anilinolactam, rhodamine Bp-nitroanilinolactam, rhodamine B- p-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluorane, -Diethylamino-7-octylaminofluorane, 3-diethylamino-7-phenylfluorane, 3-diethylamino-7- (3,4-dichloroanilino) fluorane, 3-diethylamino-7- (2-chloroanilino) fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-ethyl- Tolylamino-6-methyl-7-anilinofluorane, 3-ethyl-tolylamino-6-methyl-7-phenethylfluorane, 3-diethylamino-7- (4-nitroanilino) fluorane, etc .: (4) thiazine compounds As benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue Etc .: (5) Examples of spiro compounds include 3-methyl-spiro-dinaphthopyrans, 3-ethyl-spiro-dinaphthopyrans, 3,3′-dichloro-spiro-dinaphthopyrans, 3-benzyl-spiro-dinaphthopyrans, 3-methylnaphtho- ( 3-methoxy-benzo) -spiropyran, 3-propyl-spiro-dibenzopyran and the like. These may be used alone or in combination of two or more.

  Further, the heat-sensitive lithographic printing plate of the present invention may contain a photothermal conversion substance. By using a photothermal conversion agent, not only a thermal head but also drawing with active light such as an infrared laser becomes possible. As an example of the photothermal conversion substance, a material that efficiently absorbs light and converts it into heat is preferable. Depending on the light source used, for example, when a semiconductor laser emitting near infrared light is used as the light source, Near-infrared light absorbers having an absorption band in the infrared are preferred, such as carbon black, cyanine dyes, polymethine dyes, azurenium dyes, squalium dyes, thiopyrylium dyes, naphthoquinone dyes, anthraquinone dyes Examples include organic compounds, metal compounds such as phthalocyanine-based, azo-based, and thioamide-based organometallic complexes, iron powder, graphite powder, iron oxide powder, lead oxide, silver oxide, chromium oxide, iron sulfide, and chromium sulfide. .

  The image forming layer of the heat-sensitive lithographic printing plate of the present invention can contain inorganic pigments such as silicon dioxide, titanium dioxide, aluminum hydroxide, calcium carbonate, zinc oxide, and barium sulfate. good. In particular, better printability may be obtained by using zinc oxide or barium sulfate, and the total amount of inorganic pigment used should be 0.1 to 5% by mass relative to the total solid content of the image forming layer. Is preferred.

  In addition, preservatives, surfactants, antifoaming agents, leveling agents, pH adjusting agents, other coating aids, and the like can be added to the image forming layer of the present invention as necessary.

  The image forming layer of the present invention can be divided not only into a single layer but also into a multilayer structure. In that case, the ratio of the mass of the thermoplastic resin to the mass of the water-soluble polymer compound in the image forming layer close to the support is preferably higher than the ratio of the outermost image forming layer. The polymer compound having a polymerizable double bond group and a hydrophilic group can be added either alone or both of the image forming layer close to the support and the outermost image forming layer. Is more preferable.

The image forming layer of the heat-sensitive lithographic printing plate of the present invention has an overall dry solid content of ² to 12 g / m ² from the viewpoints of printing durability of image areas, water resistance of non-image areas and mechanical strength. It is preferable that it exists in. As a coating method in the case where the image forming layer is a multilayer, there are a method of applying and stacking sequentially, a method of simultaneous multi-layer coating by a slide hopper method, etc., but either method may be used.

  In the heat-sensitive lithographic printing plate of the present invention, an undercoat layer is appropriately provided between the support and the image forming layer depending on the purpose such as improving the adhesion between the image forming layer and the support or improving the antistatic property. It can also be provided. For example, by providing an undercoat layer composed of titanium dioxide, a binder resin, and a cross-linking agent between the support and the image forming layer, stains associated with plate pressure changes during printing can be achieved without degrading the platemaking property and printability. It becomes possible to improve.

  As the support used in the heat-sensitive lithographic printing plate of the present invention, a water-resistant support such as a plastic film, resin-coated paper, and water-resistant paper can be preferably used. Specifically, plastic films such as polyolefins such as polyethylene and polypropylene, polyethersulfone, polyester, poly (meth) acrylate, polycarbonate, polyamide, and polyvinyl chloride, and resin-coated paper with these plastics laminated or coated on the surface, melamine Paper that has been water-resistant with a wet paper strength agent such as formaldehyde resin, urea formaldehyde resin, or epoxidized polyamide resin can be suitably used.

  Next, a plate making method using the above-described heat-sensitive lithographic printing plate of the present invention will be described. Since the heat-sensitive lithographic printing plate of the present invention has a heat-sensitive image forming layer, an image can be obtained by irradiating light containing infrared light of, for example, 760 nm to 1200 nm by blending a photothermal conversion material in the image forming layer. The image portion can be formed by a solid-state laser and a semiconductor laser emitting infrared rays. In particular, laser exposure enables desired image-like recording directly from digital information of a computer. It is also possible to draw an image forming layer directly by heat with a thermal head or a heat block to form an image portion. However, the thermal head enables recording of a desired image directly from digital information of a computer. .

When a thermal head is used, a line printer using a thick film or thin film line head, a serial printer using a thin film serial head, or the like can be used. The recording energy density is preferably 10 to 100 mJ / mm ² , and the head image recording density is preferably 300 dpi or more in order to obtain a relatively high quality output image.

  EXAMPLES Hereinafter, although this invention is demonstrated using an Example, this invention is not limited by this description. In addition, unless otherwise indicated,% and a part in the following description show mass ratio.

Example 1
On one side of a polyethylene-coated paper having a thickness of about 180 μm that has been laminated on both sides, a coating solution for the following image forming layer A and image forming layer B is applied to the image forming layer A in a moisture application amount by a slide hopper coating method. the 30 g / ^{m 2,} so that the image forming layer B to 10 g / ^{m 2,} the image forming layer a from the support side, a two-layer simultaneous coating so that the image forming layer B was performed.

<Image forming layer A coating liquid-1>
Gelatin 0.7 part Polymer compound having polymerizable double bond group and hydrophilic group AP-1 0.1 part (weight average molecular weight 10,000)
Thermoplastic resin: 1.35 parts as a solid content (Lack Star 7132C manufactured by DIC Corporation, carboxylated SBR latex, Tg 60 ° C.)
Surfactant (0.5% solution) 0.4 parts Divinylsulfone hardener (5% solution) 2.0 parts Color former mixed slurry 7.0 parts The total amount was 30 parts with water.

<Image forming layer B coating solution-1>
Gelatin 0.3 part Thermoplastic resin: 0.27 part as solid content (DIC Co., Ltd. Rack Star 7132C, carboxylated SBR latex, Tg 60 ° C.)
Surfactant (0.5% solution) 0.2 part Hot melt material: 0.03 part as solid content (Montanate ester wax emulsion)
Divinylsulfone hardener (5% solution) 0.8 part Color former mixed slurry 0.3 part The total amount was 10 parts with water.

As the color former mixed slurry used for the image forming layer A coating liquid and the image forming layer B coating liquid, those prepared in advance by the following preparation method were used.
<Preparation of color former mixed slurry>
Material a (hot meltable substance): 1,2-bis (3-methylphenoxy) ethane (manufactured by Sanko Co., Ltd .: KS-232)
Material b: 4-hydroxy-4'-isopropoxy diphenyl sulfone (Nippon Soda Co., Ltd. product: D-8)
Material c: 3-dibutylamino-6-methyl-7-anilinofluorane (manufactured by Yamamoto Kasei Co., Ltd .: ODB2)

  The above materials a, b, and c are individually finely dispersed in a small dyno mill (bead mill) to 0.7 μm using zirconia beads to prepare dispersions each having a solid content concentration of about 30%. Dispersion a, Dispersion b, and Dispersion c. A color former mixed slurry was prepared by mixing 3 parts of dispersions a and b with 1 part of dispersion c at room temperature.

  After two layers were simultaneously applied at the moisture application amount, the coating film was immediately gelled with cold air at 3 ° C., and then dried with hot air at 30 ° C. After drying, a thermosensitive lithographic printing plate of Example 1 was obtained by heating for 7 days using a constant temperature and humidity chamber adjusted to a temperature of 40 ° C./humidity of 40%.

(Example 2)
Implementation was performed except that the polymer compound AP-1 having a polymerizable double bond group and a hydrophilic group used in the image forming layer A coating liquid-1 of Example 1 was changed to SP-2 (weight average molecular weight 400,000). In the same manner as in Example 1, a thermosensitive lithographic printing plate of Example 2 was obtained.

(Example 3)
Except for changing the image forming layer A coating liquid-1 and the image forming layer B coating liquid-1 of Example 1 to the image forming layer A coating liquid-2 and the image forming layer B coating liquid-2 shown below. Was the same as in Example 1 to obtain a heat-sensitive lithographic printing plate of Example 3.

<Image forming layer A coating liquid-2>
Gelatin 0.7 parts Thermoplastic resin: 1.35 parts as solid content (DIC Co., Ltd. Rack Star 7132C, carboxylated SBR latex, Tg 60 ° C.)
Surfactant (0.5% solution) 0.4 parts Divinylsulfone hardener (5% solution) 2.0 parts Color former mixed slurry 7.0 parts The total amount was 30 parts with water.

<Image forming layer B coating liquid-2>
Gelatin 0.3 part Polymer compound having a polymerizable double bond group and a hydrophilic group SP-2 0.1 part (weight average molecular weight 400,000)
Thermoplastic resin: 0.27 part as solid content (DIC Co., Ltd., Rackstar 7132C, carboxylated SBR latex, Tg 60 ° C.)
Surfactant (0.5% solution) 0.2 part Hot melt material: 0.03 part as solid content (Montanate ester wax emulsion)
Divinylsulfone hardener (5% solution) 0.8 part Color former mixed slurry 0.3 part The total amount was 10 parts with water.

Example 4
The thermal lithographic printing plate of Example 4 was prepared in the same manner as in Example 2 except that the coating liquid for image forming layer B in Example 2 was changed to Image forming layer B coating liquid-2 in Example 3. Obtained.

(Example 5)
Except that the polymer compound having a polymerizable double bond group and a hydrophilic group used in the coating liquid of the image forming layer A coating liquid 1 of Example 1 was changed to CP-3 (weight average molecular weight 400,000). In the same manner as in Example 1, a heat-sensitive lithographic printing plate of Example 5 was obtained.

(Comparative Example 1)
Heat-sensitive lithographic plate of Comparative Example 1 in the same manner as in Example 1 except that the polymer compound having a polymerizable double bond group and a hydrophilic group used in the image-forming layer A coating liquid-1 of Example 1 was omitted. A printed version was obtained.

(Comparative Example 2)
Comparative Example as in Example 1 except that the polymer compound having a polymerizable double bond group and a hydrophilic group used in the image forming layer A coating liquid-1 of Example 1 was changed to the following polymer compound. No. 2 thermal lithographic printing plate was obtained.

The thermal lithographic printing plate produced as described above was subjected to image output (recording energy density 70 to 100 mJ / mm ² ) using a thermal digital printer for CTP (Thermal Digiplater TDP-459: 1200 dpi / 120 lpi manufactured by Mitsubishi Paper Industries). , Electric capacity 330W), and a printing plate was prepared. Using this printing plate, printability was evaluated by the following method.

<Evaluation of printing durability>
Offset sheet-fed press RYOBI3200CCD for printing machine, New Champion F gloss ink H manufactured by DIC Corporation for ink, 10% diluted solution of SLM-OD manufactured by Mitsubishi Paper Co., Ltd. Using a 25% diluted solution of SLM-OD30 manufactured by Mitsubishi Paper Industries Co., Ltd., printing was performed with the plate mounted with a 50 μm thick PET film sandwiched between the plate and the plate cylinder. In the evaluation of printing durability, the number of prints that could not be printed due to a missing image was determined using the following evaluation criteria. The results are shown in Table 1.
<Evaluation criteria for printing durability>
◎: 4,000 or more ○: 3,000 or more and less than 4,000 △: 2,000 or more and less than 3,000 ×: less than 2,000

<Stain resistance evaluation and blanket stain resistance evaluation>
The above-mentioned resistance was changed except that the ink was changed to New Champion F Gross Purple S manufactured by DIC Corporation, and the liquid used for the dampening solution and the etching process was changed to a 0.5% diluted solution of SLM-OD manufactured by Mitsubishi Paper Industries Co., Ltd. 3,000 sheets were printed in the same manner as the printability evaluation. As the stain resistance evaluation, the number of sheets in which good prints could not be obtained due to background stains or meshing was determined using the following evaluation criteria. As blanket stain resistance evaluation, the blanket state after the start of printing and after the completion of 3,000 sheets was compared and judged using the following criteria. The results are shown in Table 1.
<Stain resistance evaluation criteria>
◎: 3,000 sheets good ○: 2,000 sheets or more and less than 3,000 sheets △: 1,000 sheets or more and less than 2,000 sheets ×: Less than 1,000 <Blanket stain resistance evaluation criteria>
○: The blanket ground color is sufficiently discriminable to the extent that it is the same as or slightly dirty from the start of printing.
Δ: Dirty from the start of printing, but the blanket ground color can be distinguished.
X: It is dirty from the start of printing, and the ground color of the blanket cannot be determined.

  As can be seen from the results shown in Table 1, it can be seen that the present invention provides a heat-sensitive lithographic printing plate that has good printing durability and stain resistance in a well-balanced manner and is particularly resistant to blanket stains.

Claims (1)

  An image forming layer containing a thermoplastic resin, a heat-meltable substance, and a hydrophilic binder is provided on a support, the heated portion of the image forming layer is an image portion, and the non-heated portion of the image forming layer is a non-image. A heat-sensitive lithographic printing plate used as a part, wherein the image-forming layer contains a polymer compound having a polymerizable double bond group and a hydrophilic group.