JP5161910B2 - Thermal lithographic printing plate - Google Patents

Description

  The present invention relates to a heat-sensitive printing plate using an image forming layer that undergoes phase conversion by heat, and relates 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 lithographic printing plates using various digital printers have been proposed due to 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 light 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 deposition property) recorded image to the 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 a part of a small point character or a low dot image 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. In order to accept water selectively, it does 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 an image portion and the non-heated portion as a non-image portion. Therefore, the image forming layer itself has an image portion and a non-image portion. Also serves as. For this reason, even in a heat-sensitive lithographic printing plate that uses the same phase conversion, a printing plate (water or fountain solution) 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. Unlike a heat-sensitive lithographic printing plate that removes the non-heated image-forming layer by developing the film and exposes the hydrophilic layer provided between the image-forming layer and the support, However, it contains a thermoplastic resin and a heat-meltable substance. 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 one hand, and it is extremely difficult to improve the printing durability and stain resistance in a balanced manner. there were.

  The use of an inorganic pigment in the heat-sensitive layer of a heat-sensitive lithographic printing plate is conventionally known. For example, in addition to the above-mentioned Patent Documents 1 to 3, Japanese Patent Publication No. 43-5845 (Patent Document 5) Japanese Patent Publication No. 47-14282. (Patent Document 6), JP-A-63-116891 (Patent Document 7), JP-A-01-295894 (Patent Document 8), and the like. In these prior arts, inorganic pigments are used for the purpose of increasing the hydrophilicity of the non-image area and improving the stain resistance, or improving the film strength of the coating film. However, the methods described in these documents did not provide a heat-sensitive lithographic printing plate that can satisfy printing durability and stain resistance at the same time.

  On the other hand, in Japanese Patent Laid-Open No. 05-200966 (Patent Document 9), a first heat-sensitive layer and a second heat-sensitive layer are provided on a support in this order, the second heat-sensitive layer contains an inorganic pigment, and the first heat-sensitive layer. Describes a thermosensitive lithographic printing plate which does not contain inorganic pigments. However, one of the first heat-sensitive layer and the second heat-sensitive layer is an ink-philic resin layer, and either one is an ink-repellent resin layer, and the heat-sensitive lithographic printing plate is thermally printed on the second heat-sensitive layer. It is a printing plate that forms an image portion and a non-image portion by so-called debris processing in which a portion is peeled and removed. Also, on-press development type heat-sensitive lithographic printing plates for removing non-image parts on a printing press, for example, JP-A-2005-28774 (Patent Document 10) and JP-A-2005-309417 (Patent Document 11). In the image forming layer, inorganic pigments are exemplified as fillers. However, inorganic fillers are mainly used for the purpose of contributing to developability.

JP 58-199153 A JP 59-174395 A JP 2000-190649 A Japanese Patent Laid-Open No. 2000-301846 Japanese Patent Publication No. 43-5845 Japanese Examined Patent Publication No. 47-14282 JP-A-63-116891 Japanese Patent Laid-Open No. 01-295894 Japanese Patent Laid-Open No. 05-200966 JP 2005-28774 A JP 2005-309417 A

  An object of the present invention is to provide a heat-sensitive lithographic printing plate which does not require any so-called debris processing in an ablation method, an on-press development method, etc., and has improved printing durability and stain resistance in a balanced manner.

The above problems have been solved by the following means.
(1) An image forming layer (B) having at least two image forming layers containing at least a thermoplastic resin, a heat-meltable substance, and a water-soluble polymer compound on one side of the support, and being far from the support Contains a zinc oxide or barium sulfate, a heat-sensitive lithographic printing plate.
(2) The heat-sensitive lithographic printing plate as described in (1) above, wherein the content of the zinc oxide or barium sulfate is 8 to 26% by mass with respect to the amount of the thermoplastic resin contained in the image forming layer (B).

  According to the present invention, there is no need for so-called debris processing in an ablation method, an on-press development method, or the like, and it is possible to provide a heat-sensitive lithographic printing plate having improved printing durability and stain resistance in a balanced manner.

  The heat-sensitive lithographic printing plate of the present invention has an image forming layer containing a thermoplastic resin, a heat-meltable substance, and a water-soluble polymer compound. When the image forming layer is heated and drawn with a thermal head or an infrared laser, the thermoplastic resin or heat-melting substance that is buried in the water-soluble polymer compound melts at the part where heat is applied, and part of the layer melts on the extreme surface of the layer. In this case, elution is converted to develop hydrophobicity, and ink can be received during printing. The thermoplastic resin and the heat-meltable material at the site where heat is not applied remain embedded in the water-soluble polymer compound, and the hydrophilicity inherent in the image forming layer is maintained.

  In the present invention, two image forming layers containing a thermoplastic resin, a heat-meltable substance, and a water-soluble polymer compound are provided adjacent to each other. The image forming layer closer to one support is the image forming layer (A), and the other is the image forming layer (B) far from the support. The heat-sensitive lithographic printing plate of the present invention comprises zinc oxide or barium sulfate in the image forming layer (B) on the side far from the support. The present invention is described in detail below.

<Zinc oxide>
Zinc oxide is roughly classified into a dry method and a wet method according to its production method. There are a French method and an American method in the dry method, and a German method is well known as the wet method. The French method is a method in which high-purity metallic zinc is heated, and the generated zinc vapor is burned in an oxidizing atmosphere to produce zinc oxide. On the other hand, the American method is a reducing agent such as coke on zinc ore (franknite). Is added and roasted, and the generated zinc vapor is oxidized by air and generated. Further, the wet method includes a method of thermally decomposing a zinc salt such as zinc carbonate, a method of directly depositing zinc oxide in a solution while neutralizing an alkaline solution of the zinc salt with an acid, an acidic solution of the zinc salt There is a method of direct precipitation in the liquid while neutralizing the solution. Generally, it is produced by reacting an acidic solution of zinc salt (zinc sulfate solution or zinc chloride solution) with an alkali such as soda ash, washing with water, filtering and drying, firing and pulverizing. Zinc oxide produced by these methods is commercially available from, for example, Shodo Chemical Co., Ltd., Sakai Chemical Co., Ltd., Hakusui Tech Co., Ltd., Honjo Chemical Co., Ltd., Toho Zinc Co., Ltd. Any of these can be used in the present invention.

<Barium sulfate>
Barium sulfate is barium sulfate obtained by pulverizing barite and removing iron, washing with water, and sedimentation produced by adding a sulfate aqueous solution to a barium chlorine solution and chemically precipitating. And barium sulfate. Examples of the barium sulfate produced by these methods include those commercially available from Sakai Chemical Co., Ltd., Takehara Chemical Industry Co., Ltd., Hakusuikku Co., Ltd., etc. Can be used. Further, barium sulfate may be subjected to organic polymer treatment as a post-treatment after particle formation, and may be a hydroxide or oxide of any metal element such as Al, Si and Zr, Mg, Ca Surface treatment may be performed with a phosphate of any one of metal elements such as Sr and Ba.

  In the present invention, the image forming layer (B) on the side farther from the support is preferably the outermost layer (outermost layer), whereby both printing durability and stain resistance can be achieved at a higher level. In this case, if the average particle diameter of zinc oxide or barium sulfate is too large, the contact area may decrease when printing is performed by directly contacting the image forming layer (B) with a thermal head. The reduction of the contact area may lead to a decrease in thermal efficiency and a decrease in printing durability. On the other hand, if the average particle size of zinc oxide or barium sulfate is too small, the effect on the printing durability and stain resistance will be reduced, but the contact area will be excessive depending on the particle size of zinc oxide or barium sulfate. In such a case, the sticking resistance may be lowered due to a decrease in peelability or the like. Therefore, the average particle diameter of zinc oxide or barium sulfate used in the present invention is preferably in the range of 0.1 to 1.0 μm, more preferably 0.2 to 0.5 μm.

  The shape of zinc oxide or barium sulfate used in the present invention is preferably an irregular shape, and may be any of a plate shape, a columnar shape, and a granular shape.

  Further, there is a preferable range for the content of zinc oxide or barium sulfate contained in the image forming layer (B), and it is 8 to 26% by mass with respect to the amount of the thermoplastic resin contained in the image forming layer (B). Is preferred. Thereby, printing durability and stain resistance can be made compatible at a higher level. Further, it is desirable that the total amount of the thermoplastic resin contained in the image forming layer (A) and the image forming layer (B) is used so as not to exceed a range of 5% by mass or less.

<Water-soluble polymer compound>
Examples of the water-soluble polymer compound contained in the image forming layer (A) and the image forming layer (B) of the present invention include proteins such as gelatin and gelatin derivatives or cellulose derivatives, starch, gum arabic, dextran, pullulan and the like. Examples include natural compounds such as polysaccharides and synthetic polymer compounds such as polyvinyl alcohol, modified polyvinyl alcohol, polyvinyl pyrrolidone, styrene / maleic acid copolymer salts, styrene / acrylic acid copolymer salts, and acrylamide polymers. These water-soluble polymer compounds may be used alone or in combination of two or more. In the image forming layer (A), it is preferable to use gelatin and polyvinyl alcohol in combination, while the image forming layer (B It is particularly preferred to use gelatin and a polysaccharide in combination.

  Moreover, when using water-soluble polymer together as mentioned above, there exists an optimal use ratio for each. As an optimal use ratio, in the image forming layer (A), it is preferable to use gelatin and polyvinyl alcohol in a range of 1 to 10% by mass of polyvinyl alcohol with respect to 100% by mass of gelatin. On the other hand, in the image forming layer (B), the polysaccharide is preferably used in the range of 2 to 20% by mass with respect to 100% by mass of gelatin. The total amount of the water-soluble polymer compound used in the image forming layer (A) and the image forming layer (B) is preferably 0.5 to 50% by mass with respect to the total solid content of the image forming layer.

<Thermoplastic resin>
The thermoplastic resin contained in the image-forming layer (A) and the image-forming layer (B) of the present invention is a solid organic polymer compound composed of a chain polymer and exhibiting plasticity upon heating, and the organic polymer Refers to an aqueous dispersion of a compound. Representative 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 Aqueous dispersions such as acid ester / acrylic acid ester copolymers and low melting point polyamide resins can also be used. These thermoplastic resins can be used alone or in combination of two or more. In view of the affinity with the vehicle (binder component) of the printing ink, the thermoplastic resin is preferably a synthetic rubber latex, and particularly preferably a styrene butadiene copolymer and a modified product thereof. A preferable blending amount of the thermoplastic resin is preferably 5 to 50% by mass with respect to the solid content of all the image forming layers.

  In order to easily develop 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 the liquid state during the production process, and hydrophobicity is developed even 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.

  The content ratio of the thermoplastic resin to the water-soluble polymer compound (mass of thermoplastic resin / total mass of the water-soluble polymer compound) in the image forming layer (A) of the present invention is 0.1 to 50. More preferably, it is 1-20. The content ratio of the thermoplastic resin to the water-soluble polymer compound (the mass of the thermoplastic resin / the total mass of the water-soluble polymer compound) in the image forming layer (B) is preferably 0.01 to 10, and Preferably it is 0.1-3. The content ratio of the thermoplastic resin to the water-soluble polymer compound in the image forming layer (A) is preferably higher than the content ratio in the image forming layer (B). Furthermore, it is more preferable that the difference between the content ratio in the image forming layer (A) and the content ratio in the image forming layer (B) is 0.5 or more. By adjusting to such a range, a heat-sensitive lithographic printing plate excellent in printing durability and stain resistance can be obtained.

<Hot-melting substance>
The heat-meltable substance contained in the image forming layer (A) and the image forming layer (B) of the present invention is at least one selected from compounds represented by the following general formulas (1) to (4). , And waxes such as carnauba wax, microcrystalline wax, paraffin wax and polyethylene wax, fatty acids such as lauric acid, stearic acid, oleic acid, palmitic acid, behenic acid and montanic acid, and waxes such as esters and amides thereof Is preferably used depending on the purpose. Of these, organic compounds having a melting point of 50 to 150 ° C. are 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 the temperature exceeds 150 ° C., it is difficult to melt by application of heat from a thermal head or the like, and the occurrence of image toughness or the expression of lipophilicity may be poor. A preferable blending amount of the heat-meltable substance in the image forming layer is preferably 1 to 50% by mass, and more preferably 10 to 30% by mass with respect to the total solid content of the image forming layer.

  The compound represented by the general formula (1) will be described below.

In the above formula, X ₁ represents —O— or —CO—O—, and R _{1 to} R ₆ each represents a hydrogen atom, an alkyl group, or an aryl group. n represents an integer of 1 to 10, and the substituents R _{1 to} R ₃ and R _{4 to} R ₆ may be bonded to each other to form an aromatic ring.

Among the compounds represented by the general formula (1), a compound in which X ₁ is —O— is preferable, and R ₁ and R ₆ are particularly a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R _{2 to} R _5. A compound in which is a hydrogen atom and n is an integer of 1 to 4 is particularly preferably used.

Examples of the compound represented by the general formula (1) include the following compounds, but the present invention is not limited thereto.
(1) 1- (1-naphthoxy) -2-phenoxyethane (2) 1- (2-naphthoxy) -4-phenoxybutane (3) 1- (2-isopropylphenoxy) -2- (2-naphthoxy) ethane (4) 1- (4-Methylphenoxy) -3- (2-naphthoxy) propane (5) 1- (2-methylphenoxy) -2- (2-naphthoxy) ethane (6) 1- (3-methylphenoxy ) -2- (2-naphthoxy) ethane (7) 1- (2-naphthoxy) -2-phenoxyethane (8) 1- (2-naphthoxy) -6-phenoxyhexane (9) 1-phenoxy-2- ( 2-phenylphenoxy) ethane (10) 1- (2-methylphenoxy) -2- (4-phenylphenoxy) ethane (11) 1,4-diphenoxybutane (12) 1,4-bis (4-methylphenyl) Noxy) butane (13) 1,2-di (3,4-dimethylphenoxy) ethane (14) 1-phenoxy-3- (4-phenylphenoxy) propane (15) 1- (4-tert-butylphenoxy)- 2-phenoxyethane (16) 1,2-diphenoxyethane (17) 1- (4-methylphenoxy) -2-phenoxyethane (18) 1- (2,3-dimethylphenoxy) -2-phenoxyethane (19 ) 1- (3,4-dimethylphenoxy) -2-phenoxyethane (20) 1- (4-ethylphenoxy) -2-phenoxyethane (21) 1- (4-isopropylphenoxy) -2-phenoxyethane (22 ) 1,2-bis (2-methylphenoxy) ethane (23) 1- (2-methylphenoxy) -2- (4-methylphenoxy) ethane (24) -(4-tert-Butylphenoxy) -2- (2-methylphenoxy) ethane (25) 1,2-bis (3-methylphenoxy) ethane (26) 1- (3-methylphenoxy) -2- (4 -Methylphenoxy) ethane (27) 1- (4-ethylphenoxy) -2- (3-methylphenoxy) ethane (28) 1,2-bis (4-methylphenoxy) ethane (29) 1- (2,3 -Dimethylphenoxy) -2- (4-methylphenoxy) ethane (30) 1- (2,5-dimethylphenoxy) -2- (4-methylphenoxy) ethane (31) phenoxyacetic acid-2-naphthyl (32) 2 Naphthoxyacetic acid-4-methylphenyl (33) 2-naphthoxyacetic acid-3-methylphenyl

  Next, the compound represented by the general formula (2) will be described.

In the above formula, R ₇ represents an alkyl group, an aryl group, an alkylcarbonyl group, an arylcarbonyl group, an alkylsulfonyl group, or an arylsulfonyl group. The naphthalene ring in the formula may further have a substituent, and examples of preferable substituents include an alkyl group, an aryl group, a halogen group, a hydroxy group, an alkoxy group, an aryloxy group, and an alkyloxycarbonyl group. , Alkoxycarbonyl group, aryloxycarbonyl group, carbamoyl group, sulfamoyl group and the like.

Among the substituents represented by R ₇ in the general formula (2), an alkyl group having 4 to 20 carbon atoms, an aryl group having 4 to 24 carbon atoms, an alkylcarbonyl group having 2 to 20 carbon atoms, and 7 to 20 carbon atoms. The arylcarbonyl group is more preferable. In the general formula (2), among the substituents that the naphthalene ring may further have, a halogen group, an alkyl group having 1 to 10 carbon atoms, an alkyloxycarbonyl group having 2 to 20 carbon atoms, or a 7 to 20 carbon atom. An aryloxycarbonyl group and a carbamoyl group having 2 to 25 carbon atoms are more preferable.

Examples of the compound represented by the general formula (2) include the following compounds, but the present invention is not limited thereto.
(1) 1-benzyloxynaphthalene (2) 2-benzyloxynaphthalene (3) 2-p-chlorobenzyloxynaphthalene (4) 2-p-isopropylbenzyloxynaphthalene (5) 2-dodecyloxynaphthalene (6) 2 Decanoyloxynaphthalene (7) 2-Myristoyloxynaphthalene (8) 2-p-tert-butylbenzoyloxynaphthalene (9) 2-Benzoyloxynaphthalene (10) 2-Benzyloxy-3-N- (3-dodecyl Oxypropyl) carbamoylnaphthalene (11) 2-benzyloxy-3-N-octylcarbamoylnaphthalene (12) 2-benzyloxy-3-dodecyloxycarbonylnaphthalene (13) 2-benzyloxy-3-p-tert-butylphenoxy Carbonyl naphthalene

  Next, the compound represented by the general formula (3) will be described.

In the above formula, R ₈ and R ₉ represent a hydrogen atom, a halogen group, an alkyl group having 4 or less carbon atoms, or an alkoxy group. X ₂ represents a simple bond or —O—, and n represents an integer of 1 to 4.

Examples of the compound represented by the general formula (3) include the following compounds, but the present invention is not limited thereto.
(1) Bisbenzyl oxalate (2) Bis (p-methylbenzyl) oxalate
(3) Bisoxalate (p-chlorobenzyl)
(4) Bisoxalate (m-methylbenzyl)
(5) Bisoxalate (p-ethylbenzyl)
(6) Bisoxalate (p-methoxybenzyl)
(7) Bisoxalate (2-phenoxyethyl)
(8) Bis oxalate (2-o-chlorophenoxyethyl)
(9) Bis oxalate (2-p-chlorophenoxyethyl)
(10) Bis-oxalate (2-p-ethylphenoxyethyl)
(11) Bisoxalate (2-m-methoxyphenoxyethyl)
(12) Bisoxalate (2-p-methoxyphenoxyethyl)
(13) Bis-oxalate (4-phenoxybutyl)

  Preferred examples of these exemplary compounds include bisbenzyl oxalate, bis (p-methylbenzyl) oxalate, bis (p-chlorobenzyl) oxalate, bis (m-methylbenzyl) oxalate, and bisoxalate. (P-ethylbenzyl) and bis (p-methoxybenzyl) oxalate.

  The compound represented by the general formula (4) will be described below.

In the above formula, R ₁₀ , R ₁₀ ′, R ₁₁ and R ₁₁ ′ represent a hydrogen atom, a halogen atom, an alkyl group, an aryl group, an alkoxy group, an alkylcarbonyl group, an arylcarbonyl group, an alkoxycarbonyl group or an aryloxy group. .

Examples of the compound represented by the general formula (4) include the following compounds, but the present invention is not limited thereto.
(1) 1,2-bisphenoxymethylbenzene (2) 1,3-bisphenoxymethylbenzene (3) 1,4-bis (2-methylphenoxymethyl) benzene (4) 1,4-bis (3-methyl Phenoxymethyl) benzene (5) 1,3-bis (4-methylphenoxymethyl) benzene (6) 1,3-bis (2,4-dimethylphenoxymethyl) benzene (7) 1,3-bis (2,6 -Dimethylphenoxymethyl) benzene (8) 1,4-bis (2-chlorophenoxymethyl) benzene (9) 1,2-bis (4-chlorophenoxymethyl) benzene (10) 1,3-bis (4-chloro Phenoxymethyl) benzene (11) 1,2-bis (4-octylphenoxymethyl) benzene (12) 1,3-bis (4-octylphenoxymethyl) benzene 13) 1,3-bis (4-isopropylphenyl phenoxymethyl) benzene (14) 1,4-bis (4-isopropylphenyl phenoxymethyl) benzene

  Preferred examples among these exemplary compounds include 1,2-bisphenoxymethylbenzene, 1,4-bis (2-methylphenoxymethyl) benzene, 1,4-bis (3-methylphenoxymethyl) benzene, 1,4-bis (2-chlorophenoxymethyl) benzene may be mentioned.

  Among the compounds represented by the general formulas (1) to (4), the compounds represented by the general formulas (1), (2) and (4) are preferable in that excellent printing durability can be obtained. The compounds represented by (1) and (2) are preferred, and the most preferred compound is the compound represented by the general formula (1). In addition, the above hot-melt materials may be used alone or in combination, but in the present invention, the compounds represented by the general formulas (1) to (4) and waxes are used. Each is used in combination of at least one.

  The compounds represented by the above general formulas (1) to (4) are solid substances at room temperature, but are preferably used after being subjected to a fine dispersion treatment in order to increase the reactivity with 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.

  In the present invention, the content ratio of the heat-meltable substance to the water-soluble polymer compound in the image forming layer (A) (the mass of the heat-meltable substance / the mass of the water-soluble polymer compound) has a preferred range. It is preferably 0 or more. On the other hand, the content ratio of the heat-meltable substance to the water-soluble polymer compound in the image forming layer (B) (the mass of the heat-meltable substance / the mass of the water-soluble polymer compound) also has a preferable range. It is preferable that In the present invention, the content ratio of the heat-meltable substance to the water-soluble polymer compound in the image forming layer (A) is preferably higher than the content ratio in the image forming layer (B). Is more preferably 1.0 or more. By adjusting to such a range, a heat-sensitive lithographic printing plate excellent in printing durability and stain resistance can be obtained.

<Crosslinking agent>
The image forming layer (A) and the image forming layer (B) of the present invention preferably contain a hardening agent (waterproofing agent) depending on the type of the water-soluble polymer compound. As a hardener, a material that imparts water resistance by accelerating the crosslinking of water-soluble polymer compounds such as melamine resin, epoxy resin, polyisocyanate compound, aldehyde compound, silane compound, chromium alum, divinyl sulfone, etc. Although it is possible, divinyl sulfone is particularly preferably used. The compounding amount of the hardener is preferably 0.01 to 30% by mass with respect to the solid content of the water-soluble polymer compound contained in the entire image forming layer, and more preferably 5 to 30% by mass. % Range.

  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).

<Developer>
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

<Coloring agent>
Specific examples of the color former (electron-donating dye precursor) include (1) 3,3′-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (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-dimethyla Nophthalide, 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, 3-di Tilamino-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) as a thiazine compound , Benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, etc .: ( 5) As spiro compounds, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3′-dichloro-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 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.

<Photothermal conversion material>
Furthermore, in the present invention, a photothermal conversion substance can be blended in the image forming layer. By using a photothermal conversion agent, writing with active light such as an infrared laser as well as a thermal head is 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 outside are preferable, for example, organic materials such as carbon black, cyanine dyes, polymethine dyes, azurenium dyes, squalium dyes, thiopyrylium dyes, naphthoquinone dyes, anthraquinone dyes Examples thereof include metal compounds such as compounds, 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.

  In addition, the image-forming layer (A) and the image-forming layer (B) of the present invention may contain antiseptics, surfactants, antifoaming agents, leveling agents, pH adjusting agents, other coating aids, and the like as necessary. Can be added.

The image forming layer of the heat-sensitive lithographic printing plate of the present invention has a dry solid content of 0.5 to 30 g / m ² from the viewpoints of printing durability of image areas, water resistance of non-image areas, and mechanical strength. It is preferable. In the present invention, the image forming layer (A) and the image forming layer (B) are coated by applying the image forming layer (A) on the side close to the support, and then the image forming layer (B). There are a method of sequentially applying and stacking layers, a method of simultaneously applying multiple layers by a slide hopper method, and either method may be used.

  In the heat-sensitive lithographic printing plate of the present invention, an undercoat layer comprising titanium dioxide, a binder resin, and a crosslinking agent is preferably provided between the support and the image forming layer. As a result, there is no change in the plate pressure due to contamination due to plate pressure changes during printing, specifically, slight undulations on the blanket roller of the printing press, without degrading image quality and printing durability. It is possible to improve the printing stain that occurs and develops at the extreme tip and the bottom edge of the printing paper surface.

<Titanium dioxide>
The titanium dioxide contained in the undercoat layer 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. As the surface treatment composition, alumina, silica, zinc oxide, zirconia and the like are common. 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. ) From Taipei R-580, R-930, A-100, A-220, CR-58, Titanium Industry Co., Ltd., Kronos KR-310, KR-380, KA-10, KA -20 etc., Teica Co., Ltd., Titanics JR-301, JR-600A, JR-800, JR-701 etc., DuPont Co., Ltd. Taipure R-900, R-931 etc. are mentioned.

The average particle diameter of titanium dioxide used for the undercoat layer is preferably smaller than the average dry film thickness of the undercoat layer. Titanium dioxide generally exists in the form of secondary particles, tertiary particles, etc., with some primary particles agglomerated. The average particle diameter of the titanium dioxide is, for example, titanium dioxide in a dispersion medium to which a dispersant such as polycarboxylic acid, fatty acid amine, sulfonic acid amide, ε-caprolactone, hydrostearic acid, polyester amine is added. Is dispersed using a media mill such as a ball mill, a bead mill, a sand grinder, a pressure disperser such as a high pressure homogenizer, an ultra high pressure homogenizer, an ultrasonic disperser, and a thin film swirl disperser. It is preferable to adjust appropriately. A preferable average particle size used in the titanium dioxide layer is preferably 0.1 to 1.5 μm, particularly preferably 0.2 to 1.0 μm. The average particle diameter in the present invention can be measured as a number median diameter using a laser scattering particle size distribution meter (for example, LA920 manufactured by Horiba, Ltd.). On the other hand, the dry solid content of the undercoat layer is preferably in the range of 0.5 to 20 g / m ² .

  The content of titanium dioxide used in the undercoat layer can be set in a wide range, but it is preferably used at 200 to 1000% by mass with respect to 100 parts by mass of the binder resin solid content contained in the undercoat layer. More preferably, it is 400-600 mass%. When the content of titanium dioxide is low, the concealing property may be reduced. When used in excess, the stability of the coating liquid may be reduced, or the bulk density may increase due to irregular aggregation. As a result, the surface roughness may increase and the image quality may deteriorate.

<Binder resin>
As the binder resin contained in the undercoat layer, for example, gelatin such as lime-processed gelatin, acid-processed gelatin, and enzyme-processed gelatin, and water-soluble polymers such as polysaccharides, polyvinyl alcohol, and polyvinylpyrrolidone can be used. It is preferable to use it.

<Crosslinking agent>
As the crosslinking agent contained in the undercoat layer, for example, melamine resin, epoxy resin, polyisocyanate compound, aldehyde compound, silane compound, chromium alum, divinyl sulfone and the like can be suitably used. Is preferred. The blending amount of the crosslinking agent is preferably 1 to 30% by mass, more preferably 2 to 15% by mass, based on the solid content of the binder.

<Support>
A water-resistant support is used as the support used in the heat-sensitive lithographic printing plate of the present invention, but a water-resistant support such as a plastic film, resin-coated paper, and water-resistant paper can be preferably used. Specifically, polyolefin films such as polyethylene and polypropylene, polyethersulfone, polyester, poly (meth) acrylate, polycarbonate, polyamide, and polyvinyl chloride, and plastic-coated paper with a laminated or coated plastic on the surface, melamine Paper that has been made water resistant by 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, it is possible to irradiate light containing infrared light of, for example, 760 nm to 1200 nm by blending a photothermal conversion material in the image forming layer. It is possible to form an image portion, and it is preferable to form the image portion with a solid 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 plate making is performed using a thermal head, 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 the following description, “%” and “part” represent a mass ratio unless otherwise specified.

Example 1
On one side of a polyethylene resin-coated paper having a thickness of about 180 μm that has been laminated on both sides, slide an undercoat layer coating solution of the following composition, and an image forming layer a-1 and an image forming layer b-1 coating solution. By the hopper coating method, three layers were simultaneously applied from the support side so that the undercoat layer, the image forming layer a-1, and the image forming layer b-1 (uppermost layer) were in this order. At that time, the wet coating weight, the undercoat layer coating solution 15 g / ^{m 2,} the image forming layer a-1 coating liquid 30 g / ^{m 2,} the image forming layer b-1 coating liquid to 10 g / ^{m 2} Set and went.

<Undercoat layer coating solution>
Gelatin (cow bone, alkali treatment, decalcification treatment) 0.8 parts Titanium dioxide slurry: 4.0 parts converted to TISR1 solid amount (manufactured by Sakai Chemical Co., Ltd., rutile type, primary particle size = 0.3 μm, alumina treatment)
Pigment dispersant (acrylic acid copolymerized metal salt, 10% solution) 0.2 part Surfactant (ethylhexyl sulfosuccinate, 0.5% solution) 0.05 part Hardener (divinyl sulfone, 5% solution) 2 0.0 part The total amount was made 15 parts with water.

<Image forming layer a-1 coating solution>
Gelatin (cow bone, alkali treatment, decalcification treatment) 0.8 part Polyvinyl alcohol: PVA505 0.07 part (manufactured by Kuraray Co., Ltd., saponification degree = 73.5 mol%, polymerization degree 500)
Carboxylated SBR: LUXSTAR 7132C 3.0 parts (manufactured by DIC Corporation, solid content = about 45%, anionic, Tg = about 60 ° C.)
Developer mixed slurry 8.0 parts Color former 0.7 part (3-dibutylamino-6-methyl-7-anilinofluorane, 30% slurry)
Surfactant (ethylhexyl sulfosuccinate, 0.5% solution) 0.4 part Hardener (divinyl sulfone, 5% solution) 2.0 parts The total amount was 30 parts with water.

<Image forming layer b-1 coating solution>
Gelatin (cow bone, alkali treatment, decalcification treatment) 0.4 part Water-soluble polysaccharide: Pullulan (produced by Hayashibara Shoji Co., Ltd., food additive) 0.01 part Carboxylated SBR: Lackster 7132C 0.6 part ( DIC Corporation, solid content = about 45%, anionic, Tg = about 60 ° C.)
Barium sulfate slurry: Variace B-35 solids conversion 0.03 part (manufactured by Sakai Chemical Industry Co., Ltd., average particle size = 0.3 μm)
Pigment dispersant (acrylic acid copolymerized metal salt, 10% solution) 0.002 part Color former 0.3 part (3-dibutylamino-6-methyl-7-anilinofluorane, 30% slurry)
Aqueous wax 0.3 part (n-octacosanoic acid (carbon number 28), solid content 30%)
Surfactant (ethylhexyl sulfosuccinate, 0.5% solution) 0.2 part Hardener (divinyl sulfone, 5% solution) 1.0 part The total amount was 10 parts with water.

  For the preparation of the titanium dioxide slurry used for the undercoat layer coating solution and the barium sulfate slurry used for the image forming layer b-1 coating solution, an acrylic acid copolymerized metal salt is used as a pigment dispersant. The production method is to gradually add titanium dioxide or barium sulfate under constant stirring into water to which a pigment dispersant has been added, and perform high-speed fine dispersion treatment for 30 minutes using a homomixer. Can be made. The slurry used was prepared just before preparing the coating solution.

Further, the developer mixed slurry used in the image forming layer a-1 coating solution was prepared and manufactured in advance with the following constituent chemicals.
<Constituent chemicals of developer mixed slurry>
Material a: KS-232
(Sanko Co., Ltd., sensitizer, 1,2-bis (3-methylphenoxy) ethane)
Material b: D-8
(Nippon Soda Co., Ltd., developer, 4-hydroxy-4'-isopropoxydiphenyl sulfone)
Material c: Polymeron 1318
(Arakawa Chemical Co., Ltd., dispersant, 15% aqueous solution of anionic styrene resin)

  After mixing 1 part each of material a and material b in water to which 0.7 part of the material c is added under constant stirring, any particles using zirconia beads in a small dyno mill (bead mill) A fine dispersion treatment was performed up to a diameter to obtain a developer mixed slurry. In addition, it prepared so that solid content concentration in the sum total of the material a, the material b, and the material c might be about 35%.

  For other chemicals, there was no special adjustment other than split water, except that hydrophilic polymers such as gelatin, polyvinyl alcohol and water-soluble polysaccharides were heated and dissolved in water. However, with respect to the developer mixed slurry, care was taken from the stage of preparation and with respect to the color former, so that the temperature did not exceed 45 ° C. throughout the handling.

  After three layers were simultaneously applied at the moisture application amount, the coating film was immediately gelled with cold air of 1 to 3 ° C., and then dried with hot air set 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%.

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). And an electric capacity of 330 W) to produce a printing plate. Using this printing plate, printability was evaluated by the following method.

<Print durability>
The printing press uses Heidelberg QM46 offset sheet-fed printing press. The printing ink is FusionG black N made by Dainippon Ink & Chemicals, Inc., and the SLM-OD made by Mitsubishi Paper Industries is diluted 10% for the dampening solution. Printing was performed using the same moisturizing liquid as it was for the etching liquid. For printing durability evaluation, the printing paper surface at the start and the printing paper surface at the time of printing 5,000 sheets were compared, and the attenuation ratio of 20% halftone dot and 50% halftone dot was observed with a 25 times loupe. The evaluation criteria were used. This result is also shown in Table 1.
◎: Almost no change in both 20% and 50% halftone dot portions ○: Almost no change in the 50% halftone dot portion, but attenuation can be confirmed in the 20% halftone dot portion △: Both the 20% and 50% halftone dot portions Attenuation can be confirmed ×: More than 50% attenuation is observed at 20% halftone dot part XX: Over 90% attenuation is observed at 20% halftone dot part

<Soil dirt>
The offset press is also the Heidelberg QM46 offset sheet-fed press. The printing ink is FusionG Ink S from Dainippon Ink Chemical Co., Ltd., and the Astro Mark III from Nikken Chemical Co., Ltd. is used as the dampening solution. .5% diluted solution was used and printing was started without etching. As the background stain evaluation, the following evaluation criteria were used on the 2,000th printed paper surface from the start of printing. The results are shown in Table 1.
◎: No background stain up to 1st to 2,000th sheet ○: No background stain generated from 1st to 1500th sheet △: No background stain generated from 1st to 1000th sheet ×: Printing Smudge out (5 sheets or less), or less than 1,000 background xx: Print out stain (6 sheets or more)

(Example 2)
Example except that it was changed to zinc oxide (manufactured by Sakai Chemical Industry Co., Ltd., fine zinc oxide, average particle size = 0.29 μm) instead of barium sulfate used in the image forming layer b-1 coating solution of Example 1. In the same manner as in Example 1, a thermosensitive lithographic printing plate of Example 2 was obtained. Using the obtained heat-sensitive lithographic printing plate, an image was output in the same manner as in Example 1 to produce a printing plate and evaluated. The results are shown in Table 1.

(Comparative Example 1)
A heat-sensitive lithographic printing plate of Comparative Example 1 was obtained in the same manner as in Example 1 except that the barium sulfate slurry used in the image forming layer b-1 coating solution of Example 1 was omitted. Using the obtained heat-sensitive lithographic printing plate, an image was output in the same manner as in Example 1 to produce a printing plate and evaluated. The results are shown in Table 1.

(Example 3)
The heat-sensitive type of Example 3 is the same as Example 1 except that the amount of barium sulfate slurry used in the image forming layer b-1 coating solution of Example 1 is changed from 0.03 part to 0.06 part. A lithographic printing plate was obtained. Using the obtained heat-sensitive lithographic printing plate, an image was output in the same manner as in Example 1 to produce a printing plate and evaluated. The results are shown in Table 1.

Example 4
The heat-sensitive type of Example 4 is the same as Example 1 except that the addition amount of the barium sulfate slurry used in the image forming layer b-1 coating liquid of Example 1 is changed from 0.03 part to 0.08 part. A lithographic printing plate was obtained. Using the obtained heat-sensitive lithographic printing plate, an image was output in the same manner as in Example 1 to produce a printing plate and evaluated. The results are shown in Table 1.

(Example 5)
The heat-sensitive type of Example 5 is the same as Example 1 except that the addition amount of the barium sulfate slurry used in the image forming layer b-1 coating liquid of Example 1 is changed from 0.03 part to 0.0135 part. A lithographic printing plate was obtained. Using the obtained heat-sensitive lithographic printing plate, an image was output in the same manner as in Example 1 to produce a printing plate and evaluated. The results are shown in Table 1.

(Comparative Example 2)
Except for changing barium sulfate used for the image forming layer b-1 coating solution of Example 1 to fine pore silica (Grace Devison Co., Ltd., Sylojet A25, average particle size = 0.32 μm), the same procedure as in Example 1 was performed. Thus, a heat-sensitive lithographic printing plate of Comparative Example 2 was obtained. Using the obtained heat-sensitive lithographic printing plate, an image was output in the same manner as in Example 1 to produce a printing plate and evaluated. The results are shown in Table 1.

  As can be seen from the results shown in Table 1, it can be seen that a heat-sensitive lithographic printing plate having improved printing durability and stain resistance in a balanced manner is obtained by the present invention.

Claims (2)

  At least two image forming layers containing at least a thermoplastic resin, a heat-meltable substance, and a water-soluble polymer compound are provided on one side of the support, and the image forming layer (B) far from the support is zinc oxide. Alternatively, a heat-sensitive lithographic printing plate containing barium sulfate.   The heat-sensitive lithographic printing plate according to claim 1, wherein the content of the zinc oxide or barium sulfate is 8 to 26% by mass with respect to the amount of the thermoplastic resin contained in the image forming layer (B).