JP2011167949A - Thermal type lithographic printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal type lithographic printing plate capable of improving dirt recoverability and blanket piling while holding sufficient printing durability. <P>SOLUTION: The thermal type lithographic printing plate is characterized in that it has at least two image forming layers containing a thermoplastic resin, hot-melt substance, and a water-soluble polymer compound on a water resistant support body and that the image forming layer (B) furthest away from the water resistant support body contains gelatin and polysaccharide. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a heat-sensitive lithographic printing plate using an image forming layer that undergoes phase conversion by heat, and to a heat-sensitive lithographic printing plate that does not require layer removal processing such as an ablation method or an on-machine development method. More particularly, the present invention relates to a heat-sensitive lithographic printing plate having improved non-image area stain recovery and blanking without reducing printing durability.

  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 a digital printer as described above is largely divided from the conventional optical mode type using a visible light laser and the like, and is not subject to safety light restrictions in handling. have. 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 the surface of a support 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, etc. is not sufficient. For example, the density of a transfer toner image is insufficient, and the transfer image has white spots.
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) There is a problem that a small amount of toner is irregularly transferred to the non-image area or a thin background stain is generated due to 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, in which the originally hydrophilic portion undergoes phase change and changes to hydrophobic (lipophilic).

  The lithographic printing plate is composed of an oleophilic image portion that accepts oil-based ink and a hydrophilic non-image portion that does not accept ink, and generally the non-image portion accepts water. In normal lithographic printing, both water and ink are supplied to the plate surface, the color ink is selectively received in the image area, and water is selectively received in the non-image area, and the ink in the image area is printed on a printing medium such as paper. Printing is performed by transferring the ink to the ink. Therefore, by sufficiently increasing the difference between the lipophilicity and hydrophilicity between the image area and the non-image area, when the emulsified water-ink is supplied to the plate surface, the image area is sufficiently ink, and the non-image area is Sufficient water can be received and a good print can be obtained.

  However, the above-described phase change type thermosensitive lithographic printing plate is different from a processless printing plate that transfers a grease-sensitive recorded image on a water retention layer, and has a lipophilic component and a hydrophilic component in the same layer. Therefore, the difference in lipophilicity / hydrophilicity between the image area and the non-image area was insufficient. For this reason, it is difficult to obtain a clear printed image and the printing durability is not sufficient, and when soiling occurs, excessively dampening water is used to recover the soiling normally, so-called soiling recovery property, The handleability such as the problem of inferior blanking (blanket stain) in which ink accumulates in the non-image area was not satisfactory.

  For problems such as printing durability and background smearing, JP-A-11-95417 (Patent Document 5) uses a crosslinked hydrophilic resin such as polyvinyl alcohol or carboxymethyl cellulose in the image forming layer. Although it is described that the property and water retention are improved, the level of hydrophobicity of the image area is low and the difference in hydrophobicity / hydrophilicity is sufficient because the phase conversion of the hydrophilic resin itself is used. It wasn't. 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 or polyvinyl alcohol as a hydrophilic substance. However, the difference in hydrophobicity / hydrophilicity was not sufficient.

  Japanese Patent Application Laid-Open No. 07-1849 (Patent Document 7) describes polysaccharides as an example of the hydrophilic binder contained in the image forming layer, and Japanese Patent Application Laid-Open No. 2005-81583 (Patent Document 8) uses many as hydrophilic binders. Specific examples of heat-sensitive lithographic printing plates using saccharides are described, and Japanese Patent Application Laid-Open No. 2009-196262 (Patent Document 9) describes a heat-sensitive lithographic printing plate having an image forming layer containing gelatin. In either case, the soil recoverability and the blank piling were not sufficient.

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 Japanese Patent Application Laid-Open No. 07-1849 JP 2005-81583 A JP 2009-196262 A

  An object of the present invention is to provide a heat-sensitive lithographic printing plate having improved non-image area stain recovery and blanking without reducing printing durability.

The above problems have been solved by the following means.
(1) An image forming layer (B) that has at least two image forming layers containing a thermoplastic resin, a heat-meltable substance, and a water-soluble polymer compound on the water-resistant support, and is the farthest from the water-resistant support. Is a heat-sensitive lithographic printing plate characterized in that it contains gelatin and a polysaccharide.

  According to the present invention, it is possible to provide a heat-sensitive lithographic printing plate having improved non-image area stain recovery and blanking without reducing printing durability.

  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 infrared laser, the part to which heat is applied is hydrophobic because the thermoplastic resin buried in the water-soluble polymer compound and the hot-melt material melt and ooze out to the extreme surface of the layer It becomes possible to accept ink at the time of printing. In the portion where heat is not applied, the thermoplastic resin and the heat-meltable substance remain buried in the water-soluble polymer compound, and the hydrophilicity inherent in the image forming layer is maintained.

  The heat-sensitive lithographic printing plate of the present invention has at least two image forming layers containing a thermoplastic resin, a heat-meltable substance, and a water-soluble polymer compound. For example, one image forming layer is an image forming layer (A) close to a water resistant support, and the other image forming layer is an image forming layer (B) farthest from the water resistant support. In the heat-sensitive lithographic printing plate of the present invention, gelatin and polysaccharide are used in combination as the water-soluble polymer compound of the image forming layer (B) farthest from the water-resistant support. The present invention is described in detail below.

<Water-soluble polymer compound>
Examples of the water-soluble polymer compound contained in the image forming layer (A) close to the water-resistant support include, for example, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, Examples thereof include carboxymethylcellulose, starch and derivatives thereof, gelatin, casein, sodium alginate, polyvinylpyrrolidone, styrene / maleic acid copolymer salt, styrene / acrylic acid copolymer salt and the like. These water-soluble polymer compounds may be used alone or in combination of two or more. The water-soluble polymer compounds contained in the image forming layer (A) close to the water-resistant support include gelatin and polyvinyl which are particularly rich in film formation. Alcohol and a modified product thereof are preferably selected for maintaining hydrophilicity in the non-image area, and it is particularly preferable to use gelatin and polyvinyl alcohol in combination.

  On the other hand, the image forming layer (B) farthest from the water-resistant support contains gelatin and polysaccharide as a water-soluble polymer compound. Any gelatin can be used as long as it is made from animal collagen, but gelatin made from collagen obtained from pig skin, cow skin, and cow bone is preferred. The type of gelatin is not particularly limited, but in addition to lime-treated gelatin and acid-treated gelatin, JP-B-38-4854, JP-B-39-5514, JP-B-40-12237, JP-B-42- No. 26345, US Pat. No. 2,525,753, US Pat. No. 2,594,293, US Pat. No. 2,614,928, US Pat. No. 2,763,639 US Pat. No. 3,118,766, US Pat. No. 3,132,945, US Pat. No. 3,186,846, US Pat. No. 3,312,553, Examples include gelatin derivatives described in British Patent No. 1,033,189 and the like, and these can be used alone or in combination of two or more.

  The polysaccharide used in the present invention is a saccharide in which a large number of monosaccharides not classified as monosaccharides or oligosaccharides are bonded, and is preferably water-soluble. Examples of the water-soluble polysaccharide used in the image forming layer of the present invention include starch and derivatives thereof, cellulose derivatives (for example, hydroxypropylmethylcellulose), glycogen, agarose, pectin, dextran, pullulan and the like. From the viewpoint of sex. Moreover, when using together the said gelatin and polysaccharide, there exists a preferable ratio between both, and it is preferable that polysaccharide is 2.5-20 mass% with respect to gelatin. Furthermore, water-soluble polymer compounds other than gelatin and polysaccharides may be used in combination, but their content is preferably less than 20% by mass with respect to gelatin.

  The amount of the water-soluble polymer compound contained in the image forming layer (A) close to the water-resistant support of the present invention and the image forming layer (B) farthest from the water-resistant support is the total solid content of the image forming layer. 0.5-50 mass% is preferable with respect to quantity.

<Thermoplastic resin>
The thermoplastic resin contained in the image-forming layer (A) close to the water-resistant support and the image-forming layer (B) farthest from the water-resistant support is a solid polymer that is made of a chain polymer and exhibits plasticity by heating. An organic polymer compound, which refers to an aqueous dispersion of an organic polymer 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 total solid content of the image forming layer.

  In order to make the melting and fusing effect due to heat easy to develop, 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.

  In the present invention, the ratio of the thermoplastic resin to the water-soluble polymer compound of the image forming layer (A) close to the water-resistant support is such that the heat of the image forming layer (B) farthest from the water-resistant support to gelatin and polysaccharides. It is preferable to make it higher than the ratio of the plastic resin. The ratio of thermoplastic resin to gelatin and polysaccharide in the image forming layer (B) farthest from the water-resistant support (mass of thermoplastic resin / total mass of gelatin and polysaccharide) is 0.01 to 10 Is more preferable, and 0.1 to 3 is more preferable. Further, the ratio (mass of thermoplastic resin / mass of water-soluble polymer compound) in the image forming layer (A) close to the water-resistant support also has a preferred range, preferably 0.1 to 50, and more preferably. Is 1-20. Furthermore, the difference between the ratio in the image forming layer (A) and the ratio in the image forming layer (B) is preferably 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>
Examples of the hot-melt material contained in the image forming layer (A) close to the water resistant support and the image forming layer (B) farthest from the water resistant support include carnauba wax, microcrystalline wax, paraffin wax, polyethylene wax. Waxes such as lauric acid, stearic acid, oleic acid, palmitic acid, behenic acid, montanic acid and the like, and esters, amides thereof, and compounds represented by the following general formulas (1) to (4) And an organic compound 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 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 7 carbon atoms. Twenty arylcarbonyl groups are more preferred. 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) Dibenzyl oxalate (2) Di (p-methylbenzyl) oxalate
(3) Oxalate di (p-chlorobenzyl)
(4) Oxalic acid di (m-methylbenzyl)
(5) Dioxalate (p-ethylbenzyl)
(6) Dioxalate (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 dibenzyl oxalate, di (p-methylbenzyl) oxalate, di (p-chlorobenzyl) oxalate, di (m-methylbenzyl) oxalate, and dioxalate. (P-ethylbenzyl) and di (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-diphenoxymethylbenzene (2) 1,3-diphenoxymethylbenzene (3) 1,4-di (2-methylphenoxymethyl) benzene (4) 1,4-di (3-methyl Phenoxymethyl) benzene (5) 1,3-di (4-methylphenoxymethyl) benzene (6) 1,3-di (2,4-dimethylphenoxymethyl) benzene (7) 1,3-di (2,6 -Dimethylphenoxymethyl) benzene (8) 1,4-di (2-chlorophenoxymethyl) benzene (9) 1,2-di (4-chlorophenoxymethyl) benzene (10) 1,3-di (4-chloro Phenoxymethyl) benzene (11) 1,2-di (4-octylphenoxymethyl) benzene (12) 1,3-di (4-octylphenoxymethyl) benzene (13) 1,3-di (4- Isopropyl phenyl phenoxymethyl) benzene (14) 1,4-di (4-isopropylphenyl phenoxymethyl) benzene

  Among these exemplified compounds, preferred specific examples include 1,2-diphenoxymethylbenzene, 1,4-di (2-methylphenoxymethyl) benzene, 1,4-di (3-methylphenoxymethyl) benzene, 1,4-di (2-chlorophenoxymethyl) benzene is 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). These hot-melt materials may be used alone or in combination, but they are represented by waxes and general formulas (1) to (4) from the viewpoint of printing durability. It is preferable to use a compound in combination.

  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 ratio of the compounds represented by the general formulas (1) to (4) to the gelatin and polysaccharide in the image forming layer (B) farthest from the water-resistant support (general formulas (1) to (4) ) / Mass of the compound represented by (the total mass of gelatin and polysaccharide) has a preferred range, preferably 0.5 or less. On the other hand, the ratio of the compounds represented by the general formulas (1) to (4) to the water-soluble polymer compound in the image forming layer (A) close to the water-resistant support (the compounds represented by the general formulas (1) to (4)) (Mass / water-soluble polymer compound)), there is a preferred range, and it is preferably 1.0 or more. In the present invention, the ratio of the compounds represented by the general formulas (1) to (4) to the water-soluble polymer compound in the image forming layer (A) close to the water-resistant support is the most distant from the water-resistant support. It is preferable to make it higher than the above ratio of the layer (B), and the difference in the ratio is 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) close to the water-resistant support of the present invention and the image forming layer (B) farthest from the water-resistant support are hardened according to the type of the water-soluble polymer compound. Agent). 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. However, particularly preferred hardeners are divinyl sulfone in the case of gelatin and glyoxal in the case of polyvinyl alcohol. The blending amount of the hardener is preferably 0.01 to 30% by mass, more preferably 5 to 30% by mass, based on the solid content of the water-soluble polymer compound contained in the entire image forming layer.

  The heat-sensitive lithographic printing plate of the present invention is further provided between the image forming layer (A) and the image forming layer (B) in addition to the image forming layers (A) and (B), or further than the image forming layer (A). Another image forming layer can be provided at a position close to the water-resistant support.

  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>
Further, 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.

<Inorganic pigment>
Conventionally, heat-sensitive recording paper generally binds to the thermal head by adsorbing the above-mentioned hot-melt material with an inorganic pigment with high oil absorption such as silicon dioxide, zinc oxide, titanium dioxide, aluminum hydroxide, calcium carbonate. It is formulated so as to prevent sticking phenomenon and prevent image drawing. However, when an inorganic pigment is contained in the image forming layer of the present invention, the printing durability tends to be lowered. Accordingly, the inorganic pigment is preferably less than 10% by mass, more preferably less than 5% by mass, based on the total solid content of the image forming layer.

  In addition, the image-forming layer (A) close to the water-resistant support and the image-forming layer (B) farthest from the water-resistant support are further provided with an antiseptic, a surfactant, an antifoaming agent, a leveling agent, and a pH adjusting agent. Etc. can also 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, as a method of coating the image forming layer (A) close to the water-resistant support and the image forming layer (B) farthest from the water-resistant support, the image forming layer (A) is applied, Next, there are a method in which the image forming layer (B) is sequentially applied and stacked, a method in which multiple layers are simultaneously applied by a slide hopper method, and the like.

  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 water-resistant 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. ), Typek R-580, R-930, A-100, A-220, CR-58, Titanium Industry Co., Ltd., Kronos KR-310, KR-380, KA-10, KA-20, etc., from Teika Co., Ltd., Titanics JR-301, JR-600A, JR-800, JR-701, etc., DuPont from Taipure R-900, R-931, etc. Is 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 0.3 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 average dry film thickness of the undercoat layer is preferably in the range of 1.0 to 3.0 μm, more preferably in the range of 1.0 to 1.5 μm.

  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, more preferably based on the solid content of the binder resin contained in the undercoat layer. 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, a melamine resin, an epoxy resin, a polyisocyanate compound, an aldehyde compound, a silane compound, chromium alum, divinyl sulfone, and the like can be preferably used, but the binder resin is gelatin. A particularly preferred crosslinking agent is divinyl sulfone. 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.

  The heat-sensitive lithographic printing plate of the present invention is conductive, antistatic in addition to the image forming layer (A) close to the water-resistant support, the image forming layer (B) farthest from the water-resistant support, and the undercoat layer. An anti-curl layer for adding an improvement function or preventing curling as a printing plate, a curl promoting layer for imparting a desired curl, etc. may be provided, but the image forming layer (B) farthest from the support is the most distant. A surface layer is preferred.

<Water resistant support>
As the water-resistant support that the heat-sensitive lithographic printing plate of the present invention has, 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 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 is formed by irradiating light containing infrared light of, for example, 760 nm to 1200 nm by blending a photothermal conversion substance in the image-forming layer. It is preferable to form the image portion by using a solid-state laser and a semiconductor laser that emit 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 the following description, “%” and “part” indicate mass ratio unless otherwise specified.

Example 1
Slide an undercoat layer coating solution of the following composition, and the coating solution for the image forming layer (A1) and the image forming layer (B1) on one side of a polyethylene resin-coated paper with a thickness of about 180 μm, which is laminated on both sides. By the hopper coating method, the undercoat layer coating solution is 15 g / m ² , the image forming layer (A1) coating solution is 30 g / m ² , and the image forming layer (B1) coating solution is 10 g / m ^{2 in} terms of moisture application amount. Thus, three layers were simultaneously applied so as to form an undercoat layer, an image forming layer A1, and an image forming layer B1 (uppermost layer) in this order from the support side.

<Undercoat layer coating solution>
Gelatin 0.8 part Acrylic acid copolymerized metal salt (dispersant, 10% solution) 0.2 part Titanium dioxide: TISR1 4.0 part (manufactured by Sakai Chemical Co., Ltd., rutile type, alumina treatment)
Surfactant (0.5% solution) 0.05 parts Divinylsulfone hardener (5% solution) 2.0 parts The total amount was 15 parts with water.

<Image forming layer (A1) coating solution>
Gelatin 0.8 part Polyvinyl alcohol 0.07 part Carboxylated SBR resin: LUXSTAR 7132C 3.0 part (manufactured by DIC Corporation, solid content 45% aqueous dispersion, anionic, Tg: 60 ° C.)
Developer mixed slurry 8.0 parts Color former slurry 0.7 parts Surfactant (0.5% solution) 0.4 parts Divinylsulfone hardener (5% solution) 2.0 parts 30 parts in total with water It was.

<Image forming layer (B1) coating solution>
Gelatin 0.4 part Pullulan (manufactured by Hayashibara Corporation) 0.005 part Carboxylated SBR resin: 0.6 part of Luck Star 7132C (manufactured by DIC Corporation, solid content 45% aqueous dispersion, anionic, Tg: 60 ° C)
Color developing agent slurry 0.3 part Surfactant (0.5% solution) 0.2 part Montanic acid ester wax emulsion 0.3 part (Hot-melting resin: n-octacosanoic acid (carbon number 28), solid content 30% )
Divinylsulfone hardener (5% solution) 1.0 part The total amount was 10 parts with water.

  The undercoat layer coating solution is obtained by adding titanium dioxide in water to which a dispersant has been added and subjecting it to a high-speed fine dispersion treatment for 30 minutes using a homomixer, followed by gelatin, a surfactant, and a divinylsulfone hardener. Were prepared by sequentially mixing. A part of the undercoat layer coating solution was sampled, diluted, and the average particle diameter of titanium dioxide was measured using a laser scattering type particle size distribution meter (LA920 manufactured by Horiba, Ltd.). there were.

As the developer mixed slurry used in the image forming layer (A1) coating solution, one prepared in advance by the following preparation method was used.
<Preparation of developer mixed slurry>
Material a: 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)

  After mixing the above materials a and b with a stirrer one by one, fine dispersion treatment is performed to a desired particle size using zirconia beads in a small dyno mill (bead mill), and the solid content concentration is adjusted to about 35%. A colorant mixed slurry was obtained.

As the color former slurry used in the image forming layer (A1) coating solution and the image forming layer (B1) coating solution, those prepared in advance by the following preparation method were used.
<Preparation of color former slurry>
Material c: 3-dibutylamino-6-methyl-7-anilinofluorane (manufactured by Yamamoto Kasei Co., Ltd .: ODB2)

  A fine colorant slurry was obtained by subjecting the material c to a fine dispersion treatment to a desired particle size using zirconia beads in a small dyno mill (bead mill) and adjusting the solid content concentration to about 30%.

  After three 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%. The cross section of the obtained heat-sensitive lithographic printing plate was observed using a scanning electron microscope, and the average dry film thickness of the undercoat layer was determined from the average value at any 10 locations.

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. This printing press plate was evaluated by the following method.

<Soil recovery evaluation>
QM46 manufactured by Heidelberg, an offset sheet-fed press, is used as the printing machine, FusionG black N manufactured by DIC Corporation is used as the printing ink, and Astro Mark III manufactured by Nikken Chemical Laboratory is used as the humidifier. It was diluted to 5% and used as a etchant. As a stain recovery evaluation, 300 sheets were printed, the printing machine was stopped for 15 minutes, and the number of sheets until the ink was removed from the printing paper after restarting was evaluated. The results are shown in Table 1.

<Blanpiling evaluation>
RYOBI 660 manufactured by Ryobi Co., Ltd. is used as the printing press, the printing ink is Fusion G black N manufactured by DIC, and the dampening solution is Astro Mark III manufactured by Nikken Chemical Laboratory. The SLM-OD30 manufactured by Mitsubishi Paper Industries Co., Ltd. was diluted to 25%. As a blanking evaluation, the degree of dirt on the blanket after printing 2500 sheets was evaluated. The results are shown in Table 1.
○: The blanket is not stained with ink.
Δ: Slightly dirty but no problem in practical use.
X: The blanket is soiled with ink.

<Evaluation of printing durability>
QM46 manufactured by Heidelberg, an offset sheet-fed press, is used as the printing machine, FusionG black N manufactured by DIC Corporation is used as the printing ink, and SLM-OD manufactured by Mitsubishi Paper Industries Co., Ltd. is diluted to 10%. As the etching solution, a moisturizing solution was used. As a printing durability evaluation, a 50% halftone dot on a printing paper surface at the time of printing 5000 sheets was observed with a 20-fold magnifier, and judged using the following evaluation criteria. The results are shown in Table 1.
○: 50% halftone dot pattern is reproduced without omission.
(Triangle | delta): The level which does not have a problem in practical use although the pattern of a 50% halftone dot is missing a little.
X: 50% halftone dot pattern is mostly missing and not reproduced.

(Example 2)
Except for using the image forming layer (B2) coating solution in which the amount of pullulan used in the image forming layer (B1) coating solution of Example 1 was changed from 0.005 part to 0.015 part, the same procedure as in Example 1 was performed. Thus, a heat-sensitive 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.

(Example 3)
Except for using the image forming layer (B3) coating solution in which the amount of pullulan used in the image forming layer (B1) coating solution of Example 1 was changed from 0.005 part to 0.03 part, the same procedure as in Example 1 was performed. Thus, a heat-sensitive lithographic printing plate of Example 3 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
Except for using the image forming layer (B4) coating solution in which the amount of pullulan used in the image forming layer (B1) coating solution of Example 1 was changed from 0.005 part to 0.06 part, the same procedure as in Example 1 was performed. Thus, a heat-sensitive lithographic printing plate of Example 4 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)
Except for using the image forming layer (B5) coating solution in which the amount of pullulan used in the image forming layer (B1) coating solution of Example 1 was changed from 0.005 part to 0.1 part, the same procedure as in Example 1 was performed. Thus, a heat-sensitive lithographic printing plate of Example 5 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 6)
Instead of the pullulan contained in the image forming layer (B3) coating solution used in Example 3, an image forming layer (B6) coating solution using hydroxypropyl methylcellulose (Metroze 65SH manufactured by Shin-Etsu Chemical Co., Ltd.) A heat-sensitive lithographic printing plate of Example 6 was obtained in the same manner as Example 3 except that it was used. 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)
Image forming layer (B7) coating liquid using sodium polyacrylate (AQUALIC DL522 manufactured by Nippon Shokubai Co., Ltd.) instead of gelatin contained in the image forming layer (B3) coating liquid used in Example 3 A heat-sensitive lithographic printing plate of Comparative Example 1 was obtained in the same manner as Example 3 except that was used. 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)
Example 3 is the same as Example 3 except that the image forming layer (B8) coating solution using polyethylene glycol (molecular weight 7500) is used in place of the gelatin contained in the image forming layer (B3) coating solution used in Example 3. 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.

(Comparative Example 3)
In place of the gelatin contained in the image forming layer (B3) coating solution used in Example 3, an image forming layer (B9) coating solution using polyvinyl alcohol (PVA-235 manufactured by Kuraray Co., Ltd.) was used. Was the same as in Example 3 to obtain a heat-sensitive lithographic printing plate of Comparative Example 3. 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 4)
Example 3 is the same as Example 3 except that the image forming layer (B3) coating solution used in Example 3 does not use pullulan and uses the image forming layer (B10) coating solution in which the amount of gelatin used is changed to 0.43 parts. Similarly, a heat-sensitive lithographic printing plate of Comparative Example 4 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 5)
In Example 3 except that gelatin is not used in the image forming layer (B3) coating solution used in Example 3, and the image forming layer (B11) coating solution in which the amount of pullulan is changed to 0.43 parts is used. Similarly, a heat-sensitive lithographic printing plate of Comparative Example 5 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 the present invention provides a heat-sensitive lithographic printing plate with improved stain recovery and blanking while maintaining printing durability.

Claims (1)

  The water-resistant support has at least two image forming layers containing a thermoplastic resin, a heat-meltable substance, and a water-soluble polymer compound, and the image forming layer (B) farthest from the water-resistant support is gelatin. And a thermosensitive lithographic printing plate comprising a polysaccharide.