JP2015182404A - heat-sensitive lithographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-sensitive lithographic printing plate that prevents base contamination or thickening of ink immediately after starting printing and has excellent ink receptivity even when a printing machine including an automatic printing process is used.SOLUTION: The heat-sensitive lithographic printing plate has an image forming layer comprising a thermoplastic resin, a hot-melt substance and a hydrophilic binder on a support body, in which a heated portion of the image forming layer is used as an image portion and a non-heated portion of the image forming layer is used as a non-image portion. The heat-sensitive lithographic printing plate has an outermost surface layer containing a polyether-modified polydimethylsiloxane on the image forming layer.

Description

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

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

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

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

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

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

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

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

  In order to improve the problems as described above, in JP-A-11-95417 (Patent Document 5), printing durability and water retention can be achieved by using a crosslinked hydrophilic resin such as polyvinyl alcohol or carboxymethyl cellulose in the image forming layer. However, the level of oleophilicity in the image area is low and the difference between lipophilicity / hydrophilicity is not sufficient. . JP-A-2000-75471 (Patent Document 6) uses a thermoplastic resin, a wax dispersion, a water repellent or the like as a hydrophobic substance, and uses gelatin, polyvinyl alcohol or the like as a hydrophilic substance. However, the difference in lipophilicity / hydrophilicity was not sufficient.

  Japanese Patent Laid-Open No. 2-167798 (Patent Document 7) discloses a heat-sensitive lithographic printing plate capable of obtaining good print image quality while preventing sticking by containing a hydrophilic modified silicone oil in a heat-sensitive recording layer. However, it was not satisfactory in terms of ink acceptability. In JP-A-2006-281470 (Patent Document 8), stain resistance is improved by a lithographic printing plate having a hydrophilic layer containing a polyacrylic acid compound having an average molecular weight of 10,000 or more on the outermost layer. However, in a printing machine equipped with an automatic printing process, background stains and ink entanglement may occur immediately after the start of printing, and further improvements have been desired. On the other hand, JP-A-8-90913 (Patent Document 9) discloses a heat-sensitive recording material having a protective layer containing a polyether-modified silicone oil. This is mainly for the purpose of preventing sticking. is there.

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 Laid-Open No. 2-167798 JP 2006-281470 A JP-A-8-90913

  An object of the present invention is to provide a heat-sensitive lithographic printing plate excellent in ink acceptability, which is free from background stains and ink entanglement immediately after the start of printing, even when a printing press equipped with an automatic printing process is used.

  The object of the present invention is to have an image forming layer containing a thermoplastic resin, a heat-meltable substance, and a hydrophilic binder on a support, the heated portion of the image forming layer as an image portion, and the image forming layer. A heat-sensitive lithographic printing plate using a non-heated portion of the heat-sensitive lithographic printing plate as a non-image portion, wherein the heat-sensitive lithographic printing plate has an outermost layer containing polyether-modified polydimethylsiloxane on the image-forming layer Achieved by.

  According to the present invention, even when a printing press equipped with an automatic printing process is used, it is possible to provide a thermal lithographic printing plate which is free from background stains and ink entanglement immediately after the start of printing and has excellent ink acceptability.

  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 hydrophilic binder on a support, and further polyether-modified polydimethyl ester on the image-forming layer. It has an outermost layer containing siloxane. This heat-sensitive lithographic printing plate is heated and drawn with a thermal head or an infrared laser, so that the thermoplastic resin buried in the hydrophilic binder at the part where heat is applied through the outermost layer containing the polyether-modified polydimethylsiloxane. In addition, the hot-melt material causes melting and exhibits hydrophobicity. On the other hand, the thermoplastic resin and the heat-meltable material at a portion where heat is not applied remain buried in the hydrophilic binder and do not exhibit hydrophobicity, and maintain the hydrophilicity originally possessed by the image forming layer. And the thermal lithographic printing plate of the present invention has scumming or ink entanglement immediately after the start of printing even when using a printing machine having an automatic printing process by having an outermost layer containing polyether-modified polydimethylsiloxane. A heat-sensitive lithographic printing plate excellent in ink acceptability can be obtained.

  The reason why the above-described effects can be obtained by the present invention is not clear, but is presumed as follows. Normally, in a printing press that also has an automatic printing process, after the etched printing plate is manually or automatically mounted on the plate cylinder, the pre-wetting process (the surface of the printing plate by the water foam roller) is pressed by pressing the print start button. Pre-wetting process to moisten the ink)-Inking process (Process for supplying ink onto the printing plate using an ink foam roller)-Imaging process (Plate cylinder-Rubber cylinder enters into a cylinder state, and the image is transferred to the rubber cylinder) The printing paper is automatically sent through the process and printing is started. At that time, in the image portion of the heat-sensitive lithographic printing plate of the present invention, the polyether-modified polydimethylsiloxane is quickly dissolved and removed by the water supplied to the plate surface, which may reduce the ink acceptability immediately after the start of printing. On the other hand, the hydrophilicity is improved by the polyether-modified polydimethylsiloxane in one non-image area, so that it is estimated that the background stain and ink entanglement are improved.

  The polyether-modified polydimethylsiloxane contained in the outermost layer of the heat-sensitive lithographic printing plate of the present invention is, for example, a non-reacting system in which polyalkylene oxide such as polyethylene oxide or polypropylene oxide is introduced into both ends or side chains of polydimethylsiloxane. Polydimethylsiloxane. Specifically, KF-351A, KF-6204, etc. manufactured by Shin-Etsu Chemical Co., Ltd., BYK-302, BYK-307, BYK-331, BYK-333, etc., manufactured by Big Chemie Japan, These can be used alone or in combination of two or more.

The content of the polyether-modified polydimethylsiloxane contained in the outermost layer of the heat-sensitive lithographic printing plate of the present invention is preferably 0.01 to 1.0 g / m ^2, more preferably 0.05 to 0.5 g / m ^2. . If it is less than this range, the background stain at the start of printing and ink entanglement in the halftone dot image area are likely to occur. Although not generated, it is not preferable because the number of printed sheets until the ink density in the image area reaches a desired density may increase.

  In addition, the outermost layer of the heat-sensitive lithographic printing plate of the present invention can contain antiseptics, surfactants, antifoaming agents, leveling agents, pH adjusters, other coating aids, and the like as necessary. The ratio of these to the outermost layer is preferably 5% by mass or less with respect to the total solid content of the outermost layer, and is coated on the image forming layer described later. Examples of the outermost layer coating method include a method in which the image forming layer is applied, and then the outermost layer is sequentially applied and stacked, and a method in which the image forming layer and the outermost layer are applied in layers by a slide hopper method or the like. Either method can be used.

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

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

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

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

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

  The image forming layer of the heat-sensitive lithographic printing plate of the present invention preferably contains a crosslinking agent in order to improve the film strength, adhesive strength, etc. of the image forming layer. As examples of the crosslinking agent, melamine resin, epoxy resin, polyisocyanate compound, aldehyde compound, silane compound, chromium alum, divinyl sulfone and the like can be suitably used. A particularly preferred crosslinking agent is divinyl sulfone. Further, the necessary water resistance and mechanical strength can be obtained, and the content of the crosslinking agent is 1 with respect to the solid content of the hydrophilic binder contained in the image forming layer from the viewpoint of avoiding characteristic fluctuations with time during storage. -30 mass% is preferable, More preferably, it is the range of 2-20 mass%.

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

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

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

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

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

  In addition, in the present invention, the image forming layer may contain antiseptics, surfactants, antifoaming agents, leveling agents, pH adjusting agents, other coating aids, and the like as necessary.

  Further, the image forming layer of the heat-sensitive lithographic printing plate of the present invention can be divided not only into a single layer but also into a multilayer structure. In that case, the ratio of the thermoplastic resin to the hydrophilic binder of the image forming layer close to the support may be higher than the ratio of the thermoplastic resin to the hydrophilic binder of the image forming layer remote from the support. preferable.

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

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

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

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

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

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

Example 1
First, the following image forming layer A coating solution was applied to one side of a polyethylene-coated paper having a thickness of about 180 μm and laminated on both sides so that the moisture application amount was 30 g / m ² . The coating film was gelled with cold air, and then dried with hot air at 30 ° C. Subsequently, the following image forming layer B coating solution was applied onto the image forming layer A so that the moisture application amount was 10 g / m ^2, and the coating film was gelled with cold air at 3 ° C. in the same manner. Thereafter, drying was performed with hot air of 30 ° C.

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

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

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

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

Next, the following outermost layer coating solution-1 was applied onto the image forming layer B so that the moisture application amount was 10 g / m ^2, and dried with hot air at 30 ° C. After drying, the thermosensitive lithographic printing plate of Example 1 was obtained by heating for 7 days using a thermo-hygrostat adjusted to a temperature of 40 ° C. and a humidity of 40%.
<Outermost layer coating solution-1>
0.01 part of polyether-modified polydimethylsiloxane A (BYK-302, manufactured by BYK Japan)
9.99 parts of water

(Example 2)
A heat-sensitive lithographic printing plate of Example 2 was obtained in the same manner as in Example 1 except that the outermost layer coating solution-1 of Example 1 was changed to the outermost layer coating solution-2 shown below.
<Outermost layer coating solution-2>
0.05 parts of polyether-modified polydimethylsiloxane A (BYK-302, manufactured by BYK Japan KK)
9.95 parts of water

(Example 3)
A heat-sensitive lithographic printing plate of Example 3 was obtained in the same manner as in Example 1 except that the outermost layer coating solution-1 of Example 1 was changed to the outermost layer coating solution-3 below.
<Outermost layer coating solution-3>
0.5 parts of polyether-modified polydimethylsiloxane A (BYK-302, manufactured by BYK Japan)
9.5 parts of water

Example 4
A heat-sensitive lithographic printing plate of Example 4 was obtained in the same manner as in Example 1 except that the outermost layer coating solution-1 of Example 1 was changed to the outermost layer coating solution-4 shown below.
<Outermost layer coating solution-4>
Polyether-modified polydimethylsiloxane A 1.0 part (BYK-302, manufactured by BYK Japan KK)
9.0 parts of water

(Example 5)
A heat-sensitive lithographic printing plate of Example 5 was obtained in the same manner as in Example 1 except that the outermost layer coating solution-1 of Example 1 was changed to the following outermost layer coating solution-5.
<Outermost layer coating solution-5>
0.5 parts of polyether-modified polydimethylsiloxane B (BYK-307, manufactured by BYK Japan)
9.5 parts of water

(Example 6)
A heat-sensitive lithographic printing plate of Example 6 was obtained in the same manner as in Example 1 except that the outermost layer coating solution-1 of Example 1 was changed to the following outermost layer coating solution-6.
<Outermost layer coating solution-6>
0.5 parts of polyether-modified polydimethylsiloxane C (BYK-333 manufactured by Big Chemie Japan Co., Ltd.)
9.5 parts of water

(Example 7)
A heat-sensitive lithographic printing plate of Example 7 was obtained in the same manner as in Example 1 except that the outermost layer coating liquid-1 of Example 1 was changed to the following outermost layer coating liquid-7.
<Outermost layer coating solution-7>
0.25 part of polyether-modified polydimethylsiloxane A (BYK-302 manufactured by Big Chemie Japan Co., Ltd.)
0.25 part of polyether-modified polydimethylsiloxane C (BYK-333 manufactured by Big Chemie Japan Co., Ltd.)
9.5 parts of water

(Comparative Example 1)
A thermal lithographic printing plate of Comparative Example 1 was prepared by applying the image forming layer A and the image forming layer B in the same manner as in Example 1 except that the outermost layer coating solution of Example 1 was not applied.

(Comparative Example 2)
As in Comparative Example 1, the outermost layer coating solution was not applied, and 0.5 parts of polyether-modified polydimethylsiloxane (BYK-302 manufactured by BYK Japan Japan Co., Ltd.) was added to the image forming layer B coating solution. In the same manner as in Example 1 except that the moisture application amount was 10.5 g / m ² , the thermal lithographic printing of Comparative Example 2 was provided with the image forming layer A and the image forming layer B. It was a version.

(Comparative Example 3)
A heat-sensitive lithographic printing plate of Comparative Example 3 was obtained in the same manner as in Example 1 except that the outermost layer coating solution-1 of Example 1 was changed to the outermost layer coating solution-8.
<Outermost layer coating solution-8>
Flat zinc stearate 0.5 part (manufactured by NOF Corporation, Nissan Electol MZ-2)
9.5 parts of water

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

<Printability evaluation>
Offset printing sheet double-sided printing machine RYOBI3200PCX with automatic printing process for the printing machine, New Champion F gloss ink S manufactured by DIC Corporation for ink, and 3% dilution for TDP-DL3 manufactured by Mitsubishi Paper Industries Co., Ltd. for dampening liquid The liquid and the etchant were printed using a TDP-HL 25% diluted solution manufactured by Mitsubishi Paper Industries Co., Ltd. In the automatic printing process, the etched printing plate is set in an automatic plate feeder and then the start button is pressed, so that the printing plate is mounted on the plate cylinder to the pre-wetting process (the surface of the printing plate by the water foam roller is removed). Pre-wetting step for moistening)-Inking step (Step for supplying ink onto printing plate with ink foam roller)-Imaging step (Plate cylinder-Rubber cylinder is put into cylinder, and image is transferred to rubber cylinder) The printing paper is automatically sent and printed through the process. First, the etchant is wiped thoroughly on the surface of the printing plate using absorbent cotton, then set in an automatic plate feeder and printing is started. Ink scumming in the background stain or halftone dot image portion was determined according to the following evaluation criteria.

<Ink acceptability evaluation criteria>
The density of the solid image portion of the printed material was measured with a reflection densitometer DM-620 manufactured by Dainippon Screen Mfg. Co., Ltd.
○: 10 or less △: 11 or more and 30 or less ×: 31 or more

<Evaluation criteria for ink stains on non-image area and halftone image area immediately after printing starts>
The number of printed sheets on which the non-image portion of the printed matter was free from background stain and the halftone image portion (80% or less) could be printed without ink entanglement was visually evaluated.
○: 10 or less △: 11 or more and 30 or less ×: 31 or more

  As can be seen from the results shown in Table 1, according to the present invention, even when a printing machine equipped with an automatic printing process is used, there is no background stain or ink entanglement immediately after the start of printing, and thermal lithographic printing with excellent ink acceptability. It can be seen that a plate can be obtained.

Claims (1)

  An image forming layer containing a thermoplastic resin, a heat-meltable substance, and a hydrophilic binder is provided on a support, the heated portion of the image forming layer is an image portion, and the non-heated portion of the image forming layer is a non-image. A heat-sensitive lithographic printing plate used as a part, comprising an outermost layer containing polyether-modified polydimethylsiloxane on the image forming layer.