JP2005288930A - Lithographic printing original plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithographic printing original plate for CTP, which is exposed to light in near infrared region, can be dealt with in a bright room, onto which drawing can be directly performed with laser beams, neither development nor wiping operation of which is made necessary, which is excellent in printability and in which the visibility (plate inspecting properties) of an exposed image after exposure is improved. <P>SOLUTION: This lithographic printing original plate has a hydrophilic resin photosensitive layer having a property that the hydrophilic nature of the surface of an exposed part turns into an ink-philic nature by being exposed with laser under the condition that the hydrophilic resin photosensitive layer includes fine polymer particles having voids within and/or a zirconium compound in order to improve the visibility of the exposed part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a printing original plate, and more particularly to a lithographic printing original plate using a fountain solution. In particular, it relates to an original for lithographic printing that is sensitive to near-infrared light, can be handled in a bright room, can be directly drawn on a plate with laser light, and does not require any development or wiping operation. More specifically, the present invention relates to a lithographic printing original plate in which the visibility (plate inspection) of an exposed portion after laser exposure is remarkably improved.

  Lithographic printing, so-called offset printing, is mainstream in printing on paper and is widely used. Conventionally, the printing plate used in this offset printing is to print a printed document once on paper, etc., then photograph the document to create a printing film, and expose and develop a photosensitive printing plate through the printing film. It was made by doing.

  However, in recent years, in the production of printing plates by digitizing information and increasing the output of lasers, a plate is created by scanning the laser and drawing directly on the printing plate without using the above-mentioned underprint film. A so-called CTP (Computer To Plate) method has been put to practical use. As a master plate for CTP currently in practical use, there is a photopolymer type printing plate using a photoreaction by visible light having a wavelength of around 500 nm, but this plate not only requires development but also has poor resolution. Also, there is a problem that it cannot be handled in the light room.

  In order to improve such problems, in addition to the development type lithographic printing original plate using the thermal reaction by the light irradiation in the near infrared region, the material of the part is removed by the near infrared light irradiation. An ablation type lithographic printing original plate that forms an image line portion has been proposed, but in this case as well, there are problems such as requiring wiping operation of the plate surface and requiring a lot of energy for exposure. .

  On the other hand, the present inventors comprise a hydrophilic resin photosensitive layer obtained by cross-linking an aqueous photosensitive resin composition containing a hydrophilic polymer, a crosslinking agent, a hydrophobic polymer and a light absorber. Has developed a lithographic printing plate that changes from hydrophilic to ink-philic. (Patent Document 1 (International Publication No. 01/083234)). This original plate is excellent in sensitivity and resolution because development and wiping operations are unnecessary and only the surface of the light irradiation part changes. However, on the other hand, when the hydrophilicity of the exposed portion surface changes to ink-philicity due to laser exposure, the change in the appearance of the plate surface may not necessarily be large, and the exposure image on the plate before printing may not be large. There is a need to improve the ease of content confirmation (plate inspection).

Here, Patent Document 2 (Japanese Patent Application Laid-Open No. 2001-260552) discloses a thermosensitive material having a heat-sensitive layer on a support, and polymer fine particles having voids in the heat-sensitive layer. A technology relating to a lithographic printing plate has been disclosed. By adding polymer fine particles having voids inside the plate, heat diffusion is suppressed, and heat generated by photothermal conversion can be efficiently used for image formation. It is described that the energy can be reduced and the writing time can be shortened, and at the same time, a low-power and inexpensive laser can be used, thereby reducing the cost of the system. However, since the lithographic printing original plate described in the patent is mainly for the development type, the plate inspection before the development after the normal exposure is not required, and the visibility of the exposed image (plate inspection) ) Is not described at all.
International Publication No. 01/083234 JP 2001-260552 A

  The object of the present invention is to be sensitive to light in the near-infrared region, can be handled in a bright room, can be directly drawn on the plate with laser light, and can eliminate the need for development and wiping operations, making it suitable for printing. An object of the present invention is to provide a lithographic printing original plate for CTP which is excellent and has improved visibility (plate inspection) of an exposed image after exposure.

As a result of intensive studies, the present inventors have added a specific material, compound, or the like to the hydrophilic resin photosensitive layer having the property that the hydrophilicity of the exposed portion surface changes to ink affinity by laser exposure. The inventors have found that the object can be achieved and have reached the present invention. That is, the present invention is as follows.
(1) A lithographic printing original plate having a hydrophilic resin photosensitive layer having a property that the hydrophilicity of the exposed portion surface changes to ink-philicity by laser exposure on a support, wherein the hydrophilic resin photosensitive layer is An original plate for lithographic printing, which is obtained by crosslinking a photosensitive resin composition containing polymer fine particles having voids therein and / or a zirconium compound, preferably
(2) The lithographic printing original plate as described in (1) above, which is capable of printing immediately after laser exposure according to a printed image, more preferably,
(3) The lithographic printing original plate according to (1) or (2), wherein the photosensitive resin composition further contains a hydrophilic polymer, a crosslinking agent, a hydrophobic polymer, and a light absorber.

  By using the lithographic printing original plate of the present invention, it is sensitive to light in the near-infrared region, can be handled in a bright room, can be drawn directly with laser light, and only the surface of the laser irradiation part changes, so sensitivity and resolution are improved. It is possible to provide an original plate for lithographic printing for CTP which is excellent and can eliminate steps such as development and wiping, and has improved visibility (plate inspection) of an exposed image.

The original plate for lithographic printing according to the present invention will be described in detail below.
The lithographic printing original plate of the present invention is a lithographic printing plate having a hydrophilic resin photosensitive layer having a property that the hydrophilicity of the exposed portion surface changes to ink-philicity by laser exposure directly or via another layer on a support. It is a printing master. The support used in this case is not particularly limited, and specific examples include metal plates such as aluminum plates, steel plates, stainless steel plates, and copper plates, and plastic films such as polyester, nylon, polyethylene, polypropylene, polycarbonate, and ABS resin. Paper, aluminum foil laminated paper, metal vapor deposited paper, plastic film laminated paper and the like can be mentioned. The thickness of these supports is not particularly limited, but is usually about 100 to 400 μm. Further, these supports may be subjected to surface treatment such as oxidation treatment, chromate treatment, sand blast treatment, corona discharge treatment, etc. in order to improve adhesion.

  Further, in order to improve the adhesion to the photosensitive layer or prevent the diffusion of heat, an underlayer such as a polymer may be used. The polymer used for this is not particularly limited as long as it is a polymer having adhesion between the substrate and the photosensitive layer and mechanical strength. In addition, adhesion and mechanical strength can be further increased by adding a filler to the polymer to create irregularities on the polymer surface as a primer and increase the contact area with the photosensitive layer. The underlayer may be cross-linked or not cross-linked. The underlayer can be formed by a method in which it is dissolved in an organic solvent and applied. Further, an aqueous polymer solution or an emulsion polymer can be used without using an organic solvent. In particular, the use of an emulsion polymer of the same resin as the hydrophobic polymer used in the hydrophilic photosensitive layer for the undercoat layer is desirable because the adhesion between the hydrophilic photosensitive layer and the undercoat layer layer becomes stronger and the printing durability is improved.

  Next, the hydrophilic resin photosensitive layer in the present invention will be described in detail. The lithographic printing plate precursor of the present invention is preferably a lithographic printing plate using a fountain solution, except for the light-irradiated part of the hydrophilic resin photosensitive layer, which becomes a non-image part as it is, and the photosensitive layer of the part irradiated with light is Rather than being removed by ablation, the surface of the exposed area can be changed from hydrophilic to ink-philic to form an image area. Therefore, the original plate of the present invention can be an undeveloped lithographic printing original plate that can eliminate the need for development or wiping after light irradiation.

  On the other hand, due to these characteristics, there is a case where the change in the appearance of the plate surface is not necessarily large when the hydrophilicity of the exposed portion surface is changed to the ink-philic property by laser exposure. Before printing, it may be necessary to visually check the exposed image on the plate, that is, plate inspection. In order to facilitate this, in the present invention, polymer fine particles having voids in the hydrophilic resin photosensitive layer and It has been found that it is important to contain a zirconium compound, and the visibility (plate inspection) of an exposed image can be improved by adding these compounds.

  Examples of the polymer fine particles having voids therein used in the present invention include those described in “Material Technology Vol. 11, No. 3.1993” and the like. Examples of the general production method include emulsion polymerization, gas foaming type suspension polymerization and the like.

  These polymer fine particles having voids inside are used for improving the concealment and reducing the weight as pigments for paints and coated papers, as well as providing thermal insulation as pigments for thermal papers. Applications such as suppressing heat diffusion and improving color development quality are known. As long as the object of the present invention is not impaired, the porosity of the particles (outer diameter and inner diameter = volume fraction of void portion calculated from the diameter of the void portion) is not particularly limited, but preferably 5 to 70%, More preferably, it is 10 to 60%. The particle diameter (outer diameter) is preferably 2 μm or less, more preferably 1 μm or less, and further preferably 0.1 μm or more and 0.5 μm or less from the viewpoint of the thickness of the hydrophilic resin photosensitive layer.

  As a method for producing these polymer fine particles having voids in the interior, for example, an emulsion-swelling core particle prepared by copolymerization of a carboxyl group-containing monomer is used as a seed, and styrene and / or (meta) Examples include those prepared by further alkali-treating core / shell type particles in which a shell layer is formed by additional addition / emulsion copolymerization of an acrylate-based monomer, etc. Absent.

  In the present invention, the amount of the polymer fine particles having voids in the interior is preferably 0.1% in terms of the solid content of the polymer fine particles having voids in the total amount of 100 parts by weight of the solid content in the photosensitive resin composition of the present invention. 5 to 30 parts by weight, more preferably 1 to 25 parts by weight.

Examples of the zirconium compound used in the present invention include zirconium hydroxide, zirconium sulfate, zirconium carbonate, zirconium nitrate, zirconium acetate, zirconium stearate, zirconium phosphate and the like, or ammonium salts and sodium salts thereof. A water-soluble or water-dispersible zirconium compound is preferable, and a water-soluble zirconium compound is more preferable. As a specific example, BACOTE ^™ 20 (manufactured by Magnesium Electron Co., Ltd.) is available as a commercially available product, which usually improves the water resistance strength of coated paper, improves heat resistance / wear resistance, and ink acceptability. It is said that it is highly safe and is particularly suitable for use as a waterproofing agent for binders such as paper containers and wrapping paper that come into contact with foodstuffs. When the zirconium compound is used in the present invention, its working factor is not clear, but the visibility (plate inspection) of the exposed portion of the lithographic printing original plate of the present invention is greatly improved.

  In the present invention, the amount of the zirconium compound used is preferably 0.1 to 20 parts by weight, more preferably 0.5 parts by weight in terms of the active ingredient of the zirconium compound with respect to 100 parts by weight of the total solid content in the photosensitive resin composition. In this case, the visibility (plate inspection) of the exposed portion of the lithographic printing original plate can be greatly improved.

  In the present invention, polymer fine particles having voids therein and / or zirconium compounds can be used alone or in combination, and several kinds of each may be used. In that case, when the addition amount of each component is within the above range, the plate inspection property is sufficiently improved, and the hydrophilicity of the hydrophilic resin photosensitive layer is not deteriorated, and the occurrence of stains at the time of printing. This is preferable because problems such as these are unlikely to occur.

  Furthermore, the photosensitive resin composition forming the hydrophilic resin photosensitive layer of the present invention preferably contains a hydrophilic polymer, a crosslinking agent, a hydrophobic polymer, and a light absorber. The photosensitive resin composition is preferably cross-linked after being applied to a support, and particularly preferably has a separation structure composed of a hydrophilic polymer phase and a hydrophobic polymer phase. The hydrophilic polymer can impart high water resistance that is not dissolved / removed in water by crosslinking.

  The hydrophilic polymer that can be used in the photosensitive resin composition for forming the hydrophilic resin photosensitive layer of the present invention has a hydrophilic group and a functional group that reacts with a crosslinking agent (crosslinkable functional group). desirable. Examples of the hydrophilic group of the hydrophilic polymer include hydroxyl groups, amide groups, amino groups, sulfonamido groups, oxymethylene groups, oxyethylene groups, and acidic groups such as carboxyl groups, sulfonic acid groups, and phosphonic acid groups. Alkali metal salts, alkaline earth metal salts, amine salts, and the like.

  The crosslinkable functional group includes a hydroxyl group, an amide group, an amino group, an isocyanate group, a glycidyl group, an oxazoline group, a methylol group, and a methoxymethyl group or a butoxymethyl group in which a methylol group is condensed with an alcohol such as methanol or butanol. And an alkoxy group such as carboxyl group, sulfonic acid group and phosphonic acid group, and alkali metal salts, alkaline earth metal salts and amine salts thereof.

  More specific examples of the hydrophilic polymer include the following polymers. Namely, saponified products of polyvinyl acetate, celluloses, gelatin, unsaturated monomers having hydrophilic groups and crosslinkable functional groups, N-vinylacetamide, N-vinylformamide, vinyl acetate, vinyl ether, etc. Examples thereof include polymers obtained by polymerization and copolymerization, and hydrolyzed polymers thereof.

  As specific examples of the unsaturated monomers having a hydrophilic group or a crosslinkable functional group, hydroxyethyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, Hydroxypropyl (meth) acrylate, polypropylene glycol mono (meth) acrylate, hydroxybutyl (meth) acrylate, methylol (meth) acrylamide, and methoxymethyl (which is a condensate of methylol (meth) acrylamide and methyl alcohol or butyl alcohol) And meth) acrylamide and butoxymethyl (meth) acrylamide.

  Examples of unsaturated monomers having an amide group include unsubstituted or substituted (meth) acrylamide, unsubstituted or substituted itaconic acid amide, unsubstituted or substituted fumaric acid amide, unsubstituted or substituted phthalic acid amide, N-vinylacetamide , N-vinylformamide and the like. More specific examples of unsubstituted or substituted (meth) acrylamide include (meth) acrylamide, N-methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-ethyl (meth) acrylamide, N, N- Diethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N-isopropyl (meth) acrylamide, diacetone (meth) acrylamide, methylol (meth) acrylamide, methoxymethyl (meth) acrylamide, butoxymethyl (meth) ) Acrylamide, propyl (meth) acrylamide, (meth) acryloylmorpholine, and the like. In the case of the dibasic acid amide such as itaconic acid amide, a monoamide in which one carboxyl group is amidated or a diamide in which both carboxyl groups are amidated may be used. Furthermore, examples of unsaturated monomers having a glycidyl group include glycidyl (meth) acrylate and paravinylphenyl glycidyl ether.

  Examples of unsaturated monomers having a carboxyl group include monobasic unsaturated acids such as (meth) acrylic acid, dibasic unsaturated acids such as itaconic acid, fumaric acid and maleic acid, and anhydrides thereof, monoesters and monoamides. Etc.

  Examples of unsaturated monomers having a sulfonic acid group include sulfoethyl (meth) acrylate, (meth) acrylamidomethylpropanesulfonic acid, vinylsulfonic acid, vinylmethylsulfonic acid, isopropenylmethylsulfonic acid, (meth) Sulfuric acid ester of ethylene acid or propylene oxide added to acrylic acid (for example, Eleminol RS-30 from Sanyo Chemical Industries), (meth) acryloyloxyethyl sulfonic acid, monoalkylsulfosuccinic acid ester and allyl group Reaction with a compound having an ester (for example, Eleminol JS-2 from Sanyo Chemical Industries, Ltd., Latemu S-180 or S-180S from Kao Corporation), monoalkylsulfosuccinate and glycidyl (meth) acrylate Product and Japanese milk Antox MS60 etc. of the agent Co., Ltd. has a monounsole (2- (2-hydroxyethyl) (meth) acrylate, monophosphoric acid ester of vinyl phosphoric acid, phosphoric acid mono (2-hydroxyethyl) as a polymerizable unsaturated monomer having a phosphonic acid group. Hydroxyethyl) (meth) acrylate and the like.

  These carboxyl group, sulfonic acid group and phosphonic acid group may be neutralized with an alkali metal, an alkaline earth metal or an amine. As alkali metals used for neutralization, sodium, potassium, lithium and the like, as alkaline earth metals calcium, magnesium and the like, as amines, ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, Examples include triethylamine, monoethanolamine, diethanolamine, triethanolamine, (di) methylethanolamine, (di) ethylethanolamine, and the like.

  In the polymerization, one or more of the unsaturated monomers having the hydrophilic group or the crosslinkable functional group may be used, and further, copolymerizable with these unsaturated monomers. A monomer may be used in combination. Examples of the copolymerizable monomer include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, glycidyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylamino Ethyl (meth) acrylate, phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, isopolonyl (meth) acrylate, adamantyl (meth) acrylate, cyclohexyl (meth) acrylate, styrene, α-methylstyrene, acrylonitrile, methacrylonitrile, Examples include vinyl acetate.

  In the above description, (meth) acryl, (meth) acryloyl, (meth) acrylate, and the like in (meth) acrylamide and (meth) acrylic acid are acrylic or methacrylic, acryloyl or methacryloyl, It means acrylate or methacrylate.

  The hydrophilic polymer that can be used in the present invention is unsubstituted or substituted (meta) from the viewpoint of easy ink-philicity of the photosensitive layer when irradiated with light, and excellent hydrophilicity and water resistance of the photosensitive layer. ) Polymers mainly composed of one or more monomers selected from acrylamide, N-vinylformamide, and N-vinylacetamide are preferred, and among substituted (meth) acrylamides, monomethyl (meth) acrylamide, dimethyl ( Preferred are meth) acrylamide, monoethyl (meth) acrylamide, diethyl (meth) acrylamide, and hydroxymethyl (meth) acrylamide.

  As a crosslinking agent used for the purpose of crosslinking the hydrophilic polymer in the present invention, a crosslinking reaction with the hydrophilic polymer is mainly performed to give the hydrophilic resin photosensitive layer high water resistance that is not dissolved or removed in water. For example, a known many group which reacts with a hydroxyl group, a carboxyl group, a sulfonic acid group, a glycidyl group, and in some cases an amide group, which are crosslinkable functional groups in the hydrophilic polymer. Examples thereof include polyhydric alcohol compounds, polyvalent carboxylic acid compounds and anhydrides thereof, polyvalent glycidyl compounds, polyvalent amines, polyvalent isocyanate compounds and blocked isocyanate compounds, epoxy resins, oxazoline resins, amino resins and the like.

  Among the above-mentioned crosslinking agents in the present invention, water-based epoxy resins, oxazoline resins, amino resins, water-based blocks are considered from the viewpoint of the balance between the crosslinking speed and the stability of the photosensitive resin composition and the hydrophilicity and water resistance of the photosensitive layer. Isocyanate compounds are preferred. Examples of amino resins include melamine resins, urea resins, benzoguanamine resins and glycoluril resins, and modified resins of these resins, such as carboxy-modified melamine resins. In order to accelerate the crosslinking reaction, tertiary amines are used in combination with the above-mentioned epoxy resins, and acidic compounds such as paratoluenesulfonic acid, alkylbenzenesulfonic acids, ammonium chloride are used in combination with amino resins. May be.

  The main role of the cross-linking agent is to cross-link the hydrophilic polymer and to give the hydrophilic resin photosensitive layer high water resistance that is not dissolved / removed with respect to water. When the cross-linking agent forms a polymer island phase in the hydrophilic polymer in the photosensitive layer, and the light absorber in the photosensitive layer absorbs light and converts light energy into heat energy, It includes that the island phase is foamed by the generated heat and the hydrophilicity of the surface of the light-irradiated portion is changed to the ink affinity.

  The hydrophobic polymer used in the photosensitive resin composition for forming the hydrophilic resin photosensitive layer of the present invention is preferably a polymer that forms a phase different from the hydrophilic polymer phase when the photosensitive layer is formed, Examples include ordinary polymers and polymer precursors that are polymerized to form a polymer when forming a photosensitive layer. From the viewpoint of ease of blending with hydrophilic polymers, water-dispersed polymers and polymers that are soluble in aqueous solvents And polymer precursors soluble in aqueous solvents are preferred. The term “aqueous” as used herein means a mixture of water alone and a water-miscible solvent such as methanol, ethanol, and acetone, mainly water. The aqueous dispersion polymer means polymer particles composed of fine polymer particles dispersed in an aqueous medium and a protective agent that covers the particles as necessary, and emulsion polymerization or suspension polymerization of unsaturated monomers. Disperse polymer particles produced by, hydrophobic polymer fine particles dispersed in an aqueous medium, and an organic solvent solution of hydrophobic polymer in an aqueous medium, and distill off the organic solvent as necessary. There are self-emulsification (dispersion) type and forced emulsification (dispersion) type. These aqueous dispersion polymers may or may not be crosslinked. More specifically, examples of the aqueous dispersion polymer include an aqueous dispersion vinyl polymer, a conjugated diene polymer latex, an acrylic emulsion, an aqueous dispersion polyurethane resin, an aqueous dispersion polyester resin, and an aqueous dispersion epoxy resin. .

  The role of the aqueous dispersion polymer is to form an island phase in the hydrophilic polymer in the photosensitive layer, and the light absorber in the photosensitive layer absorbs light and converts light energy into heat energy. It is presumed that the island-phase aqueous dispersion polymer is melted and fused by the heat generated at this time, and the hydrophilicity of the surface of the light-irradiated portion is changed to the ink affinity. Effectively causing this characteristic change due to light irradiation, improving the sensitivity and resolution of the lithographic printing original plate of the present invention, improving the characteristics such as eliminating the occurrence of background stains, and from the point of thinning the photosensitive layer, etc. The aqueous dispersion type polymer preferably has an average particle diameter measured by a dynamic light scattering method of 0.005 to 0.5 μm, more preferably 0.01 to 0.2 μm. The film forming temperature of the aqueous dispersion polymer is preferably 50 ° C. or lower, and desirably 30 ° C. or lower. In particular, an acrylic emulsion, an aqueous dispersion type polyurethane resin, and an aqueous dispersion type polyester resin having an average particle diameter of 0.005 to 0.5 μm and a film forming temperature of 50 ° C. or less are preferable.

  The amount of the hydrophobic polymer used in the photosensitive resin composition for forming the hydrophilic resin photosensitive layer of the present invention is preferably large from the viewpoint of making the light-irradiated part an ink-philic ink. There is a possibility of waking up. From this point, the amount of the hydrophobic polymer in the photosensitive resin composition in the present invention is preferably 70% by weight or less, and more preferably 10% by weight to 60% by weight as a solid content.

  The light absorber used in the photosensitive resin composition for forming the hydrophilic resin photosensitive layer of the present invention may be any one that absorbs light and generates heat, and the light absorber absorbs upon light irradiation. Light in a wavelength range may be used as appropriate. Specific examples of light absorbers include cyanine dyes, polymethine dyes, phthalocyanine dyes, naphthalocyanine dyes, anthracocyanine dyes, porphyrin dyes, azo dyes, benzoquinone dyes, naphthoquinone dyes, dithiol metal complexes , Metal complexes of diamine, various pigments such as nigrosine, and carbon black.

  Of these dyes, dyes that absorb light in the wavelength region of 750 to 1100 nm are preferable from the viewpoint of handling in a bright room, output of a light source used in an exposure machine, and ease of use. The absorption wavelength range of the dye can be changed depending on the length of the substituent or the conjugated system of π electrons. These light absorbers may be dissolved or dispersed in the photosensitive resin composition. Among the light absorbers described above, a hydrophilic light absorber is preferred in the present invention.

  Furthermore, in the photosensitive resin composition of the present invention, in order to control the hydrophilicity and ink affinity of the surface before and after laser exposure, a hydrophilic addition having a hydrophilic substituent is provided so long as the object of the present invention is not impaired. An agent can be contained. Here, the hydrophilic substituent is, for example, a hydroxyl group, an amide group, an amino group, a sulfonamide group, an oxymethylene group, an oxyethylene group, or an acidic group such as a carboxyl group, a sulfonic acid group, or a phosphonic acid group. These alkali metal salts, alkaline earth metal salts, amine salts and the like can be mentioned.

  The hydrophilic additive is preferably one that dissolves in water or an organic solvent, which increases the hydrophilicity of the printing plate surface by its addition and acts so that dampening water adheres to the surface immediately after the start of printing. Any compound can be used as long as it is a surfactant, a compound having a hydroxyl value of 500 mg-KOH / g or more, and among the hydrophilic polymers of the present invention, a crosslinking agent in the photosensitive resin composition A hydrophilic polymer substantially free of reactive crosslinkable functional groups is preferably used. Here, the hydroxyl value is a calculated value of the number of mg of KOH necessary for neutralizing the hydroxyl group in 1 g of the substance.

  Examples of the surfactant that can be used as the hydrophilic additive of the present invention include nonionic surfactants, and specific examples include polyethylene glycol types such as polyoxyethylene alkyl ether, polyoxyethylene polypropylene glycol ether, and polyoxyethylene. Alkyl phenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyoxyethylene alkylamine and the like, and polyhydric alcohol types such as alkyl alkanolamide, glycerin fatty acid ester, sucrose fatty acid ester, Sorbitan fatty acid ester, activator made from palm oil and castor oil, polyethylene glycol, alkylphenyl ether, alkyl ether, alkylallyl Ether, and the active agent lauryl ether system.

  Cationic activators can also be used. Examples thereof include primary amine salt systems, secondary amine salt systems, tertiary amine salt systems, quaternary ammonium salt systems, and quaternary pyridinium salt systems. , Lauryl imidazoline series, alkylamine series and the like. Amphoteric activators can also be used. Examples include alkylbetaines, amino acid types, sulfonic acid types, sulfate ester types, phosphate ester types, amine oxide types, polyoxyethylene alkylamine types, polyalkylene polyamine types, polyethylene Examples include amphoteric ones such as an imine type, a carboxylic acid type, and a sulfate type.

  Anionic activators can also be used, and specific examples thereof include sulfonate salts such as sodium alkylphenyl sulfonate, sodium alkyl naphthalene sulfonate, sodium alkyl allyl sulfonate, sodium naphthalene sulfonate, naphthalene sulfone. Examples thereof include sodium salts of acid formalin condensates, sodium polyoxyethylene alkylsulfosuccinate, sodium dialkylsulfosuccinate and sodium dialkylsulfosuccinate. Further, carboxylate salts such as sodium dialkyl succinate, sodium monoalkyl succinate, polycarboxylic acid and the like, sulfate salts such as alkyl diphenyl sulfate oxide, alkyl sulfate, sodium higher alcohol sulfate, Examples include sodium polyoxyethylene alkylsulfate ether or ammonium. Further, phosphate ester salts such as sodium alkyl ether phosphate and sodium alcohol phosphate can also be used. In particular, sodium dialkyl succinate and sodium monoalkyl sulfosuccinate are particularly preferable because the surface of the photosensitive layer is not easily eluted even when wet.

  Further, among the hydrophilic additives of the present invention, specific examples of compounds having a hydroxyl value of 500 mg-KOH / g or more include polyhydric alcohols such as glycerin, erythritol, mannitol, inositol, glucose, mannose, fructose, galactose, lactose. (Poly) saccharides such as cellobiose and maltose, cellulose and substituted products thereof, trishydroxycyclohexane, trishydroxybenzene, polyvinyl alcohol, glycoluril resin containing a hydroxyl group, and the like. The organic substance having a hydroxyl value of 500 mg-KOH / g or more that can be used in the photosensitive layer of the present invention may have an acid group. For example, pectinic acid, shikimic acid, gallic acid, carmic acid, tannic acid, diacid Examples include methylolpropionic acid, dimethylolbutyric acid, dimethylolvaleric acid, tartaric acid, gluconic acid, glycolic acid, hydroxypropionic acid, hydroxybutyric acid, and alkali metal salts and amine salts thereof. Among these, glucose, tannic acid, and hydroxymethyl type glycoluril resin are preferable.

  The hydrophilic additive of the present invention may be used singly or in combination of two or more, and the amount added is not particularly limited as long as the object of the present invention is not impaired. The range of 0.01-50 weight part is preferable with respect to 100 weight part of solid content of a hydrophilic polymer, a crosslinking agent, and a hydrophobic polymer in a resin composition. Moreover, in order to improve the applicability | paintability of the photosensitive resin composition, you may add additives, such as a repellency inhibitor, a leveling agent, and an antifoamer.

  The photosensitive resin photosensitive layer of the present invention is a photosensitive resin comprising fine polymer particles and / or a zirconium compound having voids therein, and more preferably a hydrophilic polymer, a crosslinking agent, a hydrophobic polymer and a light absorber. An aqueous dispersion of the composition may be applied to a substrate, dried and cured. The coating method varies depending on the viscosity and coating speed of the aqueous dispersion to be coated, but usually, for example, a roll coater, a blade coater, a gravure coater, a curtain flow coater, a die coater or a spray method may be used. Further, after coating, heat treatment is performed to dry and crosslink the hydrophilic resin photosensitive layer. The heating temperature is usually about 50 to 200 ° C.

  In the present invention, the ratio of the water-insoluble component in the hydrophilic resin photosensitive layer is preferably 60% by weight or more, preferably 70% by weight or more, and more preferably 80% by weight or more. The ratio of the water-insoluble component can be adjusted by appropriately changing the heating temperature and the heat treatment time, as well as the hydrophilic polymer, the crosslinking agent, and the hydrophobicity constituting the hydrophilic resin photosensitive layer of the present invention. Adjustment is also possible by changing the blending ratio of each component such as a polymer.

  Furthermore, depending on the combination of the hydrophilic polymer and the crosslinking agent, the hydrophilic additive may act as a catalyst for the crosslinking reaction in addition to imparting high hydrophilicity to the hydrophilic resin photosensitive layer. In such a system, it is possible to easily adjust the ratio of the water-insoluble component of the photosensitive layer without substantially impairing the hydrophilicity of the hydrophilic resin photosensitive layer of the present invention, and to shorten the crosslinking step. preferable. As such an example, for example, the hydrophilic polymer contains one or more substituents selected from a hydroxyl group, a methylol group, an alkoxymethyl group, an amide group, an amino group, and a carboxyl group, preferably a hydroxyl group. In the case of an amino resin, hydroxycarboxylic acids are exemplified. Specific examples include dimethylolpropionic acid, dimethylolbutyric acid, dimethylolvaleric acid, tartaric acid, gluconic acid, glycolic acid, hydroxypropionic acid, and hydroxybutyric acid.

  When the lithographic printing original plate of the present invention is irradiated with light in the absorption wavelength region of the light absorber, for example, light in the region of 750 to 1100 nm, the light absorber absorbs the light and generates heat. Due to this heat generation, the hydrophobic polymer or the self-polymerized cross-linking agent is thermally fused or foamed in the light-irradiated portion of the photosensitive layer, and the hydrophilicity is lost and the ink becomes ink-philic. At this time, if the light irradiation amount is excessively increased or a light absorber is added in a large amount, the photosensitive layer is removed and ablated by decomposition, combustion, etc., and decomposed products are formed around the irradiated portion. Such a thing must be avoided because it scatters.

  Thus, in the lithographic printing original plate of the present invention, the hydrophilicity of the surface of the photosensitive layer at the portion irradiated with light changes to ink-philic, and ink adheres to the light irradiated portion without performing development or wiping operation. And printing becomes possible.

  In the light irradiation of the lithographic printing original plate of the present invention, it is preferable to scan the convergent light at a high speed in terms of irradiation speed, and it is easy to use. Further, a high-power light source is suitable as the light source. From this point, laser light, particularly laser light having an oscillation wavelength in the wavelength range of 750 to 1100 nm, is preferable, for example, a high-power semiconductor laser of 830 nm. Or a YAG laser of 1064 nm is preferably used. Exposure machines equipped with these lasers are already on the market as so-called thermal plate setters (exposure machines).

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely using an Example, this invention is not limited to the range of these Examples.

(Synthesis of hydrophilic polymer P-1)
400 g of water was put into a 1000 cc flask, and nitrogen was bubbled to remove dissolved oxygen, followed by heating to 80 ° C. While flowing nitrogen gas through the flask, a monomer solution consisting of 105 g of acrylamide, 15 g of hydroxyethyl methacrylate and 130 g of water, and an aqueous solution of an initiator obtained by dissolving 0.6 g of potassium persulfate in 100 g of water, While maintaining the temperature at 80 ° C., it was continuously added dropwise over 2 hours. After completion of the dropping, polymerization was continued at 80 ° C. for 3 hours. Finally, 50 g of water was added to synthesize a 15% aqueous solution of hydrophilic polymer P-1.

(Creation of original plate for lithographic printing)
In order to improve adhesion, a 0.24 mm thick aluminum plate coated with a 1 μm thick polyurethane resin (Mitsui Chemicals Co., Ltd. water-dispersed urethane resin: Olester ^™ UD350, solid content 40% by weight) was previously applied as a primer. An aqueous dispersion of a photosensitive resin composition having the following composition (unit parts by weight, the same applies hereinafter) was applied using a wire bar, dried and crosslinked at 135 ° C. for 30 minutes, and a photosensitive layer having a thickness of 2 μm. Was formed into a lithographic printing original plate.

Aqueous solution of the above-mentioned hydrophilic polymer P-1 (solid content 15% by weight): 267 parts by weight Methylated melamine resin (manufactured by Mitsui Cytec Co., Ltd., Cymel ^TM 385, solid content 80% by weight): 25 parts by weight Polyurethane resin (Mitsui Chemical Co., Ltd., water-dispersed urethane resin: Olester ^™ UD350, solid content 40% by weight: 100 parts by weight Polymer fine particles having internal voids (Rohm and Haas: ROPAQUE ^™ OP-62, average particle) Diameter 0.4 μm, solid content 37% by weight): 20.3 parts by weight Cyanine dye aqueous solution (IR-125 manufactured by Nippon Photosensitive Dye Co., Ltd., solid content 5% by weight): 200 parts by weight Anionic surfactant (No. 1) Ichi Kogyo Seiyaku Co., Ltd. Neocor ^TM YSK, solid content 70 wt%): 1.43 parts by weight

(Evaluation of plate inspection)
This plate is irradiated with a semiconductor laser beam having a wavelength of 830 nm while condensing it so as to obtain an irradiation energy density of 200 mJ / cm ² , image information of 200 lines / inch is drawn, and a drawing image of the exposed portion is detected. The plate quality was evaluated by visual observation. The results are shown in Table 1.
(Print test)
At the same time, the above exposed plate is set in an offset printing machine SPRINT S-26 manufactured by Komori Corporation, and used as a 2% aqueous solution and ink of H liquid Astro Mark 3 from Nikken Chemical Laboratories as dampening water. A printing test was performed using Toyo Ink Mfg. Co., Ltd.'s HiEcho ^TM SOY. After printing about 1000 sheets, non-image area scumming occurred, image area ink deposition and post-printing The presence or absence of peeling of the printing plate was visually observed to confirm that there was no problem.

  A printing original plate was prepared and exposed in the same manner as in Example 1 except that the addition amount of polymer fine particles having voids therein was changed to 40.5 parts by weight in the formulation of the photosensitive resin composition of Example 1. Thereafter, the plate inspection property was evaluated by visual observation. The results are shown in Table 1. At the same time, a printing test was conducted, and after printing about 1,000 sheets, visually observe the occurrence of background smudges in the non-image area, ink fillability in the image area, and peeling of the printing plate after printing. , Confirmed that there was no problem.

In the formulation of the photosensitive resin composition of Example 1, instead of adding polymer fine particles having voids inside, as a zirconium compound, BACOTE ^™ 20 (manufactured by Magnesium Electron (UK), active ingredient 45% by weight) Except for adding 13.3 parts by weight, a printing original plate was prepared and exposed in the same manner as in Example 1, and then the plate inspection property was evaluated by visual observation. The results are shown in Table 1. At the same time, a printing test was conducted, and after printing about 1,000 sheets, visually observe the occurrence of background smudges in the non-image area, ink fillability in the image area, and peeling of the printing plate after printing. , Confirmed that there was no problem.

In addition to the addition of 5.6 parts by weight of BACOTE ^™ 20 (manufactured by Magnesium Electron Ltd. (UK), 45% by weight of active ingredient) as a zirconium compound in the formulation of the photosensitive resin composition of Example 1, After the printing original plate was prepared and exposed in the same manner as in Example 1, the plate inspection property was evaluated by visual observation. The results are shown in Table 1. At the same time, a printing test was conducted, and after printing about 1,000 sheets, visually observe the occurrence of background smudges in the non-image area, ink fillability in the image area, and peeling of the printing plate after printing. , Confirmed that there was no problem.
[Comparative Example a]
After preparing and exposing the printing original plate in the same manner as in Example 1 except that the composition of the photosensitive resin composition of Example 1 was changed so as not to add polymer fine particles having voids inside, the plate inspection property was obtained. Was evaluated by visual observation. The results are shown in Table 1. At the same time, a printing test was conducted, and after printing about 1,000 sheets, visually observe the occurrence of background smudges in the non-image area, ink fillability in the image area, and peeling of the printing plate after printing. , Confirmed that there was no problem.

* 1), 2): Displayed in parts by weight of solid content (active ingredient) per 100 parts by weight of total solid content in the photosensitive resin composition * 3): Evaluation results
○ You can clearly see the exposure image
△ The exposure image can be almost confirmed.
× Difficult to confirm the exposed area

  The original plate for lithographic printing of the present invention is sensitive to light in the near infrared region, can be handled in a bright room, can be directly drawn on the plate by laser light, does not require development and wiping operations, and is suitable for printing. It is excellent as an original plate for lithographic printing for CTP, which is excellent and has improved plate inspection after exposure.

Claims (3)

A lithographic printing original plate having a hydrophilic resin photosensitive layer having a property of changing the hydrophilicity of the exposed portion surface to ink-philicity by laser exposure on a support, wherein the hydrophilic resin photosensitive layer is disposed inside A lithographic printing plate precursor obtained by crosslinking a photosensitive resin composition containing polymer fine particles having voids and / or a zirconium compound. 2. The lithographic printing plate precursor according to claim 1, wherein the lithographic printing plate precursor is capable of being printed immediately after the laser exposure according to the printed image, without requiring a development process. The lithographic printing plate precursor according to claim 1 or 2, wherein the photosensitive resin composition further comprises a hydrophilic polymer, a crosslinking agent, a hydrophobic polymer, and a light absorber.