JP2007168140A - Lithographic printing original plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithographic printing original plate for CTP, which is sensible to light in near infrared region, can be dealt with in a lighted room, on which drawing can be directly made with a laser beam, the developing and wiping operation of which can be made unnecessary, which is excellent in printability and the exposure sensitivity of which is remarkably improved. <P>SOLUTION: In the lithographic printing original plate having a hydrophilic resin layer directly or through a ground layer on a support, the hydrophilic resin layer includes (a) a hydrophilic polymer, (b) a crosslinker, (c) a hydrophobic polymer and (d) a photothermic conversion material under the condition that (c) the hydrophobic polymer is an alkali-swelling particle, the change of the particle diameter of which by a dynamic light scattering method due to alkali swelling is ≥150%. <P>COPYRIGHT: (C)2007,JPO&INPIT

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 is sensitive to light in the near infrared region and can be handled in a bright room. In addition, it relates to an original for lithographic printing having various printing characteristics such as direct drawing with a laser beam on the plate and eliminating the need for development and wiping operations. More specifically, the exposure sensitivity is remarkable. Relates to an improved lithographic printing plate precursor.

  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 crosslinking a hydrophilic resin composition containing a hydrophilic polymer, a crosslinking agent, a hydrophobic polymer, and a photothermal conversion material, and the surface becomes hydrophilic by light irradiation. A master for lithographic printing has been developed that changes from ink property to ink affinity. (Patent Document 1 (International Publication No. 01/083234)). This original plate does not require a development process after laser exposure, and during printing, the surface of the original plate not exposed to laser, that is, the surface of the hydrophilic resin photosensitive layer, becomes a non-image area as it is, so that the non-image area is highly hydrophilic. is required. On the other hand, in order to improve the productivity of printing plate preparation by laser exposure, ink adhesion to the image area, resolution, and reproducibility, a relatively low power laser exposure allows sufficient hydrophilic ink from the hydrophilic surface. It is desirable to change to a surface having a property, that is, change from a non-image area to an image area. The laser power at the time of exposure that causes the above-described change from hydrophilicity to sufficient ink affinity is called exposure sensitivity, and it is further required to substantially improve the hydrophilicity and exposure sensitivity of the printing original plate. .

Here, as a technique of using a hydrophobic polymer for a printing plate, Patent Document 2 (Patent No. 3555668) discloses a self-water dispersible thermoplastic resin particle layer that can be oleophilicized by heat on a hydrophilic substrate surface. A lithographic printing plate formed, wherein the self-water dispersible thermoplastic resin is obtained by neutralizing at least a part of a synthetic resin having an acid value of 50 or more and 280 or less with a base. Has been. The particles are a copolymer of monomers having an anionic functional group such as a carboxyl group, and by having an acid value in a specific range, the water-dispersible resin particles are refined by a phase inversion emulsification method, While preventing dissolution / swelling of particles and imparting large hydrophilicity to the particles, adhesion of the resin to the substrate, abrasion resistance / oil resistance / alkali resistance of the image area, non-image area particles to each other As a means for improving the anti-fusing, an aqueous dispersion of aqueous resin particles added with polyvalent metal ions that form intermolecular crosslinks with carboxyl groups, and further with a particle adhesion inhibitor such as glycerin, It is disclosed that a printing plate is formed by applying and drying an aluminum plate that has been sharpened or anodized, that is, a substrate having a hydrophilic surface. However, this method has insufficient adhesion to the substrate of the non-image area, and when printing is performed without performing a development operation, the hydrophilicity of the non-image area is insufficient and printing smears or moistening occurs. It has the disadvantage that it is likely to cause problems such as elution and transfer to water or ink, causing contamination of printed matter and the like.
International Publication No. 01/083234 Japanese Patent No. 3555668

  The object of the present invention is to be sensitive to light in the near-infrared region, can be handled even in a bright room, can be directly drawn on a plate with laser light, can eliminate the need for development and wiping operations, and has various printing characteristics. And an original plate for lithographic printing for CTP having a significantly improved exposure sensitivity.

  As a result of intensive studies, the inventors of the present invention have developed an alkali swellable photosensitive resin composition for forming a hydrophilic resin layer in a lithographic printing original plate having a hydrophilic resin layer directly or via a base layer on a support. The inventors have found that the above object can be achieved by using particles containing particles, and have reached the present invention. That is, the present invention is as follows.

(1) In an original plate for lithographic printing having a hydrophilic resin layer on a support directly or via an underlayer, the hydrophilic resin layer comprises (a) a hydrophilic polymer, (b) a crosslinking agent, and (c) an alkali. Swellable particles, (d) comprising a photosensitive resin composition containing a photothermal conversion material. Alkali-swellable particles have an average particle size change of 150% or more by dynamic light scattering due to alkali swelling. An original lithographic printing plate.
(Here, the change in the average particle diameter by the dynamic light scattering method due to alkali swelling is that the average particle diameter in the state where the pH of the aqueous dispersion of the particles is less than 5 is d1, pH 8.5 or more after alkali treatment) (It is a numerical value calculated by d2 / d1 × 100, where d2 is the average particle diameter in the swollen state.)
(2) The lithographic printing plate precursor as described in (1), wherein the alkali-swellable particles are emulsion polymerization particles prepared from a monomer mixture containing a monomer having a carboxyl group.
(3) The lithographic printing original plate as described in (1) or (2), which is a hydrophilic resin layer having a property that the hydrophilicity of the exposed portion surface changes to ink-philicity by laser exposure.
(4) The lithographic printing plate precursor according to any one of (1), (2) and (3), which is capable of being printed immediately after laser exposure in accordance with a printed image, without requiring a development process.

  By using the lithographic printing plate precursor of the present invention, it can be exposed to light in the near-infrared region, can be handled in a bright room, can be directly drawn with laser light, and can eliminate the need for steps such as development and wiping. Therefore, it is possible to provide an original plate for lithographic printing for CTP which is excellent in various printing characteristics and has a significantly improved exposure sensitivity.

  The lithographic printing original plate of the present invention will be described in detail below. The lithographic printing original plate of the present invention is preferably a lithographic printing original plate using a fountain solution, and the non-image portion other than the light irradiated portion of the hydrophilic resin layer is left as it is, and the photosensitive layer of the portion irradiated with light is ablated. The surface of the exposed portion is preferably changed from hydrophilic to ink-philic so that an image portion can be formed. Therefore, the original plate of the present invention can be a non-developing type lithographic printing original plate that can eliminate the need for development or wiping after light irradiation.

  The lithographic printing original plate of the present invention is a lithographic printing original plate having a hydrophilic resin layer on a support directly or via an underlayer, the hydrophilic resin layer comprising (a) a hydrophilic polymer, (b) It comprises a photosensitive resin composition comprising a crosslinking agent, (c) alkali-swellable particles, and (d) a photothermal conversion material, and the (c) alkali-swellable particles are average particles obtained by a dynamic light scattering method using alkali swelling. A lithographic printing original plate having a diameter change of 150% or more. Preferably, it is a lithographic printing original plate having a hydrophilic resin layer having a property that the hydrophilicity of the exposed portion surface changes to ink-philicity by laser exposure. 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 role of the hydrophobic polymer phase is that the hydrophobic polymer phase forms an island phase in the hydrophilic polymer in the photosensitive layer, and the photothermal conversion material in the photosensitive layer absorbs light and converts light energy into heat energy. It is presumed that the island phase of the hydrophobic polymer phase 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. It is preferable that the hydrophobic polymer phase has a so-called core / shell structure in which itself is a core and is surrounded by a hydrophilic shell layer.

    (C) Alkali-swellable particles used in the present invention, that is, particles having a change in particle diameter by a dynamic light scattering method due to alkali swelling of 150% or more, can be alkalinized from the particle surface layer during alkali treatment. Particles having a structure in which a solubilized hydrophilic polymer chain spreads in water, while a non-swelling (or low-swelling) hydrophobic polymer component that is substantially unaffected by alkali exists in the center part of the particle, so-called It is considered that particles having a core / shell type structure are formed. Therefore, individual alkali-swelled particles, that is, non-swelling hydrophobic polymer components are present in the hydrophilic resin layer obtained by applying, drying and curing the photosensitive resin composition of the present invention while maintaining independence. Therefore, a fine separation structure composed of a hydrophilic polymer phase and a hydrophobic polymer phase can be easily formed, and the compatibility between the interface between the cured hydrophilic phase and the hydrophobic polymer phase composed of a hydrophilic polymer and a crosslinking agent is improved. In order to improve, in addition to the improvement of hydrophilicity and exposure sensitivity, it is expected to improve the adhesion of the hydrophilic resin phase to the substrate, which is very useful.

  The alkali-swellable particles characterized in that the change in particle diameter by the dynamic light scattering method by alkali swelling of the present invention is 150% or more can be prepared by a known emulsion polymerization method or the like. At this time, batch type batch polymerization, semi-batch type polymerization in which the monomer mixture is continuously added to the reaction system, and multistage type or gradient type in which the monomer composition added to the polymerization system is changed stepwise or continuously. Techniques such as semi-batch polymerization can be used. For example, a monomer mixture capable of forming alkali-swellable polymer particles can be prepared by one-step semi-batch emulsion polymerization, and after preparing hydrophobic polymer fine particles as the first step, alkali-swellable as the second step A monomer mixture capable of preparing a polymer that forms the particle surface can be added and polymerized to form alkali-swellable composite particles.

  As a specific component for imparting alkali swellability to the alkali-swellable particles of the present invention, a carboxyl group is suitable, and examples of components that promote swelling include a hydroxyl group, an amide group, and an N-substituted amide group. , An amino group and an N-substituted amino group, an oxymethylene group, an oxyethylene group, and the like can be present together. 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. These can be used, and one or more of these monomers can be used in combination, but acrylic acid and methacrylic acid are particularly preferred.

  Examples of the monomer constituting the hydrophobic polymer component constituting the alkali-swellable particle of the present invention include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, and 2-ethylhexyl (meth). (Meth) acrylates such as acrylate, t-butyl (meth) acrylate, hydroxyethyl (meth) acrylate, glycidyl (meth) acrylate, styrene derivatives such as styrene and α-methylstyrene, (meth) acrylonitrile, vinyl acetate, etc. Vinylesters etc. are mentioned, These 1 type or 2 types or more can be combined, or it can further be used in combination with the component which provides said alkali swelling ability.

  The alkali-swellable particles of the present invention have an average particle size by dynamic light scattering method, and the average particle size d1 when the pH of the aqueous dispersion of the particles is less than 5 is preferably 0.005 to 0.5 microns, preferably The change calculated by d2 / d1 × 100 from the average particle diameter d2 in the swollen state where the pH after alkali treatment is 8.5 or more is 0.01 to 0.3 micron is 150% or more. Is required, and is more preferably 200% or more and less than 600%. A hydrophilic resin layer made of a photosensitive resin composition using particles outside these ranges is not preferable because sufficient sensitivity may not be obtained and adhesion to a base may be inferior.

  In addition, the alkali-swellable particles of the present invention may be in a state in which the average particle size by dynamic light scattering method is swollen to 150% or more when not swollen before being blended as a photosensitive resin composition. Preferably, it is 200% or more and less than 600%. Examples of the alkali used for the swelling treatment include alkali metal salts such as sodium hydroxide, potassium hydroxide and lithium hydroxide, alkaline earth metal salts such as calcium hydroxide and magnesium hydroxide, ammonia, methylamine and dimethylamine. , Trimethylamine, ethylamine, diethylamine, triethylamine, monoethanolamine, diethanolamine, triethanolamine, amines such as (di) methylethanolamine, (di) ethylethanolamine, and a combination of one or more of these Although amines can be used, amines are preferred.

  The alkali-swellable particles used in the photosensitive resin composition for forming the hydrophilic resin layer of the present invention are preferably larger 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 alkali-swellable particles in the photosensitive resin composition in the present invention is preferably 80% by weight or less, more preferably 10% by weight to 70% by weight as the solid content.

  The hydrophilic polymer that can be used in the photosensitive resin composition for forming the hydrophilic resin layer of the present invention is not particularly limited as long as it has a hydrophilic group. Preferably, it has a hydrophilic group and a functional group (crosslinkable functional group) that reacts with the crosslinking agent. 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.

  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.

  In the present invention, the crosslinking agent (b) that can be contained in the hydrophilic resin layer improves printing durability by imparting high water resistance that the hydrophilic resin layer is not dissolved / removed in water. For example, known polyhydric alcohol compounds and polycarboxylic acid compounds that react with a hydroxyl group, carboxyl group, sulfonic acid group, glycidyl group, and in some cases an amide group, which are crosslinkable functional groups in a hydrophilic polymer. And anhydrides thereof, polyvalent glycidyl compounds, polyvalent amines, polyvalent isocyanate compounds and blocked isocyanate compounds, epoxy resins, oxazoline resins, amino resins and the like. In addition, when a crosslinking agent has self-crosslinking property, it does not necessarily need to carry out a crosslinking reaction with a hydrophilic polymer.

  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 and the like are preferable. 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 crosslink the hydrophilic polymer having the cross-linking functional group, or to dissolve in water in the hydrophilic resin layer due to the occurrence of self-crosslinking reaction when the cross-linking agent has self-crosslinking property.・ It is considered that high water resistance that is not removed is imparted, and when the crosslinking agent has self-crosslinking property, in the photosensitive layer, the crosslinking agent forms a polymer island phase in the hydrophilic polymer. When the light-to-heat conversion material absorbs light and converts light energy to heat energy, the island phase is foamed by the generated heat, and the hydrophilicity of the surface of the light irradiated portion may be changed to ink affinity. .

  The light-heat conversion material used in the photosensitive resin composition for forming the hydrophilic resin layer of the present invention may be any material that absorbs light and generates heat, and the wavelength that the light-heat conversion material absorbs upon light irradiation. The light of the region may be used as appropriate. Specific examples of photothermal conversion materials 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 photothermal conversion materials may be dissolved or dispersed in the photosensitive resin composition. Among the light-to-heat conversion materials described above, hydrophilic light-to-heat conversion materials are preferred in the present invention.

  The support used in the lithographic printing original plate of the present invention is not particularly limited, but specific examples include metal plates such as aluminum plates, steel plates, stainless plates, and copper plates, and polyester, nylon, polyethylene, polypropylene, polycarbonate, and ABS. Examples thereof include plastic films such as resin, paper, aluminum foil laminated paper, metal vapor deposited paper, and plastic film laminated paper. 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.

  Moreover, in order to improve the adhesiveness with the hydrophilic resin layer or prevent the diffusion of heat, an underlayer such as a polymer may be used between the support and the hydrophilic resin layer. The polymer used for this can be used without particular limitation as long as it is a polymer having adhesion between the support and the hydrophilic resin 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 hydrophilic resin layer. The underlayer may or may not be crosslinked. The underlayer can be formed by a method in which a polymer 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.

  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 a hydrophilic additive in the present invention include nonionic surfactants. Specific examples include polyethylene glycol types such as polyoxyethylene alkyl ether, polyoxyethylene polypropylene glycol ether, polyoxyethylene. Alkyl phenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyoxyethylene alkylamine and the like, 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, alkyl Rirueteru, and activators such as 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.

  In the present invention, the hydrophilic additive may be used singly or in combination of two or more, and the addition amount 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 hydrophilic resin layer of the present invention is obtained by applying an aqueous dispersion of a photosensitive resin composition containing a hydrophilic polymer, a crosslinking agent, alkali-swellable particles, and a photothermal conversion material to a substrate, and drying and curing. That's fine. These can be carried out by a known method as described in WO 01/083234 or the like. 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. Furthermore, after apply | coating, it heat-processes and dry and bridge | crosslink a hydrophilic resin layer. The heating temperature is usually about 50 to 250 ° C.

  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 layer. Such a system is preferable because the hydrophilicity of the hydrophilic resin photosensitive layer of the present invention is not substantially impaired and the time required for the crosslinking process can be shortened. 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 photothermal conversion material, for example, light in the region of 750 to 1100 nm, the photothermal conversion material 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 amount of light irradiation is too large or a photothermal conversion material is added in a large amount, the photosensitive layer is removed and ablated by decomposition, combustion, etc. 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.
Example 1
(Synthesis by emulsion polymerization of alkali-swellable particles P-1)
A reactor was charged with 200 g of pure water and 10 g of a 10 wt% aqueous solution of Perex SSL (manufactured by Kao Corporation), heated to 80 ° C. under a nitrogen stream, 2 g of azobiscyanovaleric acid, 0.9 g of 25% aqueous ammonia, pure A mixture of 40 g of water was added. After 10 minutes, an emulsion monomer mixture consisting of 50 g of styrene, 50 g of acrylic acid, 2 g of a 10 wt% aqueous solution of Plex SSL, and 50 g of pure water was continuously added dropwise over about 2 hours, and then the temperature was maintained at 80 ° C. for 3 hours. The polymerization reaction was completed while maintaining the temperature and cooled. The obtained polystyrene emulsion had a pH of 4.2, a solid content concentration of 24.5 wt%, and an average particle size of 136 nm as measured by a dynamic light scattering method. The polystyrene-acrylic acid copolymer emulsion was neutralized with dimethylethanolamine. However, since the thickening was remarkable, the emulsion was appropriately diluted with pure water. The pH was 8.7, the solid content concentration was 9.5 wt%, and the average particle size by dynamic light scattering method was 592 nm. The change rate of the average particle diameter due to alkali swelling is 435%. The particle size distribution was measured using LPA-3100 (manufactured by Otsuka Electronics), and the average particle size was g (G) average value. The following examination was carried out using the alkali-swelled particles.

(Creation of original plate for lithographic printing)
An aluminum plate with a thickness of 0.24 mm coated with a 1 μm-thick polyurethane resin (made by Mitsui Chemicals, Inc., water-dispersed urethane resin: Olester ^™ UD350, solid content 40% by weight) as a primer in order to improve adhesion The aqueous dispersion of the 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 150 ° C. for 20 minutes, and used for lithographic printing according to the present invention. An original version was created.

Aqueous dispersion of alkali swellable particles P-1: 57.8 parts by weight Methylated melamine resin (manufactured by Mitsui Cytec Co., Ltd., Cymel ^TM 385, solid content 80% by weight): 2.6 parts by weight Polyacrylamide resin (Mitsui Chemicals Co., Ltd., Hoplon TMH520B, solid content 20% by weight): 12.1 parts by weight Cyanine dye (λmax 784 nm, εmax 2.43 × 10 ⁵ Lmol ⁻¹ cm ^{−1 in} methanol solution) 2 parts Anionic surfactant (Neocol ^TM YSK manufactured by Daiichi Kogyo Seiyaku Co., Ltd., 70 wt% solid content): 0.28 parts Surfactant; Perfluoroalkylbetaine (Surflon ^TM S- manufactured by Seimi Chemical Co., Ltd.) 131, solid content 30 wt%): 0.033 parts ranging a semiconductor laser beam having a wavelength of 830nm from 450 to this precursor of 150 mJ / cm ^2, 50 m / Cm adjusted, by changing the irradiation energy density at ² increments at each energy density scans irradiation was carried out drawing of the image information of 175 lines / inch (exposure process).

(Print evaluation)
The above exposed plate is set in an offset printing machine SPRINT S-26 manufactured by Komori Corporation, and 2% aqueous solution of H liquid astromark 3 of Nikken Chemical Research Co., Ltd. is used as dampening water, and Toyo Ink is used as ink. Print test using HiEcho ^TM SOY manufactured by Manufacture Co., Ltd., comparing the ink landing state of the printed part transferred from the image area with different irradiation energy density at the time of exposure. Exposure sensitivity) was determined. On the other hand, it was confirmed that there was no scumming and good hydrophilicity during printing. Table 1 shows the print evaluation results.

(Water rubbing test for photosensitive layer)
The photosensitive layer surface of the lithographic printing original plate prepared as described above is rubbed with a non-woven cloth soaked in water under a constant load, and the number of reciprocating rubbing until the photosensitive layer is peeled off is used to determine the relationship between the photosensitive layer and the underlayer. Adhesiveness was assumed. The results are shown in Table 1.

Example 2
(Synthesis of alkali-swellable particles P-2 by emulsion polymerization)
A reactor was charged with 200 g of pure water and 10 g of a 10 wt% aqueous solution of Perex SSL (manufactured by Kao Corporation), heated to 80 ° C. under a nitrogen stream, 2 g of azobiscyanovaleric acid, 0.9 g of 25% aqueous ammonia, pure A mixture of 40 g of water was added. After 10 minutes, an emulsion monomer mixture consisting of 75 g of styrene, 25 g of acrylic acid, 2 g of a 10 wt% aqueous solution of Plex SSL and 50 g of pure water was continuously added dropwise over about 2 hours, and then the temperature was maintained at 80 ° C. for 3 hours. The polymerization reaction was completed while maintaining the temperature and cooled. The resulting polystyrene emulsion had a pH of 4.2, a solid content concentration of 24.7 wt%, and an average particle size of 91 nm as determined by a dynamic light scattering method. The polystyrene-acrylic acid copolymer emulsion was neutralized with dimethylethanolamine, but diluted appropriately with pure water for thickening. The pH was 9.2, the solid content concentration was 9.7 wt%, and the average particle size by dynamic light scattering method was 162 nm. The change rate of the average particle diameter due to alkali swelling is 178%. The particle size distribution was measured using LPA-3100 (manufactured by Otsuka Electronics), and the average particle size was g (G) average value. The following examination was carried out using the alkali-swelled particles.

In the formulation of the photosensitive resin composition, as described below, a printing original plate was prepared and exposed in the same manner as in Example 1 except that the above-described alkali-swellable particles were used as the hydrophobic polymer. The printing evaluation was carried out and the exposure sensitivity was determined. On the other hand, it was confirmed that there was no scumming and good hydrophilicity during printing. Further, as in Example 1, a water rubbing test was also conducted. Table 1 shows the results of the printing evaluation and the rubbing test.
Aqueous dispersion of alkali swellable particles P-2: 56.7 parts by weight

Comparative Example 1
(Synthesis of polystyrene emulsion copolymer emulsion P-3)
A reactor was charged with 200 g of pure water and 10 g of a 10 wt% aqueous solution of Perex SSL (manufactured by Kao Corporation), heated to 80 ° C. under a nitrogen stream, 2 g of azobiscyanovaleric acid, 0.9 g of 25% aqueous ammonia, pure A mixture of 40 g of water was added. After 10 minutes, an emulsion monomer mixture composed of 95 g of styrene, 5 g of acrylic acid, 2 g of a 10 wt% aqueous solution of Plex SSL, and 50 g of pure water was continuously added dropwise over about 2 hours, and then the temperature was maintained at 80 ° C. for 3 hours. The polymerization reaction was completed while maintaining the temperature and cooled. The obtained polystyrene emulsion had a pH of 4.8, a solid content concentration of 24.3 wt%, and an average particle size of 98 nm by a dynamic light scattering method. The polystyrene emulsion was neutralized with dimethylethanolamine and diluted with pure water so that the solid content concentration was about 10 wt%. The pH was 9.4, the solid content concentration was 10.2 wt%, and the average particle size determined by the dynamic light scattering method was 107 nm. The rate of change of the average particle size due to alkali swelling is 109%. The particle size distribution was measured using LPA-3100 (manufactured by Otsuka Electronics), and the average particle size was g (G) average value. The following examination was carried out using the emulsion particles. After preparing and exposing the printing original plate in the same manner as in Example 1 except that the above polystyrene-based emulsion copolymer emulsion was used as the hydrophobic polymer in the composition of the photosensitive resin composition as described below, the same The printing evaluation was carried out under the following conditions, and the exposure sensitivity was determined. On the other hand, it was confirmed that background smudges were slightly generated in the non-image area during printing. Further, as in Example 1, a water rubbing test was also conducted. Table 1 shows the results of the printing evaluation and the rubbing test.
Aqueous dispersion of the emulsion copolymer emulsion P-3: 53.9 parts by weight

  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 very useful as an original plate for lithographic printing for CTP, which is excellent and has significantly improved exposure sensitivity.

Claims (4)

In an original plate for lithographic printing having a hydrophilic resin layer on a support directly or via an underlayer, the hydrophilic resin layer comprises (a) a hydrophilic polymer, (b) a crosslinking agent, and (c) an alkali-swelling agent. Particles and (d) a photosensitive resin composition containing a photothermal conversion material, wherein the alkali-swellable particles have a change in average particle diameter by a dynamic light scattering method due to alkali swelling of 150% or more. An original for lithographic printing.
(Here, the change in the average particle diameter by the dynamic light scattering method due to alkali swelling is that the average particle diameter in the state where the pH of the aqueous dispersion of the particles is less than 5 is d1, pH 8.5 or more after alkali treatment) (It is a numerical value calculated by d2 / d1 × 100, where d2 is the average particle diameter in the swollen state.) 2. The lithographic printing plate precursor according to claim 1, wherein the alkali-swellable particles are emulsion polymerization particles prepared from a monomer mixture containing a monomer having a carboxyl group. 3. The lithographic printing plate precursor according to claim 1, wherein the lithographic printing plate precursor is a hydrophilic resin layer having a property that the hydrophilicity of the exposed portion surface changes to ink-philicity by laser exposure. The lithographic printing plate precursor according to any one of claims 1 to 3, wherein the lithographic printing plate precursor is capable of being printed immediately after being exposed to a laser according to a printed image without requiring a development process.