Original photosensitive resin printing plate

Abstract

To provide a photosensitive resin printing original plate which is excellent in adhesion between a photosensitive resin layer and an IR-sensitive layer.SOLUTION: A photosensitive resin printing original plate has a photosensitive resin layer containing a polyamide resin having a polyether structure, an intermediate layer and an IR-sensitive layer in this order on a support, in which the IR-sensitive layer contains polyvinyl alcohol having a degree of saponification of 60-100 mol% and an average degree of polymerization of 300-3,000, and the intermediate layer contains a polyamide resin having a basic nitrogen atom and / or a polyether structural unit.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a photosensitive resin printing plate precursor. [Background technology]

[0002] In the fields of letterpress printing and flexographic printing, CTP (computer to plate) technology, known as a digital image formation technology, has become common. CTP technology is a method in which an image mask is formed using digital data on the mask layer elements of a photosensitive resin printing plate precursor having mask layer elements, and then the photosensitive resin layer is irradiated with actinic rays through the image mask to partially photocure the photosensitive resin layer, thereby forming a relief pattern.

[0003] Examples of photosensitive resin printing plate precursors suitable for such CTP technology include a photosensitive resin printing plate precursor having, on a support, a photosensitive resin layer (A) containing a polyamide having a hydrophilic group and a compound having an ethylenically unsaturated bond, at least one intermediate layer (B), and a water-insoluble heat-sensitive mask layer (C) containing an infrared absorbing substance, in this order, wherein the intermediate layer (B) contains polyvinyl alcohol and / or partially saponified polyvinyl alcohol, and a polyamide having a hydrophilic group (see, for example, Patent Document 1); and a photosensitive resin printing plate precursor having at least (A) a support, (B) a photosensitive resin layer (A) containing a polyamide having a hydrophilic group and a compound having an ethylenically unsaturated bond, and a water-insoluble heat-sensitive mask layer (C) containing an infrared absorbing substance, in this order, wherein the intermediate layer (B) contains polyvinyl alcohol and / or partially saponified polyvinyl alcohol, and a polyamide having a hydrophilic group (see, for example, Patent Document 1). A water-developable photosensitive letterpress printing original plate (see, for example, Patent Document 2) has been proposed, which is composed of a (B) photosensitive resin layer, (C) an oxygen-blocking dividing layer, and (D) a water-soluble or water-dispersible heat-sensitive mask layer that contains carbon black, laminated in that order, wherein the (B) photosensitive resin layer contains a synthetic polymer compound, a photopolymerizable unsaturated compound, and a photopolymerization initiator, the synthetic polymer compound contains polyamide or polyether urea urethane that contains a tertiary nitrogen atom, and the (C) oxygen-blocking dividing layer contains polyvinyl alcohol with a saponification degree of 60 to 85 mol % and a polymerization degree of 200 to 800. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-22229 [Patent Document 2] International Publication No. 2017 / 056763 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 describes a polyamide resin having an amino group such as a piperazine ring or a polyether segment such as polyethylene glycol as a binder resin for a photosensitive resin layer in order to impart developability. However, the inventors' investigations have revealed that when a photosensitive resin layer containing such a polyamide resin is combined with a water-soluble or water-dispersible infrared-sensitive layer as described in Patent Document 2, the adhesion between the photosensitive resin layer and the infrared-sensitive layer decreases.

[0006] In view of the above problems, an object of the present invention is to provide a photosensitive resin printing plate precursor that has excellent adhesion between the photosensitive resin layer and the infrared-sensitive layer. [Means for solving the problem]

[0007] The present invention provides a photosensitive resin printing plate precursor having, on a support, a photosensitive resin layer containing a polyamide resin having a polyether structure, an intermediate layer, and an infrared-sensitive layer in this order, wherein the infrared-sensitive layer contains polyvinyl alcohol having a saponification degree of 60 to 100 mol % and an average polymerization degree of 300 to 3,000, and the intermediate layer contains a polyamide resin having a basic nitrogen atom and / or a polyether structural unit. The intermediate layer on the infrared-sensitive layer side contains polyvinyl alcohol having a saponification degree of 60 to 100 mol % and an average polymerization degree of 300 to 3,000. It is a photosensitive resin printing plate precursor. Also, a photosensitive resin printing plate precursor having, in this order, a photosensitive resin layer containing a polyamide resin having a polyether structure, an intermediate layer, and an infrared-sensitive layer on a support, wherein the infrared-sensitive layer contains polyvinyl alcohol with a saponification degree of 60 to 100 mol% and an average degree of polymerization of 300 to 3,000, the intermediate layer contains a polyamide resin having a basic nitrogen atom, and the polyamide resin having a basic nitrogen atom has a piperazine ring.Also, a photosensitive resin printing plate precursor having, in this order, a photosensitive resin layer containing a polyamide resin having a polyether structure, an intermediate layer, and an infrared-sensitive layer on a support, wherein the infrared-sensitive layer contains polyvinyl alcohol with a saponification degree of 60 to 100 mol% and an average degree of polymerization of 300 to 3,000, the intermediate layer contains a polyamide resin having a basic nitrogen atom and / or a polyether structural unit, and the infrared-sensitive layer has a carboxyl group and a lactone group. [Effects of the Invention]

[0008] The photosensitive resin printing plate precursor of the present invention has excellent adhesion between the photosensitive resin layer and the infrared-sensitive layer. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described in detail.

[0010] The photosensitive resin printing plate precursor of the present invention (hereinafter sometimes abbreviated as "printing plate precursor") has a photosensitive resin layer, an intermediate layer, and an infrared-sensitive layer on a support, in this order. The support has the function of holding the photosensitive resin layer in the printing plate precursor. The photosensitive resin layer has the function of forming a relief pattern corresponding to the image mask when irradiated with actinic rays through the image mask. The infrared-sensitive layer has the function of forming the image mask by partial decomposition and evaporation (ablation) by infrared rays. The intermediate layer has the function of adhering the photosensitive resin layer and the infrared-sensitive layer together and inhibiting the migration of low-molecular-weight components from the photosensitive resin layer to the infrared-sensitive layer.

[0011] The printing plate precursor of the present invention may further include an adhesive layer between the support and the photosensitive resin layer, if necessary, to increase the adhesive strength between the support and the photosensitive resin layer. Furthermore, the printing plate precursor of the present invention may include a protective layer on the infrared-sensitive layer, which can prevent the infrared-sensitive layer from being scratched by external forces and improve the scratch resistance of the infrared-sensitive layer in the photosensitive resin printing plate precursor.

[0012] In the printing plate precursor of the present invention, the photosensitive resin layer contains a polyamide resin having a polyether structure. The inclusion of a polyamide resin having a polyether structure improves solubility in a developer containing water as the main component. In particular, when the infrared-sensitive layer is removable with a developer containing water as the main component, the photosensitive resin layer, intermediate layer, and infrared-sensitive layer can be developed together with a developer containing water as the main component. The photosensitive resin layer preferably further contains a compound having an ethylenic double bond and a photopolymerization initiator. When the photosensitive resin layer is imagewise irradiated with light such as ultraviolet light, free radicals are generated from the photopolymerization initiator in the exposed areas of the photosensitive resin layer. The generated free radicals induce radical polymerization between compounds containing ethylenic double bonds, forming a relief for obtaining a desired printed image through a crosslinked structure. When the polyamide resin contains an ethylenic double bond, radical polymerization also occurs between the polyamide resin and the compound containing an ethylenic double bond. This further promotes photocuring and improves the image reproducibility of the printing plate.

[0013] Examples of polyether structures include polyethylene oxide and polypropylene oxide. Two or more of these may be used. Among these, polyethylene oxide is preferred, and the number-average molecular weight of the polyethylene oxide portion is preferably 200 or more and 6,000 or less. By adjusting the number-average molecular weight of the polyethylene oxide to 200 or more, solubility in a developer containing water as the main component can be improved, and aggregation of the developer waste can be suppressed. On the other hand, by adjusting the number-average molecular weight of the polyethylene oxide portion to 6,000 or less, compatibility with other components in the photosensitive resin layer can be improved. Polyamide resins containing these polyethers impart flexibility to the relief obtained by photocuring the photosensitive resin layer and can be easily adjusted to a hardness suitable for various printing methods.

[0014] Polyamide resins having polyethers can be obtained by subjecting a polyether-containing component, such as α,ω-diaminopolyoxyethylene obtained by adding acrylonitrile to both ends of polyethylene glycol or the like and then reducing the resultant with hydrogen, to a condensation polymerization or polyaddition reaction, together with other diamines, dicarboxylic acids, aminocarboxylic acids, lactams, etc., as necessary, to a polyether-containing component, such as α,ω-diaminopolyoxyethylene obtained by adding acrylonitrile to both ends of polyethylene glycol or a compound obtained by adding dicarboxylic acids such as succinic anhydride to both ends of polyethylene glycol.

[0015] Examples of diamines include hexamethylenediamine and dodecamethylenediamine. Examples of dicarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, naphthalene-2,6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, diphenyl-4,4'-dicarboxylic acid, diphenoxyethanedicarboxylic acid, and sodium 5-sulfoisophthalate; aliphatic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, and dicyclohexyl-4,4'-dicarboxylic acid; and aliphatic dicarboxylic acids such as succinic acid, oxalic acid, adipic acid, sebacic acid, and decanedicarboxylic acid. Examples of aminocarboxylic acids include ω-aminocaproic acid, ω-aminoenanthic acid, ω-aminocaprylic acid, ω-aminobergonic acid, ω-aminocapric acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid. Examples of lactams include caprolactam, enantholactam, capryllactam, laurolactam, etc. Two or more of these may be used.

[0016] Of all the components constituting the polyamide resin, i.e., the sum of aminocarboxylic acids (including lactams used as raw materials), dicarboxylic acids, and diamines, it is preferable to use 20 to 90 mol% of polyether-containing components in total. Using 20 mol% or more of polyether-containing components further improves solubility in a developer whose main component is water, and can further suppress aggregation of waste developer. It is more preferable to use 30 mol% or more of such components. On the other hand, using 90 mol% or less of polyether-containing components suppresses water absorption during storage of the printing plate, allowing the thickness precision of the printing plate to be maintained at a high level.

[0017] The weight-average molecular weight of the polyamide resin having a polyether structure is preferably 10,000 or more and 200,000 or less. Here, the weight-average molecular weight can be determined by GPC measurement. More specifically, the weight-average molecular weight can be measured using a gel permeation chromatograph-multiangle light scattering photometer manufactured by Wyatt Technology under the conditions of a column temperature of 40°C and a flow rate of 0.7 mL / min. Polyethylene oxide and polyethylene glycol are used as standard samples.

[0018] The content of the polyamide resin having a polyether structure in the photosensitive resin layer is preferably 30 to 70 mass % of the solid content.

[0019] The compound having an ethylenic double bond refers to a compound having an ethylenic double bond and a molecular weight of less than 10,000. The molecular weight of the compound having an ethylenic double bond is preferably 2,000 or less.

[0020] Examples of compounds having an ethylenic double bond include (meth)acrylates described in International Publication No. 2017 / 038970, glycerol di(meth)acrylate, (meth)acrylic acid adducts of propylene glycol diglycidyl ether, and tetrahydrofurfuryl (meth)acrylate. Two or more of these may be contained. Here, (meth)acrylate is a general term for acrylate and methacrylate, and (meth)acrylic acid is a general term for acrylic acid and methacrylic acid.

[0021] The content of the compound having an ethylenic double bond in the photosensitive resin layer is preferably from 10 to 60% by mass.

[0022] As the photopolymerization initiator, one having the function of generating radicals by self-decomposition or hydrogen abstraction upon light absorption is preferably used. Examples thereof include benzoin alkyl ethers, benzophenones, anthraquinones, benzils, acetophenones, and diacetyls. Two or more of these may be contained.

[0023] The content of the photopolymerization initiator in the photosensitive resin layer is preferably 0.1 to 10% by mass.

[0024] The photosensitive resin layer may contain, as necessary, a binder resin other than the polyamide resin having a polyether structure, a compatibility aid, an ink repellent, a polymerization inhibitor, a dye, a pigment, a surfactant, an antifoaming agent, an ultraviolet absorber, a fragrance, and the like.

[0025] The inclusion of a miscible aid in the photosensitive resin layer can improve the compatibility of the components constituting the photosensitive resin layer, suppress the bleed-out of low-molecular-weight components, and improve the flexibility of the photosensitive resin layer. Examples of miscible aids include polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, and derivatives thereof. The content of the miscible aid in the photosensitive resin layer is preferably 30% by mass or less.

[0026] By including an ink repellent agent in the photosensitive resin layer, it is possible to prevent ink from penetrating into the recesses of the relief during printing, thereby improving reproducibility. Examples of ink repellent agents include silicone compounds and fluorine-containing compounds. The content of the ink repellent agent in the photosensitive resin layer is preferably 5% by mass or less.

[0027] By including a polymerization inhibitor in the photosensitive resin layer, thermal stability can be improved. Examples of polymerization inhibitors include phenols, hydroquinones, catechols, and hydroxyamine derivatives. One or more of these may be included. The content of the polymerization inhibitor in the photosensitive resin layer is preferably 0.001 to 5% by mass.

[0028] Next, the infrared-sensitive layer will be described. The infrared-sensitive layer has the following functions: (1) efficiently absorbs infrared laser light, and the heat generated evaporates or ablates part or all of the layer, creating a difference in optical density between the laser-irradiated and unirradiated areas, i.e., a decrease in the optical density of the irradiated areas, and (2) practically blocks ultraviolet light. Note that, in this context, "practically blocking ultraviolet light" refers to an optical density of the infrared-sensitive layer of 2.0 or higher, and more preferably 2.5 or higher. Optical density is generally represented by D and is defined by the following formula: D=log 10 (100 / T)=log 10 (I0 / I) Here, T is the transmittance (unit: %), I0 is the incident light intensity when measuring the transmittance, and I is the transmitted light intensity.

[0029] The optical density in the present invention refers to a value calculated from the measured value of the transmitted light intensity at a constant incident light intensity. The optical density can be measured using an orthochromatic filter with a Macbeth transmission densitometer "TR-927" (manufactured by Kollmorgen Instruments Corp.).

[0030] The infrared-sensitive layer in the present invention contains polyvinyl alcohol and preferably further contains an infrared-absorbing substance.

[0031] The infrared-sensitive layer contains polyvinyl alcohol having a saponification degree of 60 to 100 mol % and an average degree of polymerization of 300 to 3,000. The inclusion of such polyvinyl alcohol increases the dispersibility of the infrared-absorbing substance described below and improves the film-forming properties of the infrared-sensitive layer. Furthermore, the inclusion of such polyvinyl alcohol inhibits migration of compounds having ethylenic double bonds, which are generally low-molecular-weight components with high fat solubility, to the infrared-sensitive layer, thereby inhibiting cohesive failure of the infrared-sensitive layer and improving adhesion between the photosensitive resin layer and the infrared-sensitive layer.

[0032] Here, the saponification degree and polymerization degree of polyvinyl alcohol are values ​​measured according to JIS K 6726-1994 (Testing method for polyvinyl alcohol). When the infrared-sensitive layer contains two or more types of polyvinyl alcohol, the saponification degree and polymerization degree refer to the total of the two or more types of polyvinyl alcohol.

[0033] By setting the saponification degree of the polyvinyl alcohol in the infrared-sensitive layer to 60 mol% or more, the solubility in a developer containing water as the main component can be improved, and the photosensitive resin layer, intermediate layer, and infrared-sensitive layer can all be developed using a developer containing water as the main component. Furthermore, migration of compounds containing ethylenic double bonds, which are generally low-molecular-weight components with high fat solubility, to the infrared-sensitive layer can be suppressed, cohesive failure of the infrared-sensitive layer can be suppressed, and adhesion between the photosensitive resin layer and the infrared-sensitive layer can be improved. On the other hand, the saponification degree of the polyvinyl alcohol in the infrared-sensitive layer is preferably 97% or less, which can further improve adhesion between the photosensitive resin layer and the infrared-sensitive layer.

[0034] Furthermore, by setting the average degree of polymerization of the polyvinyl alcohol contained in the infrared-sensitive layer to 300 or more, the coating strength of the infrared-sensitive layer can be improved, thereby improving the scratch resistance of the infrared-sensitive layer during the manufacturing process. Furthermore, migration of compounds containing ethylenic double bonds, which are generally low-molecular-weight components with high fat solubility, contained in the photosensitive resin layer to the infrared-sensitive layer can be suppressed, thereby suppressing cohesive failure of the infrared-sensitive layer and improving adhesion between the photosensitive resin layer and the infrared-sensitive layer. An average degree of polymerization of 1,000 or more is more preferable. On the other hand, setting the average degree of polymerization to 3,000 or less allows for easy formation of the infrared-sensitive layer. Furthermore, migration of compounds containing ethylenic double bonds, which are generally low-molecular-weight components with high fat solubility, to the infrared-sensitive layer can be suppressed, thereby suppressing cohesive failure of the infrared-sensitive layer and improving adhesion between the photosensitive resin layer and the infrared-sensitive layer. An average degree of polymerization of 2,500 or less is more preferable.

[0035] The content of polyvinyl alcohol in the infrared-sensitive layer is preferably 10% by mass or more of the total solid content in order to more easily form the infrared-sensitive layer, and is preferably 80% by mass or less of the total solid content in order to improve ablation efficiency.

[0036] The infrared absorbing material is preferably a material that has absorption characteristics in the wavelength range of 750 nm to 20,000 nm, and examples thereof include black pigments such as carbon black, carbon graphite, and cyanine black; inorganic pigments such as manganese oxide, iron oxide, chromium oxide, and copper chromite; and dyes such as phthalocyanine, substituted phthalocyanine derivatives, cyanine dyes, merocyanine dyes, polymethine dyes, and metal thiolate dyes. Two or more of these may be contained. Among these, carbon black is preferred from the viewpoints of ablation efficiency and ultraviolet absorption performance.

[0037] The carbon black preferably has an anionic group. The presence of an anionic group can enhance the dispersibility of the carbon black without using a dispersant, and therefore, the anionic group is preferably a sulfo group or a carboxyl group. The sulfo group has a large dissociation constant in water and is highly effective in suppressing the aggregation of carbon black in the infrared-sensitive layer composition dispersion liquid described below. On the other hand, the carboxyl group suppresses the aggregation of carbon black due to solvent shock, which is likely to occur when an organic solvent such as a lower alcohol is added to the infrared-sensitive layer composition dispersion liquid described below, and can suppress coating defects in the infrared-sensitive layer.

[0038] Carbon black having a carboxyl group as an anionic group preferably also has a lactone group. Carboxyl groups have a low dissociation constant in water and are easily affected by the functional groups of other components and pH, so carbon black having carboxyl groups tends to aggregate easily. However, the inclusion of lactone groups, which are hydrophilic but not ionic, acts as a steric hindrance to electrostatic interactions with other components, thereby suppressing aggregation. Therefore, carbon black having both carboxyl groups and lactone groups can improve dispersibility in polyvinyl alcohol.

[0039] The content of the infrared absorbing material in the infrared-sensitive layer is preferably 5% by mass or more of the total solid content from the viewpoint of improving ablation efficiency, while the content of the infrared absorbing material in the infrared-sensitive layer is preferably 80% by mass or less of the total solid content from the viewpoint of improving scratch resistance of the infrared-sensitive layer.

[0040] The infrared-sensitive layer in the present invention preferably contains an ultraviolet-absorbing substance that blocks ultraviolet rays. The ultraviolet-absorbing substance is preferably a substance that has absorption characteristics in the wavelength range of 300 to 400 nm, such as a benzotriazole-based compound, a triazine-based compound, or a benzophenone-based compound. Two or more of these may be contained.

[0041] The infrared-sensitive layer may contain other polymers, fillers, surfactants, coating aids, etc., to the extent that the effects of the present invention are not impaired. Examples of other polymers include polyacrylic acid, polyester, polyamide, and derivatives thereof. Two or more of these may be contained.

[0042] Next, the intermediate layer will be described. The printing plate precursor of the present invention contains a polyamide resin having a basic nitrogen atom and / or a polyether structure. The basic nitrogen atom and the polyether structure are hydrophilic groups, and the presence of such hydrophilic groups can improve solubility in a developer whose main component is water in the development step. Furthermore, by using such a polyamide resin in the intermediate layer, excellent adhesion to the photosensitive resin layer and the infrared-sensitive layer can be achieved, thereby improving adhesion between the photosensitive resin layer and the infrared-sensitive resin layer. From the viewpoint of further improving solubility in a developer whose main component is water, it is preferable for the intermediate layer to contain a basic nitrogen atom.

[0043] Examples of basic nitrogen atoms include nitrogen atoms contained in piperazine rings and amino groups such as N,N-dialkylamino groups. Two or more of these may be used. From the viewpoint of further improving solubility in a developer containing water as the main component, it is preferable for the compound to have a basic nitrogen atom in its main chain, and it is more preferable for the compound to have a piperazine ring in its main chain.

[0044] A polyamide resin having a basic nitrogen atom in the main chain can be obtained, for example, by condensation polymerization or polyaddition reaction of a component having a basic nitrogen atom, optionally together with other diamines, dicarboxylic acids, ω-amino acids, lactams, etc. As the component having a basic nitrogen atom, diamines, dicarboxylic acids, amino acids, etc. having a piperazine ring or an N,N-dialkylamino group are preferred, and those having a piperazine group are more preferred.

[0045] Examples of components having a basic nitrogen atom include N,N'-bis(aminomethyl)-piperazine, N,N'-bis(β-aminoethyl)-piperazine, N,N'-bis(γ-aminobenzyl)-piperazine, N-(β-aminoethyl)piperazine, N-(β-aminopropyl)piperazine, N-(ω-aminohexyl)piperazine, N-(β-aminoethyl)-2,5-dimethylpiperazine, N,N-bis(β-aminoethyl)-benzylamine, N,N-bis(γ-aminopropyl)-benzylamine, and N,N'-dimethyl-N,N'-bis Diamines such as (γ-aminopropyl)-ethylenediamine, N,N'-dimethyl-N,N'-bis(γ-aminopropyl)-tetramethylenediamine; N,N'-bis(carboxymethyl)-piperazine, N,N'-bis(carboxymethyl)-methylpiperazine, N,N'-bis(carboxymethyl)-2,6-dimethylpiperazine, N,N'-bis(β-carboxyethyl)-piperazine, N,N-bis(carboxymethyl)-methylamine, N,N-bis(β-carboxyethyl)-ethylamine, N,N-bis(β-carboxyethyl) dicarboxylic acids such as N-(aminomethyl)-N'-(carboxymethyl)-piperazine, N-(aminomethyl)-N'-(β-carboxyethyl)-piperazine, N-(β-aminoethyl ... and ω-amino acids such as piperazine, N-carboxymethylpiperazine, N-(β-carboxyethyl)piperazine, N-(γ-carboxyhexyl)piperazine, N-(ω-carboxyhexyl)piperazine, N-(aminomethyl)-N-(carboxymethyl)-methylamine, N-(β-aminoethyl)-N-(β-carboxyethyl)-methylamine, N-(aminomethyl)-N-(β-carboxyethyl)-isopropylamine, and N,N'-dimethyl-N-(aminomethyl)-N'-(carboxymethyl)-ethylenediamine.

[0046] Other diamines, dicarboxylic acids, ω-amino acids and lactams include those exemplified as raw materials for the polyamide resin in the photosensitive resin layer.

[0047] Examples of the polyamide resin having a polyether structure include those exemplified in the photosensitive resin layer.

[0048] The polyamide resin used in the intermediate layer preferably contains a component having a basic nitrogen atom and a component having a polyether in a total of 20 to 90 mol % of all components constituting the polyamide resin, i.e., the sum of aminocarboxylic acids (including lactams used as raw materials), dicarboxylic acids, and diamines. Using 20 mol % or more of these components further improves solubility in a water-based developer and effectively suppresses aggregation of waste developer. Using 30 mol % or more of these components is more preferable. On the other hand, using 90 mol % or less of these components suppresses water absorption during storage and maintains high thickness accuracy of the printing plate. Here, the "total of the component having a basic nitrogen atom and the component having a polyether" refers to either the component having a basic nitrogen atom or the component having a polyether when only one of them is used, or the total when both the component having a basic nitrogen atom and the component having a polyether are used.

[0049] The weight-average molecular weight of the polyamide resin having a basic nitrogen atom and / or a polyether structure is preferably 10,000 or more and 200,000 or less. The weight-average molecular weight can be determined by GPC measurement, similar to that of the polyamide resin in the photosensitive resin layer.

[0050] The printing plate precursor of the present invention may have two or more intermediate layers. For example, by having intermediate layer 1, which has better adhesion to the photosensitive resin layer, on the photosensitive resin layer side and intermediate layer 2, which has better adhesion to the infrared-sensitive layer, on the infrared-sensitive layer side, the adhesion between the photosensitive resin layer and the infrared-sensitive layer can be further improved.

[0051] When there are two intermediate layers, the intermediate layer on the infrared-sensitive layer side (hereinafter sometimes referred to as "intermediate layer 2") preferably contains polyvinyl alcohol having a saponification degree of 60 to 100 mol % and an average polymerization degree of 300 to 3,000. By containing the above-mentioned polyvinyl alcohol in the intermediate layer 2 that contacts the infrared-sensitive layer, adhesion to the infrared-sensitive layer containing polyvinyl alcohol is further improved, and therefore adhesion between the photosensitive resin layer and the infrared-sensitive resin layer can be further improved.

[0052] Here, the degree of saponification and degree of polymerization of the polyvinyl alcohol in the intermediate layer 2 can be measured in accordance with JIS K 6726-1994 (Testing method for polyvinyl alcohol), in the same manner as for the polyvinyl alcohol in the infrared-sensitive layer.

[0053] Furthermore, when there are two intermediate layers, it is preferable that the intermediate layer on the photosensitive resin layer side (hereinafter sometimes referred to as "intermediate layer 1") contains a polyamide resin having a polyether structure, which can further improve adhesion with the photosensitive resin layer.

[0054] The thickness of the intermediate layer is preferably 0.1 to 3 μm. By setting the thickness of the intermediate layer to 0.1 μm, adhesion to the infrared-sensitive layer can be further improved. The thickness of the intermediate layer is more preferably 0.3 μm or more. On the other hand, by setting the thickness of the intermediate layer to 3 μm or less, a deep relief of the recessed image can be formed, improving the reproducibility of cut-out character images, etc. The thickness of the intermediate layer is more preferably 2 μm or less. When two or more intermediate layers are present, it is preferable that the total thickness thereof is within the above range.

[0055] Next, the support will be described. Examples of the support include a plastic sheet made of polyester or the like, a synthetic rubber sheet made of styrene-butadiene rubber or the like, and a metal plate made of steel, stainless steel, aluminum or the like. From the viewpoints of handleability and flexibility, the thickness of the support is preferably in the range of 100 to 350 μm.

[0056] The support is preferably subjected to an easy-adhesion treatment, which can improve adhesion to the relief or floor layer. Examples of easy-adhesion treatment methods include mechanical treatments such as sandblasting, physical treatments such as corona discharge, and chemical treatments such as coating. Among these, from the viewpoint of adhesion, it is preferable to provide an easy-adhesion layer by coating.

[0057] The printing plate precursor of the present invention may have a protective layer on the infrared-sensitive layer, if necessary.

[0058] The protective layer may be, for example, a plastic sheet made of polyester, polyethylene, polypropylene, etc. The thickness of the protective layer is preferably 10 to 150 μm from the viewpoints of handling and flexibility.

[0059] Next, the method for producing a printing plate precursor of the present invention will be described taking as an example a case where a photosensitive resin layer, an intermediate layer, an infrared-sensitive layer and a protective layer are provided on a support.

[0060] For example, a photosensitive resin composition solution is obtained by dissolving a polyamide resin having a polyether structure, a compound having an ethylenic double bond, and other additives in a solvent, such as a water / alcohol mixed solvent, under heating.

[0061] A photosensitive resin composition solution is cast onto a support having an easy-adhesion layer if necessary, and dried to form a photosensitive resin layer. Next, a protective layer having an intermediate layer and an infrared-sensitive layer formed thereon is adhered to the photosensitive resin layer, thereby obtaining a photosensitive resin printing plate precursor. For example, the protective layer having an intermediate layer and an infrared-sensitive layer formed thereon can be formed by coating an infrared-sensitive layer composition dispersion containing the above-mentioned infrared-sensitive layer components onto the protective layer, drying it, and then coating an intermediate layer composition solution containing the above-mentioned intermediate layer components, and drying it.

[0062] A method for producing a printing plate using the photosensitive resin printing plate precursor of the present invention will now be described. The method preferably includes an exposure step of partially photocuring the photosensitive resin layer of the photosensitive resin printing plate precursor, and a development step of removing the uncured portions of the photosensitive resin layer with a liquid containing water.

[0063] In the exposure step, the photosensitive resin printing plate precursor, from which the protective layer (if any) has been removed, is attached to a digital imager having an infrared laser such as a fiber laser, and the infrared-sensitive layer is decomposed and ablated (ablated) to form an image mask. Thereafter, ultraviolet light having a wavelength of 300 to 400 nm is preferably irradiated through the image mask formed from the infrared-sensitive layer to photocure the exposed areas of the photosensitive resin layer. Examples of exposure light sources include high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, carbon arc lamps, chemical lamps, and UV-LED lamps.

[0064] In the developing step, it is preferable to remove the photosensitive resin layer in the unexposed areas with a liquid containing water. Examples of the developing device include a spray type developing device and a brush type washing machine.

[0065] Furthermore, if necessary, a post-exposure step of irradiating with ultraviolet light may be carried out after development. The post-exposure step can make the relief stronger by reaction of the compound having an unreacted ethylenic double bond.

[0066] The photosensitive resin printing plate precursor and printing plate of the present invention can be used for letterpress printing using a label printing rotary press or an intermittent rotary press, dry offset printing, flexographic printing, etc. Among these, they are more preferably used for letterpress printing and dry offset printing. [Example]

[0067] The present invention will be described in detail below with reference to examples. It should be noted that Example 2 described below should be read as Comparative Example.

[0068] <Synthesis of polyamide resin> Synthesis Example 1: Synthesis of Polyamide Resin 1 Acrylonitrile was added to both ends of polyethylene glycol with a number-average molecular weight of 600, and this was then hydrogen-reduced to obtain an equimolar salt of α,ω-diaminopolyoxyethylene and adipic acid (80 mol %), which was then melt-polymerized with an equimolar salt of hexamethylenediamine and adipic acid (20 mol %) to obtain water-soluble polyamide resin 1 having polyethylene oxide in the main chain. The weight-average molecular weight was measured using a Wyatt Technology gel permeation chromatograph-multiangle light scattering photometer at a column temperature of 40°C and a flow rate of 0.7 mL / min, using polyethylene oxide and polyethylene glycol as standard samples, and was found to be 80,000.

[0069] Synthesis Example 2: Synthesis of Polyamide Resin 2 A mixture of 40 mol % of an equimolar salt of α,ω-diaminopolyoxyethylene and adipic acid, obtained by adding acrylonitrile to both ends of polyethylene glycol with a number-average molecular weight of 600 and then hydrogenating the resulting mixture, 20 mol % of ε-caprolactam, and 40 mol % of an equimolar salt of N-(2-aminoethyl)piperazine and adipic acid, was placed in a stainless steel autoclave, and after purging the air with nitrogen gas, the mixture was heated at 180°C for 1 hour. The water was then removed to obtain water-soluble polyamide resin 2, which has a polyethylene oxide skeleton and piperazine rings in its main chain. The weight-average molecular weight was measured as in Synthesis Example 1 and found to be 70,000.

[0070] <Preparation of a support having an easy-adhesion layer> A polyester adhesive (a solution of 100 parts by mass of "Vylon" (registered trademark) 30SS (copolymer polyester, manufactured by Toyobo Co., Ltd.) and 3 parts by mass of "Coronate" (registered trademark) L (polyisocyanate, manufactured by Nippon Polyurethane Industry Co., Ltd.)) was applied to a 250 μm thick "Lumilar" (registered trademark) T60 (polyester film, manufactured by Toray Industries, Inc.) using a bar coater so that the thickness after drying would be 20 μm, and the coating was dried at 90°C for 10 minutes to form a support with an easy-adhesion layer.

[0071] <Preparation of Photosensitive Resin Layer Composition Solution> A three-neck flask equipped with a stirring spatula and a condenser was charged with 80 parts by weight of polyamide resin 1, 30 parts by weight of water, and 30 parts by weight of ethanol. The mixture was heated to 90°C with stirring for 2 hours to dissolve polyamide resin 1. After cooling to 70°C, 1.5 parts by weight of glycidimethacrylate was added and stirred for 30 minutes. 20 parts by weight of glycerin dimethacrylate, 20 parts by weight of polyalkylene glycol (PEG200) diacrylate, 20 parts by weight of 2-acryloxyethyl-2-hydroxyethyl phthalate, 15 parts by weight of pentaerythritol polyoxyethylene ether, 3 parts by weight of 2,2-dimethoxy-1,1-diphenylethane-1-one, and 0.01 parts by weight of hydroquinone monomethyl ether were then added and stirred for 30 minutes to obtain a photosensitive resin layer composition solution.

[0072] <Preparation of Infrared-Sensing Layer Composition Dispersion> Preparation example 1: Infrared sensitive layer composition dispersion 1 20 parts by weight of a 5% by mass aqueous solution of polyvinyl alcohol JL-22E (manufactured by Japan Vinyl Acetate & Poval Co., Ltd., saponification degree 80%, average degree of polymerization 2,200), 10 parts by weight of a 10% by mass aqueous dispersion of carbon black BONJET BLACK CW-1 (manufactured by Orient Chemical Industry Co., Ltd., containing carboxyl groups and lactone groups), and 5 parts by mass of "Solmix" (registered trademark) H-11 (alcohol mixture, manufactured by Nippon Alcohol Co., Ltd.) were added and mixed at room temperature to obtain a dispersion of infrared-sensitive layer composition 1. The dispersibility of the carbon black in the dispersion of infrared-sensitive composition 1 was good, and no aggregates larger than 2 μm were confirmed using a grind gauge.

[0073] Preparation Example 2: 20 parts by weight of a 5% by mass aqueous solution of polyvinyl alcohol JL-22R (manufactured by Japan Vinyl Acetate & Poval Co., Ltd., saponification degree 80%, average degree of polymerization 2,200), 10 parts by weight of a 10% by mass aqueous dispersion of "CAB-O-JET" (registered trademark) 200 (manufactured by Cabot Corporation, containing sulfo groups), and 5 parts by mass of "Solmix" (registered trademark) H-11 (alcohol mixture, manufactured by Nippon Alcohol Co., Ltd.) were added and mixed at room temperature to obtain a dispersion of infrared-sensitive layer composition 1. The dispersibility of carbon black in the dispersion of infrared-sensitive composition 2 was good, and no aggregates larger than 2 μm were confirmed using a grind gauge.

[0074] <Preparation of Intermediate Layer Composition Solution> Preparation Example 3: Intermediate Layer Composition Solution 1 10 parts by mass of the polyamide resin 1 obtained in Synthesis Example 1 was dissolved in 45 parts by mass of water and 45 parts by mass of "Solmix" (registered trademark) H-11 (alcohol mixture, manufactured by Nippon Alcohol Co., Ltd.) with stirring at 70°C for 2 hours to obtain an aqueous polyamide solution 1. The aqueous polyamide solution 1 was used as an intermediate layer composition solution 1.

[0075] Preparation Example 4: Intermediate Layer Composition Solution 2 A polyamide aqueous solution 2 was obtained in the same manner as in Preparation Example 3, except that polyamide resin 2 obtained in Synthesis Example 2 was used instead of polyamide resin 1. Aqueous polyamide solution 2 was used as intermediate layer composition solution 2.

[0076] Preparation Example 5: Intermediate Layer Composition Solution 3 Polyvinyl alcohol JL-22E (manufactured by Nippon Vinyl Acetate & Poval Co., Ltd.) with a saponification degree of 80% and an average degree of polymerization of 2,200, 45 parts by mass of water, and 45 parts by mass of "Solmix" H-11 were dissolved by stirring at 70°C for 2 hours to obtain polyvinyl alcohol aqueous solution 1. Polyvinyl alcohol aqueous solution 1 was used as intermediate layer composition solution 3.

[0077] Preparation Example 6: Intermediate Layer Composition Solution 4 Polyvinyl alcohol KL-03 (manufactured by Mitsubishi Chemical Corporation) with a saponification degree of 80% and an average polymerization degree of 300, 45 parts by mass of water, and 45 parts by mass of "Solmix" H-11 were dissolved by stirring at 70°C for 2 hours to obtain polyvinyl alcohol aqueous solution 2.

[0078] 15 parts by weight of the obtained polyvinyl alcohol aqueous solution 2 and 85 parts by weight of the polyamide aqueous solution 1 obtained in Preparation Example 3 were mixed at room temperature to obtain an intermediate layer composition solution 4.

[0079] Preparation Example 7: Intermediate Layer Composition Solution 5 50 parts by weight of the aqueous polyamide solution 2 obtained in Preparation Example 4 and 50 parts by weight of the aqueous polyvinyl alcohol solution 2 obtained in Preparation Example 6 were mixed at room temperature to obtain an intermediate layer composition solution 5.

[0080] The evaluation methods used in the examples and comparative examples are as follows.

[0081] <Number of defects in the infrared-sensitive layer in the protective layer / infrared-sensitive layer laminate> A 30 cm x 30 cm area of ​​the infrared-sensitive layer / protective layer laminate, which was an intermediate product obtained in each Example and Comparative Example, was magnified and observed using a magnifying glass, and the number of coating defects (cissing defects) of 200 μm or more in the infrared-sensitive layer was counted. The fewer the number, the better the dispersibility of carbon black in the infrared-sensitive layer.

[0082] <Adhesion between photosensitive resin layer and infrared-sensitive layer> The protective layer was peeled off from the printing plate precursor obtained in each Example and Comparative Example, and a cross-cut surface with 25 2mm-wide squares, 6 lines vertically and 6 lines horizontally, was created on the heat-sensitive infrared layer using a multi-cutter guide and a cutter knife. Next, 15mm-wide "Cellotape" (registered trademark) (CT405AP-15, manufactured by Nichiban Co., Ltd.) was applied to the cross-cut surface while taking care not to trap air bubbles, and after 5 minutes, the tape was instantly peeled off. Based on the peeling state of the infrared-sensitive layer, the adhesion between the photosensitive resin layer and the infrared-sensitive layer was evaluated according to the following criteria, with a score of 3 or less being considered acceptable. 0: No peeling observed. 1: Peeling area less than 5% 2: Peeling area is 5% or more but less than 15% 3: Peeling area is 15% or more but less than 35% 4: Peeling area 35% or more but less than 65% 5: Peeling area is 65% or more.

[0083] [Example 1] A photosensitive resin layer composition solution was cast onto the easy-adhesion layer of the support having the easy-adhesion layer obtained by the above-mentioned method, and dried at 60°C for 2 hours to form a photosensitive resin layer with a thickness of 680 μm (950 μm including the support having the easy-adhesion layer). The thickness of the photosensitive resin layer was adjusted by placing a spacer of a predetermined thickness on the support having the easy-adhesion layer and scraping off the protruding part of the photosensitive resin layer composition solution with a horizontal metal ruler.

[0084] The dispersion of infrared-sensitive layer composition 1 obtained by the above-described method was applied using a bar coater onto a 100 μm-thick protective layer, "Lumilar" (registered trademark) S10 (polyester film, manufactured by Toray Industries, Inc.), and dried at 120°C for 30 seconds to form an infrared-sensitive layer, thereby obtaining a protective layer / infrared-sensitive layer laminate. The thickness of the infrared-sensitive layer was adjusted so that the optical density (transmission mode of a Macbeth transmission densitometer "TR-927" (manufactured by Kollmorgen Instruments Corp.)) using an orthochromatic filter with the value of the protective layer set to zero was 3.0.

[0085] Next, the intermediate layer composition solution 1 obtained by the above-mentioned method was applied onto the infrared-sensitive layer of the protective layer / infrared-sensitive layer laminate using a bar coater so that the film thickness after drying would be 1.0 μm, and then dried at 120°C for 30 seconds to form an intermediate layer, thereby obtaining an intermediate layer / infrared-sensitive layer / protective layer.

[0086] A mixed solvent of 50 parts by mass of water and 50 parts by mass of ethanol was applied to the photosensitive resin layer formed by the above-mentioned method, and an intermediate layer / infrared-sensitive layer / protective layer laminate was laminated so that the intermediate layer side was on the photosensitive resin layer, thereby obtaining a printing plate precursor. The results of evaluation by the above-mentioned method are shown in Table 1.

[0087] [Example 2] A printing plate precursor was obtained in the same manner as in Example 1, except that the infrared-sensitive layer was formed from a dispersion of infrared-sensitive layer composition 2. The evaluation results are shown in Table 1.

[0088] [Examples 3 to 5] A printing plate precursor was obtained in the same manner as in Example 1, except that the intermediate layer was formed using intermediate layer composition solutions 2, 4, and 5. The evaluation results are shown in Table 1.

[0089] [Example 6] In the same manner as in Example 1, a protective layer / infrared-sensitive layer laminate was obtained.

[0090] Next, intermediate layer composition solution 5 was applied onto the infrared-sensitive layer of the protective layer / infrared-sensitive layer laminate using a bar coater so that the film thickness after drying would be 1.0 μm, and dried at 120° C. for 30 seconds to form intermediate layer 2, thereby obtaining intermediate layer 2 / infrared-sensitive layer / protective layer. Furthermore, intermediate layer composition solution 4 was applied onto intermediate layer 2 of the intermediate layer 2 / infrared-sensitive layer / protective layer using a bar coater so that the film thickness after drying would be 1.0 μm, and dried at 120° C. for 30 seconds to form intermediate layer 1, thereby obtaining intermediate layer 1 / intermediate layer 2 / infrared-sensitive layer / protective layer.

[0091] A mixed solvent of 50 parts by mass of water and 50 parts by mass of ethanol was applied to the photosensitive resin layer formed by the above-mentioned method, and an intermediate layer 1 / intermediate layer 2 / infrared-sensitive layer / protective layer laminate was laminated so that the intermediate layer 1 side was on the photosensitive resin layer, thereby obtaining a printing plate precursor. The results of evaluation by the above-mentioned method are shown in Table 1.

[0092] [Comparative Example 1] In the same manner as in Example 1, a protective layer / infrared-sensitive layer laminate was obtained.

[0093] A mixed solvent of 50 parts by mass of water and 50 parts by mass of ethanol was applied onto the photosensitive resin layer formed by the above-mentioned method, and the infrared-sensitive layer / protective layer laminate was laminated so that the infrared-sensitive layer side was on the photosensitive resin layer, thereby obtaining a printing plate precursor. The results of evaluation by the above-mentioned method are shown in Table 1.

[0094] Comparative Example 2 A printing plate precursor was obtained in the same manner as in Example 1, except that the intermediate layer was formed from intermediate layer composition solution 3. The evaluation results are shown in Table 1.

[0095] [Table 1]

Claims

1. A photosensitive resin printing plate precursor having, on a support, a photosensitive resin layer containing a polyamide resin having a polyether structure, an intermediate layer, and an infrared-sensitive layer in this order, wherein the infrared-sensitive layer contains polyvinyl alcohol having a saponification degree of 60 to 100 mol % and an average degree of polymerization of 300 to 3,000, and the intermediate layer contains a polyamide resin having a basic nitrogen atom and / or a polyether structural unit, and the photosensitive resin printing plate precursor has two or more intermediate layers, and the intermediate layer on the infrared-sensitive layer side contains polyvinyl alcohol having a saponification degree of 60 to 100 mol % and an average degree of polymerization of 300 to 3,000.

2. A photosensitive resin printing plate precursor having, on a support, a photosensitive resin layer containing a polyamide resin having a polyether structure, an intermediate layer, and an infrared-sensitive layer in this order, wherein the infrared-sensitive layer contains polyvinyl alcohol having a saponification degree of 60 to 100 mol % and an average polymerization degree of 300 to 3,000, the intermediate layer contains a polyamide resin having a basic nitrogen atom, and the polyamide resin having a basic nitrogen atom has a piperazine ring.

3. A photosensitive resin printing plate precursor comprising a support and, in this order, a photosensitive resin layer containing a polyamide resin having a polyether structure, an intermediate layer, and an infrared-sensitive layer, wherein the infrared-sensitive layer contains polyvinyl alcohol having a saponification degree of 60 to 100 mol % and an average polymerization degree of 300 to 3,000, the intermediate layer contains a polyamide resin having a basic nitrogen atom and / or a polyether structural unit, and the infrared-sensitive layer contains carbon black having a carboxyl group and a lactone group.

Images