Photosensitive printing original plate and method for manufacturing photosensitive relief printing plate

Abstract

Provided is a photosensitive printing original plate that has few mask defects (flaws) and is capable of preventing transfer of a substance from a heat-sensitive mask layer (excellent in temporal stability). This photosensitive printing original plate is formed by laminating at least a support (A), a photosensitive resin layer, and a heat-sensitive mask layer (C) in this order. The heat-sensitive mask layer (C) contains a partially saponified polyvinyl alcohol (a), an ultraviolet absorbing substance (b), and carbon black (c). The ultraviolet absorbing substance (b) contains an acrylic resin (b-1). Also provided is a method for manufacturing a photosensitive relief printing plate using the photosensitive printing original plate.

Description

Photosensitive printing plate and method for manufacturing photosensitive relief printing plate

[0001] The present invention relates to a method for producing a photosensitive printing plate precursor and a photosensitive relief printing plate.

[0002] In the field of flexographic printing, computer-to-plate (CTP) technology, also known as digital image formation technology, has become extremely common. CTP technology is a method in which information processed on a computer is output directly onto a heat-sensitive mask layer to obtain a relief pattern. This technology eliminates the need for the negative film manufacturing process, thereby reducing the cost and time required to produce negatives.

[0003] In the CTP technique, the negative film conventionally used to cover the areas that should not be photopolymerized is replaced by an integrated mask formed within the printing plate. A known method for obtaining this integrated mask is to provide a heat-sensitive mask layer that is opaque to actinic radiation on a photosensitive resin layer, and a method is widely used in which the image-wise mask is formed by dispersing and evaporating (ablating) this heat-sensitive mask layer with an infrared laser (see Patent Document 1).

[0004] The heat-sensitive mask layer needs to have a light-shielding property to prevent the transmission of actinic radiation to the photosensitive resin layer. Carbon black, which has infrared absorption ability, is generally used as a material having light-shielding properties against actinic radiation, and is dispersed in a film-forming binder. As the film-forming binder, it is known to incorporate, for example, polyvinyl alcohol, which has excellent water solubility (see Patent Document 2).

[0005] Recently, there has been a demand for higher-resolution printed images, and it has been necessary to form printed images consisting of a collection of fine lines and dots. To achieve this, it is important that the heat-sensitive mask layer is free of defects. An integrated mask is manufactured by applying a heat-sensitive mask layer to a film such as a polyester film. When applying the heat-sensitive mask layer to the film, there is a problem of mask defects (pinholes) occurring due to coating unevenness, repelling, etc. To address this problem, for example, Patent Document 3 proposes a flexographic printing plate precursor containing carbon black as an infrared absorber, a binder polymer, and a dispersant with a base number of 5 to 100 mg / mg KOH in the heat-sensitive mask layer.

[0006] Japanese Patent Publication No. 7-506201, Japanese Patent Application Laid-Open No. 2021-162667, International Publication No. WO2020 / 175422

[0007] In Patent Document 3, the frequency of mask defects (pinholes) is reduced by dispersing carbon black with a dispersant, but mask defects (pinholes) in which pigment is partially missing due to insufficient dispersion of carbon black remain. Therefore, further improvements are desired to eliminate the drawbacks of photosensitive relief printing plates caused by mask defects (pinholes) and to form higher-resolution printed images.

[0008] In order to solve the problems of the conventional technology, the present inventors have been engaged in development of a method of blending an ultraviolet absorber together with carbon black in the heat-sensitive mask layer. Based on the findings independently obtained by the present inventors through research and development, a new problem has emerged in which the ultraviolet absorber migrates from the heat-sensitive mask layer into the photosensitive resin layer during storage, inhibiting photocuring and reducing the reproducibility of high-resolution printed images on the photosensitive relief printing plate.

[0009] The present invention was devised in view of the above-mentioned circumstances, and its object is to provide a photosensitive printing original plate and a method for producing a photosensitive letterpress printing plate that has few defects and can prevent material migration from the heat-sensitive mask layer to the photosensitive resin layer (resulting in excellent stability over time).

[0010] As a result of extensive research into achieving the above-mentioned object, the present inventors have found that the above-mentioned problems can be solved by having the (C) heat-sensitive mask layer in the photosensitive printing plate precursor contain (a) partially saponified polyvinyl alcohol, (b) an ultraviolet-absorbing substance, and (c) carbon black, and the (b) ultraviolet-absorbing substance contains a specific ultraviolet-absorbing substance, thereby completing the present invention.

[0011] That is, the present invention comprises the following configurations (1) to (8): (1) A photosensitive printing plate blank comprising at least (A) a support, (B) a photosensitive resin layer, and (C) a heat-sensitive mask layer laminated in this order, the (C) heat-sensitive mask layer containing (a) partially saponified polyvinyl alcohol, (b) an ultraviolet-absorbing substance, and (c) carbon black, and the (b) ultraviolet-absorbing substance contains (b-1) an acrylic resin. (2) The photosensitive printing plate blank according to (1), wherein the (a) partially saponified polyvinyl alcohol has a saponification degree of 60 to 90 mol %. (3) The photosensitive printing plate blank according to (1), wherein the (b-1) acrylic resin is an aqueous resin. (4) The photosensitive printing plate blank according to (1), wherein the (b-1) acrylic resin has a benzotriazole skeleton. (5) The photosensitive printing plate blank according to (1), wherein the (b-1) acrylic resin has a glass transition temperature (Tg) of -50°C or higher and 100°C or lower. (6) The photosensitive printing plate blank according to (1), wherein the (c) carbon black contains 60 parts by mass or more per 100 parts by mass of the (a) partially saponified polyvinyl alcohol. (7) The photosensitive printing plate blank according to (1), wherein the (c) carbon black to the (b-1) acrylic resin in the (C) heat-sensitive mask layer has a mass ratio of 60:40 to 99:1. (8) A method for producing a photosensitive relief printing plate having non-image areas and image areas, comprising: a mask formation step of forming an image on the (C) heat-sensitive mask layer of the photosensitive printing original plate described in any one of (1) to (7) to form a mask; an exposure step of exposing the (B) photosensitive resin layer imagewise through the mask after the mask formation step; and a development step of developing using an aqueous developer after the exposure step to form non-image areas and image areas.

[0012] According to the present invention, it is possible to provide a photosensitive printing plate precursor and a photosensitive letterpress printing plate that are capable of producing high-resolution printed images because the defects of photosensitive letterpress printing plates are reduced and the photosensitive printing plate precursor has excellent stability over time.

[0013] Hereinafter, embodiments of the present invention will be described in detail. Note that the following embodiments are merely examples for explaining the present invention, and are not intended to limit the present invention to the following content. The present invention can be implemented in various modifications within the scope of its gist.

[0014] In this specification, the expressions "contain" and "comprise" include the concepts of "contain," "include," "consist essentially of," and "consist only of."

[0015] In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in an example or a value that can be unambiguously derived from an example. Furthermore, in this specification, a numerical value connected with "to" means a numerical range that includes the numbers before and after "to" as the upper and lower limits.

[0016] <Photosensitive Printing Original Plate> The photosensitive printing original plate of the present invention comprises at least (A) a support, (B) a photosensitive resin layer, and (C) a heat-sensitive mask layer laminated in this order. The (B) photosensitive resin layer is composed of a photosensitive resin composition, and an adhesive layer may be provided between the (A) support and the (B) photosensitive resin layer.

[0017] The adhesive layer is provided to bond (A) the support and (B) the photosensitive resin layer. The adhesive layer may be formed of one layer or multiple layers. The adhesive layer preferably contains a binder component and a pigment, and further contains a leveling agent and a curing agent.

[0018] Examples of binder components used in the adhesive layer include polyester resins, epoxy resins, polyamide resins, polyimide resins, phenolic resins, butadiene resins, polyurethane resins, polystyrene-polyisoprene copolymer resins, etc. These can be used alone or in combination. Among these, particularly preferred binder components are polyester resins and polyurethane resins in terms of solvent resistance.

[0019] <(A) Support> The (A) support is not particularly limited, but is preferably a material that is flexible and has excellent dimensional stability. Examples include metal supports such as steel, aluminum, copper, and nickel, and thermoplastic resin supports such as polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, and polycarbonate film. Among these, polyethylene terephthalate film is particularly preferred because of its excellent dimensional stability and sufficiently high viscoelasticity. The thickness of the support is desirably 50 to 350 μm, preferably 100 to 250 μm, in terms of mechanical properties, shape stability, and ease of handling during printing plate making.

[0020] <(B) Photosensitive Resin Layer> The photosensitive printing original plate of the present invention has a (B) photosensitive resin layer on an (A) support. The (B) photosensitive resin layer is composed of a known photosensitive resin composition and is not particularly limited. The photosensitive resin composition may be composed of, for example, (i) a synthetic polymer compound, (ii) a compound having an ethylenic double bond, and (iii) a photopolymerization initiator. In addition to the above components (i) to (iii), the photosensitive resin composition may further contain other additives such as a thermal polymerization inhibitor, a plasticizer, a dye, a pigment, a fragrance, or an antioxidant. Components (i) to (iii) of the photosensitive resin composition are described in detail below.

[0021] <(i) Synthetic Polymer Compound> The (i) synthetic polymer compound is not particularly limited, and a conventionally known soluble synthetic polymer compound can be used. Examples thereof include polyetheramides (e.g., JP 55-79437 A), polyetheresteramides (e.g., JP 58-113537 A), tertiary nitrogen-containing polyamides (e.g., JP 50-76055 A), ammonium salt-type tertiary nitrogen atom-containing polyamides (e.g., JP 53-36555 A), addition polymers of amide compounds having one or more amide bonds and organic diisocyanate compounds (e.g., JP 58-140737 A), addition polymers of diamines having no amide bonds and organic diisocyanate compounds (e.g., JP 4-97154 A), and modified polyvinyl alcohols (WO 2014 / 021322 International Publication). From the viewpoint of forming a high-definition printed image, it is preferable that the synthetic polymer compound contains a tertiary nitrogen atom-containing polyamide and an ammonium salt type tertiary nitrogen atom-containing polyamide.

[0022] The content of the synthetic polymer compound in the photosensitive resin layer (B) is preferably 30 to 70% by mass.

[0023] <(ii) Compound Having an Ethylenic Double Bond> (ii) A 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. Examples of compounds having an ethylenic double bond include (meth)acrylates, which are esters of (meth)acrylic acid and alcohol compounds, and addition reaction products of (meth)acrylic acid and glycidyl compounds, and (meth)acrylamides, which are amides of (meth)acrylic acid and amine group-containing compounds. These compounds may be used alone or in combination of two or more. Here, (meth)acrylate is a general term for acrylates and methacrylates, and (meth)acrylic acid is a general term for acrylic acid and methacrylic acid. From the viewpoint of forming high-resolution printed images, it is preferable that the compound having an ethylenic double bond include (meth)acrylates, which are esters of (meth)acrylic acid and alcohol compounds, and addition reaction products of (meth)acrylic acid and glycidyl compounds.

[0024] The content of the compound having an ethylenic double bond in the photosensitive resin layer (B) is preferably 10 to 60% by mass.

[0025] <(iii) Photopolymerization Initiator> Examples of the (iii) photopolymerization initiator include benzophenones, benzoins, acetophenones, benzils, benzoin alkyl ethers, benzyl alkyl ketals, anthraquinones, and thioxanthones. Specific examples include benzophenone, phenyl ketones, chlorobenzophenone, benzoin, acetophenone, benzil, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzil dimethyl ketal, benzil diethyl ketal, benzil diisopropyl ketal, anthraquinone, 1-hydroxycyclohexan-1-yl phenyl ketone, 2-ethylanthraquinone, 2-methylanthraquinone, 2-allylanthraquinone, 2-chloroanthraquinone, thioxanthone, and 2-chlorothioxanthone. These may be used alone or in combination of two or more. From the viewpoint of forming a high-definition printed image, it is preferable that the photopolymerization initiator contains benzyl dimethyl ketal, benzyl diethyl ketal, or benzyl diisopropyl ketal.

[0026] The content of the photopolymerization initiator in the photosensitive resin layer (B) is preferably 0.1 to 10% by mass.

[0027] <(C) Heat-sensitive Mask Layer> The photosensitive printing original plate of the present invention has (C) a heat-sensitive mask layer on (B) a photosensitive resin layer, which has the functions of absorbing infrared laser light and converting it into heat, and blocking ultraviolet light.

[0028] The (C) heat-sensitive mask layer contains (a) partially saponified polyvinyl alcohol, (b) an ultraviolet-absorbing substance, and (c) carbon black, and the (b) ultraviolet-absorbing substance contains (b-1) an acrylic resin. The (C) heat-sensitive mask layer may contain other additives, such as a polymerization inhibitor, a surfactant, a defoaming agent, or a fragrance, in addition to the above components (a) to (c). The components (a) to (c) of the (C) heat-sensitive mask layer are described in detail below.

[0029] <(a) Partially Saponified Polyvinyl Alcohol> The degree of saponification of the (a) partially saponified polyvinyl alcohol is preferably 60 mol % or more and 90 mol % or less. Within this range, the solubility of the (C) heat-sensitive mask layer in a developer containing water as a main component can be further improved, resulting in good developability and dispersibility of carbon black.

[0030] The average degree of polymerization of the (a) partially saponified polyvinyl alcohol is preferably in the range of 300 to 3,000, more preferably 800 to 2,500. Here, the average degree of polymerization of the (a) partially saponified polyvinyl alcohol refers to the average degree of polymerization of all the (a) partially saponified polyvinyl alcohols contained in the (C) heat-sensitive mask layer. When two or more types are contained, it refers to the average degree of polymerization of the two or more (a) partially saponified polyvinyl alcohols as a whole. An average degree of polymerization of the (a) partially saponified polyvinyl alcohol in the range of 300 to 3,000 is preferred because better film strength and coating film formability can be obtained. The average degree of polymerization can be determined by dividing the number average molecular weight of the polyvinyl alcohol before saponification by the molecular weight of the polyvinyl alcohol.

[0031] The content of (a) partially saponified polyvinyl alcohol is preferably 10 to 80 parts by mass, more preferably 20 to 70 parts by mass, and even more preferably 30 to 60 parts by mass, per 100 parts by mass of the solid content in the (C) heat-sensitive mask layer. When the content of (a) partially saponified polyvinyl alcohol is 10 to 80 parts by mass per 100 parts by mass of the solid content in the (C) heat-sensitive mask layer, ablation is easy, and good water-developability and good coating film-formability are likely to be obtained.

[0032] Examples of a method for setting the saponification degree of the (a) partially saponified polyvinyl alcohol in the (C) heat-sensitive mask layer to 60 mol % or more and 90 mol % or less include a method of using a partially saponified polyvinyl alcohol having a saponification degree of 60 to 90 mol %, and a method of using two or more types of partially saponified polyvinyl alcohols so that the average saponification degree of all the (a) partially saponified polyvinyl alcohols is 60 mol % or more and 90 mol % or less.

[0033] <(b) UV-Absorbing Substance> The (b) UV-absorbing substance is characterized by containing (b-1) an acrylic resin. This suppresses UV transmission through mask defects (pinholes) in the photosensitive printing plate precursor, thereby suppressing defects in the photosensitive relief printing plate. Furthermore, the (b) UV-absorbing substance can be prevented from migrating from the (C) heat-sensitive mask layer into the (B) photosensitive resin layer, resulting in good stability over time for the photosensitive printing plate precursor and achieving high-resolution print image reproducibility. As a result, it becomes possible to form print images with fine lines or clusters of dots measuring 10 to 20 μm.

[0034] The (b) ultraviolet absorbing substance is preferably a substance that absorbs ultraviolet rays in a wide wavelength range. Examples include benzotriazole-based ultraviolet absorbing substances, benzophenone-based ultraviolet absorbing substances, conjugated diene-based ultraviolet absorbing substances, avobenzone-based ultraviolet absorbing substances, azoresorcinol-based ultraviolet absorbing substances, and triazine-based ultraviolet absorbing substances. From the viewpoint of excellent absorption ability of UVB (280 to 320 nm) and UVA (320 to 400 nm) light, it is preferable to use a benzotriazole-based ultraviolet absorbing substance.

[0035] In this specification, the term "(b-1) acrylic resin" refers to a resin containing at least one structural unit selected from the group consisting of a structural unit derived from acrylic acid, a structural unit derived from methacrylic acid, a structural unit derived from an acrylic acid ester, and a structural unit derived from a methacrylic acid ester.

[0036] The concept of (b-1) acrylic resin includes, for example, a homopolymer of acrylic acid, a homopolymer of methacrylic acid, a homopolymer of an acrylic acid ester, a homopolymer of a methacrylic acid ester, a copolymer of acrylic acid and another monomer, a copolymer of methacrylic acid and another monomer, a copolymer of an acrylic acid ester and another monomer, a copolymer of a methacrylic acid ester and another monomer, and the like.

[0037] The acrylic resin (b-1) has an ultraviolet absorbing skeleton. Examples of the ultraviolet absorbing skeleton include a benzotriazole skeleton, a benzophenone skeleton, an avobenzone skeleton, an azoresorcinol skeleton, and a triazine skeleton. From the viewpoint of excellent light absorption ability and suppressing ultraviolet light transmission through mask defect (pinhole) portions, it is preferable that the acrylic resin (b-1) has a benzotriazole skeleton.

[0038] The acrylic resin (b-1) is preferably a copolymer of a monomer having an ultraviolet absorbing skeleton and a monomer for forming the acrylic resin.

[0039] The monomer having an ultraviolet absorbing skeleton in the (b-1) acrylic resin is contained in an amount of preferably 20% by mass or more and 90% by mass or less, more preferably 30% by mass or more and 80% by mass or less, and even more preferably 40 parts by mass or more and 70% by mass or less, in the (b-1) acrylic resin.

[0040] Examples of monomers having a benzotriazole skeleton include monomers having a resorcinol-type benzotriazole skeleton and monomers having an alkanolphenol-type benzotriazole skeleton. Examples of monomers having a resorcinol-type benzotriazole skeleton include, but are not limited to, 2-acryloyloxyethyl-2-(2-hydroxy-4-methoxyphenyl)-2H-benzotriazole-5-carboxylate, 2-methacryloyloxyethyl-2-(2-hydroxy-4-methoxyphenyl)-2H-benzotriazole-5-carboxylate, 2-methacryloyloxyethyl-2-(4-benzoyloxy-2-hydroxyphenyl)-2H-benzotriazole-5-carboxylate, 2-methacryloyloxyethyl-2-(2-hydroxy-4-methacryloyloxyphenyl)-2H-benzotriazole-5-carboxylate, and 2-methacryloyloxyethyl-2-(2-hydroxy-4-octyloxyphenyl)-2H-benzotriazole-5-carboxylate. These may be used alone or in combination of two or more.

[0041] Examples of monomers having an alkanolphenol type benzotriazole skeleton include 2-[2-hydroxy-5-(methacryloyloxymethyl)phenyl]-2H-benzotriazole, 2-[2-hydroxy-5-(acryloyloxymethyl)phenyl]-2H-benzotriazole, 2-[2-hydroxy-5-(methacryloyloxyethyl)phenyl]-2H-benzotriazole, 2-[2-hydroxy-5-(acryloyloxyethyl)phenyl]-2H-benzotriazole, 2-[2-hydroxy-5-(methacryloyloxyethyl)phenyl]-2H-benzotriazole, 2-[2-hydroxy-5-(acryloyloxypropyl)phenyl]-2H-benzotriazole, 2-[2-hydroxy-5-(methacryloyloxybutyl)phenyl]-2H-benzotriazole, 2-[2-hydroxy-5-(acryloyloxybutyl)phenyl]-2H-benzotriazole, 2-[2-hydroxy-5-(methacryloyloxyhexyl)phenyl]-2H-benzotriazole, 2-[2-hydroxy-5-(acryloyloxyhexyl)phenyl] -2H-benzotriazole, 2-[2-hydroxy-3-t-butyl-5-(methacryloyloxyethyl)phenyl]-2H-benzotriazole, 2-[2-hydroxy-3-t-butyl-5-(acryloyloxyethyl)phenyl]-2H-benzotriazole, 2-[2-hydroxy-5-(methacryloyloxyethyl)phenyl]-5-chloro-2H-benzotriazole, 2-[2-hydroxy-5-(acryloyloxyethyl)phenyl]-5-chloro-2H-benzotriazole, 2-[2-hydroxy-5-(methacryloyloxyethyl)phenyl]-5-chloro-2H-benzotriazole, 2-[2-hydroxy-5-(acryloyloxyethyl)phenyl]-5-methoxy-2H-benzotriazole, 2-[2-hydroxy-5-(methacryloyloxyethyl)phenyl]-5-cyano-2H-benzotriazole, 2-[2-hydroxy-5-(acryloyloxyethyl)phenyl]-5-cyano-2H-benzotriazole, 2-[2-hydroxy-5-(methacryloyloxyethyl)phenyl]-5-t-butyl-2H-benzotriazole,Examples of the monomers include, but are not limited to, 2-[2-hydroxy-5-(acryloyloxyethyl)phenyl]-5-t-butyl-2H-benzotriazole, 2-[2-hydroxy-5-(methacryloyloxyethyl)phenyl]-5-nitro-2H-benzotriazole, and 2-[2-hydroxy-5-(acryloyloxyethyl)phenyl]-5-nitro-2H-benzotriazole. These may be used alone or in combination of two or more. Furthermore, a monomer having a resorcinol-type benzotriazole skeleton and a monomer having an alkanolphenol-type benzotriazole skeleton may be used in combination.

[0042] Specific examples of monomers for forming acrylic resins include (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, acetoxyethyl (meth)acrylate, phenyl (meth)acrylate, 2-methyl (meth)acrylate, ... 2-(2-methoxyethoxy)ethyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, diethylene glycol monophenyl ether (meth)acrylate, triethylene glycol monomethyl ether (meth)acrylate, triethylene glycol monoethyl ether Examples of such acrylates include methyl ether (meth)acrylate, dipropylene glycol monomethyl ether (meth)acrylate, polyethylene glycol monomethyl ether (meth)acrylate, polypropylene glycol monomethyl ether (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polybutylene glycol mono(meth)acrylate, polyethylene glycol-polypropylene glycol mono(meth)acrylate, hydroxyphenyl (meth)acrylate, hydroxybenzyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and phenoxydiethylene glycol (meth)acrylate. These acrylates may be used alone or in combination of two or more.

[0043] The polymerization method used in copolymerizing the monomer having a benzotriazole skeleton with the monomer for forming the acrylic resin can be a conventionally known solution polymerization method, emulsion polymerization method, suspension polymerization method, bulk polymerization method, etc. Also, the preparation method, such as the method for mixing raw materials containing the monomer having a benzotriazole skeleton, can be a known method and is not particularly limited.

[0044] Specific examples of commercially available acrylic resins having a benzotriazole skeleton include the water-based New Coat UVA series (e.g., New Coat UVA-101, New Coat UVA-102, New Coat UVA-103, New Coat UVA-104, New Coat UVA-204W) manufactured by Shin-Nakamura Chemical Co., Ltd., and the solvent-based Vanaresin UVA series (e.g., Vanaresin UVA-5080, hydroxyl group-introduced Vanaresin UVA-5080 (OHV20), Vanaresin UVA-55T, high hydroxyl value type Examples of such an absorbent include Vanaresin UVA-55MHB, Vanaresin UVA-7075, hydroxyl group-introduced Vanaresin UVA-7075 (OHV20), and Vanaresin UVA-73T, UV absorbers for aqueous coatings (e.g., ULS-1700) and UV absorbers for solvent-based coatings (ULS-935LH, ULS-1935LH, ULS-1933D) manufactured by Lion Specialty Chemicals Co., Ltd., and aqueous acrylic urethane resins (e.g., Sannalon MW-022) manufactured by Yamanan Synthetic Chemicals Co., Ltd. These may be used alone or in combination of two or more.

[0045] From the viewpoint of preventing the (b) ultraviolet absorber from migrating from the (C) heat-sensitive mask layer into the (B) photosensitive resin layer (excellent stability over time), the weight-average molecular weight of the (b-1) acrylic resin is preferably 1,000 to 200,000. More preferably, the weight-average molecular weight is 2,000 to 100,000. The weight-average molecular weight of the (b) ultraviolet-absorbing substance containing the (b-1) acrylic resin can be determined in polystyrene equivalent terms using gel permeation chromatography (GPC).

[0046] From the viewpoint of suppressing ultraviolet light transmittance in the mask defect (pinhole) portion, the content of the (b-1) acrylic resin in the (C) heat-sensitive mask layer is preferably 1.0 mass% or more and 40 mass% or less, and more preferably 1.5 mass% or more and 30 mass% or less, relative to the total solid content of the (C) heat-sensitive mask layer.

[0047] The acrylic resin (b-1) is preferably a water-based acrylic resin. This allows the heat-sensitive mask layer (C) to have high developability in a water-based developer. The water-based acrylic resin is a water-soluble or water-dispersible resin, and refers to a resin that is soluble or dispersible in at least 1 g per 100 ml of water at 50°C, preferably at least 5 g per 100 ml of water at 50°C.

[0048] The aqueous acrylic resin can be obtained, for example, by copolymerizing a known hydrophilic monomer component as a monomer for forming the acrylic resin, or by introducing a hydroxyl group, a carboxyl group, or a sulfonium group into the side chain and / or terminal of the acrylic resin. To improve water dispersibility, a known surfactant may also be used.

[0049] The hydrophilic monomer component is preferably a hydroxyl group-containing monomer, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, hydroxyphenyl (meth)acrylate, or hydroxybenzyl (meth)acrylate, which has a hydroxyl group bonded to an alkyl group or aromatic ring contained in the above acrylic esters.

[0050] Specific examples of water-based acrylic resins include the water-based Newcoat UVA series manufactured by Shin-Nakamura Chemical Co., Ltd., ULS-1700, an ultraviolet absorber for water-based coatings manufactured by Lion Specialty Chemicals Co., Ltd., and Sannalon MW-022, a water-based acrylic urethane resin manufactured by Yamanan Synthetic Chemical Industry Co., Ltd.

[0051] The glass transition temperature (Tg) of the (b-1) acrylic resin is preferably −50° C. or higher and 100° C. or lower, more preferably −40° C. or higher and 80° C. or lower, and even more preferably −30° C. or higher and 50° C. or lower, from the viewpoints of improving the flexibility of the heat-sensitive mask layer, improving compatibility with partially saponified polyvinyl alcohol, and further suppressing defects in the photosensitive relief printing plate.

[0052] <(c) Carbon Black> (c) Carbon black acts as an infrared absorber, absorbing infrared rays and converting them into heat, and also functions to block ultraviolet light. In addition to (c) carbon black, the infrared absorbing material may also include a material having absorption characteristics in the wavelength range of 750 nm to 20,000 nm. In addition to carbon black, examples of infrared absorbing materials include black pigments such as 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. In addition to carbon black, two or more infrared absorbing materials may be included.

[0053] From the viewpoint of improving ablation efficiency, the content of (c) carbon black in the (C) heat-sensitive mask layer is preferably 30 parts by mass or more, more preferably 70 parts by mass or more, per 100 parts by mass of the partially saponified polyvinyl alcohol (a). In this case, the shielding property against actinic radiation is even more excellent, and the ablation efficiency is good.

[0054] The content of (c) carbon black in the (C) heat-sensitive mask layer is preferably 20% by mass or more and 60% by mass or less, more preferably 25% by mass or more and 55% by mass or less, even more preferably 30% by mass or more and 50% by mass or less, and even more preferably 35% by mass or more and 45% by mass or less, relative to the total solid content of the (C) heat-sensitive mask layer, for the reasons of suppressing mask defects (pinholes), providing better shielding properties against chemical radiation, and providing good ablation efficiency.

[0055] The optical density of the heat-sensitive mask layer (C) is preferably 2.0 or more, because it provides better shielding properties against actinic radiation and good ablation efficiency. The upper limit is not particularly limited, but from the viewpoint of operability, it is, for example, 5.0 or less. The optical density can be measured, for example, using a black-and-white transmission densitometer DM-520 (Dainippon Screen Mfg. Co., Ltd.).

[0056] The thickness of the heat-sensitive mask layer (C) is preferably 0.5 to 3.5 μm, more preferably 1.0 to 3.0 μm. If the thickness is equal to or greater than the lower limit, a certain level of optical density can be obtained without requiring advanced coating techniques. Furthermore, if the thickness is equal to or less than the upper limit, evaporation of the heat-sensitive mask layer (C) does not require high energy consumption, which is advantageous in terms of cost.

[0057] The mass ratio of (c) carbon black to (b-1) acrylic resin in the (C) heat-sensitive mask layer is preferably 60:40 to 99:1. It is more preferably 65:35 to 98:2. It is even more preferably 70:30 to 90:10. By incorporating (b-1) acrylic resin relative to (c) carbon black at the above mass ratio, mask defects (pinholes) can be further suppressed, and ultraviolet light transmittance in areas with mask defects (pinholes) can be further reduced. As a result, defects in the photosensitive letterpress printing plate can be further suppressed, making it easier to achieve high-resolution printed image reproducibility.

[0058] <Cover film> The photosensitive printing plate blank of the present invention may have a cover film on the (C) heat-sensitive mask layer. The cover film is a layer for protecting the photosensitive printing plate blank, and is preferably a flexible cover film. The cover film is preferably a peelable film, and examples thereof include polyethylene terephthalate film, polyethylene naphthalate film, and polybutylene terephthalate film.

[0059] The surface of the cover film (the surface on which the (C) heat-sensitive mask layer is formed) may be subjected to a release treatment to prevent adhesion of the (C) heat-sensitive mask layer and improve the releasability of the cover film. Examples of such a release treatment include a method of forming a release layer by applying a release agent to the surface of the cover film. Examples of the release agent include silicone-based release agents and alkyl-based release agents. The thickness of the cover film is preferably 25 to 250 μm.

[0060] <Functional Layer> The photosensitive printing original plate of this embodiment may include an optional functional layer between the photosensitive resin layer (B) and the heat-sensitive mask layer (C). The functional layer is not particularly limited, but for example, an oxygen barrier layer and / or an adhesive layer may be provided.

[0061] The oxygen barrier layer can be provided to obtain a photosensitive relief printing plate with even better reproducibility of high-resolution printed images. The presence of the oxygen barrier layer can prevent the radical-generating compound from reacting with oxygen during the radical polymerization reaction due to exposure, thereby preventing the polymerization reaction from being inhibited.

[0062] When an oxygen barrier layer is provided, examples of the binder polymer in the oxygen barrier layer include polyvinyl alcohol, partially saponified polyvinyl acetate, alkyl cellulose, cellulose-based polymers, and polyamides. These polymers may be used alone or in combination of two or more polymers. Examples of binder polymers that are preferred in terms of oxygen barrier properties include polyvinyl alcohol, partially saponified polyvinyl acetate, and polyamides. Examples of partially saponified polyvinyl acetate include partially saponified polyvinyl acetate with a saponification degree of 60 to 98 mol%. Examples of polyamides include polyamide resins containing a basic nitrogen atom in the molecule and polyamide resins containing an alkylene glycol structural unit in the molecule. An oxygen barrier layer containing a polyamide resin containing a basic nitrogen atom in the molecule and a polyamide resin containing an alkylene glycol structural unit in the molecule (Japanese Patent No. 7243076) is preferred.

[0063] The adhesive layer can be provided to improve the adhesion between the (B) photosensitive resin layer and the (C) heat-sensitive mask layer, which tends to further improve the handling properties.

[0064] <Method for producing photosensitive printing blank> The method for producing the photosensitive printing blank of the present invention is not particularly limited, and examples include a method in which a heat-sensitive mask layer composition is applied to a cover film and dried to obtain a laminate I consisting of a (C) heat-sensitive mask layer / cover film, and then an adhesive is applied to the surface of an (A) support to obtain a laminate II in which a photosensitive resin layer composition is applied to the adhesive-coated surface of the (A) support, and then the (C) heat-sensitive mask layer side of the laminate I and the (B) photosensitive resin layer side of the laminate II are bonded together using a laminator to produce a photosensitive printing blank in which the (A) support, (B) photosensitive resin layer, and (C) heat-sensitive mask layer are laminated in this order.

[0065] <Method for manufacturing photosensitive relief printing plate> A method for manufacturing a photosensitive relief printing plate of the present invention having non-image areas and image areas includes a mask formation step of forming an image on the (C) heat-sensitive mask layer of the photosensitive printing original plate of the present invention described above to form a mask, an exposure step of exposing the (B) photosensitive resin layer to imagewise light through the mask after the mask formation step, and a development step of developing using an aqueous developer after the exposure step to form non-image areas and image areas.

[0066] <Mask Forming Step> The mask forming step is a step of forming an image on the heat-sensitive mask layer (C) to form a mask to be used in the exposure step described below. Here, the heat-sensitive mask layer (C) is formed by irradiating the heat-sensitive mask layer (C) with an IR laser in an imagewise manner, whereby heat is generated by the action of an infrared absorber (carbon black), and the heat decomposes the thermally decomposable compound, thereby selectively removing the heat-sensitive mask layer.

[0067] Examples of suitable IR lasers include an ND / YAG laser (1064 nm) or a diode laser (e.g., 830 nm). Laser systems suitable for computer-assisted platemaking are commercially available, and for example, CDI (Esco Graphics) can be used. This laser system includes a rotating cylindrical drum that holds the printing plate, an IR laser irradiation device, and a layout computer, and image information is transferred directly from the layout computer to the laser device.

[0068] <Exposure Step> The exposure step is a step of exposing the (B) photosensitive resin layer imagewise through the mask obtained in the above-mentioned mask formation step, and irradiating the entire surface of the (B) photosensitive resin layer with actinic rays through the imagewise mask (main exposure). This induces crosslinking and / or polymerization in the area irradiated with the actinic rays, thereby allowing curing.

[0069] Although the exposure step can be performed with the plate attached to the laser cylinder, it is more common to remove the plate from the laser device and irradiate it with a conventional flat irradiation unit, which is advantageous in that it can accommodate non-standard plate sizes. As the actinic ray, ultraviolet light having an emission peak at a wavelength of 330 to 380 nm can be used. As the light source, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a metal halide lamp, a xenon lamp, a zirconium lamp, a carbon arc lamp, an ultraviolet fluorescent lamp, an LED-UV (an ultraviolet light source using a light-emitting diode), etc. can be used.

[0070] <Developing Step> The developing step is a step of forming non-image areas and image areas by developing using a developer. The developer used in the developing step is not particularly limited, and any conventionally known developer can be used, but from the viewpoint of reducing the environmental load, it is preferable to use an aqueous developer containing 50% by mass or more of water. The content of water in the aqueous developer is preferably 80 to 99.9% by mass, and more preferably 90 to 99.9% by mass, based on the total mass of the aqueous developer.

[0071] <Rinsing Step> The method for producing a photosensitive relief printing plate of the present invention preferably includes, after the developing step described above, a rinsing step in which the surfaces of the non-image areas and image areas formed in the developing step are rinsed with water.

[0072] Examples of rinsing means in the rinsing step include a method of washing with tap water, a method of spraying high-pressure water, and a method of brushing the surfaces of the non-image areas and image areas mainly in the presence of water using a conveying brush-type washing machine as a developing machine for the photosensitive relief printing plate.

[0073] <Back Exposure Step> The method for producing a photosensitive relief printing plate of the present invention preferably includes a back exposure step of irradiating the support side of the photosensitive printing plate precursor with ultraviolet light before the mask formation step or the exposure step.

[0074] <Post-exposure step> The method for producing a photosensitive relief printing plate of the present invention preferably includes a post-exposure step of irradiating the photosensitive printing plate precursor with ultraviolet light from the photosensitive resin layer side thereof after the developing step or the rinsing step described above.

[0075] The effects of using the photosensitive resin composition of the present invention will be demonstrated by the following examples, but the present invention is not limited thereto. Note that parts in the examples mean parts by mass. Furthermore, the numerical values ​​showing the composition ratios in the tables also mean parts by mass.

[0076] Example 1 (A) Preparation of Support A polyester resin solution was prepared using 100 parts of "Vylon 30SS" (a product of Toyobo MC Co., Ltd., solids concentration 30%, molecular weight 20,000-25,000), a solution in which 0.5 parts of dihydrothio-p-toluidine as an ultraviolet absorber was dissolved in 3.6 parts of dimethylaminoacetamide, and a solution in which 0.2 parts of "U-CAT SA102" (a product of San-Apro Co., Ltd., a DBU-octylate salt composition) as a catalyst was dissolved in 0.7 parts of dioxane. Next, a solution in which 10.2 parts of "Coronate L" (a product of Nippon Polyurethane Industry Co., Ltd.) as a polyfunctional isocyanate was dissolved in 1.4 parts of ethyl acetate was prepared to obtain an adhesive composition solution. This solution was uniformly applied to a 250 μm thick transparent polyester film support and dried in a 120°C hot air dryer for 1 minute to obtain a support having a transparent adhesive layer with a coating thickness of 20 μm.

[0077] <Preparation of heat-sensitive mask layer coating liquid> Partially saponified polyvinyl alcohol and an ultraviolet absorbing substance were dissolved in water according to the composition (mass ratio) of the heat-sensitive mask layer coating liquid shown in Table 1 below, and carbon black was dispersed therein to prepare a dispersion liquid, which was used as the heat-sensitive mask layer coating liquid.

[0078] <(C) Preparation of heat-sensitive mask layer and laminate (I)> As a cover film, the heat-sensitive mask layer coating liquid was applied to a PET film (Toyobo Co., Ltd., E5000, thickness 100 μm) so that the heat-sensitive mask layer had a thickness of 1.5 μm, and the film was dried at 120°C for 5 minutes to prepare a cover film with a heat-sensitive mask layer laminated thereon, thereby obtaining laminate (I).

[0079] <(B) Preparation of Synthetic Polymer Compound A for Photosensitive Resin Layer> 396 parts of ε-caprolactam, 469 parts of adipic acid, 341 parts of 1,4-bis(3-aminopropyl)piperazine, 199 parts of 1,3-bis(aminomethyl)cyclohexane, 34 parts of isophoronediamine, 5 parts of a 50% aqueous solution of hypophosphorous acid, and 1,000 parts of water were charged into an autoclave, purged with nitrogen, sealed, and gradually heated. Once the internal pressure reached 0.4 MPa, water was distilled off until the pressure could no longer be maintained. The pressure was returned to normal over approximately two hours, and the reaction was continued at normal pressure for one hour. The maximum polymerization reaction temperature was 255°C. This yielded a tertiary nitrogen atom-containing polyamide (polymer compound A). The composition of polymer compound A was measured by H-NMR, confirming that there was no difference between the charged composition and the polymer composition.

[0080] <Preparation of Laminate (II)> 55.0 parts of synthetic polymer compound A was added to a mixture of 62 parts of methanol and 10 parts of water, which was heated to 65°C and dissolved. 9.0 parts of diethylene glycol, 5.0 parts of lactic acid as a quaternizing agent, and 0.1 parts of hydroquinone monomethyl ether were added and stirred for another 30 minutes to dissolve the polyamide. The polyamide was then converted into an ammonium salt and made water-soluble. 2.5 parts of glycidyl methacrylate (GMA), 1.0 parts of benzyl dimethyl ketal as a photopolymerization initiator, 13 parts of glycerin dimethacrylate (Light Ester G101P manufactured by Kyoeisha Chemical Co., Ltd.), and 14.5 parts of propylene glycol diglycidyl ether acrylic acid adduct (Epoxy Ester 70PA manufactured by Kyoeisha Chemical Co., Ltd.) were then added and stirred for 30 minutes to dissolve the mixture. The temperature was then gradually increased to distill off the methanol and water, and the mixture was concentrated until the temperature inside the vessel reached 110°C. At this stage, a fluid and viscous photosensitive resin layer composition was obtained. A composition for a photosensitive resin layer was cast onto the adhesive composition side of the support prepared above to obtain a laminate (II).

[0081] <Preparation of Photosensitive Printing Original Plate> The heat-sensitive mask layer side of the laminate (I) prepared above and the photosensitive resin layer of the laminate (II) were bonded together so as to be in contact with each other, and a laminator was used to form a sheet-like laminate photosensitive printing original plate having a total thickness of 1,080 μm.

[0082] (Examples 2 to 7, Comparative Examples 1 and 2) A heat-sensitive mask layer coating solution was prepared in the same manner as in Example 1 according to the composition (mass ratio) shown in Table 1 below, and a photosensitive printing original plate having a sheet-like laminate with a total thickness of 1080 μm was formed.

[0083] Details of each material used in the heat-sensitive mask layer coating liquids of Examples 1 to 7 and Comparative Examples 1 and 2 are shown below. (Partially saponified polyvinyl alcohol) Kuraray Poval 44-88 (saponification degree 87-89 mol%, average polymerization degree approximately 4400, manufactured by Kuraray Co., Ltd.) Kuraray Poval 35-80 (saponification degree 78.5-80.5 mol%, average polymerization degree approximately 3500, manufactured by Kuraray Co., Ltd.) Kuraray Poval L-10 (saponification degree 71.5-80.5 mol%, average polymerization degree approximately 1000, manufactured by Kuraray Co., Ltd.) (Ultraviolet absorbing substance) ULS-1700 (Tg: -26°C)...Lion Specialty Chemicals Co., Ltd. Newcoat UVA-101 (Tg: 7°C)...Shin-Nakamura Chemical Co., Ltd. Sannalon MW-022 (Tg: 25°C)...Yamanami Synthetic Chemical Co., Ltd. Tinuvin 326 (2-(5-chloro-2H-benzotriazol-2-yl)-4-methyl-6-tert-butylphenol: non-acrylic resin ultraviolet absorbing substance, Tg: none)...BASF Japan Ltd. (carbon black) NAF5091 Black...Dainichiseika Color & Chemicals Mfg. Co., Ltd.

[0084]

[0085] The performance of each of the photosensitive printing original plates thus obtained was evaluated as follows.

[0086] <Optical Density> The optical density of the heat-sensitive mask layer of the laminate (I) was measured using a black-and-white transmission densitometer DM-520 (Dainippon Screen Mfg. Co., Ltd.). The optical density must be 2.3 or more, and preferably 2.5 or more.

[0087] <Number of mask defects in the heat-sensitive mask layer of the photosensitive printing plate> The cover film was peeled off from the photosensitive printing plate obtained from each example and comparative example, and an area of ​​30 cm x 30 cm was observed under magnification from the heat-sensitive mask layer side using a magnifying glass, and the number of mask defects (pinholes) of 100 μm or more in the heat-sensitive mask layer was counted.

[0088] <Number of defects on photosensitive relief printing plate> After observation with the loupe, the photosensitive printing plate was wrapped around a CDI4530 manufactured by Esko Graphics, and an image was imaged at a resolution of 4000 dpi with a grid-like image pattern having a line width of 90 μm and a spacing of 90 μm. Thereafter, the illuminance was increased to 3.4 mW / cm. ２ The photosensitive resin surface was irradiated with ultraviolet light for 5 minutes from a distance of 5 cm above the surface using a chemical lamp adjusted to 100°C. The plate was then developed with tap water at 25°C using a brush washer (120 μmφ nylon brush, JW-A2-PD model, manufactured by Nippon Denshi Seiki Co., Ltd.) to obtain a relief image. After hot air drying at 60°C for 10 minutes, the plate was then irradiated with ultraviolet light from an ultra-high pressure mercury lamp for 30 seconds to produce a 30 cm square photosensitive relief printing plate. The resulting photosensitive relief printing plate was observed under magnification using a magnifying glass, and the number of defects of 100 μm or more (areas where a convex portion of the image was missing) on ​​the photosensitive relief printing plate was counted. Evaluation was performed according to the following criteria, and the results are summarized in Table 2. ◯: (Number of defects in the heat-sensitive mask layer) ≥ (Number of defects in the photosensitive relief printing plate), and the number of defects in the photosensitive relief printing plate is 0. △: (Number of defects in the heat-sensitive mask layer) > (Number of defects in the photosensitive relief printing plate). ×: (Number of defects in the heat-sensitive mask layer) ≤ (Number of defects in the photosensitive relief printing plate).

[0089]

[0090] <Evaluation of temporal stability of photosensitive printing plate> To evaluate the temporal stability of the photosensitive printing plate, the photosensitive printing plate was prepared and then (i) stored for 15 days in an environment at 20° C., and (ii) stored for 90 days in an environment at 50° C., and the image reproducibility of the prepared photosensitive relief printing plate was evaluated. The images used for evaluation were images with independent dots (independent points) having diameters of 200, 300, 400, 500, and 600 μm and independent lines (independent lines) having widths of 40, 60, 80, 100, 120, and 140 μm, and the photosensitive relief printing plates were prepared in the same manner as in <Number of defects in photosensitive relief printing plate>. The stability over time was evaluated for the diameter of the smallest reproduced independent point and the width of the smallest reproduced independent line for each of the photosensitive relief printing plates obtained from (i) and (ii) above, as follows, and the results are summarized in Table 3. ◯: When comparing the photosensitive relief printing plates obtained from (i) and (ii), no change was observed in the reproducibility of the smallest independent point or the smallest independent line. Δ: When comparing the photosensitive relief printing plates obtained from (i) and (ii), the plate obtained from (ii) was worse in only one of the reproducibility of the smallest independent point or the reproducibility of the smallest independent line. ×: When comparing the photosensitive relief printing plates obtained from (i) and (ii), the plate obtained from (ii) was worse in both the reproducibility of the independent points and the reproducibility of the lines.

[0091]

[0092] As can be seen from Tables 2 and 3, all of Examples 1 to 7, which satisfy the requirements of the present invention, have few defects in the photosensitive relief printing plates, and when photosensitive relief printing plates are produced from photosensitive printing plates stored for 15 days at 20°C and for 90 days at 50°C, the reproducibility of isolated points and isolated lines remains unchanged and is good. This demonstrates that the photosensitive printing plates of the present invention have excellent stability over time and can reproduce high-resolution printed images. Comparative Example 1 did not contain a UV-absorbing substance, so it was not possible to suppress UV transmission in areas with mask defects (pinholes). Comparative Example 2 did not contain an acrylic resin as a UV-absorbing substance, so it had poor stability over time and was unable to reproduce high-resolution printed images.

[0093] The present invention provides a photosensitive printing plate precursor and a photosensitive relief printing plate that are capable of producing high-resolution printed images because they have few of the defects of photosensitive relief printing plates and have excellent stability over time. Therefore, the present invention is extremely useful in the industry.

Claims

1. A photosensitive printing original plate comprising at least (A) a support, (B) a photosensitive resin layer, and (C) a heat-sensitive mask layer laminated in this order, wherein the (C) heat-sensitive mask layer contains (a) partially saponified polyvinyl alcohol, (b) an ultraviolet-absorbing substance, and (c) carbon black, and the (b) ultraviolet-absorbing substance contains (b-1) an acrylic resin.

2. The photosensitive printing plate precursor according to claim 1, wherein the degree of saponification of the (a) partially saponified polyvinyl alcohol is 60 to 90 mol %.

3. The photosensitive printing plate precursor according to claim 1, wherein the acrylic resin (b-1) is a water-based resin.

4. The photosensitive printing plate precursor according to claim 1, wherein the acrylic resin (b-1) has a benzotriazole skeleton.

5. The photosensitive printing plate precursor according to claim 1, wherein the glass transition temperature (Tg) of the acrylic resin (b-1) is -50°C or higher and 100°C or lower.

6. The photosensitive printing plate precursor according to claim 1, wherein the (c) carbon black is contained in an amount of 60 parts by mass or more per 100 parts by mass of the (a) partially saponified polyvinyl alcohol.

7. The photosensitive printing plate precursor according to claim 1, wherein the mass ratio of the (c) carbon black to the (b-1) acrylic resin in the (C) heat-sensitive mask layer is 60:40 to 99:

1.

8. A method for producing a photosensitive relief printing plate having non-image areas and image areas, comprising: a mask formation step of forming an image on the (C) heat-sensitive mask layer of the photosensitive printing original plate described in any one of claims 1 to 7 to form a mask; an exposure step of exposing the (B) photosensitive resin layer to imagewise light through the mask after the mask formation step; and a development step of developing using an aqueous developer after the exposure step to form non-image areas and image areas.

Images