JP7713181B1 - Method for manufacturing photosensitive printing plate and photosensitive relief printing plate - Google Patents

Abstract

The present invention provides a photosensitive printing plate having few mask defects (faults) and capable of preventing migration of substances from the heat-sensitive mask layer (excellent stability over time). The photosensitive printing plate is formed by laminating at least (A) a support, (B) a photosensitive resin layer, and (C) a heat-sensitive mask layer in this order, the heat-sensitive mask layer (C) containing (a) partially saponified polyvinyl alcohol, (b) an ultraviolet absorbing substance, and (c) carbon black, and the ultraviolet absorbing substance (b) contains (b-1) an acrylic resin. The present invention also provides a method for producing a photosensitive relief printing plate using the photosensitive printing plate.

Description

The present invention relates to a method for producing a photosensitive printing plate and a photosensitive letterpress printing plate.

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 has eliminated the need for the negative film manufacturing process, reducing the cost and time required to make negatives.

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

The heat-sensitive mask layer needs to have light-shielding properties to prevent the penetration of chemical radiation into the photosensitive resin layer. Carbon black, which has infrared absorbing properties, is generally used as a material that has light-shielding properties against chemical radiation, and is dispersed in a film-forming binder. As a film-forming binder, it is known to incorporate, for example, polyvinyl alcohol, because of its excellent water solubility (see Patent Document 2).

In addition, in recent years, there has been a demand for higher-definition printed images, and it is necessary to form printed images that are 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, for example, by applying a heat-sensitive mask layer onto a film such as a polyester film. When applying a heat-sensitive mask layer onto a film, there is a problem that mask defects (pinholes) occur due to uneven coating, repelling, etc. In response to this problem, for example, Patent Document 3 proposes a flexographic printing original plate in which the heat-sensitive mask layer contains carbon black as an infrared absorbing agent, a binder polymer, and a dispersant with a base number of 5 to 100 mg/KOH mg.

Special table number 7-506201 JP 2021-162667 A International Publication No. WO2020/175422

In Patent Document 3, the occurrence frequency of mask defects (pinholes) is reduced by dispersing carbon black with a dispersant, but mask defects (pinholes) in which the pigment is partially removed due to insufficient dispersion of carbon black do not disappear. Therefore, further improvements are desired to eliminate the defects of photosensitive letterpress printing plates caused by mask defects (pinholes) and to form higher-resolution printed images.

In order to solve the problems of the conventional technology, the present inventors have been developing a method of compounding an ultraviolet absorber together with carbon black in the heat-sensitive mask layer. According to the knowledge that the present inventors have independently acquired 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 letterpress printing plate.

The present invention was devised in light of the above-mentioned situation, and its purpose is to provide a photosensitive printing original plate and a method for producing a photosensitive letterpress printing plate which have few defects and can prevent migration of substances from the heat-sensitive mask layer to the photosensitive resin layer (resulting in excellent stability over time).

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

That is, the present invention comprises the following (1) to (8).
(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, the heat-sensitive mask layer (C) containing (a) partially saponified polyvinyl alcohol, (b) an ultraviolet absorbing substance, and (c) carbon black, and the ultraviolet absorbing substance (b) contains (b-1) an acrylic resin.
(2) The photosensitive printing plate precursor according to (1), wherein the degree of saponification of the partially saponified polyvinyl alcohol (a) is 60 to 90 mol %.
(3) The photosensitive printing plate precursor according to (1), wherein the acrylic resin (b-1) is a water-based resin.
(4) The photosensitive printing original plate according to (1), wherein the acrylic resin (b-1) has a benzotriazole skeleton.
(5) The photosensitive printing original plate according to (1), wherein the glass transition temperature (Tg) of the acrylic resin (b-1) is from −50° C. to 100° C.
(6) The photosensitive printing original plate according to (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 original plate according to (1), wherein a mass ratio of the (c) carbon black to the (b-1) acrylic resin in the (C) heat-sensitive mask layer is from 60:40 to 99:1.
(8) A method for producing a photosensitive letterpress 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.

According to the present invention, since the photosensitive letterpress printing plate has few defects and the photosensitive printing plate base has excellent stability over time, it is possible to provide a photosensitive printing plate base and a photosensitive letterpress printing plate capable of producing high-resolution printed images.

Hereinafter, an embodiment of the present invention will be described in detail.
It should be noted that the following embodiments are merely illustrative and are not intended to limit the scope of the present invention. The present invention can be practiced in various modified forms within the scope of the invention.

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

In the numerical ranges described in this specification in stages, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of a numerical range of another stage. In addition, 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 "~" means a numerical range that includes the numerical values before and after "~" as the upper and lower limits.

<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 made of a photosensitive resin composition, and an adhesive layer may be provided between the (A) support and the (B) photosensitive resin layer.

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. In addition, the adhesive layer preferably contains a binder component and a pigment, and further contains a leveling agent and a hardener.

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., which can be used alone or in combination. Among these, particularly preferred binder components are polyester resins and polyurethane resins in terms of solvent resistance.

<(A) Support>
The (A) support is not particularly limited, but is preferably a material that is flexible and has excellent dimensional stability, and examples thereof 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 view of mechanical properties, shape stability, and ease of handling during printing plate making.

<(B) Photosensitive resin layer>
The photosensitive printing original plate of the present invention has a photosensitive resin layer (B) on a support (A). The photosensitive resin layer (B) is composed of a known photosensitive resin composition, and is not particularly limited. The photosensitive resin composition is composed of, for example, (i) a synthetic polymer compound, (ii) a compound having an ethylenic double bond, and (iii) a photopolymerization initiator. 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, in addition to the above components (i) to (iii).
The components (i) to (iii) of the photosensitive resin composition will be described in detail below.

<(i) Synthetic polymer compound>
(i) The synthetic polymer compound is not particularly limited, and a conventionally known soluble synthetic polymer compound can be used, for example, polyetheramide (e.g., JP-A-55-79437, etc.), polyetheresteramide (e.g., JP-A-58-113537, etc.), tertiary nitrogen-containing polyamide (e.g., JP-A-50-76055, etc.), ammonium salt type tertiary nitrogen atom-containing polyamide (e.g., JP-A-53-36555, etc.), addition polymer of amide compound having one or more amide bonds and organic diisocyanate compound (e.g., JP-A-58-140737, etc.), addition polymer of diamine having no amide bond and organic diisocyanate compound (e.g., JP-A-4-97154, etc.), modified polyvinyl alcohol (WO2014/021322 International Publication, etc.), and the like. 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.

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

<(ii) Compound Having an Ethylenic Double Bond>
(ii) 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. Examples of the compound having an ethylenic double bond include (meth)acrylate, which is an ester of (meth)acrylic acid and an alcohol compound, or an addition reaction product of (meth)acrylic acid and a glycidyl compound, and (meth)acrylamide, which is an amidation product of (meth)acrylic acid and an amine group-containing compound. These may be contained alone or in combination of two or more. 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. From the viewpoint of forming a high-definition printed image, it is preferable to include, as the compound having an ethylenic double bond, an ester of (meth)acrylic acid and an alcohol compound, or an addition reaction product of (meth)acrylic acid and a glycidyl compound, which is an (meth)acrylate.

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

<(iii) Photopolymerization initiator>
(iii) Examples of photopolymerization initiators 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, benzyl dimethyl ketal, benzyl diethyl ketal, benzyl diisopropyl ketal, anthraquinone, 1-hydroxycyclohexan-1-yl phenyl ketone, 2-ethyl anthraquinone, 2-methyl anthraquinone, 2-allylanthraquinone, 2-chloro anthraquinone, thioxanthone, and 2-chloro thioxanthone. 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 to include benzyl dimethyl ketal, benzyl diethyl ketal, and benzyl diisopropyl ketal as the photopolymerization initiator.

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

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

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

<(a) Partially Saponified Polyvinyl Alcohol>
The degree of saponification of the partially saponified polyvinyl alcohol (a) is preferably 60 mol % or more and 90 mol % or less. Within this range, the heat-sensitive mask layer (C) can have improved solubility in a developer mainly composed of water, and good developability and dispersibility of carbon black can be obtained.

The average degree of polymerization of the partially saponified polyvinyl alcohol (a) is preferably in the range of 300 to 3000, more preferably 800 to 2500. Here, the average degree of polymerization of the partially saponified polyvinyl alcohol (a) refers to the average degree of polymerization of the entire partially saponified polyvinyl alcohol (a) contained in the heat-sensitive mask layer (C), and when two or more types are contained, it refers to the average degree of polymerization of the entire two or more types of partially saponified polyvinyl alcohol (a). When the average degree of polymerization of the partially saponified polyvinyl alcohol (a) is in the range of 300 to 3000, it is preferable in terms of obtaining better film strength and coating film formability. The average degree of polymerization can be obtained by dividing the number average molecular weight of the polyvinyl alcohol before saponification by the molecular weight of the polyvinyl alcohol.

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

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

(b) Ultraviolet absorbing substance
The (b) ultraviolet absorbing material is characterized by containing (b-1) acrylic resin. This makes it possible to suppress the ultraviolet transmittance of the mask defect (pinhole) portion in the photosensitive printing plate, thereby suppressing defects in the photosensitive letterpress printing plate. In addition, since the (b) ultraviolet absorbing material can be suppressed from migrating from the (C) heat-sensitive mask layer into the (B) photosensitive resin layer, the photosensitive printing plate has good stability over time, and high-definition printed image reproducibility can be achieved. As a result, it becomes possible to form a printed image of a collection of fine lines or dots of 10 to 20 μm.

(b) The 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 light absorption ability of UVB (280 to 320 nm) and UVA (320 to 400 nm), it is preferable to use a benzotriazole-based ultraviolet absorbing substance.

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

(b-1) The concept of acrylic resin includes, for example, homopolymers of acrylic acid, homopolymers of methacrylic acid, homopolymers of acrylic esters, homopolymers of methacrylic esters, copolymers of acrylic acid and other monomers, copolymers of methacrylic acid and other monomers, copolymers of acrylic esters and other monomers, copolymers of methacrylic esters and other monomers, etc.

The acrylic resin (b-1) has an ultraviolet absorbing skeleton. Examples of ultraviolet absorbing skeletons 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 transmission through mask defect (pinhole) areas, it is preferable that the acrylic resin (b-1) has a benzotriazole skeleton.

(b-1) It is preferable that the acrylic resin is a copolymer of a monomer having an ultraviolet absorbing skeleton and a monomer for forming the acrylic resin.

The monomer having an ultraviolet absorbing skeleton in the (b-1) acrylic resin is preferably contained in an amount of 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% by mass or more and 70% by mass or less, in the (b-1) acrylic resin.

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 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, 2-methacryloyloxyethyl-2-(2-hydroxy-4-octyloxyphenyl)-2H-benzotriazole-5-carboxylate, and the like, but are not limited thereto. These may be used alone or in combination of two or more.

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-(methacryloyloxypropyl)phenyl]-2H-benzotriazole, and 2-[2-hydroxy-5-(acryloyl 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-(acryloyloxyethyl)phenyl]-5-chloro-2H-benzotriazole, 2-[2-hydroxy-5-(acryloyloxyethyl)phenyl]-5-chloro-2H-benzotriazole, 2-[2-hydroxy-5-(methacryloyloxyethyl)phenyl]-5-methoxy-2H-benzotriazole, 2-[2-hydroxy-5-(acryloyloxyethyl)phenyl]-5-methoxy-2H-benzotriazole, 2-[2-hydroxy-5-(acryloyloxyethyl)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, 2-[2-hydroxy-5-(acryloyloxyethyl)phenyl]-5-t-butyl-2H-benzotriazole, 2-[2-hydroxy-5-(methacryloyloxyethyl)phenyl]-5-nitro-2H-benzotriazole, 2-[2-hydroxy-5-(acryloyloxyethyl)phenyl]-5-nitro-2H-benzotriazole, etc. can be mentioned, but are not limited to these. In addition, these can be used alone or two or more types can be used. Furthermore, a monomer having a resorcinol type benzotriazole skeleton and a monomer having an alkanolphenol type benzotriazole skeleton can be used in combination.

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-methylethyl (meth)acrylate, ethylhexyl ... 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 the acrylates include ethyl 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 may be used alone or in combination of two or more.

The polymerization method for 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 the raw materials containing the monomer having a benzotriazole skeleton, can be a known method and is not particularly limited.

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 Yamanami Synthetic Chemicals Co., Ltd. These may be used alone or in combination of two or more.

From the viewpoint of suppressing migration of the (b) ultraviolet absorber from the (C) heat-sensitive mask layer into the (B) photosensitive resin layer (excellent stability over time), it is preferable that the weight average molecular weight of the (b-1) acrylic resin is 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 material containing the (b-1) acrylic resin can be determined in polystyrene equivalent terms using gel permeation chromatography (GPC).

In order to suppress ultraviolet light transmittance in the mask defect (pinhole) portion, the content of (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.

(b-1) The acrylic resin is preferably a water-based acrylic resin. This allows the heat-sensitive mask layer (C) to be highly developable in a water-based developer. A water-based acrylic resin is a resin that is water-soluble or water-dispersible, and means 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.

Water-based acrylic resins can be obtained, for example, by copolymerizing known hydrophilic monomer components as monomers for forming the acrylic resin, or by introducing hydroxyl groups, carboxyl groups, or sulfonium groups into the side chains and/or ends of the acrylic resin. To improve water dispersibility, known surfactants may also be used.

Hydrophilic monomer components are preferably hydroxyl-containing monomers. Examples of hydroxyl-containing monomers include those in which a hydroxyl group is bonded to the alkyl group or aromatic ring of the above acrylic acid esters, 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, and hydroxybenzyl (meth)acrylate.

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 Co., Ltd.

(b-1) The glass transition temperature (Tg) of the acrylic resin is preferably -50°C or higher and 100°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 letterpress printing plate. It is more preferably -40°C or higher and 80°C or lower. It is even more preferably -30°C or higher and 50°C or lower.

<(c) Carbon Black>
(c) Carbon black acts as an infrared absorbing agent, absorbing infrared rays and converting them into heat, and also has the function of blocking ultraviolet light. In addition to (c) carbon black, the infrared absorbing material may contain a material having an absorption characteristic in the wavelength range of 750 nm to 20,000 nm. In addition to carbon black, examples of the infrared absorbing material 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, the infrared absorbing material may contain two or more types of materials.

From the viewpoint of improving the ablation efficiency, the content of (c) carbon black in the (C) heat-sensitive mask layer is preferably 30 parts by mass or more, and 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 chemical radiation is more excellent, and the ablation efficiency is good.

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 solids content of the (C) heat-sensitive mask layer, for the reasons of suppressing mask defects (pinholes), providing better shielding properties for chemical radiation, and providing good ablation efficiency.

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

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

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. Also, it is more preferably 65:35 to 98:2. Even more preferably, it is 70:30 to 90:10. By incorporating (b-1) acrylic resin in the above mass ratio relative to (c) carbon black, mask defects (pinholes) can be further suppressed, and ultraviolet light transmittance in the mask defect (pinhole) area can be further suppressed. As a result, defects in the photosensitive letterpress printing plate can be further suppressed, making it easier to achieve high-resolution reproducibility of printed images.

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

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 suppress adhesion of the (C) heat-sensitive mask layer and to improve the removability of the cover film. Examples of such a release treatment include a method of applying a release agent to the surface of the cover film to form a release layer. 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.

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

The oxygen barrier layer can be provided to obtain a photosensitive letterpress printing plate with even better reproducibility of high-definition printed images. The inclusion of the oxygen barrier layer can prevent the radical generating compound from reacting with oxygen during the radical polymerization reaction caused by exposure to light, thereby preventing the polymerization reaction from being inhibited.

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 types of polymers. Examples of binder polymers that are preferable 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 basic nitrogen atoms in the molecule and polyamide resins containing alkylene glycol structural units in the molecule, and 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 (Patent No. 7243076) is preferred.

In addition, an adhesive layer can be provided to improve the adhesion between the (B) photosensitive resin layer and the (C) heat-sensitive mask layer. This tends to further improve the ease of handling.

<Method of manufacturing a photosensitive printing plate>
The method for producing the photosensitive printing original plate of the present invention is not particularly limited, but examples include a method in which a composition for a heat-sensitive mask layer is applied to a cover film and dried to obtain a laminate I consisting of a heat-sensitive mask layer (C) and a cover film, and then a laminate II is obtained in which a composition for a photosensitive resin layer is applied to the adhesive-coated surface of an (A) support having an adhesive coated thereon, 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 with a laminator to produce a photosensitive printing original plate in which the (A) support, the (B) photosensitive resin layer, and the (C) heat-sensitive mask layer are laminated in this order.

<Method of manufacturing a photosensitive relief printing plate>
A method for producing a photosensitive letterpress printing plate having non-image areas and image areas of the present invention includes a mask formation step of forming an image on the heat-sensitive mask layer (C) of the photosensitive printing original plate of the present invention described above to form a mask, an exposure step of exposing the photosensitive resin layer (B) to light in an imagewise manner 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.

<Mask Forming Process>
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 later. Here, the heat-sensitive mask layer (C) is formed by generating heat due to the action of an infrared absorbing agent (carbon black) when the heat-sensitive mask layer (C) is irradiated with an IR laser in an imagewise manner, and the heat-decomposable compound is decomposed by the action of the generated heat, thereby selectively removing the heat-sensitive mask layer.

Examples of suitable IR lasers include ND/YAG lasers (1064 nm) or diode lasers (e.g., 830 nm). Laser systems suitable for computer-assisted platemaking are commercially available, and can be, for example, CDI (Esco Graphics). 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.

<Exposure process>
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 the (B) photosensitive resin layer is entirely irradiated with actinic rays through the imagewise mask (main exposure), thereby inducing crosslinking and/or polymerization in the region irradiated with the actinic rays, and thus curing the layer.

The exposure process can be performed with the plate attached to the laser cylinder, but 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 active light, ultraviolet light with an emission peak at a wavelength of 330 to 380 nm can be used. As the light source, low-pressure mercury lamps, high-pressure mercury lamps, extra-high-pressure mercury lamps, metal halide lamps, xenon lamps, zirconium lamps, carbon arc lamps, ultraviolet fluorescent lamps, LED-UV (ultraviolet light source using light-emitting diodes), etc. can be used.

<Developing process>
The developing step is a step of forming a non-image area and an image area by developing using a developer. The developer used in the developing step is not particularly limited, and a 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 contained in the aqueous developer is preferably 80 to 99.9% by mass, more preferably 90 to 99.9% by mass, based on the total mass of the aqueous developer.

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

Rinsing methods used in the rinsing process include washing with tap water, spraying with high-pressure water, and using a conveying brush-type washing machine as a developing machine for photosensitive letterpress printing plates to brush the surfaces of the non-image and image areas mainly in the presence of water.

<Back exposure process>
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 original plate with ultraviolet light prior to the above-mentioned mask formation step or the above-mentioned exposure step.

<Post-exposure process>
The method for producing a photosensitive letterpress printing plate of the 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 above-mentioned developing step or the above-mentioned rinsing step.

The effects of using the photosensitive resin composition of the present invention are shown in the following examples, but the present invention is not limited thereto. Note that parts in the examples mean parts by mass. The numerical values showing the composition ratios in the tables also mean parts by mass.

Example 1
<(A) Preparation of Support>
As a polyester resin solution, 100 parts of "Vylon 30SS" (product of Toyobo MC Co., Ltd., solid content concentration 30%, molecular weight 20000-25000) was mixed with a solution of 0.5 parts of dihydrothio-p-toluidine as an ultraviolet absorber dissolved in 3.6 parts of dimethylaminoacetamide, and a solution of 0.2 parts of "U-CAT SA102" (product of San-Apro Co., Ltd., DBU-octylate salt composition) as a catalyst dissolved in 0.7 parts of dioxane. Next, a solution of 10.2 parts of "Coronate L" (product of Nippon Polyurethane Industry Co., Ltd.) as a polyfunctional isocyanate dissolved in 1.4 parts of ethyl acetate was mixed to obtain an adhesive composition solution. This solution was uniformly applied to a transparent polyester film support having a thickness of 250 μm, and dried for 1 minute in a 120° C. hot air dryer to obtain a support having a transparent adhesive layer having a coating film of 20 μm.

<Preparation of Heat-Sensitive Mask Layer Coating Solution>
Partially saponified polyvinyl alcohol and an ultraviolet absorbing substance were dissolved in water according to the composition (mass ratio) shown in the heat-sensitive mask layer coating liquid 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.

<(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 produce a cover film with a laminated heat-sensitive mask layer, thereby obtaining a laminate (I).

<(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 50% aqueous hypophosphorous acid solution, and 1000 parts of water were charged into an autoclave, substituted with nitrogen, sealed, and gradually heated. When the internal pressure reached 0.4 MPa, water was distilled off until the pressure could no longer be maintained, and the pressure was returned to normal pressure in about 2 hours, and then the reaction was carried out at normal pressure for 1 hour. The maximum polymerization reaction temperature was 255°C. As a result, a tertiary nitrogen atom-containing polyamide (polymer compound A) was obtained. The composition of polymer compound A was measured by H-NMR, and it was confirmed that there was no difference between the charged composition and the polymer composition.

<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 to dissolve, and 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, and the polyamide was converted to an ammonium salt to make it water-soluble. Then, 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 added and stirred for 30 minutes to dissolve. Next, the temperature was gradually increased to distill off methanol and water, and the mixture was concentrated until the temperature inside the kettle reached 110°C. At this stage, a viscous photosensitive resin layer composition with fluidity 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).

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

(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 1,080 μm was formed.

Details of each material used in the heat-sensitive mask layer coating liquid 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 about 4400, manufactured by Kuraray Co., Ltd.)
Kuraray Poval 35-80 (saponification degree 78.5-80.5 mol%, average polymerization degree approx. 3500, manufactured by Kuraray Co., Ltd.)
Kuraray Poval L-10 (saponification degree 71.5-80.5 mol%, average polymerization degree approx. 1000, manufactured by Kuraray Co., Ltd.)
(Ultraviolet absorbing material)
・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) ... Sannan Synthetic Chemicals 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 Co., Ltd.

The performance of each photosensitive printing plate obtained in this manner was evaluated as follows.

<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 is preferably 2.5 or more.

<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 original plate obtained from each Example and Comparative Example, and an area of 30 cm x 30 cm was magnified and observed 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.

<Number of defects on photosensitive letterpress printing plate>
After observation with the loupe, the photosensitive printing plate was wrapped around CDI4530 manufactured by Esko Graphics, and an image was imaged with a grid-like image pattern with a line width of 90 μm and intervals of 90 μm at a resolution of 4000 dpi. Then, ultraviolet rays were irradiated for 5 minutes from a distance of 5 cm above the surface of the photosensitive resin using a chemical lamp with an illuminance adjusted to 3.4 mW/cm ^2. Next, the plate was developed with tap water at 25°C using a brush-type washer (120 μmφ nylon brush, JW-A2-PD type manufactured by Nippon Denshi Seiki Co., Ltd.) to obtain a relief image. After drying with hot air at 60°C for 10 minutes, the plate was irradiated with ultraviolet rays for 30 seconds using an ultra-high pressure mercury lamp to produce a photosensitive letterpress printing plate of 30 cm square. The obtained photosensitive letterpress printing plate was magnified and observed using a loupe, and the number of defects of 100 μ or more (parts where the convex parts of the image were missing) on the photosensitive letterpress printing plate was counted.
The evaluation was carried out 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 letterpress printing plate) and the number of defects in the photosensitive letterpress printing plate is 0. △: (Number of defects in the heat-sensitive mask layer) > (Number of defects in the photosensitive letterpress printing plate).
×: (number of defects in the heat-sensitive mask layer)≦(number of defects in the photosensitive letterpress printing plate)

<Evaluation of temporal stability of photosensitive printing original plate>
In order to evaluate the stability over time of the photosensitive printing plate, the photosensitive printing plate was prepared, and then (i) the photosensitive printing plate was stored for 15 days in an environment at 20° C., and (ii) the photosensitive printing plate was stored for 90 days in an environment at 50° C., and the image reproducibility of the photosensitive letterpress printing plate was evaluated. The images used for the evaluation were images with independent points (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 letterpress printing plate was prepared in the same manner as in <Number of defects in photosensitive letterpress printing plate>. The stability over time was evaluated by evaluating the diameter of the smallest independent point reproduced and the width of the smallest independent line reproduced for each photosensitive letterpress printing plate obtained from (i) and (ii) above as follows, and the results are summarized in Table 3.
◯: In comparing the photosensitive letterpress printing plates obtained from (i) and (ii), no change was observed in the reproducibility of the minimum independent point or the minimum independent line. Δ: In comparing the photosensitive letterpress printing plates obtained from (i) and (ii), the plate obtained from (ii) was worse in only either the reproducibility of the minimum independent point or the reproducibility of the minimum independent line. ×: In comparing the photosensitive letterpress printing plates obtained from (i) and (ii), the plate obtained from (ii) was worse in both the reproducibility of independent points and the reproducibility of lines.

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 letterpress printing plate, and when a photosensitive letterpress printing plate is produced from a photosensitive printing plate stored in a 20°C environment for 15 days and in a 50°C environment for 90 days, the reproducibility of the independent points and independent lines is good and unchanged. Therefore, it was found that the photosensitive printing plate of the present invention has excellent stability over time and can reproduce high-definition printed images. In Comparative Example 1, since no ultraviolet absorbing substance was blended, it was not possible to suppress the ultraviolet transmittance of the mask defect (pinhole) portion. In Comparative Example 2, since no acrylic resin was included as an ultraviolet absorbing substance, the stability over time was poor and a high-definition printed image could not be reproduced.

The present invention provides a photosensitive printing plate and a photosensitive letterpress printing plate that are capable of producing high-definition printed images because they have few defects and the photosensitive printing plate has excellent stability over time. Therefore, the present invention is extremely useful in the industry.

Claims (8)

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, the heat-sensitive mask layer (C) containing (a) partially saponified polyvinyl alcohol, (b) an ultraviolet absorbing substance, and (c) carbon black, and the ultraviolet absorbing substance (b) contains (b-1) an acrylic resin. 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 %. A photosensitive printing plate precursor as described in claim 1, wherein the (b-1) acrylic resin is a water-based resin. A photosensitive printing plate precursor as described in claim 1, wherein the (b-1) acrylic resin has a benzotriazole skeleton. A photosensitive printing plate according to claim 1, wherein the glass transition temperature (Tg) of the (b-1) acrylic resin is -50°C or higher and 100°C or lower. The photosensitive printing plate precursor described in claim 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. A photosensitive printing plate as described in 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. A method for producing a photosensitive letterpress 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 plate according to any one of claims 1 to 7 to form a mask; an exposure step of exposing the (B) photosensitive resin layer to light in an imagewise manner 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.