Flexographic printing plate original plate and method for manufacturing flexographic printing plate

Abstract

The present invention addresses the problem of providing a flexographic printing plate original plate having improved reproducibility of microcells when made into a flexographic printing plate, and a method for manufacturing a flexographic printing plate using the same. This flexographic printing plate original plate has a support, a photosensitive resin layer, an intermediate layer, and an infrared ablation layer in this order. The photosensitive resin layer contains a base polymer, water-dispersible particles, a photopolymerizable unsaturated compound, and a photopolymerization initiator. The intermediate layer contains a copolymer represented by formula (1).

Description

Flexographic printing plate precursor and method for manufacturing flexographic printing plate

[0001] The present invention relates to a flexographic printing plate precursor and a method for producing a flexographic printing plate using the same.

[0002] A flexographic printing plate master generally comprises a photosensitive resin layer (photosensitive layer) made of a photosensitive resin composition on a support made of a polyester film, etc. A flexographic printing plate is made by exposing the surface of the photosensitive resin layer of the master to light with a predetermined image and then removing the resin in the unexposed areas.

[0003] In a so-called analog type flexographic printing plate precursor, a negative film on which a predetermined image has already been formed is placed on a photosensitive resin layer, and the predetermined image is exposed onto the surface of the photosensitive resin layer through this negative film. In contrast, in a LAM (Laser Ablation Mask) type flexographic printing plate precursor, an infrared ablation layer is previously provided on the photosensitive resin layer, and a desired negative pattern is created by directly drawing digitized negative image information on the infrared ablation layer using an infrared laser, and then the predetermined image is exposed onto the surface of the photosensitive resin layer through this negative pattern.

[0004] As an example of such a LAM type flexographic printing plate precursor, Patent Document 1 describes a flexographic printing plate precursor in which a support, a photosensitive resin layer, and an infrared ablation layer containing a binder polymer and an infrared absorbing substance are laminated.

[0005] JP 2012-137515 A

[0006] The present inventors have attempted to form a fine concave-convex pattern (hereinafter also abbreviated as "microcells") on the surface of the image area of ​​a known flexographic printing plate precursor described in Patent Document 1, particularly a flexographic printing plate precursor having a photosensitive resin layer containing water-dispersible particles, in order to improve ink transferability when the flexographic printing plate is made into a flexographic printing plate. Flexographic printing plates having a photosensitive resin layer that does not contain water-dispersible particles are often used for paper media applications that have excellent ink transferability and do not require the formation of microcells. Specifically, the present inventors provided an intermediate layer on top of the photosensitive resin layer, a "protective layer for preventing polymerization inhibition by oxygen in the photosensitive resin layer" described in International Publication No. 2009 / 141930. They found that although the reproducibility of the microcells was slightly improved when the flexographic printing plate was made into a flexographic printing plate, there was still room for improvement.

[0007] Therefore, an object of the present invention is to provide a flexographic printing plate precursor that provides good reproducibility of microcells when made into a flexographic printing plate, and a method for producing a flexographic printing plate using the same.

[0008] As a result of extensive research aimed at achieving the above object, the present inventors have found that a flexographic printing plate precursor having, in this order, a support, a predetermined photosensitive resin layer, an intermediate layer containing a specific polyvinyl alcohol-based copolymer, and an infrared ablation layer exhibits good microcell reproducibility when made into a flexographic printing plate, and have completed the present invention. That is, the present inventors have found that the above object can be achieved by the following configuration.

[0009] [1] A flexographic printing plate precursor having, in this order, a support, a photosensitive resin layer, an intermediate layer, and an infrared ablation layer, wherein the photosensitive resin layer contains a base polymer, water-dispersible particles, a photopolymerizable unsaturated compound, and a photopolymerization initiator, and the intermediate layer contains a copolymer represented by formula (1) described below. [2] The flexographic printing plate precursor according to [1], wherein the base polymer is a diene rubber. [3] The flexographic printing plate precursor according to [1] or [2], wherein the content of the photopolymerization initiator is 1.5% by mass or more and less than 5.0% by mass based on the total solid content of the photosensitive resin layer. [4] The flexographic printing plate precursor according to any one of [1] to [3], wherein the content of the water-dispersible particles is 10% by mass or more and less than 50% by mass based on the total solid content of the photosensitive resin layer. [5] The flexographic printing plate precursor according to [2], wherein the diene rubber is a butadiene rubber. [6] A method for producing a flexographic printing plate having non-image areas and image areas, comprising: a mask forming step of forming an image on an infrared ablation layer of the flexographic printing plate precursor according to any one of [1] to [5] to form a mask; an exposure step of imagewise exposing a photosensitive resin layer of the flexographic printing plate precursor through the mask after the mask forming step; and a development step of developing with a developer after the exposure step to form non-image areas and image areas.

[0010] According to the present invention, it is possible to provide a flexographic printing plate precursor that exhibits good reproducibility of microcells when made into a flexographic printing plate, and a method for producing a flexographic printing plate using the same.

[0011] FIG. 1 is a schematic cross-sectional view showing an example of a flexographic printing plate precursor of the present invention.

[0012] The present invention will be described in detail below. The following description of the constituent elements may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the upper and lower limits. Furthermore, in this specification, within a numerical range described in stages, the upper or lower limit described in a certain numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, within a numerical range described in this specification, the upper or lower limit described in a certain numerical range may be replaced with a value shown in the Examples. Furthermore, in this specification, each component may be a single substance corresponding to the component, or two or more substances may be used in combination. Here, when two or more substances are used in combination for each component, the content of that component refers to the total content of the substances used in combination, unless otherwise specified. In addition, in this specification, "(meth)acrylic" is a notation representing "acrylic" or "methacrylic", and "(meth)acryloyl" is a notation representing "acryloyl" or "methacryloyl".

[0013] [Flexographic Printing Plate Precursor] The flexographic printing plate precursor of the present invention is a flexographic printing plate precursor having, in this order, a support, a photosensitive resin layer, an intermediate layer, and an infrared ablation layer. The photosensitive resin layer of the flexographic printing plate precursor of the present invention contains a base polymer, water-dispersible particles, a photopolymerizable unsaturated compound, and a photopolymerization initiator. Furthermore, the intermediate layer of the flexographic printing plate precursor of the present invention contains a copolymer represented by formula (1) described below.

[0014] Fig. 1 is a schematic cross-sectional view showing an example of a flexographic printing plate precursor of the present invention. The flexographic printing plate precursor 10 shown in Fig. 1 has, in this order, a support 1, a photosensitive resin layer 2, an intermediate layer 3, and an infrared ablation layer 4. The flexographic printing plate precursor of the present invention may also have a cover sheet 5, as shown in Fig. 1.

[0015] In the present invention, as described above, a flexographic printing plate precursor having, in this order, a support, a predetermined photosensitive resin layer, an intermediate layer containing a copolymer represented by Formula (1) described below, and an infrared ablation layer exhibits good microcell reproducibility when made into a flexographic printing plate. While the details of this are unclear, the present inventors speculate as follows: First, an embodiment in which the "protective layer for preventing oxygen-induced polymerization inhibition of the photosensitive resin layer" described in International Publication No. 2009 / 141930 is provided as an intermediate layer exhibits poor microcell reproducibility, as shown in Comparative Example 3 described below. This is thought to be because the polyvinyl alcohol copolymer contained in the intermediate layer has a high degree of saponification and functions satisfactorily as an oxygen-blocking layer. However, when forming (developing) a fine uneven structure such as microcells, light leakage from the convex portions (exposed portions) and chain reaction of radical polymerization reactions in the exposed portions (particularly near the boundary with the unexposed portions) cause polymerization reactions to proceed in the concave portions (unexposed portions), making it difficult to form the concave portions. In particular, in an environment where oxygen is blocked, the radical polymerization reaction is more likely to proceed, and the polymerization reaction proceeds even in the recesses (non-exposed areas), which is thought to be why recesses are not formed. Therefore, in the present invention, by using an intermediate layer containing a copolymer represented by formula (1) described below, a certain amount of oxygen is allowed to pass through, which makes it possible to suppress the polymerization reaction in the recesses (non-exposed areas) caused by leaked light or a chain reaction of radical polymerization reactions, and therefore it is thought that this has resulted in good reproducibility of microcells. Below, the layer configuration of each of the flexographic printing plate precursors of the present invention will be described in detail.

[0016] [Support] The material used for the support of the flexographic printing plate precursor of the present invention is not particularly limited, but materials with high dimensional stability are preferably used. Examples include metals such as steel, stainless steel, and aluminum; polyesters (for example, PET (polyethylene terephthalate), PBT (polybutylene terephthalate), and PEN (polyethylene naphthalate)), PI (polyimide), polyamide, LCP (liquid crystal polymer), and PAN (polyacrylonitrile); plastic resins such as polyvinyl chloride; synthetic rubbers such as styrene-butadiene rubber; plastic resins reinforced with glass fibers (epoxy resins, phenolic resins, and the like); cloth, and paper. From the viewpoints of dimensional stability and easy availability, the support is preferably a polymer film or cloth, and more preferably a polymer film. The form of the support is determined depending on whether the polymer layer is in the form of a sheet or a sleeve.

[0017] Examples of fabrics that can be used include plain-woven or twill-woven fabrics or various knitted fabrics, and nonwoven fabrics made from natural fibers such as cotton, linen, silk, and wool, and synthetic fibers such as acetate, vinylon, vinylidene, polyvinyl chloride, acrylic, polypropylene, polyethylene, polyurethane, fluorine-based filaments, polychlor, rayon, nylon, polyamide, and polyester. Examples of polymer films include films made from various polymers such as polyester (e.g., PET (polyethylene terephthalate), PBT (polybutylene terephthalate), and PEN (polyethylene naphthalate)), PI (polyimide), polyamide, LCP (liquid crystal polymer), and PAN (polyacrylonitrile); plastic resins such as polyvinyl chloride; synthetic rubbers such as styrene-butadiene rubber; and glass-fiber-reinforced plastic resins (e.g., epoxy resins and phenolic resins). Among these, polyester films are preferred from the viewpoint of dimensional stability, etc. Examples of polyester films include PET film, PBT film, and PEN film, but PET (polyethylene terephthalate) film is preferred from the viewpoint of dimensional stability, etc.

[0018] The thickness of the support is not particularly limited, but from the viewpoint of dimensional stability and handling, it is preferably 5 to 3000 μm, more preferably 50 to 2000 μm, and even more preferably 100 to 1000 μm.

[0019] [Photosensitive Resin Layer] The photosensitive resin layer of the flexographic printing plate precursor of the present invention contains a base polymer, water-dispersible particles, a photopolymerizable unsaturated compound, and a photopolymerization initiator.

[0020] <Base Polymer> The base polymer is not particularly limited, and examples thereof include thermoplastic polymers. The thermoplastic polymer is not particularly limited as long as it is a polymer that exhibits thermoplasticity, and specific examples thereof include polystyrene resins, polyester resins, polysulfone resins, polyethersulfone resins, polyimide resins, acrylic resins, acetal resins, epoxy resins, polycarbonate resins, rubber, and thermoplastic elastomers. These may be used alone or in combination of two or more. Among these, rubber and thermoplastic elastomers are preferred, rubber is more preferred, and diene rubber is even more preferred, because they facilitate the formation of a soft and flexible film.

[0021] Specific examples of the diene rubber include butadiene rubber (BR), nitrile rubber (NBR), acrylic rubber, epichlorohydrin rubber, urethane rubber, isoprene rubber, styrene-isoprene rubber, styrene-butadiene rubber (SBR), and ethylene-propylene copolymers, which may be used alone or in combination of two or more. Of these, butadiene rubber is preferred because it provides better microcell reproducibility when made into a flexographic printing plate (hereinafter, also referred to as "better effects of the present invention").

[0022] The content of the base polymer is preferably 1 to 50% by mass, more preferably 5 to 40% by mass, and even more preferably 7 to 30% by mass, based on the total solid content of the photosensitive resin layer.

[0023] <Water-Dispersible Particles> The water-dispersible particles are not particularly limited, but are preferably polymers because they provide superior effects of the present invention. Specific examples of the polymer include diene polymers (e.g., polybutadiene, natural rubber, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, methyl methacrylate-butadiene copolymer, polychloroprene, polyisoprene), polyurethane, vinylpyridine polymer, butyl polymer, thiokol polymer, acrylate polymer, and polymers obtained by copolymerizing these polymers with other components such as acrylic acid and methacrylic acid. These may be used alone or in combination of two or more. The polymer is preferably a diene polymer, and more preferably polybutadiene. Furthermore, the polymer preferably does not have reactive functional groups (e.g., (meth)acryloyloxy groups) at both ends.

[0024] The polymer is preferably a polymer obtained by removing water from a water-dispersed latex. Specific examples of the water-dispersed latex include the water-dispersed latexes of the specific examples of the polymers described above.

[0025] The content of the water-dispersible particles is preferably 5 to 80% by mass relative to the total solid content of the photosensitive resin layer, and is more preferably 10% by mass or more but less than 50% by mass, and even more preferably 20 to 45% by mass, because this improves the reproducibility of microcells when made into a flexographic printing plate and also improves printing durability.

[0026] <Photopolymerizable Unsaturated Compound> The photopolymerizable unsaturated compound is not particularly limited, but may be either a monofunctional monomer or a polyfunctional monomer, or these may be used in combination, for the reason that the effects of the present invention are more excellent.

[0027] (Monofunctional Monomer) The monofunctional monomer is preferably a compound having one ethylenically unsaturated group, because the effect of the present invention is more excellent. Examples of the ethylenically unsaturated group include radical polymerizable groups including (meth)acryloyl group, vinyl group, styryl group, allyl group, etc., and among them, (meth)acryloyl group and C(O)OCH=CH２ is preferred, and a (meth)acryloyl group is more preferred.

[0028] Examples of compounds having one ethylenically unsaturated group include N-vinyl compounds such as N-vinylformamide; (meth)acrylamide compounds such as (meth)acrylamide, N-methylol(meth)acrylamide, diacetone(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, (meth)acryloylmorpholine, and (meth)acrylamide; 2-Hydroxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, carbitol (meth)acrylate, cyclohexyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, benzyl (meth)acrylate, tridecyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, glycidyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl phthalate, methoxy-polyethylene glycol (meth)acrylate, 2-(meth)acryloyloxyethyl (meth)acrylate compounds such as ethyl-2-hydroxyethyl phthalate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethoxylated phenyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, nonylphenol EO adduct (meth)acrylate, phenoxy-polyethylene glycol (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalate, lactone-modified (meth)acrylate, stearyl (meth)acrylate, isoamyl (meth)acrylate, isomyristyl (meth)acrylate, isostearyl (meth)acrylate, and cyclic trimethylolpropane formal (meth)acrylate;Methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, t-butyl vinyl ether, n-octadecyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, dodecyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, cyclohexylmethyl vinyl ether, 4-methylcyclohexylmethyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether monovinyl ether compounds such as ethoxyethoxyethyl vinyl ether, methoxypolyethylene glycol vinyl ether, tetrahydrofurfuryl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexylmethyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chloroethyl vinyl ether, chlorobutyl vinyl ether, chloroethoxyethyl vinyl ether, phenylethyl vinyl ether, phenoxypolyethylene glycol vinyl ether, cyclohexanedimethanol monovinyl ether, and isopropenyl ether-O-propylene carbonate; and the like. EO represents ethylene oxide.

[0029] The content of the monofunctional monomer is preferably 0.1 to 30% by mass, and more preferably 1 to 10% by mass, based on the total solid content of the photosensitive resin layer, because this provides a better effect of the present invention.

[0030] (Polyfunctional Monomer) The polyfunctional monomer is preferably a compound having two ethylenically unsaturated groups, because the effects of the present invention are more excellent. Specific examples of the ethylenically unsaturated groups are as described above.

[0031] Examples of compounds having two ethylenically unsaturated groups include glycol di(meth)acrylate compounds such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetrapropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, ethoxylated neopentyl glycol di(meth)acrylate, and propoxylated neopentyl glycol di(meth)acrylate; divinyl ether compounds such as ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, and cyclohexanedimethanol divinyl ether; and di(meth)acrylate compounds of bisphenol A such as bisphenol A diglycidyl ether (meth)acrylic acid adduct, modified bisphenol A di(meth)acrylate, PO adduct di(meth)acrylate of bisphenol A, and EO adduct di(meth)acrylate of bisphenol A. PO represents propylene oxide, and EO represents ethylene oxide.

[0032] The content of the polyfunctional monomer is preferably 0.1 to 30% by mass based on the total solid content of the photosensitive resin layer, because this provides better effects of the present invention.

[0033] <Photopolymerization initiator> The photopolymerization initiator is not particularly limited, and examples thereof include alkylphenones, acetophenones, benzoin ethers, benzophenones, thioxanthones, anthraquinones, benzils, biacetyls, etc. More specific examples thereof include benzyl dimethyl ketal, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, methyl-o-benzoyl benzoate, 1-hydroxycyclohexyl phenyl ketone, etc.

[0034] The content of the photopolymerization initiator is preferably 0.5 to 10% by mass, based on the total solid content of the photosensitive resin layer. In order to improve the reproducibility of microcells when made into a flexographic printing plate and also improve printing durability, the content is more preferably 1.5% by mass or more and less than 5.0% by mass, and even more preferably 2.5 to 4.5% by mass.

[0035] <Polymerization inhibitor> The photosensitive resin layer preferably contains a polymerization inhibitor (stabilizer) for the reason that the effects of the present invention are more excellent. Examples of polymerization inhibitors include phenols, hydroquinones, and catechols. When the photosensitive resin layer contains a polymerization inhibitor, the content of the polymerization inhibitor is preferably 0.01 to 5 mass %, and more preferably 0.01 to 0.5 mass %, relative to the total solid content of the photosensitive resin layer.

[0036] <Telechelic Polymer> The photosensitive resin layer preferably contains a telechelic polymer, because the effects of the present invention are more excellent. In this specification, the term "telechelic polymer" refers to a polymer having reactive functional groups at both ends.

[0037] (Main Chain) The polymer constituting the main chain of the telechelic polymer is not particularly limited, and examples thereof include thermoplastic polymers. The thermoplastic polymer is not particularly limited as long as it is a polymer that exhibits thermoplasticity, and specific examples thereof include polystyrene resin, polyester resin, polyamide resin, polysulfone resin, polyethersulfone resin, polyimide resin, acrylic resin, acetal resin, epoxy resin, polycarbonate resin, rubber, and thermoplastic elastomer. Among these, rubber and thermoplastic elastomer are preferred, rubber is more preferred, and diene rubber is even more preferred, because they facilitate the formation of a softer and more flexible film.

[0038] Specific examples of the rubber include butadiene rubber (BR), nitrile rubber (NBR), acrylic rubber, epichlorohydrin rubber, urethane rubber, isoprene rubber, styrene-isoprene rubber, styrene-butadiene rubber (SBR), ethylene-propylene copolymer, chlorinated polyethylene, etc., and these may be used alone or in combination of two or more. Among these, from the viewpoints of good water developability and drying properties and image reproducibility, at least one rubber selected from the group consisting of butadiene rubber (BR), styrene-butadiene rubber (SBR), and nitrile rubber (NBR) is preferred, and butadiene rubber and styrene-butadiene rubber are more preferred.

[0039] Examples of the thermoplastic elastomer include PB (polybutadiene-based thermoplastic elastomer), polyisoprene-based thermoplastic elastomer, polyolefin-based thermoplastic elastomer, and acrylic-based thermoplastic elastomer. Specific examples include SB (polystyrene-polybutadiene), SBS (polystyrene-polybutadiene-polystyrene), SIS (polystyrene-polyisoprene-polystyrene), SEBS (polystyrene-polyethylene / polybutylene-polystyrene), ABS (acrylonitrile butadiene styrene copolymer), ACM (acrylic acid ester rubber), ACS (acrylonitrile-chlorinated polyethylene styrene copolymer), acrylonitrile styrene copolymer, syndiotactic 1,2-polybutadiene, polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate, and the like. Of these, PB, SBS, and SIS are particularly preferred because of their excellent water-developability and from the viewpoints of drying properties and image reproducibility.

[0040] (Terminal) The telechelic polymer has reactive functional groups at both terminals. The reactive functional group is not particularly limited, but is preferably an ethylenically unsaturated group, because the effects of the present invention are more excellent. The ethylenically unsaturated group is preferably a vinyl group (CH ２ ═CH—), allyl group (CH ２ =CH-CH ２ -), (meth)acryloyl group, or (meth)acryloyl group is preferred, and (meth)acryloyloxy group is more preferred.

[0041] The telechelic polymer may have reactive functional groups at both ends of the polymer constituting the main chain via divalent linking groups. The divalent linking groups are not particularly limited, and examples thereof include linear, branched, or cyclic divalent aliphatic hydrocarbon groups (e.g., alkylene groups such as methylene, ethylene, and propylene), divalent aromatic hydrocarbon groups (e.g., phenylene), -O-, -S-, -SO ２ -, -NRL-, -CO-, -NH-, -COO-, -CONRL-, -O-CO-O-, -SO ３ -, -NHCOO-, -SO２ Examples include NRL-, -NH-CO-NH-, and a group consisting of a combination of two or more of these (e.g., an alkyleneoxy group, an alkyleneoxycarbonyl group, an alkylenecarbonyloxy group, etc.), where RL represents a hydrogen atom or an alkyl group (preferably having 1 to 10 carbon atoms).

[0042] (Molecular Weight) The weight average molecular weight (Mw) of the telechelic polymer is preferably 6,000 or more, more preferably 7,000 or more, even more preferably 8,000 or more, and particularly preferably 9,000 or more, because the effects of the present invention are more excellent. There is no particular upper limit for the Mw of the telechelic polymer, but because the effects of the present invention are more excellent, it is preferably 500,000 or less, more preferably 100,000 or less. Here, the weight average molecular weight is measured by gel permeation chromatography (GPC) and calculated using standard polystyrene. Specifically, for example, GPC is performed using an HLC-8220GPC (manufactured by Tosoh Corporation), three columns (4.6 mm ID x 15 cm, manufactured by Tosoh Corporation) are used, and THF (tetrahydrofuran) is used as the eluent. The conditions are a sample concentration of 0.35% by mass, a flow rate of 0.35 mL / min, a sample injection amount of 10 μL, and a measurement temperature of 40°C, and an IR detector is used. In addition, a calibration curve is prepared from eight samples of "Standard Sample TSK Standard, Polystyrene" manufactured by Tosoh Corporation: "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000", and "n-propylbenzene".

[0043] (HSP Value) The HSP (Hansen Solubility Parameter) value of the telechelic polymer is not particularly limited, but is preferably 8 to 12, more preferably 8.5 to 11, and even more preferably 8.5 to 10.5, for reasons of better effects of the present invention.

[0044] (Content) When the photosensitive resin layer contains a telechelic polymer, the content of the telechelic polymer is preferably 1 to 50 mass %, and more preferably 5 to 40 mass %, based on the total solid content of the photosensitive resin layer, because the effects of the present invention are more excellent.

[0045] <Plasticizer> The photosensitive resin layer preferably contains a plasticizer, since this improves flexibility.

[0046] Specific examples of plasticizers include liquid rubber, oil, polyester, and phosphoric acid compounds. Specific examples of liquid rubber include liquid polybutadiene, liquid polyisoprene, and those modified with maleic acid or epoxy groups. Specific examples of oils include paraffin, naphthene, and aroma. Specific examples of polyesters include adipic acid polyesters. Specific examples of phosphoric acid compounds include phosphoric acid esters.

[0047] When the photosensitive resin layer contains a plasticizer, the content of the plasticizer is preferably 0.1 to 40% by mass, and more preferably 5 to 30% by mass, relative to the total solid content of the photosensitive resin layer, in order to further improve flexibility.

[0048] <Surfactant> The photosensitive resin layer preferably contains a surfactant from the viewpoint of improving water developability. Examples of the surfactant include cationic surfactants, anionic surfactants, and nonionic surfactants. Among these, anionic surfactants are preferred because they provide better effects of the present invention.

[0049] Specific examples of the anionic surfactant include: aliphatic carboxylates such as sodium laurate and sodium oleate; higher alcohol sulfates such as sodium lauryl sulfate, sodium cetyl sulfate and sodium oleyl sulfate; polyoxyethylene alkyl ether sulfates such as sodium polyoxyethylene lauryl ether sulfate; polyoxyethylene alkyl allyl ether sulfates such as sodium polyoxyethylene octyl phenyl ether sulfate and sodium polyoxyethylene nonyl phenyl ether sulfate; alkyl sulfonates such as alkyl diphenyl ether disulfonates, sodium dodecyl sulfonate and sodium dialkyl sulfosuccinate; alkyl allyl sulfonates such as alkyl disulfonates, sodium dodecyl benzene sulfonate, sodium dibutyl naphthalene sulfonate and sodium triisopropyl naphthalene sulfonate; higher alcohol phosphates such as disodium lauryl phosphate monoester and sodium lauryl phosphate diester; polyoxyethylene alkyl ether phosphates such as disodium polyoxyethylene lauryl ether phosphate monoester and sodium polyoxyethylene lauryl ether phosphate diester; and the like. These may be used alone or in combination of two or more.

[0050] Among these, sulfonic acid surfactants such as alkyl sulfonates and alkyl aryl sulfonates are preferred because they provide good water developability.

[0051] When the photosensitive resin layer contains a surfactant, the content of the surfactant is preferably 0.1 to 20 mass %, and more preferably 1 to 10 mass %, relative to the total solid content of the photosensitive resin layer, from the viewpoints of developability and drying property after development.

[0052] <Other Additives> Additives such as ultraviolet absorbers, dyes, pigments, antifoaming agents, and fragrances may be added to the photosensitive resin layer as appropriate to improve various properties, as long as the effects of the present invention are not impaired.

[0053] <Method for Producing Photosensitive Resin Layer> The method for producing the photosensitive resin layer is not particularly limited, but examples include a method in which a resin composition containing the above-mentioned components is prepared and then coated on the above-mentioned support.

[0054] The thickness of the photosensitive resin layer is preferably 0.01 to 10 mm, and more preferably 0.2 to 6 mm.

[0055] [Intermediate Layer] <Copolymer> The intermediate layer of the flexographic printing plate precursor of the present invention is a layer containing a copolymer represented by the following formula (1).

[0056] In the above formula (1), R １ represents an alkyl group having 1 to 6 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, and an n-hexyl group. Of these, a methyl group is preferred. In the following, R in the above formula (1) １ is represented by a methyl group is also called "partially saponified polyvinyl acetate".

[0057] In the above formula (1), m and n represent the content (mol %) of each repeating unit, and the molar ratio represented by the following formula (i) satisfies 60 to 75 mol %. Note that, hereinafter, the molar ratio represented by the following formula (i) will also be simply referred to as "molar ratio". m / (m+n)×100 (i)

[0058] The molar ratio represented by the formula (i) can be measured by a diffuse reflectance method. Here, the diffuse reflectance method is a method in which measurement light is diffusely reflected on the surface of a sample when it reaches the light-receiving part from the light-emitting part of a near-infrared analyzer, thereby obtaining a near-infrared absorption spectrum. Measurement by the diffuse reflectance method is performed, for example, at room temperature and a measurement wavelength of 4000 cm. －１ ~12,000 cm －１ , resolution: 8cm －１If the number of integrations is 64, the molar ratio can be measured in about one minute. Specifically, first, the near-infrared absorption spectra of multiple polyvinyl alcohol (PVA) copolymer samples with specified molar ratios are measured by chemical analysis such as titration, and a calibration curve is created in advance from the measurement results by multiple regression analysis, principal component regression analysis, partial least squares method, etc., comparing the molar ratio with the chart of the PVA copolymer sample. Next, the near-infrared absorption spectrum of the intermediate layer sample to be measured is measured, and the molar ratio is determined from the previously prepared calibration curve. Note that there are no particular limitations on the near-infrared spectrometer as long as it is equipped with a multivariate analyzer, and examples include Bruker Optics' "Vector22 / N (trade name)," Nicolet's "Antaris (trade name)," Perkin-Elmer's "Spectrum One NTS (trade name)," and Buchi's "NIRlex (trade name)." When two or more copolymers represented by the formula (1) are contained, the molar ratio of each copolymer can be calculated by multiplying the molar ratio of each copolymer by the mass ratio of each copolymer and adding up the results. On the other hand, the molar ratio represented by the formula (i) can also be said to be the degree of saponification of the copolymer represented by the formula (1), i.e., the modified PVA, and can also be measured by a titration method in accordance with JIS K 6726 (1994).

[0059] The molar ratio represented by the above formula (i) is preferably 65 to 75 mol%, and more preferably 70 to 75 mol%, because this improves the reproducibility of microcells when made into a flexographic printing plate and also improves printing durability.

[0060] The weight-average molecular weight of the copolymer represented by the above formula (1) is preferably 10,000 to 200,000. Here, the weight-average molecular weight can be determined by GPC (Gel Permeation Chromatography) measurement. More specifically, the weight-average molecular weight can be measured using a gel permeation chromatograph-multiangle light scattering photometer manufactured by Wyatt Technology under the conditions of a column temperature of 40°C and a flow rate of 0.7 mL / min. Polyethylene oxide and polyethylene glycol are used as standard samples.

[0061] The content of the copolymer represented by the above formula (1) is preferably more than 50% by mass, more preferably 55 to 95% by mass, and even more preferably 60 to 90% by mass, based on the total solid content of the intermediate layer.

[0062] <Plasticizer> The intermediate layer preferably contains a plasticizer to further improve flexibility. Examples of the plasticizer include the same plasticizers as those described above as optional components in the photosensitive resin layer. When the intermediate layer contains a plasticizer, the content of the plasticizer is preferably 5 to 45% by mass, and more preferably 10 to 40% by mass, of the total solid content of the intermediate layer to further improve flexibility.

[0063] <Method for Producing Intermediate Layer> The method for producing the intermediate layer is not particularly limited, but examples thereof include a method in which a composition containing the above-described components is prepared and then applied to the above-described photosensitive resin layer.

[0064] The thickness of the intermediate layer is preferably 0.1 to 6 μm, and more preferably 0.2 to 3 μm.

[0065] [Infrared ablation layer] The infrared ablation layer of the flexographic printing plate precursor of the present invention is a masking portion that covers the surface of the intermediate layer. The infrared ablation layer is a portion that can be removed by an infrared laser, and the remaining portion blocks (absorbs) ultraviolet light, thereby masking the underlying intermediate layer and photosensitive resin layer so that the ultraviolet light is not irradiated onto the layer. Such an infrared ablation layer can be formed using a resin composition containing a binder polymer and an infrared-absorbing substance.

[0066] <Binder Polymer> Examples of the binder polymer contained in the resin composition include a rubber component and a resin component. Specific examples of the rubber component include butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), acrylic rubber, epichlorohydrin rubber, urethane rubber, isoprene rubber (IR), styrene-isoprene rubber (SIR), styrene-butadiene rubber (SBR), ethylene-propylene copolymer, and chlorinated polyethylene. These may be used alone or in combination of two or more. Specific examples of the resin component include (meth)acrylic resin, polystyrene resin, polyester resin, polyamide resin, polysulfone resin, polyethersulfone resin, polyimide resin, acrylic resin, acetal resin, epoxy resin, and polycarbonate resin. Among these, the polymer component corresponding to the rubber component is preferably butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), or styrene butadiene rubber (SBR), and more preferably acrylonitrile butadiene rubber (NBR).Furthermore, the polymer component corresponding to the resin component is preferably a (meth)acrylic resin.

[0067] <Infrared absorbing material> The infrared absorbing material contained in the resin composition is not particularly limited as long as it is a material that can absorb infrared rays and convert them into heat.Specific examples of infrared absorbing materials include black pigments (e.g., carbon black, aniline black, cyanine black, etc.), green pigments (e.g., phthalocyanine, naphthalocyanine, etc.), rhodamine dyes, naphthoquinone dyes, polymethine dyes, diimonium salts, azoimonium dyes, chalcogen dyes, carbon graphite, iron powder, diamine metal complexes, dithiol metal complexes, phenolthiol metal complexes, mercaptophenol metal complexes, aryl aluminum metal salts, inorganic compounds containing crystal water, copper sulfate, metal oxides (e.g., cobalt oxide, tungsten oxide, etc.), and metal powders (e.g., bismuth, tin, tellurium, aluminum, etc.).Among these, carbon black, carbon graphite, etc. are preferred from the viewpoint of having ultraviolet absorbing properties.

[0068] In addition to the binder polymer and infrared absorbing material described above, the infrared ablation layer may contain various additives such as surfactants, plasticizers, ultraviolet absorbing materials, release agents, dyes, pigments, antifoaming agents, and fragrances.

[0069] The method for producing the infrared ablation layer is not particularly limited, but examples thereof include a method in which a resin composition containing the above-mentioned components is prepared and then coated on the above-mentioned intermediate layer.

[0070] The thickness of the infrared ablation layer is preferably 0.1 to 6 μm, and more preferably 0.5 to 3 μm.

[0071] [Cover sheet] The flexographic printing plate precursor of the present invention may have a cover sheet, as shown in Figure 1. Such a cover sheet is not particularly limited, but is preferably a transparent polymer film, and may be a single layer or a laminate of two or more layers. Here, "transparent" as used in the present invention means that the transmittance of visible light is 60% or more, preferably 80% or more, and particularly preferably 90% or more. Examples of materials for the polymer film include cellulose-based polymers; acrylic polymers having acrylic acid ester polymers such as polymethyl methacrylate and lactone ring-containing polymers; thermoplastic norbornene-based polymers; polycarbonate-based polymers; polyester-based polymers such as polyethylene terephthalate, polyethylene naphthalate, and fluorine-containing polyester polymers; styrene-based polymers such as polystyrene and acrylonitrile-styrene copolymers (AS resins); polyolefin-based polymers such as polyethylene, polypropylene, ethylene-propylene copolymers, and polybutadiene; vinyl chloride-based polymers; amide-based polymers such as nylon and aromatic polyamides; imide-based polymers; sulfone-based polymers; polyethersulfone-based polymers; polyetheretherketone-based polymers; polyphenylene sulfide-based polymers; vinylidene chloride-based polymers; vinyl alcohol-based polymers; vinyl butyral-based polymers; arylate-based polymers; polyoxymethylene-based polymers; epoxy-based polymers; and polymers containing mixtures of these polymers.

[0072] The surface of the cover sheet (the surface on which the infrared ablation layer is formed) may be subjected to a release treatment to reduce adhesion of the infrared ablation layer and improve the releasability of the cover sheet. Examples of such a release treatment include applying a release agent to the surface of the cover sheet to form a release layer. Examples of the release agent include silicone-based release agents and alkyl-based release agents.

[0073] The thickness of the cover sheet is preferably 25 to 250 μm.

[0074] [Method for manufacturing flexographic printing plate] The method for manufacturing a flexographic printing plate of the present invention is a method for manufacturing a flexographic printing plate having non-image areas and image areas, and includes: a mask forming step of forming an image on the infrared ablation layer of the flexographic printing plate precursor of the present invention described above to form a mask; an exposure step of imagewise exposing the photosensitive resin layer of the flexographic printing plate precursor of the present invention described above through the mask after the mask forming step; and a development step of developing with a developer after the exposure step to form non-image areas and image areas.

[0075] [Mask Forming Step] The mask forming step is a step of forming an image on the infrared ablation layer and forming a mask to be used in the exposure step described below. Here, when the infrared ablation layer is irradiated with an infrared laser, heat is generated by the action of the infrared absorbing material, and the infrared ablation layer is removed by the action of the heat, i.e., laser ablation. Therefore, by selectively laser ablating the infrared ablation layer based on image data, an image mask capable of forming a latent image on the photosensitive resin layer can be obtained.

[0076] For infrared laser irradiation, an exposure light source having an oscillation wavelength in the range of 750 nm to 3000 nm is used. Examples of such lasers include solid-state lasers such as ruby ​​lasers, alexandrite lasers, perovskite lasers, Nd-YAG lasers, and emerald glass lasers; semiconductor lasers such as InGaAsP, InGaAs, and GaAsAl; and dye lasers such as rhodamine dyes. Fiber lasers in which these light sources are amplified by fiber can also be used. Among these, an exposure light source having an oscillation wavelength of 900 to 1200 nm is preferably used, and a fiber laser is more preferably used, because this increases the sensitivity of the infrared ablation layer.

[0077] [Exposure Step] The exposure step is a step of exposing the photosensitive resin layer to ultraviolet light in an imagewise manner through the mask obtained in the mask formation step. By irradiating the photosensitive resin layer with ultraviolet light in an imagewise manner, crosslinking and / or polymerization can be induced in the areas irradiated with ultraviolet light, thereby enabling curing.

[0078] [Developing Step] The developing step is a step of forming non-image areas and image areas by developing with a developer.

[0079] The developer used in the development step is not particularly limited, and any conventionally known developer can be used. However, from the viewpoint of reducing the environmental impact, it is preferable to use a developer containing 50% by mass or more of water (hereinafter also referred to as "aqueous developer"). The developer may be an aqueous solution or a suspension (e.g., an aqueous dispersion). The content of water in the aqueous developer is preferably 80 to 99.99% by mass, and more preferably 90 to 99.9% by mass, based on the total mass of the aqueous developer.

[0080] [Rinsing Step] The method for producing a flexographic printing plate of the present invention preferably includes, after the 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.

[0081] 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 batch-type or conveying-type brush-type washing machine known as a developing machine for flexographic printing plates.

[0082] The present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the examples shown below.

[0083] [Synthesis of Partially Saponified Polyvinyl Acetate A (Mole Ratio 63%)] Partially saponified polyvinyl acetate A was synthesized as follows. 50 parts by mass of vinyl acetate and 60 parts by mass of methanol were polymerized at 60°C under nitrogen substitution, and when the degree of polymerization reached 500, the polymerization was stopped by cooling. Next, unreacted vinyl acetate was removed to obtain a methanol solution of polyvinyl acetate. A NaOH methanol solution (10% concentration) was added to the obtained solution to deacetylate the R １was represented by a methyl group, and the molar ratio represented by the above formula (i) was 63 mol %, thereby obtaining a partially saponified polyvinyl acetate A (degree of polymerization: 500).

[0084] [Synthesis of Partially Saponified Polyvinyl Acetate B (50% Molar Ratio)] Partially saponified polyvinyl acetate B was synthesized as follows. 50 parts by mass of vinyl acetate and 60 parts by mass of methanol were polymerized at 60°C under nitrogen substitution, and when the degree of polymerization reached 500, the polymerization was stopped by cooling. Next, unreacted vinyl acetate was removed to obtain a methanol solution of polyvinyl acetate. A NaOH methanol solution (7% concentration) was added to the obtained solution to deacetylate the R １ is represented by a methyl group, and a partially saponified polyvinyl acetate B (degree of polymerization: 500) having a molar ratio of 50 mol % represented by the above formula (i) was obtained.

[0085] [Example 1] [Preparation of infrared ablation layer-forming composition] 100 parts by mass of carbon black and 3 parts by mass of plasticizer were added to 100 parts by mass of a binder polymer consisting of 50 parts by mass of acrylic resin A (Hyperl M5000, Tg: 65°C, manufactured by Negami Chemical Industrial Co., Ltd.) and 50 parts by mass of NBR, and 812 parts by mass of methyl isobutyl ketone as a solvent was further added and mixed by blade stirring. The resulting mixture was dispersed using a three-roll mill, and then methyl isobutyl ketone was further added so that the solids content was 15% by mass, thereby preparing an infrared ablation layer-forming composition.

[0086] [Preparation of intermediate layer-forming composition] A partially saponified polyvinyl acetate (GOHSENOL NK-05R, molar ratio: 71 to 75, manufactured by Mitsubishi Chemical Corporation) and a plasticizer (SUNFLEX SE270, manufactured by Sanyo Chemical Industries, Ltd., aliphatic polyhydric alcohol-based polyether polyol, solids concentration 85%) were mixed in a mass ratio of 65 / 35 to obtain an intermediate layer-forming composition.

[0087] [Preparation of Photosensitive Resin Layer-Forming Composition] 63.6 parts by mass of a water-dispersible latex (Nipol LX111NF, a water-dispersible latex of polybutadiene, solids content 55%, manufactured by Zeon Corporation), 10 parts by mass of a telechelic polymer (BAC-45, manufactured by Osaka Organic Chemical Industry Ltd.) (a polybutadiene having acryloyloxy groups at both ends, Mw=10,000), and 12 parts by mass of 1,9-nonanediol dimethacrylate (NK Ester NOD-N, manufactured by Shin-Nakamura Chemical Co., Ltd.) were mixed, and the water was evaporated for 3 hours in a dryer heated to 60°C, to obtain a mixture containing water-dispersible particles. This mixture, 20 parts by mass of butadiene rubber (NF35R, manufactured by Asahi Kasei Corporation), 16 parts by mass of plasticizer (Diana Process Oil PW-32, manufactured by Idemitsu Kosan Co., Ltd.), and 4.3 parts by mass of surfactant (Rapisol A-90, active content 90%, manufactured by NOF Corporation) were kneaded for 45 minutes in a kneader set at 110° C. Thereafter, 0.1 parts by mass of BHT (butylhydroxytoluene) as a thermal polymerization inhibitor and 3.5 parts by mass of Irgacure 651 as a photopolymerization initiator were added to the kneader, and the mixture was kneaded for 5 minutes to prepare a composition for forming a photosensitive resin layer.

[0088] [Preparation of Flexographic Printing Plate Precursor] The infrared ablation layer-forming composition prepared as described above was applied to a 125 μm-thick PET film (cover sheet) coated with a silicone-based release agent using a bar coater so that the coating thickness after drying would be 1 μm, and the application was dried at 120° C. for 5 minutes to obtain a laminate X consisting of an infrared ablation layer / cover sheet. Next, the intermediate layer-forming composition prepared as described above was applied to a 125 μm-thick PET film (cover sheet) coated with a silicone-based release agent using a bar coater so that the coating thickness after drying would be 1 μm, and the application was dried at 120° C. for 5 minutes to obtain a laminate Y consisting of an intermediate layer / cover sheet. Next, the side of laminate X on which the infrared ablation layer was formed and the side of laminate Y on which the intermediate layer was formed were laminated together, and pressed in a press heated to 120° C. to a thickness of 2 μm to obtain a laminate Z in which the cover sheet, infrared ablation layer, intermediate layer, and cover sheet were laminated in this order. Next, the cover sheet on the surface of the intermediate layer of Laminate Z was peeled off to obtain Laminate A, in which the cover sheet, infrared ablation layer, and intermediate layer were laminated in this order. Next, an adhesive was applied to one surface of a 125 μm-thick PET film (support) to form an adhesive layer on the support. The photosensitive layer-forming composition prepared as described above was then sandwiched between the adhesive layer on the support and the intermediate layer of Laminate A, and pressed in a press heated to 120° C. so that the photosensitive resin layer had a thickness of 1.5 mm, thereby producing the flexographic printing plate precursor of Example 1, in which the support, adhesive layer, photosensitive resin layer, intermediate layer, infrared ablation layer, and cover sheet were laminated in this order.

[0089] [Preparation of Flexographic Printing Plate] Using the obtained flexographic printing plate precursor, a flexographic printing plate was produced by the following procedure. The equipment used in each step is as follows. <Equipment, etc.> Imaging machine: CDI Spark 4835 Inline (manufactured by ESKO) Ultraviolet exposure machine: Concept 302 ECDLF (product name) (manufactured by Glunz & Jensen) Washing machine: C-Touch 2530 Water Wash Plate Processor (manufactured by GS Trading) Washing solution: aqueous solution (concentration: 0.5% by mass) of Finish Power & Pure Powder SP (manufactured by Reckitt Benckiser Japan KK)

[0090] (1) Backside Exposure Step Backside exposure was carried out by exposing the backside of the flexographic printing plate precursor to light for 10 seconds at an energy of 80 W using the above-mentioned ultraviolet exposure machine.

[0091] (2) Mask Formation Step Next, the cover sheet was peeled off, and the photosensitive resin layer was imaged by ablation using the imaging machine. The image used was a 100% solid image, 1 cm wide and 1 cm long, as well as a 2% halftone image, 1 cm wide and 1 cm long. More specifically, RIP was performed using the RIP software Automation Engine Pilot at a resolution of 4000 dpi and a line count of 175 lpi. The 100% solid image was an MCWSI pattern, which is a microcell pattern.

[0092] (3) Exposure Step Using the above ultraviolet exposure device, the main exposure was carried out by exposing the front surface (the back surface of the back surface) at 80 W for 360 seconds.

[0093] (4) Development Step Next, development was carried out for 12 minutes using the above-mentioned washing machine and washing solution.

[0094] (5) Drying Step Next, drying was carried out using hot air at 60°C until the moisture was removed.

[0095] (6) Post-exposure step Next, the photosensitive resin layer was exposed for 180 seconds (post-exposure) using the ultraviolet exposure machine, thereby preparing a flexographic printing plate having an image area.

[0096] Examples 2 to 10 and Comparative Examples 1 to 4 Flexographic printing plate precursors and flexographic printing plates were prepared according to the same procedure as in Example 1, except that the type and content (mass%) of each component in the intermediate layer and photosensitive resin layer were changed as shown in Tables 1 and 2 below. In Example 10, as shown in Table 2 below, 48.8 parts by mass of partially saponified polyvinyl acetate (GOHSENOL KL-03, molar ratio: 78.5 to 82, manufactured by Mitsubishi Chemical Corporation) and 16.2 parts by mass of partially saponified polyvinyl acetate B (the synthetic product described above, molar ratio: 50) were used in combination. Therefore, the molar ratio represented by formula (i) above can be calculated as 71.4 to 74.0 mol % by multiplying the molar ratio of each copolymer by its mass ratio and adding up the results. This value could also be confirmed by titration according to JIS K 6726 (1994).

[0097] [Evaluation] [Microcell Reproducibility] The microcell reproducibility of the obtained flexographic printing plate was evaluated using the following method. First, the surface of the solid image area of ​​the flexographic printing plate was confocal measured at 0.1 μm height intervals using a hybrid laser microscope OPTELICS (registered trademark) HYBRID (manufactured by Lasertec Corporation) with a 50xApo objective lens (high numerical aperture (high NA)) to obtain three-dimensional data. The evaluation range was an area of ​​300 μm in length and 300 μm in width. From the image observed using the three-dimensional data, 100 or more convex portions were observed, and the number of convex portions that were reproduced without chipping was determined. Next, the image reproduction percentage was calculated using the following formula: Image reproduction percentage = (number of convex portions reproduced without chipping) / (number evaluated) × 100. Evaluation was performed according to the following criteria. The results are shown in Tables 1 and 2 below. To obtain a printed matter with a higher solid density, the image reproduction of the microcell is preferably C to A, more preferably B to A, and even more preferably A. If the image reproduction is less than 80%, the ink transferred to the printed matter will be largely uneven, resulting in a deterioration in the solid density. <Evaluation criteria> A: Image reproduction is 98% or more B: Image reproduction is 90% or more but less than 98% C: Image reproduction is 80% or more but less than 90% D: Image reproduction is 70% or more but less than 80% E: Image reproduction is less than 70%

[0098] [Printing durability] The printing durability of the obtained flexographic printing plates was evaluated by the following method. A flexographic printing machine (TLF-270, manufactured by Taiyo Kikai) was used as the printing machine. The obtained flexographic printing plate was attached to the plate cylinder (drum) via cushion tape (manufactured by Lohmann) and installed on the printing machine. Thereafter, printing was carried out at a printing speed of 150 m / min under the condition that the kiss touch (printing pressure at which the entire image begins to be inked) was set to 0 (standard printing pressure) and the printing pressure was increased by 80 μm from there. The printing substrate used for evaluation was sampled every 5 km up to 25 km under the above conditions. The printing substrate was a flexographic printing plate coated with Aurora Coat 84.9 g / m ２ (manufactured by Nippon Paper Industries Co., Ltd.) was used. The ink used was a water-based flexographic ink, Hydric FCF (manufactured by Dainichiseika Chemicals Co., Ltd.). The number of missing dots in a 2% halftone dot image on the printed material was then counted. The printing distance where 25 dots out of 4,746 dots at the start were missing was defined as the end point, and the distance to the end point was evaluated according to the following criteria. The results are shown in Tables 1 and 2 below. In practice, C to A are preferred, B to A are more preferred, and A is even more preferred. <Evaluation criteria> A: 25 km or more B: 20 ​​km or more but less than 25 km C: 15 km or more but less than 20 km D: 10 km or more but less than 15 km E: Less than 10 km

[0099]

[0100]

[0101] The results shown in Tables 1 and 2 above indicate that when no intermediate layer is provided, the reproducibility of microcells is poor when a flexographic printing plate is produced (Comparative Example 1). Furthermore, even when the copolymer represented by formula (1) is used in the intermediate layer, the reproducibility of microcells is poor when the molar ratio represented by formula (i) exceeds 75 mol% (Comparative Examples 2 and 3). Furthermore, even when the copolymer represented by formula (1) is used in the intermediate layer, the reproducibility of microcells is poor when a flexographic printing plate is produced (Comparative Example 4) when the molar ratio represented by formula (i) is less than 60 mol%.

[0102] In contrast, when a copolymer represented by the above formula (1) having a molar ratio represented by the above formula (i) of 60 to 75 mol% was used in the intermediate layer, it was found that the reproducibility of microcells was improved when the flexographic printing plate was made (Examples 1 to 10). In particular, a comparison between Example 1 and Example 2 revealed that when the content of water-dispersible particles was 10% by mass or more but less than 50% by mass relative to the total solids content of the photosensitive resin layer, the reproducibility of microcells was improved when the flexographic printing plate was made, and the printing durability was also improved. Furthermore, a comparison between Example 1 and Examples 3 to 6 revealed that when the content of photopolymerization initiator was 1.5% by mass or more but less than 5.0% by mass relative to the total solids content of the photosensitive resin layer, the reproducibility of microcells was improved when the flexographic printing plate was made, and the printing durability was also improved. Furthermore, a comparison between Example 1 and Example 8 revealed that when the base polymer of the photosensitive resin layer was butadiene rubber, the reproducibility of microcells was improved. Furthermore, a comparison of Examples 1, 7, and 9 revealed that when the molar ratio represented by the above formula (i) is 65 to 75 mol %, the reproducibility of microcells becomes better when the flexographic printing plate is made, and the printing durability also becomes good.

[0103] REFERENCE SIGNS LIST 1 Support 2 Photosensitive resin layer 3 Intermediate layer 4 Infrared ablation layer 5 Cover sheet 10 Flexographic printing plate precursor

Claims

1. A flexographic printing plate precursor having, in this order, a support, a photosensitive resin layer, an intermediate layer, and an infrared ablation layer, wherein the photosensitive resin layer contains a base polymer, water-dispersible particles, a photopolymerizable unsaturated compound, and a photopolymerization initiator, and the intermediate layer contains a copolymer represented by the following formula (1): In the formula (1), R １ represents an alkyl group having 1 to 6 carbon atoms. m and n represent the content (mol %) of each repeating unit, and the molar ratio represented by the following formula (i) satisfies 60 to 75 mol %: m / (m+n)×100 (i) 2. The flexographic printing plate precursor according to claim 1, wherein the base polymer is a diene rubber.

3. The flexographic printing plate precursor according to claim 1 or 2, wherein the content of the photopolymerization initiator is 1.5% by mass or more and less than 5.0% by mass based on the total solid content of the photosensitive resin layer.

4. The flexographic printing plate precursor according to claim 1 or 2, wherein the content of the water-dispersible particles is 10% by mass or more and less than 50% by mass based on the total solid content of the photosensitive resin layer.

5. The flexographic printing plate precursor according to claim 2, wherein the diene rubber is a butadiene rubber.

6. A method for producing a flexographic printing plate having non-image areas and image areas, comprising the steps of: a mask formation step of forming an image on an infrared ablation layer of the flexographic printing plate precursor described in claim 1 or 2 to form a mask; an exposure step of exposing a photosensitive resin layer of the flexographic printing plate precursor in an imagewise manner through the mask after the mask formation step; and a development step of developing using a developer after the exposure step to form non-image areas and image areas.

Images