Photosensitive resin composition for original flexographic printing plate, and original flexographic printing plate obtained using said composition

Abstract

Provided is a photosensitive resin composition for an original flexographic printing plate, the photosensitive resin composition having both high water developability and mechanical strength. The photosensitive resin composition for an original flexographic printing plate is characterized by comprising a water-dispersible latex (A), a photopolymerizable unsaturated group-containing compound (B), a hydrophilic polymer (C), and a photopolymerization initiator (D), the hydrophilic polymer (C) containing a conjugated diene-based polymer (c) having at least one hydroxyl group at a side chain and / or a terminal and at least one photopolymerizable unsaturated group at a side chain and / or a terminal. Also provided is an original flexographic printing plate in which a photosensitive resin layer produced by using the photosensitive resin composition is provided on a support body.

Description

Photosensitive resin composition for flexographic printing plate precursor and flexographic printing plate precursor obtained using the same

[0001] The present invention relates to a photosensitive resin composition for a flexographic printing plate precursor and a flexographic printing plate precursor obtained using the same.

[0002] Typically, a flexographic printing original plate has a structure in which a photosensitive resin layer is provided on a support. The photosensitive resin composition that forms the photosensitive resin layer generally contains a polymer compound such as a latex or an elastomer, a photopolymerizable unsaturated compound, and a photopolymerization initiator as essential components, and may also contain additives such as a stabilizer and a plasticizer, as needed.

[0003] A known method for producing a printing plate from a flexographic printing plate precursor involves exposing a photosensitive resin layer imagewise and developing the unexposed portions of the photosensitive resin layer to produce a printing plate having an image area. Conventional photosensitive resin compositions used in the production of flexographic printing plates include those developed with organic solvents. However, the production of these printing plates poses problems related to the working environment and environmental conservation, such as toxicity and flammability. Therefore, there is a need to reduce the use of organic solvents, and there is a growing demand for water-developable photosensitive resin compositions. However, photosensitive resin compositions contain hydrophobic polymers, which can lead to problems such as reduced water-developability, reduced workability, and reduced productivity. To solve this problem, photosensitive resin compositions with high water-developability have been proposed. For example, Patent Document 1 proposes a photosensitive resin composition containing a hydrophobic polymer, a hydrophilic polymer, an ethylenically unsaturated monomer, a photopolymerization initiator, and a diene polymer containing one or more hydrophilic functional groups.

[0004] JP 2015-14685 A

[0005] The photosensitive resin composition of Patent Document 1 has good water-developability, but has the drawback of being insufficient in mechanical strength and poor in printing durability during printing because the hydrophilic functional groups are removed from the photosensitive resin layer by development.

[0006] The present invention has been made to solve the above-mentioned problems of the conventional art, and an object of the present invention is to provide a photosensitive resin composition for a flexographic printing plate precursor that has both high water-developability and mechanical strength, and a flexographic printing plate precursor obtained from the composition.

[0007] As a result of intensive research to solve the above-mentioned problems, the present inventors have found that a polymer having a hydrophilic functional group in a photosensitive resin composition has a photopolymerizable functional group and is photo-crosslinked with other components, thereby achieving higher water-developability and preventing detachment from the photosensitive resin layer due to development, and have completed the present invention. That is, the present invention comprises the following (1) to (8): (1) A photosensitive resin composition for a flexographic printing plate precursor, comprising (A) a water-dispersible latex, (B) a photopolymerizable unsaturated group-containing compound, (C) a hydrophilic polymer, and (D) a photopolymerization initiator, wherein the hydrophilic polymer (C) contains (c) a conjugated diene-based polymer having at least one hydroxyl group in a side chain and / or at a terminal and at least one photopolymerizable unsaturated group in a side chain and / or at a terminal. (2) The photosensitive resin composition for a flexographic printing plate precursor according to (1), characterized in that the (c) conjugated diene-based polymer having at least one hydroxyl group in a side chain and / or terminal and at least one photopolymerizable unsaturated group in a side chain and / or terminal contains an acrylonitrile skeleton. (3) The photosensitive resin composition for a flexographic printing plate precursor according to (1), characterized in that the content of the (C) hydrophilic polymer per 100 parts by mass of the (A) water-dispersible latex is 5 to 45 parts by mass. (4) The photosensitive resin composition for a flexographic printing plate precursor according to (1), characterized in that the mass ratio of the (B) photopolymerizable unsaturated group-containing compound to the (C) hydrophilic polymer is 95:5 to 40:60. (5) The photosensitive resin composition for a flexographic printing plate precursor according to (1), wherein the (B) photopolymerizable unsaturated group-containing compound contains a photopolymerizable unsaturated compound having a number-average molecular weight of 100 or more and 600 or less, and a photopolymerizable unsaturated compound having a number-average molecular weight of more than 600 and 20,000 or less. (6) The photosensitive resin composition for a flexographic printing plate precursor according to (1), wherein the contents of the (A) water-dispersible latex, the (B) photopolymerizable unsaturated group-containing compound, the (C) hydrophilic polymer, and the (D) photopolymerization initiator in the photosensitive resin composition for a flexographic printing plate precursor are 10 to 80% by mass, 8 to 55% by mass, 5 to 45% by mass, and 0.1 to 10% by mass, respectively.(7) The photosensitive resin composition for a flexographic printing plate precursor according to (1), wherein the content of the conjugated diene polymer having at least one hydroxyl group in a side chain and / or at a terminal and at least one photopolymerizable unsaturated group in a side chain and / or at a terminal in the hydrophilic polymer (C) is 90% by mass or more. (8) A flexographic printing plate precursor, comprising a support and a photosensitive resin layer prepared using the photosensitive resin composition for a flexographic printing plate precursor according to any one of (1) to (7).

[0008] According to the present invention, it is possible to provide a photosensitive resin composition for a flexographic printing plate precursor, which has higher water-developability and better mechanical strength than conventionally known photosensitive resin compositions. Therefore, a flexographic printing plate obtained using the composition has excellent printing durability and can be suitably used for high-quality mass printing.

[0009] Preferred embodiments of the present invention will be described in detail below. The following description of the components is based on representative embodiments and specific examples, and the present invention is not limited to such embodiments and specific examples.

[0010] In this specification, the expressions "contain" and "comprise" include the concepts of "contain," "include," "consist essentially of," and "consist only of."

[0011] In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in an example or a value that can be unambiguously derived from an example. Furthermore, in this specification, a numerical value connected with "to" means a numerical range that includes the numbers before and after "to" as the upper and lower limits.

[0012] <Photosensitive Resin Composition> The photosensitive resin composition for a flexographic printing plate precursor of the present invention is used to form a photosensitive resin layer in a flexographic printing plate precursor, which serves as a precursor material for obtaining a relief plate for flexographic printing.

[0013] The photosensitive resin composition for a flexographic printing original plate of the present invention contains (A) a water-dispersible latex, (B) a photopolymerizable unsaturated group-containing compound, (C) a hydrophilic polymer, and (D) a photopolymerization initiator, and is characterized in that the (C) hydrophilic polymer contains (c) a conjugated diene-based polymer having at least one hydroxyl group in a side chain or at a terminal and at least one photopolymerizable unsaturated group in a side chain or at a terminal.

[0014] <(A) Water-dispersible latex> As the (A) water-dispersible latex, a conventionally known synthetic polymer compound used in a flexographic printing plate precursor can be used.

[0015] Specifically, the water-dispersible latex (A) may be a polymer obtained by polymerizing a conjugated diene hydrocarbon or a copolymer latex obtained by copolymerizing a conjugated diene hydrocarbon with a monoolefin-based unsaturated compound, such as butadiene latex, isoprene latex, chloroprene latex, styrene-butadiene latex, styrene-butadiene-styrene latex, styrene-isoprene latex, styrene-isoprene-styrene latex, styrene-chloroprene latex, acrylonitrile-butadiene latex, acrylonitrile-isoprene latex, methyl methacrylate-butadiene latex, methyl methacrylate-isoprene latex, methyl methacrylate-butadiene-styrene latex, acrylonitrile-butadiene-styrene latex, and acrylonitrile-isoprene-styrene latex. These latexes may be copolymerized with a hydrophilic group such as a carboxyl group, a sulfonic acid group, or a polyalkylene glycol, or may have a hydrophilic functional group obtained by emulsion polymerization. (A) The water-dispersible latexes may be used alone or in combination of two or more. From the viewpoints of the properties of the flexographic printing plate, i.e., mechanical strength, impact resilience of the plate surface, strength-elongation properties, and printing plate hardness, and the properties of the flexographic printing plate precursor, i.e., dimensional stability in the unexposed state and water-developability, it is preferable to contain one or more water-dispersible latexes selected from the group consisting of butadiene latex, acrylonitrile-butadiene latex, styrene-butadiene latex, methyl methacrylate-butadiene latex, and isoprene latex, and from the viewpoint of water-developability, it is more preferable to contain both butadiene latex and acrylonitrile-butadiene latex.

[0016] The water-dispersible latex (A) is preferably a conjugated diene polymer obtained from a water-dispersed latex. The conjugated diene polymer obtained from a water-dispersed latex is preferably an intramolecularly crosslinked polymer obtained by removing water from the water-dispersed latex. Since many different synthetic latexes are commercially available as conjugated diene polymers obtained from a water-dispersed latex, a desired one may be appropriately obtained from among them. The water-dispersible latex (A) may be used as is, or may be used as a solid resin after drying to remove water. If desired, it may be modified with (meth)acrylic, carboxy, silicone, fluorine, or the like. Since many different synthetic and natural latexes are commercially available as the water-dispersible latex (A), an appropriate one may be selected from among them.

[0017] The content of the water-dispersible latex (A) in the photosensitive resin composition of the present invention is preferably 10 to 80% by mass, more preferably 20 to 75% by mass, and even more preferably 30 to 70% by mass, relative to 100% by mass of the photosensitive resin composition. When the content of the water-dispersible latex (A) is within the range of 10 to 80% by mass, the balance between mechanical strength and water developability tends to be good.

[0018] <(B) Photopolymerizable Unsaturated Group-Containing Compound> The (B) photopolymerizable unsaturated group-containing compound usually has one or more photopolymerizable unsaturated groups. In the present invention, the photopolymerizable unsaturated group refers to an unsaturated group that can undergo radical polymerization by light.

[0019] The photopolymerizable unsaturated group is not particularly limited as long as it can be radically polymerized by light, but is preferably at least one selected from the group consisting of a (meth)acryloyl group and a (meth)acryloyloxy group.

[0020] As the (B) photopolymerizable unsaturated group-containing compound, any known compound used in flexographic printing original plates can be used, but it is preferable to use a photopolymerizable unsaturated group-containing compound having a number average molecular weight of 100 or more and 600 or less.

[0021] Examples of photopolymerizable unsaturated group-containing compounds having a number average molecular weight of 100 or more and 600 or less include linear, branched, and cyclic monofunctional monomers such as hexyl (meth)acrylate, nonane (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, 2-ethyl-2-butylpropanediol (meth)acrylate, hydroxyethyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxyethyl phthalate, (meth)acrylic acid dimer, ECH-modified allyl acrylate, benzyl acrylate, caprolactone (meth)acrylate, dicyclopentenyl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, and cyclohexyl (meth)acrylate. In addition, hexanediol di(meth)acrylate, nonanediol di(meth)acrylate, dodecanediol di(meth)acrylate, 2-butyl-2-ethylpropane di(meth)acrylate, neopentyl glycol di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, ECH-modified phthalic acid di(meth)acrylate, dicyclopentadiene di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate Also included are linear, branched, and cyclic polyfunctional compounds such as 5-hydroxy-1,3-adamantyl di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, ECH-modified glycerol tri(meth)acrylate, trimethylolpropane benzoate (meth)acrylate, EO(PO)-modified trimethylolpropane tri(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. The photopolymerizable unsaturated group-containing compounds having a number average molecular weight of 100 to 600 can be used alone or in combination of two or more. Only one type may be used alone, or two or more types may be used in combination to achieve a good balance between mechanical strength and water developability.

[0022] From the viewpoint of exhibiting better mechanical strength and water-developability, the photopolymerizable unsaturated group-containing compound having a number average molecular weight of 100 to 600 preferably has one, two, three, or four photopolymerizable unsaturated groups, more preferably has one, two, or three photopolymerizable unsaturated groups, even more preferably has two or three photopolymerizable unsaturated groups, and even more preferably has three photopolymerizable unsaturated groups.

[0023] The (B) photopolymerizable unsaturated group-containing compound preferably includes a photopolymerizable unsaturated group-containing compound having a number-average molecular weight of more than 600 and not more than 20,000, in addition to a photopolymerizable unsaturated group-containing compound having a number-average molecular weight of 100 to 600. Here, the photopolymerizable unsaturated group-containing compound having a number-average molecular weight of 100 to 600 forms a dense crosslinked network upon crosslinking and curing with a photopolymerization initiator, while the photopolymerizable unsaturated group-containing compound having a number-average molecular weight of more than 600 and not more than 20,000 forms a loose crosslinked network upon crosslinking and curing with a photopolymerization initiator. By combining these, the mechanical strength of the flexographic printing plate can be further improved.

[0024] Examples of photopolymerizable unsaturated group-containing compounds having a number average molecular weight of more than 600 and not more than 20,000 include polymers in which photopolymerizable unsaturated groups are bonded to the terminals and / or side chains of conjugated diene polymers, and urethane (meth)acrylates. Examples of conjugated diene polymers include butadiene polymers, isoprene polymers, chloroprene polymers, styrene-chloroprene copolymers, acrylonitrile-butadiene copolymers, acrylonitrile-isoprene copolymers, methyl methacrylate-isoprene copolymers, acrylonitrile-isoprene copolymers, methyl methacrylate-isoprene copolymers, methyl methacrylate-chloroprene copolymers, methyl acrylate-butadiene copolymers, methyl acrylate-isoprene copolymers, methyl acrylate-chloroprene copolymers, methyl acrylate-chloroprene copolymers, acrylonitrile-butadiene-styrene copolymers, and acrylonitrile-chloroprene-styrene copolymers. Among these, butadiene polymers, isoprene polymers, and acrylonitrile-butadiene copolymers are preferred in terms of rubber elasticity and photocurability, and butadiene polymers and isoprene polymers are particularly preferred. These compounds may be used alone or in combination of two or more to improve the physical properties of the desired printing plate.

[0025] The photopolymerizable unsaturated group-containing compound having a number-average molecular weight of more than 600 and not more than 20,000 preferably has a number-average molecular weight of 1,000 or more and 15,000 or less, more preferably 1,500 or more and 10,000 or less, and even more preferably 2,000 or more and 7,000 or less, from the viewpoint of exhibiting better mechanical strength and water-developability.

[0026] From the viewpoint of exhibiting better mechanical strength and water-developability, the photopolymerizable unsaturated group-containing compound having a number average molecular weight of more than 600 and not more than 20,000 preferably has one, two, three, or four photopolymerizable unsaturated groups, more preferably has one, two, or three photopolymerizable unsaturated groups, more preferably has two or three photopolymerizable unsaturated groups, and even more preferably has two photopolymerizable unsaturated groups. Also, it is preferable that the photopolymerizable unsaturated group is at a terminal, and more preferably has photopolymerizable unsaturated groups at both terminals.

[0027] The content of the photopolymerizable unsaturated group-containing compound (B) in the photosensitive resin composition of the present invention is preferably 8 to 55% by mass, more preferably 15 to 48% by mass, and even more preferably 20 to 46% by mass, relative to 100% by mass of the photosensitive resin composition. A content within the above range is preferred in that a better balance between mechanical strength and water developability is achieved, and good printing durability of the printing plate can be obtained.

[0028] The content of the photopolymerizable unsaturated group-containing compound having a number average molecular weight of 100 to 600 in the photosensitive resin composition of the present invention is preferably 3 to 25 mass%, more preferably 5 to 20 mass%, and still more preferably 7 to 13 mass%, relative to 100 mass% of the photosensitive resin composition, from the viewpoint of obtaining better mechanical strength and higher water-developability.

[0029] The content of the photopolymerizable unsaturated compound having a number average molecular weight of more than 600 and not more than 20,000 in the photosensitive resin composition of the present invention is preferably 5 to 30% by mass, more preferably 10 to 25% by mass, and still more preferably 14 to 23% by mass, relative to 100% by mass of the photosensitive resin composition, from the viewpoint of obtaining better mechanical strength and higher water-developability.

[0030] In the photosensitive resin composition of the present invention, the ratio of the content of the photopolymerizable unsaturated group-containing compound having a number-average molecular weight of 100 or more and 600 or less to the content of the photopolymerizable unsaturated group-containing compound having a number-average molecular weight of more than 600 and 20,000 or less is, in terms of obtaining better mechanical strength and higher water-developability, preferably 2.0 or less, more preferably 1.2 or less, and even more preferably 1.0 or less. The lower limit of this ratio is not particularly limited, but is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.5 or more.

[0031] The number average molecular weight of the (B) photopolymerizable unsaturated group-containing compound can be measured by gel permeation chromatography (GPC). Measurement of the number average molecular weight by gel permeation chromatography (GPC) can be performed, for example, under the following conditions: GPC apparatus: HLC-8320GPC (manufactured by Tosoh Corporation) Columns: TSKGelSuperHM-H x 2, TSKGelSuperH2000 (manufactured by Tosoh Corporation) Mobile phase: chloroform Flow rate: 0.6 ml / min Concentration: 0.1% Column temperature: 40°C Detector: RI, UV 254 nm Conversion: polystyrene

[0032] <(C) Hydrophilic Polymer> The (C) hydrophilic polymer includes (c) a conjugated diene polymer having at least one hydroxyl group in a side chain and / or at a terminal and at least one photopolymerizable unsaturated group in a side chain and / or at a terminal. The photopolymerizable unsaturated group refers to an unsaturated group capable of radical polymerization by light. By including (c) a conjugated diene polymer having at least one hydroxyl group in a side chain and / or at a terminal and at least one photopolymerizable unsaturated group in a side chain and / or at a terminal as the (C) hydrophilic polymer, it is presumed that better water-developability can be exhibited, peeling off of the photosensitive resin layer due to development can be prevented, and mechanical strength can be improved.

[0033] The (C) hydrophilic polymer has a conjugated diene polymer structure, which allows for good flexographic printing plate properties, such as the mechanical strength, impact resilience, strength-elongation properties, resin plate hardness, and durability against water-based inks during printing, as well as good flexographic printing plate properties, such as good dimensional stability when unexposed. Additionally, the (C) hydrophilic polymer has at least one hydroxyl group in its side chain and / or terminal, which increases its hydrophilicity and allows it to strongly attract water molecules during water development, resulting in good water developability. Furthermore, the (C) hydrophilic polymer has at least one photopolymerizable unsaturated group in its side chain and / or terminal, which allows it to be crosslinked and cured by a photopolymerization initiator to form a crosslinked network, resulting in improved mechanical strength and a printing plate with long printing life.

[0034] (c) Examples of methods for producing a conjugated diene polymer having at least one hydroxyl group in a side chain and / or at a terminal and at least one photopolymerizable unsaturated group in a side chain and / or at a terminal include a method in which the terminal of a polymer obtained by polymerizing a conjugated diene hydrocarbon or a copolymer obtained by copolymerizing a conjugated diene hydrocarbon and a monoolefin unsaturated compound is modified with an unsaturated compound having a carboxy group, and the carboxy group is further modified with an epoxy compound having a photopolymerizable unsaturated group; a method in which a copolymer obtained by copolymerizing a conjugated diene hydrocarbon and an unsaturated compound having a carboxy group is modified with an epoxy compound having a photopolymerizable unsaturated group; and a method in which a copolymer obtained by copolymerizing a conjugated diene hydrocarbon with a monoolefin unsaturated compound and an unsaturated compound having a carboxy group is modified with an epoxy compound having a photopolymerizable unsaturated group.

[0035] (c) A preferred method for producing a conjugated diene polymer having at least one hydroxyl group in a side chain and / or at a terminal and at least one photopolymerizable unsaturated group in a side chain and / or at a terminal is to modify the terminal of a polymer obtained by polymerizing a conjugated diene hydrocarbon or a copolymer obtained by copolymerizing a conjugated diene hydrocarbon and a monoolefin unsaturated compound with an unsaturated compound having a carboxy group, and then further modify the carboxy group with an epoxy compound having a photopolymerizable unsaturated group.

[0036] Specific examples of the polymer obtained by polymerizing the above-mentioned conjugated diene hydrocarbon or the copolymer obtained by copolymerizing the conjugated diene hydrocarbon with a monoolefin-based unsaturated compound include butadiene polymer, isoprene polymer, chloroprene polymer, styrene-butadiene copolymer, styrene-butadiene-styrene copolymer, styrene-isoprene copolymer, styrene-isoprene-styrene copolymer, styrene-chloroprene copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-isoprene copolymer, acrylonitrile-butadiene-styrene copolymer, and acrylonitrile-isoprene-styrene copolymer.

[0037] Examples of the unsaturated compound having a carboxy group include acrylic acid, methacrylic acid, crotonic acid, ω-carboxy-polycaprolactone (n≈2) monoacrylate, monocarboxylic acids such as 2-(meth)acryloyloxyethyl phthalate, and 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate.

[0038] Examples of the epoxy compound having a photopolymerizable unsaturated group include glycidyl (meth)acrylate, allyl glycidyl ether, 3,4-epoxycyclohexyl (meth)acrylate, 2-glycidyloxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, and 3,4-epoxycyclohexylmethyl (meth)acrylate.

[0039] (c) The photopolymerizable unsaturated group in the conjugated diene polymer having at least one hydroxyl group in a side chain and / or at a terminal and at least one photopolymerizable unsaturated group in a side chain and / or at a terminal is preferably at least one selected from the group consisting of a (meth)acryloyl group and a (meth)acryloyloxy group, from the viewpoint of further improving mechanical strength.

[0040] (c) In order to obtain a better balance between mechanical strength and water-developability, the conjugated diene polymer having at least one hydroxyl group at a side chain and / or terminal and at least one photopolymerizable unsaturated group at a side chain and / or terminal preferably has one, two, three, or four photopolymerizable unsaturated groups, more preferably one, two, or three photopolymerizable unsaturated groups, even more preferably one or two photopolymerizable unsaturated groups, and even more preferably two photopolymerizable unsaturated groups. The photopolymerizable unsaturated groups are more preferably present at the terminals of the conjugated diene polymer, and even more preferably present at both terminals of the conjugated diene polymer.

[0041] (c) The hydroxyl group in the conjugated diene polymer having at least one hydroxyl group at a side chain and / or a terminal and at least one photopolymerizable unsaturated group at a side chain and / or a terminal is preferably located on the side chain, from the viewpoint of achieving a better balance between mechanical strength and water developability.

[0042] From the viewpoint of achieving a better balance between mechanical strength and water-developability, the conjugated diene polymer preferably has one, two, three, or four hydroxyl groups, more preferably has one, two, or three hydroxyl groups, even more preferably has one or two hydroxyl groups, and even more preferably has two hydroxyl groups.

[0043] (c) The conjugated diene-based polymer having at least one hydroxyl group at a side chain and / or a terminal and at least one photopolymerizable unsaturated group at a side chain and / or a terminal preferably has an epoxy ester structure at a terminal, more preferably has an epoxy ester structure at both terminals, from the viewpoint of obtaining high water-developability and good mechanical strength.

[0044] (c) As a conjugated diene polymer having at least one hydroxyl group at a side chain and / or terminal and at least one photopolymerizable unsaturated group at a side chain and / or terminal, from the viewpoint of improving hydrophilicity and obtaining good water-developability, the conjugated diene polymer preferably contains an acrylonitrile skeleton. (c) The content of bound acrylonitrile in a conjugated diene polymer having at least one hydroxyl group at a side chain and / or terminal and at least one photopolymerizable unsaturated group at a side chain and / or terminal is preferably 10 mol% or more, more preferably 15 mol% or more, from the viewpoint of hydrophilicity due to polarity. The content of bound acrylonitrile is preferably 40 mol% or less. If the content of bound acrylonitrile exceeds 40 mol%, the water resistance of the relief on the printing plate may be deteriorated. Furthermore, from the viewpoints of the mechanical strength of the flexographic printing plate, the impact resilience of the printing plate surface, the strength-elongation properties, the resin plate hardness, etc., it is preferable that (c) the conjugated diene polymer having at least one hydroxyl group at the side chain and / or terminal and at least one photopolymerizable unsaturated group at the side chain and / or terminal has a butadiene skeleton. From the viewpoint of exhibiting higher mechanical strength, it is more preferable that (c) the conjugated diene polymer having at least one hydroxyl group at the side chain and / or terminal and at least one photopolymerizable unsaturated group at the side chain and / or terminal has an acrylonitrile skeleton and a butadiene skeleton.

[0045] (c) As the conjugated diene polymer having at least one hydroxyl group in a side chain and / or at a terminal and at least one photopolymerizable unsaturated group in a side chain and / or at a terminal, a structure having epoxy ester groups at both terminals of a copolymer having an acrylonitrile skeleton and a butadiene skeleton is preferred.

[0046] (c) The number average molecular weight of the conjugated diene polymer having at least one hydroxyl group in a side chain and / or at a terminal and at least one photopolymerizable unsaturated group in a side chain and / or at a terminal is preferably 1,000 to 30,000, more preferably 1,500 to 20,000, and particularly preferably 2,000 to 6,000.

[0047] (c) The conjugated diene polymer having at least one hydroxyl group in a side chain and / or at a terminal and at least one photopolymerizable unsaturated group in a side chain and / or at a terminal may be used alone or in combination of two or more, and may be modified as necessary.

[0048] The hydrophilic polymer (C) preferably contains 90% by mass or more of (c) a conjugated diene polymer having at least one hydroxyl group in a side chain and / or terminal and at least one photopolymerizable unsaturated group in a side chain and / or terminal. The hydrophilic polymer (C) may contain other hydrophilic polymers in addition to the conjugated diene polymer (c) having at least one hydroxyl group in a side chain and / or terminal and at least one photopolymerizable unsaturated group in a side chain and / or terminal, as long as the effects of the present invention are not impaired. The content of the hydrophilic polymer other than the conjugated diene polymer (c) having at least one hydroxyl group in a side chain and / or terminal and at least one photopolymerizable unsaturated group in a side chain and / or terminal in the hydrophilic polymer (C) is preferably less than 10% by mass, more preferably 5% by mass or less, even more preferably 3% by mass or less, and even more preferably 1% by mass or less.

[0049] In the hydrophilic polymer (C), (c) the hydrophilic polymer other than the conjugated diene polymer having at least one hydroxyl group in the side chain and / or at the end and at least one photopolymerizable unsaturated group in the side chain and / or at the end includes -COOH, -COOM (M is a monovalent, divalent or trivalent metal ion or a substituted or unsubstituted ammonium ion), -OH, -NH ２ , -SO ３Preferred are those having a hydrophilic group such as a phosphate group, and specific examples include polymers of (meth)acrylic acid or salts thereof, copolymers of (meth)acrylic acid or salts thereof and alkyl (meth)acrylate, copolymers of (meth)acrylic acid or salts thereof and styrene, copolymers of (meth)acrylic acid or salts thereof and vinyl acetate, copolymers of (meth)acrylic acid or salts thereof and acrylonitrile, polyvinyl alcohol, carboxymethyl cellulose, polyacrylamide, hydroxyethyl cellulose, polyethylene oxide, polyethyleneimine, polyurethanes having a -COOM group, polyureaurethanes having a -COOM group, polyamic acids having a -COOM group, and salts or derivatives thereof. These may be used alone or in combination of two or more.

[0050] The content of the hydrophilic polymer (C) relative to 100 parts by mass of the water-dispersible latex (A) in the photosensitive resin composition of the present invention is preferably 5 to 45 parts by mass, more preferably 10 to 30 parts by mass, and even more preferably 11 to 20 parts by mass. When the content of the hydrophilic polymer (C) relative to 100 parts by mass of the water-dispersible latex (A) in the photosensitive resin composition is 5 to 45 parts by mass, the relief can exhibit higher water developability and better mechanical strength while maintaining its water resistance.

[0051] The content of (c) the conjugated diene polymer having at least one hydroxyl group in a side chain and / or terminal and at least one photopolymerizable unsaturated group in a side chain and / or terminal relative to 100 parts by mass of (A) the water-dispersible latex in the photosensitive resin composition of the present invention is preferably 5 to 45 parts by mass, more preferably 10 to 30 parts by mass, and even more preferably 11 to 20 parts by mass. When the content of (c) the conjugated diene polymer having at least one hydroxyl group in a side chain and / or terminal and at least one photopolymerizable unsaturated group in a side chain and / or terminal relative to 100 parts by mass of (A) the water-dispersible latex is within the range of 5 to 45 parts by mass, the relief can exhibit higher water developability and better mechanical strength while maintaining its water resistance.

[0052] The content ratio of the photopolymerizable unsaturated group-containing compound (B) to the hydrophilic polymer (C) in the photosensitive resin composition of the present invention is preferably 95:5 to 40:60 by mass, more preferably 95:5 to 50:50 by mass, and even more preferably 90:10 to 70:30 by mass. When the content ratio of the hydrophilic polymer (C) is within the range of 95:5 to 40:60 by mass, the water resistance of the relief can be maintained while achieving higher water developability and better mechanical strength.

[0053] The content ratio of the (B) photopolymerizable unsaturated group-containing compound to the (c) conjugated diene polymer having at least one hydroxyl group in a side chain and / or terminal and at least one photopolymerizable unsaturated group in a side chain and / or terminal in the photosensitive resin composition of the present invention is preferably (component (B)):(component (c))=95:5 to 40:60 by mass, more preferably 95:5 to 50:50, and even more preferably 90:10 to 70:30. When the content ratio of the (B) photopolymerizable unsaturated group-containing compound to the (c) conjugated diene polymer having at least one hydroxyl group in a side chain and / or terminal and at least one photopolymerizable unsaturated group in a side chain and / or terminal is within the above range, the relief can exhibit higher water developability and better mechanical strength while maintaining its water resistance.

[0054] <(D) Photopolymerization Initiator> The (D) photopolymerization initiator is not particularly limited as long as it can polymerize a polymerizable carbon-carbon unsaturated group by light. Among these, those that have the function of generating radicals by self-decomposition or hydrogen abstraction upon light absorption are preferably used. Examples of such photopolymerization initiators include benzoin alkyl ethers, benzophenones, anthraquinones, benzils, acetophenones, and diacetyls. The content of the (D) photopolymerization initiator in the photosensitive resin composition of the present invention is preferably 0.1 to 10% by mass, more preferably 0.5 to 8% by mass, and even more preferably 0.7 to 5% by mass, based on 100% by mass of the photosensitive resin composition. When the content of the (D) photopolymerization initiator is within the range of 0.1 to 10% by mass, good polymerization initiation efficiency, good mechanical strength, and good image reproducibility tend to be obtained.

[0055] <Other Components> In addition to the above-described components (A) to (D), the photosensitive resin composition of the present invention may contain other components, such as a plasticizer, an ultraviolet absorber, a thermal polymerization inhibitor (stabilizer), a surface tension modifier, an anti-aggregation agent, a thermoplastic resin elastomer, a solid rubber, a dye, a pigment, or an anti-foaming agent, as appropriate, for the purpose of improving various properties, within a range that does not impair the effects of the present invention.

[0056] The plasticizer imparts flexibility to the photosensitive resin layer, and examples thereof include liquid rubber, oil, polyester, and phosphoric acid compounds. Examples of liquid rubber include liquid compounds having a conjugated diene structure. Examples of oil include paraffin, naphthene, and aroma. Examples of polyester include adipic acid polyester. Examples of phosphoric acid compounds include phosphoric acid esters. Among these, liquid polybutadiene is preferred from the viewpoint of compatibility with polymers obtained by polymerizing conjugated dienes. The content of the plasticizer in the photosensitive resin composition of the present invention is preferably up to 40% by mass.

[0057] The ultraviolet absorber broadens the allowable exposure time range of the photosensitive resin layer. Examples of ultraviolet absorbers include benzophenone-based, salicylate-based, benzotriazole-based, acrylonitrile-based, metal complex salt-based, hindered amine-based, anthraquinone-based, azo-based, coumarin-based, and furan-based compounds. Among these, benzotriazole-based compounds are preferred from the viewpoint of exposure latitude. The content of the ultraviolet absorber in the photosensitive resin composition of the present invention is preferably up to 0.1% by mass.Specific examples of the benzotriazole-based ultraviolet absorber include 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol] ], 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, 2-tert-butyl-6-(5-chloro-2H-benzotriazol-2-yl)-4-methylphenol, 2-(5-chloro-2-benzotriazolyl)-6-tert-butyl-p-cresol, 2-(2'-hydroxy-5'-tert-butylphenyl)-2H-benzotriazole, 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2-(2H-benzotriazo 2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol], 2-(3,5-di-tert-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2-(2H-benzotriazol-2-yl)-p-cresol, 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2- Benzotriazol-2-yl-4,6-di-tert-butylphenol, 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-(tert-butyl)phenol, 2-(2H-benzotriazol-2-yl)-4,6-di-tert-butylphenol, 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, 2-(2H-benzotriazol-2-yl)-4-methyl-6-(3,4,5,6-tetrahydrophthalimidylmethyl)phenol, and the like.

[0058] The thermal polymerization inhibitor (stabilizer) enhances the thermal stability and storage stability of the photosensitive resin composition during production, and examples thereof include phenols, hydroquinones, and catechols. Examples include quinones such as hydroquinone, benzoquinone, and naphthoquinone, alkyl- and aryl-substituted hydroquinones, p-methoxyphenol, p-butylpyrocatechol, pyrogallol, β-naphthol, 2,6-di-t-butyl-4-methylphenol, t-butylcresols such as 2,6-di-t-butyl-p-cresol, phenothiazine, pyridine, nitrobenzene, nitro compounds such as dinitrobenzene and nitrosonaphthol, and hydroxylamine derivatives. Specific examples of hydroxylamine derivatives include cupferron derivatives such as N-nitrosophenylhydroxylamine aluminum salt and N-nitrosophenylhydroxylamine ammonium salt, cupferron analogues such as N-benzoylphenylhydroxylamine, benzohydroxamic acid, and 3-hydroxyl-1,3-diphenyltriazine, as well as N,N-diethylhydroxylamine and N-(t-butyl)hydroxylamine hydrochloride. The content of the thermal polymerization inhibitor (stabilizer) in the photosensitive resin composition of the present invention is preferably up to 5% by mass.

[0059] A surface tension modifier adjusts the surface tension of a printing plate, and by adjusting the surface tension of the printing plate, it is possible to adjust ink transferability and ink clogging on the printing plate. Examples of surface tension modifiers include paraffin oil, long-chain alkyl compounds, surfactants, fatty acid amides, silicone oil, modified silicone oil, fluorine compounds, and modified fluorine compounds. Among these, modified silicone oils having an amino group or an aromatic ring are preferred. The surface tension modifier may contain a photopolymerizable group in the molecule.

[0060] <Flexographic Printing Plate> The flexographic printing plate precursor of the present invention has a structure in which a photosensitive resin layer prepared using the photosensitive resin composition of the present invention described above is provided on a support. The photosensitive resin layer can be formed from the photosensitive resin composition of the present invention by any known method, including melt molding, hot pressing, casting, melt extrusion, and solution casting. The flexographic printing plate precursor can be produced by laminating the formed photosensitive resin layer on a support. Conventional supports such as steel, aluminum, glass, and plastic films such as polyester films can be used, and films with a thickness ranging from 50 to 500 μm are generally used. If necessary, a known adhesive layer may be provided to improve adhesion between the support and the photosensitive resin layer. A cover film provided with an infrared ablation layer or a cover film provided with a slip coat layer or release layer may be further laminated on the surface of the photosensitive resin layer opposite the support. The cover film is generally a plastic film such as a polyester film having a thickness of 50 to 200 μm. An oxygen barrier layer can be provided between the infrared ablation layer and the photosensitive resin layer.

[0061] The oxygen barrier layer can be combined with a known oxygen barrier layer. Examples of binder polymers in the oxygen barrier layer include polyvinyl alcohol, partially saponified vinyl acetate, alkyl cellulose, cellulose-based polymers, and polyamides. These binder polymers are not limited to a single type, and two or more types can be used in combination. Preferred binder polymers in terms of oxygen barrier properties are polyvinyl alcohol, partially saponified vinyl acetate, and polyamides. Examples of partially saponified vinyl acetate include those with a saponification rate of 60 to 98 mol%. Examples of polyamides include polyamide resins containing a basic nitrogen atom in the molecule and polyamide resins containing an alkylene glycol structural unit in the molecule. An oxygen barrier layer containing a polyamide resin containing a basic nitrogen atom in the molecule and a polyamide resin containing an alkylene glycol structural unit in the molecule is preferred. For example, the one described in Japanese Patent No. 7243076 can be used.

[0062] To produce a flexographic printing plate from a flexographic printing plate precursor, backside exposure is performed from the support side, followed by peeling off the top cover film to leave an infrared ablation layer on the photosensitive resin layer. An image is then formed on the infrared ablation layer using an imaging device, and the entire surface is then irradiated with actinic rays from above. Alternatively, the top cover film of a flexographic printing plate precursor that does not have an infrared ablation layer is peeled off, a negative film is placed on the photosensitive resin layer, and the entire surface is then irradiated with actinic rays from above through the negative film. This method allows only the exposed areas to harden and become insolubilized. Actinic rays can be emitted from sources such as high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, chemical lamps, and LEDs, typically with wavelengths centered around 300 to 450 nm. The unexposed areas are then removed with an appropriate solvent or water containing a surfactant, post-exposed, and further exposed to a germicidal lamp to obtain a flexographic printing plate with a clear image area. As the developing device, it is preferable to use a spray type developing device, a brush type developing device, or the like.

[0063] The infrared ablation layer used in the flexographic printing plate precursor can be combined with a known infrared ablation layer. The infrared ablation layer is preferably water-developable. Specific examples of the infrared ablation layer include an infrared ablation layer combining a polar group-containing polyamide and a butyral resin (e.g., the layer described in Japanese Patent No. 4200510 can be used), an infrared ablation 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 (e.g., the layer described in Japanese Patent No. 6414375 can be used), an infrared ablation layer containing a polymer having the same structure as the polymer in the photosensitive resin layer and an acrylic resin (e.g., the layer described in Japanese Patent No. 5710961 can be used), an infrared ablation layer containing a polymer having an acidic group with an acid value of 10 to 400 mgKOH / g (e.g., the layer described in Japanese Patent No. 6810251 can be used), and an infrared ablation layer containing an anionic polymer and a polymer having an ester bond in the side chain and a degree of saponification of 0% to 90%.

[0064] The effects of the flexographic printing plate precursor using the photosensitive resin composition of the present invention will be shown by the following examples, but the present invention is not limited thereto. The numerical values ​​showing the composition ratios in the tables mean the parts by mass of the solid components after volatilizing the solvent.

[0065] Example 1 Preparation of Photosensitive Resin Composition (A) Butadiene latex (Nipol LX111NF, non-volatile content 55%, manufactured by Zeon Corporation) as a hydrophobic polymer was placed in a container so that the solid content was 50 parts by mass, followed by (B) 20 parts by mass of oligobutadiene acrylate having acryloyloxy groups at both ends as a photopolymerizable unsaturated group-containing compound (ABU-4, number average molecular weight (Mn): 5400, manufactured by Kyoeisha Chemical Co., Ltd.), 17 parts by mass of trimethylolpropane trimethacrylate (Light Ester TMP, molecular weight: 338, manufactured by Kyoeisha Chemical Co., Ltd.), and (C) both-end methacrylate-modified acrylonitrile-butadiene copolymer 1 (Hypro 1300X33LC) as a hydrophilic polymer. A dope was prepared by mixing 3 parts by mass of (VTBNX, bound acrylonitrile content 18 mol%, number average molecular weight (Mn): 3900, manufactured by HUNTSMAN), 1 part by mass of (D) photopolymerization initiator (Irgacure 651: benzyl dimethyl ketal), 9 parts by mass of butadiene oligomer (LBR-352, manufactured by Kuraray Co., Ltd.) as a plasticizer, and 0.1 parts by mass of 4-methoxyphenol as a heat stabilizer in a container. The dope was charged into a pressure kneader, and tetrahydrofuran and water were removed under reduced pressure at 80°C to obtain a photosensitive resin composition.

[0066] Preparation of Flexographic Printing Plate: A carbon black dispersion (AMBK-8, manufactured by Orient Chemical Industry Co., Ltd.), a copolymer polyamide (PA223, manufactured by Toyobo MC Co., Ltd.), propylene glycol, and methanol were mixed in a mass ratio of 45 / 5 / 5 / 45 to obtain an infrared ablation layer coating solution. After a release treatment was applied to both sides of a polyester film (E5000, manufactured by Toyobo Co., Ltd., thickness 100 μm), the infrared ablation layer coating solution was applied using a bar coater so that the coating thickness after drying was 2 μm. The film was then dried at 120°C for 5 minutes to obtain a film laminate (I). The optical density (OD value) was 2.3. The optical density was measured using a black-and-white transmission densitometer DM-520 (manufactured by Dainippon Screen Mfg. Co., Ltd.). Next, the photosensitive resin composition was placed on the adhesive side of a support prepared by coating a polyester film (Toyobo Co., Ltd., E5000, thickness 100 μm) with a copolymer polyester adhesive to a thickness of 25 μm, and the film laminate (I) was then superimposed on top of the support. Lamination was performed at 100°C using a heat press to obtain a flexographic printing original plate having the polyester support, adhesive layer, photosensitive resin layer, infrared ablation layer, and cover film laminated in this order. The total thickness of the plate was 1.70 mm.

[0067] Preparation of a Printing Plate from a Flexographic Printing Plate: The printing plate was back-exposed from the polyester support side for 10 seconds. The cover film was then peeled off. The plate was wrapped around an Eskographics CDI 4530 and ablated at a resolution of 4000 dpi using a test image with a 175 lpi screen ruling, a minimum of 0.3% and a maximum of 10% halftone dots in 0.3% increments, a minimum of 50 μm and a maximum of 300 μm in 50 μm increments, and a solid area on the infrared ablation layer. After ablation, the plate was removed and returned to its flat surface, and a main exposure was performed for 7 minutes. The plate was then developed for 8 minutes in an A&V developer (Stuck System, 1% laundry soap solution, 40°C), and water droplets on the plate surface were removed with a water-blowing stick. The plate was then dried in a 60°C dryer for 10 minutes. Subsequently, post-exposure was carried out for 7 minutes, and finally, irradiation with a germicidal lamp was carried out for 5 minutes to obtain a flexographic printing plate. Back exposure, main exposure, and post-exposure were carried out using a Philips TL-K 40W / 10R lamp (peak wavelength 370 nm, illuminance at 350 nm 10 mW / cm２ ) and the germicidal lamp was a Panasonic germicidal lamp GL-40 (peak wavelength 250 nm, illuminance at 250 nm is 4.5 mW / cm ２ The resulting printing plate had a relief depth of 0.3 mm, and it was confirmed that halftone dots with a diameter of 16 μm were reproduced on the printing plate.

[0068] (Examples 2 to 8), (Comparative Examples 1 to 3) Photosensitive resin compositions, flexographic printing original plates, and flexographic printing plates were prepared in the same manner as in Example 1, except that the composition of the photosensitive resin layer (photosensitive resin composition) in the printing original plate was changed as shown in Table 1 below.

[0069] The materials other than those used in Example 1 are as follows. As the (A) water-dispersible latex in Example 8, a styrene-butadiene latex (Nipol LX110, non-volatile content 41%, manufactured by Nippon Zeon Co., Ltd.) was used. As the (C) hydrophilic polymer in Example 2, an acrylonitrile-butadiene copolymer 2 containing methacrylate-modified epoxy ester groups at both ends (Hypro 1300X43LC VTBNX, bound acrylonitrile amount 21.5 mol%, number average molecular weight (Mn): 3700, manufactured by HUNTSMAN) was used. As the (C) hydrophilic polymer in Comparative Example 1, a butadiene oligomer modified with hydroxyl groups at both ends (G-1000, number average molecular weight: 1400, manufactured by Nippon Soda Co., Ltd.) was used. As the hydrophilic polymer (C) of Comparative Example 2, an acrylonitrile-butadiene copolymer modified with carboxyl groups at both ends (Hypro 1300X13 CTBN, bound acrylonitrile content 26 mol%, number average molecular weight (Mn): 3150, manufactured by HUNTSMAN) was used.

[0070] The flexographic printing plates obtained in Examples 1 to 8 and Comparative Examples 1 to 3 were evaluated for water developability and mechanical strength by the following methods.

[0071] (1) Water-developability The relief surface and the convex surface of the prepared flexographic printing plate were set at 0 mm, and the depth of the unexposed area scraped off by developing with water was measured to determine the relief depth. This was used as an index of water-developability. A deeper relief depth means better water-developability; if the relief depth is 0.20 mm or more, the water-developability is good, and if it is 0.40 mm or more, it is even better.

[0072] (2) Mechanical Strength of Photosensitive Resin Composition After photocuring a photosensitive resin composition heat-pressed to a thickness of 1 mm, a test piece was extracted using an ASTM-D 1822-S type mold, and the test piece was pulled at a test speed of 200 mm / min using a Tensilon tensile tester (crosshead 100 kg used) to measure elongation and strength. The obtained elongation and strength were multiplied to obtain a value (kg% / mm ２ The multiplication of the elongation and strength was evaluated as a ⊚ when the value obtained by multiplying the elongation and strength was 200 or more, ◯ when it was 100 or more but less than 200, and × when it was less than 100.

[0073] Details of the photosensitive resin compositions of Examples 1 to 8 and Comparative Examples 1 to 3 and the evaluation results are shown in Table 1.

[0074]

[0075] As can be seen from Table 1, all of Examples 1 to 8, which satisfy the requirements of the present invention, have deep relief depths, excellent water-developability, and high mechanical strength. Compared to Example 7, Comparative Examples 1 and 2 have good water-developability but significantly poorer mechanical strength because the (C) hydrophilic polymer does not have a photopolymerizable unsaturated group. Comparative Example 3, which does not contain a (C) hydrophilic polymer, exhibits excellent mechanical strength, but has shallow relief depths and poor water-developability.

[0076] The flexographic printing original plate obtained using the photosensitive resin composition of the present invention maintains high water-developability, and the printing plate obtained using the same has good mechanical strength, resulting in excellent printing durability and enabling high-quality mass printing. Therefore, the present invention is extremely useful in the art.

Claims

1. A photosensitive resin composition for a flexographic printing plate precursor, comprising (A) a water-dispersible latex, (B) a photopolymerizable unsaturated group-containing compound, (C) a hydrophilic polymer, and (D) a photopolymerization initiator, wherein the hydrophilic polymer (C) comprises (c) a conjugated diene-based polymer having at least one hydroxyl group in a side chain and / or at a terminal and at least one photopolymerizable unsaturated group in a side chain and / or at a terminal.

2. A photosensitive resin composition for flexographic printing plates according to claim 1, characterized in that the (c) conjugated diene polymer having at least one hydroxyl group in a side chain and / or at an end and at least one photopolymerizable unsaturated group in a side chain and / or at an end contains an acrylonitrile skeleton.

3. The photosensitive resin composition for flexographic printing original plates according to claim 1, characterized in that the content of the hydrophilic polymer (C) is 5 to 45 parts by mass per 100 parts by mass of the water-dispersible latex (A).

4. The photosensitive resin composition for flexographic printing original plates according to claim 1, characterized in that the mass ratio of the (B) photopolymerizable unsaturated group-containing compound to the (C) hydrophilic polymer is 95:5 to 40:

60.

5. A photosensitive resin composition for flexographic printing original plates as described in claim 1, characterized in that the (B) photopolymerizable unsaturated group-containing compound contains a photopolymerizable unsaturated compound having a number average molecular weight of 100 or more and 600 or less, and a photopolymerizable unsaturated compound having a number average molecular weight of more than 600 and 20,000 or less.

6. The photosensitive resin composition for flexographic printing plate precursors according to claim 1, wherein the contents of the (A) water-dispersible latex, the (B) photopolymerizable unsaturated group-containing compound, the (C) hydrophilic polymer, and the (D) photopolymerization initiator in the photosensitive resin composition for flexographic printing plate precursors are 10 to 80% by mass, 8 to 55% by mass, 5 to 45% by mass, and 0.1 to 10% by mass, respectively.

7. A photosensitive resin composition for flexographic printing plates as described in claim 1, characterized in that the content of (c) a conjugated diene-based polymer having at least one hydroxyl group in a side chain and / or at an end and at least one photopolymerizable unsaturated group in a side chain and / or at an end in (C) the hydrophilic polymer is 90 mass% or more.

8. A flexographic printing plate precursor, comprising a support and a photosensitive resin layer formed on the support, the photosensitive resin layer being prepared using the photosensitive resin composition for a flexographic printing plate precursor according to any one of claims 1 to 7.

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