Photosensitive resin composition for flexographic printing plate, method for producing flexographic printing plate, and printing method

Abstract

To provide a photosensitive resin structure for a flexographic printing plate having an infrared ablation layer which enables formation of micro-cells even in the case where resolution is increased.SOLUTION: A photosensitive resin structure for a flexographic printing plate has (A) a support, (B) a photosensitive resin composition layer, and (C) a water-soluble infrared ablation layer containing carbon black and a resin a, wherein a primary particle diameter of the carbon black is 13-19 nm, and R of Expression (1) by a Hansen solubility parameter value of the resin a and a Hansen solubility parameter value of the carbon black is 13.1 to 17.0. Expression (1): R=(4α2+β2+γ2)0.5. In the Expression (1), α is an absolute value of a difference between δd of the resin a and δd of the carbon black, β is an absolute value of a difference between δp of the resin a and δp of the carbon black, γ is an absolute value of a difference between δh of the resin a and δh of the carbon black, δd is energy by intermolecular dispersion force, δp is energy by intermolecular dipolar interaction, and δh is energy by an intermolecular hydrogen bond.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a photosensitive resin construct for a flexographic printing plate, a method for producing a flexographic printing plate, and a printing method. [Background technology]

[0002] In the manufacturing process of flexographic printing plates, a method of directly drawing a digital image with a laser using CTP (Computer To Plate) technology without using a negative film is widely used. In this CTP technology, the master plate used to manufacture a flexographic printing plate generally comprises a substrate such as a PET (polyethylene terephthalate) resin, on which a photosensitive resin composition layer, an infrared ablation layer that can be ablated by infrared light, and a cover film are laminated in this order.

[0003] An infrared ablation layer that can be ablated by infrared radiation generally contains an infrared absorbing agent, which is a material that is opaque to radiation other than infrared radiation, and a resin. A common development method is to irradiate the photosensitive resin composition layer with active light using the ablation layer as a mask, to cause the photosensitive resin composition to react in the same shape as the transparent portion formed in the ablation layer, and finally to remove the unexposed portions of the ablation layer and photosensitive resin composition layer that are no longer needed by dissolving or swelling them in a developer and applying external force such as a brush.

[0004] In recent years, aqueous developers have become popular as they have a lower environmental impact, and accordingly, ablation layers that can be developed with aqueous developers are being considered. For example, Patent Document 1 proposes a technique of using a water-soluble polyamide resin in the ablation layer, and Patent Document 2 proposes a technique of using an acrylic resin and NBR in combination.

[0005] In addition to the above-mentioned environmental impact issues, there has been a demand in recent years for higher resolution printing, and studies are being conducted to improve the resolution of anilox rolls that supply ink to flexographic printing plates. On the other hand, as the resolution of anilox rolls increases, the size of the cells that transfer ink becomes smaller, which reduces the amount of ink transferred to the flexographic printing plate, causing unevenness within the flexographic printing plate to appear in the print.To address this issue, research is being conducted into a technology that places microcells on the surface of the flexographic printing plate, thereby increasing the amount of ink transferred from the anilox roll to the flexographic printing plate. In this specification, the term "microcell" refers to a minute concave-convex portion provided at the top of a solid portion of a flexographic printing plate. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6358523 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-137515 Summary of the Invention [Problem to be solved by the invention]

[0007] However, even if the above-mentioned technology of arranging microcells on the surface of a flexographic printing plate is used, when the ablation resolution is increased from the conventional 2540 DPI to 4000 to 5080 DPI, it becomes difficult to obtain uniform microcells, and there is a problem that when a high-resolution anilox roll is used, density unevenness occurs in solid areas.

[0008] In view of the above-mentioned problems of the conventional art, the present invention aims to provide a photosensitive resin construct for a flexographic printing plate having an infrared ablation layer that has uniform in-plane ablation properties by an infrared laser and can uniformly form microcells in order to improve density unevenness within a solid area while maintaining water-developability, and a method for manufacturing a flexographic printing plate and a printing method using the same. [Means for solving the problem]

[0009] As a result of extensive research into solving the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by a photosensitive resin construct for a flexographic printing plate, which has a photosensitive resin composition layer and an infrared ablation layer of a specific configuration, and have thus completed the present invention. That is, the present invention is as follows.

[0010] [1] A photosensitive resin construct for a flexographic printing plate, comprising at least (A) a support, (B) a photosensitive resin composition layer, and (C) a water-soluble infrared ablation layer containing carbon black and a resin a, laminated in this order, The carbon black has a primary particle diameter of 13 nm or more and 19 nm or less, R calculated by the following formula (1) using the Hansen solubility parameter value (HSP value) of the resin a and the Hansen solubility parameter value (HSP value) of the carbon black is 13.1 or more and 17.0 or less. Photosensitive resin composition for flexo printing plates. R=(4α 2 +β 2 +γ 2 ) 0.5 ...Equation (1) α = absolute value of the difference between δd of resin a and δd of carbon black β = absolute value of the difference between δp of resin a and δp of carbon black γ = absolute value of the difference between δh of resin a and δh of carbon black δd: Energy due to intermolecular dispersion forces δp: Energy due to intermolecular dipole interactions δh: Energy due to intermolecular hydrogen bonds [2] The photosensitive resin construct for a flexographic printing plate according to [1] above, wherein the resin a comprises at least one selected from the group consisting of polyamide, polybutyral, polyvinyl alcohol, poly(meth)acrylate, and modified or partially saponified products thereof. [3] The DBP absorption of the carbon black is 40 cm 3 / 100g or more 80cm 3 The photosensitive resin construct for flexographic printing plates according to [1] or [2] above, wherein the composition is in a weight percent of 100g / 100g. [4] The photosensitive resin construct for flexographic printing plates according to any one of [1] to [3], wherein the blending mass ratio of the resin a to the carbon black (resin a / carbon black) in the infrared ablation layer (C) is 90 / 10 to 50 / 50. [5] 1. A method for producing a flexographic printing plate, comprising: The photosensitive resin construct for a flexographic printing plate according to any one of [1] to [4] above, (A) the step of irradiating with ultraviolet light from the support side; (C) a step of irradiating the infrared ablation layer with infrared rays to draw and process a pattern; (B) a step of irradiating the photosensitive resin composition layer with ultraviolet light to perform pattern exposure; a step of removing the unexposed areas of the (C) infrared ablation layer and the (B) photosensitive resin composition layer; A method for producing a flexographic printing plate comprising: [6] A manufacturing process for manufacturing a flexographic printing plate by the manufacturing method described in [5] above; a step of applying ink to the raised portions of the flexographic printing plate obtained in the manufacturing step; transferring the ink to a substrate; A printing method including: [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a photosensitive resin construct for a flexographic printing plate having an infrared ablation layer that can uniformly form microcells even when the resolution is increased without impairing water-developability, and a method for producing a flexographic printing plate and a printing method using the same. [Brief explanation of the drawings]

[0012] [Figure 1] 1 shows a schematic cross-sectional view of a photosensitive resin construct for a flexographic printing plate according to an embodiment of the present invention. [Figure 2] 1 shows a schematic diagram of a method for manufacturing a flexographic printing plate. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention (hereinafter also referred to as "the present embodiment") will be described in detail. It should be noted that the following embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be implemented in various modifications within the scope of its gist.

[0014] [Photosensitive resin composition for flexo printing plates] The photosensitive resin construct for a flexographic printing plate of this embodiment is At least (A) a support, (B) a photosensitive resin composition layer, and (C) a water-soluble infrared ablation layer containing carbon black and resin a are laminated in this order. The carbon black has a primary particle diameter of 13 nm or more and 19 nm or less, R calculated by the following formula (1) using the Hansen solubility parameter (HSP value) of the resin a and the Hansen solubility parameter (HSP value) of the carbon black is 13.1 or more and 17.0 or less. R=(4α 2 +β 2 +γ 2 ) 0.5 ...Equation (1) α = absolute value of the difference between δd of resin a and δd of carbon black β = absolute value of the difference between δp of resin a and δp of carbon black γ = absolute value of the difference between δh of resin a and δh of carbon black δd: Energy due to intermolecular dispersion forces δp: Energy due to intermolecular dipole interactions δh: Energy due to intermolecular hydrogen bonds

[0015] By having the above-mentioned constitution, it is possible to obtain a photosensitive resin structure for flexographic printing plates having an infrared ablation layer that can uniformly form microcells even when the resolution is increased without impairing water developability.

[0016] ((A) Support) The support (A) used in the photosensitive resin construct for flexographic printing plates of this embodiment is not limited to the following, but examples thereof include polyester films, polyamide films, polyacrylonitrile films, and polyvinyl chloride films. Among these, polyester film is preferred as the support (A). The polyester used for the (A) support is not limited to the following, but examples thereof include polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. The thickness of the (A) support is not particularly limited, but is preferably 50 to 300 μm. Furthermore, for the purpose of increasing the adhesive strength between the (A) support and the (B) photosensitive resin composition layer described later, an adhesive layer may be provided on the (A) support. The adhesive layer is not particularly limited, but examples thereof include the adhesive layers described in WO 2004 / 104701.

[0017] ((B) Photosensitive resin composition layer) The photosensitive resin construct for a flexographic printing plate of this embodiment has (A) a support and (B) a photosensitive resin composition layer on the support. The (B) photosensitive resin composition layer may be laminated directly onto the (A) support, or may be laminated indirectly via the above-mentioned adhesive layer or the like. The (B) photosensitive resin composition layer contains, for example, but not limited to, a thermoplastic elastomer (b-1), and preferably may further contain an ethylenically unsaturated compound (b-2), a photopolymerization initiator (b-3), and a liquid diene. Furthermore, the (B) photosensitive resin composition layer may further contain auxiliary additive components, if necessary. Each component of the (B) photosensitive resin composition layer will be described in detail below.

[0018] <Thermoplastic elastomer (b-1)> The thermoplastic elastomer (b-1) is not limited to the following, but examples thereof include copolymers having structural units derived from monovinyl-substituted aromatic hydrocarbons and structural units derived from conjugated dienes. The thermoplastic elastomer (b-1) may further have structural units derived from other monomers. The use of such a thermoplastic elastomer tends to further improve the printing durability of flexographic printing plates produced using the photosensitive resin construct for flexographic printing plates of this embodiment.

[0019] The thermoplastic elastomer (b-1) may be a random copolymer or a block copolymer, but is preferably a block copolymer having a polymer block of a monovinyl-substituted aromatic hydrocarbon and a polymer block of a conjugated diene. The use of such a thermoplastic elastomer tends to further improve the printing durability of a flexographic printing plate produced using the photosensitive resin construct for a flexographic printing plate of this embodiment.

[0020] Examples of the monovinyl-substituted aromatic hydrocarbon constituting the thermoplastic elastomer (b-1) include, but are not limited to, styrene, t-butylstyrene, 1,1-diphenylethylene, N,N-dimethyl-p-aminoethylstyrene, N,N-diethyl-p-aminoethylstyrene, vinylpyridine, p-methylstyrene, p-methoxystyrene, tertiary butylstyrene, α-methylstyrene, 1,1-diphenylethylene, etc. These may be used alone or in combination of two or more. Among these, styrene is preferred as the monovinyl-substituted aromatic hydrocarbon from the viewpoint that the (B) photosensitive resin composition layer can be smoothly molded at a relatively low temperature.

[0021] Conjugated dienes constituting the thermoplastic elastomer (b-1) include, but are not limited to, butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, chloroprene, etc. These may be used alone or in combination of two or more. Among these, butadiene is preferred as the conjugated diene from the viewpoint of printing durability of a flexographic printing plate produced using the photosensitive resin construct for a flexographic printing plate of this embodiment.

[0022] From the viewpoint of viscosity at room temperature, the number average molecular weight (Mn) of the thermoplastic elastomer (b-1) is preferably from 20,000 to 300,000, and more preferably from 50,000 to 200,000. The number average molecular weight can be measured by gel permeation chromatography (GPC) and is expressed as a polystyrene-equivalent molecular weight. When the thermoplastic elastomer (b-1) is a block copolymer having a polymer block made of a monovinyl-substituted aromatic hydrocarbon and a polymer block made of a conjugated diene, the thermoplastic elastomer (b-1) includes, for example, a linear block copolymer represented by the following general formula group (I) and / or a linear block copolymer or a radial block copolymer represented by the following general formula group (II): General formula group (I): (AB) n , A-(BA) n , A-(BA) n -B, B-(AB) n General formula group (II): [(AB) k ] m -X, [(AB) k -A] m-X, [(BA) k ] m -X, [(BA) k -B] m -X In the general formula groups (I) and (II), A represents a polymer block made of a monovinyl-substituted aromatic hydrocarbon. B represents a polymer block made of a conjugated diene. X represents a residue of a coupling agent selected from the group consisting of silicon tetrachloride, tin tetrachloride, epoxidized soybean oil, polyhalogenated hydrocarbon compounds, carboxylic acid ester compounds, polyvinyl compounds, bisphenol-type epoxy compounds, alkoxysilane compounds, halogenated silane compounds, and ester-based compounds, or a residue of a polymerization initiator such as a polyfunctional organolithium compound. In the general formula groups (I) and (II), n, k and m each represent an integer of 1 or more, for example, 1 to 5.

[0023] The content of conjugated dienes and monovinyl-substituted aromatic hydrocarbons in the thermoplastic elastomer (b-1) was measured by a nuclear magnetic resonance spectrometer ( 1 H-NMR) can be used to measure the 1 Measurements can be performed using a JNM-LA400 (manufactured by JEOL, trade name) as the H-NMR measuring instrument, deuterated chloroform as the solvent, a sample concentration of 50 mg / mL, an observation frequency of 400 MHz, TMS (tetramethylsilane) as the chemical shift standard, a pulse delay of 2.904 seconds, 64 scans, a pulse width of 45°, and a measurement temperature of 25°C. In the thermoplastic elastomer (b-1), the copolymerization ratio (mass ratio) of the monovinyl-substituted aromatic hydrocarbon to the conjugated diene, monovinyl-substituted aromatic hydrocarbon / conjugated diene, is preferably in the range of 10 / 80 to 90 / 20, more preferably 10 / 90 to 85 / 15, and even more preferably 10 / 90 to 60 / 40, from the viewpoint of the printing durability of a flexographic printing plate produced using the photosensitive resin construct for a flexographic printing plate of this embodiment.

[0024] In the copolymerization ratio (mass ratio), if the proportion of the monovinyl-substituted aromatic hydrocarbon is 10 or more, the (B) photosensitive resin composition layer has sufficient hardness, allowing appropriate printing to be performed with normal printing pressure. In addition, if the proportion of the monovinyl-substituted aromatic hydrocarbon is 90 or less in the copolymerization ratio (mass ratio), the (B) photosensitive resin composition layer has appropriate hardness, allowing the ink to be sufficiently transferred to the printing object in the printing process. If necessary, other functional groups may be introduced into the thermoplastic elastomer (b-1), or the thermoplastic elastomer (b-1) may be chemically modified by hydrogenation or the like, or may be copolymerized with other components. From the viewpoint of the printing durability of a flexographic printing plate obtained using the photosensitive resin construct for a flexographic printing plate of this embodiment, the content of the thermoplastic elastomer (b-1) in the (B) photosensitive resin composition layer is preferably 40% by mass or more, more preferably 40% by mass or more and 80% by mass or less, even more preferably 45% by mass or more and 80% by mass or less, and even more preferably 45% by mass or more and 75% by mass or less, when the total amount of the (B) photosensitive resin composition layer is taken as 100% by mass.

[0025] <Ethylenically unsaturated compound (b-2)> As described above, the (B) photosensitive resin composition layer preferably contains an ethylenically unsaturated compound (b-2). The ethylenically unsaturated compound (b-2) is a compound having a radically polymerizable unsaturated double bond. Examples of such ethylenically unsaturated compounds (b-2) include, but are not limited to, olefins such as ethylene, propylene, vinyltoluene, styrene, and divinylbenzene; acetylenes; (meth)acrylic acid and / or derivatives thereof; haloolefins; unsaturated nitriles such as acrylonitrile; unsaturated amides and derivatives thereof such as acrylamide and methacrylamide; unsaturated dicarboxylic acids and derivatives thereof such as maleic anhydride, maleic acid, and fumaric acid; vinyl acetates; N-vinylpyrrolidone; N-vinylcarbazole; and N-substituted maleimide compounds. Among these, (meth)acrylic acid and / or a derivative thereof is preferred as the ethylenically unsaturated compound (b-2) from the viewpoint of ultraviolet curability and printing durability of the cured (B) photosensitive resin composition layer. Examples of the derivatives include, but are not limited to, alicyclic compounds having a cycloalkyl group, a bicycloalkyl group, a cycloalkenyl group, a bicycloalkenyl group, or the like; aromatic compounds having a benzyl group, a phenyl group, a phenoxy group, or a naphthalene skeleton, an anthracene skeleton, a biphenyl skeleton, a phenanthrene skeleton, a fluorene skeleton, or the like; compounds having an alkyl group, a halogenated alkyl group, an alkoxyalkyl group, a hydroxyalkyl group, an aminoalkyl group, a glycidyl group, or the like; ester compounds with polyhydric alcohols such as alkylene glycol, polyoxyalkylene glycol, polyalkylene glycol, and trimethylolpropane; and compounds having a polysiloxane structure such as polydimethylsiloxane and polydiethylsiloxane.

[0026] The ethylenically unsaturated compound (b-2) may also be a heteroaromatic compound containing elements such as nitrogen and sulfur.

[0027] Examples of the (meth)acrylic acid and / or derivatives thereof include, but are not limited to, diacrylates and dimethacrylates of alkanediols such as hexanediol and nonanediol; diacrylates and dimethacrylates of ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol, and butylene glycol; trimethylolpropane tri(meth)acrylate; dimethyloltricyclodecane di(meth)acrylate; isobornyl(meth)acrylate; phenoxypolyethylene glycol (meth)acrylate; pentaerythritol tetra(meth)acrylate, and the like. These may be used alone or in combination of two or more.

[0028] From the viewpoint of the mechanical strength of a flexographic printing plate obtained using the photosensitive resin construct for a flexographic printing plate of this embodiment, it is preferable to use at least one type of (meth)acrylate as the ethylenically unsaturated compound (b-2), and it is more preferable to use at least one type of bifunctional (meth)acrylate.

[0029] The number average molecular weight (Mn) of the ethylenically unsaturated compound (b-2) is preferably 100 or more from the viewpoint of improving the non-volatility of the ethylenically unsaturated compound (b-2) during production and / or storage of the photosensitive resin construct for flexographic printing plates of this embodiment, and is preferably less than 1,000 from the viewpoint of compatibility with other components, and more preferably 200 or more and 800 or less. From the viewpoint of printing durability of a flexographic printing plate obtained using the photosensitive resin construct for a flexographic printing plate of this embodiment, the content of the ethylenically unsaturated compound (b-2) in the (B) photosensitive resin composition layer is preferably 2% by mass or more and 30% by mass or less, more preferably 2% by mass or more and 25% by mass or less, and even more preferably 2% by mass or more and 20% by mass or less, when the total amount of the (B) photosensitive resin composition layer is taken as 100% by mass.

[0030] <Photopolymerization initiator (b-3)> The (B) photosensitive resin composition layer preferably contains a photopolymerization initiator (b-3). The photopolymerization initiator (b-3) is a compound that absorbs light energy and generates radicals, and examples of the photopolymerization initiator include a degradable photopolymerization initiator, a hydrogen abstraction photopolymerization initiator, and a compound having a moiety that functions as a hydrogen abstraction photopolymerization initiator and a moiety that functions as a degradable photopolymerization initiator in the same molecule.

[0031] Examples of such photopolymerization initiator (b-3) include, but are not limited to, benzophenone, 4,4-bis(diethylamino)benzophenone, 3,3',4,4'-benzophenonetetracarboxylic anhydride, 3,3',4,4'-tetramethoxybenzophenone, and other benzophenones; anthraquinones, such as t-butylanthraquinone and 2-ethylanthraquinone; thioxanthones, such as 2,4-diethylthioxanthone, isopropylthioxanthone, and 2,4-dichlorothioxanthone; Michler's ketone; diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 1-hydroxycyclohexyl-phenyl ketone, 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, 2-methyl-1-( acetophenones such as 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone, trichloroacetophenone, etc.; benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, etc.; acylphosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, etc.; methylbenzoyl formate; 1,7-bisacridinylheptane; 9-phenylacridine; and azo compounds such as azobisisobutyronitrile, diazonium compounds, and tetrazene compounds. These may be used alone or in combination of two or more. Among these, from the viewpoint of the printing durability of a flexographic printing plate produced using the photosensitive resin construct for a flexographic printing plate of this embodiment, a compound having a carbonyl group is preferred as the photopolymerization initiator (b-3), and aromatic carbonyl compounds such as benzophenones and thioxanthones are more preferred.

[0032] From the viewpoint of printing durability of a flexographic printing plate produced using the photosensitive resin construct for a flexographic printing plate of this embodiment, the content of the photopolymerization initiator (b-3) in the (B) photosensitive resin composition layer is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 5% by mass or less, and even more preferably 0.5% by mass or more and 5% by mass or less, when the total amount of the (B) photosensitive resin composition layer is taken as 100% by mass.

[0033] <Liquid diene> The (B) photosensitive resin composition layer preferably contains a liquid diene. Liquid dienes are compounds that contain liquid carbon-carbon double bonds. In this specification, the term "liquid" in "liquid diene" means that the diene has the property of being easily fluid and deformable and being able to solidify into the deformed shape upon cooling. Liquid dienes have elastomeric properties, which means that when an external force is applied, they instantly deform in response to the external force and quickly recover their original shape when the external force is removed.

[0034] Examples of liquid dienes include, but are not limited to, liquid polybutadiene, liquid polyisoprene, modified liquid polybutadiene, modified liquid polyisoprene, liquid acrylonitrile-butadiene copolymer, and liquid styrene-butadiene copolymer. The liquid diene is a copolymer containing 50% by mass or more of a diene component. Among these, from the viewpoint of the mechanical properties of the photosensitive resin construct for a flexographic printing plate of this embodiment and the flexographic printing plate using the same, liquid polybutadiene is preferred as the liquid diene.

[0035] Furthermore, the 1,2-vinyl bond content of the liquid diene, preferably liquid polybutadiene, is preferably 1% or more and 80% or less, more preferably 5% or more and 70% or less, and even more preferably 5% or more and 65% or less, from the viewpoint of ensuring appropriate hardness of the photosensitive resin construct for flexographic printing plates of this embodiment and the flexographic printing plates using the same. Here, the "1,2-vinyl bond content" refers to the proportion of conjugated diene monomers incorporated via 1,2-bonds among those incorporated via 1,2-bonds, 3,4-bonds, and 1,4-bonds. The 1,2-vinyl bond content of the liquid polybutadiene 1 It can be determined from the peak ratio of H-NMR (magnetic resonance spectrum). 1,2-Polybutadiene, which is a liquid polybutadiene having a 1,2-vinyl bond, has a vinyl double bond in the side chain, and therefore has high reactivity in radical polymerization, and is preferable from the viewpoint of increasing the hardness of the (B) photosensitive resin composition layer.

[0036] Furthermore, liquid polybutadiene is typically a mixture of 1,2-polybutadiene having 1,2-vinyl bonds and 1,4-polybutadiene having 1,4-vinyl bonds. However, in order to improve the flexibility of the photosensitive resin construct for flexographic printing plates of this embodiment and the flexographic printing plates using the same, it is effective to include 1,4-polybutadiene in the liquid diene. 1,4-Polybutadienes include cis-type 1,4-polybutadienes and trans-type 1,4-polybutadienes. Both cis-type and trans-type 1,4-polybutadienes have a vinyl group, which is a double bond, present inside, making them less reactive in radical polymerization and capable of forming flexible resins.

[0037] When a mixture of liquid polybutadienes having different 1,2-vinyl bond contents is used, the average value thereof is used as the 1,2-vinyl bond content. (B) From the viewpoint of easily adjusting the reactivity of the photosensitive resin composition layer, it is preferable to adjust the total 1,2-vinyl bond content by mixing a liquid polybutadiene having a 1,2-vinyl bond content of 10% or less with a liquid polybutadiene having a 1,2-vinyl bond content of 80% or more, and more preferably to adjust the total 1,2-vinyl bond content by mixing a liquid polybutadiene having a 1,2-vinyl bond content of 5% or less with a liquid polybutadiene having a 1,2-vinyl bond content of 80% or more.

[0038] Furthermore, the number average molecular weight of the liquid diene is not particularly limited as long as it is liquid at 20°C. However, from the viewpoint of printing durability and handling of a flexographic printing plate obtained using the photosensitive resin construct for a flexographic printing plate of this embodiment, it is preferably 500 or more and 60,000 or less, more preferably 500 or more and 50,000 or less, and even more preferably 800 or more and 50,000 or less.

[0039] From the viewpoint of the printing durability of the photosensitive resin construct for a flexographic printing plate of this embodiment and the flexographic printing plate using the same, the content of the liquid diene in the (B) photosensitive resin composition layer is preferably 10% by mass or more and 40% by mass or less, more preferably 15% by mass or more and 40% by mass or less, and even more preferably 20% by mass or more and 40% by mass or less, when the total amount of the (B) photosensitive resin composition layer is taken as 100% by mass.

[0040] <Auxiliary additive ingredients> Examples of auxiliary additive components include, but are not limited to, polar group-containing polymers, plasticizers other than liquid dienes, thermal polymerization inhibitors other than stabilizers, antioxidants, ultraviolet absorbers, dyes and pigments, etc.

[0041] Examples of polar group-containing polymers include, but are not limited to, water-soluble or water-dispersible copolymers having polar groups such as hydrophilic groups such as carboxyl groups, amino groups, hydroxyl groups, phosphoric acid groups, and sulfonic acid groups, and salts thereof. More specific examples include carboxyl group-containing acrylonitrile-butadiene rubber, carboxyl group-containing styrene-butadiene rubber, carboxyl group-containing aliphatic conjugated diene polymers, emulsion polymers of ethylenically unsaturated compounds having phosphoric acid groups or carboxyl groups, sulfonic acid group-containing polyurethanes, and carboxyl group-containing butadiene latexes. These polar group-containing polymers may be used alone or in combination of two or more. Among these, from the viewpoint of obtaining high resolution in a flexographic printing plate using the present construction, a carboxyl group-containing butadiene latex is preferred as the polar group-containing polymer.

[0042] Plasticizers other than liquid dienes include, but are not limited to, hydrocarbon oils such as naphthenic oil and paraffin oil; liquid diene-based conjugated diene rubbers such as liquid acrylonitrile-butadiene copolymer and liquid styrene-butadiene copolymer; polystyrene having a number average molecular weight of 2000 or less; and ester-based plasticizers such as sebacate esters and phthalate esters. These other plasticizers may have a hydroxyl group or a carboxyl group, and may also have a photopolymerizable reactive group such as a (meth)acryloyl group. The other plasticizers may be used alone or in combination of two or more.

[0043] As the thermal polymerization inhibitor and antioxidant, those commonly used in the field of resin materials or rubber materials can be used, specifically, phenol-based materials. Examples of such phenolic materials include, but are not limited to, vitamin E, tetrakis-(methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate)methane, 2,5-di-t-butylhydroquinone, 2,6-di-t-butyl-p-cresol, and 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate. The thermal polymerization inhibitor and the antioxidant may be used alone or in combination of two or more.

[0044] Examples of the ultraviolet absorber include, but are not limited to, known benzophenone compounds, salicylate compounds, acrylonitrile compounds, metal complex salt compounds, and hindered amine compounds. Furthermore, the dyes and pigments shown below may be used as ultraviolet absorbers. Examples of such ultraviolet absorbers include, but are not limited to, 2-ethoxy-2'-ethyloxalic acid bisanilide, 2,2'-dihydroxy-4-methoxybenzophenone, and the like. Dyes and pigments are effective as coloring means for improving visibility. Examples of dyes include, but are not limited to, water-soluble basic dyes, acid dyes, direct dyes, etc., and water-insoluble sulfide dyes, oil-soluble dyes, disperse dyes, etc. In particular, anthraquinone dyes, indigoid dyes, and azo dyes are preferred, and azo oil-soluble dyes, etc. are more preferred. Examples of pigments include, but are not limited to, natural pigments, synthetic inorganic pigments, synthetic organic pigments, etc. Examples of synthetic organic pigments include azo pigments, triphenylmethane pigments, quinoline pigments, anthraquinone pigments, and phthalocyanine pigments.

[0045] The total amount of the auxiliary additive components described above is preferably 0% by mass or more and 10% by mass or less, more preferably 0% by mass or more and 5% by mass or less, and even more preferably 0% by mass or more and 3% by mass or less, when the total amount of the (B) photosensitive resin composition layer is taken as 100% by mass.

[0046] (C) Infrared ablation layer The photosensitive resin construct for flexographic printing plates of this embodiment has an infrared ablation layer (C) laminated on the above-mentioned photosensitive resin composition layer (B). (C) The infrared ablation layer contains carbon black and a predetermined resin a, is ablated by an infrared laser, and functions as a light blocking layer for rays other than infrared rays. In addition, the infrared ablation layer (C) is water-soluble.

[0047] <Resin a> Resin a contained in the infrared ablation layer (C) constituting the photosensitive resin construct for flexographic printing plates of this embodiment is preferably water-soluble or water-dispersible so as not to impair the water solubility of the ablation layer (C) and the water-developability of the flexographic printing plate. Such resin a is not limited to the following, but examples thereof include at least one selected from the group consisting of polyamide, polybutyral, polyvinyl alcohol, poly(meth)acrylate, and modified or partially saponified products thereof. Among these, polyamide, polyvinyl alcohol, and modified or partially saponified products thereof are preferred from the viewpoint of achieving both water developability and ablation properties.

[0048] <Carbon black> The photosensitive resin construct for flexographic printing plates of this embodiment contains carbon black in the infrared ablation layer (C), which has a primary particle diameter of 13 nm or more and 19 nm or less. Basically, the smaller the primary particle size of carbon black, the higher the laser sensitivity and the easier it is to form microcells, and the water developability also tends to improve. By making the primary particle size of the carbon black 13 nm or more, it is possible to prevent the self-aggregation force between the carbon black particles from becoming too large, resulting in good dispersibility and even higher laser sensitivity. Furthermore, by using carbon black with a primary particle size of 19 nm or less, desired high laser sensitivity and water developability can be obtained, and good microcells can be formed. In order to form the infrared ablation layer (C) more easily and stably, it is preferable that the primary particle diameter of the carbon black is not too small, and the primary particle diameter of the carbon black is preferably 15 nm or more and 19 nm or less. Furthermore, from the viewpoint of achieving excellent removability of the (C) infrared ablation layer at the interface with the (B) photosensitive resin composition layer after laser ablation, the primary particle diameter of the carbon black is more preferably 15 nm or more and 18 nm or less, and even more preferably 15 nm or more and 17 nm or less. By achieving excellent removability of the infrared ablation layer at the interface with the (B) photosensitive resin composition layer, it is possible to obtain a photosensitive resin structure for flexographic printing plates having uniform shielding properties for light rays other than infrared rays and having an excellent shape, and a flexographic printing plate using the same. The primary particle size of the carbon black contained in the (C) infrared ablation layer can be determined by observation with an electron microscope, specifically by the method described in the Examples.

[0049] The primary particle size of the carbon black contained in the (C) infrared ablation layer can be controlled to fall within the above-mentioned range by selecting a carbon black having an appropriate particle size from various commercially available products.

[0050] Furthermore, it is preferable that the carbon black has a small structure, because a small structure increases the contact area between the carbon black and resin a, improving dispersibility and thereby improving the uniformity of microcells. Specifically, the DBP absorption of carbon black is 40 cm 3 / 100g or more 80cm 3 / 100g or less is preferable, 50cm 3 / 100g or more 80cm 3 / 100g or less is more preferable, and 53cm 3 / 100g or more 80cm 3 / 100g or less is more preferable, and 56cm 3 / 100g or more 80cm 3 It is even more preferable that the weight ratio is 1 / 100g or less. The above-mentioned effects are obtained within this range.

[0051] The DBP absorption amount is the amount of DBP (dibutyl phthalate) absorbed by 100 g of carbon black, and can be measured by the method specified in JIS K6217-4. Specifically, it can be measured by the method described in the Examples below. The larger the structure, the larger the DBP absorption amount, and the smaller the structure, the smaller the DBP absorption amount. (C) The DBP absorption amount of the carbon black contained in the infrared ablation layer can be controlled within the above-mentioned range by selecting an appropriate value from various commercially available products.

[0052] Carbon black is classified into, for example, furnace black, channel black, thermal black, acetylene black, lamp black, etc. depending on the method of production, but furnace black is preferred in order to obtain the desired properties. Furnace black is a carbon black obtained by injecting petroleum-based or coal-based oil as a raw material into high-temperature gas and causing incomplete combustion, and can be produced by a widely known method. As for the carbon black, any carbon black that has been conventionally used to form a black matrix can be used as long as it satisfies the above-mentioned various conditions.

[0053] To obtain uniform microcells, the (C) infrared ablation layer must be uniform within the plane. To achieve this, it is important that the carbon black disperses well, and the relationship between the resin a and the carbon black in the (C) infrared ablation layer is also important. The dispersibility of the carbon black in the resin a tends to deteriorate if the polarities are too close or too far apart.

[0054] In the photosensitive resin construct for flexographic printing plates of this embodiment, the Hansen solubility parameter (HSP value) is used as an index for the combination of the resin a and the carbon black used in the infrared ablation layer (C). In order to improve the dispersibility of carbon black in resin a, the difference between the HSP values (Hansen solubility parameters (hereinafter, sometimes referred to as "HSP values") of resin a and the carbon black is important. The Hansen Solubility Parameter (HSP value) is a value used to predict the solubility of a substance, which was announced by Charles M. Hansen in 1967, and is a parameter based on the idea that "two substances with similar intermolecular interactions are likely to dissolve in each other." The HSP value is calculated by the following three parameters (unit: MPa 0.5 ) is composed of δd: Energy due to intermolecular dispersion forces δp: Energy due to intermolecular dipole interactions δh: Energy due to intermolecular hydrogen bonds These three parameters can be considered as coordinates in a three-dimensional space (Hansen space), and when the HSP values of two substances are placed in Hansen space, the closer the distance between the two points, the more likely they are to dissolve in each other. As explained in the March 2010 issue of Chemical Industry (Kagaku Kogyosha), the Hansen solubility parameters of various substances can be obtained by using the computer software "HSPiP: Hansen Solubility Parameters in Practice." In the photosensitive resin construct for flexographic printing plates of this embodiment, the Hansen solubility parameters used are those obtained using the computer software "HSPiP: Hansen Solubility Parameters in Practice."

[0055] In the photosensitive resin construct for a flexographic printing plate of this embodiment, R calculated by the following formula (1) is 13.1 or more and 17.0 or less. Equation (1): R=(4α 2 +β 2 +γ 2 ) 0.5 R is preferably 14.0 or more and 17.0 or less, more preferably 15.0 or more and 17.0 or less, and even more preferably 15.5 or more and 17.0 or less. In the formula (1), α, β, and γ are as shown below. α = absolute value of difference between δd of resin a and δd of carbon black β = absolute value of the difference between δp of resin a and δp of carbon black γ = absolute value of the difference between δh of resin a and δh of carbon black δd: Energy due to intermolecular dispersion forces δp: Energy due to intermolecular dipole interactions δh: Energy due to intermolecular hydrogen bonds

[0056] When R calculated by the formula (1) is within the above range, the dispersibility of the carbon black is improved, and the dispersibility of carbon black having a small particle size in particular can be maintained at a good level, thereby increasing the laser sensitivity.

[0057] (C) The Hansen solubility parameter (HSP value) of resin a in the infrared ablation layer and the Hansen solubility parameter (HSP value) of carbon black can be controlled within the above numerical range by selecting the composition of resin a and the type of carbon black. The HSP value of carbon black can be controlled by adjusting the polarity of the surface. Specifically, when carbon black is oxidized to increase its polarity (low pH), the HSP value of the carbon black shifts to the higher polarity side. Furthermore, the smaller the particle size of the carbon black, the more the HSP value of the carbon black tends to become higher if it is already high polarity, and lower if it is already low polarity. By adjusting the HSP values of these resin a and carbon black, the value of R in the above formula (1) can be controlled to fall within the above numerical range.

[0058] The carbon black content is preferably 10% by mass or more and 70% by mass or less, more preferably 20% by mass or more and 60% by mass or less, and even more preferably 30% by mass or more and 50% by mass or less, based on the total amount of the infrared ablation layer (C). When the carbon black content is within the above range, laser sensitivity and shielding properties tend to be further improved. The blending mass ratio of the resin a to the carbon black (resin a / carbon black) in the infrared ablation layer (C) is preferably 90 / 10 to 50 / 50, more preferably 80 / 20 to 50 / 50, even more preferably 75 / 25 to 55 / 45, and even more preferably 70 / 30 to 60 / 40. When the blending mass ratio (resin a / carbon black) is within the above range, the laser sensitivity and shielding properties tend to be further improved.

[0059] The infrared ablation layer (C) of the photosensitive resin construct for flexographic printing plates of this embodiment should have a thicker film thickness in order to ensure light-blocking properties against ultraviolet rays during the step of subjecting the photosensitive resin construct for flexographic printing plates of this embodiment to an exposure treatment, and a thinner film thickness in order to enhance ablation properties. From the above viewpoints, the thickness of the infrared ablation layer (C) is preferably 0.1 μm or more and 20 μm or less, more preferably 0.5 μm or more and 15 μm or less, and even more preferably 1.0 μm or more and 10 μm or less.

[0060] As for the non-infrared shielding effect of the infrared ablation layer (C), the optical density of the infrared ablation layer (C) is preferably 2 or more, and more preferably 3 or more. The optical density can be measured using a D200-II transmission densitometer (manufactured by GretagMacbeth Co., Ltd.) The optical density is measured by ISO visual, and the light to be measured is in the wavelength range of about 400 to 750 nm.

[0061] The infrared ablation layer (C) may contain a dispersant to aid in the dispersion of the carbon black. As the dispersant, for example, a compound having an adsorption portion capable of interacting with the surface functional groups of carbon black and a resin-compatible portion compatible with resin a is preferred. The adsorption moiety of the dispersant is not limited to the following, but examples thereof include an amino group, an amide group, a urethane group, a carboxyl group, a carbonyl group, a sulfone group, and a nitro group, with an amino group, an amide group, and a urethane group being preferred. Examples of the resin compatible portion include, but are not limited to, saturated alkyl, unsaturated alkyl, polyether, polyester, poly(meth)acrylic, and polyol.

[0062] Methods for forming the (C) infrared ablation layer include, but are not limited to, a method in which a solution of resin a is first prepared using a predetermined solvent, carbon black and a dispersant are added thereto, the carbon black is dispersed in the solution of resin a, and then the solution is coated on a cover film such as a polyester film, and then this cover film is laminated or press-bonded to the (B) photosensitive resin composition layer to transfer a non-infrared shielding layer that can be ablated with an infrared laser. Methods for dispersing carbon black in a solution of resin a include, but are not limited to, forced stirring with a stirring blade, stirring using ultrasound or various mills, and a combination of these methods is effective. Alternatively, a method in which resin a, carbon black, and a dispersant are pre-mixed using an extruder or kneader and then dissolved in a solvent is also effective for achieving good dispersibility of carbon black. Carbon black may also be forcedly dispersed in a solution of resin a. The solvent for the solution or dispersion used to form the infrared ablation layer can be appropriately selected in consideration of the solubility of the resin a and carbon black used. A single solvent may be used, or two or more solvents may be mixed and used.

[0063] Furthermore, for example, mixing a low-boiling point solvent with a high-boiling point solvent to control the evaporation rate of the solvent is effective in improving the film quality of the infrared ablation layer (C). A cover film can be used to form the infrared ablation layer (C) of the photosensitive resin construct for flexographic printing plates of this embodiment. The cover film is preferably a film with excellent dimensional stability, such as a polyethylene terephthalate film. The cover film may be provided with a release treatment, an antistatic treatment, or other functions as required. The infrared ablation layer can be formed using a cover film by the method described in the Examples below.

[0064] ((D) Middle layer) The photosensitive resin construct for flexographic printing plates of this embodiment may further have one or more (D) intermediate layers between the (B) photosensitive resin composition layer and the (C) infrared ablation layer. (D) The intermediate layer can be, for example, but not limited to, an oxygen inhibition layer, an adhesive layer, and / or a protective layer. Each layer will be described below.

[0065] To produce a high-resolution print with highlight areas, it is necessary to form minute dots on the flexographic printing plate. From the viewpoint of forming such minute dots, the (D) intermediate layer is preferably an oxygen inhibition layer having oxygen inhibition ability. When the (B) photosensitive resin composition layer is cured by ultraviolet irradiation, the curing proceeds through radical polymerization. If oxygen is present during this radical polymerization, the radical-generating compound reacts with the oxygen, suppressing the polymerization reaction. If the polymerization reaction is suppressed in this manner, unreacted portions may remain in the exposed areas of the (B) photosensitive resin composition layer. These unreacted portions are removed in the fourth step of the flexographic printing plate manufacturing method described below, resulting in a pattern ultimately formed on the flexographic printing plate with curved edges. This is because the portion of the (B) photosensitive resin composition layer facing the (C) infrared ablation layer is particularly susceptible to polymerization inhibition by oxygen, making it more likely that unreacted portions will form in the (B) photosensitive resin composition layer directly below the (C) infrared ablation layer. On the other hand, if the amount of oxygen present during UV curing is reduced, the polymerization reaction is less likely to be inhibited, and the pattern that is finally formed will have a shape with flat portions at the tip. Therefore, when attempting to produce a pattern with flat portions at the tip, it is effective to reduce the oxygen that comes into contact with the photosensitive resin composition layer (B) by making the intermediate layer (D) have oxygen inhibition ability.

[0066] The (D) intermediate layer may also be an adhesive layer that improves the adhesion between the (B) photosensitive resin composition layer and the (C) infrared ablation layer, which tends to further improve handleability.

[0067] Furthermore, the (D) intermediate layer may also have the function of protecting the (C) infrared ablation layer. In conventional flexographic printing plate manufacturing processes, when the (C) infrared ablation layer laminated with a cover film is fed, the (C) infrared ablation layer may come into contact with the roll or may become tightly wound during film roll transportation, causing the (C) infrared ablation layer and the cover film laminated thereon to rub against each other within the roll. This may result in physical chipping of the (C) infrared ablation layer, resulting in the formation of pinholes. Furthermore, when the (B) photosensitive resin composition layer and the (C) infrared ablation layer are laminated by a method in which the (B) photosensitive resin composition layer is coated onto the (C) infrared ablation layer while being extruded, pinholes may be formed due to friction that occurs when the heated and melted photosensitive resin composition flows over the (C) infrared ablation layer. In order to prevent the occurrence of pinholes in the infrared ablation layer (C), it is preferable that the intermediate layer (D) constituting the photosensitive resin construct for flexographic printing plates of this embodiment has the physical strength and heat resistance required for a protective layer.

[0068] [Method for manufacturing flexographic printing plates] The method for producing a flexographic printing plate of this embodiment uses the photosensitive resin construct for a flexographic printing plate of this embodiment, and includes the following steps: (A) a first step of irradiating ultraviolet light from the support side; (C) a second step of irradiating infrared light onto the infrared ablation layer to draw and process a pattern; (B) a third step of irradiating ultraviolet light onto the photosensitive resin composition layer (B) using the infrared ablation layer (C) on which the pattern has been drawn and processed as a mask to perform pattern exposure; and (C) a fourth step of removing unexposed portions of the infrared ablation layer (C) and the photosensitive resin composition layer (B). Thereafter, a post-exposure treatment step is carried out as necessary, and a flexographic printing plate (relief printing plate) is obtained from the cured product of the photosensitive resin composition layer. From the viewpoint of imparting releasability, the surface of the flexographic printing plate may be brought into contact with a liquid containing a silicone compound and / or a fluorine compound.

[0069] FIG. 1 shows a schematic cross-sectional view of a photosensitive resin construct for a flexographic printing plate. FIG. 2 is a schematic diagram showing a method for producing a flexographic printing plate using the photosensitive resin construct for a flexographic printing plate of this embodiment. Each step will be described in detail below.

[0070] (First step) In the first step, the method of irradiating the photosensitive resin composition layer (B) with ultraviolet light from the support (A) side is not particularly limited, and can be carried out using a known irradiation unit. The wavelength of the ultraviolet light irradiated in this case is preferably 150 to 500 nm, more preferably 300 to 400 nm. Examples of ultraviolet light sources that can be used include, but are not limited to, low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, zirconium lamps, carbon arc lamps, and ultraviolet fluorescent lamps. The first step may be carried out before or after the second step described below.

[0071] (Second step) In the second step, the method for irradiating the infrared ablation layer (C) with infrared rays to form a pattern is not particularly limited, and can be performed using a known irradiation unit. Note that the infrared ablation layer (C) can be irradiated with infrared rays from the infrared ablation layer side. When the photosensitive resin structure for flexographic printing plates of this embodiment has a cover film, the cover film is first peeled off before infrared irradiation. Then, infrared rays are irradiated onto the (C) infrared ablation layer in a pattern to decompose the resin in the irradiated areas and draw a pattern. This allows a mask (C') of the (C) infrared ablation layer to be formed on the (B) photosensitive resin composition layer. To form microcells in the process described below, a suitable method is, for example, the method of drawing a microcell pattern described in JP-A-2019-517944 on an infrared ablation layer. In the second step, suitable infrared lasers include, for example, ND / YAG lasers (e.g., 1064 nm) and diode lasers (e.g., 830 nm). Laser systems suitable for the CTP platemaking technology are commercially available, and for example, the diode laser system CDI Spark (ESKO GRAPHICS) can be used. This laser system includes a rotating cylindrical drum that holds the photosensitive resin structure for the flexographic printing plate of this embodiment, an IR laser irradiation device, and a layout computer, and image information is directly sent from the layout computer to the laser device.

[0072] (Third step) In the third step, the (B) photosensitive resin composition layer is irradiated with ultraviolet light using the (C) infrared ablation layer on which the pattern has been drawn as a mask, thereby forming a pattern. The light passing through the mask accelerates the curing reaction of the (B) photosensitive resin composition layer, and the pattern formed in the (C) infrared ablation layer is transferred to the (B) photosensitive resin composition layer with the concaves and convexes reversed. The ultraviolet light may be irradiated onto the entire surface of the photosensitive resin structure for flexographic printing plates of this embodiment. The third step can be performed with the photosensitive resin construct for a flexographic printing plate of this embodiment attached to a laser cylinder, but generally, the photosensitive resin construct for a flexographic printing plate is removed from the laser device and irradiated using a conventional irradiation unit, which can be the same as the unit exemplified for ultraviolet irradiation in the first step.

[0073] (Fourth step) The fourth step is a step of removing the unexposed areas of (B) the infrared ablation layer and (C) the photosensitive resin composition layer. The removal method in the fourth step (development step) is not particularly limited, and any conventionally known method can be applied. Specifically, as described above, the (B) photosensitive resin composition layer of the photosensitive resin construct for flexographic printing plates is exposed to light, and then the unexposed portions are washed away with a washing liquid for water development. Thereafter, a flexographic printing plate is produced by optionally post-exposing the plate. When an intermediate layer (D) is present between the infrared ablation layer (C) and the photosensitive resin composition layer (B), it may be removed simultaneously in the development step. As the washing liquid for water development, water, an alkaline aqueous solution, a neutral detergent, or a surfactant can be suitably used.

[0074] Examples of surfactants include anionic surfactants, amphoteric surfactants, nonionic surfactants, etc. These may be used alone or in combination of two or more. Examples of anionic surfactants include, but are not limited to, sulfate ester salts, higher alcohol sulfate esters, higher alkyl ether sulfate ester salts, sulfated olefins, alkylbenzene sulfonates, α-olefin sulfonates, phosphate ester salts, and dithiophosphate ester salts. Examples of amphoteric surfactants include, but are not limited to, amino acid type amphoteric surfactants and betaine type amphoteric surfactants. Examples of nonionic surfactants include, but are not limited to, polyethylene glycol surfactants such as higher alcohol ethylene oxide adducts, alkylphenol ethylene oxide adducts, fatty acid ethylene oxide adducts, polyhydric alcohol fatty acid ester ethylene oxide adducts, higher alkylamine ethylene oxide adducts, fatty acid amide ethylene oxide adducts, and polypropylene glycol ethylene oxide adducts; and polyhydric alcohol surfactants such as glycerol fatty acid esters, pentaerythritol fatty acid esters, sorbitol and sorbitan fatty acid esters, polyhydric alcohol alkyl esters, and alkanolamine fatty acid amides.

[0075] The alkaline aqueous solution may contain a pH adjuster. The pH adjuster may be either an organic material or an inorganic material, but is preferably one that can adjust the pH to 9 or higher. Examples of pH adjusters include, but are not limited to, sodium hydroxide, sodium carbonate, potassium carbonate, sodium silicate, sodium metasilicate, and sodium succinate.

[0076] [Flexographic printing method] The printing method using the flexographic printing plate obtained by the method for producing a flexographic printing plate of this embodiment is not particularly limited, as long as it is a method in which ink is applied to the raised portions of the flexographic printing plate and the ink is transferred to a substrate. [Example]

[0077] The present embodiment will be described in more detail below with reference to specific examples and comparative examples, but the present invention is not limited to the following examples and comparative examples.

[0078] [Method for measuring Hansen Solubility Parameter (HSP)] Hansen solubility parameters were measured using the PC software HSPiP. To measure the HSP of resin a in the infrared ablation layer, the following solvents were used: water, acetone, 2-butanol, cyclohexanone, methanol, ethanol, ethyl acetate, hexane, butyl acetate, isobutyl acetate, MEK (methyl ethyl ketone), propylene glycol 1-monomethyl ether 2-acetate (PMA), THF (tetrahydrofuran), toluene, and xylene. 10 g of each solvent was placed in a 20 mL vial and mixed with 0.1 g of resin a. After 24 hours, the presence or absence of residual solvent was confirmed, and those that showed no residual solvent were considered dissolved. The results were then entered into the Sphere program, i.e., whether or not the resin dissolved in each solvent, and the HSP was calculated by running the software. In the HSP measurement of carbon black, the same solvents as those used in the measurement of resin a in the infrared ablation layer were used. 10 g of each solvent was placed in a 20 mL vial, and 0.1 g of carbon black was mixed therein and gently shaken by hand. After standing for 30 minutes, the presence or absence of turbidity was confirmed, and those showing turbidity were regarded as the dispersed state. Subsequently, the HSP was determined in the same manner as in the case of the resin. The value of R was calculated by the following formula (1). R=(4α 2 +β 2 +γ 2 ) 0.5 ···Formula (1) α = absolute value of the difference between δd of carbon black and δd of resin a β = absolute value of the difference between δp of resin a and δp of carbon black γ = absolute value of the difference between δh of resin a and δh of carbon black δd: energy due to intermolecular dispersion force δp: energy due to intermolecular dipole interaction δh: energy due to intermolecular hydrogen bond

[0079] 〔Evaluation of primary particle diameter of carbon black〕 After cutting the photosensitive resin composition for flexographic printing plate into an appropriate size, it was resin-embedded using an ultraviolet curable resin. After resin-embedding, a cross-section prepared by the cryomicrotome method was used as a SEM observation sample. <00005​​​​​​​​​​​​​​​​​​​​[DBP absorption amount of carbon black] The DBP absorption amount of carbon black was measured by the method specified in JIS K6217-4.

[0081] [Production of photosensitive resin constituent for flexographic printing plate] In the following examples and comparative examples, photosensitive resin compositions for flexographic printing plates were produced.

[0082] ((1) Preparation of Photosensitive Resin Composition Layer) <(1-1) Synthesis of Hydrophilic Copolymer> A pressure-resistant reactor equipped with a stirrer and a temperature-controlling jacket was initially charged with 125 parts by mass of water and 2 parts by mass of "ADEKA REASOAP" (manufactured by Asahi Denka Kogyo Co., Ltd.), an ammonium salt of (α-sulfo(1-nonylphenoxy)methyl-2-(2-propenyloxy)ethoxy-poly(oxy-1,2-ethanediyl) as a reactive emulsifier, and the internal temperature was raised to 80°C. 10 parts by mass of styrene, 60 parts by mass of butadiene, 23 parts by mass of butyl acrylate, 5 parts by mass of methacrylic acid, An oily mixed solution of a monomer mixture consisting of 2 parts by mass of acrylic acid and 2 parts by mass of t-dodecyl mercaptan, and an aqueous solution consisting of 28 parts by mass of water, 1.2 parts by mass of sodium peroxodisulfate, 0.2 parts by mass of sodium hydroxide, and 2 parts by mass of the ammonium salt of (α-sulfo(1-nonylphenoxy)methyl-2-(2-propenyloxy)ethoxy-poly(oxy-1,2-ethanediyl) were added at a constant flow rate over 5 hours for the oily mixed solution and 6 hours for the aqueous solution. The temperature was then maintained at 80°C for 1 hour to complete the polymerization reaction, and a copolymer latex was obtained, which was then cooled. Furthermore, the pH of the produced copolymer latex was adjusted to 7 with sodium hydroxide, and then unreacted monomers were removed by steam stripping. The mixture was then filtered through a 200-mesh wire screen, and finally the solid content of the filtrate was adjusted to 40% by mass, thereby obtaining an aqueous dispersion of the hydrophilic copolymer. The resulting aqueous dispersion of the hydrophilic copolymer was dried up in a vacuum dryer at 50° C. to remove water, thereby obtaining a hydrophilic copolymer.

[0083] ((1-2) Preparation of base film (support)) To prepare a solution for the adhesive layer to be coated on the support (base film), 55 parts by weight of Tufprene 912 (trade name, manufactured by Asahi Kasei Corporation), a block copolymer of styrene and 1,3-butadiene, 38 parts by weight of paraffin oil (average carbon number 33, average molecular weight 470, density at 15°C 0.868), 2.5 parts by weight of 1,9-nonanediol diacrylate, 1.5 parts by weight of 2,2-dimethoxyphenylacetophenone, 3 parts by weight of Epoxy Ester 3000M (trade name, manufactured by Kyoeisha Chemical Co., Ltd.), and 1.5 parts by weight of Varifast Yellow 3150 (trade name, manufactured by Orient Chemical Industry Co., Ltd.) were dissolved in toluene to obtain a solution with a solids content of 25%. Then, using a knife coater, the solution was applied to one side of a 100 μm thick polyester film so that the ultraviolet transmittance (UV transmittance) was 10%, and dried at 80°C for 1 minute to obtain a support (base film) with an adhesive layer. The UV transmittance of the support was calculated by measuring the transmission intensity using an ultraviolet exposure device AFP-1500 (trade name, manufactured by Asahi Kasei Corporation) and a UV illuminance meter MO-2 type (trade name, manufactured by Oak Manufacturing Co., Ltd., UV-35 filter).

[0084] ((1-3) Production of Laminate of Support and Photosensitive Resin Composition Layer) 32 parts by mass of the hydrophilic copolymer prepared in (1-1) above and 28 parts by mass of a styrene-butadiene-styrene copolymer [D-KX405: manufactured by Kraton] were mixed at 140°C using a pressure kneader, and then a liquid mixture of 32 parts by mass of liquid polybutadiene [LBR-352: manufactured by Kuraray], 8 parts by mass of 1,9-nonanediol diacrylate, 5 parts by mass of 1,6-hexanediol dimethacrylate, 2 parts by mass of 2,2-dimethoxyphenylacetophenone, 1 part by mass of 2,6-di-t-butyl-p-cresol, and 1 part by mass of carbinol-modified silicone oil [KF-6000: manufactured by Shin-Etsu Chemical Co., Ltd.] was added little by little over 15 minutes, and then kneaded for an additional 20 minutes to obtain a photosensitive resin composition. Next, the photosensitive resin composition was loaded into an extrusion molding machine, and the adhesive layer-forming surface of the support was bonded to one side of the photosensitive resin composition layer extruded from the T-die. A release film (Diafoil MRV100, manufactured by Mitsubishi Chemical Corporation) was then bonded to the side of the photosensitive resin composition layer opposite the support-laminating side, thereby obtaining a laminate of the support and the photosensitive resin composition layer.

[0085] ((2) Manufacturing of infrared ablation layer laminate) <Production Example of Infrared Ablation Layer Laminate 1> 6.5 parts by mass of AQ nylon A-90 (manufactured by Toray Industries, Inc.) as resin a, 54.0 parts by mass of water, and 36.0 parts by mass of ethanol were mixed together to dissolve resin a in the solvent. Thereafter, 3.5 parts by mass of carbon black (manufactured by Mitsubishi Chemical, #970) was further added, and the mixture was then mixed for 4 hours in a bead mill to obtain a carbon black dispersion. The carbon black dispersion obtained as described above was coated onto a 100 μm thick PET film that served as a cover film so that the film thickness after drying would be 5.0 μm, and the coating was dried at 90°C for 2 minutes to obtain infrared ablation layer laminate 1, which was a laminate of an infrared ablation layer and a cover film.

[0086] <Production Examples of Infrared Ablation Layer Laminates 2 to 13> Infrared ablation layer laminates 2 to 13 were obtained in the same manner as infrared ablation layer laminate 1, except that the resin a and carbon black used and their ratios were changed as shown in Table 1 below. The resin a and carbon black in Table 1 are shown below. #970, #1000, #2650, #2300, #850: Mitsubishi Chemical carbon black MA8: Mitsubishi Chemical carbon black Ketjenblack EC300J: Carbon black manufactured by Lion Specialty Chemicals POVAL 3-98: Polyvinyl alcohol resin manufactured by Kuraray AQ Nylon A-90: Toray Polyamide S-LEC BL-5Z: Polyvinyl butyral resin manufactured by Sekisui Chemical

[0087] [Table 1]

[0088] ((3) Production of photosensitive resin components for flexographic printing plates) Example 1 <Production of Photosensitive Resin Constituent 1 for Flexographic Printing Plate> The release film was peeled off from the laminate of the support and the photosensitive resin composition layer, and the infrared ablation layer laminate 1 was laminated in an environment of 25°C and 40% humidity so that the infrared ablation layer was in contact with the photosensitive resin composition layer.The laminate was then placed on a hot plate set to 120°C so that the cover film surface was in contact with the heating part of the hot plate, and heat was applied for 1 minute to obtain the photosensitive resin structure 1 for flexographic printing plates of Example 1. The evaluation was carried out by cutting out the photosensitive resin construct 1 for flexographic printing plates into a size of 15 cm x 10 cm.

[0089] [Examples 2 to 10], [Comparative Examples 1 to 3] <Production of Photosensitive Resin Constituents 2 to 13 for Flexographic Printing Plates> Photosensitive resin constructs 2 to 13 for flexographic printing plates were obtained in the same manner as for photosensitive resin construct 1 for flexographic printing plates, except that the infrared ablation layer laminate used was changed as shown in Table 2 below.

[0090] [Evaluation of photosensitive resin constituents for flexographic printing plates] <Evaluation of microcell drawing properties> The photosensitive resin construct for flexographic printing plates was placed on an Esko CDI Crystal 4260, and a WSI pattern described in JP-A-2019-517944 was drawn at a size of 10 mm x 10 mm at 10 mm intervals in a total of 40 locations at a resolution of 4000 dpi, a laser intensity of 3.0 J, and a Boost setting value of 260. After that, 18 of the ablated areas, excluding 22 on the periphery, were observed using a laser microscope (Keyence Corporation, product name: VK-X100, objective lens 100x), and the maximum depth ablated by the laser was used as an index value for laser sensitivity, which was evaluated according to the following criteria: C or higher was considered good. A: All holes penetrate the ablation layer, and the "length between the interface with the photosensitive resin composition layer and the surface of the infrared ablation layer" is 0.50 or more on average at 18 locations. B: All holes penetrate the ablation layer, and the "length between the interface with the photosensitive resin composition layer and the surface of the infrared ablation layer" is 0.45 or more and less than 0.50 on average at 18 locations. C: All holes penetrate the ablation layer, and the "length between the interface with the photosensitive resin composition layer and the surface of the infrared ablation layer" is 0.40 or more and less than 0.45 on average at 18 locations. D: All holes penetrate the ablation layer, and the "length of the interface with the photosensitive resin composition layer / surface of the infrared ablation layer" is 0.30 or more and less than 0.40 on average at 18 locations E: Some have not penetrated the ablation layer.

[0091] <Evaluation of developability in aqueous developers> A developing machine (JOW-A3-P) manufactured by Nippon Denshi Seiki Co., Ltd. was filled with a 1% aqueous solution of Nissan soap, and the cover film of the infrared ablation layer of the photosensitive resin construct for flexographic printing plates was peeled off, followed by development at a liquid temperature of 40°C. The plate was then dried at 60°C for 10 minutes. The time required for development to 0.8 mm was measured. Similarly, the release film was peeled off from the laminate of the support and the photosensitive resin composition layer, and development was carried out. The developability of the infrared ablation layer was evaluated based on how much the development time changed due to the presence of the infrared ablation layer. A grade of C or higher was judged to be good. (Evaluation criteria) A: Even with the infrared ablation layer, the development time was reduced by less than 30 seconds. B: The presence of the infrared ablation layer worsened the development time by 30 seconds or more and less than 1 minute. C: The presence of the infrared ablation layer worsened the development time by 1 minute or more but less than 2 minutes. D: The presence of the infrared ablation layer worsened the development time by 2 minutes or more and less than 5 minutes. E: The presence of the infrared ablation layer meant that sufficient cleaning was not possible even after adding 5 minutes or more.

[0092] [Preparation of flexographic printing plates and evaluation of flexographic printing plates] ((4) Manufacture of flexographic printing plates) The photosensitive resin compositions for flexographic printing plates of Examples 1 to 10 and Comparative Examples 1 to 3 were exposed to ultraviolet light from the support (PET coated with adhesive) side using an ultraviolet exposure machine (JE-A2-SS manufactured by Nippon Denshi Seiki Co., Ltd.) so that the pattern height (RD) after curing was approximately 0.6 mm. Next, the photosensitive resin construct for flexographic printing plates was placed in an Esko CDI Crystal 4260, and a WSI pattern described in JP-A-2019-517944 was drawn at a resolution of 4000 dpi, a laser intensity of 3.0 J, and a Boost setting value of 260, in a total of 40 locations with a size of 10 mm x 10 mm and 10 mm intervals, and then exposed to 8000 mJ in an atmospheric environment from the side of the infrared ablation layer using the exposure machine. After exposure, a developing machine (JOW-A3-P) manufactured by Nippon Denshi Seiki was filled with a 1% aqueous solution of Nissan soap, and development was carried out at a liquid temperature of 40° C. to remove the unexposed areas. After drying at 60°C for 10 minutes, the plate was post-exposed with an ultraviolet sterilization lamp and an ultraviolet chemical lamp to remove surface tackiness, thereby obtaining a flexographic printing plate.

[0093] (Flexographic printing plate evaluation: printing unevenness) Actual printing evaluation was carried out using a flexographic printing plate. An AI-3 type flexographic printing machine (manufactured by Iyo Kikai) was used, and Process X Cyan (trade name, manufactured by Toyo Ink Mfg. Co., Ltd.) was used as the solvent ink, and OPP film was used as the printing substrate. The anilox roll is 1200 lpi (cell volume 2.2 cm 3 / m 2) and 3M1020 (trade name, manufactured by Sumitomo 3M Limited) was used for the cushion tape, and 10 m of printing was performed at a printing speed of 100 m / min. For the final printed portion corresponding to the flexographic printing plate, the print density was measured using eXact Basic (manufactured by X-rite) for 18 portions of the formed WSI pattern, excluding 22 portions on the periphery. The unevenness of print density was evaluated based on the difference between the maximum and minimum print density values at all 18 points. A grade of C or higher was considered good. A: The difference between the maximum and minimum print density is less than 0.05 B: The difference between the maximum and minimum print density is 0.05 or more and less than 0.08 C: The difference between the maximum and minimum print density values is 0.08 or more and less than 0.11 D: The difference between the maximum and minimum print density values is 0.11 or more and less than 0.14 E: The difference between the maximum and minimum print density values is 0.14 or more

[0094] The evaluation results of the photosensitive resin constructs for flexographic printing plates and the flexographic printing plates in Examples 1 to 10 and Comparative Examples 1 to 3 are shown in Table 2 below.

[0095] [Table 2] [Industrial Applicability]

[0096] The photosensitive resin support structure of the present invention has industrial applicability in the field of flexographic printing plate manufacturing. [Explanation of symbols]

[0097] (A) Support (B) Photosensitive resin composition layer (B') Printing pattern (C) Infrared ablation layer (C') Infrared ablation layer mask

Claims

1. A photosensitive resin construct for a flexographic printing plate, comprising at least (A) a support, (B) a photosensitive resin composition layer, and (C) a water-soluble infrared ablation layer containing carbon black and a resin a, laminated in this order, The carbon black has a primary particle diameter of 13 nm or more and 19 nm or less, R calculated by the following formula (1) using the Hansen solubility parameter (HSP value) of the resin a and the Hansen solubility parameter (HSP value) of the carbon black is 13.1 or more and 17.0 or less. Photosensitive resin composition for flexo printing plates. R=(4a) ２ +b ２ +c ２ ) ０．５ ・・・formula (1) α = absolute value of the difference between δd of resin a and δd of carbon black β = absolute value of the difference between δp of resin a and δp of carbon black γ = absolute value of the difference between δh of resin a and δh of carbon black δd: Energy due to intermolecular dispersion forces δp: Energy due to intermolecular dipole interactions δh: Energy due to hydrogen bonds between molecules

2. The resin a includes at least one selected from the group consisting of polyamide, polybutyral, polyvinyl alcohol, poly(meth)acrylate, and modified or partially saponified products thereof. The photosensitive resin construct for a flexographic printing plate according to claim 1.

3. The DBP absorption of the carbon black is 40 cm ３ / 100g or more 80cm ３ / 100g, The photosensitive resin construct for a flexographic printing plate according to claim 1 or 2.

4. The blending mass ratio of the resin a to the carbon black in the infrared ablation layer (C) (resin a / carbon black) is 90 / 10 to 50 / 50, The photosensitive resin construct for a flexographic printing plate according to any one of claims 1 to 3.

5. 1. A method for producing a flexographic printing plate, comprising: The photosensitive resin construct for a flexographic printing plate according to any one of claims 1 to 4, (A) the step of irradiating with ultraviolet light from the support side; (C) a step of irradiating the infrared ablation layer with infrared rays to draw and process a pattern; (B) a step of irradiating the photosensitive resin composition layer with ultraviolet light to perform pattern exposure; a step of removing the unexposed areas of the (C) infrared ablation layer and the (B) photosensitive resin composition layer; A method for producing a flexographic printing plate comprising:

6. a manufacturing step of manufacturing a flexographic printing plate by the manufacturing method according to claim 5; a step of applying ink to the raised portions of the flexographic printing plate obtained in the manufacturing step; transferring the ink to a substrate; A printing method including:

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