JP7724169B2 - Photosensitive resin composition for flexographic printing plate, method for producing flexographic printing plate, and printing method - Google Patents

Description

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.

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

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.

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 for the ablation layer, and Patent Document 2 proposes a technique of using an acrylic resin and NBR in combination.

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.

Patent No. 6358523 JP 2012-137515 A

However, even when using the above-mentioned technology of placing microcells on the surface of a flexographic printing plate, when the ablation resolution increases from the conventional 2540 DPI to 4000-5080 DPI, it becomes difficult to obtain uniform microcells, resulting in the problem of uneven density in solid areas when using a high-resolution anilox roll.

In view of the problems with the prior art discussed above, the present invention aims to provide a photosensitive resin construct for flexographic printing plates that has an infrared ablation layer that is uniform in-plane ablation by an infrared laser and can uniformly form microcells, thereby improving density unevenness within a solid area while maintaining water-developability, as well as a method for manufacturing a flexographic printing plate and a printing method using the same.

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.

[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=(4α ² +β ² +γ ² ) ^0.5 ...Formula (1)
α = absolute value of difference between δd of resin a and δd of carbon black β = absolute value of difference between δp of resin a and δp of carbon black γ = absolute value of 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 photosensitive resin construct for flexographic printing plates according to [1] or [2] above, wherein the carbon black has a DBP absorption of 40 cm ³ /100 g or more and 80 cm ³ /100 g or less.
[4]
[4] The photosensitive resin construct for a flexographic printing plate 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:

The present invention provides a photosensitive resin construct for flexographic printing plates that has an infrared ablation layer that can uniformly form microcells even when high resolution is achieved without impairing water developability, as well as a method for manufacturing a flexographic printing plate and a printing method using the same.

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. 1 shows a schematic diagram of a method for manufacturing a flexographic printing plate.

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.

[Photosensitive resin composition for flexographic 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 ...Formula (1)
α = absolute value of difference between δd of resin a and δd of carbon black β = absolute value of difference between δp of resin a and δp of carbon black γ = absolute value of 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 bonding

By having the above-mentioned configuration, a photosensitive resin composition for flexographic printing plates can be obtained that has an infrared ablation layer that can uniformly form microcells even when high resolution is achieved without compromising water developability.

((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 support (A) is not limited to the following, but examples thereof include polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate.
The thickness of the support (A) 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.

((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 on 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 is 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 photosensitive resin composition layer (B) will be described in detail below.

<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. 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.

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

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.

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.

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 in terms of 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):
(A-B) _n , A-(B-A) _n , A-(B-A) _n -B, B-(A-B) _n
General formula group (II):
[(A-B) _k ] _m -X, [(A-B) _k -A] _m -X, [(B-A) _k ] _m -X, [(B-A) _k -B] _m -X
In the general formula groups (I) and (II), A represents a polymer block composed of a monovinyl-substituted aromatic hydrocarbon. B represents a polymer block composed 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.

The contents of conjugated dienes and monovinyl-substituted aromatic hydrocarbons in the thermoplastic elastomer (b-1) can be measured using a nuclear magnetic resonance ( ¹ H-NMR) spectrometer. Specifically, ^{the 1} H-NMR measurement can be performed using a JNM-LA400 (trade name, manufactured by JEOL) as the measurement 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, the number of scans of 64, 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 in the range of 10/90 to 85/15, and even more preferably in the range of 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.

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 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.

<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 its derivatives are 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 derivative 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.

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

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.

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.

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.

<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.

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; 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.

From the viewpoint of the printing durability of a flexographic printing plate manufactured 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.

<Liquid diene>
The photosensitive resin composition layer (B) preferably contains a liquid diene.
Liquid dienes are compounds that have a liquid carbon-carbon double bond.
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.

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.

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 a flexographic printing plate of this embodiment and the flexographic printing plate 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 can be determined from the peak ratio in ^{the 1H} -NMR (magnetic resonance spectrum) of the liquid polybutadiene.
1,2-Polybutadiene, which is a liquid polybutadiene having a 1,2-vinyl bond, has a vinyl double bond in a 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.

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 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. In both cis-type and trans-type 1,4-polybutadienes, the presence of a vinyl group, which is a double bond, within the polymer makes it possible to form a flexible resin with low reactivity in radical polymerization.

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.

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 the printing durability and handling properties of the flexographic printing plate obtained using the photosensitive resin construct for flexographic printing plates 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.

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.

<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.

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, 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.

Examples of 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.

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, 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenyl acrylate, and the like.
The thermal polymerization inhibitor and the antioxidant may be used alone or in combination of two or more.

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.
The dyes and pigments shown below may also be used as ultraviolet absorbers.
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.

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.

((C) Infrared Ablation Layer)
The photosensitive resin construct for a flexographic printing plate of this embodiment has the infrared ablation layer (C) laminated on the photosensitive resin composition layer (B) described above.
(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.
The infrared ablation layer (C) is water-soluble.

<Resin a>
Resin a contained in the infrared ablation layer (C) constituting the photosensitive resin construct for a flexographic printing plate 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.

<Carbon black>
The photosensitive resin construct for a flexographic printing plate 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, thereby obtaining good dispersibility and even higher laser sensitivity.
Furthermore, when the primary particle size of the carbon black is 19 nm or less, desired high laser sensitivity and water developability can be obtained, and good microcells can be formed.
In order to more easily and stably form the infrared ablation layer (C), 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 infrared ablation layer (C) at the interface with the photosensitive resin composition layer (B) 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 photosensitive resin composition layer (B), 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 an excellent shape, and a flexographic printing plate using the same.
The primary particle size of the carbon black contained in the infrared ablation layer (C) can be determined by observation with an electron microscope. Specifically, it can be determined by the method described in the Examples.

(C) The primary particle size of the carbon black contained in the infrared ablation layer can be controlled within the above numerical range by selecting a carbon black with an appropriate particle size from various commercially available products.

Furthermore, it is preferable that the carbon black has a small structure, since a small structure increases the contact area between the carbon black and the resin a, improving dispersibility and thereby improving the uniformity of the microcells.
Specifically, the DBP absorption of the carbon black is preferably 40 cm ³ /100 g or more and 80 cm ³ /100 g or less, more preferably 50 cm ³ /100 g or more and 80 cm ³ /100 g or less, even more preferably 53 cm ³ /100 g or more and 80 cm ³ /100 g or less, and even more preferably 56 cm ³ /100 g or more and 80 cm ³ /100 g or less. Within this range, the above-mentioned effects are observed.

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.
The DBP absorption amount of the carbon black contained in the infrared ablation layer (C) can be controlled within the above range by selecting an appropriate value from various commercially available products.

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.

To obtain uniform microcells, the (C) infrared ablation layer must be uniform within its surface. To achieve this, good carbon black dispersibility is important, and the relationship between resin a and carbon black in the (C) infrared ablation layer is also important. The dispersibility of carbon black in resin a tends to deteriorate if the polarities are too close or too far apart.

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 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 composed of the following three parameters (unit: MPa ^0.5 ):
δd: Energy due to intermolecular dispersion forces
δp: Energy due to intermolecular dipole interactions
δh: Energy due to hydrogen bonds between molecules
These three parameters can be considered as coordinates in a three-dimensional space (Hansen space). 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."

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.
Formula (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 difference between δp of resin a and δp of carbon black γ = Absolute value of 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 bonding

By ensuring that R calculated by formula (1) falls within the above range, the dispersibility of the carbon black is improved, and the dispersibility of carbon black with a small particle size in particular can be maintained at a good level, thereby increasing laser sensitivity.

(C) The Hansen solubility parameter (HSP value) of resin a and the Hansen solubility parameter (HSP value) of carbon black in the infrared ablation layer can be controlled within the above-mentioned 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 its surface. Specifically, when carbon black is oxidized to increase its polarity (low pH), the HSP value of the carbon black shifts toward the high-polarity side. Furthermore, the smaller the particle size of the carbon black, the more highly polar the HSP value of the carbon black tends to become, and the more less polar the HSP value of the carbon black tends to become.
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.

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 in the range of 90/10 to 50/50, more preferably 80/20 to 50/50, even more preferably 75/25 to 55/45, and still 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.

The infrared ablation layer (C) of the photosensitive resin construct for flexographic printing plates of this embodiment should have a thicker film thickness from the viewpoint of ensuring light-shielding 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 should have a thinner film thickness from the viewpoint of increasing 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.

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). The optical density is measured by the so-called visual sense (ISO visual), and the light to be measured has a wavelength range of about 400 to 750 nm.

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 the carbon black and a resin-compatible portion compatible with the 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.

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 resultant 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-kneaded 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 resin a in a solution state.
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. Only one solvent may be used, or two or more solvents may be mixed and used.

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 structure 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.

((D) Middle class)
The photosensitive resin construct for a flexographic printing plate of this embodiment may further include one or more (D) intermediate layers between the (B) photosensitive resin composition layer and the (C) infrared ablation layer.
The (D) 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.

In order to produce a high-definition print having 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 irradiation with ultraviolet light, the curing proceeds by radical polymerization. If oxygen is present during this radical polymerization, the radical-generating compound reacts with 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, and the pattern ultimately formed on the flexographic printing plate will have a shape 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, and unreacted portions are likely to occur 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 a flat portion at its tip. Therefore, when attempting to produce a pattern with a flat portion at its tip, it is effective to reduce the amount of oxygen that comes into contact with the photosensitive resin composition layer (B) by making the intermediate layer (D) have oxygen inhibition ability.

Furthermore, the (D) intermediate layer may be an adhesive layer that improves the adhesion between the (B) photosensitive resin composition layer and the (C) infrared ablation layer. This tends to further improve handleability.

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 on 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 a flexographic printing plate of this embodiment has the physical strength and heat resistance required for a protective layer.

[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, to obtain a flexographic printing plate (relief printing plate) made of a 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.

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.

(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 performed 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.

(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 on an infrared ablation layer as described in JP-A-2019-517944.
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 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 construct 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.

(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 performing pattern exposure. During this process, the light passing through the mask promotes the curing reaction of the (B) photosensitive resin composition layer, and the pattern formed on 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.

(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 photosensitive resin composition layer (B) 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.

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.

The alkaline aqueous solution may also contain a pH adjuster. The pH adjuster may be either an organic or 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.

[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.

The present embodiment will be explained in more detail below using specific examples and comparative examples, but the present invention is not limited in any way by the following examples and comparative examples.

[Method for measuring Hansen Solubility Parameter (HSP)]
Hansen solubility parameters were measured using the personal computer software HSPiP.
To measure the HSP of resin a in the infrared ablation layer, 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 were used as solvents. 10 g of each solvent was placed in a 20 mL vial, and 0.1 g of resin a was mixed therein. After 24 hours, the presence or absence of residual solvent was confirmed, and those with no residual solvent were considered to be in a dissolved state. Next, the above results, i.e., the results of whether or not each solvent dissolved, were input using the Sphere program, and the HSP was calculated by calculation on the software.
The HSP of carbon black was also measured using the same solvent as that used to measure resin a in the infrared ablation layer. 10 g of each solvent was placed in a 20 mL vial, 0.1 g of carbon black was mixed therein, and the mixture was gently shaken by hand. After leaving the mixture to stand for 30 minutes, the presence or absence of black turbidity was confirmed, and those that exhibited turbidity were considered to be in a dispersed state. The HSP was then determined in the same manner as for 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 difference between δd of resin a and δd of carbon black β = Absolute value of difference between δp of resin a and δp of carbon black γ = Absolute value of 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 bonding

[Evaluation of primary particle size of carbon black]
The photosensitive resin construct for flexographic printing plates was cut to an appropriate size and then embedded in a UV-curable resin. After embedding in the resin, a cross section was prepared by a cryomicrotome method and used as a SEM observation sample.
<Cross-section processing conditions>
Equipment used: Ultramicrotome UC6 (manufactured by LEICA)
Set temperature: -80℃
Set cutting thickness: 100 nm
<SEM observation conditions>
Measuring device: Scanning electron microscope S4800 (Hitachi)
Acceleration voltage: 1.0 kV
Observation magnification: 5000 times. The minor axis diameters of 10 randomly selected particles of carbon black were measured from the cross-sectional SEM image obtained, and the average value (number average) was taken as the primary particle diameter of the carbon black.

[DBP absorption of carbon black]
The DBP absorption of carbon black was measured by the method specified in JIS K6217-4.

[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.

((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 a reactive emulsifier, ammonium salt of (α-sulfo(1-nonylphenoxy)methyl-2-(2-propenyloxy)ethoxy-poly(oxy-1,2-ethanediyl) "ADEKA REASOAP" (manufactured by Asahi Denka Kogyo Co., Ltd.), 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 t-dodecyl mercaptan and 2 parts by mass of acrylic acid, 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 over 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 netting, 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.

((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 mass of Tufprene 912 (trade name, manufactured by Asahi Kasei Corporation), which is a block copolymer of styrene and 1,3-butadiene, 38 parts by mass of paraffin oil (average carbon number 33, average molecular weight 470, density at 15°C 0.868), 2.5 parts by mass of 1,9-nonanediol diacrylate, 1.5 parts by mass of 2,2-dimethoxy-phenylacetophenone, 3 parts by mass of Epoxy Ester 3000M (trade name, manufactured by Kyoeisha Chemical Co., Ltd.), and 1.5 parts by mass 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%.
Thereafter, using a knife coater, the mixture was applied to one side of a 100 μm thick polyester film so as to give an ultraviolet transmittance (UV transmittance) of 10%, and then dried at 80° C. for 1 minute to obtain a support (base film) having 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).

((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 the mixture was kneaded for a further 20 minutes to obtain a photosensitive resin composition.
Next, a photosensitive resin composition was placed in an extrusion molding machine, and the adhesive layer-forming surface of the support was bonded to one surface of the photosensitive resin composition layer extruded from a T-die. A release film (Diafoil MRV100, manufactured by Mitsubishi Chemical Corporation) was then bonded to the surface of the photosensitive resin composition layer opposite to the support-lamination side, thereby obtaining a laminate of the support and the photosensitive resin composition layer.

((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 Corporation, #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 would serve 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 is a laminate of an infrared ablation layer and a cover film.

<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: Carbon black manufactured by Mitsubishi Chemical MA8: Carbon black manufactured by Mitsubishi Chemical Ketjenblack EC300J: Carbon black manufactured by Lion Specialty Chemicals POVAL 3-98: Polyvinyl alcohol resin manufactured by Kuraray AQ Nylon A-90: Polyamide manufactured by Toray S-LEC BL-5Z: Polyvinyl butyral resin manufactured by Sekisui Chemical

((3) Production of photosensitive resin constituent for flexographic printing plate)
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 infrared ablation layer laminate 1 was laminated in an environment of a temperature of 25°C and a humidity of 40% 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 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.

[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.

[Evaluation of photosensitive resin constituents for flexographic printing plates]
<Evaluation of microcell drawing properties>
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 size of 10 mm x 10 mm and 10 mm intervals at 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.
Thereafter, 18 locations of the ablation area, excluding 22 locations 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. A grade of C or higher was considered good.
A: All holes penetrate the ablation layer, and the "length of the interface with the photosensitive resin composition layer/surface of the infrared ablation layer" averaged over 18 locations is 0.50 or more. B: All holes penetrate the ablation layer, and the "length of the interface with the photosensitive resin composition layer/surface of the infrared ablation layer" averaged over 18 locations is 0.45 or more and less than 0.50. C: All holes penetrate the ablation layer, and the "length of the interface with the photosensitive resin composition layer/surface of the infrared ablation layer" averaged over 18 locations is 0.40 or more and less than 0.45. 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" averaged over 18 locations is 0.30 or more and less than 0.40. E: Some holes do not penetrate the ablation layer.

<Evaluation of developability in aqueous developer>
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 resulting material was 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 presence of 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 increased the development time by 1 minute or more and 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 prevented sufficient cleaning even after adding 5 minutes or more.

[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 from the support (PET coated with an 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 would be about 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 spaced 10 mm apart, and then the pattern was exposed to 8000 mJ in the air from the infrared ablation layer side 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 to an ultraviolet sterilization lamp and an ultraviolet chemical lamp to remove surface tackiness, thereby obtaining a flexographic printing plate.

(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, 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 used was 1200 lpi (cell volume 2.2 cm ³ /m ² ), and the cushion tape was 3M1020 (trade name, manufactured by Sumitomo 3M Limited). The printing speed was 100 m/min, and 10 m was printed. For the final printed location corresponding to the flexographic printing plate, the print density was measured using eXact Basic (manufactured by X-rite) at 18 locations of the formed WSI pattern, excluding 22 locations 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 judged to be good.
A: The difference between the maximum and minimum print density values is less than 0.05. B: The difference between the maximum and minimum print density values 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.

The evaluation results for 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.

The photosensitive resin support structure of the present invention has industrial applicability in the field of flexographic printing plate manufacturing.

(A) Support (B) Photosensitive resin composition layer (B') Printing pattern (C) Infrared ablation layer (C') Mask for infrared ablation layer

Claims (6)

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=(4α ² +β ² +γ ² ) ^0.5 ...Formula (1)
α = absolute value of difference between δd of resin a and δd of carbon black β = absolute value of difference between δp of resin a and δp of carbon black γ = absolute value of 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 bonding 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. The carbon black has a DBP absorption of 40 cm ³ /100 g or more and 80 cm ³ /100 g or less.
The photosensitive resin construct for a flexographic printing plate according to claim 1 or 2. 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. 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: 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: