Flexographic printing plate master and flexographic printing plate

Abstract

To provide: a flexographic printing plate precursor which has excellent water developability and with which a flexographic printing plate having excellent printing durability, handleability, and rear end ink receptivity can be obtained; and a flexographic printing plate obtained by exposing and developing the flexographic printing plate precursor.SOLUTION: A water-developable flexographic printing plate precursor according to the present invention has a photosensitive layer containing: water-dispersible particles; a polymer having reactive functional groups at both ends thereof and having a weight average molecular weight of at least 5,000; and a polyfunctional monomer having three or more ethylenically unsaturated groups.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a flexographic printing plate original and a flexographic printing plate.

Background Art

[0002] Flexographic printing is a printing method in which ink is applied to the convex portions of a printing plate using an anilox roll or the like and transferred to a printing object. As a flexographic printing plate used for flexographic printing, for example, a flexographic printing plate original having a photosensitive layer, which has been imagewise exposed and developed, is used. On the other hand, from the viewpoints of improving the working environment and conserving the global environment, there is a movement in various industries to reduce the use of organic solvents, and there is a demand for a flexographic printing plate original that can be developed with an aqueous developer. For example, Claim 1 of Patent Document 1 discloses a photosensitive resin composition that can be developed with an aqueous developer when used as a flexographic printing plate original.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Under such circumstances, when the present inventor produced a flexographic printing plate original using the photosensitive resin composition described in the examples of Patent Document 1, it was confirmed that the original was indeed excellent in developability (water developability) with an aqueous developer. However, on the other hand, when a flexographic printing plate was produced using the above flexographic printing plate original, it was revealed that although chipping of the image portion hardly occurred (excellent in printing durability and handling properties), white spots were likely to occur at the rear end (the rear end build-up property was insufficient).

[0005] Therefore, in view of the above circumstances, the object of the present invention is to provide a flexographic printing plate master that exhibits excellent water-developability and excellent print resistance, handling properties, and trailing edge ink adhesion when made into a flexographic printing plate, as well as a flexographic printing plate obtained by exposing and developing the above flexographic printing plate master. [Means for solving the problem]

[0006] As a result of diligent research into the above-mentioned problems, the inventors of the present invention have found that the above-mentioned problems can be solved by using in combination water-dispersible particles, a polymer with a weight-average molecular weight of 5,000 or more having reactive functional groups at both ends, and a polyfunctional monomer having three or more ethylenically unsaturated groups, leading to the present invention. In other words, the inventors have found that the above problem can be solved by the following configuration.

[0007] (1) A water-developable flexographic printing plate master having a photosensitive layer containing water-dispersible particles, a polymer with a weight-average molecular weight of 5,000 or more having reactive functional groups at both ends, and a polyfunctional monomer having three or more ethylenically unsaturated groups. (2) The water-developable flexographic printing plate according to (1) above, wherein the photosensitive layer further contains a monofunctional monomer. (3) The water-developable flexographic printing plate according to (2) above, wherein in the photosensitive layer, the ratio of the content of monofunctional monomers to the content of polyfunctional monomers is 0.5 or less by mass ratio. (4) A water-developable flexographic printing plate according to any one of (1) to (3) above, wherein the ratio of the content of the polyfunctional monomer to the content of the polymer in the photosensitive layer is 3.0 or less by mass ratio. (5) A flexographic printing plate having an image area and a non-image area, A flexographic printing plate in which the image portion is obtained by exposing the photosensitive layer of a water-developable flexographic printing plate master described in any of (1) to (4) above to an image and developing it. [Effects of the Invention]

[0008] As shown below, the present invention provides a flexographic printing plate master that exhibits excellent water-developability and, when made into a flexographic printing plate, excellent print resistance, handling properties, and trailing edge ink adhesion, as well as a flexographic printing plate obtained by exposing and developing the above-mentioned flexographic printing plate master. [Modes for carrying out the invention]

[0009] The present invention will be described in detail below. The following description of the constituent elements may be based on typical embodiments of the present invention, but the present invention is not limited to such embodiments. In this specification, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower and upper limits, respectively. Furthermore, each component may be used alone or in combination of two or more. When two or more components are used in combination, the "content" of each component refers to the total content unless otherwise specified. Furthermore, "(meth)acrylic" is a notation that represents "acrylic" or "methacrylic," "(meth)acrylate" is a notation that represents "acrylate" or "methacrylate," and "(meth)acryloyl" is a notation that represents "acryloyl" or "methacryloyl."

[0010] [Water-developable flexographic printing plates] The water-developable flexographic printing plate of the present invention (hereinafter also referred to as "the printing plate of the present invention") is a water-developable flexographic printing plate having a photosensitive layer containing water-dispersible particles, a polymer with a weight-average molecular weight of 5,000 or more having reactive functional groups at both ends (hereinafter also referred to as "specific polymer"), and a polyfunctional monomer having three or more ethylenically unsaturated groups (hereinafter also referred to as "specific monomer").

[0011] The printing plate master of the present invention has the above-mentioned effects because it has the above-mentioned configuration. The reason for this is not clear, but it is thought that a polymer with a weight-average molecular weight of 5,000 or more having reactive functional groups at both ends (a specific polymer) and a polyfunctional monomer with three or more ethylenically unsaturated groups (a specific monomer) form a three-dimensional structure with excellent toughness and rubber elasticity.

[0012] The following describes, first, the photosensitive layer of the printing plate of the present invention, and then a preferred embodiment of the printing plate of the present invention.

[0013] [Photosensitive layer] The photosensitive layer of the printing plate master of the present invention (hereinafter also referred to as "the photosensitive layer of the present invention") has a photosensitive layer containing water-dispersible particles, a polymer (specific polymer) having reactive functional groups at both ends and a weight-average molecular weight of 5,000 or more, and a polyfunctional monomer (specific monomer) having three or more ethylenically unsaturated groups. The following describes each component contained in the photosensitive layer.

[0014] <Water dispersible particles> As described above, the photosensitive layer of the present invention contains water-dispersible particles. While there are no particular limitations on the water-dispersible particles, polymers are preferred because they exhibit superior water dispersibility, resulting in superior print durability, handling, and trailing edge ink adhesion of the resulting flexographic printing plate, as well as superior development reproducibility, solid color quality, and a wider printing pressure latitude. Hereinafter, "superior water dispersibility, resulting in superior print durability, handling, and trailing edge ink adhesion of the resulting flexographic printing plate, as well as superior development reproducibility, solid color quality, and a wider printing pressure latitude" will also be referred to as "superior effects of the present invention." Specific examples of the above polymer include diene polymers (e.g., polybutadiene, natural rubber, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, methyl methacrylate-butadiene copolymer, polychloroprene, polyisoprene), polyurethanes, vinyl pyridine polymers, butyl polymers, thiokol polymers, acrylate polymers, polymers obtained by copolymerizing these polymers with other components such as acrylic acid and methacrylic acid, etc. These may be used alone or in combination of two or more. The above polymer is preferably a diene polymer, and more preferably polybutadiene, for reasons that the effects of the present invention are more excellent. The above polymer preferably does not have reactive functional groups (e.g., (meth)acryloyloxy groups) at both ends.

[0015] The above polymer is preferably a polymer obtained by removing water from an aqueous dispersion latex, for reasons that the effects of the present invention are more excellent. Specific examples of the above aqueous dispersion latex include the aqueous dispersion latexes of the specific examples of the above polymers.

[0016] In the photosensitive layer of the present invention, the content of the water-dispersible particles is preferably 5 to 80% by mass, more preferably 10 to 50% by mass, and even more preferably 20 to 40% by mass, based on the total solid content of the photosensitive layer of the present invention, for reasons that the effects of the present invention are more excellent.

[0017] <Specific polymer> As described above, the photosensitive layer of the present invention contains a polymer (specific polymer) having reactive functional groups at both ends and a weight average molecular weight of 5,000 or more. The specific polymer is a polymer having reactive functional groups at both ends and a weight average molecular weight of 5,000 or more. <ID= The specific polymer preferably does not have water dispersibility. In this specification, "telechelic polymer" refers to a polymer having reactive functional groups at both ends, and "specific polymer" refers to a telechelic polymer with a weight-average molecular weight of 5,000 or more.

[0018] (Main chain) The polymers that make up the main chain of a particular polymer are not particularly limited, but examples include thermoplastic polymers. The above-mentioned thermoplastic polymer is not particularly limited as long as it is a polymer exhibiting thermoplasticity. Specific examples include polystyrene resin, polyester resin, polyamide resin, polysulfone resin, polyethersulfone resin, polyimide resin, acrylic resin, acetal resin, epoxy resin, polycarbonate resin, rubber, and thermoplastic elastomers. Of these, rubber and thermoplastic elastomers are preferred, rubber is more preferred, and diene rubber is even more preferred, because they facilitate the formation of more flexible and pliable films.

[0019] Specifically, examples of the above-mentioned rubbers include butadiene rubber (BR), nitrile rubber (NBR), acrylic rubber, epichlorohydrin rubber, urethane rubber, isoprene rubber, styrene-isoprene rubber, styrene-butadiene rubber, ethylene-propylene copolymer, and chlorinated polyethylene. These may be used individually or in combination of two or more. Of these, at least one rubber selected from the group consisting of butadiene rubber (BR) and nitrile rubber (NBR) is preferred, with butadiene rubber being more preferred, due to its superior water-developability, drying properties, and image reproducibility.

[0020] Examples of the above-mentioned thermoplastic elastomers include polybutadiene-based thermoplastic elastomers, polyisoprene-based thermoplastic elastomers, polyolefin-based thermoplastic elastomers, and acrylic-based thermoplastic elastomers. Specifically, examples include SB (polystyrene-polybutadiene), SBS (polystyrene-polybutadiene-polystyrene), SIS (polystyrene-polyisoprene-polystyrene), SEBS (polystyrene-polyethylene / polybutylene-polystyrene), ABS (acrylonitrile butadiene styrene copolymer), ACM (acrylic acid ester rubber), ACS (acrylonitrile chlorinated polyethylene styrene copolymer), acrylonitrile styrene copolymer, syndiotactic 1,2-polybutadiene, and polymethyl methacrylate-polybutyl acrylate-polymethyl methacrylate. Of these, SBS and SIS are particularly preferred from the viewpoint of better water developability, as well as drying properties and image reproducibility.

[0021] (end) The specific polymer has reactive functional groups at both ends. The above-mentioned reactive functional group is not particularly limited, but it is preferably an ethylenically unsaturated group because it provides superior effects of the present invention. The above ethylenically unsaturated group is preferably a vinyl group (CH2=CH-), an allyl group (CH2=CH-CH2-), a (meth)acryloyl group, or a (meth)acryloyl group, and more preferably a (meth)acryloyloxy group, for reasons that the effects of the present invention are superior.

[0022] The specific polymer may have reactive functional groups at both ends of the polymer constituting the main chain via divalent linking groups. The above-mentioned divalent linking groups are not particularly limited, but include, for example, linear, branched, or cyclic divalent aliphatic hydrocarbon groups (e.g., alkylene groups such as methylene, ethylene, and propylene groups), divalent aromatic hydrocarbon groups (e.g., phenylene group), -O-, -S-, -SO2-, and -NR. L -, -CO-, -NH-, -COO-, -CONR L-, -O-CO-O-, -SO3-, -NHCOO-, -SO2NR L -, -NH-CO-NH- or groups formed by combining two or more of these (for example, alkylene oxy group, alkylene oxycarbonyl group, alkylene carbonyl oxy group, etc.). Here, R L This represents a hydrogen atom or an alkyl group (preferably with 1 to 10 carbon atoms).

[0023] (molecular weight) The weight-average molecular weight (Mw) of the specific polymer is 5,000 or more. The Mw of the specific polymer is preferably 6,000 or more, more preferably 7,000 or more, even more preferably 8,000 or more, and particularly preferably 9,000 or more, for reasons that the effects of the present invention are superior. There is no particular upper limit to the Mw of the specific polymer, but it is preferably 500,000 or less, and more preferably 100,000 or less, for reasons that the effects of the present invention are superior. Here, the weight-average molecular weight is measured by gel permeation chromatography (GPC) and converted to standard polystyrene. Specifically, for example, the GPC uses HLC-8220GPC (manufactured by Tosoh Corporation), with three columns (TSKgeL Super HZM-H, TSKgeL SuperHZ4000, TSKgeL SuperHZ2000, manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) and THF (tetrahydrofuran) as the eluent. The conditions are a sample concentration of 0.35 mass%, a flow rate of 0.35 mL / min, a sample injection volume of 10 μL, and a measurement temperature of 40°C, and the measurement is performed using an IR detector. Furthermore, the calibration curve will be prepared using eight samples from Tosoh Corporation's "Standard Samples TSK standard, polystyrene": "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000", and "n-propylbenzene".

[0024] (HSP value) The HSP (Hansen solubility parameter) value of the specific polymer is not particularly limited, but it is preferably 8 to 12, more preferably 8.5 to 11, and even more preferably 8.5 to 10.5, for reasons that the effects of the present invention are superior.

[0025] (Content) In the photosensitive layer of the present invention, the content of the specific polymer is preferably 1 to 50% by mass, more preferably 5 to 40% by mass, even more preferably 7 to 30% by mass, and particularly preferably 10 to 20% by mass, relative to the total solid content of the photosensitive layer of the present invention, for reasons that the effects of the present invention are superior.

[0026] <Specific monomers> As described above, the photosensitive layer of the present invention contains a polyfunctional monomer (specific monomer) having three or more ethylenically unsaturated groups. The above-mentioned specific monomers are not particularly limited as long as they are compounds having three or more ethylenically unsaturated groups. The above ethylenically unsaturated group is preferably a vinyl group (CH2=CH-), an allyl group (CH2=CH-CH2-), a (meth)acryloyl group, or a (meth)acryloyl group, and more preferably a (meth)acryloyloxy group, for reasons that the effects of the present invention are superior. Examples of specific monomers include pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, and triallyl trimelitate.

[0027] In the photosensitive layer of the present invention, the content of specific monomers is preferably 1 to 40% by mass, more preferably 2 to 30% by mass, even more preferably 5 to 30% by mass, and particularly preferably 10 to 20% by mass, based on the total solid content of the photosensitive layer of the present invention, for reasons that the effects of the present invention are superior.

[0028] <Specific monomers / specific polymers> In the photosensitive layer of the present invention, the ratio of the content of the specific monomer to the content of the specific polymer described above is preferably 5.0 or less by mass, more preferably 3.0 or less, even more preferably 2.0 or less, and particularly preferably 1.5 or less, for reasons that the effects of the present invention are superior. The lower limit of the above ratio is not particularly limited, but it is preferably 0.2 or more, more preferably 0.4 or more, even more preferably 0.6 or more, and particularly preferably 0.7 or more. Hereinafter, the ratio (mass ratio) of the content of the specified monomer to the content of the specified polymer mentioned above will also be referred to as "specified monomer / specified polymer".

[0029] <Optional ingredients> The photosensitive layer of the present invention may contain components other than those described above (optional components).

[0030] (Monofunctional monomer) The photosensitive layer of the present invention preferably contains a monofunctional monomer for reasons that the effects of the present invention are superior. The above monofunctional monomer is preferably a compound having one ethylenically unsaturated group, for reasons that the effects of the present invention are superior. Specific examples of the above ethylenically unsaturated group are as described above.

[0031] Examples of compounds having one ethylenically unsaturated group include, N-vinyl compounds such as N-vinylformamide; (meth)acrylamide compounds such as (meth)acrylamide, N-methylol(meth)acrylamide, diacetone(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, (meth)acryloylmorpholine, and (meth)acrylamide; 2-Hydroxyethyl (meth)acrylate, Butoxyethyl (meth)acrylate, Carbitol (meth)acrylate, Cyclohexyl (meth)acrylate, Tetrahydrofurfuryl (meth)acrylate, Benzyl (meth)acrylate, Tridecyl (meth)acrylate, 2-Phenoxyethyl (meth)acrylate, Glycidyl (meth)acrylate, Isobornyl (meth)acrylate, Dicyclopentenyl (meth)acrylate, Dicyclopentenyloxyethyl (meth)acrylate, Dicyclopentanyl (meth)acrylate, 2-Hydroxy-3-Phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl phthalate, Methoxy-polyethylene glycol (meth)acrylate, 2-(meth)acryloyloxyethyl phthalate (meth)acrylate compounds such as 2-hydroxyethylphthalic acid, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethoxylated phenyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinic acid, nonylphenol EO adduct (meth)acrylate, phenoxy-polyethylene glycol (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, lactone-modified (meth)acrylate, stearyl (meth)acrylate, isoamyl (meth)acrylate, isomiristyl (meth)acrylate, isostearyl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, and others; Methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, t-butyl vinyl ether, n-octadecyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, dodecyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, cyclohexylmethyl vinyl ether, 4-methylcyclohexylmethyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether Monovinyl ether compounds such as ethoxyethoxyethyl vinyl ether, methoxypolyethylene glycol vinyl ether, tetrahydrofryl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexylmethyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chloroethyl vinyl ether, chlorobutyl vinyl ether, chloroethoxyethyl vinyl ether, phenylethyl vinyl ether, phenoxypolyethylene glycol vinyl ether, cyclohexanedimethanol monovinyl ether, isopropenyl ether-O-propylene carbonate, etc. These are some examples. Note that EO stands for ethylene oxide.

[0032] In the photosensitive layer of the present invention, the content of monofunctional monomers is preferably 0.1 to 30% by mass, and more preferably 1 to 10% by mass, relative to the total solid content of the photosensitive layer of the present invention, for reasons that the effects of the present invention are superior.

[0033] In the photosensitive layer of the present invention, the ratio of the content of the monofunctional monomers to the content of the specific monomers described above is preferably 1.0 or less by mass, more preferably 0.5 or less, and even more preferably 0.4 or less, for reasons that the effects of the present invention are superior. The lower limit of the above ratio is not particularly limited, but it is preferably 0.1 or more, and more preferably 0.2 or more. Hereinafter, the ratio (mass ratio) of the content of the monofunctional monomers mentioned above to the content of the specific monomers mentioned above will also be referred to as "monofunctional monomer / specific monomer".

[0034] (2-functional monomer) The photosensitive layer of the present invention preferably contains a difunctional monomer for reasons that the effects of the present invention are superior. The above-mentioned bifunctional monomer is preferably a compound having two ethylenically unsaturated groups, for reasons that the effects of the present invention are superior. Specific examples of the above-mentioned ethylenically unsaturated groups are as described above.

[0035] Examples of compounds having two ethylenically unsaturated groups include, Glycol di(meth)acrylate compounds such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetrapropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, ethoxylated neopentyl glycol di(meth)acrylate, and propoxylated neopentyl glycol di(meth)acrylate; Divinyl ether compounds such as ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, and cyclohexanedimethanol divinyl ether; Bisphenol A diglycidyl ether (meth)acrylate adducts, modified bisphenol A di(meth)acrylates, bisphenol A PO adduct di(meth)acrylates, bisphenol A EO adduct di(meth)acrylates, and other bisphenol A di(meth)acrylate compounds; These are some examples. Note that PO represents propylene oxide and EO represents ethylene oxide.

[0036] In the photosensitive layer of the present invention, the content of the difunctional monomer is preferably 0.1 to 30% by mass relative to the total solid content of the photosensitive layer of the present invention, for reasons that the effects of the present invention are superior.

[0037] (Hydrophobic polymer) The photosensitive layer of the present invention preferably contains a hydrophobic polymer for reasons that the effects of the present invention are superior. It is preferable that the above hydrophobic polymer does not have reactive functional groups (e.g., (meth)acryloyloxy groups) at either end. Furthermore, it is preferable that the above hydrophobic polymer is not water-dispersible.

[0038] Specific examples and preferred embodiments of the hydrophobic polymer described above are the same as the polymers constituting the main chain of the specific polymer described above. The hydrophobic polymer described above is preferably rubber, more preferably diene rubber, and even more preferably butadiene rubber, for reasons that it provides superior effects of the present invention. The weight-average molecular weight (Mw) of the hydrophobic polymer is not particularly limited, but is preferably 200,000 or more, more preferably 300,000 to 2,000,000, even more preferably 300,000 to 1,500,000, and particularly preferably 300,000 to 700,000, for reasons that the effects of the present invention are superior.

[0039] In the photosensitive layer of the present invention, the hydrophobic polymer content is preferably 5 to 60% by mass, and more preferably 10 to 40% by mass, relative to the total solid content of the photosensitive layer of the present invention, for reasons that the effects of the present invention are superior.

[0040] (Photopolymerization initiator) The photosensitive layer of the present invention preferably contains a photopolymerization initiator for reasons that the effects of the present invention are superior. The photopolymerization initiator is not particularly limited, but examples of photopolymerization initiators include alkylphenones, acetophenones, benzoin ethers, thioxanthones, anthraquinones, benzyls, and biacetyls. More specifically, examples include benzyldimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, methyl-o-benzoylbenzoate, and 1-hydroxycyclohexylphenyl ketone.

[0041] In the photosensitive layer of the present invention, the content of the photopolymerization initiator is preferably 0.3 to 15% by mass, and more preferably 0.5 to 10% by mass, relative to the total solid content of the photosensitive layer of the present invention, from the viewpoint of sensitivity and other factors.

[0042] (Plasticizer) The photosensitive layer of the present invention preferably contains a plasticizer for the reason that its flexibility is further improved.

[0043] Examples of plasticizers include liquid rubber, oil, polyester, and phosphate compounds. Examples of liquid rubber include, for instance, liquid polybutadiene, liquid polyisoprene, or modified versions thereof with maleic acid or epoxy groups. Examples of oils include paraffin, naphthenes, and aromatic oils. Examples of polyesters include, for instance, adipic acid-based polyesters. Examples of phosphate compounds include, for instance, phosphate esters.

[0044] In the photosensitive layer of the present invention, the plasticizer content is preferably 0.1 to 40% by mass, and more preferably 5 to 30% by mass, relative to the total solid content of the photosensitive layer of the present invention, for the reason that flexibility is further improved.

[0045] (Surfactants) From the viewpoint of further improving water-developability, the photosensitive layer of the present invention preferably contains a surfactant. Examples of surfactants include cationic surfactants, anionic surfactants, and nonionic surfactants. Among these, anionic surfactants are preferred because they offer superior effects compared to those of the present invention.

[0046] Examples of anionic surfactants include, for instance, Aliphatic carboxylates such as sodium laurate and sodium oleate; Higher alcohol sulfates such as sodium lauryl sulfate, sodium cetyl sulfate, and sodium oleyl sulfate; Polyoxyethylene alkyl ether sulfate salts such as sodium polyoxyethylene lauryl ether sulfate; Polyoxyethylene alkyl allyl ether sulfate salts such as sodium polyoxyethylene octylphenyl ether sulfate and sodium polyoxyethylene nonylphenyl ether sulfate; Alkyl sulfonates such as alkyldiphenyl ether disulfonates, sodium dodecyl sulfonate, and sodium dialkyl sulfosuccinate; Alkylallyl sulfonates such as alkyl disulfonates, sodium dodecylbenzenesulfonate, sodium dibutylnaphthalenesulfonate, and sodium triisopropylnaphthalenesulfonate; Higher alcohol phosphate salts such as sodium lauryl phosphate monoester disodium and sodium lauryl phosphate diester sodium; Polyoxyethylene alkyl ether phosphate salts such as polyoxyethylene lauryl ether phosphate disodium and polyoxyethylene lauryl ether phosphate diester sodium; These are some examples. These may be used individually or in combination of two or more.

[0047] Of these, sulfonic acid-based surfactants such as alkyl sulfonates and alkyl allyl sulfonates are preferred because they offer even better water-developability.

[0048] In the photosensitive layer of the present invention, the surfactant content is preferably 0.1 to 20% by mass, and more preferably 1 to 10% by mass, relative to the total solid content of the photosensitive layer of the present invention, from the viewpoint of developability and drying properties after development.

[0049] (Thermal polymerization inhibitor) The photosensitive layer of the present invention may contain a thermal polymerization inhibitor (stabilizer) to enhance thermal stability during mixing and storage stability. Examples of thermal polymerization inhibitors include phenols, hydroquinones, and catechols.

[0050] In the photosensitive layer of the present invention, the content of the thermal polymerization inhibitor is preferably 0.001 to 5% by mass relative to the total solid content of the photosensitive layer of the present invention, for reasons that the effects of the present invention are superior.

[0051] (Other additives) The photosensitive layer of the present invention may be further enriched with additives such as ultraviolet absorbers, dyes, pigments, defoamers, and fragrances, to the extent that they do not impair the effects of the present invention, for the purpose of improving various properties.

[0052] <Method for creating a photosensitive layer> The method for producing the photosensitive layer of the present invention is not particularly limited, but examples include preparing a composition (photosensitive resin composition) containing the above-mentioned components and applying it to a substrate or the like.

[0053] [Preferred Embodiment] The printing plate of the present invention is preferably an analog printing plate in which a negative film (with an image already formed on it) is placed in close contact with the photosensitive layer during use, or a LAM (Laserablation Mask) printing plate included in the CTP (Computerto Plate) system in which an infrared ablation layer is already in contact with the photosensitive layer, for reasons that the effects of the present invention are superior.

[0054] For analog printing plates, it is preferable that they consist of an adhesive layer, such as an adhesive, that bonds the substrate to the photosensitive layer, the photosensitive layer of the present invention, an anti-adhesion layer to prevent the surface of the photosensitive layer from sticking, and a protective film to prevent scratches on the photosensitive layer before use, all laminated in this order on a substrate, for reasons that the effects of the present invention are superior. Examples of the above-mentioned substrates include, for example, plastic films or plastic sheets such as polyethylene terephthalate (PET) film; metal sheets such as stainless steel or aluminum; rubber sheets such as butadiene rubber; and so on. In the case of analog printing plates, the protective film is removed before use, and the negative film, which already has the image formed on it, is placed in close contact with the exposed anti-adhesion layer.

[0055] An analog printing plate can be manufactured, for example, by applying an adhesive to one side of a substrate, applying an anti-tack agent to one side of a protective film, sandwiching the aforementioned photosensitive resin composition between the substrate with the adhesive applied and the protective film with the anti-tack agent applied, and pressing it so that the thickness of the photosensitive layer becomes a predetermined thickness.

[0056] The LAM printing plate differs from the analog printing plate in that it has an infrared ablation layer between the photosensitive layer and the protective film, but otherwise its structure is the same as that of the analog printing plate. Specifically, it consists of an adhesive layer, a photosensitive layer, an infrared ablation layer, and a protective film, all laminated in that order on a substrate. When using the LAM printing plate, the protective film is removed, exposing the infrared ablation layer.

[0057] An infrared ablation layer is a layer capable of removing areas irradiated by an infrared laser, and it also possesses the function of blocking ultraviolet light transmission to a practical level. By forming an image on it, it can function as a negative or positive.

[0058] The infrared ablation layer is mainly composed of binders such as resin or rubber, infrared absorbing materials, ultraviolet absorbing materials, and plasticizers. The infrared ablation layer can be manufactured, for example, by dissolving the above materials in a solvent, applying the mixture to a substrate, and then drying it to remove the solvent.

[0059] A printing plate master for the LAM method can be manufactured, for example, by applying an adhesive to one side of a substrate in advance, applying an infrared ablation layer to one side of a protective film in advance, sandwiching the above-mentioned photosensitive resin composition between the substrate with the adhesive applied and the protective film with the infrared ablation layer applied, and pressing it so that the thickness of the photosensitive layer becomes a predetermined thickness.

[0060] In any printing plate, the thickness of the photosensitive layer is preferably in the range of 0.01 to 10 mm, for reasons that the effects of the present invention are superior. If the thickness of the photosensitive layer is 0.01 mm or more, sufficient relief depth can be ensured.

[0061] [Flexographic printing version] The flexographic printing plate of the present invention (hereinafter also referred to as "the printing plate of the present invention") is a flexographic printing plate having an image portion and a non-image portion. Here, the image portion is an image portion obtained by exposing the photosensitive layer (the photosensitive layer of the present invention) of the printing plate master of the present invention described above to an image and developing it. The printing plate of the present invention is preferably obtained by the following method for reasons of superior print resistance, handling, and ink adhesion at the trailing edge.

[0062] To form a relief image on the photosensitive layer of a printing plate, first, ultraviolet light is irradiated from the substrate side of the printing plate (back exposure).

[0063] When using an analog printing plate, the protective film is removed, and the negative film with the image already formed is placed in close contact with the exposed anti-adhesion layer. On the other hand, when using a LAM printing plate, the protective film is removed, and the desired image is formed by irradiating the exposed infrared ablation layer with an infrared laser or similar method.

[0064] Next, the photosensitive layer is cured by irradiating it with ultraviolet light from above the negative film or infrared ablation layer (main exposure). Ultraviolet light can usually be emitted using high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, carbon arc lamps, chemical lamps, etc., which emit light with a wavelength of 300-400 nm. The photosensitive layer hardens in the areas irradiated with ultraviolet light. In the photosensitive layer covered with the negative film or infrared ablation layer, there will be hardened areas that have been irradiated with ultraviolet light and unhardened areas that have not been irradiated with ultraviolet light.

[0065] Next, a relief image is formed by removing the uncured portion of the photosensitive layer in the developing solution. An aqueous developer is used as the developing solution. An aqueous developer consists of water with surfactants and pH adjusters added as needed. The uncured portion of the photosensitive layer can be removed by washing it out using, for example, a spray-type developing device or a brush-type washing machine.

[0066] Next, the printing plate is removed from the developing solution and dried. Then, if necessary, the entire dried printing plate is exposed to ultraviolet light (post-exposure). This yields a flexographic printing plate. [Examples]

[0067] The present invention will be described in more detail below with reference to examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the examples shown below.

[0068] [Manufacturing of flexographic printing plates] The flexographic printing plates for the examples and comparative examples were manufactured as follows. The manufactured flexographic printing plates correspond to the printing plates of the LAM method described above.

[0069] <Example 1>

[0070] (Preparation of photosensitive resin composition) 63.6 parts by mass of water-dispersible latex (Nipol LX111NF, manufactured by ZEON Japan, water-dispersible latex of polybutadiene, solids content 55%), 10 parts by mass of telechelic polymer (BAC-45, manufactured by Osaka Organic Chemical Industry Co., Ltd.) (polybutadiene having acryloyloxy groups at both ends, Mw=10,000) (corresponding to the specified polymer mentioned above), 10 parts by mass of polyfunctional monomer (Light Ester TMP, manufactured by Kyoeisha Chemical Co., Ltd.) (trimethylolpropane trimethacrylate) (corresponding to the specified monomer mentioned above), and 3 parts by mass of monofunctional monomer (Light Ester IB-X, manufactured by Kyoeisha Chemical Co., Ltd.) (isobornyl methacrylate) were mixed, and the water was evaporated in a dryer heated to 60°C for 3 hours to obtain a mixture containing the polymer obtained from the water-dispersible latex (corresponding to the water-dispersible particles mentioned above), the specified polymer, the specified monomer, and the monofunctional monomer. This mixture, along with 20 parts by mass of butadiene rubber (Asahi Kasei, NF35R), 15 parts by mass of plasticizer (Idemitsu, Diana Process Oil PW-32), and 4.4 parts by mass of surfactant (NOF Corporation, Rapizol A-90, 90% effective content), was kneaded for 45 minutes in a kneader set to 110°C. Then, 0.2 parts by mass of a thermal polymerization inhibitor and 3 parts by mass of a photopolymerization initiator (Tokyo Chemical Industry Co., Ltd., benzyldimethyl ketal) were added to the kneader and kneaded for 5 minutes to obtain a photosensitive resin composition.

[0071] (Fabrication of laminates for infrared ablation layer) 50 parts by mass of acrylic resin (Hyperl M-5000, manufactured by Negami Kogyo), 50 parts by mass of elastomer (Nipol DN-101, manufactured by Nippon Zeon), and 100 parts by mass of carbon black (MA-8, manufactured by Mitsubishi Chemical) were mixed with 812 parts by mass of methyl isobutyl ketone and stirred by a feather. The resulting mixture was dispersed in a paint shaker, and then methyl isobutyl ketone was added to obtain a polymer / carbon black dispersion (coating liquid for infrared ablation layer) until the solid content was 15% by mass. Next, a coating solution for the infrared ablation layer was applied to one side of a 75 μm thick PET film (protective film) using a bar coater to a dry thickness of 1.0 μm. After drying in an oven set to 140°C for 5 minutes, a laminate (infrared ablation layer laminate) was fabricated in which an infrared ablation layer was formed on the protective film.

[0072] (Preparation of flexographic printing plates) An adhesive layer was formed on one side of a 125 μm thick PET film (substrate) by applying an adhesive to the substrate. Then, the photosensitive resin composition prepared as described above was sandwiched between the adhesive layer and the infrared ablation layer of the laminate for the infrared ablation layer prepared as described above. By pressing with a press heated to 80°C so that the thickness of the photosensitive resin composition layer (photosensitive layer) was 1 mm, a flexographic printing plate master was produced having the substrate, adhesive layer, photosensitive layer, infrared ablation layer, and protective film in this order.

[0073] <Examples other than Example 1 and comparative examples> A flexographic printing plate master was manufactured following the same procedure as in Example 1, except that the types of each component in the photosensitive resin composition and their mass ratio (mass%) to the total solid content were changed as shown in Table 1.

[0074] [Manufacturing of flexographic printing plates] The obtained flexographic printing plate was exposed to light for 15 seconds from a distance of 15 cm from the substrate side using an exposure apparatus consisting of 15 40W chemical lamps (back exposure). After that, the protective film was peeled off and a negative pattern was formed on the infrared ablation layer using an ESKO CDI Spark 2120. Then, using the same exposure apparatus, it was exposed to light for 8 minutes from a distance of 15 cm from the infrared ablation layer side (main exposure). After that, development was performed for 10 minutes using a brush-type washing machine (liquid temperature 50°C) containing an aqueous developer solution adjusted to a concentration of 0.5% detergent (Miyoshi Soap, additive-free dishwashing soap). After that, it was dried using 60°C hot air until the moisture was removed. Finally, using the same exposure apparatus, it was exposed to light for 8 minutes from a distance of 15 cm from the photosensitive layer side (post exposure). In this way, a flexographic printing plate was obtained.

[0075] 〔evaluation〕 The obtained flexographic printing plates and flexographic printing plates were evaluated as follows.

[0076] <Water developability> The thickness of the non-image areas of the obtained flexographic printing plates was measured using a constant-pressure thickness gauge. The plates were then evaluated according to the following criteria. The results are shown in Table 1. In practical terms, A is preferable. (Evaluation Criteria) A: Non-image area thickness is less than 700 μm B: Non-image area thickness is 700 μm or more and less than 800 μm C: Non-image area thickness is 800 μm or more

[0077] <Durability and handling> The obtained flexographic printing plates were tested using a continuous load scratch strength tester (HEIDON TYPE:18) under conditions of a 500g load and a reciprocating speed of 100mm / min. A cotton cloth was used as the abrasive material, and the image area was rubbed four times. Ten independent dots with a diameter of 500μm, which were identified before the abrasion test, were evaluated after the abrasion test to see if any chipping or breakage had occurred in the independent dots according to the following criteria. The results are shown in Table 1. From the viewpoint of both print durability and handling, a score of 2 to 4 is preferable for practical purposes, 3 to 4 is more preferable, and 4 is even preferable. (Evaluation Criteria) 4 points: None of the 10 independent dots are missing or broken. 3 points: One of the 10 independent dots is missing or broken. 2 points: Two out of the ten independent dots are missing or broken. 1 point: Three or more of the ten independent dots are missing or broken.

[0078] <Rear end flesh attachment> The ink adhesion properties at the rear end of the obtained flexographic printing plates were evaluated as follows. A flexographic printing press (Taiyo Kikai, TLF-270) was used. The resulting flexographic printing plate was stretched onto the plate cylinder (drum) via cushion tape (Lohmann) and installed in the printing press. Then, with the kiss touch (the printing pressure at which the entire image begins to be imprinted) set to 0 (reference printing pressure), printing was performed at a printing speed of 150 m / min with a pressing depth of 80 μm from that point. The substrate used for evaluation was sampled after being pressed 5,000 times under the above conditions. The substrate used was a 50 μm OPP film (Abe Paper Industry). The ink used was a water-based flexographic ink, Hydric FCF (Dainichi Seika). The trailing edge of the image area on the substrate was observed with a 20x microscope (Keyence, VHX-1000) and evaluated according to the following criteria. The results are shown in Table 1. In practical terms, a score of 2 to 4 is preferable, 3 to 4 is more preferable, and 4 is even more preferable. (Evaluation Criteria) 4 points: No problems with the amount of material adhering to the material. 3 points: The concentration at the rear end is slightly lower. Two points: Intermittent white patches can be observed in the width direction of the rear end. 1 point: White areas are observed across the entire width of the rear edge.

[0079] [Table 1]

[0080] The following provides details about some of the components listed in Table 1. • ZEON Japan Nipol LX111NF: Polybutadiene water-dispersible latex, 55% solids content • Manufactured by A&L Japan: Smartex PA-3974: Water-dispersible latex of methyl methacrylate-butadiene copolymer, solids content 50% • BAC-45 manufactured by Osaka Organic Chemical Industry Co., Ltd.: Polybutadiene with acryloyloxy groups at both ends, Mw=10,000 (corresponds to the specified polymer mentioned above) • Light ester TMP (trimethylolpropane trimethacrylate) manufactured by Kyoeisha Chemical Co., Ltd. (corresponds to the specified monomers mentioned above) • NK Ester A-GLY-9E manufactured by Shin-Nakamura Kogyo Kagaku (structure shown below) (corresponds to the specified monomer mentioned above) [ka] • Light Ester IB-X (Isobornyl Methacrylate) manufactured by Kyoeisha Chemical Co., Ltd. • Asahi Kasei NF35R (butadiene rubber) (does not fall under either of the above-mentioned water-dispersible particles or specific polymers) • NK Ester NOD-N (1,9-nonanediol dimethacrylate) manufactured by Shin-Nakamura Kogyo Kagaku Co., Ltd.

[0081] In Table 1, "monofunctional monomer / specific monomer" refers to the "monofunctional monomer / specific monomer" described above. Also, in Table 1, "specific monomer / specific polymer" refers to the "specific monomer / specific polymer" described above.

[0082] As can be seen from Table 1, the flexographic printing plate master having a photosensitive layer containing water-dispersible particles, a specific polymer, and a specific monomer exhibited excellent water-developability and, when made into a flexographic printing plate, showed excellent print durability, handling properties, and trailing edge ink adhesion. A comparison of the examples showed that Examples 1-9 and 11, in which the "specific monomer / specific polymer" ratio was 3.0 or less, exhibited superior rear end adhesion. In particular, Examples 1-2, 5-9 and 11, in which the "specific monomer / specific polymer" ratio was 2.0 or less, exhibited even superior rear end adhesion. Furthermore, a comparison between the examples showed that Examples 1-10, in which the "monofunctional monomer / specific monomer" ratio was 0.5 or less, exhibited superior print durability and handling properties. In particular, Examples 1-5 and 7-10, in which the "monofunctional monomer / specific monomer" ratio was 0.4 or less, exhibited even superior print durability and handling properties.

[0083] On the other hand, Comparative Example 1, in which the photosensitive layer does not contain water-dispersible particles, and Comparative Example 2, in which the photosensitive layer does not contain a specific polymer, And, Comparative example in which the photosensitive layer does not contain a specific monomer. 3 is The print exhibited insufficient water-developability, print durability, handling properties, or trailing edge ink adhesion.

[0084] Furthermore, flexographic printing plates and flexographic printing plates were manufactured and evaluated in the same manner as in the above-mentioned examples and comparative examples, except that analog printing plates were used instead of LAM printing plates, following the same procedure. The results were the same as those shown in Table 1.

Claims

1. The device has a photosensitive layer containing water-dispersible particles, a polymer with a weight-average molecular weight of 5,000 or more having ethylenically unsaturated groups at both ends, and a polyfunctional monomer having three or more ethylenically unsaturated groups. The polyfunctional monomer is pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, or a compound having a structure that can be represented by the following formula: A water-developable flexographic printing plate master in which the ratio of the content of the polyfunctional monomer to the content of the polymer in the photosensitive layer is 3.0 or less by mass ratio. 【Chemistry 1】

2. The water-developable flexographic printing plate according to claim 1, wherein the photosensitive layer further contains a monofunctional monomer.

3. The water-developable flexographic printing plate according to claim 2, wherein in the photosensitive layer, the ratio of the content of the monofunctional monomer to the content of the polyfunctional monomer is 0.5 or less by mass ratio.

4. A flexographic printing plate having an image area and a non-image area, A flexographic printing plate in which the image portion is an image portion obtained by exposing the photosensitive layer of a water-developable flexographic printing plate master according to any one of claims 1 to 3 in an image-like manner and developing it.

Images