WO2020090978A1

WO2020090978A1 - Flexographic printing plate precursor, and flexographic printing plate

Info

Publication number: WO2020090978A1
Application number: PCT/JP2019/042783
Authority: WO
Inventors: 優介難波
Original assignee: 富士フイルム株式会社
Priority date: 2018-10-31
Filing date: 2019-10-31
Publication date: 2020-05-07
Also published as: JPWO2020090978A1; JP2023083372A; JP7366924B2

Abstract

The purpose of the present invention is 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. The 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.

Description

Flexographic printing plate original and flexographic printing plate

The present invention relates to a flexographic printing plate precursor and a flexographic printing plate.

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 medium. As the flexographic printing plate used in flexographic printing, for example, a flexographic printing plate precursor having a photosensitive layer, which is imagewise exposed and developed, is used.
On the other hand, there is a movement from various industries to reduce the use of organic solvents from the viewpoint of improving the working environment and preserving the global environment, and flexographic printing plate precursors are also required to be developable with an aqueous developer. Has been.
For example, claim 1 of Patent Document 1 discloses a photosensitive resin composition which can be developed with an aqueous developer when used as a flexographic printing plate precursor.

Japanese Patent Laid-Open No. 2008-58957

Under such circumstances, when the present inventor produced a flexographic printing plate precursor using the photosensitive resin composition described in Example of Patent Document 1, it was confirmed that the flexographic printing plate precursor was certainly excellent in developability (water developability) with an aqueous developer. On the other hand, when a flexographic printing plate was prepared using the above flexographic printing plate precursor, chipping and folding of the image area was less likely to occur (excellent in printing durability and handling), but white at the rear edge. It became clear that slip-out easily occurs (the rear end part has insufficient inking property).

Therefore, in view of the above situation, the present invention is excellent in water developability, and exhibits excellent printing durability, handling property and rear end inking property when made into a flexographic printing plate, a flexographic printing plate precursor, Another object is to provide a flexographic printing plate obtained by exposing and developing the above flexographic printing plate precursor.

As a result of diligent studies on the above problems, the present inventor has water-dispersible particles, a polymer having reactive functional groups at both ends and having a weight average molecular weight of 5,000 or more, and three or more ethylenically unsaturated groups. The inventors have found that the above problem can be solved by using a polyfunctional monomer in combination, and completed the present invention.
That is, the present inventor has found that the above problems can be solved by the following configurations.

(1) A photosensitive layer containing water-dispersible particles, a polymer having a reactive functional group at both ends and having a weight average molecular weight of 5,000 or more, and a polyfunctional monomer having three or more ethylenically unsaturated groups. A water-developable flexographic printing plate precursor.
(2) The water-developable flexographic printing plate precursor as described in (1) above, wherein the photosensitive layer further contains a monofunctional monomer.
(3) The water-developable flexographic printing according to (2), wherein the ratio of the content of the monofunctional monomer to the content of the polyfunctional monomer in the photosensitive layer is 0.5 or less in terms of mass ratio. Original edition.
(4) The photosensitive layer as described in any one of (1) to (3) above, wherein the ratio of the content of the polyfunctional monomer to the content of the polymer is 3.0 or less in terms of mass ratio. Water-developable flexographic printing plate precursor.
(5) A flexographic printing plate having an image portion and a non-image portion,
Flexographic printing, wherein the image area is an image area obtained by imagewise exposing and developing the photosensitive layer of the water-developable flexographic printing plate precursor according to any one of (1) to (4) above. Edition.

As shown below, according to the present invention, excellent in water developability, and, when it is a flexographic printing plate, showing excellent printing durability, handling property and rear end inking property, flexographic printing plate precursor, In addition, a flexographic printing plate obtained by exposing and developing the above flexographic printing plate precursor can be provided.

Hereinafter, the present invention will be described in detail.
The description of the constituents described below may be made based on a typical embodiment of the present invention, but the present invention is not limited to such an embodiment.
In the present specification, the numerical range represented by “to” means a range including the numerical values before and after “to” as the lower limit value and the upper limit value.
In addition, each component may be used alone or in combination of two or more. Here, when two or more kinds of each component are used in combination, the content of the component means the total content unless otherwise specified.
Further, "(meth) acrylic" is a notation representing "acrylic" or "methacrylic", "(meth) acrylate" is a notation representing "acrylate" or "methacrylate", and "(meth) acryloyl" Is a notation representing "acryloyl" or "methacryloyl".

[Water-developable flexographic printing plate precursor]
The water-developable flexographic printing plate precursor of the invention (hereinafter, also referred to as “printing plate precursor of the invention”) has water-dispersible particles and a weight average molecular weight of 5,000 or more having reactive functional groups at both ends. Water-developable flexographic printing having a photosensitive layer containing a polymer (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") The original version.

Since the printing plate precursor of the present invention has such a configuration, it can be considered that the above-mentioned effects can be obtained. Although the reason for this is not clear, a polymer having a reactive functional group at both ends and having a weight average molecular weight of 5,000 or more (specific polymer) and a polyfunctional monomer having three or more ethylenically unsaturated groups (specific monomer) are used. Is considered to form a three-dimensional structure excellent in toughness and rubber elasticity.

Hereinafter, first, the photosensitive layer of the printing plate precursor of the invention will be described, and then preferred embodiments of the printing plate precursor of the invention will be described.

[Photosensitive layer]
The photosensitive layer of the printing plate precursor of the present invention (hereinafter, also referred to as “the photosensitive layer of the present invention”) is a water-dispersible particle and a polymer having a reactive functional group at both ends and having a weight average molecular weight of 5,000 or more. It has a photosensitive layer containing (specific polymer) and a polyfunctional monomer (specific monomer) having three or more ethylenically unsaturated groups.
Hereinafter, each component contained in the photosensitive layer will be described.

<Water dispersible particles>
As described above, the photosensitive layer of the present invention contains water-dispersible particles.
The water-dispersible particles are not particularly limited, but the water dispersibility is more excellent, the flexographic printing plate obtained has more printing durability, handling property and rear end part inking property, and is excellent in development reproducibility and solid quality. A polymer is preferable for the reason that the pressure latitude becomes wide. Hereinafter, "more excellent water dispersibility, printing durability of the resulting flexographic printing plate, handling property and trailing edge part inking property are more excellent, development reproducibility and solid quality are excellent, and printing pressure latitude is wide" Is also referred to as "the effect of the present invention is more excellent".
Specific examples of the polymer include diene-based polymers (eg, polybutadiene, natural rubber, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, methylmethacrylate-butadiene copolymer, polychloroprene, polyisoprene), polyurethane. , Vinyl pyridine polymers, butyl polymers, thiochol polymers, acrylate polymers, polymers obtained by copolymerizing these polymers with other components such as acrylic acid and methacrylic acid, and the like. They may be used alone or in combination of two or more.
The polymer is preferably a diene polymer, more preferably polybutadiene, for the reason that the effects of the present invention are more excellent.
The polymer preferably does not have a reactive functional group (for example, a (meth) acryloyloxy group) at both ends.

The above-mentioned polymer is preferably a polymer obtained by removing water from the water-dispersed latex because the effect of the present invention is more excellent. Specific examples of the above water-dispersed latex include the water-dispersed latex of the above-mentioned specific examples of the polymer.

The content of the water-dispersible particles in the photosensitive layer of the present invention is preferably 5 to 80% by mass based on the total solid content of the photosensitive layer of the present invention, because the effects of the present invention are more excellent. The amount is more preferably 10 to 50% by mass, further preferably 20 to 40% by mass.

<Specific polymer>
As described above, the photosensitive layer of the present invention contains a polymer (specific polymer) having a reactive functional group at both ends and having a weight average molecular weight of 5,000 or more.
The specific polymer is a polymer having reactive functional groups at both ends and having a weight average molecular weight of 5,000 or more.
It is preferable that the specific polymer does not have water dispersibility.
In the present specification, "telechelic polymer" refers to a polymer having reactive functional groups at both ends, and "specific polymer" is a telechelic polymer having a weight average molecular weight of 5,000 or more. Say

(Main chain)
The polymer constituting the main chain of the specific polymer is not particularly limited, and examples thereof include thermoplastic polymers.
The thermoplastic polymer is not particularly limited as long as it is a polymer exhibiting thermoplasticity, and specific examples thereof include polystyrene resin, polyester resin, polyamide resin, polysulfone resin, polyether sulfone resin, polyimide resin, acrylic resin, acetal resin. , Epoxy resin, polycarbonate resin, rubber, thermoplastic elastomer and the like.
Of these, rubber and thermoplastic elastomers are preferred, rubber is more preferred, and diene rubber is even more preferred, because a softer and more flexible film is likely to be formed.

Specific examples of the rubber include butadiene rubber (BR), nitrile rubber (NBR), acrylic rubber, epichlorohydrin rubber, urethane rubber, isoprene rubber, styrene isoprene rubber, styrene butadiene rubber, ethylene-propylene copolymer. , Chlorinated polyethylene and the like, and these may be used alone 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 used for the reason that the water developability is better, and from the viewpoint of the drying property and the image reproducibility. Preferably, butadiene rubber is more preferable.

Examples of the thermoplastic elastomer include polybutadiene-based thermoplastic elastomer, polyisoprene-based thermoplastic elastomer, polyolefin-based thermoplastic elastomer, and acrylic-based thermoplastic elastomer. Specifically, for example, SB (polystyrene-polybutadiene), SBS (polystyrene-polybutadiene-polystyrene), SIS (polystyrene-polyisoprene-polystyrene), SEBS (polystyrene-polyethylene / polybutylene-polystyrene), ABS (acrylonitrile-butadiene-styrene) Polymer), ACM (acrylic ester rubber), ACS (acrylonitrile chlorinated polyethylene styrene copolymer), acrylonitrile styrene copolymer, syndiotactic 1,2-polybutadiene, polymethyl methacrylate-polybutyl acrylate-poly Examples thereof include methyl methacrylate. Among these, SBS and SIS are particularly preferable from the viewpoints of better water developability, and the viewpoint of drying property and image reproducibility.

(End)
The specific polymer has reactive functional groups at both ends.
The reactive functional group is not particularly limited, but is preferably an ethylenically unsaturated group because the effects of the present invention are more excellent.
The ethylenically unsaturated group is a vinyl group (CH ₂ ═CH—), an allyl group (CH ₂ ═CH—CH ₂ —), a (meth) acryloyl group, or, for the reason that the effects of the present invention are more excellent. It is preferably a (meth) acryloyl group, and more preferably a (meth) acryloyloxy group.

The specific polymer may have a reactive functional group at both ends of the polymer constituting the main chain via a divalent linking group.
The divalent linking group is not particularly limited, but is, for example, a linear, branched or cyclic divalent aliphatic hydrocarbon group (for example, an alkylene group such as a methylene group, an ethylene group or a propylene group), a divalent group. Aromatic hydrocarbon group (eg, phenylene group), —O—, —S—, —SO ₂ —, —NR _L —, —CO—, —NH—, —COO—, —CONR _L —, —O —CO—O—, —SO ₃ —, —NHCOO—, —SO ₂ NR _L —, —NH—CO—NH— or a group combining two or more thereof (eg, an alkyleneoxy group, an alkyleneoxycarbonyl group, Alkylene carbonyloxy group) and the like. Here, R _L represents a hydrogen atom or an alkyl group (preferably having 1 to 10 carbon atoms).

(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, and further preferably 8,000 or more, for the reason that the effects of the present invention are more excellent. It is particularly preferable that it is 1,000 or more. Although the upper limit of Mw of the specific polymer is not particularly limited, it is preferably 500,000 or less, more preferably 100,000 or less for the reason that the effects of the present invention are more excellent.
Here, the weight average molecular weight is measured by a gel permeation chromatographic method (GPC) method, and is calculated by conversion with standard polystyrene. Specifically, for example, HLC-8220GPC (manufactured by Tosoh Corporation) is used as the GPC, and TSKgeL Super HZM-H, TSKgeL Super HZ4000, TSKgeL Super HZ2000 (manufactured by Tosoh Corporation, 4.6 mm ID × 15 cm) are used as columns. This is used, and THF (tetrahydrofuran) is used as an eluent. As conditions, the sample concentration is 0.35% by mass, the flow rate is 0.35 mL / min, the sample injection amount is 10 μL, the measurement temperature is 40 ° C., and an IR detector is used. The calibration curve is “standard sample TSK standard, polystyrene” manufactured by Tosoh Corporation: “F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, “A-5000”, It is prepared from 8 samples of "A-2500", "A-1000" and "n-propylbenzene".

(HSP value)
The HSP (Hansen solubility parameter) value of the specific polymer is not particularly limited, but is preferably 8 to 12, more preferably 8.5 to 11, and more preferably 8 to 11 for the reason that the effects of the present invention are more excellent. It is more preferably 5 to 10.5.

(Content)
The content of the specific polymer in the photosensitive layer of the present invention is preferably 1 to 50% by mass based on the total solid content of the photosensitive layer of the present invention, for the reason that the effects of the present invention are more excellent. It is more preferably 40% by mass, further preferably 7 to 30% by mass, and particularly preferably 10 to 20% by mass.

<Specific monomer>
As described above, the photosensitive layer of the present invention contains a polyfunctional monomer (specific monomer) having three or more ethylenically unsaturated groups.
The specific monomer is not particularly limited as long as it is a compound having three or more ethylenically unsaturated groups.
The ethylenically unsaturated group is a vinyl group (CH ₂ ═CH—), an allyl group (CH ₂ ═CH—CH ₂ —), a (meth) acryloyl group, or, for the reason that the effects of the present invention are more excellent. It is preferably a (meth) acryloyl group, and more preferably a (meth) acryloyloxy group.
Specific monomers include, for example, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, trimethylolethane tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, Tetramethylolmethane tetra (meth) acrylate, triallyl trimellitate and the like can be mentioned.

The content of the specific monomer in the photosensitive layer of the present invention is preferably 1 to 40% by mass, based on the total solid content of the photosensitive layer of the present invention, for the reason that the effects of the present invention are more excellent. It is more preferably 30% by mass, further preferably 5 to 30% by mass, and particularly preferably 10 to 20% by mass.

<Specific monomer / Specific polymer>
In the photosensitive layer of the present invention, the ratio of the content of the above-mentioned specific monomer to the content of the above-mentioned specific polymer is preferably 5.0 or less in terms of mass ratio because the effect of the present invention is more excellent. , 3.0 or less is more preferable, 2.0 or less is more preferable, and 1.5 or less is particularly preferable. The lower limit of the ratio is not particularly limited, but is preferably 0.2 or more, more preferably 0.4 or more, further preferably 0.6 or more, and more preferably 0.7 or more. Particularly preferred.
Hereinafter, the ratio (mass ratio) of the content of the specific monomer described above to the content of the specific polymer described above is also referred to as “specific monomer / specific polymer”.

<Arbitrary ingredients>
The photosensitive layer of the present invention may contain a component (optional component) other than the above-mentioned components.

(Monofunctional monomer)
The photosensitive layer of the present invention preferably contains a monofunctional monomer because the effects of the present invention are more excellent.
The monofunctional monomer is preferably a compound having one ethylenically unsaturated group for the reason that the effects of the present invention are more excellent. Specific examples of the ethylenically unsaturated group are as described above.

Examples of the compound having one ethylenically unsaturated group include:
N-vinyl compounds such as N-vinylformamide;
(Meth) acrylamide, N-methylol (meth) acrylamide, diacetone (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, (meth) (Meth) acrylamide compounds such as 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 phthalic acid, methoxy-polyethylene glycol (meth) acrylate, 2- (meth) a Lylyloxyethyl-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, isomyristyl (meth) acrylate, isostearyl (meth) acrylate, cyclic trimethylolpropane formal (meth) acrylate The (meth) acrylate compound;
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-methylcyclohexyl methyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, Toxyethoxyethyl vinyl ether, methoxy polyethylene glycol vinyl ether, tetrahydrofurfuryl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexylmethyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chloro Monovinyl ether compounds such as ethyl vinyl ether, chlorobutyl vinyl ether, chloroethoxyethyl vinyl ether, phenylethyl vinyl ether, phenoxy polyethylene glycol vinyl ether, cyclohexanedimethanol monovinyl ether, isopropenyl ether-O-propylene carbonate;
Etc. In addition, EO shows ethylene oxide.

The content of the monofunctional monomer in the photosensitive layer of the present invention is preferably 0.1 to 30% by mass based on the total solid content of the photosensitive layer of the present invention, because the effects of the present invention are more excellent. It is more preferably 1 to 10% by mass.

In the photosensitive layer of the present invention, the ratio of the content of the monofunctional monomer described above to the content of the specific monomer described above is 1.0 or less in terms of mass ratio because the effect of the present invention is more excellent. It is preferably 0.5 or less, more preferably 0.4 or less. The lower limit of the ratio is not particularly limited, but is preferably 0.1 or more, more preferably 0.2 or more.
Hereinafter, the ratio (mass ratio) of the content of the above-mentioned monofunctional monomer to the content of the above-mentioned specific monomer is also referred to as "monofunctional monomer / specific monomer".

(Bifunctional monomer)
The photosensitive layer of the present invention preferably contains a bifunctional monomer because the effects of the present invention are more excellent.
The bifunctional monomer is preferably a compound having two ethylenically unsaturated groups, because the effects of the present invention are more excellent. Specific examples of the ethylenically unsaturated group are as described above.

Examples of the compound having two ethylenically unsaturated groups include, for example,
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, di Propylene 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, propoxylated neopentyl glycol Glycol di (meth) acrylate compounds such as 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, cyclohexanedimethanol divinyl ether;
Of bisphenol A such as bisphenol A diglycidyl ether (meth) acrylic acid adduct, modified bisphenol A di (meth) acrylate, PO adduct of bisphenol A di (meth) acrylate, EO adduct of bisphenol A di (meth) acrylate, etc. Di (meth) acrylate compound;
Etc. PO is propylene oxide and EO is ethylene oxide.

The content of the bifunctional monomer in the photosensitive layer of the present invention is preferably 0.1 to 30% by mass based on the total solid content of the photosensitive layer of the present invention, because the effects of the present invention are more excellent. ..

(Hydrophobic polymer)
The photosensitive layer of the present invention preferably contains a hydrophobic polymer because the effects of the present invention are more excellent.
The hydrophobic polymer preferably does not have a reactive functional group (for example, a (meth) acryloyloxy group) at both ends. Further, it is preferable that the hydrophobic polymer does not have water dispersibility.

Specific examples and preferable embodiments of the above hydrophobic polymer are the same as the polymers constituting the main chain of the above-mentioned specific polymer.
The hydrophobic polymer is preferably a rubber, more preferably a diene rubber, and even more preferably a butadiene rubber, for the reason that the effects of the present invention are more excellent.
The weight average molecular weight (Mw) of the hydrophobic polymer is not particularly limited, but is preferably 200,000 or more, and preferably 300,000 to 2,000,000 for the reason that the effects of the present invention are more excellent. Is more preferable, 300,000 to 1,500,000 is more preferable, 300,000 to 700,000 is particularly preferable.

The content of the hydrophobic polymer in the photosensitive layer of the present invention is preferably 5 to 60 mass% with respect to the total solid content of the photosensitive layer of the present invention, for the reason that the effects of the present invention are more excellent. It is more preferably from about 40% by mass.

(Photopolymerization initiator)
The photosensitive layer of the present invention preferably contains a photopolymerization initiator because the effects of the present invention are more excellent.
The photopolymerization initiator is not particularly limited, and examples thereof include photopolymerization initiators such as alkylphenones, acetophenones, benzoin ethers, benzophenones, thioxanthones, anthraquinones, benzyls, and biacetyls.
More specifically, for example, benzyl dimethyl ketal, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, methyl-o-benzoylbenzoate, 1-hydroxycyclohexyl phenyl ketone and the like can be mentioned.

The content of the photopolymerization initiator in the photosensitive layer of the present invention is preferably 0.3 to 15% by mass based on the total solid content of the photosensitive layer of the present invention, from the viewpoint of sensitivity and the like. It is more preferably from about 10% by mass.

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

Specific examples of the plasticizer include liquid rubber, oil, polyester, and phosphoric acid compounds.
Specific examples of the liquid rubber include liquid polybutadiene, liquid polyisoprene, and those obtained by modifying these with maleic acid or an epoxy group.
Specific examples of the oil include paraffin, naphthene, and aroma.
Specific examples of the polyester include adipic acid-based polyester.
Specific examples of the phosphoric acid compound include phosphoric acid esters.

The content of the plasticizer in the photosensitive layer of the present invention is preferably 0.1 to 40% by mass based on the total solid content of the photosensitive layer of the present invention, for the reason of further improving flexibility. It is more preferably 30% by mass.

(Surfactant)
The photosensitive layer of the present invention preferably contains a surfactant from the viewpoint of further improving water developability.
Examples of the surfactant include a cationic surfactant, an anionic surfactant, and a nonionic surfactant. Among them, anionic surfactants are preferable because the effects of the present invention are more excellent.

As the anionic surfactant, specifically, for example,
Aliphatic carboxylates such as sodium laurate and sodium oleate;
Higher alcohol sulfate salts such as sodium lauryl sulfate, sodium cetyl sulfate and sodium oleyl sulfate;
Polyoxyethylene lauryl ether sulfate sodium salt and other polyoxyethylene alkyl ether sulfate salts;
Polyoxyethylene alkyl allyl ether sulfuric acid ester salts such as sodium polyoxyethylene octyl phenyl ether sulfuric acid ester and sodium polyoxyethylene nonyl phenyl ether sulfuric acid ester;
Alkyl sulfonates such as alkyl diphenyl ether disulfonate, sodium dodecyl sulfonate, sodium dialkyl sulfosuccinate;
Alkyl allyl sulfonates such as alkyl disulfonate, sodium dodecylbenzene sulfonate, sodium dibutyl naphthalene sulfonate, sodium triisopropyl naphthalene sulfonate;
Higher alcohol phosphoric acid ester salts such as disodium lauryl phosphoric acid monoester and sodium lauryl phosphoric acid diester;
Polyoxyethylene lauryl ether phosphate monoester disodium, polyoxyethylene lauryl ether phosphate diester sodium, and other polyoxyethylene alkyl ether phosphate ester salts;
Etc. These may be used alone or in combination of two or more.

Among these, sulfonic acid type surfactants such as alkyl sulfonates and alkyl allyl sulfonates are preferable because the water developability is further improved.

The content of the surfactant in the photosensitive layer of the present invention is preferably 0.1 to 20% by mass based on the total solid content of the photosensitive layer of the present invention from the viewpoint of developability and drying property after development. Preferably, it is 1 to 10% by mass, and more preferably.

(Thermal polymerization inhibitor)
The photosensitive layer of the present invention may contain a thermal polymerization inhibitor (stabilizer) from the viewpoints of enhancing the thermal stability during kneading, enhancing the storage stability, and the like.
Examples of thermal polymerization inhibitors include phenols, hydroquinones, and catechols.

The content of the thermal polymerization inhibitor in the photosensitive layer of the present invention is 0.001 to 5% by mass based on the total solid content of the photosensitive layer of the present invention, because the effects of the present invention are more excellent. preferable.

(Other additives)
In the photosensitive layer of the present invention, an additive such as an ultraviolet absorber, a dye, a pigment, a defoaming agent, and a fragrance can be appropriately added within the range not impairing the effects of the present invention for the purpose of improving various characteristics. ..

<Method for preparing photosensitive layer>
The method for producing the photosensitive layer of the present invention is not particularly limited, and examples thereof include a method of preparing a composition (photosensitive resin composition) containing each of the above-mentioned components, and coating the composition on a substrate or the like.

[Preferred embodiment]
The printing plate precursor of the present invention is a so-called analog type printing plate precursor in which a negative film (on which an image has already been formed) is brought into close contact with the photosensitive layer at the time of use because the effects of the present invention are more excellent. Alternatively, it is preferably a printing plate precursor of a LAM (Laseration mask) system included in a so-called CTP (Computer to plate) system in which an infrared ablation layer is in close contact with a photosensitive layer in advance.

The analog type printing plate precursor is, for the reason that the effects of the present invention are more excellent, on the substrate, an adhesive layer made of an adhesive or the like for adhering the substrate and the photosensitive layer, the photosensitive layer of the present invention, and the photosensitive layer surface. It is preferable that an anti-adhesion layer for preventing the sticking of the photosensitive layer and a protective film for preventing scratches on the photosensitive layer before use are laminated in this order.
Specific examples of the substrate include a plastic film or a plastic sheet such as a polyethylene terephthalate (PET) film; a metal sheet such as stainless steel or aluminum; a rubber sheet such as butadiene rubber;
When using the analog type printing plate precursor, the protective film is peeled off at the time of use, and a negative film on which an image is formed in advance is adhered onto the exposed anti-adhesion layer.

The analog type printing plate precursor is, for example, one side of the substrate is pre-coated with an adhesive, one side of the protective film is pre-coated with an anti-adhesive agent, the photosensitive resin composition described above, a substrate pre-coated with an adhesive. It can be manufactured by sandwiching it between a protective film coated with an anti-adhesive agent in advance and pressing it so that the thickness of the photosensitive layer becomes a predetermined thickness.

The LAM printing plate precursor is different from the analog printing plate precursor in that it has an infrared ray ablation layer between the photosensitive layer and the protective film, and other configurations are the same as those of the analog printing plate precursor. It is the structure of. That is, the adhesive layer, the photosensitive layer, the infrared ablation layer, and the protective film are laminated in this order on the substrate. When using the LAM type printing plate precursor, the protective film is peeled off and the infrared ablation layer is exposed.

The infrared ablation layer is a layer capable of removing a portion irradiated with an infrared laser, and is a layer which itself has a function of blocking transmission of ultraviolet rays at a practical level and forms an image on it. As a result, it can act as a negative or a positive.

The infrared ablation layer is mainly composed of a binder resin or rubber, an infrared absorbing substance, an ultraviolet absorbing substance, a plasticizer, and the like. The infrared ablation layer can be produced, for example, by dissolving the above material in a solvent, applying the solution to a base material, and drying the solution to remove the solvent.

The LAM printing plate precursor is, for example, a substrate on which one side of a substrate is coated with an adhesive in advance, one side of a protective film is coated with an infrared ablation layer in advance, and the photosensitive resin composition is coated with an adhesive in advance. It can be manufactured by sandwiching it between a protective film coated with an infrared ablation layer in advance and pressing it so that the photosensitive layer has a predetermined thickness.

In any of the printing plate precursors, the thickness of the photosensitive layer is preferably in the range of 0.01 to 10 mm because the effects of the present invention are more excellent. If the thickness of the photosensitive layer is 0.01 mm or more, a sufficient relief depth can be secured.

[Flexographic printing plate]
The flexographic printing plate of the present invention (hereinafter, also referred to as “printing plate of the present invention”) is a flexographic printing plate having an image portion and a non-image portion.
Here, the image area is an image area obtained by imagewise exposing and developing the photosensitive layer (the photosensitive layer of the invention) included in the printing plate precursor of the invention.
The printing plate of the present invention is preferably obtained by the following method, because it is more excellent in printing durability, handling property, and rear end portion inking property.

To form a relief image on the photosensitive layer of the printing plate precursor, first, UV irradiation is performed from the substrate side of the printing plate precursor (back exposure).

When using an analog printing plate precursor, peel off the protective film and adhere the negative film on which an image is formed in advance onto the exposed anti-adhesion layer. On the other hand, when using the LAM printing plate precursor, the protective film is peeled off, and the exposed infrared ablation layer is irradiated with an infrared laser to form a desired image.

Next, the photosensitive layer is cured by irradiating ultraviolet rays from above the negative film or infrared ablation layer (main exposure). Ultraviolet rays can be usually irradiated by a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a metal halide lamp, a xenon lamp, a carbon arc lamp, a chemical lamp, or the like, which can irradiate light having a wavelength of 300 to 400 nm. The photosensitive layer is cured by irradiation with ultraviolet rays. The photosensitive layer covered with the negative film or the infrared ablation layer has a cured portion irradiated with ultraviolet rays and an uncured portion not irradiated with ultraviolet rays.

Next, a relief image is formed by removing the uncured portion of the photosensitive layer in a developing solution. A water-based developer (water-based developer) is used as the developer. The water-based developer is made of water to which a surfactant, a pH adjuster, or the like is added, if necessary. The uncured portion of the photosensitive layer can be removed by washing out the uncured portion using, for example, a spray type developing device or a brush type washing machine.

Next, remove the printing plate material from the developer and dry it. Then, if necessary, the dried printing plate material is irradiated with ultraviolet rays (post-exposure). This gives a flexographic printing plate.

The present invention will be described in more detail below with reference to examples. The materials, usage amounts, ratios, processing contents, processing procedures, and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be limitedly interpreted by the following examples.

[Manufacture of flexographic printing plate precursor]
The flexographic printing plate precursors of Examples and Comparative Examples were manufactured as follows. The manufactured flexographic printing plate precursor corresponds to the above-mentioned LAM printing plate precursor.

(Preparation of photosensitive resin composition)
63.6 parts by mass of water-dispersed latex (Nipol LX111NF manufactured by Japan ZEON, water-dispersed latex of polybutadiene, solid content 55%) and telechelic polymer (BAC-45 manufactured by Osaka Organic Chemical Industry) (acryloyloxy group at both ends) With polybutadiene having Mw = 10,000) (corresponding to the above-mentioned specific polymer) and 10 parts by mass of a polyfunctional monomer (Kyoeisha Chemical Co., Ltd., light ester TMP) (trimethylolpropane trimethacrylate) (corresponding to the above-mentioned specific monomer). 10 parts by mass and 3 parts by mass of a monofunctional monomer (Kyoeisha Chemical Co., Ltd., light ester IB-X) (isobornyl methacrylate) were mixed, and water was evaporated for 3 hours in a dryer heated to 60 ° C. to obtain water. Polymer obtained from dispersed latex (corresponding to the above water-dispersible particles) and specific poly A mixture containing the mer, the specific monomer and the monofunctional monomer was obtained.
This mixture, 20 parts by mass of butadiene rubber (NF35R manufactured by Asahi Kasei), 15 parts by mass of a plasticizer (manufactured by Idemitsu, Diana Process Oil PW-32), and a surfactant (manufactured by NOF CORPORATION, Rapisol A-90, effective ingredient) 90%) 4.4 parts by mass were kneaded in a kneader set at 110 ° C. for 45 minutes. Then, 0.2 part by mass of a thermal polymerization inhibitor and 3 parts by mass of a photopolymerization initiator (manufactured by Tokyo Chemical Industry Co., benzyl dimethyl ketal) were put into a kneader and kneaded for 5 minutes to prepare a photosensitive resin composition. Got

(Preparation of laminated body for infrared ablation layer)
Acrylic resin (Negami Kogyo, Hyper M-5000) 50 parts by mass, elastomer (Nippon Zeon, Nipol DN-101) 50 parts by mass, carbon black (Mitsubishi Chemical, MA-8) 100 parts by mass and methyl. 812 parts by mass of isobutyl ketone was added and mixed by stirring with a blade. The resulting mixed liquid was dispersed with a paint shaker, and then methyl isobutyl ketone was further added so that the solid content was 15% by mass to obtain a polymer / carbon black dispersion (infrared ablation layer coating liquid). Obtained.
Then, on one side of a PET film (protective film) having a thickness of 75 μm, a coating liquid for infrared ablation layer was applied with a bar coater so that the thickness after drying was 1.0 μm, and then set at 140 ° C. By drying in the oven for 5 minutes, a laminate having an infrared ablation layer formed on the protective film (infrared ablation layer laminate) was produced.

(Preparation of flexographic printing plate precursor)
An adhesive was applied to one side of a 125 μm thick PET film (substrate) to form an adhesive layer on the substrate. Then, the photosensitive resin composition prepared as described above is sandwiched between the adhesive layer and the infrared ablation layer of the infrared ablation layer laminate prepared as described above to form a layer of the photosensitive resin composition (photosensitive layer). A flexographic printing plate precursor having a substrate, an adhesive layer, a photosensitive layer, an infrared ablation layer and a protective film in this order was prepared by pressing with a press machine heated to 80 ° C. so that the thickness of the layer) was 1 mm.

<Examples other than Example 1 and Comparative Examples>
A flexographic printing plate precursor was produced according to the same procedure as in Example 1 except that the kind of each component in the photosensitive resin composition and the mass ratio (% by mass) to the total solid content were changed as shown in Table 1.

[Manufacture of flexographic printing plates]
The obtained flexographic printing plate precursor was exposed (back exposure) for 15 seconds from a distance of 15 cm from the substrate side using an exposure device in which 15 40 W chemical lamps were arranged. Then, the protective film was peeled off, and a negative pattern was formed on the infrared ablation layer using CDI Spark2120 manufactured by ESKO. Then, using the said exposure apparatus, it exposed (main exposure) from the infrared ablation layer side from the distance of 15 cm for 8 minutes. After that, development is carried out for 10 minutes using a brush-type washing machine (liquid temperature 50 ° C) containing an aqueous developer adjusted so that the concentration of detergent (made by Miyoshi soap, additive-free dishwashing soap) is 0.5%. It was Then, it was dried using hot air at 60 ° C. until the water content was removed. After that, exposure (post-exposure) was carried out for 8 minutes from a distance of 15 cm from the photosensitive layer side using the above-mentioned exposure apparatus.
In this way, a flexographic printing plate was obtained.

[Evaluation]
The following evaluations were performed on the obtained flexographic printing plate precursor and flexographic printing plate.

<Water developability>
About the obtained flexographic printing plate, the thickness of the non-image part was measured using the constant pressure thickness measuring device. And the following criteria evaluated.
The results are shown in Table 1. Practically, 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

<Printing durability and handling>
About the obtained flexographic printing plate, a continuous weight type scratching strength tester (HEIDON TYPE: 18) was used, a cotton waste was used as a rubbing member under a load of 500 g and a reciprocating speed of 100 mm / min, and an image portion was formed. Rubbed 4 times. With respect to 10 independent small dots having a diameter of 500 μm, which were specified before the rubbing test, whether or not the individual small dots were broken after the rubbing test was evaluated based on the following criteria.
The results are shown in Table 1. From the viewpoints of both printing durability and handleability, practically, it is preferably 2 to 4 points, more preferably 3 to 4 points, and further preferably 4 points.
(Evaluation criteria)
4 points: none of 10 independent dots, not broken 3 points: 1 out of 10 independent dots, broken 2 points: 10 independent dots Two of them are missing or broken 1 point: 3 or more of 10 independent dots are missing or broken

<Rear end part inking property>
The flexographic printing plate thus obtained was evaluated for its rear end inking property as follows.
A flexo printer (manufactured by Taiyo Kikai, TLF-270) was used as the printer. The flexographic printing plate thus obtained was attached to a plate cylinder (drum) via a cushion tape (manufactured by Lohmann) and set on a printing machine. After that, a kiss touch (printing pressure at which the entire surface of the image starts to be inked) was set to 0 (reference printing pressure), and printing was performed at a printing speed of 150 m / min under the condition that 80 μm was pushed in from there. The printing medium used for evaluation was sampled after being pressed 5,000 times under the above conditions. As the material to be printed, a 50 μm OPP film (manufactured by Abe Paper Industry) was used. As the ink, water-based flexo ink and Hydric FCF (manufactured by Dainichiseika) were used. Then, the rear end portion of the image portion on the printing medium was observed with a 20 times microscope (VHX-1000, manufactured by KEYENCE) and evaluated according to the following criteria.
The results are shown in Table 1. Practically, it is preferably 2 to 4 points, more preferably 3 to 4 points, and further preferably 4 points.
(Evaluation criteria)
4 points: No inking defects at all 3 points: The density of the rear edge is slightly low 2 points: White spots are observed in the widthwise direction of the rear edge 1 point: The widthwise direction of the rear edge White spots are confirmed over the entire surface

The details of some components in Table 1 are shown below.
-Nipol LX111NF manufactured by Japan ZEON: water dispersion latex of polybutadiene, solid content 55%
・ Nippon A & L Smartex PA-3974: Water-dispersed latex of methyl methacrylate-butadiene copolymer (methyl methacrylate-butadiene copolymer), solid content 50%
BAC-45 manufactured by Osaka Organic Chemical Industry: polybutadiene having an acryloyloxy group at both ends, Mw = 10,000 (corresponding to the above-mentioned specific polymer)
-Kyoeisha Chemical Co., Ltd. ABU-2S: polybutadiene having acryloyloxy groups at both ends, Mw = less than 5,000 (because Mw is less than 5,000, it does not correspond to the above-mentioned specific polymer).
・ Kyoeisha Chemical's light ester TMP (trimethylolpropane trimethacrylate) (corresponding to the above-mentioned specific monomer)
・ Shin-Nakamura Kogyo Kagaku NK Ester A-GLY-9E (structure below)

・ Kyoeisha Chemical Light Ester IB-X (isobornyl methacrylate)
Asahi Kasei NF35R (butadiene rubber) (Neither of the above-mentioned water-dispersible particles nor the specific polymer)
・ Shin-Nakamura Industrial Chemical NK ester NOD-N (1,9-nonanediol dimethacrylate)

In Table 1, "monofunctional monomer / specific monomer" represents "monofunctional monomer / specific monomer" described above. Moreover, in Table 1, "specific monomer / specific polymer" represents the above-mentioned "specific monomer / specific polymer".

As can be seen from Table 1, the flexographic printing plate precursor having a photosensitive layer containing water-dispersible particles, a specific polymer and a specific monomer has excellent water developability and excellent printing durability when used as a flexographic printing plate. In addition, handling property and rear end part inking property were exhibited.
From the comparison between the examples, Examples 1 to 9 and 11 in which the above-mentioned “specific monomer / specific polymer” was 3.0 or less showed more excellent rear end part inking property. Among them, Examples 1 to 2, 5 to 9 and 11 in which the above-mentioned “specific monomer / specific polymer” was 2.0 or less showed further excellent rear end part inking property.
Further, from the comparison between Examples, Examples 1 to 10 in which the above-mentioned “monofunctional monomer / specific monomer” was 0.5 or less showed more excellent printing durability and handleability. Among them, Examples 1 to 5 and 7 to 10 in which the above-mentioned “monofunctional monomer / specific monomer” was 0.4 or less showed further excellent printing durability and handling property.

On the other hand, Comparative Example 1 in which the photosensitive layer does not contain water-dispersible particles, Comparative Example 2 in which the photosensitive layer does not contain a specific polymer, Comparative Example 3 in which the photosensitive layer does not contain a specific monomer, and the photosensitive layer does not contain a specific monomer (2 Comparative Example 4 (containing a functional monomer) and Comparative Example 5 in which the photosensitive layer does not contain a specific polymer (containing a polymer having reactive functional groups at both ends and having a weight average molecular weight of less than 5,000) are water. Any of the developing property, printing durability, handling property and trailing edge part inking property was insufficient.

Further, with respect to the above-mentioned Examples and Comparative Examples, a flexographic printing plate precursor and a flexographic printing plate were manufactured according to the same procedure except that an analog type printing plate original plate was used instead of the LAM type printing plate original plate, and evaluated in the same manner. As a result, the same results as in Table 1 were obtained.

Claims

Water having a photosensitive layer containing water-dispersible particles, a polymer having a reactive functional group at both ends and having a weight average molecular weight of 5,000 or more, and a polyfunctional monomer having three or more ethylenically unsaturated groups, Developable flexographic printing plate precursor.
The water-developable flexographic printing plate precursor according to claim 1, wherein the photosensitive layer further contains a monofunctional monomer.
The water-developable flexographic printing plate precursor according to claim 2, wherein the ratio of the content of the monofunctional monomer to the content of the polyfunctional monomer in the photosensitive layer is 0.5 or less in terms of mass ratio.
4. The water-developable flexo according to claim 1, 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 in terms of mass ratio. Original printing plate.
A flexographic printing plate having an image part and a non-image part,
A flexographic printing plate, wherein the image area is an image area obtained by imagewise exposing and developing the photosensitive layer of the water-developable flexographic printing plate precursor according to any one of claims 1 to 4. ..