Photosensitive resin printing master for letterpress printing

Abstract

The present application provides a photopolymer printing original plate for relief printing, which has excellent resistance to swelling of an oily ink containing an ester compound. A photopolymer printing original plate for relief printing, which has a photosensitive resin layer formed from a photosensitive resin composition containing at least a high molecular compound (A), a dibasic acid diester (B) represented by the following general formula (I), a photopolymerizable compound (C), and a photopolymerization initiator (D), characterized in that the content of the dibasic acid diester (B) in the photosensitive resin composition is 2.5 to 15 mass %.(In the formula, R 1 represents a divalent aliphatic hydrocarbon group having 2 to 8 carbon atoms, a divalent aromatic hydrocarbon group having 6 to 14 carbon atoms, or a divalent aliphatic cyclic hydrocarbon group having 4 to 14 carbon atoms; R 2 and R 3 may be the same as or different from each other, and represent a linear or branched aliphatic hydrocarbon group having 1 to 12 carbon atoms.)

Description

TECHNICAL FIELD

[0001] The present application relates to a photopolymer printing original plate for relief printing, which is excellent in swelling resistance to an oily ink, and particularly to a photopolymer printing original plate for relief printing, which is excellent in swelling resistance to an oily ink containing an ester compound used for label printing on cloth. BACKGROUND

[0002] As a method of producing a printing plate by developing a printing original plate, a method of using a developer containing an organic solvent has been performed in the past, but from the viewpoint of the working environment, a method of producing a printing plate by developing using water or an aqueous developer to which a surfactant or the like is added in water has been proposed (see, for example, Patent Documents 1 to 3).

[0003] In these conventional proposals, it is generally disclosed that by containing a plasticizer in the printing original plate, the hardness can be reduced and the resilience rate can be improved, but on the other hand, when a plasticizer is contained, the mechanical strength of the obtained printing plate becomes insufficient, and there is a problem of print durability such as cracking of the printing plate and relief image defects during long-run printing.

[0004] In addition, an oily ink containing an ester compound is used in the use of printing labels on cloth, but the conventional printing plate swells by absorbing the ink during printing, and there is a problem of line thickening of the printed matter when long-run printing is performed.

[0005] [Related Art Documents]

[0006] [Patent Documents]

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 3-198058

[0008] Patent Document 2: International Publication No. 2014 / 034213

[0009] Patent Document 3: Japanese Patent Application Laid-Open No. 2003-287887 SUMMARY

[0010] [Problems to be Solved by the Invention]

[0011] The present application was completed in order to solve the problems of the above-described conventional technology, and an object thereof is to provide a photopolymer printing original plate for relief printing, which is excellent in swelling resistance to an oily ink, and particularly to provide a photopolymer printing original plate for relief printing, which is excellent in swelling resistance to an oily ink containing an ester compound.

[0012] [Means for solving the problem]

[0013] The present inventors have conducted intensive studies in order to achieve the object and have found that a printing master having excellent resistance to swelling with oily ink can be obtained by incorporating a specific amount of dibasic acid diester into a photosensitive resin layer constituting a printing master, thereby completing the present invention.

[0014] That is, the present invention has the following (1) to (6).

[0015] (1) A photosensitive resin printing master for relief printing, having a photosensitive resin layer formed from a photosensitive resin composition containing at least a high molecular compound (A), a dibasic acid diester (B) represented by the following general formula (I), a photopolymerizable compound (C), and a photopolymerization initiator (D), characterized in that the content of the dibasic acid diester (B) in the photosensitive resin composition is 2.5 to 15 mass%.

[0016]

[0017] (In the formula, R 1 represents a divalent aliphatic hydrocarbon group having 2 to 8 carbon atoms, a divalent aromatic hydrocarbon group having 6 to 14 carbon atoms, or a divalent aliphatic cyclic hydrocarbon group having 4 to 14 carbon atoms; R 2 and R 3 may be the same as or different from each other and represent a linear or branched aliphatic hydrocarbon group having 1 to 12 carbon atoms.)

[0018] (2) The photosensitive resin printing master for relief printing according to (1), characterized in that the dibasic acid diester (B) is at least one selected from the group consisting of succinic acid diester, glutaric acid diester, adipic acid diester, pimelic acid diester, suberic acid diester, azelaic acid diester, sebacic acid diester, and phthalic acid diester.

[0019] (3) The photosensitive resin printing master for relief printing according to (1) or (2), characterized in that the high molecular compound (A) is a latex having a butadiene skeleton and / or an isoprene skeleton.

[0020] (4) The photosensitive resin printing master for relief printing according to (3), characterized in that the latex is a polybutadiene latex, a styrene-butadiene copolymer latex, an acrylonitrile-butadiene copolymer latex, a methyl methacrylate-butadiene copolymer latex, a polyisoprene latex, or a latex obtained by further copolymerizing acrylic acid or methacrylic acid with the above-mentioned copolymer latex.

[0021] (5) The photopolymerizable resin printing plate precursor for relief printing according to (4), characterized in that the latex is at least one water-dispersible latex selected from the group consisting of polybutadiene latex, styrene-butadiene copolymer latex, acrylonitrile-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, and latex obtained by further copolymerizing acrylic acid or methacrylic acid with the above-mentioned copolymer latex.

[0022] (6) The photopolymerizable resin printing plate precursor for relief printing according to (1) or (2), characterized in that the high molecular compound (A) is a polyamide resin composed of a polyamide and / or a polyamide block copolymer, and / or a partially saponified polyvinyl acetate resin.

[0023] [Effects of Invention]

[0024] According to the present application, it is possible to provide a photopolymerizable resin printing plate precursor for relief printing, which is less swollen by absorption of ink even when an oily ink containing an ester-based compound is used, and thus hardly causes line thickening of an image of a printed matter even when long-term printing is performed. DETAILED DESCRIPTION

[0025] The photopolymerizable resin printing plate precursor for relief printing of the present application has a photosensitive resin layer formed of a photosensitive resin composition containing at least a high molecular compound (A), a dibasic acid diester (B) represented by the following general formula (I), a photopolymerizable compound (C), and a photopolymerization initiator (D). Hereinafter, each component of the photosensitive resin composition will be described.

[0026] The high molecular compound (A) is not particularly limited as long as it is used in the art, but from the viewpoint of suitability as a relief printing plate precursor, it is preferably

[0027] (i) a latex having a butadiene skeleton and / or an isoprene skeleton,

[0028] (ii) a polyamide resin composed of a polyamide and / or a polyamide block copolymer, and / or

[0029] (iii) a partially saponified polyvinyl acetate resin.

[0030] (i) As the latex having a butadiene skeleton and / or an isoprene skeleton, any of the conventionally known latexes can be appropriately selected, and for example, a polybutadiene latex, a styrene-butadiene copolymer latex, an acrylonitrile-butadiene copolymer latex, a methyl methacrylate-butadiene copolymer latex, a polyisoprene latex, or the like can be used. These latexes can be modified with (meth)acrylic, carboxyl, silicone, fluorine, or the like as desired. In addition, as these latexes, since many various kinds of synthetic latexes and natural latexes are commercially available, any of these can be appropriately selected.

[0031] Among these, from the viewpoint of hardness and rubber elasticity, a water-dispersible latex having a butadiene skeleton in the molecular chain is preferably used. As such a water-dispersible latex, specifically, a polybutadiene latex, a styrene-butadiene copolymer latex, an acrylonitrile-butadiene copolymer latex, a methyl methacrylate-butadiene copolymer latex, and a latex obtained by copolymerizing acrylic acid or methacrylic acid with the above copolymer are preferable, and a polybutadiene latex, an acrylonitrile-butadiene copolymer latex are more preferable.

[0032] (ii) The polyamide resin composed of a polyamide and / or a polyamide block copolymer can be a high molecular compound containing 50% by mass or more (preferably 70% by mass or more) of a structural unit composed of an amide bond in a block form in the molecule. Examples thereof include a polyether amide, a polyether ester amide, a tertiary nitrogen-containing polyamide, an ammonium salt type tertiary nitrogen-containing polyamide, an addition polymer of an amide compound having one or more amide bonds and an organic diisocyanate compound, and the like, among which, the ammonium salt type tertiary nitrogen-containing polyamide is preferable. Furthermore, in the case of containing the tertiary nitrogen-containing polyamide and the ammonium salt type tertiary nitrogen-containing polyamide, the development property can be improved when an organic acid is contained. As the organic acid, acetic acid, lactic acid, methacrylic acid can be given, but is not limited thereto.

[0033] (iii) The partially saponified polyvinyl acetate resin is not particularly limited as long as it is used in the art, but from the viewpoint of the image reproducibility of the relief printing plate, a partially saponified polyvinyl acetate resin having a saponification degree of 70 to 95 mol% and an average polymerization degree of 1500 to 3400 is preferable.

[0034] In the photosensitive resin composition, the mixing amount of the high molecular compound (A) is preferably 30 to 80% by mass, and more preferably 40 to 75% by mass. When the mixing amount is less than the above lower limit, there is a possibility that the strength as a printing plate is insufficient, and when the mixing amount is more than the above upper limit, there is a possibility that the water development requires time.

[0035] The dibasic acid diester (B) is a compound obtained by esterifying an organic acid having a structure that can dissociate 2 protons in water, and specifically, a compound represented by the following general formula (I).

[0036]

[0037] (In the formula, R 1 represents a divalent aliphatic hydrocarbon group having 2 to 8 carbon atoms, a divalent aromatic hydrocarbon group having 6 to 14 carbon atoms, or a divalent aliphatic cyclic hydrocarbon group having 4 to 14 carbon atoms; R 2 and R 3 may be the same as or different from each other, and represent a linear or branched aliphatic hydrocarbon group having 1 to 12 carbon atoms.)

[0038] As the dibasic acid diester having such a structure, specifically, there can be mentioned dimethyl oxalate, dimethyl malonate, dimethyl succinate, dimethyl glutarate, dimethyl tartrate, dimethyl adipate, dimethyl glutamate, dimethyl sebacate, dimethyl hexafluorosilicate, diethyl oxalate, diethyl malonate, diethyl succinate, diethyl glutarate, diethyl tartrate, diethyl adipate, diethyl glutamate, diethyl sebacate, diethyl hexafluorosilicate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, di(2-ethylhexyl) phthalate, diisononyl phthalate, ethyl phthalyl ethyl glycolate, dibutyl adipate, diisobutyl adipate, di(2-ethylhexyl) adipate, diisononyl adipate, diisodecyl adipate, di[2-(2-butoxyethoxy)ethyl] adipate, di(2-ethylhexyl) azelate, dibutyl sebacate, and the like. These can be used each alone or in combination of two or more.

[0039] Among these, the dibasic acid diester is preferably a succinate, glutarate, adipate, pimelate, suberate, azelate, sebacate, or phthalate.

[0040] By mixing such a dibasic acid diester in the photosensitive resin layer, a printing plate excellent in resistance to swelling of an oily ink containing an ester compound can be obtained. In particular, the swelling of the printing plate is caused by absorption of the ester compound of the oily ink containing the ester compound into the photosensitive resin layer at the time of printing, but by containing the dibasic acid diester, absorption of the ester compound can be suppressed.

[0041] The mixed amount of the dibasic acid diester (B) in the photosensitive resin composition must be 2.5 to 15 mass%, and preferably 3.0 to 10 mass%. Since the dibasic acid diester has an effect of inhibiting the phenomenon in which an ester compound contained in the oily ink is absorbed into the photosensitive resin layer, when the mixed amount is less than the above lower limit, the resistance to swelling of the oily ink is poor. On the other hand, when the mixed amount is more than the above upper limit, the physical properties are reduced due to the dibasic acid diester, and the print durability during long-term printing is poor, which is not preferable.

[0042] The photopolymerizable compound (C) is preferably a photopolymerizable oligomer, and particularly preferably a conjugated diene-based ethylenic polymer having an ethylenic unsaturated group bonded to the terminal and / or side chain of the conjugated diene polymer, and the number average molecular weight is 500 or more and 10,000 or less.

[0043] The conjugated diene-based polymer constituting the conjugated diene-based ethylenic polymer is constituted by a homopolymer of a conjugated diene unsaturated compound or a copolymer of a conjugated diene unsaturated compound and a mono-ethylenic unsaturated compound. As such a homopolymer of a conjugated diene unsaturated compound or a copolymer of a conjugated diene unsaturated compound and a mono-ethylenic unsaturated compound, a butadiene polymer, an isoprene polymer, a chloroprene polymer, a styrene-chloroprene copolymer, an acrylonitrile-butadiene copolymer, an acrylonitrile-isoprene copolymer, a methyl methacrylate-isoprene copolymer, an acrylonitrile-isoprene copolymer, a methyl methacrylate-isoprene copolymer, a methyl methacrylate-chloroprene copolymer, a methyl acrylate-butadiene copolymer, a methyl acrylate-isoprene copolymer, a methyl acrylate-chloroprene copolymer, a methyl acrylate-chloroprene copolymer, an acrylonitrile-butadiene-styrene copolymer, an acrylonitrile-chloroprene-styrene copolymer, and the like can be given. Among these, from the viewpoint of rubber elasticity and photocurability, a butadiene polymer, an isoprene polymer, an acrylonitrile-butadiene copolymer are preferable, and a butadiene polymer, an isoprene polymer are particularly preferable.

[0044] The method of introducing terminal and / or side chain ethylenically unsaturated groups into the diene polymer is not particularly limited, and examples include (i) a method in which the terminal hydroxyl group of a hydroxyl-terminated conjugated diene polymer obtained by a dehydration reaction of a monoethylenically unsaturated carboxylic acid such as (meth)acrylic acid with hydrogen peroxide as a polymerization initiator is ester-bonded, or a method in which an alkyl ester of a monoethylenically unsaturated carboxylic acid such as methyl (meth)acrylate or ethyl (meth)acrylate is ester-bonded to the above hydroxyl group by a transesterification reaction, (ii) a method in which an ethylenically unsaturated alcohol such as allyl alcohol or vinyl alcohol is reacted with a conjugated diene polymer obtained by copolymerizing a conjugated diene compound with an ethylenically unsaturated compound containing at least partially an unsaturated carboxylic acid (ester), and the like.

[0045] As the component of the photopolymerizable compound (C), in addition to the above-mentioned photopolymerizable oligomer, an alkyl methacrylate can be used. As the alkyl methacrylate, a linear alkyl methacrylate having 8 to 18 carbon atoms is preferred.

[0046] Specific examples include (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate; (meth)acrylic acid cycloalkyl esters such as cyclohexyl (meth)acrylate; (meth)acrylic acid halogenated alkyl esters such as chloroethyl (meth)acrylate and chloropropyl (meth)acrylate; (meth)acrylic acid alkoxyalkyl esters such as methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, and butoxyethyl (meth)acrylate; (meth)acrylic acid phenoxyalkyl esters such as phenoxyethyl (meth)acrylate and nonylphenoxyethyl (meth)acrylate; and the like, with particular preference given to n-lauryl methacrylate, alkyl (C12-13) methacrylate, tridecyl methacrylate, alkyl (C12-15) methacrylate, and the like.

[0047] The mixing amount of the photopolymerizable compound (C) in the photosensitive resin composition is preferably 5 to 70% by mass, and more preferably 10 to 60% by mass. When the mixing amount is less than the above lower limit, there is a possibility that the time required for curing by ultraviolet irradiation will significantly lengthen, and when the mixing amount is greater than the above upper limit, there is a possibility that the depth of the grooves, characters, and the like will become extremely shallow.

[0048] The photopolymerization initiator (D) is not particularly limited as long as it is a photopolymerization initiator capable of polymerizing a polymerizable carbon-carbon unsaturated group by light. A conventionally known photopolymerization initiator is used, and a photopolymerization initiator having a function of generating a radical by light absorption, by self-decomposition, or by hydrogen abstraction is particularly preferred. For example, benzoin alkyl ethers, benzophenones, anthraquinones, benzils, phenylethanones, diacetyls, and the like can be given. The mixing amount of the photopolymerization initiator (D) is preferably in the range of 0.1 to 50 parts by mass, and more preferably in the range of 0.3 to 10 parts by mass, relative to 100 parts by mass of the high molecular compound (A). When the mixing amount is less than the above lower limit, there is a possibility that the initiation efficiency decreases and the image reproducibility is poor. When the mixing amount is more than the above upper limit, there is a possibility that the sensitivity is excessively high and the control of the exposure time becomes difficult.

[0049] A plasticizer can also be further added to the photosensitive resin composition. The plasticizer is not particularly limited as long as it is a plasticizer having a property of generally softening a plate material, but a plasticizer having good compatibility with the high molecular compound (A) and the photopolymerizable compound (C) is preferred.

[0050] Further, in order to improve the heat stability of the photosensitive resin composition, a conventionally known polymerization inhibitor can be added to the photosensitive resin composition. As the preferred polymerization inhibitor, phenols, hydroquinones, catechols, and the like can be given. The mixing amount thereof is generally used in the range of 0.001 to 5% by mass relative to the entire photosensitive resin composition.

[0051] In addition, as other arbitrary components, dyes, pigments, viscosity adjusting agents, antifoaming agents, ultraviolet absorbers, perfumes, anti-aggregation agents, surfactants, and the like can be given.

[0052] Next, the method for manufacturing the printing master plate of the present application will be described. First, the above components are prepared, and a photosensitive resin composition is manufactured by mixing them. Next, the obtained photosensitive resin composition is formed into a layer to obtain a photosensitive resin layer. Specifically, a method in which the components of the photosensitive resin composition are mixed using an extruder, kneader, or the like, and then the photosensitive resin layer of the desired thickness is formed by hot press molding, calendering, or extrusion molding can be given. In the obtained photosensitive resin layer, in order to maintain the precision as a printing plate, a support such as polyester can be provided on the side opposite to the surface that will become the relief plate. In addition, since the photosensitive resin layer can become tacky depending on its composition, in order to make the contact with the transparent image carrier (negative film) that is overlaid thereon good, and in order to enable the reuse of the image carrier, a flexible film layer that can be developed in an aqueous system can be provided on the surface thereof. These supports and flexible film layers can be attached to the photosensitive resin layer by roll lamination after the sheet is formed. In addition, heating and pressurization can be performed after lamination to obtain a photosensitive resin layer with good precision.

[0053] Next, the method for obtaining a printing plate from the printing master plate of the present application will be described. First, the photosensitive resin layer in the printing master plate of the present application is subjected to light irradiation through a transparent image carrier, and the irradiated portions are photocured to form an image. Then, the non-irradiated portions are removed (developed) using an aqueous developer, and thus a relief plate (printing plate) is obtained.

[0054] As the active light source for photocuring, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultraviolet fluorescent lamp, a carbon arc lamp, a xenon lamp, a zircon lamp, sunlight, or the like can be given.

[0055] As the aqueous developer, water alone can be used, or a developer obtained by mixing a nonionic, anionic, or the like surfactant, a pH adjuster as necessary, a detergent, or the like with water can be used.

[0056] Specific examples of the nonionic surfactant are polyoxyalkylene alkyl or alkenyl ether, polyoxyalkylene alkyl or alkenyl phenyl ether, polyoxyalkylene alkyl or alkenyl amine, polyoxyalkylene alkyl or alkenyl amide, an oxirane / propylene oxide block adduct, or the like. Specific examples of the anionic surfactant are a linear alkylbenzene sulfonate having an alkyl group with an average carbon atom number of 8 to 16, an α-olefin sulfonate with an average carbon atom number of 10 to 20, a dialkyl sulfosuccinate with a carbon atom number of 4 to 10 in the alkyl or alkenyl group, a sulfonate of a fatty acid lower alkyl ester, an alkyl sulfate with an average carbon atom number of 10 to 20, an alkyl ether sulfate having a linear or branched alkyl or alkenyl group with an average carbon atom number of 10 to 20 and to which 0.5 to 8 moles of oxirane on average are added, a saturated or unsaturated fatty acid salt with an average carbon atom number of 10 to 22, or the like.

[0057] In addition, as the pH adjuster, sodium borate, sodium carbonate, sodium silicate, sodium metasilicate, sodium succinate, sodium acetate, and the like can be given. Among these, from the viewpoint of solubility in water, sodium silicate is preferred.

[0058] In addition, as the washing aid, amines such as monoethanolamine, diethanolamine, triethanolamine, ammonium salts such as tetramethylammonium hydroxide, and alkanes can be given. The washing aid can improve the washing ability by being used in combination with the above-mentioned surfactant and pH adjuster.

[0059] These surfactants, pH adjusters, and washing aids are used in a mixed amount in a range of 0.1 to 50% by mass (preferably 1 to 10% by mass) in water.

[0060] After development, the plate is usually dried in an oven at about 60°C for 15 to 120 minutes.

[0061] Depending on the composition of the photosensitive resin composition constituting the photosensitive resin layer, there can be cases where stickiness remains on the surface of the plate even after the end of drying. In such cases, the stickiness can be removed by a known surface treatment method. As the surface treatment method, exposure treatment by active light having a wavelength of 300 nm or less is desirable.

[0062] The photosensitive resin composition of the present application is most suitable for use in relief printing using an oily ink containing an ester compound for printing of cloth labels, but is not limited to this use, and can also be used for flexographic printing, lithographic printing, gravure printing, hole printing, and a photoresist.

[0063] Examples

[0064] The effects of the present application will be shown by the following examples, but the present application is not limited to these examples. In addition, the parts in the examples indicate mass parts, and the values indicating the composition ratio in the table also indicate mass parts.

[0065] Examples 1 to 11 and Comparative Examples 1 to 3 (Examples in which a latex is used as the high molecular compound (A))

[0066] Each component was mixed so as to become the mixed composition (mass parts) described in Table 1, and kneaded in a kneader at 100°C, whereby the photosensitive resin compositions of Examples 1 to 11 and Comparative Examples 1 to 3 were prepared.

[0067] [Table 1]

[0068]

[0069] The details of each mixed component used in Table 1 are as follows.

[0070] Polymer compound (A)

[0071] • Butadiene latex (Nipol LX111NF, non-volatile content 55%, manufactured by Zeon Corporation, Japan)

[0072] • Acrylonitrile-butadiene latex (Nipol SX1503, non-volatile content 42%, manufactured by Zeon Corporation, Japan)

[0073] Dibasic acid diester (B)

[0074] • Dimethyl succinate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0075] • Dimethyl glutarate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0076] • Dimethyl adipate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0077] • Dimethyl pimelic acid (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0078] • Dimethyl suberate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0079] • Dimethyl azelate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0080] • Dimethyl sebacate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0081] • Dimethyl phthalate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0082] • Di(2-ethylhexyl) adipate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0083] Photopolymerizable compound (C)

[0084] • Oligomeric butadiene acrylate (ABU-4, manufactured by Kyoeisha Chemical Co., Ltd.)

[0085] • Lauryl methacrylate (LIGHT ESTER L, manufactured by Kyoeisha Chemical Co., Ltd.)

[0086] • Dihydroxymethyl tricyclodecane diacrylate (LIGHT ACRYLATE DCP-A, manufactured by Kyoeisha Chemical Co., Ltd.)

[0087] Photopolymerization initiator (D)

[0088] • Benzil dimethyl ketal (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0089] Other components

[0090] • Hydroquinone monomethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0091] A film obtained by coating a polyester adhesive layer onto a 125 μm thick polyethylene terephthalate film and a film obtained by coating an anti-adhesion layer (polyvinyl alcohol) onto the same polyethylene terephthalate film are sandwiched together with the photosensitive resin compositions of the various embodiments and comparative examples obtained above, such that the adhesive layer, the anti-adhesion layer and the photosensitive resin composition are in contact, and the mixture is hot-pressed at 105°C and 100 kg / cm². 2 The pressure is applied for 1 minute, thereby creating a printing master with a total thickness of 1.825 mm and a photosensitive resin layer with a thickness of 1.7 mm.

[0092] Next, an illuminance of 17.5 W / m² at 365 nm was used. 2 A UV lamp (Anderson & Vreeland FR20T12-BL-9-BP) was used to back-exposure the prepared printing master from the base side, resulting in a relief depth of 0.8 mm. Then, a negative containing images of the letter T with raised 3, 5, and 10 dots, along with a solid image and a gray step guide, was placed on the master for a main exposure, achieving a gray step guide reproduction of 15 levels. The negative was then removed, and the master was developed for 8 minutes in neutral water at 40°C with 4% sodium alkylnaphthalene sulfonate, followed by drying at 60°C for 10 minutes. A 5-minute post-exposure was then performed using the same UV lamp. Finally, a 5-minute surface treatment was applied with a germicidal lamp to obtain the evaluation relief.

[0093] Examples 12-21 and Comparative Examples 4-6 (Examples using polyamide resin or partially saponified polyvinyl acetate resin as polymer compound (A))

[0094] The components were mixed in a reactor to form the mixture (parts by mass) shown in Table 2, and concentrated until the temperature inside the reactor reached 110°C, thus preparing the photosensitive resin compositions of Examples 12-21 and Comparative Examples 4-6.

[0095] [Table 2]

[0096]

[0097] The details of each component used in Table 2 are as follows.

[0098] Polymer compound (A)

[0099] Polymer 1 synthesized in the following order

[0100] • Polymer 2 synthesized in the following order

[0101] • Partially saponified polyvinyl acetate (Gohsenol TM KH-17 manufactured by Mitsubishi Chemical, degree of saponification 78.5-81.5%, average polymerization degree 1700)

[0102] Dibasic acid diester (B)

[0103] • Dimethyl succinate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0104] • Dimethyl glutarate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0105] • Dimethyl adipate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0106] • Dimethyl pimelic acid (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0107] • Dimethyl suberate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0108] • Dimethyl azelate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0109] • Dimethyl sebacate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0110] • Dimethyl phthalate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0111] • Di(2-ethylhexyl) adipate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0112] Photopolymerizable compound (C)

[0113] • Acrylic acid adduct of propylene glycol diglycidyl ether (EPOXY ESTER 70PA, KAYARAD Co., Ltd.)

[0114] • Glycerol dimethyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0115] • Tetrahydrofurfuryl methacrylate (LIGHT ESTER THF (1000), KAYARAD Co., Ltd.)

[0116] Photopolymerization initiator (D)

[0117] • Benzil dimethyl ketal (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0118] Other components

[0119] • Diethylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0120] • N-ethyltoluene sulfonamide (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0121] • Lactic acid (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0122] • Pentaerythritol polyoxyethylene ether (manufactured by Nikko Chemicals Co., Ltd.)

[0123] • 1,4-naphthoquinone (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0124] • Hydroquinone monomethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0125] (Synthesis of Polymer 1)

[0126] ε-caprolactam 50 parts, N,N'-bis(γ-aminopropyl)piperazine adipate 56 parts, 1,3-bisaminomethylcyclohexane adipate 6.3 parts, and water 10 parts were charged into a reactor, which was closed after being sufficiently replaced with nitrogen and slowly heated. From the time when the internal pressure reached 10 kg / cm 2 2, the water in the reactor was slowly distilled off, and the pressure was returned to the normal pressure in 1 hour, and then the reaction was carried out under the normal pressure for 1.0 hour. The maximum polymerization temperature was 220°C. In this way, a transparent pale yellow alcohol-soluble oligomer having a number average molecular weight of about 3,000, a specific viscosity of 1.5, and a block structure in which both terminals were substantially primary amino groups and amide bonds were combined was obtained. After 46 parts of this oligomer were dissolved in 200 parts of methanol, 9 parts of an organic diisocyanate compound having isocyanate groups at both terminals, which was obtained by reacting 1000 parts of polypropylene glycol (weight average molecular weight: 1000) with 369 parts of hexamethylene diisocyanate, were slowly added with stirring. The reaction of both (oligomer and organic diisocyanate compound) was completed at 65°C in about 15 minutes. After the solution was left in a Petri dish coated with Teflon (registered trademark), methanol was evaporated and removed, and then the solution was dried under reduced pressure to obtain a polyamide block copolymer (polymer 1). The polyamide block copolymer was a high molecular compound having a specific viscosity of 2.0, a block component containing 82% by mass of a structural unit composed of an amide bond, and a urea bond and a urethane bond in addition to the amide bond.

[0127] (Synthesis of Polymer 2)

[0128] ε-caprolactam 55 parts, N,N'-bis(γ-aminopropyl)piperazine adipate 40 parts, 1,3-bisaminomethylcyclohexane adipate 7.5 parts, and water 100 parts were charged into a reactor, which was closed after being sufficiently replaced with nitrogen and slowly heated. From the time when the internal pressure reached 10 kg / cm 2The reaction was started at the time point of 0.5 hours after the start of the reaction, the water in the reactor was distilled off slowly, and the pressure was returned to the normal pressure in 1 hour, and then the reaction was carried out for 1.0 hour under the normal pressure to obtain a polyamide (polymer 2). The specific viscosity of the polyamide was 2.4, and it was a high molecular compound composed of only amide bonds.

[0129] A film obtained by applying a polyester-based adhesive layer to a polyethylene terephthalate film having a thickness of 125 μm was laminated to a film obtained by applying a tack-preventing layer (polyvinyl alcohol) to the same polyethylene terephthalate film, so that the adhesive layer and the tack-preventing layer were in contact with the photosensitive resin composition of each of the examples and comparative examples obtained as described above, to produce a printing master having a total thickness of 1.825 mm and a photosensitive resin layer having a thickness of 1.7 mm

[0130] Next, the printing master produced was subjected to back exposure from the base side using an ultraviolet lamp (lamp FR20T12-BL-9-BP manufactured by Anderson & Vreeland) having an illuminance of 17.5 W / m 2 at 365 nm, so that the relief depth became 0.8 mm. Then, a negative film containing an image of a letter T having reliefs of 3 dots, 5 dots and 10 dots and a solid image, and a gray scale were placed on the master, and main exposure was performed so that the gray scale reproduced 15 levels. Then, the negative film was removed, and development was performed using tap water at 25°C for 3 minutes, and warm air drying at 70°C for 10 minutes. Then, after-exposure was performed using the same ultraviolet lamp for 2 minutes to obtain a relief for evaluation.

[0131] Evaluation of the printing master obtained from the photosensitive resin composition of each of the examples and comparative examples was performed using the relief for evaluation, and image reproducibility, printability (line thickening) and print durability (relief chipping resistance) were evaluated. The results are shown in Table 3. In addition, printability (line thickening) and print durability (relief chipping resistance) were evaluated for both cases of label printing using an oily ink containing an ester compound and flexographic printing using an aqueous ink. The specific evaluation steps were as follows.

[0132] (Image reproducibility)

[0133] Image reproducibility was evaluated in terms of the smallest relief letter that could be reproduced. Specifically, "O" indicates that a relief letter of 3 dots could be reproduced, "Δ" indicates that a relief letter of 5 dots could be reproduced, "X" indicates that a relief letter of 10 dots could be reproduced, and "X X" indicates that a letter of 10 dots could not be reproduced.

[0134] (Printability and print durability at the time of label printing)

[0135] The evaluation relief was printed with a label printer (Shanghai Huanye Machine PT 2 / 1). Specifically, 8000 m (50000 shots) were printed using Fabrifast MIXING BLACK (ink containing dimethyl succinate, dimethyl adipate, dimethyl glutarate) manufactured by Perfectos as the oil-based ink, using Nylon Taffeta as the substrate.

[0136] (Printability)

[0137] The printability (line thickening) was evaluated in terms of the ratio of the vertical line width of the 5pt T letter of the print after 100 shots and the print after 50000 shots. Specifically, O was indicated when the ratio of the line width was 1.0 or more and less than 1.5, Δ was indicated when the ratio of the line width was 1.5 or more and less than 2.0, X was indicated when the ratio of the line width was 2.0 or more, and XX was indicated when the relief could not be printed.

[0138] (Print durability)

[0139] The print durability (resistance of the relief to dropping) was evaluated by the presence or absence of dropping of the relief after 50000 shots. Specifically, O was indicated when there was no dropping of the relief, and X was indicated when dropping of the relief was found.

[0140] (Printability and print durability at the time of flexographic printing)

[0141] The evaluation relief was printed with a flexographic printer (FPR302 manufactured by MCK Co., Ltd.). Specifically, 8000 m (50000 shots) were printed using ROBOT INK (ink containing propyl acetate) manufactured by Inktech Limited as the oil-based ink, using PPC50 / OPT1 / GB82 manufactured by Oji Tac Corporation as the substrate.

[0142] (Printability)

[0143] The printability (line thickening) was evaluated in terms of the ratio of the vertical line width of the 5pt T letter of the print after 100 shots and the print after 50000 shots. Specifically, O was indicated when the ratio of the line width was 1.0 or more and less than 1.5, Δ was indicated when the ratio of the line width was 1.5 or more and less than 2.0, X was indicated when the ratio of the line width was 2.0 or more, and XX was indicated when the relief could not be printed.

[0144] (Print durability)

[0145] The evaluation of the printing durability (resistance to drop of the relief) was judged by the presence or absence of drop of the relief after 50,000 times of exposure printing. Specifically, no drop of the relief was indicated as O, and drop of the relief was indicated as X.

[0146] [Table 3]

[0147]

[0148] As is apparent from Table 3, the image reproducibility, the printing property (line thickening), and the printing durability (resistance to drop of the relief) of Examples 1 to 21 satisfying the requirements of the present application were all excellent. In contrast, the printing property (line thickening) of Comparative Examples 1, 4 not containing the binary acid diester (B) at all and Comparative Examples 2, 5 containing the binary acid diester (B) in an amount less than the lower limit were poor. The printing durability (resistance to drop of the relief) of Comparative Examples 3, 6 containing the binary acid diester (B) in an amount more than the upper limit was poor.

[0149] Industrial applicability

[0150] The printing plate obtained from the photosensitive resin printing plate precursor for relief printing of the present application is small in swelling of the printing plate caused by absorption of ink even when an oily ink containing an ester compound is used, and thus hardly causes line thickening of the image of the printed matter even when long-term printing is performed. Therefore, the present application can perform long-term printing in flexographic printing including label printing, and is expected to make a great contribution to the field.

Claims

1. A photosensitive resin printing master for relief printing, having a photosensitive resin layer formed from a photosensitive resin composition containing at least a high molecular compound A, a dibasic acid diester B, a photopolymerizable compound C, and a photopolymerization initiator D, characterized in that, the content of the dibasic acid diester B in the photosensitive resin composition is 2.5 to 15 mass%, the dibasic acid diester B is at least one selected from the group consisting of succinic acid diester, glutaric acid diester, adipic acid diester, pimelic acid diester, suberic acid diester, azelaic acid diester, sebacic acid diester, and phthalic acid diester.

2. The photopolymer printing plate precursor for letterpress printing according to claim 1, characterized in that, the high molecular compound A is a latex having a butadiene skeleton and / or an isoprene skeleton.

3. The photopolymer printing plate precursor for relief printing according to claim 1 or 2, characterized in that, the latex is a polybutadiene latex, a styrene-butadiene copolymer latex, an acrylonitrile-butadiene copolymer latex, a methyl methacrylate-butadiene copolymer latex, a polyisoprene latex, or a latex obtained by further copolymerizing acrylic acid or methacrylic acid with the above copolymer latex.

4. The photopolymer printing plate precursor for letterpress printing according to claim 3, characterized in that, the latex is at least one water-dispersible latex selected from the group consisting of a polybutadiene latex, a styrene-butadiene copolymer latex, an acrylonitrile-butadiene copolymer latex, a methyl methacrylate-butadiene copolymer latex, and a latex obtained by further copolymerizing acrylic acid or methacrylic acid with the above copolymer latex.

5. The photopolymer printing plate precursor for relief printing according to claim 1 or 2, characterized in that, the high molecular compound A is a polyamide resin composed of a polyamide and / or a polyamide block copolymer, and / or a partially saponified polyvinyl acetate resin.

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