Photosensitive resin printing plate for relief printing

Abstract

To provide a photosensitive resin printing original plate for letterpress printing which is excellent in swelling resistance to oil-based ink containing an ester-based compound.SOLUTION: A photosensitive resin printing original plate for letterpress printing has a photosensitive resin layer composed of a photosensitive resin composition containing a polymer compound (A), a dibasic diester (B) represented by general formula (I), a photopolymerizable compound (C), and a photopolymerization initiator (D). The polymer compound (A) is a latex having a butadiene skeleton and / or an isoprene skeleton, and when the latex is the latex having the butadiene skeleton, the latex is at least one kind of a water-dispersible latex selected from the group consisting of a polybutadiene latex, a styrene-butadiene copolymer latex, an acrylonitrile-butadiene copolymer latex, and a methyl methacrylate-butadiene copolymer latex. The content of the dibasic diester (B) in the photosensitive resin composition is 2.5 to 15 mass%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a photosensitive resin printing plate precursor for letterpress printing that has excellent swelling resistance to oil-based inks, and in particular to a photosensitive resin printing plate precursor for letterpress printing that has excellent swelling resistance to oil-based inks containing ester compounds used in tag printing on fabrics. [Background technology]

[0002] Conventionally, a method for producing a printing plate by developing a printing master plate has been to use a developer made of an organic solvent. However, due to concerns about the working environment, a method for producing a printing plate by developing with water or an aqueous developer in which a surfactant or the like is added to water has been proposed (see, for example, Patent Documents 1 to 3).

[0003] These conventional proposals generally disclose that the hardness can be reduced and the impact resilience can be improved by incorporating a plasticizer into the printing plate precursor. However, on the other hand, the inclusion of a plasticizer results in insufficient mechanical strength of the resulting printing plate, which can lead to problems with printing durability, such as cracking of the printing plate and loss of relief image during long-run printing.

[0004] Furthermore, when printing on cloth tags, oil-based inks containing ester compounds are used, but conventional printing plates absorb the ink and swell during printing, causing the lines to thicken during long-run printing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 3-198058 [Patent Document 2] International Publication No. 2014 / 034213 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-287887 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made to solve the problems of the prior art, and an object of the present invention is to provide a photosensitive resin printing plate precursor for letterpress printing that has excellent resistance to swelling with oil-based inks, and in particular to provide a photosensitive resin printing plate precursor for letterpress printing that has excellent resistance to swelling with oil-based inks that contain ester compounds. [Means for solving the problem]

[0007] As a result of extensive research to achieve this object, the present inventors have discovered that by incorporating a specific amount of a dibasic acid diester into the photosensitive resin layer that constitutes the printing plate blank, a printing plate blank having excellent resistance to swelling with oil-based inks can be obtained, leading to the completion of the present invention.

[0008] That is, the present invention has the following features (1) to (6). (1) A photosensitive resin printing plate precursor for letterpress printing having a photosensitive resin layer made of a photosensitive resin composition containing at least a polymer compound (A), a dibasic acid diester (B) represented by the following general formula (I), a photopolymerizable compound (C), and a photopolymerization initiator (D), wherein the content of the dibasic acid diester (B) in the photosensitive resin composition is 2.5 to 15 mass %. TIFF0007759566000001.tif27137 (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 or different and represent a linear or branched aliphatic hydrocarbon group having 1 to 12 carbon atoms.) (2) The photosensitive resin printing plate precursor for letterpress printing according to (1), wherein the dibasic acid diester (B) is at least one selected from the group consisting of succinic acid diesters, glutaric acid diesters, adipic acid diesters, pimelic acid diesters, suberic acid diesters, azelaic acid diesters, sebacic acid diesters, and phthalic acid diesters. (3) The photosensitive resin printing plate precursor for letterpress printing according to (1) or (2), wherein the polymer compound (A) is a latex having a butadiene skeleton and / or an isoprene skeleton. (4) The photosensitive resin printing plate precursor for letterpress printing according to (3), characterized in that the latex is polybutadiene latex, styrene-butadiene copolymer latex, acrylonitrile-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, polyisoprene latex, or a latex obtained by further copolymerizing the above copolymer latex with acrylic acid or methacrylic acid. (5) The photosensitive resin printing plate precursor for letterpress 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 the copolymer latex with acrylic acid or methacrylic acid. (6) A photosensitive resin printing plate precursor for letterpress printing according to (1) or (2), characterized in that the polymer compound (A) is a polyamide resin consisting of polyamide and / or polyamide block copolymer, and / or a partially saponified polyvinyl acetate resin. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a photosensitive resin printing plate precursor for relief printing which exhibits minimal swelling of the printing plate due to ink absorption, even when an oil-based ink containing an ester compound is used, and therefore produces almost no line thickening of the printed image even when printing is carried out in a long run. DETAILED DESCRIPTION OF THE INVENTION

[0010] The photosensitive resin printing original plate for relief printing of the present invention has a photosensitive resin layer made of a photosensitive resin composition containing at least a polymer compound (A), a dibasic acid diester (B) represented by the following general formula (I), a photopolymerizable compound (C), and a photopolymerization initiator (D). Each component of the photosensitive resin composition will be described below.

[0011] The polymer compound (A) is not particularly limited as long as it is used in this field. However, from the viewpoint of suitability for a relief printing plate precursor, (i) a latex having a butadiene skeleton and / or an isoprene skeleton, (ii) a polyamide resin comprising a polyamide and / or a polyamide block copolymer, and / or (iii) Partially saponified polyvinyl acetate resin is preferred.

[0012] (i) The latex having a butadiene skeleton and / or an isoprene skeleton may be appropriately selected from conventionally known latexes, such as polybutadiene latex, styrene-butadiene copolymer latex, acrylonitrile-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, and polyisoprene latex. These latexes may be modified with (meth)acrylic, carboxy, silicone, fluorine, or the like, as desired. Many different synthetic and natural latexes are commercially available, and an appropriate latex may be selected from these.

[0013] Among these, a water-dispersed latex containing a butadiene skeleton in the molecular chain is preferably used from the viewpoint of hardness and rubber elasticity.Specific examples of such a water-dispersed latex include polybutadiene latex, styrene-butadiene copolymer latex, acrylonitrile-butadiene copolymer latex, methyl methacrylate-butadiene copolymer latex, and copolymer latexes obtained by copolymerizing the above copolymers with acrylic acid or methacrylic acid, and more preferably polybutadiene latex and acrylonitrile-butadiene copolymer latex.

[0014] (ii) Polyamide resins made of polyamides and / or polyamide block copolymers can be polymeric compounds containing 50% by weight or more, preferably 70% by weight or more, of structural units composed of amide bonds in the form of blocks in the molecule. Examples include polyetheramides, polyetheresteramides, tertiary nitrogen-containing polyamides, ammonium salt-type tertiary nitrogen-containing polyamides, and addition polymers of amide compounds having one or more amide bonds and organic diisocyanate compounds. Among these, ammonium salt-type tertiary nitrogen-containing polyamides are preferred. Furthermore, when tertiary nitrogen-containing polyamides and ammonium salt-type tertiary nitrogen-containing polyamides are used, the development properties are improved by adding an organic acid. Examples of organic acids include, but are not limited to, acetic acid, lactic acid, and methacrylic acid.

[0015] (iii) The partially saponified polyvinyl acetate resin is not particularly limited as long as it is one that is used in this field, but from the viewpoint of image reproducibility of letterpress printing plates, 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 preferred.

[0016] The blending amount of the polymer compound (A) in the photosensitive resin composition is preferably 30 to 80% by mass, more preferably 40 to 75% by mass. If the blending amount is less than the lower limit, the strength of the printing plate may be insufficient, and if the blending amount is more than the upper limit, the water development may take a long time.

[0017] The dibasic acid diester (B) is a compound obtained by esterifying an organic acid having a structure capable of separating two protons in water, and specifically, is a compound represented by the following general formula (I). TIFF0007759566000002.tif27137 (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 or different and represent a linear or branched aliphatic hydrocarbon group having 1 to 12 carbon atoms.)

[0018] Specific examples of dibasic acid diesters having such a structure include 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, and diethyl hexafluorosilicate. Examples of suitable esters include ethyl, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, bis(2-ethylhexyl) phthalate, diisononyl phthalate, ethylphthalyl ethyl glycolate, dibutyl adipate, diisobutyl adipate, bis(2-ethylhexyl) adipate, diisononyl adipate, diisodecyl adipate, bis[2-(2-butoxyethoxy)ethyl] adipate, bis(2-ethylhexyl) azelate, and dibutyl sebacate. These may be used alone or in combination of two or more.

[0019] Of these, 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 are preferred.

[0020] By incorporating such a dibasic acid diester into the photosensitive resin layer, it is possible to obtain a printing plate that has excellent resistance to swelling caused by oil-based inks containing ester compounds. In particular, swelling of the printing plate occurs when the ester compounds of the oil-based inks containing ester compounds are absorbed into the photosensitive resin layer during printing, but the inclusion of a dibasic acid diester can suppress absorption of the ester compounds.

[0021] The amount of dibasic acid diester (B) in the photosensitive resin composition must be 2.5 to 15% by mass, and preferably 3.0 to 10% by mass. The dibasic acid diester has the effect of suppressing the phenomenon in which an ester compound contained in an oil-based ink is absorbed into the photosensitive resin layer. Therefore, if the amount is less than the lower limit, swelling resistance to oil-based ink is poor. On the other hand, if the amount is more than the upper limit, the physical properties caused by the dibasic acid diester are reduced, resulting in poor print durability during long-run printing, which is undesirable.

[0022] The photopolymerizable compound (C) is preferably a photopolymerizable oligomer, and in particular, a conjugated diene-based ethylenic polymer in which an ethylenically unsaturated group is bonded to the end and / or side chain of the conjugated diene-based polymer, and preferably has a number average molecular weight of 500 or more and 10,000 or less.

[0023] The conjugated diene polymer constituting the conjugated diene ethylenic polymer is composed of a homopolymer of a conjugated diene unsaturated compound or a copolymer of a conjugated diene unsaturated compound and a monoethylenically unsaturated compound. Examples of such homopolymers of conjugated diene unsaturated compounds or copolymers of conjugated diene unsaturated compounds and monoethylenically unsaturated compounds include butadiene polymers, isoprene polymers, chloroprene polymers, styrene-chloroprene copolymers, acrylonitrile-butadiene copolymers, acrylonitrile-isoprene copolymers, methyl methacrylate-isoprene copolymers, acrylonitrile-isoprene copolymers, methyl methacrylate-isoprene copolymers, methyl methacrylate-chloroprene copolymers, methyl acrylate-butadiene copolymers, methyl acrylate-isoprene copolymers, methyl acrylate-chloroprene copolymers, methyl acrylate-chloroprene copolymers, acrylonitrile-butadiene-styrene copolymers, and acrylonitrile-chloroprene-styrene copolymers. Among these, butadiene polymers, isoprene polymers, and acrylonitrile-butadiene copolymers are preferred in terms of rubber elasticity and photocurability, and butadiene polymers and isoprene polymers are particularly preferred.

[0024] The method for introducing an ethylenically unsaturated group into the terminal and / or side chain of a conjugated diene polymer is not particularly limited, and examples thereof include: (i) a method in which a monoethylenically unsaturated carboxylic acid such as (meth)acrylic acid is ester-bonded to the terminal hydroxyl group of a hydroxyl-terminated conjugated diene polymer obtained using hydrogen peroxide as a polymerization initiator by a dehydration reaction, or a method in which a monoethylenically unsaturated carboxylic acid alkyl ester such as methyl (meth)acrylate or ethyl (meth)acrylate is ester-bonded to the terminal hydroxyl group by a transesterification reaction; and (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 and an ethylenically unsaturated compound at least partially containing an unsaturated carboxylic acid (ester).

[0025] As the photopolymerizable compound (C), in addition to the above-mentioned photopolymerizable oligomer, alkyl methacrylate can be used. As the alkyl methacrylate, those having 8 to 18 carbon atoms and being linear are preferred.

[0026] Specifically, alkyl (meth)acrylates 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; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate; and halogenated alkyl (meth)acrylates such as chloroethyl (meth)acrylate and chloropropyl (meth)acrylate. Examples of the alkyl (meth)acrylate include alkoxyalkyl (meth)acrylates such as acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, and butoxyethyl (meth)acrylate; and phenoxyalkyl (meth)acrylates such as phenoxyethyl (meth)acrylate and nonylphenoxyethyl (meth)acrylate. Particularly preferred examples include n-lauryl methacrylate, alkyl (C12-13) methacrylate, tridecyl methacrylate, and alkyl (C12-15) methacrylate.

[0027] The 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. If the amount is less than the lower limit, the time required for curing by ultraviolet irradiation may be significantly long, and if the amount is more than the upper limit, the depth of the recessed lines, recessed letters, etc. may become extremely shallow.

[0028] The photopolymerization initiator (D) can be any known initiator capable of polymerizing a polymerizable carbon-carbon unsaturated group by light. In particular, initiators capable of generating radicals by self-decomposition or hydrogen abstraction upon light absorption are preferred. Examples include benzoin alkyl ethers, benzophenones, anthraquinones, benzils, acetophenones, and diacetyls. The amount of photopolymerization initiator (D) is preferably 0.1 to 50 parts by mass, more preferably 0.3 to 10 parts by mass, per 100 parts by mass of polymer compound (A). If the amount is less than the lower limit, the initiation efficiency may decrease, potentially resulting in poor image reproducibility. If the amount is more than the upper limit, the sensitivity may be too high, potentially making it difficult to control the exposure time.

[0029] A plasticizer can also be added to the photosensitive resin composition. The plasticizer is not particularly limited as long as it generally has the property of softening the printing plate, but it is preferable that the plasticizer has good compatibility with the polymer compound (A) and the photopolymerizable compound (C).

[0030] In addition, to improve the thermal stability of the photosensitive resin composition, a conventionally known polymerization inhibitor can be added to the photosensitive resin composition. Preferred polymerization inhibitors include phenols, hydroquinones, and catechols. The amount of these to be added is generally in the range of 0.001 to 5% by mass based on the total weight of the photosensitive resin composition.

[0031] Other optional components include dyes, pigments, viscosity modifiers, antifoaming agents, ultraviolet absorbers, fragrances, anti-aggregating agents, surfactants, and the like.

[0032] Next, a method for producing a printing blank of the present invention will be described. First, the above-mentioned components are prepared and mixed to produce a photosensitive resin composition. Next, the resulting photosensitive resin composition is molded into a layer to obtain a photosensitive resin layer. Specifically, the components of the photosensitive resin composition are mixed using an extruder or kneader, and then a photosensitive resin layer of the desired thickness is formed by hot press molding, calendaring, or extrusion molding. To maintain the precision of the resulting photosensitive resin layer as a printing plate, a support such as polyester may be provided on the side opposite the relief surface. Furthermore, since the photosensitive resin layer may become sticky depending on its composition, a flexible film layer that can be developed with an aqueous system may be provided on its surface to improve contact with the transparent image carrier (negative film) to be placed on top of it and to enable the image carrier to be reused. These supports and flexible film layers can be adhered to the photosensitive resin layer by roll lamination after sheet molding. Furthermore, hot pressing after lamination can also be performed to obtain a photosensitive resin layer with high precision.

[0033] Next, a method for obtaining a printing plate from the printing plate blank of the present invention will be described. First, the photosensitive resin layer in the printing plate blank of the present invention is irradiated with light through a transparent image carrier, and the irradiated areas are photocured to form an image. Then, the unirradiated areas are removed (developed) using an aqueous developer to obtain a relief (printing plate).

[0034] Examples of actinic ray sources used for photocuring include low-pressure mercury lamps, high-pressure mercury lamps, ultraviolet fluorescent lamps, carbon arc lamps, xenon lamps, zirconium lamps, and sunlight.

[0035] The aqueous developer may be water alone or water containing a nonionic or anionic surfactant, and if necessary, a pH adjuster, a cleaning aid, or the like.

[0036] Specific examples of nonionic surfactants include polyoxyalkylene alkyl or alkenyl ethers, polyoxyalkylene alkyl or alkenyl phenyl ethers, polyoxyalkylene alkyl or alkenyl amines, polyoxyalkylene alkyl or alkenyl amides, ethylene oxide / propylene oxide block adducts, etc. Specific examples of anionic surfactants include linear alkylbenzene sulfonates having an alkyl group with an average of 8 to 16 carbon atoms, α-olefin sulfonates having an average of 10 to 20 carbon atoms, dialkyl sulfosuccinates having an alkyl or alkenyl group with 4 to 10 carbon atoms, sulfonates of lower alkyl fatty acid esters, alkyl sulfates having an average of 10 to 20 carbon atoms, alkyl ether sulfates having a linear or branched alkyl or alkenyl group with an average of 10 to 20 carbon atoms and to which an average of 0.5 to 8 moles of ethylene oxide have been added, and saturated or unsaturated fatty acid salts having an average of 10 to 22 carbon atoms.

[0037] Examples of pH adjusters include sodium borate, sodium carbonate, sodium silicate, sodium metasilicate, sodium succinate, sodium acetate, etc. Among these, sodium silicate is preferred in terms of its solubility in water.

[0038] Examples of cleaning aids include amines such as monoethanolamine, diethanolamine, and triethanolamine, ammonium salts such as tetramethylammonium hydroxide, and paraffinic hydrocarbons. The cleaning ability of cleaning aids can be improved by using them in combination with the above-mentioned surfactants and pH adjusters.

[0039] These surfactants, pH adjusters, and cleaning aids are added and mixed with water in an appropriate mixing ratio of 0.1 to 50% by mass, preferably 1 to 10% by mass.

[0040] After development, the plate is typically dried in an oven at about 60°C for 15 to 120 minutes.

[0041] Depending on the composition of the photosensitive resin composition that constitutes the photosensitive resin layer, stickiness may remain on the plate surface even after drying. In such cases, the stickiness can be removed by a known surface treatment method. The preferred surface treatment method is exposure to actinic rays with a wavelength of 300 nm or less.

[0042] The photosensitive resin composition of the present invention is most suitable for use in letterpress printing using oil-based ink containing an ester compound, such as for printing on cloth tags, but is not limited to this application, and can also be used for flexographic printing, lithographic printing, intaglio printing, stencil printing, and as a photoresist. [Example]

[0043] The effects of the present invention will be shown by the following examples, but the present invention is not limited thereto. In the examples, parts mean parts by mass, and the numerical values ​​showing the composition ratios in the tables also mean parts by mass.

[0044] Examples 1 to 11 and Comparative Examples 1 to 3 (Examples in which latex was used as polymer compound (A)) The components were blended to obtain the composition (parts by mass) shown in Table 1, and kneaded in a kneader at 100° C. to prepare the photosensitive resin compositions of Examples 1 to 11 and Comparative Examples 1 to 3.

[0045] [Table 1]

[0046] Details of each compounding component used in Table 1 are as follows: Polymer compound (A) Butadiene latex (Nipol LX111NF, non-volatile content 55%, manufactured by Zeon Corporation) Acrylonitrile-butadiene latex (Nipol SX1503, non-volatile content 42%, manufactured by Zeon Corporation) Dibasic acid diester (B) Dimethyl succinate (Tokyo Chemical Industry Co., Ltd.) Dimethyl glutarate (Tokyo Chemical Industry Co., Ltd.) Dimethyl adipate (Tokyo Chemical Industry Co., Ltd.) Dimethyl pimelate (Tokyo Chemical Industry Co., Ltd.) Dimethyl suberate (Tokyo Chemical Industry Co., Ltd.) Dimethyl azelaate (Tokyo Chemical Industry Co., Ltd.) Dimethyl sebacate (Tokyo Chemical Industry Co., Ltd.) Dimethyl phthalate (Tokyo Chemical Industry Co., Ltd.) Bis(2-ethylhexyl) adipate (Tokyo Chemical Industry Co., Ltd.) Photopolymerizable compound (C) Oligobutadiene acrylate (ABU-4, manufactured by Kyoeisha Chemical Co., Ltd.) Lauryl methacrylate (Light Ester L, manufactured by Kyoeisha Chemical Co., Ltd.) Dimethyloltricyclodecane diacrylate (Light Acrylate DCP-A, manufactured by Kyoeisha Chemical Co., Ltd.) Photopolymerization initiator (D) Benzyl dimethyl ketal (Tokyo Chemical Industry Co., Ltd.) Other ingredients Hydroquinone monomethyl ether (Tokyo Chemical Industry Co., Ltd.)

[0047] The photosensitive resin compositions of the Examples and Comparative Examples thus obtained were sandwiched between a 125 μm thick polyethylene terephthalate film coated with a polyester adhesive layer and another polyethylene terephthalate film coated with an anti-sticking layer (polyvinyl alcohol) so that the adhesive layer and the anti-sticking layer were in contact with the photosensitive resin composition, and then heated at 105°C and 100 kg / cm in a heat press. 2 A printing original plate having a total thickness of 1.825 mm and a photosensitive resin layer thickness of 1.7 mm was prepared by pressing the plate at a pressure of 0.055 for 1 minute.

[0048] Next, the prepared printing plate was exposed to light at an illuminance of 17.5 W / m at 365 nm. 2Using a 1000-millimeter UV lamp (F20T12-BL-9-BP, manufactured by Anderson & Vreeland), back exposure was performed from the base side to a relief depth of 0.8 mm. A negative film containing an image of a raised 3-point, 5-point, and 10-point letter T and a solid image, along with a step guide, was then placed on the master plate, and a main exposure was performed so that the step guide reproduced 15 steps. The negative film was then removed, and the plate was developed for 8 minutes in neutral water at 40°C containing 4% by weight of sodium alkylnaphthalenesulfonate, followed by drying at 60°C for 10 minutes. This was followed by a 5-minute post-exposure using the same UV lamp. The plate was then surface-treated by irradiating it with a germicidal lamp for 5 minutes, yielding a relief for evaluation.

[0049] Examples 12 to 21 and Comparative Examples 4 to 6 (Examples in which polyamide resin or partially saponified polyvinyl acetate resin was used as polymer compound (A)) The components were mixed in a kettle to obtain the composition (parts by mass) shown in Table 2, and the mixture was concentrated until the temperature inside the kettle reached 110°C, thereby preparing the photosensitive resin compositions of Examples 12 to 21 and Comparative Examples 4 to 6.

[0050] [Table 2]

[0051] Details of each component used in Table 2 are as follows: Polymer compound (A) Polymer 1 was synthesized using the following procedure: Polymer 2 was synthesized using the following procedure: Partially saponified polyvinyl acetate (Gohsenol TM KH-17 manufactured by Mitsubishi Chemical, degree of saponification 78.5~81.5%, average degree of polymerization 1700) Dibasic acid diester (B) Dimethyl succinate (Tokyo Chemical Industry Co., Ltd.) Dimethyl glutarate (Tokyo Chemical Industry Co., Ltd.) Dimethyl adipate (Tokyo Chemical Industry Co., Ltd.) Dimethyl pimelate (Tokyo Chemical Industry Co., Ltd.) Dimethyl suberate (Tokyo Chemical Industry Co., Ltd.) Dimethyl azelaate (Tokyo Chemical Industry Co., Ltd.) Dimethyl sebacate (Tokyo Chemical Industry Co., Ltd.) Dimethyl phthalate (Tokyo Chemical Industry Co., Ltd.) Bis(2-ethylhexyl) adipate (Tokyo Chemical Industry Co., Ltd.) Photopolymerizable compound (C) Propylene glycol diglycidyl ether acrylic acid adduct (Epoxy Ester 70PA, Kyoeisha Chemical Co., Ltd.) Glycerol dimethacrylate (Tokyo Chemical Industry Co., Ltd.) Tetrahydrofurfuryl methacrylate (Light Ester THF (1000) manufactured by Kyoeisha Chemical Co., Ltd.) Photopolymerization initiator (D) Benzyl dimethyl ketal (Tokyo Chemical Industry Co., Ltd.) Other ingredients Diethylene glycol (Tokyo Chemical Industry Co., Ltd.) N-ethyltoluenesulfonic acid amide (Tokyo Chemical Industry Co., Ltd.) Lactic acid (Tokyo Chemical Industry Co., Ltd.) Pentaerythritol polyoxyethylene ether (manufactured by Nippon Nyukazai Co., Ltd.) 1,4-Naphthoquinone (Tokyo Chemical Industry Co., Ltd.) Hydroquinone monomethyl ether (Tokyo Chemical Industry Co., Ltd.)

[0052] (Synthesis of Polymer 1) 50 parts of ε-caprolactam, 56 parts of N,N'-bis(γ-aminopropyl)piperazine adipate, 6.3 parts of 1,3-bisaminomethylcyclohexane adipate, and 10 parts of water were placed in a reactor, which was then thoroughly purged with nitrogen, sealed, and gradually heated until the internal pressure reached 10 kg / cm. 2Once the pressure reached 1.0, the water in the reactor was slowly distilled off, and the pressure was returned to normal over 1 hour. The reaction was then continued at normal pressure for 1.0 hour. The maximum polymerization temperature was 220°C. This resulted in a transparent, pale yellow, alcohol-soluble oligomer with a specific viscosity of 1.5, essentially primary amino groups at both ends, amide bonds bonded in block form, and a number-average molecular weight of approximately 3,000. 46 parts of this oligomer was dissolved in 200 parts of methanol, and then 9 parts of an organic diisocyanate compound substantially end-terminally with isocyanate groups, obtained by reacting 1,000 parts of polypropylene glycol (weight-average molecular weight: 1,000) with 369 parts of hexamethylene diisocyanate, was gradually added with stirring. The reaction between the two was completed in approximately 15 minutes at 65°C. The solution was transferred to a Teflon®-coated Petri dish, the methanol was evaporated, and the mixture was dried under reduced pressure to obtain a polyamide block copolymer (Polymer 1). This polyamide block copolymer had a specific viscosity of 2.0, contained 82% by mass of block components of structural units consisting of amide bonds, and was a polymer compound containing urea bonds and urethane bonds in addition to the amide bonds.

[0053] (Synthesis of Polymer 2) 55 parts of ε-caprolactam, 40 parts of N,N'-bis(γ-aminopropyl)piperazine adipate, 7.5 parts of 1,3-bisaminomethylcyclohexane adipate, and 100 parts of water were placed in a reactor, which was then thoroughly purged with nitrogen, sealed, and gradually heated until the internal pressure reached 10 kg / cm. 2 After reaching this point, water in the reactor was gradually distilled off to return the pressure to normal over 1 hour, and the reaction was continued at normal pressure for 1.0 hour to obtain polyamide (Polymer 2). The specific viscosity of this polyamide was 2.4, and it was a polymer compound consisting only of amide bonds.

[0054] The photosensitive resin compositions of each of the Examples and Comparative Examples obtained in this manner were sandwiched between a 125 μm thick polyethylene terephthalate film coated with a polyester adhesive layer and another film coated with the same polyethylene terephthalate film with an anti-sticking layer (polyvinyl alcohol), so that the adhesive layer and the anti-sticking layer were in contact with the photosensitive resin composition, to produce a printing original plate having a total laminator thickness of 1.825 mm and a photosensitive resin layer thickness of 1.7 mm.

[0055] Next, the prepared printing plate was exposed to light at an illuminance of 17.5 W / m at 365 nm. 2 Using a 1000-millimeter UV lamp (F20T12-BL-9-BP, Anderson & Vreeland), the plate was back-exposed from the base side to a relief depth of 0.8 mm. A step guide and a negative film containing an image of a raised 3-point, 5-point, and 10-point letter T and a solid image were then placed over the master, and the plate was subjected to a main exposure so that the step guide reproduced 15 steps. The negative film was then removed, and the plate was developed in tap water at 25°C for 3 minutes and dried in warm air at 70°C for 10 minutes. The plate was then post-exposed for 2 minutes using the same UV lamp to obtain a relief for evaluation.

[0056] The printing original plates obtained from the photosensitive resin compositions of each Example and Comparative Example were evaluated for image reproducibility, printability (line thickening), and print durability (relief chipping resistance) using the evaluation relief. The results are shown in Table 3. The printability (line thickening) and print durability (relief chipping resistance) were evaluated for both tag printing using oil-based ink containing an ester compound and flexographic printing using water-based ink. The specific evaluation procedures are as follows.

[0057] (Image reproducibility) Image reproducibility was evaluated based on the smallest point of the convex characters that could be reproduced. Specifically, 3-point convex characters that could be reproduced were marked with a circle, 5-point convex characters that could be reproduced were marked with a triangle, 10-point convex characters that could be reproduced were marked with an ×, and 10-point characters that could not be reproduced were marked with an ××.

[0058] (Printability and print durability when printing tags) The evaluation relief was printed using a tag printing machine (Shanghai Huanye Machine PT 2 / 1). Specifically, 8,000 m (50,000 shots) of printing was performed using Perfectos Fabrifast MIXING BLACK (an ink containing dimethyl succinate, dimethyl adipate, and dimethyl glutarate) as the oil-based ink and Nylon Taffeta as the substrate. (Printability) Printability (line thickening) was evaluated based on the ratio of the vertical line width of a 5pt T letter between the print after 100 shots and the print after 50,000 shots. Specifically, a line width ratio of 1.0 or greater but less than 1.5 was marked as ◯, 1.5 or greater but less than 2.0 as △, 2.0 or greater as ×, and reliefs that could not be printed were marked as XX.

[0059] (Printing durability) Print durability (resistance to chipping of the relief) was evaluated by determining whether chipping occurred in the relief after 50,000 shots of printing. Specifically, a sample with no chipping in the relief was marked with ◯, and a sample with chipping in the relief was marked with ×.

[0060] (Printability and print durability in the case of flexographic printing) The evaluation relief was printed using a flexographic printing machine (MCK Corporation: FPR302). Specifically, ROBOT INK (Inktech Limited: propyl acetate-containing ink) was used as the oil-based ink, and PPC50 / OPT1 / GB82 (Oji Tack Co., Ltd.) was used as the substrate. 8000 m (50,000 shots) of printing was performed. (Printability) Printability (line thickening) was evaluated based on the ratio of the vertical line width of a 5pt T letter between the print after 100 shots and the print after 50,000 shots. Specifically, a line width ratio of 1.0 or greater but less than 1.5 was marked as ◯, 1.5 or greater but less than 2.0 as △, 2.0 or greater as ×, and reliefs that could not be printed were marked as XX.

[0061] (Printing durability) Print durability (resistance to chipping of the relief) was evaluated by determining whether chipping occurred in the relief after 50,000 shots of printing. Specifically, a sample with no chipping in the relief was marked with ◯, and a sample with chipping in the relief was marked with ×.

[0062] [Table 3]

[0063] As can be seen from Table 3, all of Examples 1 to 21, which satisfy the requirements of the present invention, are excellent in image reproducibility, printability (line thickening), and print durability (relief chipping resistance). In contrast, Comparative Examples 1 and 4, which contain no dibasic acid diester (B), and Comparative Examples 2 and 5, which contain too little dibasic acid diester (B), are poor in printability (line thickening). Comparative Examples 3 and 6, which contain too much dibasic acid diester (B), are poor in print durability (relief chipping resistance). [Industrial Applicability]

[0064] The printing plates obtained from the photosensitive resin printing original plate for letterpress printing of the present invention exhibit little swelling due to ink absorption, even when oil-based inks containing ester compounds are used, and therefore, even when long-run printing is carried out, there is almost no line thickening of the printed image. Therefore, the present invention enables long-run printing in flexographic printing, including tag printing, and is expected to make a significant contribution to the industry.

Claims

[Claim 1] A photosensitive resin printing original plate for letterpress printing having a photosensitive resin layer made of a photosensitive resin composition containing at least a polymer compound (A), a dibasic acid diester (B) represented by the following general formula (I), a photopolymerizable compound (C), and a photopolymerization initiator (D), wherein the polymer compound (A) is a latex having a butadiene skeleton and / or an isoprene skeleton, and when the latex is a latex having a butadiene skeleton, the latex is selected from the group consisting of (i) polybutadiene latex, (ii) styrene-butadiene copolymer latex, (iii) acrylonitrile-butadiene copolymer latex, (iv) methyl methacrylate latex, (v) methyl methacrylate latex, (vi) methyl methacrylate latex, (vii) methyl methacrylate latex, (viii ... a photosensitive resin printing plate precursor for relief printing, characterized in that the photosensitive resin composition contains at least one water-dispersible latex selected from the group consisting of (i) an acrylate-butadiene copolymer latex, and (ii) a latex obtained by copolymerizing the copolymer latex with acrylic acid or methacrylic acid; and (iii) the dibasic acid diester (B) is at least one selected from the group consisting of succinic acid diesters, glutaric acid diesters, adipic acid diesters, pimelic acid diesters, suberic acid diesters, and azelaic acid diesters; and 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 or different and represent a linear or branched aliphatic hydrocarbon group having 1 to 12 carbon atoms.

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