Water-based flexographic ink, printed matter and laminate

Abstract

To provide a water-based flexographic ink capable of obtaining a printed matter having good storage stability and good leveling property and blocking resistance and a laminate having good laminate strength.SOLUTION: There is provided a water-based flexographic ink comprising a pigment, an aqueous urethane resin and / or an aqueous acrylic urethane resin, water and an organic solvent, wherein the organic solvent includes two or more alcohol solvents (A) having different boiling points, the alcohol solvents (A) includes an alcohol solvent (a1) which is a glycol monoalkyl ether having a boiling point of 115 to 180°C and an alcohol solvent (a2) having a boiling point lower than the boiling point of the alcohol solvent (a1) and the water-based flexographic ink contains 0.5 to 9.5 mass% of the alcohol solvent (a1) and 0.5 to 8.5 mass% of the alcohol solvent (a2) in the total mass of the water-based flexographic ink and has a surface tension of 28 to 35 mN / m.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to water-based flexographic inks, printed matter and laminates. [Background technology]

[0002] In recent years, the printing ink industry has been calling for the use of water-based inks due to increasing demands for reducing the environmental impact and safety during printing. Flexographic printing is a useful method for printing with water-based inks. Flexographic printing is a type of relief printing in which ink is applied to a resin relief plate via an anilox roll and then transferred from the relief plate to a plastic substrate or other material. Flexographic printing excels in high-speed printing, and can reproduce fine characters and sharp expressions even with a small amount of ink transferred.

[0003] Water-based inks contain water as a dispersion medium, but because water has high surface tension, it has problems such as poor wettability to the substrate during printing and poor transfer, which reduces printability, such as leveling. To address this issue, the addition of organic solvents to water-based inks has been actively investigated to reduce surface tension (Patent Document 1). In particular, when printing with water-based flexographic inks, drying of the ink on the printing plate is likely to cause printing defects such as plate entanglement. Therefore, it is necessary to prevent the ink from drying, and therefore organic solvents with high boiling points are used. However, the addition of organic solvents changes the dissolution state of the pigment dispersion resin, which can significantly reduce storage stability.

[0004] Furthermore, when the above-mentioned water-based inks are printed on non-permeable substrates such as film substrates, the permeation drying that occurs when printing on paper substrates cannot be expected, resulting in a high likelihood of poor drying. Residual moisture and organic solvent components in the printed layer can cause blocking (the phenomenon of ink bleeding through to the back), and blocking is particularly likely to occur when printing at high speeds, as the drying rate is further reduced. When printed materials are laminated, residual moisture and organic solvent components in the printed material can sometimes cause the laminate to lack sufficient strength after processing.

[0005] Patent Document 2 discloses an invention for a water-based flexographic ink and a method for producing printed matter that exhibits excellent plate adhesion and dot gain in overprinting when printed on non-permeable substrates such as film substrates. However, because the ink contains a large amount of high-boiling organic solvents, there is a concern that poor drying may occur when the drying temperature is low or when printing at high speeds, leading to winding blocking. Furthermore, organic solvents remaining in the printed layer may reduce the laminate strength when a laminate is produced.

[0006] Patent Document 3 discloses an invention of a water-based flexographic ink that has good printability, such as plate adhesion, and good blocking resistance, and also produces little overlapping halftone dot unevenness in printed matter. However, because it contains a large amount of alcohol solvent with a relatively low boiling point, the ink has insufficient storage stability, and depending on the printing environment, a large amount of organic solvent remains in the printed layer, which can reduce the laminate strength when a laminate is produced. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-146563 [Patent Document 2] Japanese Patent Application Publication No. 2019-203051 [Patent Document 3] Patent No. 7265066 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a water-based flexographic ink that has good storage stability and is capable of producing printed matter with good leveling properties and blocking resistance, as well as laminates with good lamination strength. [Means for solving the problem]

[0009] As a result of extensive research, the present inventors have found that the above problems can be solved by using the water-based flexographic ink described below, and have thus achieved the present invention.

[0010] That is, the present invention provides an aqueous flexographic ink containing a pigment, an aqueous urethane resin and / or an aqueous acrylic urethane resin, water, and an organic solvent, the organic solvent contains two or more alcohol solvents (A) having different boiling points, The alcohol solvent (A) is an alcohol solvent (a1) which is a glycol monoalkyl ether having a boiling point of 115 to 180°C; and an alcohol solvent (a2) having a boiling point lower than that of the alcohol solvent (a1), In the total mass of the water-based flexographic ink, The alcohol solvent (a1) is contained in an amount of 0.5 to 9.5% by mass, The alcohol solvent (a2) is contained in an amount of 0.5 to 8.5% by mass, The water-based flexographic ink has a surface tension of 28 to 35 mN / m.

[0011] That is, the present invention relates to the above water-based flexographic ink, wherein the glycol monoalkyl ether solvent (a1) having a boiling point of 115 to 180°C is a propylene glycol monoalkyl ether solvent having a boiling point of 115 to 180°C.

[0012] That is, the present invention relates to the above water-based flexographic ink, wherein the content of the alcohol solvent (a2) is 2 to 8.5% by mass based on the total mass of the water-based flexographic ink.

[0013] That is, the present invention relates to the above-mentioned water-based flexographic ink, wherein the alcohol solvent (A) further contains a glycol solvent (a3).

[0014] That is, the present invention relates to a printed matter having a substrate 1 and a printed layer formed from the above-mentioned water-based flexographic ink.

[0015] The present invention relates to a laminate having a substrate 1, a print layer formed from the above-mentioned water-based flexographic ink, an adhesive layer, and a substrate 2 in this order. [Effects of the Invention]

[0016] The present invention makes it possible to provide a water-based flexographic ink that has good storage stability and is capable of producing printed matter with good leveling properties and blocking resistance, as well as laminates with good lamination strength. DETAILED DESCRIPTION OF THE INVENTION

[0017] The following describes in detail an embodiment of the present invention, but the following description is an example (typical example) of an embodiment of the present invention, and the present invention is not limited to these contents as long as it does not deviate from the gist of the present invention.

[0018] In the present invention, the above-mentioned "water-based flexographic ink" may be simply referred to as "water-based ink" or "ink", but these terms have the same meaning.

[0019] <Water-based flexographic ink> The water-based ink of the present invention is a water-based flexographic ink containing a pigment, a water-based urethane resin and / or a water-based acrylic urethane resin, water, and an organic solvent, the organic solvent contains two or more alcohol solvents (A) having different boiling points, The alcohol solvent (A) is an alcohol solvent (a1) which is a glycol monoalkyl ether having a boiling point of 115 to 180°C; and an alcohol solvent (a2) having a boiling point lower than that of the alcohol solvent (a1), In the total mass of the water-based flexographic ink, The alcohol solvent (a1) is contained in an amount of 0.5 to 9.5% by mass, The alcohol solvent (a2) is contained in an amount of 0.5 to 8.5% by mass, The water-based flexographic ink has a surface tension of 28 to 35 mN / m. The water-based flexographic ink preferably contains additives as needed.

[0020] The ink of the present invention contains the alcohol solvent (a1) and the alcohol solvent (a2) in specific mass amounts, which provides excellent storage stability of the ink and reduces the surface tension of the ink, thereby improving the leveling of printed matter. Furthermore, the glycol monoalkyl ether solvent (a1) has a specific boiling point range, which reduces the amount of water and organic solvent remaining in the printed layer after drying, i.e., prevents insufficient drying, and improves blocking resistance when formed into a printed matter and lamination strength when formed into a laminate. The above considerations regarding the effects are merely examples and do not limit the present invention.

[0021] <Pigments> The aqueous ink of the present invention contains a pigment. Examples of pigments that can be used include achromatic inorganic pigments such as carbon black, titanium oxide, and calcium carbonate, and chromatic organic pigments such as yellow, magenta, cyan, and black. The organic pigment is preferably blended in at a ratio of 5 to 30% by mass based on 100% by mass of the aqueous ink. Titanium oxide is preferably blended in at a ratio of 10 to 60% by mass based on 100% by mass of the aqueous ink.

[0022] Examples of organic pigments include insoluble azo pigments such as toluidine red, toluidine maroon, Hansa yellow, benzidine yellow, and pyrazolone red; soluble azo pigments such as litol red, heliobordeaux, pigment scarlet, and permanent red 2B; derivatives of vat dyes such as alizarin, indanthrone, and thioindigo maroon; phthalocyanine organic pigments such as phthalocyanine blue and phthalocyanine green; quinacridone organic pigments such as quinacridone red and quinacridone magenta; perylene organic pigments such as perylene red and perylene scarlet; and isoindolinone. isoindolinone-based organic pigments such as perinone yellow and isoindolinone orange; pyranthrone-based organic pigments such as pyranthrone red and pyranthrone orange; thioindigo-based organic pigments; condensed azo-based organic pigments; benzimidazolone-based organic pigments; quinophthalone-based organic pigments such as quinophthalone yellow; isoindoline-based organic pigments such as isoindoline yellow; and other pigments such as flavanthrone yellow, acylamide yellow, nickel azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, and dioxazine violet.

[0023] Examples of organic pigments by Color Index (CI) number include CI Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 109, 110, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 180, 185; CI Pigment Orange 16, 36, 43, 51, 55, 59, 61; and CI Pigment Red 9, 48, 49, 52, 53, 54, 55, 56, 57, 58, 59, 60. 3, 57, 97, 122, 123, 149, 168, 177, 180, 192, 202, 206, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, CI Pigment Violet 19, 23, 29, 30, 37, 40, 50, CI Pigment Blue 15, 15:1, 15:3, 15:4, 15:6, 22, 60, 64, CI Pigment Green 7, 36, CI Pigment Brown 23, 25, 26, etc.

[0024] Specific examples of titanium oxide include "Tipaeque CR-50, 50-2, 57, 80, 90, 93, 95, 953, 97, 60, 60-2, 63, 67, 58, 58-2, 85," "Tipaeque R-820, 830, 930, 550, 630, 680, 670, 580, 780, 780-2, 850, 855," "Tipaeque A-100, 220," "Tipaeque W-10," "Tipaeque PF-740, 744," and "TTO-55 (A)" manufactured by Ishihara Sangyo Kaisha. ), 55(B), 55(C), 55(D), 55(S), 55(N), 51(A), 51(C)", "TTO-S-1, 2", "TTO-M-1, 2", Teika's "Titanix JR-301, 403, 405, 600A, 605, 600E, 603, 805, 806, 701, 800, 808", "Titanix JA-1, C, 3, 4, 5", DuPont's "Tipure R-900, 902, 960, 706, 931", etc.

[0025] <Water-based urethane resin and / or water-based acrylic urethane resin> The water-based ink of the present invention contains a water-based urethane resin and / or a water-based acrylic urethane resin. By containing a water-based urethane resin and / or a water-based acrylic urethane resin, the water-based ink has excellent storage stability, and the leveling and blocking resistance of printed matter, as well as excellent lamination strength when formed into a laminate, are excellent. The total content of the aqueous urethane resin and the aqueous acrylic urethane resin (either may be 0) is preferably 1 to 30 mass %, more preferably 5 to 15 mass %, of the total mass of the ink in terms of solid content mass ratio.

[0026] <Water-based urethane resin> The aqueous ink of the present invention may contain an aqueous urethane resin. The aqueous urethane resin in the present invention does not include the aqueous acrylic urethane resin described below. The aqueous urethane resin is preferably a resin having a terminal hydroxyl group, which is obtained by a condensation reaction between a polyol and a polyisocyanate. The aqueous urethane resin may also be an aqueous urethane urea resin obtained by reacting a urethane prepolymer having an isocyanate group at its terminal, which is a condensation reaction product between a polyol and a polyisocyanate, with a chain extender.

[0027] The acid value of the aqueous urethane resin is preferably 15 to 60 mgKOH / g, more preferably 20 to 55 mgKOH / g, more preferably 25 to 50 mgKOH / g, and even more preferably 25 to 45 mgKOH / g. Within the above range, the acidic groups are neutralized with a base, resulting in sufficient dispersibility and solubility in water, and the ink also exhibits excellent storage stability, leveling properties, and blocking resistance. The acid value is the amount of acid in 1 g of resin calculated by titrating the acid with an alkali, converted into mg of potassium hydroxide, and is measured in accordance with JIS K0070.

[0028] The hydroxyl value of the aqueous urethane resin is preferably 0.1 to 30 mgKOH / g, and more preferably 1 to 25 mgKOH / g. This is because the aqueous urethane resin has good solubility in water, which results in good storage stability of the ink and also good lamination strength of the laminate. The hydroxyl value is the amount of hydroxyl groups per 1 g of resin calculated by esterifying or acetylating the hydroxyl groups in the resin and back-titrating the remaining acid with an alkali, converted into mg of potassium hydroxide, and measured in accordance with JIS K0070.

[0029] The weight average molecular weight of the aqueous urethane resin is preferably 5,000 to 100,000, more preferably 10,000 to 80,000, and even more preferably 20,000 to 70,000.

[0030] The content of the aqueous urethane resin is preferably 1 to 30 mass %, more preferably 5 to 15 mass %, of the total mass of the ink in terms of solid content mass ratio.

[0031] <Polyol> The aqueous urethane resin preferably contains structural units derived from a polyether polyol and / or structural units derived from a polyester polyol, and also preferably contains structural units derived from a polyol having a carboxy group.

[0032] (Polyether polyol) From the viewpoint of pigment dispersibility and ink storage stability, the polyether polyol preferably contains at least one selected from the group consisting of polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. The polyether polyols can be used alone or in combination of two or more. These may be copolymerized polyether polyols, or may be used in combination with a single polyether polyol. Polyether polyols other than those listed above can also be used in combination. Examples include polymers or copolymers of methylene oxide, 1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, and the like.

[0033] The content of the polyether polyol-derived structural units is preferably 5 to 85 mass %, more preferably 10 to 80 mass %, and even more preferably 15 to 75 mass %, of the total mass of the solid content of the aqueous urethane resin. The above range is preferable because it provides excellent ink solubility and lubricity, and excellent leveling and blocking resistance during printing.

[0034] (polyester polyol) The polyester polyol is preferably, for example, a condensation product of a dibasic acid and a diol. From the viewpoints of plate entanglement resistance, blocking resistance, and laminate strength, it is preferable that the dibasic acid contains at least one selected from the group consisting of adipic acid, succinic acid, sebacic acid, azelaic acid, and dimer acid.

[0035] The diol preferably includes a branched diol, and also preferably includes both a branched diol and a linear diol. Here, the linear diol is a diol having a linear structure with two or more carbon atoms, such as alkylene glycol, dialkylene glycol, trialkylene glycol, or other diol. Furthermore, the branched diol is a diol in which at least one hydrogen atom of the hydrocarbon group of an alkylene glycol is substituted with a non-hydrogen atom.

[0036] Examples of the branched diol include 2-butyl-2-ethyl-1,3-propanediol (hereinafter also referred to as BEPG), 2-methyl-1,3-propanediol (hereinafter also referred to as MPO), 3-methyl-1,5-pentanediol (hereinafter also referred to as MPD), neopentyl glycol (hereinafter also referred to as NPG), 1,2-propylene glycol (hereinafter also referred to as PG), 2,4-diethyl-1,5-pentanediol, 1,3-butanediol, dipropylene glycol, etc. Among these, MPD and NPG are preferred.

[0037] The linear diol is preferably an alkylene glycol, and examples of such compounds include ethylene glycol (also referred to as EG), diethylene glycol, 1,3-propanediol (also referred to as 1,3-PD), 1,4-butanediol (also referred to as 1,4-BD), 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,4-butynediol, 1,4-butylenediol, diethylene glycol, and triethylene glycol. Among these, linear diols having 8 or less carbon atoms, preferably 6 or less carbon atoms, are preferred, and EG, 1,3-PD, 1,4-BD, 1,5-pentanediol, 1,6-hexanediol, and 1,8-octanediol are more preferred.

[0038] The mass ratio of branched diol to linear diol (branched diol: linear diol) in the raw material diols of the polyester polyol is preferably 10:90 to 90:10, more preferably 20:80 to 80:20, and even more preferably 30:70 to 70:30.

[0039] The branched diol and the linear diol may each be present in one polyester polyol, or a polyester polyol containing only a branched diol and a polyester polyol containing only a linear diol may be used as a mixture raw material to produce an aqueous urethane resin.

[0040] The content of the polyester polyol-derived structural units in the total mass of the aqueous urethane resin is preferably 20 to 80 mass%, more preferably 30 to 70 mass%, and even more preferably 40 to 60 mass%, which is preferable because the above ranges result in excellent storage stability, leveling properties, blocking resistance, and laminate strength of the laminate.

[0041] (Polyol having a carboxy group) In order to dissolve or disperse the aqueous urethane resin in an aqueous medium, the aqueous urethane resin must be hydrophilic. The polyether polyols and polyester polyols listed above are also hydrophilic, but it is preferable to use a polyol having a carboxyl group in combination. The carboxyl group is preferably neutralized with a basic compound.

[0042] Examples of polyols having a carboxy group include dimethylolalkanoic acids such as dimethylolacetic acid, dimethylolpropionic acid, dimethylolbutanoic acid, 2,2-dimethylolbutyric acid, and 2,2-dimethylolpentanoic acid, dihydroxysuccinic acid, dihydroxypropionic acid, and dihydroxybenzoic acid. These carboxy group-containing polyols can be used alone or in combination. Among these, dimethylolpropionic acid and dimethylolbutanoic acid are preferred.

[0043] When a polyol having a carboxy group is contained, the content of the polyol having a carboxy group is preferably 1 to 50 mass %, more preferably 2 to 30 mass %, and even more preferably 3 to 15 mass %, of the total mass of the aqueous urethane resin. The above range is preferable because it results in excellent storage stability, leveling properties, blocking resistance, and laminate strength of the laminate.

[0044] (Other polyols) Other suitable polyols include polycarbonate polyols. Examples of polycarbonate polyols include those obtained by reacting a polyol with a carbonate compound such as a dialkyl carbonate, an alkylene carbonate, or a diaryl carbonate. The polyols exemplified above as components of polyester polyols can be used as polyols constituting the polycarbonate polyol. Examples of dialkyl carbonates include dimethyl carbonate and diethyl carbonate, examples of alkylene carbonates include ethylene carbonate, and examples of diaryl carbonates include diphenyl carbonate.

[0045] (Chain extension reaction with polyamines) In the synthesis of aqueous urethane resins, a chain extension reaction using a polyamine may be carried out as needed. The chain extension reaction is carried out by synthesizing a urethane prepolymer with an excess of isocyanate groups, followed by reaction with a diamine or other polyamine as a chain extender. This reaction is preferably carried out when neutralizing the resin to make it aqueous, as it significantly increases the viscosity of the resin solution. Chain extension can further increase the molecular weight of the aqueous urethane resin. Furthermore, the introduction of urea bonds can be expected to further improve the cohesive strength of the aqueous urethane resin.

[0046] Examples of polyamines include diamines such as hydrazine, ethylenediamine, propylenediamine, 1,4-tetramethylenediamine, 2-methyl-1,5-pentanediamine, hexamethylenediamine, nonamethylenediamine, xylylenediamine, isophoronediamine, piperazine and its derivatives, phenylenediamine, tolylenediamine, xylenediamine, adipic acid dihydrazide, and isophthalic acid dihydrazide; triamines such as diethylenetriamine; Diols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-bis(β-hydroxyethoxy)benzene, 1,4-cyclohexanediol, bis(β-hydroxyethyl)terephthalate, and xylylene glycol; triols such as trimethylolpropane; pentaols such as pentaerythritol; Amino alcohols such as N-(β-aminoethyl)ethanolamine Known chain extenders such as the above can be used. If a monofunctional monoamine or monool is used in combination, it is also possible to control the molecular weight by terminating the chain extension.

[0047] (Polyisocyanate) The polyisocyanate in the present invention is preferably a diisocyanate, and various known aromatic, aliphatic, or alicyclic diisocyanates can be used as such compounds. For example, 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl isocyanate, dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, tolylene diisocyanate, butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, 2,2,4-trimethylsilyl methyl ether ... Representative examples include trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, cyclohexane-1,4-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, lysine diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, methylcyclohexane diisocyanate, m-tetramethylxylylene diisocyanate, and dimer diisocyanate in which the carboxyl groups of dimer acid are converted to isocyanate groups. These can be used alone or in combination of two or more. Among these, isophorone diisocyanate, tolylene diisocyanate, and 4,4'-diphenylmethane diisocyanate are preferred, and isophorone diisocyanate is more preferred from the viewpoint of solubility.

[0048] <Method of manufacturing water-based urethane resin> The method for producing the aqueous urethane resin is not particularly limited, and it can be produced by a known method. For example, as described in Japanese Patent No. 4900136, a method of polymerizing a polyol and a polyisocyanate without using an organic solvent can be mentioned. More specifically, for example, after charging the polyol and the polyisocyanate, the atmosphere is purged with dry nitrogen and the reaction is carried out at 90°C to 220°C for 10 minutes to 5 hours. Thereafter, a neutralizing agent is added while cooling to obtain the resin.

[0049] <Water-based acrylic urethane resin> The aqueous acrylic urethane resin is preferably an aqueous emulsion acrylic urethane resin, and for example, the aqueous emulsion acrylic urethane resin may be a core-shell aqueous acrylic urethane resin. Examples of aqueous acrylic urethane resins include alternating copolymers of acrylic resin moieties and urethane resin moieties, and so-called graft polymers in which the main chain is a urethane resin moiety and the side chain is an acrylic resin moiety, or the main chain is an acrylic resin moiety and the side chain is a urethane resin moiety, and the core-shell aqueous acrylic urethane resin is preferred.

[0050] When the aqueous acrylic urethane resin is in the form of an emulsion, the average particle size is preferably 60 nm to 1000 nm, more preferably 60 nm to 400 nm, where the average particle size is measured by dynamic light scattering.

[0051] Furthermore, the core-shell aqueous acrylic urethane resin preferably has an acrylic resin portion in the core portion and a urethane resin portion in the shell portion. However, the core may be configured with the urethane resin portion as the core portion and the water-solubilized acrylic resin portion as the shell portion. The mass ratio of the urethane resin portion to the acrylic resin portion in the total mass of the aqueous acrylic urethane resin is preferably 9:1 to 5:5, more preferably 8:2 to 6:4. When the mass ratio of the urethane resin portion to the acrylic resin portion in the total mass of the aqueous acrylic urethane resin is within the above range, it is preferable because the storage stability, leveling properties, blocking resistance, and laminate strength of the laminate are excellent.

[0052] The mass average molecular weight of the core-shell type acrylic urethane resin is preferably 5,000 to 50,000 for the shell portion and 50,000 to 1,000,000 for the core portion.

[0053] The acid value of the aqueous urethane acrylic resin is preferably 10 to 110 mgKOH / g, more preferably 30 to 60 mgKOH / g, and even more preferably 40 to 50 mgKOH / g. If the acid value is within the above range, the acidic groups are neutralized with a base, resulting in sufficient dispersibility and solubility in water, and excellent storage stability, leveling properties, and blocking resistance.

[0054] (urethane resin part) The urethane resin portion of the aqueous acrylic urethane resin can be formed by a condensation reaction between a polyol and a polyisocyanate, and preferably has a terminal hydroxyl group. Alternatively, the urethane resin portion may be a urethane urea resin portion obtained by reacting a urethane prepolymer having an isocyanate group at its terminal, which is a condensation reaction product of a polyol and a polyisocyanate, with a chain extender (referred to as chain extension). The polyol preferably includes a polyether polyol and a polyol having a carboxy group, and may also include other polyols. The polyol, polyisocyanate, and chain extender used in the aqueous urethane resin can preferably be the compounds exemplified in the description of the aqueous urethane resin. The mass average molecular weight of the urethane resin portion is preferably 1,000 to 1,000,000, more preferably 5,000 to 50,000.

[0055] (acrylic resin part) The acrylic resin portion of the aqueous acrylic urethane resin is composed of an acrylic monomer and the like. Examples of acrylic monomers constituting the acrylic resin portion include aromatic alkyl group-containing acrylic monomers such as benzyl acrylate, benzyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, phenoxydiethylene glycol acrylate, phenoxydiethylene glycol methacrylate, phenoxytetraethylene glycol acrylate, phenoxytetraethylene glycol methacrylate, phenoxyhexaethylene glycol acrylate, phenoxyhexaethylene glycol methacrylate, phenyl acrylate, and phenyl methacrylate; Further, linear or branched alkyl group-containing acrylic monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, heptyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, and tetradecyl (meth)acrylate; Examples include, but are not limited to, alicyclic alkyl group-containing acrylic monomers such as cyclohexyl (meth)acrylate and isobornyl (meth)acrylate. In addition to the acrylic monomer, aromatic monomers such as styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, and vinylnaphthalene may also be contained.

[0056] Among the above, from the viewpoints of compatibility with the urethane resin portion, adhesion to substrates, and blocking resistance, it is preferable to contain a (meth)acrylic acid alkyl ester, and more preferable to contain a (meth)acrylic acid alkyl ester in which the alkyl group has 1 to 4 carbon atoms. That is, it is one or more selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, and t-butyl (meth)acrylate. It is also preferable to further contain the above-mentioned hydroxyl group-containing acrylic monomer.

[0057] The content of the (meth)acrylic acid alkyl ester is preferably 60 to 100 mass %, more preferably 70 to 100 mass %, and even more preferably 80 to 100 mass %, of the total mass of the acrylic monomers constituting the acrylic resin portion.

[0058] The mass average molecular weight of the acrylic resin portion is preferably 1,000 to 1,000,000.

[0059] The glass transition temperature of the acrylic resin portion is preferably −70° C. to 110° C., more preferably −30 to 90° C., and further preferably −10 to 70° C. Specifically, when the glass transition temperatures of the homopolymers of the monomers blended as the acrylic resin portion are Tg1 to Tgm and the mass ratios of the monomers used as the acrylic resin portion are W1 to Wm, the glass transition temperature can be expressed by the following FOX formula: 1 / Tg=(W1 / Tg1)+(W2 / Tg2)+…+(Wm / Tgm) W1+W2+…+Wm=1 Alternatively, measurements by differential scanning calorimetry (DSC) may be used, as these provide similar values.

[0060] [Method of manufacturing core-shell type water-based acrylic urethane resin] The core-shell aqueous acrylic urethane resin can be produced by any known method, without any particular limitations. For example, as described in Japanese Patent No. 6565337, a water-soluble urethane resin is first produced by a known method, and then an acrylic monomer is added to the aqueous urethane resin solution and polymerized. More specifically, for example, a polyol and a polyisocyanate are reacted at 40 to 120°C to synthesize a urethane prepolymer, and the acidic groups are neutralized and dispersed in an aqueous medium to form an aqueous urethane resin solution. The resin can be obtained by adding an acrylic monomer and a polymerization initiator to the aqueous urethane resin solution, incorporating the acrylic monomer in the urethane resin, and then polymerizing the acrylic monomer at 30 to 100°C.

[0061] <Basic compounds> When the aqueous urethane resin and / or aqueous acrylic urethane resin has acid groups, the acid groups are preferably neutralized with a basic compound. The neutralization may be carried out before producing an ink using the aqueous urethane resin and / or aqueous acrylic urethane resin, or may be carried out by adding a basic compound as a neutralizing agent to the ink after producing an ink containing the aqueous urethane resin and / or aqueous acrylic urethane resin, or both.

[0062] Examples of the basic compound used for the neutralization include organic amines, ammonia, metal salts, etc. Among these, ammonia and organic amines are preferred.

[0063] (organic amine) The basic compound used for neutralization is more preferably an organic amine, and examples thereof include alkylamines such as trimethylamine, triethylamine, and butylamine, 2-dimethylaminoethanol, 2-diethylaminoethanol, diethanolamine, triethanolamine, aminomethylpropanol, and morpholine, with triethylamine and dimethylethanolamine being more preferred.

[0064] <Water> The water-based ink of the present invention contains water. From the viewpoint of ink storage stability and blocking resistance, the water content is preferably 30 to 70 mass %, more preferably 35 to 65 mass %, and even more preferably 40 to 60 mass %, based on the total mass of the water-based flexographic ink.

[0065] <Organic solvents> The water-based ink of the present invention contains an alcohol solvent (A) which is an organic solvent. The alcohol solvent (A) used in the present invention is a solvent that has a hydroxyl group and is compatible with water. The alcohol solvent (A) comprises at least an alcohol solvent (a1) which is a glycol monoalkyl ether having a boiling point of 115 to 180°C, and an alcohol solvent (a2) having a boiling point lower than that of the alcohol solvent (a1), In the total mass of the water-based flexographic ink, The alcohol solvent (a1) is contained in an amount of 0.5 to 9.5% by mass, The alcohol solvent (a2) is contained in an amount of 0.5 to 8.5% by mass. The organic solvent may include an organic solvent other than the alcohol solvent (A), and may include an alcohol solvent (A) other than the alcohol solvent (a1) and the alcohol solvent (a2). The water-based ink of the present invention preferably contains an organic solvent in an amount of 1.0 to 25.0 mass %, more preferably 1.5 to 20.0 mass %, and even more preferably 2.0 to 18.0 mass %, based on the total mass of the water-based ink.

[0066] <Alcohol solvent (a1)> The alcohol solvent (a1) used in the present invention is a glycol monoalkyl ether having a boiling point of 115 to 180°C. Examples of the alcohol solvent (a1) include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, and propylene glycol monobutyl ether. These may be used alone or in combination of two or more. Among the glycol monoalkyl ethers having a boiling point of 115 to 180°C, propylene glycol monoalkyl ethers having a boiling point of 115 to 180°C are more preferred from the viewpoint of leveling properties.

[0067] The content of the alcohol solvent (a1) is 0.5 to 9.5 mass% of the total mass of the aqueous ink, preferably 1.0 to 9.0 mass%, more preferably 1.5 to 8.0 mass%, and even more preferably 2.0 to 7.0 mass%. Within this range, the storage stability of the ink is excellent, and the leveling property and blocking resistance of the printed matter, as well as the lamination strength when formed into a laminate, are improved.

[0068] <Alcohol solvent (a2)> The alcohol solvent (a2) contained in the water-based ink of the present invention is a solvent having a boiling point lower than that of the alcohol solvent (a1) coexisting in the water-based ink. When two or more alcohol solvents (a1) are used, an alcohol solvent (a2) having a boiling point lower than that of any of the alcohol solvents (a1) is selected. The alcohol solvent (a2) preferably has a boiling point lower than 115°C. Examples of the alcohol solvent (a2) include monohydric alcohol solvents such as ethanol (boiling point 78.37°C), 1-propanol (boiling point 97°C), 2-propanol (boiling point 82.3°C), 1-butanol (boiling point 117.7°C), 2-methyl-1-propanol (boiling point 108°C), 2-butanol (boiling point 100°C), and 2-methyl-2-propanol (boiling point 82.2°C), which can be used alone or in combination of two or more. Among these, 1-propanol and 2-propanol are preferred.

[0069] The content of the alcohol solvent (a2) is 0.5 to 8.5 mass% of the total mass of the aqueous ink, preferably 2.0 to 8.5 mass%, more preferably 2.5 to 8 mass%, and even more preferably 3.0 to 7.5 mass%. Within this range, the storage stability of the ink is excellent, and the leveling and blocking resistance of the printed matter, as well as the lamination strength when formed into a laminate, are improved.

[0070] <Glycol solvent (a3)> The water-based ink of the present invention preferably further contains a glycol solvent (a3). The glycol solvent (a3) ​​in the present invention is a type of alcohol, which is a compound having a structure in which one hydrogen atom bonded to each of two carbon atoms of an aliphatic hydrocarbon having two or more carbon atoms or a cyclic aliphatic hydrocarbon is substituted with a hydroxy group, and which has a boiling point of 188.2°C or higher. Examples of glycol solvents (a3) ​​include ethylene glycol (boiling point 197.3°C), 1,3-propanediol (boiling point 213°C), propylene glycol (boiling point 188.2°C), 1,2-butanediol (boiling point 192°C), 1,4-butanediol (boiling point 228°C), pentylene glycol (boiling point 210°C), 1,2-hexanediol (boiling point 223°C), 1,6-hexanediol (boiling point 249°C), diethylene glycol (boiling point 245°C), triethylene glycol (boiling point 276°C), and tetraethylene glycol (boiling point 275°C). Among these, propylene glycol is preferred. The content of glycol solvent (a3) ​​is 0.5 to 12% by mass, preferably 1 to 11% by mass, more preferably 1.5 to 10% by mass, and even more preferably 2.0 to 9% by mass, based on the total mass of the aqueous ink. Within the above range, the leveling properties of printed matter are improved.

[0071] <Additives> Suitable additives that can be used in the water-based ink include a curing agent, an antiblocking agent, a thickener, a rheology modifier, an antifoaming agent, a leveling agent, an antiseptic, a surface tension modifier, polyolefin particles, and the like.

[0072] (Polyolefin particles) The water-based ink of the present invention preferably further contains polyolefin particles for the purposes of improving the rub resistance of the ink film and improving the drying properties of the water-based ink.

[0073] The melting point of the polyolefin particles is preferably 90 to 140°C, more preferably 95 to 135°C, and even more preferably 95 to 125°C. The average particle size of the polyolefin particles is preferably 0.5 to 10 μm, more preferably 0.5 to 8 μm, and even more preferably 0.5 to 5 μm. The average particle size is measured using the Coulter Counter method. Polyolefin particles with the above particle size and melting point form a strong ink coating that is compatible with aqueous urethane resins and / or aqueous acrylic urethane resins, and promote improvement in water-rub resistance.

[0074] The content of polyolefin particles is preferably 0.5 to 5 mass % in terms of solid content of the total mass of the water-based ink. When the content is 0.5 mass % or more, water-rubbing resistance is improved, and when it is used at 5 mass % or less, the storage stability of the water-based ink is also improved.

[0075] The polyolefin particles may be commercially available, such as Chemipearl W100, W200, W300, W310, W306, W400, W401, W4005, W410, W500, WF640, W700, W800, W900, W950, WH201, and WP100 manufactured by Mitsui Chemicals, Inc.

[0076] (hydrazide additives) The water-based ink of the present invention may contain a hydrazide additive for the purposes of improving adhesion to the substrate, room temperature crosslinking of the resin (if it contains a keto group), etc. An example of the hydrazide additive is adipic acid hydrazide.

[0077] (Antifoaming agent) Known defoaming agents can be used. Examples of such defoaming agents include hydrophobic polydimethylsiloxane-based defoaming agents, polysiloxanes containing long-chain alkyl groups or aralkyl groups, polyoxyalkylene chain-containing polysiloxanes, and defoaming agents that are reaction products of silicones having alkylene oxide chains and alcoholic hydroxyl groups with isocyanate compounds. The amount of defoaming agent used is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, of the total mass of the aqueous ink.

[0078] <Water-based ink manufacturing method> As described in JP 2020-186344 A, for example, aqueous inks can be produced by dissolving and / or dispersing resins, color pigments, and the like in water and a specified amount of solvent (pigment dispersion). Then, additives, liquid media, and the like are blended into the resulting dispersion as needed to produce aqueous inks. Commonly used dispersing machines for pigment dispersion include, for example, roller mills, ball mills, pebble mills, attritors, and sand mills. Among these, dispersion using a sand mill, gamma mill, or other bead mill is preferred.

[0079] The viscosity of the aqueous ink produced by the above method is preferably in the range of 10 mPa·s or more to prevent pigment sedimentation and ensure adequate dispersion, and 1000 mPa·s or less to ensure workability during ink production and printing. The above viscosity is measured at 25°C using a Brookfield viscometer. Viscometers such as those manufactured by Tokimec Co., Ltd. can be used.

[0080] <Surface tension of water-based ink> From the viewpoint of sufficient wettability on a substrate and excellent leveling properties, the water-based ink of the present invention has a surface tension of 28 to 35 mN / m, preferably 29 to 35 mN / m, more preferably 30 to 35 mN / m, and particularly preferably 30 to 34 mN / m. The surface tension can be measured, for example, using a surface tensiometer (CBVP-Z manufactured by Kyowa Interface Science Co., Ltd.) by the platinum plate method in an environment of 25°C.

[0081] <Printed material> The printed matter in this embodiment has a printed layer made of the water-based flexographic ink of the present invention on a substrate 1. The printed matter has a printed layer formed, for example, on the surface of a substrate by printing using the water-based ink described above by a flexographic printing method.

[0082] (Flexographic printing method) In flexographic printing, ink is supplied from an ink container directly or via an ink supply pump or the like to an anilox roller with an uneven surface. The ink supplied to the anilox roller is transferred to the plate surface by contact with the raised areas, and then finally transferred to the substrate by contact between the plate surface and the substrate, forming a pattern and / or characters.

[0083] <Base material> The substrate is wound up and comes in a roll of a specified width. This differs from pre-cut sheets of paper. The width of the substrate is selected based on the width of the printing press used and the width of the image (design) portion of the gravure plate. When printing multiple colors of ink on top of each other, there are no particular restrictions on the order in which the inks are printed.

[0084] (Base material 1) The type and thickness of the substrate 1 are not particularly limited, but a plastic substrate is preferred. Specific examples of substrates that can be used for printed matter include polyolefin resins such as polyethylene and polypropylene; polyester resins such as polyethylene terephthalate, polyethylene naphthalate, polycarbonate, and polylactic acid; polyamide resins such as nylon 6 and nylon 12; polystyrene resins such as polystyrene, AS resin, and ABS resin; chlorine-containing resins such as polyvinyl chloride and polyvinylidene chloride; ethylene-vinyl alcohol copolymer resins; cellophane; paper; metal foils such as aluminum, stainless steel, and iron; or film or sheet-like materials made of composite materials of these. Among these, polyolefin resins and / or polyester resins are preferred.

[0085] The substrate 1 is preferably treated to enhance adhesion on the surface to be printed (the surface in contact with the printing layer). Examples of such treatments include corona discharge treatment, ultraviolet / ozone treatment, plasma treatment, oxygen plasma treatment, and primer treatment. For example, corona discharge treatment generates hydroxyl groups, carboxyl groups, carbonyl groups, and the like on the substrate. These functional groups can form hydrogen bonds with the resin in the ink if it has functional groups such as hydroxyl groups.

[0086] <Laminate> The laminate in this embodiment comprises, in this order, a substrate 1, a printed layer made of the aqueous flexographic ink of the present invention, and a substrate 2. The laminate can be obtained, for example, by further laminating the printed layer of the above-mentioned printed material. The laminate can be obtained by applying an anchor coat or adhesive to the printed layer, drying it, and then bonding it to the substrate 2. The substrate 2 may be the same as or different from the substrate 1, and preferably has thermoplastic properties (heat sealability). For example, an unstretched polyolefin substrate can be used. In the laminate, the printed layer made of water-based ink is positioned as an intermediate layer (for example, substrate 1 / printed layer / adhesive layer / substrate 2).

[0087] Suitable lamination methods include non-solvent lamination, dry lamination, and extrusion lamination, with non-solvent lamination being preferred.

[0088] (Non-sol lamination method) The non-solvent lamination method involves applying a solvent-free adhesive to the printed layer of the resulting printed material, then laminating it with a sealant substrate by pressure bonding. The most common adhesives used are two-component polyol / isocyanate adhesives, such as Toyo-Morton's EA-N373A / EA-N373B.

[0089] (dry lamination method) The dry lamination method involves diluting the adhesive with an organic solvent to an appropriate viscosity, applying it to the printed layer of the resulting printed material, drying it, and then laminating it by pressing it onto the sealant substrate. The most common adhesive is a two-component polyol / isocyanate type, and specific examples include Toyo-Morton's TM-250HV / CAT-RT86L-60, TM-550 / CAT-RT37, and TM-314 / CAT-14B.

[0090] (Extrusion lamination method) The extrusion lamination method involves melting a thermoplastic resin onto the printed layer of a printed material, extruding it into a film through a slit die called a T-die, and then laminating it onto a substrate. An anchor coating agent is often applied to the printed layer of the printed material before lamination. Alternatively, molten resin can be extruded onto the printed layer of the printed material, and a sealant substrate can be attached using a separate unwinder. Anchor coating agents that can be used include imine-, butadiene-, and isocyanate-based anchor coating agents. Examples of suitable anchor coating agents include Toyo-Morton's EL-420 (imine-based), EL-452 (butadiene-based), EL-530A / B (isocyanate-based), and EL-540 / CAT-RT32 (isocyanate-based). Examples of suitable molten resins include low-density polyethylene, polypropylene, and ethylene-vinyl acetate copolymers. Examples of suitable resins include Novatec LD LC600A (low-density polyethylene) from Japan Polyethylene Corporation. [Example]

[0091] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited by these examples. In the examples, "parts" means "parts by mass" and "%" means "% by mass."

[0092] <Mass average molecular weight, number average molecular weight> The mass average molecular weight (Mw) and number average molecular weight (Mn) were measured by GPC (gel permeation chromatography) and calculated as molecular weights using polystyrene as a standard substance. The measurement conditions are shown below. GPC equipment: Showa Denko Shodex GPC-104 Columns: The following columns were used in series. Showa Denko Shodex LF-404 (2 pieces) Showa Denko Shodex LF-G Detector: RI (differential refractometer) Measurement conditions: Column temperature 40°C Eluent: tetrahydrofuran Flow rate: 0.3mL / min

[0093] <Hydroxyl value and acid value> It was determined according to the method described in JIS K0070.

[0094] [Synthesis Example 1] Synthesis of aqueous urethane resin PU01 solution A four-necked 2000 ml flask equipped with a reflux condenser, dropping funnel, gas inlet, stirrer, and thermometer was charged with 40 parts of PTG-2000SN (polytetramethylene glycol with a number-average molecular weight of 2000, manufactured by Hodogaya Chemical Co., Ltd.), 25 parts of PEG2000 (polyethylene glycol with a number-average molecular weight of 2000), and 10 parts of DMBA (dimethylol butanoic acid, manufactured by HighChem Co., Ltd.). The atmosphere in the flask was purged with dry nitrogen, and 25 parts of isophorone diisocyanate (isophorone diisocyanate, manufactured by Evonik Degussa Japan Co., Ltd.) was added with stirring, and the temperature was gradually raised to 100 °C. The reaction was continued for an additional 180 minutes to obtain aqueous urethane resin PU01. Next, 50 parts of isopropyl alcohol was added while cooling, followed by 350 parts of ion-exchanged water containing 6.7 parts of 10% aqueous ammonia, yielding 500 parts of an aqueous urethane resin PU01 solution with a solids content of 20% by weight. The water-based urethane resin PU01 has a mass average molecular weight of 35,000 and an acid value of 35 mgKOH / g.

[0095] [Synthesis Example 2] Synthesis of aqueous urethane resin PU02 solution A four-necked 2000 ml flask equipped with a reflux condenser, dropping funnel, gas inlet, stirrer, and thermometer was charged with 40 parts of PTG-2000SN, 25 parts of PEG2000, and 10 parts of DMBA. The atmosphere in the flask was replaced with dry nitrogen, and 25 parts of IPDI was added with stirring. The temperature was gradually raised to 100 °C. The reaction was continued for an additional 180 minutes to obtain aqueous urethane resin PU02. Next, while cooling, 400 parts of ion-exchanged water containing 6.7 parts of 10% aqueous ammonia was added to obtain 500 parts of aqueous urethane resin PU02 solution with a solids content of 20% by weight. The aqueous urethane resin PU02 had a mass average molecular weight of 35,000 and an acid value of 35 mg KOH / g.

[0096] [Synthesis Example 3] (Synthesis of aqueous acrylic urethane resin PUA01 solution) A reaction vessel equipped with a reflux condenser, dropping funnel, gas inlet, stirrer, and thermometer was charged with 45.0 parts of PEG2000 (polyethylene glycol with a number-average molecular weight of 2000), 67.5 parts of PTG2000 (polytetramethylene glycol with a number-average molecular weight of 2000), 22.5 parts of 2,2-dimethylolpropionic acid, 70.0 parts of isophorone diisocyanate, 30.0 parts of methylenebis(4,1-cyclohexylene) diisocyanate, and 500.0 parts of NMP. After adding 2.0 parts of dibutyltin dilaurate as a catalyst, the mixture was heated at 80-90°C for 6 hours under a nitrogen atmosphere. The reaction mixture was cooled to 80°C, and 11.9 parts of triethylamine were added and mixed. The reaction mixture was then added to 1288 parts of water with vigorous stirring. 85.0 parts of isophorone diamine was then added to obtain a urethane resin solution. To 350 parts of the resulting urethane resin solution, 3.0 parts acrylic acid, 7.0 parts methyl acrylate, 13.0 parts methyl methacrylate, 7.0 parts butyl methacrylate, and 90.0 parts water were added and heated to 50°C. Next, 9.5 parts of a 1% by weight aqueous solution of ascorbic acid and 2.5 parts of a 7% by weight aqueous solution of butyl peroxide were added. After the heat generation subsided, the mixture was heated to 50°C and distilled off to obtain an aqueous acrylic urethane resin PUA01 solution with a solids content of 20%. The resulting aqueous acrylic urethane resin PUA01 was a core-shell type aqueous acrylic urethane resin with a urethane resin shell and an acrylic resin core. The acid value was 43.8 mgKOH / g, the weight average molecular weight (Mw) of the shell was 4,0000, and the weight average molecular weight (Mw) of the core was 300,000, and the weight ratio of the urethane resin to the acrylic resin was 7:3.

[0097] (Example 1) Preparation of water-based flexographic ink (INK1) and creation of printed matter A mixture of 40.0 parts of pigment (titanium oxide Typec CR-80 manufactured by Ishihara Sangyo Kaisha), 35.0 parts of the aqueous urethane resin PU01 solution from Synthesis Example 1, 15.4 parts of ion-exchanged water, 0.3 parts of adipic acid hydrazide, and 1.0 part of 1-propanol was stirred for 10 minutes with a stirrer, and then dispersed for 10 minutes using an Eiger mill (a bead mill manufactured by Eiger) to obtain a pigment dispersion. To the pigment dispersion, 3.0 parts of polyolefin particles (Chemipearl W500 manufactured by Mitsui Chemicals, Inc., solids content 40.0%), 5.0 parts of propylene glycol monopropyl ether, 0.05 parts of an antifoaming agent (TEGO Foamex 852 silicone antifoaming agent manufactured by Evonik Japan Co., Ltd.), and 0.2 parts of a basic compound (28% by mass aqueous ammonia solution) were added and kneaded to obtain a water-based ink (INK1).

[0098] The above water-based ink (INK1) was printed on a flexographic plate (photopolymer plate, KODAK FLEXCEL NXH digital flexographic plate, 1.14mm thick, 175 lpi) and an anilox roll (1200 lpi, 3 cc / m 2Using a flexographic printing machine (MIRAFLEX CM) equipped with a printer, 10,000 m of printing was performed on substrate 1 (polyethylene terephthalate substrate (PET) E5100, film thickness 12 μm) at a speed of 300 m / min, to obtain a printed matter. The drying conditions were drying temperature: 100°C between color dryers, 100°C in tunnel dryers.

[0099] (Examples 2 to 24 and Comparative Examples 1 to 8) Preparation of Water-Based Inks (INK2 to 32) and Creation of Printed Matter Water-based inks INK2 to INK32 of Examples 2 to 24 and Comparative Examples 1 to 8 were prepared in the same manner as in Example 1 above, except that the raw materials and ratios shown in Tables 1, 2, and 3 were used. Printing was carried out using each ink in the same manner as above, and printed matter was obtained for each ink. Water-based acrylic resin solution: JONCRYL60J manufactured by BASF Japan Ltd., weight average molecular weight 8500, acid value 215 mg KOH / g, solid content 34% by mass

[0100] [Table 1]

[0101] [Table 2]

[0102] [Table 3]

[0103] <Surface tension of water-based ink> The surface tension of the water-based ink was measured using an automatic surface tensiometer CBVP-Z manufactured by Kyowa Interface Science Co., Ltd., in an environment of 25°C by the Wilhelmey method.

[0104] (Examples 1 to 24 and Comparative Examples 1 to 8) Preparation of Laminates A polyisocyanate adhesive (EA-N373A / EA-N373B, manufactured by Toyo-Morton) was applied to each printed layer of the above-mentioned printed material, and then a nonsol laminating machine was used to attach substrate 2 (CPP, manufactured by Toray Industries, Inc., film thickness 60 μm) to the coated surface at a line speed of 50 m / min. After lamination, the laminate was aged at 40°C for 48 hours to obtain laminates.

[0105] The ink, printed matter and laminate were evaluated for storage stability, leveling property, blocking resistance and laminate strength by the methods described below.

[0106] [Storage stability] The viscosity of the aqueous inks obtained above was evaluated at 25°C by Zahn cup #4 flow time at the time of ink preparation. Next, 100 ml of each ink was placed in an identical airtight bottle, capped, and left to stand at 70°C for 5 days. The viscosity after standing was then evaluated at 25°C using the same method as for the viscosity at the time of ink preparation. The difference between the viscosity after standing and the viscosity at the time of ink preparation was then determined, and the storage stability was evaluated based on the change in viscosity of the ink indicated by this difference. The evaluation criteria are as follows: A: Ink viscosity change is less than 2 seconds using Zahn cup #4 (excellent) B: Ink viscosity change is between 2 seconds and 4 seconds using Zahn cup #4 (good) C: Ink viscosity change is between 4 and 8 seconds using Zahn Cup #4 (usable) D: Ink viscosity change is 8 seconds or more with Zahn cup #4 (bad) The practical level is rated A to C.

[0107] [Leveling] The leveling ability of the solid areas (100% halftone dot areas) of the prints obtained in the above Examples and Comparative Examples was evaluated by visually checking for uneven density and the presence or absence of pinholes. The evaluation criteria were as follows: A: There is no uneven density in the solid area, no pinholes, and a uniform film is formed. (Excellent) B: Some density unevenness is observed in the solid area, but no pinholes are observed (good). C: Slight density unevenness and pinholes are observed in the solid areas. (Usable) D: Uneven density and / or pinholes are noticeable in solid areas (poor). The practical level is rated A to C.

[0108] [Blocking resistance] The printed matter obtained in the above Examples and Comparative Examples was wound into a roll after printing, and then rewound from the outside of the roll to the core, and the blocking resistance was evaluated based on the ink absorption and peel resistance. Note that the above-mentioned conditions for evaluating blocking resistance during winding are stricter than those for evaluation by simple press load and pressure, and the evaluation criteria are as follows: A: No ink is removed and there is no peeling resistance when rewinding (excellent) B: No ink is removed and there is slight peeling resistance when rewound (good) C: No ink loss and weak peel resistance when rewound (usable) D: Ink is removed and there is strong peeling resistance when rewound (bad) The practical level is rated A to C.

[0109] [Laminate strength] The laminate was cut into a size of 15 mm wide x 100 mm long, and the printed layer was peeled off from the substrate 2 at the edge by about 5 mm. The edges of the printed layer and substrate 2 were then fixed with jigs, and the laminate strength was evaluated based on the peel strength measured at a 90° peel angle and a peel speed of 300 mm / min using an Intesco Model 201 universal tensile tester. The evaluation criteria were as follows: A: Peel strength is 1.5N / 15mm or more (excellent) B: Peel strength is 1.0N / 15mm or more and less than 1.5N / 15mm (good) C: Peel strength is 0.5N / 15mm or more and less than 1.0N / 15mm (usable) D: Peel strength is less than 0.5N / 15mm (defective) The practical level is rated A to C.

[0110] <Evaluation results> As shown in Tables 1 and 2, the aqueous inks obtained in the Examples had practical levels of storage stability, leveling ability, blocking resistance, and lamination strength. On the other hand, as shown in Table 3, the aqueous inks of the Comparative Examples did not meet practical levels in at least one of storage stability, leveling ability, blocking resistance, and lamination strength.

Claims

1. An aqueous flexographic ink containing a pigment, an aqueous urethane resin and / or an aqueous acrylic urethane resin, water, and an organic solvent, the organic solvent contains two or more alcohol solvents (A) having different boiling points, The alcohol solvent (A) is an alcohol solvent (a1) which is a glycol monoalkyl ether having a boiling point of 115 to 180°C; and an alcohol solvent (a2) having a boiling point lower than that of the alcohol solvent (a1), In the total mass of the water-based flexographic ink, The alcohol solvent (a1) is contained in an amount of 0.5 to 9.5% by mass, The alcohol solvent (a2) is contained in an amount of 0.5 to 8.5% by mass, A water-based flexographic ink having a surface tension of 28 to 35 mN / m.

2. 2. The water-based flexographic ink according to claim 1, wherein the glycol monoalkyl ether solvent (a1) having a boiling point of 115 to 180°C is a propylene glycol monoalkyl ether solvent having a boiling point of 115 to 180°C.

3. 3. The water-based flexo ink according to claim 1, wherein the content of the alcohol solvent (a2) is 2 to 8.5% by mass based on the total mass of the water-based flexo ink.

4. 3. The water-based flexographic ink according to claim 1, wherein the alcohol solvent (A) further contains a glycol solvent (a3).

5. A printed matter comprising a substrate 1 and a printing layer formed from the aqueous flexographic ink according to claim 1 or 2.

6. A laminate comprising a substrate 1, a printing layer formed from the aqueous flexographic ink according to claim 1 or 2, an adhesive layer, and a substrate 2 in this order.

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