Photocurable ink composition for ink-jet printing

Abstract

To provide a photocurable ink composition for inkjet printing, which generates little odor, hardly causes banding, has excellent folding resistance of printed matter obtained when printed on a substrate, and has excellent tackiness.SOLUTION: Provided is a photocurable ink composition for inkjet printing, comprising 5-50 mass% of cyclohexyl 2-(allyloxymethyl)acrylate, 5 mass% or more of an acylphosphine oxide-based photoinitiator, 1-30 mass% of a polyfunctional photocurable compound, and 5-35 mass% of a nitrogen-containing monofunctional photocurable compound. The polyfunctional photocurable compound includes an amine-modified oligomer.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a photocurable ink composition for inkjet printing. More specifically, the present invention relates to a photocurable ink composition for inkjet printing that has little odor, is less likely to cause banding, and provides a printed matter having excellent folding resistance and tackiness when printed on a substrate. [Background technology]

[0002] Conventionally, active energy ray-curable inks have been developed that have low odor and excellent bending resistance when printed on a substrate. Patent Document 1 discloses an active energy ray-curable ink that contains a photopolymerization initiator and a diallyl phthalate resin.

[0003] Incidentally, an active energy ray-curable ink containing alkyl 2-allyloxymethylacrylate is known (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-210975 A [Patent Document 2] JP 2019-2009 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the ink compositions described in Patent Documents 1 and 2 all had insufficient odors, were prone to banding during printing, and were prone to cracking when printed on a substrate and folded, and also had insufficient tackiness.

[0006] The present invention has been made in consideration of such conventional problems, and has an object to provide a photocurable ink composition for inkjet printing that has little odor, is less likely to cause banding, and when printed on a substrate, produces a printed product with excellent folding resistance and tackiness. [Means for solving the problem]

[0007] The present inventors conducted intensive research to solve the above problems, and as a result, found that the above problems could be solved by a photocurable ink composition for inkjet printing that contains a specific amount of 2-(allyloxymethyl)cyclohexyl acrylate, an acylphosphine oxide-based photopolymerization initiator, a multifunctional photopolymerizable compound, and a nitrogen-containing monofunctional photopolymerizable compound, in which the multifunctional photopolymerizable compound contains an amine-modified oligomer, and completed the present invention. The present invention that solves the above problems mainly comprises the following configuration.

[0008] (1) A photocurable ink composition for inkjet printing, comprising 5 to 50 mass % of cyclohexyl 2-(allyloxymethyl)acrylate, 5 mass % or more of an acylphosphine oxide-based photopolymerization initiator, 1 to 30 mass % of a polyfunctional photopolymerizable compound, and 5 to 35 mass % of a nitrogen-containing monofunctional photopolymerizable compound, wherein the polyfunctional photopolymerizable compound contains an amine-modified oligomer.

[0009] According to this configuration, the photocurable ink composition for inkjet printing has little odor, is less likely to cause banding, has excellent curing properties, and when printed on a substrate, the resulting printed matter has excellent folding resistance and excellent tackiness.

[0010] (2) The photocurable ink composition for ink-jet printing according to (1), wherein the content of the 2-(allyloxymethyl)cyclohexyl acrylate is 5 to 35 mass %.

[0011] According to this configuration, the photocurable ink composition for ink-jet printing has less odor, is less likely to cause banding, and the resulting printed matter has better folding resistance and tackiness.

[0012] (3) The photocurable ink composition for inkjet printing according to (1) or (2), wherein the acylphosphine oxide photopolymerization initiator comprises at least one selected from the group consisting of 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0013] According to this configuration, the photocurable inkjet printing ink has a low viscosity, and the resulting printed matter has even better abrasion resistance.

[0014] (4) The photocurable ink composition for ink-jet printing according to any one of (1) to (3), wherein the content of the amine-modified oligomer is 1.5 to 12 mass %.

[0015] According to this configuration, the photocurable ink composition for ink-jet printing has a relatively low viscosity and excellent curability.

[0016] (5) The photocurable ink composition for ink-jet printing according to any one of (1) to (4), wherein the content of the polyfunctional photopolymerizable compound is 10 to 30 mass %.

[0017] According to this configuration, the photocurable ink composition for ink-jet printing has even more excellent abrasion resistance and tackiness.

[0018] (6) The photocurable ink composition for inkjet printing according to any one of (1) to (5), wherein the nitrogen-containing monofunctional photopolymerizable compound contains at least one selected from the group consisting of acryloylmorpholine, vinylmethyloxazolidinone, vinylcaprolactam, and N,N-dimethylacrylamide, and the content of the nitrogen-containing monofunctional photopolymerizable compound is 10 to 25 mass %.

[0019] According to this configuration, the photocurable ink composition for ink-jet printing has even more excellent tackiness and can have a low ink viscosity. Effect of the Invention

[0020] According to the present invention, it is possible to provide a photocurable ink composition for inkjet printing which has little odor, is less likely to cause banding, and when printed on a substrate, the resulting printed matter has excellent folding resistance and excellent tackiness. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] <Photocurable ink composition for inkjet printing> A photocurable ink composition for inkjet printing (hereinafter also referred to as ink composition) according to one embodiment of the present invention contains 5 to 50 mass % of 2-(allyloxymethyl)cyclohexyl acrylate, 5 mass % or more of an acylphosphine oxide-based photopolymerization initiator, 1 to 30 mass % of a polyfunctional photopolymerizable compound, and 5 to 35 mass % of a nitrogen-containing monofunctional photopolymerizable compound. The polyfunctional photopolymerizable compound contains an amine-modified oligomer.

[0022] (Cyclohexyl 2-(allyloxymethyl)acrylate) The content of 2-(allyloxymethyl)cyclohexyl acrylate in the ink composition may be 5% by mass or more, and preferably 10% by mass or more. The content of 2-(allyloxymethyl)cyclohexyl acrylate in the ink composition may be 50% by mass or less, and preferably 40% by mass or less, and more preferably 35% by mass or less. When the content of 2-(allyloxymethyl)cyclohexyl acrylate is within the above range, the ink composition has less odor, is less likely to cause banding, and the resulting printed matter has excellent folding resistance and tackiness. In particular, when the content of 2-(allyloxymethyl)cyclohexyl acrylate is 5 to 35% by mass, the ink composition has less odor, is less likely to cause banding, and the resulting printed matter has excellent folding resistance and tackiness.

[0023] (Acylphosphine oxide photopolymerization initiator) The ink composition of the present embodiment contains 5% by mass or more of an acylphosphine oxide-based photopolymerization initiator. The acylphosphine oxide-based photopolymerization initiator is not particularly limited. Examples of the acylphosphine oxide-based photopolymerization initiator include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,6-dimethoxybenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenylphosphine oxide, 2,3,5,6-tetramethylbenzoyldiphenylphosphine oxide, 2,6-dimethylbenzoyldimethylphosphine oxide, 4-methylbenzoyldiphenylphosphine oxide, 4-ethyl ... phenylphosphine oxide, 4-isopropylbenzoyldiphenylphosphine oxide, 1-methylcyclohexanoylbenzoyldiphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,3,3-trimethyl-pentylphosphine oxide, and the like, and preferably includes at least one selected from the group consisting of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. By including at least one selected from the group consisting of 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide as the acylphosphine oxide photopolymerization initiator, the ink composition can obtain good curability.

[0024] The content of the acylphosphine oxide-based photopolymerization initiator in the ink composition may be 5% by mass or more, and is preferably 6% by mass or more. The content of the acylphosphine oxide-based photopolymerization initiator in the ink composition is preferably 15% by mass or less, and more preferably 10% by mass or less. By having the content of the acylphosphine oxide-based photopolymerization initiator within the above range, the ink composition has a low viscosity, and the resulting printed matter has even better abrasion resistance.

[0025] (Polyfunctional photopolymerizable compound) The ink composition of this embodiment contains 1 to 30% by mass of a polyfunctional photopolymerizable compound. The polyfunctional photopolymerizable compound may contain an amine-modified oligomer. By containing the amine-modified oligomer, the ink composition has excellent curing properties, is less susceptible to banding, has excellent tackiness, and the resulting printed matter has even better folding resistance.

[0026] The amine-modified oligomer is not particularly limited. For example, the amine-modified oligomer is a reactive oligomer having an amino group and a functional group that crosslinks or polymerizes by irradiation with actinic rays in the molecule, and is also called a reactive amine coinitiator, a reactive amine synergist, an acrylate-modified amine synergist, an amine acrylate, or the like.

[0027] A number of amine-modified oligomers are commercially available. By way of example, commercially available amine modified oligomers include CN371, CN373, CN383, CN386, CN501, CN550, and CN551 manufactured by Sartomer; EBECRYL80 and EBECRYL7100 manufactured by Daicel-Allnex; GENOMER 5142, GENOMER 5161, and GENOMER 5275 manufactured by RAHN; Miramer AS2010 and Miramer AS5142 manufactured by Miwon; and Etercure 641, Etercure 6410, Etercure 6411, Etercure 6412, Etercure 6413, Etercure 6417, Etercure 6420, Etercure 6422, Etercure 6423, Etercure 6424, Etercure 6425, Etercure 6426, Etercure 6427, Etercure 6428, Etercure 6429, Etercure 6430, Etercure 6431, Etercure 6432, Etercure 6433, Etercure 6434, Etercure 6435, Etercure 6436, Etercure 6437, Etercure 6438, Etercure 6439, Etercure 6440, Etercure 6441, Etercure 6442, Etercure 6443, Etercure 6444, Etercure 6445, Etercure 6446, Etercure 6447, Etercure 6448, Etercure 6449, Etercure 6450, Etercure 6425, Etercure 6430, Etercure 645, and Etercure 647, etc.

[0028] The amine-modified oligomer of this embodiment is preferably an acrylated amine compound such as CN371, CN373, CN383, or CN386 (manufactured by Sartomer), and more preferably CN371, CN386 (manufactured by Sartomer), or EBECRYL80 (manufactured by Daicel-Allnex), which has two or more photopolymerizable functional groups in the molecule. When the amine-modified oligomer is included, the content of the amine-modified oligomer in the ink composition is preferably 3% by mass or more, and more preferably 5% by mass or more. In addition, the content of the amine-modified oligomer in the ink composition is preferably 20% by mass or less, and more preferably 15% by mass or less.

[0029] The polyfunctional photopolymerizable compound other than the amine-modified oligomer is not particularly limited. For example, the polyfunctional photopolymerizable compound other than the amine-modified oligomer is preferably a bifunctional monomer such as hexanediol diacrylate, or a trifunctional monomer such as alkoxy-modified trimethylolpropane triacrylate.

[0030] The content of the polyfunctional photopolymerizable compound in the ink composition may be 1% by mass or more, preferably 10% by mass or more, and more preferably 15% by mass or more. The content of the polyfunctional photopolymerizable compound in the ink composition may be 30% by mass or less, and more preferably 25% by mass or less. When the content of the polyfunctional photopolymerizable compound is within the above range, the ink composition has excellent tackiness and abrasion resistance. In particular, when the content of the polyfunctional photopolymerizable compound is 10 to 30% by mass, the ink composition has even more excellent abrasion resistance and tackiness.

[0031] The content of the amine-modified oligomer in the ink composition is preferably 1.5% by mass or more, and more preferably 3.0% by mass or more. The content of the amine-modified oligomer in the ink composition is preferably 12% by mass or less, and more preferably 10.0% by mass or less. By having the content of the amine-modified oligomer within the above range, the ink composition has a relatively low viscosity and excellent curability.

[0032] (Nitrogen-containing monofunctional photopolymerizable compound) The ink composition of the present embodiment contains 5 to 35% by mass of a nitrogen-containing monofunctional photopolymerizable compound. The nitrogen-containing monofunctional photopolymerizable compound is not particularly limited. For example, the nitrogen-containing monofunctional photopolymerizable compound is preferably acryloylmorpholine, vinylmethyloxazolidinone, vinylcaprolactam, N,N-dimethylacrylamide, N,N-diethylacrylamide, or isopropylacrylamide, and more preferably at least one selected from the group consisting of acryloylmorpholine, vinylmethyloxazolidinone, vinylcaprolactam, and N,N-dimethylacrylamide. By containing at least one selected from the group consisting of acryloylmorpholine, vinylmethyloxazolidinone, vinylcaprolactam, and N,N-dimethylacrylamide, the ink composition has excellent tackiness and a relatively low viscosity.

[0033] The content of the nitrogen-containing monofunctional photopolymerizable compound in the ink composition may be 5% by mass or more, and preferably 10% by mass or more. The content of the nitrogen-containing monofunctional photopolymerizable compound in the ink composition may be 35% by mass or less, and preferably 25% by mass or less. By having the content of the nitrogen-containing monofunctional photopolymerizable compound within the above range, the ink composition has even more excellent tackiness.

[0034] (optional ingredient) The ink composition of the present embodiment may further contain optional components in addition to a predetermined amount of 2-(allyloxymethyl) cyclohexyl acrylate, an acylphosphine oxide-based photopolymerization initiator, a multifunctional photopolymerizable compound, and a nitrogen-containing monofunctional photopolymerizable compound. The optional components are not particularly limited. For example, the optional components are photopolymerizable compounds other than those described above, photopolymerization initiators other than those described above, sensitizers, additives, pigments, dispersants, etc.

[0035] Photopolymerizable compounds other than those mentioned above The photopolymerizable compound other than the above that can be blended in the ink composition of the present embodiment is not particularly limited. For example, the photopolymerizable compound other than the above may be a monofunctional acrylate such as methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isoamyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, decyl acrylate, lauryl acrylate, stearyl acrylate, isobornyl acrylate, cyclohexyl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, or benzyl acrylate. Monofunctional halogen-containing acrylates such as 2,2,2-trifluoroethyl acrylate, 2,2,3,3-tetrafluoropropyl acrylate, 1H-hexafluoroisopropyl acrylate, 1H,1H,5H-octafluoropentyl acrylate, 1H,1H,2H,2H-heptadecafluorodecyl acrylate, 2,6-dibromo-4-butylphenyl acrylate, 2,4,6-tribromophenoxyethyl acrylate, and 2,4,6-tribromophenol 3EO adduct acrylate, 2-methoxyethyl acrylate, 1,3-Butylene glycol methyl ether acrylate, butoxyethyl acrylate, methoxytriethylene glycol acrylate, methoxypolyethylene glycol #400 acrylate, methoxydipropylene glycol acrylate, methoxytripropylene glycol acrylate, methoxypolypropylene glycol acrylate, ethoxydiethylene glycol acrylate, ethyl carbitol acrylate, 2-ethylhexyl carbitol acrylate, tetrahydrofurfuryl acrylate, phenoxyethyl acrylate, phenoxydiethylene glycol acrylate, phenoxypolyethylene glycol acrylate, cresyl polyethylene glycol acrylate monofunctional ether group-containing acrylates such as acrylate, 2-(vinyloxyethoxy)ethyl acrylate, p-nonylphenoxyethyl acrylate, p-nonylphenoxy polyethylene glycol acrylate, and glycidyl acrylate; and monofunctional carboxyl acrylates such as β-carboxyethyl acrylate, succinic acid monoacryloyloxyethyl ester, ω-carboxypolycaprolactone monoacrylate, 2-acryloyloxyethyl hydrogen phthalate, 2-acryloyloxypropyl hydrogen phthalate, 2-acryloyloxypropyl hexahydrohydrogen phthalate, and 2-acryloyloxypropyl tetrahydrohydrogen phthalate.

[0036] In the case where these photopolymerizable compounds are included, the content of the photopolymerizable compounds is not particularly limited. For example, the content of the photopolymerizable compounds in the ink composition is preferably 5% by mass or more, more preferably 20% by mass or more. The content of the photopolymerizable compounds in the ink composition is preferably 50% by mass or less, more preferably 40% by mass or less.

[0037] Photopolymerization initiators other than those mentioned above The photopolymerization initiator other than the above that can be blended in the ink composition of the present embodiment is not particularly limited. For example, the photopolymerization initiator other than the above is 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, benzil dimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, etc.

[0038] In the case where these photopolymerization initiators are included, the content of the photopolymerization initiator is not particularly limited. For example, the content of the photopolymerization initiator in the ink composition is preferably 0.5% by mass or more. The content of the photopolymerization initiator in the ink composition is preferably 15% by mass or less, and more preferably 12% by mass or less.

[0039] Sensitizer The sensitizer is not particularly limited. For example, the sensitizer is preferably an anthracene-based sensitizer, a thioxanthone-based sensitizer, or the like, more preferably a thioxanthone-based sensitizer. Specifically, the sensitizer is an anthracene-based sensitizer such as 9,10-dibutoxyanthracene, 9,10-diethoxyanthracene, 9,10-dipropoxyanthracene, or 9,10-bis(2-ethylhexyloxy)anthracene, or a thioxanthone-based sensitizer such as 2,4-diethylthioxanthone, 2-isopropylthioxanthone, or 4-isopropylthioxanthone. Representative examples of commercially available products include DBA and DEA (manufactured by Kawasaki Chemical Industries, Ltd.) as an anthracene-based sensitizer, and DETX and ITX (manufactured by Lambson) as a thioxanthone-based sensitizer.

[0040] When the sensitizer is contained, the content of the sensitizer is not particularly limited. For example, the content of the sensitizer in the ink composition is preferably 0.5% by mass or more, and more preferably 0.8% by mass or more. The content of the sensitizer in the ink composition is preferably 2.0% by mass or less, and more preferably 1.5% by mass or less. When the content of the sensitizer is within the above range, the ink composition has excellent curability and can suppress yellowing of the coating film.

[0041] In addition, when a thioxanthone-based sensitizer is included as a sensitizer, the ink composition is likely to change color to yellow. Therefore, since the ink composition has a yellowish hue compared to the color based on the pigment (original hue), it is preferable to appropriately determine the content of the thioxanthone-based sensitizer for each color. Specifically, in the white ink composition and the clear ink composition, which are easily affected by changes in color, it is preferable that the ink composition does not include a thioxanthone-based sensitizer as a sensitizer. In addition, since changes in hue are likely to be a problem in the magenta ink composition and the cyan ink composition, it is preferable to use the photosensitizer in a range where no problems occur in the hue. In addition, since the black ink composition and the yellow ink composition are unlikely to affect the hue even if they change color, and have poorer photopolymerizability than other hues, it is preferable to use a thioxanthone-based sensitizer in combination as a photopolymerization initiator.

[0042] Additives The ink composition of the present embodiment may contain an additive. The additive is not particularly limited. Examples of the additive include a surface conditioner, a surfactant, a plasticizer, a polymerization inhibitor, an ultraviolet absorber, a light stabilizer, and an antioxidant.

[0043] The surface conditioner is not particularly limited, and examples thereof include silicone-based surface conditioners, acrylic-based surface conditioners, vinyl-based surface conditioners, fluorine-based surface conditioners, and acetylene glycol-based surface conditioners.

[0044] In the case where the surface conditioner is included, the content of the surface conditioner is not particularly limited. As an example, the content of the surface conditioner in the ink composition is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more. The content of the surface conditioner in the ink composition is preferably 1.5% by mass or less, and more preferably 1% by mass or less. By having the content of the surface conditioner within the above range, the ink composition has excellent wettability to the substrate and improved abrasion resistance.

[0045] Pigments The ink composition of the present embodiment may contain a pigment. There are no particular limitations on the pigment. For example, the pigment may be any of various organic pigments and inorganic pigments.

[0046] Examples of organic pigments include dye lake pigments, azo-based, benzimidazolone-based, phthalocyanine-based, quinacridone-based, anthraquinone-based, dioxazine-based, indigo-based, thioindigo-based, perylene-based, perinone-based, diketopyrrolopyrrole-based, isoindolinone-based, nitro-based, nitroso-based, anthraquinone-based, flavanthrone-based, quinophthalone-based, pyranthrone-based, and indanthrone-based pigments.

[0047] Inorganic pigments include colored pigments such as titanium oxide, red ocher, antimony red, cadmium yellow, cobalt blue, ultramarine, Prussian blue, iron black, chromium oxide green, carbon black, and graphite (including achromatic colored pigments such as white and black), as well as extender pigments such as calcium carbonate, kaolin, clay, barium sulfate, aluminum hydroxide, and talc.

[0048] Specific examples of pigments for each representative hue of the ink composition of this embodiment are as follows: Yellow pigments include CI Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 42, 73, 74, 75, 81, 83, 87, 93, 95, 97, 98, 108, 109, 114, 120, 128, 129, 138, 139, 150, 151, 155, 166, 180, 184, 185, 213, etc., and preferably CI Pigment Yellow 150, 155, 180, 213, etc.

[0049] Magenta pigments include CI Pigment Red 5, 7, 12, 19, 22, 38, 48:1, 48:2, 48:4, 49:1, 53:1, 57, 57:1, 63:1, 101, 102, 112, 122, 123, 144, 146, 149, 168, 177, 178, 179, 180, 184, 185, 190, 202, 209, 224, 242, 254, 255, 270, CI Pigment Violet 19, and the like, and preferably CI Pigment Red 122, 202, Pigment Violet 19, and the like.

[0050] Cyan pigments include CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 18, 22, 27, 29, 60, etc., and preferably CI Pigment Blue 15:4, etc.

[0051] The black pigment is carbon black (CI Pigment Black 7) or the like.

[0052] The white pigment is titanium oxide, aluminum oxide, or the like, and is preferably titanium oxide or the like that has been surface-treated with various materials such as alumina or silica.

[0053] In the case where a pigment is included, the content of the pigment is not particularly limited. For example, the content of the pigment other than white is preferably 0.5% by mass or more, more preferably 2.0% by mass or more, in the ink composition. The content of the pigment other than white is preferably 10% by mass or less, more preferably 7% by mass or less, in the ink composition. On the other hand, the content of the white pigment is preferably 8% by mass or more, more preferably 10% by mass or more, in the ink composition. The content of the white pigment is preferably 18% by mass or less, more preferably 15% by mass or less, in the ink composition. When the content of the pigment is within the above range, the ink composition has excellent color reproducibility.

[0054] Dispersants The ink composition of the present embodiment may contain a dispersant. The dispersant is not particularly limited. Examples of the dispersant include polyvinyl alcohol, acrylic acid resin, styrene-acrylic acid resin, and vinyl acetate resin. Examples of the acrylic acid resin include polyacrylic acid, acrylic acid-acrylonitrile copolymer, and acrylic acid-acrylic acid alkyl ester copolymer.

[0055] When a dispersant is included, the content of the dispersant is not particularly limited. For example, the content of the dispersant is preferably 10% by mass or more, and more preferably 15% by mass or more, relative to 100% by mass of the pigment. The content of the dispersant is preferably 60% by mass or less, and more preferably 50% by mass or less, relative to 100% by mass of the pigment. When the content of the dispersant is within the above range, the ink composition has excellent dispersion stability.

[0056] Returning to the description of the ink composition as a whole, the ink composition of this embodiment preferably has a viscosity of 20.0 mPa·s or less, and more preferably 15.0 mPa·s or less, at 25° C. Viscosity adjusters and the like are blended into the ink composition as necessary. In this embodiment, the viscosity can be measured at 25° C. using an E-type viscometer (RE100L type viscometer, manufactured by Toki Sangyo Co., Ltd.).

[0057] <Method of preparing ink composition> The method for preparing the ink composition of the present embodiment is not particularly limited. For example, the ink composition may be prepared by dispersing and mixing using a dispersing machine such as a wet circulation mill, a bead mill, a ball mill, a sand mill, an attritor, a roll mill, a DCP mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a high-pressure homogenizer (such as a Microfluidizer, Nanomizer, Ultimizer, Genus PY, or DeBEE2000), or a pearl mill.

[0058] <Manufacturing method of printed matter> Next, a method for producing a printed matter using the ink composition of this embodiment will be described.

[0059] The method for producing a printed matter of the present embodiment includes a step of printing the ink composition described above onto a substrate by an inkjet method.

[0060] The substrate is not particularly limited. For example, the substrate may be a resin substrate, paper, capsule, gel, metal foil, glass, wood, cloth, or the like. The ink composition of the present embodiment exhibits excellent bending resistance even when the substrate is folded after being printed on the substrate. Therefore, the ink composition is particularly suitable for use when the substrate is a substrate used for applications in which the substrate is folded, such as a cardboard sheet.

[0061] When the substrate is a corrugated board sheet such as a C liner or a K liner, the ink composition may be applied directly to the corrugated board sheet, or may be applied after providing a primer layer on the corrugated board sheet or performing a corona discharge treatment or the like. That is, in recent years, waste paper or recycled paper may be used for the corrugated board sheet in order to be environmentally friendly. When a K liner is used as the corrugated board sheet, the surface has rough unevenness, the color is unclear, and the ink has high permeability when printed. Therefore, when the ink composition is printed on the corrugated board sheet, the brown color of the liner base paper, which is the base, is likely to cause a decrease in print quality. In particular, when the color of the base is expressed in the printed portion, the inkjet image appears dull, and the appearance of the printed matter may be impaired. In order to eliminate the above-mentioned unevenness, etc., a primer layer is appropriately provided on such a corrugated board sheet.

[0062] The primer layer is provided for the purpose of adjusting the whiteness and color of the liner base paper that constitutes the cardboard sheet and increasing the whiteness of the base, etc. The primer layer can be formed by applying a precoat agent containing a pigment and an adhesive.

[0063] The pigment is not particularly limited. For example, the pigment may be titanium dioxide (anatase, rutile), aluminum hydroxide, barium sulfate, calcium carbonate, amorphous silica, clay, or other extender pigments. The content of the white pigment is preferably 20 to 85 parts by mass, more preferably 20 to 80 parts by mass, in 100 parts by mass of the precoat agent.

[0064] In this embodiment, the binder resin used in the precoat agent for the cardboard is preferably an aqueous resin. The aqueous resin is preferably a natural resin, a synthetic resin, etc., and more preferably a starch derivative, casein, shellac, a polyvinyl alcohol derivative, an acrylic resin, or a maleic acid resin. More specifically, the aqueous resin is preferably an aqueous acrylic resin copolymerized with acrylic acid or methacrylic acid and its alkyl ester, or styrene as a main monomer component, an aqueous styrene-acrylic resin, an aqueous styrene-maleic acid resin, an aqueous styrene-acrylic acid-maleic acid resin, an aqueous polyurethane resin, an aqueous polyester resin, etc. The content of the binder resin is preferably 1 to 25 parts by mass, more preferably 1 to 15 parts by mass, in 100 parts by mass of the precoat agent.

[0065] The aqueous medium that can be used in the precoat agent of this embodiment can be water or a mixture of water and a water-miscible solvent.The water-miscible solvent can be lower alcohols, polyhydric alcohols, and their alkyl ethers or alkyl esters.Specifically, the water-miscible solvent can be lower alcohols such as methyl alcohol, ethyl alcohol, normal propyl alcohol, and isopropyl alcohol, polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, and glycerin, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoacetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monoacetate, diethylene glycol monomethyl ether, and dipropylene glycol monomethyl ether.

[0066] In addition to the components listed above, the precoat used in this embodiment may contain various additives, such as film-forming agents, pigment dispersants or pigment dispersing resins, antiblocking agents, wetting agents, viscosity adjusters, pH adjusters, defoamers, and general surfactants, which may be appropriately selected as necessary.

[0067] The method of producing a precoat agent using these various materials is not particularly limited. As an example, a method of producing a precoat agent is generally a method of mixing and kneading a white pigment, an aqueous binder resin, water, a water-miscible solvent as required, and a pigment dispersant or a pigment dispersing resin, and further adding and mixing an additive, water, a water-miscible solvent as required, and the remaining predetermined materials.

[0068] The precoat agent of the present embodiment can be easily obtained by mixing the required amounts of the above-mentioned components and mixing and dispersing them using a high-speed stirrer such as a homomixer or a lab mixer, or a disperser such as a three-roll mill or a bead mill.

[0069] When a primer layer is provided, the thickness of the primer layer (the amount of the precoat agent applied) is not particularly limited. The primer layer has a solid content of 0.1 to 5 g / m 2 By having the thickness of the primer layer (amount of application of the precoat agent) within the above range, the whiteness and color of the corrugated cardboard sheet can be easily adjusted appropriately.

[0070] Returning to the description of the ink composition, the method for curing the ink composition is not particularly limited. For example, the ink composition can be cured by irradiating light after being ejected onto a substrate. The light source for irradiating light is not particularly limited. For example, the light source may be ultraviolet light, an electron beam, visible light, a light-emitting diode (LED), or the like.

[0071] Specifically, the ink composition is discharged onto a substrate by supplying the ink composition to a printer head of an inkjet printer and discharging the ink composition from the printer head onto the substrate so that the coating has a thickness of 1 to 20 μm. Exposure to light and curing (curing of an image) can be performed by irradiating the ink composition applied to the substrate as an image with light.

[0072] As described above, the ink composition of the present embodiment has little odor, is less likely to cause banding, and when printed on a substrate, the resulting printed matter has excellent folding resistance and excellent tackiness. EXAMPLES

[0073] The present invention will be described in more detail below with reference to the following examples. The present invention is not limited to these examples. Unless otherwise specified, "%" means "% by mass" and "parts" means "parts by mass".

[0074] The raw materials and preparation methods used are shown below. 2-(Allyloxymethyl) cyclohexyl acrylate: AOMA-CH, manufactured by Nippon Shokubai Co., Ltd. Methyl 2-(allyloxymethyl)acrylate: AOMA, manufactured by Nippon Shokubai Co., Ltd. (Polyfunctional photopolymerizable compound) CN371: Sartomer, amine-modified oligomer EO(3) modified trimethylolpropane triacrylate PO(3) modified trimethylolpropane triacrylate Hexanediol diacrylate (Nitrogen-containing monofunctional photopolymerizable compound) Acryloylmorpholine Vinylmethyloxazolidinone Vinylcaprolactam (Other photopolymerizable compounds) Isobornyl acrylate Benzyl acrylate Lauryl acrylate Ethyl Carbitol Acrylate (Acylphosphine oxide photopolymerization initiator) TPO: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (Lambson) TPOL: Ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide Omnirad 819: Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (IGM Resins BV) (Other photoinitiators) Omnirad 184: 1-Hydroxycyclohexyl phenyl ketone (IGM Resins BV) (sensitizer) DETX: 2,4-diethylthioxanthone (Lambson) (Additives) BYK-315N: Polyester modified polymethylalkylsiloxane, solid content 25% by mass, solvent component: mixture of methoxypropyl acetate and phenoxyethanol in a mass ratio of 1 / 1 (manufactured by BYK-Chemie) (Pigments) PB15:4: Pigment Blue 15:4 PR122: Pigment Red 122 PY155: Pigment Yellow 155 PBk7: Pigment Black 7 (Dispersant) SS32000: Solsperse32000 (manufactured by Lubrizol)

[0075] (Photocurable ink composition for inkjet printing) The materials were mixed by stirring so as to obtain the composition (mass %) shown in Table 1, thereby obtaining photocurable ink compositions for inkjet printing of Examples 1 to 11 and Comparative Examples 1 to 6.

[0076] (base material) PET film: E5100, manufactured by Toyobo Co., Ltd. PVC plate: T938, manufactured by Takiron C.I. Co., Ltd.

[0077] <Evaluation of Photocurable Ink Composition for Inkjet Printing and Printed Matter> The photocurable ink compositions for inkjet printing of Examples 1 to 11 and Comparative Examples 1 to 6 were evaluated for viscosity, coating odor, curability, bending resistance, banding, tackiness, and abrasion resistance according to the following evaluation methods and criteria. The results are shown in Table 1.

[0078] [Table 1]

[0079] (Measurement of Viscosity of Photocurable Ink Composition for Inkjet Printing) The viscosity of the photocurable ink composition for ink jet printing was measured using an E-type viscometer (RE100L type viscometer, manufactured by Toki Sangyo Co., Ltd.) at a temperature of 25° C. and a rotor rotation speed of 20 rpm.

[0080] (Paint film odor) The photocurable ink jet printing ink compositions obtained in the Examples and Comparative Examples were applied to the surface of a PET film using a bar coater No. 6, and then irradiated with ultraviolet light to obtain a cured coating film. The resulting cured coating film was cut to a size of 8 cm x 12 cm, placed in a 24 cm x 34 cm ziplock bag, and left at 25°C for 1 hour. The bag was then opened and the odor at the opening was evaluated on the following 5-point scale. 5: No odor was detected. 4: A slight odor was detected. 3: Moderate odor was detected. 2: A strong odor was detected. 1: A very strong odor was detected. Ten people performed similar evaluations and the arithmetic mean of the evaluation results was obtained.

[0081] (curable) The photocurable ink jet printing ink compositions obtained in the Examples and Comparative Examples were printed on the surface of a PET film using a commercially available ink jet printer, and the ink was printed at 1500 mJ / cm 2 The resulting coating film was rubbed with a cotton swab, and the curability was evaluated based on the marks left and the touch of the fingers according to the following evaluation criteria. ○: No marks or stickiness were left behind. △: No marks were left, but it was a little sticky. ×: Traces were left and there was a lot of stickiness.

[0082] (Bending resistance) The photocurable ink composition for ink jet printing obtained in each of the Examples and Comparative Examples was applied to the surface of a PET film using a bar coater No. 12, and then irradiated with ultraviolet light to obtain a cured coating film. The resulting coating film was folded 180 degrees and the state of the coating film was visually evaluated according to the following criteria. ○: No cracks were observed in the coating. △: Slight cracking of the coating film. ×: The coating film was cracked.

[0083] (Banding) The photocurable ink composition for inkjet printing obtained in each of the Examples and Comparative Examples was printed on the surface of a PVC film using a commercially available inkjet printer, and the coating film was cured by exposure to ultraviolet light. The gloss at a measurement angle of 60° was measured using a variable-angle gloss meter (product name: GlossMeter VG7000, manufactured by Nippon Denshoku Industries Co., Ltd.) and evaluated according to the following evaluation criteria. ○: The measured value was 15.0 or more. △: The measured value was 10.0 or more and less than 15.0. ×: The measured value was less than 10.0.

[0084] (tackiness) The photocurable ink composition for ink jet printing obtained in each of the Examples and Comparative Examples was applied to the surface of each of two PET films using a No. 4 bar coater, and then irradiated with ultraviolet light to obtain a cured coating film. The resulting two cured coating films on the surfaces of the PET films were temporarily overlapped with each other, and after 30 seconds, they were peeled off by hand. The degree of adhesion was evaluated according to the following criteria. ○: No tack was observed. △: Slight tack was observed. ×: Tack was observed.

[0085] (Abrasion resistance) The photocurable ink jet printing ink compositions obtained in the Examples and Comparative Examples were applied to the surface of a PVC plate (T938, manufactured by Takiron CI Co., Ltd.) using a bar coater No. 6, and then irradiated with ultraviolet light to obtain a cured coating film. The obtained coating film was rubbed 100 times against white bleached cloth using a Gakushin color fastness tester at a load of 500 g and a speed of 60 rpm. The degree of peeling of the coating film and the degree of color transfer to the white bleached cloth were evaluated according to the following evaluation criteria. ◯: No color transfer occurred or color transfer occurred over less than 5% of the fabric area. △: Color transfer occurred over 5% or more but less than 70% of the fabric area. ×: Color transfer occurred over 70% or more of the fabric area.

[0086] As shown in Table 1, the photocurable inkjet printing ink composition of the present invention has little odor, excellent curability, is less likely to cause banding, and when printed on a substrate, the printed matter obtained has excellent folding resistance and excellent tackiness. On the other hand, the photocurable inkjet printing ink composition of Comparative Example 1, which does not contain 2-(allyloxymethyl)cyclohexyl acrylate, has a strong odor and the results of folding resistance and tackiness are poor. The photocurable inkjet printing ink composition of Comparative Example 2, which contains an excess of 2-(allyloxymethyl)cyclohexyl acrylate, has poor tackiness. The photocurable inkjet printing ink composition of Comparative Example 3, which contains methyl 2-(allyloxymethyl)acrylate instead of 2-(allyloxymethyl)cyclohexyl acrylate, has a strong odor. The photocurable inkjet printing ink composition of Comparative Example 4, which contains a small amount of acylphosphine oxide-based photopolymerization initiator, has poor curability. The photocurable inkjet printing ink composition of Comparative Example 5, which does not contain an amine-modified oligomer, has poor curability and tackiness. The photocurable ink composition for ink-jet printing of Comparative Example 6, which did not contain a nitrogen-containing monofunctional photopolymerizable compound, showed poor curability.

Claims

1. Contains 5 to 50 mass % of cyclohexyl 2-(allyloxymethyl)acrylate; Contains 5% by mass or more of an acylphosphine oxide-based photopolymerization initiator, Contains 1 to 30% by mass of a multifunctional photopolymerizable compound; Contains 5 to 35% by mass of a nitrogen-containing monofunctional photopolymerizable compound, The photocurable ink composition for ink-jet printing, wherein the multifunctional photopolymerizable compound contains an amine-modified oligomer.

2. 2. The photocurable ink composition for ink-jet printing according to claim 1, wherein the content of the cyclohexyl 2-(allyloxymethyl)acrylate is 5 to 35% by mass.

3. 3. The photocurable ink composition for ink-jet printing according to claim 1, wherein the acylphosphine oxide photopolymerization initiator comprises at least one selected from the group consisting of 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

4. The photocurable ink composition for ink-jet printing according to any one of claims 1 to 3, wherein the content of the amine-modified oligomer is 1.5 to 12 mass %.

5. 5. The photocurable ink composition for ink-jet printing according to claim 1, wherein the content of the polyfunctional photopolymerizable compound is 10 to 30% by mass.

6. the nitrogen-containing monofunctional photopolymerizable compound includes at least one selected from the group consisting of acryloylmorpholine, vinylmethyloxazolidinone, vinylcaprolactam, and N,N-dimethylacrylamide; 6. The photocurable ink composition for ink-jet printing according to claim 1, wherein the content of the nitrogen-containing monofunctional photopolymerizable compound is 10 to 25% by mass.

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