Active energy ray curable inkjet printing ink

Abstract

To sufficiently enhance the curability of an active energy ray-curable ink composition for inkjet printing, which contains (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide as a photopolymerization initiator, and preferably to improve the solvent resistance of a cured product. [Solution] An active energy ray curable ink composition for inkjet printing, which has a viscosity of 5 cps or more and 80 cps or less at room temperature, comprises: 10% by mass or more of a monofunctional monomer, 1 to 15% by mass of an amine-modified oligomer, and (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide, based on the ink composition; and when the ink composition further contains a black pigment, the ink composition contains a sensitizer.

Description

[Technical field]

[0001] The present invention relates to an actinic radiation-curable ink for inkjet printing, and more specifically to an actinic radiation-curable ink for inkjet printing that contains TMO ((2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide) as a photoinitiator. [Background technology]

[0002] An active energy ray curable ink composition is an ink composition that can be cured by irradiation with active energy rays such as ultraviolet rays or electron beams. An active energy ray curable ink composition can be a solvent-free or low-solvent ink and has fast drying properties, so that it can be printed on various printing substrates. In other words, an active energy ray curable ink composition can provide an effect of preventing ink bleeding even when printed on a printing substrate with low absorbency.

[0003] Furthermore, it is also known to use an active energy ray-curable ink composition as an ink for inkjet printing. Patent Document 1 discloses an active energy ray-curable inkjet ink composition containing a colorant, a monofunctional monomer, a bifunctional oligomer, a photopolymerization initiator, and a surface tension adjuster.

[0004] The actinic energy ray-curable ink composition may contain a photoinitiator (photopolymerization initiator), depending on the type of actinic energy ray used for curing. Photoinitiators can generally be broadly classified into several types, examples of which include benzophenone-based, thioxanthone-based, acetophenone-based, and acylphosphine-based compounds.

[0005] As one of the photoinitiators, (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide (sometimes abbreviated as TMO) has been proposed, and its preparation has also been studied (Patent Documents 2 and 3). Ink compositions containing TMO have also been proposed; an ink containing TMO in combination with a modified epoxy resin acrylate prepolymer and a reactive diluent has been presented (Patent Document 4). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2009-299057 A [Patent Document 2] Special Publication No. 2002-531460 [Patent Document 3] Special Publication No. 2022-520286 [Patent Document 4] CN118240419A Summary of the Invention [Problem to be solved by the invention]

[0007] Photoinitiators may be a cause for concern due to their toxicity as chemical substances; for example, the acylphosphine photoinitiator TPO (diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide) is sometimes cited as a cause for concern due to its biological toxicity. Acylphosphine photoinitiators may also have insufficient curability, resulting in insufficient hardness of the cured product; they may also cause discoloration (e.g., yellowing) of the cured product, or the viscosity stability of the ink composition may be insufficient.

[0008] The photopolymerization initiator may have low solubility (for example, low solubility in a reactive diluent such as a monofunctional monomer), and depending on the type, the solvent resistance of the cured product of the ink composition may not be sufficiently improved. Therefore, an object of the present invention is to sufficiently increase the curability of an active energy ray-curable ink jet printing ink composition containing TMO as a photopolymerization initiator, and preferably improve the solvent resistance of the cured product. [Means for solving the problem]

[0009] The present invention relates to an actinic ray-curable ink composition for ink-jet printing as described below. [1] An actinic energy ray-curable ink composition for inkjet printing, having a viscosity at room temperature of 5 cps or more and 80 cps or less, comprising: The ink composition comprises: 10% by mass or more of a monofunctional monomer, based on the ink composition; 1 to 15% by mass of an amine-modified oligomer, based on the ink composition; and (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide, and when the ink composition further contains a black pigment, the ink composition contains a sensitizer.

[0010] The present invention preferably relates to an actinic ray-curable ink composition for ink-jet printing as described below. [2] The ink composition according to [1] above, further comprising a sensitizer and a colorant. [3] The ink composition according to [1] above, which contains a white pigment or a transparent extender pigment, or which does not contain a pigment component.

[0011] [4] The ink composition according to any one of [1] to [3] above, wherein the content of (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide is 2 to 12 mass % relative to the ink composition. [5] The ink composition according to any one of [1] to [4], wherein the monofunctional monomer includes a monofunctional monomer having a molecular weight of 500 or less, and the content of the monofunctional monomer having a molecular weight of 500 or less is 10 mass % or more relative to the ink composition. [6] The ink composition according to any one of [1] to [5] above, wherein the monofunctional monomer includes a nitrogen-containing monofunctional monomer. [7] The ink composition according to any one of [1] to [6] above, further comprising 2 mass % or more of a polyfunctional monomer based on the total amount of the polymerizable components. [8] The ink composition according to any one of [1] to [7] above, wherein the ink composition does not contain diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide. Effect of the Invention

[0012] The ink composition for inkjet printing of the present invention has properties as an actinic energy ray-curable ink, and can enhance the solvent resistance of the cured product while resolving issues that can arise with ink compositions containing conventional photoinitiators (improved curability, suppression of yellowing of the cured product, and improved viscosity stability of the ink composition). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] [1. Active energy ray curable ink composition for inkjet printing] The ink composition for ink-jet printing of the present invention (also simply referred to as "ink composition") is an ink composition that can be cured by exposure to active energy rays. Examples of active energy rays include ultraviolet rays irradiated from light-emitting diodes (LEDs) or various lamps or electrodes, electron beams, visible light, and the like. From an environmental perspective, it is preferable to use a light-emitting diode (LED) that generates ultraviolet rays with an emission peak wavelength in the range of 350 to 420 nm as the light source of the active energy rays.

[0014] The ink composition of the present invention has a viscosity that allows inkjet printing, specifically, the viscosity at room temperature (25°C) is 5 cps or more, and may be 10 cps or more; on the other hand, it is 80 cps or less, preferably 60 cps or less, more preferably 40 cps or less, and may be 30 cps or less. The viscosity of the ink composition can be measured using an E-type viscometer at a temperature of 25°C and a rotor rotation speed of 20 rpm.

[0015] The ink composition for inkjet printing of the present invention contains A) a monofunctional monomer and an amine-modified oligomer as polymerizable components, and B) (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide as a photopolymerization initiator. The ink composition may also contain a polyfunctional monomer (other than the amine-modified oligomer) as a polymerizable component. The ink composition may also contain a colorant as necessary, and in that case, it is preferable for the ink composition to contain a sensitizer. In particular, when the ink composition contains a black pigment, the ink composition contains a sensitizer.

[0016] [1-1. Photopolymerizable component] The polymerizable components contained in the ink composition can be roughly divided into A) monofunctional monomers, B) reactive oligomers, and C) polyfunctional monomers.

[0017] [1-1A. Monofunctional Monomers] The monofunctional monomer as a polymerizable component is typically a compound having one ethylenically unsaturated bond. The monofunctional monomer can be broadly classified into nitrogen-containing monofunctional monomers and other monofunctional monomers (unsaturated carboxylic acid compounds, alkyl (meth)acrylate compounds, hydroxyl group-containing (meth)acrylate compounds, halogen-containing (meth)acrylate compounds, ether group-containing (meth)acrylate compounds, carboxyl group-containing (meth)acrylate compounds, other (meth)acrylate compounds, and styrene compounds). In this specification, "(meth)acrylic" means "acrylic and / or methacrylic", and "(meth)acrylic acid" means "acrylic acid and / or methacrylic acid".

[0018] At least a part of the monofunctional monomers as the polymerizable component preferably has a molecular weight of 500 or less, more preferably 400 or less, and even more preferably 300 or less. A monofunctional monomer having a molecular weight of a certain amount or less easily dissolves a photopolymerization initiator in the ink composition. The proportion of monofunctional monomers having a molecular weight of 500 or less is preferably at least 50% by mass, more preferably 60% by mass or more, even more preferably 70% by mass or more, and may be 80% by mass or more, or may be 90% by mass or more, based on the total amount of the monofunctional monomers.

[0019] <Nitrogen-containing monofunctional monomer> The nitrogen-containing monofunctional monomer can improve the curing property of the ink composition. Examples of the nitrogen-containing monofunctional monomer are selected from acryloylmorpholine, vinylmethyloxazolidinone, vinylcaprolactam, and N,N-dimethylacrylamide, acrylonitrile, (meth)acrylamide, diethylacrylamide, N-vinylcarbazole, N-vinylacetamide, N-vinylpyrrolidone, N-vinylformamide, N-hydroxymethyl(meth)acrylamide, diacetoneacrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, lactone-modified flexible acrylate, etc. These nitrogen-containing monofunctional monomers can be used alone or in combination of two or more.

[0020] <Unsaturated carboxylic acid compounds> Examples of the unsaturated carboxylic acid compound include unsaturated carboxylic acids such as (meth)acrylic acid, itaconic acid, crotonic acid, isocrotonic acid, fumaric acid, and maleic acid, as well as salts and acid anhydrides thereof.

[0021] <Alkyl (meth)acrylate compounds> Examples of the alkyl(meth)acrylate compounds include methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, i-butyl(meth)acrylate, t-butyl acrylate, amyl(meth)acrylate, isoamyl(meth)acrylate, hexyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, octyl(meth)acrylate, decyl(meth)acrylate, dodecyl(meth)acrylate, isooctyl(meth)acrylate, lauryl(meth)acrylate, stearyl(meth)acrylate, isostearyl(meth)acrylate, isopropyl ... Sodecyl (meth)acrylate, isomyristyl (meth)acrylate, octadecyl (meth)acrylate, dicyclopentanyl (meth)acrylate, tridecyl (meth)acrylate, nonyl (meth)acrylate, hexadecyl (meth)acrylate, myristyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, norbornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, 1-adamantyl (meth)acrylate, 3,5,5-trimethylcyclohexyl acrylate, 4-t-butylcyclohexyl (meth)acrylate, and the like.

[0022] <Hydroxyl group-containing (meth)acrylate compounds> Examples of the hydroxyl group-containing (meth)acrylate compounds include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, hydroxypentyl (meth)acrylate, 2-hydroxy-3-methoxypropyl (meth)acrylate, 2-hydroxy-3-butoxypropyl (meth)acrylate, diethylene glycol mono(meth)acrylate, triethylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, dipropylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, and the like. Examples of the (poly)alkylene glycol-modified (meth)acrylates include ethylene glycol mono(meth)acrylate, 1,6-hexanediol mono(meth)acrylate, glycerin mono(meth)acrylate, 2-hydroxy-3-chloropropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-hydroxy-3-allyloxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-ethylhexyl EO-modified (meth)acrylate, o-phenylphenol EO-modified acrylate, p-cumylphenol EO-modified (meth)acrylate, and nonylphenol EO-modified (meth)acrylate.

[0023] <Halogen-containing (meth)acrylate compounds> Examples of halogen-containing (meth)acrylate compounds include trifluoromethyl (meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate, 1H-hexafluoroisopropyl (meth)acrylate, 1H,1H,5H-octafluoropentyl (meth)acrylate, 1H,1H,2H,2H-heptadecafluorodecyl (meth)acrylate, 2,6-dibromo-4-butylphenyl (meth)acrylate, 2,4,6-tribromophenoxyethyl (meth)acrylate, and 2,4,6-tribromophenol 3EO (ethylene oxide) adduct (meth)acrylate.

[0024] <Ether group-containing (meth)acrylate compounds> Examples of the ether group-containing (meth)acrylate compounds include 1,3-butylene glycol methyl ether (meth)acrylate, methoxytriethylene glycol (meth)acrylate, methoxydipropylene glycol (meth)acrylate, methoxytripropylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, ethyl carbitol (meth)acrylate, 2-ethylhexyl carbitol (meth)acrylate, and tetrahydrofurfuryl ether (meth)acrylate. (meth)acrylate, cresyl polyethylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, p-nonylphenoxyethyl (meth)acrylate, p-nonylphenoxy polyethylene glycol (meth)acrylate, glycidyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxy-polyethylene glycol (meth)acrylate, hexaethylene glycol monophenyl ether mono (meth)acrylate, diethylene glycol monobutyl ether acrylate, dipropylene glycol monomethyl ether (meth)acrylate, 3-methoxybutyl (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxypropylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate (EO repeating unit number 400, 700, etc.), 2-(2-ethoxyethoxy)ethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl acrylate, ethoxyethyl acrylate, ethoxyethoxyethyl (Meth)acrylate, butoxyethyl (meth)acrylate, alkoxylated 2-phenoxyethyl (meth)acrylate (ethoxylated 2-phenoxyethyl (meth)acrylate, propoxylated 2-phenoxyethyl (meth)acrylate, etc.), alkoxylated nonylphenyl (meth)acrylate (ethoxylated (4) nonylphenol acrylate, etc.), 2-phenoxyethyl (meth)acrylate, paracumylphenoxyethylene glycol (meth)acrylate, methylphenoxyethyl acrylate, ethoxylated succinic acid (meth)acrylate,Examples of the alkoxy-based and / or phenoxy-based (meth)acrylates include ethoxylated tribromophenyl acrylate and ethoxylated nonylphenyl (meth)acrylate.

[0025] <Carboxyl group-containing (meth)acrylate compounds> Examples of the carboxyl group-containing (meth)acrylate compound include β-carboxyethyl (meth)acrylate, succinic acid monoacryloyloxyethyl ester, ω-carboxypolycaprolactone mono(meth)acrylate, 2-(meth)acryloyloxyethyl hydrogen phthalate, 2-(meth)acryloyloxypropyl hydrogen phthalate, 2-(meth)acryloyloxypropyl hexahydrohydrogen phthalate, and 2-(meth)acryloyloxypropyl tetrahydrohydrogen phthalate.

[0026] <Other (meth)acrylate compounds> Other (meth)acrylate compounds include, for example, benzyl acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, acryloylmorpholine, morpholinoethyl (meth)acrylate, trimethylsiloxyethyl (meth)acrylate, diphenyl-2-(meth)acryloyloxyethyl phosphate, 2-(meth)acryloyloxyethyl acid phosphate, caprolactone-modified 2-(meth)acryloyloxyethyl phosphate, Diethyl acid phosphate, 2-hydroxy-1-(meth)acryloxy-3-methacryloxypropane, acryloxyethyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate, 2-(meth)acryloyloxypropyl phthalate, tricyclodecane monomethylol (meth)acrylate, (meth)acrylic acid dimer, diethylaminoethyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl hexa Hydrophthalic acid, 2-ethylhexyl-diglycol (meth)acrylate, aminoethyl (meth)acrylate, ethyl carbitol acrylate, ethyl diglycol acrylate, dimethylaminoethyl acrylate benzyl chloride quaternary salt, tribromophenyl (meth)acrylate, 1,4-cyclohexanedimethanol mono (meth)acrylate, cresol (meth)acrylate, trimethylolpropane formal (meth)acrylate, neopentyl glycol (meth)acrylic acid ammonium Examples of the acrylates include benzoic acid esters, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, 1-(meth)acryloylpiperidin-2-one, 2-(meth)acrylic acid-1,4-dioxaspiro[4,5]dec-2-ylmethyl, N-(meth)acryloyloxyethylhexahydrophthalimide, γ-butyrolactone (meth)acrylate, caprolactone-modified tetrahydrofurfuryl acrylate, imide acrylate, vinyl (meth)acrylate, and maleimide.

[0027] <Styrene-based compounds> Examples of styrene-based compounds include styrene, vinyltoluene, p-hydroxystyrene, p-chlorostyrene, p-bromostyrene, p-methylstyrene, p-methoxystyrene, pt-butoxystyrene, pt-butoxycarbonylstyrene, pt-butoxycarbonyloxystyrene, 2,4-diphenyl-4-methyl-1-pentene, and divinylbenzene.

[0028] As the compound having one ethylenically unsaturated bond, "other compounds having one ethylenically unsaturated bond" other than the above-mentioned compounds can be used. Examples of such compounds include vinyl acetate, vinyl monochloroacetate, vinyl benzoate, vinyl pivalate, vinyl butyrate, vinyl laurate, divinyl adipate, vinyl crotonate, vinyl 2-ethylhexanoate, three-membered ring compounds (e.g., vinylcyclopropanes, 1-phenyl-2-vinylcyclopropanes, 2-phenyl-3-vinyloxiranes, 2,3-divinyloxiranes, etc.), cyclic ketene acetals (e.g., 2-methylene-1,3-dioxepane, podioxolanes, 2-methylene-4-phenyl-1,3-dioxepane, 4,7-dimethyl-2-methylene-1,3-dioxepane, 5,6-benzo-2-methylene-1,3-dioxepane, etc.).

[0029] These monofunctional monomers can be used alone or in combination of two or more kinds.

[0030] The ink composition of the present invention contains a polymerizable component, and the monofunctional monomer is contained as the polymerizable component in an amount of 10% by mass or more, preferably 15% by mass or more, based on the ink composition; on the other hand, the monofunctional monomer is contained in an amount of 80% by mass or less, more preferably 70% by mass or less, based on the ink composition. The monofunctional monomer is a polymerizable component that can also function as a diluent in the ink composition, and by containing the monofunctional monomer in an amount of 10% by mass or more based on the ink composition, the photopolymerization initiator (TMO: 2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide) can be sufficiently dissolved to ensure the compatibility of the ink composition. The monofunctional monomer can also improve the foldability of the product of the ink composition.

[0031] The ink composition of the present invention preferably contains a nitrogen-containing monofunctional monomer as a polymerizable component; the content of the nitrogen-containing monofunctional monomer is preferably 20% by mass or more, more preferably 30% by mass or more, and may be 50% by mass or more, based on the total amount of the monofunctional monomers. The nitrogen-containing monofunctional monomer easily dissolves the photopolymerization initiator, and is preferable as the monofunctional monomer of the ink composition of the present invention containing TMO, which is a photopolymerization initiator with low solubility.

[0032] [1-1B. Reactive Oligomers] The ink composition of the present invention contains a reactive oligomer as a polymerizable component. An oligomer is a component that polymerizes an ethylenically unsaturated bond in the molecule to obtain a high molecular weight. Since the oligomer is a relatively high molecular weight component before polymerization, it can impart appropriate viscosity and elasticity to the ink composition. In addition, the oligomer has a relatively high polarity, and may impart adhesion to a non-absorbent printing substrate to the ink composition after curing. A reactive oligomer is an oligomer that has one or more polymerizable functional groups (ethylenically unsaturated bonds) in the molecule.

[0033] The oligomer contained in the ink composition is preferably an amine-modified oligomer. The amine-modified oligomer is a reactive oligomer having, in the molecule, an amino group and two or more functional groups that crosslink or polymerize when irradiated with active energy rays. The amine-modified oligomer is preferably a reactive oligomer having, in the molecule, two amino groups and two functional groups that crosslink or polymerize when irradiated with active energy rays. The amine-modified oligomer is also sometimes called a reactive amine coinitiator, a reactive amine synergist, an acrylate-modified amine synergist, an amine acrylate, or the like.

[0034] The viscosity of the oligomer (preferably the amine-modified oligomer) is not limited, but a viscosity of 2000 cps or less at 25° C. is particularly preferred in order to bring the viscosity of the entire photocurable ink composition for ink jet printing into an appropriate range.

[0035] The content of the amine-modified oligomer in the ink composition is 1% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more, based on the total content of the ink composition; on the other hand, it is 15% by mass or less, preferably 13% by mass or less, more preferably 10% by mass or less. By making the content of the amine-modified oligomer 1% by mass or more, the curability of the ink composition can be improved, and the solvent resistance of the cured coating film can be improved. In addition, by making the content of the amine-modified oligomer 15% by mass or less, the viscosity of the ink composition can be suppressed to improve the ejection stability, while making it easier to ensure the stretchability of the cured printed film. The ink composition of the present invention contains TMO as a polymerization initiator, and TMO has relatively low solubility in reactive diluents (such as monofunctional monomers). Therefore, the curability of the ink composition of the present invention and the solvent resistance of the cured coating film may not be sufficiently improved, so by containing the amine-modified oligomer, these properties are improved.

[0036] Amine-modified oligomers are also available commercially. Examples of commercially available amine modified oligomers include CN371, CN373, CN383, CN386, CN501, CN550, and CN551 from Sartomer; EBECRYL80 and EBECRYL7100 from Daicel-Allnex; GENOMER 5142, GENOMER 5161, and GENOMER 5275 from RAHN; Miramer AS2010 and Miramer AS5142 from Miwon; and Etercure 641, Etercure 6410, Etercure 6411, Etercure 6412, Etercure 6413, Etercure 6417, Etercure 6420, Etercure 6422, Etercure 6423, Etercure 6425, Etercure 6430, 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 6451, Etercure 6452, Etercure 6453, Etercure 6454, Etercure 6455, Etercure 6456, Etercure 6457, Eter Examples of preferred amine-modified oligomers include CN371, CN373, CN383, CN386 (manufactured by Sartomer Co., Ltd.), and other acrylated amine compounds, and more preferred are CN371, CN386 (manufactured by Sartomer Co., Ltd.), EBECRYL80 (manufactured by Daicel-Allnex Co., Ltd.), and other compounds having two or more photopolymerizable functional groups in the molecule.

[0037] [1-1C. Multifunctional Monomers] The polyfunctional monomer as the polymerizable component is a monomer having two or more ethylenically unsaturated bonds, and for example, a polyfunctional (meth)acrylate compound or a vinyl ether group-containing (meth)acrylate compound can be used. The polyfunctional (meth)acrylate compound may be a bifunctional di(meth)acrylate compound, a trifunctional tri(meth)acrylate compound, or a higher functional (meth)acrylate compound.

[0038] Examples of bifunctional monomers include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, pentyl glycol di(meth)acrylate, and neopentyl glycol di(meth)acrylate. di(meth)acrylate, hydroxypivalyl hydroxypivalate di(meth)acrylate, hydroxypivalyl hydroxypivalate dicaprolactonate di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,2-hexanediol di(meth)acrylate, 1,5-hexanediol di(meth)acrylate, 2,5-hexanediol di(meth)acrylate, 1,7-heptanediol di(meth)acrylate, 1,8-octanediol di(meth)acrylate, 1,2-octanediol di(meth)acrylate Acrylate, 1,9-nonanediol di(meth)acrylate, 1,2-decanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, 1,2-dodecanediol di(meth)acrylate, 1,14-tetradecanediol di(meth)acrylate, 1,2-tetradecanediol di(meth)acrylate, 1,16-hexadecanediol di(meth)acrylate, 1,2-hexadecanediol di(meth)acrylate, 2-methyl-2,4-pentanediol Dimethylol octane di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 2-methyl-2-propyl-1,3-propanediol di(meth)acrylate, 2,4-dimethyl-2,4-pentanediol di(meth)acrylate, 2,2-diethyl-1,3-propanediol di(meth)acrylate, 2,2,4-trimethyl-1,3-pentanediol di(meth)acrylate, dimethylol octane di(meth)acrylate, 2-ethyl-1,3-hexanediol di(meth)acrylate, 2,5-dimethyl-2,5-Hexanediol di(meth)acrylate, 2-methyl-1,8-octanediol di(meth)acrylate, 2-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, 2,4-diethyl-1,5-pentanediol di(meth)acrylate, 1,2-hexanediol di(meth)acrylate, 1,5-hexanediol di(meth)acrylate, 2,5-hexanediol di(meth)acrylate, 2-methyl-2,4-pentanedi(meth)acrylate, 2,4-diethyl-1,5-pentanediol di(meth)acrylate, tricyclodecanedimethylol di(meth)acrylate, tricyclodecanedimethylol dicaprolactonate di(meth)acrylate, bis Examples of the di(meth)acrylate include phenol A tetraethylene oxide adduct di(meth)acrylate, bisphenol F tetraethylene oxide adduct di(meth)acrylate, bisphenol S tetraethylene oxide adduct di(meth)acrylate, hydrogenated bisphenol A tetraethylene oxide adduct di(meth)acrylate, hydrogenated bisphenol F tetraethylene oxide adduct di(meth)acrylate, hydrogenated bisphenol A di(meth)acrylate, hydrogenated bisphenol F di(meth)acrylate, bisphenol A tetraethylene oxide adduct dicaprolactonate di(meth)acrylate, and bisphenol F tetraethylene oxide adduct dicaprolactonate di(meth)acrylate.

[0039] Examples of trifunctional monomers include trimethylolpropane EO-modified tri(meth)acrylate, glycerin tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane tricaprolactonate tri(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolhexane tri(meth)acrylate, trimethyloloctane tri(meth)acrylate, and pentaerythritol tri(meth)acrylate.

[0040] Examples of monomers having 4 or more functional groups include pentaerythritol tetra(meth)acrylate, pentaerythritol tetracaprolactonate tetra(meth)acrylate, diglycerol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, ditrimethylolpropane tetracaprolactonate tetra(meth)acrylate, ditrimethylolethane tetra(meth)acrylate, ditrimethylolbutane tetra(meth)acrylate, and ditrimethylol. Examples of the acrylate include hexane tetra(meth)acrylate, ditrimethylol octane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol hepta(meth)acrylate, tripentaerythritol octa(meth)acrylate, and tripentaerythritol polyalkylene oxide hepta(meth)acrylate.

[0041] The polyfunctional monomer may be a vinyl ether group-containing (meth)acrylate-based compound; examples thereof include 2-vinyloxyethyl (meth)acrylate, 3-vinyloxypropyl (meth)acrylate, 1-methyl-2-vinyloxyethyl (meth)acrylate, 2-vinyloxypropyl (meth)acrylate, 4-vinyloxybutyl (meth)acrylate, 1-methyl-3-vinyloxypropyl (meth)acrylate, 1-vinyloxymethylpropyl (meth)acrylate, 2-methyl-3-vinyloxyethyl (meth)acrylate, 4-vinyloxybutyl (meth)acrylate, 1-methyl-3-vinyloxypropyl (meth)acrylate, 1-vinyloxymethylpropyl (meth)acrylate, 2-methyl-3-vinyloxyethyl (meth)acrylate, 4-vinyloxybutyl (meth)acrylate, 4-vinyloxybutyl (meth)acrylate, 4-vinyloxybutyl (meth)acrylate, 4-vinyloxybutyl (meth)acrylate, 4-vinyloxybutyl (meth)acrylate, 4-vinyloxyethyl ... (meth)acrylate-3-methyl-3-vinyloxypropyl, (meth)acrylate-1,1-dimethyl-2-vinyloxyethyl, (meth)acrylate-3-vinyloxybutyl, (meth)acrylate-1-methyl-2-vinyloxypropyl, (meth)acrylate-2-vinyloxybutyl, (meth)acrylate-4-vinyloxycyclohexyl, (meth)acrylate-5-vinyloxypentyl, (meth)acrylate-6-vinyloxyhexyl, (meth)acrylate-4-vinyloxymethylcyclohexylmethyl , (meth)acrylate-3-vinyloxymethylcyclohexylmethyl, (meth)acrylate-2-vinyloxymethylcyclohexylmethyl, (meth)acrylate-p-vinyloxymethylphenylmethyl, (meth)acrylate-m-vinyloxymethylphenylmethyl, (meth)acrylate-o-vinyloxymethylphenylmethyl, (meth)acrylate-2-(vinyloxyethoxy)ethyl, (meth)acrylate-2-(vinyloxyisopropoxy)ethyl, (meth)acrylate-2-(vinyloxyethoxy)propyl, (meth)acrylate Examples of the copolymer include 2-(vinyloxyethoxy)isopropyl (meth)acrylate, 2-(vinyloxyisopropoxy)propyl (meth)acrylate, 2-(vinyloxyisopropoxy)isopropyl (meth)acrylate, 2-(vinyloxyethoxyethoxy)ethyl (meth)acrylate, 2-(vinyloxyethoxyisopropoxy)ethyl (meth)acrylate, 2-(vinyloxyisopropoxyethoxy)ethyl (meth)acrylate, and 2-(vinyloxyisopropoxyisopropoxy)ethyl (meth)acrylate.

[0042] The ink composition of the present invention may or may not contain a polyfunctional monomer, but from the viewpoint of the scratch resistance and solvent resistance of the printed cured product, it preferably contains 2% by mass or more, more preferably 3% by mass or more, and even more preferably 4% by mass or more of the polyfunctional monomer relative to the total of the polymerizable components; on the other hand, it preferably contains 80% by mass or less, more preferably 60% by mass or less, and even more preferably 40% by mass or less of the polyfunctional monomer. By making the content of the polyfunctional monomer 2% by mass or more, the scratch resistance and solvent resistance of the cured printed film can be improved; on the other hand, if it exceeds 80% by mass, the flexibility (stretchability) of the cured printed film tends to decrease.

[0043] [1-2. Photopolymerization initiator] The ink composition of the present invention contains a photopolymerization initiator. The photopolymerization initiator generates active species such as radicals upon irradiation with active energy rays, thereby initiating photopolymerization of the active energy ray-curable composition.

[0044] The ink composition of the present invention contains (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide as a photopolymerization initiator. (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide is a compound represented by the following structural formula, and is sometimes abbreviated as "TMO". [ka]

[0045] TMO is an acylphosphine photopolymerization initiator, but is considered to be less toxic than another acylphosphine photopolymerization initiator, TPO (diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide). In other words, TPO is designated as Category 1B for reproductive toxicity, but TMO is not.

[0046] TMO has a lower solubility than TPO and is relatively difficult to dissolve in the ink composition. Therefore, in an active energy ray-curable ink composition containing TMO, it is necessary to adjust the composition of the photopolymerizable component so that TMO is easily compatible. Therefore, the ink composition of the present invention contains a monofunctional monomer in an amount of 10% by mass or more based on the ink composition.

[0047] In addition, the actinic radiation-curable ink composition containing TPO often has insufficient solvent resistance in the cured product, whereas the combination of TMO and an amine-modified oligomer can improve the solvent resistance of the cured product of the ink composition.

[0048] The content of TMO in the ink composition of the present invention is preferably 2 mass% or more, more preferably 4 mass% or more, and even more preferably 6 mass% or more, relative to the total amount of the ink composition; on the other hand, it is preferably 16 mass% or less, and even more preferably 14 mass% or less.

[0049] The ink composition of the present invention may contain other photopolymerization initiators together with TMO. Examples of other photopolymerization initiators include acylphosphine oxide compounds, triazine compounds, aromatic ketone compounds, aromatic onium salt compounds, organic peroxides, thioxanthone compounds, thiophenyl compounds, anthracene compounds, hexaarylbisimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, halogenated hydrocarbon compounds and alkylamine compounds, iodonium salt compounds and sulfonium salt compounds. However, it is preferable that the ink composition of the present invention does not contain TPO, which is designated as reproductive toxicity category 1B.

[0050] [1-3. Coloring materials or pigments] The ink composition of the present invention may contain a colorant. The colorant is a component that imparts a color other than white to the ink composition, and imparts black or other colors. The colorant may be a pigment or a dye, but is preferably a pigment (colored pigment). The ink composition of the present invention may also contain a pigment. The pigment is a component that is added to impart coloring power, hiding power, etc. to the ink composition; the pigments can be broadly classified into white pigments, colored pigments (other than white), transparent extender pigments, metal powders, and the like. The pigments can also be broadly classified into organic pigments and inorganic pigments.

[0051] The ink composition of the present invention may contain a white pigment or a transparent extender pigment, or may not contain a pigment; that is, the ink composition of the present invention may be a white ink or a transparent ink. When the cured product of the white ink or transparent ink turns yellow, the color change is often noticeable (easily visible). When an ink composition containing a photopolymerization initiator is cured, the cured product may turn yellow; however, the TMO, which is a photopolymerization initiator contained in the ink composition of the present invention, has the property of not easily causing the cured product to turn yellow. Therefore, the ink composition of the present invention may be preferably a white ink or a transparent ink. In addition, when the ink composition of the present invention contains a white pigment or a transparent extender pigment, or does not contain a pigment, it may not be necessary to contain a sensitizer.

[0052] On the other hand, the ink composition of the present invention may contain a colorant, that is, the ink composition of the present invention may be a black ink or a color ink. When the ink composition contains a colorant, it is preferable that the ink composition contains a sensitizer, as described below.

[0053] Examples of white pigments include titanium dioxide (such as Pigment White 7), aluminum oxide, zinc oxide, zinc sulfide, antimony oxide, and zirconium oxide, with titanium dioxide being preferred. The white pigment may be surface-treated with various materials such as alumina and silica. Examples of transparent extender pigments include silicon oxide (silica), barium sulfate, aluminum oxide (alumina), calcium carbonate, magnesium carbonate, with silica or alumina being preferred.

[0054] Examples of color 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, flavanthrone-based, quinophthalone-based, pyranthrone-based, and indanthrone-based organic pigments, as well as various inorganic pigments.

[0055] Examples of preferred color pigments include yellow pigments such as disazo yellow (pigment yellow 12, pigment yellow 13, pigment yellow 14, pigment yellow 17, pigment yellow 1), Hansa yellow, pigment yellow 150, and pigment yellow 155; magenta pigments such as brilliant carmine 6B, lake red C, watching red, quinacridone, pigment red 122, and pigment red 254; cyan pigments such as phthalocyanine blue, phthalocyanine green, alkali blue, and pigment blue 15:4; colored pigments such as red iron oxide, antimony red, cadmium yellow, cobalt blue, Prussian blue, ultramarine blue, iron black, chromium oxide green, carbon black (pigment black 7, etc.), and graphite; and metal powders such as aluminum paste and bronze powder.

[0056] Examples of yellow pigments include CI Pigment Yellow (PY) 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, and 213.

[0057] Examples of magenta pigments include CI Pigment Red (PR) 5, 7, 12, 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, and CI Pigment Violet 19.

[0058] Examples of cyan pigments include CI Pigment Blue (PB) 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 18, 22, 27, 29, and 60.

[0059] Examples of black pigments include carbon black (CI Pigment Black 7). As described below, when the ink composition of the present invention contains a black pigment, it further contains a sensitizer. Since the ink composition containing a black pigment may not have sufficient curability when irradiated with active energy rays, the ink composition contains a sensitizer to enhance the curability of the ink composition.

[0060] The content of the pigment in the ink composition varies depending on the type of pigment and the desired degree of coloring, and is not particularly limited: in the case of a black pigment or a colored pigment, it is, for example, about 1.0 to 10.0 mass% relative to the entire ink composition; and in the case of a white pigment or an extender pigment, it may be, for example, about 1.0 to 20.0 mass% relative to the entire ink composition.

[0061] [1-4. Sensitizers] The ink composition of the present invention may contain a sensitizer, and the sensitizer can improve the curability of the ink composition. When the ink composition of the present invention contains a black pigment, it preferably contains a sensitizer, and when it contains a colorant (a colorant other than white), it preferably contains a sensitizer. This is because when the ink composition is irradiated with active energy rays, the colorant contained in the ink composition may block the active energy rays, making it difficult to cure the ink composition. Sensitizers can generally be roughly divided into non-polymer sensitizers and polymer sensitizers. Any sensitizer may be contained in the ink composition of the present invention, but polymer sensitizers may be preferred because they can suppress migration from the coating film.

[0062] Examples of non-polymeric sensitizers include anthracene-based sensitizers such as 9,10-dibutoxyanthracene, 9,10-diethoxyanthracene, 9,10-dipropoxyanthracene, and 9,10-bis(2-ethylhexyloxy)anthracene; and thioxanthone-based sensitizers such as 2,4-diethylthioxanthone, 2-isopropylthioxanthone, and 4-isopropylthioxanthone. The sensitizer is preferably a thioxanthone-based sensitizer.

[0063] Examples of polymeric sensitizers include thioxanthone polymeric photosensitizers, acylphosphine polymeric sensitizers, and other polymeric sensitizers. Examples of thioxanthone polymeric photosensitizers include Omnipol TX ((2-carboxymethoxythioxanthone)-(polytetramethylene glycol 250) diester) (number average molecular weight: 660) (manufactured by IGM Resins BV), Genopol TX-1 (number average molecular weight: 820) (manufactured by RaHN), and the like. Examples of acylphosphine polymeric sensitizers include SpeedCure 7010 (molecular weight 1839) (manufactured by Lambson). Further, other polymeric sensitizers include oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propane) (manufactured by Lamberti, "ESACURE KIP 150" and "ESACURE 1"), polyethylene glycol 200-di(β-4(4-(2-dimethylamino-2-benzyl)butanonylphenyl)piperazine) (manufactured by IGM, "Omnipol 910"), (carboxymethoxymethoxybenzophenone)-(polyethylene glycol 250) diester (manufactured by IGM, "Omnipol BP"), and the like.

[0064] The content of the sensitizer in the ink composition is preferably 0.3 parts by mass or more, and more preferably 1.0 part by mass or more, relative to 100 parts by mass of the total of the polymerizable components; on the other hand, it is preferably 10 parts by mass or less, and more preferably 9 parts by mass or less.

[0065] [1-5. Other ingredients] The ink composition of the present invention may further contain a polymerization inhibitor, a pigment dispersant, a leveling agent, and other additives.

[0066] [1-5A. Polymerization inhibitors] The ink composition of the present invention may contain a polymerization inhibitor. The polymerization inhibitor can suppress the occurrence of unintended polymerization reactions (such as polymerization reactions that occur in the absence of active energy radiation irradiation). Examples of polymerization inhibitors include hydroquinone, dibutylhydroxytoluene, hydroquinone monomethyl ether, and phenothiazine. The content of the polymerization inhibitor in the ink composition is, for example, about 0.01 to 5.0% by mass.

[0067] [1-5B. Pigment dispersants] When the ink composition of the present invention contains a pigment, it may further contain a pigment dispersant for dispersing the pigment. The pigment dispersant is preferably a polymeric pigment dispersant, and is also preferably a pigment dispersant containing a basic group. Examples of the pigment dispersant containing a basic group include polymeric pigment dispersants such as a basic group-containing polyester-based pigment dispersant, a basic group-containing acrylic-based pigment dispersant, a basic group-containing urethane-based pigment dispersant, and a basic group-containing carbodiimide-based pigment dispersant, as well as an anionic surfactant.

[0068] The polymeric pigment dispersant is not particularly limited, but may be a straight-chain polymer having a pigment-affinity moiety consisting of a basic group at least at the end of the main chain (at one end or both ends) due to a block or graft structure. The polymeric pigment dispersant may contain 2 to 3,000 basic groups in one molecule and may have a number average molecular weight of 1,000 to 1,000,000.

[0069] The content of the pigment dispersant in the ink composition is preferably 1.0 to 200.0 parts by mass when the total amount of the pigments is taken as 100 parts by mass.

[0070] [1-5C. Leveling agents (surface conditioners)] The ink composition of the present invention may contain a leveling agent. The leveling agent may also enhance the ejection stability of the ink composition. Examples of the leveling agent include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants, and silicone surfactants.

[0071] Specific examples of silicone surfactants as leveling agents include polyether-modified silicone oils such as hydroxyl-containing polyether-modified polydimethylsiloxane and polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, polyester-modified methylalkyl polysiloxane, etc. Silicone surfactants can be obtained from the market, and are available as BYK-307, BYK-315, BYK-315N, BYK-331, BYK-333, BYK-347, BYK-348, BYK-349, BYK-345, BYK-377, BYK-378, BYK-3455 (BYK), etc.

[0072] The content of the surface conditioner in the ink composition is preferably in the range of 0.05 to 2.50% by mass with respect to the ink composition.

[0073] [1-5D.Other Additives] Examples of other additives that may be included include various additives such as a solvent, an ultraviolet absorber, an antioxidant, an antifoaming agent, a storage improver, an antifungal agent, an antirust agent, a thickener, a moisturizing agent, a pH adjuster, etc. The content of the solvent in the ink composition is preferably 10.0% by mass or less, more preferably 5.0% by mass or less, and even more preferably 2.0% by mass or less, and the ink composition may not be included.

[0074] 2. Preparation of Ink Composition The ink composition of the present invention can be prepared according to a conventionally known method. For example, the ink composition can be obtained by dispersing and mixing each component 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 (Microfluidizer, Nanomizer, Ultimizer, Genus PY, DeBEE2000, etc.), a pearl mill, etc., and adjusting the viscosity as necessary.

[0075] In addition, when the ink composition contains a pigment, the pigment, the pigment dispersant, and a portion of the polymerizable component are mixed to obtain a base ink composition (also called a pigment dispersion) in advance, and the remaining amounts of the above components are added to the base ink composition so as to obtain the desired composition, thereby preparing the ink composition.

[0076] [3. Inkjet printing of ink composition] The ink composition of the present invention can be used for printing with an inkjet printer. The type of inkjet printer that can be used is not particularly limited, and may be a line head type (single pass type) or a serial head type (multi-pass type). A continuous type inkjet printer may also be used, and in this case, a conductivity imparting agent can be further added to adjust the electrical conductivity of the ink composition.

[0077] The ink composition is supplied to a printer head of an inkjet printing device, and the ink composition is ejected from the printer head onto a substrate to be printed. The ink composition is ejected from the printer head onto the substrate to be printed (printing of an image) so that the coating film on the substrate to be printed has a thickness of, for example, 1 to 60 μm.

[0078] The ink composition that has landed on the substrate to be printed is cured by exposure to active energy rays. Examples of active energy rays include ultraviolet rays, electron beams, and visible light irradiated from light-emitting diodes (LEDs), various lamps, and electrodes. From an environmental perspective, it is preferable to use a light-emitting diode (LED) that generates ultraviolet rays with an emission peak wavelength in the range of 350 to 420 nm as the light source.

[0079] The substrate to be printed is not particularly limited, as long as it is a substrate to which a conventionally known photocurable inkjet printing ink composition can be applied. Examples of substrates include plastic, paper, capsules, gel, metal foil, glass, wood, cloth, etc. The cured coating film of the ink composition of the present invention has the characteristics of excellent abrasion resistance and stretchability. Therefore, it may be preferable to print the ink composition of the present invention on a flexible substrate, such as a plastic film.

[0080] Examples of plastics constituting the printing substrate include polyester-based polymers (e.g., polyethylene terephthalate (PET), polyethylene naphthalate, etc.), cellulose-based polymers (e.g., diacetyl cellulose, triacetyl cellulose (TAC), etc.), polycarbonate-based polymers, polyacrylic-based polymers (e.g., polymethyl methacrylate, etc.), vinyl chloride-based polymers, polyolefin-based polymers (e.g., polyethylene, polypropylene, polyolefin polymers having a cyclic or norbornene structure, ethylene-propylene copolymers, etc.), polyamide-based polymers (e.g., nylon, aromatic polyamide polymers, etc.), polystyrene-based polymers (e.g., polystyrene, acrylonitrile-styrene copolymers, etc.), polyimide-based polymers, polysulfone-based polymers, polyethersulfone-based polymers, polyetherketone-based polymers, polyphenylsulfide-based polymers, polyvinyl alcohol-based polymers, polyvinylidene chloride-based polymers, polyvinyl butyral-based polymers, polyarylate-based polymers, polyoxymethylene-based polymers, and polyepoxy-based polymers, as well as blends of these polymers. EXAMPLES

[0081] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to the description of the examples.

[0082] A. Preparation of Ink Composition Tables 1 to 4 show the raw materials used in the preparation of the ink compositions of the examples and comparative examples.

[0083] A-1. Pigments Pigment Yellow 150 Pigment Red 122 Pigment Red 254 Pigment Blue 15:4 Pigment Black 7 Pigment White 7 AEROXIDE(registered trademark) ALU-C: Alumina fine particles (Evonik) AEROSIL® R9200: Silica microparticles (Evonik)

[0084] A-2. Pigment dispersants Solsperse 56000: Pigment dispersion resin, amine value 39 mg KOH / g (Lubrizol) ·BYKJET9151: Pigment dispersion resin (BYK) Solsperse 36000: Pigment dispersion resin, acid value 45 mg KOH / g (Lubrizol) AJISPER PB821: Pigment dispersion resin (Ajinomoto Fine-Techno Co., Ltd.)

[0085] A-3. Monofunctional monomers 4HBA (4-hydroxybutyl acrylate) Molecular weight: 144.2 Benzyl acrylate Molecular weight: 162.2 ·VCAP (N-vinylcaprolactam) Molecular weight: 139.2 Acryloylmorpholine Molecular weight: 141.17

[0086] A-4. Oligomer ·CN371NS: Amine modified oligomer (Sartomer) Miramer PE-210: Bisphenol A epoxy acrylate (MIWON)

[0087] A-5. Multifunctional monomers · EO modified trimethylolpropane triacrylate: Miramer M3130 (Toyo Chemicals Co., Ltd.) Dipropylene glycol diacrylate 1,6-Hexanediol diacrylate

[0088] A-6. Photopolymerization initiator TMO: (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide ·TPO: Diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide BAPO: Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide TPOL: (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide

[0089] A-7. Sensitizers DETX: 2,4-diethylthioxanthone Speedcure 7010: Polymeric thioxanthone (Sartomer)

[0090] A-8. Other additives ·Irgastab UV22: Polymerization inhibitor (BASF) Lunacure500: Polymerization inhibitor (DKSH) ·BYK-377: Silicone surface conditioner (BYK) ESACURE A198: Aminobenzoate compound (IGM RESINS BV)

[0091] According to the formulations shown in Tables 1 to 4, the components were blended and mixed with stirring to prepare ink compositions for ink-jet printing of each of the Examples and Comparative Examples.

[0092] B. Evaluation of ink composition and its cured coating (printed matter) The ink compositions and their cured products produced in each of the Examples and Comparative Examples were evaluated for the following items, and the evaluation results are shown in Tables 1 to 4.

[0093] B-1. Viscosity of ink composition The viscosity (cps) of the ink composition immediately after preparation was measured using an E-type viscometer (product name: RE100L type viscometer, manufactured by Toki Sangyo Co., Ltd.) at a temperature of 25° C. and a rotor rotation speed of 20 rpm.

[0094] B-2. Solvent resistance of cured coating film The cured coating film of each ink composition printed on a PVC plate (T938 manufactured by Takiron CI Co., Ltd.) was rubbed 5 times with 200 g of bleached cloth containing 30% ethanol in water using a Gakushin type fastness tester (manufactured by Daiei Scientific Instruments Co., Ltd.). The degree to which the coating was removed was visually observed and evaluated according to the following criteria. ○: No paint film was removed △: There are scratches on the surface of the coating ×: Paint film is clearly peeled off

[0095] B-3. ​​Bendability of cured coating film (printed matter) The cured coating of each ink composition printed on PET (E5100 manufactured by Toyobo Co., Ltd.) was folded at an angle of 180 degrees, and the state of cracks was visually inspected. ○: No fine cracks or other breakages in the coating △: Fine cracks appear on the coating ×: Obvious cracks in the coating

[0096] B-4. LED curability (surface curability) of ink composition Each ink composition was applied to the surface of a PET film using a bar coater No. 4 to obtain each coating. Then, the ink composition was applied to the surface of a PET film using an LED irradiation device (398 nm, 500 mj / cm 2 After the light exposure, the ink coating was lightly rubbed with a cotton swab to evaluate the condition of the coating and the cotton swab. ○: No traces of the cotton swab left on the coating △: There are some traces of the cotton swab on the coating. ×: Ink adheres to the cotton swab

[0097] B-5. Compatibility of photopolymerization initiators In the ink compositions of the respective Examples and Comparative Examples, the components except for the pigment and the pigment dispersant were stirred and mixed at room temperature using a disperser, the time until the photopolymerization initiator was dissolved was measured, and the ink compositions were evaluated according to the following evaluation criteria. 〇: Dissolves within 1 hour △: Dissolves in 1 to 2 hours ×: Not dissolved even after 2 hours or more

[0098] B-6. Yellowing of cured coating film The cured coating of each ink composition printed on a white PVC plate was measured for color with a spectrophotometer X-Rite eXact (manufactured by X-Rite Corporation), and the color was evaluated according to the b* value according to the following criteria. ○: b* value is less than 0. ×: b* value is 0 or greater.

[0099] B-7. Pencil hardness of cured coating According to JIS K 5600-5-4:1999 General Testing Method for Paints, the test was carried out on the cured coating film printed on the substrate. The hardness of the hardest pencil that did not cause cohesive failure was recorded as the pencil hardness. 〇:2H or more △: B to H ×: 2B or less

[0100] B-8. Viscosity stability of ink composition Each of the ink compositions obtained in the examples and comparative examples was allowed to stand for 3 weeks at an ambient temperature of 60°C, and then the viscosity was measured using an E-type viscometer. The viscosity increase rate (%) was calculated using the following formula, and the viscosity stability was evaluated in accordance with the following evaluation criteria: viscosity increase rate (%) = ((viscosity value after standing at 60°C for 3 weeks / viscosity value after standing at 25°C for 3 weeks) x 100) - 100. ○: Viscosity increase rate is less than 10% △: Viscosity increase rate is 10% to 20% ×: Viscosity increase rate is over 20%

[0101] [Table 1]

[0102] [Table 2]

[0103] As shown in Comparative Examples 1 and 2 in Table 2, the ink composition containing TPO as a photopolymerization initiator had insufficient solvent resistance of the cured coating film. Also, as shown in Comparative Examples 3 and 4 in Table 2, the ink composition containing TPOL or a combination of TPOL and BAPO as a photopolymerization initiator had insufficient solvent resistance of the cured coating film, and the LED curability and pencil hardness of the cured coating film were also insufficient. Also, the viscosity stability of the ink composition was deteriorated. Note that, as shown in Comparative Example 4, the ink composition containing a combination of TPOL and BAPO as a photopolymerization initiator showed yellowing of the cured coating film. In contrast, each Example (Table 1) containing TMO as a photopolymerization initiator was evaluated as sufficient in all evaluation items.

[0104] As shown in Comparative Example 5 in Table 2, the ink composition not containing the amine-modified oligomer had reduced LED curability and insufficient solvent resistance, even though it contained other oligomers. Thus, it can be seen that the ink composition not containing the amine-modified oligomer, which is a reactive oligomer, cannot achieve both LED curability and solvent resistance, even if it contains TMO as a photopolymerization initiator. In addition, as shown in Comparative Example 6 in Table 2, the ink composition with a low content of monofunctional monomer (3 mass % relative to the ink composition) was not sufficiently compatible with the photopolymerization initiator, and the LED curability of the cured coating film was insufficient. In addition, in Comparative Example 6, the bending property of the cured coating film was also reduced. In contrast, in each Example (Table 1) containing the amine-modified oligomer and a predetermined amount of monofunctional monomer, sufficient evaluation was obtained in each evaluation item.

[0105] As can be seen from a comparison with Examples 1 to 5, 6, 7, and 8 in Table 1, sufficient evaluations were obtained in all evaluation items, regardless of whether the pigment contained a white pigment or a transparent extender pigment, or whether the pigment did not contain any pigment.

[0106] As can be seen from a comparison between Example 1 and Example 2 in Table 1, the content of TMO can be adjusted, and by combining it with other photopolymerization initiators, sufficient evaluations can be obtained in all evaluation items.

[0107] As can be seen from a comparison of Example 1 with Examples 3 and 4 in Table 1, the content of the amine-modified oligomer can be adjusted, for example, by the balance with the polyfunctional monomer.

[0108] As can be seen from a comparison between Example 1 and Example 5 in Table 1, it is possible to adjust the content of the monofunctional monomer (particularly, the nitrogen-containing monomer).

[0109] [Table 3]

[0110] [Table 4]

[0111] As shown in Comparative Examples 7 and 8 in Table 4, the ink compositions containing TPO as a photopolymerization initiator did not have sufficient solvent resistance in the cured coating film. Also, as shown in Comparative Examples 9 and 10 in Table 4, the ink compositions containing TPOL or a combination of TPOL and BAPO as a photopolymerization initiator did not have sufficient solvent resistance in the cured coating film, and the LED curability and pencil hardness of the cured coating film were also insufficient. Furthermore, the viscosity stability of the ink composition was deteriorated. In contrast, each of Examples 9 to 17 (Table 3), which contained TMO as a photopolymerization initiator, was evaluated as being practically sufficient in all evaluation items.

[0112] As shown in Comparative Example 11 in Table 4, when a black pigment was included, the ink composition that did not include a sensitizer exhibited reduced LED curability and hardness of the cured coating film.

[0113] As shown in Comparative Example 12 in Table 4, the ink composition that did not contain the amine-modified oligomer had reduced LED curability, even though it contained other oligomers. Also, as shown in Comparative Example 13 in Table 4, the ink composition with a low content of monofunctional monomer (3 mass % relative to the ink composition) had insufficient compatibility with the photopolymerization initiator, and the LED curability of the cured coating film was insufficient. In addition, in Comparative Example 13, the bending property of the cured coating film also decreased. In contrast, each of Examples 9 to 17 (Table 3), which contained an amine-modified oligomer and a predetermined amount of monofunctional monomer, was evaluated as being practically sufficient in each evaluation item.

[0114] As can be seen from the comparison with Examples 9 to 14, 15, 16, and 17 in Table 3, sufficient evaluations were obtained in all evaluation items, whether the pigment contained a black pigment or various color pigments.

[0115] As can be seen from a comparison between Examples 9 and 10 in Table 3, the content of TMO can be adjusted, and by combining it with other photopolymerization initiators or by appropriately selecting a sensitizer, sufficient evaluations can be obtained in all evaluation items.

[0116] As can be seen from a comparison of Example 9 with Examples 11 and 12 in Table 3, the content of the amine-modified oligomer can be adjusted, for example, by adjusting the balance with the polyfunctional monomer. Also, as can be seen from a comparison of Example 9 with Example 13 in Table 3, the content of the monofunctional monomer (particularly, the nitrogen-containing monofunctional monomer) can also be adjusted, for example, by adjusting the balance with the polyfunctional monomer. Furthermore, as can be seen from a comparison of Example 9 with Example 14 in Table 3, the content of the sensitizer can also be adjusted to a certain extent. [Industrial Applicability]

[0117] The active energy ray curable ink jet printing ink composition of the present invention contains TMO, which has low biological toxicity, as a photopolymerization initiator, and can therefore be used as an ink composition with high biological safety. Furthermore, since the ink composition as an active energy ray curable ink jet printing ink composition has excellent ink properties and physical properties of the cured coating film, and in particular, has excellent solvent resistance, it can be applied to various applications of the active energy ray curable ink jet printing ink composition so far, and is expected to be applied to new applications.

Claims

1. An actinic ray-curable ink composition for ink-jet printing, having a viscosity at room temperature of 5 cps or more and 80 cps or less, comprising: a monofunctional monomer in an amount of 10% by mass or more relative to the ink composition; an amine-modified oligomer in an amount of 1 to 15% by mass based on the ink composition; (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide, The ink composition further contains a sensitizer when the ink composition further contains a black pigment.

2. The ink composition of claim 1 further comprising a sensitizer and a colorant.

3. 2. The ink composition according to claim 1, which contains a white pigment or a transparent extender pigment, or which does not contain a pigment component.

4. The ink composition according to any one of claims 1 to 3, wherein the content of (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide is 2 to 12 mass % based on the ink composition.

5. 4. The ink composition according to claim 1, wherein the monofunctional monomer includes a monofunctional monomer having a molecular weight of 500 or less, and a content of the monofunctional monomer having a molecular weight of 500 or less is 10 mass % or more with respect to the ink composition.

6. The ink composition according to any one of claims 1 to 3, wherein the monofunctional monomer comprises a nitrogen-containing monofunctional monomer.

7. The ink composition according to any one of claims 1 to 3, further comprising 2 mass % or more of a polyfunctional monomer based on the total amount of the polymerizable components.

8. The ink composition according to any one of claims 1 to 3, wherein the ink composition does not contain diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide.

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