Active energy ray curable inkjet printing ink

Abstract

In an active energy ray curable inkjet printing ink composition containing (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide as a photopolymerization initiator, the curability is sufficiently enhanced, and preferably, the solvent resistance of the cured product is improved. [Solution] An active energy ray curable ink for inkjet printing having a viscosity of 5 cps or more and 80 cps or less at room temperature, comprising: 10% by mass or more of a monofunctional monomer relative to the ink composition, 1 to 15% by mass of an amine-modified oligomer relative to the ink composition, and (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide, and further comprising a black pigment, a sensitizer.

Description

Technical Field

[0001] The present invention relates to an ink for active energy ray-curable inkjet printing, and more specifically, to an ink for active energy ray-curable inkjet printing containing TMO ((2,4,6-trimethylbenzoyl) bis(p-tolyl) phosphine oxide) as a photoinitiator.

Background Art

[0002] An active energy ray-curable ink composition is an ink composition that can be cured by irradiating active energy rays such as ultraviolet rays or electron beams. The active energy ray-curable ink composition can be a solvent-free or low-solvent ink and has quick drying properties, so it can be printed on various printing substrates. That is, the active energy ray-curable ink composition can prevent ink bleeding even when printed on a printing substrate with low absorbency, and the like.

[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 energy ray-curable inkjet ink composition containing a colorant, a monofunctional monomer, a bifunctional oligomer, a photoinitiator, and a surface tension modifier.

[0004] An active energy ray-curable ink composition may contain a photoinitiator (photo polymerization initiator), depending on the type of active energy rays for curing. Photoinitiators can generally be roughly classified into several types, and examples thereof include compounds such as benzophenone-based, thioxanthone-based, acetophenone-based, and acylphosphine-based compounds.

[0005] (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide (sometimes abbreviated as TMO) has been proposed as a photoinitiator, and its manufacturing method is also being studied (Patent Documents 2 and 3). Furthermore, ink compositions containing TMO have also been proposed; an ink containing TMO together 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] Japanese Patent Publication No. 2009-299057 [Patent Document 2] Special Publication No. 2002-531460 [Patent Document 3] Special Publication No. 2022-520286 [Patent Document 4] CN118240419A [Overview of the project] [Problems that the invention aims to solve]

[0007] Photoinitiators can raise concerns about their chemical toxicity; for example, TPO (diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide), an acylphosphine-based photoinitiator, has been linked to concerns about its biotoxicity. Furthermore, acylphosphine-based photoinitiators may result in insufficient curing properties, leading to inadequate hardness of the cured product; discoloration (such as yellowing) of the cured product, or insufficient viscosity stability of the ink composition.

[0008] Photopolymerization initiators may have low solubility (for example, low solubility in reactive diluents such as monofunctional monomers), and depending on the type, the solvent resistance of the cured product of the ink composition may not be sufficiently improved. Therefore, the present invention aims to sufficiently improve the curability of an active energy ray curable inkjet 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 the following active energy ray curable inkjet printing ink composition. [1] An active energy ray curable inkjet printing ink composition having a viscosity of 5 cps or more and 80 cps or less at room temperature: An ink composition comprising: 10% by mass or more of a monofunctional monomer relative to the ink composition; 1 to 15% by mass of an amine-modified oligomer relative to the ink composition; and (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide, and further comprising a black pigment, a sensitizer.

[0010] The present invention preferably relates to the following active energy ray curable inkjet printing ink compositions. [2] The ink composition according to [1], further comprising a sensitizer and a coloring agent. [3] The ink composition according to [1], 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], wherein the content of (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide is 2 to 12% by mass relative to the ink composition. [5] The ink composition according to any one of [1] to [4], wherein the monofunctional monomer comprises a monofunctional monomer with a molecular weight of 500 or less, and the content of the monofunctional monomer with a molecular weight of 500 or less is 10% by mass or more relative to the ink composition. [6] The ink composition according to any one of [1] to [5], wherein the monofunctional monomer comprises a nitrogen-containing monofunctional monomer. [7] The ink composition according to any one of [1] to [6], further comprising 2% by mass or more of polyfunctional monomers relative to the total amount of polymerizable components. [8] The ink composition according to any one of [1] to [7], wherein the ink composition does not contain diphenyl (2,4,6-trimethylbenzoyl)phosphine oxide. [Effects of the Invention]

[0012] The inkjet printing ink composition of the present invention has the properties of an active energy ray curable ink, and can solve problems that may occur with conventional ink compositions containing photoinitiators (improvement of curability, suppression of yellowing of cured products, and improvement of viscosity stability of the ink composition) while also improving the solvent resistance of the cured product. [Modes for carrying out the invention]

[0013] [1. Regarding active energy ray curing ink compositions for inkjet printing] The inkjet printing ink composition 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 light, electron beams, and visible light emitted 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 light with an emission peak wavelength in the range of 350 to 420 nm as the light source for the active energy rays.

[0014] The ink composition of the present invention has a viscosity suitable for 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 under conditions of 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) as a polymerizable component, a monofunctional monomer, an amine-modified oligomer, and B) as a photopolymerization initiator, (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide. Further, the ink composition may contain a polyfunctional monomer (other than the amine-modified oligomer) as a polymerizable component. Further, the ink composition can contain a colorant as needed, and in that case, it is preferable to contain a sensitizer. In particular, when the ink composition contains a black pigment, it contains a sensitizer.

[0016] [1-1. Photopolymerizable component] The polymerizable component contained in the ink composition can be roughly classified into A) a monofunctional monomer, B) a reactive oligomer, and C) a polyfunctional monomer.

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

[0018] It is preferable that the molecular weight of at least a part of the monofunctional monomers as the overlapping component is 500 or less, more preferably 400 or less, and still more preferably 300 or less. Monofunctional monomers having a molecular weight below a certain level are easy to dissolve a photoinitiator in the ink composition. It is preferable that the proportion of the monofunctional monomers having a molecular weight of 500 or less is at least 50% by mass or more, more preferably 60% by mass or more, still 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 of the monofunctional monomers.

[0019] <Nitrogen-containing monofunctional monomer> The nitrogen-containing monofunctional monomer can improve the curability of the ink composition. Examples of the nitrogen-containing monofunctional monomer include acryloylmorpholine, vinylmethyl oxazolidinone, 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 rosin acrylate, etc. These nitrogen-containing monofunctional monomers can be used alone or in combination of two or more.

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

[0021] <Alkyl (meth)acrylate-based compound> Examples of 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, i Examples include sodecyl (meth)acrylate, isomiristyl (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, and 4-t-butylcyclohexyl (meth)acrylate.

[0022] <Hydroxyl group-containing (meth)acrylate compounds> Examples of 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, and polypropylene Examples include polyalkylene glycol-modified (meth)acrylates such as ylene 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 (meth)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) addition (meth)acrylate.

[0024] <Ether group-containing (meth)acrylate compounds> Examples of 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 tetrahydrofur Glycidyl (meth)acrylate, glycidyl 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, dipropyl Glycol monomethyl ether (meth)acrylate, 3-methoxybutyl (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxypropylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate (EO repeating units 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 include alkoxy and / or phenoxy (meth)acrylates such as ethoxylated tribromophenyl acrylate and ethoxylated nonylphenyl (meth)acrylate.

[0025] <Carboxyl group-containing (meth)acrylate compounds> Examples of carboxyl group-containing (meth)acrylate compounds include β-carboxyethyl (meth)acrylate, monoacryloyloxyethyl succinate, 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, and caprolactone-modified-2-(meth)acryloyloxyethyl phosphate. Cethyl acid phosphate, 2-hydroxy-1-(meth)acryloxy-3-methacryloxypropane, acrylicoxyethyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate, 2-(meth)acryloyloxypropyl phthalate, tricyclodecane monomethylol (meth)acrylate, (meth)acrylate 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)acrylate Examples include fermented acid esters, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, 1-(meth)acryloylpiperidine-2-one, 2-(meth)acrylate-1,4-dioxaspiro[4,5]decy-2-ylmethyl, N-(meth)acryloyloxyethylhexahydrophthalimide, γ-butyrolactone (meth)acrylate, caprolactone-modified tetrahydrofurfuryl acrylate, imide acrylate, vinyl (meth)acrylate, maleimide, etc.

[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 a compound having one ethylenically unsaturated bond, "other compounds having one ethylenically unsaturated bond" other than the aforementioned compounds can be used. Examples of such compounds include vinyl acetate, monochlorovinyl acetate, 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, posioxolanes, 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 individually or in combination of two or more.

[0030] The ink composition of the present invention contains polymerizable components, preferably containing 10% by mass or more, and more preferably 15% by mass or more, of monofunctional monomers relative to the ink composition; on the other hand, preferably 80% by mass or less, and more preferably 70% by mass or less. Monofunctional monomers are polymerizable components that can also function as diluents in the ink composition, and by containing 10% by mass or more of them relative to the ink composition, the photopolymerization initiator (TMO: 2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide) can be sufficiently dissolved, ensuring the compatibility of the ink composition. Furthermore, monofunctional monomers can improve the foldability of the effect product of the ink composition.

[0031] The ink composition of the present invention preferably contains a nitrogen-containing monofunctional monomer as a polymerizable component; however, 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 monofunctional monomers. The nitrogen-containing monofunctional monomer readily dissolves the photopolymerization initiator and is therefore preferred as a monofunctional monomer in 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 whose ethylenically unsaturated bonds within the molecule polymerize to become a high molecular weight component. Since oligomers are relatively high molecular weight components before polymerization, they can impart appropriate viscosity and elasticity to the ink composition. Furthermore, oligomers are relatively polar, which can impart non-absorbent adhesion to the printing substrate to the cured ink composition. A reactive oligomer is an oligomer that has one or more polymerizable functional groups (ethylenically unsaturated bonds) within its molecule.

[0033] The oligomer contained in the ink composition is preferably an amine-modified oligomer. An amine-modified oligomer is a reactive oligomer having two or more amino groups and functional groups that crosslink or polymerize upon irradiation with active energy rays within its molecule. Preferably, an amine-modified oligomer is a reactive oligomer having two amino groups and two functional groups that crosslink or polymerize upon irradiation with active energy rays within its molecule. Amine-modified oligomers are also sometimes referred to as reactive amine co-initiators, reactive amine synergists, acrylate-modified amine synergists, amine acrylates, etc.

[0034] The viscosity of the oligomer (preferably an amine-modified oligomer) is not limited, but it is particularly preferable that the viscosity at 25°C be 2000 cps or less in order to bring the overall viscosity of the photocurable inkjet printing ink composition within an appropriate range.

[0035] The content of amine-modified oligomers in the ink composition is 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more, relative to the total amount of the ink composition; on the other hand, it is 15% by mass or less, preferably 13% by mass or less, and more preferably 10% by mass or less. By setting the content of amine-modified oligomers to 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. Furthermore, by setting the content of amine-modified oligomers to 15% by mass or less, the viscosity of the ink composition is suppressed, improving discharge 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 its cured coating film may not be sufficiently improved, so these properties are improved by including amine-modified oligomers.

[0036] Amine-modified oligomers are also available from the market. Examples of amine-modified oligomers available on the market include CN371, CN373, CN383, CN386, CN501, CN550, and CN551 from Sartomer; EBECRYL80 and EBECRYL7100 from Daicel Ornex; 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, and Etercure from Changxing Chemical Co., Ltd. Examples include 6430, Etercure 645, and Etercure 647. Preferred amine-modified oligomers are preferably acrylic amine compounds such as CN371, CN373, CN383, and CN386 (manufactured by Sartomer), and even more preferably CN371, CN386 (manufactured by Sartomer), EBECRYL80 (manufactured by Daicel Ornex), etc., which have two or more photopolymerizable functional groups in the molecule.

[0037] [1-1C. Polyfunctional monomers] The polyfunctional monomer used as the polymerizable component is a monomer having two or more ethylenically unsaturated bonds, and examples include polyfunctional (meth)acrylate compounds and vinyl ether group-containing (meth)acrylate compounds. The polyfunctional (meth)acrylate compound may be a bifunctional di(meth)acrylate compound, a trifunctional tri(meth)acrylate compound, or a polyfunctional (meth)acrylate compound with more than two functions.

[0038] Examples of difunctional 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, hydroxypivalyl hydroxypivalate di(meth)acrylate, hydroxypivalyl hydroxypivalate dicaprolactone 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-hexadecanediolic acid di(meth)acrylate, 1,2-hexadecanediolic acid di(meth)acrylate, 2-methyl-2,4-pentanediol All 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 octanedi(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-pentanediol di(meth)acrylate, 2,4-diethyl-1,5-pentanediol di(meth)acrylate, tricyclodecanedimethylol di(meth)acrylate, tricyclodecanedimethylol dicaprolactone di(meth)acrylate, bis Examples 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 dicaprolactone di(meth)acrylate, and bisphenol F tetraethylene oxide adduct dicaprolactone di(meth)acrylate.

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

[0040] Examples of monomers with four or more functionalities include pentaerythritol tetra(meth)acrylate, pentaerythritol tetracaprolactone tetra(meth)acrylate, diglycerin tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, ditrimethylolpropane tetracaprolactone tetra(meth)acrylate, ditrimethylolethane tetra(meth)acrylate, ditrimethylolbutane tetra(meth)acrylate, and ditrimethylol Examples include hexanetetra(meth)acrylate, ditrimethyloloctanetetra(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 compound; examples include (meth)acrylate-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-vinyl Xypropyl, 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 , (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 include (t) 2-(vinyloxyethoxy)isopropyl acrylate, (meth) 2-(vinyloxyisopropoxy)propyl meth) acrylate, (meth) 2-(vinyloxyisopropoxy)isopropyl meth) acrylate, (meth) 2-(vinyloxyethoxyethoxy)ethyl meth) acrylate, (meth) 2-(vinyloxyisopropoxyethoxy)ethyl meth) acrylate, and (meth) 2-(vinyloxyisopropoxyisopropoxy)ethyl meth) acrylate.

[0042] The ink composition of the present invention may or may not contain polyfunctional monomers, but from the viewpoint of 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 total polymerizable components as polyfunctional monomers; 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 polyfunctional monomers. By setting the polyfunctional monomer content to 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, there is a tendency for the flexibility (stretchability) of the cured printed film to decrease.

[0043] [1-2. Photopolymerization Initiators] The ink composition of the present invention contains a photopolymerization initiator. The photopolymerization initiator generates active species such as radicals when irradiated with active energy rays, thereby initiating the 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 one of the acylphosphine-based photopolymerization initiators, but it is considered to have lower toxicity compared to another acylphosphine-based photopolymerization initiator, TPO (diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide). In other words, TPO is designated as reproductive toxicity category 1B, but TMO does not have that designation.

[0046] TMO has lower solubility compared to TPO and is relatively difficult to dissolve in ink compositions. Therefore, in active energy ray curable ink compositions containing TMO, it is necessary to adjust the composition of photopolymerizable components so that TMO is easily compatible. For this reason, the ink composition of the present invention contains 10% by mass or more of monofunctional monomers relative to the ink composition.

[0047] Furthermore, active energy ray curable ink compositions containing TPO sometimes exhibited insufficient solvent resistance in their cured products. In contrast, combining TMO with amine-modified oligomers can improve the solvent resistance of the cured ink compositions.

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

[0049] The ink composition of the present invention may contain other photopolymerization initiators along 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, etc. 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. Colorants or pigments] The ink composition of the present invention may contain a coloring agent. The coloring agent is a component that imparts a color other than white to the ink composition, and imparts black or other colors. The coloring agent may be a pigment or a dye, but it is preferably a pigment (coloring pigment). The ink composition of the present invention may also contain a pigment. It is a component added to the ink composition to impart coloring power, opacity, etc.; pigments can be broadly classified into white pigments, (other than white) coloring pigments, transparent extender pigments, metal powders, etc. 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 it may not contain a pigment; in other words, the ink composition of the present invention may be a white ink or a transparent ink. When the cured product of a white ink or a 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, TMO, which is a photopolymerization initiator contained in the ink composition of the present invention, has the characteristic of not easily causing the cured product to turn yellow. For this reason, it may be preferable that the ink composition of the present invention be a white ink or a transparent ink. Furthermore, if the ink composition of the present invention contains a white pigment or a transparent extender pigment, or if it does not contain a pigment, it may not be necessary to include a sensitizer.

[0052] On the other hand, the ink composition of the present invention may contain a coloring agent; that is, the ink composition of the present invention may be a black ink or a colored ink. As described below, if the ink composition contains a coloring agent, it is preferable to include a sensitizer.

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

[0054] Examples of coloring pigments include dye lake pigments, azo, benzimidazolone, phthalocyanine, quinacridone, anthraquinone, dioxazine, indigo, thioindico, perylene, perinone, diketopyrrolopyrrole, isoindolinone, nitro, nitroso, flavanthrone, quinophthalone, pyranthrone, and indanthrone organic pigments, as well as various inorganic pigments.

[0055] Examples of preferred coloring 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, watchmaking 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, 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 CIPigment 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 CIPigment 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 CIPigment Violet 19.

[0058] Examples of cyan pigments include CIPigment 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 (CIPigment Black 7). As described later, if the ink composition of the present invention contains a black pigment, it further contains a sensitizer. Ink compositions containing black pigments may not have sufficient curability when irradiated with active energy rays, so a sensitizer is included to improve the curability of the ink composition.

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

[0061] [1-4. Sensitizers] The ink composition of the present invention may contain a sensitizer, which can improve the curability of the ink composition. When the ink composition of the present invention contains a black pigment, it is preferable to contain a sensitizer, and when it contains a coloring agent (a coloring agent other than white), it is preferable to contain a sensitizer. This is because when the ink composition is irradiated with active energy rays, the coloring agent contained in the ink composition may block the active energy rays, making it difficult to cure the ink composition. Sensitizers can generally be broadly classified into non-polymeric sensitizers and polymeric sensitizers. The ink composition of the present invention may contain either type of sensitizer, but polymeric sensitizers are sometimes preferred because they can suppress migration from the coating film.

[0062] Examples of non-molecular-weight 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 photosensitizers include thioxanthone-based polymeric photosensitizers, acylphosphine-based polymeric photosensitizers, and other polymeric photosensitizers. Examples of thioxanthone-based polymeric photosensitizers include Omnipol TX ((2-carboxymethoxythioxanthone)-(polytetramethylene glycol 250) diester) (number average molecular weight: 660) (manufactured by IGM Resins BV) and Genopol TX-1 (number average molecular weight: 820) (manufactured by RaHN). An example of an acylphosphine-based polymeric photosensitizer is SpeedCure 7010 (molecular weight 1839) (manufactured by Lambson). Furthermore, other polymeric sensitizers include oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propane) (Lamberti, "ESACURE KIP 150", "ESACURE1"), polyethylene glycol 200-di(β-4(4-(2-dimethylamino-2-benzyl)butanonylphenyl)piperazine) (IGM, "Omnipol 910"), and (carboxymethoxymethoxybenzophenone)-(polyethylene glycol 250) diester (IGM, "Omnipol BP").

[0064] The sensitizer content in the ink composition is preferably 0.3 parts by mass or more, and more preferably 1.0 part by mass or more, when the total polymerizable components are 100 parts by mass; 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 polymerization inhibitors, pigment dispersants, leveling agents, 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 unintended polymerization reactions (such as polymerization reactions that occur without irradiation with active energy rays). 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 Dispersant] If 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 polymer-based pigment dispersant, and more preferably a pigment dispersant containing a basic group. Examples of pigment dispersants containing a basic group include polymer-based pigment dispersants such as basic group-containing polyester-based pigment dispersants, basic group-containing acrylic-based pigment dispersants, basic group-containing urethane-based pigment dispersants, and basic group-containing carbodiimide-based pigment dispersants, as well as anionic surfactants.

[0068] Polymeric pigment dispersants are not particularly limited, but may be linear polymers having a pigment-affinity moiety consisting of basic groups at least at the ends of the main chain (one or both ends) by a block or graft structure. Polymeric pigment dispersants may contain 2 to 3,000 basic groups per molecule and may have a number-average molecular weight of 1,000 to 1,000,000.

[0069] The pigment dispersant content in the ink composition is preferably 1.0 to 200.0 parts by mass, based on a total pigment content of 100 parts by mass.

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

[0071] Specific examples of silicone-based surfactants used as leveling agents include polyether-modified silicone oils such as hydroxyl-containing polyether-modified polydimethylsiloxane and polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane and polyester-modified methylalkylpolysiloxane. Silicone-based surfactants are also available from the market 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 Corporation), etc.

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

[0073] [1-5D. Other Additives] Other additives may include solvents, UV absorbers, antioxidants, defoamers, preservatives, fungicides, rust inhibitors, thickeners, humectants, pH adjusters, and various other additives. The solvent is preferably present in the ink composition at 10.0% by mass or less, more preferably at 5.0% by mass or less, even more preferably at 2.0% by mass or less, and may not be present at all.

[0074] [2. Preparation of the ink composition] The ink composition of the present invention can be prepared according to conventionally known methods. For example, the components can be dispersed and mixed using a disperser such as a wet circulation mill, bead mill, ball mill, sand mill, attritor, roll mill, DCP mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, high-pressure homogenizer (microfluidizer, nanomizer, ultimateizer, Genus PY, DeBEE2000, etc.), or pearl mill, and the viscosity can be adjusted as necessary to obtain the ink composition.

[0075] Furthermore, if the ink composition contains a pigment, a base ink composition (also called a pigment dispersion) can be obtained in advance by mixing the pigment, a pigment dispersant, and a portion of the polymerizable components, and the remaining portion of the above components can be added to it to prepare the ink composition to achieve the desired composition.

[0076] [3. Inkjet Printing of Ink Compositions] The ink composition of the present invention can be used for printing with an inkjet printing device. The type of inkjet printing device 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). It may also be a continuous type inkjet printing device, in which case a conductivity imparting agent can be added to adjust the conductivity of the ink composition.

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

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

[0079] The substrate to be printed on is not particularly limited, and is not limited to any substrate to which a conventionally known photocurable inkjet printing ink composition can be applied. Examples of substrates include plastics, paper, capsules, gels, metal foils, glass, wood, and cloth. The cured coating film of the ink composition of the present invention has excellent abrasion resistance and stretchability. Therefore, it is sometimes 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 substrate to be printed include one or more selected from the group consisting of polyester polymers (e.g., polyethylene terephthalate (PET), polyethylene naphthalate, etc.), cellulosic polymers (e.g., diacetylcellulose, triacetylcellulose (TAC), etc.), polycarbonate polymers, polyacrylic polymers (e.g., polymethyl methacrylate, etc.), vinyl chloride polymers, polyolefin polymers (e.g., polyethylene, polypropylene, polyolefin polymers having a cyclic or norbornene structure, ethylene-propylene copolymer polymers, etc.), polyamide polymers (e.g., nylon, aromatic polyamide polymers, etc.), polystyrene polymers (e.g., polystyrene, acrylonitrile-styrene copolymer polymers, etc.), polyimide polymers, polysulfone polymers, polyethersulfone polymers, polyetherketone polymers, polyphenyl sulfide polymers, polyvinyl alcohol polymers, polyvinylidene chloride polymers, polyvinyl butyral polymers, polyarylate polymers, polyoxymethylene polymers, and polyepoxy 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 shall not be construed as being limited based on the description of the examples.

[0082] A. Preparation of ink composition Tables 1 to 4 show the raw materials used to prepare the ink compositions for each example and comparative example.

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

[0084] A-2. Pigment Dispersant • Solsperse 56000: Pigment dispersion resin, amine value 39 mg KOH / g (Lubrizol) • BYKJET9151: Pigment dispersion resin (BYK Corporation) • 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. Oligomers • CN371NS: Amine-modified oligomer (Sartomer Co., Ltd.) • Miramer PE-210: Bisphenol A epoxy acrylate (MIWON Co.)

[0087] A-5. Polyfunctional monomers • EO-modified trimethylolpropane (EO)3triacrylate: Miramer M3130 (Toyo Chemicals Co., Ltd.) • Dipropylene glycol diacrylate • 1,6-Hexanediol diacrylate

[0088] A-6. Photopolymerization Initiators 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: High molecular weight thioxanthone (Sartomer Co.)

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

[0091] Inkjet printing ink compositions for each example and comparative example were prepared by blending and stirring each component according to the formulations shown in Tables 1 to 4.

[0092] B. Evaluation of ink compositions and their cured coating films (printed materials) The ink compositions and cured products prepared in each example and comparative example 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 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 coatings of each ink composition printed on a PVC board (T938, manufactured by Takiron CI Co., Ltd.) were evaluated using a Japan Society for the Promotion of Science (JSPS) type fastness tester (manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd.). The degree to which the coating was removed was visually observed when the coating was rubbed five times with a bleaching cloth containing 30% ethanol water, and the following criteria were used for evaluation. ○: No paint film removed △: There are scratches on the surface of the paint film. ×: Clear evidence of paint film chipping is visible.

[0095] B-3. ​​Flexibility of cured coatings (printed materials) The cured coatings of each ink composition printed on PET (E5100, manufactured by Toyobo Co., Ltd.) were bent at a 180-degree angle, and the state of cracking was visually inspected. ○: No fine cracks or other fissures appear in the coating. △: Fine cracks appear in the paint film. ×: Obvious cracks appear in the paint film.

[0096] B-4. LED curability (surface curability) of ink compositions Each ink composition was applied to the surface of a PET film using a bar coater No. 4 to obtain each coated product. Then, an LED irradiation device (398 nm, 500 mJ / cm²) was used. 2 The sample was irradiated with LED light using a cotton swab. After light irradiation, the ink coating was lightly rubbed with a cotton swab, and the condition of the coating and the cotton swab was evaluated. ○: No cotton swab marks are left on the coating. △: Slight marks from the cotton swab are visible on the paint film. ×: Ink gets on the cotton swab.

[0097] B-5. Compatibility of photopolymerization initiators In the ink compositions of each example and comparative example, each component except the pigment and pigment dispersant was stirred and mixed in a disperser at room temperature, and the time until the photopolymerization initiator dissolved was measured and evaluated according to the evaluation criteria below. ○: Dissolve within 1 hour △: Dissolves in 1 to 2 hours ×: Does not dissolve even after more than 2 hours.

[0098] B-6. Yellowing of the hardened coating film The cured coating films of each ink composition printed on white PVC boards were color-measured using a spectrophotometer X-Rite eXact (manufactured by x-rite), and evaluated according to the following criteria based on their b* values. ○: The b* value is less than 0. ×: The value of b is greater than or equal to 0.

[0099] B-7. Pencil hardness of hardened coating film In accordance with JIS K 5600-5-4:1999 General Test Methods for Paints, cured coatings printed on substrates were tested. The hardness of the hardest pencil that did not exhibit cohesive failure was defined as the pencil hardness. 〇:2H or more △: From B to H ×: 2B or less

[0100] B-8. Viscosity Stability of Ink Compositions After allowing each ink composition obtained in the examples and comparative examples to stand for 3 weeks at an ambient temperature of 60°C, the viscosity was measured using an E-type viscometer, and the viscosity increase rate (%) was calculated using the following formula. Viscosity stability was then evaluated according to the following evaluation criteria: Viscosity increase rate (%) = ((Viscosity value after standing for 3 weeks at 60°C / Viscosity value after standing for 3 weeks at 25°C) × 100) - 100. ○: Thickening rate less than 10% △: Thickening rate is 10% to 20% ×: Thickening rate exceeds 20%

[0101] [Table 1]

[0102] [Table 2]

[0103] As shown in Comparative Examples 1 and 2 of Table 2, the ink compositions containing TPO as a photopolymerization initiator did not exhibit sufficient solvent resistance in their cured coatings. Furthermore, as shown in Comparative Examples 3 and 4 of Table 2, the ink compositions containing TPOL, or a combination of TPOL and BAPO, as a photopolymerization initiator, did not exhibit sufficient solvent resistance in their cured coatings, nor did they exhibit sufficient LED curability or pencil hardness. The viscosity stability of the ink compositions also deteriorated. In addition, as shown in Comparative Example 4, the ink composition containing a combination of TPOL and BAPO as a photopolymerization initiator showed yellowing in its cured coating. In contrast, each example (Table 1) containing TMO as a photopolymerization initiator obtained satisfactory evaluations in all evaluation items.

[0104] As shown in Comparative Example 5 in Table 2, ink compositions that did not contain amine-modified oligomers showed reduced LED curability and insufficient solvent resistance, despite containing other oligomers. Thus, even when TMO is included as a photopolymerization initiator, ink compositions that do not contain the reactive oligomer amine-modified oligomer cannot achieve both LED curability and solvent resistance. Furthermore, as shown in Comparative Example 6 in Table 2, ink compositions with a low monofunctional monomer content (3% by mass relative to the ink composition) did not have sufficient compatibility with the photopolymerization initiator, resulting in insufficient LED curability of the cured coating film. In addition, the flexibility of the cured coating film was also reduced in Comparative Example 6. In contrast, each example (Table 1) containing amine-modified oligomers and a predetermined amount of monofunctional monomers obtained sufficient evaluations for each evaluation item.

[0105] As can be seen from the comparison with Examples 1-5, 6, 7, and 8 in Table 1, sufficient evaluations were obtained for each evaluation item whether the pigment included a white pigment or a transparent extender pigment, or whether it did not contain any pigment.

[0106] As can be seen from the comparison between Example 1 and Example 2 in Table 1, the TMO content is adjustable, and by combining it with other photopolymerization initiators, sufficient evaluation can be obtained for each evaluation item.

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

[0108] As can be seen from the comparison between Example 1 and Example 5 in Table 1, the content of monofunctional monomers (especially nitrogen-containing monomers) can be adjusted.

[0109] [Table 3]

[0110] [Table 4]

[0111] As shown in Comparative Examples 7 and 8 of Table 4, ink compositions containing TPO as a photopolymerization initiator did not exhibit sufficient solvent resistance in their cured coatings. Furthermore, as shown in Comparative Examples 9 and 10 of Table 4, ink compositions containing TPOL, or a combination of TPOL and BAPO, as a photopolymerization initiator, did not exhibit sufficient solvent resistance in their cured coatings, nor did they exhibit sufficient LED curability or pencil hardness. The viscosity stability of the ink compositions also deteriorated. In contrast, Examples 9 to 17 (Table 3), which contained TMO as a photopolymerization initiator, obtained practically sufficient evaluations in all evaluation items.

[0112] As shown in Comparative Example 11 of Table 4, when a black pigment was included, the ink composition without a sensitizer showed reduced LED curability and hardness of the cured coating film.

[0113] As shown in Comparative Example 12 of Table 4, ink compositions without amine-modified oligomers exhibited reduced LED curability despite containing other oligomers. Furthermore, as shown in Comparative Example 13 of Table 4, ink compositions with a low monofunctional monomer content (3% by mass relative to the ink composition) did not adequately match the photopolymerization initiator, resulting in insufficient LED curability of the cured coating film. In Comparative Example 13, the flexibility of the cured coating film also decreased. In contrast, Examples 9-17 (Table 3), which contained amine-modified oligomers and a predetermined amount of monofunctional monomers, obtained practically sufficient evaluations for each evaluation item.

[0114] As can be seen from the comparison with Examples 9-14, 15, 16, and 17 in Table 3, sufficient evaluations were obtained for each evaluation item whether the pigment included black pigment or various color pigments.

[0115] As can be seen from the comparison between Example 9 and Example 10 in Table 3, the TMO content is adjustable, and by combining it with other photopolymerization initiators or appropriately selecting sensitizers, sufficient evaluation can be obtained for each evaluation item.

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

[0117] The active energy ray-curable inkjet printing ink composition of the present invention contains TMO, which has low biotoxicity, as a photopolymerization initiator, and can therefore be used as an ink composition with high biological safety. Furthermore, it exhibits excellent ink properties and cured film properties as an active energy ray-curable inkjet printing ink composition, and in particular, has excellent solvent resistance. Therefore, it can be applied to various applications of conventional active energy ray-curable inkjet printing ink compositions and is expected to be applied to new applications.

Claims

1. An active energy ray curable inkjet printing ink composition having a viscosity of 5 cps or more and 80 cps or less at room temperature: The ink composition contains 10% by mass or more of a monofunctional monomer, The ink composition contains 1 to 15% by mass of an amine-modified oligomer, (2,4,6-trimethylbenzoyl)bis(p-tolyl)phosphine oxide, An ink composition further containing a black pigment, or containing a sensitizer.

2. The ink composition according to claim 1, further comprising a sensitizer and a coloring agent.

3. The ink composition according to claim 1, comprising a white pigment or a transparent extender pigment, or not comprising 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% by mass relative to the ink composition.

5. The ink composition according to any one of claims 1 to 3, wherein the monofunctional monomer comprises a monofunctional monomer with a molecular weight of 500 or less, and the content of the monofunctional monomer with a molecular weight of 500 or less is 10% by mass or more relative to the ink composition.

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

7. The ink composition according to any one of claims 1 to 3, further comprising 2% by mass or more of polyfunctional monomers relative to the total amount of 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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