Ink composition

Abstract

To provide an ink composition which has excellent re-solubility and dischargeability, further suppresses odor, and can form a printed layer of high hardness.SOLUTION: An ink composition contains a pigment, a polymerizable compound, and a photopolymerization initiator, wherein the polymerizable compound contains at least an aminoacrylate (A), the photopolymerization initiator contains at least a hydrogen-extractive photopolymerization initiator (B), an amount of the aminoacrylate (A) contained in the ink composition is 10 to 30 mass%, and an amount of the hydrogen-extractive photopolymerization initiator (B) contained in the ink composition is 1.0 to 15.0 mass%.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an ink composition, and more particularly to an ink composition which is excellent in resolubility and ejection property, and furthermore suppresses odor and is capable of forming a printed layer with high hardness. [Background technology]

[0002] When a photocurable ink composition is used for printing on a substrate, the ink composition is required to have additional properties in addition to photocurability depending on the application of the substrate. For example, in order to prevent the surface of the printed plastic substrate from being scratched, the printed layer formed on the substrate is often required to have high hardness.

[0003] A photocurable ink composition usually contains a polymerizable compound and a photopolymerization initiator, and a radical polymerization initiator is preferable as the photopolymerization initiator. Generally, a method is adopted in which a polymerization initiation species (radicals) is generated by light absorption by the photopolymerization initiator, and a polymerization reaction of the polymerizable compound is carried out to form a film. α-Aminoacetophenone type photopolymerization initiators (e.g., Omnirad 907 manufactured by IGM, etc.) and acylphosphine oxide type photopolymerization initiators (e.g., Omnirad TPO manufactured by IGM, etc.) are known as photopolymerization initiators suitable for use in ink compositions that have excellent photocurability and can form a highly hard printed layer.

[0004] However, α-aminoacetophenone type photopolymerization initiators and acylphosphine oxide type photopolymerization initiators are classified as Norrish type I photopolymerization initiators (intramolecular cleavage type photopolymerization initiators) that undergo a cleavage reaction within one molecule under light irradiation. Intramolecular cleavage type photopolymerization initiators are substances that generate radicals through intramolecular cleavage, and these radicals start the polymerization of polymerizable compounds, but the intramolecular cleavage also produces low molecular weight compounds, which causes odor problems.

[0005] Therefore, the present inventors focused on a Norrish type II photopolymerization initiator as a radical polymerization initiator, in which an excited photopolymerization initiator undergoes a bimolecular reaction with another molecule (co-initiator) to generate an initiating radical.

[0006] JP 2021-161159 A (Patent Document 1) describes an ink composition comprising a photopolymerizable compound and a photopolymerization initiator, wherein the photopolymerizable compound comprises a monofunctional polymerizable compound A and a polymerizable compound B, and the monofunctional polymerizable compound A has a glass transition temperature Tg of 25°C or higher and 60°C or lower of a polymer obtained by polymerizing the monofunctional polymerizable compound A, and the polymerizable compound B has a repeating sequence having a structure including an amino group and an ether group, and is a polymerizable compound having two or more (meth)acrylate groups, and the photopolymerization initiator comprises at least a hydrogen abstraction type initiator. In the examples of Patent Document 1, JRCURE TPO [diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide], which is an intramolecular cleavage type photopolymerization initiator, is used as the main photopolymerization initiator, but DETX (2,4-diethylthioxanthone), which is a hydrogen abstraction type photopolymerization initiator, is used in combination with this JRCURE TPO, and Genomer 5271 (amine acrylate) is used as polymerizable compound B. For this reason, the ink composition described in Patent Document 1 is recognized as using an intramolecular cleavage type photopolymerization initiator as the main photopolymerization initiator, but from the use of DETX and Genomer 5271, it is recognized as using a Norrish type II photopolymerization initiator as part of the radical polymerization initiator. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2021-161159 A Summary of the Invention [Problem to be solved by the invention]

[0008] By using a Norrish type II photopolymerization initiator in the ink composition, the odor problem caused by the use of a Norrish type I photopolymerization initiator (intramolecular cleavage type photopolymerization initiator) can be eliminated, but the hardness of the printed layer is not sufficient, so there is room for further investigation.

[0009] Therefore, an object of the present invention is to provide an ink composition that is excellent in resolubility and ejection property, suppresses odor, and is capable of forming a printed layer with high hardness. [Means for solving the problem]

[0010] As a result of intensive research into achieving the above object, the present inventors have found that by incorporating an aminoacrylate and a hydrogen abstraction type photopolymerization initiator into an ink composition and adjusting the amounts of the aminoacrylate and hydrogen abstraction type photopolymerization initiator contained in the ink composition to 10 to 30 mass % and 1.0 to 15.0 mass %, respectively, it is possible to provide an ink composition that has excellent re-solubility and ejection stability, and furthermore, suppresses odor and is capable of forming a printed layer with high hardness, thereby completing the present invention.

[0011] Therefore, the ink composition of the present invention is an ink composition containing a pigment, a polymerizable compound, and a photopolymerization initiator, The polymerizable compound contains at least an aminoacrylate (A), the photopolymerization initiator contains at least a hydrogen abstraction type photopolymerization initiator (B), the amount of the amino acrylate (A) contained in the ink composition is 10 to 30 mass %, The amount of the hydrogen abstraction type photopolymerization initiator (B) contained in the ink composition is 1.0 to 15.0% by mass.

[0012] In a preferred embodiment of the ink composition of the present invention, the photopolymerizable compound includes a monofunctional polymerizable compound (C), a bifunctional polymerizable compound (D), and a trifunctional or higher functional polymerizable compound (E), and the monofunctional polymerizable compound (C), the bifunctional polymerizable compound (D), and the trifunctional or higher functional polymerizable compound (E) are polymerizable compounds different from the amino acrylate (A).

[0013] In another preferable embodiment of the ink composition of the present invention, the mass ratio (D / E) of the bifunctional polymerizable compound (D) to the tri- or higher functional polymerizable compound (E) contained in the ink composition is 30 / 70 to 80 / 20.

[0014] In another preferable embodiment of the ink composition of the present invention, the photopolymerization initiator contains an intramolecular cleavage type photopolymerization initiator (F), and the amount of the intramolecular cleavage type photopolymerization initiator (F) contained in the ink composition is 3.0 mass % or less.

[0015] In another preferable embodiment of the ink composition of the present invention, the mass ratio (B / F) of the hydrogen abstraction type photopolymerization initiator (B) to the intramolecular cleavage type photopolymerization initiator (F) contained in the ink composition is 2.0 or more.

[0016] In another preferable embodiment of the ink composition of the present invention, the mass ratio (A / B) of the aminoacrylate (A) to the hydrogen abstraction type photopolymerization initiator (B) contained in the ink composition is 1.0 to 30.0. Effect of the Invention

[0017] According to the present invention, it is possible to provide an ink composition that is excellent in resolubility and ejection stability, and further has a reduced odor and is capable of forming a printed layer with high hardness. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to an ink composition comprising a pigment, a polymerizable compound, and a photopolymerization initiator.

[0019] The ink composition of the present invention contains a polymerizable compound and a photopolymerization initiator, and is an ink composition that can be cured by irradiation with active energy rays such as ultraviolet rays, visible light, and electron beams, and is therefore suitable as an active energy ray-curable ink composition.

[0020] The polymerizable compound is a compound having a functional group exhibiting radical polymerizability (e.g., a polymerizable unsaturated group such as a carbon-carbon double bond constituting an acryloyl group, a methacryloyl group, a vinyl group, or an allyl group), and is capable of causing a polymerization reaction via the functional group exhibiting radical polymerizability. The carbon-carbon double bond exhibiting radical polymerizability is also called an "ethylenically unsaturated double bond". The polymerizable compound may be used alone or in combination of two or more kinds.

[0021] Polymerizable compounds are classified into monofunctional polymerizable compounds and polyfunctional polymerizable compounds. Here, examples of monofunctional polymerizable compounds include monofunctional polymerizable monomers having one functional group exhibiting radical polymerizability (e.g., monofunctional polymerizable monomers having one polymerizable unsaturated group) and monofunctional polymerizable oligomers having one functional group exhibiting radical polymerizability (e.g., monofunctional polymerizable oligomers having one polymerizable unsaturated group). Examples of polyfunctional polymerizable compounds include polyfunctional polymerizable monomers having two or more functional groups exhibiting radical polymerizability (e.g., polyfunctional polymerizable monomers having two or more polymerizable unsaturated groups) and polyfunctional polymerizable oligomers having two or more functional groups exhibiting radical polymerizability (e.g., polyfunctional polymerizable oligomers having two or more polymerizable unsaturated groups).

[0022] In the ink composition of the present invention, the polymerizable compound preferably contains both a monofunctional polymerizable compound and a polyfunctional polymerizable compound, and more preferably contains a monofunctional polymerizable compound, a bifunctional polymerizable compound, and a trifunctional or higher functional polymerizable compound. A bifunctional polymerizable compound is a polyfunctional polymerizable compound having two functional groups exhibiting radical polymerizability, and a trifunctional or higher functional polymerizable compound is a polyfunctional polymerizable compound having three or more functional groups exhibiting radical polymerizability.

[0023] The amount of the polymerizable compound contained in the ink composition of the present invention is preferably from 50 to 98% by mass, and more preferably from 70 to 96% by mass. The amount of the monofunctional polymerizable compound contained in the ink composition of the present invention is preferably from 10 to 60% by mass, and more preferably from 20 to 40% by mass. The amount of the polyfunctional polymerizable compound contained in the ink composition of the present invention is preferably from 40 to 85% by mass, and more preferably from 45 to 75% by mass. The amount of the bifunctional polymerizable compound contained in the ink composition of the present invention is preferably from 20 to 65% by mass, and more preferably from 30 to 55% by mass. The amount of the tri- or higher functional polymerizable compound contained in the ink composition of the present invention is preferably from 5 to 40% by mass, and more preferably from 10 to 30% by mass.

[0024] In the ink composition of the present invention, the polymerizable compound includes at least an aminoacrylate. The aminoacrylate is a compound having an amino group and an acryloyl group and / or a methacryloyl group. Here, the amino group refers to a functional group having a structure of -NH2 or a functional group in which one or two hydrogen atoms of -NH2 are substituted with an organic group (e.g., a hydrocarbon group, etc.). In the present invention, the aminoacrylate is a compound having one or more amino groups and one or more functional groups exhibiting radical polymerizability, and one or more of the functional groups exhibiting radical polymerizability are an acryloyl group or a methacryloyl group. In this specification, the aminoacrylate is referred to as component (A) and is also referred to as "aminoacrylate (A)".

[0025] The ink composition of the present invention uses at least a Norrish type II photopolymerization initiator in which an excited photopolymerization initiator reacts with another molecule (co-initiator) to generate an initiating radical, and here, the aminoacrylate (A) is a substance that acts as a co-initiator that reacts with the excited photopolymerization initiator. On the other hand, the aminoacrylate (A) is also a compound having a functional group that exhibits radical polymerizability, and is therefore classified as a polymerizable compound in the present invention. In addition, in the present invention, a hydrogen abstraction type photopolymerization initiator is used as a photopolymerization initiator that becomes excited by absorbing light, reacts with the co-initiator (component (A) in the present invention) to generate an initiating radical. In this specification, the hydrogen abstraction type photopolymerization initiator is referred to as component (B) and is also referred to as "hydrogen abstraction type photopolymerization initiator (B)".

[0026] Amine-based materials have a radical chain transfer effect, which may result in a lower molecular weight of the polymer formed. However, when aminoacrylate (A) is used together with hydrogen abstraction type photopolymerization initiator (B), even if the polymerization reaction is terminated due to radical chain transfer, it is possible to polymerize again from the periphery of the amino group in the chain, so that a polymer with a high molecular weight is easily formed, and excellent photocurability and high hardness are obtained. According to the present invention, as described below, by adjusting the amount of aminoacrylate (A) and hydrogen abstraction type photopolymerization initiator (B) contained in the ink composition to a specific range, an ink composition that is excellent in photocurability and can form a printing layer with high hardness can be provided. In addition, the ink composition of the present invention uses a type II type photopolymerization initiator in which an excited state photopolymerization initiator reacts with another molecule (co-initiator) to generate an initiation radical, and therefore odor caused by the use of a photopolymerization initiator can be suppressed compared to ink compositions that use an intramolecular cleavage type photopolymerization initiator as the main photopolymerization initiator.

[0027] The amount of aminoacrylate (A) contained in the ink composition of the present invention is 10 to 30% by mass, and preferably 15 to 25% by mass. If the amount of aminoacrylate (A) is less than 10% by mass, it is difficult to form a highly hard printed layer, and if the amount of aminoacrylate (A) is more than 30% by mass, the viscosity of the ink composition increases, and the ejection properties of the ink composition tend to deteriorate.

[0028] The aminoacrylate (A) preferably has one or more functional groups exhibiting radical polymerizability, and more preferably has two to four functional groups.

[0029] The aminoacrylate (A) can be obtained by reacting (meth)acrylic acid or (meth)acrylate with an amine compound. Examples of methods for preparing the aminoacrylate (A) include an esterification reaction between (meth)acrylic acid or (meth)acryloyl chloride and an alkanolamine, an addition reaction between a (meth)acrylic acid ester of a polyhydric alcohol and a monoamine or diamine, and an addition reaction between a (meth)acrylate and an alkanolamine.

[0030] Examples of alkanolamines that can be used in the preparation of the aminoacrylate (A) include N,N-dimethylethanolamine, diethanolamine, triethanolamine, diisopropanolamine, N-methyldiethanolamine, 2-amino-2-methyl-1-propanol, and the like.

[0031] The (meth)acrylic acid ester of a polyhydric alcohol that can be used to prepare the aminoacrylate (A) can be prepared, for example, by reacting (meth)acrylic acid with an alcohol having two or more hydroxyl groups. Examples of the alcohol having two or more hydroxyl groups include 1,6-hexanediol, glycerin, trimethylolpropane, trimethylolethane, and pentaerythritol.

[0032] Examples of monoamines that can be used in the preparation of the aminoacrylate (A) include methylamine, n-butylamine, n-hexylamine, 2-ethylhexylamine, cyclohexylamine, ethanolamine, and benzylamine.

[0033] Examples of diamines that can be used in the preparation of the aminoacrylate (A) include ethylenediamine, tetramethylenediamine, 1,5-pentamethylenediamine, and hexamethylenediamine.

[0034] The amino acrylate (A) may also be referred to as a reactive amine coinitiator, a reactive amine synergist, an acrylate-modified amine synergist, an amine acrylate, and the like.

[0035] Commercially available aminoacrylates (A) include, for example, "Aron DA (dimethylaminoethyl acrylate)" (product name) manufactured by Toagosei Co., Ltd., "MIRAMER AS5142" (trade name) manufactured by Miwon Co., Ltd., "CN371 NS" (trade name), "CN550" (trade name), and "CN551 NS" (trade name) manufactured by Arkema, "EBECRYL 7100," "EBECRYL 80," "EBECRYL 81" (trade name), and "EBECRYL 83" (trade name) manufactured by Cytec, and "GC1100Z" and "GC1000W" (trade name) manufactured by Qualipoly Chemical Corporation.

[0036] The aminoacrylate (A) may be used alone or in combination of two or more kinds.

[0037] In the ink composition of the present invention, the polymerizable compound preferably includes, in addition to the aminoacrylate (A), a monofunctional polymerizable compound not corresponding to the aminoacrylate (A), a bifunctional polymerizable compound not corresponding to the aminoacrylate (A), and a trifunctional or higher polymerizable compound not corresponding to the aminoacrylate (A). In this specification, the monofunctional polymerizable compound not corresponding to the aminoacrylate (A) is referred to as component (C) and is also referred to as "monofunctional polymerizable compound (C)", the bifunctional polymerizable compound not corresponding to the aminoacrylate (A) is referred to as component (D) and is also referred to as "bifunctional polymerizable compound (D)", and the trifunctional or higher polymerizable compound not corresponding to the aminoacrylate (A) is referred to as component (E) and is also referred to as "trifunctional or higher polymerizable compound (E)".

[0038] The monofunctional polymerizable compound (C) is preferably a monofunctional polymerizable monomer, and specific examples thereof include isoamyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate, methoxydipropylene glycol (meth)acrylate, and ethyl carbitol (meth)acrylate. acrylate, 2-(2'-vinyloxyethoxy)ethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 4-t-butylcyclohexyl (meth)acrylate, cyclohexyl (meth)acrylate, N-(meth)acryloylmorpholine, tetrahydrofurfuryl (meth)acrylate, (2-methyl-2-ethyl-1,3-Dioxolan-4-yl)methyl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, gamma-butyrolactone (meth)acrylate, N-vinylcaprolactam, N-(meth)acryloyloxyethylhexahydrophthalimide, 1-(meth)acryloylpyrrolidin-2-one, 1-(meth)acryloylpiperidin-2-one, N-vinyl-2-pyrrolidone, N-vinylimidazole, dimethylacrylamide, hydroxyethyl (meth)acrylamide , diethylacrylamide, isopropylacrylamide, dimethylaminopropyl (meth)acrylamide, diacetone acrylamide, Nn-butoxymethylacrylamide, N-isobutoxymethylacrylamide, N-methoxymethylacrylamide, N-methylol acrylamide, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, benzyl (meth)acrylate, neopentyl glycol (meth)acrylic acid benzoate, iso Bornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, γ-(meth)acryloxypropyltrimethoxysilane, γ-(meth)acryloxypropyltriethoxysilane, γ-(meth)acryloxypropylmethyldimethoxysilane, γ-(meth)acryloxypropylmethyldiethoxysilane, γ-(meth)acryloxypropylmethyldipropoxysilane, γ-(meth)acryloxypropylmethyldipropoxysilane, Examples of the monomer include acryloxybutylphenyldimethoxysilane, γ-(meth)acryloxypropyldimethylmethoxysilane, γ-(meth)acryloxypropyldiethylmethoxysilane, β-(meth)acryloxyethyltrimethoxysilane, β-(meth)acryloxyethyltriethoxysilane, polyoxyethylene mono(meth)acrylate, polyoxypropylene mono(meth)acrylate, polyoxybutylene mono(meth)acrylate, and those modified with alkylene glycol. Among these, monofunctional polymerizable monomers with an elongated alkyl chain or alkylene glycol chain are preferred because the odor is reduced due to the increase in molecular weight compared to before the chain elongation.

[0039] The amount of the monofunctional polymerizable compound (C) contained in the ink composition of the present invention is, as described above, preferably 10 to 60% by mass, and more preferably 20 to 40% by mass. The monofunctional polymerizable compound (C) may be used alone or in combination of two or more kinds.

[0040] The bifunctional polymerizable compound (D) includes a bifunctional polymerizable monomer and a bifunctional polymerizable oligomer. Examples of the polymerizable monomer corresponding to the bifunctional polymerizable compound (D) include 1,3-butylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,7-heptanediol di(meth)acrylate, 1,8-octanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, 2-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 2-methyl-1,8-octanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, dipropionate, Examples of the di(meth)acrylate include ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, PO (propylene oxide) modified neopentyl glycol di(meth)acrylate, cyclohexane dimethanol diacrylate, tricyclodecane dimethanol diacrylate, dimethylol-tricyclodecane di(meth)acrylate, dicyclopentanyl diacrylate, bisphenol A di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate.

[0041] Examples of the tri- or higher functional polymerizable compound (E) include tri- or higher functional polymerizable monomers and tri- or higher functional polymerizable oligomers. Examples of the polymerizable monomer corresponding to the trifunctional or higher polymerizable compound (E) include trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, ethoxylated glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, EO-modified diglycerin tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, EO-modified dipentaerythritol hexa(meth)acrylate, and glycerin tri(meth)acrylate.

[0042] The polymerizable oligomer corresponding to the bifunctional polymerizable compound (D) or the trifunctional or higher polymerizable compound (E) is preferably an acrylic oligomer. The acrylic oligomer is an oligomer having an acryloyl group or a methacryloyl group as a functional group exhibiting radical polymerizability.

[0043] The number of functional groups of the polymerizable oligomer is preferably 2 to 6, and the molecular weight of the polymerizable oligomer is preferably 800 to 20000. The molecular weight of the polymerizable oligomer is a weight average molecular weight calculated in terms of polystyrene.

[0044] Specific examples of acrylic oligomers include polyurethane acrylic oligomer [acrylic oligomer having multiple urethane bonds (-NHCOO-)], polyester acrylic oligomer [acrylic oligomer having multiple ester bonds (-COO-)], polyepoxy acrylic oligomer [acrylic oligomer having multiple epoxy groups], silicone acrylic oligomer [acrylic oligomer having multiple siloxane bonds (-SiO-)], polybutadiene acrylic oligomer [acrylic oligomer having multiple butadiene units], etc.

[0045] Further, the following acrylic oligomers are known: Beam Set 550B, Beam Set 575, Beam Set AQ-19 (manufactured by Arakawa Chemical Industries, Ltd.), AH-600, UA-306H, UA-306T, UA-306I, UA-510H, UF-8001G (Kyoeisha Chemical Co., Ltd.), CN929, CN959, CN962, CN963, CN964, CN965NS, CN966NS, CN980NS, CN981NS, CN982, CN983NS, CN985, CN996NS, CN2920, CN2921, CN8881NS, CN8883NS, CN9001NS, CN973, CN978NS, CN970, CN971, CN972, CN975NS, CN2270, CN2271, CN2273, CN2274 (manufactured by Arkema), U-6LPA, U-10HA, U-10PA, UA-1100H, U-15HA, UA-33H, U-200PA, UA-160TM, UA-290TM, UA-4200, UA-4400, UA-122P (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.), New Frontier R-1235, R-1220, RST-402, R-1304, R-1214, R-1302XT, GX-8801A, R-1603, R-1150D (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), EBECRYL230, EBECRYL270, EBECRYL280 / 15IB, EBECRYL284, EBECRYL4858, EBECRYL8210, EBECRYL8307, EBECRYL8402, EBECRYL8409, EBECRYL8411, EBECRYL8804, EBECRYL8807, EBECRYL9270, KRM7735, EBECRYL4820, EBECRYL8311, EBECRYL8701, EBECRYL8210, EBECRYL8405, KRM8528 (manufactured by Daicel-Allnex), UV-1700B, UV-6300B, UV-7550B, UV-7600B, UV-7605B, UV-7610B, UV-7630B, UV-7640B, UV-7650B, UV-6630B, UV-7000B, UV-7510B, UV-3000B, UV-3200B, UV-3300B, UV-3310B, UV-3700B, UV6640B (manufactured by Mitsubishi Chemical Corporation), Aronix M-6100, M-6250, M-6500, M-7100, M-7300K, M-8030, M-8060, M-8100, M-8530, M-8560, M-9050 (manufactured by Toagosei Co., Ltd.)

[0046] The amount of the bifunctional polymerizable compound (D) contained in the ink composition of the present invention is preferably 20 to 65% by mass, and more preferably 30 to 55% by mass. The bifunctional polymerizable compound (D) may be used alone or in combination of two or more kinds.

[0047] The amount of the tri- or higher functional polymerizable compound (E) contained in the ink composition of the present invention is preferably 5 to 40 mass %, more preferably 10 to 30 mass %. The tri- or higher functional polymerizable compound (E) may be used alone or in combination of two or more kinds.

[0048] When the ink composition of the present invention contains a bifunctional polymerizable compound (D) and a trifunctional or higher polymerizable compound (E), the mass ratio (D / E) of the bifunctional polymerizable compound (D) to the trifunctional or higher polymerizable compound (E) contained in the ink composition is preferably 30 / 70 to 80 / 20, more preferably 50 / 50 to 75 / 25. By blending the bifunctional polymerizable compound (D) and the trifunctional or higher polymerizable compound (E) in the above specified mass ratio, the hardness of the printed layer can be increased while maintaining adhesion to the substrate.

[0049] In the ink composition of the present invention, the polymerizable compound preferably contains a monofunctional polymerizable monomer having a heterocycle or an aromatic ring, and the monofunctional polymerizable monomer having a heterocycle is preferably one containing an oxygen atom in the heterocycle. By using a monofunctional polymerizable monomer having a heterocycle or an aromatic ring, the pigment dispersion stability can be improved. In addition, from the viewpoint of improving the pigment dispersion stability, the amount of the monofunctional polymerizable monomer having a heterocycle and / or an aromatic ring contained in the ink composition of the present invention is preferably 2 to 60% by mass, more preferably 5 to 40% by mass. The monofunctional polymerizable monomer having a heterocycle or an aromatic ring may be used alone or in combination of two or more kinds.

[0050] Examples of the monofunctional polymerizable monomer having a heterocycle include N-acryloylmorpholine, N-methacryloylmorpholine, γ-butyrolactone (meth)acrylate, N-vinylcaprolactam, N-acryloyloxyethylhexahydrophthalimide, N-methacryloyloxyethylhexahydrophthalimide, 1-acryloylpyrrolidin-2-one, 1-methacryloylpyrrolidin-2-one, 1-acryloylpiperidine-2-one, 1-methacryloylpiperidine-2-one, N-vinyl-2-pyrrolidone, N-vinylimidazole, tetrahydrofurfuryl (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, and cyclic trimethylolpropane formal (meth)acrylate. Among these, tetrahydrofurfuryl (meth)acrylate is particularly preferred.

[0051] Examples of monofunctional polymerizable monomers having an aromatic ring include benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxy-polyethylene glycol (meth)acrylate, etc. Among these, phenoxyethyl (meth)acrylate is particularly preferred.

[0052] When the ink composition of the present invention contains a monofunctional polymerizable monomer having a heterocycle or an aromatic ring, the amount of the monofunctional polymerizable monomer having a heterocycle or an aromatic ring is preferably 10 mass % or more of the total amount of the monofunctional polymerizable compound (C) contained in the ink composition, and it is more preferable that the monofunctional polymerizable compound (C) contained in the ink composition is composed only of the monofunctional polymerizable monomer having a heterocycle or an aromatic ring.

[0053] The photopolymerization initiator has the effect of initiating polymerization of the above-mentioned polymerizable compound by irradiation with active energy rays. The photopolymerization initiator used in the ink composition of the present invention is classified as a radical polymerization initiator. In the ink composition of the present invention, the photopolymerization initiator contains at least a hydrogen abstraction type photopolymerization initiator (B). The hydrogen abstraction type photopolymerization initiator (B) corresponds to a Norrish type II photopolymerization initiator in which an excited photopolymerization initiator causes a bimolecular reaction with another molecule (co-initiator) to generate an initiation radical. In the field of photopolymerization initiators, Norrish type II photopolymerization initiators are also called two-molecule photopolymerization initiators, and a combination of a photopolymerization initiator that becomes excited by absorbing light and a co-initiator that reacts with the excited photopolymerization initiator is sometimes called a Norrish type II photopolymerization initiator. In the present invention, however, the aminoacrylate (A) that acts as a co-initiator is classified as a polymerizable compound, and a photopolymerization initiator that becomes excited by absorbing light, reacts with the co-initiator (component (A) in the present invention) to generate an initiation radical is called a hydrogen abstraction type photopolymerization initiator (B). For the classification of photopolymerization initiators, please refer to, for example, Photopolymerization Initiators, Chapter 1, Section 3, Photopolymerization Initiators (pages 93-103) in the Optical Application Technology and Materials Dictionary, published by Industrial Technology Service Center Co., Ltd. on April 26, 2006.

[0054] The hydrogen abstraction type photopolymerization initiator (B) has a different photopolymerization initiation mechanism from Norrish type I photopolymerization initiators (intramolecular cleavage type photopolymerization initiators), and therefore can solve the odor problem caused by the use of Norrish type I photopolymerization initiators (intramolecular cleavage type photopolymerization initiators).

[0055] The amount of the hydrogen abstraction type photopolymerization initiator (B) contained in the ink composition of the present invention is 1.0 to 15.0% by mass, preferably 2.0 to 10.0% by mass, and more preferably 3.0 to 8.0% by mass. When the amount of the hydrogen abstraction type photopolymerization initiator (B) is less than 1.0% by mass, a sufficient amount of radicals is not generated for the curing reaction, and a printed layer with high hardness is not obtained. In addition, the hydrogen abstraction type photopolymerization initiator (B) dissolved in the ink composition may precipitate, for example, during low-temperature storage. However, when the amount of the hydrogen abstraction type photopolymerization initiator (B) is 15.0% by mass or less, the precipitated hydrogen abstraction type photopolymerization initiator (B) can be redissolved by storing the ink composition at room temperature (about 23° C.) for a certain period of time (for example, about one day). Therefore, the ink composition of the present invention is an ink composition with excellent resolubility. On the other hand, when the amount of the hydrogen abstraction type photopolymerization initiator (B) exceeds 15.0 mass %, the hydrogen abstraction type photopolymerization initiator (B) precipitates from an ink composition, and the precipitate remains even when stored at room temperature (about 23° C.) for a certain period of time (for example, about one day).

[0056] Furthermore, the mass ratio (A / B) of the aminoacrylate (A) to the hydrogen abstraction type photopolymerization initiator (B) contained in the ink composition of the present invention is preferably 1.0 to 30.0, and more preferably 1.0 to 10.0. By setting the mass ratio (A / B) to 1.0 or more, a printed layer with high hardness is easily formed, and by setting the mass ratio (A / B) to 30.0 or less, an ink composition with excellent discharge properties is easily prepared.

[0057] The hydrogen abstraction type photopolymerization initiator (B) is a photopolymerization initiator that becomes excited by absorbing light and causes a bimolecular reaction with the aminoacrylate (A), and anthraquinone type photopolymerization initiators, benzophenone type photopolymerization initiators, thioxanthone type photopolymerization initiators, etc. are suitable. Anthraquinone type photopolymerization initiators include, for example, 2-methylanthraquinone, etc., benzophenone type photopolymerization initiators include, for example, benzophenone, etc., and thioxanthone type photopolymerization initiators include, for example, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, etc. The hydrogen abstraction type photopolymerization initiator (B) may be used alone or in combination of two or more.

[0058] In the ink composition of the present invention, the photopolymerization initiator preferably contains a small amount of an intramolecular cleavage type photopolymerization initiator in a range where no odor problem occurs in addition to the hydrogen abstraction type photopolymerization initiator (B). In this specification, the intramolecular cleavage type photopolymerization initiator is the (F) component, and is also referred to as the "intramolecular cleavage type photopolymerization initiator (F)". By using the intramolecular cleavage type photopolymerization initiator (F) in addition to the hydrogen abstraction type photopolymerization initiator (B), the curing speed can be increased. The amount of the intramolecular cleavage type photopolymerization initiator (F) contained in the ink composition of the present invention is preferably 3.0 mass% or less, and more preferably 0.5 to 2.0 mass%. The intramolecular cleavage type photopolymerization initiator (F) may be used alone or in combination of two or more.

[0059] The intramolecular cleavage type photopolymerization initiator (F) includes a benzoin type photopolymerization initiator, a benzyl ketal type photopolymerization initiator, an α-hydroxyacetophenone type photopolymerization initiator, an α-aminoacetophenone type photopolymerization initiator, an acylphosphine oxide type photopolymerization initiator, an oxime ester type photopolymerization initiator, and the like.

[0060] Specific examples of the intramolecular cleavage type photopolymerization initiator (F) are as follows: Benzoin-type photopolymerization initiators include 2,2-dimethoxy-1,2-diphenylethan-1-one (2,2-dimethoxy-2-phenylacetophenone), etc. Examples of benzyl ketal type photopolymerization initiators include α,α-dimethoxy-α-phenylacetophenone (Irgacure 651 (BASF product name)), etc. Examples of α-hydroxyacetophenone type photopolymerization initiators include 1-hydroxy-cyclohexyl-phenyl-ketone (Omnirad 184 (product name of IGM Resins BV)), 2-hydroxy-2-methyl-1-phenylpropan-1-one (Omnirad 1173 (product name of IGM Resins BV)), and 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methylpropanone (Omnirad 2959 (product name of IGM Resins BV)). Examples of α-aminoacetophenone type photopolymerization initiators include 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholino)-1-propanone (Irgacure 907 (BASF product name)), 2-benzyl-2-dimethylamino-1-[4-(4-morpholino)phenyl]-1-butanone (Irgacure 369 (BASF product name)), etc. Examples of acylphosphine oxide type photopolymerization initiators include bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (Omnirad 819 (product name of IGM Resins BV)), ethylphenyl(2,4,6-trimethylbenzoyl)phosphinate (SPeedCure TPO-L (product name of Arkema)), 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (Omnirad TPO (product name of IGM Resins BV)), etc. Examples of the oxime ester type photopolymerization initiator include 1,2-octanedione, 1-[4-(phenylthio)-2-(O-benzoyloxime)] (Irgacure OXE01 (BASF product name)), ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime) (Irgacure OXE02 (BASF product name)), and the like.

[0061] The mass ratio (B / F) of the hydrogen abstraction type photopolymerization initiator (B) to the intramolecular cleavage type photopolymerization initiator (F) contained in the ink composition of the present invention is preferably 2.0 or more, and more preferably 4.0 or more.

[0062] The pigment used in the ink composition of the present invention is not particularly limited, and any known pigment that is usually used in inks can be used.

[0063] Specific examples of pigments include: CIPigment Yellow 1, 2, 3, 4, 5, 6, 7, 9, 10, 12, 13, 14, 15, 16, 17, 24, 32, 34, 35, 36, 37, 41, 42, 43, 49, 53, 55, 60, 61, 62, 63, 65, 73, 74, 75, 77, 81, 83, 87, 93, 94, 95, 97, 98, 99, 100, 101, 104, 105, 106, 108, 109, 110, 111, 113, 114, 116, 117, 119, 120, 123, 124, 126, 127, 128, 129, 130, 133, 138, 139, 150, 151, 152, 153, 154, 155, 165, 167, 168, 169, 170, 172, 173, 174, 175, 176, 179, 180, 181, 182, 183, 184, 185, 191, 193, 194, 199, 205, 206, 209, 212, 213, 214, 215, 219, CIPigment Orange 1, 2, 3, 4, 5, 13, 15, 16, 17, 19, 20, 21, 24, 31, 34, 36, 38, 40, 43, 46, 48, 49, 51, 60, 61, 62, 64, 65, 66, 67, 68, 69, 71, 72, 73, 74, 81, C.I.Pigment Red 1、2、3、4、5、6、7、8、9、10、11、12、14、15、16、17、18、21、22、23、31、32、38、41、48、48:1、48:2、48:3、48:4、48:5、49、52、52:1、52:2、53:1、54、57:1、58、60:1、63、64:1、68、81:1、83、88、89、95、101、104、105、108、112、114、119、122、123、136、144、146、147、149、150、164、166、168、169、170、171、172、175、176、177、178、179、180、181、182、183、184、185、187、188、190、193、194、200、202、206、207、208、209、210、211、213、214、216、220、220、221、224、226、237、238、239、242、245、247、248、251、253、254、255、256、257、258、260、262、263、264、266、268、269、270、271、272、279、 C.I.Pigment Violet 1、2、3、3:1、3:3、5:1、13、15、16、17、19、23、25、27、29、31、32、36、37、38、42、50、 C.I.Pigment Blue 1、15、15:1、15:2、15:3、15:4、15:5、15:6、16、17:1、24、24:1、25、26、27、28、29、36、56、60、61、62、63、75、79、80、 C.I.Pigment Green 1、4、7、8、10、15、17、26、36、50、 C.I.Pigment Brown 5、6、23、24、25、32、41、42、 C.I.Pigment Black 1、6、7、9、10、11、20、26、28、31、32、34、 C.I.Pigment White 1、2、4、5、6、7、11、12、18、19、21、22、23、26、27、28、 Examples include aluminum flakes, glass flakes, pearl pigments, and hollow particles.

[0064] The amount of pigment contained in the ink composition of the present invention is, for example, 1 to 20% by mass. The pigment may be used alone or in combination of two or more kinds.

[0065] The ink composition of the present invention may further contain a pigment dispersant as necessary in order to disperse the pigment. The content of the pigment dispersant in the ink composition is, for example, 0.1 to 5 mass %. The pigment dispersant may be used alone or in combination of two or more kinds.

[0066] Specific examples of pigment dispersants include: ANTI-TERRA-U, ANTI-TERRA-U100, ANTI-TERRA-204, ANTI-TERRA-205, DISPERBYK-101, DISPERBYK-102, DISPERBYK-103, DISPERBYK-106, DISPERBYK-108, DISPERBYK-109, DISPERBYK-110, DISPERBYK-111, DISPERBYK-112, DISPERBYK-116, DISPERBYK-130, DISPERBYK-140, DISPERBYK-142, DISPERBYK-145, DISPERBYK-161, DISPERBYK-162, DISPERBYK-163, DISPERBYK-164, DISPERBYK-166, DISPERBYK-167, DISPERBYK-168, DISPERBYK-170, DISPERBYK-171, DISPERBYK-174, DISPERBYK-180, DISPERBYK-182, DISPERBYK-183, DISPERBYK-184, DISPERBYK-185, DISPERBYK-2000, DISPERBYK-2001, DISPERBYK-2008, DISPERBYK-2009, DISPERBYK-2020, DISPERBYK-2025, DISPERBYK-2050, DISPERBYK-2070, DISPERBYK-2096, DISPERBYK-2013, DISPERBYK-2150, DISPERBYK-2155, DISPERBYK-2163, DISPERBYK-2164, BYK-P104, BYK-P104S, BYK-P105, BYK-9076, BYK-9077, BYK-220S, BYKJET-9150, BYKJET-9151 (all manufactured by BYK Japan), Solsperse3000, Solsperse5000, Solsperse9000, Solsperse11200, Solsperse13240, Solsperse13650, Solsperse13940, Solsperse16000, Solsperse17000, Solsperse18000, Solsperse20000, Solsperse21000, Solsperse24000SC, Solsperse24000GR, Solsperse26000, Solsperse27000, Solsperse28000, Solsperse32000, Solsperse32500, Solsperse32550, Solsperse32600, Solsperse33000, Solsperse34750, Solsperse35100, Solsperse35200, Solsperse36000, Solsperse36600, Solsperse37500, Solsperse38500, Solsperse39000, Solsperse41000, Solsperse54000, Solsperse55000, Solsperse56000, Solsperse71000, Solsperse76500, SolsperseJ180, SolsperseJ200, SolsperseX300 (all manufactured by Lubrizol), Disparlon DA-7301, Disparlon DA-325, Disparlon DA-375, Disparlon DA-234 (all manufactured by Kusumoto Chemical Industries, Ltd.), FLOHREN AF-1000, FLOHREN DOPA-15B, FLOHREN DOPA-15BHFS, FLOHREN DOPA-17HF, FLOHREN DOPA-22, FLOHREN DOPA-33, FLOHREN G-600, FLOHREN G-700, FLOHREN G-700AMP, FLOHREN G-700DMEA, FLOHREN G-820, FLOHREN G-900, FLOHREN GW-1500, FLOHREN KDG-2400, FLOHREN NC-500, FLOHREN WK-13E, (all manufactured by Kyoeisha Chemical Co., Ltd.), TEGO Dispers610, TEGO Dispers610S, TEGO Dispers630, TEGO Dispers650, TEGO Dispers652, TEGO Dispers655, TEGO Dispers662C, TEGO Dispers670, TEGO Dispers685, TEGO Dispers700, TEGO Dispers710, TEGO Dispers740W, LIPOTIN A, LIPOTIN BL, LIPOTIN DB, LIPOTIN SB (both manufactured by Evonik Degussa), PB821, PB822, PN411, PA111 (all manufactured by Ajinomoto Fine-Techno Co., Ltd.), Texahol 963, Texahol 964, Texahol 987, Texahol P60, Texahol P61, Texahol P63, Texahol 3250, Texahol SF71, Texahol UV20, Texahol UV21 (all manufactured by Cognis), Examples include BorchiGenSN88 and BorchiGen0451 (both manufactured by Borchias).

[0067] The ink composition of the present invention may further contain a surface conditioner from the viewpoint of improving wettability, etc. The surface conditioner means a substance that has a hydrophilic moiety and a hydrophobic moiety in its molecular structure and can adjust the surface tension of the ink composition by adding it.

[0068] Specific examples of the surface conditioner that can be used in the ink composition of the present invention include anionic surface conditioners such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates, and fatty acid salts; nonionic surface conditioners such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, and polyoxyethylene-polyoxypropylene block copolymers; cationic surface conditioners such as alkylamine salts and quaternary ammonium salts; acrylic surface conditioners, silicon surface conditioners, and fluorine surface conditioners. Silicon surface conditioners and acrylic surface conditioners are particularly preferred, and commercially available products from BYK, Evonik, and Dow Corning Toray can be used. Furthermore, in the case of a silicon surface conditioner, it is preferred that the silicon surface conditioner is a polyether modified silicone oil and has an HLB value of 7.6 to 12.

[0069] The amount of the surface conditioner can be appropriately selected depending on the purpose of use, but is preferably, for example, 0.01 to 1 mass % in the ink composition. The surface conditioner may be used alone or in combination of two or more kinds.

[0070] Specific examples of the surface conditioner include BYK-300, BYK-302, BYK-306, BYK-307, BYK-310, BYK-313, BYK-315N, BYK-320, BYK-322, BYK-323, BYK-325, BYK-326, BYK-330, BYK-331, BYK-333, BYK-342, BYK-345, BYK-346, BYK-347, BYK-348, BYK-349, BYK-350, BYK-354, BYK-355, BYK-356, BYK-358N, BYK-361N, BYK-370, BYK-375, BYK-377, BYK-378, BYK-381, BYK-392, BYK-394, BYK-399, BYK-3440, BYK-3441, BYK-3455, BYK-3550, BYK-3560, BYK-3565, BYK-3760, BYK-DYNWET 800N, BYK-SILCLEAN 3700, BYK-SILCLEAN 3701, BYK-SILCLEAN 3720, BYK-UV3500, BYK-UV3505, BYK-UV3510, BYK-UV3530, BYK-UV3535, BYK-UV3570, BYK-UV3575, BYK-UV3576 (manufactured by BYK-Chemie Japan Co., Ltd. as above), TEGO Flow 300, TEGO Flow 370, TEGO Flow 425, TEGO Flow ATF 2, TEGO Flow ZFS 460, TEGO Glide 100, TEGO Glide 110, TEGO Glide 130, TEGO Glide 406, TEGO Glide 410, TEGO Glide 411, TEGO Glide 415, TEGO Glide 432, TEGO Glide 435, TEGO Glide 440, TEGO Glide 450, TEGO Glide 482, TEGO GlideA 115, TEGO GlideB 1484, TEGO GlideZG 400 (manufactured by Evonik Japan Co., Ltd. as above), 501W ADDITIVE, FZ-2104, FZ-2110, FZ-2123, FZ-2164, FZ-2191, FZ-2203, FZ-2215, FZ-2222, FZ-5609, L-7001, L-7002, L-7604, OFX-0193, OFX-0309 FLUID, OFX-5211 FLUID, SF 8410 FLUID, SH3771, SH 3746 FLUID, SH 8400 FLUID, SH 8700 FLUID, Y-7006 (all manufactured by Dow Corning Toray Co., Ltd.), Examples of such compounds include KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-640, KF-642, KF-643, KF-644, KF-945, KF-6004, KF-6011, KF-6012, KF-6015, KF-6017, KF-6020, KF-6204, X-22-2516, and X-22-4515 (all manufactured by Shin-Etsu Chemical Co., Ltd.).

[0071] The ink composition of the present invention may contain an ultraviolet absorbing agent. The ultraviolet absorbing agent has the effect of absorbing ultraviolet rays and preventing deterioration caused by ultraviolet rays. Examples of the ultraviolet absorbing agent include cyanoacrylate-based compounds, benzophenone-based compounds, benzoate-based compounds, benzotriazole-based compounds, hydroxyphenyltriazine-based compounds, benzylidene camphor-based compounds, inorganic fine particles, and the like.

[0072] Specific examples of ultraviolet absorbents include: 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone-2-hydroxy-4-benzyloxybenzophenone, Bis(5-benzoyl-4-hydroxy-2-methoxyphenyl)methane, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2-hydroxy-4-methoxy-2'-carboxybenzophenone, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole 2-[2'-hydroxy-3',5'-bis(α,α-(dimethylbenzyl)phenyl]benzotriazole, 2-(2'-hydroxy-3',5'-di-t-butylphenyl)benzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-t-amylphenyl)benzotriazole, 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole, 2,2'-methylene-bis[4-(1,1,3,3-tetramethylbutyl)-6-(2N-benzotriazol-2-yl)phenol], Condensation products of methyl-3-[3-t-butyl-5-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]propionate with polyethylene glycol, 2-(2-hydroxyphenyl)benzotriazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2,6-di-t-butylphenyl-3',5'-di-t-butyl-4'-hydroxybenzoate, Examples thereof include hexadecyl-3,5-di-t-butyl-4-hydroxybenzoate.

[0073] The amount of the ultraviolet absorbent contained in the ink composition of the present invention is preferably within the range of 0.1 to 15% by mass, more preferably 0.5 to 10% by mass, and even more preferably 1 to 5% by mass. If the amount of the ultraviolet absorbent is too large, the film may not be sufficiently cured. The ultraviolet absorbent may be used alone or in combination of two or more kinds, but it is preferable that the ultraviolet absorbent contains at least two kinds of ultraviolet absorbents. By using multiple kinds of ultraviolet absorbents with different structures, the effect of the ultraviolet absorbent can be further sustained.

[0074] The ink composition of the present invention may contain a radical scavenger. The radical scavenger can capture free radicals and improve light stability. In addition, substances that react with free radicals and have the function of preventing polymerization reactions (so-called polymerization inhibitors) are also included in the radical scavenger.

[0075] Examples of the radical scavenger include hindered amine compounds, hydroquinone compounds, phenol compounds, phenothiazine compounds, nitroso compounds, and N-oxyl compounds, and it is particularly preferable to use a nitroso compound and a phenol compound in combination.

[0076] Specific examples of the radical scavenger include hindered amine compounds such as bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, 1-{2-(3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy)ethyl}-2,2,6,6-tetramethylpiperidine, and 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro{4.5}decane-2,4-dione, phenol, o-, m-, or p-cresol. phenolic compounds such as 2-t-butyl-4-methylphenol, 6-t-butyl-2,4-dimethylphenol, 2,6-di-t-butyl-4-methylphenol, 2-t-butylphenol, 4-t-butylphenol, 2,4-di-t-butylphenol, 2-methyl-4-t-butylphenol, 4-t-butyl-2,6-dimethylphenol, hydroquinone, hydroquinone monomethyl ether, methylhydroquinone, 2,5-di-t-butyl Hydroquinone compounds such as 4-methylbenzcatechin, t-butylhydroquinone, 3-methylbenzcatechin, 2-methyl-p-hydroquinone, 2,3-dimethylhydroquinone, trimethylhydroquinone, t-butylhydroquinone, benzoquinone, t-butyl-p-benzoquinone, and 2,5-diphenyl-p-benzoquinone; phenothiazine compounds; nitroso-based compounds such as N-nitroso-N-phenylhydroxylamine ammonium and N-nitroso-N-phenylhydroxylamine aluminum salt; and N-oxyl-based compounds such as 4-hydroxy-2,2,6,6-tetramethyl-piperidine-N-oxyl, 4-oxo-2,2,6,6-tetramethyl-piperidine-N-oxyl, and 4-methoxy-2,2,6,6-tetramethyl-piperidine-N-oxyl.

[0077] The amount of the radical scavenger contained in the ink composition of the present invention is preferably 5% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less. If the amount of the radical scavenger is too large, it may cause poor curing. The lower limit of the content of the radical scavenger is, for example, 0.01% by mass or more, preferably 0.1% by mass or more, and even more preferably 0.5% by mass or more. The radical scavenger may be used alone or in combination of two or more kinds.

[0078] The ink composition of the present invention may contain a resin. The resin has the role of forming a coating on the substrate while capturing solid components such as pigments, and contributes to improving the adhesion of the ink composition to the substrate.

[0079] Specific examples of resins include polyvinyl acetate, vinyl chloride-vinyl acetate copolymer, vinyl chloride resin, chlorinated rubber, chlorinated polyethylene resin, chlorinated polypropylene resin, chlorinated ethylene-vinyl acetate resin, acrylic resin, polystyrene resin, polyamide resin, polyurethane resin, polyolefin resin, silicone resin, fluororesin, epoxy resin, polyester resin, ketone resin, phenol resin, polyvinyl alcohol, polyvinyl alcohol derivatives (anion-modified polyvinyl alcohol, etc.), cellulose, cellulose derivatives (hydroxymethylcellulose, hydroxyethylcellulose, cellulose acetate, etc.), rosin resin, alkyd resin, alginic acid, alginic acid derivatives (propylene glycol alginate, etc.), etc. Modified products of these resins are also included. For example, in the case of a resin having a hydroxyl group, modifications such as hydroxyalkyl etherification and carboxylic acid modification can be mentioned.

[0080] The amount of the resin contained in the ink composition of the present invention is preferably 15% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less. If the amount of the resin is too large, it may cause poor curing. The resin may be used alone or in combination of two or more kinds.

[0081] The ink composition of the present invention may contain, as other components, additives such as a silane coupling agent, an antioxidant, a plasticizer, an anti-rust agent, a solvent, an antibacterial agent, an antiviral agent, a viscosity adjuster, a filler, an antifoaming agent, a charge control agent, a stress relaxation agent, a penetrating agent, a light-guiding material, a glittering material, a magnetic material, and a fluorescent material, as necessary.

[0082] The ink composition of the present invention can be used as various color inks such as cyan ink, magenta ink, yellow ink, black ink, orange ink, green ink, violet ink, light cyan ink, and light magenta ink.

[0083] The ink composition of the present invention can be prepared by mixing various components appropriately selected as necessary. In addition, it is preferable to filter the ink composition using a filter in order to prevent clogging of the nozzles of the head due to impurities, etc.

[0084] The ink composition of the present invention preferably has a viscosity at 40°C of 5 to 25 mPa·s, more preferably 5 to 20 mPa·s. When the ink viscosity at 40°C is within the above specified range, good jetting properties can be obtained. The ink viscosity can be measured using a cone-plate viscometer. The temperature at which the ink is jetted is preferably 30°C to 50°C.

[0085] The ink composition of the present invention preferably has a surface tension of 20 to 35 mN / m, more preferably 23 to 33 mN / m, at 25° C. When the ink surface tension at 25° C. is within the above-specified range, good jetting properties can be obtained. The ink surface tension can be measured by a plate method.

[0086] As the printing means for the ink composition of the present invention, various printing means such as gravure printing, offset printing, flexographic printing, screen printing, coater printing, inkjet printing, etc. can be used, but inkjet printing is particularly preferred. For inkjet printing, various inkjet printers can be used. Examples of inkjet printers include inkjet printers that eject the ink composition by a charge control method or a piezoelectric method. In addition, large inkjet printers, specifically inkjet printers intended for printing on articles produced on industrial lines, can also be suitably used.

[0087] The layer formed by printing using the ink composition of the present invention is cured by irradiation with active energy rays such as ultraviolet rays. A high pressure mercury lamp, a metal halide lamp, an LED lamp, etc. can be used as a light source of the active energy rays. In addition, the wavelength of the active energy rays irradiated to cure this layer preferably overlaps with the absorption wavelength of the photopolymerization initiator, and the main wavelength of the active energy rays is preferably 350 to 400 nm. The integrated light amount of the active energy rays is 100 to 2000 mJ / cm. 2 It is preferable that the range is .

[0088] The ink composition of the present invention can be used to perform surface finishing such as glossy or matte finishes by appropriately selecting the ejection conditions for inkjet printing and the subsequent curing conditions. For example, if the ink composition spreads and then cures after a period of time, it will have a glossy finish, and if the ink droplets are cured while remaining in the form of lenses, it will have a matte finish.

[0089] Examples of substrates on which printing is performed with the ink composition of the present invention include plastic substrates such as epoxy resins, ABS resins, polycarbonates, polyvinyl chloride, polystyrene, acrylic resins, such as polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), and polyolefins, such as polypropylene (PP), metal substrates such as steel, zinc-plated steel, tin-plated steel, stainless steel, magnesium alloys, aluminum, aluminum alloys, titanium, and titanium alloys, inorganic substrates other than metals, such as cement, mortar, concrete, slate, gypsum, calcium silicate, glass, ceramics, calcium carbonate, marble, and artificial marble, wood substrates such as wood, paper substrates, and composite substrates in which two or more of these substrates are combined, etc. Examples of composite substrates include composite substrates such as wood fiber reinforced cement boards, fiber reinforced cement boards, and fiber reinforced cement-calcium silicate boards, metal substrates that have been subjected to various surface treatments, such as oxidation treatments, and plastic substrates whose surfaces are coated with inorganic substances (for example, plastic substrates coated with glass).

[0090] The substrate may have various shapes, for example, a two-dimensional substrate such as a film, sheet, or plate, or a three-dimensional substrate that is a complex three-dimensional object, etc. The surface of the substrate may be smooth or may have irregularities.

[0091] The surface of the substrate may be subjected to pretreatment such as degreasing, chemical conversion treatment, and polishing, or may be coated with a sealer or primer.

[0092] Specific examples of substrates include plastic materials such as PVC sheets, tarpaulin, pladan (plastic cardboard), and acrylic sheets; papers such as coated paper (specifically, resin-coated paper), art paper, cast paper, lightly coated paper, fine paper, synthetic paper, and inkjet paper; wooden building materials made from wood such as veneer, plywood, particle board, and medium-density fiberboard (MDF); inorganic building materials such as ceramic siding boards, flexible boards, calcium silicate boards, gypsum slag barite boards, wood chip cement boards, pulp cement boards, precast concrete boards, lightweight aerated concrete (ALC) boards, and gypsum boards; metal building materials such as aluminum, iron, and stainless steel, PCM steel plates, tiles, and glass plates.

[0093] The substrate on which printing is performed with the ink composition of the present invention may have a layer formed from a white ink disposed on a part or the entire surface. By providing a layer formed from a white ink, a printed layer having good color development can be formed. The layer formed from the white ink may contain a white pigment, other pigments, resin, ultraviolet absorber, radical scavenger, antioxidant, plasticizer, rust inhibitor, algae inhibitor, fungicide, antibacterial agent, antiviral agent, filler, charge control agent, light guiding material, glittering material, magnetic material, phosphor, wax, etc.

[0094] Examples of the white ink include various inks such as organic solvent-based inks that use an organic solvent as the main solvent, water-based inks that use water as the main solvent, and photocurable inks that use a polymerizable compound, but photocurable inks are preferred. Examples of components that can be used in the photocurable ink include the components that can be used in the ink composition of the present invention described above.

[0095] As the printing means for the white ink, various printing means such as gravure printing, offset printing, flexographic printing, screen printing, coater printing, inkjet printing, etc. can be used, with inkjet printing being particularly preferred.

[0096] An additional layer (e.g., a coating film or a printed film) may be formed on the layer formed by printing using the ink composition of the present invention. For example, a coating film formed by paint, a printed film formed by ink, etc. may be formed. The additional layer may contain a resin, a pigment, an ultraviolet absorber, a radical scavenger, an antioxidant, a plasticizer, an anti-rust agent, an anti-algae agent, an anti-fungal agent, an antibacterial agent, an antiviral agent, a filler, a charge control agent, a light-guiding material, a glittering material, a magnetic material, a phosphor, a wax, etc.

[0097] Examples of the paint and ink used in forming the further layer include organic solvent-based paint and ink using an organic solvent as the main solvent, water-based paint and ink using water as the main solvent, photocurable paint and ink using a polymerizable compound, powder paint, and various other paints and inks, etc. Here, examples of components that can be used in the case of photocurable ink include the above-mentioned components that can be used in the ink composition of the present invention.

[0098] The means for forming the additional layer is not particularly limited. For example, in the case of paint, various coating means such as air spray, airless spray, roll coater, flow coater, electrostatic coating, etc. can be used. In addition, in the case of ink, various printing means such as gravure printing, offset printing, flexographic printing, screen printing, coater printing, inkjet printing, etc. can be used. EXAMPLES

[0099] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0100] <Preparation of Ink Composition> Mixtures containing the components shown in Tables 1 to 5 in the amounts (parts by mass) shown in Tables 1 to 5 were stirred and dissolved to homogenize, and then filtered to prepare the actinic ray-curable ink compositions shown in Examples 1 to 28 and Comparative Examples 1 to 4.

[0101] Details of the components shown in Tables 1 to 5 are given below. 1) Monarch 1000 (Cabot Corporation), carbon black (Pigment Black 7) 2) Heliogen Blue L7101F (Sun Chemical), β-modified copper phthalocyanine (Pigment Blue 15:4) 3) Fastogen Super Magenta RG (DIC), quinacridone pigment (Pigment Red 122) 4) Pigment Yellow E4GN (Lanxess), Nickel Azomethine Complex (Pigment Yellow 150) 5) Light Acrylate THF-A (Kyoeisha Chemical Co., Ltd.), Tetrahydrofurfuryl acrylate 6) Light Acrylate PO-A (Kyoeisha Chemical Co., Ltd.), Phenoxyethyl Acrylate 7) Light Acrylate 1,6HX-A (Kyoeisha Chemical Co., Ltd.), 1,6-Hexanediol diacrylate 8) DPGDA (Daicel Allnex), dipropylene glycol diacrylate 9) Light Acrylate PE-4A (Kyoeisha Chemical Co., Ltd.), Pentaerythritol Tetraacrylate 10) Light Acrylate DPE-6A (Kyoeisha Chemical Co., Ltd.), Dipentaerythritol Hexaacrylate 11) EBECRYL 7100 (manufactured by Daicel Allnex), bifunctional amino acrylate 12) EBECRYL 80 (manufactured by Daicel Allnex), a tetrafunctional amine-modified highly reactive polyether acrylate 13) Q-1301 (Fujifilm Wako Pure Chemical Industries, Ltd.), N-nitrosophenyl hydroxyamine aluminum salt 14) Yoshinox BHT (API Corporation), butylated hydroxytoluene 15) MEHQ (Tokyo Chemical Industry Co., Ltd.), 4-Methoxyphenol 16) SpeedCure DETX (Arkema), 2,4-diethylthioxanthone 17) SpeedCure 2-ITX (Arkema), 2-isopropylthioxanthone 18) Omnirad 819 (former Irgacure 819) (IGM Resins BV), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide 19) BYK-UV 3500 (manufactured by BYK-Chemie), silicone-based surface conditioner

[0102] <Creating printed matter> The ink composition prepared was applied to a commercially available PET film (HK-33WF, manufactured by Higashiyama Film Co., Ltd.: 70 mm × 150 mm × thickness 188 μm) using a bar coater #5, and then activated energy rays (LED 385 nm) were applied at 1000 mW / cm 2 , 1000mJ / cm 2 The obtained print was used for evaluation of odor and hardness.

[0103] <Resolubility> The prepared ink composition was stored at 5°C for 7 days, and then stored at 23°C for 1 day, after which the ink composition was filtered through a SUS mesh filter (pore size: 5 µm). The presence or absence of precipitates on the SUS mesh filter after filtration was visually confirmed to evaluate the resolubility of the ink composition. The evaluation criteria were as follows. The results are shown in Tables 1 to 5. (Evaluation Criteria) ○: No precipitate ×: Precipitates present

[0104] <Odor> A sensory test of the odor of printed matter (immediately after production) was conducted by 10 panelists in a room with a room temperature of 23°C and 50% RH. Evaluation was made on a three-point scale of "no odor," "slight odor," and "odor," with "no odor" given 0 points, "slight odor" given 1 point, and "odor" given 2 points, and the odor was evaluated by adding up the scores given by each panelist. The evaluation criteria were as follows. The results are shown in Tables 1 to 5. Printed matter rated "good" is one in which odor is suppressed. (Evaluation Criteria) ○: The total score of 10 people is 5 points or less. ×: The total score of 10 people is 6 points or more.

[0105] <Dischargeability> Using an inkjet recording device equipped with a piezoelectric inkjet nozzle, the ink composition of each Example or Comparative Example was filled into the nozzle. The temperature during ink ejection was set to 50° C., and a solid pattern image (recording resolution 720×600 dpi) was printed on the surface of a commercially available PET film (HK-33WF manufactured by Higashiyama Film: 70 mm×150 mm×thickness 188 μm). The ejection properties of each ink composition were evaluated at this time. The evaluation criteria were as follows. The results are shown in Tables 1 to 5. Ink compositions rated as "good" are ink compositions with excellent ejection properties. (Evaluation Criteria) ◯: No missing parts and a good printed image were obtained. ×: Missing spots occur, and color unevenness occurs in the printed image.

[0106] <Hardness of the printing layer> The pencil hardness of the printed matter produced by the above method was measured in accordance with JIS K 5600-5-4:1999. The evaluation criteria were as follows. The results are shown in Tables 1 to 5. Printed matters rated as "good" are printed matters with high hardness. (Evaluation Criteria) ○: Pencil hardness is 2H or more ×: Pencil hardness is H or less

[0107] [Table 1]

[0108] [Table 2]

[0109] [Table 3]

[0110] [Table 4]

[0111] [Table 5]

[0112] In the table, the item "Hydrogen abstraction type photopolymerization initiator (B) / intramolecular cleavage type photopolymerization initiator (F)" indicates the mass ratio (B / F) of the hydrogen abstraction type photopolymerization initiator (B) contained in the ink composition to the intramolecular cleavage type photopolymerization initiator (F), the item "Aminoacrylate (A) / Hydrogen abstraction type photopolymerization initiator (B)" indicates the mass ratio (A / B) of the aminoacrylate (A) contained in the ink composition to the hydrogen abstraction type photopolymerization initiator (B), and the item "Bifunctional polymerizable compound (D) / Trifunctional or higher functional polymerizable compound (E)" indicates the mass ratio (D / E) of the bifunctional polymerizable compound (D) to the trifunctional or higher functional polymerizable compound (E) contained in the ink composition.

[0113] The ink compositions of Examples 1 to 28 were inks with excellent resolubility and ejection properties, and furthermore, the ink compositions were able to form a printed layer of high hardness with reduced odor. On the other hand, when the amount of aminoacrylate in the ink composition was less than 10% by mass (Comparative Example 1), a printed layer of high hardness was not obtained, and when the amount of aminoacrylate in the ink composition was more than 30% by mass (Comparative Example 2), the ejection properties of the ink were poor. Furthermore, when the amount of hydrogen abstraction type photopolymerization initiator contained in the ink composition was less than 1.0% by mass (Comparative Example 3), a printed layer of high hardness was not obtained, and when the amount of hydrogen abstraction type photopolymerization initiator contained in the ink composition was more than 15.0% by mass (Comparative Example 4), the resolubility was poor.

Claims

1. An ink composition comprising a pigment, a polymerizable compound, and a photopolymerization initiator, The polymerizable compound contains at least an amino acrylate (A), the photopolymerization initiator contains at least a hydrogen abstraction type photopolymerization initiator (B), the amount of the amino acrylate (A) contained in the ink composition is 10 to 30% by mass, The ink composition, wherein the amount of the hydrogen abstraction type photopolymerization initiator (B) contained in the ink composition is 1.0 to 15.0% by mass.

2. 2. The ink composition according to claim 1, wherein the photopolymerizable compound comprises a monofunctional polymerizable compound (C), a bifunctional polymerizable compound (D), and a tri- or higher functional polymerizable compound (E), and the monofunctional polymerizable compound (C), the bifunctional polymerizable compound (D), and the tri- or higher functional polymerizable compound (E) are polymerizable compounds different from the amino acrylate (A).

3. 3. The ink composition according to claim 2, wherein a mass ratio (D / E) of the bifunctional polymerizable compound (D) to the tri- or higher functional polymerizable compound (E) contained in the ink composition is 30 / 70 to 80 / 20.

4. 2. The ink composition according to claim 1, wherein the photopolymerization initiator comprises an intramolecular cleavage type photopolymerization initiator (F), and the amount of the intramolecular cleavage type photopolymerization initiator (F) contained in the ink composition is 3.0 mass % or less.

5. 5. The ink composition according to claim 4, wherein a mass ratio (B / F) of the hydrogen abstraction type photopolymerization initiator (B) to the intramolecular cleavage type photopolymerization initiator (F) contained in the ink composition is 2.0 or more.

6. 2. The ink composition according to claim 1, wherein a mass ratio (A / B) of the aminoacrylate (A) to the hydrogen abstraction type photopolymerization initiator (B) contained in the ink composition is 1.0 to 30.0.

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