Active energy ray curable ink composition and method for producing printed matter

Abstract

Provided is an actinic ray-curable ink composition that exhibits excellent curability even when irradiated with LEDs and excellent storage stability. The present invention relates to a compound represented by the general formula (1): JPEG2026041878000008.jpg27127 (In the formula, R 1 , R 2 represents H, an alkyl group, or the like.), and when the photopolymerization initiator (b) is an acylphosphine compound (b-1), the ink composition contains, as an essential component, one or more of a mercapto-modified (meth)acrylate (a) or an anthracene compound (c); and when the photopolymerization initiator (b) is a phosphinate ester compound (b-2), the ink composition contains, as an essential component, one or more of (a), (b-1), or (c).

Description

[Technical Field]

[0001] The present invention relates to an actinic ray-curable ink composition that can be used to produce various printed materials. [Background technology]

[0002] Printing using an inkjet recording device does not require a printing plate; instead, ink is ejected from a nozzle onto a recording material. Because there is no contact between the nozzle and the recording material, inkjet recording devices are unique in that they can print well not only on paper substrates, but also on substrates with curved or irregularly shaped surfaces, such as plastics and metals. For this reason, inkjet printing is expected to see expanded use in a wide range of industrial fields. In particular, actinic radiation-curable inkjet inks, which are cured by exposure to actinic radiation such as ultraviolet rays, have a low content of volatile organic compounds (VOCs) and require less energy for drying and other processes during the printing process, and are therefore attracting attention as an environmentally friendly technology. Mercury lamps and metal halide lamps are widely known as light sources used to cure actinic ray-curable inkjet inks. However, in recent years, there has been a demand for mercury-free devices from the perspective of environmental protection, and light-emitting diodes (LEDs) and laser diodes (LDs) are expected to be used as light sources for photocurable inkjet inks because they are small, have a long lifespan, are highly efficient, and are low-cost. Ink compositions such as those described in Patent Documents 1 and 2 have been disclosed as actinic ray-curable inkjet inks that are cured using an LED as a light source. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-206875 [Patent Document 2] International Publication No. 2021 / 111884 Summary of the Invention [Problem to be solved by the invention]

[0004] The light emitted by an LED has a single peak, and the spread of the wavelength width of this peak is extremely small (half-value width: ±5 to 10 μm). Therefore, an ink composition that exhibits excellent curability when irradiated with light from a metal halide lamp does not necessarily exhibit excellent curability when irradiated with light from an LED. While it is conceivable to increase the amount of polymerization initiator in the ink composition to improve curability, this may cause problems with the stability of the ink composition, production costs, etc. In Patent Documents 1 and 2, compounds to be incorporated into ink compositions are selected from the viewpoint of improving curability and taking into consideration the properties of the resulting coating film, such as hardness and adhesion. On the other hand, there is a growing demand for environmental considerations and safety considerations for the compounds themselves to be incorporated into ink compositions. In other words, there is still room for improvement in the curability and stability of ink compositions that are cured using an LED as a light source.

[0005] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by selecting a specific polymerizable monomer and photopolymerization initiator and blending a specific sensitizer. They have also found that such an ink composition has excellent dischargeability as an inkjet ink composition, and the formed coating film is inhibited from coloring and has excellent physical properties. An object of the present invention is to provide an actinic ray-curable ink composition that exhibits excellent curability even when irradiated with light from an LED light source and also exhibits excellent storage stability. [Means for solving the problem]

[0006] The present invention has the following aspects. [1] An acylphosphine compound (b-1) and the following general formula (1)

[0007] [ka]

[0008] (In the formula, R 1 represents a hydrogen atom or an alkyl group, and R 2 represents a hydrogen atom, an alkyl group, or an acyl group; and When the photopolymerization initiator (b) is the acylphosphine compound (b-1), it contains at least one of the following components (a) and (c) as an essential component: When the photopolymerization initiator (b) is the phosphinic acid ester compound (b-2), the actinic ray-curable inkjet ink composition comprises, as an essential component, one or more of the following component (a), the acylphosphine compound (b-1), and component (c): Mercapto-modified (meth)acrylate (a) Anthracene compounds (c) [2] The actinic ray-curable inkjet ink composition according to [1], wherein the photopolymerization initiator (b) is contained in an amount of 0.1 to 15% by mass relative to the total mass of the composition. [3] The actinic ray-curable inkjet ink composition according to [1] or [2], wherein the mercapto-modified (meth)acrylate (a) is contained in an amount of 0.1 to 25% by mass relative to the total mass of the composition. [4] The actinic ray-curable inkjet ink composition according to any one of [1] to [3], wherein the anthracene compound (c) is contained in an amount of 0.05 to 5% by mass relative to the total mass of the composition. [5] The actinic ray-curable inkjet ink composition according to any one of [1] to [4], which contains the photopolymerization initiator (b) and the anthracene compound (c). [6] The actinic ray-curable inkjet ink composition according to any one of [1] to [5], comprising the mercapto-modified (meth)acrylate (a) and the photopolymerization initiator (b). [7] The actinic ray-curable inkjet ink composition according to any one of [1] to [6], wherein the photopolymerization initiator (b) comprises the acylphosphine compound (b-1) and the phosphinic acid ester compound (b-2). [8] The actinic ray-curable inkjet ink composition according to any one of [1] to [7], wherein the photopolymerization initiator (b) comprises two or more of the phosphinic acid ester compounds (b-2). [9] The actinic ray-curable inkjet ink composition according to any one of [1] to [8], which is an ultraviolet ray-curable inkjet ink composition.

[10] A method for producing a printed matter, comprising a step of ejecting the actinic energy ray-curable inkjet ink composition according to any one of [1] to [9] onto a recording medium and curing the ink by irradiating it with actinic energy rays. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an actinic ray-curable ink composition that exhibits excellent curability even when irradiated with light from an LED light source and also exhibits excellent storage stability. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention relates to an acylphosphine compound (b-1) and a compound represented by the following general formula (1):

[0011] [ka]

[0012] (In the formula, R 1 represents a hydrogen atom or an alkyl group, and R 2 represents a hydrogen atom, an alkyl group, or an acyl group; and When the photopolymerization initiator (b) is the acylphosphine compound (b-1), it contains at least one of the following components (a) and (c) as an essential component: When the photopolymerization initiator (b) is the phosphinic acid ester compound (b-2), the present invention provides an actinic ray-curable inkjet ink composition (hereinafter simply referred to as "the ink composition") that contains, as an essential component, one or more of the following component (a), the acylphosphine compound (b-1), and component (c): Mercapto-modified (meth)acrylate (a) Anthracene compounds (c)

[0013] In this specification, "(meth)acrylate" is a term that collectively refers to acrylate, methacrylate, and both. "(meth)acrylic" is a term that collectively refers to acrylic, methacrylic, and both. "(meth)acryloyloxy group" is a term that collectively refers to acryloyloxy group, methacryloyloxy group, and both. The components of the ink composition are described below. Note that the present invention is not limited to the components of these embodiments, and any other components may be added, or any component that exhibits the same function may be substituted.

[0014] The mercapto-modified (meth)acrylate (a) in the ink composition can be obtained, for example, by subjecting a polyfunctional thiol compound to a Michael addition reaction with a stoichiometric excess of a di- or higher functional polyfunctional (meth)acrylate compound. Examples of polyfunctional thiol compounds include 1,6-hexanedithiol, ethylene glycol di-2-mercaptoacetate, pentaerythritol tetrakis(2-mercaptoacetate), trimethylolpropane tris(2-mercaptoacetate), ethylene glycol bis(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionate), and trimethylolpropane tris(3-mercaptopropionate). In addition, reaction products of at least one of these compounds with polyisocyanates [1,3-bis(2-isocyanato-2-propyl)benzenetetrathiol, isophorone diisocyanate, hexamethylene diisocyanate, etc.] are also included in the category of polyfunctional thiol compounds.

[0015] Examples of the polyfunctional (meth)acrylate to be reacted with the polyfunctional thiol compound in a Michael addition reaction include ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 2-methyl-1,8-octanediol di(meth)acrylate, and 2-butyl-2-ethyl-1,3-propanediol di(meth)acrylate. Glycol (meth)acrylates such as ol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, ethoxylated (2) neopentyl glycol di(meth)acrylate [a compound obtained by diacrylate of a neopentyl glycol ethylene oxide 2-mol adduct], and propoxylated (2) neopentyl glycol di(meth)acrylate [a compound obtained by diacrylate of a neopentyl glycol propylene oxide 2-mol adduct]; di(meth)acrylate of tris(2-hydroxyethyl)isocyanurate; alkylene glycol (meth)acrylates such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetrapropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and bis(4-acryloxypolyethoxyphenyl)propane; Pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, tetramethylolmethane tri(meth)acrylate, dimethyloltricyclodecane di(meth)acrylate ) acrylate, modified glycerin tri(meth)acrylate, modified bisphenol A di(meth)acrylate, propylene oxide (PO) adduct tri(meth)acrylate of glycerin, ethylene oxide (EO) adduct tri(meth)acrylate of glycerin, propylene oxide (PO) adduct di(meth)acrylate of bisphenol A, ethylene oxide (EO) adduct di(meth)acrylate of bisphenol A, dipentaerythritol hexa(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, etc.

[0016] The mercapto-modified (meth)acrylate (a) is also available as a commercially available product, and examples thereof include Miramer ES100, Miramer ES110N, and Miramer ES4420 manufactured by MIWON Corporation, and ADDITOL LED01 manufactured by Daicel-Allnex Corporation.

[0017] When the ink composition contains the mercapto-modified (meth)acrylate (a) as an essential component, the content of the mercapto-modified (meth)acrylate (a) is preferably in the range of 0.1 to 25 mass %, more preferably in the range of 4 to 20 mass %, and even more preferably in the range of 9 to 15 mass %, relative to the total mass of the ink composition. When the ink composition contains the mercapto-modified (meth)acrylate (a) in the above range, the ink composition has good curability, and the storage stability of the ink composition and the performance of the coating film are improved.

[0018] The weight average molecular weight (Mw) of the mercapto-modified (meth)acrylate (a) is preferably 5,000 or less, more preferably 3,000 or less, and even more preferably 2,000 or less, from the viewpoint of ensuring the molecular mobility of the mercapto-modified (meth)acrylate (a) in the ink composition and achieving excellent UV-LED curability.

[0019] The ink composition may further contain another polymerizable compound different from the mercapto-modified (meth)acrylate (a). Examples of the other polymerizable compound include a monofunctional polymerizable compound and a polymerizable compound having two or more polymerizable groups (hereinafter referred to as a "polyfunctional polymerizable compound"). Here, the polymerizable group refers to a group having a polymerizable unsaturated double bond.

[0020] The monofunctional polymerizable compound is preferably a compound that has a polymerizable unsaturated double bond and is liquid at 25°C, and its molecular weight is preferably 60 to 2000, more preferably 100 to 1000. The viscosity of the monofunctional polymerizable compound is preferably 1000 mPa·s or less, more preferably 300 mPa·s or less, and is preferably 1 mPa·s or more, more preferably 3 mPa·s or more.

[0021] Examples of the monofunctional polymerizable compound include a compound having a heterocyclic structure, a monofunctional (meth)acrylate having a linear or cyclic aliphatic group, a monofunctional (meth)acrylate having an alkyleneoxy group, a monofunctional (meth)acrylate having an aromatic hydrocarbon group, and a monovinyl ether compound.

[0022] Examples of compounds having a heterocyclic structure include N-vinylcaprolactam, N-vinylpyrrolidone, (meth)acryloylmorpholine, N-(meth)acryloyloxyethylhexahydrophthalimide, tetrahydrofurfuryl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, etc. Among these, N-vinylcaprolactam is preferred because it is highly safe, widely available, and relatively inexpensive, and provides good curability and adhesion of the cured coating film to the recording medium.

[0023] Examples of monofunctional (meth)acrylates having a linear or cyclic aliphatic group include isoamyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, decyl (meth)acrylate, isomyristyl (meth)acrylate, isostearyl (meth)acrylate, tricyclodecane dimethanol mono(meth)acrylate, adamantyl (meth)acrylate, cyclohexane dimethanol mono(meth)acrylate, trimethylcyclohexyl (meth)acrylate, isobornyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and dicyclopentenyloxyethyl (meth)acrylate.

[0024] Examples of monofunctional (meth)acrylates having an alkyleneoxy group include methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, ethoxyethoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-ethylhexyl diglycol (meth)acrylate, diethylene glycol mono(meth)acrylate, diethylene glycol monobutyl ether (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, and methoxypropylene glycol (meth)acrylate.

[0025] Examples of monofunctional (meth)acrylates having an aromatic hydrocarbon group include 2-phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, etc. Among these, 2-phenoxyethyl (meth)acrylate is preferred, and 2-phenoxyethyl acrylate is more preferred from the viewpoints of inkjet ejection properties, adhesion of the coating film obtained by curing, and flexibility (elongation resistance) at low temperatures.

[0026] The polyfunctional polymerizable compound may be any of a monomer, an oligomer, and a polymer. In this specification, "monomer" refers to a compound having a molecular weight (weight average molecular weight when there is a molecular weight distribution) of 1,000 or less. The molecular weight of the monomer (weight average molecular weight when there is a molecular weight distribution) is 50 to 1,000. "Oligomer" generally refers to a polymer having a finite number of monomer-based structural units (generally 5 to 100) and having a weight average molecular weight of more than 1,000 and less than 30,000. "Polymer" refers to a polymer having a weight average molecular weight of 30,000 or more. The weight average molecular weight is a value measured by gel permeation chromatography (GPC) and calculated as a standard polystyrene equivalent value.

[0027] Examples of the polyfunctional polymerizable compound include polyfunctional (meth)acrylates, divinyl ether compounds, trivinyl ether compounds, urethane (meth)acrylates, and amino (meth)acrylates. Examples of the polyfunctional (meth)acrylate include compounds similar to the bifunctional or higher polyfunctional (meth)acrylate compounds that undergo a Michael addition reaction with a polyfunctional thiol to form the mercapto-modified (meth)acrylate (a). Examples of divinyl ether compounds or trivinyl ether compounds include ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, and trimethylolpropane trivinyl ether. Examples of the urethane (meth)acrylate include aliphatic urethane (meth)acrylate, aromatic urethane (meth)acrylate, etc. The weight average molecular weight of the urethane (meth)acrylate is preferably 1,000 to 30,000, more preferably 2,000 to 20,000.

[0028] The amino(meth)acrylate is an amine-modified (meth)acrylate having an amino group. The number average molecular weight of the amino(meth)acrylate is preferably 2,000 to 20,000, more preferably 2,000 to 10,000, and even more preferably 2,000 to 5,000. Commercially available amino(meth)acrylates can also be used, such as EBECRYL 7100 and EBECRYL 80 manufactured by Daicel-Allnex Corporation.

[0029] When the ink composition further contains another polymerizable compound, the other polymerizable compound may be used alone or in combination of two or more. The amount of the other polymerizable compound varies depending on the performance to be imparted to the ink composition, but is generally preferably contained in the range of 50 to 75 mass % of the total ink composition, and more preferably contained in the range of 60 to 70 mass %.

[0030] The photopolymerization initiator (b) in the ink composition is an acylphosphine compound (b-1) and a compound represented by the following general formula (1):

[0031] [ka]

[0032] (In the formula, R 1 represents a hydrogen atom or an alkyl group, and R 2 represents a hydrogen atom, an alkyl group or an acyl group.)

[0033] Examples of the acylphosphine compound (b-1) include 2-methylbenzoyldiphenylphosphine oxide, bis(2,6-dichlorobenzoyl)phenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,6-dimethoxybenzoyldiphenylphosphine oxide, 2,6-dichlorobenzoyldiphenylphosphine oxide, bis(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis(2,6-dichlorobenzoyl)-4-propylphenylphosphine oxide, bis(2,6-dichlorobenzoyl)-1-naphthylphosphine oxide, bis(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and bis(2,6-dimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide. The ink composition may contain one type of acylphosphine compound (b-1) alone, or two or more types of acylphosphine compounds (b-1) in combination.

[0034] In the phosphinic acid ester compound (b-2) represented by the general formula (1), R 1 and R 2Examples of the alkyl group represented by include alkyl groups preferably having 1 to 6 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a butyl group, a pentyl group, and a hexyl group. R 2 Examples of the acyl group represented by include acyl groups preferably having 1 to 20 carbon atoms, such as an acetyl group, a propionyl group, and a benzoyl group. Of these, a benzoyl group is preferred. Such an acyl group may be further substituted with one or more substituents.

[0035] Examples of the phosphinate ester compound (b-2) include methyl phenyl(2,4,6-trimethylbenzoyl)phosphinate, ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate, methyl (3-benzoyl-2,4,6-trimethylbenzoyl)phenylphosphinate, ethyl (3-benzoyl-2,4,6-trimethylbenzoyl)phenylphosphinate, isopropyl pivaloylphenylphosphinate, etc. The ink composition may contain one type of phosphinate ester compound (b-2) alone, or two or more types of phosphinate ester compounds (b-2) in combination.

[0036] Considering the use of an ultraviolet light-emitting diode (UV-LED) light source as the source of active energy rays, the acylphosphine compound (b-1) as the photopolymerization initiator (b) corresponding to the wavelength of light emitted from the UV-LED light source is preferably phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide or 2,4,6-trimethylbenzoyldiphenylphosphine oxide.Furthermore, the phosphinate compound (b-2) as the photopolymerization initiator (b) is preferably ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate or ethyl (3-benzoyl-2,4,6-trimethylbenzoyl)phenylphosphinate. The photopolymerization initiator (b) may contain two or more acylphosphine compounds (b-1), may contain two or more phosphinate ester compounds (b-2), or may contain one or more acylphosphine compounds (b-1) and one or more phosphinate ester compounds (b-2).

[0037] The ink composition may further contain a photopolymerization initiator other than the acylphosphine compound (b-1) and the phosphinate ester compound (b-2). Examples of such other photopolymerization initiators include benzoin isobutyl ether, 2,4-diethylthioxanthone (also called 2,4-diethylthioxanthen-9-one), 2-isopropylthioxanthone, methylbenzoyl formate, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, benzil dimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-(4-isopropylphenyl)-2-hydroxybenzoyl ketone, benzoin ethyl ether, benzil dimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-(4-isopropylphenyl)-2-hydroxybenzoyl ketone, benzoin ethyl ether, benzoin ... hydroxy-2-methylpropan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, benzophenone, 4-phenylbenzophenone, isophthalphenone, 4-benzoyl-4'-methyldiphenyl sulfide, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-(4-morpholinophenyl)-butan-1-one, 1-{4-[(4-benzoylphenyl)sulfanyl]phenyl}-2-methyl-2-[(4-methylphenyl)sulfonyl]propan-1-one, and the like.

[0038] The content of the photopolymerization initiator (b) in the entire ink composition is preferably 0.1 to 15% by mass, and more preferably 2 to 10% by mass, from the viewpoints of improving the curability of the ink composition, the storage stability of the ink composition, suppressing coloration of the coating film formed, and improving the performance of the coating film. When the above-described other photopolymerization initiators are further used in addition to the acylphosphine compound (b-1) and the phosphinic acid ester compound (b-2) as the photopolymerization initiator (b), the total amount thereof is preferably 0.1 to 15% by mass, and more preferably 2 to 10% by mass, of the total amount of the ink composition.

[0039] Examples of the anthracene compound (c) in the ink composition include 9,10-diethoxyanthracene, 9,10-dipropyloxyanthracene, 9,10-dibutoxyanthracene, 9,10-dipentyloxyanthracene, 9,10-dihexyloxyanthracene, 9,10-diheptyloxyanthracene, 9,10-dioctyloxyanthracene, 9,10-dinonyloxyanthracene, and 9,10-didecyloxyanthracene. 9,10-dialkanoyloxyanthracenes such as 9,10-diacetyloxyanthracene, 9,10-dipropanoyloxyanthracene, 9,10-dibutanoyloxyanthracene, 9,10-dipentanoyloxyanthracene, 9,10-dihexanoyloxyanthracene, 9,10-diheptanoyloxyanthracene, and 9,10-dioctanoyloxyanthracene.

[0040] In addition, in the ink composition, a sensitizer different from the anthracene compound (c) may be used in combination with the anthracene compound (c). Examples of such sensitizers include trimethylamine, methyldimethanolamine, triethanolamine, p-diethylaminoacetophenone, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, N,N-dimethylbenzylamine, and 4,4'-bis(diethylamino)benzophenone.

[0041] When the ink composition contains an anthracene compound (c) as an essential component, the content of the anthracene compound (c) relative to the total mass of the ink composition is preferably 0.05 to 5 mass%, and more preferably 0.05 to 1 mass%, from the viewpoints of improving the curability of the ink composition, the storage stability of the ink composition, suppressing coloration of the coating film formed, and improving the performance of the coating film. The anthracene compound (c) is generally considered to be a sensitizer in this technical field, but when the ink composition contains the anthracene compound (c) as an essential component together with the photopolymerization initiator (b), the effects of the present invention described above are more effectively exhibited.

[0042] As described above, the ink composition contains at least one photopolymerization initiator (b) selected from the group consisting of acylphosphine compounds (b-1) and phosphinic acid ester compounds (b-2). When the photopolymerization initiator (b) is the acylphosphine compound (b-1), the ink composition contains, as an essential component, one or more of a mercapto-modified (meth)acrylate (a) or an anthracene compound (c). When the photopolymerization initiator (b) is the phosphinic acid ester compound (b-2), the ink composition contains, as an essential component, one or more of a mercapto-modified (meth)acrylate (a), an acylphosphine compound (b-1), or an anthracene compound (c). From the viewpoint of improving the curability of the ink composition, improving the storage stability of the ink composition, suppressing coloration of the formed coating film, and improving the performance of the coating film, <1> The ink composition of the present invention in an embodiment containing both an acylphosphine compound (b-1) and a phosphinic acid ester compound (b-2) as the photopolymerization initiator (b); <2> the ink composition of an embodiment including a photopolymerization initiator (b) and an anthracene compound (c); <3> The ink composition of an embodiment comprising a mercapto-modified (meth)acrylate (a) and a photopolymerization initiator (b); <4> The photopolymerization initiator (b) contains both an acylphosphine compound (b-1) and a phosphinic acid ester compound (b-2), or contains two or more kinds of phosphinic acid ester compounds (b-2). <2> or <3> The ink composition according to the embodiment of the present invention is preferably <5> An ink composition containing all of the mercapto-modified (meth)acrylate (a), the photopolymerization initiator (b), and the anthracene compound (c) is more preferred.

[0043] The ink composition may contain a colorant in addition to the mercapto-modified (meth)acrylate (a), the photopolymerization initiator (b), and the anthracene compound (c). From the viewpoint of applicability to a wide range of industrial fields, the ink composition preferably contains a colorant. Examples of colorants include pigments and dyes, such as phthalocyanine pigments used in cyan ink, quinacridone pigments used in magenta ink, azo pigments used in yellow ink, carbon black used in black ink, and white pigments that can be used in white ink.

[0044] Examples of phthalocyanine pigments used in cyan ink include CI Pigment Blue 1, 2, 3, 15:3, 15:4, 16:6, 16, 17:1, 75, and 79. Examples of quinacridone pigments used in magenta ink include CI Pigment Red 122, CI Pigment Red 202, CI Pigment Red 209, and CI Pigment Violet 19. Examples of azo pigments used in yellow ink include monoazo and disazo pigments such as CI Pigment Yellow 120, 151, 154, 175, 180, 181, 1, 65, 73, 74, 116, 12, 13, 17, 81, 83, 150, 155, 214, and 128.

[0045] Examples of carbon black used in black inks include Mitsubishi Chemical Corporation's No. 2300, No. 900, MCF88, No. 33, No. 40, No. 45, No. 52, MA7, MA8, MA11, MA100, and No. 2200B; Columbia Corporation's Raven 5750, 5250, 5000, 3500, 1255, and 700; Cabot Corporation's Regal 400R, 330R, 660R, Mogul L, 700, Monarch 800, 880, 900, 1000, 1100, 1300, and 1400; and Degussa's Color Black FW1, FW2, FW2V, FW18, and FW200, Color Black S150, S160, and S170. 35, 35 U, 35 V, 140U, Special Black 6, 5, 4A, 4, etc. The volume average particle size of the various pigments described above is preferably in the range of 10 to 300 nm, and more preferably 50 to 200 nm.

[0046] The white pigment usable in the white ink can be any known inorganic white pigment without any particular limitation. Examples of inorganic white pigments include alkaline earth metal sulfates or carbonates, silicas such as finely powdered silicic acid and synthetic silicates, calcium silicate, alumina, alumina hydrate, titanium oxide, zinc oxide, talc, clay, etc. The surface of the silicas, etc. may be treated by various surface treatment methods. When titanium oxide is used as the white pigment, its volume average particle size is preferably 100 to 500 nm, and more preferably 150 nm to 400 nm from the viewpoint of obtaining an ink with even better ejection stability and high color development of printed images.

[0047] To obtain sufficient image density and lightfastness of the printed image, the various pigments described above are preferably contained in the ink composition in an amount ranging from 1 to 20% by mass, more preferably from 1 to 10% by mass, and even more preferably from 1 to 5% by mass. Furthermore, the magenta ink preferably has a higher pigment concentration than the other color inks. Specifically, the pigment concentration is preferably at least 1.2 times, more preferably from 1.2 to 4 times, that of the other color inks.

[0048] The various pigments described above may be used in combination with pigment dispersants or pigment derivatives (synergists) to enhance dispersion stability in the ink composition, specifically, dispersion stability for the mercapto-modified (meth)acrylate (a), photopolymerization initiator (b), and anthracene compound (c). Examples of pigment dispersants include Ajinomoto Fine-Techno Co., Inc.'s Ajisper (Ajisper is a registered trademark) PB821, PB822, and PB824; Lubrizol's Solsperse (Solsperse is a registered trademark) 24000GR, 32000, 33000, and 39000; Kusumoto Chemicals Co., Ltd.'s Disparlon DA-703-50; and BASF's EFKA (EFKA is a registered trademark) PX4701 and PX4703. Examples of pigment derivatives include sulfonic acid derivatives of pigments.

[0049] The amount of pigment dispersant used is preferably in the range of 10 to 100% by mass relative to the pigment, and more preferably in the range of 20 to 60% by mass from the viewpoint of obtaining an ink with even better ejection stability and pigment dispersibility.

[0050] The ink composition may further contain a surfactant as a dispersant to improve dispersibility and ease of handling. Examples of surfactants include anionic surfactants such as dialkyl sulfosuccinates, alkyl naphthalene sulfonates, and fatty acid salts; nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, acetylene glycols, and polyoxyethylene-polyoxypropylene block copolymers; and cationic surfactants such as alkylamine salts and quaternary ammonium salts.

[0051] Furthermore, as the surfactant, a compound having a silicone chain, a silicone surfactant having a polyether chain at the side chain or end and a polysiloxane structure in the main chain, and a fluorine-based surfactant having a perfluoroalkyl chain, an oily fluorine-based compound (e.g., fluorine oil), and a solid fluorine compound resin (e.g., tetrafluoroethylene resin), which is preferably a hydrophobic organic fluoro compound, may be used. Examples of silicone surfactants and fluorine surfactants include BYK306, 307, 310, 313, 320, 331, 333, 350, 377, and 378 from BYK Chemie; Shin-Etsu Chemical's KF series and X-22 series, silicones with both ends of the X-21 series substituted with organic groups, silicones with one end substituted with an organic group, silicones with both side chain ends substituted with organic groups, and silicones with side chains substituted with organic groups; and DIC's Megafac F series. The content of the surfactant in the ink composition is preferably 0.05 to 1% by mass, and more preferably 0.1 to 0.8% by mass, of the total ink composition, from the viewpoints of ensuring ejection stability and setting the surface tension within a desired range.

[0052] In addition to the above-mentioned components, the ink composition may further contain, if necessary, a polymerization inhibitor such as hydroquinone, di-t-butylhydroquinone, p-methoxyphenol, benzoquinone, dibutylhydroxytoluene, nitrosamine salts, hindered amine compounds, 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), etc. When a polymerization inhibitor is contained, the amount thereof is preferably in the range of 0.01 to 2% by mass of the total amount of the ink composition.

[0053] The ink composition may contain additives such as ultraviolet absorbers, antioxidants, surface tension adjusters, fluorescent brightening agents, anti-fading agents, conductive salts, etc. Furthermore, from the viewpoint of further improving adhesion to substrates such as plastic substrates, the ink composition may contain non-reactive resins such as acrylic resins, epoxy resins, terpene phenol resins, and rosin esters.

[0054] The viscosity of the ink composition at 25° C. is preferably in the range of 3 to 30 mPa·s, and more preferably in the range of 5 to 20 mPa·s from the viewpoint of improving inkjet ejection stability.

[0055] The ink composition can be produced, for example, by dispersing the pigment in a mixture of the above-described mercapto-modified (meth)acrylate (a), a colorant such as a pigment, a pigment dispersant, and, if necessary, other polymerizable compounds using a conventional disperser such as a beads mill, and then adding the photopolymerization initiator (b) and the anthracene compound (c), and, if necessary, further adding optional additives such as a polymerization inhibitor and a surface tension adjuster, followed by stirring and dissolving. The present ink composition can also be produced by first producing a high-concentration pigment dispersion (mill base) containing a pigment, a pigment dispersant, a resin, and the like using a conventional dispersing machine such as a bead mill, and then supplying the above-mentioned mercapto-modified (meth)acrylate (a), photopolymerization initiator (b), anthracene compound (c), and optional additional components, followed by stirring and mixing. Here, as the dispersing machine, in addition to a bead mill, various known and commonly used dispersing machines such as an ultrasonic homogenizer, a high-pressure homogenizer, a paint shaker, a ball mill, a roll mill, a sand mill, a sand grinder, a Dyno Mill, a Dispermat, an SC Mill, and a Nanomizer can be used.

[0056] The ink composition is cured by irradiation with actinic radiation, preferably ultraviolet radiation, etc. As the light source for ultraviolet radiation, light sources typically used for actinic radiation-curable inkjet recording inks, such as metal halide lamps, xenon lamps, carbon arc lamps, chemical lamps, low-pressure mercury lamps, high-pressure mercury lamps, and UV-LED lamps, can be used. The ink composition has excellent curability when irradiated with light, particularly from a UV-LED lamp as a light source.

[0057] The ink composition can be suitably used for printing by an inkjet recording method using an inkjet recording apparatus. As the inkjet recording method, any of the conventionally known methods can be used, such as a method of ejecting droplets by utilizing the vibration of a piezoelectric element (a recording method using an inkjet head that forms ink droplets by the mechanical deformation of an electrostrictive element) or a method that utilizes thermal energy. The ink composition can be ejected onto a substrate, which is a recording medium, using an inkjet recording device and cured by irradiating with active energy rays to produce a printed material, such as an advertisement, a signboard, a guide board, or a promotional item. As mentioned above, this ink composition has excellent curing properties, particularly when exposed to light using a UV-LED lamp as a light source, and is suitable for mercury-free printing from an environmental perspective. The irradiation energy of UV-LED light is 50 to 1000 mJ / cm 2 The range is preferably 200 to 800 mJ / cm 2 The range is more preferable.

[0058] The ink composition can be easily printed on curved or irregularly shaped substrates. Examples of substrate materials include acrylonitrile-butadiene-styrene (ABS) resin, ABS-based polymer alloys such as polyvinyl chloride / ABS resin, polyamide / ABS resin, polycarbonate / ABS resin, and polybutylene terephthalate / ABS resin, and resins commonly used for injection molding, such as acrylonitrile-acrylic rubber-styrene resin, acrylonitrile-styrene resin, acrylonitrile-ethylene rubber-styrene resin, (meth)acrylate-styrene resin, polycarbonate resin, acrylic resin, methacrylic resin, and polypropylene resin.

[0059] Films can also be used as the substrate. Examples of films include thermoplastic resin films used for food packaging materials, such as polyethylene terephthalate (PET) film, polystyrene film, polyamide film, polyacrylonitrile film, polyolefin films such as polyethylene film (LLDPE: low-density polyethylene film, HDPE: high-density polyethylene film) and polypropylene film (CPP: unstretched polypropylene film, OPP: biaxially oriented polypropylene film), polyvinyl alcohol film, and ethylene-vinyl alcohol copolymer film. Films that have been stretched, such as uniaxially or biaxially stretched, or whose surfaces have been subjected to flame treatment or corona discharge treatment, can also be used. [Example]

[0060] EXAMPLES The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to these examples. The compounds used in the present examples are shown below.

[0061] <Pigments> C1: Fastogen Blue TGR (phthalocyanine pigment, CI Pigment Blue 15:4, manufactured by DIC) <Pigment dispersant> Solsperse 32000 (manufactured by Lubrizol)

[0062] <Mercapto-modified (meth)acrylate (a)> Miramer ES-110N: A mixture of pentaerythritol tetrakis(3-mercaptopropionate) and trimethylolpropane triacrylate (manufactured by MIWON) <Polymerizable compound> Miramer M222: Dipropylene glycol diacrylate (manufactured by MIWON) Miramer M3130: Trimethylolpropane ethylene oxide modified triacrylate (manufactured by MIWON) Miramer M240: (MIWON) V#200: Cyclic trimethylolpropane formal acrylate (Osaka Organic Chemical Industry Co., Ltd.) PO-A: Phenoxyethyl acrylate (Kyoeisha Chemical Co., Ltd.) V-Cap: N-vinylcaprolactam (Ashland) IBXA: Isobornyl acrylate (Osaka Organic Chemical Industry Co., Ltd.) <Additives (surfactants)> KF-54: Methylphenylpolysiloxane (Shin-Etsu Chemical Co., Ltd.)

[0063] <Photopolymerization initiator: acylphosphine compound (b-1)> Omnirad 819: Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (acylphosphine oxide; manufactured by IGM Resins BV) <Photopolymerization initiator: phosphinic acid ester compound (b-2)> Omnirad TPO-L: Ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate (phosphinic acid ester; manufactured by IGM Resins BV) SpeedCure Xkm: (3-benzoyl-2,4,6-trimethylbenzoyl)phenylphosphinate ethyl (phosphinate ester; manufactured by Lambson Japan) <Photopolymerization initiator> Kayacure DETX-S: 2,4-diethylthioxanthen-9-one (manufactured by Nippon Kayaku Co., Ltd.) <anthracene compound (c)> UVS-581: "Anthracure (registered trademark) UV-581", manufactured by Air Water Performance Chemicals Inc. UVS-1101: "Anthracure (registered trademark) UV-1101" manufactured by Air Water Performance Chemicals Inc. <Sensitizer> Kayacure EPA: Ethyl p-dimethylaminobenzoate (manufactured by Nippon Kayaku Co., Ltd.)

[0064] [Example of pigment dispersion preparation] 10 parts by mass of pigment (C1), 4.5 parts by mass of pigment dispersant (Solsperse 32000), and 85.5 parts by mass of PO-A were mixed, stirred with a mixer for 1 hour, and then treated with a bead mill for 2 hours to obtain pigment dispersion 1 used in each of the examples and comparative examples.

[0065] Examples 1 to 11, Comparative Examples 1 to 7 1. Preparation of Ink Composition According to the blending ratios shown in Tables 1 and 2, pigment dispersion 1 and each component were placed in a container and mixed with stirring to prepare ink compositions 1 to 18.

[0066] 2. Evaluation of ink composition 2-1. Curability The obtained ink composition was dropped onto a polycarbonate plate "Carboglass (registered trademark) Polish" (trade name, manufactured by AGC Corporation) and coated using a spin coater to a film thickness of 2 μm and a film thickness of 6 μm. Next, UV-LED light (emission wavelength: 395 nm, peak intensity: 1000 mW / cm) was applied using an LED irradiation device (manufactured by Hamamatsu Photonics) equipped with a stage movement device. 2 ) to cure the ink, and the cumulative amount of irradiation energy (mJ / cm) until the ink becomes tack-free. 2 ) was measured.

[0067] 2-2. Stability The resulting ink composition was placed in a plastic container and allowed to stand for 30 days at 60° C. The viscosity at 25° C. was measured before and after standing, and the rate of change in viscosity was calculated according to the following formula. Viscosity change rate (%) = 100 x [viscosity after leaving at 60°C for 30 days] / viscosity before leaving

[0068] The evaluation results are shown in Tables 1 and 2. From these results, it can be seen that an ink composition containing at least one photopolymerization initiator (b) selected from the group consisting of acylphosphine compounds (b-1) and phosphinic acid ester compounds (b-2), and containing one or more of mercapto-modified (meth)acrylate (a) or anthracene compound (c) as an essential component when the photopolymerization initiator (b) is the acylphosphine compound (b-1), or containing one or more of mercapto-modified (meth)acrylate (a), acylphosphine compound (b-1), or anthracene compound (c) as an essential component when the photopolymerization initiator (b) is the phosphinic acid ester compound (b-2), has improved UV sensitivity and a long integrated light intensity (mJ / cm) of irradiation energy until curing. 2 ) can be reduced, resulting in excellent curability, and the ink composition also has excellent storage stability. Preferably, when the ink composition contains all of the above-mentioned mercapto-modified (meth)acrylate (a), the acylphosphine compound (b-1) and the phosphinic acid ester compound (b-2) as the photopolymerization initiator (b), and the anthraquinone compound (c), the UV curability and storage stability are further improved (Example 11).

[0069] [Table 1]

[0070] [Table 2] [Industrial Applicability]

[0071] The actinic energy ray-curable ink composition of the present invention exhibits excellent curability even when irradiated with light from an LED light source and also exhibits excellent storage stability. Such ink composition is useful in a variety of applications, including printed matter, graphics fields such as signs, signboards, displays, card printing, and smartphone covers, as well as automotive interiors, home appliances, and membrane switches.

Claims

1. The following general formula (1) 【Chemistry 1】 (In the formula, R １ represents a hydrogen atom or an alkyl group, R ２ represents a hydrogen atom, an alkyl group, or an acyl group), and An actinic ray-curable inkjet ink composition comprising, as essential components, a cyclic monofunctional polymerizable compound containing cyclic trimethylolpropane formal acrylate and N-vinylcaprolactam as other polymerizable compounds in addition to the mercapto-modified (meth)acrylate (a).

2. one or more photopolymerization initiators (b) containing an acylphosphine compound (b-1); An actinic ray-curable inkjet ink composition comprising, as essential components, a cyclic monofunctional polymerizable compound containing cyclic trimethylolpropane formal acrylate and N-vinylcaprolactam as other polymerizable compounds in addition to the mercapto-modified (meth)acrylate (a).

3. 3. The actinic ray-curable inkjet ink composition according to claim 1, wherein the photopolymerization initiator (b) is contained in an amount of 0.1 to 15% by mass relative to the total mass of the composition.

4. 4. The actinic ray-curable inkjet ink composition according to claim 1, wherein the mercapto-modified (meth)acrylate (a) is contained in an amount of 0.1 to 25% by mass relative to the total mass of the composition.

5. The actinic ray-curable inkjet ink composition according to any one of claims 1 to 4, wherein the anthracene compound (c) is contained in an amount of 0.05 to 5% by mass relative to the total mass of the composition.

6. The actinic ray-curable inkjet ink composition according to claim 5 , comprising the photopolymerization initiator (b) and the anthracene compound (c).

7. 2. The actinic ray-curable inkjet ink composition according to claim 1, further comprising an acylphosphine compound (b-1) as the photopolymerization initiator (b).

8. The photopolymerization initiator (b) may be a compound represented by the following general formula (1): 【Chemistry 1】 (In the formula, R １ represents a hydrogen atom or an alkyl group, R ２ represents a hydrogen atom, an alkyl group, or an acyl group.

9. 9. The actinic ray-curable inkjet ink composition according to claim 1, wherein the cyclic monofunctional polymerizable compound is contained in an amount of 51.4 to 63.4% by mass relative to the total mass of the composition.

10. 10. The actinic ray-curable inkjet ink composition according to claim 1, wherein the other polymerizable compound is contained in an amount of 60.6 to 73.6% by mass relative to the total mass of the composition.

11. 9. The actinic ray-curable inkjet ink composition according to claim 1, wherein the photopolymerization initiator (b) comprises two or more types of the phosphinic acid ester-based compound (b-2).

12. The actinic ray-curable ink-jet ink composition according to any one of claims 1 to 11, which is an ultraviolet ray-curable ink-jet ink composition.

13. A method for producing a printed matter, comprising a step of ejecting the actinic energy ray-curable inkjet ink composition according to any one of claims 1 to 12 onto a recording medium and curing the ink by irradiating the ink with actinic energy rays.

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