Active energy ray-curable ink composition for inkjet printing

Abstract

The present invention is an active energy ray-curable ink composition for inkjet printing, which contains a photopolymerizable compound that contains (A) a hydroxyl group-containing polyfunctional monomer, (B) a monomer and / or oligomer having an amino group and / or an amide group, and (C) a monofunctional monomer other than (B), the ratio of the hydroxyl group-containing polyfunctional monomer is 2-20% by mass, and the ratio of the monofunctional monomer is 50% by mass or more. The active energy ray-curable ink composition for inkjet printing has excellent adhesion, bendability, extensibility, alcohol resistance, and printing image quality.

Description

Technical Field

[0001] This invention relates to an ink composition for inkjet printing that is cured by active energy rays. Background Technology

[0002] Previously, the following approach was proposed: in active energy ray curable inkjet printing inks, a larger amount of monofunctional monomers were formulated to improve adhesion to the substrate (for example, Patent Documents 1-3).

[0003] Background Technology Documents Patent documents Patent Document 1: International Publication No. 2007 / 055332 Patent Document 2: International Publication No. 2013 / 027672 Patent document 3: Japanese Patent Application Publication No. 2014-70135. Summary of the Invention

[0004] [The problem the invention aims to solve] While increasing the number of monofunctional monomers improves adhesion and elongation, it reduces resistance to solvents and inks. For example, in single-pass printing, a portion of the cured coating dissolves in the secondary ink, making it difficult for dots to spread on the coating and negatively impacting print quality. To achieve adequate image quality, more multifunctional monomers must be formulated; however, this reduces properties such as adhesion, making it difficult to balance image quality with adhesion and elongation.

[0005] Therefore, the objective of this invention is to provide an active energy ray curable ink composition for inkjet printing that exhibits excellent adhesion, flexibility, elongation, alcohol resistance, and print quality.

[0006] [Technical means to solve the problem] That is, the present invention is configured as follows.

[0007] [1] An active energy ray curable ink composition for inkjet printing, comprising a photopolymerizable compound, wherein the photopolymerizable compound comprises (A) a hydroxyl-containing polyfunctional monomer, (B) a monomer and / or oligomer having an amino and / or amide group, and (C) a monofunctional monomer other than (B), wherein the proportion of the hydroxyl-containing polyfunctional monomer in the photopolymerizable compound is 2% by mass or more and 20% by mass or less, and the proportion of the monofunctional monomer is 50% by mass or more.

[0008] [2] According to the active energy ray curable inkjet printing ink composition described in [1], wherein, preferably, the ratio of the monomers and / or oligomers having amino and / or amide groups in the photopolymerizable compound is 10% by mass or more and 40% by mass or less.

[0009] [3] The active energy ray curable inkjet printing ink composition described in [1] or [2] preferably contains polyfunctional monomers other than those described in (A) and (B), wherein the total ratio of the hydroxyl-containing polyfunctional monomer to the polyfunctional monomer in the photopolymerizable compound is 20% by mass or less.

[0010] [4] The active energy ray curable inkjet printing ink composition according to any one of [1] to [3], wherein preferably the monomer and / or oligomer having amino and / or amide groups contains acryloylmorpholine and / or N-vinylcaprolactam.

[0011] [5] According to the active energy ray curable inkjet printing ink composition described in [4], the monomer and / or oligomer having amino and / or amide groups preferably contain an acrylated amine compound having two photopolymerizable functional groups and two amino groups in the molecule.

[0012] [6] The active energy ray curable inkjet printing ink composition according to any one of [1] to [5], wherein preferably the total percentage of photopolymerizable compounds containing photopolymerizable compounds with a glass transition temperature of 10°C or less is 20% by mass or more.

[0013] [7] The active energy ray curable inkjet printing ink composition according to any one of [1] to [6] is preferably containing a colorant.

[0014] [The effects of the invention] The active energy ray curable ink composition for inkjet printing according to the present invention, by containing specific photopolymerizable components, exhibits excellent adhesion, flexibility, elongation, alcohol resistance, and print quality. Detailed Implementation

[0015] The active energy ray curable ink composition for inkjet printing (hereinafter also referred to as ink composition) of the present invention will be described in detail below.

[0016] The active energy ray curable ink composition for inkjet printing of the present invention contains a photopolymerizable compound, wherein the photopolymerizable compound contains (A) a hydroxyl-containing polyfunctional monomer, (B) a monomer and / or oligomer having an amino and / or amide group, and (C) a monofunctional monomer other than (B), wherein the proportion of the hydroxyl-containing polyfunctional monomer in the photopolymerizable compound is 2% by mass or more and 20% by mass or less, and the proportion of the monofunctional monomer is 50% by mass or more.

[0017] <(A) Hydroxyl-containing polyfunctional monomer> The hydroxyl-containing polyfunctional monomer only needs to have two or more photopolymerizable functional groups and hydroxyl groups within its molecule. Examples include: 2-hydroxy-3-methacryloylpropyl acrylate, glyceryl diacrylate, EO-modified diacrylate of isocyanuric acid, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, and tripentaerythritol penta(meth)acrylate. The hydroxyl-containing polyfunctional monomer can be used alone or in combination of two or more. Regarding adhesion, the hydroxyl-containing polyfunctional monomer is preferably one that has two photopolymerizable functional groups and a hydroxyl group within its molecule.

[0018] In the photopolymerizable compound, the proportion of the hydroxyl-containing polyfunctional monomer is 2% to 20% by mass. If the proportion of the hydroxyl-containing polyfunctional monomer in the photopolymerizable compound is less than 2% by mass, alcohol resistance and image quality (dot diameter) will decrease; if it is more than 20% by mass, adhesion, flexibility, and elongation will decrease. More preferably, the proportion of the hydroxyl-containing polyfunctional monomer in the photopolymerizable compound is 5% to 12% by mass.

[0019] <(B) Monomers and / or oligomers having amino and / or amide groups> Examples of monomers and / or oligomers having amino and / or amide groups include, for instance, various (meth)acrylamide monomers such as acrylamide and acryloylmorpholine, vinylamide monomers such as N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, N-vinylcaprolactam, N-vinylcarbazole, and vinylmethyloxazolidinone, as well as acrylated amine compounds with trade names “CN371”, “CN373”, “CN386”, “CN501”, “CN550”, and “CN551” (all manufactured by Sartoma). Among these, monomers having amino and / or amide groups are preferred, acryloylmorpholine and / or N-vinylcaprolactam are more preferred, and it is even more preferred that acrylated amine compounds having two photopolymerizable functional groups and two amino groups within the molecule are used in combination with acryloylmorpholine and / or N-vinylcaprolactam. The monomers and / or oligomers having amino and / or amide groups can be used alone or in combination of two or more.

[0020] The content of monomers and / or oligomers having amino and / or amide groups can be arbitrarily determined. From the viewpoint of curability, the ratio of monomers and / or oligomers having amino and / or amide groups in the photopolymerizable compound is preferably 10% by mass or more and 40% by mass or less, more preferably 15% by mass or more and 30% by mass or less. If the ratio of monomers and / or oligomers having amino and / or amide groups in the photopolymerizable compound is less than 10% by mass, then the curability and tackiness may decrease.

[0021] <(C) Monofunctional Monomer> As other than (B) described above (hereinafter also referred to as monofunctional monomers), any known monofunctional monomer used in ink compositions for active energy ray curable inkjet printing is acceptable. Examples include: butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, isomyristyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, isobornyl (meth)acrylate, lauryl (meth)acrylate. Cyclomethylolpropane acetal (meth)acrylate, cyclohexyl methacrylate, butylcyclohexyl acrylate, trimethylcyclohexyl acrylate, adamantyl methacrylate, dicyclopentyl methacrylate, dicyclopentenyl methacrylate acrylates, styrene, benzyl methacrylate, 2-phenoxyethyl methacrylate and its ethylene oxide modified derivatives, ethyl carbitol (meth)acrylate, 2-methoxyethyl acrylate, polyethylene glycol (meth)acrylate, isoamyl methacrylate, hydroxymethyl methacrylate, (methyl)methacrylate Hydroxyethyl acrylate, (meth)acrylate, hydroxypropyl acrylate, (meth)acrylate, hydroxybutyl acrylate, (meth)acrylate, hydroxyphenoxypropyl acrylate, 2-ethylhexyl-diethylene glycol (meth)acrylate, 2-acryloyloxyethyl hexahydrophthalic acid, butoxyethyl acrylate, ethoxydiethylene glycol (meth)acrylate, ethyl carbitol acrylate, methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypropylene glycol (meth)acrylate, tetrahydrofurfuryl acrylate, (meth)acrylate (2-methyl-2-ethyl- 1,3-Dioxacyclopentan-4-yl)methyl acrylate, (3-ethyloxacyclobutan-3-yl)methyl methacrylate, phenol glycol-modified acrylates, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-acryloyloxyethyl succinate, 2-acryloyloxyethyl phthalate, 2-acryloyloxyethyl-2-hydroxyethyl phthalate, lactone-modified flexible acrylates, tert-butylcyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl acrylate, ethyleneoxyethoxyethyl (meth)acrylate, etc. The monofunctional monomers can be used alone or in combination of two or more.

[0022] In the photopolymerizable compound, the proportion of the monofunctional monomer is 50% by mass or more. From the viewpoint of flexibility or elongation, the proportion of the monofunctional monomer in the photopolymerizable compound is preferably 50% by mass or more and 90% by mass or less, more preferably 60% by mass or more and 85% by mass or less.

[0023] <Multifunctional monomers other than (A) and (B)> Examples of polyfunctional monomers other than (A) and (B) described above (hereinafter also referred to as polyfunctional monomers) include known polyfunctional (meth)acrylate compounds having two or more vinyl unsaturated bonds, such as the following polyfunctional (meth)acrylate compounds or (meth)acrylate compounds containing vinyl ether groups. These polyfunctional monomers may be used alone or in combination of two or more.

[0024] Examples of polyfunctional (meth)acrylate compounds include: ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, propylene glycol dimethacrylate, dipropylene glycol dimethacrylate, tripropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, butanediol dimethacrylate, pentylene glycol dimethacrylate, neopentylene glycol dimethacrylate, and hydroxyneopentyl hydroxyneopentyl ester dimethacrylate. Hydroxypentanoyl hydroxypentanoate dicaprolactone di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,2-hexanediol di(meth)acrylate, 1,5-hexanediol di(meth)acrylate, 2,5-hexanediol di(meth)acrylate, 1,7-heptanediol di(meth)acrylate, 1,8-octanediol di(meth)acrylate, 1,2-octanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,2-decanediol di(meth)acrylate Ester, 1,12-dodecanediol di(meth)acrylate, 1,2-dodecanediol di(meth)acrylate, 1,14-tetradecanediol di(meth)acrylate, 1,2-tetradecanediol di(meth)acrylate, 1,16-hexadecanediol di(meth)acrylate, 1,2-hexadecanediol di(meth)acrylate, 2-methyl-2,4-pentanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 2-methyl-2-propyl-1,3-propanediol di(meth)acrylate, 2,4- Dimethyl-2,4-pentanediol di(meth)acrylate, 2,2-diethyl-1,3-propanediol di(meth)acrylate, 2,2,4-trimethyl-1,3-pentanediol di(meth)acrylate, dimethylol octane di(meth)acrylate, 2-ethyl-1,3-hexanediol di(meth)acrylate, 2,5-dimethyl-2,5-hexanediol di(meth)acrylate, 2-methyl-1,8-octanediol di(meth)acrylate, 2-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, 2,4-diethyl-1,5-Pentanediol di(meth)acrylate, tricyclodecane dihydroxymethyl di(meth)acrylate, tricyclodecane dihydroxymethyl dicaprolactone di(meth)acrylate, cyclohexanediethanol di(meth)acrylate, dicyclopentyl di(meth)acrylate, bisphenol A tetraethylene oxide adduct di(meth)acrylate, bisphenol F tetraethylene oxide adduct di(meth)acrylate, bisphenol S tetraethylene oxide adduct di(meth)acrylate, hydrogenated bisphenol A tetraethylene oxide adduct di(meth)acrylate, hydrogenated bisphenol F tetraethylene oxide adduct di(meth)acrylate Acrylates, hydrogenated bisphenol A di(meth)acrylate, hydrogenated bisphenol F di(meth)acrylate, bisphenol A tetraethylene oxide adduct dicaprolactone di(meth)acrylate, bisphenol F tetraethylene oxide adduct dicaprolactone di(meth)acrylate, etc., di(meth)acrylates of polyols such as glycerol, pentaerythritol, diglycerol, dimethylolpropane and dipentaerythritol, etc., difunctional monomers, glycerol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane tricaprolactone tri(meth)acrylate, trimethylolpropane Trifunctional monomers such as tri(meth)acrylate, trimethylolhexane tri(meth)acrylate, and trimethyloloctane tri(meth)acrylate; and their 3EO (ethylene oxide) modified, 6EO modified, and 9EO modified (3EO modified trimethylolpropane tri(meth)acrylate, 3EO modified trimethylolethane tri(meth)acrylate, 3EO modified trimethylolhexane tri(meth)acrylate, etc.), trimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, and pentaerythritol tetracaprolactone tetra(meth)acrylate. Monomers with four or more functionalities include acrylates, diglycerides tetra(meth)acrylates, di-trimethylolpropane tetra(meth)acrylates, di-trimethylolpropane tetracaprolactone tetra(meth)acrylates, di-trimethylolethane tetra(meth)acrylates, di-trimethylolbutane tetra(meth)acrylates, di-trimethylolhexane tetra(meth)acrylates, di-trimethyloloctane tetra(meth)acrylates, dipentaerythritol hexa(meth)acrylates, tripentaerythritol octa(meth)acrylates, and tripentaerythritol polyepoxide hepta(meth)acrylates. Among these, preferred examples include trimethylolpropane triacrylate (TMPTA; trifunctional), di-trimethylolpropane tetraacrylate (DITMPTA; tetrafunctional), dipentaerythritol hexaacrylate (DPHA; hexafunctional), and hexanediol diacrylate (HDDA; difunctional).

[0025] Examples of (meth)acrylate compounds containing an vinyl ether group include, for example: 2-ethoxyethyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 1-methyl-2-ethoxyethyl (meth)acrylate, 2-ethoxypropyl (meth)acrylate, 4-ethoxybutyl (meth)acrylate, 1-methyl-3-ethoxypropyl (meth)acrylate, 1-ethoxymethylpropyl (meth)acrylate, 2-methyl-3-ethoxypropyl (meth)acrylate, 3-methyl-3-ethoxypropyl (meth)acrylate, 1,1-dimethyl-2-ethoxyethyl (meth)acrylate, 3-ethoxybutyl (meth)acrylate, 1-methyl-2-ethoxypropyl (meth)acrylate, 2-ethoxybutyl (meth)acrylate, 4-ethoxycyclohexyl (meth)acrylate, 5-ethoxypentyl (meth)acrylate, 6-ethoxyhexyl (meth)acrylate, and so on. 4-Ethyloxymethylcyclohexyl acrylate, 3-Ethyloxymethylcyclohexyl acrylate, 2-Ethyloxymethylcyclohexyl acrylate, p-Ethyloxymethylphenyl acrylate, m-Ethyloxymethylphenyl acrylate, o-Ethyloxymethylphenyl acrylate, 2-(Ethyloxyisopropoxy)ethyl acrylate, 2-(Ethyloxyethoxy)propyl acrylate, (methyl) 2-(vinyloxyethoxy)isopropyl acrylate, 2-(vinyloxyisopropoxy)propyl acrylate, 2-(vinyloxyisopropoxy)isopropyl acrylate, 2-(vinyloxyethoxyethoxy)ethyl acrylate, 2-(vinyloxyethoxyisopropoxy)ethyl acrylate, 2-(vinyloxyisopropoxyethoxy)ethyl acrylate, 2-(vinyloxyisopropoxyethoxy)ethyl acrylate, etc.

[0026] When using the multifunctional monomer, the proportion of the multifunctional monomer in the photopolymerizable compound is preferably 5% by mass or less, more preferably 3% by mass or less. Furthermore, when using the multifunctional monomer, the total proportion of the (A) hydroxyl-containing multifunctional monomer to the multifunctional monomer in the photopolymerizable compound is preferably 2% by mass or more and 20% by mass or less.

[0027] From the viewpoint of flexibility or elongation, in the ink composition, the total percentage of photopolymerizable compounds with a glass transition temperature of 10°C or less included in the photopolymerizable compound is preferably 20% by mass or more and 60% by mass or less, more preferably 25% by mass or more and 50% by mass or less. Examples of photopolymerizable compounds with a glass transition temperature of 10°C or less include: methyl acrylate, ethyl acrylate, n-butyl acrylate, n-hexyl methacrylate, 2-ethylhexyl (meth)acrylate, isononyl acrylate, tetrahydrofurfuryl (meth)acrylate, isooctyl (meth)acrylate, isoamyl acrylate, isomyristyl acrylate, lauryl acrylate, benzyl acrylate, phenoxyethyl acrylate, ethyl carbitol acrylate, etc. In addition, examples of multifunctional monomers and / or multifunctional oligomers with a glass transition temperature of 10°C or below include: polyethylene glycol (400) diacrylate, polyethylene glycol (600) diacrylate, alkylhexanediol diacrylate, ethoxylated (30) bisphenol A diacrylate, alkylhexanediol diacrylate, ethoxylated (3) trimethylolpropane triacrylate, ethoxylated (6) trimethylolpropane triacrylate, ethoxylated (9) trimethylolpropane triacrylate, propoxylated (3) trimethylolpropane triacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol (600) dimethacrylate, ethoxylated (10) bisphenol A dimethacrylate, 1,12-dodecanediol dimethacrylate, urethane acrylate oligomers, polyester acrylate oligomers, etc.

[0028] <Photopolymerization Initiator> The ink composition may contain a photopolymerization initiator. Furthermore, when using an electron beam as an active energy ray, it may or may not contain a photopolymerization initiator. The photopolymerization initiator may be used alone or in combination of two or more types.

[0029] Examples of photopolymerization initiators include, for instance, bis-2,6-dimethoxybenzoyl-2,4,4-trimethylpentylphosphine oxide, 2,4,6-trimethylbenzyl-diphenylphosphine oxide (TPO), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, or SB-PI719), ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide (TPOL), and other acylphosphine oxide-based polymerization initiators; -Hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propanoyl)-benzyl]-phenyl}-2-methyl-propane-1-one (Omnirad 127), 2-hydroxy-4'-hydroxyethoxy-2-methylphenylacetone (Omnirad 2959), 1-hydroxycyclohexylphenyl ketone (Omnirad 184), oligomeric {2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]acetone} (ESACURE) ONE), 2-hydroxy-2-methyl-1-phenylpropane-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, bis[4-(2-hydroxy-2-methylpropanoyl)phenyl] ether (KIP160) and other α-hydroxy ketone polymerization initiators; benzophenone compounds (4,4'-diethylaminobenzophenone, etc.), 2-methyl-1-(4-methylthio)phenyl-2-morpholinylpropane-1-one, 4'-(methylthio)-α-morpholinyl- α-Methylacetone, phenylthio compounds (4-benzoyl-4'-methyldiphenyl sulfide), thioxanthone compounds (2,4-diethylthioxanthone, 1-chloro-4-propoxythioxanthone, isopropylthioxanthone), 2,2-dimethyl-2-hydroxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-benzyl-2-dimethylamino-1-(morpholinylphenyl)-butane-1-one, 4-benzoyl-4'-methyldiphenyl sulfide, ethyl milchlerone, polymer-type initiators (Omnipol TP, Omnipol BP), 1-[4-(4-benzoylphenyl mercapto)phenyl]-2-methyl-2-(4-methylphenylsulfonyl)propane-1-one (ESACURE1001M).

[0030] The content of the photopolymerization initiator is not particularly limited. For example, when using ultraviolet (UV) light or ultraviolet light-emitting diodes (LEDs) as the light source, the content of the photopolymerization initiator in the ink composition is preferably 3% by mass or more, more preferably 4% by mass or more. Furthermore, the content of the photopolymerization initiator in the ink composition is preferably 25% by mass or less, more preferably 15% by mass or less. By keeping the content of the photopolymerization initiator within these ranges, the ink composition can possess sufficient curability, internal curing properties, and low cost.

[0031] <Sensitizer> To promote curability under ultraviolet light using light-emitting diodes (LEDs) as a light source, the ink composition may further incorporate a photosensitizer (compound) and a polymerization initiator. This photosensitizer (compound) possesses light absorption characteristics in a wavelength region primarily composed of ultraviolet light above 400 nm, and exhibits a sensitizing function for the curing reaction when light passes through this wavelength range. Furthermore, the phrase "exhibits a sensitizing function when light passes through wavelengths above 400 nm" refers to having light absorption characteristics in a wavelength region above 400 nm. By using such a sensitizer, the ink composition of the present invention can promote LED curability.

[0032] Examples of anthracene sensitizers include, for example, anthracene-based sensitizers such as 9,10-dibutoxyanthracene, 9,10-diethoxyanthracene, 9,10-dipropoxyanthracene, and 9,10-bis(2-ethylhexyloxy)anthracene; and thioxanthone-based sensitizers such as 4-isopropylthioxanthone, with thioxanthone-based sensitizers being preferred. Representative commercially available examples include anthracene-based sensitizers with trade names such as "DBA" and "DEA" (manufactured by Kawasaki Chemical Industry Co., Ltd.), and thioxanthone-based sensitizers with trade names such as "DETX," "ITX," "CPTX" (manufactured by Lambson Corporation), and "Omnipol TX" (manufactured by IGM Corporation). These sensitizers can be used alone or in combination of two or more.

[0033] In the ink composition, the content of the sensitizer is preferably 0-8% by mass. Even if it exceeds 8% by mass, the effect will not be improved, which is considered excessive addition and is not ideal.

[0034] Furthermore, when using thioxanthone-based sensitizers, there is a tendency for the ink composition for reactive energy radiation-cured inkjet printing to turn yellow, resulting in a yellowish hue compared to the original hue based on pigments, etc. Therefore, it is preferable to appropriately determine the content of the thioxanthone-based sensitizer for each color. Specifically, in white ink compositions and transparent ink compositions that are easily affected by hue changes, it is preferable not to include thioxanthone-based compounds as sensitizers. In addition, in magenta ink compositions and cyan ink compositions, hue changes can become a problem, so it is preferable to use them within a range where hue will not cause problems. Furthermore, in black ink compositions and yellow ink compositions, even if discoloration occurs, it will not affect the hue, and the reactive energy radiation polymerization is weaker than that of other hues, so it is preferable to use thioxanthone-based compounds as sensitizers.

[0035] <Coloring agent> The ink composition may also contain colorants of various hues, thereby obtaining ink compositions of various colors. There are no particular limitations on such colorants; pigments and dyes conventionally used in commonly used light-curing inkjet printing ink compositions can be used. Considering lightfastness, organic or inorganic pigments are preferred.

[0036] Examples of organic pigments include, for example, dye lake pigments, azo-based, benzimidazolone-based, phthalocyanine-based, quinacridone-based, anthraquinone-based, dioxazine-based, indigo-based, thioindigo-based, dinaphthalene-based, pyrene-based, diketopyrrolopyrrole-based, isoindolinone-based, nitro-based, nitroso-based, flavonoid-based, quinophthalone-based, pinantrone-based, and indanthrene-based pigments. Examples of inorganic pigments include, for example, carbon black, titanium dioxide, iron oxide, graphite, iron black, chromium oxide green, and aluminum hydroxide.

[0037] In addition, the following pigments can be cited as specific examples of pigments representing various hues.

[0038] Examples of yellow pigments used in yellow ink compositions include, for example, CI Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 42, 73, 74, 75, 81, 83, 87, 93, 95, 97, 98, 108, 109, 114, 120, 128, 129, 138, 139, 150, 151, 155, 166, 180, 184, 185, 213, etc., with CI Pigment Yellow 150, 155, 180, 213 being more preferred.

[0039] Examples of magenta pigments used in magenta ink compositions include, for example, CI Pigment Red 5, 7, 12, 22, 38, 48:1, 48:2, 48:4, 49:1, 53:1, 57, 57:1, 63:1, 101, 102, 112, 122, 123, 144, 146, 149, 168, 177, 178, 179, 180, 184, 185, 190, 202, 209, 224, 242, 254, 255, 270, and CI Pigment Violet 19, with CI Pigment Red 122, 202, and Pigment Violet 19 being preferred examples.

[0040] Examples of cyan pigments used in cyan ink compositions include, for example, CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 18, 22, 27, 29, 60, etc., with CI Pigment Blue 15:4 being a preferred example.

[0041] Examples of black pigments used in black ink compositions include, for example, carbon black (CI Pigment Black 7).

[0042] As a white pigment used in white ink compositions, examples include titanium oxide, aluminum oxide, etc., and titanium oxide that has been surface-treated with various materials such as aluminum oxide and silicon dioxide is preferred.

[0043] The pigment content in the ink composition is preferably 1 to 20% by mass relative to the total amount of the ink composition. If the pigment content is less than 1% by mass, there is a tendency for the image quality of the obtained printed matter to decrease. On the other hand, if it exceeds 20% by mass, there is a tendency for it to adversely affect the viscosity characteristics of the ink composition.

[0044] <Pigment Dispersant> The ink composition may also contain a pigment dispersant as needed. The pigment dispersant is used to improve the dispersibility of the pigment and the storage stability of the ink composition. Conventional pigment dispersants can be used without particular limitation, but polymeric dispersants are preferred. Examples of pigment dispersants include, for instance, carbodiimide-based dispersants, polyester amine-based dispersants, fatty acid amine-based dispersants, modified polyacrylate-based dispersants, modified polyurethane-based dispersants, multi-chain polymeric nonionic dispersants, and polymeric ionic surfactants. The pigment dispersant can be used alone or in combination of two or more.

[0045] When the total amount of pigment used is set to 100 parts by weight, it is preferable to contain 1 to 200 parts by weight of the pigment dispersant. If the content of the pigment dispersant is less than 1 part by weight, the pigment dispersibility and the storage stability of the ink composition may decrease. On the other hand, it may contain more than 200 parts by weight, but the effect may not be different. A more preferred lower limit for the content of the pigment dispersant is 5 parts by weight, and a more preferred upper limit is 60 parts by weight.

[0046] <Other Ingredients> To achieve various functionalities as needed, a variety of additives can be added to the ink composition. Specifically, it may also contain surfactants, organic solvents, polymerization inhibitors, light stabilizers, surface treatment agents, UV absorbers, antioxidants, defoamers, mildew inhibitors, rust inhibitors, thickeners, humectants, pH adjusters, and other additives. Additionally, a resin that functions as a medium but does not cure may be formulated, or it may not be formulated.

[0047] <Surfactant (homogenizer)> The surfactant (homogenizer) is not particularly limited. Examples include nonionic surfactants, cationic surfactants, anionic surfactants, and betaine surfactants. More specifically, examples of surfactants include silicone surfactants such as polyether-modified silicone oil, polyester-modified polydimethylsiloxane, and polyester-modified methylalkyl polysiloxane, as well as fluorinated surfactants and acetylene surfactants.

[0048] Examples of silicone surfactants include: BYK-307, BYK-315N, BYK-331, BYK-333, BYK-347, BYK-348, BYK-349, BYK-345, BYK-377, BYK-378, and BYK-3455 (manufactured by BYK-Chemie).

[0049] Examples of fluorinated surfactants include: F-410, F-444, F-553 (manufactured by DIC), FS-65, FS-34, FS-35, FS-31, and FS-30 (manufactured by DuPont).

[0050] Examples of acetylene-based surfactants include: DYNOL 607, DYNOL 609, Olfine E1004, Olfine E1010, Olfine E1020, Olfine PD-001, Olfine PD-002W, Olfine PD-004, Olfine PD-005, Olfine EXP.4001, Olfine EXP.4200, Olfine EXP.4123, Olfine EXP.4300 (manufactured by Nissin Chemical Industry Co., Ltd.), Surfynol 104 E, Surfynol 104 H, Surfynol 104 A, Surfynol 104 BC, Surfynol 104 DPM, Surfynol 104 PA, Surfynol 104 PG-50, and Surfynol... 420, Surfynol 440, Surfynol 465 (manufactured by EVONIK), etc.

[0051] When formulating the surfactant, the content of the surfactant is not particularly limited. For example, in terms of improving the ejection stability of the ink composition from the inkjet head, the content of the surfactant in the ink composition is preferably 0.005% by mass or more, more preferably 0.01% by mass or more. Furthermore, the content of the surfactant in the ink composition is preferably 1.5% by mass or less, more preferably 1% by mass or less.

[0052] <Organic Solvents> The organic solvent is not particularly limited, and examples include ester-based organic solvents, ether-based organic solvents, ether-ester-based organic solvents, ketone-based organic solvents, aromatic hydrocarbon solvents, and nitrogen-containing organic solvents. When an organic solvent is incorporated, the content of the organic solvent is not particularly limited; for example, in the ink composition, it is preferably 5% by mass or less, more preferably 2% by mass or less.

[0053] <Polymerization Inhibitor> The polymerization inhibitor is not particularly limited. For example, hindered amines such as N-CH3 type, NH type, and N-OR type, as well as phenolic, amine, sulfur-based, and phosphorus-based polymerization inhibitors can be cited.

[0054] <Ultraviolet Absorber> Examples of such ultraviolet absorbers include: benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, salicylates-based ultraviolet absorbers, hydroxyphenyltriazine-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, nickel complex salt-based ultraviolet absorbers, etc.

[0055] <Antioxidants> Examples of antioxidants include phenolic antioxidants, amine antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants.

[0056] <Defoamer> Examples of defoamers include silicone-based defoamers and Pronic (registered trademark)-based defoamers.

[0057] <Preparation of Ink Compositions> There are no particular limitations on the method for preparing the ink composition. All the materials can be added and mixed using a bead mill or a three-roll mill. Alternatively, a concentrated liquid-based ink can be obtained in advance by mixing pigments, pigment dispersants, and photopolymerizable compounds. Photopolymerizable compounds, photopolymerization initiators, and surfactants, etc., added to this concentrated liquid-based ink in a manner that forms the desired ink composition, can then be used to prepare the ink.

[0058] As a substrate for printing the ink composition, a substrate made of materials such as flooring, acrylic, vinyl chloride, polyethylene terephthalate, or polycarbonate is preferred. However, as long as it is a substrate conventionally used for printing photocurable inkjet printing ink compositions (paper, plastic film, capsule, gel, metal foil, glass, cloth, etc.), printing can be performed without any problems.

[0059] Specifically, a method for printing and curing the ink composition can be exemplified as follows: the ink composition is sprayed onto a substrate using a low-viscosity inkjet head, and then the coating of the ink composition of the present invention sprayed onto the substrate is exposed to light to cure it. For example, the spraying onto the substrate (image printing) can be performed by supplying the ink composition to a corresponding low-viscosity printhead of an inkjet printer, and spraying the ink composition from the printhead onto the substrate with a coating thickness of, for example, 1 to 60 μm. Furthermore, the exposure and curing using light (image curing) can be performed by irradiating the coating of the ink composition applied to the substrate in the form of an image with light.

[0060] As an inkjet recording printing apparatus for printing the ink composition, an inkjet recording printing apparatus equipped with an inkjet head can be used. Furthermore, when using a continuous inkjet recording printing apparatus, a conductivity-imparting agent is added to the ink composition to adjust the conductivity.

[0061] Examples of light sources for curing the coating include ultraviolet (UV), ultraviolet light (LED), electron beams, and visible light. From an environmental perspective, LEDs that produce ultraviolet light with a peak emission wavelength in the range of 350–420 nm and electron beams are preferred. Ultraviolet light using an LED as the light source is defined as "light irradiated from an LED that produces ultraviolet light with a peak emission wavelength in the range of 350–420 nm."

[0062] Example The present invention will now be described in more detail through examples. The present invention is not limited to these examples.

[0063] The following shows the raw materials used.

[0064] <(A) Hydroxyl-containing polyfunctional monomer> 2-Hydroxy-3-methacryloylpropyl acrylate: Manufactured by Shin-Nakamura Chemical Co., Ltd. Glyceryl diacrylate: Manufactured by Dong-A Synthetic Co., Ltd. Isocyanuric acid EO-modified diacrylate: Manufactured by Dong-A Synthetic Co., Ltd. <(B) Monomers and / or oligomers having amino and / or amide groups> Acryloylmorpholine: ACMO, manufactured by KJ Chemicals. Vinylcaprolactam: VCAP, manufactured by ISP Japan. Amine-modified oligomers: Acrylated amine compounds with two photopolymerizable functional groups and two amino groups within the molecule. CN371NS: Manufactured by Sartoma. <(C) Monofunctional monomers other than those described in (B)> Benzyl acrylate: Miramer M1182HP, manufactured by MIWON, glass transition temperature 6°C Phenoxyethyl acrylate: Miramer M140, manufactured by MIWON, glass transition temperature 5°C Ethyl carbitol acrylate: Viscoat #190, manufactured by Osaka Organic Chemicals Co., Ltd., glass transition temperature -67°C Isobornyl acrylate: IBXA, manufactured by Osaka Organic Chemicals Co., Ltd., glass transition temperature 88°C <Multifunctional monomers other than (A) and (B)> 1,6-Hexanediol diacrylate: SR238NS, manufactured by Sartoma 3-Methyl-1,5-pentanediol diacrylate: SR341, manufactured by Sartoma <Photopolymerization Initiator> TPO: 2,4,6-Trimethylbenzoyl-diphenylphosphine oxide, manufactured by Lambson. <Sensitizer> DETX: 2,4-Diethylthioxanthone, manufactured by Lambson Company <Polymerization Inhibitor> MEHQ: Hydroquinone Monomethyl Ether <Surfactant (homogenizer)> BYK-315N: Silicone-based surface conditioner, 100% solids, manufactured by BYK-Chemie. <Coloring agent> PB15:4 PR122 PY150 PBk7 <Pigment Dispersant> Dispersant 1: SS32000, manufactured by Lubrizol Corporation, Japan Dispersant 2: PB821: Manufactured by Ajinomoto Fine-Techno Co., Ltd. <Substrate> Acrylic resin board (Acrylite L·S manufactured by Mitsubishi Chemical Co.) PVC sheet (T938 manufactured by CITakiron) PVC80 (manufactured by Lindeco) <Preparation of ink compositions for inkjet printing that are cured by active energy rays> Using an Eiger mill (using 0.5 mm diameter zirconia beads as the medium), a mixture of raw materials, excluding the photopolymerization initiator, sensitizer, polymerization inhibitor, and homogenizer, was dispersed according to the formulation (mass %) shown in Table 1 to obtain a concentrated liquid base. Using the obtained concentrated liquid base, the photopolymerization initiator, sensitizer, polymerization inhibitor, and homogenizer were formulated according to the formulation (mass %) shown in Table 1 to obtain the active energy radiation curable inkjet printing ink compositions of Examples 1-12 and Comparative Examples 1-6.

[0065] <Evaluation of Printed Materials> Using the active energy radiation-curable ink compositions for inkjet printing from Examples 1-12 and Comparative Examples 1-6, the substrate adhesion, flexibility, elongation, alcohol resistance, and image quality (dot diameter) of the ink compositions were evaluated according to the following evaluation methods and criteria. The results are shown in Table 1. Furthermore, the printing conditions were as follows: printing on a substrate using a single-pass printer (head: Ricoh M5320), followed by LED irradiation (irradiation energy 500 mJ) for curing.

[0066] <Substrate Adhesion> The cured coatings of various ink compositions printed on an acrylic resin board (Acrylite L·S manufactured by Mitsubishi Chemical Co., Ltd.) were cross-cut using a cutting blade. Transparent tape (product name: Sellotape (registered trademark), manufactured by Mitsubishi Chemical Co., Ltd.) was applied to the cut portions and then peeled off. The degree of peeling of the cured coatings was then evaluated according to the following criteria.

[0067] [Evaluation Criteria] 5: Coating peeling rate is less than 5%. 4. The peeling rate of the coating is 5% or more but less than 15%. 3: The peeling rate of the coating is more than 15% but less than 35%. 2: The peeling rate of the coating is above 35% but less than 65%. 1: Coating peeling exceeds 65% A relative evaluation of 5 to 1 is given visually in the form described above.

[0068] Set 5 or 4 as the passing standard.

[0069] <Flexibility> The cracks in the cured coating of each ink composition printed on a PVC board (T938 manufactured by CITakiron) were visually observed when bent to 180°C, and evaluated using the following criteria.

[0070] 5. The coating is free of cracks. 4: Cracks occur in less than 10% of the entire bending area. 3: Cracks occur in 10% to 30% of the entire bending area. 2: Cracks occur in 30% to 50% of the entire bending area. 1. Cracks appeared in more than 50% of the bending area. A relative evaluation of 5 to 1 is given visually in the form described above.

[0071] Set 5 or 4 as the passing standard.

[0072] <Extensibility> The cured coatings of each ink composition printed on a PVC board (T938 manufactured by CITakiron) were cut into 2 cm × 5 cm pieces to visually observe the cracks in the coating when it was extended to 100%, and evaluated according to the following criteria.

[0073] [Evaluation Criteria] 5. No cracks in the coating under 100% elongation. 4: Cracks form at an extension rate of 75% to less than 100%. 3: Cracks form when the extension is between 50% and 75%. 2: Cracks occur when the extension is between 25% and 50%. 1: Cracks occur at an elongation of less than 25%. A relative evaluation of 5 to 1 is given visually in the form described above.

[0074] Set 5 or 4 as the passing standard.

[0075] <Alcohol Resistance> For each ink composition cured coating printed on a PVC board (T938 manufactured by CITakiron), the coating was rubbed 10 times with a cotton swab containing 50% ethanol to visually observe the coating peeling at this time, and evaluated according to the following criteria.

[0076] [Evaluation Criteria] 5: Even after rubbing with a cotton swab 10 times, the coating did not peel off. 4: The coating peeled off after rubbing with a cotton swab 8 or 9 times. 3: The coating peeled off after rubbing with a cotton swab 6 or 7 times. 2: The coating peeled off after rubbing with a cotton swab 4 or 5 times. 1: The coating peeled off after rubbing with a cotton swab 2 or 3 times. A relative evaluation of 5 to 1 is given visually in the form described above.

[0077] Set 5 or 4 as the passing standard.

[0078] <Image Quality (Pixel Diameter)> The same ink compositions were printed at a low print rate onto coatings of various ink compositions printed on PVC80 (manufactured by Lintec Corporation). Using a UV-LED lamp manufactured by Phoseon Technology, at a distance of 2 cm between the lamp and the ink coating surface, a cumulative UV light intensity of 180 mJ / cm² was achieved. 2 The coating was then cured. The surface of the coating was observed using a microscope manufactured by Keyence, and the diameter of the printed dots was measured.

[0079] [Evaluation Criteria] 5: Dot diameter is 75 μm or larger 4: Dot diameter is 70 μm or larger and less than 75 μm 3: Dot diameter is 65 μm or larger and less than 70 μm 2: Dot diameter is 60 μm or larger and less than 65 μm 1: Dot diameter less than 60 μm Set 5 or 4 as the passing standard.

[0080] [Table 1]

Claims

1. An active energy ray-curable ink composition for inkjet printing, comprising a photopolymerizable compound. The photopolymerizable compound contains (A) a hydroxyl-containing polyfunctional monomer, (B) a monomer and / or oligomer having amino and / or amide groups, and (C) a monofunctional monomer other than (B). In the photopolymerizable compound, the proportion of the hydroxyl-containing polyfunctional monomer is more than 2% by mass and less than 20% by mass, and the proportion of the monofunctional monomer is more than 50% by mass.

2. The active energy ray curable ink composition for inkjet printing according to claim 1, wherein, In the photopolymerizable compound, the ratio of monomers and / or oligomers having amino and / or amide groups is more than 10% by mass and less than 40% by mass.

3. The active energy ray curable inkjet printing ink composition according to claim 1 or 2, comprising multifunctional monomers other than those described in (A) and (B). In the photopolymerizable compound, the total ratio of the hydroxyl-containing polyfunctional monomer to the polyfunctional monomer is less than 20% by mass.

4. The active energy ray curable ink composition for inkjet printing according to claim 1 or 2, wherein, The monomers and / or oligomers having amino and / or amide groups contain acryloylmorpholine and / or N-vinylcaprolactam.

5. The active energy ray curable ink composition for inkjet printing according to claim 4, wherein, The monomers and / or oligomers having amino and / or amide groups contain acrylated amine compounds having two photopolymerizable functional groups and two amino groups within the molecule.

6. The active energy ray curable ink composition for inkjet printing according to claim 1 or 2, wherein, The total percentage of photopolymerizable compounds containing photopolymerizable compounds with a glass transition temperature of 10°C or less is 20% by mass or more.

7. The active energy ray curable ink composition for inkjet printing according to claim 1 or 2, wherein it contains a colorant.

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