Actinic radiation curable ink composition for inkjet printing

Abstract

This actinic radiation curable ink composition is for inkjet printing, and comprises a photopolymerizable compound. The photopolymerizable compound contains (A) a hydroxy 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 proportion of the hydroxy group-containing polyfunctional monomer in the photopolymerizable compound is 2-20 mass%. The proportion of the monofunctional monomer in the photopolymerizable compound is at least 50 mass%. The actinic radiation curable ink composition for inkjet printing has excellent adhesiveness, flexibility, stretchability, alcohol resistance, and print image quality.

Description

Active energy ray curable ink composition for inkjet printing

[0001] The present invention relates to an actinic ray-curable ink composition for ink-jet printing.

[0002] In the past, it has been proposed to incorporate a large amount of monofunctional monomers into actinic ray-curable inkjet printing inks in order to improve adhesion to the substrate (for example, Patent Documents 1 to 3).

[0003] International Publication No. 2007 / 055332 International Publication No. 2013 / 027672 Japanese Patent Application Laid-Open No. 2014-70135

[0004] Increasing the amount of monofunctional monomer improves adhesion and stretchability, but reduces resistance to solvents and inks, and for example, during single-pass printing, there is a problem that the cured coating film partially dissolves in the secondary color ink, making it difficult for dots to spread on the coating film and adversely affecting print quality. In order to achieve sufficient image quality, it is necessary to incorporate a large amount of polyfunctional monomer, but in that case, physical properties such as adhesion decrease, making it difficult to achieve both image quality and adhesion / stretchability.

[0005] Therefore, an object of the present invention is to provide an actinic ray-curable ink composition for inkjet printing that is excellent in adhesion, flexibility, stretchability, alcohol resistance, and print image quality.

[0006] That is, the present invention has the following configurations. [1] An actinic ray-curable ink composition for inkjet printing containing a photopolymerizable compound, wherein the photopolymerizable compound 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), wherein the proportion of the hydroxyl group-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. [2] The actinic ray-curable ink composition for inkjet printing according to item [1] above, wherein the proportion of the monomer and / or oligomer having an amino group and / or an amide group in the photopolymerizable compound is 10% by mass or more and 40% by mass or less. [3] The actinic-energy-ray-curable ink composition for inkjet printing according to [1] or [2], which preferably contains a polyfunctional monomer other than (A) and (B), and the total proportion of the hydroxyl group-containing polyfunctional monomer and the polyfunctional monomer in the photopolymerizable compound is 20% by mass or less. [4] The actinic-energy-ray-curable ink composition for inkjet printing according to any of [1] to [3], which preferably contains acryloylmorpholine and / or N-vinylcaprolactam as the monomer and / or oligomer having an amino group and / or an amide group. [5] The actinic-energy-ray-curable ink composition for inkjet printing according to [4], which preferably contains an acrylated amine compound having two photopolymerizable functional groups and two amino groups in the molecule. [6] The actinic-energy-ray-curable ink composition for inkjet printing according to any of [1] to [5], which preferably contains 20% by mass or more of photopolymerizable compounds having a glass transition temperature of 10° C. or less as the photopolymerizable compound. [7] The actinic ray-curable ink composition for inkjet printing according to any one of [1] to [6] above, which preferably contains a colorant.

[0007] The actinic ray-curable ink composition for ink jet printing of the present invention contains a specific photopolymerizable component, and as a result, the composition has excellent adhesion, flexibility, stretchability, alcohol resistance, and print quality.

[0008] The actinic ray-curable ink composition for inkjet printing (hereinafter also referred to as ink composition) of the present invention will be described in detail below.

[0009] The actinic energy ray-curable ink composition for inkjet printing of the present invention contains a photopolymerizable compound, and the photopolymerizable compound 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), and the proportion of the hydroxyl group-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.

[0010] <(A) Hydroxyl Group-Containing Polyfunctional Monomer> The hydroxyl group-containing polyfunctional monomer may have two or more photopolymerizable functional groups and a hydroxyl group in the molecule. Examples include 2-hydroxy-3-methacrylpropyl acrylate, glycerin diacrylate, isocyanuric acid EO-modified diacrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, and tripentaerythritol penta(meth)acrylate. The hydroxyl group-containing polyfunctional monomer may be used alone or in combination of two or more. From the viewpoint of adhesion, the hydroxyl group-containing polyfunctional monomer preferably has two photopolymerizable functional groups and a hydroxyl group in the molecule.

[0011] The proportion of the hydroxyl group-containing polyfunctional monomer in the photopolymerizable compound is 2% by mass or more and 20% by mass or less. If the proportion of the hydroxyl group-containing polyfunctional monomer in the photopolymerizable compound is less than 2% by mass, alcohol resistance and image quality (dot diameter) will decrease, and if it is more than 20% by mass, adhesion, flexibility, and stretchability will decrease. It is more preferable that the proportion of the hydroxyl group-containing polyfunctional monomer in the photopolymerizable compound is 5% by mass or more and 12% by mass or less.

[0012] <(B) Monomer and / or Oligomer Having an Amino Group and / or an Amide Group> Examples of the monomer and / or oligomer having an amino group and / or an amide group include various (meth)acrylamide-based monomers such as acrylamide and acryloylmorpholine; vinylamide-based monomers such as N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide, N-vinylcaprolactam, N-vinylcarbazole and vinylmethyloxazolidinone; and acrylated amine compounds such as trade names "CN371," "CN373," "CN386," "CN501," "CN550," and "CN551" (all manufactured by Sartomer Corporation). Among these, it is preferable to use a monomer having an amino group and / or an amide group, it is more preferable to use acryloylmorpholine and / or N-vinylcaprolactam, and it is even more preferable to use an acrylated amine compound having two photopolymerizable functional groups and two amino groups in the molecule in combination with acryloylmorpholine and / or N-vinylcaprolactam. The monomer and / or oligomer having an amino group and / or an amide group may be used alone or in combination of two or more types.

[0013] The content of the monomer and / or oligomer having an amino group and / or an amide group can be determined arbitrarily. From the viewpoint of curability, the proportion of the monomer and / or oligomer having an amino group and / or an amide group in the photopolymerizable compound is preferably 10% by mass or more and 40% by mass or less, and more preferably 15% by mass or more and 30% by mass or less. If the proportion of the monomer and / or oligomer having an amino group and / or an amide group in the photopolymerizable compound is less than 10% by mass, the curability and tackiness may be reduced.

[0014] <(C) Monofunctional Monomer> The monofunctional monomer other than (B) (hereinafter also referred to as monofunctional monomer) may be any monofunctional monomer that is used in known actinic energy ray-curable ink compositions for inkjet printing, and examples thereof include butyl (meth)acrylate, isobutyl (meth)acrylate, tertiary butyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, isomyristyl (meth)acrylate, and stearyl (meth)acrylate. Acrylates such as acrylate, isostearyl (meth)acrylate, isobornyl (meth)acrylate, lauryl (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, cyclohexyl (meth)acrylate, butylcyclohexyl acrylate, trimethylcyclohexyl acrylate, adamantyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and dicyclopentenyl (meth)acrylate, styrene, benzyl (meth)acrylate acrylate, 2-phenoxyethyl (meth)acrylate and its ethylene oxide modified products, ethyl carbitol (meth)acrylate, 2-methoxyethyl acrylate, polyethylene glycol (meth)acrylate, isoamyl (meth)acrylate, hydroxymethyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxyphenoxypropyl (meth)acrylate, 2-ethylhexyl-diglycol (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 (meth)acrylate, (2-methyl-2-ethyl-1,Examples of the monofunctional monomers include (3-dioxolan-4-yl)methyl (meth)acrylate, (3-ethyloxetan-3-yl)methyl methacrylate, phenol ethylene glycol modified acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-acryloyloxyethyl succinate, 2-acryloyloxyethyl phthalate, 2-acryloyloxyethyl-2-hydroxyethyl phthalate, lactone modified flexible acrylate, t-butylcyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl acrylate, and vinyloxyethoxyethyl (meth)acrylate. The monofunctional monomers may be used alone or in combination of two or more.

[0015] The proportion of the monofunctional monomer in the photopolymerizable compound is 50% by mass or more, and from the viewpoint of flexibility and stretchability, the proportion of the monofunctional monomer in the photopolymerizable compound is preferably 50% by mass or more and 90% by mass or less, and more preferably 60% by mass or more and 85% by mass or less.

[0016] <Polyfunctional Monomer Other than (A) and (B)> Examples of polyfunctional monomers other than (A) and (B) (hereinafter also referred to as polyfunctional monomers) include known polyfunctional monomers having two or more ethylenically unsaturated bonds, such as the following polyfunctional (meth)acrylate compounds and vinyl ether group-containing (meth)acrylate compounds. The polyfunctional monomers may be used alone or in combination of two or more.

[0017] Examples of polyfunctional (meth)acrylate compounds include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, pentyl glycol di(meth)acrylate, Neopentyl glycol di(meth)acrylate, hydroxypivalyl hydroxypivalate di(meth)acrylate, hydroxypivalyl hydroxypivalate dicaprolactonate di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,2-hexanediol di(meth)acrylate, 1,5-hexanediol di(meth)acrylate, 2,5-hexanediol di(meth)acrylate, 1,7-heptanediol di(meth)acrylate, 1,8-octanediol di(meth)acrylate, 1,2-octanediol di(meth)acrylate Nonanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,2-decanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, 1,2-dodecanediol di(meth)acrylate, 1,14-tetradecanediol di(meth)acrylate, 1,2-tetradecanediol di(meth)acrylate, 1,16-hexadecanediol di(meth)acrylate, 1,2-hexadecanediol di(meth)acrylate, 2-methyl 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, tricyclodecanedimethylol di(meth)acrylate, tricyclodecanedimethylol dicaprolactonate di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, bicyclohexyl methylol 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, hydrogenated bisphenol A di(meth)acrylate, hydrogenated bisphenol F di(meth)acrylate, bisphenol A tetraethylene oxide Bifunctional monomers such as di(meth)acrylates of polyhydric alcohols such as adduct dicaprolactonate di(meth)acrylate, bisphenol F tetraethylene oxide adduct dicaprolactonate di(meth)acrylate, glycerin, pentaerythritol, diglycerin, ditrimethylolpropane, and dipentaerythritol, glycerin tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane tricaprolactonate tri(meth)acrylate, trimethylolethane tri(meth)acrylate, trifunctional monomers such as trimethylolpropane tri(meth)acrylate, trimethylolhexane tri(meth)acrylate, trimethyloloctane tri(meth)acrylate, etc.; and 3EO (ethylene oxide) modified products, 6EO modified products, 9EO modified products thereof (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 tetra- or higher functional monomers such as pentaerythritol tetracaprolactonate tetra(meth)acrylate, diglycerin tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, ditrimethylolpropane tetracaprolactonate tetra(meth)acrylate, ditrimethylolethane tetra(meth)acrylate, ditrimethylolbutane tetra(meth)acrylate, ditrimethylolhexane tetra(meth)acrylate, ditrimethyloloctane tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol octa(meth)acrylate, and tripentaerythritol polyalkylene oxide hepta(meth)acrylate. Among these, preferred examples include trimethylolpropane triacrylate (TMPTA; trifunctional), ditrimethylolpropane tetraacrylate (DITMPTA; tetrafunctional), dipentaerythritol hexaacrylate (DPHA; hexafunctional), and hexanediol diacrylate (HDDA; bifunctional).

[0018] Examples of vinyl ether group-containing (meth)acrylate compounds include 2-vinyloxyethyl (meth)acrylate, 3-vinyloxypropyl (meth)acrylate, 1-methyl-2-vinyloxyethyl (meth)acrylate, 2-vinyloxypropyl (meth)acrylate, 4-vinyloxybutyl (meth)acrylate, 1-methyl-3-vinyloxypropyl (meth)acrylate, 1-vinyloxymethylpropyl (meth)acrylate, and 2-methyl-3-vinyloxypropyl (meth)acrylate. vinyl, (meth)acrylate-3-methyl-3-vinyloxypropyl, (meth)acrylate-1,1-dimethyl-2-vinyloxyethyl, (meth)acrylate-3-vinyloxybutyl, (meth)acrylate-1-methyl-2-vinyloxypropyl, (meth)acrylate-2-vinyloxybutyl, (meth)acrylate-4-vinyloxycyclohexyl, (meth)acrylate-5-vinyloxypentyl, (meth)acrylate-6-vinyloxyhexyl, (meth)acrylate-4-vinyloxymethylcyclohexyl xylmethyl, (meth)acrylate-3-vinyloxymethylcyclohexylmethyl, (meth)acrylate-2-vinyloxymethylcyclohexylmethyl, (meth)acrylate-p-vinyloxymethylphenylmethyl, (meth)acrylate-m-vinyloxymethylphenylmethyl, (meth)acrylate-o-vinyloxymethylphenylmethyl, (meth)acrylate-2-(vinyloxyisopropoxy)ethyl, (meth)acrylate-2-(vinyloxyethoxy)propyl, (meth)acrylate-2-( (vinyloxyethoxy)isopropyl (meth)acrylate, 2-(vinyloxyisopropoxy)propyl (meth)acrylate, 2-(vinyloxyisopropoxy)isopropyl (meth)acrylate, 2-(vinyloxyethoxyethoxy)ethyl (meth)acrylate, 2-(vinyloxyethoxyisopropoxy)ethyl (meth)acrylate, 2-(vinyloxyisopropoxyethoxy)ethyl (meth)acrylate, 2-(vinyloxyisopropoxyisopropoxy)ethyl (meth)acrylate, and 2-(vinyloxyisopropoxyisopropoxy)ethyl (meth)acrylate.

[0019] When the polyfunctional monomer is used, the proportion of the polyfunctional monomer in the photopolymerizable compound is preferably 5% by mass or less, more preferably 3% by mass or less. Furthermore, when the polyfunctional monomer is used, the total proportion of the hydroxyl group-containing polyfunctional monomer (A) and the polyfunctional monomer in the photopolymerizable compound is preferably 2% by mass or more and 20% by mass or less.

[0020] In the ink composition, from the viewpoint of flexibility and stretchability, the total proportion of the photopolymerizable compounds contained in the photopolymerizable compound and having a glass transition temperature of 10° C. or less is preferably 20% by mass or more and 60% by mass or less, and more preferably 25% by mass or more and 50% by mass or less. Examples of the photopolymerizable compound having a glass transition temperature of 10° C. or less include the components described above. Examples of monofunctional monomers having a glass transition temperature of 10° C. or less include methyl acrylate, ethyl acrylate, n-butyl acrylate, n-hexyl methacrylate, 2-ethylhexyl (meth)acrylate, iso-nonyl acrylate, tetrahydrofurfuryl (meth)acrylate, isooctyl (meth)acrylate, isoamyl acrylate, isomyristyl acrylate, lauryl acrylate, benzyl acrylate, phenoxyethyl acrylate, and ethyl carbitol acrylate. Furthermore, examples of polyfunctional monomers and / or polyfunctional oligomers having a glass transition temperature of 10°C or lower include polyethylene glycol (400) diacrylate, polyethylene glycol (600) diacrylate, alkoxylated hexanediol diacrylate, ethoxylated (30) bisphenol A diacrylate, alkoxylated neopentyl glycol 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, and polyester acrylic oligomers.

[0021] <Photopolymerization initiator> The ink composition may contain a photopolymerization initiator. When an electron beam is used as the active energy ray, the ink composition may or may not contain a photopolymerization initiator. The photopolymerization initiator may be used alone or in combination of two or more types.

[0022] Examples of the photopolymerization initiator include acylphosphine oxide polymers such as 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), and ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide (TPOL). Initiators: 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-propan-1-one (Omnirad 127), 2-hydroxy-4'-hydroxyethoxy-2-methylpropiophenone (Omnirad 2959), 1-hydroxycyclohexyl phenyl ketone (Omnirad 184), oligo{2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone} (ESACURE α-hydroxyketone polymerization initiators such as 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, and bis[4-(2-hydroxy-2-methylpropanoyl)phenyl]ether (KIP160);Benzophenone compounds (such as 4,4'-diethylaminobenzophenone), 2-methyl-1-(4-methylthio)phenyl-2-morpholinopropan-1-one, 4'-(methylthio)-α-morpholino-α-methylpropiophenone, thiophenyl 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-(morpholinophenyl)-butan-1-one, 4-benzoyl-4'-methyldiphenyl sulfide, ethyl Michler's ketone, polymeric initiators (Omnipol TP, Omnipol BP), 1-[4-(4-benzoylphenylsulfanyl)phenyl]-2-methyl-2-(4-methylphenylsulfonyl)propan-1-one (ESACURE1001M);

[0023] The content of the photopolymerization initiator is not particularly limited. For example, when ultraviolet light (UV) or ultraviolet light (light-emitting diode (LED)) is used as the light source, the content of the photopolymerization initiator in the ink composition is preferably 3% by mass or more, and 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, and more preferably 15% by mass or less. When the content of the photopolymerization initiator is within the above range, the ink composition can have sufficient curability, internal curability, and low cost.

[0024] <Sensitizer> In order to promote curing properties with ultraviolet light emitted from a light-emitting diode (LED) as a light source, the ink composition may further contain a photosensitizer (compound) that has light absorption properties in the wavelength range of 400 nm or more, mainly ultraviolet light, and exhibits a sensitizing function for the curing reaction when exposed to light in that wavelength range. The phrase "exhibiting a sensitizing function when exposed to light with a wavelength of 400 nm or more" refers to having light absorption properties in the wavelength range of 400 nm or more. By using such a sensitizer, the LED curing properties of the ink composition of the present invention can be promoted.

[0025] Examples of the sensitizer include anthracene-based sensitizers such as 9,10-dibutoxyanthracene, 9,10-diethoxyanthracene, 9,10-dipropoxyanthracene, and 9,10-bis(2-ethylhexyloxy)anthracene; and thioxanthone-based sensitizers such as 4-isopropylthioxanthone, with thioxanthone-based sensitizers being preferred. Representative examples of commercially available products include anthracene-based sensitizers under the trade names "DBA" and "DEA" (all manufactured by Kawasaki Chemical Industries, Ltd.), and thioxanthone-based sensitizers under the trade names "DETX," "ITX," and "CPTX" (all manufactured by Lambson) and "Omnipol TX" (manufactured by IGM). The sensitizers may be used alone or in combination of two or more types.

[0026] The content of the sensitizer in the ink composition is preferably 0 to 8% by mass. If the content exceeds 8% by mass, no improvement in effect is observed, and it is undesirable to add too much.

[0027] In addition, when a thioxanthone-based sensitizer is used as the sensitizer, it tends to discolor the actinic ray-curable inkjet printing ink composition yellow, resulting in a hue that is more yellowish than the color (original hue) based on the pigment, etc., and therefore it is preferable to appropriately determine the content of the thioxanthone-based sensitizer for each color. Specifically, it is preferable not to include a thioxanthone-based compound as a sensitizer in white ink compositions and clear ink compositions, which are susceptible to changes in hue. Furthermore, since changes in hue are problematic for magenta ink compositions and cyan ink compositions, it is preferable to use a thioxanthone-based compound within a range that does not cause problems with hue. Furthermore, it is preferable to use a thioxanthone-based compound in combination as a sensitizer in black ink compositions and yellow ink compositions, because discoloration does not affect the hue and actinic ray polymerizability is poorer than for other hues.

[0028]

[0043] <Colorant> The ink composition may contain a colorant of each hue to obtain an ink composition of each color. As such a colorant, any pigment or dye that has conventionally been used in ordinary photocurable ink jet printing ink compositions may be used without any particular limitation. However, in consideration of light resistance, pigments such as organic pigments or inorganic pigments are preferred.

[0029] Examples of the organic pigments include dye lake pigments, azo-based, benzimidazolone-based, phthalocyanine-based, quinacridone-based, anthraquinone-based, dioxazine-based, indigo-based, thioindigo-based, perylene-based, perinone-based, diketopyrrolopyrrole-based, isoindolinone-based, nitro-based, nitroso-based, flavanthrone-based, quinophthalone-based, pyranthrone-based, and indanthrone-based pigments. Examples of the inorganic pigments include carbon black, titanium oxide, red iron oxide, graphite, iron black, chromium oxide green, and aluminum hydroxide.

[0030] Specific examples of pigments for each representative hue include the following:

[0031] Examples of yellow pigments for use in the yellow ink composition include C.I. 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, and 213, and preferably C.I. Pigment Yellow 150, 155, 180, and 213.

[0032] Examples of magenta pigments for use in the magenta ink composition include C.I. 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, C.I. Pigment Violet 19, and the like, and preferably C.I. Pigment Red 122, 202, C.I. Pigment Violet 19, and the like.

[0033] Examples of cyan pigments for use in the cyan ink composition include C.I. Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 18, 22, 27, 29, and 60, and preferably C.I. Pigment Blue 15:4.

[0034] Examples of black pigments for use in black ink compositions include carbon black (C.I. Pigment Black 7).

[0035] Examples of white pigments for use in the white ink composition include titanium oxide and aluminum oxide, and preferably titanium oxide that has been surface-treated with various materials such as alumina and silica.

[0036] The content of the pigment in the ink composition is preferably 1 to 20% by mass relative to the total amount of the ink composition. If the content of the pigment is less than 1% by mass, the image quality of the resulting printed matter tends to be reduced. On the other hand, if the content of the pigment is more than 20% by mass, the viscosity characteristics of the ink composition tend to be adversely affected.

[0037] <Pigment Dispersant> The ink composition may 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, and any conventionally used pigment dispersant can be used without particular limitation, but it is preferable to use a polymer dispersant. Examples of the pigment dispersant include 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 dispersants may be used alone or in combination of two or more types.

[0038] The pigment dispersant is preferably contained in an amount of 1 to 200 parts by mass, assuming the total amount of pigments used is 100 parts by mass. If the content of the pigment dispersant is less than 1 part by mass, the pigment dispersibility and storage stability of the ink composition may decrease. On the other hand, although it may be contained in an amount exceeding 200 parts by mass, there may be no difference in effect. The lower limit of the content of the pigment dispersant is more preferably 5 parts by mass, and the upper limit is more preferably 60 parts by mass.

[0039] <Other Components> Various additives can be added to the ink composition to exhibit various functionalities as needed. Specifically, various additives such as surfactants, organic solvents, polymerization inhibitors, light stabilizers, surface treatment agents, ultraviolet absorbers, antioxidants, antifoaming agents, antifungal agents, rust inhibitors, thickeners, moisturizers, and pH adjusters may be contained. Furthermore, a resin that functions as a vehicle but is not curable may or may not be blended.

[0040] <Surfactant (Leveling Agent)> The surfactant (leveling agent) is not particularly limited, and examples thereof include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants, etc. More specific examples of the surfactant include silicone surfactants such as polyether-modified silicone oil, polyester-modified polydimethylsiloxane, and polyester-modified methylalkylpolysiloxane, fluorine-based surfactants, and acetylene-based surfactants.

[0041] 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).

[0042] Examples of fluorine-based surfactants include F-410, F-444, and F-553 (manufactured by DIC Corporation), and FS-65, FS-34, FS-35, FS-31, and FS-30 (manufactured by DuPont).

[0043] 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 104E, Surfynol 104H, Surfynol 104A, Surfynol 104BC, Surfynol 104DPM, Surfynol 104PA, Surfynol 104PG-50, Surfynol 420, Surfynol 440, and Surfynol 465 (manufactured by EVONIK).

[0044] When a surfactant is blended, the content of the surfactant is not particularly limited. For example, in order to improve the ejection stability of the ink composition from an inkjet head, the content of the surfactant in the ink composition is preferably 0.005% by mass or more, and 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, and more preferably 1% by mass or less.

[0045] <Organic Solvent> The organic solvent is not particularly limited, and examples thereof include ester-based organic solvents, ether-based organic solvents, ether ester-based organic solvents, ketone-based organic solvents, aromatic hydrocarbon solvents, nitrogen-containing organic solvents, etc. When an organic solvent is blended, the content of the organic solvent is not particularly limited, and is, for example, preferably 5% by mass or less, and more preferably 2% by mass or less, of the ink composition.

[0046] <Polymerization Inhibitor> The polymerization inhibitor is not particularly limited, and examples thereof include hindered amines such as N-CH3 type, N-H type, and N-OR type, as well as phenol-based, amine-based, sulfur-based, and phosphorus-based polymerization inhibitors.

[0047] <Ultraviolet Absorber> Examples of the ultraviolet absorber include benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, hydroxyphenyltriazine-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, and nickel complex salt-based ultraviolet absorbers.

[0048] <Antioxidant> Examples of the antioxidant include phenol-based antioxidants, amine-based antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants.

[0049] <Antifoaming Agent> Examples of the antifoaming agent include silicone-based antifoaming agents and Pluronic (registered trademark)-based antifoaming agents.

[0050] <Preparation of Ink Composition> The method for preparing the ink composition is not particularly limited, and the ink composition can be prepared by adding all of the above-mentioned materials and mixing them using a bead mill, a three-roll mill, etc. Alternatively, a concentrated base ink can be obtained in advance by mixing a pigment, a pigment dispersant, and a photopolymerizable compound, and then additives such as a photopolymerizable compound, a photopolymerization initiator, and, if necessary, a surfactant can be added to the concentrated base ink to obtain the desired ink composition.

[0051] The substrate onto which the ink composition is printed is preferably, for example, a substrate made of flooring, acrylic, vinyl chloride, polyethylene terephthalate, polycarbonate, or the like, but any substrate onto which a conventional photocurable inkjet printing ink composition can be printed (paper, plastic film, capsule, gel, metal foil, glass, cloth, or the like) can be printed without any problems.

[0052] Specific examples of methods for printing and curing the ink composition include a method in which the ink composition is ejected onto a substrate using a low-viscosity inkjet head, and then the coating film of the ink composition of the present invention that has landed on the substrate is exposed to light and cured. For example, ejection onto a substrate (printing of an image) can be performed by supplying the ink composition to a printer head compatible with low viscosity inks of an inkjet recording printer, and ejecting the ink composition from the printer head so that the coating film has a thickness of, for example, 1 to 60 μm on the substrate. Furthermore, exposure to light and curing (curing of an image) can be performed by irradiating light onto the coating film of the ink composition that has been applied to the substrate as an image.

[0053] As the ink jet recording printer for printing the ink composition, an ink jet recording printer equipped with an ink jet head can be used. When a continuous type ink jet recording printer is used, a conductivity imparting agent is further added to the ink composition to adjust the electrical conductivity.

[0054] Examples of light sources for curing the coating film include ultraviolet light (UV), ultraviolet light (light-emitting diodes (LEDs)), electron beams, and visible light, with light-emitting diodes (LEDs) and electron beams emitting ultraviolet light with a peak emission wavelength in the range of 350 to 420 nm being preferred from an environmental perspective. Ultraviolet light emitted from a light-emitting diode (LED) as a light source refers to "light irradiated from a light-emitting diode that generates ultraviolet light with a peak emission wavelength in the range of 350 to 420 nm."

[0055] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0056] The raw materials used are shown below. <(A) Hydroxyl Group-Containing Polyfunctional Monomer> 2-Hydroxy-3-methacrylpropyl acrylate: manufactured by Shin-Nakamura Chemical Co., Ltd. Glycerin diacrylate: manufactured by Toagosei Co., Ltd. Isocyanuric acid ED-modified diacrylate: manufactured by Toagosei Co., Ltd. <(B) Monomer and / or Oligomer Having an Amino Group and / or an Amido Group> Acroylmorpholine: ACMO, manufactured by KJ Chemicals Co., Ltd. Vinyl caprolactam: VCAP, manufactured by ISP Japan Co., Ltd. Amine-modified oligomer: acrylated amine compound having two photopolymerizable functional groups and two amino groups in the molecule, CN371NS: manufactured by Sartomer Co., Ltd. <(C) Monofunctional Monomer Other than (B)> Benzyl acrylate: Miramer M1182HP, manufactured by MIWON Co., Ltd., glass transition temperature 6°C Phenoxyethyl acrylate: Miramer M140, manufactured by MIWON Co., Ltd., glass transition temperature 5°C Ethyl carbitol acrylate: Viscoat #190, manufactured by Osaka Organic Chemical Industry, Ltd., glass transition temperature -67°C Isobornyl acrylate: IBXA, manufactured by Osaka Organic Chemical Industry, Ltd., glass transition temperature 88°C <Polyfunctional monomers other than (A) and (B)> 1,6-hexanediol diacrylate: SR238NS, manufactured by Sartomer Corporation 3-methyl-1,5-pentanediol diacrylate: SR341, manufactured by Sartomer Corporation <Photopolymerization initiator> TPO: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, manufactured by Lambson Corporation <Sensitizer> DETX: 2,4-diethylthioxanthone, manufactured by Lambson Corporation <Polymerization inhibitor> MEHQ: hydroquinone monomethyl ether <Surfactant (leveling agent)> BYK-315N: Silicone-based surface conditioner, 100% solids, manufactured by BYK-Chemie Co., Ltd. <Colorant> PB15:4 PR122 PY150 PBk7 <Pigment dispersant> Dispersant 1: SS32000, manufactured by Lubrizol Japan Dispersant 2: PB821: manufactured by Ajinomoto Fine-Techno Co., Ltd. <Substrate> Acrylic plate (Acrylite L / S manufactured by Mitsubishi Chemical Corporation) PVC plate (T938 manufactured by Takiron C.I. Co., Ltd.) PVC80 (manufactured by Lintec Corporation)

[0057] <Production of active energy ray-curable ink composition for inkjet printing> A mixture of raw materials other than the photopolymerization initiator, sensitizer, polymerization inhibitor, and leveling agent blended to the formulation (mass %) shown in Table 1 was dispersed using an Eiger mill (using zirconia beads with a diameter of 0.5 mm as media) to obtain a concentrated base. Using the obtained concentrated base, the photopolymerization initiator, sensitizer, polymerization inhibitor, and leveling agent were blended to the formulation (mass %) shown in Table 1, to obtain active energy ray-curable inkjet printing ink compositions of Examples 1 to 12 and Comparative Examples 1 to 6.

[0058] <Evaluation of Printed Matter> Using the actinic ray-curable ink jet printing ink compositions of Examples 1 to 12 and Comparative Examples 1 to 6, the ink compositions were evaluated for substrate adhesion, flexibility, stretchability, alcohol resistance, and image quality (dot diameter) according to the following evaluation methods and criteria. The results are shown in Table 1. The printing conditions were as follows: printing on the substrate using a single-pass printer (head: M5320 manufactured by Ricoh Co., Ltd.), followed by curing by LED irradiation (irradiation energy 500 mJ).

[0059] <Adhesion to substrate> A cured coating film of each ink composition printed on an acrylic plate (Acrylite L / S manufactured by Mitsubishi Chemical Corporation) was cross-cut with a cutter knife, and cellophane tape (product name: Cellotape (registered trademark), manufactured by Nichiban Co., Ltd.) was applied to the cut area and then peeled off to evaluate the degree of peeling of the cured coating film according to the following criteria. [Evaluation criteria] 5: Less than 5% of the coating film peeled off 4: 5% to less than 15% of the coating film peeled off 3: 15% to less than 35% of the coating film peeled off 2: 35% to less than 65% of the coating film peeled off 1: More than 65% of the coating film peeled off A relative evaluation of 5 to 1 was given by visual inspection. A score of 5 or 4 was considered acceptable.

[0060] <Flexibility> A cured coating film of each ink composition printed on a PVC plate (T938 manufactured by Takiron Co., Ltd.) was visually inspected for cracks in the coating film when bent at 180°C, and rated according to the following criteria: 5: No cracks in the coating film 4: Cracks occurred in less than 10% of the entire bent area 3: Cracks occurred in 10% or more but less than 30% of the entire bent area 2: Cracks occurred in 30% or more but less than 50% of the entire bent area 1: Cracks occurred in more than 50% of the entire bent area A relative rating of 5 to 1 was given by visual inspection. A rating of 5 or 4 was considered acceptable.

[0061] <Stretchability> A cured coating film of each ink composition printed on a PVC plate (T938 manufactured by Takiron Co., Ltd.) was cut into a piece of 2 cm x 5 cm, and the coating film was visually inspected for cracks when stretched to 100%, and rated according to the following criteria. [Evaluation criteria] 5: No cracks in coating film at 100% stretching 4: Cracks occur at stretching from 75% to less than 100% 3: Cracks occur at stretching from 50% to 75% or less 2: Cracks occur at stretching from 25% to 50% or less 1: Cracks occur at stretching of 25% or less A relative rating of 5 to 1 was given by visual inspection. A rating of 5 or 4 was considered acceptable.

[0062] <Alcohol resistance> A cured coating film of each ink composition printed on a PVC plate (T938 manufactured by Takiron Co., Ltd.) was rubbed 10 times with a cotton swab containing 50% ethanol, and the degree of removal of the coating film was visually observed and evaluated according to the following criteria: [Evaluation criteria] 5: No removal of coating film even after rubbing 10 times with the cotton swab 4: Removal of coating film observed after rubbing 8 or 9 times with the cotton swab 3: Removal of coating film observed after rubbing 6 or 7 times with the cotton swab 2: Removal of coating film observed after rubbing 4 or 5 times with the cotton swab 1: Removal of coating film observed after rubbing 2 or 3 times with the cotton swab A relative evaluation of 5 to 1 was given by visual observation. A score of 5 or 4 was considered acceptable.

[0063] <Image quality (dot diameter)> The same ink was printed at a low printing rate on a coating of each ink composition printed on PVC80 (manufactured by Lintec Corporation), and the ink was irradiated with a UV-LED lamp manufactured by Phoseon Technologies, Inc. at a distance of 2 cm from the lamp to the ink-coated surface, with a UV integrated light amount of 180 mJ / cm. ２ The coating surface was observed with a microscope manufactured by Keyence Corporation, and the diameter of the printed dots was measured. [Evaluation criteria] 5: Dot diameter is 75 μm or more 4: Dot diameter is 70 μm or more and less than 75 μm 3: Dot diameter is 65 μm or more and less than 70 μm 2: Dot diameter is 60 μm or more and less than 65 μm 1: Dot diameter is less than 60 μm A score of 5 or 4 was considered acceptable.

[0064]

Claims

1. An active energy ray-curable ink composition for inkjet printing, comprising a photopolymerizable compound, the photopolymerizable compound comprising (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), and in the photopolymerizable compound, the proportion of the hydroxyl group-containing polyfunctional monomer 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.

2. The active energy ray-curable ink composition for inkjet printing according to claim 1, wherein the proportion of the monomer and / or oligomer having an amino group and / or an amide group in the photopolymerizable compound is 10% by mass or more and 40% by mass or less.

3. The active energy ray-curable ink composition for inkjet printing according to claim 1 or 2, further comprising a polyfunctional monomer other than (A) and (B), wherein the total ratio of the hydroxyl group-containing polyfunctional monomer and the polyfunctional monomer in the photopolymerizable compound is 20 mass % or less.

4. The actinic ray-curable ink composition for ink-jet printing according to claim 1 or 2, wherein the monomer and / or oligomer having an amino group and / or an amide group contains acryloylmorpholine and / or N-vinylcaprolactam.

5. The active energy ray-curable ink composition for inkjet printing according to claim 4, wherein the monomer and / or oligomer having an amino group and / or an amide group contains an acrylated amine compound having two photopolymerizable functional groups and two amino groups in the molecule.

6. The active energy ray-curable ink composition for ink-jet printing according to claim 1 or 2, wherein the total proportion of photopolymerizable compounds having a glass transition temperature of 10° C. or lower contained in the photopolymerizable compound is 20 mass % or more.

7. The actinic ray curable ink composition for ink-jet printing according to claim 1 or 2, which contains a colorant.

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