Ultraviolet-curable ink composition for inkjet printing

Abstract

The present invention provides an ultraviolet-curable ink composition for inkjet printing, which comprises a polymerization component and a photopolymerization initiator, the polymerization component comprising (A) a multifunctional amine-modified oligomer, (B) a nitrogen-containing monomer, (C) an aromatic ring-containing monomer, and (D) a multifunctional monomer, (A) comprising an acrylated amine compound having 2 photopolymerizable functional groups and 2 amino groups within the molecule, (B) comprising at least any one of acryloylmorpholine or vinylcaprolactam, (C) comprising benzyl acrylate and phenoxyethyl acrylate, (D) comprising at least any one of dipropylene glycol diacrylate, 1,6-hexanediol diacrylate, or ethoxylated trimethylolpropane triacrylate, the content of (A) being 0.8-11.0 mass%, the content of (C) being 32.0-75.0 mass%, and the content of (D) being 1.5-14.0 mass%.

Description

Technical Field

[0001] This invention relates to a UV-curable inkjet printing ink composition. More specifically, this invention relates to a UV-curable inkjet printing ink composition that, for example, when printed on label substrates (coated paper, PE, etc.), can achieve both excellent flexibility and image quality. Background Technology

[0002] Previously, UV-curable inks have been used in fields such as inkjet printing due to their fast drying time, absence of volatile solvents, and printability on various substrates (e.g., Patent Document 1). Inkjet printing can easily and inexpensively produce images, and therefore has been applied in various fields, from general printing to special printing. Furthermore, there is a need for an inkjet printing ink composition that can also be printed on various substrates that are stretched or bent after printing.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: International Publication No. 2017 / 134962 Summary of the Invention

[0006] The ink composition described in Patent Document 1, for example, has room for improvement in flexibility and image quality when printed on label substrates (coated paper, PE, etc.).

[0007] The present invention was made in view of such existing problems, and its object is to provide, for example, an ultraviolet-curable inkjet printing ink composition that can achieve both excellent flexibility and image quality when printed on label substrates (coated paper, PE, etc.).

[0008] In order to solve the above-mentioned problems, the inventors conducted in-depth research and found that by using specific polyfunctional amine-modified oligomers, nitrogen-containing monomers, aromatic ring-containing monomers and polyfunctional monomers as polymerization components, the above-mentioned problems can be solved simultaneously, thus completing the present invention.

[0009] One aspect of the present invention for solving the above-mentioned problems is a UV-curable inkjet printing ink composition comprising a polymerizing component and a photopolymerization initiator, wherein the polymerizing component comprises (A) a polyfunctional amine-modified oligomer, (B) a nitrogen-containing monomer, (C) an aromatic ring-containing monomer, and (D) a polyfunctional monomer, wherein the (A) polyfunctional amine-modified oligomer comprises an acryloylamine compound having two photopolymerizable functional groups and two amino groups within the molecule, and the (B) nitrogen-containing monomer comprises acryloylmorpholine or ethylene. The oligomer contains at least one of the following: (C) benzyl acrylate and phenoxyethyl acrylate; (D) a polyfunctional monomer contains at least one of dipropylene glycol diacrylate, 1,6-hexanediol diacrylate, or ethoxylated trimethylolpropane triacrylate; the content of the polyfunctional amine modified oligomer in (A) is 0.8 to 11.0% by mass; the content of the aromatic ring monomer in (C) is 32.0 to 75.0% by mass; and the content of the polyfunctional monomer in (D) is 1.5 to 14.0% by mass. Detailed Implementation

[0010] <UV-curable ink composition for inkjet printing>

[0011] An embodiment of the present invention provides an ultraviolet-curable inkjet printing ink composition (hereinafter also referred to as an ink composition) comprising a polymerizing component and a photopolymerization initiator. The polymerizing component comprises (A) a polyfunctional amine-modified oligomer, (B) a nitrogen-containing monomer, (C) an aromatic ring-containing monomer, and (D) a polyfunctional monomer. (A) The polyfunctional amine-modified oligomer comprises an acryloylamine compound having two photopolymerizable functional groups and two amino groups within its molecule. (B) The nitrogen-containing monomer comprises at least one of acryloylmorpholine or vinylcaprolactam. (C) The aromatic ring-containing monomer comprises benzyl acrylate and phenoxyethyl acrylate. (D) The polyfunctional monomer comprises at least one of dipropylene glycol diacrylate, 1,6-hexanediol diacrylate, or ethoxylated trimethylolpropane triacrylate. The content of (A) the polyfunctional amine-modified oligomer is 0.8 to 11.0% by mass. The content of (C) the aromatic ring-containing monomer is 32.0 to 75.0% by mass. (D) The content of polyfunctional monomers is 1.5 to 14.0% by mass. These will be explained separately below.

[0012] ((A) Polyfunctional amine modified oligomers)

[0013] (A) A polyfunctional amine-modified oligomer is contained as a polymerizing component, which is an acrylamide compound having two photopolymerizable functional groups and two amino groups in the molecule.

[0014] Acrylamide compounds having two photopolymerizable functional groups and two amino groups within their molecules are not particularly limited. As an example, the photopolymerizable functional groups in acrylamide compounds can be functional groups capable of forming cross-links between molecules through polymerization reactions using visible light or invisible light containing ionizing radiation such as ultraviolet rays or electron beams. Furthermore, photopolymerizable functional groups include any of the following: narrowly defined photopolymerizable functional groups that are directly activated by light irradiation to carry out photopolymerization reactions; and broadly defined photopolymerizable functional groups that initiate and promote polymerization reactions through the action of active species generated by the photopolymerization initiator when light irradiation is performed with the photopolymerizable functional group and a photopolymerization initiator coexisting.

[0015] The photopolymerizable functional group is a functional group with photoradical polymerization reactivity such as an olefinic double bond, or a functional group with photocationic polymerization reactivity such as an epoxy cyclic ether group. Among these, the photopolymerizable functional group is preferably an olefinic double bond such as (meth)acryloyl, vinyl, or allyl, and more preferably (meth)acryloyl. Acrylate amine compounds having two photopolymerizable functional groups and two amino groups within the molecule preferably have both photopolymerizable functional groups being (meth)acryloyl, and the amine value is 130–142 mg KOH / g. It should be noted that in this embodiment, the amine value refers to the amine value per 1g of solid component, which is determined by potentiometric titration (e.g., using COMTITE (AUTOTITRATOR COM-900, BURET B-900, TITSTATION K-900), manufactured by Hiranuma Sangyo Co., Ltd.) using a 0.1N hydrochloric acid aqueous solution and converted to the equivalent of potassium hydroxide.

[0016] Acrylamide compounds having two photopolymerizable functional groups and two amino groups within the molecule are preferably acrylamide compounds obtained by reacting difunctional (meth)acrylates with amine compounds. The difunctional (meth)acrylates are alkylene glycol dimethacrylates such as 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, propylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, neopentyl glycol dimethacrylate, etc., dimethacrylates of ethylene oxide adducts of bisphenol A, and dimethacrylates of ethylene oxide adducts of bisphenol F. This includes bisphenol epoxide alkoxide esters such as acrylates, di(meth)acrylates of ethylene oxide adducts of bisphenol S, di(meth)acrylates of ethylene oxide adducts of thiobisphenols, di(meth)acrylates of ethylene oxide adducts of brominated bisphenol A, di(meth)acrylates of polyalkylene glycols such as polyethylene glycol di(meth)acrylate and polypropylene glycol di(meth)acrylate, and di(meth)acrylates of neopentyl glycol hydroxypentanoate. Among these, the difunctional (meth)acrylate is preferably 1,6-hexanediol di(meth)acrylate.

[0017] Amine compounds include benzylamine, phenethylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, n-pentylamine, isopentylamine, n-hexylamine, cyclohexylamine, n-heptylamine, n-octylamine, 2-ethylhexylamine, n-nonylamine, n-decylamine, n-dodecylamine, n-tetradecylamine, n-hexadecylamine, n-octadecylamine, and other monofunctional amine compounds, as well as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, 1,6-hexamethylenediamine, and 1,8- Polyfunctional amine compounds include octamethylenediamine, 1,12-dodecylethylenediamine, o-phenylenediamine, p-phenylenediamine, m-phenylenediamine, o-xylylenediamine, p-xylylenediamine, m-xylylenediamine, menthanediamine, bis(4-amino-3-methylcyclohexylmethane), isophoronediamine, 1,3-diaminocyclohexane, and spirocyclohexyl acetal diamines. Additionally, amine compounds can also be high molecular weight polyfunctional amine compounds such as polyethyleneimine, polyvinylamine, and polyallylamine.

[0018] The aforementioned acrylamide compound is preferably a compound obtained by reacting 1,6-hexanediol di(meth)acrylate with an amine compound. Specifically, the acrylamide compound is CN371 (manufactured by Sartomer), EB7100 (EBECRYL 7100, manufactured by Cytec), Agi008 (manufactured by DSM), etc.

[0019] The content of component (A) in the ink composition is preferably 0.8% by mass or more, more preferably 1.0% by mass or more. Furthermore, the content of component (A) in the ink composition is preferably 11.0% by mass or less, more preferably 10.0% by mass or less. With the content of component (A) within the above range, the ink composition exhibits excellent curability, as well as excellent storage stability and ejection stability.

[0020] (B) Nitrogen-containing monomers)

[0021] (B) A nitrogen-containing monomer is contained as a polymerization component, including at least one of acrylomorpholine or vinylcaprolactam. From the perspective of excellent curability and image quality, both acrylomorpholine and vinylcaprolactam are preferred.

[0022] The content of component (B) in the ink composition is preferably 10.0% by mass or more, more preferably 12.0% by mass or more. Furthermore, the content of component (B) in the ink composition is preferably 33.0% by mass or less, more preferably 31.0% by mass or less. With the content of component (B) within the above range, the ink composition exhibits excellent curability and scratch resistance.

[0023] It should be noted that component (B) may also contain other nitrogen-containing monomers besides acrylamide and vinylcaprolactam. Other nitrogen-containing monomers include acrylonitrile, (meth)acrylamide, N-methoxymethacrylamide, diacetone acrylamide, N,N-dimethylacrylamide, diethylacrylamide, etc., N-vinylcarbazole, N-vinylacetamide, N-vinylpyrrolidone, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, hydroxymethyl(meth)acrylamide, di(2-hydroxyethyl)(meth)acrylamide, di(3-hydroxypropyl)(meth)acrylamide, di(4-hydroxybutyl)(meth)acrylamide, etc., and 1-3 molar adducts of these N-hydroxyalkyl(C1-5)(meth)acrylamides in ethylene oxide or propylene oxide, N-vinylcaprolactam, vinylmethyloxazolidinone, (meth)acryloylpyrrolidone, (meth)acryloylpiperidine, etc.

[0024] ((C) Monomers containing aromatic rings)

[0025] (C) Contains aromatic ring monomers as polymerizing components, including benzyl acrylate and phenoxyethyl acrylate.

[0026] The content of component (C) in the ink composition is preferably 32.0% by mass or more, more preferably 34.0% by mass or more. Furthermore, the content of component (C) in the ink composition is preferably 75.0% by mass or less, more preferably 70.0% by mass or less. With the content of component (C) within the above range, the ink composition has the advantage that the image quality is good in the high-concentration areas of the printing on label substrates (coated paper, PE, etc.).

[0027] It should be noted that component (C) may also contain other aromatic ring monomers besides benzyl acrylate and phenoxyethyl acrylate. Such other aromatic ring monomers include phenyl methacrylate, benzyl methacrylate, phenoxyethyl methacrylate, phenoxypropyl methacrylate, phenoxydiethylene glycol (meth)acrylate, phenoxydipropylene glycol (meth)acrylate, and other phenoxydialkylene glycol (meth)acrylates; phenoxy polyethylene glycol (meth)acrylate, phenoxy polyethylene glycol-polypropylene glycol-(meth)acrylate, etc.

[0028] ((D) Multifunctional monomer)

[0029] (D) A multifunctional monomer is contained as a polymerizing component, including at least one of dipropylene glycol diacrylate, 1,6-hexanediol diacrylate or ethoxylated trimethylolpropane triacrylate.

[0030] The content of component (D) in the ink composition is preferably 1.5% by mass or more, more preferably 2.0% by mass or more. Furthermore, the content of component (D) in the ink composition is preferably 14.0% by mass or less, more preferably 13.0% by mass or less. When the content of component (D) is within the above range, the curability of the coating film of the ink composition becomes good.

[0031] It should be noted that component (D) may also contain other multifunctional monomers besides dipropylene glycol diacrylate, 1,6-hexanediol diacrylate and ethoxylated trimethylolpropane triacrylate. Other such multifunctional monomers include trimethylolpropane tri(meth)acrylate, vinyloxyethoxyethyl(meth)acrylate, EO (10 mol or 20 mol) modified bisphenol A diacrylate, polyethylene glycol (400) di(meth)acrylate, polyethylene glycol (600) diacrylate, ethoxylated (30) bisphenol A diacrylate, alkoxylated neopentyl glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol (600) dimethacrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate, dipropylene glycol dimethacrylate, triethylene glycol di(meth)acrylate, and tripropylene glycol di(meth)acrylate. Acrylates, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dimethyloltricyclodecane di(meth)acrylate, neopentyl glycol di(meth)acrylate with hydroxypentanoic acid, polytetramethylene glycol diacrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate and its ethylene oxide modified derivatives, dipentaerythritol penta(meth)acrylate and its ethylene oxide modified derivatives, dipentaerythritol hexa(meth)acrylate and its ethylene oxide modified derivatives, urethane (meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate, pentaerythritol ethoxytetraacrylate, caprolactam-modified dipentaerythritol hexaacrylate, ethoxylated bisphenol A diacrylate, alkoxylated tetrahydrofurfuryl acrylate, etc.

[0032] (Photopolymerization initiator)

[0033] The ink composition of this embodiment contains a photopolymerization initiator.

[0034] There are no particular limitations on photopolymerization initiators. For example, photopolymerization initiators include benzophenone, diethylthioxanone, 2-methyl-1-(4-methylthio)phenyl-2-morpholinopropane-1-one, 4-benzoyl-4'-methyldiphenyl sulfide, 1-chloro-4-propoxythioxanone, isopropylthioxanone, 2-hydroxy-2-methyl-1-phenylpropane-1-one, 1-hydroxycyclohexylphenyl ketone, bis-2,6-dimethoxybenzoyl-2,4,4-trimethylpentylphosphine oxide, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, 2,2-dimethyl-2-hydroxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,4,6-trimethylbenzyl-diphenylphosphine oxide, 2-benzyl-2-dimethylamino-1-(morpholinophenyl)-butane-1-one, etc. Such photopolymerization initiators are commercially available, for example, from BASF under trade names such as Irgacure 907, Irgacure 369, Irgacure 184, Irgacure 379, Irgacure 819, and TPO, and from Lamberti under trade names such as DETX. Photopolymerization initiators can also be used in combination.

[0035] The content of the photopolymerization initiator is not particularly limited. As an 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 15% by mass or less, more preferably 10% by mass or less. By keeping the content of the photopolymerization initiator within the above ranges, the ink composition can achieve sufficient curability, internal curing, and low cost.

[0036] (Sensitizer)

[0037] The ink composition of this embodiment preferably contains a sensitizer. By including a sensitizer, for example, it is possible to promote the curability of the ink composition relative to ultraviolet light using a light-emitting diode (LED) as a light source. This sensitizer exhibits light absorption characteristics primarily in the ultraviolet wavelength region above 400 nm, and thus readily exhibits a sensitizing function for the curing reaction through light in this wavelength range. It should be noted that the phrase "exhibits a sensitizing function through light with wavelengths above 400 nm" refers to having light absorption characteristics in the wavelength region above 400 nm. By using such a sensitizer, the LED curability of the ink composition of this embodiment can be promoted.

[0038] The preferred sensitizers are anthracene-based sensitizers and thioxanthone-based sensitizers, with thioxanthone-based sensitizers being more preferred. Photosensitizers may also be used in combination. Specifically, photosensitizers include anthracene-based sensitizers such as 9,10-dibutoxyanthracene, 9,10-diethoxyanthracene, 9,10-dipropoxyanthracene, and 9,10-bis(2-ethylhexyloxy)anthracene, and thioxanthone-based sensitizers such as 2,4-diethylthioxanthone, 2-isopropylthioxanthone, and 4-isopropylthioxanthone. Representative examples of commercially available products include DBA and DEA (manufactured by Kawasaki Chemical Industry Co., Ltd.) as anthracene-based sensitizers, and DETX and ITX (manufactured by Lambson Corporation) as thioxanthone-based sensitizers.

[0039] When a sensitizer is included, the sensitizer content in the ink composition is preferably greater than 0 and less than 3.5% by mass. By keeping the sensitizer content within the above range, the ink composition readily enhances the effects achieved by incorporating the sensitizer.

[0040] (Coloring agent)

[0041] The ink composition of this embodiment preferably contains a colorant. By including a colorant, the ink composition can be made into ink compositions of various colors.

[0042] There are no particular limitations on the colorant. For example, conventionally used pigments and dyes can be used without particular restriction, preferably organic or inorganic pigments. Colorants can also be used in combination.

[0043] Organic pigments include dye lake pigments, azo pigments, benzimidazole pigments, phthalocyanine pigments, quinacridone pigments, anthraquinone pigments, dioxazine pigments, indigo pigments, thio-indigo pigments, perylene pigments, pyrene pigments, diketopyrrole pigments, isoindolinetone pigments, nitro pigments, nitroso pigments, anthraquinone pigments, flavonoid pigments, quinolinetone pigments, pinanthrone pigments, and indigo pigments, etc.

[0044] Inorganic pigments include colored pigments such as titanium dioxide, iron oxide red, antimony red, cadmium yellow, cobalt blue, ultramarine, cyanine blue, iron black, chromium oxide green, carbon black, and graphite (also including achromatic pigments such as white and black) as well as extender pigments such as calcium carbonate, kaolin, clay, barium sulfate, aluminum hydroxide, and talc.

[0045] The specific examples of pigments representing each hue in the ink composition of this embodiment are described below. The yellow pigments are CI pigment yellows 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., preferably CI pigment yellows 150, 155, 180, 213, etc. The content of the yellow pigment is not particularly limited. As an example, the content of the yellow pigment in the ink composition is preferably 1.0% by mass or more, more preferably 1.5% by mass or more. Furthermore, the content of the yellow pigment in the ink composition is preferably 4.0% by mass or less, more preferably 3.5% by mass or less.

[0046] The magenta pigment is 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, CI Pigment Violet 19, etc., preferably CI Pigment Red 122, 202, Pigment Violet 19, etc. The content of magenta pigment is not particularly limited. As an example, the content of magenta pigment in the ink composition is preferably 1.8% by mass or more, more preferably 2.3% by mass or more. In addition, the content of magenta pigment in the ink composition is preferably 4.8% by mass or less, more preferably 4.3% by mass or less.

[0047] The cyan pigment is CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 18, 22, 27, 29, 60, etc., preferably CI Pigment Blue 15:4, etc. The content of the cyan pigment is not particularly limited. As an example, the content of the cyan pigment in the ink composition is preferably 1.0% by mass or more, more preferably 1.5% by mass or more. Furthermore, the content of the cyan pigment in the ink composition is preferably 4.0% by mass or less, more preferably 3.5% by mass or less.

[0048] The black pigment is carbon black (CI pigment 7), etc. The content of the black pigment is not particularly limited. As an example, the content of the black pigment in the ink composition is preferably 1.0% by mass or more, more preferably 1.5% by mass or more. Furthermore, the content of the black pigment in the ink composition is preferably 4.0% by mass or less, more preferably 3.5% by mass or less.

[0049] The white pigment is titanium dioxide, aluminum oxide, etc., preferably titanium dioxide that has been surface-treated with various materials such as aluminum oxide and silicon dioxide. The content of the white pigment is not particularly limited. As an example, the content of white pigment in the ink composition is preferably 10% by mass or more, more preferably 13% by mass or more. Furthermore, the content of white pigment in the ink composition is preferably 23% by mass or less, more preferably 19% by mass or less.

[0050] The colorant content in the ink composition is preferably 1% by mass or more. Furthermore, the colorant content in the ink composition is preferably 20% by mass or less. When the colorant content is within the above range, the resulting printed matter from the ink composition exhibits suitable image quality and excellent viscosity characteristics.

[0051] (Pigment dispersant)

[0052] Pigment dispersants are appropriately formulated to improve the dispersibility of pigments and the storage stability of ink compositions.

[0053] There are no particular limitations on pigment dispersants. For example, pigment dispersants include carbodiimide dispersants, polyester amine dispersants, fatty acid amine dispersants, modified polyacrylate dispersants, modified polyurethane dispersants, multi-chain polymeric nonionic dispersants, and polymeric ionic surfactants. Pigment dispersants can also be used in combination.

[0054] When a pigment dispersant is incorporated, the content of the pigment dispersant is not particularly limited. When the pigment is set to 100% by mass, the content of the pigment dispersant is preferably 1 to 200% by mass. When the content of the pigment dispersant is within the above range, the resulting ink composition exhibits excellent storage stability.

[0055] (Other ingredients)

[0056] The ink composition of this embodiment may also contain various additives such as surfactants, organic solvents, polymerization inhibitors, shelf-enhancing agents, ultraviolet absorbers, antioxidants, defoamers, mildew inhibitors, rust inhibitors, thickeners, humectants, and pH adjusters as other components.

[0057] (Surfactant (leveling agent))

[0058] There are no particular limitations on surfactants (leveling agents). If we were to give an example, surfactants could include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants, etc. More specifically, surfactants could be silicone-based surfactants such as polyether-modified silicone oils, polyester-modified polydimethylsiloxanes, polyester-modified methylalkyl polysiloxanes, fluorinated surfactants, acetylene-based surfactants, etc.

[0059] 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).

[0060] Fluorinated surfactants include F-410, F-444, F-553 (manufactured by DIC Corporation), FS-65, FS-34, FS-35, FS-31, and FS-30 (manufactured by DuPont).

[0061] The acetylene-based surfactants are 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, and Surfynol... 440, Surfynol 465 (manufactured by EVONIK), etc.

[0062] When a surfactant is used, the surfactant content is not particularly limited. However, to improve the ejection stability of the ink composition in the inkjet head, the surfactant content is preferably 0.005% by mass or more, more preferably 0.01% by mass or more. Furthermore, the surfactant content is preferably 1.5% by mass or less, more preferably 1% by mass or less.

[0063] (solvent)

[0064] The ink composition can also be combined with a solvent. The solvent can be an ester-based organic solvent, an ether-based organic solvent, an ether-ester-based organic solvent, a ketone-based organic solvent, an aromatic hydrocarbon solvent, a nitrogen-containing organic solvent, etc.

[0065] When a solvent is used, the solvent content is not particularly limited. As an example, the solvent content in the ink composition is preferably 5% by mass or less, more preferably 2% by mass or less.

[0066] (polymerization inhibitor)

[0067] There are no particular limitations on the polymerization inhibitor. For example, the polymerization inhibitor could be a hindered amine, phenolic, amine, sulfur-based, or phosphorus-based inhibitor, such as N-CH3, NH, or N-OR type inhibitors.

[0068] (Preservation enhancer)

[0069] The preservation enhancers are of the N-CH3 type, NH type, N-OR type, etc.

[0070] (UV absorber)

[0071] 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.

[0072] (Antioxidants)

[0073] Antioxidants include phenolic antioxidants, amine antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants.

[0074] (Defoamer)

[0075] The defoamers include silicone-based defoamers and Pluronic (registered trademark)-based defoamers.

[0076] Returning to the overall description of the ink composition, the viscosity of the ink composition in this embodiment at 25°C is preferably 30 mPa·s or less, more preferably 20 mPa·s or less. The ink composition may be formulated with viscosity modifiers or the like as needed. It should be noted that in this embodiment, the viscosity can be measured at 25°C using an E-type viscometer (RE100L type viscometer, manufactured by Toki Sangyo Co., Ltd.).

[0077] The resulting ink composition can be printed onto a suitable substrate using an inkjet printer to form an inkjet image. The substrate is not particularly limited. Examples include plastic substrates such as flexible vinyl chloride, rigid vinyl chloride, polystyrene, expanded polystyrene, PMMA, polypropylene, polyethylene, PET, and polycarbonate, or mixtures or modifications thereof; paper substrates such as high-quality paper, art paper, coated paper, and cast coated paper; and metal substrates such as glass and stainless steel. Among these, the ink composition of this embodiment is particularly preferred when applied to label substrates (coated paper, PE, etc.) for reasons such as avoiding excessive crosslinking density and imparting flexibility to the coating film.

[0078] In summary, the ink composition of this embodiment can achieve both excellent flexibility and image quality when printed on substrates such as label substrates (coated paper, PE, etc.).

[0079] The present invention has been described above as one embodiment. The present invention is not particularly limited to the above embodiment. It should be noted that the above embodiment mainly describes an invention having the following configuration.

[0080] (1) A UV-curable inkjet printing ink composition comprising a polymerizing component and a photopolymerization initiator, wherein the polymerizing component comprises (A) a polyfunctional amine-modified oligomer, (B) a nitrogen-containing monomer, (C) an aromatic ring-containing monomer, and (D) a polyfunctional monomer, wherein the (A) polyfunctional amine-modified oligomer comprises an acryloylamine compound having two photopolymerizable functional groups and two amino groups within its molecule, and the (B) nitrogen-containing monomer comprises at least one of acryloylmorpholine or vinylcaprolactam. C) The aromatic ring monomer includes benzyl acrylate and phenoxyethyl acrylate, and the above (D) polyfunctional monomer includes at least one of dipropylene glycol diacrylate, 1,6-hexanediol diacrylate or ethoxylated trimethylolpropane triacrylate, the content of the above (A) polyfunctional amine modified oligomer is 0.8 to 11.0% by mass, the content of the above (C) aromatic ring monomer is 32.0 to 75.0% by mass, and the content of the above (D) polyfunctional monomer is 1.5 to 14.0% by mass.

[0081] Based on this composition, the UV-curable ink composition for inkjet printing can achieve both excellent flexibility and image quality when printed on substrates such as label substrates (coated paper, PE, etc.).

[0082] (2) The UV-curable ink composition for inkjet printing according to (1), wherein the nitrogen-containing monomer (B) is 10.0% to 33.0% by mass.

[0083] Based on this composition, the curing properties of the UV-curable ink composition for inkjet printing become good.

[0084] Example

[0085] The present invention will now be described in more detail with reference to the embodiments. The present invention is not limited to these embodiments. It should be noted that, unless otherwise specified, "%" refers to "mass %" and "parts" refers to "parts by mass".

[0086] The raw materials used are shown below.

[0087] <Coloring agent>

[0088] PB15:4

[0089] PR122

[0090] PY150

[0091] PBk7

[0092] PW6

[0093] <Pigment Dispersant>

[0094] Dispersant 1: PX4701, manufactured by BASF

[0095] Dispersant 2: S56000, manufactured by Lubrizol Corporation, Japan.

[0096] Dispersant 3: BYKJET9151, manufactured by BYK-Chemie.

[0097] Dispersant 4: PB821, manufactured by Ajinomoto Fine Chemicals Co., Ltd.

[0098] <(A) Polyfunctional amine modified oligomers>

[0099] Amine-modified oligomers: Acrylatesamine compounds with two photopolymerizable functional groups and two amino groups within the molecule, CN371NS: manufactured by Sartamer.

[0100] <(C) Contains aromatic ring monomers and other monomers>

[0101] Benzyl acrylate: Miramer M1182HP, manufactured by MIWON.

[0102] Phenoxyethyl acrylate: Miramer M140, manufactured by MIWON.

[0103] Isoborneol acrylate: IBXA, manufactured by Osaka Organic Chemical Industry Co., Ltd.

[0104] Ethyl carbitol acrylate: Viscoat #190, manufactured by Osaka Organic Chemicals Co., Ltd.

[0105] tert-butylcyclohexyl acrylate: SR217, manufactured by Sartomer

[0106] <(D) Multifunctional Monomer>

[0107] Dipropylene glycol diacrylate: Agisyn 2833, manufactured by DSM-AGI.

[0108] 1,6-Hexanediol diacrylate: SR238NS, manufactured by Sartomer.

[0109] (EO)TMPTA (ethoxylated trimethylolpropane triacrylate): Miramer M3110, manufactured by MIWON.

[0110] <(B) Nitrogen-containing monomers>

[0111] Acryloylmorpholine: ACMO, manufactured by KJ Chemical Co., Ltd.

[0112] Vinylcaprolactam: VCAP, manufactured by ISP Japan Co., Ltd.

[0113] <Photopolymerization Initiator>

[0114] TPO: 2,4,6-Trimethylbenzoyl-diphenylphosphine oxide, manufactured by Lambson.

[0115] <Sensitizer>

[0116] DETX: 2,4-Diethylthioxanthone, manufactured by Lambson Company

[0117] <Polymerization Inhibitor>

[0118] MEHQ: Hydroquinone Monomethyl Ether

[0119] UV22: Quinone polymerization inhibitor, manufactured by Kromachem.

[0120] Leveling agent

[0121] BYK-315N: Silicone-based surface conditioner, 100% solids, manufactured by BYK-Chemie Japan Co., Ltd.

[0122] <Substrate>

[0123] PVC: IJ180, manufactured by 3M, used for outdoor and indoor signage graphics.

[0124] Coated paper: Tetsubishi Art Paper, manufactured by Mitsubishi Paper Corporation, with excellent whiteness, smoothness, and high gloss.

[0125] PET: Lumirror T60, manufactured by Toray Industries, Inc., characterized by its high toughness, chemical resistance, and excellent electrical insulation.

[0126] (UV-curable ink composition for inkjet printing)

[0127] The mixture obtained by combining all raw materials except photoinitiator, sensitizer, polymerization inhibitor, and leveling agent according to the formulation (mass %) in Table 1 was dispersed using an Eiger mill (using 0.5 mm diameter zirconia beads as the medium) to obtain a concentrated base. Using the obtained concentrated base, the photoinitiator, sensitizer, polymerization inhibitor, and leveling agent were combined according to the formulation (mass %) in Table 1 to obtain the UV-curable inkjet printing ink compositions of Examples 1-14 and Comparative Examples 1-7.

[0128] <Evaluation of UV-curable inkjet printing ink compositions and printed materials>

[0129] Using the UV-curable ink compositions of Examples 1-14 and Comparative Examples 1-7, the specific gravity, viscosity, surface tension, adhesion, flexibility, LED curability, image quality, and printhead ejection properties of the ink compositions were evaluated according to the following evaluation methods and criteria. The results are shown in Table 1.

[0130] [Table 1]

[0131] Table 1

[0132]

[0133]

[0134] (Viscosity of UV-curable inkjet printing ink composition)

[0135] The viscosity of the UV-curable ink composition for inkjet printing was measured using an E-type viscometer (RE100L type viscometer, manufactured by Toki Sangyo Co., Ltd.) at a temperature of 25°C and a rotor speed of 20 rpm.

[0136] (Specific gravity of UV-curable inkjet printing ink composition)

[0137] The specific gravity of the UV-curable ink composition for inkjet printing was determined using a Cap-Lussac type hydrometer.

[0138] (Surface tension)

[0139] The surface tension of the UV-curable ink composition for inkjet printing was measured using a dynamic wettability tester (WET-6000, manufactured by Lesca Co., Ltd.) at a temperature of 25°C.

[0140] (Seamless fit)

[0141] The adhesion of UV-curable inkjet printing ink compositions was evaluated using a cross-cut test. Test pieces were created by applying the active energy ray-curable ink composition to PVC, coated paper, or PET substrates, followed by UV curing. One hundred square pieces of the cured coating were formed by cross-cutting the cured film on the substrate using a utility knife. Cellulose tape (Cellotape, a registered trademark, manufactured by Nichiban Co., Ltd.) was then applied to the cut sections and peeled off. The number of square pieces remaining on the substrate without peeling off the tape was counted for evaluation. Table 1 shows 100 / 100, indicating good adhesion where none of the square pieces were peeled off and all remained on the substrate.

[0142] (Flexibility)

[0143] A UV-curable inkjet printing ink composition for printing on coated paper is evaluated by bending the printed text 180° according to the following evaluation criteria.

[0144] ○: No grid cracks or fine cracks were produced in the coating when bending.

[0145] △: When bent, tiny cracks are produced.

[0146] ×: When bent, the grid lines crack.

[0147] (LED curability)

[0148] The inkjet recording device and the UV-curable inkjet printing ink composition were placed at an ambient temperature of 25°C for 24 hours to maintain the temperature of both components at 25°C. Then, at 25°C, the UV-curable inkjet printing ink composition was continuously printed (text) onto a PVC film. Using a UV-LED lamp manufactured by Phoseon Technology, with a distance of 2 cm between the lamp and the ink coating surface, a UV cumulative light intensity of 180 mJ / cm² was achieved. 2 Allow it to cure. Rub the resulting cured coating with a cotton swab and evaluate the curing properties based on the removal of the swab, according to the following evaluation criteria.

[0149] ○: Not removed.

[0150] ×: Sometimes removed.

[0151] (Image quality)

[0152] Regarding the adhesion of UV-curable ink compositions for inkjet printing, coated paper prints are prepared, and the areas with a 70% print density of the coated paper prints are visually confirmed. If there is no unevenness, it is marked as ○.

[0153] (Ejection stability)

[0154] At an ambient temperature of 25°C, an inkjet recording device equipped with inkjet nozzles and a UV-curable inkjet printing ink composition were placed for 24 hours to maintain the temperature of both the inkjet recording device and the UV-curable inkjet printing ink composition at 25°C. Then, at 25°C, the UV-curable inkjet printing ink composition was used to continuously print (print) on a PCB sheet, and the ejection stability was evaluated according to the following evaluation criteria.

[0155] ○: The ink composition does not cause printing disorder and can be sprayed out stably.

[0156] △: The ink composition exhibits slight printing irregularities, but can still be ejected in a generally stable manner.

[0157] ×: The ink composition has printing irregularities or cannot be sprayed out stably.

[0158] As shown in Table 1, the UV-curable inkjet printing ink compositions of Examples 1-14 of the present invention are easy to eject, easy to cure, have excellent adhesion, and excellent flexibility of the coated paper. Furthermore, the resulting inkjet images have excellent image quality. On the other hand, the UV-curable inkjet printing ink compositions of Comparative Examples 1-3, which do not contain benzyl acrylate and phenoxyethyl acrylate (C), have poor image quality and printhead ejection performance. Additionally, the UV-curable inkjet printing ink compositions of Comparative Examples 4-5, which have polyfunctional monomer content outside the scope of the present invention (D), have poor flexibility and LED curing performance. Furthermore, the UV-curable inkjet printing ink compositions of Comparative Examples 6-7, which have polyfunctional amine-modified oligomer content outside the scope of the present invention (A), have poor flexibility and LED curing performance.

Claims

1. A UV-curable ink composition for inkjet printing, comprising a polymerizing component and a photopolymerization initiator, The polymeric components include (A) polyfunctional amine-modified oligomers, (B) nitrogen-containing monomers, (C) aromatic ring-containing monomers, and (D) polyfunctional monomers. The (A) polyfunctional amine-modified oligomer comprises an acrylamide compound having two photopolymerizable functional groups and two amino groups within the molecule. The nitrogen-containing monomer (B) comprises at least one of acrylomorpholine or vinylcaprolactam. The aromatic ring monomer (C) comprises benzyl acrylate and phenoxyethyl acrylate. The (D) multifunctional monomer comprises at least one of dipropylene glycol diacrylate, 1,6-hexanediol diacrylate, or ethoxylated trimethylolpropane triacrylate. The content of the (A) polyfunctional amine-modified oligomer is 0.8–11.0% by mass. The content of nitrogen-containing monomer (B) is 10.0% to 33.0% by mass. The content of the aromatic ring monomer in (C) is 32.0% to 75.0% by mass. The content of the (D) multifunctional monomer is 1.5–14.0% by mass. The contents of (A), (B), (C) and (D) are all based on the total mass of the UV-curable inkjet printing ink composition.

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