Active energy ray curable flexographic inks and printed materials

Abstract

To provide an active energy ray-curable flexographic ink that achieves both good printability and high opacity, and a printed material using the active energy ray-curable flexographic ink. [Solution] An active energy ray-curable flexographic ink comprising a radical polymerizable compound, a white pigment, and a dispersant, wherein the dispersant is a dispersant having a phosphate group. Preferably, the acid value of the dispersant is 50 to 500 mg KOH / g.

Description

Technical Field

[0001] The present invention relates to an active energy ray-curable flexographic ink and a printed matter using the active energy ray-curable flexographic ink.

Background Art

[0002] Active energy ray-curable inks are solvent-free and instantaneously cured and dried by active energy rays. Therefore, they are excellent in environmental compatibility and printing workability, and high-quality printed matters can be obtained. They are widely used from the field of printed information such as magazines and leaflets to the field of packages for food packaging such as paper containers.

[0003] Among the printing methods using these active energy ray-curable inks, flexographic printing has attracted attention because the printing plate used for the printing is made of a flexible and elastic photosensitive resin or the like and can be printed on a substrate with unevenness.

[0004] In flexographic printing, white flexographic ink is used for purposes such as white underprinting (printing white ink over colored ink to make characters and patterns appear distinct), so high hiding power is required. To achieve high hiding power, it is necessary to increase the content of white pigment in the ink. As a result, the fluidity of the ink decreases and the transferability to the substrate deteriorates, which causes a decrease in hiding power. In particular, active energy ray-curable inks have lower fluidity compared to other curable inks such as aqueous inks, which leads to poor ink transferability and a decrease in density stability during long runs, resulting in a decrease in hiding power. (See Patent Document 1)

[0005] Also, when printing white ink in flexographic printing, an anilox roll with a large cell volume is used to improve high hiding power. However, this causes a problem that ink adheres to the side surfaces of the convex portions and concave portions of the printing plate, resulting in a decrease in print quality.

[0006] Patent Document 2 presents a method for manufacturing printed materials that have excellent opacity, which involves printing a white active energy ray-curable offset ink onto a substrate and then printing a white active energy ray-curable flexographic ink onto it. However, the method described in this document combines multiple printing methods, which presents the problem that it cannot be printed using a conventional flexographic printing press.

[0007] Patent Document 3 describes a white active energy ray curable flexographic ink, but the evaluation was performed using a simple color spreading machine (RI tester), and there is no description of its opacity or printability when printed on a flexographic printing press. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2014-101472 [Patent Document 2] International Publication No. 2023 / 013571 [Patent Document 3] Japanese Patent Publication No. 2024-054635 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] The object of the present invention is to provide an active energy ray-curable flexographic ink that can achieve both good printability and high opacity, and a printed material using the active energy ray-curable flexographic ink. [Means for solving the problem]

[0010] The inventors of this invention conducted extensive research to solve the above problems and, as a result, discovered that the above problems can be solved by the activated energy ray curable flexographic ink described below, thus completing the present invention.

[0011] In other words, the present invention is an active energy ray curable flexographic ink comprising [1] a radical polymerizable compound, a white pigment, and a dispersant, The present invention relates to an active energy ray-curable flexographic ink in which the dispersant is a dispersant having a phosphate group.

[0012] Furthermore, the present invention relates to the active energy ray curable flexographic ink described in [1] above, wherein the acid value of the dispersant is 50 to 500 mg KOH / g.

[0013] Furthermore, the present invention relates to the active energy ray curable flexographic ink described in [1] or [2] above, wherein the blending ratio of the dispersant is 0.1 to 50% by mass relative to the white pigment.

[0014] Furthermore, the present invention [4] further relates to an active energy ray curable flexographic ink according to any one of the above [1] to [3], comprising an antifoaming agent.

[0015] Furthermore, the present invention relates to the active energy ray curable flexographic ink described in [4] above, wherein the [5] defoaming agent is a non-silicone defoaming agent.

[0016] Furthermore, the present invention relates to an active energy ray curable flexographic ink as described in any of [1] to [5] above, wherein the [6] white pigment is titanium dioxide.

[0017] Furthermore, the present invention relates to an ultraviolet-curable flexographic ink according to any one of the above [1] to [6], wherein the blending ratio of [7] white pigment is 40 to 60% by mass with respect to the entire flexographic ink.

[0018] Furthermore, the present invention relates to an active energy ray curable flexographic ink according to any one of the above [1] to [7], wherein the viscosity (at 25°C, 100 rpm) in an [8]E-type viscometer is 100 to 1500 mPa·s.

[0019] Furthermore, the present invention relates to an active energy ray curable flexographic ink according to any of the above [1] to [8], wherein the thixotropic index calculated by the following formula 1 is 1.00 to 1.40. formula 1 Thixotropic index = (viscosity at 25°C and 10 rpm in an E-type viscometer) / (viscosity at 25°C and 100 rpm in an E-type viscometer)

[0020] The present invention further relates to an active energy ray-curable flexographic ink according to any one of [1] to [9] above, further containing a photoinitiator.

[0021] The present invention also relates to a printed matter having a substrate and a cured product of the active energy ray-curable flexographic ink according to any one of [1] to

[10] above.

Effects of the Invention

[0022] According to the present invention, it is possible to provide an active energy ray-curable flexographic ink capable of achieving both good printing suitability and high hiding power, and a printed matter using the active energy ray-curable flexographic ink.

Modes for Carrying Out the Invention

[0023] Hereinafter, the modes for carrying out the present invention will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the gist thereof.

[0024] The terms used in this embodiment will be explained. “(meth)acryloyl” means acryloyl and / or methacryloyl, and “(meth)acrylate” means acrylate and / or methacrylate. “EO” refers to ethylene oxide, and “EO modification” means ethylene oxide modification. “PO” refers to propylene oxide, and “PO modification” means propylene oxide modification. In addition, in (XO)n (X is E or P) in the name of the radical polymerizable compound, n means the average number of XO in one molecule.

[0025] In this embodiment, the numerical range indicated using "~" includes the numbers before and after "~" as the minimum and maximum values, respectively. In the multiple numerical ranges described in stages in this embodiment, the upper or lower limit of a numerical range in one stage can be arbitrarily combined with the upper or lower limit of a numerical range in another stage. Furthermore, unless otherwise specified, the materials and compounds exemplified in this embodiment may be used individually or in combination of two or more.

[0026] The active energy ray-curable flexographic ink of the present invention comprises a radical polymerizable compound, a white pigment, and a dispersant, and the printed material has a layer of cured active energy ray-curable flexographic ink on a substrate.

[0027] <Radical polymerizable compounds> The active energy ray-curable flexographic ink of the present invention contains a radical polymerizable compound. The radical polymerizable compound is a compound having an ethylenically unsaturated bond that can be radically polymerized, and it is sufficient if the compound has at least one ethylenically unsaturated bond in its molecule, and includes those in chemical forms such as monomers, oligomers, and polymers. The radical polymerizable compound may be used alone or in combination of two or more. Examples of radical polymerizable compounds include unsaturated carboxylic acids such as (meth)acrylic acid, itaconic acid, and maleic acid and their salts, anhydrides having an ethylenically unsaturated groups, acrylonitrile, styrene, and various unsaturated polyesters, unsaturated polyethers, unsaturated polyamides, and unsaturated urethanes. More specifically, radical polymerizable compounds include 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, β-carboxyethyl (meth)acrylate, 4-tert-butylcyclohexanol (meth)acrylate, tetrahydrofurfuryl acrylate, alkoxylated tetrahydrofurfuryl acrylate, caprolactone (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isoamyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, isodecyl (meth)acrylate, 3,3,5-trimethylcyclohexanol (meth)acrylate, and cyclohexyl Monofunctional radical polymerizable compounds such as methyl(meth)acrylate, isobornyl(meth)acrylate, norbornyl(meth)acrylate, dicyclopentanyl(meth)acrylate, dicyclopentenyl(oxyethyl)(meth)acrylate, 1,4-cyclohexanedimethanol(meth)acrylate, cyclic trimethylolpropaneformal(meth)acrylate, benzyl(meth)acrylate, EO-modified (2)nonylphenol acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate, acryloylmorpholin, N-vinylcarbazole, 1-vinylimidazole, N-vinyl-2-pyrrolidone, N-vinylcaprolactam, and N-vinylformamide; 1,3-Butylene glycol di(meth)acrylate, 1,4-Butanediol di(meth)acrylate, 3-Methyl-1,5-Pentanediol di(meth)acrylate, 1,6-Hexanediol di(meth)acrylate, 1,9-Nonanediol di(meth)acrylate, 1,10-Decanediol di(meth)acrylate, 1,2-Dodecanediol di(meth)acrylate, Neopentyl glycol di(meth)acrylate, Polyethylene glycol (200) di(meth)acrylate, Polyethylene glycol (300) di(meth)acrylate, Polyethylene glycol (400) di(meth)acrylate, Polyethylene glycol (600) di(meth)acrylate, Hi Difunctional radical polymerizable compounds such as neopentyl glycol di(meth)acrylate droxypivalate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, EO-modified (2) 1,6-hexanediol di(meth)acrylate, PO-modified (2) neopentyl glycol di(meth)acrylate, (neopentyl glycol-modified) trimethylolpropane di(meth)acrylate, dimethylol tricyclodecane di(meth)acrylate, EO-modified (4) bisphenol A di(meth)acrylate, PO-modified (4) bisphenol A di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, and (2-(2-vinyloxyethoxy)ethyl acrylate); Trifunctional radical polymerizable compounds such as trimethylolpropane tri(meth)acrylate, EO-modified (3) trimethylolpropane tri(meth)acrylate, EO-modified (6) trimethylolpropane tri(meth)acrylate, EO-modified (9) trimethylolpropane tri(meth)acrylate, PO-modified (3) trimethylolpropane tri(meth)acrylate, PO-modified (6) trimethylolpropane tri(meth)acrylate, PO-modified (9) trimethylolpropane tri(meth)acrylate, ε-caprolactone-modified tris-(2-acryloxyethyl) isocyanurate, ethoxylated isocyanurate tri(meth)acrylate, and pentaerythritol tri(meth)acrylate; Tetrafunctional radical polymerizable compounds such as pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, EO-modified (4) pentaerythritol tetra(meth)acrylate, PO-modified (4) pentaerythritol tetra(meth)acrylate, EO-modified (4) ditrimethylolpropane tetra(meth)acrylate, and PO-modified (4) ditrimethylolpropane tetra(meth)acrylate; Pentafunctional radical polymerizable compounds such as dipentaerythritol penta(meth)acrylate, EO-modified (5) dipentaerythritol penta(meth)acrylate, and PO-modified (5) dipentaerythritol penta(meth)acrylate; Examples include hexafunctional radical polymerizable compounds such as dipentaerythritol hexa(meth)acrylate, EO-modified (6) dipentaerythritol hexa(meth)acrylate, and PO-modified (6) dipentaerythritol hexa(meth)acrylate. Furthermore, the radical polymerizable compound may be a mono- or polyalkylene oxide modified compound other than those mentioned above. Furthermore, as radical polymerizable compounds, urethane acrylates such as aliphatic urethane acrylates and aromatic urethane acrylates can be used as unsaturated urethanes; polyester acrylates can be used as unsaturated polyesters; polyether acrylates can be used as unsaturated polyethers; and epoxy acrylates and the like can also be used.

[0028] <White pigment> The active energy ray-curable flexographic ink of the present invention contains a white pigment. Any known pigment can be used as the white pigment in the active energy ray-curable flexographic ink of the present invention, but inorganic pigments are preferred from the viewpoint of weather resistance. The amount of white pigment is preferably 40% to 60% by mass, and more preferably 45% to 55% by mass, based on the total amount of active energy ray-curable flexographic ink. Examples of inorganic pigments include titanium dioxide, zinc oxide, zinc sulfide, barium sulfate, calcium carbonate, silica, mica, talc, and pearl. Titanium dioxide is preferred from the viewpoint of opacity.

[0029] <Titanium Oxide> In this invention, either anatase-type or rutile-type titanium dioxide can be used, but it is preferable to use the rutile-type titanium dioxide to improve the opacity of printed materials. Furthermore, it can be manufactured by any method, such as the chlorine method or the sulfuric acid method, but titanium dioxide manufactured by the chlorine method is preferable because it provides higher opacity.

[0030] Examples of the rutile-type titanium dioxide include Typake CR-50, Typake CR-50-2, Typake CR-57, Typake CR-58, Typake CR-60, Typake CR-60-2, Typake CR-80, Typake CR-90, Typake R-550, Typake R-820, Typake R-830, and Typake R-930, all manufactured by Ishihara Sangyo Co., Ltd. Examples of the anatase-type titanium dioxide include Typake A-100 and Typake A-220, all manufactured by Ishihara Sangyo Co., Ltd. Examples of the zinc sulfide include Sactris HD-S, all manufactured by Sactris Inc.

[0031] <Dispersant> The active energy ray-curable flexographic ink of the present invention contains a dispersant having a phosphate group. The inclusion of a dispersant having a phosphate group tends to reduce the thixotropy of the active energy ray-curable flexographic ink and improve ink transferability from the printing plate to the substrate. Furthermore, the improved ink transferability from the printing plate to the substrate makes it less likely for ink to adhere to the convex and concave parts of the printing plate, and tends to improve plate adhesion. The acid value of the dispersant is preferably 50 mg KOH / g to 500 mg KOH / g, and more preferably 70 mg KOH / g to 200 mg KOH / g. When the acid value of the dispersant is within the above range, the thixotropy of the active energy ray-curable flexographic ink can be further reduced, and ink transferability and plate adhesion tend to improve even further. The dispersant content is preferably 0.1 to 50% by mass, and more preferably 2 to 15% by mass, relative to the white pigment. The dispersant content is preferably 0.04 to 15% by mass of the total composition, and more preferably 1 to 7% by mass.

[0032] Examples of dispersants having a phosphate group include DISPERBYK-102 (acid value 101 mg KOH / g), DISPERBYK-111 (acid value 129 mg KOH / g), DISPERBYK-145 (acid value 76 mg KOH / g), DISPERBYK-180 (acid value 94 mg KOH / g) from Bic Chemie, and TEGODispers655 (acid value 190 mg KOH / g) from Evonik.

[0033] The active energy ray-curable flexographic ink of the present invention tends to exhibit particularly good printability, such as plate adhesion and long-run suitability, as well as high opacity, when using a dispersant having a phosphate group and titanium dioxide as a white pigment. This is presumed to be because titanium dioxide has many basic sites on its surface compared to other white pigments, causing the dispersant having a phosphate group to adsorb strongly to the titanium dioxide, significantly improving dispersion stability.

[0034] <Antifoaming agent> The active energy ray curable flexographic ink of the present invention preferably contains an antifoaming agent. The use of an antifoaming agent tends to improve ink transferability and opacity. This is thought to be because the use of an antifoaming agent reduces foam in the ink, allowing for efficient ink transfer from the cells of the anilox roll to the printing plate. Furthermore, the antifoaming agent is preferably a non-silicone antifoaming agent. This is because it can improve leveling properties with respect to the substrate and provide uniform opacity within the surface. Examples of non-silicone defoaming agents include acrylic resins, vinyl ether resins, butadiene resins, silicone resins, fluororesins, and modified resins thereof (excluding the aforementioned dispersants). In particular, it is preferable to contain at least one resin selected from acrylic resins, vinyl ether resins, and butadiene resins. These may be used individually or in combination of two or more. Examples of non-silicone defoaming agents include BYK-054, BYK-1791, and BYK-1794 from Bic Chemie, and TEGOAirex920 and TEGOAirex922 from Evonik. Examples of silicone defoaming agents include TEGOAirex900, TEGOAirex980, and TEGOFoamex N from Evonik.

[0035] The amount of defoaming agent is preferably 0.01 to 5% by mass, and more preferably 0.1 to 3% by mass, based on the total amount of active energy ray-curable flexographic ink.

[0036] <Photopolymerization initiator> The active energy ray curable flexographic ink of the present invention may have a photopolymerization initiator added to it. When using a photopolymerization initiator, the available photopolymerization initiators include, but are not limited to, photocleavage initiators, hydrogen abstraction initiators, and hybrid types such as photopolymerization initiators in which cleavage sites and hydrogen abstraction sites coexist within the molecule, and photopolymerization initiators in which hydrogen abstraction sites and proton donor sites coexist. One type of photopolymerization initiator may be used alone, or two or more types may be used. The content of the photopolymerization initiator is preferably 1 to 15% by mass, and more preferably 5 to 10% by mass, based on the total amount of the active energy ray curable flexographic ink.

[0037] Examples of photocleavage initiators include α-aminoalkylphenone compounds, α-hydroxyalkylphenone compounds, and acylphosphine oxide compounds. α-hydroxyalkylphenone compounds and acylphosphine oxide compounds are particularly preferred from the viewpoint of preventing yellowing.

[0038] More specifically, examples of α-aminoalkylphenone compounds include 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one, 2-benzyl-2-dimethylamino-1-(4-piperidinophenyl)-butan-1-one, 1-[4-(butylsulfanyl)phenyl]-2-methyl-2-(morpholin-4-yl)propan-1-one, 3,6-bis(2-methyl-2-morpholinopropanonyl)-9-butylcarbazole, and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one. These can be used individually or in combination of two or more.

[0039] Examples of α-hydroxyalkylphenone compounds include 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-[4-(2-hydroxymethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, and 2-hydroxy-1-[4-[4-(2-hydroxy-2-methylpropionyl)-benzyl]phenyl]-2-methylpropan-1-one. These can be used individually or in combination of two or more.

[0040] Examples of acylphosphine oxide compounds include diphenylacylphenylphosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, 2,4,6-trimethylbenzoyl-bis(4-methylphenyl)phosphine oxide, and ethoxyphenyl(2,4,6-trimethylbenzoyl)phosphine oxide. These can be used individually or in combination of two or more types.

[0041] Furthermore, examples of hydrogen abstraction type polymerization initiators include dialkylbenzophenone compounds and thioxanthone compounds.

[0042] More specifically, examples of dialkylaminobenzophenone compounds include 4,4'-dialkylaminobenzophenones such as 4,4'-bis-(dimethylamino)benzophenone and 4,4'-bis-(diethylamino)benzophenone, and 4-benzoyl-4'-methyldiphenyl sulfide. Dialkylaminobenzophenone compounds may be used alone or in combination of two or more types. Examples of thioxanthone compounds include 2,4-diethylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diisopropylthioxanthone, 2-isopropylthioxanthone, 4-diisopropylthioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-dichlorothioxanthone, 2-chlorothioxanthone, 1-chloro-4-propoxythioxanthone, and 2-hydroxy-3-(3,4-dimethyl-9-oxo-9Hthioxanthone-2-yloxy)-N,N,N-trimethyl-1-propanamine hydrochloride. These may be used individually or in combination of two or more.

[0043] Examples of sensitizers include benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 2,3,4-trimethylbenzophenone, 4-phenylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, 4-(1,3-acryloyl-1,4,7,10,13-pentaoxotridecyl)benzophenone, methyl-o-benzoylbenzoate, [4-(methylphenylthio)phenyl]phenylmethanone, (4-benzoylbenzyl)trimethylammonium chloride, and 2-hydroxy Examples include 2-methyl-1-phenylpropan-1-one, 1-(4-isopropylphenyl)2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-styrylpropan-1-one polymer, diethoxyacetophenone, dibutoxyacetophenone, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and benzoin n-butyl ether. These may be used individually or in combination of two or more.

[0044] For example, in applications where migration reduction of low molecular weight molecules is required, such as in food products, high molecular weight versions of the above initiators may also be used. Examples of high molecular weight initiators include Omnipol BP, Genopol BP, Omnipol ASA, Genopol AB, Omnipol910, Omnipol TX, and Omnipol TP. These may be used individually or in combination of two or more.

[0045] <Other ingredients> The active energy ray curable flexographic ink of the present invention may further optionally contain other components such as colorants, resins, radical polymerization inhibitors, waxes, antistatic agents, ultraviolet absorbers, antioxidants, and antioxidants (preservatives).

[0046] The active energy ray-curable flexographic ink of the present invention may include a coloring agent such as a colored pigment or dye with coloring properties. The colored pigment may be either an inorganic pigment or an organic pigment, and various known pigments can be used.

[0047] Examples of inorganic pigments include lead yellow, zinc yellow, Prussian blue, cadmium red, iron oxide, ultramarine, carbon black, graphite, aluminum powder, and iron oxide. Examples of organic pigments include soluble azo pigments such as β-naphthol-based, β-oxynaphthoic acid-based, β-oxynaphthoic acid-based anilide-based, acetoacetate anilide-based, and pyrazolone-based pigments; insoluble azo pigments such as β-naphthol-based, β-oxynaphthoic acid-based anilide-based, acetoacetate anilide-based monoazo, acetoacetate anilide-based disazo, and pyrazolone-based pigments; phthalocyanine-based pigments such as copper phthalocyanine blue, halogenated (chlorinated or brominated) copper phthalocyanine blue, sulfonated copper phthalocyanine blue, and metal-free phthalocyanine; polycyclic pigments and heterocyclic pigments such as quinacridone-based, dioxazine-based, slene-based (pyrantrone, anthantrone, indanthrone, anthrapyrimidine, flavanthrone, thioindigo-based, anthraquinone-based, perinone-based, perylene-based, etc.); isoindolone-based, metal complex-based, and quinophthalone-based pigments.

[0048] The active energy ray curable flexographic ink of the present invention may contain a resin. The use of a resin can impart appropriate elasticity to the printing ink and contribute to the dispersion of color pigments. Examples of resins included in the present invention include polyvinyl chloride, acrylic resin, epoxy resin, polyester resin, polyurethane resin, cellulose derivatives (e.g., ethylcellulose, cellulose acetate, nitrocellulose), vinyl chloride-vinyl acetate copolymer, polyamide resin, polyvinyl acetal resin, diallyl phthalate resin, non-phthalate allyl resin, alkyd resin, rosin-modified alkyd resin, petroleum resin, urea resin, and synthetic rubber such as butadiene-acrylonitrile copolymer. Furthermore, these resins can be modified before use. Examples include chlorination, bromination, amine modification, and carboxylic acid modification. The resin may be used alone or in combination of two or more types.

[0049] The active energy ray curable flexographic ink of the present invention may contain a radical polymerization inhibitor. Examples of radical polymerization inhibitors include (alkyl)phenol, hydroquinone, catechol, resorcinol, p-methoxyphenol, t-butylcatechol, t-butylhydroquinone, pyrogallol, 1,1-picrylhydrazyl, phenothiazine, p-benzoquinone, nitrosobenzene, 2,5-di-tert-butyl-p-benzoquinone, dithiobenzoyl disulfide, picric acid, cuperone, aluminum N-nitrosophenylhydroxylamine, tri-p-nitrophenylmethyl, N-(3-oxyanilino-1,3-dimethylbutylidene)aniline oxide, dibutylcresol, cyclohexanone oxime cresol, guaiacol, o-isopropylphenol, butyraldoxime, methyl ethyl ketoxime, and cyclohexanone oxime. These may be used individually or in combination of two or more.

[0050] The active energy ray curable flexographic ink of the present invention may contain wax. Examples of waxes include natural waxes such as carnauba wax, wood wax, lanolin, montane wax, paraffin wax, microcrystalline wax, and rice wax, as well as synthetic waxes such as Fischertrops wax, polyethylene wax, polypropylene wax, polytetrafluoroethylene wax, polyamide wax, and silicon compounds.

[0051] The active energy ray-curable flexographic ink of the present invention preferably contains substantially no solvent. Substantially, the solvent content is 5% by mass, preferably 3% by mass or less, based on the total amount of active energy ray-curable flexographic ink.

[0052] The active energy ray-curable flexographic ink of the present invention preferably contains substantially no water. "Substantially no water" means that the amount of water is 5% by mass or less, and preferably 3% by mass or less, based on the total amount of the active energy ray-curable flexographic ink.

[0053] <Method for manufacturing flexographic ink> The method for producing the active energy ray-curable flexographic ink of the present invention may be the same as that for conventional active energy ray-curable ink compositions, for example, by using the above-mentioned ink components at a temperature between room temperature and 100°C. For production, equipment for kneading, mixing, and / or preparation such as a kneader, three-roll machine, attritor, sand mill, gate mixer, and Scandex can be used.

[0054] <Viscosity> The viscosity of the active energy ray-curable flexographic ink of the present invention is preferably 100 to 1500 mPa·s, and more preferably 200 to 1000 mPa·s. This viscosity is the viscosity measured by an E-type viscometer (25°C, 100 rpm). When the viscosity is within the above range, the transferability of the active energy ray-curable flexographic ink to the substrate during printing is improved, and good opacity can be obtained. Furthermore, the thixotropic index calculated by the following formula 1 is preferably 1.00 to 1.40, more preferably 1.00 to 1.20, and even more preferably 1.00 to 1.10. When the thixotropic index is within the above range, the transferability of the active energy ray-curable flexographic ink to the substrate during printing is improved, and good opacity can be obtained.

[0055] formula 1 Thixotropic index = (Viscosity at 25°C and 10 rpm on an E-type viscometer) / (Viscosity at 25°C and 100 rpm on an E-type viscometer)

[0056] <Printed material> In embodiments of the present invention, the printed material comprises a substrate and a layer of a cured product of an active energy ray-curable flexographic ink. The cured product can be formed by printing and curing the active energy ray-curable flexographic ink using the above printing method.

[0057] <Activated energy rays> In this invention, the active energy rays used to cure the active energy ray-curable flexographic ink refer to energy rays that have the property of causing chemical changes in the irradiated material, such as ultraviolet rays and electron beams. Examples include energy rays generated by mercury lamps, xenon lamps, metal hydride lamps, ultraviolet light-emitting diodes (UV-LEDs), ultraviolet laser diodes (UV-LDs) with wavelengths of 365 nm, 385 nm, 395 nm, and 405 nm, and gas and solid-state lasers.

[0058] <Base material> The printed material of the present invention has a base material. The substrate for printing the active energy ray-curable flexographic ink in the present invention can be any material on which printing ink can be printed. Examples include paper substrates, resin substrates, metal substrates, wood, and the like. The thickness of the paper substrate is not particularly limited. The surface of the paper substrate may be vapor-deposited with a metal such as aluminum for the purpose of providing design appeal. Furthermore, the paper substrate may be surface-coated with acrylic resin, urethane resin, polyester resin, polyolefin resin, or other resins, and may also be subjected to surface treatments such as corona treatment. For example, specific examples of surface-treated paper substrates include coated paper and art paper.

[0059] Examples of resin substrates include polyolefin substrates such as polyethylene and polypropylene, polyester substrates such as polyethylene terephthalate and polylactic acid, polycarbonate substrates, polystyrene-based substrates such as polystyrene, AS resin, and ABS resin, nylon substrates, polyamide substrates, polyvinyl chloride substrates, polyvinylidene chloride substrates, cellophane substrates, paper substrates, aluminum substrates, or substrates made from composite materials thereof.

[0060] Furthermore, a vapor-deposited substrate can be used, which is a substrate onto which an inorganic compound such as silica, alumina, or aluminum has been vapor-deposited. In addition, the vapor-deposited surface may be coated with polyvinyl alcohol or the like.

[0061] The substrate is preferably treated for easy adhesion on the surface to be printed (the surface in contact with the printing layer). Specific examples of easy adhesion treatments include corona discharge treatment, ultraviolet / ozone treatment, plasma treatment, oxygen plasma treatment, and primer treatment. Furthermore, if sufficient adhesion cannot be obtained with a polyethylene terephthalate substrate, surface treatments such as acrylic coating, polyester treatment, or polyvinylidene chloride treatment may be applied.

[0062] <Printing method> Flexographic printing presses include CI-type multi-color flexographic printing presses and unit-type multi-color flexographic printing presses. Ink supply methods include chamber type and two-roll type, and the appropriate printing press can be used. The printing plate can be any suitable plate, such as a photopolymer substrate that hardens resin under UV light, or a rubber plate with an engraved image. While chrome-plated anilox rolls and ceramic anilox rolls are commonly used for anilox rolls, the type of anilox roll used is not limited to these, as long as it is compatible with flexographic printing presses.

[0063] <Examples> The present invention will be described in more detail below with reference to examples, but these examples do not limit the scope of the present invention in any way. In this invention, "parts" refers to "parts by mass," and "%" refers to "mass%."

[0064] Details of the materials listed in Table 1 below are provided below. <Radical polymerizable compounds> MIRAMER PE210: Manufactured by MIWON, Bisphenol A type epoxy acrylate EBECRYL450: Manufactured by Daicel Ornex Co., Ltd., polyester acrylate Beam set 550B: Manufactured by Arakawa Chemical Industries, Ltd., urethane acrylate MIRAMER LR3130: Manufactured by MIWON, EO-modified (3) trimethylolpropane triacrylate TPGDA: Tripropylene glycol diacrylate, manufactured by Daicel Ornex Co., Ltd. <Resin> Beamset 255: Manufactured by Arakawa Chemical Industries, Ltd., made of styrene-acrylic resin. CAB-551-0.01: Cellulose resin, manufactured by Eastman Chemical Company. <White pigment> Typeque CR-90: Manufactured by Ishihara Sangyo Co., Ltd., chlorine-processed rutile-type titanium dioxide. Typeque A-220: Manufactured by Ishihara Sangyo Co., Ltd., sulfuric acid-processed anatase-type titanium dioxide. Sactris HD-S: Manufactured by Sactris, zinc sulfide. <Dispersant> DISPERBYK-111: A dispersant containing a phosphate group, manufactured by Bic Chemie (acid value 129 mg KOH / g). Solspers 3000: A dispersant manufactured by Lubrizol, which does not contain phosphate groups (acid value 32.5 mg KOH / g). DISPERBYK-145: A dispersant containing a phosphate group, manufactured by Bic Chemie (acid value 129 mg KOH / g). DISPERBYK-180: A dispersant containing a phosphate group, manufactured by Bic Chemie (acid value 94 mg KOH / g). TEGODispers655: A dispersant containing phosphate groups, manufactured by Evonik (acid value 190 mg KOH / g). <Photopolymerization initiator> OMNIRAD TPO-L: Ethoxyphenyl (2,4,6-trimethylbenzoyl)phosphine oxide, manufactured by IGM Resins. OMNIRAD 1173: Manufactured by IGM Resins, 2-hydroxy-2-methyl-1-phenylpropan-1-one <Antifoaming agent> TEGOAirex920: A non-silicone antifoaming agent manufactured by Evonik. BYK-054: Non-silicone defoaming agent manufactured by Big Chemie Co., Ltd. TEGOFoamex N: Silicone-based defoamer manufactured by Evonik.

[0065] <Example 1> Ink composition 1 was obtained by continuous printing using a three-roll mill according to the composition (parts) shown in Table 1.

[0066] <Examples 2-24, Comparative Examples 1-2> Ink compositions 2 to 26 (Examples 2, Comparative Examples 1 to 2, and Examples 3 to 24) were manufactured in accordance with Example 1, with the only changes being made to the composition shown in Table 1.

[0067] [Table 1]

[0068] [Table 1]

[0069] The obtained active energy ray-curable flexographic ink was used to create printed materials according to the following procedure, and the results were evaluated. The results are shown in Table 1.

[0070] <Creating printed materials> The obtained active energy ray curing flexographic ink was tested on a NeilPeter FA-17 (manufactured by NeilPeter, printing speed: 150 m / min, anilox roll: Zecher 160 lpi, 11 cc / cm²). 2 The printing plate was coated onto a treated OPP substrate (biaxially oriented polypropylene film, FOR, manufactured by Futamura Chemical Co., Ltd., film thickness 20 μm) using a DuPont Cyrel EASY ESXR printing plate, and cured by irradiation with ultraviolet light using one GEW E2C (air-cooled mercury lamp, 140 W / cm) lamp. The printing plate has a solid printing area and a halftone printing area. Sufficient ink volume was ensured even for long-run printing by circulating active energy ray curing flexographic ink through the chamber. Printed materials were obtained 1 minute, 5 minutes, 10 minutes, 20 minutes, and 30 minutes after the start of printing. For the evaluation of "Opacity" and "Plate Entanglement" below, the printed material obtained 30 minutes after the start of printing was used, and for the evaluation of "Long-Run Suitability" below, the printed materials obtained 1 minute, 5 minutes, 10 minutes, 20 minutes, and 30 minutes after the start of printing were used.

[0071] <Method for measuring opacity> Opacity test paper was prepared by printing and curing FD Carton X (an active energy ray curing ink manufactured by Toyo Ink Co., Ltd.) black ink onto Hokuetsu Maricoat (coated cardboard manufactured by Hokuetsu Corporation). A print obtained 30 minutes after the start of printing was placed on the opacity test paper, and the black ink density of the solid print area was measured using a spectrophotometer (X-rite eXact2, manufactured by X-rite). A lower black ink density indicates higher opacity. A practical level is 3 or higher. The black ink density measured on the opacity test paper alone was 2.00. (Evaluation Criteria) 5: Ink density is 0.20 or less 4: Ink density greater than 0.20 and less than or equal to 0.25 3: Ink density greater than 0.25 but less than or equal to 0.35 2: Ink density greater than 0.35 but less than or equal to 0.45 1: Ink density greater than 0.45

[0072] <Evaluation methods related to editions> The halftone print areas of the printed material obtained 30 minutes after the start of printing were visually inspected to evaluate printing defects caused by plate entanglement. The practical level is 3 or higher. (Evaluation Criteria) 5: No printing defects whatsoever 4: Very small printing defects are visible. 3: Minor printing defects are visible. 2: Significant printing defects are observed. 1: Extremely large printing defects are visible.

[0073] <Method for evaluating suitability for long-distance races> The printed materials obtained at 1 minute, 5 minutes, 10 minutes, 20 minutes, and 30 minutes after the start of printing were placed on opacity test paper, and the ink density of the solid printed areas was measured using a spectrophotometer (X-rite eXact2, manufactured by X-rite). Using the ink density of the solid printed area of ​​the printed material at 1 minute after the start of printing as a baseline, a change in the ink density of the solid printed area of ​​the printed materials at 5 minutes, 10 minutes, 20 minutes, and 30 minutes after the start of printing was considered to have changed if the change was 0.03 or more. A practical level is 3 or higher. (Evaluation Criteria) 5: No change in opacity was observed even 30 minutes after the start of printing. 4. Changes in opacity were observed 30 minutes after the start of printing. 3: Changes in opacity were observed 20 minutes after the start of printing. 2: Changes in opacity were observed 10 minutes after the start of printing. 1: Changes in opacity were observed 5 minutes after printing began.

[0074] Examples 1 to 24 all demonstrated good opacity, plate retention, and long-run suitability. Comparative Examples 1 and 2 all exhibited poor opacity, plate entanglement, and long-run suitability.

[0075] Based on the above, the present invention makes it possible to provide an active energy ray-curable flexographic ink that achieves both good printability, such as plate retention and long-run suitability, and high opacity, as well as printed materials using the active energy ray-curable flexographic ink.

Claims

1. An active energy ray curable flexographic ink comprising a radical polymerizable compound, a white pigment, and a dispersant, An active energy ray-curable flexographic ink, wherein the dispersant is a dispersant having a phosphate group.

2. The active energy ray-curable flexographic ink according to claim 1, wherein the acid value of the dispersant is 50 to 500 mg KOH / g.

3. The active energy ray curable flexographic ink according to claim 1, wherein the proportion of the dispersant is 0.1 to 50% by mass relative to the white pigment.

4. Furthermore, the active energy ray curable flexographic ink according to claim 1, further comprising an antifoaming agent.

5. The active energy ray curable flexographic ink according to claim 4, wherein the defoaming agent is a non-silicone defoaming agent.

6. The active energy ray curable flexographic ink according to claim 1, wherein the white pigment is titanium dioxide.

7. The ultraviolet-curable flexographic ink according to claim 1, wherein the proportion of white pigment in the blend is 40 to 60% by mass of the total flexographic ink.

8. The active energy ray curable flexographic ink according to claim 1, wherein the viscosity (at 25°C and 100 rpm) measured in an E-type viscometer is 100 to 1500 mPa·s.

9. The active energy ray-curable flexographic ink according to claim 1, wherein the thixotropic index calculated by the following formula 1 is between 1.00 and 1.

40. Formula 1 Thixotropic index = (Viscosity at 25°C and 10 rpm using an E-type viscometer) / (Viscosity at 25°C and 100 rpm using an E-type viscometer)

10. Furthermore, the active energy ray curable flexographic ink according to claim 1, further comprising a photopolymerization initiator.

11. A printed article comprising a substrate and a cured product of an active energy ray-curable flexographic ink according to any one of claims 1 to 10.

Images