Active energy ray-curable ink set, method for producing printed material, and printed material

Abstract

To provide an active energy ray-curable ink set that achieves excellent printing quality and curability in multicolor printing, and to provide a method for producing a printed material using the ink set, and a printed material obtained using the ink set.SOLUTION: There is provided an ink set for printing ink A followed by printing ink B, wherein a tack value of the ink A (TA) is 4.7 or more and 12 or less, a tack value of the ink B (TB) is 4.5 or more and 10 or less, and 5≥TA-TB≥0.2, the ink A being at least one ink selected from the group consisting of a red ink, a blue ink and a black ink, the ink B being a yellow ink, and the yellow ink, the red ink, the blue ink and the black ink each comprising 10-25 mass% of a colorant, a (meth)acrylate compound and two or more photopolymerization initiators.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an actinic radiation-curable ink set that exhibits excellent print quality and curability in multicolor printing, and to a method for producing a printed item using the same, and the printed item. [Background technology]

[0002] Active energy ray-curable inks are solvent-free and instantly cure and dry with active energy rays, making them environmentally friendly, easy to print, and capable of producing high-quality printed matter. As such, they are widely used in a wide range of fields, from printing information such as magazines and flyers to packaging for food packaging such as paper containers.

[0003] Typically, in lithographic offset printing using oil-based inks, multicolor overprinting is performed in the following order: black ink, indigo ink, crimson ink, and yellow ink. However, in lithographic offset printing using active energy ray-curable inks, a phenomenon has been observed in which the gloss of the overlapping areas of printed materials is reduced compared to prints using oil-based inks. Active energy ray-curable offset inks that improve the gloss of the overprinted areas have been proposed, but the print quality and curing properties have remained insufficient. (Patent Document 1)

[0004] There has also been a proposal for a multi-color wet overprinting method for cylindrical objects, in which an offset printing machine is used to create a tack difference in the inks, thereby printing a multi-color layered ink image applied to a blanket roller onto the cylindrical object being printed in a single operation. However, this method uses a mixture of ultraviolet-curable ink and heat-curable ink, and is a printing method for cylindrical objects, and is not a method that can be used for printing on sheet substrates (Patent Document 2).

[0005] Also, a method for multicolor wet overprinting using an offset printing method has been proposed, in which a difference in tackiness is created between each of the inks printed on the surface of the substrate by adjusting the temperature of the inks, and the inks with the difference in tackiness are used to print multicolor wet overprints on the surface of the substrate, with a single baking step; however, this method is difficult to apply to actinic energy ray-curable inks, and it has been difficult to obtain sufficient print quality (Patent Document 3).

[0006] In recent years, in addition to conventional light sources such as high-pressure mercury lamps and metal halide lamps, various types of light sources have come into use, such as light sources that use ozone-free metal halide lamps that do not generate ozone and emit ultraviolet light in the range of 230 to 420 nm, and light-emitting diodes (UV-LEDs) that emit ultraviolet light with a peak emission wavelength in the range of 350 to 420 nm. Inventions have been made that combine multiple photopolymerization initiators with different absorption wavelengths to match the wavelength ranges of these various light sources, but it has been difficult to achieve sufficient curing properties in multicolor printing (Patent Document 4). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-79314 [Patent Document 2] Japanese Patent Application Publication No. 7-285262 [Patent Document 3] Japanese Patent Application Publication No. 57-117991 [Patent Document 4] Patent No. 6861282 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention provides an actinic ray-curable ink set that exhibits excellent print quality and curability in multicolor printing, and also provides a method for producing a printed item using the same, and the printed item. [Means for solving the problem]

[0009] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by the actinic energy ray-curable ink set described below, and have thus completed the present invention.

[0010] That is, the present invention is an ink set for printing ink A and then printing ink B in contact with ink A, The tack value (referred to as TA) of the ink A at a temperature of 30°C and a rotation speed of 400 rpm is 4.7 to 12, The ink B has a tack value (TB) of 4.5 to 10 at a temperature of 30°C and a rotation speed of 400 rpm; 5≧TA-TB≧0.2, The ink A is one or more inks selected from the group consisting of an active energy ray-curable crimson ink, an active energy ray-curable indigo ink, and an active energy ray-curable black ink, Ink B is an active energy ray-curable yellow ink, the active energy ray-curable yellow ink, the active energy ray-curable crimson ink, the active energy ray-curable indigo ink, and the active energy ray-curable black ink each contain a colorant, a (meth)acrylate compound, and two or more photopolymerization initiators; The ink set relates to the ink set, wherein the content of the colorant is 10 to 25% by mass of the total amount of the ink.

[0011] The present invention also relates to the ink set described above, wherein the photopolymerization initiator comprises an α-aminoalkylphenone-based initiator and a thioxanthone-based initiator.

[0012] The present invention also relates to the above ink set, wherein the content of the photopolymerization initiator is 2 to 15% by mass based on the total amount of the ink.

[0013] The present invention also relates to the above ink set, wherein the α-aminoalkylphenone initiator comprises 2-benzyl-2-dimethylamino-1-(4-piperidinophenyl)-butan-1-one.

[0014] The present invention also relates to the ink set described above, wherein the (meth)acrylate compound contains a compound having three or more (meth)acryloyl groups.

[0015] The present invention also relates to the above ink set, wherein the content of the (meth)acrylate compound is 10 to 70% by mass of the total amount of the ink.

[0016] The present invention also relates to a printed matter obtained by printing the ink set on a substrate and curing the ink set with active energy rays.

[0017] The present invention also relates to the above printed matter, wherein the substrate is a paper substrate or a film substrate.

[0018] The present invention also provides a method for producing a printed matter, which comprises printing ink A, printing ink B so as to be in contact with ink A, and curing the ink B with active energy rays, The ink A has a tack value (referred to as TA) of 4.7 to 12 at a set temperature of 30°C and a rotation speed of 400 rpm, The ink B has a tack value (TB) of 4.5 to 10 at a set temperature of 30°C and a rotation speed of 400 rpm, 5≧TA-TB≧0.2, The ink A is one or more inks selected from the group consisting of an active energy ray-curable crimson ink, an active energy ray-curable indigo ink, and an active energy ray-curable black ink, Ink B is an active energy ray-curable yellow ink, the active energy ray-curable yellow ink, the active energy ray-curable crimson ink, the active energy ray-curable indigo ink, and the active energy ray-curable black ink each contain a colorant, a (meth)acrylate compound, and two or more photopolymerization initiators; The present invention relates to a method for producing a printed matter, wherein the content of the colorant is 10 to 25% by mass of the total amount of the ink. [Effects of the Invention]

[0019] The present invention makes it possible to provide an actinic ray-curable ink set that is excellent in print quality and curability in multicolor printing, and to provide a method for producing printed matter and printed matter using the same. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments described below, and various modifications are possible within the scope of the gist of the present invention.

[0021] The terms used in this specification are explained below. "(Meth)acrylate" means acrylate and / or methacrylate, and "(meth)acryloyl" means acryloyl and / or methacryloyl. Furthermore, "PO" stands for "propylene oxide," and "EO" stands for "ethylene oxide."

[0022] <Active energy ray curable ink set> The ink set of the present invention is an ink set for printing ink A, and then printing ink B in contact with ink A, The ink A has a tack value (referred to as TA) of 4.7 to 12 at a temperature of 30°C and a rotation speed of 400 rpm; The ink B has a tack value (TB) of 4.5 to 10 at a temperature of 30°C and a rotation speed of 400 rpm; 5≧TA-TB≧0.2, The ink A is one or more inks selected from the group consisting of an active energy ray-curable crimson ink (hereinafter also referred to as "crimson ink"), an active energy ray-curable indigo ink (hereinafter also referred to as "indigo ink"), and an active energy ray-curable black ink (hereinafter also referred to as "black ink"); The ink B is an active energy ray-curable yellow ink (hereinafter also referred to as "yellow ink"). the yellow ink, the crimson ink, the indigo ink, and the black ink each contain a colorant, a (meth)acrylate compound, and two or more photopolymerization initiators; The ink set has a content of the colorant of 10 to 25% by mass of the total amount of the ink.

[0023] The ink set of the present invention may contain a yellow ink and one or more inks selected from the group consisting of a crimson ink, an indigo ink, and a black ink, and may also contain inks of other colors.

[0024] [Coloring agent] The yellow ink, crimson ink, indigo ink, and black ink in the present invention contain a colorant. As the colorant, at least one of a pigment and a dye can be used, but from the viewpoint of lightfastness, it is preferable to use a pigment.

[0025] The pigment used in the present invention is not particularly limited, and any known pigment can be used. Both inorganic and organic pigments can be used.

[0026] Examples of inorganic pigments include carbon blacks such as furnace black, lamp black, acetylene black, and channel black, iron oxide, and titanium oxide.

[0027] Examples of organic pigments include soluble azo pigments such as β-naphthol, β-hydroxynaphthoic acid, β-hydroxynaphthoic acid anilide, acetoacetic acid anilide, and pyrazolone; Examples of suitable pigments include insoluble azo pigments such as β-naphthols, β-oxynaphthoic acid anilides, monoazo acetoacetate anilides, disazo acetoacetate anilides, and pyrazolones; phthalocyanine pigments such as copper phthalocyanine blue, halogenated (e.g., chlorinated or brominated) copper phthalocyanine blue, sulfonated copper phthalocyanine blue, and metal-free phthalocyanine; and polycyclic and heterocyclic pigments such as quinacridones, dioxazines, threnes (pyranthrones, anthanthrones, indanthrones, anthrapyrimidines, flavanthrones, thioindigo, anthraquinones, perinones, and perylenes), isoindolinones, metal complexes, quinophthalones, and diketopyrrolopyrroles.

[0028] More specifically, examples of yellow pigments used in yellow inks include CI Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 18, 24, 73, 74, 75, 83, 93, 95, 97, 98, 100, 108, 109, 110, 114, 120, 128, 129, 138, 139, 174, 150, 151, 154, 155, 167, 180, 185, and 213.

[0029] The red pigments used in red ink are CI Pigment RED 1, 3, 5, 19, 21, 22, 31, 38, 42, 43, 48:1, 48:2, 48:3, 48:4, 48:5, 49:1, 50, 52, 53:1, 57:1, 57:2, 58:4, 63:1, 81, 81:1, 81:2, 81:3, 81:4, 83, 90, 104, 108, 11 2, 114, 122, 144, 146, 148, 149, 150, 166, 168, 169, 170, 172, 173, 176, 177, 178, 184, 185, 187, 193, 202, 209, 214, 242, 254, 255, 264, 266, 269, CI Pigment Violet 19, etc.

[0030] Indigo pigments used in indigo ink include CI Pigment Blue 1, 2, 14, 15, 15:1, 15:2, 15:3, 15:4, 60, 62, etc.

[0031] Examples of black pigments used in black ink include CI Pigment Black 1, 6, 7, 9, 10, 11, 28, 26, and 31.

[0032] Furthermore, colorants that can be used to adjust the color of the ink or when using inks of other colors include green pigments such as CI Pigment Green 1, 2, 3, 4, 7, 8, 10, 15, 17, 26, 36, 45, and 50; purple pigments such as CI Pigment Violet 1, 2, 3, 4, 5:1, 12, 13, 15, 16, 17, 19, 23, 25, 29, 31, 32, 36, 37, 39, and 42; and orange pigments such as CI Pigment Orange 13, 16, 20, 34, 36, 38, 39, 43, 51, 61, 63, 64, and 74.

[0033] In the present invention, the above pigments may be used alone or in combination of two or more.

[0034] The content of the colorant in the present invention is 10 to 25% by mass, and preferably 12 to 20% by mass, based on the total mass of the ink. If it is less than 10% by mass, the coloring strength of the ink will be low, and if it is more than 25% by mass, the fluidity of the printing ink will not be ensured.

[0035] [(Meth)acrylate compounds] The yellow ink, crimson ink, indigo ink, and black ink in the present invention contain a (meth)acrylate compound. The (meth)acrylate compound is not particularly limited as long as it is a compound having one or more (meth)acryloyl groups in the molecule.

[0036] Specific examples of the (meth)acrylate compound having 1 or 2 (meth)acryloyl groups include 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, β-carboxylethyl (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- Monofunctional (meth)acrylate compounds having one (meth)acryloyl group, such as trimethylcyclohexanol (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, norbornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (oxyethyl) (meth)acrylate, 1,4-cyclohexanedimethanol (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, benzyl (meth)acrylate, EO-modified (2) nonylphenol acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate, and acryloylmorpholine; 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, neopentyl glycol hydroxypivalate di(meth)acrylate, dipropylene glycol di(meth)acrylate Examples of the difunctional (meth)acrylate compound include bifunctional (meth)acrylate compounds having two (meth)acryloyl groups, such as ethylene glycol diacrylate, 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, dimethyloltricyclodecane di(meth)acrylate, EO-modified (4) bisphenol A di(meth)acrylate, PO-modified (4) bisphenol A di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, dimethyloltricyclodecane di(meth)acrylate, dicyclopentanyl di(meth)acrylate, and tris(2-hydroxyethyl)isocyanurate di(meth)acrylate.

[0037] Specific examples of compounds having three or more (meth)acryloyl groups include trifunctional (meth)acrylate compounds having three (meth)acryloyl groups, such as trimethylolpropane tri(meth)acrylate, EO-modified (3) trimethylolpropane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, EO-modified (4) trimethylolpropane tri(meth)acrylate, PO-modified (3) trimethylolpropane tri(meth)acrylate, ε-caprolactone-modified tris-(2-acryloxyethyl)isocyanurate, ethoxylated isocyanuric acid tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, and pentaerythritol tri(meth)acrylate; tetrafunctional (meth)acrylate compounds such as pentaerythritol tetra(meth)acrylate and ditrimethylolpropane tetra(meth)acrylate; Examples thereof include pentafunctional (meth)acrylate compounds such as dipentaerythritol penta(meth)acrylate, and hexafunctional (meth)acrylate compounds such as dipentaerythritol hexa(meth)acrylate.

[0038] In addition, as the (meth)acrylate compound, urethane (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate, etc. can also be used.

[0039] Urethane (meth)acrylates include, for example, those obtained by reacting a diisocyanate with a (meth)acrylate having a hydroxyl group, and those obtained by reacting an isocyanate group-containing urethane prepolymer obtained by reacting a polyol with a polyisocyanate under conditions of an excess of isocyanate groups with a (meth)acrylate having a hydroxyl group. Alternatively, they can also be obtained by reacting a hydroxyl group-containing urethane prepolymer obtained by reacting a polyol with a polyisocyanate under conditions of an excess of hydroxyl groups with a (meth)acrylate having an isocyanate group.

[0040] Commercially available products that can be used as urethane (meth)acrylates include "EBECRYL 220", "EBECRYL 230", "EBECRYL 270", "EBECRYL 284", "EBECRYL 280 / 15IB", "EBECRYL 4491", "EBECRYL 4683", "EBECRYL 4858", "EBECRYL 8307", "EBECRYL 8402", "EBECRYL 8411", "EBECRYL 8413", "EBECRYL 8804", "EBECRYL 8807", "EBECRYL 9270", "KRM7735", "KRM8191", "EBECRYL 8800", "EBECRYL 294 / 25H D", "EBECRYL 4220", "EBECRYL 4513", and "EBECRYL 4738", "EBECRYL 4820", "EBECRYL 8311", "EBECRYL 4740", "EBECRYL 9260", "EBECRYL 8701", "KRM 8667", "KRM 8296", "EBECRYL 210", "EBECRYL 246 / 20HEMA", "EBECRYL 1271", "EBECRYL 286", "EBECRYL 4859", "EBECRYL 8409", "EBECRYL 8465", "EBECRYL 8809", "EBECRYL 8810", "EBECRYL 8811", "EBECRYL 1258", "EBECRYL 4101", Arakawa Chemical Industries, Ltd.'s "Beamset 550B", Miwon Specialty Chemical's "Miramer UA5095X2", "Miramer UA5216", "Miramer SC2404", "Miramer SC2565", "Miramer MU3603", "Miramer PU3701", "Miramer PU210", "Miramer PU256", "Miramer PU217", "Miramer PU2030I", "Miramer PU2050", "Miramer PU2100", "Miramer PU2034C”, “Miramer PU2200”, “Miramer PU2300C”, “Miramer PU2560”, “MiramerPU320", "Miramer PU330", "Miramer PU340", "Miramer PU3000", "Miramer PU3200", "Miramer PU3210", "Miramer PU3450", etc.

[0041] Furthermore, as the urethane (meth)acrylate, the urethane (meth)acrylate described in Japanese Patent No. 7428842 can also be used.

[0042] The polyester (meth)acrylate can be obtained, for example, by reacting a polyester polycarboxylic acid obtained by polycondensing a polybasic acid and a polyhydric alcohol with a hydroxyl group-containing (meth)acrylate or the like.

[0043] Examples of epoxy (meth)acrylates include those obtained by esterifying the glycidyl group of an epoxy resin with (meth)acrylic acid to change the functional group to a (meth)acrylate group, such as a (meth)acrylic acid adduct of a bisphenol A type epoxy resin and a (meth)acrylic acid adduct of a novolac type epoxy resin.

[0044] Commercially available epoxy (meth)acrylates include "EBECRYL 600," "EBECRYL 605," "EBECRYL 645," "EBECRYL 648," "EBECRYL 860," "EBECRYL 3500," "EBECRYL 3603," "EBECRYL 3700," "EBECRYL 3701," "EBECRYL 3702," and "EBECRYL 3708" manufactured by Daicel-Allnex Corporation, and "Miramer PE230," "Miramer PE210," "Miramer PE310," "Miramer EA2235," "Miramer EA2255," "Miramer EA2280," and "Miramer ME2100" manufactured by Miwon Specialty Chemical Co., Ltd.

[0045] In the yellow ink, crimson ink, indigo ink, and black ink of the present invention, the (meth)acrylate compound may be used alone or in combination of two or more.

[0046] In the yellow ink, crimson ink, indigo ink, and black ink of the present invention, the content of the (meth)acrylate compound is preferably 10 to 70 mass % based on the total mass of the ink, and more preferably 30 to 65 mass %.

[0047] From the viewpoint of curability, the yellow ink, crimson ink, indigo ink, and black ink of the present invention preferably contain a (meth)acrylate compound having three or more (meth)acryloyl groups. The content of the compound having three or more (meth)acryloyl groups in the ink of the present invention is preferably 20 to 70 mass %, more preferably 30 to 65 mass %, and even more preferably 40 to 65 mass %, based on the total mass of the ink.

[0048] [Photopolymerization initiator] The yellow ink, crimson ink, indigo ink, and black ink in the present invention contain a photopolymerization initiator. The polymerization initiator in the present invention is a compound that undergoes a chemical change to generate radicals through the action of light or through interaction with the electronically excited state of the sensitizing dye, and among these, a photoradical polymerization initiator is preferred from the viewpoint that polymerization can be initiated by means of exposure to light.

[0049] The yellow ink, crimson ink, indigo ink, and black ink of the present invention use two or more types of photopolymerization initiators. By using two or more types of photopolymerization initiators with different absorption wavelengths under low irradiation energy conditions, such as conventional metal halide lamps and high-pressure mercury lamps, as well as ozone-less metal halide lamps that do not generate ozone and UV-LED lamps, compared to when a single type is used, the photoinitiators can absorb light emitted by the metal halide lamp or UV-LED lamp more efficiently, making it possible to achieve excellent ink curing properties.

[0050] The photopolymerization initiator is preferably two or more selected from the group consisting of α-aminoalkylphenone initiators, thioxanthone initiators, benzophenone initiators, dialkoxyacetophenone initiators, α-hydroxyalkylphenone initiators, and acylphosphine oxide initiators, and it is particularly preferable to use α-aminoalkylphenone initiators and thioxanthone initiators.

[0051] Because ultraviolet light sources such as metal halide lamps or high-pressure mercury lamps emit a wide range of wavelengths, the photopolymerization initiator used must also be selected to efficiently cover a wide range of wavelengths in the ultraviolet region of 200 to 420 nm. The maximum absorption wavelength of α-aminoalkylphenone initiators is 300 to 350 nm, and the maximum absorption wavelength of thioxanthone initiators is 370 to 400 nm. Therefore, by using these two types in particular, efficient light absorption by the photoinitiator occurs during multicolor printing, making it possible to achieve excellent ink curing properties.

[0052] α-Aminoalkylphenone initiators include 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 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, 1,2-octanedione, 1-[4-(phenylthio)-, 2-(O-benzoyloxime)], ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime), 3,6-bis(2-methyl-2-morpholinopropanonyl) )-9-butylcarbazole, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)-benzyl]-phenyl}-2-methyl-propan-1-one, 2,2-dimethoxy-1,2-diphenylethan-1-one, 2,2-diethoxy-1,2-diphenylethan-1-one, etc., which may be used alone or in combination of two or more. In particular, from the viewpoint of curability, 2-benzyl-2-dimethylamino-1-(4-piperidinophenyl)-butan-1-one is preferred.

[0053] Examples of thioxanthone initiators include 2,4-diethylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diisopropylthioxanthone, 2-isopropylthioxanthone, 4-diisopropylthioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-dichlorothioxanthone, α-[(4-benzoylphenoxy)acetyl]-ω-{[(4-benzoylphenoxy)acetyl]oxy}poly(oxybutane-1,4-diyl), 2-chlorothioxanthone, 1-chloro-4-propoxythioxanthone, and 2-hydroxy-3-(3,4-dimethyl-9-oxo-9H-thioxanthone-2-yloxy-N,N,N-trimethyl-1-propanamine hydrochloride.

[0054] Examples of the benzophenone initiator include benzophenone, 4-methylbenzophenone, 4-phenylbenzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(dimethylamino)benzophenone, and [4-(methylphenylthio)phenyl]-phenylmethanone.

[0055] Examples of the dialkoxyacetophenone initiator include 2,2-dimethoxy-2-phenylacetophenone, dimethoxyacetophenone, and diethoxyacetophenone.

[0056] Examples of α-hydroxyalkylphenone initiators include 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxymethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, and 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one.

[0057] Examples of the acylphosphine oxide initiator 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.

[0058] To ensure sufficient curability, the amount of photopolymerization initiator added is preferably 2 to 15% by mass based on the total mass of the ink, and more preferably 3 to 12% by mass of the total mass of the ink.

[0059] When ultraviolet light is used as the active energy ray for curing the ink set of the present invention, a photosensitizer can be used in combination to further improve the curability. Examples of photosensitizers include amines such as triethanolamine, methyldiethanolamine, dimethylethanolamine, triisopropanolamine, methyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, (2-dimethylamino)ethyl benzoate, (n-butoxy)ethyl 4-dimethylaminobenzoate, and 2-ethylhexyl 4-dimethylaminobenzoate.

[0060] [resin] The yellow ink, crimson ink, indigo ink and black ink of the present invention may contain a resin in order to improve the durability of the cured coating film and the offset suitability during printing.

[0061] The resin is preferably one that has excellent compatibility with the (meth)acrylate compound, and examples thereof include diallyl phthalate resin, rosin-modified resin, polyvinyl chloride, poly(meth)acrylic acid ester, epoxy resin, polyester resin, polyurethane resin, cellulose derivatives (e.g., ethyl cellulose, cellulose acetate, nitrocellulose), vinyl chloride-vinyl acetate copolymer, polyamide resin, polyvinyl acetal resin, alkyd resin, petroleum resin, urea resin, and synthetic rubber such as butadiene-acrylonitrile copolymer.

[0062] Examples of rosin-modified resins include resins described in WO 2017 / 164246, JP 2019-178323 A, and JP 2019-199492 A.

[0063] [Extender pigment] In the present invention, the yellow ink, crimson ink, indigo ink and black ink may contain an extender pigment. As the extender pigment, inorganic fine particles are preferably used.

[0064] Specific examples of extender pigments include inorganic extender pigments such as lime carbonate powder, precipitated calcium carbonate, precipitated barium sulfate, gypsum, clay (China clay), silica, diatomaceous earth, talc, kaolin, alumina white, barium sulfate, aluminum stearate, calcium stearate, calcium carbonate, magnesium carbonate, barite powder, and abrasive powder, as well as silicone and glass beads. These inorganic fine particles can add effects such as adjusting the flowability of the composition, preventing misting, and preventing penetration into printing substrates such as paper. The extender pigments may be used alone or in combination of two or more. The content of the extender pigment is preferably 1 to 20% by mass based on the total mass of the ink.

[0065] [Photopolymerization inhibitor] A photopolymerization inhibitor can be added to the yellow ink, crimson ink, indigo ink, and black ink of the present invention. By including a photopolymerization inhibitor, excellent storage stability can be achieved.

[0066] From the viewpoint of storage stability, examples of the photopolymerization inhibitor include nitroso compounds, phenolic compounds, quinone compounds, and piperidine compounds.

[0067] Examples of nitroso compounds include nitrosobenzene, aluminum N-nitrosophenylhydroxylamine, tri-p-nitrophenylmethyl, picric acid, cupferron, butyraldoxime, methyl ethyl ketoxime, and cyclohexanone oxime.

[0068] Examples of the phenolic compounds include (alkyl)phenols, p-methoxyphenols, o-isopropylphenol, catechol, resorcinol, t-butylcatechol, pyrogallol, dibutylcresol, and guaiacol.

[0069] Examples of quinone compounds include hydroquinone, t-butylhydroquinone, p-benzoquinone, and 2,5-di-tert-butyl-p-benzoquinone.

[0070] Examples of the piperidine compounds include phenothiazine.

[0071] It is also possible to use photopolymerization inhibitors other than the above-mentioned nitroso compounds, phenolic compounds, quinone compounds, and piperidine compounds (also referred to as "other photopolymerization inhibitors"). Specific examples of other photopolymerization inhibitors include 1,1-picrylhydrazyl, dithiobenzoyl disulfide, N-(3-oxyanilino-1,3-dimethylbutylidene)aniline oxide, cyclohexanone oxime cresol, etc.

[0072] The blending amount of the polymerization inhibitor is preferably 0.01 to 5% by mass of the total amount of the ink.

[0073] [Additives] The yellow ink, crimson ink, indigo ink, and black ink of the present invention may further contain various additives depending on the purpose, such as a pigment dispersant, an anti-friction agent, an anti-blocking agent, a slipping agent, etc. The various additives can be added to the composition by a conventional method. When various additives are added, it is preferable to adjust the blending amount within a range that does not impair the effects of other materials. The blending amount of various additives is preferably 15 mass % or less of the total amount of ink.

[0074] <Tack value> In the present invention, the tack value is a value that represents the dynamic viscoelasticity of the ink, and is a value measured by measuring the force required to tear an ink film between two rollers rotating in contact with each other. In the present invention, a Digital Incometer D-2 (manufactured by Toyo Seiki Seisakusho, Ltd.) conforming to JIS K 5701 is used, and the tack value is the value measured 60 seconds after the start of measurement at a measurement temperature of 30°C and a rotation speed of 400 rpm, applying 1.31 cc of ink as a measurement sample.

[0075] In the present invention, the tack value (TB) of ink B (yellow ink) is 4.5 to 10, and the tack value (TA) of ink A (crimson ink, indigo ink, and black ink) is 4.7 to 12.

[0076] The tack value can be set by adjusting the blending ratio of the colorant, resin, and (meth)acrylate compound to be blended. For example, the tack value can be reduced by increasing the blending ratio of the (meth)acrylate compound.

[0077] If the TB is less than 4.5, smearing occurs during printing, making it impossible to form an image and achieving good print quality. Also, if the TB is greater than 10, the leveling is poor, gloss is insufficient, and sufficient print quality cannot be ensured. Furthermore, the paper may stick too strongly to the substrate, causing problems such as paper peeling and making it impossible to print.

[0078] If the TA is less than 4.7, smearing occurs during printing, making it impossible to form an image and achieving good print quality. If the TA is greater than 12, the leveling is poor, the gloss is insufficient, and sufficient print quality cannot be ensured. In addition, the paper may stick too strongly to the substrate, causing problems such as paper peeling and making it impossible to print.

[0079] In the present invention, the printing order is as follows: ink A, which is one or more inks selected from crimson ink, indigo ink, and black ink, is printed, and then ink B, which is yellow ink, is printed.

[0080] The difference in tack value between ink A and ink B (TA-TB) is 0.2 or more and 5 or less, and preferably 0.5 or more and 3 or less. If TA-TB is less than 0.2, the yellow ink does not transfer, and therefore good print quality cannot be obtained. If the TA-TB ratio exceeds 5, the amount of yellow ink transferred will be large, resulting in insufficient curing, or the target color will not be expressed. If TB is greater than TA, the yellow ink does not transfer and the underlying colors (previously printed crimson ink, indigo ink, and black ink) end up being mixed in.

[0081] In the present invention, the methods for preparing the yellow ink, crimson ink, indigo ink, and black ink are not particularly limited. For example, the inks can be prepared by a conventional method using a roll mill, a ball mill, a bead mill, or the like.

[0082] <Printed material> The printed matter of the present invention can be obtained by printing the ink set of the present invention onto a substrate and curing it with actinic radiation. The printing order is as follows: first, one or more inks selected from the active energy ray-curable crimson ink, the active energy ray-curable indigo ink, and the active energy ray-curable black ink are printed, and then the active energy ray-curable yellow ink is printed.

[0083] Examples of substrates used for printed matter in the present invention include coated paper such as art paper, coated paper, and cast paper; uncoated paper such as fine paper, medium-quality paper, and newsprint; synthetic paper such as Yupo paper; and plastic films such as PET (polyethylene terephthalate), PP (polypropylene), and OPP (biaxially oriented polypropylene).

[0084] Methods for printing the ink set of the present invention onto a substrate include resin letterpress printing, offset printing (normal lithographic printing using dampening water and waterless lithographic printing not using dampening water), flexographic printing, gravure printing, screen printing, etc. Among these, offset printing is preferred as the printing method.

[0085] In this specification, the term "active energy rays" typically refers to ultraviolet rays, electron beams, X-rays, ionizing radiation such as α-rays, β-rays, and γ-rays, microwaves, high-frequency waves, etc., but may be any energy species capable of generating radical active species, including visible light, infrared light, and laser beams. Examples of ultraviolet light sources include LEDs, ultra-high pressure mercury lamps, high pressure mercury lamps, medium pressure mercury lamps, low pressure mercury lamps, metal halide lamps, xenon lamps, carbon arc lamps, helium-cadmium lasers, YAG lasers, excimer lasers, and argon lasers. In particular, the use of LEDs, high pressure mercury lamps, and metal halide lamps is preferred in the present invention.

[0086] The ink set of the present invention is applicable to printed materials such as various printed materials for books, various printed materials for packaging such as paper, various printed materials for plastics, printed materials for stickers / labels, and fine art printed materials. [Example]

[0087] 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 this specification, "parts" means parts by mass, and "%" means % by mass.

[0088] Details of the various measurements carried out in the following examples are as follows.

[0089] Manufacturing Example 1 [Production of active energy ray curable yellow ink 1] As the pigment, 13.0 parts of yellow pigment, as photopolymerization initiators, 5.0 parts of OMNIRAD 930 and 2.0 parts of OMNIRAD DETX, as resins, 8.0 parts of rosin-modified resin, as (meth)acrylate compounds, 10.0 parts of urethane acrylate, 21.9 parts of MIRAMERM 600, 22.0 parts of MIRAMERM 410, and 6.0 parts of MIRAMER LR3130, as extender pigments, 2.5 parts of Neolite EG-290 and 3.0 parts of High Filler Talc 5000PJ, as additives, 1.5 parts of AJISPER PB821 and 5.0 parts of wax, and 0.1 part of Q-1301 as a polymerization inhibitor were added, and the mixture was stirred and mixed using a mixer and dispersed using a three-roll mill to prepare active energy ray-curable yellow ink 1.

[0090] Manufacturing Examples 2 to 53 [Production of active energy ray curable yellow inks 2 to 18, active energy ray curable red inks 1 to 15, active energy ray curable blue inks 1 to 11, and active energy ray curable black inks 1 to 9] Except for changing the raw materials and amounts listed in Table 1, active energy ray-curable yellow inks 2 to 18, active energy ray-curable crimson inks 1 to 15, active energy ray-curable indigo inks 1 to 11, and active energy ray-curable black inks 1 to 9 were obtained in the same manner as active energy ray-curable yellow ink 1. Note that unless otherwise specified, the numerical values ​​in the tables represent "parts by mass," and blank spaces indicate that no ingredients were blended.

[0091] [Table 1]

[0092] [Table 1]

[0093] [Table 1]

[0094] [Table 1]

[0095] [Table 1]

[0096] The method for producing the active energy ray-curable yellow ink 1 and the abbreviations in Table 1 are as follows: [Coloring agent] Yellow pigment: Lionol Yellow 1314 manufactured by Toyo Color Co., Ltd. Red pigment: No. 6516 Carmine 6B manufactured by Daido Chemical Industry Co., Ltd. Indigo pigment: Lionol Blue FG7330 manufactured by Toyo Color Co., Ltd. Black pigment: MA-11 manufactured by Mitsubishi Chemical Corporation [Photopolymerization initiator] OMNIRAD930: α-aminoalkylphenone initiator, 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one, manufactured by IGM OMNIRAD389: α-aminoalkylphenone initiator, 2-benzyl-2-dimethylamino-1-(4-piperidinophenyl)-butan-1-one, manufactured by IGM Luna637A: α-aminoalkylphenone initiator manufactured by DKSH Japan Co., Ltd. APi980: α-aminoalkylphenone initiator manufactured by Shenzhen Youwei Technology Holdings Group OMNIRADDETX: 2,4-diethylthioxanthone, manufactured by IGM OMNIRADEMK: 4,4'-bis(diethylamino)benzophenone manufactured by IGM OMNIRADOMBB: o-Methylbenzoyl benzoate manufactured by IGM OMNIRAD1173: 2-hydroxy-2-methylpropiophenone, manufactured by IGM [resin] Rosin-modified resin: Resin 4 described in paragraph 0076 of WO 2017 / 164246 was used. DAP-A: Diallyl phthalate resin, manufactured by Osaka Soda Co., Ltd. [(Meth)acrylate compounds] Urethane acrylate: Resin composition 7 described in paragraph 0060 of Japanese Patent No. 7428842 was used (urethane acrylate / dipentaerythritol hexaacrylate / trimethylolpropane EO-modified triacrylate / tertiary butyl hydroquinone = 49.8 / 45 / 5 / 0.2). MIRAMER M600: Dipentaerythritol hexaacrylate, manufactured by Bigen Specialty Chemical Co., Ltd. MIRAMER M410: Manufactured by Bigen Specialty Chemical Co., Ltd., ditrimethylolpropane tetraacrylate MIRAMER LR3130: Manufactured by Bigen Specialty Chemical Co., Ltd., trimethylolpropane EO-modified triacrylate [Extender pigment] Neolite EG-290: Takehara Chemical Industry Co., Ltd.: Calcium carbonate High Filler 5000PJ: Matsumura Sangyo Co., Ltd.: Talc [Polymerization inhibitor] Q-1301: Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., nitroso-based compound, N-nitrosophenylhydroxylamine aluminum salt [Additives (dispersants)] Ajisper PB821: Pigment dispersant manufactured by Ajinomoto Fine-Techno Co., Ltd. [Additives (wax)] Sanwax 161P: Polyethylene resin manufactured by Sanyo Chemical Industries

[0097] (Printed matter production) Examples 1 to 37, Comparative Examples 1 to 15 Using the obtained active energy ray-curable ink, printing was carried out in the order shown in Table 2 (printing order from top to bottom) under the following printing conditions. (Printing conditions) ·Printing machine LITHRONE26 (manufactured by Komori Corporation) ·Base material Paper: Oji Paper Co., Ltd., OK Top Coat + (79.1 g / m 2 ) ·Printing speed 10,000 pieces / hour ·light source One metal halide lamp (output 120W / cm), manufactured by Eye Graphics ·Print density Using FDLPCPR (each color) CM manufactured by Toyo Ink Co., Ltd., the machine was set to achieve the following concentrations. Yellow ink: 1.40, Crimson ink: 1.50, Indigo ink: 1.60, Black ink: 1.75

[0098] [Table 2]

[0099] [Table 2]

[0100] [Print quality] <Print quality evaluation method> Print quality is evaluated by the trapping rate. Trapping during printing refers to the state in which later-printed ink overlaps previously printed ink in offset printing. Using the printed matter produced as described above, the areas where the inks overlap were measured using an X-rite spectrophotometer (eXact) to measure the trapping rate of later-printed ink on previously printed ink. A print quality rating of 3 or higher is considered to be at a practically acceptable level, with 4 or higher being even more preferable, providing clear prints. (Print quality evaluation criteria) 5: Trapping rate 60% or more to less than 100%, providing very clear prints 4: Trapping rate of 50% or more to less than 60%, providing very clear prints 3: Trapping rate of less than 40% to more than 50%, providing clear prints that meet the requirements. 2: Trapping rate: less than 40% - more than 20%, the target color cannot be expressed 1: Trapping rate less than 20% - Post-print ink does not adhere or the base color is mixed The target color cannot be expressed due to the roughness. -: A condition in which stains occur during offset printing, or the paper sticks too strongly to the substrate, causing problems such as peeling, making it impossible to obtain printed material of sufficient quality.

[0101] [Curability] Using the printed matter produced as described above, the printed surface was rubbed 30 times with a cotton swab soaked in MEK (methyl ethyl ketone) in the areas where the ink overlapped, and then the condition of the printed surface was visually observed. The evaluation criteria are shown below, with a score of 3 or higher being practically preferable. 5: No change in the printed surface. 4: Peeling is observed on part of the printed surface (less than 10% of the area). 3: Peeling is observed on part of the printed surface (less than 10-30% of the area). 2: Peeling is observed on part of the printed surface (less than 30-50% of the area). 1: Peeling is observed on part (more than 50% of the area) or all of the printed surface.

[0102] Table 2 shows the evaluation results of the print quality and curability of the printed matter for Examples 1 to 37 and Comparative Examples 1 to 15.

[0103] As shown in Table 2, in Examples 1 to 37, the print quality and curability were within the practical range. On the other hand, in Comparative Example 1, the tack value of the yellow ink is greater than that of the red ink, and the trapping rate is low and does not reach a practical level. In Comparative Example 2, the tack value of the yellow ink was low, causing smearing during offset printing, making it impossible to form an image, and good print quality was not obtained. In Comparative Example 3, the difference in tack between the yellow ink and the red ink was large, the trapping rate was high, and the red ink was printed in excess, so the curing properties did not reach a practical level. Comparative Examples 4, 5, 11, and 12 show no difference in tack with the yellow ink, and the trapping is low, not reaching a practical level. In Comparative Examples 6, 7, and 13, the amount of photopolymerization initiator in the ink was insufficient, and the curability did not reach a practical level. In Comparative Example 8, the pigment concentration in the yellow ink was low, so it was necessary to increase the amount of ink, which resulted in staining during offset printing, making it impossible to form an image, and failing to obtain good print quality. In Comparative Examples 9, 10 and 14, the pigment concentration in the ink was high, resulting in insufficient curing properties and not reaching a practical level. In Comparative Example 15, the tack value of the yellow ink is lower than the other three colors, but because it is printed as the first color, the trapping rates of the black ink, indigo ink, and crimson ink are low and do not reach a practical level.

[0104] As described above, the present invention makes it possible to provide an actinic ray-curable ink set that is excellent in print quality and curability in multicolor printing, and to provide a method for producing printed matter and printed matter using the same.

Claims

1. An ink set for printing ink A and then printing ink B in contact with ink A, The tack value (referred to as TA) of the ink A at a temperature of 30°C and a rotation speed of 400 rpm is 4.7 to 12, the tack value (TB) of the ink B at a temperature of 30°C and a rotation speed of 400 rpm is 4.5 to 10; 5≧TA−TB≧0.2, the ink A is one or more inks selected from the group consisting of an active energy ray-curable crimson ink, an active energy ray-curable indigo ink, and an active energy ray-curable black ink, Ink B is an active energy ray-curable yellow ink, the active energy ray-curable yellow ink, the active energy ray-curable crimson ink, the active energy ray-curable indigo ink, and the active energy ray-curable black ink each contain a colorant, a (meth)acrylate compound, and two or more photopolymerization initiators; The ink set has a content of the colorant of 10 to 25% by mass based on the total amount of the ink.

2. 2. The ink set according to claim 1, wherein the photopolymerization initiator comprises an α-aminoalkylphenone-based initiator and a thioxanthone-based initiator.

3. 2. The ink set according to claim 1, wherein the content of the photopolymerization initiator is 2 to 15% by mass of the total amount of the ink.

4. 3. The ink set of claim 2, wherein the α-aminoalkylphenone initiator comprises 2-benzyl-2-dimethylamino-1-(4-piperidinophenyl)-butan-1-one.

5. The ink set according to claim 1 , wherein the (meth)acrylate compound includes a compound having three or more (meth)acryloyl groups.

6. 2. The ink set according to claim 1, wherein the content of the (meth)acrylate compound is 10 to 70% by mass of the total amount of the ink.

7. A printed matter obtained by printing the ink set according to any one of claims 1 to 6 onto a substrate and curing the ink set with actinic radiation.

8. The printed matter according to claim 7, wherein the substrate is a paper or film substrate.

9. A method for producing a printed matter, comprising printing ink A, printing ink B so as to be in contact with ink A, and curing the ink B with active energy rays, The ink A has a tack value (referred to as TA) of 4.7 to 12 at a set temperature of 30°C and a rotation speed of 400 rpm, The tack value (TB) of the ink B at a set temperature of 30°C and a rotation speed of 400 rpm is 4.5 to 10, 5≧TA−TB≧0.2, the ink A is one or more inks selected from the group consisting of an active energy ray-curable crimson ink, an active energy ray-curable indigo ink, and an active energy ray-curable black ink, Ink B is an active energy ray-curable yellow ink, the active energy ray-curable yellow ink, the active energy ray-curable crimson ink, the active energy ray-curable indigo ink, and the active energy ray-curable black ink each contain a colorant, a (meth)acrylate compound, and two or more photopolymerization initiators; A method for producing a printed matter, wherein the content of the colorant is 10 to 25% by mass of the total amount of the ink.

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