Active ray-curable ink composition for inkjet printing

Abstract

Provided is an active-ray-curable ink composition for inkjet printing, which is capable of reducing the gloss difference between a low-print-rate portion and a high-print-rate portion, has excellent curability, and also has excellent recoatability when a varnish composition is applied to an obtained coating film. This active-ray-curable ink composition for inkjet printing contains a polymerizable compound, a polymerization initiator, and a gelling agent, and the wetting index of a cured coating film formed by inkjet printing is 40 mN / m or more.

Description

Technical Field

[0001] The present invention relates to an active radiation-curable inkjet printing ink composition. More specifically, the present invention relates to an active radiation-curable inkjet printing ink composition that can reduce the gloss difference between low-printing rate areas and high-printing rate areas, exhibits excellent curability, and exhibits excellent recoatability when a clearcoat composition is applied to the resulting coating film. Background Art

[0002] Conventionally, UV-curable inkjet inks have produced a significant gloss difference between low- and high-print ratio areas, particularly in single-pass applications. Consequently, techniques for reducing this gloss difference include using extender pigments (silicon dioxide, alumina) with a diameter of 1 μm or larger, and using gelling agents such as fatty acid amides to produce low-gloss printed materials (e.g., Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-40760 Summary of the Invention

[0006] However, the method using extender pigments tends to deteriorate in ejection stability when using extender pigments with larger particle sizes in high-definition inkjet printers. Furthermore, the method described in Patent Document 1 causes the gelling agent to float on the printed surface, which can easily cause pinholes and craters when applying a varnish in post-processing.

[0007] The present invention has been made in view of such conventional problems, and its object is to provide an active radiation-curable inkjet printing ink composition that can reduce the gloss difference between low-printing rate areas and high-printing rate areas, has excellent curability, and also has excellent recoatability when a varnish composition is applied to the resulting coating film.

[0008] An active radiation-curable inkjet printing ink composition according to one embodiment of the present invention that solves the above-mentioned problems comprises a polymerizable compound, a polymerization initiator, and a gelling agent, and has a wetting index of 40 mN / m or higher for a cured coating film formed by inkjet printing. DETAILED DESCRIPTION

[0009] <Active radiation-curable inkjet printing ink composition>

[0010] An active radiation-curable inkjet printing ink composition (hereinafter referred to as an ink composition) according to one embodiment of the present invention comprises a polymerizable compound, a polymerization initiator, and a gelling agent. The cured coating film formed by inkjet printing exhibits a wetting index of 40 mN / m or greater. These are described below.

[0011] (color material)

[0012] The ink composition of this embodiment may also contain a coloring material (pigment). The pigment is not particularly limited. For example, the pigment is various organic pigments and inorganic pigments.

[0013] Organic pigments include dye lake pigments, azo pigments, benzimidazolone pigments, phthalocyanine pigments, quinacridone pigments, anthraquinone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, perylene pigments, pyrenone pigments, diketopyrrolopyrrole pigments, isoindolinone pigments, nitro pigments, nitroso pigments, xanthrone pigments, quinophthalone pigments, pyranthrone pigments, and indanthrone pigments.

[0014] Inorganic pigments include colored pigments such as titanium oxide, red iron oxide, antimony red, cadmium yellow, cobalt blue, ultramarine, Prussian blue, iron black, chromium oxide green, carbon black, graphite, etc. (also including achromatic coloring pigments such as white and black) and extender pigments such as calcium carbonate, kaolin, clay, barium sulfate, aluminum hydroxide, and talc.

[0015] Specific examples of representative pigments of various hues in the ink composition of this embodiment are as follows. Yellow pigments include CI Pigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 42, 73, 74, 75, 81, 83, 87, 93, 95, 97, 98, 108, 109, 114, 120, 128, 129, 138, 139, 150, 151, 155, 166, 180, 184, 185, and 213, with CI Pigment Yellow 150, 155, 180, and 213 being preferred.

[0016] Magenta pigments include CI Pigment Red 5, 7, 12, 19, 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, and the like, preferably CI Pigment Red 122, 202, and Pigment Violet 19.

[0017] 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.

[0018] The black pigment is carbon black (CI Pigment Black 7) or the like.

[0019] The pigment content is not particularly limited. For example, the pigment content in the ink composition is preferably 0.5% by mass or greater, and more preferably 2% by mass or greater. Furthermore, the pigment content in the ink composition is preferably 20% by mass or less, and more preferably 10% by mass or less. When the pigment content is within this range, the ink composition exhibits excellent color reproducibility.

[0020] The ink composition of this embodiment may also contain a pigment dispersant. The pigment dispersant is not particularly limited. Examples thereof include carbodiimide dispersants, polyesteramine dispersants, fatty acid amine dispersants, modified polyacrylate dispersants, modified polyurethane dispersants, multi-chain polymer nonionic dispersants, and polymer ion active agents.

[0021] When preparing the pigment dispersant, the content of the pigment dispersant is preferably 1.0 to 100% by mass, more preferably 5.0 to 60.0% by mass relative to the pigment, from the perspective of improving the dispersibility of the pigment and the storage stability of the ink composition.

[0022] It should be noted that the ink composition of this embodiment can reduce the gloss difference between the low-printing rate portion and the high-printing rate portion of the obtained printed material even when the extender pigment is not included. Therefore, the extender pigment is not essential and may not be included.

[0023] When an extender pigment is included, the extender pigment is not particularly limited and includes, for example, clay, talc, mica, kaolinite (kaolin), barium sulfate, magnesium sulfate, calcium carbonate, silicon oxide, aluminum oxide, bentonite, heavy calcium carbonate, barium carbonate, zirconium oxide, aluminum oxide, and the like.

[0024] If the particle size of the extender pigment is large, the gloss difference of the resulting printed material may increase. Therefore, the average particle size of the extender pigment is preferably 0.001 to 0.2 μm, more preferably 0.01 to 0.1 μm.

[0025] When an extender pigment is included, the content of the extender pigment is not particularly limited. For example, the extender pigment content in the ink composition is preferably greater than 0% by mass, and more preferably greater than 1% by mass. Furthermore, the extender pigment may be included to the extent that it does not impair the ink ejection performance.

[0026] (Polymerizable compound)

[0027] The polymerizable compound can be a known polymerizable compound used in an active radiation curable inkjet ink composition. For example, the polymerizable compound is a monomer or oligomer having a photopolymerizable unsaturated bond.

[0028] The monomer having one photopolymerizable unsaturated bond is an alkyl methacrylate or alkyl acrylate such as methyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, methacrylate, butyl acrylate, and 2-ethylhexyl acrylate; an aralkyl methacrylate or aralkyl acrylate such as benzyl methacrylate and benzyl acrylate; an alkoxyalkyl methacrylate or alkoxyalkyl acrylate such as butoxyethyl methacrylate and butoxyethyl acrylate; an aminoalkyl methacrylate or aminoalkyl acrylate such as N,N-dimethylaminoethyl methacrylate and N,N-dimethylaminoethyl acrylate; a methacrylate or acrylate of a polyalkylene glycol monoalkyl ether such as diethylene glycol monoethyl ether, triethylene glycol monobutyl ether, and dipropylene glycol monomethyl ether; a methacrylate or acrylate of a polyalkylene glycol monoaryl ether such as hexaethylene glycol monophenyl ether; isobornyl methacrylate or isobornyl acrylate; glyceryl methacrylate or glyceryl acrylate; 2-hydroxyethyl methacrylate or 2-hydroxyethyl acrylate, and the like.

[0029] The monomers having two or more photopolymerizable unsaturated bonds are bisphenol A dimethacrylate, 1,4-butanediol dimethacrylate, 1,3-butanediol dimethacrylate, diethylene glycol dimethacrylate, glycerol dimethacrylate, neopentyl glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol tetramethacrylate, diquaternary Pentaerythritol hexamethacrylate, dipentaerythritol pentamethacrylate, bisphenol A diacrylate, 1,4-butanediol diacrylate, 1,3-butanediol diacrylate, diethylene glycol diacrylate, glycerol diacrylate, neopentyl glycol diacrylate, polyethylene glycol diacrylate, polypropylene glycol diacrylate, tetraethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, dipentaerythritol pentaacrylate, etc.

[0030] The oligomer having a photopolymerizable unsaturated bond is an oligomer obtained by appropriately polymerizing the above-mentioned monomers.

[0031] The content of the photopolymerizable compound is not particularly limited. For example, the content of the photopolymerizable compound can be appropriately determined in consideration of the physical properties of the cured coating film.

[0032] (Polymerization initiator)

[0033] The polymerization initiator is not particularly limited. For example, the polymerization initiator includes benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, triazine-based photopolymerization initiators, and acylphosphine oxide-based photopolymerization initiators.

[0034] The content of the polymerization initiator is not particularly limited. For example, the content of the polymerization initiator in the ink composition is preferably 3% by mass or greater, and more preferably 4% by mass or greater. Furthermore, the content of the polymerization initiator in the ink composition is preferably 15% by mass or less, and more preferably 10% by mass or less. When the content of the polymerization initiator is within this range, the ink composition tends to have sufficient external and internal curing properties.

[0035] (Gelling agent)

[0036] The gelling agent is not particularly limited. As an example, the gelling agent preferably contains at least one of a fatty acid ester containing a C12 to C18 hydrocarbon chain or a fatty acid amide containing a C12 to C18 hydrocarbon chain.

[0037] The fatty acid ester containing a C12-C18 hydrocarbon chain is not particularly limited. For example, fatty acid ester containing a C12-C18 hydrocarbon chain includes ester hydrocarbons such as ethylene glycol distearate, isopropyl myristate, isopropyl palmitate, octyldodecyl myristate, octyl palmitate, isooctyl palmitate, octyl stearate, isooctyl stearate, butyl stearate, myristyl myristate, stearyl stearate, isopropyl isostearate, 2-hexyldecyl isostearate, propylene glycol isostearate, octyl isopalmitate, and polyglyceryl monoisostearate; and sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monoisostearate, and sorbitan tristearate.

[0038] The fatty acid amide containing a C12 to C18 hydrocarbon chain is not particularly limited. Examples of the fatty acid amide include stearyl oleamide, stearic acid amide, and ricinoleic acid amide.

[0039] Among the above, the gelling agent preferably contains two or more C12 to C18 hydrocarbon chains. This makes it easier for the obtained coating film to further reduce the gloss difference between the low printing rate portion and the high printing rate portion.

[0040] The melting point of the gelling agent is preferably 36°C or higher. Furthermore, the melting point of the gelling agent is more preferably 67°C or lower. When the melting point is within this range, the ink composition exhibits excellent discharge stability when printed materials are produced using, for example, an inkjet printer equipped with a print head adjusted to 35 to 60°C.

[0041] The gelling agent content is preferably 2% by mass or greater, more preferably 5% by mass or greater. Furthermore, the gelling agent content is preferably 15% by mass or less, more preferably 12% by mass or less. When the gelling agent content is within this range, the ink composition tends to suppress the gloss difference between the low-printing rate portion and the high-printing rate portion of the resulting printed material.

[0042] (Optional ingredient)

[0043] The ink composition of this embodiment may appropriately contain the following components in addition to the above-mentioned components.

[0044] Sensitizer

[0045] The sensitizer is not particularly limited. For example, the sensitizer is preferably an anthracene sensitizer, a thioxanthone sensitizer, etc., and more preferably a thioxanthone sensitizer. Specifically, the sensitizer is an anthracene sensitizer such as 9,10-dibutoxyanthracene, 9,10-diethoxyanthracene, 9,10-dipropoxyanthracene, 9,10-bis(2-ethylhexyloxy)anthracene, and a thioxanthone sensitizer such as 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone. Representative examples of commercially available products include DBA and DEA (manufactured by Kawasaki Chemicals Co., Ltd.) as an anthracene sensitizer, and DETX and ITX (manufactured by Lambson Corporation) as a thioxanthone sensitizer.

[0046] When a sensitizer is included, the sensitizer content is not particularly limited. For example, the sensitizer content is preferably 0.5% by mass or greater, and more preferably 0.8% by mass or greater, in the ink composition. Furthermore, the sensitizer content is preferably 3% by mass or less, and more preferably 2% by mass or less, in the ink composition. A sensitizer content within this range has the advantage of suppressing color changes over time in the cured coating film of the ink composition.

[0047] ·Polymerization inhibitor

[0048] The polymerization inhibitor is not particularly limited, but examples thereof include phenolic compounds such as butylated hydroxytoluene, tocopheryl acetate, nitrosamine, benzotriazole, and hindered amines.

[0049] When a polymerization inhibitor is included, the amount is not particularly limited. For example, the amount of polymerization inhibitor is preferably 0.5 parts by mass or greater, and more preferably 0.8 parts by mass or greater, per 100 parts by mass of the polymerizable components. Furthermore, the amount of polymerization inhibitor is preferably 2.0 parts by mass or less, and more preferably 1.2 parts by mass or less, per 100 parts by mass of the polymerizable components. When the amount of polymerization inhibitor is within this range, the ink composition can be prevented from undergoing polymerization reactions during storage, thereby thickening the ink composition.

[0050] UV absorbers

[0051] Examples of the ultraviolet absorber include benzophenone ultraviolet absorbers, benzotriazole ultraviolet absorbers, salicylate ultraviolet absorbers, hydroxyphenyltriazine ultraviolet absorbers, cyanoacrylate ultraviolet absorbers, and nickel complex salt ultraviolet absorbers.

[0052] When a UV absorber is contained, the content of the UV absorber can be adjusted appropriately.

[0053] Antioxidants

[0054] The antioxidants include phenolic antioxidants, amine antioxidants, sulfur antioxidants, phosphorus antioxidants and the like.

[0055] When an antioxidant is contained, the content of the antioxidant can be adjusted appropriately.

[0056] Leveling agent

[0057] Leveling agents include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants, etc.

[0058] When a leveling agent is included, the amount thereof is not particularly limited. For example, to improve the stability of the ink composition during ejection from an inkjet head, the amount of the leveling agent in the ink composition is preferably 0.005% by mass or greater, and more preferably 0.01% by mass or greater. Furthermore, the amount of the leveling agent in the ink composition is preferably 1.5% by mass or less, and more preferably 1% by mass or less.

[0059] The cured coating film formed by inkjet printing of the ink composition of this embodiment has a wetting index of 40 mN / m or greater. If the wetting index is less than 40 mN / m, the resulting coating film will have poor recoatability when a varnish composition is applied, and pinholes and craters are likely to form. The wetting index can be measured as follows: According to JIS K6768, various standard wettability indicators with a range of 22.7 dyn / cm to 70 dyn / cm manufactured by Wako Pure Chemical Industries, Ltd. are prepared. The indicators are applied to the surface of the cured coating film using a cotton swab, and the index level immediately preceding the appearance of craters is determined.

[0060] From the perspective of improving the ejection stability of the ink composition, the viscosity of the ink composition of this embodiment is preferably 100 mPa·s or less at 45°C, more preferably 50 mPa·s or less, and even more preferably 20 mPa·s or less. Furthermore, the viscosity of the ink composition is preferably 1 mPa·s or greater at 45°C, more preferably 5 mPa·s or greater. The viscosity of the ink composition can be designed to suit various inkjet devices. In this embodiment, the viscosity can be measured using an E-type viscometer (RE100L, manufactured by Toki Seizo Co., Ltd.) at 45°C and 20 rpm.

[0061] The ink composition of this embodiment can reduce the gloss difference between the low-printing rate portion and the high-printing rate portion of the resulting coating film. The gloss difference can be evaluated by measuring the gloss value of the cured coating film at 100% print rate for each ink composition printed on coated paper (OK Top Coat) at 25°C using a gloss meter (BYK). In this embodiment, the gloss value is preferably 60 or less.

[0062] In summary, according to this embodiment, the ink composition has excellent curability and the gloss difference between the low printing rate portion and the high printing rate portion of the obtained coating film is reduced.

[0063] The varnish composition is not particularly limited. As an example, the varnish composition is water-based varnish AC Coat V-181 manufactured by Sakata Ink Co., Ltd.

[0064] In addition to the aforementioned curability and gloss difference reduction effects, the coating film of the ink composition of this embodiment has a wetting index of 40 mN / m or greater. Therefore, even when the above-mentioned varnish composition is applied, pinholes and craters are less likely to form, and recoatability is excellent.

[0065] <Method for Preparing Ink Composition>

[0066] The method for preparing the ink composition of this embodiment is not particularly limited. For example, the ink composition can be prepared by dispersion and mixing using a dispersing machine such as a wet circulation mill, a bead mill, a ball mill, a sand mill, an attritor, a roller mill, a DCP mill, a blender, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a high-pressure homogenizer (e.g., Microfluidizer, Nanomizer, Ultimizer, GenusPY, DeBEE2000), or a pearl mill.

[0067] <Printed matter manufacturing method and printed matter>

[0068] The method for producing a printed article according to one embodiment of the present invention includes the step of ejecting the ink composition from an inkjet printing device onto a substrate.

[0069] The substrate is not particularly limited, but examples thereof include plastic substrates, paper, metal foil, glass, wood, and cloth. The plastic substrate is a substrate composed of one or more selected from polyester polymers (e.g., polyethylene terephthalate (PET), polyethylene naphthalate, etc.), cellulose polymers (e.g., diacetyl cellulose, triacetyl cellulose (TAC), etc.), polycarbonate polymers, polyacrylic acid polymers (e.g., polymethyl methacrylate, etc.), vinyl chloride polymers, polyolefin polymers (e.g., polyethylene, polypropylene, cyclic or norbornene-structured polyolefin polymers, ethylene-propylene copolymer polymers, etc.), polyamide polymers (e.g., nylon, aromatic polyamide polymers, etc.), polystyrene polymers (e.g., polystyrene, acrylonitrile-styrene copolymer polymers, etc.), polyimide polymers, polysulfone polymers, polyethersulfone polymers, polyetherketone polymers, polyphenylene sulfide polymers, polyvinyl alcohol polymers, polyvinylidene chloride polymers, polyvinyl butyrate polymers, polyacrylate polymers, polyoxymethylene polymers, polyepoxy polymers, blends of these polymers, etc.

[0070] An inkjet printer supplies an ink composition to a print head, ejects the ink composition from the print head onto a substrate to be printed, and then cures the ink composition by exposing it to active radiation. Active radiation includes ultraviolet rays, electron beams, and visible light emitted from light-emitting diodes (LEDs), various lamps, and electrodes.

[0071] The coating film obtained by the above operation has a reduced gloss difference between the low print rate portion and the high print rate portion, and is also excellent in recoatability when the varnish composition is applied.

[0072] The above describes one embodiment of the present invention. The present invention is not particularly limited to the above embodiment. It should be noted that the above embodiment mainly describes the invention having the following configuration.

[0073] (1) An active radiation-curable inkjet printing ink composition comprising a polymerizable compound, a polymerization initiator, and a gelling agent, wherein a cured coating film formed by inkjet printing has a wetting index of 40 mN / m or more.

[0074] This configuration provides excellent curability of the active radiation-curable inkjet printing ink composition, reduces the gloss difference between the low and high printing rate portions of the resulting coating film, and provides excellent recoatability when a varnish composition is applied.

[0075] (2) The active radiation-curable inkjet printing ink composition according to (1), wherein the gelling agent contains at least one of a fatty acid ester containing a C12-C18 hydrocarbon chain or a fatty acid amide containing a C12-C18 hydrocarbon chain, and contains two of the C12-C18 hydrocarbon chains in the molecule.

[0076] According to such a configuration, the obtained coating film can easily further reduce the gloss difference between the low printing rate portion and the high printing rate portion.

[0077] (3) The active radiation-curable inkjet printing ink composition according to (1) or (2), wherein the content of the gelling agent is 2% by mass or more.

[0078] According to such a configuration, the obtained coating film can easily further reduce the gloss difference between the low printing rate portion and the high printing rate portion.

[0079] Example

[0080] The present invention will be described in more detail below by way of examples. The present invention is not limited to these examples. It should be noted that, unless otherwise specified, "%" means "mass %" and "parts" means "mass parts."

[0081] The raw materials used and the preparation method are shown below.

[0082] (Color material (pigment))

[0083] PY155 Pigment Yellow 155

[0084] PR122 Pigment Red 122

[0085] PB15:4 Pigment Blue 15:4

[0086] P.Bk.7 Pigment Black 7

[0087] (Pigment Dispersant)

[0088] SS32000 (copolymer containing a basic functional group (amine value: 31.2 mgKOH / g), manufactured by Japan Lubrizol Co., Ltd.)

[0089] SS56000 (copolymer containing a basic functional group (amine value: 39.0 mgKOH / g), manufactured by Japan Lubrizol Co., Ltd.)

[0090] (Polymerizable compound)

[0091] CN371NS (amine-modified oligomer, multifunctional monomer, manufactured by Sartomer)

[0092] ACMO (acryloylmorpholine, a monomer containing an acrylamide skeleton (monofunctional), manufactured by KJ Chemical Co., Ltd.)

[0093] DMAA (N,N-dimethylacrylamide, a monomer containing an acrylamide skeleton (monofunctional), manufactured by KJ Chemical Co., Ltd.)

[0094] 4HBA (4-hydroxybutyl acrylate, monofunctional monomer, manufactured by Osaka Organic Chemical Industry Co., Ltd.)

[0095] V190 (ethyl carbitol acrylate, monofunctional monomer, manufactured by Osaka Organic Chemical Industry Co., Ltd.)

[0096] HDDA (1,6-hexanediol diacrylate, a multifunctional monomer, manufactured by Osaka Organic Chemical Industry Co., Ltd.)

[0097] Aronix M-933 (high hydroxyl value pentaerythritol acrylate, multifunctional monomer, manufactured by Toagosei Co., Ltd.)

[0098] (Gelling agent)

[0099] Exceparl MY-M (myristyl myristate, melting point 36-46°C, manufactured by Kao Chemical Co., Ltd.)

[0100] Exceparl SS (stearyl stearate, melting point 56-66°C, manufactured by Kao Chemical Co., Ltd.)

[0101] Emanon 3201M-V (ethylene glycol distearate, melting point 60-65°C, manufactured by Kao Chemical Co., Ltd.)

[0102] Nikka Amid SO (n-stearyl oleamide, melting point 67°C, manufactured by Mitsubishi Chemical Corporation)

[0103] Excel P-40 (glycerol fatty acid ester, melting point 56-60°C, manufactured by Kao Chemical Co., Ltd.)

[0104] Excel S-95 (glyceryl monostearate, melting point 65-70°C, manufactured by Kao Chemical Co., Ltd.)

[0105] Fatty acid amide T (stearic acid amide, melting point 97-102°C, manufactured by Kao Chemical Co., Ltd.)

[0106] Diamido L200 (erucamide, melting point 80°C, manufactured by Mitsubishi Chemical Corporation)

[0107] Diamido O-200T (oleamide, melting point 70-75°C, manufactured by Mitsubishi Chemical Corporation)

[0108] Diamido Y (lauric acid amide, melting point 99°C, manufactured by Mitsubishi Chemical Corporation)

[0109] (Polymerization initiator)

[0110] TPO (2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, manufactured by Lambson)

[0111] TPOL (ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide)

[0112] BAPO (bis(2,4,6-trimethylbenzoyl)-diphenylphosphine oxide)

[0113] (Sensitizer)

[0114] DETX (diethylthioxanthone, manufactured by Lambson)

[0115] (Polymerization Inhibitor)

[0116] UV22 (quinone polymerization inhibitor, manufactured by Kromachem)

[0117] (Surface Conditioner (Leveling Agent))

[0118] BYK-377 (polyether-modified silicone surfactant, manufactured by BYK Japan)

[0119] <Examples 1 to 13 and Comparative Examples 1 to 7>

[0120] The materials were stirred and mixed according to the formulations shown in Tables 1 and 2 (the proportions of each material are expressed in mass %) to produce the active radiation-curable inkjet printing ink compositions of Examples 1 to 13 and Comparative Examples 1 to 7. The following evaluations were performed using the resulting ink compositions. The results are shown in Tables 1 and 2.

[0121] [Table 1]

[0122]

[0123] [Table 2]

[0124] Table 2

[0125]

[0126] LED curing properties

[0127] The ink composition was applied to a coated paper (OK Top Coat) using a #4 bar coater at 40°C. The UV-LED lamp manufactured by Phoseon Technology was used with a distance of 2 cm between the lamp and the ink-coated surface and an irradiation time of 1 second (the cumulative UV light dose per second was 60 mJ / cm 2 ) until the stickiness on the surface disappears, and the number of irradiations is evaluated according to the following evaluation criteria.

[0128] (Evaluation Criteria)

[0129] ○: The number of irradiation times was 1.

[0130] ×: The number of irradiation times was 2 or more.

[0131] <Gloss value>

[0132] The ink composition was printed using a Ricoh UV inkjet printing evaluation device equipped with a GEN6 head (600 dpi, droplet volume (5 to 50 pL)) at a print head temperature of 45°C. The ink composition was then LED-cured using the same method as described above to produce a coating film. The gloss value of the cured coating film was measured using a gloss meter (BYK Gloss Meter) and evaluated according to the following criteria.

[0133] (Evaluation Criteria)

[0134] ○: Gloss value is 60 or less.

[0135] ×: The gloss value exceeds 60.

[0136] <Recoatability>

[0137] The ink composition was printed using a Ricoh UV inkjet printing evaluation device equipped with a GEN6 head (600 dpi, droplet volume (5-50 pL)) at a print head temperature of 45°C. The resulting coating film was then LED-cured using the same method as described above. The resulting coating film's wetting index was measured in accordance with JIS-K6768 and evaluated according to the following criteria. When the wetting index was 40 mN / m or higher, the Sakata Ink Co., Ltd. varnish (water-based varnish AC Coat V-181) applied using a bar coater showed no craters, indicating good recoatability.

[0138] (Evaluation Criteria)

[0139] ○: The wetting index is 40 mN / m or more.

[0140] ×: The wetting index is less than 40 mN / m.

[0141] As shown in Tables 1 and 2, the ink compositions of Examples 1 to 13 of the present invention have excellent curability. In addition, the obtained coating films have a small gloss difference and excellent recoatability.

Claims

1. An active radiation curable inkjet printing ink composition comprising a polymerizable compound, a polymerization initiator, and a gelling agent. The wetting index of the cured coating film formed by inkjet printing is 40 mN / m or more.

2. The active radiation-curable inkjet printing ink composition according to claim 1, wherein The gelling agent contains at least one of a fatty acid ester containing a C12 to C18 hydrocarbon chain or a fatty acid amide containing a C12 to C18 hydrocarbon chain. The molecule contains two C12 to C18 hydrocarbon chains.

3. The active radiation-curable ink composition for inkjet printing according to claim 1 or 2, wherein The content of the gelling agent is 2% by mass or more.

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