Photocurable inkjet printing ink composition

Abstract

The present invention provides a photocurable ink composition for inkjet printing, comprising a pigment, a photopolymerizable compound and a photopolymerization initiator, wherein the photopolymerizable compound comprises 5 to 30% by mass of an amine-modified oligomer and 5 to 30% by mass of N,N-dimethylacrylamide, and the photopolymerization initiator comprises at least one of ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and the total amount of ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide is 12% by mass or less.

Description

Technical Field

[0001] The present invention relates to a photocurable inkjet printing ink composition. More specifically, the present invention relates to a photocurable inkjet printing ink composition that does not require a large amount of polymerization initiator and has excellent various properties. Background Art

[0002] Conventionally, a photocurable inkjet ink composition containing TPOL (ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide) and Irgacure 819 (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide) is known (Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-137735 Summary of the invention

[0006] However, the ink composition described in Patent Document 1 requires a certain amount of initiator or more in order to provide sufficient curing properties. However, when a large amount of initiator is added in consideration of curing properties, the coating performance is poor. In addition, according to the revision of safety information in recent years, it is necessary to design the compounding to exclude TPO ((2,4,6-trimethylbenzoyl) diphenylphosphine oxide).

[0007] The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a photocurable inkjet printing ink composition that does not require a large amount of polymerization initiator and has excellent various properties.

[0008] The present inventors have conducted intensive studies to solve the above problems and have found that a photocurable inkjet printing ink composition containing a pigment, a photopolymerizable compound, and a predetermined photopolymerization initiator can solve the above problems, thereby completing the present invention.

[0009] A photocurable ink composition for inkjet printing according to one embodiment of the present invention for solving the above-mentioned problems comprises a pigment, a photopolymerizable compound and a photopolymerization initiator, wherein the photopolymerizable compound comprises 5 to 30% by mass of an amine-modified oligomer and 5 to 30% by mass of N,N-dimethylacrylamide, and the photopolymerization initiator comprises at least one of ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and the total amount of ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide is 12% by mass or less.

[0010] According to such a configuration, the photocurable inkjet printing ink composition does not require a large amount of polymerization initiator and is excellent in various properties. DETAILED DESCRIPTION

[0011] <Photocurable inkjet printing ink composition>

[0012] A photocurable ink composition for inkjet printing (hereinafter also referred to as an ink composition) according to one embodiment of the present invention comprises a pigment, a photopolymerizable compound, and a photopolymerization initiator. The photopolymerizable compound comprises 5 to 30% by mass of an amine-modified oligomer and 5 to 30% by mass of N,N-dimethylacrylamide. The photopolymerization initiator comprises at least one of ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide or bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. The total amount of ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide is 12% by mass or less.

[0013] (pigment)

[0014] The pigment is not particularly limited and can be, for example, various organic pigments or inorganic pigments.

[0015] The 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, anthraquinone pigments, flavonoid pigments, quinophthalone pigments, pyranthrone pigments, and indanthrone pigments.

[0016] 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 physical pigments such as calcium carbonate, kaolin, clay, barium sulfate, aluminum hydroxide, talc, etc.

[0017] Specific examples of pigments for each representative hue of 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, 213, etc., preferably CI Pigment Yellow 150, 155, 180, 213, etc.

[0018] 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, Pigment Violet 19, and the like.

[0019] 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.

[0020] The black pigment is carbon black (CI Pigment Black 7) or the like.

[0021] The white pigment is titanium oxide, aluminum oxide, or the like, and titanium oxide or the like surface-treated with various materials such as aluminum oxide and silicon dioxide is preferred.

[0022] The content of the pigment is not particularly limited. For example, the content of the pigment other than the white pigment is preferably 0.5% by mass or more in the ink composition, and more preferably 1% by mass or more. In addition, the content of the pigment other than the white pigment is preferably 10% by mass or less in the ink composition, and more preferably 7% by mass or less. On the other hand, the content of the white pigment is preferably 8% by mass or more in the ink composition, and more preferably 10% by mass or more. In addition, the content of the white pigment is preferably 18% by mass or less in the ink composition, and more preferably 15% by mass or less. By having the content of the pigment within the above range, the ink composition has the following advantages: it has moderate tinting power and does not adversely affect the coating properties of the cured coating.

[0023] (Photopolymerizable compound)

[0024] The photopolymerizable compound contains 5 to 30% by mass of an amine-modified oligomer and 5 to 30% by mass of N,N-dimethylacrylamide.

[0025] Amine modified oligomers

[0026] The amine-modified oligomer is not particularly limited. For example, the amine-modified oligomer is an oligomer of an acrylated amine compound having two photopolymerizable functional groups and two amino groups in the molecule, that is, acrylated amine compounds such as CN371, CN373, CN383, and CN386 (manufactured by Sartomer).

[0027] The content of the amine-modified oligomer in the ink composition may be 5% by mass or more, preferably 10% by mass or more. In addition, the content of the amine-modified oligomer in the ink composition may be 30% by mass or less, preferably 20% by mass or less. When the content of the amine-modified oligomer is less than 5% by mass, the surface curing property, viscosity, and friction resistance tend to be poor. On the other hand, when the content of the amine-modified oligomer exceeds 30% by mass, the viscosity of the ink composition tends to be too high, or the balance of performance tends to be poor.

[0028] ·N,N-dimethylacrylamide

[0029] The content of N,N-dimethylacrylamide in the ink composition can be 5% by mass or more, preferably 10% by mass or more. In addition, the content of N,N-dimethylacrylamide in the ink composition can be 30% by mass or less, preferably 20% by mass or less. When the content of N,N-dimethylacrylamide is less than 5% by mass, there is a tendency for curability to decrease. On the other hand, when the content of N,N-dimethylacrylamide exceeds 30% by mass, there is a tendency for substrate adhesion to decrease.

[0030] (Photopolymerization Initiator)

[0031] The photopolymerization initiator contains at least one of ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0032] The ink composition of the present embodiment only needs to contain ethoxy (2,4,6-trimethylbenzoyl) phenylphosphine oxide and bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide in a total amount of 12% by mass or less, preferably 3% by mass or more. In addition, the total amount of ethoxy (2,4,6-trimethylbenzoyl) phenylphosphine oxide and bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide is preferably 10% by mass or less, more preferably 9% by mass or less. When the total amount of ethoxy (2,4,6-trimethylbenzoyl) phenylphosphine oxide and bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide exceeds 12% by mass, there is a tendency for banding to decrease.

[0033] (Optional ingredient)

[0034] The ink composition of the present embodiment may appropriately contain the following components in addition to the above components.

[0035] Organic solvents

[0036] The organic solvent is not particularly limited. For example, the organic solvent is propylene carbonate, diethylene glycol dialkyl ether, dipropylene glycol alkyl ether acetate, etc. Organic solvents may also be used in combination.

[0037] The diethylene glycol dialkyl ether is preferably diethylene glycol ethyl methyl ether or diethylene glycol diethyl ether.

[0038] The dipropylene glycol alkyl ether acetate is preferably a dipropylene glycol alkyl ether acetate having an alkyl group with 6 or less carbon atoms, and more preferably a dipropylene glycol alkyl ether acetate having an alkyl group with 3 or less carbon atoms.

[0039] In order to adjust the drying property and further improve the anti-spotting property, an alkylene glycol derivative having a flash point of 50 to 150° C. may be used in combination with the organic solvent.

[0040] The alkylene glycol derivatives having a flash point of 50 to 150° C. are (poly)ethylene glycol dialkyl ethers such as triethylene glycol dimethyl ether, triethylene glycol diethyl ether, and tetraethylene glycol dimethyl ether, (poly)propylene glycol dialkyl ethers such as propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, tetrapropylene glycol diethyl ether, and tetrapropylene glycol dimethyl ether, (poly)propylene glycol monoalkyl ethers such as propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol monoethyl ether, (poly)propylene glycol monoalkyl ethers such as propylene glycol monoethyl ether acetate, propylene glycol monobutyl ether acetate, dipropylene glycol monomethyl ether acetate, dipropylene glycol monoethyl ether acetate, and dipropylene glycol monobutyl ether acetate, and (poly)propylene glycol monoalkyl ether monoalkyl esters such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and ethylene glycol monobutyl ether. , diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether and the like (poly)ethylene glycol monoalkyl ethers, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether acetate and the like (poly)ethylene glycol monoalkyl ether monoalkyl esters, ethylene glycol diacetate, diethylene glycol diacetate, triethylene glycol diacetate and the like (poly)ethylene glycol diesters, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol monopropyl ether acetate, triethylene glycol monoethyl ether acetate, triethylene glycol monobutyl ether acetate and the like (poly)ethylene glycol monoether monoesters, etc.

[0041] In addition, organic solvents such as ethylene glycol diethyl ether, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and propylene glycol monomethyl ether acetate having a flash point outside the range of 50 to 150° C. may be used in combination within a range that does not significantly change the flash point of the entire solvent.

[0042] Other photopolymerizable monomers

[0043] The ink composition of the present embodiment may contain other monofunctional or polyfunctional photopolymerizable monomers in addition to the above-mentioned amine-modified oligomer and N,N-dimethylacrylamide.

[0044] ·Monofunctional photopolymerizable monomer

[0045] The monofunctional photopolymerizable monomer is not particularly limited. For example, the monofunctional photopolymerizable monomer is benzyl methacrylate, butyl (meth)acrylate, ethyl carbitol (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-methoxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, diethylene glycol monoethyl ether (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, caprolactone (meth)acrylate, methoxytripropylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, EO (ethylene oxide) modified succinic acid (meth)acrylate and other monofunctional (meth)acrylates, acryloyl morpholine, acrylonitrile, acrylamide, diethylacrylamide, vinylmethyl oxazolidinone, styrene, (meth)acrylic acid, etc.

[0046] In the case of containing a monofunctional photopolymerizable monomer, the content of the monofunctional photopolymerizable monomer is not particularly limited. For example, the content of the monofunctional photopolymerizable monomer is preferably 40% by mass or more, more preferably 50% by mass or more in the ink composition. In addition, the content of the monofunctional photopolymerizable monomer is preferably 80% by mass or less, more preferably 70% by mass or less in the ink composition. When the content of the monofunctional photopolymerizable monomer is within the above range, the cured coating film of the ink composition has the advantage of excellent coating film resistance such as abrasion resistance.

[0047] ·Multifunctional photopolymerizable monomer

[0048] The multifunctional photopolymerizable monomer is not particularly limited. For example, the multifunctional photopolymerizable monomer is a compound having a plurality of carbon-carbon unsaturated bonds in the molecule, such as vinyloxyethoxyethyl (meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, butanediol di(meth)acrylate, dipropylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, (poly)alkylene glycol di(meth)acrylate, dihydroxymethyl-tricyclodecane di(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, polytetramethylene glycol diacrylate, Trimethylolpropane tri(meth)acrylate and its ethylene oxide modified products, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate and its ethylene oxide modified products, dipentaerythritol penta(meth)acrylate and its ethylene oxide modified products, dipentaerythritol hexa(meth)acrylate and its ethylene oxide modified products, urethane (meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate, pentaerythritol ethoxy tetraacrylate, caprolactam-modified dipentaerythritol hexaacrylate, ethoxylated bisphenol A diacrylate, alkoxylated tetrahydrofurfuryl acrylate, etc.

[0049] In the case of containing a multifunctional photopolymerizable monomer, the content of the multifunctional photopolymerizable monomer is not particularly limited. For example, the content of the multifunctional photopolymerizable monomer is preferably 10% by mass or more, more preferably 12% by mass or more in the ink composition. In addition, the content of the multifunctional photopolymerizable monomer is preferably 20% by mass or less, more preferably 18% by mass or less in the ink composition. When the content of the multifunctional photopolymerizable monomer is within the above range, the cured coating film of the ink composition has the advantage of excellent adhesion to the substrate.

[0050] The ink composition of this embodiment may also contain an acrylic resin. The acrylic resin is not limited. For example, the acrylic resin may include a polymer composed of a (meth)acrylate soluble in an organic solvent and a copolymer thereof. The (meth)acrylate is, for example, an alkyl (meth)acrylate such as ethyl (meth)acrylate, propyl (meth)acrylate, or butyl (meth)acrylate; a hydroxyalkyl (meth)acrylate such as hydroxymethyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, or hydroxypentyl (meth)acrylate.

[0051] In addition, the acrylic resin is BR-60 (Tg: 75°C), BR-64 (Tg: 55°C), BR-75 (Tg: 90°C), BR-77 (Tg: 80°C), BR-83 (Tg: 105°C), BR-87 (Tg: 105°C), BR-88 (Tg: 105°C), BR-90 (Tg: 65°C), BR-93 (Tg: 50°C), BR-95 (Tg: 80°C), BR-105 (Tg: 50°C), BR-106 (Tg: 50°C), BR-107 (Tg: 50°C), BR-108 (Tg: 90°C), BR-113 (Tg: 75°C), BR-115 (Tg: 50°C), and BR-116 (Tg: 50°C) manufactured by Mitsubishi Chemical Corporation.

[0052] When an acrylic resin is included, the content of the acrylic resin is not particularly limited. For example, the content of the acrylic resin in the ink composition is preferably 1% by mass or more, and more preferably 1.5% by mass or more. In addition, the content of the acrylic resin in the ink composition is preferably 5% by mass or less, and more preferably 4% by mass or less.

[0053] The ink composition of this embodiment may also contain vinyl chloride resin, vinyl chloride-vinyl acetate resin and ethylene-vinyl acetate resin, styrene-acrylic resin, styrene-maleic acid resin, rosin resin, rosin ester resin, petroleum resin, coumarone indene resin, terpene phenol resin, phenolic resin, ketone resin, urethane resin, melamine resin, urea resin, epoxy resin, cellulose resin, xylene resin, alkyd resin, aliphatic hydrocarbon resin, butyral resin, maleic acid resin, fumaric acid resin, etc. within a range that does not reduce performance.

[0054] Other photopolymerization initiators

[0055] The photopolymerization initiator other than the above that can be formulated in the ink composition of the present embodiment is not particularly limited. For example, the photopolymerization initiator other than the above is 1-hydroxycyclohexyl phenyl ketone, benzoin ethyl ether, benzyl dimethyl ketal, 2-hydroxy-2-methyl-1-phenylpropane-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one, and 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropane-1-one.

[0056] When these photopolymerization initiators are included, the content of these photopolymerization initiators is not particularly limited. For example, the content of the photopolymerization initiator is preferably 0.5% by mass or more, and more preferably 1% by mass or more in the ink composition. In addition, the content of the photopolymerization initiator is preferably 5% by mass or less, and more preferably 3% by mass or less in the ink composition.

[0057] Sensitizer

[0058] 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, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, etc. Thioxanthone sensitizers, etc. For representative examples of commercial products, anthracene sensitizers are DBA and DEA (manufactured by Kawasaki Chemicals Co., Ltd.), and thioxanthone sensitizers are DETX and ITX (manufactured by Lambson Corporation).

[0059] When a sensitizer is included, the content of the sensitizer is not particularly limited. For example, the content of the sensitizer is preferably 0.5% by mass or more, more preferably 0.8% by mass or more in the ink composition. In addition, the content of the sensitizer is preferably 3% by mass or less, more preferably 2% by mass or less in the ink composition. When the content of the sensitizer is within the above range, there is an advantage that the color change of the cured coating film of the ink composition over time can be suppressed.

[0060] It should be noted that when a thioxanthone-based sensitizer is included as a sensitizer, the ink composition is prone to discoloration to yellow. Therefore, the ink composition becomes a hue that is more yellowish than the color based on the pigment (original hue), and therefore, it is preferred to appropriately determine the content of the thioxanthone-based sensitizer for each color. Specifically, it is preferred that the ink composition does not contain a thioxanthone-based sensitizer as a sensitizer in a white ink composition and a transparent ink composition that are susceptible to changes in color perception. In addition, in a magenta ink composition and a cyan ink composition, since a vinylamide compound is used in combination as a photopolymerizable compound, the cured coating film that is discolored to yellow fades, and changes in hue are prone to become a problem. Therefore, the photosensitizer is preferably used within a range where the hue does not cause problems. In addition, even if the black ink composition and the yellow ink composition are discolored, it is difficult to affect the hue, and the photopolymerization is insufficient compared to other hues, and therefore, it is preferred to use a thioxanthone-based sensitizer as a photopolymerization initiator in combination.

[0061] Surface conditioner

[0062] The surface conditioner is not particularly limited, and examples thereof include silicone-based surface conditioners, acrylic-based surface conditioners, vinyl-based surface conditioners, fluorine-based surface conditioners, and acetylene glycol-based surface conditioners.

[0063] When a surface conditioner is included, the content of the surface conditioner is not particularly limited. For example, the content of the surface conditioner is preferably 0.1% by mass or more, more preferably 0.5% by mass or more in the ink composition. In addition, the content of the surface conditioner is preferably 1.5% by mass or less, more preferably 1% by mass or less in the ink composition. When the content of the surface conditioner is within the above range, the ink composition has the advantages of showing good discharge stability and excellent printing quality.

[0064] Dispersants

[0065] The dispersant is not particularly limited and is, for example, an ionic or nonionic surfactant, an anionic, cationic or nonionic polymer compound, or the like. Among these, the dispersant is preferably a polymer compound, and preferred are carbodiimide compounds described in Japanese Patent Application Publication No. 2004-083872, International Publication No. 2003 / 076527, and International Publication No. 2004 / 000950, Agisper PB821 and 822 (manufactured by Ajinomoto Fine Technology Co., Ltd.) as copolymers containing basic functional groups (the acid value and amine value are both 10 to 20 mgKOH / g), Solsperse 56000 (manufactured by The Lubrizol Corporation of Japan), Solsperse 32000 (manufactured by The Lubrizol Corporation of Japan), Solsperse 39000 (manufactured by The Lubrizol Corporation of Japan), and DISPERBYK (manufactured by BYK Chemie Japan Co., Ltd.).

[0066] When a dispersant is included, the content of the dispersant is not particularly limited. For example, the content of the dispersant is preferably 10% by mass or more, and more preferably 15% by mass or more, relative to 100% by mass of the pigment. In addition, the content of the dispersant is preferably 60% by mass or less, and more preferably 50% by mass or less, relative to 100% by mass of the pigment. When the content of the dispersant is within the above range, the ink composition has the advantage of excellent viscosity stability.

[0067] Returning to the overall description of the ink composition, the viscosity of the ink composition of the present embodiment is not particularly limited. For example, the viscosity (25°C) of the ink composition is preferably 30.0 mPa·s or less, and more preferably 20.0 mPa·s or less. When the viscosity of the ink composition is within the above range, the ink composition is easily discharged from the nozzle for inkjet printing. It should be noted that the viscosity can be measured using an E-type viscometer (trade name: RE100L type viscometer, manufactured by Toki Sangyo Co., Ltd.) at 25°C and 20 rpm.

[0068] As described above, according to the present embodiment, an ink composition that does not require a large amount of polymerization initiator and can form a coating film with excellent performance can be obtained.

[0069] <Method for preparing ink composition>

[0070] The method for preparing the ink composition of the present embodiment is not particularly limited. For example, the ink composition can be prepared by dispersing and mixing using a disperser such as a wet circulation mill, a bead mill, a ball mill, a sand mill, an attritor, a roller mill, a DCP mill, a stirrer, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a high-pressure homogenizer (Microfluidizer, Nanomizer, Ultimizer, GenusPY, DeBEE2000, etc.), or a bead mill.

[0071] <Application of ink composition>

[0072] The ink composition of the present embodiment can be used in known applications including paper substrates, and is particularly suitable for use on a surface layer of a substrate that is required to have abrasion resistance and is made of a non-absorbent material.

[0073] Non-absorbent materials include metals, resins, ceramics, and the like. Among these, the ink composition is preferably used for a surface layer having a resin as a base material, and is preferably used for a surface layer composed of a vinyl chloride polymer or an ethylene-vinyl acetate copolymer, a vinyl chloride resin, polyethylene terephthalate, polycarbonate, and the like as a resin, from the viewpoint of water resistance and the like. In addition, when the resin is composed of polyethylene terephthalate (PET), a vinyl chloride resin, a polycarbonate, a tarpaulin, an acrylic resin, and the like, the ink composition has excellent adhesion and the like.

[0074] The method for printing and curing the ink composition of the present embodiment is not particularly limited. For example, the method for printing and curing is a method in which the ink composition is discharged onto a substrate using an inkjet head, and then the coating of the ink composition landed on the substrate is exposed to light to cure it. The discharge to the substrate (printing of the image) can be implemented by supplying the ink composition to a printer head corresponding to a low viscosity of an inkjet recording printer, and discharging it from the printer head in a manner such that the film thickness of the coating becomes 1 to 60 μm relative to the substrate. In addition, exposure and curing (curing of the image) using light can be implemented by irradiating the coating of the ink composition applied to the substrate as an image with light.

[0075] The inkjet printer may be a conventionally used inkjet printer. In addition, the light source for curing the coating film may be ultraviolet light (UV lamp), ultraviolet light (light emitting diode (LED)), electron beam, visible light, etc.

[0076] An embodiment of the present invention has been described above. 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 configurations.

[0077] (1) A photocurable ink composition for inkjet printing, comprising a pigment, a photopolymerizable compound, and a photopolymerization initiator, wherein the photopolymerizable compound comprises 5 to 30% by mass of an amine-modified oligomer and 5 to 30% by mass of N,N-dimethylacrylamide, and the photopolymerization initiator comprises at least one of ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and the total amount of ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide is 12% by mass or less.

[0078] According to such a configuration, the photocurable inkjet printing ink composition does not require a large amount of polymerization initiator and is excellent in various properties.

[0079] Example

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

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

[0082] (Amine modified oligomer)

[0083] CN371 (manufactured by Sartomer)

[0084] (Photopolymerizable compound)

[0085] N,N-dimethylacrylamide (monofunctional photopolymerizable compound, Tg: 119°C)

[0086] N-vinyl caprolactam (monofunctional photopolymerizable compound, Tg: 125°C)

[0087] Benzyl acrylate (monofunctional photopolymerizable compound, Tg: 11°C)

[0088] Isobornyl acrylate (monofunctional photopolymerizable compound, Tg: 88°C)

[0089] Acryloylmorpholine (monofunctional photopolymerizable compound, Tg: 145°C)

[0090] 1,6-Hexanediol diacrylate (bifunctional photopolymerizable compound, Tg: 43°C)

[0091] (Photopolymerization Initiator)

[0092] TPOL: Ethoxy (2,4,6-trimethylbenzoyl) phenylphosphine oxide

[0093] Omnirad 819: Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (manufactured by IGM Resins BV)

[0094] TPO: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (manufactured by Lambson)

[0095] (Sensitizer)

[0096] DETX: diethylthioxanthone (produced by Lambson)

[0097] (Surface Conditioner)

[0098] BYK-315N: polyester-modified polymethylalkylsiloxane surfactant, solid content 25% by mass, solvent component: a mixture of methoxypropyl acetate and phenoxyethanol in a mass ratio of 1:1 (manufactured by BYK Chemie Japan Co., Ltd.)

[0099] (Color material (pigment))

[0100] PB15:4 Pigment Blue 15:4

[0101] PR122 Pigment Red 122

[0102] PY150 Pigment Yellow 150

[0103] P.Bk.7 Pigment Black 7

[0104] (Dispersant)

[0105] Solsperse 32000 (manufactured by Japan Lubrizol Co., Ltd.)

[0106] PB821 (manufactured by Ajinomoto Fine Technology Co., Ltd.)

[0107] <Examples 1 to 8 and Comparative Examples 1 to 7>

[0108] The materials were stirred and mixed according to the formulation in Table 1 (the formulation ratio of each material is mass %) to obtain photocurable inkjet printing ink compositions of Examples 1 to 8 and Comparative Examples 1 to 7. The following evaluations were performed using the obtained ink compositions. The results are shown in Table 1.

[0109] [Table 1]

[0110]

[0111] <Viscosity>

[0112] The viscosity of the photocurable inkjet printing ink composition was measured using an E-type viscometer (trade name: RE100L type viscometer, manufactured by Toki Sangyo Co., Ltd.) at a temperature of 25° C. and a rotor rotation speed of 20 rpm.

[0113] <Discharge stability>

[0114] An inkjet recording device equipped with an inkjet nozzle for low-viscosity ink and each ink composition were left to stand for 24 hours under a 25° C. environment to adjust the temperature of the inkjet recording device and the ink composition to 25° C. Then, each ink composition was used to continuously print on PVC80 (manufactured by Lintec Corporation) at 25° C., and evaluation was performed according to the following evaluation criteria.

[0115] (Evaluation Criteria)

[0116] ◯: The ink composition has no printing disturbance and can be stably discharged.

[0117] △: The ink composition was slightly printed in a disordered manner, but was discharged in a substantially stable manner.

[0118] ×: The ink composition has printing disturbance or cannot be discharged stably.

[0119] <Viscosity stability>

[0120] Each ink composition was placed in a sealed glass bottle and allowed to stand for 3 weeks in an environment of 25° C. and 60° C., and then the viscosity was measured using an E-type viscometer.

[0121] The viscosity increase ratio (%) was calculated by the formula ((viscosity value after standing at 60° C. for 3 weeks / viscosity value after standing at 25° C. for 3 weeks)×100))−100, and the evaluation was performed according to the following evaluation criteria.

[0122] (Evaluation Criteria)

[0123] ○: The viscosity increase ratio is less than 10%.

[0124] △: The viscosity increase ratio is 10% or more and less than 20%.

[0125] ×: The viscosity increase ratio is 20% or more.

[0126] <Curing properties>

[0127] In an environment of 25°C, an inkjet recording device equipped with an inkjet nozzle for low-viscosity ink and each ink composition were placed for 24 hours to keep the temperature of the inkjet recording device and the ink composition at 25°C. Then, each ink composition was continuously printed on PVC80 (manufactured by Lintec Co., Ltd.) at 25°C, and then a UV-LED light lamp manufactured by Phoseon Technology was used at a distance of 2 cm between the lamp and the ink coating surface, with a UV cumulative light dose of 180 mJ / cm 2 The coating film surface was touched with a finger, the coating film state was visually confirmed, and evaluation was performed according to the following evaluation criteria.

[0128] (Evaluation Criteria)

[0129] ○: There are no fingerprints on the coating film.

[0130] △: Fingerprints slightly adhere to the coating film.

[0131] ×: Fingerprints are attached to the coating film.

[0132] <Adhesion to substrate>

[0133] Each ink composition obtained in the examples and comparative examples was printed on the surface of an acrylic plate (Acrylite L·S, manufactured by Mitsubishi Chemical Corporation) using a commercially available inkjet printer, and then irradiated with ultraviolet light to obtain a cured coating film. The obtained coating film was cross-cut with a cutter, and a cellophane tape (product name: Cellotape (registered trademark), manufactured by Nichiban Co., Ltd.) was attached to the cut portion, and the peeling of the cured coating film was evaluated according to the following evaluation criteria by peeling it off.

[0134] (Evaluation Criteria)

[0135] ○: The peeling rate of the cured coating film was 0%.

[0136] △: The peeling rate of the cured coating film is more than 0% and less than 20%.

[0137] ×: The peeling rate of the cured coating film is 20% or more.

[0138] <Bending resistance>

[0139] Each ink composition obtained in Examples and Comparative Examples was printed on the surface of a PET film (E5100, manufactured by Toyobo Co., Ltd.) using a commercially available inkjet printer, and irradiated with ultraviolet light to obtain a cured coating film. The obtained coating film was bent at 180°, the state of cracks was visually confirmed, and evaluated according to the following evaluation criteria.

[0140] (Evaluation Criteria)

[0141] ○: The coating film has no cracks such as fine cracks.

[0142] △: Fine cracks occurred in the coating film.

[0143] ×: Clear cracks occurred in the coating film.

[0144] <Friction resistance>

[0145] Each ink composition obtained in the examples and comparative examples was printed on the surface of a PVC plate (T938, manufactured by Takiron-ci Co., Ltd.) using a commercially available inkjet printer, and irradiated with ultraviolet light to obtain a cured coating film. The obtained coating film was rubbed 100 times with a bleached cloth at a load of 500 g using a Gakushin type fastness tester (manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd.), and the rubbing state of the coating film at this time was visually observed and evaluated according to the following evaluation criteria.

[0146] (Evaluation Criteria)

[0147] ○: The coating film was not rubbed off.

[0148] △: There are scratches on the surface of the coating film.

[0149] ×: The coating film was obviously rubbed off.

[0150] <Solvent resistance>

[0151] Each ink composition obtained in the examples and comparative examples was printed on the surface of a PVC plate (T938, manufactured by Takiron-ci Co., Ltd.) using a commercially available inkjet printer, and irradiated with ultraviolet light to obtain a cured coating film. The obtained coating film was rubbed 10 times with a bleached cloth containing ethanol at a load of 200 g using a Gakushin type fastness tester (manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd.), and the rubbing state of the coating film at this time was visually observed and evaluated according to the following evaluation criteria.

[0152] (Evaluation Criteria)

[0153] ○: The coating film was not rubbed off.

[0154] △: There are scratches on the surface of the coating film.

[0155] ×: The coating film was obviously rubbed off.

[0156] <Zone>

[0157] Each ink composition obtained in the examples and comparative examples was printed on the surface of a PVC plate (T938, manufactured by Takiron-ci Co., Ltd.) using a commercially available inkjet printer, and irradiated with ultraviolet light to obtain a cured coating film. The glossiness of the obtained coating film was measured at a measurement angle of 60° using a variable angle gloss meter (Gross Meter VG7000, manufactured by Nippon Denshoku Industries Co., Ltd.), and the following criteria were used for evaluation.

[0158] (Evaluation Criteria)

[0159] ○: The measured value is 15.0 or more.

[0160] △: The measured value is 10.0 or more and less than 15.0.

[0161] ×: The measured value is less than 10.0.

[0162] As shown in Table 1, the photocurable ink composition for inkjet printing of the present invention is excellent in discharge stability, viscosity stability, curability, substrate adhesion, bending resistance, friction resistance, solvent resistance, and banding. On the other hand, the ink composition of Comparative Example 1 containing an excessive amount of photopolymerization initiator has poor evaluation results for bending resistance and banding. The evaluation results for banding of Comparative Example 2, which does not use ethoxy (2,4,6-trimethylbenzoyl) phenylphosphine oxide and bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide, are poor. The evaluation results for substrate adhesion of the ink composition of Comparative Example 3 containing an excessive amount of photopolymerizable compound are poor. The evaluation results for curability of the ink composition of Comparative Example 4 with a small content of photopolymerizable compound are poor. The evaluation results for viscosity stability of the ink composition of Comparative Example 5 not containing N,N-dimethylacrylamide are poor. The evaluation results for curability and bending resistance of the ink composition of Comparative Example 6 with a small content of amine-modified oligomers are poor. The evaluation result of banding of the ink composition of Comparative Example 7 containing an excessive amount of the amine-modified oligomer was poor.

Claims

1. A photocurable inkjet printing ink composition comprising a pigment, a photopolymerizable compound and a photopolymerization initiator, wherein: The photopolymerizable compound contains 5 to 30% by mass of an amine-modified oligomer and 5 to 30% by mass of N,N-dimethylacrylamide. The photopolymerization initiator comprises ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and does not comprise (2,4,6-trimethylbenzoyl)diphenylphosphine oxide. The total amount of ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide is 12% by mass or less.

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