Electron beam curable inkjet ink, printed matter using the same, and image forming method

Abstract

To provide an electron beam-curable inkjet ink that can quickly form a printed image having low migration, scratch resistance, and high image quality.SOLUTION: An electron beam-curable inkjet ink contains a polymerizable compound (A) having, in each molecule, a C6-30 long-chain alkyl group, a hydrogen bonding group, and a polymerizable group, a polymerizable compound (B) excluding the component (A), and a colorant (C).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electron beam curable inkjet ink, a printed matter using the same, and an image forming method.

Background Art

[0002] An inkjet recording method using an inkjet printer is a method of ejecting ink droplets from a printer and attaching them to a recording medium such as paper or a resin film to perform printing. Since this method is easy to miniaturize and speed up, it has rapidly spread in recent years and is also being applied for industrial uses. <了

[0003] As a type of inkjet ink, an ultraviolet curable inkjet ink that cures by irradiating ultraviolet rays is known. An ultraviolet curable inkjet ink is generally a composition containing a polymerizable compound, a photoinitiator, and a colorant. When droplets of an ultraviolet curable inkjet ink land on the surface of a recording medium and the landed droplets are irradiated with ultraviolet rays, the reaction of the polymerizable compound in the ink proceeds, and a cured film in which the droplets are cured is formed on the surface of the recording medium. Compared with solvent-based and water-based types, ultraviolet curable inkjet inks are expected to be applied to packaging materials because they have characteristics such as high-speed curing and general-purpose substrates.

[0004] However, low molecular compounds such as unreacted photoinitiators, decomposition products of photoinitiators, and unreacted polymerizable compounds remain in the cured film obtained by curing an ultraviolet curable inkjet ink, and migration and odor have become problems. Therefore, especially when printing on food packaging materials, it is essential to reduce unreacted photoinitiators and decomposition products of photoinitiators that are likely to emit odors.

[0005] As an inkjet ink that solves the problems of migration and odor while maintaining the excellent high-speed curing and general-purpose substrate properties of ultraviolet curable inkjet, there is an electron beam curable inkjet ink.

[0006] Electron beam curable inkjet inks can cure ink droplets using the high energy of electron beams without the need for photoinitiators. Therefore, migration and odor generation caused by photoinitiators can be prevented.

[0007] Various studies have been conducted to take advantage of these aspects of electron beam-curable inkjet inks.

[0008] Patent Document 1 discloses an electron beam-curable inkjet ink containing a colorant, dipropylene glycol diacrylate as a polymerizable compound, and 2-(2-vinyloxyethoxy)ethyl acrylate. However, when performing color printing with this ink, the droplets of each color ink mix with each other between the time the droplets are placed on the substrate and the electron beam is irradiated, resulting in a decrease in image quality.

[0009] Patent Document 2 discloses an electron beam-curable inkjet ink containing a photopolymerizable compound including a trifunctional or polyfunctional compound, a linear alkylaldehyde with 6 to 9 carbon atoms, and a gelling agent, as a technique to solve the problem of ink droplets mixing after being deposited in an electron beam-curable inkjet ink. However, when this ink is applied to food packaging materials, the unreactable linear alkylaldehyde and gelling agent may migrate to the food, resulting in insufficient reduction of migration. Furthermore, the linear alkylaldehyde inhibits the reactivity of the polymerizable compound, resulting in insufficient scratch resistance of the cured film. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Patent No. 6477113 [Patent Document 2] Japanese Patent Publication No. 2019-104845 [Overview of the project] [Problems that the invention aims to solve]

[0011] This invention has been made in view of these circumstances, and aims to provide an electron beam-curable inkjet ink that exhibits low migration, excellent abrasion resistance, and the ability to form high-quality printed images at high speed. [Means for solving the problem]

[0012] In other words, the present invention relates to the following [1] to [7]. In this application, "(numerical value 1) to (numerical value 2)" indicates that upper and lower limits are included. [1] An electron beam curable inkjet ink comprising a polymerizable compound (A) having a long-chain alkyl group with 6 to 30 carbon atoms, a hydrogen bonding group, and a polymerizable group in its molecule, a polymerizable compound (B) other than component (A), and a colorant (C). [2] The electron beam curable inkjet ink according to the preceding paragraph [1], wherein component (A) is a reaction product of a carboxylic acid (a) having 6 to 30 carbon atoms and an epoxy compound (b) having a polymerizable group. [3] The electron beam curable inkjet ink according to the preceding paragraph [1], wherein component (A) is a reaction product of an epoxy compound (c) having 6 to 30 carbon atoms and a carboxylic acid (d) having a polymerizable group. [4] An electron beam curable inkjet ink according to any one of the preceding paragraphs [1] to [3], wherein the content of component (A) in the total amount of electron beam curable inkjet ink is 0.5 to 90% by weight. [5] An electron beam curable inkjet ink as described in any one of the preceding paragraphs [1] to [4], wherein the solidification initiation temperature is 20°C or higher and less than 100°C. [6] A printed material using an electron beam-curable inkjet ink as described in any one of the preceding items [1] to [5]. [7] An image forming method comprising the following steps (1) to (3). (Step 1) A step of heating the electron beam curable inkjet ink described in any one of the preceding items [1] to [5] above to a temperature above the ink solidification start temperature. (Step 2) The step of ejecting droplets of the electron beam curable inkjet ink according to any one of [1] to [5] above from the nozzles of the ejection head and landing them on the surface of the substrate (Step 3) The step of further irradiating with an electron beam to cure the ink

Advantages of the Invention

[0013] The present invention can provide an electron beam curable inkjet ink that is excellent in low migration and abrasion resistance and can form a high-quality printed image at high speed.

Brief Description of the Drawings

[0014] [Figure 1] The 1H-NMR chart of Synthesis Example 1 is shown. [Figure 2] The chart for measuring the coagulation start temperature of Example 1 is shown. [Figure 3] The chart for measuring the coagulation start temperature of Comparative Example 1 is shown.

Modes for Carrying Out the Invention

[0015] In this specification, "C.I." is an abbreviation for Color Index. Also, "(meth)acrylate" means "acrylate" and / or "methacrylate". Further, in this specification, "%" and "parts" are described on a weight basis unless otherwise specified.

[0016] [Electron Beam Curable Inkjet Ink] The electron beam curable inkjet ink of the present invention contains a polymerizable compound (A) having a long-chain alkyl group having 6 to 30 carbon atoms, a hydrogen-bonding group, and a polymerizable group in the molecule (hereinafter, also simply referred to as "component (A)"), a polymerizable compound (B) other than component (A) (hereinafter, also simply referred to as "component (B)"), and a colorant (C) (hereinafter, also simply referred to as "component (C)").

[0017] [A polymerizable compound having a long-chain alkyl group with 6 to 30 carbon atoms, a hydrogen bonding group, and a polymerizable group in the molecule] Component (A) has a long-chain alkyl group with 6 to 30 units, a hydrogen-bonding group, and a polymerizable group within its molecule. Because the droplets of the electron beam-curable inkjet ink of the present invention contain component (A), when ejected from the nozzle of the ejection head and landed on the substrate surface, the droplets solidify and do not mix easily, thus enabling the formation of high-resolution images. Furthermore, since component (A) has polymerizable groups, it can be fixed within the cured film by electron beam irradiation, achieving low migration.

[0018] Long-chain alkyl groups with 6 to 30 carbon atoms are more preferably linear alkyl groups with 12 to 22 carbon atoms. Alkyl groups with fewer than 6 carbon atoms do not allow ink droplets to solidify easily when they land on the substrate surface, causing them to mix and resulting in poor image quality. Alkyl groups with more than 30 carbon atoms result in poor scratch resistance of the cured film. With 6 or more carbon atoms, ink droplets solidify easily when they land on the substrate surface, resulting in high-quality images, and with 30 or fewer carbon atoms, the scratch resistance of the cured film is not insufficient. In addition, alkyl groups with 6 or more carbon atoms also have the effect of lowering the viscosity of the ink.

[0019] Examples of hydrogen-bonding groups in component (A) include hydroxyl groups, urethane groups, urea groups, amide groups, carboxyl groups, and ester groups. The presence of hydrogen-bonding groups makes it easier for ink droplets to solidify when they land on the substrate surface. Among the hydrogen-bonding groups, hydroxyl groups, urethane groups, and amide groups are preferred, with hydroxyl groups being more preferred from the viewpoint of curability and glossiness of printed materials.

[0020] The polymerizable group of component (A) is not particularly limited as long as it undergoes polymerization by electron beam irradiation, but examples include acrylic groups, methacrylic groups, vinyl groups, vinyl ether groups, and allyl groups. From the viewpoint of productivity, acrylic groups and methacrylic groups, which have a fast curing rate, are preferred.

[0021] The method for obtaining component (A) is not particularly limited, but it can be obtained by reacting a carboxylic acid (a) having 6 to 30 carbon atoms (hereinafter also simply referred to as "component (a)") with an epoxy compound (b) having a polymerizable group (hereinafter also simply referred to as "component (b)"), or by reacting an epoxy compound (c) having 6 to 30 carbon atoms (hereinafter also simply referred to as "component (c)") with a carboxylic acid (d) having a polymerizable group (hereinafter also simply referred to as "component (d)").

[0022] When reacting component (a) and component (b), component (b) is mixed with component (a) so that the amount of epoxy groups is 1.0 to 1.2 equivalents, preferably 1.05 to 1.1 equivalents, per equivalent of carboxylic acid groups, and the reaction is carried out at a reaction temperature of 80 to 120°C to obtain the desired component (A). When reacting component (c) and component (d), component (d) is mixed with component (c) so that the amount of carboxylic acid groups is 1.0 to 1.2 equivalents, preferably 1.05 to 1.1 equivalents, per equivalent of epoxy groups, and the reaction is carried out at a reaction temperature of 80 to 120°C to obtain the desired component (A).

[0023] To accelerate the above reaction, it is preferable to use catalysts such as triphenylphosphine, 2,4,6-tris(dimethylaminomethyl)phenol, triethanolamine, tetraethylammonium chloride, and trimethylglycine, with trimethylglycine being particularly preferred because it is a natural product safe for the human body. Furthermore, to prevent polymerization during the reaction, polymerization inhibitors such as paramethoxyphenol, methylhydroquinone, and dibutylhydroxytoluene can also be used.

[0024] Examples of component (a) include caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid, and those that do not have a branched structure or an unsaturated structure are preferred.

[0025] Examples of component (b) include glycidyl acrylate, glycidyl metharylate (trade name: GMA, manufactured by Mitsubishi Chemical Corporation), 3,4-epoxycyclohexyl methyl acrylate, 3,4-epoxycyclohexyl methyl methacrylate (trade name: Cyclomer M-100, manufactured by Daicel Corporation), β-methylglycidyl (meth)acrylate, 4-hydroxybutyl acrylate glycidyl ether (trade name: 4HBAGE, manufactured by Mitsubishi Chemical Corporation), 1,2-epoxy-4-vinylcyclohexane (trade name: Celoxide 2000, manufactured by Daicel Corporation), allyl glycidyl ether, allylphenyl glycidyl ether, Epocalic VNBB-ME, etc.

[0026] Examples of component (c) include 1,2-epoxyhexane, 1,2-epoxyheptane, 1,2-epoxyoctane, 1,2-epoxynonane, 1,2-epoxydecane, 1,2-epoxyundecane, 1,2-epoxydodecane, 1,2-epoxytridecane, 1,2-epoxytetradecane, 1,2-epoxypentadecane, 1,2-epoxyhexadecane, 1,2-epoxyheptadecane, 1,2-epoxyoctadecane, 1,2-epoxynonadecane, 1,2-epoxyicosane, cetylglycidyl ether, laurylglycidyl ether, stearylglycidyl ether, 1,6-hexanediol diglycidyl ether, 1,12-dodecanediol diglycidyl ether, etc.

[0027] Examples of component (d) include acrylic acid, methacrylic acid, 2-carboxyethyl acrylate, crotonic acid, and itaconic acid, but from the viewpoint of curability, acrylic acid and 2-carboxyethyl acrylate are preferred.

[0028] In the electron beam curable inkjet ink of the present invention, component (A) can be used by mixing one or more components in any proportion. The content of component (A) in the total amount of the electron beam curable inkjet ink of the present invention is preferably 0.5 to 90% by weight, more preferably 1 to 80% by weight, particularly preferably 3 to 50% by weight, and most preferably 5 to 20% by weight. If the content is less than 0.5% by weight, when the ink droplets land on the substrate surface, the droplets do not solidify easily and mix together, resulting in poor image quality. If the content is more than 90% by weight, the scratch resistance of the cured film becomes poor.

[0029] [Polymerizable compounds other than component (A) (B)] The electron beam curable inkjet ink of the present invention contains polymerizable compounds other than component (A) as component (B). Component (B) includes alkyl(meth)acrylates with 5 to 25 carbon atoms such as isooctyl(meth)acrylate, isoamyl(meth)acrylate, lauryl(meth)acrylate, isodecyl(meth)acrylate, stearyl(meth)acrylate, cetyl(meth)acrylate, isomiristyl(meth)acrylate, isostearyl(meth)acrylate, and tridecyl(meth)acrylate, as well as benzyl(meth)acrylate, tetrahydrofurfuryl(meth)acrylate, and phenoxyethyl(meth)acrylate. (meth)acrylamide, N-hydroxyethylacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, acryloylmorpholine, allyloxymethyl methyl acrylate, 2-(2-vinyloxyethoxy)ethyl acrylate, 2-(2-vinyloxyethoxy)ethyl methacrylate, phenylglycidyl (meth)acrylate, tricyclodecane (meth)acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl (meth)acrylate, isobornyl (meth) (Meth)acrylates having a cyclic skeleton such as acrylate, dicyclopentanyl (meth)acrylate, 1-adamantyl acrylate, 2-methyl-2-adamantyl acrylate, 2-ethyl-2-adamantyl acrylate, 1-adamantyl methacrylate, polypropylene oxide-modified nonylphenyl (meth)acrylate, dicyclopentadieneoxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, etc. )acrylates, alkyl (meth)acrylates having hydroxyl groups such as alkyl (meth)acrylates, ethoxydiethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, polypropylene oxide-modified nonylphenyl (meth)acrylate, and other polyalkylene glycol (meth)acrylates, caprolactone-modified tetrafurfuryl (meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,7-heptanediol di(meth)acrylate,Di(meth)acrylates of aliphatic hydrocarbon diols having 5 to 12 carbon atoms, such as 1,8-octanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 2-n-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, tricyclodecanedimethanol di(meth)acrylate, and di(meth)acrylate. Xane glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, alkylene oxide modified bisphenol A type di(meth)acrylate, caprolactone modified hydroxypivalate neopentyl glycol di(meth)acrylate and trimethylolpropane tri(meth)acrylate, trimethyloloctanet tri(meth)acrylate, and other trimethylol C2-C10 alkane tri(meth)acrylates, trimethylolpropane polyethoxytri(meth)acrylate Trimethylol C2-C10 alkane polyalkoxy tri(meth)acrylates such as acrylate, trimethylolpropane polypropoxy tri(meth)acrylate, trimethylolpropane polyethoxypolypropoxy tri(meth)acrylate, tris[(meth)acroyloxyethyl]isocyanurate, pentaerythritol tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, and other alkylene oxide-modified tri(meth)acrylates. Limethylolpropane tri(meth)acrylate, pentaerythritol polyethoxytetra(meth)acrylate, pentaerythritol polypropoxytetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy(meth)acrylate oligomer, aliphatic urethane(meth)acrylate oligomer,(Meth)acrylate compounds such as aromatic urethane (meth)acrylate oligomers and polyester (meth)acrylate oligomers, monofunctional vinyl ether compounds including butyl vinyl ether, butyl propenyl ether, butyl butenyl ether, hexyl vinyl ether, ethylhexyl vinyl ether, phenyl vinyl ether, benzyl vinyl ether, ethyl ethoxy vinyl ether, acetyl ethoxyethoxy vinyl ether, cyclohexyl vinyl ether and adamantyl vinyl ether, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol vinyl ether, butylene divinyl ether, dibutylene glycol divinyl ether, neopentyl glycol divinyl ether, cyclohexanediol divinyl ether, cyclohexanedimethanol divinyl ether, norbornyl dimethanol divinyl ether, isobainyl divinyl ether, divinylresorcinol and Examples include bifunctional vinyl ether compounds containing divinylhydroquinone, as well as vinyl ether compounds with three or more functions, such as glycerin trivinyl ether, glycerin ethylene oxide adduct trivinyl ether (6 moles of ethylene oxide added), trimethylolpropane trivinyl ether, trivinyl ether ethylene oxide adduct trivinyl ether (3 moles of ethylene oxide added), pentaerythritol trivinyl ether, and ditrimethylolpropane hexavinyl ether, and their oxyethylene adducts; aromatic vinyl compounds such as styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, vinylnaphthalene, indene, divinylbenzene, and diallyl phthalate; vinyl ester compounds such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate, and divinyl adipate; and allyl compounds such as allyl acetate, allyl benzoate, diallyl adipate, diallyl terephthalate, diallyl isophthalate, and diallyl phthalate.

[0030] From the viewpoint of reactivity and solubility of component (A), acryloylmorpholine, allyloxymethyl methyl acrylate, 2-(2-vinyloxyethoxy)ethyl acrylate, 2-(2-vinyloxyethoxy)ethyl methacrylate, phenylglycidyl (meth)acrylate, neopentyl glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, polyethylene glycol diacrylate, polytetramethylene glycol diacrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, and ethylene oxide-modified trimethylolpropane triacrylate are particularly preferred.

[0031] From the viewpoint of imparting flexibility to the ink after curing, lauryl acrylate, isodecyl acrylate, stearyl acrylate, cetyl acrylate, isomiristyl acrylate, isostearyl acrylate, tridecyl acrylate, polypropylene glycol diacrylate, polyethylene glycol diacrylate, polytetramethylene glycol diacrylate, 1,9-nonanediol diacrylate, 1,10-decanediol diacrylate, 1,12-dodecanediol diacrylate, aliphatic urethane acrylate oligomers, and aromatic urethane acrylate oligomers are particularly preferred.

[0032] In the electron beam curable inkjet ink of the present invention, component (B) can be used by mixing one or more components in any proportion. The content of component (B) in the total amount of the electron beam curable inkjet ink of the present invention is preferably 10 to 99.5% by weight, more preferably 20 to 99% by weight, and particularly preferably 50 to 95% by weight.

[0033] [Coloring agent (C)] The electron beam-curable inkjet ink of the present invention contains a colorant as component (C). Component (C) can be a dye or a pigment, and from the viewpoint of obtaining an image with good weather resistance, the colorant is preferably a pigment. Depending on the color of the image to be formed, the pigment can be selected from, for example, yellow pigment, red or magenta pigment, blue or cyan pigment, and black pigment, and examples of pigments include inorganic pigments, organic pigments, extender pigments, and hollow particles.

[0034] Examples of the inorganic pigments mentioned above include carbon black, metal oxides, hydroxides, sulfides, ferrocyanides, and metal chlorides.

[0035] If the above ink is black ink and the above pigment is the above inorganic pigment, then the inorganic pigment contained in the black ink is preferably carbon black such as thermal black, acetylene black, oil furnace black, gas furnace black, lamp black, gas black, and channel black. Specific examples of carbon black include, for example, the Raven series from Columbia Carbon; the Monarch series, Regal series, and Mogul series from Cabot; the ColorBlack series, Printex series, SpecIalBlack series, and Nerox series from Orion Engineered Carbons; and the MA series, MCF series, No. 25, No. 33, No. 40, No. 47, No. 52, No. 900, and No. 2300 from Mitsubishi Chemical Corporation. If the above ink is a white ink and the above pigment is an inorganic pigment, examples of inorganic pigments contained in the white ink include oxides, nitrides, and oxidized nitrides of metals such as zinc, silicon, aluminum, titanium, strontium, and zirconium; and inorganic compounds such as various glasses and silica, with titanium dioxide and zinc oxide being preferred.

[0036] Examples of the above organic pigments include azo, disazo, phthalocyanine, quinacridone, isoindolinone, dioxazine, perylene, perinone, thioindigo, antholaquinone, and quinophthalone, with disazo being preferred.

[0037] Examples of the above organic pigments include CIPigment Yellow 1, 2, 3, 12, 13, 14, 16, 17, 24, 55, 73, 74, 75, 83, 93, 94, 95, 97, 98, 108, 114, 128, 129, 138, 139, 150, 151, 154, 155, 180, 185, 193, 199, 202, 213, and other yellows; CIPigment Red Red 5, 7, 12, 48, 48:1, 57, 88, 112, 122, 123, 146, 149, 150, 166, 168, 177, 178, 179, 184, 185, 202, 206, 207, 254, 255, 257, 260, 264, 269, 272, etc.; CIPigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:6, 16, 22, 25, 60, 66, 80, etc.; CIPigment Violet 19, 23, 29, 37, 38, 50, etc.; CIPigment Orange 13, 16, 43, 68, 69, 71, 73, etc.; CIPigment Examples of pigments include greens such as Green 7, 36, and 54, and blacks such as CIPigment Black 1.

[0038] Examples of the extender pigments mentioned above include silica, calcium carbonate, talc, clay, barium sulfate, and white carbon. Extender pigments are often used in combination with other colorants.

[0039] As the hollow particles mentioned above, known hollow particles described in, for example, U.S. Patent No. 4,880,465, Japanese Patent No. 3,562,754, Japanese Patent No. 6026234, Japanese Patent No. 5459460, Japanese Patent Publication No. 2003-268694, Japanese Patent No. 4902216, etc., can be used, and it is particularly preferable to use them as a white pigment.

[0040] Examples of the above-mentioned disperse dyes include known disperse dyes or known oil-soluble dyes. Among the known disperse dyes, CIDispers-based disperse dyes are preferred. Specific examples include, for instance, CIDispers Yellow 9, 23, 33, 42, 49, 54, 58, 60, 64, 66, 71, 76, 79, 83, 86, 90, 93, 99, 114, 116, 119, 122, 126, 149, 160, 163, 165, 180, 183, 186, 198, 200, 211, 224, 226, 227, 231, 237, etc.; CIDispers Red 60, 73, 88, 91, 92, 111, 127, 131, 143, 145, 146, 152, 153, 154, 167, 179, 191, 192, 206, 221, 258, 283, etc.; CIDispers Orange Disperse dyes in various colors include orange (9, 25, 29, 30, 31, 32, 37, 38, 42, 44, 45, 53, 54, 55, 56, 61, 71, 73, 76, 80, 96, 97, etc.), violet (CIDispers Violet 25, 27, 28, 54, 57, 60, 73, 77, 79, 79:1, etc.), and blue (CIDispers Blue 27, 56, 60, 79:1, 87, 143, 165, 165:1, 165:2, 181, 185, 197, 202, 225, 257, 266, 267, 281, 341, 353, 354, 358, 364, 365, 368, etc.). Among the known solvent dyes mentioned above, CISolvent-based disperse dyes are preferred.

[0041] The average particle size of component (C) is preferably 30 nm to 300 nm, and more preferably 50 nm to 250 nm. In this specification, the average particle size refers to the average particle size of particles measured using the laser light scattering method.

[0042] In the electron beam curable inkjet ink of the present invention, component (C) can be used by mixing one or more components in any proportion. The content of component (C) in the total amount of the electron beam curable inkjet ink of the present invention is preferably 0.1 to 40% by weight, more preferably 0.5 to 20% by weight, particularly preferably 1 to 10% by weight, and most preferably 2 to 7% by weight.

[0043] [Optional ingredients] The electron beam-curable inkjet ink of the present invention may optionally contain various additives such as surface tension modifiers, pigment dispersants, ultraviolet absorbers, defoamers, antioxidants, light stabilizers (e.g., hindered amine compounds), silane coupling agents, and metal adhesion promoters, as well as organic solvents.

[0044] (Surface tension modifier) The electron beam-curable inkjet ink of the present invention may further contain a surfactant as a surface tension modifier. Examples of such surfactants include anionic, nonionic, silicon-based, and fluorine-based surfactants. Among these, it is preferable that the surfactant be selected from the group consisting of nonionic and silicon-based surfactants.

[0045] Examples of the above-mentioned anionic surfactants include alkyl sulfocarboxylates, α-olefin sulfonates, polyoxyethylene alkyl ether acetates, polyoxyethylene alkyl ether sulfates, N-acyl amino acids or their salts, N-acyl methyl taurates, alkyl sulfates, polyoxyalkyl ether sulfates, alkyl sulfates, polyoxyethylene alkyl ether phosphates, rosinic acid soaps, castor oil sulfates, lauryl alcohol sulfates, alkylphenol type phosphates, alkyl type phosphates, alkylaryl sulfonates, diethyl sulfosaturates, diethylhexyl sulfosaturates, and dioctyl sulfosaturates.

[0046] Examples of nonionic surfactants include ether-based surfactants such as polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, and polyoxyethylene distyrenated phenyl ether (e.g., Emulgen A-60, A-90, A-500 manufactured by Kao Corporation); ester-based surfactants such as polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, and polyoxyethylene stearate; and acetylene glycol (or acetylene alcohol)-based surfactants such as 2,4,7,9-tetramethyl-5-decine-4,7-diol, 3,6-dimethyl-4-octin-3,6-diol, and 3,5-dimethyl-1-hexyn-3-ol (e.g., Surfinol manufactured by Evonik Japan Co., Ltd.). Examples include 104, 104PG50, 82, 420, 440, 465, 485, Olphine STG, etc.; and polyglycol ether-based compounds.

[0047] Examples of silicone-based surfactants include polyether-modified siloxanes and polyether-modified polydimethylsiloxanes. Examples include Dynol 960 and 980 from Air Products Corporation; Silface SAG001, SAG002, SAG003, SAG005, SAG503A, SAG008, SAG009, SAG010, KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640, KF-642, KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, KF-6017 from Nisshin Chemical Co., Ltd.; and BYK Additives & Examples include BYK-306, 307, 333, 347, 348, BYK-UV3500, UV-3510, UV-3530, UV3570, 345, 347, 348, 349, 3455, LP-X23288, LP-X23289, LP-X23347 from Instruments; and TEGO Twin 4000, TEGO Wet KL 245, 250, 260, 265, 270, 280, TEGO Rad 2010, 2011, 2100, 2200N, 2250, 2300, 2500, 2600, 2700 from Evonic Tego Chemie.

[0048] Examples of fluorinated surfactants include perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in their side chains. Specific examples of commercially available products include Capstone FS-30 and FS-31 (manufactured by Chemours).

[0049] Among the surfactants mentioned above, surfactants containing polymerizable groups are preferred from the viewpoint of migration, and examples include BYK-UV3500, BYK-UV3510, BYK-UV3530, BYK-UV3570, TEGO Rad 2010, 2011, 2100, 2200N, 2250, 2300, 2500, 2600, 2700, etc.

[0050] (Pigment dispersant) The electron beam curable inkjet ink of the present invention can use a pigment dispersant. Examples of pigment dispersants include polyurethane skeletons, polyacrylic skeletons, polyester skeletons, polyamide skeletons, polyimide skeletons, and polyurea skeletons. Specifically, examples include Solspers 24000GR, 32000, 33000, 35000, 39000, 41000, 53000, and J180 (manufactured by Lubrizol), and Adisper PB821, 822, 824, 827, and 711 (manufactured by Ajinomoto Fine Techno Co., Ltd.).

[0051] (UV absorber) The electron beam-curable inkjet ink of the present invention may contain an ultraviolet absorber to improve weather resistance. Examples of ultraviolet absorbers include benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, hydroxyphenyltriazine-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, and nickel complex salt-based ultraviolet absorbers. However, 2-(2'-hydroxy-5'-methacryloyloxyethylphenyl)-2H-benztriazole (trade name: RUVA-93, manufactured by Otsuka Chemical Co., Ltd.), which contains polymerizable groups, is preferred due to its low migration risk.

[0052] (Antioxidant) Specific examples of antioxidants include, for example, BHT, 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine, pentaerythrityl tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,2-thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], triethylene glycol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], and 1,6-hexanediol-bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate]. Examples include octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, N,N-hexamethylenebis(3,5-di-t-butyl-4-hydroxyhydrocinnamamide), 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tris-(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, octylated diphenylamine, 2,4-bis[(octylthio)methyl-O-cresol, isooctyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], dibutylhydroxytoluene, etc.

[0053] (Light stabilizer) Specific examples of light stabilizers include, for example, 1,2,2,6,6-pentamethyl-4-piperidyl alcohol, 2,2,6,6-tetramethyl-4-piperidyl alcohol, 1,2,2,6,6-pentamethyl-4-piperidyl (meth)acrylate, tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, tetrakis(2,2,6,6-totramethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, 1,2,3,4-butanetetracarboxylic acid and 1,2,2,6,6 -Mixed esterified product of pentamethyl-4-piperidinol and 3,9-bis(2-hydroxy-1,1-dimethylethyl)-2,4,8,10-tetraoxaspiro[5.5]undecane, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(1-undecaneoxy-2,2,6,6-tetramethylpiperidine-4-yl) carbonate, 2,2,6,6-tetramethyl-4-piperidyl methacrylate, bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(1,2,2,6,6- Pentamethyl-4-piperidinyl) sebacate, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, 1-[2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]ethyl]-4-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-tetramethylpiperidine, 1,2,2,6,6-pentamethyl-4-piperidinyl-methacrylate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl)[[3,5-bis(1,1-dimethyl Ethyl)-4-hydroxyphenyl]methyl]butylmalonate, bis(2,2,6,6-tetramethyl-1(octyloxy)-4-piperidinyl) decandioate, reaction product of 1,1-dimethylethyl hydroperoxide and octane, N,N',N'',N'''-tetrakis-(4,6-bis-(butyl-(N-methyl-2,2,6,6-tetramethylpiperidine-4-yl)amino)-triazine-2-yl)-4,7-diazadecane-1,10-diamine, dibutylamine·1,3,5-triazine·N,N'-bis(2,2,6,Polycondensate of 6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine, poly[[6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidyl)imino]hexamethylene[(2,2,6,6-tetramethyl-4-piperidyl)imino]], polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, 2 ,2,4,4-tetramethyl-20-(β-lauryloxycarbonyl)ethyl-7-oxa-3,20-diazadispiro[5,1,11,2]heneicosane-21-one, β-alanine, N,-(2,2,6,6-tetramethyl-4-piperidinyl)-dodecyl ester / tetradecyl ester, N-acetyl-3-dodecyl-1-(2,2,6,6-tetramethyl-4-piperidinyl)pyrrolidine-2,5-dione, 2,2,4,4-tetramethyl-7-oxa-3,20-diazadispiro[5,1,11,2]heneicosane -21-one, 2,2,4,4-tetramethyl-21-oxa-3,20-diazadicyclo-[5,1,11,2]-heneycosane-20-propanoate dodecyl ester / tetradecyl ester, propanedioc acid, [(4-methoxyphenyl)-methylene]-bis(1,2,2,6,6-pentamethyl-4-piperidinyl) ester, higher fatty acid ester of 2,2,6,6-tetramethyl-4-piperidinol, 1,3-benzenedicarboxyamide, N,N'-bis(2,2,6,6-tetramethyl-4-piperi Hindered amine compounds such as dinyl, benzophenone compounds such as octabenzone, 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol, 2-(2-hydroxy-5-methylphenyl)benzotriazole, 2-[2-hydroxy-3-(3,4,5,6-tetrahydrophthalimidomethyl)-5-methylphenyl]benzotriazole, 2-(3-tert-butyl-2-hydroxy-5-methylphenyl)-5-chlorobenzotriazole, 2-(2-hydroxy-3,Examples include benzotriazole compounds such as 5-di-tert-pentylphenyl)benzotriazole, reaction products of methyl 3-(3-(2H-benzotriazole-2-yl)-5-tert-butyl-4-hydroxyphenyl)propionate and polyethylene glycol, 2-(2H-benzotriazole-2-yl)-6-dodecyl-4-methylphenol, benzoate compounds such as 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate, and triazine compounds such as 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[(hexyl)oxy]phenol. However, 1,2,2,6,6-pentamethyl-4-piperidyl (meth)acrylate (trade name: LA-82, manufactured by Adeka Corporation), which contains polymerizable groups, is preferred due to its low migration risk.

[0054] (Silane coupling agent) The electron beam-curable inkjet ink of the present invention may contain a silane coupling agent to improve substrate adhesion. Specific examples of silane coupling agents include, for example, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-(2-aminoethyl)3-aminopropylmethyldimethoxysilane, γ-mercapproppropyltrimethoxysilane, N-(2-aminoethyl)3-aminopropylmethyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, vinyltrimethoxysilane, and N-(2-(vinylbenzylamino)ethyl)3-aminopropyltrimethoxysilane hydrochloride. Silane coupling agents such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, and 3-chloropropyltrimethoxysilane; titanium coupling agents such as isopropyl(N-ethylaminoethylamino) titanate, isopropyltriisostearoyl titanate, titanium di(dioctyl pyrophosphate) oxyacetate, tetraisopropyl di(dioctyl phosphite) titanate, and neoalkoxytri(pN-(β-aminoethyl)aminophenyl) titanate;Examples include zirconium or aluminum-based coupling agents such as Zr-acetylacetonate, Zr-methacrylate, Zr-propionate, neoalkoxyzirconate, neoalkoxytrisneodecanoylzirconate, neoalkoxytris(dodecanoyl)benzenesulfonylzirconate, neoalkoxytris(ethylenediaminoethyl)zirconate, neoalkoxytris(m-aminophenyl)zirconate, ammonium zirconium carbonate, Al-acetylacetonate, Al-methacrylate, and Al-propionate. However, vinyltrimethoxysilane (product name: KBM-1003, manufactured by Shin-Etsu Chemical Co., Ltd.), 3-methacryloxypropylmethyldimethoxysilane (product name: KBM-502, manufactured by Shin-Etsu Chemical Co., Ltd.), 3-methacryloxypropyltrimethoxysilane (product name: KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.), 3-methacryloxypropyltriethoxysilane (product name: KBE-503, manufactured by Shin-Etsu Chemical Co., Ltd.), and 3-acryloxypropyltrimethoxysilane (product name: KBM-5103, manufactured by Shin-Etsu Chemical Co., Ltd.), which contain polymerizable groups, are preferred due to their low migration risk.

[0055] (Metal adhesion enhancer) The electron beam curable inkjet ink of the present invention may contain a metal adhesion promoter to improve adhesion to metal substrates such as aluminum. Specific examples of metal adhesion promoters include, for example, ethylene oxide-modified phenoxyphosphate (meth)acrylate, ethylene oxide-modified butoxyphosphate (meth)acrylate, ethylene oxide-modified octyloxyphosphate (meth)acrylate, ethylene oxide-modified phosphate di(meth)acrylate, ethylene oxide-modified phosphate tri(meth)acrylate, and caprolactone-modified ethylene oxide-modified phosphate di(meth)acrylate. However, ethylene oxide-modified phosphate dimethacrylate (trade name: KAYAMER PM-2, manufactured by Nippon Kayaku Co., Ltd.) and caprolactone-modified ethylene oxide-modified phosphate dimethacrylate (trade name: KAYAMER PM-21, manufactured by Nippon Kayaku Co., Ltd.) are preferred because they are readily available and have a low migration risk.

[0056] (Organic solvents) The electron beam-curable inkjet ink of the present invention may contain an organic solvent to adjust the storage stability, ejection stability, ink splatter properties, etc. Examples of organic solvents include alcohols, ketones, ethers, esters, nitrogen-containing compounds, amides, and the like.

[0057] [Method for preparing electron beam-curable inkjet ink] The electron beam curable inkjet ink of the present invention can be prepared using conventionally known preparation methods. A preferred preparation method for the electron beam curable inkjet ink of the present invention when it contains a pigment as a coloring agent is described below. A primary dispersion is prepared by pre-mixing component (C), a portion of component (B), and any optional component (more specifically, a pigment dispersant, etc.) using a disperser, and then dissolving or dispersing each component. Examples of dispersers include dispersers, container-driven media mills (more specifically, ball mills, centrifugal mills, and planetary ball mills, etc.), high-speed rotary mills (more specifically, sand mills, etc.), and media stirring mills (more specifically, stirring tank type mills, etc.).

[0058] Next, component (A), the remaining component (B), and the additives as needed are added to the obtained primary dispersion and mixed uniformly using a stirrer. Examples of stirrers include a dispenser, a three-way motor, a homogenizer, and a magnetic stirrer. In this way, electron beam curable inkjet ink can be obtained. Alternatively, the electron beam curable inkjet ink may be mixed using a mixer such as a line mixer. Furthermore, to further refine the particles in the electron beam curable inkjet ink, the electron beam curable inkjet ink may be mixed using a disperser such as a bead mill or a high-pressure jet mill.

[0059] [Physical properties] The electron beam-curable inkjet ink of the present invention preferably has a viscosity of 100 mPa·s or less at 50°C, and more preferably 30 mPa·s or less. In this invention, viscosity can be measured using an E-type viscometer (TV-22: manufactured by Toki Sangyo Co., Ltd.).

[0060] The electron beam curable inkjet ink of the present invention preferably has a solidification start temperature of 20°C or higher and less than 100°C. When the solidification start temperature of the ink is 20°C or higher, the ink solidifies quickly after landing on the substrate, suppressing ink bleeding. When the solidification start temperature of the ink is less than 100°C, the ink melted by heating can be ejected from the inkjet head, allowing for more stable ink ejection. The ink solidifies more quickly, and the ink can be ejected at a lower temperature. From the viewpoint of energy load, it is more preferable that the solidification start temperature of the ink is 30°C or higher and less than 80°C.

[0061] The ink solidification start temperature can be determined by measuring the change in the ink's heat content using a differential scanning calorimeter. In this invention, the ink solidification start temperature was defined as the temperature at which the exothermic peak rose when an ink sample was held at 90°C for 3 minutes and then cooled at 10°C / min.

[0062] [Image forming method] The manufacturing process for printed materials using the electron beam curable inkjet ink of the present invention will be described. In the method for manufacturing printed materials of the present invention, an image is formed on the surface of a substrate by the following steps (1) to (3). (Step 1) A step of heating electron beam curable inkjet ink to a temperature above the ink solidification start temperature. (Step 2) The process of ejecting ink droplets from the nozzle of the ejection head and landing them on the substrate surface. (Step 3) The process of curing the ink by irradiating it with an electron beam.

[0063] (Process 1) In this process, the ink tank, inkjet head, and the flow path connecting the ink tank and inkjet head are heated to a temperature above the ink solidification start temperature. If the ink does not reach a viscosity that allows it to be ejected by the inkjet head even after reaching the ink solidification start temperature, it is heated to a temperature that allows for ejection.

[0064] (Process 2) The electron beam curable inkjet ink of the present invention is preferably ejected by an inkjet method. As a means of ejecting ink by the inkjet method, it is preferable to use an inkjet head. Preferred inkjet heads include, for example, a charge control method that ejects ink using electrostatic attraction, a drop-on-demand method (pressure pulse method) that utilizes the vibration pressure of a piezoelectric element, an acoustic inkjet method that converts an electrical signal into an acoustic beam and irradiates the ink to eject ink using the radiation pressure, and a thermal inkjet (bubble jet®) method that heats the ink to form bubbles and utilizes the resulting pressure. The pressure pulse method using a piezoelectric element is particularly preferred. It is also possible to use a multi-pass method, a single-pass method (one-pass printing method), etc.

[0065] Specific examples of substrates include glass, quartz, aluminum, paper (e.g., plain paper without an ink-receiving layer, media used in gravure printing and offset printing, inkjet-specific paper with an ink-receiving layer, inkjet-specific film, glossy paper, etc.), and plastic films (e.g., polyolefin resin, polyamide resin, polyester resin, polycycloolefin resin, cellulose acetate, acrylic resin, chlorinated polyolefin resin, polyethersulfone resin, polyethylene, polystyrene, polycarbonate resin, polyethylene naphthalate, nylon, polyvinyl acetal, etc.). Among these, polyolefin resin, polyamide resin, and polyester resin are preferred for packaging, and polypropylene, polyethylene, polyethylene terephthalate, and nylon are even more preferred.

[0066] The surface of a substrate may be uneven, which can lead to a deterioration in image quality. Therefore, when using a substrate for printing, it is preferable to homogenize the substrate by applying a surface modification treatment. As for the surface modification treatment, known surface modification treatments selected from corona discharge treatment, plasma treatment, and flame treatment are preferred. It is generally known that the effect of surface modification treatment decreases over time. For this reason, it is preferable to perform the surface modification treatment process and the inkjet recording process consecutively, and it is preferable to perform the surface modification treatment process immediately before the inkjet recording process. It is also preferable to modify the outermost surface of the substrate using a pretreatment agent or the like.

[0067] (Step 3) In the method for manufacturing printed materials of the present invention, the deposited ink is cured by irradiating it with an electron beam.

[0068] The electron beam acceleration voltage should be such that sufficient energy reaches the interior of the ink to cause a sufficient reaction of the polymerizable compound, without causing significant degradation of the substrate. For example, from the viewpoint of minimizing migration while suppressing substrate degradation, the electron beam acceleration voltage is preferably 10 to 150 kV, and more preferably 30 to 120 kV.

[0069] Because electron beams, when used in the atmosphere, can decompose oxygen and generate large amounts of ozone, electron beam irradiation devices are used under low oxygen concentrations. In this invention, the oxygen concentration is preferably 1000 ppm or less. Furthermore, an oxygen concentration of 50 to 500 ppm is even more preferable in terms of quality and productivity, as it allows for sufficient ink curing and maintains a sufficient printing speed.

[0070] The electron beam-curable inkjet ink of the present invention exhibits low migration and high abrasion resistance, making it suitable for printing on various types of packaging and other printing applications. [Examples]

[0071] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" and "%" in this text refer to weight.

[0072] [Synthesis Example 1] In a flask equipped with a thermometer, condenser, and stirrer, 427.12 g of toluene, 284.97 g of stearic acid (NAA-180, manufactured by NOF Corporation, neutralization value 196.9 mg KOH / g), 142.15 g of glycidyl methacrylate (GMA, manufactured by Mitsubishi Gas Chemical Company, Inc.), 1.3 g of dibutylhydroxytoluene, and 1.3 g of trimethylglycine (Aminocoat, manufactured by Asahi Kasei Chemicals Corporation) were charged and reacted at 120°C for 24 hours. Then, the toluene was removed by distillation under reduced pressure to obtain a solid reaction product (A-1). 1 The 1H-NMR chart is shown in Figure 1. 1 H-NMR(400MHz, CDCl3) δ(ppm)=6.15(s,1H),6.12(s,1H),5.62(s,1H),4.26-4.14(m,5H),2.35(t,2H),1.96(s,1H),1.61(br,2H),1.25(br,28H),0.88(t,3H)

[0073] [Preparation Example 1]: Preparation of Dispersion 10g of Solspers 32000 (manufactured by Lubrizol) and 70g of dipropylene glycol diacrylate (DPGDA) were placed in a dispersion vessel and stirred to prepare a homogeneous liquid. 20g of CIPigmnet Blue 15:4 (manufactured by Dainichi Seika Kogyo, CHROMOFINEBLUE 4851) was added, followed by 100g of 0.3mm glass beads, and the mixture was dispersed in a sand mill for 6 hours. After dispersion, dipropylene glycol diacrylate was added to achieve a pigment concentration of 12%, and the mixture was filtered through glass fiber filter paper GA-100 (manufactured by Toyo Roshi Co., Ltd.) to remove the glass beads used in dispersion and prepare a 12% pigment dispersion.

[0074] [Preparation Example 2]: Ink Preparation Using A-1 obtained in Synthesis Example 1, the pigment dispersion obtained in Preparation Example 1, BYK-UV3510 (manufactured by BYK Chemie, polyether-modified polydimethylsiloxane), and dipropylene glycol diacrylate (DPGDA), the components in the ink were mixed so that they matched those shown in Table 1. After filtering out impurities using a 3 μm membrane filter, inkjet inks for Example 1 and Comparative Example 1 were obtained.

[0075] [Table 1]

[0076] (viscosity measurement) The viscometer was an E-type viscometer (TV-22: manufactured by Toki Sangyo Co., Ltd.) and measured at 50°C.

[0077] (Measurement of solidification start temperature) Using a differential scanning calorimeter (DSC Q2000: TA Instruments), the solidification onset temperature was measured by holding an ink sample (2 mg) at 90°C for 3 minutes and then cooling it to -20°C at 10°C / min. The measurement chart for Example 1 is shown in Figure 2, and the measurement chart for Comparative Example 1 is shown in Figure 3. The solidification onset temperature of the ink in Example 1 was 31°C. No exothermic peak was observed in the ink of Comparative Example 1 during solidification. [Industrial applicability]

[0078] The electron beam-curable inkjet ink of the present invention exhibits low migration, excellent scratch resistance, and superior image quality, and is expected to be a useful electron beam-curable inkjet ink for food and pharmaceutical packaging.

Claims

1. An electron beam-curable inkjet ink containing: a polymerizable compound (A) having a long-chain alkyl group having from 6 to 30 carbon atoms in the molecule, a hydrogen-bonding group, and a polymerizable group; a polymerizable compound (B) other than component (A); and a colorant (C).

2. 2. The electron beam curable inkjet ink according to claim 1, wherein the component (A) is a reaction product of a carboxylic acid (a) having from 6 to 30 carbon atoms and an epoxy compound (b) having a polymerizable group.

3. 2. The electron beam curable inkjet ink according to claim 1, wherein the component (A) is a reaction product of an epoxy compound (c) having 6 to 30 carbon atoms and a carboxylic acid (d) having a polymerizable group.

4. 4. The electron beam curable inkjet ink according to claim 1, wherein the content of component (A) in the total amount of the electron beam curable inkjet ink is 0.5 to 90% by weight.

5. 5. The electron beam curable inkjet ink according to claim 1, wherein the solidification initiation temperature is 20°C or higher and lower than 100°C.

6. A printed matter using the electron beam curable inkjet ink according to any one of claims 1 to 5.

7. An image forming method comprising the following steps (Step 1) to (Step 3). (Step 1) A step of heating the electron beam curable inkjet ink according to any one of claims 1 to 5 to a temperature equal to or higher than the ink solidification initiation temperature. (Step 2) A step of ejecting droplets of the electron beam curable inkjet ink according to any one of claims 1 to 5 from the nozzles of an ejection head and causing them to land on the surface of a substrate. (Step 3) A step of further curing the ink by irradiating it with electron beams

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