Inkjet inks and prints

Abstract

To provide an inkjet ink and a printed matter which has a low viscosity, reduced skin irritation and excellent adhesion to a substrate, hardly shows a streaky feeling on the inkjet image obtained and has further reduced cost and to provide a printed matter.SOLUTION: There is provided an inkjet ink which contains (1) at least one component of a urethane diacrylate oligomer or an amine acrylate, (ii) a specific amount of a component represented by the formula (I), (iii) a component which is a linear aliphatic (meth)acrylate monomer, (iv) a specific amount of a component which is a (meth)acrylate monomer having an aliphatic heterocyclic ring containing an oxygen atom in the molecule and a photoradical polymerization initiator.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an inkjet ink and a printed matter, and more particularly to an inkjet ink and a printed matter that have low viscosity, reduced skin irritation, excellent adhesion to a substrate, are less likely to produce streaks in the resulting inkjet images, and are produced at lower cost. [Background technology]

[0002] Conventionally, techniques have been developed for producing prints by applying inkjet ink to a substrate using an inkjet method (for example, Patent Document 1). The inkjet ink described in Patent Document 1 has low viscosity, excellent storage stability, and can produce prints that are both formable and solvent-resistant. However, when prints are produced using the inkjet method, the resulting prints are prone to a phenomenon in which streaks appear in the inkjet image. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-162415 Summary of the Invention [Problem to be solved by the invention]

[0004] The inkjet ink described in Patent Document 1 has room for improvement in terms of adhesion to substrates and skin irritation. Furthermore, the inkjet ink described in Patent Document 1 contains a large amount of specific components such as methyl 2-(allyloxymethyl)acrylate, which makes it expensive.

[0005] The present invention has been made to solve these problems, and aims to provide an inkjet ink and a printed matter that have low viscosity, reduced skin irritation, excellent adhesion to substrates, are less likely to produce streaks in the resulting inkjet images, and are produced at lower costs. [Means for solving the problem]

[0006] The inkjet ink and printed matter of the present invention that solve the above problems mainly include the following components.

[0007] (1) An ink-jet ink comprising the following components (i), (ii), (iii), and (iv), and a photoradical polymerization initiator, wherein the content of component (ii) in the ink-jet ink is 5 to 20% by mass, and the content of component (iv) in the ink-jet ink is 20 to 60% by mass. <Component (i)> At least one of a urethane diacrylate oligomer and an amine acrylate. <Component (ii)> A compound represented by the following formula (I): [ka] (In formula (I), R 1 represents a hydrogen atom or a monovalent organic group. The organic group is composed of a hydrocarbon and may have an ether group. The hydrogen atom of the hydrocarbon may be substituted with a halogen atom. <Ingredient (iii)> Linear aliphatic (meth)acrylate monomer. <Component (iv)> A (meth)acrylate monomer that has an aliphatic heterocycle containing an oxygen atom in the molecule.

[0008] According to this configuration, the inkjet ink has low viscosity, reduced skin irritation, and excellent adhesion to substrates. Furthermore, since the inkjet ink contains a small amount of the expensive component (ii), costs can be further reduced. Furthermore, inkjet images obtained by applying the inkjet ink are less likely to have streaks.

[0009] (2) In the inkjet ink according to (1), when the component (i) contains the urethane diacrylate oligomer, the urethane diacrylate oligomer contains at least one of a polyester-based urethane diacrylate oligomer and a polycarbonate-based urethane diacrylate oligomer.

[0010] According to this configuration, the viscosity of the resulting inkjet ink is more likely to be reduced and the storage stability is excellent.

[0011] (3) The ink-jet ink according to (2), wherein the polyester-based urethane diacrylate oligomer or polycarbonate-based urethane diacrylate oligomer of the component (i) has a number average molecular weight (Mn) of 1,000 to 10,000.

[0012] According to this configuration, the viscosity of the resulting inkjet ink is more likely to be reduced, and printed matter obtained using the inkjet ink has better formability.

[0013] (4) The ink-jet ink according to any one of (1) to (3), wherein the compound represented by formula (I) is methyl 2-(allyloxymethyl)acrylate.

[0014] According to this configuration, the viscosity of the inkjet ink can be more easily reduced, and printed matter obtained using the inkjet ink can have both excellent substrate adhesion and formability.

[0015] (5) The ink-jet ink according to any one of (1) to (4), wherein the heterocyclic skeleton of the component (iv) includes at least one of a morpholine skeleton, a tetrahydrofuran skeleton, a dioxane skeleton, and a dioxolane ring.

[0016] According to this configuration, a printed matter obtained using the inkjet ink has excellent adhesion to a substrate.

[0017] (6) The inkjet ink according to any one of (1) to (5), further comprising a surface conditioner.

[0018] According to this configuration, the printed image obtained using the inkjet ink is less likely to have streaks.

[0019] (7) The ink-jet ink according to any one of (1) to (6), which has a viscosity at 30° C. of 5 to 50 mPa·s.

[0020] According to this configuration, the ink-jet ink has a sufficiently low viscosity, is easy to handle, and has excellent ejection stability during ink-jet printing.

[0021] (8) The ink-jet ink according to any one of (1) to (7), which has a surface tension of 35 dyne / cm or less.

[0022] According to this configuration, the ink-jet ink has excellent ejection stability during ink-jet printing, and the ink-jet ink is also likely to form clear ink-jet images.

[0023] (9) An inkjet printed matter having an inkjet image printed using the inkjet ink according to any one of (1) to (8).

[0024] According to this configuration, the resulting print has excellent adhesion of the inkjet image (inkjet layer) to the substrate, and the inkjet image is less likely to have streaks. [Effects of the Invention]

[0025] According to the present invention, it is possible to provide an inkjet ink and a printed matter which have low viscosity, reduced skin irritation, excellent adhesion to a substrate, are less likely to produce streaks in the resulting inkjet images, and are produced at a lower cost. DETAILED DESCRIPTION OF THE INVENTION

[0026] <Inkjet ink> An inkjet ink according to one embodiment of the present invention comprises the following components (i), (ii), (iii), (iv), and a photoradical polymerization initiator. The content of component (ii) in the inkjet ink is 5 to 20% by mass. The content of component (iv) in the inkjet ink is 20 to 60% by mass. Each of these components will be described below. <Component (i)> At least one of a urethane diacrylate oligomer and an amine acrylate. <Component (ii)> A compound represented by the following formula (I): [ka] (In formula (I), R 1 represents a hydrogen atom or a monovalent organic group. The organic group is composed of a hydrocarbon and may have an ether group. The hydrogen atom of the hydrocarbon may be substituted with a halogen atom. <Ingredient (iii)> Linear aliphatic (meth)acrylate monomer. <Component (iv)> A (meth)acrylate monomer that has an aliphatic heterocycle containing an oxygen atom in the molecule.

[0027] (Component (i)) Component (i) includes at least one of a urethane diacrylate oligomer and an amine acrylate. By including component (i), the inkjet ink can impart appropriate flexibility to the resulting inkjet image. This allows the inkjet image to easily adapt to deformations when the printed matter is molded, making it less susceptible to cracking. Furthermore, the inkjet ink has excellent UV curability.

[0028] Urethane diacrylate oligomer The urethane diacrylate oligomer is not particularly limited. Examples of the urethane diacrylate oligomer include polyester-based urethane diacrylate oligomers, polycarbonate-based urethane diacrylate oligomers, and polyether-based urethane diacrylate oligomers. Among these, it is preferable that the urethane diacrylate oligomer contains at least one of polyester-based urethane diacrylate oligomers and polycarbonate-based urethane diacrylate oligomers, since the resulting inkjet ink has a lower viscosity and excellent storage stability.

[0029] The polyester-based urethane diacrylate oligomer is an oligomer produced, for example, by reacting a polyester diol with a (meth)acrylate monomer having a functional group capable of reacting with the polyester diol.

[0030] The polyester diol is not particularly limited. Examples of the polyester diol include polyethylene adipate diol, polybutylene adipate diol, polyethylene butylene adipate diol, polyhexamethylene isophthalate adipate diol, polyethylene succinate diol, polybutylene succinate diol, polyethylene sebacate diol, polybutylene sebacate diol, poly-ε-caprolactone diol, poly(3-methyl-1,5-pentylene adipate) diol, and a polycondensate of 1,6-hexanediol and dimer acid.

[0031] The number average molecular weight (Mn) of the polyester diol is preferably 500 or more, more preferably 900 or more, and even more preferably 1200 or more. Furthermore, Mn is preferably 9000 or less, and more preferably 8000 or less. By having Mn within the above range, printed matter obtained using the inkjet ink can have both excellent formability and solvent resistance. In this embodiment, Mn (and the weight average molecular weight (Mw) described below) can be calculated as a polystyrene-equivalent value measured by gel permeation chromatography (GPC), for example.

[0032] The viscosity of the polyester diol is not particularly limited. For example, the viscosity of the polyester diol (at 25° C.) is preferably 100,000 mPa·s or less, and more preferably 50,000 mPa·s or less.

[0033] The (meth)acrylate monomer having a functional group capable of reacting with a polyester diol is not particularly limited. For example, the functional group is a blocked isocyanate functional group or an isocyanate functional group. Among these, the (meth)acrylate monomer preferably contains a blocked isocyanate functional group as a functional group capable of reacting with a polyester diol, since this further improves the storage stability of the resulting inkjet ink.

[0034] The blocked isocyanate functional group is a functional group in which an isocyanate group (-NCO) is protected by a thermally detachable protecting group, and is formed by reacting an isocyanate group with a blocking agent.

[0035] The blocking agent is not particularly limited. Examples of the blocking agent include alcohols such as methanol, ethanol, isopropanol, n-butanol, 1-methoxy-2-propanol, 2-ethoxyhexanol, 2-N,N-dimethylaminoethanol, 2-ethoxyethanol, and cyclohexanol; phenols such as phenol, o-nitrophenol, p-chlorophenol, o-cresol, m-cresol, and p-cresol; lactams such as ε-caprolactam and γ-caprolactam; acetone oxime; and methyl ethyl ketone oxime. Examples of suitable blocking agents include oximes such as methyl ethyl ketone oxime, methyl isobutyl ketone oxime, cyclohexanone oxime, acetophenone oxime, and benzophenone oxime; pyrazoles such as pyrazole, 3,5-dimethylpyrazole, and 3-methylpyrazole; thiols such as dodecanethiol and benzenethiol; and active methylene compounds such as malonic acid diesters, acetoacetic acid esters, malonic acid dinitrile, acetylacetone, methylene disulfone, dibenzoylmethane, dipivaloylmethane, and acetone dicarboxylic acid diesters. Blocking agents may also be used in combination. Among these, it is preferable that the blocking agent contains diethyl malonate, dimethylpyrazole, or methyl ethyl ketone oxime, as this easily achieves both reactivity upon heat treatment of the resulting printed matter and storage stability of the ink.

[0036] The (meth)acrylate monomer having the functional group is not particularly limited, and examples thereof include isocyanate-containing (meth)acrylates such as 2-isocyanate ethyl methacrylate and 2-isocyanate ethyl acrylate.

[0037] The number average molecular weight (Mn) of the polyester-based urethane diacrylate oligomer is preferably 1000 or more, and more preferably 1200 or more. Furthermore, Mn is preferably 10000 or less, and more preferably 8000 or less. When Mn is within the above range, printed matter obtained using the inkjet ink can have better formability.

[0038] The polycarbonate-based urethane diacrylate oligomer can be produced, for example, by reacting a polycarbonate diol with a (meth)acrylate monomer having a functional group capable of reacting with the polycarbonate diol.

[0039] The polycarbonate diol is not particularly limited. For example, the polycarbonate diol is a polycarbonate diol made from a diol such as 1,4-butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,9-nonanediol, or 2-methyl-1,8-octanediol.

[0040] The number average molecular weight (Mn) of the polycarbonate diol is preferably 500 or more, more preferably 900 or more, and even more preferably 1200 or more. Furthermore, Mn is preferably 9000 or less, and more preferably 8000 or less. When Mn is within the above range, printed matter obtained using the inkjet ink can have better moldability.

[0041] The viscosity of the polycarbonate diol is not particularly limited. For example, the viscosity of the polyester diol (at 25° C.) is preferably 100,000 mPa·s or less, and more preferably 50,000 mPa·s or less.

[0042] The (meth)acrylate monomer having a functional group capable of reacting with polycarbonate diol is not particularly limited. For example, the (meth)acrylate monomer having a functional group capable of reacting with polycarbonate diol may be the same as that described above in relation to the polyester-based urethane diacrylate oligomer.

[0043] The number average molecular weight (Mn) of the polycarbonate-based urethane diacrylate oligomer is preferably 1,000 or more, and more preferably 1,500 or more. Furthermore, Mn is preferably 10,000 or less, and more preferably 9,000 or less. When Mn is within the above range, printed matter obtained using the inkjet ink can have both excellent formability and solvent resistance.

[0044] Amine acrylate Amine acrylate is a compound having at least one amino group and at least one (meth)acryloyl group. The amine acrylate has at least one amino group per molecule, preferably 1 to 6 amino groups, more preferably 1 to 3 amino groups, and even more preferably 1 or 2 amino groups. When the number of amino groups per molecule of the amine acrylate is within the above range, the viscosity of the resulting inkjet ink is likely to be lowered.

[0045] The amine acrylate has at least one (meth)acryloyl group per molecule, preferably 1 to 6 (meth)acryloyl groups, more preferably 1 to 4 (meth)acryloyl groups, and even more preferably 1 or 2 (meth)acryloyl groups. When the number of (meth)acryloyl groups per molecule of the amine acrylate is within the above range, the inkjet ink has excellent reactivity.

[0046] The viscosity of the amine acrylate at 25°C is preferably 1 mPa·s or more, more preferably 3 mPa·s or more, and even more preferably 5 mPa·s or more. The viscosity of the amine acrylate at 25°C is preferably 2000 mPa·s or less, more preferably 1500 mPa·s or less, and even more preferably 1000 mPa·s or less. When the viscosity of the amine acrylate at 25°C is within the above range, the ink composition has excellent ejection stability.

[0047] Examples of amine acrylates include the following products: RAHN: GENOMER5161, GENOMER5275 Sartomer: CN371, CN373, CN383, CN384, CN386, CN501, CN550, CN551 Daicel Cytec: EBECRYL7100, EBECRYL80, EBECRYL81, EBECRYL83, EBECRYL84, EBECRYLP115 BASF: Laromer PO77F (LR8946), Laromer LR8956, Laromer LR8996, Laromer PO94F (LR8894) Cognis: Photomer4771, Photomer4775, Photomer4967, Photomer5096, Photomer5662, Photomer5930 DoubleBondChemicals: DoublecureEPD, DoublecureOPD, Doublecure115, Doublecure225, Doublecure645, PolyQ222, PolyQ226, PolyQ224, PolyQ101

[0048] Returning to the explanation of component (i) as a whole, the content of component (i) is not particularly limited. For example, the content of component (i) in the ink composition is preferably 1% by mass or more, and more preferably 3% by mass or more. Furthermore, the content of component (i) in the ink composition is preferably 25% by mass or less, and more preferably 20% by mass or less. When the content of component (i) is within the above range, the inkjet ink has better adhesion to the substrate.

[0049] (Component (ii)) Component (ii) is a compound represented by the following formula (I). Component (ii) is blended to lower the viscosity of the inkjet ink and to improve both the formability and solvent resistance of the resulting print. Furthermore, when the inkjet ink is applied to a substrate, component (ii) penetrates into the substrate. This tends to improve the adhesion of the resulting inkjet image (inkjet layer) to the substrate.

[0050] [ka]

[0051] In formula (I), R 1 represents a hydrogen atom or a monovalent organic group. The organic group is composed of a hydrocarbon and may have an ether group. The hydrogen atom of the hydrocarbon may be substituted with a halogen atom.

[0052] The organic group may be linear, branched, or may contain a cyclic structure. The hydrocarbon group is not particularly limited. Examples of the hydrocarbon group include a chain saturated hydrocarbon group having 1 or more carbon atoms, a chain unsaturated hydrocarbon group having 3 or more carbon atoms, an alicyclic hydrocarbon group having 3 or more carbon atoms, and an aromatic hydrocarbon group having 6 or more carbon atoms. Among these, the hydrocarbon group is preferably a chain saturated hydrocarbon group having 1 to 30 carbon atoms, a chain unsaturated hydrocarbon group having 3 to 30 carbon atoms, an alicyclic hydrocarbon group having 4 to 30 carbon atoms, or an aromatic hydrocarbon group having 6 to 30 carbon atoms. The substituent is not particularly limited. Examples of the substituent include a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom, a cyano group, or a trimethylsilyl group.

[0053] The chain saturated hydrocarbon group is not particularly limited. Examples of the chain saturated hydrocarbon group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-amyl group, a sec-amyl group, a tert-amyl group, a neopentyl group, an n-hexyl group, a sec-hexyl group, an n-heptyl group, an n-octyl group, a sec-octyl group, a tert-octyl group, a 2-ethylhexyl group, a capryl group, a nonyl group, a decyl group, an undecyl group, a lauryl group, a tridecyl group, a myristyl group, a pentadecyl group, a cetyl group, a heptadecyl group, a stearyl group, a nonadecyl group, an eicosyl group, a seryl group, and a melissyl group.

[0054] The chain unsaturated hydrocarbon group is not particularly limited, and examples thereof include a crotyl group, a 1,1-dimethyl-2-propenyl group, a 2-methyl-butenyl group, a 3-methyl-2-butenyl group, a 3-methyl-3-butenyl group, a 2-methyl-3-butenyl group, an oleyl group, a linole group, and a linolene group.

[0055] The alicyclic hydrocarbon group is not particularly limited, and examples thereof include a cyclopentyl group, a cyclopentylmethyl group, a cyclohexyl group, a cyclohexylmethyl group, a 4-methylcyclohexyl group, a 4-tert-butylcyclohexyl group, a tricyclodecanyl group, an isobornyl group, an adamantyl group, a dicyclopentanyl group, and a dicyclopentenyl group.

[0056] The aromatic hydrocarbon group is not particularly limited, and examples thereof include a phenyl group, a methylphenyl group, a dimethylphenyl group, a trimethylphenyl group, a 4-tert-butylphenyl group, a benzyl group, a diphenylmethyl group, a diphenylethyl group, a triphenylmethyl group, a cinnamyl group, a naphthyl group, and an anthranyl group.

[0057] The hydrocarbon group having an ether bond is not particularly limited. Examples of the hydrocarbon group having an ether bond include chain ether groups such as a methoxyethyl group, a methoxyethoxyethyl group, a methoxyethoxyethoxyethyl group, a 3-methoxybutyl group, an ethoxyethyl group, and an ethoxyethoxyethyl group; groups having both an alicyclic hydrocarbon group and a chain ether group such as a cyclopentoxyethyl group, a cyclohexyloxyethyl group, a cyclopentoxyethoxyethyl group, a cyclohexyloxyethoxyethyl group, and a dicyclopentenyloxyethyl group; groups having both an aromatic hydrocarbon group and a chain ether group, such as an oxyethyl group or a phenoxyethoxyethyl group; and cyclic ether groups, such as a glycidyl group, a β-methylglycidyl group, a β-ethylglycidyl group, a 3,4-epoxycyclohexylmethyl group, a 2-oxetanemethyl group, a 3-methyl-3-oxetanemethyl group, a 3-ethyl-3-oxetanemethyl group, a tetrahydrofuranyl group, a tetrahydrofurfuryl group, a tetrahydropyranyl group, a dioxazolanyl group, and a dioxanyl group.

[0058] In this embodiment, R in formula (I) 1 is preferably a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms, and more preferably a methyl group. 1 When the compound is a compound in which R is a methyl group (e.g., methyl 2-(allyloxymethyl)acrylate), the viscosity of the inkjet ink is likely to be lowered. In addition, the resulting printed matter can have both excellent substrate adhesion and formability.

[0059] The content of component (ii) in the inkjet ink may be 5% by mass or more, and preferably 7% by mass or more. The content of component (ii) in the inkjet ink may be 20% by mass or less, and preferably 15% by mass or less. If the content of component (ii) is less than 5% by mass, it is difficult to achieve a low viscosity of the inkjet ink. Furthermore, it is difficult for the inkjet ink to have both moldability and solvent resistance. On the other hand, if the content of component (ii) exceeds 20% by mass, the inkjet ink is likely to be expensive. Furthermore, the inkjet ink is likely to have poor adhesion to the substrate. Furthermore, the inkjet ink is likely to cause skin irritation.

[0060] (ingredient (iii)) Component (iii) contains a linear aliphatic (meth)acrylate monomer. Component (iii) is blended to enable the inkjet ink to exhibit excellent solvent resistance to a wider variety of solvents. Component (iii) also imparts flexibility to the resulting inkjet image (inkjet layer). This allows the inkjet image to easily adapt to deformations when the printed matter is molded, making it less susceptible to cracking and other problems.

[0061] The linear aliphatic (meth)acrylate monomer is not particularly limited. Examples of linear aliphatic (meth)acrylate monomers include isooctyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, and cetyl (meth)acrylate. Among these, the linear aliphatic (meth)acrylate monomer is preferably isooctyl (meth)acrylate or tridecyl (meth)acrylate because of its relatively low viscosity. The linear aliphatic (meth)acrylate monomer may be used in combination.

[0062] The content of component (iii) is not particularly limited. For example, the content of component (iii) in the inkjet ink is preferably 5% by mass or more, and more preferably 8% by mass or more. Furthermore, the content of component (iii) in the inkjet ink is preferably 25% by mass or less, and more preferably 20% by mass or less. By keeping the content of component (iii) within the above range, the inkjet ink can exhibit excellent solvent resistance to a wider variety of solvents.

[0063] (Component (iv)) Component (iv) is a (meth)acrylate monomer having an aliphatic heterocycle containing an oxygen atom in the molecule. Component (iv) can improve the adhesion between the substrate and the inkjet image (inkjet layer) obtained by applying the inkjet ink. Furthermore, by incorporating component (iv), the amount of component (ii) can be reduced relatively while maintaining excellent adhesion. This allows the inkjet ink to have reduced skin irritation and be produced at low cost.

[0064] Component (iv) is not particularly limited. For example, component (iv) is preferably a (meth)acrylate monomer containing at least one heterocyclic skeleton selected from the group consisting of a morpholine skeleton, a tetrahydrofuran skeleton, a dioxane skeleton, and a dioxolane ring. This allows the inkjet ink to easily achieve adhesion to a substrate.

[0065] The (meth)acrylate monomer having a morpholine skeleton in the molecule is acryloylmorpholine or the like.

[0066] (Meth)acrylate monomers having a tetrahydrofuran skeleton in the molecule include tetrahydrofurfuryl (meth)acrylate and alkoxylated tetrahydrofurfuryl acrylate.

[0067] An example of a (meth)acrylate monomer having a dioxolane skeleton in the molecule is (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate.

[0068] Examples of the (meth)acrylate monomer having a dioxane skeleton in the molecule include cyclic trimethylolpropane formal acrylate, dioxane glycol diacrylate, and dioxane glycol diacrylate.

[0069] The content of component (iv) in the inkjet ink may be 20% by mass or more, and preferably 30% by mass or more. The content of component (iv) in the inkjet ink may be 60% by mass or less, and preferably 55% by mass or less. If the content of component (iv) is less than 20% by mass, the inkjet ink is likely to have poor adhesion to the substrate. Furthermore, the inkjet ink is likely to cause skin irritation. On the other hand, if the content of component (iv) exceeds 60% by mass, the inkjet ink will not easily achieve the desired performance due to the reduced proportions of other components added.

[0070] (Photoradical polymerization initiator) The photoradical polymerization initiator is added to the inkjet ink in order to appropriately cure the inkjet ink by ultraviolet light.

[0071] The photoradical polymerization initiator is not particularly limited. Examples of the photoradical polymerization initiator include alkylphenone compounds, benzophenone compounds, benzoin compounds, thioxanthone compounds, halomethylated triazine compounds, halomethylated oxadiazole compounds, biimidazole compounds, oxime ester compounds, titanocene compounds, benzoic acid ester compounds, and acridine compounds. The photoradical polymerization initiators may be used in combination.

[0072] The alkylphenone compound is not particularly limited. For example, the alkylphenone compound may be 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, etc.

[0073] The benzophenone-based compound is not particularly limited, and examples thereof include benzophenone, 4,4'-bis(dimethylamino)benzophenone, and 2-carboxybenzophenone.

[0074] The benzoin-based compound is not particularly limited, and examples thereof include benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether.

[0075] The thioxanthone compound is not particularly limited, and examples thereof include thioxanthone, 2-ethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, and 2,4-diethylthioxanthone.

[0076] The halomethylated triazine compound is not particularly limited. Examples of the halomethylated triazine compound include 2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-sec-triazine, 2-(4-methoxynaphthyl)-4,6-bis(trichloromethyl)-sec-triazine, 2-(4-ethoxynaphthyl)-4,6-bis(trichloromethyl)-sec-triazine, and 2-(4-ethoxycarboxynylnaphthyl)-4,6-bis(trichloromethyl)-sec-triazine.

[0077] The halomethylated oxadiazole compound is not particularly limited. Examples of the halomethylated oxadiazole compound include 2-trichloromethyl-5-[β-(2'-benzofuryl)vinyl]-1,3,4-oxadiazole, 2-trichloromethyl-5-[β-(2'-(6"-benzofuryl)vinyl)]-1,3,4-oxadiazole, and 2-trichloromethyl-5-furyl-1,3,4-oxadiazole.

[0078] The biimidazole compound is not particularly limited, and examples thereof include 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, 2,2'-bis(2,4-dichlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole, and 2,2'-bis(2,4,6-trichlorophenyl)-4,4',5,5'-tetraphenyl-1,2'-biimidazole.

[0079] The oxime ester compound is not particularly limited, and examples thereof include 1-[4-(phenylthio)-, 2-(O-benzoyloxime)]-1,2-octanedione and 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime)ethanone.

[0080] The titanocene compound is not particularly limited. An example of the titanocene compound is bis(η5-2,4-cyclopentadien-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium.

[0081] The benzoate ester compound is not particularly limited, and examples thereof include p-dimethylaminobenzoic acid and p-diethylaminobenzoic acid.

[0082] The acridine compound is not particularly limited, and an example of the acridine compound is 9-phenylacridine.

[0083] The content of the photoradical polymerization initiator is not particularly limited. For example, the content of the photoradical polymer in the inkjet ink is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more. Furthermore, the content of the photoradical polymer in the inkjet ink is preferably 15% by mass or less, and more preferably 12% by mass or less. By having the content of the photoradical polymer within the above range, the inkjet ink can be appropriately cured by ultraviolet light.

[0084] (optional ingredient) The inkjet ink of this embodiment may contain optional components well known in the field of inkjet inks, in addition to the above-mentioned components (i) to (iv) and the photoradical polymerization initiator. Examples of optional components include other monomers than those mentioned above, surface conditioners, binder resins, solvents, curing catalysts, slip agents (leveling agents), dispersants, polymerization accelerators, polymerization inhibitors, penetration accelerators, wetting agents (moisturizing agents), fixing agents, antifungal agents, preservatives, antioxidants, chelating agents, thickeners, etc.

[0085] Other monomers The inkjet ink may contain other monomers that can be polymerized by irradiation with ultraviolet light to form a cured film. Examples of such other monomers include various monofunctional monomers and polyfunctional monomers.

[0086] The monofunctional monomer is not particularly limited. Examples of the monofunctional monomer include acrylamide derivatives such as dimethylacrylamide, diethylacrylamide, and diisopropylacrylamide, isoalkyl (meth)acrylates such as isobornyl acrylate, dicyclopentenyl acrylate, dicyclopentanyl acrylate, dicyclopentanyloxyethyl acrylate, benzyl (meth)acrylate, and isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-ethylhexyl carbitol (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate. acrylate, 2-acryloyloxyethyl succinate, isopropyl (meth)acrylate, amyl (meth)acrylate, t-butyl (meth)acrylate, isoamyl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, butoxyethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, cyclohexyl (meth)acrylate, ethoxyethyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, dicyclopentadienyl (meth)acrylate, tricyclodecanyl (meth)acrylate, bornyl (meth)acrylate, diacetone acrylamide, isobutoxymethyl (meth)acrylamide, N-vinylpyrrolidone, N-vinylcaprolactam, t-octyl (meth)acrylamide, and the like.

[0087] The polyfunctional monomer is not particularly limited. Examples of the polyfunctional monomer include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, polyethylene glycol di(meth)acrylates such as ethylene glycol di(meth)acrylate and tetraethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane trioxyethyl (meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, and epoxy (meth)acrylates in which (meth)acrylates are added to diglycidyl ethers of bisphenol A.

[0088] When other monomers are contained, the content of the other monomers is not particularly limited. For example, the content of the other monomers in the inkjet ink is preferably 1% by mass or more, more preferably 5% by mass or more. Furthermore, the content of the other monomers in the inkjet ink is preferably 50% by mass or less, more preferably 40% by mass or less. When the content of the other monomers is less than 1% by mass, the effects of including the other monomers tend to be less pronounced. On the other hand, when the content of the other monomers exceeds 50% by mass, the contents of components (i), (ii), (iii), and (iv) become so small that the effects of this embodiment tend to be less pronounced.

[0089] Surface conditioner The inkjet ink of this embodiment preferably further contains a surface conditioner. The surface conditioner is not particularly limited. Examples of the surface conditioner include an acrylic surface conditioner, a silicone surface conditioner, and a fluorine-based surface conditioner. By including a surface conditioner, the inkjet ink can further reduce skin irritation. Furthermore, the inkjet ink has better ejection stability during inkjet printing. Furthermore, the inkjet ink is likely to form clear inkjet images.

[0090] Binder resin The binder resin can be contained, for example, to adjust the viscosity of the inkjet ink, or to adjust the hardness and shape of the resulting print.

[0091] The type of binder resin is not particularly limited. Examples of the binder resin include epoxy resin, diallyl phthalate resin, silicone resin, phenol resin, unsaturated polyester resin, polyimide resin, polyurethane resin, melamine resin, urea resin, ionomer resin, ethylene ethyl acrylate resin, acrylonitrile acrylate styrene copolymer resin, acrylonitrile styrene resin, acrylonitrile chlorinated polyethylene styrene copolymer resin, ethylene vinyl acetate resin, ethylene vinyl alcohol copolymer resin, acrylonitrile butadiene styrene copolymer resin, vinyl chloride resin, chlorinated polyethylene resin, polyvinylidene chloride resin, cellulose acetate resin, polyoxymethylene resin, polyamide resin, polyarylate resin, etc. Examples of binder resins include acrylate resins, thermoplastic polyurethane elastomers, polyether ether ketone resins, polyether sulfone resins, polyethylene, polypropylene, polycarbonate resins, polystyrene, polystyrene-maleic acid copolymer resins, polystyrene-acrylic acid copolymer resins, polyphenylene ether resins, polyphenylene sulfide resins, polybutadiene resins, polybutylene terephthalate resins, acrylic resins, methacrylic resins, methylpentene resins, polylactic acid, polybutylene succinate resins, butyral resins, formal resins, polyvinyl alcohol, polyvinylpyrrolidone, ethyl cellulose, carboxymethyl cellulose, gelatin, and copolymer resins thereof. The binder resin may be appropriately selected taking into consideration solvent resistance, film strength, viscosity, thermal stability, non-coloring properties, water resistance, chemical resistance, etc. Binder resins may also be used in combination.

[0092] When a binder resin is contained, the content of the binder resin is not particularly limited. For example, the binder resin is preferably contained in the inkjet ink in an amount of 5% by mass or more, more preferably 10% by mass or more, calculated as solid content. Furthermore, the binder resin is preferably contained in the inkjet ink in an amount of 20% by mass or less, more preferably 15% by mass or less. If the binder resin content is less than 5% by mass, it tends to be difficult to obtain the desired performance as a binder. On the other hand, if the binder resin content exceeds 20% by mass, the viscosity of the inkjet ink increases, and the ejection stability during inkjet printing tends to decrease.

[0093] ·solvent A solvent may be added to the inkjet ink of this embodiment to reduce the viscosity of the ink. The type of solvent is not particularly limited. Examples of the solvent include water, glycol ether-based solvents, acetate-based solvents, alcohol-based solvents, ketone-based solvents, ester-based solvents, hydrocarbon-based solvents, fatty acid ester-based solvents, and aromatic solvents. The solvents may be used in combination.

[0094] When a solvent is contained, the content of the solvent is not particularly limited. For example, the content of the solvent in the inkjet ink is preferably 5% by mass or more, and more preferably 10% by mass or more. Furthermore, the content of the solvent in the inkjet ink is preferably 50% by mass or less, and more preferably 30% by mass or less. If the content of the solvent is less than 5% by mass, the effect of reducing the viscosity of the inkjet ink may not be sufficiently achieved. On the other hand, if the content of the solvent exceeds 50% by mass, the proportion of the ultraviolet-curable resin that can be added to the inkjet ink decreases, which may require a thermal drying step during inkjet processing or may result in poor drying of the ink, making it difficult to achieve the desired performance.

[0095] ·Curing catalyst The curing catalyst is not particularly limited. Examples of the curing catalyst include organic acid salts, alcoholates, and chelate compounds of metals such as tin, titanium, zirconium, iron, antimony, bismuth, manganese, zinc, and aluminum; amines such as hexylamine and dodecylamine; amine salts such as hexylamine acetate and dodecylamine phosphate; quaternary ammonium salts such as benzyltrimethylammonium acetate; and alkali metal salts such as potassium acetate. More specifically, the curing catalyst includes organic bismuth compounds such as bismuth octoate and bismuth neodecanoate; organic tin compounds such as dibutyltin dilaurate, dibutyltin dioctoate, dimethyltin dineodecanoate, and stannous octoate; and organic titanium compounds such as tetrabutyl titanate, tetraisopropyl titanate, diisopropoxybis(acetylacetone)titanium, and diisopropoxybis(ethylacetoacetate)titanium. The curing catalysts may be used in combination.

[0096] Polymerization inhibitor A polymerization inhibitor may be suitably added to prevent the polymerization reaction of the inkjet ink before curing.

[0097] The polymerization inhibitor is not particularly limited. Examples of the polymerization inhibitor include methylhydroquinone, t-butylhydroquinone, 4-methoxynaphthol, 1,4-benzoquinone, methoquinone, dibutylhydroxytoluene, N-nitrosophenylhydroxylamine aluminum salt, 1,4-naphthoquinone, and 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (4-hydroxyTEMPO).

[0098] Returning to the description of the inkjet ink as a whole, there are no particular limitations on the viscosity of the inkjet ink. For example, the viscosity of the inkjet ink is preferably 5 mPa·s or more, and more preferably 6 mPa·s or more, at 30°C. Furthermore, the viscosity of the inkjet ink is preferably 50 mPa·s or less, and more preferably 40 mPa·s or less, at 30°C. When the viscosity is within the above range, the inkjet ink has a sufficiently low viscosity, is easy to handle, and exhibits excellent ejection stability during inkjet printing. In this embodiment, the viscosity can be measured using a Brookfield viscometer (TVB-20LT, manufactured by Toki Sangyo Co., Ltd.).

[0099] The method for adjusting the viscosity to within the above range is not particularly limited. For example, the viscosity can be adjusted by the amount and type of each component used. The viscosity may also be adjusted using a viscosity adjuster such as a thickener, if necessary.

[0100] The surface tension of the inkjet ink is not particularly limited. The surface tension of the inkjet ink is preferably 20 dyne / cm or more, more preferably 25 dyne / cm or more, at 25°C. The surface tension of the inkjet ink is preferably 35 dyne / cm or less, more preferably 30 dyne / cm or less, at 25°C. When the surface tension is within the above range, the inkjet ink has excellent ejection stability. The inkjet ink also has excellent ejection stability during inkjet printing. The inkjet ink also easily forms clear inkjet images. In this embodiment, the surface tension can be measured using a static surface tensiometer (plate method) (CBVP-A3, manufactured by Kyowa Interface Science Co., Ltd.).

[0101] The method for preparing the inkjet ink of this embodiment is not particularly limited. As an example, the inkjet ink can be prepared by mixing the materials to be used, dispersing the mixture using a dispersing machine such as a roll mill, a ball mill, a colloid mill, a jet mill, or a bead mill, and then filtering the mixture.

[0102] As described above, the inkjet ink of this embodiment has low viscosity, reduced skin irritation, and excellent adhesion to substrates. Furthermore, the inkjet ink contains a small amount of the expensive component (ii), which makes it easier to reduce costs. Furthermore, inkjet images obtained by applying the inkjet ink are less likely to have streaks.

[0103] <Manufacturing method for printed items> A method for producing a printed matter according to one embodiment of the present invention includes an inkjet step of applying the inkjet ink described above onto a substrate, and an ultraviolet irradiation step of irradiating the applied inkjet ink with ultraviolet light. According to this embodiment, an inkjet print is produced on which an inkjet image is formed by printing using the inkjet ink. The resulting print has excellent adhesion of the inkjet image (inkjet layer) to the substrate, and is less likely to have streaks. Each of these steps will be described below.

[0104] (Inkjet process) The inkjet process is a process of applying the inkjet ink described above to a substrate. The substrate is not particularly limited. Examples of the substrate include metal plates such as steel plates, aluminum, and stainless steel; plastic plates or films such as acrylic, polycarbonate, ABS, polypropylene, polyester, and vinyl chloride; ceramic plates, concrete, wood, and glass. The substrate may also be a polyester fiber such as cationic dyeable polyester (CDP) fiber, polyethylene terephthalate (PET) fiber, polybutylene terephthalate (PBT) fiber, polytrimethylene terephthalate (PTT) fiber, wholly aromatic polyester fiber, or polylactic acid fiber; or a fabric made of acetate fiber, triacetate fiber, polyurethane fiber, nylon fiber, or a composite fiber thereof. These may be selected appropriately depending on the application. When the substrate is a fabric, it is preferable to treat the fabric with a pretreatment agent before printing. Examples of pretreatment agents include water-soluble polymers, water-insoluble inert organic compounds, flame retardants, ultraviolet absorbers, anti-reducing agents, antioxidants, pH adjusters, hydrotropic agents, anti-foaming agents, penetrating agents, microporous forming agents, etc. Examples of methods for applying these pretreatment agents to fabrics include padding, spraying, dipping, coating, laminating, gravure printing, and inkjet printing.

[0105] In the inkjet process, the method of applying the inkjet ink to the substrate by the inkjet recording method is not particularly limited, and examples of such methods include continuous methods such as a charge modulation method, a microdot method, a charge spray control method, and an ink mist method, and on-demand methods such as a piezo method, a pulse jet method, a bubble jet (registered trademark) method, and an electrostatic suction method.

[0106] The amount of ink applied is not particularly limited. For example, the amount of ink applied is 1 g / m 2 of the substrate. 2 It is preferable that the content is 2 g / m or more. 2 It is more preferable that the amount of ink applied is 150 g / m or more. 2 Preferably, it is 50 g / m or less. 2By keeping the amount of ink applied within the above range, the printed matter can be easily expressed satisfactorily while maintaining excellent formability.

[0107] (Ultraviolet irradiation process) The ultraviolet ray irradiation step is a step in which the applied inkjet ink is irradiated with ultraviolet rays.

[0108] The curing conditions for the inkjet ink are not particularly limited. For example, the UV irradiation intensity is 50 mW / cm. 2 It is preferable that the power is 100 mW / cm or more. 2 It is more preferable that the UV irradiation intensity is 2000 mW / cm or more. 2 Preferably, it is 1000 mW / cm or less. 2 When the UV irradiation intensity is within the above range, the resulting printed matter is appropriately cured and is less likely to yellow.

[0109] The UV irradiation energy (integral light amount) is not particularly limited. For example, the integrated light amount is 50 mJ / cm 2 Preferably, it is 100 mJ / cm or more. 2 It is more preferable that the integrated light amount is 1500 mJ / cm or more. 2 Preferably, it is 1200 mJ / cm or less. 2 When the integrated light amount is within the above range, the resulting printed matter is appropriately cured and is less likely to yellow.

[0110] (Optional process) The method for producing a printed matter of this embodiment may employ any other steps in addition to the inkjet step and the ultraviolet irradiation step. The method for producing a printed matter of this embodiment preferably includes the following shaping step.

[0111] (Formation process) The shaping step is a step of shaping the substrate after the ultraviolet irradiation step. By employing the shaping step, the obtained printed matter can be formed into various shapes.

[0112] More specifically, in the shaping step, the substrate (printed material) that has undergone the ultraviolet irradiation step is integrated with, for example, a molded resin layer to form a molded body. The resin that forms the molded resin layer is not particularly limited. For example, the resin that forms the molded resin layer may be a known thermoplastic resin such as a polyolefin resin such as polyethylene or polypropylene, a polystyrene resin, a polyvinyl chloride resin, a poly(meth)acrylate resin, an acrylic resin, a polyacetal resin, a polyester resin such as polyethylene terephthalate or polybutylene terephthalate, a polyamide resin, a polycarbonate resin, a polyphenylene sulfide resin, or a polyimide resin. The resins may be used in combination.

[0113] The method for producing the molded body is not particularly limited. For example, the molded body can be produced by injection molding or the like. Injection molding may be general injection molding, injection compression molding, injection press molding, or the like. More specifically, the molded body can be molded by an insert molding method that involves the following first and second steps.

[0114] The first step is a step of preforming the printed matter. In the first step, the printed matter is shaped into a desired design shape by a thermoforming method such as vacuum forming or pressure forming.

[0115] The second step is injection molding using a pre-shaped printed material. In the second step, the shaped body is placed in a mold cavity and molten resin is injected to integrate the shaped body and the molded resin layer. This results in the above-mentioned molded body. The temperature of the molten resin during injection molding is not particularly limited. For example, the melting temperature is preferably 180°C or higher, more preferably 200°C or higher. Furthermore, the melting temperature is preferably 320°C or lower, more preferably 300°C or lower. As described above, the coating film formed by the inkjet ink used in this embodiment exhibits excellent adhesion. Therefore, the coating film is less likely to cause damage or peeling of the pattern during insert molding, and has excellent thermoformability.

[0116] That is, the resulting print exhibits excellent adhesion. Therefore, the coating film is less likely to be damaged during the shaping process, etc., resulting in excellent formability. Furthermore, the inkjet image is less likely to have streaks. [Example]

[0117] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0118] The raw materials and preparation methods used are shown below. (color pigments) Color pigment 1: Y masterbatch: 15 parts by mass of a yellow pigment (CROMOPHTAL YELLOW D1085, manufactured by BASF), 10 parts by mass of a dispersant (solsperse33000, manufactured by Lubrizol Japan, Inc.), and 75 parts by mass of IBXA (isobornyl acrylate, manufactured by Kyoeisha Chemical Co., Ltd.) were mixed in a mixer and filtered to prepare a Y masterbatch. Color pigment 2: M masterbatch: 15 parts by mass of a red pigment (Ink Jet Red E5B 02, manufactured by Clariant Japan K.K.), 10 parts by mass of a dispersant (solsperse32000, manufactured by Lubrizol Japan Corp.), and 75 parts by mass of IBXA (isobornyl acrylate, manufactured by Kyoeisha Chemical Co., Ltd.) were mixed in a mixer and filtered to prepare an M masterbatch. Color pigment 3: C masterbatch: 15 parts by mass of a blue pigment (Hostaperm Blue BT617D, manufactured by Clariant Japan K.K.), 10 parts by mass of a dispersant (solsperse33000, manufactured by Lubrizol Japan Corp.), and 75 parts by mass of IBXA (isobornyl acrylate, manufactured by Kyoeisha Chemical Co., Ltd.) were mixed in a mixer and filtered to prepare C masterbatch. Color pigment 4: K masterbatch: 15 parts by mass of black pigment (NIPEX35, manufactured by Orion Engineered Carbons Co., Ltd.), 10 parts by mass of dispersant (solsperse33000, manufactured by Lubrizol Japan Co., Ltd.), and 75 parts by mass of IBXA (isobornyl acrylate, manufactured by Kyoeisha Chemical Co., Ltd.) were mixed in a mixer and filtered to prepare a K masterbatch. (Component (i) and comparative substitutes) UV-curable oligomer 1: CN991, polyester urethane acrylate, Mn: 3000, manufactured by Arkema Co., Ltd. UV-curable oligomer 2: EBECRYL7100, amine acrylate, Mn:1000, manufactured by Daicel Allnex Co., Ltd. UV-curable oligomer 3: EBECRYL4513, urethane triacrylate, Mn:2000, manufactured by Daicel Allnex Co., Ltd. (Component (ii)) UV-curable monomer 1: FX-AO-MA, 2-(allyloxymethyl)methyl acrylate, manufactured by Nippon Shokubai Co., Ltd. UV-curable monomer 2: FX-AO-CHA, 2-(allyloxymethyl) cyclohexyl acrylate, manufactured by Nippon Shokubai Co., Ltd. (ingredient (iii)) UV-curable monomer 3: SR489, linear aliphatic (meth)acrylate monomer, manufactured by Sartomer (Component (iv)) UV-curable monomer 4: ACMO, acryloylmorpholine, aliphatic heterocyclic acrylic monomer (morpholine skeleton), manufactured by KJ Chemicals Co., Ltd. UV-curable monomer 5: SR531, cyclic trimethylolpropane formal acrylate, aliphatic heterocyclic acrylic monomer (dioxane skeleton), manufactured by Sartomer UV-curable monomer 6: SR217, 4-tert-butylcyclohexanol acrylate, aliphatic cyclic acrylic monomer, manufactured by Arkema Co., Ltd. (surface conditioner) Surface conditioner: Megafac F-556, manufactured by DIC Corporation (Photoradical polymerization initiator) Photopolymerization initiator 1: Omnirad 184, 1-hydroxycyclohexyl phenyl ketone, manufactured by IGM Resins BV Photopolymerization initiator 2: Omnirad819, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, manufactured by IGM Resins BV (polymerization inhibitor) Polymerization inhibitor 1: 4-hydroxy Tempo, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl, manufactured by Shanghai SABO Biochemical Technology Co., Ltd.

[0119] (Examples 1 to 10, Comparative Examples 1 to 4) Inkjet inks were prepared according to the formulations (unit: parts by mass) shown in Table 1 below. The viscosity of each inkjet ink was evaluated using the following evaluation method. The resulting inkjet ink was applied to a substrate (ABS film solid-printed with white screen ink; screen ink: MRX-HF, manufactured by Teikoku Ink Mfg. Co., Ltd.) using an inkjet printer under the following recording conditions to a film thickness of 250 μm (inkjet process), and then irradiated with ultraviolet light (conditions described below) (ultraviolet irradiation process) to prepare evaluation samples. The inkjet image (inkjet layer) of each evaluation sample was evaluated for printed image design (streaks), adhesion (initial adhesion), adhesion (after thermoforming), and skin irritation using the following evaluation methods. The results are shown in Table 1.

[0120] <Inkjet printer recording conditions> Nozzle diameter 40μm Voltage 70V Pulse width 10μs Drive frequency 10kHz Resolution: 400 x 800 dpi Application amount: 15g / m 2 <Ultraviolet irradiation conditions> Lamp type: Metal halide lamp, manufactured by Integration Irradiation intensity (measurement wavelength 365nm) 240mW / cm 2 Accumulated light intensity (measured at 365 nm): 720 mJ / cm 2 Irradiation height: 45cm <Heat treatment conditions> Equipment: Constant temperature dryer DY300, manufactured by Yamato Scientific Co., Ltd. Heat treatment temperature: 80℃ Heat treatment time: 180 minutes

[0121] <Evaluation method> (ink viscosity) Measurement was carried out at 30°C using a Brookfield viscometer (TVB-20LT, manufactured by Toki Sangyo Co., Ltd.). (Printed image design (streaks)) The obtained evaluation sample was visually observed and evaluated for the presence or absence of streaks according to the following evaluation criteria. ◯: The printed image was clear and free of streaks. △: The printed image had streaks. ×: The printed image had many streaks and looked white. (Adhesion (initial adhesion)) After inkjet printing, the relative adhesion between the substrate and the ink layer was evaluated using the cross-cut method (25 squares, 2 mm wide) in accordance with JIS K 5600, and the adhesion (initial adhesion) was evaluated according to the following evaluation criteria. ○: The inkjet image was not peeled off. ×: The inkjet image was peeled off. (Adhesion (after thermoforming)) For the printed matter after thermoforming and the printed matter after inkjet printing, the relative adhesion between the substrate and the ink layer was evaluated using the cross-cut method (25 squares with a width of 2 mm) in accordance with JIS K 5600, and the adhesion (after thermoforming) was evaluated according to the following evaluation criteria. ○: The inkjet image was not peeled off. △: The inkjet image peeled off. ×: The inkjet image was lifted from the substrate or cracked. (Skin irritation) Wearing rubber gloves (material: natural rubber, latex gloves, non-powdered, chlorinated, manufactured by Reetec Corporation), inkjet ink was applied to the rubber gloves, and then the ink was wiped off after 5 minutes. Skin irritation was evaluated according to the following evaluation criteria. ○: Almost no irritation was felt on the skin. △: Slight discomfort felt on the skin. ×: Strong irritation was felt on the skin.

[0122] [Table 1]

[0123] As shown in Table 1, the inkjet inks of Examples 1 to 10 all had low viscosity. Furthermore, the resulting prints had little or no streaking, and excellent adhesion between the inkjet image (inkjet layer) and the substrate. Furthermore, the inkjet inks caused little or no skin irritation.

Claims

1. The composition includes the following components (i), (ii), (iii), and (iv), and a photoradical polymerization initiator, the content of the component (ii) in the inkjet ink is 5 to 20% by mass, the content of the component (iv) in the inkjet ink is 20 to 60% by mass, An inkjet ink having a surface tension of 35 dyne / cm or less. <Component (i)> At least one of a urethane diacrylate oligomer and an amine acrylate. <Component (ii)> A compound represented by the following formula (I): 【Chemical 1】 (In formula (I), R 1 represents a hydrogen atom or a monovalent organic group. The organic group is composed of a hydrocarbon and may have an ether group. The hydrogen atom of the hydrocarbon may be substituted with a halogen atom. <Component (iii)> Linear aliphatic (meth)acrylate monomer. <Component (iv)> A (meth)acrylate monomer that has an aliphatic heterocycle containing an oxygen atom in the molecule.

2. An inkjet ink as described in claim 1, wherein the heterocyclic skeleton of component (iv) includes at least one of a morpholine skeleton, a tetrahydrofuran skeleton, a dioxane skeleton, and a dioxolane ring.

3. An inkjet ink as described in claim 1 or 2, further comprising a surface conditioner.

4. An inkjet ink described in any one of claims 1 to 3, having a viscosity at 30°C of 5 to 50 mPa·s.

5. An inkjet printed matter having an inkjet image printed using the inkjet ink according to any one of claims 1 to 4.

Images