Radiation-curable inkjet ink composition and recording device

Abstract

This invention provides a radiation-curable inkjet ink composition that exhibits excellent curability, abrasion resistance, flexibility retention, low odor, continuous printing stability, and initial viscosity. [Solution] A radiation-curable inkjet ink composition comprising a hydroxyl group-containing monofunctional monomer and / or an ether cyclic structure-containing monofunctional monomer, a nitrogen-containing heterocyclic structure-containing monofunctional monomer, a difunctional monomer, and a polymerization initiator, wherein the difunctional monomer comprises a vinyl ether group-containing (meth)acrylate represented by the following formula (1), the content of the vinyl ether group-containing (meth)acrylate is 20% by mass or more of the total amount of the ink composition, and the polymerization initiator comprises ethylphenyl (2,4,6-trimethylbenzoyl) phosphinate. H2C=CR 1 -CO-OR 2 -O-CH=CH-R 3 (1)

Description

[Technical Field]

[0001] The present invention relates to a radiation-curable inkjet ink composition and a recording device. [Background technology]

[0002] Inkjet recording methods are rapidly developing in various fields because they enable the recording of high-resolution images with relatively simple equipment. In the process, various studies are being conducted to improve various properties. For example, Patent Document 1 describes a radiation-curable inkjet composition that has low viscosity and can form a coating film with excellent abrasion resistance, and comprises vinylmethyl oxazolidinone and a vinyl ether group-containing (meth)acrylate having a predetermined structure. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-042321 [Overview of the project] [Problems that the invention aims to solve]

[0004] Studies are being conducted to improve the curability, flexibility, and other properties of recorded materials, including the inkjet composition described in Patent Document 1. [Means for solving the problem]

[0005] The radiation-curable inkjet composition of the present invention comprises a hydroxyl group-containing monofunctional monomer and / or an ether cyclic structure-containing monofunctional monomer, a nitrogen-containing heterocyclic structure-containing monofunctional monomer, a difunctional monomer, and a polymerization initiator. The difunctional monomer comprises a vinyl ether group-containing (meth)acrylate represented by the following formula (1), the content of which is 20% by mass or more of the total amount of the ink composition, and the polymerization initiator comprises ethylphenyl (2,4,6-trimethylbenzoyl) phosphinate. H2C=CR 1 -CO-OR 2 -O-CH=CH-R 3 (1) (In the formula, R 1 R is a hydrogen atom or a methyl group, 2 R is a divalent organic residue with 2 to 20 carbon atoms. 3 (This refers to a hydrogen atom or a monovalent organic residue with 1 to 11 carbon atoms.)

[0006] The recording device of the present invention includes an inkjet head that ejects the above-mentioned radiation-curable inkjet ink composition. [Brief explanation of the drawing]

[0007] [Figure 1] An example of a recording device used in this embodiment is shown. [Figure 2] Table 1 shows the composition and evaluation results of the radiation-curable inkjet ink composition used in the examples. [Figure 3] Table 2 shows the composition and evaluation results of the radiation-curable inkjet ink compositions used in the examples. [Modes for carrying out the invention]

[0008] The embodiments of the present invention (hereinafter referred to as "these embodiments") will be described in detail below, with reference to the drawings as necessary. However, the present invention is not limited thereto, and various modifications are possible without departing from its essence.

[0009] 1. Radiation-curable inkjet ink composition The radiation-curable inkjet ink composition of the present embodiment (hereinafter also referred to as "ink composition") includes a hydroxyl group-containing monofunctional monomer and / or an ether cyclic structure-containing monofunctional monomer, a nitrogen-containing heterocyclic structure-containing monofunctional monomer, a bifunctional monomer, and a polymerization initiator. The bifunctional monomer includes a vinyl ether group-containing (meth)acrylate represented by the following formula (1), and the content of the vinyl ether group-containing (meth)acrylate is 20% by mass or more based on the total amount of the ink composition. The polymerization initiator includes ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate (hereinafter also referred to as "TPO-L"). H2C=CR 1 -CO-OR 2 -O-CH=CH-R 3 (1) (In the formula, R 1 is a hydrogen atom or a methyl group, R 2 is a divalent organic residue having 2 to 20 carbon atoms, and R 3 is a hydrogen atom or a monovalent organic residue having 1 to 11 carbon atoms.)

[0010] By using a nitrogen-containing heterocyclic structure-containing monofunctional monomer and a bifunctional monomer of a vinyl ether group-containing (meth)acrylate having a predetermined structure, the curability of the ink composition can be improved and the viscosity suitable for ejection can be adjusted. However, it has been found that after the formation of the coating film, as time passes, the coating film becomes hard and brittle.

[0011] Therefore, in the present embodiment, in addition to the nitrogen-containing heterocyclic structure-containing monofunctional monomer and the bifunctional monomer of the vinyl ether group-containing (meth)acrylate having a predetermined structure, a hydroxyl group-containing monofunctional monomer or an ether cyclic structure-containing monofunctional monomer is used to maintain the flexibility of the coating film over time.

[0012] In addition, in this embodiment, in view of the relatively high viscosity of the hydroxyl group-containing monofunctional monomer or the ether cyclic structure-containing monofunctional monomer, from the perspective of continuous printing stability in the inkjet method, TPO-L, which is liquid at room temperature, is used as the polymerization initiator. Thereby, both the maintenance of flexibility over time and the compatibility of continuous printing stability are achieved.

[0013] The radiation-curable inkjet composition of this embodiment cures by irradiating radiation. Examples of the radiation include ultraviolet rays, electron beams, infrared rays, visible light rays, X-rays, etc. The radiation is preferably ultraviolet rays from the viewpoints that the radiation source is easily available and widely used, and that materials suitable for curing by irradiation with ultraviolet rays are easily available and widely used.

[0014] Hereinafter, each component contained in the radiation-curable inkjet composition of this embodiment will be described in detail.

[0015] 1.1. Polymerizable Compound In this embodiment, a compound that cures by irradiating radiation is generally referred to as a polymerizable compound. Examples of the polymerizable compound include a monofunctional monomer having one polymerizable functional group, an oligomer containing one or more polymerizable functional groups, and a polyfunctional monomer having two or more polymerizable functional groups. Further, the polyfunctional monomer includes a bifunctional monomer having two polymerizable functional groups and a polyfunctional monomer having three or more polymerizable functional groups.

[0016] In this embodiment, an oligomer is a multimer composed of polymerizable compounds as constituent components and is a compound having one or more polymerizable functional groups. In this embodiment, those having a molecular weight of 1000 or more are defined as oligomers, and those having a molecular weight of less than 1000 are defined as monomers.

[0017] 1.1.1. Monofunctional Monomer The ink composition of this embodiment contains a nitrogen-containing heterocyclic monofunctional monomer. The inclusion of the nitrogen-containing heterocyclic monofunctional monomer improves curability and allows the viscosity to be within a suitable range. The ink composition of this embodiment also contains a hydroxyl group-containing monofunctional monomer or an ether cyclic structure-containing monofunctional monomer. The inclusion of the hydroxyl group-containing monofunctional monomer or an ether cyclic structure-containing monofunctional monomer improves the maintenance of flexibility.

[0018] The ink composition of this embodiment may also contain other monofunctional monomers. These other monofunctional monomers are not particularly limited, but examples include nitrogen-containing monofunctional monomers other than nitrogen-containing heterocyclic monofunctional monomers, alicyclic group-containing monofunctional monomers, aliphatic group-containing monofunctional monomers, and aromatic ring-containing monofunctional monomers. These monofunctional monomers may be used individually or in combination of two or more.

[0019] The total content of monofunctional monomers is preferably 30% to 80% by mass, 37% to 70% by mass, 40% to 60% by mass, or 45% to 55% by mass, relative to the total amount of polymerizable compounds. When the monofunctional monomer content is within the above range, curability, abrasion resistance, flexibility retention, and continuous printing stability are further improved, and the initial viscosity tends to be within a more suitable range.

[0020] The total content of monofunctional monomers is preferably 20% to 80% by mass, 30% to 60% by mass, 35% to 50% by mass, or 38% to 45% by mass, relative to the total amount of the ink composition. When the content of monofunctional monomers is within the above range, curability, abrasion resistance, flexibility retention, and continuous printing stability are further improved, and the initial viscosity tends to be within a more suitable range.

[0021] 1.1.1.1. Nitrogen-containing heterocyclic monofunctional monomers The nitrogen-containing heterocyclic monofunctional monomer is not particularly limited, but examples include monofunctional monomers containing an ε-caprolactam structure such as N-vinylcaprolactam; monofunctional monomers containing an oxazoline structure such as 5-methyl-3-vinyloxazolidine-2-one; monofunctional monomers containing a morpholine structure such as acryloylmorpholine; monofunctional monomers containing a carbazole structure such as N-vinylcarbazole; and monofunctional monomers containing a pyrrolidone structure such as N-vinylpyrrolidone. Among these, it is preferable to include one or more selected from the group consisting of monofunctional monomers containing an ε-caprolactam structure, monofunctional monomers containing an oxazoline structure, and monofunctional monomers containing a morpholine structure. When the ink composition contains the above compounds, the curability, abrasion resistance, and continuous printing stability are further improved, and the initial viscosity tends to be within a more suitable range.

[0022] The content of nitrogen-containing heterocyclic monofunctional monomers is preferably 1% to 30% by mass, 10% to 27% by mass, and 17% to 23% by mass, relative to the total amount of the ink composition. When the content of nitrogen-containing heterocyclic monofunctional monomers is within the above range, the curability, abrasion resistance, and continuous printing stability are further improved, and the initial viscosity tends to be within a more suitable range.

[0023] 1.1.1.2. Hydroxyl group-containing monofunctional monomers The hydroxyl group-containing monofunctional monomer is not particularly limited, but examples include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1,4-cyclohexanedimethanol mono(meth)acrylate, and 2-hydroxy-3-phenoxypropyl acrylate. Among these, 4-hydroxybutyl (meth)acrylate is preferred. By using such compounds, the adhesion, abrasion resistance, maintenance of flexibility, and continuous printing stability of the ink coating film are further improved, and the initial viscosity tends to be within a more favorable range.

[0024] The content of hydroxyl group-containing monofunctional monomers is preferably 1% to 30% by mass, 5% to 25% by mass, and 8% to 15% by mass, relative to the total amount of the ink composition. When the content of hydroxyl group-containing monofunctional monomers is within the above range, scratch resistance, flexibility retention, and continuous printing stability are further improved, and the initial viscosity tends to be within a more suitable range.

[0025] 1.1.1.3. Monofunctional monomers containing ether cyclic structures The monofunctional monomer containing the ether cyclic structure is not particularly limited as long as it contains a cyclic ether skeleton such as tetrahydrofuran or tetrahydropyran, but examples include cyclic trimethylolpropane formal (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, and (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate. Among these, it is preferable to use cyclic trimethylolpropane formal (meth)acrylate and / or tetrahydrofurfuryl (meth)acrylate. By using such compounds, abrasion resistance, flexibility retention, and continuous printing stability tend to be improved, and the initial viscosity tends to be within a more suitable range.

[0026] The content of the ether cyclic structure-containing monofunctional monomer is preferably 1% to 30% by mass, 7% to 25% by mass, and 12% to 23% by mass, relative to the total amount of the ink composition. When the content of the ether cyclic structure-containing monofunctional monomer is within the above range, scratch resistance, flexibility retention, and continuous printing stability are further improved, and the initial viscosity tends to be within a more suitable range.

[0027] 1.1.1.4. Monofunctional monomers containing alicyclic groups Monofunctional monomers containing alicyclic groups are not particularly limited as long as they are monomers having one or more saturated or unsaturated carbon rings that do not have aromaticity. Examples include monomers having monocyclic hydrocarbon groups such as 4-tert-butylcyclohexyl acrylate and 3,3,5-trimethylcyclohexyl acrylate; monomers having unsaturated polycyclic hydrocarbon groups such as dicyclopentenyl acrylate and dicyclopentenyloxyethyl acrylate; and monomers having saturated polycyclic hydrocarbon groups such as dicyclopentanyl acrylate, isobornyl acrylate, and 4-tetra-butylcyclohexyl acrylate.

[0028] The content of alicyclic group-containing monofunctional monomers is preferably 1% to 20% by mass, 3% to 17% by mass, and 7% to 12% by mass, relative to the total amount of the ink composition. When the content of alicyclic group-containing monofunctional monomers is within the above range, scratch resistance, curability, and continuous printing stability are further improved, and the initial viscosity tends to be within a more suitable range.

[0029] 1.1.1.5. Aromatic ring-containing monofunctional monomers The ink composition of this embodiment preferably contains an aromatic ring-containing monofunctional monomer. Including such a compound tends to further improve the solubility of the acylphosphine polymerization initiator and further improve the curability of the coating film. The aromatic ring-containing monofunctional monomer is not particularly limited, but examples include phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, alkoxylated 2-phenoxyethyl (meth)acrylate, ethoxylated nonylphenyl (meth)acrylate, alkoxylated nonylphenyl (meth)acrylate, p-cumylphenol EO modified (meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate.

[0030] The content of aromatic ring-containing monofunctional monomers is preferably 1% to 30% by mass, 3% to 25% by mass, 6% to 17% by mass, or 8% to 15% by mass, relative to the total amount of the ink composition. When the content of aromatic ring-containing monofunctional monomers is within the above range, curability, scratch resistance, and continuous printing stability are further improved, and the initial viscosity tends to be within a more suitable range.

[0031] 1.1.2. Polyfunctional monomers The total content of polyfunctional monomers is preferably 20% to 70% by mass, 30% to 65% by mass, 40% to 60% by mass, or 45% to 55% by mass, relative to the total amount of polymerizable compounds. When the polyfunctional monomer content is within the above range, curability, abrasion resistance, flexibility retention, and continuous printing stability are further improved, and the initial viscosity tends to be within a more suitable range.

[0032] The total content of polyfunctional monomers is preferably 15% to 60% by mass, 30% to 57% by mass, or 40% to 50% by mass, relative to the total amount of the ink composition. When the polyfunctional monomer content is within the above range, curability, abrasion resistance, flexibility retention, and continuous printing stability are further improved, and the initial viscosity tends to be within a more suitable range.

[0033] 1.1.2.1. Vinyl ether group-containing (meth)acrylates The ink composition of this embodiment contains a vinyl ether group-containing (meth)acrylate represented by the following formula (1) (hereinafter simply referred to as "vinyl ether group-containing (meth)acrylate"). By including such a compound, the curability is improved and the initial viscosity can be set within a suitable range. H2C=CR 1 -CO-OR 2 -O-CH=CH-R 3 ... (1) (In the formula, R 1 R is a hydrogen atom or a methyl group, 2R is a divalent organic residue with 2 to 20 carbon atoms. 3 (This refers to a hydrogen atom or a monovalent organic residue with 1 to 11 carbon atoms.)

[0034] In the above equation (1), R 2 The divalent organic residues having 2 to 20 carbon atoms represented by are not particularly limited, but include, for example, linear, branched, or cyclic alkylene groups having 2 to 20 carbon atoms that may be substituted, alkylene groups having 2 to 20 carbon atoms that may have oxygen atoms in their structure due to ether and / or ester bonds, and divalent aromatic groups having 6 to 11 carbon atoms that may be substituted.

[0035] In the above equation (1), R 3 The monovalent organic residue having 1 to 11 carbon atoms represented by is not particularly limited, but examples include linear, branched, or cyclic alkyl groups having 1 to 10 carbon atoms, which may be substituted, and aromatic groups having 6 to 11 carbon atoms, which may be substituted.

[0036] Specific examples of vinyl ether group-containing (meth)acrylates are not particularly limited, but include, for example, 2-vinyloxyethyl (meth)acrylate, 3-vinyloxypropyl (meth)acrylate, 1-methyl-2-vinyloxyethyl (meth)acrylate, 2-vinyloxypropyl (meth)acrylate, 4-vinyloxybutyl (meth)acrylate, 1-methyl-3-vinyloxypropyl (meth)acrylate, 1-vinyloxymethylpropyl (meth)acrylate, 2-methyl-3-vinyloxypropyl (meth)acrylate, and 1,1- Dimethyl-2-vinyloxyethyl, 3-vinyloxybutyl (meth)acrylate, 1-methyl-2-vinyloxypropyl (meth)acrylate, 2-vinyloxybutyl (meth)acrylate, 4-vinyloxycyclohexyl (meth)acrylate, 6-vinyloxyhexyl (meth)acrylate, 4-vinyloxymethylcyclohexylmethyl (meth)acrylate, 3-vinyloxymethylcyclohexylmethyl (meth)acrylate, 2-vinyloxymethylcyclohexylmethyl (meth)acrylate, p-vinyloxymethylphenylmethyl (meth)acrylate m-vinyloxymethylphenylmethyl (meth)acrylate, o-vinyloxymethylphenylmethyl (meth)acrylate, 2-(2-vinyloxyethoxy)ethyl (meth)acrylate, 2-(2-vinyloxyethoxy)ethyl (meth)acrylate, 2-(vinyloxyisopropoxy)ethyl (meth)acrylate, 2-(vinyloxyethoxy)propyl (meth)acrylate, 2-(vinyloxyethoxy)isopropyl (meth)acrylate, 2-(vinyloxyisopropoxy)propyl (meth)acrylate, 2-(vinyloxyisopropyl) (Poxy)isopropyl, (meth)acrylate 2-(vinyloxyethoxyethoxy)ethyl, (meth)acrylate 2-(vinyloxyethoxyisopropoxy)ethyl, (meth)acrylate 2-(vinyloxyisopropoxyethoxy)ethyl, (meth)acrylate 2-(vinyloxyisopropoxyisopropoxy)ethyl, (meth)acrylate 2-(vinyloxyethoxyethoxy)propyl, (meth)acrylate 2-(vinyloxyethoxyisopropoxy)propyl, (meth)acrylate 2-(vinyloxyisopropoxyethoxy)propyl,(meth)acrylate 2-(vinyloxyisopropoxyisopropoxy)propyl, (meth)acrylate 2-(vinyloxyethoxyethoxy)isopropyl, (meth)acrylate 2-(vinyloxyethoxyisopropoxy)isopropyl, (meth)acrylate 2-(vinyloxyisopropoxyethoxy)isopropyl, (meth)acrylate 2-(vinyloxyisopropoxyisopropoxy)isopropyl, (meth)acrylate 2-(vinyloxyethoxyethoxyethoxy)ethyl, (meth)acrylate 2-(vinyloxy Examples include ethyl thylene(thiethoxyethoxyethoxyethoxy), ethyl (meth)acrylate (2-(isopropenoxyethoxy)), ethyl (meth)acrylate (2-(isopropenoxyethoxyethoxy)), ethyl (meth)acrylate (2-(isopropenoxyethoxyethoxyethoxy)), polyethylene glycol monovinyl ether (meth)acrylate, and polypropylene glycol monovinyl ether (meth)acrylate.

[0037] The content of vinyl ether group-containing (meth)acrylate is 20% by mass or more, preferably 25% by mass or more, 30% by mass or more, and 32% by mass or more, relative to the total amount of the ink composition. The content of vinyl ether group-containing (meth)acrylate is preferably 50% by mass or less, 40% by mass or less, and 37% by mass or less, relative to the total amount of the ink composition. When the content of vinyl ether group-containing (meth)acrylate is within the above range, storage stability, abrasion resistance, curability, and continuous printing stability are further improved, and the initial viscosity tends to be within a more suitable range.

[0038] 1.1.2.2. Other bifunctional (meth)acrylates The ink composition of this embodiment may also contain other difunctional monomers, and while not particularly limited, examples of other difunctional monomers include difunctional (meth)acrylates. Examples of difunctional (meth)acrylates include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, dipropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and 2-hydroxy-1,3-di(meth)acryloxypropane. Among these, it is preferable to use 1,6-hexanediol di(meth)acrylate and / or dipropylene glycol di(meth)acrylate. Using such compounds tends to further improve abrasion resistance, curability, and continuous printing stability, and the initial viscosity tends to be within a more suitable range.

[0039] The content of other difunctional monomers is preferably 1% to 30% by mass, 3% to 20% by mass, and 7% to 15% by mass, relative to the total amount of the ink composition. When the content of difunctional monomers is within the above range, scratch resistance, curability and continuous printing stability are further improved, and the initial viscosity tends to be within a more suitable range.

[0040] 1.3. Oligomers While not particularly limited, examples of oligomers include urethane acrylate oligomers with a repeating urethane structure, polyester acrylate oligomers with an ester repeating ester structure, and epoxy acrylate oligomers with an epoxy repeating ester structure. A commercially available example of a urethane acrylate oligomer is CN9893 (aliphatic urethane acrylate oligomer, product name of Sartomer Co., Ltd.).

[0041] The oligomer content is preferably 0.1% to 15% by mass, 1% to 10% by mass, or 2% to 7% by mass, relative to the total amount of the ink composition. When the oligomer content is within the above range, the curability, abrasion resistance, and continuous printing stability are further improved, and the initial viscosity tends to be within a more suitable range.

[0042] 1.2. Polymerization Initiators The ink composition of this embodiment contains TPO-L. By using TPO-L, which is liquid at room temperature, the viscosity can be kept within a suitable range while improving the maintenance of flexibility. The ink composition of this embodiment may also contain other polymerization initiators. Other polymerization initiators are not particularly limited as long as they generate active species when irradiated with radiation, but examples of known polymerization initiators include acylphosphine oxide polymerization initiators other than TPO-L, alkylphenone polymerization initiators, titanocene polymerization initiators, and thioxanthone polymerization initiators. These polymerization initiators can be used individually or in combination of two or more.

[0043] The polymerization initiator content is preferably 1% to 20% by mass, 3% to 15% by mass, and 7% to 12% by mass, relative to the total amount of the ink composition. When the polymerization initiator content is within the above range, scratch resistance, curability, low odor, and continuous printing stability are further improved, and the initial viscosity tends to be within a more suitable range.

[0044] 1.2.1.TPO-L TPO-L is an acylphosphine oxide polymerization initiator that is liquid at room temperature. A commercially available example of TPO-L is Omnirad TPO-L (trade name of IGM Resins BV).

[0045] The content of ethylphenyl (2,4,6-trimethylbenzoyl) phosphinate (TPO-L) is preferably 1% to 15% by mass, 5% to 13% by mass, and 8% to 11% by mass, relative to the total amount of the ink composition. When the TPO-L content is within the above range, curability, abrasion resistance, low odor, and continuous printing stability are further improved, and the initial viscosity tends to be within a more favorable range.

[0046] 1.2.2. Acylphosphine oxide polymerization initiators other than TPO-L Acylphosphine oxide polymerization initiators other than TPO-L are not particularly limited, but examples include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide. Among these, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide is preferred. The inclusion of these compounds tends to improve abrasion resistance, curability, low odor, and continuous printing stability, and the initial viscosity tends to be within a more favorable range.

[0047] Examples of commercially available acylphosphine oxide polymerization initiators include Omnirad 819 (bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, trade name of ISM Resins BV).

[0048] The content of acylphosphine oxide polymerization initiators other than TPO-L is preferably 1% to 15% by mass, 2% to 10% by mass, and 3% to 7% by mass, relative to the total amount of the ink composition. When the content of acylphosphine oxide polymerization initiators is within the above range, scratch resistance, curability, low odor, and continuous printing stability are further improved, and the initial viscosity tends to be within a more suitable range.

[0049] The ink composition in this embodiment may contain a thioxanthone-based polymerization initiator as a polymerization initiator. The thioxanthone-based polymerization initiator is not particularly limited, but may include low molecular weight thioxanthone initiators with a molecular weight of less than 500, such as 2,4-diethylthioxanthone and 2-isopropylthioxanthone, or polybutylene glycol bis(9-oxo-9H-thioxanthenyloxy)acetate and 1,3-di({α-[1-chloro-9-oxo-9H-thioxanthen-4-yl)oxy]acetylpoly[oxy(1-methylethylene)]}oxy)-2, Examples include 2-bis({α-[1-chloro-9-oxo-9H-thioxanthene-4-yl)oxy]acetylpoly[oxy(1-methylethylene)]}oxymethyl)propane and α-[2-[(9-oxo-9H-thioxanthenyl)oxy]acetyl]-ω-[[2-[(9-oxo-9H-thioxanthenyl)oxy]acetyl]oxy]poly(oxy-1,4-butanediyl), which are high molecular weight thioxanthone initiators with a molecular weight of 500 or more.

[0050] 1.3 Polymerization Inhibitors The ink composition of this embodiment may contain a polymerization inhibitor. The polymerization inhibitor is not particularly limited, but examples include phenol compounds, quinone compounds, amine compounds, nitro compounds, oxime compounds, sulfur compounds, and oxyl compounds. These polymerization inhibitors may be used individually or in combination of two or more.

[0051] Examples of phenol compounds are not particularly limited, but include p-methoxyphenol, cresol, tert-butylcatechol, di-tert-butylpara-cresol, hydroquinone monomethyl ether, α-naphthol, 3,5-di-tert-butyl-4-hydroxytoluene, 2,2'-methylenebis(4-methyl-6-tert-butylphenol), 2,2'-methylenebis(4-ethyl-6-butylphenol), and 4,4'-thiobis(3-methyl-6-tert-butylphenol). A commercially available example of a phenol compound is MEHQ (p-methoxyphenol, manufactured by Kanto Chemical Co., Ltd.).

[0052] The quinone compounds are not particularly limited, but examples include p-benzoquinone, anthraquinone, naphthoquinone, phenanthraquinone, p-xyloquinone, p-toluquinone, 2,6-dichloroquinone, 2,5-diphenyl-p-benzoquinone, 2,5-diacetoxy-p-benzoquinone, 2,5-dicapoxy-p-benzoquinone, 2,5-diasiloxy-p-benzoquinone, hydroquinone, 2,5-dibutylhydroquinone, mono-t-butylhydroquinone, monomethylhydroquinone, and 2,5-di-t-amylhydroquinone.

[0053] The amine compounds are not particularly limited, but examples include phenyl-β-naphthylamine, p-benzylaminophenol, di-β-naphthylparaphenylenediamine, dibenzylhydroxylamine, phenylhydroxylamine, diethylhydroxylamine, compounds having a 2,2,6,6-tetramethylpiperidine skeleton, compounds having a 2,2,6,6-tetramethylpiperidine-N-alkyl skeleton, and compounds having a 2,2,6,6-tetramethylpiperidine-N-acyl skeleton.

[0054] Examples of nitro compounds include, but are not limited to, dinitrobenzene, trinitrotoluene, picric acid, and their derivatives. Examples of oxime compounds include, but are not limited to, quinone dioxime and cyclohexanone oxime. Examples of sulfur compounds include, but are not limited to, phenothiazine.

[0055] The oxyl compound is not particularly limited, but examples include derivatives of 2,2,6,6-tetramethylpiperidinyl-1-oxyl. Examples of derivatives of 2,2,6,6-tetramethylpiperidinyl-1-oxyl include 4-acetamido-2,2,6,6-tetramethylpiperidinyl-1-oxyl, 4-amino-2,2,6,6-tetramethylpiperidinyl-1-oxyl, 4-carboxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl, 4-(2-chloroacetamide)-2,2,6,6-tetramethylpiperidinyl-1-oxyl, 4-cyano-2,2,6,6-tetramethylpiperidinyl-1-oxyl, 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl, and 4-hydroxybenzo-A Examples include to-2,2,6,6-tetramethylpiperidinyl-1-oxyl, 4-(2-iodoacetamide)-2,2,6,6-tetramethylpiperidinyl-1-oxyl, 4-isothiocyanate-2,2,6,6-tetramethylpiperidinyl-1-oxyl, 4-methacryloyloxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl, 4-methoxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl, 4-oxo-2,2,6,6-tetramethylpiperidinyl-1-oxyl, and 4-(2-propynyloxy)-2,2,6,6-tetramethylpiperidinyl-1-oxyl. A commercially available example of an oxyl compound is Adeka Stab LA-7RD (4-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl, a trade name of ADEKA Corporation).

[0056] The polymerization inhibitor content is preferably 0.01% to 5.0% by mass, 0.05% to 3.0% by mass, or 0.1% to 1.0% by mass, relative to the total amount of the ink composition. When the polymerization inhibitor content is within the above range, scratch resistance, curability, maintenance of flexibility, low odor, and continuous printing stability tend to be further improved.

[0057] 1.4. Surfactants The ink composition of this embodiment may contain a surfactant. Examples of surfactants include acetylene glycol-based surfactants, fluorine-based surfactants, and silicone-based surfactants. These surfactants may be used individually or in combination of two or more.

[0058] The acetylene glycol-based surfactant is not particularly limited, but examples include 2,4,7,9-tetramethyl-5-decine-4,7-diol and alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decine-4,7-diol. A commercially available acetylene glycol-based surfactant is, for example, Surfinol 465 (trade name of Nisshin Chemical Industry Co., Ltd.).

[0059] Examples of fluorinated surfactants include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphate esters, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl betaines, and perfluoroalkylamine oxide compounds.

[0060] Examples of silicone-based surfactants are not particularly limited, but include polysiloxane compounds and polyether-modified organosiloxanes. Examples of commercially available silicone-based surfactants include BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-348, BYK-UV3500, BYK-UV3510, BYK-UV3530, and BYK-UV3570 (product names of BYK Corporation).

[0061] The surfactant content is preferably 0.01% to 5% by mass, 0.1% to 3% by mass, or 0.3% to 1% by mass, relative to the total amount of the ink composition. By keeping the surfactant content within the above ranges, scratch resistance, curability, flexibility retention, and continuous printing stability tend to be improved, and the initial viscosity tends to be within a more suitable range.

[0062] 1.5. Dispersant The ink composition of this embodiment may contain a dispersant. The dispersant is not particularly limited, but examples include dispersants commonly used to prepare pigment dispersions, such as polymer dispersants. Specifically, examples include polyoxyalkylenes, polyalkylene polyamines, vinyl polymers and copolymers, acrylic polymers and copolymers, polyesters, polyamides, polyimides, polyurethanes, amino polymers, silicon-containing polymers, sulfur-containing polymers, fluorine-containing polymers, and epoxy resins. These dispersants may be used individually or in combination of two or more.

[0063] Commercially available dispersants include the Ajisper series (manufactured by Ajinomoto Fine Techno Co., Ltd.), Solsperse 32000, for example, Solsperse 36000 (a product name from Noveon Corporation), the Disparbic series (manufactured by BYK Corporation), and the Disparon series (manufactured by Kusumoto Chemical Co., Ltd.).

[0064] The dispersant content is preferably 0.1% to 5% by mass, 0.5% to 3% by mass, or 1% to 2% by mass, relative to the total amount of the ink composition. By keeping the dispersant content within the above ranges, scratch resistance and continuous printing stability are further improved, and the initial viscosity tends to be within a more suitable range.

[0065] 1.6. Colorants The ink composition of this embodiment may contain a colorant. The colorant may be either a pigment or a dye. The pigment is not particularly limited, but examples include organic pigments and inorganic pigments. These colorants may be used individually or in combination of two or more.

[0066] Examples of organic pigments include azo pigments such as azo lake pigments, insoluble monoazo pigments, insoluble disazo pigments, condensed azo pigments, and chelate azo pigments; polycyclic pigments such as phthalocyanine pigments, quinacridone pigments, perylene pigments, perinone pigments, anthraquinone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments; dye chelates such as basic dye type chelates and acid dye type chelates; and nitro pigments and nitroso pigments.

[0067] Examples of inorganic pigments include titanium dioxide, iron oxide yellow, iron oxide brown, chromium oxide, Prussian blue, ultramarine, molybdenum red, iron oxide black, lead yellow, complex oxide pigments, and carbon black.

[0068] Examples of carbon black used as a black pigment include CI (Colour Index Generic Name) Pigment Black 1, 7, and 11. Examples of commercially available carbon black include No.2300, No.900, MCF88, No.33, No.40, No.45, No.52, MA7, MA8, MA100, No.2200B (product names from Mitsubishi Chemical Corporation), Raven 5750, 5250, 5000, 3500, 1255, 700 (product names from Columbia Carbon Corporation), Rega1 400R, 330R, 660R, Mogul L, Monarch 700, 800, 880, 900, 1000, 1100, 1300, 1400 (product names from CABOT Corporation), Color Black FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Printex 35, U, V, 140U, and Special Black. Examples include 6, 5, 4A, and 4 (product names of Degussa). Carbon black manufactured by known methods such as the contact method, furnace method, and thermal method may also be used.

[0069] Examples of white pigments include CI Pigment White 6, 18, and 21.

[0070] Examples of yellow pigments include CI Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 16, 17, 24, 34, 35, 37, 53, 55, 65, 73, 74, 75, 81, 83, 93, 94, 95, 97, 98, 99, 108, 109, 110, 113, 114, 117, 120, 124, 128, 129, 133, 138, 139, 147, 151, 153, 154, 155, 167, 172, and 180.

[0071] For magenta pigments, use CI Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 40, 41, 42, 48(Ca), 48(Mn), 57(Ca), 57:1, 88, 112, 114, 122, 123, 144, 146, 149, 150, 166, 168, 170, 171, 175, 176, 177, 178, 179, 184, 185, 187, 202, 209, 219, 224, 245, or CI Pigment Violet. Numbers 19, 23, 32, 33, 36, 38, 43, and 50 can be cited.

[0072] Examples of cyan pigments include CI Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:34, 15:4, 16, 18, 22, 25, 60, 65, 66, and CI Bat Blue 4 and 60.

[0073] In addition to black, white, yellow, magenta, and cyan, other pigments include, for example, CI Pigment Green 7, 10, CI Pigment Brown 3, 5, 25, 26, and CI Pigment Orange 1, 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, and 63.

[0074] The dyes used are not particularly limited and include acid dyes, direct dyes, reactive dyes, and basic dyes. Specifically, examples include CI Acid Yellow 17, 23, 42, 44, 79, 142; CI Acid Red 52, 80, 82, 249, 254, 289; CI Acid Blue 9, 45, 249; CI Acid Black 1, 2, 24, 94; CI Food Black 1, 2; CI Direct Yellow 1, 12, 24, 33, 50; CI Direct Red 1, 4, 9, 80, 81, 225, 227; CI Direct Blue 1, 2, 15, 71, 86, 87, 98; CI Direct Black 19, 38, 51, 71, 154; CI Reactive Red 14, 32, 55, 79, 249; and CI Reactive Black 3, 4, 35.

[0075] The colorant content is preferably 0.1% to 10% by mass, 1% to 5% by mass, or 2% to 4% by mass, relative to the total amount of the ink composition. When the colorant content is within the above range, scratch resistance and continuous printing stability are further improved, and the initial viscosity tends to be within a more favorable range.

[0076] 1.7. Other ingredients In addition to the above-mentioned components, various additives such as chelating agents, softening agents, solubilizers, viscosity modifiers, ultraviolet absorbers, antioxidants, and corrosion inhibitors may be included as needed.

[0077] 2. Method for preparing an ink composition Ink compositions can be prepared, for example, by mixing each component in any order and removing impurities and foreign matter by filtration or other methods as needed. Methods for mixing the components include sequentially adding each component to a container equipped with a stirring device such as a mechanical stirrer or magnetic stirrer, and then stirring and mixing them. Filtration methods include centrifugal filtration and filter filtration.

[0078] 3. Recording media The recording medium material used in this embodiment is not particularly limited, but examples include glass, paper, metal, wood, plastics, and materials whose surfaces have been processed. Examples of plastics include polyvinyl chloride, polyethylene terephthalate, polypropylene, polyethylene, polycarbonate, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, and polyvinyl acetal.

[0079] 4. Recording Method The inkjet recording method according to this embodiment includes an adhesion step of ejecting the above-mentioned radiation-curable inkjet composition from an inkjet head and adhering it to a shrink film or flexible packaging film, and an irradiation step of irradiating the adhered radiation-curable inkjet composition with radiation.

[0080] 5. Recording device The recording device of this embodiment includes an inkjet head having a nozzle for ejecting the above-mentioned ink composition onto a recording medium, and preferably also includes an LED irradiator for irradiating the ink composition attached to the recording medium with ultraviolet light, and a carriage on which the inkjet head is mounted.

[0081] The inkjet head may be either a line-type head or a serial-type head. In the case of a line-type head, the head has a length approximately equal to the width of the recording medium. In the case of a serial-type head, a primary scan in the width direction of the recording medium and a secondary scan in the flow direction intersecting the width direction are repeated, and the radiation-curable inkjet ink composition is ejected during the primary scan.

[0082] The amount of polymerization initiator can be increased to a similar amount as exemplified above, but for example, it should be 15% by mass or less relative to the total amount of ink.

[0083] A serial printer having the above configuration can irradiate the ink with ultraviolet light multiple times, and therefore tends to produce better physical properties of the ink coating, such as curability, even when using an ink composition with an amount of polymerization initiator within the above range.

[0084] As an example of a recording device, Figure 1 shows a perspective view of a serial printer. As shown in Figure 1, the serial printer 20 comprises a transport unit 220 and a recording unit 230. The transport unit 220 transports the recording medium F supplied to the serial printer to the recording unit 230 and discharges the recorded recording medium outside the serial printer after recording. Specifically, the transport unit 220 has feed rollers and transports the fed recording medium F in the sub-scanning direction T1.

[0085] Furthermore, the recording unit 230 includes an inkjet head 231 that ejects an ink composition onto the recording medium F sent from the transport unit 220, an LED irradiator 232 that irradiates the attached ink composition with ultraviolet light, a carriage 234 on which these are mounted, and a carriage movement mechanism 235 that moves the carriage 234 in the main scanning directions S1 and S2 of the recording medium F.

[0086] The inkjet head 231 is shorter than the width of the recording medium F, and as the carriage moves, it repeatedly performs a primary scan in the width direction of the recording medium F and a secondary scan in the flow direction intersecting the width direction. When performing the primary scan, the inkjet head 231 ejects the ink composition onto the recording medium F.

[0087] The LED irradiator 232 irradiates the ink composition attached to the recording medium with ultraviolet light. The ultraviolet light irradiation may be performed in the same main scan as the main scan in which the ink composition was ejected, or in a different main scan, for example, in the main scan following the main scan in which the ink composition was ejected. The ultraviolet light irradiation may be performed multiple times on the attached ink composition in the same main scan or in multiple different main scans. By doing so, even when using an ink composition with a small amount of polymerization initiator, it tends to be possible to improve the physical properties of the ink coating film, such as curability.

[0088] Although Figure 1 shows an LED irradiator mounted on a carriage, the system is not limited to this configuration, and may also have an LED irradiator that is not mounted on a carriage. [Examples]

[0089] The present invention will be described more specifically below using examples and comparative examples. The present invention is not limited in any way by the following examples.

[0090] Figures 2 and 3 show Tables 1 and 2 illustrating the composition of each composition in the examples and comparative examples.

[0091] 1. Preparation of the ink composition Each example ink composition is obtained by placing the components into a mixing tank to achieve the composition shown in Table 1, mixing and stirring, and then filtering through a membrane filter. Unless otherwise specified, the numerical values ​​for each component in the table represent mass percent. Furthermore, in the table, the numerical values ​​for each content represent the mass percent of the solid content of the active ingredient.

[0092] The abbreviations and product component details used in the ink composition are as follows:

[0093] [Monofunctional monomer] • PEA (Phenoxyethyl Acrylate) • VMOX (5-methyl-3-vinyloxazolidine-2-one) • 4HBA (4-hydroxybutyl acrylate) DA-141 (2-hydroxy-3-phenoxypropyl acrylate) • CTFA (Cyclic Trimethylol Propane Formal Acrylate) • THFA (Tetrahydrofurfurylacrylate) IBXA (isobornyl acrylate) • ACMO (Acryloylmorpholin) nVC (N-vinylcaprolactam) [Bifunctional monomer] VEEA (2-(2-vinyloxyethoxy)ethyl acrylate) • 1,6-HDDA (1,6-hexanediol diacrylate) • DPGDA (Dipropylene Glycol Diacrylate) [Oligomer] • CN9893 (Aliphatic urethane acrylate oligomer, product name manufactured by Sartomer Co., Ltd.) [Polymerization initiator] • Omnirad 819 (Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, brand name of ISM Resins BV) • Omnirad TPO-L (ethyl(2,4,6-trimethylbenzoyl)-phenylphosphenate, trade name of IGM Resins BV) [Polymerization inhibitor] • MEHQ (p-methoxyphenol, manufactured by Kanto Chemical Co., Ltd.) • LA-7RD (Product name "ADEKA Stab LA-7RD", 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl, manufactured by ADEKA) [Surfactants] • BYK UV3500 (silicone-based surfactant, BYK brand name) [Dispersant] • S 36000 ("Solsperse 36000", polymer dispersant, Lubrizol brand name) • S 32000 ("Solsperse 32000", polymer dispersant, Lubrizol brand name) [Pigments] • PB15:3 (CI Pigment Blue 15:3, Cyan Pigment) • Carbon black (black pigment) [water] ·Pure water

[0094] 2. Evaluation Method 2.1. Evaluation of initial viscosity The viscosity of each ink composition was measured at 20°C using a rotational viscometer rheometer MCR-301 (product name manufactured by Anton Paar). The evaluation criteria are as follows. (Evaluation Criteria) A: Less than 10 mPa·s B: 10~15 mPa·s C: 15~20 mPa·s D: 21mPa·s or more

[0095] 2.2. Evaluation of curing properties Each example of the ink composition, in an amount that results in a cured film thickness of 8 μm, is applied to PET50A PL-Shin (PET film, product name of Lintec Corporation), and the number of ultraviolet light irradiations required for curing is measured. Curing is determined by rubbing with a cotton swab; whether ink adheres to the swab or whether scratches appear on the cured ink on the recording medium. Ultraviolet light irradiation is performed using an ultraviolet light-emitting diode (peak wavelength 395 nm) with an irradiation energy of 50 mJ / cm² per irradiation. 2 Perform the action in such a way. (Evaluation Criteria) AA: 1 time A: 2 times B: 3~5 times C: 6 or more times

[0096] 2.3. Evaluation of abrasion resistance Each example of ink composition was filled into a modified SC-R5050 printer (product name manufactured by Seiko Epson Corporation), and a solid pattern (ink adhesion amount 12 mg / inch) was printed on the recording medium. 2 Print the image shown. After leaving it at room temperature for 30 minutes, cut the ink-coated area into a 30 x 150 mm rectangle and rub it 100 times using a water-moistened plain weave cloth with a JSPS-type abrasion resistance tester (load 500 g). Visually observe the degree of ink peeling and evaluate it according to the following evaluation criteria. (Evaluation Criteria) A: Rank 1 (No damage) B: Rank 2-3 (linear scratches) C: Rank 4 (Surface damage) D: Rank 5 (Peeling)

[0097] 2.4. Evaluation of the ability to maintain flexibility Using a bar coater, the ink composition for each example is applied to a polyethylene film (PEN-050501 (product name from AS ONE Corporation)) to a thickness of 10 μm. Then, a metal halide lamp (manufactured by I-Graphics Corporation) is used to heat the film at 400 mJ / cm². 2The coating is hardened using energy to form a film. A strip of the coating, 1 cm wide and 7 cm long, is cut directly from the polyethylene film on which the above coating has been formed to prepare test specimens. For each test specimen, the elongation immediately after application and the elongation after being left in a 70°C environment for 20 minutes are measured using a tensile testing machine TENSILON (product name of ORIENTEC). The elongation is calculated as {(length at crack - length before stretching) / length before stretching × 100} when a crack occurs when pulled at 10 mm / min. The rate of change between the elongation immediately after application and the elongation after being left in a 70°C environment for 20 minutes is determined and evaluated as the maintenance of flexibility. The rate of change is calculated as {(elongation immediately after application - elongation after being left in a 70°C environment for 20 minutes) / elongation immediately after application × 100}. Note that being left in a 70°C environment for 20 minutes corresponds to the elongation after being left at room temperature for 10 days. (Evaluation Criteria) A: Change rate less than 20% B: Change rate less than 40% C: Change rate less than 60% D: Change rate of 60% or more

[0098] 2.5. Evaluation of Odor Properties Using a bar coater, the ink composition for each example is applied to a polyvinyl chloride film JT5829R (product name from MACtac) to a thickness of 10 μm. Then, a metal halide lamp (manufactured by I-Graphics) is used to heat the film at 400 mJ / cm². 2 The coating is hardened using energy to form a film. The film is then left at room temperature for one day, and its odor is evaluated by sensory evaluation. Specifically, 10 panelists smell the patterns and evaluate the odor using a 6-level odor intensity scale according to the following evaluation criteria. (Evaluation Criteria) A: Odor rank 2 or lower B: Odor rank 3 C: Odor rank 4 D: Odor rank 5

[0099] 2.6. Evaluation of Continuous Printing Stability Using an inkjet head with a nozzle diameter of 20 μm (360 nozzles), each example ink composition was continuously ejected at a drive frequency of 15 kHz. Every 5 minutes, a check was performed to confirm whether ink was being ejected from all nozzles. Continuous ejection was performed for a maximum total of 50 minutes, and continuous printing stability was evaluated according to the following evaluation criteria. A: No nozzles failed to dispense after 50 minutes. B: 20-50 minutes, no non-dispensing nozzles. C: No dispensing nozzle present within 15 minutes.

[0100] 3. Evaluation Results Tables 1 and 2 show that the radiation-curable inkjet ink composition of this embodiment tends to have improved curability, abrasion resistance, flexibility retention, low odor, and continuous printing stability, as well as an initial viscosity within a more suitable range. [Explanation of Symbols]

[0101] 20...Serial printer, 220...Transport unit, 230...Recording unit, 231...Inkjet head, 232...LED illuminator, 234...Carriage, 235...Carriage movement mechanism, F...Recording medium, S1, S2...Main scanning direction, T1...Sub-scanning direction

Claims

1. A hydroxyl group-containing monofunctional monomer and / or an ether cyclic structure-containing monofunctional monomer, Nitrogen-containing heterocyclic monofunctional monomers, Difunctional monomers and A polymerization initiator is included, The aforementioned bifunctional monomer comprises a vinyl ether group-containing (meth)acrylate represented by the following formula (1): The content of the vinyl ether group-containing (meth)acrylate is 20% by mass or more relative to the total amount of the ink composition. The polymerization initiator comprises ethylphenyl (2,4,6-trimethylbenzoyl) phosphinate. Radiation-curable inkjet ink composition. H ２ C=CR １ -CO-OR ２ -O-CH=CH-R ３ (1) (In the formula, R １ R is a hydrogen atom or a methyl group, ２ R is a divalent organic residue having 2 to 20 carbon atoms. ３ (This is a hydrogen atom or a monovalent organic residue having 1 to 11 carbon atoms.)

2. The nitrogen-containing heterocyclic monofunctional monomer has one or more structures selected from the group consisting of oxazoline structures, morpholine structures, and ε-caprolactam structures. The radiation-curable inkjet ink composition according to claim 1.

3. The hydroxyl group-containing monofunctional monomer includes 4-hydroxybutyl (meth)acrylate. The radiation-curable inkjet ink composition according to claim 1.

4. The ether cyclic structure-containing monofunctional monomer comprises cyclic trimethylolpropaneformal (meth)acrylate and / or tetrahydrofurfuryl (meth)acrylate. The radiation-curable inkjet ink composition according to claim 1.

5. The content of the vinyl ether group-containing (meth)acrylate is 50% by mass or less relative to the total amount of the ink composition. The radiation-curable inkjet ink composition according to claim 1.

6. The aforementioned bifunctional monomer further comprises 1,6-hexanediol di(meth)acrylate and / or dipropylene glycol di(meth)acrylate. The radiation-curable inkjet ink composition according to claim 1.

7. The polymerization initiator further comprises bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide. The radiation-curable inkjet ink composition according to claim 1.

8. Further comprising an aromatic ring-containing monofunctional monomer, The radiation-curable inkjet ink composition according to claim 1.

9. The content of the ethylphenyl (2,4,6-trimethylbenzoyl) phosphinate is 1 to 15% by mass relative to the total amount of the ink composition. The radiation-curable inkjet ink composition according to claim 1.

10. The system comprises an inkjet head that ejects the radiation-curable inkjet ink composition described in claim 1, Recording device.

11. An inkjet head that ejects the radiation-curable inkjet ink composition described in claim 1 onto a recording medium, An LED irradiator that irradiates the ink composition adhering to the recording medium with ultraviolet light, A carriage equipped with the aforementioned inkjet head, The inkjet head repeatedly performs a primary scan in the width direction of the recording medium and a secondary scan in the flow direction intersecting the width direction, and ejects the radiation-curable inkjet ink composition during the primary scan. The content of the polymerization initiator is 15% by mass or less relative to the total amount of the ink composition. Recording device.

Images