Radiation-curable inkjet composition and inkjet method

Abstract

To provide a radiation-curable inkjet composition which has low viscosity and can form a coating film excellent in stretchability.SOLUTION: The radiation-curable inkjet composition contains a monofunctional (meth)acrylate monomer and vinyl methyl oxazolidinone.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a radiation-curable ink-jet composition and an ink-jet method. [Background technology]

[0002] Inkjet recording methods are capable of recording high-resolution images using relatively simple equipment and have been rapidly developing in various fields. In the process, various studies have been conducted to improve various properties. For example, Patent Document 1 discloses a radiation-curable inkjet ink composition containing 20% ​​to 50% by mass of a vinyl ether group-containing (meth)acrylate and 5% to 15% by mass of N-vinylcaprolactam, with the aim of providing a radiation-curable inkjet ink composition having excellent abrasion resistance, adhesion, and alcohol resistance, as well as a recorded matter and an inkjet recording method using the same.

[0003] Furthermore, Patent Document 2 discloses a photocurable inkjet ink composition containing 40% by mass or more and 75% by mass or less of a vinyl ether group-containing (meth)acrylate, 1% by mass or more and 20% by mass or less of a urethane (meth)acrylate oligomer, and a photopolymerization initiator, with the aim of providing a photocurable inkjet ink that is low in viscosity and highly reactive, yet capable of providing printed matter with excellent film properties, particularly stretchability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-116934 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-162688 Summary of the Invention [Problem to be solved by the invention]

[0005] However, while N-vinylcaprolactam as used in Patent Document 1 provides excellent coating film adhesion and abrasion resistance, it has a low boiling point, making it difficult to handle at room temperature. Furthermore, it also tends to increase the viscosity of the ink, making it difficult to use extensively in inkjet inks. Furthermore, urethane acrylate oligomers as used in Patent Document 2 tend to increase the viscosity of the ink, making it difficult to use extensively in inkjet inks. Furthermore, their multifunctionality results in poor coating film stretchability. Inks with these problems are likely to be unsuitable for signage applications, in particular. Therefore, a radiation-curable inkjet composition that produces inks with minimal increase in viscosity and excellent stretchability is desired. [Means for solving the problem]

[0006] The radiation-curable inkjet composition of the present invention is a radiation-curable inkjet composition containing a monofunctional (meth)acrylate monomer and vinylmethyloxazolidinone.

[0007] The content of vinylmethyloxazolidinone in the radiation-curable inkjet composition is preferably 5 to 40% by mass relative to the total amount of the radiation-curable inkjet composition.

[0008] The radiation curable ink jet composition preferably contains the monofunctional (meth)acrylate monomer in an amount of 10 to 50% by mass relative to the total amount of the radiation curable ink jet composition.

[0009] The radiation-curable inkjet composition preferably contains a vinyl ether group-containing (meth)acrylate represented by the following general formula (1). 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, and R 2 is a divalent organic residue having 2 to 20 carbon atoms, and R 3is a hydrogen atom or a monovalent organic residue having 1 to 11 carbon atoms.

[0010] The content of the vinyl ether group-containing (meth)acrylate in the radiation-curable inkjet composition is preferably 10 to 50% by mass relative to the total amount of the radiation-curable inkjet composition.

[0011] In the radiation-curable inkjet composition, the monofunctional (meth)acrylate monomer preferably includes at least one of an alicyclic monofunctional (meth)acrylate, a monofunctional (meth)acrylate having a cyclic ether structure, or a monofunctional (meth)acrylate having a crosslinked condensed ring structure.

[0012] The radiation-curable inkjet composition preferably contains a polyfunctional (meth)acrylate, and the content of the polyfunctional (meth)acrylate is preferably 2 to 20% by mass relative to the total amount of the radiation-curable inkjet composition.

[0013] The radiation-curable inkjet composition preferably contains a urethane acrylate oligomer, and the content of the urethane acrylate oligomer is preferably 1 to 10% by mass relative to the total amount of the radiation-curable inkjet composition.

[0014] The radiation-curable ink jet composition preferably contains a derivative of 2,2,6,6-tetramethylpiperidinyl-1-oxyl as a polymerization inhibitor.

[0015] The radiation-curable ink jet composition preferably contains an acylphosphine oxide initiator as a photopolymerization initiator.

[0016] The radiation-curable ink jet composition preferably contains a fluorescent brightening agent.

[0017] The inkjet method of the present invention is an inkjet method comprising: a discharge step of discharging the radiation curable inkjet composition from a liquid ejection head to adhere it to a recording medium; and an irradiation step of irradiating the radiation curable inkjet composition adhered to the recording medium with radiation. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a perspective view showing a serial inkjet device according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail with reference to the drawings as necessary, but the present invention is not limited to this, and various modifications are possible without departing from the spirit of the present invention. In the drawings, the same elements are given the same reference numerals, and redundant explanations will be omitted. Furthermore, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

[0020] In this specification, "(meth)acryloyl" means at least one of acryloyl and its corresponding methacryloyl, "(meth)acrylate" means at least one of acrylate and its corresponding methacrylate, and "(meth)acrylic" means at least one of acrylic and its corresponding methacrylic.

[0021] 1. Radiation-curable inkjet composition The radiation-curable inkjet composition according to this embodiment (hereinafter also simply referred to as "composition") contains a monofunctional (meth)acrylate monomer and vinylmethyloxazolidinone. If necessary, the composition may also contain a photopolymerization initiator, a fluorescent brightener, a surfactant, a polymerization inhibitor, and the like. Here, vinylmethyloxazolidinone refers to a compound represented by the following chemical formula: [ka]

[0022] When used as a component of radiation-curable inkjet compositions, vinylmethyloxazolidinone has a lower viscosity than other N-vinyl compounds, making it less likely to increase the viscosity of the composition and suitable for inkjet printing. Vinylmethyloxazolidinone can also improve the adhesion and abrasion resistance of coating films. Furthermore, it has been found that the use of vinylmethyloxazolidinone in combination with a monofunctional (meth)acrylate monomer further improves stretchability.

[0023] The radiation-curable ink jet composition according to this embodiment is a composition that is ejected from an ink jet head by an ink jet method. Hereinafter, a radiation-curable ink composition will be described as one embodiment of the radiation-curable ink jet composition, but the composition according to this embodiment may be a composition other than an ink composition, for example, a composition used for 3D modeling.

[0024] The radiation-curable inkjet composition of this embodiment is cured by irradiation with radiation. Examples of radiation include ultraviolet light, electron beams, infrared light, visible light, and X-rays. As the radiation, ultraviolet light is preferred because radiation sources are readily available and widely used, and materials suitable for curing by ultraviolet radiation are readily available and widely used.

[0025] The components that may be contained in the radiation-curable ink jet composition according to this embodiment, its physical properties, and a production method will be described below.

[0026] 1.1. Polymerizable compounds In this embodiment, compounds that are cured by irradiation with radiation are collectively referred to as polymerizable compounds. Polymerizable compounds include monofunctional monomers having one polymerizable functional group and polyfunctional monomers having multiple polymerizable functional groups, and may also include oligomers having one or more polymerizable functional groups as needed. Each polymerizable compound may be used alone or in combination of two or more.

[0027] The polymerizable compound of this embodiment contains a monofunctional (meth)acrylate monomer and vinylmethyloxazolidinone, and may contain other polymerizable compounds as needed. The other polymerizable compounds are not particularly limited, and examples thereof include monofunctional monomers other than the monofunctional (meth)acrylate monomer and vinylmethyloxazolidinone, polyfunctional monomers, and oligomers such as urethane oligomers.

[0028] 1.1.1. Monofunctional (meth)acrylate monomers The monofunctional (meth)acrylate monomer is not particularly limited, and examples thereof include alicyclic monofunctional (meth)acrylate monomers, monofunctional (meth)acrylate monomers having a cyclic ether structure, monofunctional (meth)acrylate monomers having a crosslinked condensed ring structure, aliphatic group-containing monofunctional (meth)acrylate monomers, and aromatic group-containing monofunctional (meth)acrylate monomers. Among these, alicyclic monofunctional (meth)acrylate monomers, monofunctional (meth)acrylate monomers having a cyclic ether structure, and monofunctional (meth)acrylate monomers having a crosslinked condensed ring structure are preferred. By using such monomers, the curability of the composition and the abrasion resistance, stretchability, and adhesion of the coating film tend to be further improved.

[0029] The content of the monofunctional (meth)acrylate monomer is preferably 5 to 55 mass %, more preferably 10 to 50 mass %, even more preferably 15 to 45 mass %, and particularly preferably 20 to 40 mass %, relative to the total amount of the composition. When the content of the monofunctional (meth)acrylate monomer is within the above range, the curability of the composition and the abrasion resistance, stretchability, and adhesion of the coating film tend to be further improved.

[0030] Hereinafter, examples of monofunctional (meth)acrylate monomers will be shown, but the monofunctional (meth)acrylate monomers in this embodiment are not limited to the following.

[0031] 1.1.1.1. Alicyclic monofunctional (meth)acrylate monomers The alicyclic monofunctional (meth)acrylate monomer is not particularly limited, but examples thereof include isobornyl (meth)acrylate (IBXA), trimethylcyclohexane (meth)acrylate (TMCHA), tert-butylcyclohexanol acrylate (TBCHA), 2-(meth)acrylic acid-1,4-dioxaspiro[4,5]dec-2-ylmethyl, and the like. By using vinylmethyloxazolidinone and the alicyclic monofunctional (meth)acrylate monomer in combination, the adhesion and abrasion resistance of the coating film tend to be further improved. Note that in this embodiment, the alicyclic monofunctional monomer is not a compound having a crosslinked fused ring structure.

[0032] The content of the alicyclic monofunctional (meth)acrylate monomer is preferably 5 to 55 mass %, more preferably 10 to 50 mass %, and even more preferably 15 to 45 mass %, relative to the total amount of the composition. When the content of the alicyclic monofunctional (meth)acrylate monomer is within the above range, the adhesion and abrasion resistance of the coating film tend to be further improved.

[0033] 1.1.1.2. Monofunctional (meth)acrylate monomers with cyclic ether structures The monofunctional (meth)acrylate monomer having a cyclic ether structure is not particularly limited, but examples thereof include tetrahydrofurfuryl acrylate (THFA), cyclic trimethylolpropane formal acrylate (CTFA), and (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate (MEDOL-10). The combined use of vinylmethyloxazolidinone and a monofunctional (meth)acrylate monomer having a cyclic ether structure tends to further improve the adhesion and abrasion resistance of the coating film. Furthermore, the odor of the composition tends to be reduced.

[0034] The content of the monofunctional (meth)acrylate monomer having a cyclic ether structure is preferably 5 to 55 mass %, more preferably 10 to 50 mass %, and even more preferably 15 to 45 mass %, relative to the total amount of the composition. When the content of the monofunctional monomer having a cyclic ether structure is within the above range, the adhesion and abrasion resistance of the coating film tend to be further improved.

[0035] 1.1.1.3. Monofunctional (meth)acrylate monomers with bridged condensed ring structures A bridged condensed ring structure refers to a structure in which two or more ring structures share a side in a one-to-one relationship and two or more non-adjacent elements of the same or different ring structures are linked together. Monofunctional (meth)acrylate monomers having a bridged condensed ring structure are not particularly limited, but examples include dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and dicyclopentanyl (meth)acrylate. In addition to the above, other examples of bridged condensed ring structures include the following: The combined use of vinylmethyloxazolidinone and a monofunctional (meth)acrylate having a bridged condensed ring structure tends to further improve the adhesion and abrasion resistance of the coating film. Furthermore, the stretchability of the coating film tends to further improve. [ka]

[0036] The content of the monofunctional (meth)acrylate monomer having a crosslinked fused ring structure relative to the total amount of the composition is preferably 5 to 45 mass %, more preferably 10 to 40 mass %, and even more preferably 15 to 35 mass %. When the content of the monofunctional (meth)acrylate having a crosslinked fused ring structure relative to the total amount of the composition is within the above range, the adhesion and abrasion resistance of the coating film tend to be further improved.

[0037] 1.1.1.4. Other monofunctional (meth)acrylate monomers The other monofunctional (meth)acrylate monomer is not particularly limited, and examples thereof include aromatic group-containing monofunctional monomers and aliphatic group-containing monofunctional monomers. Use of such monomers tends to further improve the curability of the composition and the abrasion resistance, stretchability, and adhesion of the coating film.

[0038] 1.1.1.4.1. Aliphatic monofunctional (meth)acrylate monomers The aliphatic monofunctional (meth)acrylate monomer is not particularly limited, but examples thereof include isoamyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, isomyristyl (meth)acrylate, isostearyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, butoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate.

[0039] 1.1.1.4.2. Aromatic group-containing monofunctional (meth)acrylate monomers The aromatic group-containing monofunctional monomer is not particularly limited, but examples thereof 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.

[0040] 1.1.2. Vinylmethyloxazolidinone The use of vinylmethyloxazolidinone makes it possible to keep the viscosity of the composition low, and to further improve the stretchability of the coating film that is formed, as well as the adhesion and abrasion resistance of the coating film.

[0041] The content of vinylmethyloxazolidinone is preferably 3 to 40 mass %, more preferably 5 to 40 mass %, even more preferably 10 to 35 mass %, and particularly preferably 15 to 30 mass %, relative to the total amount of the composition. When the content of vinylmethyloxazolidinone relative to the total amount of the composition is within the above range, the viscosity of the composition tends to be further reduced, and the stretchability, adhesion, and scratch resistance of the coating film tend to be further improved.

[0042] 1.1.3. Nitrogen-containing monofunctional monomers other than vinylmethyloxazolidinone In addition to the vinylmethyloxazolidinone, a nitrogen-containing monofunctional monomer may be contained. The nitrogen-containing monofunctional monomer other than vinylmethyloxazolidinone is not particularly limited, but examples thereof include nitrogen-containing monofunctional vinyl monomers such as N-vinylcaprolactam, N-vinylformamide, N-vinylcarbazole, N-vinylacetamide, and N-vinylpyrrolidone; nitrogen-containing monofunctional acrylate monomers such as acryloylmorpholine; and nitrogen-containing monofunctional acrylamide monomers such as (meth)acrylamide, N-hydroxymethyl(meth)acrylamide, diacetoneacrylamide, N,N-dimethyl(meth)acrylamide, and dimethylaminoethyl acrylate benzyl chloride quaternary salt.

[0043] Among these, it is preferable to contain either a nitrogen-containing monofunctional vinyl monomer or a nitrogen-containing monofunctional acrylate monomer, and a monomer having a nitrogen-containing heterocyclic structure such as N-vinylcaprolactam, N-vinylcarbazole, N-vinylpyrrolidone, or acryloylmorpholine is more preferable, and N-vinylcaprolactam is even more preferable.

[0044] The use of such nitrogen-containing monofunctional monomers tends to further improve the scratch resistance of the coating film.Furthermore, nitrogen-containing monofunctional vinyl monomers having a nitrogen-containing heterocyclic structure, such as N-vinylcaprolactam, tend to further improve the flexibility and adhesion of the coating film.

[0045] The content of the nitrogen-containing monofunctional monomer other than vinylmethyloxazolidinone is preferably 1 to 15 mass %, more preferably 3 to 12 mass %, and even more preferably 5 to 10 mass %, relative to the total amount of the composition. When the content of the nitrogen-containing monofunctional monomer relative to the total amount of the composition is within the above range, the viscosity of the composition tends to be kept low, while the adhesion and scratch resistance of the coating film tend to be further improved.

[0046] 1.1.4. Multifunctional Monomers Examples of the polyfunctional monomer of the present embodiment include vinyl ether group-containing (meth)acrylate and polyfunctional (meth)acrylate, but the polyfunctional monomer is not limited to these.

[0047] The content of the polyfunctional monomer relative to the total amount of the composition is preferably 5 to 50 mass%, more preferably 10 to 50 mass%, even more preferably 15 to 45 mass%, and particularly preferably 20 to 40 mass%. When the content of the polyfunctional monomer relative to the total amount of the composition is within the above range, the abrasion resistance, stretchability, and adhesion of the coating film tend to be further improved.

[0048] Examples of polyfunctional monomers are given below, but the polyfunctional monomers in this embodiment are not limited to the following.

[0049] 1.1.4.1 Vinyl ether group-containing (meth)acrylates The vinyl ether group-containing (meth)acrylate is not particularly limited, and examples thereof include compounds represented by the following formula (1): By including such a vinyl ether group-containing (meth)acrylate, the viscosity of the composition tends to decrease, and the ejection stability tends to be improved. Furthermore, the curability of the composition is improved, and the improved curability also allows for faster recording speeds. 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, and 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.

[0050] In the above formula (1), R 2Examples of the divalent organic residue having 2 to 20 carbon atoms represented by the formula (I) include a linear, branched, or cyclic alkylene group having 2 to 20 carbon atoms, which may be substituted; an alkylene group having 2 to 20 carbon atoms and having an oxygen atom due to an ether bond and / or an ester bond in its structure, which may be substituted; and a divalent aromatic group having 6 to 11 carbon atoms, which may be substituted. Among these, alkylene groups having 2 to 6 carbon atoms, such as an ethylene group, an n-propylene group, an isopropylene group, and a butylene group, and alkylene groups having 2 to 9 carbon atoms and having an oxygen atom due to an ether bond in its structure, such as an oxyethylene group, an oxy-n-propylene group, an oxyisopropylene group, and an oxybutylene group, are preferred. Furthermore, from the viewpoint of further reducing the viscosity of the composition and further improving the curability of the composition, R 2 is an alkylene group having 2 to 9 carbon atoms and an oxygen atom by an ether bond in the structure, such as an oxyethylene group, an oxy-n-propylene group, an oxyisopropylene group, or an oxybutylene group, and more preferably has a glycol ether chain.

[0051] In the above formula (1), R 3 Suitable monovalent organic residues having 1 to 11 carbon atoms and represented by the formula (I) are 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. Among these, alkyl groups having 1 to 2 carbon atoms, such as methyl or ethyl groups, and aromatic groups having 6 to 8 carbon atoms, such as phenyl and benzyl groups, are preferably used.

[0052] When each of the above organic residues is a group that may be substituted, the substituent is divided into a group containing carbon atoms and a group not containing carbon atoms. First, when the above substituent is a group containing carbon atoms, the carbon atom is counted in the number of carbon atoms of the organic residue. Examples of the group containing carbon atoms include, but are not limited to, a carboxyl group and an alkoxy group. Next, examples of the group not containing carbon atoms include, but are not limited to, a hydroxyl group and a halo group.

[0053] Specific examples of the compound of formula (1) include, but are not limited to, 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, 1,1-dimethyl-2-vinyloxyethyl (meth)acrylate, ) 3-vinyloxybutyl 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-vinyloxymethylphenyl (meth)acrylate Methyl, o-vinyloxymethylphenylmethyl (meth)acrylate, 2-(2-vinyloxyethoxy)ethyl (meth)acrylate, 2-(2-vinyloxyethoxy)ethyl acrylate, 2-(vinyloxyisopropoxy)ethyl (meth)acrylate, 2-(vinyloxyethoxy)propyl (meth)acrylate, 2-(vinyloxyethoxy)isopropyl (meth)acrylate, 2-(vinyloxyisopropoxy)propyl (meth)acrylate, 2-(vinyloxyisopropoxy)isopropyl (meth)acrylate, 2-(vinyloxyethoxy)isopropyl (meth)acrylate, 2-(vinyloxyethoxy)ethyl (meth)acrylate (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-(vinyloxyisopropoxyisopropoxy)propyl,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-(vinyloxyethoxyethoxyethoxyethoxy)ethyl (meth)acrylate Examples of suitable acrylates include ethyl (meth)acrylate, 2-(isopropenoxyethoxy)ethyl (meth)acrylate, 2-(isopropenoxyethoxyethoxy)ethyl (meth)acrylate, 2-(isopropenoxyethoxyethoxy)ethyl (meth)acrylate, 2-(isopropenoxyethoxyethoxyethoxy)ethyl (meth)acrylate, polyethylene glycol monovinyl ether (meth)acrylate, and polypropylene glycol monovinyl ether (meth)acrylate. Among these specific examples, 2-(2-vinyloxyethoxy)ethyl acrylate is particularly preferred in that it is easy to balance the curability and viscosity of the composition. In this embodiment, 2-(2-vinyloxyethoxy)ethyl acrylate is also referred to as VEEA.

[0054] The content of the vinyl ether group-containing (meth)acrylate relative to the total amount of the composition is preferably 5 to 50% by mass, more preferably 10 to 50% by mass, even more preferably 15 to 45% by mass, and particularly preferably 20 to 40% by mass. When the content of the vinyl ether group-containing (meth)acrylate relative to the total amount of the composition is 5% by mass or more, curability tends to be further improved, the viscosity of the composition tends to be reduced, and discharge stability tends to be further improved. Furthermore, when the content of the vinyl ether group-containing (meth)acrylate relative to the total amount of the composition is 50% by mass or less, adhesion of the coating film tends to be further improved.

[0055] 1.1.4.2 Multifunctional (meth)acrylates Use of a polyfunctional (meth)acrylate tends to further improve curability. The polyfunctional (meth)acrylate is not particularly limited, and examples thereof include dipropylene glycol di(meth)acrylate (DPGDA), diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, dipropylene glycol dimethacrylate, tripropylene glycol di(meth)acrylate (TPGDA), polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate (NPGDA), propoxylated (2) neopentyl glycol di(meth)acrylate (NPG(2PO)DA), dimethylol-tricyclodecane di(meth)acrylate, and EO (ethylene oxide) derivatives of bisphenol A. Examples of the hydroxyl group-modified (meth)acrylate include bifunctional (meth)acrylates such as hydroxyl group-modified di(meth)acrylate of bisphenol A, hydroxyl group-modified di(meth)acrylate of bisphenol A, hydroxyl group-modified di(meth)acrylate of hydroxyl group, dipentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, glycerin propoxy tri(meth)acrylate, caprolactone-modified trimethylolpropane tri(meth)acrylate, pentaerythritol ethoxy tetra(meth)acrylate, and caprolactam-modified dipentaerythritol hexa(meth)acrylate. Among these, tripropylene glycol di(meth)acrylate (TPGDA) and propoxylated (2) neopentyl glycol di(meth)acrylate (NPG(2PO)DA) are preferred.

[0056] The content of the polyfunctional (meth)acrylate relative to the total amount of the composition is preferably 2 to 20 mass%, more preferably 2 to 15 mass%, and even more preferably 2 to 10 mass%. When the content of the polyfunctional (meth)acrylate relative to the total amount of the composition is within the above range, curability tends to be further improved.

[0057] Oligomers The oligomer of this embodiment refers to a polymer having one or more polymerizable functional groups, which is a polymerizable compound as a constituent component. The polymerizable compound referred to here is not limited to the monofunctional monomer and polyfunctional monomer described above. In this embodiment, an oligomer is defined as a compound having a molecular weight of 1000 or more, and a monomer is defined as a compound having a molecular weight of 1000 or less.

[0058] Such oligomers are not particularly limited, but examples thereof include urethane acrylate oligomers in which the repeating unit is a urethane, polyester acrylate oligomers in which the repeating unit is an ester, and epoxy acrylate oligomers in which the repeating unit is an epoxy.

[0059] Among these, urethane acrylate oligomers are preferred, aliphatic urethane acrylate oligomers and aromatic urethane acrylate oligomers are more preferred, and aliphatic urethane acrylate oligomers are even more preferred. Furthermore, the urethane acrylate oligomer is preferably a tetrafunctional or lower urethane acrylate oligomer, and more preferably a difunctional urethane acrylate oligomer. By using such an oligomer, the viscosity tends to be further reduced, and curability and adhesion tend to be further improved.

[0060] The content of the oligomer is preferably 1 to 15 mass %, more preferably 1 to 10 mass %, and even more preferably 2 to 7 mass %, relative to the total amount of the composition. When the content of the oligomer relative to the total amount of the composition is within the above range, the viscosity tends to be further reduced, and the curability and adhesion tend to be further improved.

[0061] 1.2. Photoinitiators The photopolymerization initiator is not particularly limited as long as it generates active species upon irradiation with radiation, and examples thereof include known photopolymerization initiators such as acylphosphine oxide-based photopolymerization initiators, alkylphenone-based polymerization initiators, titanocene-based polymerization initiators, and thioxanthone-based photopolymerization initiators. Among these, acylphosphine oxide-based photopolymerization initiators and thioxanthone-based photopolymerization initiators are preferred, with acylphosphine oxide-based photopolymerization initiators being more preferred. Use of such photopolymerization initiators tends to further improve the curability of the composition, particularly the curability in a curing process using UV-LED light. The photopolymerization initiators may be used alone or in combination of two or more.

[0062] The content of the photopolymerization initiator is preferably 3 to 17 mass %, more preferably 5 to 15 mass %, and even more preferably 7 to 12 mass %, relative to the total amount of the composition. When the content of the photopolymerization initiator is within the above range, the curability of the composition and the solubility of the photopolymerization initiator tend to be further improved.

[0063] 1.2.1. Acylphosphine oxide photoinitiators The acylphosphine oxide photopolymerization initiator is not particularly limited, but examples thereof include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide.

[0064] Commercially available examples of such acylphosphine oxide photopolymerization initiators include Omnirad 819 (bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide), IRGACURE 1800 (a mixture of bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide and 1-hydroxycyclohexylphenyl ketone in a mass ratio of 25:75), and SpeedCure TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide).

[0065] The content of the acylphosphine oxide photopolymerization initiator is preferably 3 to 15 mass %, more preferably 5 to 12 mass %, and even more preferably 7 to 10 mass %, relative to the total amount of the composition. When the content of the acylphosphine oxide photopolymerization initiator is within the above range, the curability of the composition and the solubility of the photopolymerization initiator tend to be further improved.

[0066] 1.2.2. Thioxanthone photoinitiators The thioxanthone-based photopolymerization initiator is not particularly limited, but examples thereof include thioxanthone, 2-methylthioxanthone, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, and 2-chlorothioxanthone.

[0067] Commercially available thioxanthone compounds include, for example, Speedcure DETX (2,4-diethylthioxanthone).

[0068] The content of the thioxanthone-based photopolymerization initiator is preferably 1 to 5 mass %, more preferably 1 to 3 mass %, relative to the total amount of the composition. When the content of the thioxanthone-based photopolymerization initiator is within the above range, the curability of the composition tends to be further improved.

[0069] 1.3. Optical brighteners The fluorescent brightening agent is not particularly limited, but can absorb light with a wavelength of about 300 to 450 nm and emit light with a wavelength of about 400 to 500 nm. Examples of such fluorescent brightening agents are not particularly limited, but include naphthalene benzoxazolyl derivatives, thiophene benzoxazolyl derivatives, stilbene benzoxazolyl derivatives, coumarin derivatives, styrene biphenyl derivatives, pyrazolone derivatives, stilbene derivatives, styryl derivatives of benzene and biphenyl, bis(benzazol-2-yl) derivatives, carbostyryl, naphthalimide, dibenzothiophene-5,5'-dioxide derivatives, pyrene derivatives, and pyridotriazole. These may be used alone or in combination of two or more.

[0070] Commercially available fluorescent whitening agents include, for example, Telalux OB and Telalux KCB.

[0071] The content of the fluorescent brightening agent is preferably 0.1 to 1 mass %, more preferably 0.1 to 0.5 mass %, relative to the total amount of the composition. When the content of the fluorescent brightening agent is within the above range, the curability of the composition tends to be further improved.

[0072] 1.4. Polymerization inhibitors Examples of the polymerization inhibitor include, but are not limited to, p-methoxyphenol, hydroquinone monomethyl ether (MEHQ), 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, hydroquinone, cresol, t-butylcatechol, 3,5-di-t-butyl-4-hydroxytoluene, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-butylphenol), and 4,4'-thiobis(3-methyl-6-t-butylphenol), hindered amine compounds, 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO), and derivatives of 2,2,6,6-tetramethylpiperidinyl-1-oxyl.

[0073] Among these, 2,2,6,6-tetramethylpiperidinyl-1-oxyl or a derivative thereof is preferred. The derivative of 2,2,6,6-tetramethylpiperidinyl-1-oxyl is not particularly limited, but examples thereof 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-chloroacetamido)-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-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl. Examples of the polymerization inhibitor include benzoate-2,2,6,6-tetramethylpiperidinyl-1-oxyl, 4-(2-iodoacetamido)-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. Among these, 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl is more preferred. By using such a polymerization inhibitor, the storage stability of the composition tends to be further improved.

[0074] The content of the polymerization inhibitor is preferably 0.1 to 0.5% by mass, more preferably 0.1 to 0.3% by mass, relative to the total amount of the composition. When the content of the polymerization inhibitor is within the above range, the storage stability of the composition tends to be further improved.

[0075] 1.5.Surfactants The surfactant is not particularly limited, but examples thereof include acetylene glycol surfactants, fluorine-based surfactants, and silicone-based surfactants.

[0076] The acetylene glycol surfactant is not particularly limited, but examples thereof include alkylene oxide adducts of 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 2,4,7,9-tetramethyl-5-decyne-4,7-diol, and alkylene oxide adducts of 2,4-dimethyl-5-decyne-4-ol and 2,4-dimethyl-5-decyne-4-ol.

[0077] The fluorine-based surfactant is not particularly limited, but examples thereof include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphates, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl betaines, and perfluoroalkyl amine oxide compounds.

[0078] Examples of silicone surfactants include polysiloxane compounds, polyester-modified silicones, and polyether-modified organosiloxanes. Examples of polyester-modified silicones include BYK-347, 348, BYK-UV3500, 3510, and 3530 (all manufactured by BYK Additives & Instruments). Examples of polyether-modified silicones include BYK-3570 (manufactured by BYK Additives & Instruments).

[0079] The content of the surfactant is preferably 0.1 to 1 mass %, more preferably 0.2 to 0.8 mass %, relative to the total mass of the composition. When the content of the surfactant is within the above range, the wettability of the composition tends to be further improved.

[0080] 1.6.Other Ingredients The radiation-curable ink jet composition according to this embodiment may further contain additives such as coloring materials such as pigments and dyes, and dispersants for pigments and the like, as needed.

[0081] 1.7. Method for producing the composition The production (preparation) of the radiation-curable ink jet composition is carried out by mixing the components contained in the composition and stirring the mixture to ensure a sufficient homogeneous mixture. In this embodiment, the preparation of the radiation-curable ink jet composition preferably includes a step of subjecting a mixture of a polymerization initiator and at least a portion of the monomers to at least one of ultrasonic treatment and heating treatment during the preparation process. This reduces the amount of dissolved oxygen in the prepared composition, resulting in a radiation-curable ink jet composition with excellent ejection stability and storage stability. The mixture may contain at least the components described above, and may further contain other components contained in the radiation-curable ink jet composition, or may contain all of the components contained in the radiation-curable ink jet composition. The monomer contained in the mixture may be at least a portion of the monomers contained in the radiation-curable ink jet composition.

[0082] 2. Inkjet method The inkjet method according to this embodiment includes a discharge step of discharging the radiation curable inkjet composition using a predetermined liquid ejecting head to adhere it to a recording medium, and an irradiation step of irradiating the radiation curable inkjet composition adhered to the recording medium with radiation.

[0083] 2.1.Discharge process In the ejection process, the heated composition is ejected from a liquid ejection head and adhered to a recording medium. More specifically, a pressure generating means is driven to eject the composition filled in the pressure generating chamber of the liquid ejection head from the nozzle. This ejection method is also called an ink jet method.

[0084] The liquid jet head 10 used in the ejection process includes a line head that performs recording by a line method and a serial head that performs recording by a serial method.

[0085] In the line method using a line head, for example, a liquid jet head having a width equal to or greater than the recording width of the recording medium is fixed to an inkjet device. The recording medium is then moved in the sub-scanning direction (the longitudinal direction of the recording medium, the transport direction), and ink droplets are ejected from the nozzles of the liquid jet head in conjunction with this movement to record an image on the recording medium.

[0086] In the serial method using a serial head, for example, a liquid ejection head is mounted on a carriage that can move in the width direction of the recording medium. The carriage is then moved in the main scanning direction (the lateral or width direction of the recording medium), and ink droplets are ejected from the nozzle openings of the head in conjunction with this movement, thereby recording an image on the recording medium.

[0087] 2.2.Irradiation process In the irradiation step, the radiation-curable inkjet composition attached to the recording medium is irradiated with radiation. When irradiated with radiation, a polymerization reaction of the monomers is initiated, curing the composition and forming a coating film. If a polymerization initiator is present, it generates active species (initiation species) such as radicals, acids, and bases, and the polymerization reaction of the monomers is promoted by the function of the initiation species. Furthermore, if a photosensitizer is present, it absorbs radiation and becomes excited, and upon contact with the polymerization initiator, it promotes the decomposition of the polymerization initiator, thereby achieving a more rapid curing reaction.

[0088] Examples of the radiation include ultraviolet light, infrared light, visible light, and X-rays. The radiation source is provided downstream of the liquid jet head and irradiates the composition with the radiation. The radiation source is not particularly limited, but examples thereof include ultraviolet light-emitting diodes. Use of such a radiation source can reduce the size and cost of the device. Because ultraviolet light-emitting diodes as an ultraviolet light source are small, they can be installed inside the inkjet device.

[0089] For example, ultraviolet light-emitting diodes can be attached to a carriage (both ends along the medium width direction and / or the medium transport direction side) on which a liquid jet head that ejects the radiation-curable inkjet composition is mounted. Furthermore, due to the composition of the radiation-curable inkjet composition described above, curing can be achieved at low energy and high speed. The irradiation energy is calculated by multiplying the irradiation time by the irradiation intensity. Therefore, the irradiation time can be shortened, and the printing speed can be increased. On the other hand, the irradiation intensity can also be reduced. This reduces the temperature rise of the printed material, which also leads to a reduction in the odor of the cured film.

[0090] 3. Inkjet device The inkjet device of this embodiment includes a liquid jet head having a nozzle for ejecting a composition and a pressure chamber to which the composition is supplied, a radiation source for irradiating the composition with radiation, and uses the radiation-curable inkjet composition as the composition. The inkjet device may also include a heating unit for heating the composition within the liquid jet head, within the ink flow path, or on a recording medium.

[0091] As an example of an inkjet device, a perspective view of a serial printer is shown in Fig. 1. As shown in Fig. 1, the serial printer 20 includes a conveying unit 220 and a recording unit 230. The conveying unit 220 conveys the recording medium F fed to the serial printer to the recording unit 230, and ejects the recording medium after recording outside the serial printer. Specifically, the conveying unit 220 has feed rollers and conveys the fed recording medium F in the sub-scanning direction T1.

[0092] The recording unit 230 also includes an inkjet head 231 that ejects a composition onto the recording medium F sent from the conveying unit 220, a radiation source 232 that irradiates the adhered composition with radiation, a carriage 234 that carries these, and a carriage moving mechanism 235 that moves the carriage 234 in the main scanning directions S1 and S2 of the recording medium F.

[0093] In the case of a serial printer, an inkjet head 131 having a length smaller than the width of the recording medium is provided, and the head moves to perform recording in multiple passes (multi-pass). In addition, in a serial printer, the head 231 and radiation source 232 are mounted on a carriage 234 that moves in a predetermined direction, and the head moves in conjunction with the movement of the carriage, thereby ejecting the composition onto the recording medium. In this way, recording is performed in two or more passes (multi-pass). A pass is also called a main scan. A sub-scan is performed to transport the recording medium between passes. In other words, main scans and sub-scans are performed alternately.

[0094] Although FIG. 1 shows an embodiment in which the radiation source is mounted on a carriage, the present invention is not limited to this, and the radiation source may be one that is not mounted on a carriage.

[0095] Furthermore, the inkjet device of this embodiment is not limited to the serial printer, but may be the line printer described above.

[0096] 4. Records The recorded matter of this embodiment is obtained by adhering the radiation-curable inkjet composition to a recording medium and curing it. The composition has good stretchability and adhesion, which can prevent cracking or chipping of the coating film when post-processing such as cutting or bending is performed. Therefore, the recorded matter of this embodiment can be suitably used for signage and the like.

[0097] The material of the recording medium is not particularly limited, but examples include plastics such as 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, as well as plastics with treated surfaces, glass, paper, metal, and wood. [Example]

[0098] The present invention will be described in more detail below using examples and comparative examples, but the present invention is not limited to the following examples.

[0099] 1. Preparation of Inkjet Composition First, the pigment, dispersant, and VEEA were weighed and placed in a tank for pigment dispersion, and a ceramic bead mill with a diameter of 1 mm was placed in the tank and stirred to obtain a pigment dispersion in which the pigment was dispersed in the monomer.

[0100] Next, the remaining monomers, polymerization initiator, and polymerization inhibitor were placed in a stainless steel mixing tank so as to obtain the compositions shown in Tables 1 and 2, and the mixture was mixed and stirred to completely dissolve. The pigment dispersion obtained above was then added, and the mixture was further mixed and stirred at room temperature for one hour. The resulting mixture was then filtered through a 5 μm membrane filter to obtain the radiation-curable inkjet composition for each example. The numerical values ​​for each component shown in each example in the tables represent mass % unless otherwise specified. Furthermore, when each of the inkjet compositions shown in Tables 1 and 2 was recorded on a polycarbonate film using an inkjet printer such as the one shown in FIG. 1, it was confirmed that good recording was achieved.

[0101] [Table 1]

[0102] [Table 2]

[0103] <Pigments> Pigment Blue 15:3 (PB15:3) <Dispersant> Solsperse 36000 (Lubrizol polymer dispersant) <Vinylmethyloxazolidinone> VMOX (vinylmethyloxazolidinone, manufactured by BASF) <Monofunctional (meth)acrylate monomer> IBXA (Osaka Organic Chemical Industry, Ltd., isobornyl acrylate) TMCHA (product name "SR420", manufactured by Sartomer Corporation, 3,3,5-trimethylcyclohexane acrylate) CTFA (product name "Viscoat #200", manufactured by Osaka Organic Chemical Industry Ltd., cyclic trimethylolpropane formal acrylate) THFA (trade name "Viscoat #150", manufactured by Osaka Organic Chemical Industry Ltd., tetrahydrofurfuryl acrylate) MEDOL-10 (trade name "MEDOL-10", manufactured by Osaka Organic Chemical Industry Ltd., (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate) FA-511AS (Hitachi Chemical Co., Ltd., dicyclopentenyl acrylate) FA-512AS (Hitachi Chemical Co., Ltd., dicyclopentenyloxyethyl acrylate) FA-513AS (Hitachi Chemical Co., Ltd., dicyclopentanyl acrylate) <Polyfunctional Monomer> VEEA (2-(2-vinyloxyethoxy)ethyl acrylate, manufactured by Nippon Shokubai Co., Ltd.) NPG(2PO)DA (trade name "SR9003", Sartomer, propoxylated (2) neopentyl glycol diacrylate) TPGDA (trade name "Viscoat #310HP", manufactured by Osaka Organic Chemical Industry Ltd., tripropylene glycol diacrylate) <Oligomer> EC6101 (product name "ETERCURE6101", manufactured by Choko Materials Industry Co., Ltd., aliphatic urethane acrylate oligomer) CN9893 (Sartomer Corporation, aliphatic urethane acrylate oligomer) <Photopolymerization initiator> Omnirad 819 (Resins BV, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide) SpeedCure TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide, manufactured by Lambson) Speedcure DETX (2,4-diethylthioxanthen-9-one, manufactured by Lambson) <Fluorescent whitening agents> TELALUX OB (Clariant Japan, 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene) <Surfactant> BYK-UV3500 (BYK Additives & Instruments, polyether-modified polydimethylsiloxane with acryloyl groups) <Polymerization inhibitor> LA-7RD (product name "ADK STAB LA - 7RD, ADEKA Corporation, 4-hydroxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl) MEHQ (product name "p-methoxyphenol", manufactured by Kanto Chemical Co., Ltd., hydroquinone monomethyl ether)

[0104] 2. Evaluation Method 2.1. Viscosity evaluation Using a rotational viscometer (product name "DVM-E type rotational viscometer (manufactured by Tokyo Keiki Co., Ltd.)"), the viscosity of each radiation-curable inkjet composition was measured in an environment of 20°C using a DVM-E type cone with a cone angle of 1°34' and a cone radius of 2.4 cm, at a rotation speed of 10 rpm. The evaluation criteria were as follows: (Evaluation criteria) AA: Viscosity of 15 mPa·s or less A: Viscosity over 15 mPa·s and 20 mPa·s or less B: Viscosity over 20 mPa·s and 25 mPa·s or less C: Viscosity over 25 mPa·s and 30 mPa·s or less D: Viscosity exceeds 30 mPa·s

[0105] 2.2. Evaluation of curability A cotton swab weighted tackiness evaluation was performed. Specifically, each radiation-curable inkjet composition was applied to a polyvinyl chloride medium using a bar coater so that the inkjet composition was applied to a thickness of 10 μm, and then irradiated with ultraviolet light at a predetermined irradiation intensity and a speed of 0.04 sec / cm. An LED with a peak wavelength of 395 nm was used as the light source. The coating surface was then rubbed with a cotton swab, and the curability was evaluated based on the irradiation intensity at which the cotton swab did not become colored. The evaluation criteria were as follows: (Evaluation criteria) AA: Irradiation intensity is 0.5W / cm 2 less than A: Irradiation intensity is 0.5W / cm 2 More than 2.5W / cm 2 less than B: Irradiation intensity is 2.5W / cm 2 End

[0106] 2.3.Evaluation of adhesion A cured coating film was prepared on a polyvinyl chloride film in the same manner as in the evaluation of stretchability described above, and the resulting coating film was evaluated by a cross-cut test in accordance with JIS K5600-5-6.

[0107] More specifically, a cutter blade was placed perpendicular to the coating film, and squares were cut with 1 mm spacing between each square to create a 10 x 10 grid. A piece of transparent adhesive tape (25 mm wide) approximately 75 mm long was attached to the grid, and the tape was rubbed thoroughly with a finger so that the cured film was visible through it. Next, within 5 minutes of application, the tape was firmly peeled off the cured film at an angle close to 60° in 0.5 to 1.0 seconds, and the condition of the grid was visually observed. The evaluation criteria are as follows: (Evaluation criteria) AA: No peeling of the cured film was observed on the lattice. A: Peeling of the cured film was observed in less than 50% of the lattice. B: Peeling of the cured film was observed in more than 50% of the lattice.

[0108] 2.4. Evaluation of abrasion resistance The cured coating film prepared in the above curability evaluation was subjected to a micro-scratch test in accordance with JIS R3255. For the measurement, an ultra-thin film scratch tester (CSR-5000, manufactured by Nanotec Co., Ltd.) was used to measure the load capacity as a measure of abrasion resistance. Micro-scratching was performed while applying a load, and the load capacity was determined as the load when the stylus reached the media surface. The higher the load capacity, the better the abrasion resistance. Measurements were performed with a stylus diameter of 15 μm, amplitude of 100 μm, and scratch speed of 10 μm / sec. The evaluation criteria are shown below. (Evaluation criteria) AA: 30 mN / cm 2 End A: 25 mN / cm 2 More than 30mN / cm 2 less than B: 20 ​​mN / cm 2 More than 25mN / cm 2 less than C: 20mN / cm 2 less than

[0109] 2.5. Evaluation of stretchability Each radiation-curable inkjet composition was applied to a polyvinyl chloride film (JT5829R, manufactured by MACtac) using a bar coater to a thickness of 10 μm. Then, a metal halide lamp (manufactured by iGraphics) was used to apply the inkjet composition to the film at 400 mJ / cm. 2 The coating was cured with an energy of 100 sq. m to form a coating film. The release paper was peeled off from the PVC film on which the coating was formed, and test specimens were cut into strips measuring 1 cm wide and 8 cm long. The elongation percentage as an indicator of extensibility was measured for each test specimen using a tensile tester (TENSILON, manufactured by ORIENTEC). The elongation percentage was the value at which a crack occurred when pulled at 5 mm / min. The value was calculated using {(length at crack - length before stretching) / length before stretching x 100}. The evaluation criteria are shown below. (Evaluation criteria) AA: 300% or more A: 250% or more but less than 300% B: 200% or more but less than 250% C: Less than 200%

[0110] 2.6. Storage stability Each radiation-curable inkjet composition was filled into a glass bottle and stored at 60°C for 14 days. The viscosity before and after storage was estimated to confirm the change in viscosity before and after storage. The evaluation criteria are as follows: (Evaluation criteria) A: Viscosity increase rate is less than 5% B: Viscosity increase rate is 5% or more and less than 15% C: Viscosity increase rate is 15% or more

[0111] 3. Evaluation Results The compositions and evaluation results of the radiation-curable inkjet compositions used in each example are shown in Tables 1 and 2. Tables 1 and 2 show that the radiation-curable inkjet compositions of Examples 1 to 35, which contain a monofunctional (meth)acrylate monomer and vinylmethyloxazolidinone, have low viscosity and excellent stretchability, as well as excellent curability, adhesion, abrasion resistance, and storage stability.

[0112] Specifically, comparing each Example with Comparative Example 1, it is found that the inclusion of vinylmethyloxazolidinone reduces viscosity and further improves stretchability, curability, adhesion, and abrasion resistance. Also, comparing each Example with Comparative Example 2, it is found that the inclusion of a monofunctional (meth)acrylate monomer further improves stretchability.

[0113] Furthermore, by comparing Example 35 with other Examples, it can be seen that the use of 2,2,6,6-tetramethylpiperidinyl-1-oxyl or its derivative as a polymerization inhibitor further improves the storage stability in a system containing a monofunctional (meth)acrylate monomer and vinylmethyloxazolidinone. [Explanation of symbols]

[0114] 20... serial printer, 220... conveying section, 230... recording section, 231... inkjet head, 232, 233... light source, 234... carriage, 235... carriage moving mechanism, F... recording medium, S1, S2... main scanning direction, T1... sub-scanning direction

Claims

1. a monofunctional (meth)acrylate monomer; vinylmethyloxazolidinone, a urethane acrylate oligomer, the monofunctional (meth)acrylate monomer includes at least one of a monofunctional (meth)acrylate monomer having a cyclic ether structure and a monofunctional (meth)acrylate monomer having a crosslinked condensed ring structure; the content of the urethane acrylate oligomer is 1 to 10% by mass relative to the total amount of the radiation-curable inkjet composition; Radiation-curable inkjet compositions.

2. a monofunctional (meth)acrylate monomer; vinylmethyloxazolidinone, a polyfunctional (meth)acrylate monomer; a urethane acrylate oligomer, The polyfunctional (meth)acrylate monomer includes at least one of tripropylene glycol di(meth)acrylate and propoxylated (2) neopentyl glycol di(meth)acrylate, the content of the urethane acrylate oligomer is 1 to 10% by mass relative to the total amount of the radiation-curable inkjet composition; Radiation-curable inkjet compositions.

3. Contains optical brighteners, The radiation-curable ink jet composition according to claim 1 or 2.

4. The optical brightener comprises 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene), The radiation-curable ink jet composition according to claim 3 .

5. the content of the vinylmethyloxazolidinone is 5 to 40% by mass relative to the total amount of the radiation-curable inkjet composition; The radiation-curable ink jet composition according to any one of claims 1 to 4.

6. the content of the monofunctional (meth)acrylate monomer is 10 to 50% by mass relative to the total amount of the radiation-curable inkjet composition; The radiation-curable ink jet composition according to any one of claims 1 to 5.

7. The vinyl ether group-containing (meth)acrylate is represented by the following general formula (1): H 2 C=CR 1 -CO-OR 2 -O-CH=CH-R 3 ・・・ (1) (In the formula, R 1 is a hydrogen atom or a methyl group, and 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. The radiation-curable ink jet composition according to any one of claims 1 to 6.

8. the content of the vinyl ether group-containing (meth)acrylate is 10 to 50% by mass relative to the total amount of the radiation-curable inkjet composition; The radiation-curable ink jet composition according to claim 7.

9. the monofunctional (meth)acrylate monomer contains at least one of an alicyclic monofunctional (meth)acrylate, a monofunctional (meth)acrylate having a cyclic ether structure, or a monofunctional (meth)acrylate having a crosslinked condensed ring structure; The radiation-curable ink jet composition according to claim 2 .

10. The monofunctional (meth)acrylate monomer further includes an alicyclic monofunctional (meth)acrylate. The radiation-curable ink jet composition according to claim 1 .

11. Contains a polyfunctional (meth)acrylate monomer, the content of the polyfunctional (meth)acrylate monomer is 2 to 20% by mass relative to the total amount of the radiation-curable inkjet composition; The radiation-curable ink jet composition according to any one of claims 1 to 9.

12. The polymerization inhibitor contains 2,2,6,6-tetramethylpiperidinyl-1-oxyl or a derivative thereof. The radiation-curable ink jet composition according to any one of claims 1 to 11.

13. The photopolymerization initiator includes an acylphosphine oxide initiator. The radiation-curable ink jet composition according to any one of claims 1 to 12.

14. a discharge step of discharging the radiation curable ink jet composition according to any one of claims 1 to 13 from a liquid jet head and depositing it onto a recording medium; an irradiation step of irradiating the radiation-curable inkjet composition adhered to the recording medium with radiation, Inkjet method.

Images