Radiation-curable inkjet ink composition

Abstract

To provide a radiation curable inkjet composition having low viscosity and excellent abrasion resistance.SOLUTION: A radiation curable inkjet composition according to an embodiment of the invention contains a polymerizable compound. The polymerizable compound contains at least one of glycerin diacrylate and glycerin triacrylate. The combined content of the glycerin diacrylate and the glycerin triacrylate is 20 mass% or more relative to the total amount of the inkjet composition.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Inkjet recording methods, which enable the recording of high-resolution images with relatively simple equipment, are undergoing rapid development in various fields. Within this context, various studies are being conducted on the abrasion resistance of inkjet compositions that harden when irradiated with radiation. For example, Patent Document 1 discloses an ultraviolet-curable inkjet composition containing dipropylene glycol diacrylate as a polyfunctional polymerizable compound. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2012-207084 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, while polyfunctional polymerizable compounds readily provide abrasion resistance to coating films, they tend to have high viscosity, and when included in large quantities, the increased viscosity can easily reduce ejection stability. In other words, there is a need for a radiation-curable inkjet composition that suppresses viscosity increases and exhibits excellent abrasion resistance. [Means for solving the problem]

[0005] One aspect of the radiation-curable inkjet composition according to the present invention is: A radiation-curable inkjet composition containing a polymerizable compound, The polymerizable compound comprises at least one of glycerin diacrylate and glycerin triacrylate. The inkjet composition contains 20% by mass or more of the glycerin diacrylate and the glycerin triacrylate in total, relative to the total amount of the inkjet composition. [Modes for carrying out the invention]

[0006] Embodiments of the present invention will be described below. The embodiments described below are examples of the present invention. The present invention is not limited in any way to the embodiments described below, and includes various modifications that can be implemented without changing the gist of the present invention. Not all of the configurations described below are necessarily essential to the present invention.

[0007] 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.

[0008] 1. Radiation-curable inkjet composition A radiation-curable inkjet composition according to one embodiment of the present invention is a radiation-curable inkjet composition comprising a polymerizable compound, wherein the polymerizable compound comprises at least one of glycerin diacrylate and glycerin triacrylate, and the total amount of glycerin diacrylate and glycerin triacrylate is 20% by mass or more of the total amount of the inkjet composition.

[0009] Glycerin diacrylate and glycerin triacrylate are polyfunctional polymerizable compounds that can effectively improve abrasion resistance while having relatively low viscosity. Therefore, even when these compounds are present in relatively high concentrations, it is possible to suppress the increase in viscosity of the composition and obtain a radiation-curable inkjet composition with excellent abrasion resistance. Furthermore, good ejection stability, curability, and adhesion tend to be achieved.

[0010] Note that the "radiation-curable inkjet composition" according to this embodiment is a composition that is ejected from an inkjet head by an inkjet method and used. Hereinafter, as an embodiment of the radiation-curable inkjet composition, a radiation-curable ink composition (hereinafter, also referred to as "ink composition" or "ink") will be described. However, the composition according to this embodiment may be a composition other than the ink composition, for example, a composition used for 3D printing.

[0011] In addition, the radiation-curable inkjet composition according to this embodiment cures by irradiating radiation. Examples of the radiation include ultraviolet rays, electron beams, infrared rays, visible light rays, X-rays, active energy rays, etc. Ultraviolet rays are preferable as the radiation in terms of the easy availability and wide use of the radiation source, and the easy availability and wide use of materials suitable for curing by ultraviolet radiation.

[0012] Hereinafter, in the radiation-curable inkjet composition (hereinafter, also simply referred to as "composition") according to this embodiment, the components, physical properties, and manufacturing method that may be included will be described.

[0013] 1.1 Polymerizable compound The radiation-curable inkjet composition according to this embodiment contains a polymerizable compound. The polymerizable compound is a general term for compounds that cure by irradiating radiation. The polymerizable compound includes a monofunctional monomer having one polymerizable functional group and a polyfunctional monomer having a plurality of polymerizable functional groups, and may include an oligomer having one or more polymerizable functional groups as needed. Each polymerizable compound may be used alone or in combination of two or more.

[0014] 1.1.1 Glycerol diacrylate and glycerol triacrylate The polymerizable compound according to this embodiment includes at least one of glycerol diacrylate and glycerol triacrylate.

[0015] Examples of commercially available products of such compounds include, for example, Aronix (registered trademark) M-920 (glyceryl di / triacrylate), M-930 (glyceryl triacrylate), etc. (both are product names manufactured by Toagosei Co., Ltd.).

[0016] The radiation-curable inkjet composition according to this embodiment contains a total of 20% by mass or more, preferably 25% by mass or more, more preferably 30% by mass or more, still more preferably 35% by mass or more, and particularly preferably 40% by mass or more of glycerol diacrylate and glycerol triacrylate based on the total amount of the inkjet composition. When the total amount is 20% by mass or more, an increase in the viscosity of the composition can be suppressed, and the composition can have excellent abrasion resistance.

[0017] The upper limit is not particularly limited, but it is preferable to contain a total of 70% by mass or less, more preferably 65% by mass or less, still more preferably 60% by mass or less, and particularly preferably 55% by mass or less of glycerol diacrylate and glycerol triacrylate based on the total amount of the inkjet composition. When the total amount is 70% by mass or less, an increase in the viscosity of the composition can be more easily suppressed, and the composition tends to have a preferable viscosity as an inkjet composition.

[0018] In addition, when the polymerizable compound contains either glycerol diacrylate or glycerol triacrylate, it is also preferable that the content of glycerol diacrylate or glycerol triacrylate be the above content.

[0019] 1.1.2 Monofunctional Monomers The polymerizable compound may contain monofunctional monomers. While not particularly limited, examples of monofunctional monomers include aromatic group-containing monofunctional monomers, nitrogen-containing monofunctional monomers, alicyclic group-containing monofunctional monomers, monofunctional monomers containing cyclic ether structures, urethane acrylates, aliphatic group-containing monofunctional monomers, and hydroxyl group-containing monofunctional monomers. Other monofunctional monomers may also be included as needed. While not particularly limited, conventionally known monofunctional monomers having polymerizable functional groups, particularly those with unsaturated double bonds between carbon atoms, can be used.

[0020] The monofunctional monomer content is preferably less than 60% by mass, more preferably less than 35% by mass, even more preferably less than 30% by mass, even more preferably less than 25% by mass, particularly preferably less than 20% by mass, and most particularly preferably less than 15% by mass, relative to the total amount of polymerizable compounds. When the monofunctional monomer content is particularly less than 35% by mass relative to the total amount of polymerizable compounds, the viscosity increase of the composition tends to be suppressed and the abrasion resistance can be improved. Furthermore, there is no particular lower limit to the monofunctional monomer content, but it is preferably 7% by mass or more, and more preferably 10% by mass or more, relative to the total amount of polymerizable compounds.

[0021] From a similar viewpoint, the content of monofunctional monomers is preferably 45% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less, particularly preferably 20% by mass or less, and most particularly preferably 15% by mass or less, based on the total amount of the composition. There is no particular lower limit to the content of monofunctional monomers, but it is preferably 6% by mass or more, and more preferably 11% by mass or more, based on the total amount of the composition.

[0022] The following are examples of monofunctional monomers, but the monofunctional monomers in this embodiment are not limited to those listed below.

[0023] [Aromatic group-containing monofunctional monomers] The aromatic group-containing monofunctional monomer is not particularly limited as long as it has an aromatic group, 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.

[0024] Among these, phenoxyethyl (meth)acrylate and benzyl (meth)acrylate are preferred, phenoxyethyl (meth)acrylate is more preferred, and phenoxyethyl acrylate (PEA) is even more preferred. By using such aromatic group-containing monomers, the solubility of polymerization initiators that are solid at room temperature tends to be further improved, and the curability of the composition can be improved. In particular, the solubility tends to be good when using acyl phosphine oxide-based polymerization initiators or thioxanthone-based polymerization initiators that are solid at room temperature. Furthermore, by using phenoxyethyl (meth)acrylate, odor tends to be further reduced.

[0025] If the composition contains an aromatic group-containing monofunctional monomer, its content is preferably 1 to 30% by mass, more preferably 3 to 20% by mass, and even more preferably 5 to 10% by mass, relative to the total amount of the composition. When the content of the aromatic group-containing monofunctional monomer relative to the total amount of the composition is within the above range, the viscosity of the composition tends to decrease further, and the abrasion resistance of the coating film tends to improve further.

[0026] [Nitrogen-containing monofunctional monomers] The nitrogen-containing monofunctional monomer is not particularly limited, but examples include nitrogen-containing monofunctional vinyl monomers such as vinylmethyloxazolidinone (VMOX), N-vinylcaprolactam, N-vinylformamide, N-vinylcarbazole, N-vinylacetamide, and N-vinylpyrrolidone; nitrogen-containing monofunctional acrylate monomers such as acryloylmorpholin; 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. Nitrogen-containing monofunctional vinyl monomers are preferred, and vinylmethyloxazolidinone (VMOX) is particularly preferred. Using such nitrogen-containing monofunctional monomers tends to further improve the abrasion resistance of the coating film.

[0027] If nitrogen-containing monofunctional monomers are included, their content is preferably 5 to 30% by mass, and more preferably 10 to 20% by mass, relative to the total amount of the composition. Having the nitrogen-containing monofunctional monomer content within the above range may further improve the abrasion resistance of the coating film.

[0028] [Monofunctional monomers containing alicyclic groups] The 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 tert-butylcyclohexanol acrylate and 2-(meth)acrylic acid-1,4-dioxaspiro[4,5]decy-2-ylmethyl; monomers having unsaturated polycyclic hydrocarbon groups such as dicyclopentenyl acrylate and dicyclopentenyloxyethyl acrylate; and monomers having saturated polycyclic hydrocarbon groups such as dicyclopentanyl acrylate and isobornyl acrylate (IBXA). Monomers having saturated polycyclic hydrocarbon groups are preferred, and isobornyl acrylate (IBXA) is particularly preferred. By using such monofunctional monomers containing alicyclic groups, it is easier to adjust the glass transition temperature of the coating film to a low level, and it is possible to improve the stretchability of the coating film and enhance adhesion and abrasion resistance.

[0029] The content of the alicyclic group-containing monofunctional monomer is preferably 5 to 50% by mass, more preferably 5 to 30% by mass, and even more preferably 10 to 20% by mass, based on the total amount of the composition. When the content of the alicyclic group-containing monofunctional monomer is within the above range, the abrasion resistance of the coating film tends to improve further.

[0030] [Monofunctional monomers containing cyclic ether structures] Monofunctional monomers containing a cyclic ether structure are not particularly limited as long as they contain a cyclic ether skeleton such as tetrahydrofuran or tetrahydropyran. Examples include cyclic trimethylolpropane formal acrylate (CTFA), cyclic trimethylolpropane formal methacrylate, tetrahydrofurfuryl acrylate (THFA), and tetrahydrofurfuryl methacrylate. Among these, cyclic trimethylolpropane formal acrylate (CTFA) and tetrahydrofurfuryl acrylate (THFA) are preferred. When using such monofunctional monomers containing a cyclic ether structure, it is easier to adjust the glass transition temperature of the coating film to a low level, and the stretchability of the coating film tends to be increased, improving adhesion and abrasion resistance.

[0031] If the composition contains monofunctional monomers including a cyclic ether structure, the content is preferably 5 to 30% by mass, and more preferably 10 to 25% by mass, relative to the total amount of the composition. Having the content of monofunctional monomers including a cyclic ether structure within the above range may further improve the adhesion of the coating film.

[0032] [Urethane acrylate] The urethane acrylate is not particularly limited as long as it is a (meth)acrylic acid ester having a urethane bond. Examples include (methylcarbamoyloxy)ethyl (meth)acrylate, (ethylcarbamoyloxy)ethyl (meth)acrylate, (propylcarbamoyloxy)ethyl (meth)acrylate, (butylcarbamoyloxy)ethyl (meth)acrylate, (methylcarbamoyloxy)ethoxyethyl (meth)acrylate, (ethylcarbamoyloxy)ethoxyethyl (meth)acrylate, (propylcarbamoyloxy)ethoxyethyl (meth)acrylate, and (butylcarbamoyloxy)ethoxyethyl (meth)acrylate. Using such urethane acrylates tends to further reduce the viscosity of the composition and further improve the abrasion resistance of the resulting coating film.

[0033] If urethane acrylate is included, its content is preferably 0.5 to 7.5% by mass, more preferably 1.0 to 5.0% by mass, and even more preferably 2.0 to 4.0% by mass, relative to the total amount of the composition. When the urethane acrylate content relative to the composition is within the above range, the viscosity of the composition tends to decrease further, and the abrasion resistance of the resulting coating film tends to improve further.

[0034] [Aliphatic group-containing monofunctional monomer] There are no particular limitations on the aliphatic group-containing monofunctional monomer, but examples include monomers represented by the following general formula (II). H2C=CR 4 -CO-OR 5 ... (II) (In formula (II), R4 R represents a hydrogen atom or a methyl group. 5 (This represents a linear or branched aliphatic group with 4 to 20 carbon atoms.)

[0035] Such aliphatic group-containing monofunctional monomers are not particularly limited as long as they are saturated or unsaturated, linear or branched monomers that do not have a carbon ring. Examples include isoamyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, isononyl (meth)acrylate, isomiristyl (meth)acrylate, isostearyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, butoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate. Among these, saturated linear or branched aliphatic group-containing monofunctional monomers are preferred, and lauryl (meth)acrylate and isononyl (meth)acrylate are more preferred. By using such aliphatic group-containing monofunctional monomers, the viscosity of the composition tends to decrease further, and the adhesion of the coating film tends to improve further.

[0036] If the composition contains an aliphatic group-containing monofunctional monomer, its content is preferably 1.0 to 17% by mass, more preferably 3.0 to 15% by mass, and even more preferably 5.0 to 12% by mass, relative to the total amount of the composition. When the content of the aliphatic group-containing monofunctional monomer relative to the composition is within the above range, the viscosity of the composition tends to decrease further, and the adhesion of the coating film tends to improve further.

[0037] [Hydroxy 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 acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, ethylene glycol monovinyl ether, diethylene glycol monovinyl ether, and 2-(meth)acryloyloxy-2-hydroxypropyl phthalate. By using such hydroxyl group-containing monofunctional monomers, the viscosity of the composition tends to decrease further, and the adhesion of the coating film tends to improve further.

[0038] If a hydroxyl group-containing monofunctional monomer is included, its content is preferably 1.0 to 35% by mass, more preferably 3.0 to 25% by mass, and even more preferably 5.0 to 15% by mass, relative to the total amount of the composition. When the content of the hydroxyl group-containing monofunctional monomer relative to the composition is within the above range, the viscosity tends to decrease further, and the adhesion of the resulting coating film tends to improve further.

[0039] [Other monofunctional monomers] Other monofunctional monomers that may be used, in addition to those mentioned above, include, for example, unsaturated carboxylic acids such as (meth)acrylic acid, itaconic acid, crotonic acid, isocrotonic acid, and maleic acid; salts of the unsaturated carboxylic acids; esters, urethanes, amides, and anhydrides of unsaturated carboxylic acids; acrylonitrile, styrene, various unsaturated polyesters, unsaturated polyethers, and unsaturated polyamides.

[0040] The above monofunctional monomers may be used individually or in combination of two or more.

[0041] Among these, it is preferable that the polymerizable compound (monofunctional monomer) contains one or more selected from isobornyl acrylate (IBXA), cyclic trimethylolpropane formal acrylate (CTFA), and tetrahydrofurfuryl acrylate (THFA). Including such polymerizable compounds (monofunctional monomers) makes it easier to adjust the glass transition temperature of the coating film to a relatively high level, which tends to improve the stretchability of the coating film and further enhance abrasion resistance.

[0042] 1.1.3 Polyfunctional monomers The polymerizable compound may contain polyfunctional monomers other than the glycerin diacrylate and glycerin triacrylate described above. Such polyfunctional monomers are not particularly limited, but examples include vinyl group-containing (meth)acrylates, bifunctional (meth)acrylates, and trifunctional or more polyfunctional (meth)acrylates. However, the polyfunctional monomers are not limited to those described above.

[0043] The content of polyfunctional monomers other than glycerin diacrylate and glycerin triacrylate is preferably 5 to 50% by mass, and more preferably 10 to 40% by mass, based on the total amount of the composition. When the content is within this range, it may be possible to further suppress viscosity increase and improve abrasion resistance of the composition.

[0044] [Vinyl group-containing (meth)acrylate] The vinyl group-containing (meth)acrylate is not particularly limited, but examples include compounds represented by the following general formula (I). The vinyl group-containing (meth)acrylate represented by the following general formula (I) is a polyfunctional monomer that has relatively low viscosity and excellent curability. Therefore, by including such polymerizable compounds, it is possible to suppress the increase in viscosity of the composition while further improving abrasion resistance and curability. H2C=CR 1 -CO-OR 2 -O-CH=CH-R 3 ... (I) (In the formula, R 1 R is a hydrogen atom or a methyl group,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.)

[0045] In the general formula (I), R 2 Examples of the divalent organic residue having 2 to 20 carbon atoms represented by include linear, branched or cyclic alkylene groups having 2 to 20 carbon atoms which may be substituted, alkylene groups having 2 to 20 carbon atoms which may be substituted and have an oxygen atom due to an ether bond and / or an ester bond in the structure, and divalent aromatic groups 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 which have an oxygen atom due to an ether bond in the structure such as an oxyethylene group, an oxy n-propylene group, an oxyisopropylene group, and an oxybutylene group are preferable. Further, from the viewpoint of making the composition have a lower viscosity and further improving the abrasion resistance, curability, etc. of the composition, R 2 is more preferably a compound having a glycol ether chain which is an alkylene group having 2 to 9 carbon atoms having an oxygen atom due to an ether bond in the structure such as an oxyethylene group, an oxy n-propylene group, an oxyisopropylene group, and an oxybutylene group.)

[0046] In the general formula (I), R 3 Examples of the monovalent organic residue having 1 to 11 carbon atoms represented by include linear, branched or cyclic alkyl groups having 1 to 11 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 a methyl group or an ethyl group, and aromatic groups having 6 to 8 carbon atoms such as a phenyl group and a benzyl group are preferably used.)

[0047] If any of the above organic residues are groups that may be substituted, the substituents can be divided into groups containing carbon atoms and groups that do not contain carbon atoms. First, if the substituent is a group containing carbon atoms, that carbon atom is counted in the number of carbon atoms of the organic residue. Examples of groups containing carbon atoms include, but are not limited to, carboxyl groups and alkoxy groups. Next, examples of groups that do not contain carbon atoms include, but are not limited to, hydroxyl groups and halo groups.

[0048] Specific examples of compounds of the above general formula (I) 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 (meth)acrylate. , (meth)acrylate 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-vinyloxymethyl Phenylmethyl, o-vinyloxymethylphenylmethyl (meth)acrylate, 2-(2-vinyloxyethoxy)ethyl methacrylate, 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-(vinyloxy) Toxiethoxy)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-(vinyloxyethoxyethoxyethoxyethoxy) Examples include ethyl acrylate, 2-(isopropenoxyethoxy)ethyl (meth)acrylate, 2-(isopropenoxyethoxyethoxy)ethyl (meth)acrylate, 2-(isopropenoxyethoxyethoxyethoxy)ethyl (meth)acrylate, 2-(isopropenoxyethoxyethoxyethoxyethoxy)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 due to its ease of balancing the curability, abrasion resistance, and viscosity of the composition. In this embodiment, 2-(2-vinyloxyethoxy)ethyl acrylate may also be referred to as VEEA.

[0049] The content of vinyl group-containing (meth)acrylate, particularly the vinyl group-containing (meth)acrylate represented by the above general formula (I), is preferably 5 to 40% by mass, more preferably 10 to 35% by mass, and even more preferably 15 to 30% by mass, based on the total amount of the composition. When the content is within the above range, the viscosity of the composition tends to decrease, and the curability and abrasion resistance tend to improve further.

[0050] [Difunctional (meth)acrylate] The difunctional (meth)acrylate is not particularly limited, but examples include dipropylene glycol diacrylate (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 diacrylate (TPGDA), tripropylene glycol dimethacrylate, polypropylene glycol di(meth)acrylate, and 1,4-butanediol. Examples include 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, ethylene oxide (EO) adduct di(meth)acrylate of bisphenol A, propylene oxide (PO) adduct di(meth)acrylate of bisphenol A, neopentyl glycol di(meth)acrylate of hydroxypivalate, and polytetramethylene glycol di(meth)acrylate.

[0051] If a bifunctional (meth)acrylate is included, its content is preferably 1 to 30% by mass, and more preferably 2 to 20% by mass, relative to the total amount of the composition.

[0052] [Multifunctional (meth)acrylates with three or more functions] There are no particular limitations on polyfunctional (meth)acrylates with three or more functions, but examples include trimethylolpropane tri(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, glycerin propoxytri(meth)acrylate, caprolactone-modified trimethylolpropane tri(meth)acrylate, pentaerythritol ethoxytetra(meth)acrylate, and caprolactam-modified dipentaerythritol hexa(meth)acrylate.

[0053] If the composition contains a polyfunctional (meth)acrylate with three or more functions, its content is preferably 5 to 30% by mass, and more preferably 10 to 20% by mass, relative to the total amount of the composition.

[0054] 1.1.4 Oligomers An oligomer is a polymer composed of a polymerizable compound and has one or more polymerizable functional groups. The polymerizable compound referred to herein is not limited to the monofunctional monomers and polyfunctional monomers described above. In this embodiment, compounds with a molecular weight of 1000 or more are defined as oligomers, and compounds with a molecular weight of 1000 or less are defined as monomers.

[0055] Such oligomers are not particularly limited, but examples 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.

[0056] 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 less urethane acrylate oligomer, and more preferably a bifunctional urethane acrylate oligomer. Using such oligomers tends to further reduce viscosity and improve abrasion resistance, etc.

[0057] Examples of commercially available oligomers include CN9893 (a bifunctional aliphatic urethane oligomer, manufactured by Sartomer).

[0058] When oligomers are used, their content is preferably 0.5 to 10% by mass, more preferably 0.5 to 5% by mass, and even more preferably 1 to 3% by mass, relative to the total amount of the composition. When the content is within the above range, viscosity tends to decrease further and abrasion resistance and other properties tend to improve further.

[0059] 1.2 Polymerization Initiators [2,4,6-trimethylbenzoylphenylphosphinate ethyl] The radiation-curable inkjet composition according to this embodiment preferably contains ethyl 2,4,6-trimethylbenzoylphenylphosphinate as a polymerization initiator, and other polymerization initiators may be used as needed. Since ethyl 2,4,6-trimethylbenzoylphenylphosphinate is a polymerization initiator that is liquid at room temperature, it has excellent compatibility with glycerin diacrylate and glycerin triacrylate, and tends to further improve abrasion resistance and curability. In the following, when simply referred to as "acylphosphine oxide polymerization initiator," it means an acylphosphine oxide polymerization initiator other than ethyl 2,4,6-trimethylbenzoylphenylphosphinate.

[0060] The content of ethyl 2,4,6-trimethylbenzoylphenylphosphinate is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, even more preferably 2.0% by mass or more, even more preferably 2.5% by mass or more, and even more preferably 3.0% by mass or more, based on the total amount of the composition. By having an ethyl 2,4,6-trimethylbenzoylphenylphosphinate content of 0.5% by mass or more relative to the total amount of the composition, the curability and abrasion resistance of the composition are further improved, and even when other polymerization initiators are used, the amount of other polymerization initiators used is relatively reduced, so the solubility of the polymerization initiator tends to be further improved.

[0061] Furthermore, the content of ethyl 2,4,6-trimethylbenzoylphenylphosphinate is preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and even more preferably 7.5% by mass or less, relative to the total amount of the composition. When the content of ethyl 2,4,6-trimethylbenzoylphenylphosphinate relative to the total amount of the composition is 20% by mass or less, the viscosity of the composition tends to decrease further.

[0062] Furthermore, the content of ethyl 2,4,6-trimethylbenzoylphenylphosphinate is preferably 10 to 100% by mass, more preferably 20 to 80% by mass, and even more preferably 30 to 60% by mass, relative to the total amount of polymerization initiator. When the content of ethyl 2,4,6-trimethylbenzoylphenylphosphinate relative to the total amount of polymerization initiator is within the above range, the curability and abrasion resistance of the composition are further improved, and even when other polymerization initiators are used, the amount of other polymerization initiators used is relatively reduced, so the solubility of the polymerization initiator tends to improve. In addition, the viscosity of the composition also tends to decrease.

[0063] A commercially available product may be used as ethyl 2,4,6-trimethylbenzoylphenylphosphinate, such as Omnirad TPO-L (manufactured by IGM Resins BV).

[0064] [Other polymerization initiators] Other polymerization initiators are not particularly limited as long as they generate active species upon irradiation with radiation, but known polymerization initiators such as acylphosphine oxide polymerization initiators, thioxanthone polymerization initiators, alkylphenone polymerization initiators, and benzophenone polymerization initiators can be found. Among these, acylphosphine oxide polymerization initiators and thioxanthone polymerization initiators are preferred, and acylphosphine oxide polymerization initiators are more preferred. Using such polymerization initiators improves the curability and abrasion resistance of the composition, and in particular, the curability by the UV-LED light curing process tends to be improved. The polymerization initiator may be used alone or in combination of two or more types.

[0065] The content of other polymerization initiators is preferably 1.0 to 10.0% by mass, more preferably 1.0 to 8.0% by mass, and even more preferably 2.0 to 7.0% by mass, based on the total amount of the composition. When the content of other polymerization initiators is within the above range, the curability, abrasion resistance, etc. of the composition and the solubility of the polymerization initiator tend to be further improved.

[0066] Furthermore, the total content of polymerization initiators, including ethyl 2,4,6-trimethylbenzoylphenylphosphinate and other polymerization initiators, is preferably 5.0 to 19% by mass, more preferably 6.0 to 17% by mass, and even more preferably 7.0 to 15% by mass. When the total content of polymerization initiators is within the above range, the curability, abrasion resistance, and solubility of the polymerization initiators of the composition tend to be further improved.

[0067] Acylphosphine oxide polymerization initiators 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.

[0068] Examples of commercially available acylphosphine oxide polymerization 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-hydroxycyclohexyl-phenyl ketone in a mass ratio of 25:75), and Omnirad TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide).

[0069] The content of the acylphosphine oxide polymerization initiator is preferably 2.0% by mass or more, more preferably 2.0 to 10% by mass, and even more preferably 2.0 to 8% by mass, based on the total amount of the composition. When the content of the acylphosphine oxide polymerization initiator is within the above range, the curability, abrasion resistance, and solubility of the polymerization initiator of the composition tend to be further improved.

[0070] The thioxanthone polymerization initiators are not particularly limited, but examples include thioxanthone, 2-methylthioxanthone, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2-chlorothioxanthone, and 2,4-diethylthioxanthone, 2,4-diethylthioxanthene-9-one, diesters of carboxymethoxythioxanthone and polytetramethylene glycol, and 1,3-di({α-[1-chloro-9-oxo-9H-thioxanthene-4-yl]oxy}acetylpoly[oxy(1-methylethylene)])oxy)-2,2-bis({α-[1-chloro-9-oxo-9H-thioxanthene-4-yl]oxy}acetylpoly[oxy(1-methylethylene)])oxymethylpropane).

[0071] Furthermore, a thioxanthone-based polymerization initiator may be used in combination with the polymerization initiator as a sensitizer. The sensitizer content is preferably 0.1% by mass or more, more preferably 0.5 to 10% by mass, and even more preferably 1.0 to 5.0% by mass, based on the total amount of the composition. A commercially available sensitizer is, for example, Speedcure DETX (manufactured by Lambson, 2,4-diethylthioxanthene-9-one).

[0072] There are no particular limitations on alkylphenone polymerization initiators, but examples include 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, and 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one.

[0073] Benzophenone-based polymerization initiators are not particularly limited, but examples include 4,4'-bis(diethylamino)benzophenone, 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, and 4,4'-diaminobenzophenone.

[0074] 1.3 Fluorescent whitening agents The radiation-curable inkjet composition according to this embodiment may contain a fluorescent whitening agent. The inclusion of a fluorescent whitening agent may suppress yellowing of the cured product. Furthermore, the inclusion of a fluorescent whitening agent may improve curability and enhance the whiteness of the cured product. Yellowing of the cured product can be confirmed, for example, using a general-purpose colorimeter.

[0075] Examples of fluorescent whitening agents include, but are not limited to, naphthalene-benzoxazoyl derivatives such as 1,4-bis-(2-benzoxazoyl)naphthalene, thiophene-benzoxazoyl derivatives such as 2,5-thiophene-diylbis(5-tert-butyl-1,3-benzoxazole), stilbene-benzoxazoyl derivatives, coumarin derivatives, styrene-biphenyl derivatives, pyrazolone derivatives, stilbene derivatives, styryl derivatives of benzene and biphenyl, bis(benzazole-2-yl) derivatives, carbostyryl, naphthalimide, dibenzothiophene-5,5'-dioxide derivatives, pyrene derivatives, and pyridotriazole.

[0076] Examples of commercially available fluorescent whitening agents include Telalux OB, Telalux KCB, Telalux KS, Telalux KS-N (all manufactured by Clariant Japan), and Tinopal OB-CO and Tinopal NFW LIQ (both manufactured by BASF).

[0077] When a fluorescent whitening agent is used, its content is preferably 0.01% by mass or more and 1.0% by mass or less, and more preferably 0.07% by mass or more and 0.70% by mass or less, relative to the total amount of the composition.

[0078] 1.4 Surfactants The radiation-curable inkjet composition according to this embodiment may contain a surfactant. The surfactant is not particularly limited, but examples include acetylene glycol-based surfactants, fluorine-based surfactants, and silicone-based surfactants.

[0079] 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, as well as 2,4-dimethyl-5-decine-4-ol and alkylene oxide adducts of 2,4-dimethyl-5-decine-4-ol. These are some examples.

[0080] The fluorine-based surfactant is not particularly limited, but examples include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphate esters, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl betaines, and perfluoroalkylamine oxide compounds.

[0081] Examples of silicone-based surfactants include polysiloxane compounds, polyester-modified silicones, or polyether-modified organosiloxanes. Examples of polyester-modified silicones include BYK-347, 348, 3510, and 3530 (all manufactured by BYK Additives & Instruments), while examples of polyether-modified silicones include BYK-3570 and BYK-UV3500 (manufactured by BYK Additives & Instruments).

[0082] The surfactant content is preferably 0.1 to 1% by mass, and more preferably 0.2 to 0.8% by mass, based on the total mass of the composition. A surfactant content within this range tends to improve the wettability of the composition.

[0083] 1.5 Polymerization inhibitors The radiation-curable inkjet composition according to this embodiment may contain a polymerization inhibitor to further improve the storage stability of the composition. The polymerization inhibitor may be used alone or in combination of two or more types.

[0084] Polymerization inhibitors 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, and others.

[0085] In addition, commercially available polymerization inhibitors include ADEKA LA-7RD (2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl), LA-52, LA-57, LA-62, LA-63P, LA-68LD, LA-77Y, LA-77G, LA-81, LA-82 (1,2,2,6,6-pentamethyl-4-piperidyl methacrylate), LA-87 (all are trade names of ADEKA), IRGASTAB UV 10 (4,4'-[1,10-dioxo-1,10-decanediyl)bis(oxy)]bis[2,2,6,6-tetramethyl]-1-piperidinyloxy) (CAS.2516-92-9), TINUVIN 123 (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl), and TINUVIN Examples include 111FDL, TINUVIN 144, TINUVIN 152, TINUVIN 292, TINUVIN 765, TINUVIN 770DF, TINUVIN 5100, SANOL LS-2626, CHIMASSORB 119FL, CHIMASSORB 2020 FDL, CHIMASSORB 944 FDL, TINUVIN 622 LD (all BASF brand names), FA-711HM, FA-712HM (2,2,6,6-tetramethylpiperidinyl methacrylate, Hitachi Chemical Co., Ltd. brand name), etc.

[0086] When a polymerization inhibitor is used, its content is preferably 0.01% by mass or more and 1.0% by mass or less, more preferably 0.1% by mass or more and 0.5% by mass or less, and even more preferably 0.1% by mass or more and 0.2% by mass or less, relative to the total amount of the composition.

[0087] 1.6 Colorants The radiation-curable inkjet composition according to this embodiment may further contain a colorant. The colorant can be at least one of a pigment and a dye.

[0088] The total content of colorants is preferably 0.1% by mass or more and 10.0% by mass or less, and more preferably 0.5% by mass or more and 5.0% by mass or less, relative to the total amount of the composition. The radiation-curable inkjet composition according to this embodiment may also be a clear ink that does not contain colorants, or contains colorants to an extent not intended for coloring (e.g., 0.1% by mass or less).

[0089] Furthermore, when using pigments, a pigment dispersion may be prepared in advance and used in the radiation-curable inkjet composition. The pigment dispersion may contain polymerizable compounds, dispersants for dispersing the pigment (described later), etc.

[0090] [Pigments] When pigments are used as colorants, the weather resistance of the composition can sometimes be improved. Both inorganic and organic pigments can be used.

[0091] As inorganic pigments, carbon blacks (CI Pigment Black 7) such as furnace black, lamp black, acetylene black, and channel black, as well as iron oxide and titanium dioxide can be used.

[0092] Examples of organic pigments include azo pigments such as insoluble azo pigments, condensed azo pigments, azo lakes, and chelated azo pigments; polycyclic pigments such as phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments; dye chelates (e.g., basic dye type chelates, acid dye type chelates, etc.); dye lakes (basic dye type lakes, acid dye type lakes); nitro pigments; nitroso pigments; carbon black; aniline black; and daylight fluorescent pigments.

[0093] Examples of black pigments include No.2300, No.900, MCF88, No.33, No.40, No.45, No.52, MA7, MA8, MA100, No.2200B, etc. (all product names from Mitsubishi Chemical Corporation), Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, etc. (all from Carbon Columbia), Rega1 400R, Rega1 330R, Rega1 660R, Mogul L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc. (all from Cabot Japan) Examples of Degussa products include: Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Special Black 6, Special Black 5, Special Black 4A, Special Black 4, etc.

[0094] Examples of white pigments include CI Pigment White 6, 18, 21, metal oxides, barium sulfate, calcium carbonate, and other metal compounds. Examples of metal oxides include titanium dioxide, zinc oxide, silica, alumina, and magnesium oxide.

[0095] 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, 167, 172, and 180.

[0096] For magenta pigments, use CI Pigment Red 1, 2, 3, 4, 5, 6, 7, 8. Examples include 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, and CI Pigment Violet 19, 23, 32, 33, 36, 38, 43, 50.

[0097] 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.

[0098] In addition, other color pigments besides magenta, cyan, and yellow 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.

[0099] The above pigments may be used individually or in combination of two or more.

[0100] 〔dye〕 Dyes may be used as colorants. The dyes used are not particularly limited and include acid dyes, direct dyes, reactive dyes, and basic dyes. Dyes may be used individually or in combination of two or more.

[0101] There are no particular restrictions on the dyes used, but for example, 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, 55, 58, 86, 132, 14 Examples include 2, 144, 173, CI Direct Red 1, 4, 9, 80, 81, 225, 227, CI Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202, CI Direct Black 19, 38, 51, 71, 154, 168, 171, 195, CI Reactive Red 14, 32, 55, 79, 249, and CI Reactive Black 3, 4, 35.

[0102] [Dispersant] If the radiation-curable inkjet composition contains a pigment, a dispersant may be further included to improve pigment dispersibility. The dispersant may be used alone or in combination of two or more types.

[0103] The dispersant is not particularly limited, but examples include dispersants commonly used to prepare pigment dispersions, such as polymer dispersants. Specific examples include those mainly composed of one or more of the following: polyoxyalkylene, polyalkylene polyamine, vinyl polymers and copolymers, acrylic polymers and copolymers, polyester, polyamide, polyimide, polyurethane, amino polymer, silicon-containing polymer, sulfur-containing polymer, fluorine-containing polymer, and epoxy resin.

[0104] Commercially available polymer dispersants include the Ajisper series from Ajinomoto Fine Techno, the Solspers series (Solsperse 36000, etc.) available from Avecia and Noveon, the Disparbic series from BYK Additives & Instruments, and the Disparon series from Kusumoto Chemical Co., Ltd.

[0105] When a dispersant is used, its content is preferably 0.01% by mass or more and 1.0% by mass or less, and more preferably 0.1% by mass or more and 0.5% by mass or less, relative to the total amount of the composition.

[0106] 1.7 Other Ingredients The radiation-curable inkjet composition according to this embodiment may further contain various additives as needed, such as chain transfer agents, crosslinking agents, antioxidants, preservatives, flame retardants, antistatic agents, and organic or inorganic fillers.

[0107] 1.8 Physical properties of the composition The viscosity of the radiation-curable inkjet composition according to this embodiment at 20°C is preferably 15 mPa·s or less, more preferably 10 mPa·s or less, and even more preferably less than 6 mPa·s. Because the viscosity of the composition at 20°C is within the above range, an appropriate amount of the composition is ejected from the nozzle, further reducing deviations and scattering of the composition, making it suitable for use in inkjet recording devices.

[0108] Viscosity can be measured using a viscoelasticity tester MCR-300 (manufactured by Pysica) at a temperature of 20°C, by increasing the shear rate from 10 to 1000 and reading the viscosity at a shear rate of 200.

[0109] The surface tension of the radiation-curable inkjet composition according to this embodiment at 20°C is preferably 20 mN / m to 40 mN / m. When the surface tension of the radiation-curable inkjet composition at 20°C is within this range, the composition is less likely to wet the liquid-repellent treated nozzle surface. As a result, the composition is ejected normally and in the appropriate amount from the nozzle, and flight deviation and scattering of the composition can be further reduced, making it suitable for use in inkjet recording devices.

[0110] Surface tension can be measured using an automatic surface tension meter CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.) by checking the surface tension when a platinum plate is wetted with a radiation-curable inkjet composition in an environment of 20°C.

[0111] 1.9 Method for producing the composition The production (preparation) of a radiation-curable inkjet composition can be carried out, for example, by mixing each component contained in the composition and stirring so that the components are sufficiently and uniformly mixed. In this embodiment, the preparation of the radiation-curable inkjet composition preferably includes a step in the preparation process in which a mixture of a polymerization initiator and at least a portion of the monomers is subjected to at least one of ultrasonic treatment and heating treatment. This makes it possible to reduce the amount of dissolved oxygen in the prepared composition, resulting in a radiation-curable inkjet composition with excellent ejection stability and storage stability. The above mixture only needs to contain at least the above components, and may further contain other components contained in the radiation-curable inkjet composition, or may contain all components contained in the radiation-curable inkjet composition. The monomers contained in the mixture only need to be at least a portion of the monomers contained in the radiation-curable inkjet composition.

[0112] 2. Examples The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "%" below refers to mass.

[0113] 2.1 Preparation of radiation-curable inkjet compositions First, the colorant, dispersant, and a portion of each polymerizable compound were weighed and placed in a tank for pigment dispersion. 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 colorant was dispersed in monomers. Next, the remaining polymerizable compounds, polymerization initiator, sensitizer, surfactant, and polymerization inhibitor were placed in a stainless steel container (mixture tank) to obtain the compositions shown in Tables 1 and 2 below. After mixing and stirring until completely dissolved, the pigment dispersion obtained above was added, and the mixture was further mixed and stirred at room temperature for 1 hour. Finally, it was filtered through a 5 μm membrane filter to obtain the radiation-curable inkjet compositions for each example and comparative example. The numerical values ​​of each component shown in each example in the table represent mass %.

[0114] [Table 1]

[0115] [Table 2]

[0116] Further explanation is provided regarding the information in Tables 1 and 2 above. [Pigment dispersion] Cyan pigment: Pigment Blue 15:3 Dispersant: Product name "Solsperse36000", manufactured by Lubrizol, polymer dispersant [Polymerizable compound] IBXA: Isobornyl acrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd. PEA: Phenoxyethyl acrylate, product name "Viscoat #192", manufactured by Osaka Organic Chemical Industry Co., Ltd. M-920: Product name "Arronix (registered trademark) M-920", manufactured by Toagosei Co., Ltd., glycerin / triacrylate M-930: Product name "Aronix (registered trademark) M-930", manufactured by Toagosei Co., Ltd., glycerin triacrylate DPGDA: Dipropylene glycol diacrylate, manufactured by Shin-Nakamura Chemical Industry Co., Ltd. TPGDA: Tripropylene glycol diacrylate, manufactured by Shin-Nakamura Chemical Industry Co., Ltd. VEEA: 2-(2-vinyloxyethoxy)ethyl acrylate, manufactured by Nippon Shokubai Co., Ltd. THFA: Tetrahydrofurfuryl acrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd. CTFA: Cyclic trimethylolpropane formal acrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd. VMOX: Vinylmethyloxazolidinone, manufactured by BASF. CN9893:2-functional aliphatic urethane oligomer, manufactured by Sartomer.

[0117] [Polymerization initiator] Omnirad 819: Trade name, manufactured by IGM, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, acylphosphine oxide polymerization initiator. Omnirad TPO-L: Trade name, manufactured by IGM, ethyl 2,4,6-trimethylbenzoylphenylphosphinate Omnirad TPO: Brand name, manufactured by IGM, 2,4,6-trimethylbenzoyldiphenylphosphine oxide [Sensitizer] DETX: Product name "Speedcure DETX", manufactured by LAMBSON, 2,4-diethylthioxanthene-9-one [Surfactants] BYK-UV3500: A polyether-modified polydimethylsiloxane with acrylic groups, manufactured by BYK Additives & Instruments. [Polymerization inhibitors] LA-7RD: Product name "ADEKA LA-7RD", manufactured by 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

[0118] 2.2 Evaluation Method 2.2.1 Initial Viscosity of Ink The viscosity of each radiation-curable inkjet composition was measured at 20°C using a rotational viscometer (product name "Rheometer MCR-301," manufactured by Anton Paar). The evaluation criteria are as follows. (Evaluation Criteria) A: Viscosity less than 6 mPa·s B: Viscosity of 6 mPa·s or more, and less than 10 mPa·s. C: Viscosity of 10 mPa·s or more, and less than 15 mPa·s. D: Viscosity of 15 mPa·s or higher

[0119] 2.2.2 Scratch resistance The cured coating film prepared for the adhesion evaluation described below was subjected to a micro-scratch test in accordance with JIS R3255. A super-thin film scratch tester (CSR-5000, Nanotec Co., Ltd.) was used to measure the load-bearing capacity as an indicator of abrasion resistance. The load-bearing capacity was defined as the load at which the stylus reached the media surface during micro-scratching while applying a load. 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 as follows. (Evaluation Criteria) A: 30 mN / cm 2 That's all. B: 25 mN / cm 2 More than 30mN / cm 2 less than C: 20 mN / cm² 2 More than 25mN / cm 2 less than D: 20 mN / cm 2 less than

[0120] 2.2.3 Adhesion Each radiation-curable inkjet composition was applied to a polyvinyl chloride film using a bar coater to a coating thickness of 10 μm, with an integrated energy of 200 mJ / cm². 2 Ultraviolet light was irradiated to achieve the desired result. An LED with a peak wavelength of 395 nm was used as the light source. The resulting coating was then evaluated using a cross-cut test in accordance with JIS K5600-5-6.

[0121] More specifically, a cutter was used to make 1mm grids by applying the blade of a cutting tool perpendicular to the coating film, creating a 10x10 grid. A transparent adhesive tape (25mm wide) approximately 75mm long was attached to the grid, and the tape was rubbed thoroughly with a finger so that the hardened film was visible through it. Next, within 5 minutes of attaching the tape, the tape was carefully peeled off the hardened 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) A: Peeling of the cured film was observed in less than 10% of the grid. B: Peeling of the cured film was observed in 10% to less than 35% of the grid. C: Peeling of the cured film was observed in more than 35% of the lattice.

[0122] 2.2.4 Curability The following evaluation criteria were used to determine the composition of each radiation-curable inkjet composition based on the content of monofunctional monomers relative to the total amount of polymerizable compounds. (Evaluation Criteria) A: The content of monofunctional monomers relative to the total amount of polymerizable compounds is 20% by mass or less. B: The content of monofunctional monomers relative to the total amount of polymerizable compounds is greater than 20% by mass and less than or equal to 35% by mass. C: The content of monofunctional monomers relative to the total amount of polymerizable compounds exceeds 35% by mass.

[0123] 2.2.5 Solubility during preparation Using components other than the colorant and dispersant, pigment-free compositions were prepared in the same manner as in each of the above examples and comparative examples, and thoroughly stirred to prepare each radiation-curable inkjet composition. Then, the presence or absence of undissolved polymerization initiator was visually inspected. Compositions without undissolved polymerization initiator were placed in a 0°C constant temperature bath, removed after 24 hours, and allowed to return to room temperature. Afterward, the presence or absence of precipitated polymerization initiator was visually inspected again. The evaluation criteria are as follows. (Evaluation Criteria) A: No undissolved polymer initiator or precipitation was observed after stirring at room temperature or after storage at 0°C. B: After stirring at room temperature, there was no undissolved polymerization initiator, but precipitation of the polymerization initiator was observed after storage at 0°C. C: After stirring at room temperature, undissolved polymerization initiator was observed.

[0124] 2.3 Evaluation Results The evaluation results are shown in Tables 1 and 2 above.

[0125] Based on the evaluation results shown in Tables 1 and 2 above, the radiation-curable inkjet composition according to the present invention, which contains a polymerizable compound and comprises at least one of glycerin diacrylate and glycerin triacrylate, and contains a total of 20% by mass or more of glycerin diacrylate and glycerin triacrylate relative to the total amount of the inkjet composition, showed suppressed viscosity increase and excellent abrasion resistance.

[0126] In contrast, the radiation-curable inkjet compositions in each comparative example that were not part of the present invention showed insufficient viscosity and abrasion resistance in one or more of the properties.

[0127] Based on the results from Examples 15, 20, and Example 14, etc., when the content of monofunctional monomers relative to the total amount of polymerizable compound was less than 35% by mass, the viscosity, abrasion resistance, etc., were superior.

[0128] As a supplement to the results of Examples 7 and 8, when ethyl 2,4,6-trimethylbenzoylphenylphosphinate was included as the polymerization initiator, compatibility was superior, and curability was particularly excellent.

[0129] Based on the results from Example 19 and Example 1, it was found that a lower viscosity could be achieved when the total content of glycerin diacrylate and glycerin triacrylate relative to the total amount of the inkjet composition was 70% by mass or less.

[0130] The following conclusions can be drawn from the embodiments described above.

[0131] One embodiment of a radiation-curable inkjet composition is: A radiation-curable inkjet composition containing a polymerizable compound, The polymerizable compound comprises at least one of glycerin diacrylate and glycerin triacrylate. The inkjet composition contains 20% by mass or more of the glycerin diacrylate and the glycerin triacrylate in total, relative to the total amount of the inkjet composition.

[0132] In one embodiment of the above radiation-curable inkjet composition, The content of monofunctional monomers may be less than 35% by mass relative to the total amount of polymerizable compounds.

[0133] In any embodiment of the above radiation-curable inkjet composition, The polymerizable compound may contain one or more selected from isobornyl acrylate, cyclic trimethylolpropaneformal acrylate, and tetrahydrofurfuryl acrylate.

[0134] In any embodiment of the above radiation-curable inkjet composition, The radiation-curable inkjet composition may contain ethyl 2,4,6-trimethylbenzoylphenylphosphinate as a polymerization initiator.

[0135] In any embodiment of the above radiation-curable inkjet composition, The polymerizable compound may include a vinyl group-containing (meth)acrylate represented by the following general formula (I). H2C=CR 1 -CO-OR 2 -O-CH=CH-R 3 ... (I) (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.)

[0136] In any embodiment of the above radiation-curable inkjet composition, The inkjet composition may contain 70% by mass or less of the glycerin diacrylate and glycerin triacrylate in total, relative to the total amount of the inkjet composition.

[0137] The present invention is not limited to the embodiments described above, and various modifications are possible. For example, the present invention includes configurations that are substantially identical to the configurations described in the embodiments, for example, configurations that have the same function, method and result, or configurations that have the same purpose and effect. The present invention also includes configurations in which non-essential parts of the configurations described in the embodiments are replaced. Furthermore, the present invention includes configurations that produce the same effects or achieve the same purpose as the configurations described in the embodiments. Furthermore, the present invention includes configurations that add known technology to the configurations described in the embodiments.

Claims

1. A radiation-curable inkjet composition containing a polymerizable compound, The polymerizable compound is glycerin diacrylate and glycerin triacrylate, It includes at least one of the following: Including colorants, The polymerizable compound comprises a monofunctional monomer, The polymerizable compound includes a vinyl group-containing (meth)acrylate represented by the following general formula (I): The polymerization initiator contains ethyl 2,4,6-trimethylbenzoylphenylphosphinate, The inkjet composition contains a total of 20% by mass or more of the glycerin diacrylate and the glycerin triacrylate, The inkjet composition contains 11% by mass or more and less than 30% by mass of monofunctional monomers, The total amount of the inkjet composition contains 5% by mass or more and 20% by mass or less of the vinyl group-containing (meth)acrylate represented by the following general formula (I), The vinyl group-containing (meth)acrylate includes 2-(2-vinyloxyethoxy)ethyl acrylate. Radiation-curable inkjet ink composition. H 2 C=CR 1 -CO-OR 2 -O-CH=CH-R 3 ... (I) (In the formula, R1 is a hydrogen atom or a methyl group, R2 is a divalent organic residue having 2 to 20 carbon atoms, and R3 is a hydrogen atom or a monovalent organic residue having 1 to 11 carbon atoms.)

2. The radiation-curable inkjet ink composition according to claim 1, wherein the content of monofunctional monomers is less than 35% by mass relative to the total amount of polymerizable compounds.

3. The radiation-curable inkjet ink composition according to claim 1, wherein the polymerizable compound comprises one or more selected from isobornyl acrylate, cyclic trimethylolpropaneformal acrylate, and tetrahydrofurfuryl acrylate.

4. The radiation-curable inkjet ink composition according to claim 1, comprising 70% by mass or less of the glycerin diacrylate and the glycerin triacrylate in total, based on the total amount of the inkjet composition.

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