Radiation-curable inkjet composition and ink set

Abstract

To provide a radiation curable ink jet composition that can prevent a printed coating from cracking (coating cracking) when installed outside while increasing the coverage of the color gamut.SOLUTION: A radiation curable ink jet composition includes polymerizable compounds and a colorant, the polymerizable compounds including a monofunctional polymerizable compound in an amount of 78 mass% or more with respect to a total mass of the polymerizable compounds, and the colorant including at least one selected from the group consisting of C.I. Pigment Orange 36, C.I. Pigment Orange 38, C.I. Pigment Orange 43, C.I. Pigment Orange 64, C.I. Pigment Orange 71, C.I. Pigment Red 177, C.I. Pigment Red 179, C.I. Pigment Red 224, C.I. Pigment Red 254, C.I. Pigment Red 255, C.I. Pigment Violet 23, C.I. Pigment Violet 32, C.I. Pigment Violet 37, C.I. Pigment Violet 39, C.I. Pigment Green 7, C.I. Pigment Green 36, C.I. Pigment Blue 15:6, C.I. Pigment Blue 25, and C.I. Pigment Blue 60.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to radiation-curable inkjet compositions and ink sets. [Background technology]

[0002] In recent years, radiation-curable inkjet compositions, which harden when irradiated with radiation, have been used in inkjet recording methods to form images with high water resistance, solvent resistance, and abrasion resistance on the surface of recording media.

[0003] Furthermore, in order to increase the color gamut coverage in images formed by radiation-curable inkjet compositions, studies are being conducted on inks of colors other than the commonly used cyan, magenta, yellow, and black inks (special color inks).

[0004] For example, Patent Document 1 discloses an ultraviolet-curable orange ink containing a pigment such as CI Pigment Orange 36 and a polyfunctional photopolymerizable compound such as TPGDA (tripropylene glycol diacrylate) or TMPTA (trimethylolpropane triacrylate). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2018 / 131400 [Overview of the project] [Problems that the invention aims to solve]

[0006] However, even if an image with increased color gamut coverage is formed using spot inks, there is a problem that the print coating is prone to cracking when such printed materials are installed outdoors. On the other hand, if the image is formed without using spot inks in order to prevent the print coating from cracking, it is not possible to increase the color gamut coverage. Therefore, there is a need to increase the color gamut coverage while preventing cracking of the print coating (coating crack) when installed outdoors. [Means for solving the problem]

[0007] One aspect of the radiation-curable inkjet composition according to the present invention is: The polymerizable compound contains 78% by mass or more of a monofunctional polymerizable compound relative to the total amount of the polymerizable compound. The colorants include at least one selected from the group consisting of CI Pigment Orange 36, CI Pigment Orange 38, CI Pigment Orange 43, CI Pigment Orange 64, CI Pigment Orange 71, CI Pigment Red 177, CI Pigment Red 179, CI Pigment Red 224, CI Pigment Red 254, CI Pigment Red 255, CI Pigment Violet 23, CI Pigment Violet 32, CI Pigment Violet 37, CI Pigment Violet 39, CI Pigment Green 7, CI Pigment Green 36, CI Pigment Blue 15:6, CI Pigment Blue 25, and CI Pigment Blue 60.

[0008] One embodiment of the ink set according to the present invention is: The present invention comprises a cyan ink composition, a magenta ink composition, a yellow ink composition, a black ink composition, and a radiation-curable inkjet composition according to the above embodiment. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below. The embodiments described below illustrate examples of the present invention. The present invention is not limited to the following embodiments, and also includes various modified forms implemented within the scope of not changing the gist of the present invention. Note that not all of the configurations described below are essential configurations of the present invention.

[0010] 1. Radiation-curable inkjet composition The radiation-curable inkjet composition according to an embodiment of the present invention contains, as a polymerizable compound, a monofunctional polymerizable compound in an amount of 78% by mass or more based on the total amount of the polymerizable compounds, and as a colorant, at least one selected from the group consisting of C.I. Pigment Orange 36, C.I. Pigment Orange 38, C.I. Pigment Orange 43, C.I. Pigment Orange 64, C.I. Pigment Orange 71, C.I. Pigment Red 177, C.I. Pigment Red 179, C.I. Pigment Red 224, C.I. Pigment Red 254, C.I. Pigment Red 255, C.I. Pigment Violet 23, C.I. Pigment Violet 32, C.I. Pigment Violet 37, C.I. Pigment Violet 39, C.I. Pigment Green 7, C.I. Pigment Green 36, C.I. Pigment Blue 15:6, C.I. Pigment Blue 25, and C.I. Pigment Blue 60 (hereinafter also referred to as "specific pigment").

[0011] Even if an image with an increased color gamut coverage rate is formed using a special ink containing a specific pigment as a colorant, when such a printed matter is installed outdoors, cracks in the printed coating film are likely to occur. On the other hand, when forming an image without using a special ink containing a specific pigment as a colorant, it is impossible to increase the color gamut coverage rate. In contrast, according to the radiation-curable inkjet composition (hereinafter, also referred to as "inkjet composition" or simply "composition") according to the present embodiment, by containing a specific pigment as a colorant, while increasing the color gamut coverage rate, by containing a monofunctional polymerizable compound in a predetermined amount or more with respect to the total amount (100% by mass) of the polymerizable compounds, the stretchability of the coating film can be improved, and cracks (coating film cracks) in the printed coating film during outdoor installation can be prevented. That is, according to the radiation-curable inkjet composition according to the present embodiment, it is possible to provide a radiation-curable inkjet composition that can expand the color gamut and protect the expanded color gamut.

[0012] Hereinafter, each component contained in the radiation-curable inkjet composition according to the present embodiment will be described.

[0013] 1.1. Polymerizable Compound The radiation-curable inkjet composition according to the present embodiment contains, as a polymerizable compound, 78% by mass or more of a monofunctional polymerizable compound (hereinafter, also referred to as "monofunctional monomer") with respect to the total amount of the polymerizable compounds.

[0014] 1.1.1. Monofunctional Polymerizable Compound The amount of monofunctional polymerizable compounds in the radiation-curable inkjet composition according to this embodiment is 78% by mass or more of the total amount of polymerizable compounds (100% by mass). Preferably, it is 82% by mass or more, more preferably 90% by mass or more, and even more preferably 93% by mass or more. When the amount of monofunctional monomers is within the above range, the stretchability of the coating film is improved, and cracking of the coating film can be prevented even when installed outdoors. Furthermore, there is no particular upper limit to the amount of monofunctional polymerizable compounds, but preferably it is 99% by mass or less of the total amount of polymerizable compounds (100% by mass), more preferably 98% by mass or less, and even more preferably 97% by mass or less. When the amount of monofunctional monomers is 99% by mass or less of the total amount of polymerizable compounds, the abrasion resistance tends to be further improved.

[0015] Furthermore, the monofunctional monomer content is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 82% by mass or more, relative to the total amount of the composition (100% by mass). When the monofunctional monomer content is 70% by mass or more relative to the total amount of the composition, the flexibility and adhesion of the coating film tend to be further improved. Furthermore, the upper limit of the monofunctional monomer content is preferably 92% by mass or less, more preferably 90% by mass or less, and even more preferably 88% by mass or less, relative to the total amount of the composition (100% by mass). When the monofunctional monomer content is 92% by mass or less relative to the total amount of the composition, the abrasion resistance tends to be further improved.

[0016] The monofunctional polymerizable compounds included in the radiation-curable inkjet composition according to this embodiment are not particularly limited, but examples include monofunctional acrylates having polycyclic hydrocarbon groups, nitrogen-containing monofunctional monomers, aromatic group-containing monofunctional monomers, and saturated aliphatic group-containing monofunctional monomers. Other monofunctional monomers may also be included as needed. The other monofunctional monomers are not particularly limited, but conventionally known monofunctional monomers having polymerizable functional groups, particularly polymerizable functional groups having unsaturated double bonds between carbon atoms, can be used.

[0017] The following are examples of monofunctional monomers, but the monofunctional monomers in this embodiment are not limited to those listed below.

[0018] 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.

[0019] 1.1.1.1. Monofunctional acrylates having polycyclic hydrocarbon groups The monofunctional acrylate having polycyclic hydrocarbon groups is not particularly limited, but examples include acrylates having unsaturated polycyclic hydrocarbon groups such as dicyclopentenyl acrylate (DCPA) and dicyclopentenyloxyethyl acrylate; and acrylates having saturated polycyclic hydrocarbon groups such as dicyclopentanyl acrylate and isobornyl acrylate (IBXA). Among these, acrylates having saturated polycyclic hydrocarbon groups are preferred, and it is more preferable that they contain at least isobornyl acrylate (IBXA). Using such monofunctional acrylates having polycyclic hydrocarbon groups tends to further improve the abrasion resistance of the coating film.

[0020] The content of monofunctional acrylate having polycyclic hydrocarbon groups is preferably 5 to 45% by mass, more preferably 10 to 40% by mass, and even more preferably 15 to 35% by mass, relative to the total amount of polymerizable compounds (100% by mass). When the content of monofunctional acrylate having polycyclic hydrocarbon groups relative to the total amount of polymerizable compounds is within the above range, the abrasion resistance of the coating film tends to be further improved.

[0021] The content of monofunctional acrylates having polycyclic hydrocarbon groups is preferably 5 to 40% by mass, more preferably 10 to 40% by mass, and even more preferably 15 to 35% by mass, relative to the total amount of the composition (100% by mass). When the content of monofunctional acrylates having polycyclic hydrocarbon groups relative to the total amount of the composition is within the above range, the abrasion resistance of the coating film tends to be further improved.

[0022] 1.1.1.2. Nitrogen-containing monofunctional monomers The nitrogen-containing monofunctional monomers are not particularly limited, but examples include nitrogen-containing monofunctional vinyl monomers such as N-vinylcaprolactam (NVC), vinylmethyloxazolidinone (VMOX), N-vinylformamide, N-vinylcarbazole, N-vinylacetamide, and N-vinylpyrrolidone; nitrogen-containing monofunctional acrylate monomers such as acryloylmorpholine (ACMO); 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. In this invention, "N-vinyl compound" refers to nitrogen-containing monofunctional vinyl monomers and does not include nitrogen-containing monofunctional acrylate monomers and nitrogen-containing monofunctional acrylamide monomers.

[0023] Among these, it is preferable to include either a nitrogen-containing monofunctional vinyl monomer or a nitrogen-containing monofunctional acrylate monomer, more preferably a monomer having a nitrogen-containing heterocyclic structure such as N-vinylcaprolactam (NVC), vinylmethyloxazolidinone (VMOX), N-vinylcarbazole, N-vinylpyrrolidone, or acryloylmorpholine (ACMO), and even more preferably acryloylmorpholine (ACMO).

[0024] Using such nitrogen-containing monofunctional monomers tends to improve the abrasion 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 of the coating film, while nitrogen-containing monofunctional acrylate monomers having a nitrogen-containing heterocyclic structure, such as acryloylmorpholine, tend to further reduce the odor of the composition.

[0025] The nitrogen-containing monofunctional monomer content is preferably 5 to 40% by mass, more preferably 5 to 35% by mass, and even more preferably 5 to 30% by mass, relative to the total amount of polymerizable compounds (100% by mass). A nitrogen-containing monofunctional monomer content of 5% by mass or more relative to the total amount of polymerizable compounds tends to improve the abrasion resistance of the coating film. Furthermore, a nitrogen-containing monofunctional monomer content of 40% by mass or less relative to the total amount of polymerizable compounds tends to improve adhesion.

[0026] The nitrogen-containing monofunctional monomer content is preferably 5 to 35% by mass, more preferably 5 to 30% by mass, and even more preferably 5 to 25% by mass, relative to the total amount of the composition (100% by mass). A nitrogen-containing monofunctional monomer content of 5% by mass or more relative to the total amount of the composition tends to improve the abrasion resistance of the coating film. Furthermore, a nitrogen-containing monofunctional monomer content of 35% by mass or less relative to the total amount of the composition tends to improve adhesion.

[0027] Furthermore, the content of the N-vinyl compound is preferably 5% by mass or less, more preferably 4% by mass or less, even more preferably 3% by mass or less, and particularly preferably 2.5% by mass or less, based on the total amount of polymerizable compounds (100% by mass). When the content of the N-vinyl compound is within the above range, the resulting coating film tends to be smoother, and thus the color development tends to improve.

[0028] The content of the N-vinyl compound is preferably 5% by mass or less, more preferably 4% by mass or less, even more preferably 3% by mass or less, and particularly preferably 2.5% by mass or less, based on the total amount (100% by mass) of the composition. When the content of the N-vinyl compound is within the above range, the resulting coating film tends to be smoother, and thus the color development tends to improve.

[0029] 1.1.1.3. Aromatic group-containing monofunctional monomers The aromatic group-containing monofunctional monomer is not particularly limited, but examples include phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, alkoxylated 2-phenoxyethyl (meth)acrylate, ethoxylated nonylphenyl (meth)acrylate, alkoxylated nonylphenyl (meth)acrylate, p-cumylphenol EO-modified (meth)acrylate, and 2-hydroxy-3-phenoxypropyl (meth)acrylate. 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 monofunctional monomers, the solubility of the polymerization initiator tends to be further improved, and the curability of the composition tends to be further improved. In particular, the solubility tends to be good when using acylphosphine oxide-based polymerization initiators or thioxanthone-based polymerization initiators. Furthermore, using phenoxyethyl (meth)acrylate tends to further reduce odor.

[0030] In this embodiment, the aromatic group-containing monofunctional monomer is not a compound having a polycyclic hydrocarbon group.

[0031] Examples of aromatic group-containing monofunctional monomers, expressed in other terms, include compounds represented by the following general formulas (1) and (2).

[0032] CH2=CR 4 -COOR5 -Ar ··· (1) CH2=CR 4 -COO-Ar ··· (2) (In the above equations (1) and (2), R 4 is a hydrogen atom or a methyl group. In formula (1) above, Ar, which represents the aromatic ring skeleton, has at least one aryl group, and the carbon atoms constituting the aryl group are R 5 It is a monovalent organic residue bound to the group represented by R, and also R 5 is a divalent organic residue having 1 to 4 carbon atoms. In formula (2) above, Ar, representing the aromatic ring skeleton, is a monovalent organic residue having at least one aryl group, with the carbon atoms constituting the aryl group bonded to the -COO- in the formula.

[0033] In the general formula (1) above, R 5 The groups represented by are preferably linear, branched, or cyclic alkylene groups having 1 to 4 carbon atoms, which may be substituted, and alkylene groups having 1 to 4 carbon atoms that have an oxygen atom in their structure due to ether and / or ester bonds, which may be substituted. Among these, alkylene groups having 1 to 4 carbon atoms such as ethylene, n-propylene, isopropylene, and butylene, and alkylene groups having 1 to 4 carbon atoms that have an oxygen atom in their structure due to ether bonds, such as oxyethylene, oxy-n-propylene, oxyisopropylene, and oxybutylene, are preferably used. When the above organic residue is an optional group, the substituent is not particularly limited, but examples include carboxyl, alkoxy, hydroxyl, and halo groups, and when the substituent is a group containing a carbon atom, that carbon atom is counted in the number of carbon atoms of the organic residue.

[0034] In the general formulas (1) and (2) above, the aryl group included in the Ar (aryl) (aromatic ring skeleton) is not limited to the following, but examples include the phenyl group and the naphthyl group. The number of aryl groups is one or more, preferably one or two. A Riehl group is a group in which, among the carbon atoms constituting the group, R in formula (1) 5The carbon atoms other than the carbon atom bonded to the organic residue represented by formula (2), the carbon atom bonded to -COO- in formula (2), and the carbon atoms that link the aryl groups together if there are multiple aryl groups may be substituted. If substituted, the number of substitutions per aryl group is one or more, preferably one or two. The substituents are not particularly limited, but examples include linear, branched, or cyclic alkyl and alkoxy groups having 1 to 10 carbon atoms, carboxyl groups, halo groups, and hydroxyl groups.

[0035] The content of aromatic group-containing monofunctional monomers is preferably 30 to 55% by mass, more preferably 35 to 50% by mass, and even more preferably 40 to 45% by mass, relative to the total amount of polymerizable compounds (100% by mass). When the content of aromatic group-containing monofunctional monomers relative to the total amount of polymerizable compounds is within the above range, the abrasion resistance of the coating film tends to improve further.

[0036] The content of aromatic group-containing monofunctional monomers is preferably 20 to 50% by mass, more preferably 25 to 45% by mass, and even more preferably 30 to 40% by mass, relative to the total amount of the composition (100% by mass). When the content of aromatic group-containing monofunctional monomers relative to the total amount of the composition is within the above range, the abrasion resistance of the coating film tends to be further improved.

[0037] 1.1.1.4. Monofunctional monomers containing saturated aliphatic groups The saturated aliphatic group-containing monofunctional monomers are not particularly limited, but examples include alicyclic group-containing monofunctional monomers such as tert-butylcyclohexanol acrylate (TBCHA) and 2-(meth)acrylate-1,4-dioxaspiro[4,5]decy-2-ylmethyl; linear or branched aliphatic group-containing monofunctional monomers such as isoamyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, isomiristyl (meth)acrylate, isostearyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, butoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate; and lactone-modified flexible (meth)acrylates. Among these, monofunctional monomers containing alicyclic groups are preferred. Using such saturated aliphatic group-containing monofunctional monomers tends to further improve the curability of the composition.

[0038] In this embodiment, the saturated aliphatic group-containing monofunctional monomer is not a compound having a polycyclic hydrocarbon group.

[0039] The content of saturated aliphatic group-containing monofunctional monomers is preferably 1 to 20% by mass, more preferably 3 to 15% by mass, and even more preferably 5 to 12% by mass, relative to the total amount of polymerizable compounds (100% by mass). When the content of saturated aliphatic group-containing monofunctional monomers is 1% by mass or more relative to the total amount of polymerizable compounds, the flexibility and adhesion of the coating film tend to be further improved. Furthermore, when the content of saturated aliphatic group-containing monofunctional monomers is 20% by mass or less relative to the total amount of polymerizable compounds, the abrasion resistance of the coating film tends to be further improved.

[0040] The content of saturated aliphatic group-containing monofunctional monomers is preferably 1 to 15% by mass, more preferably 3 to 12% by mass, and even more preferably 5 to 10% by mass, relative to the total amount of the composition (100% by mass). When the content of saturated aliphatic group-containing monofunctional monomers is 1% by mass or more relative to the total amount of the composition, the flexibility and adhesion of the coating film tend to be further improved. Furthermore, when the content of saturated aliphatic group-containing monofunctional monomers is 15% by mass or less relative to the total amount of the composition, the abrasion resistance of the coating film tends to be further improved.

[0041] 1.1.1.5. Others 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, unsaturated polyamides, and unsaturated urethanes.

[0042] 1.1.2. Polyfunctional polymerizable compounds The radiation-curable inkjet composition according to this embodiment may contain a polyfunctional polymerizable compound (hereinafter also referred to as "polyfunctional monomer"). Examples of polyfunctional monomers include vinyl ether group-containing (meth)acrylates, bifunctional (meth)acrylates, and trifunctional or more polyfunctional (meth)acrylates. However, the polyfunctional monomer is not limited to those described above.

[0043] The polyfunctional monomer content is preferably 0.01% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, relative to the total amount of polymerizable compounds (100% by mass). When the polyfunctional monomer content is 1% by mass or more relative to the total amount of polymerizable compounds, the abrasion resistance tends to be further improved. Furthermore, the upper limit of the polyfunctional monomer content 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% by mass or less, relative to the total amount of polymerizable compounds (100% by mass). When the polyfunctional monomer content is 20% by mass or less relative to the total amount of polymerizable compounds, the flexibility and adhesion of the coating film tend to be further improved.

[0044] Furthermore, the polyfunctional monomer content is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, relative to the total amount of the composition (100% by mass). When the polyfunctional monomer content is 1% by mass or more relative to the total amount of the composition, the abrasion resistance tends to be further improved. Furthermore, the upper limit of the polyfunctional monomer content 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 8% by mass or less, relative to the total amount of the composition (100% by mass). When the polyfunctional monomer content is 20% by mass or less relative to the total amount of the composition, the flexibility and adhesion of the coating film tend to be further improved.

[0045] The following are examples of polyfunctional monomers, but the polyfunctional monomers in this embodiment are not limited to those listed below.

[0046] 1.1.2.1. 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 (3). 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 further improved. In addition, the curability of the composition is further improved, and along with the improvement of the curability, it becomes possible to increase the recording speed. CH2=CR 1 -COOR 2 -O-CH=CH-R 3 ··· (3) (In the formula, R 1 is a hydrogen atom or a methyl group, R 2 is a divalent organic residue having 2 to 20 carbon atoms, and R 3 is a hydrogen atom or a monovalent organic residue having 1 to 11 carbon atoms.)

[0047] In the above formula (3), examples of the divalent organic residue having 2 to 20 carbon atoms represented by R 2 include linear, branched or cyclic, optionally substituted alkylene groups having 2 to 20 carbon atoms, optionally substituted alkylene groups having 2 to 20 carbon atoms having an oxygen atom due to an ether bond and / or an ester bond in the structure, and optionally substituted divalent aromatic groups having 6 to 11 carbon atoms. 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 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 are preferable. Further, from the viewpoint of further reducing the viscosity of the composition and further improving the curability of the composition, R 2 is more preferably a compound having a glycol ether chain in which it 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.

[0048] In the above formula (3), R 3As monovalent organic residues having 1 to 11 carbon atoms, suitable options include linear, branched, or cyclic alkyl groups having 1 to 10 carbon atoms, which may be substituted, and aromatic groups having 6 to 11 carbon atoms, which may be substituted. 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.

[0049] 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.

[0050] Specific examples of compounds of formula (3) 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, 1,1-dimethyl-2-vinyloxyethyl (meth)acrylate, (methyl-2-vinyloxyethyl (meth)acrylate, (methyl-2-vinyloxyethyl (meth)acrylate) (Meth) 3-vinyloxybutyl acrylate, (meth) 1-methyl-2-vinyloxypropyl acrylate, (meth) 2-vinyloxybutyl acrylate, (meth) 4-vinyloxycyclohexyl acrylate, (meth) 6-vinyloxyhexyl acrylate, (meth) 4-vinyloxymethylcyclohexylmethyl acrylate, (meth) 3-vinyloxymethylcyclohexylmethyl acrylate, (meth) 2-vinyloxymethylcyclohexylmethyl acrylate, (meth) p-vinyloxymethylphenylmethyl acrylate, (meth) m-vinyloxymethylphenyl methyl, 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-(vinyloxyethyl) Xyethoxy)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 and viscosity of the composition. In this embodiment, 2-(2-vinyloxyethoxy)ethyl acrylate may also be referred to as VEEA.

[0051] The content of vinyl ether group-containing (meth)acrylate is preferably 0.5 to 20% by mass, more preferably 0.75 to 15% by mass, and even more preferably 1 to 10% by mass, relative to the total amount of polymerizable compounds (100% by mass). When the content of vinyl ether group-containing (meth)acrylate relative to the total amount of polymerizable compounds is within the above range, the viscosity of the composition tends to decrease and the discharge stability tends to improve further.

[0052] The content of vinyl ether group-containing (meth)acrylate is preferably 0.5 to 20% by mass, more preferably 0.75 to 15% by mass, and even more preferably 1 to 12% by mass, based on the total amount of the composition (100% by mass). When the content of vinyl ether group-containing (meth)acrylate relative to the total amount of polymerizable compounds is within the above range, the viscosity of the composition tends to decrease and the discharge stability tends to improve further.

[0053] 1.1.2.2. Two-Functional (Meth)acrylates 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 di(meth)acrylate, polypropylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate. 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.

[0054] 1.1.2.3. Polyfunctional (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.

[0055] 1.1.3. Glass transition temperature of polymerizable compounds In the radiation-curable inkjet composition according to this embodiment, the weighted average of the glass transition temperatures of each homopolymer in the polymerizable compound, weighted by the mass ratio of the respective contents of the polymerizable compound, is preferably 42°C or higher, more preferably 44°C or higher, even more preferably 46°C or higher, and particularly preferably 48°C or higher. When the weighted average of the glass transition temperatures of each homopolymer is within the above range, the abrasion resistance of the coating film at room temperature can be improved. Furthermore, there is no particular upper limit to the weighted average of the glass transition temperatures of each homopolymer, but it is preferably 60°C or lower, more preferably 55°C or lower, and even more preferably 55°C or lower.

[0056] This section explains how to calculate the weighted average of glass transition temperatures. The weighted average value of glass transition temperatures is Tg All The glass transition temperature (Tg) of the homopolymer of each polymerizable compound is determined. N The mass ratio of the polymerizable compound is X N (Assuming mass %). N is a number ranging from 1 onwards, depending on the type of polymerizable compound contained in the radiation-curable inkjet composition. For example, if three types of polymerizable compounds are used, Tg1, Tg2, and Tg3 will be produced. The glass transition temperature of each polymerizable compound homopolymer can be obtained from the Safety Data Sheet (SDS) or catalog information of that polymerizable compound. Weighted average Tg of glass transition temperature All This is the glass transition temperature Tg calculated for each polymerizable compound. N and the content X N It is the sum of the products of [the specified values]. Therefore, equation (4) below holds true. Tg All =ΣTg N ×X N ...(4)

[0057] Furthermore, the weighted average of the glass transition temperatures can be adjusted by the glass transition temperature of the polymerizable compound used and the mass ratio of the polymerizable compound used.

[0058] 1.2. Colorants The radiation-curable inkjet composition according to this embodiment contains, as a colorant, at least one selected from the group consisting of CI Pigment Orange 36, CI Pigment Orange 38, CI Pigment Orange 43, CI Pigment Orange 64, CI Pigment Orange 71, CI Pigment Red 177, CI Pigment Red 179, CI Pigment Red 224, CI Pigment Red 254, CI Pigment Red 255, CI Pigment Violet 23, CI Pigment Violet 32, CI Pigment Violet 37, CI Pigment Violet 39, CI Pigment Green 7, CI Pigment Green 36, CI Pigment Blue 15:6, CI Pigment Blue 25, and CI Pigment Blue 60 (hereinafter also referred to as "specific pigment").

[0059] The radiation-curable inkjet composition according to this embodiment can increase the color gamut coverage by including at least one of the above-mentioned specific pigments as a colorant.

[0060] Furthermore, among these specific pigments, it is more preferable to include CI Pigment Orange 43 or CI Pigment Red 254. When CI Pigment Orange 43 or CI Pigment Red 254 is included as a colorant, it is possible to further improve the color gamut coverage when combined with the cyan ink composition, magenta ink composition, yellow ink composition, and black ink composition described later. In addition, it is possible to prevent fading when the colorant is exposed to sunlight.

[0061] The lower limit of the colorant content is preferably 1% by mass or more, and more preferably 2% by mass or more, based on the total amount (100% by mass) of the radiation-curable inkjet composition. The upper limit of the colorant content is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, based on the total amount (100% by mass) of the radiation-curable inkjet composition. When the colorant content is within the above range, the color gamut coverage tends to improve.

[0062] <Dispersant> The radiation-curable inkjet composition according to this embodiment preferably further contains a dispersant to improve pigment dispersibility. The dispersant may be used alone or in combination of two or more types.

[0063] 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.

[0064] 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.

[0065] The dispersant content is preferably 0.1 to 2% by mass, more preferably 0.1 to 1.5% by mass, and even more preferably 0.5 to 1.0% by mass, based on the total amount of the composition (100% by mass).

[0066] <Other colorants> The radiation-curable inkjet composition according to this embodiment may contain colorants other than the specific pigments described above. Other colorants that can be used include pigments and dyes.

[0067] Both inorganic and organic pigments can be used as pigments.

[0068] As inorganic pigments, carbon blacks (CI (Colour Index Generic Name) 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.

[0069] Examples of organic pigments include azo pigments such as insoluble azo pigments, condensed azo pigments, azo lakes, and chelate 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; aniline black; and daylight fluorescent pigments.

[0070] More specifically, the black pigments used are carbon black, such as No. 2300, No. 900, MCF88, No. 33, No. 40, No. 45, No. 52, MA7, MA8, MA100, No. 2200B, etc. (all manufactured by Mitsubishi Chemical Corporation), Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, etc. (all manufactured by 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 Examples include the 1400 (manufactured by CABOT JAPAN KK), 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, and Special Black 4 (all manufactured by Degussa).

[0071] Examples of white pigments include CI Pigment White 6, 18, and 21.

[0072] 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.

[0073] Examples of magenta-based pigments include CI Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 40, 41, 42, 48(Ca), 48(Mn), 57(Ca), 57:1, 88, 112, 114, 123, 144, 146, 149, 150, 166, 168, 170, 171, 175, 176, 178, 184, 185, 187, 202, 209, 219, 245, or CI Pigment Violet 19, 33, 36, 38, 43, 50.

[0074] 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, 65, 66, and CI Bat Blue 4 and 60.

[0075] In addition, pigments other than magenta, cyan, and yellow include, for example, CI Pigment Green 10, CI Pigment Brown 3, 5, 25, 26, and CI Pigment Orange 1, 2, 5, 7, 13, 14, 15, 16, 24, 34, 40, and 63.

[0076] The above pigments may be used individually or in combination of two or more. When using the above pigments, the average particle size is preferably 300 nm or less, and more preferably 50 nm to 200 nm. When the average particle size is within the above range, the reliability of the radiation-curable inkjet composition, such as ejection stability and dispersion stability, is further improved, and images with superior quality can be formed. Here, the average particle size in this specification is measured by dynamic light scattering (Dv). 50 This was used as the value.

[0077] Furthermore, the dyes used are not particularly limited and include acid dyes, direct dyes, reactive dyes, and basic dyes. Examples of dyes include CI Acid Yellow 17, 23, 42, 44, 79, 142; CI Acid Red 52, 80, 82, 249, 254, 289; CI Acid Blue 9, 45, 249; CI Acid Black 1, 2, 24, 94; CI Food Black 1, 2; CI Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 142, 144. Examples include 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.

[0078] The above dyes may be used individually or in combination of two or more.

[0079] 1.3. Other ingredients The radiation-curable inkjet composition according to this embodiment may contain polymerization initiators, polymerization inhibitors, slip agents, etc.

[0080] <Polymerization initiator> The radiation-curable inkjet composition according to this embodiment preferably contains a polymerization initiator that generates active species upon irradiation with radiation. The polymerization initiator may be used alone or in combination of two or more types.

[0081] While not particularly limited, known polymerization initiators such as acylphosphine oxide-based polymerization initiators, alkylphenone-based polymerization initiators, titanocene-based polymerization initiators, and thioxanthone-based polymerization initiators are examples. Among these, acylphosphine oxide-based polymerization initiators are preferred. Using such polymerization initiators improves the curability of the composition, and in particular, the curability by the UV-LED light curing process tends to be improved.

[0082] 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.

[0083] Examples of commercially available acylphosphine oxide polymerization initiators include IRGACURE 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 IRGACURE TPO (2,4,6-trimethylbenzoyldiphenylphosphine oxide) (all manufactured by BASF).

[0084] The polymerization initiator content is preferably 1 to 20% by mass, more preferably 3 to 15% by mass, even more preferably 5 to 10% by mass, and particularly preferably 7 to 9% by mass, based on the total amount (100% by mass) of the composition. When the polymerization initiator content is within the above range, the curability of the composition and the solubility of the polymerization initiator tend to be further improved.

[0085] <Polymerization inhibitors> The radiation-curable inkjet composition according to this embodiment may further contain a polymerization inhibitor. The polymerization inhibitor may be used alone or in combination of two or more types.

[0086] 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.

[0087] The polymerization inhibitor content is preferably 0.05 to 1% by mass, and more preferably 0.05 to 0.5% by mass, based on the total amount (100% by mass) of the composition.

[0088] <Slip agent> The radiation-curable inkjet composition according to this embodiment may further contain a slip agent. The slip agent may be used alone or in combination of two or more types.

[0089] As a slip agent, a silicone-based surfactant is preferred, and a polyester-modified silicone or a polyether-modified silicone is more preferred. Examples of polyether-modified silicones include BYK-378, 3455, BYK-UV3500, 3510, and 3530 (all manufactured by BYK Additives & Instruments), while an example of a polyester-modified silicone is BYK-3570 (manufactured by BYK Additives & Instruments).

[0090] The slip agent content is preferably 0.01 to 2% by mass, and more preferably 0.05 to 1% by mass, based on the total amount of the composition (100% by mass).

[0091] Furthermore, the radiation-curable inkjet composition according to this embodiment may further contain a photosensitizer.

[0092] 1.4. Physical Properties The viscosity of the radiation-curable inkjet composition according to this embodiment at 20°C is preferably 25 mPa·s or less, and more preferably 5 mPa·s to 25 mPa·s. Since 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 the composition's flight deviation and scattering, making it suitable for use in inkjet recording devices. The viscosity can be measured using a viscoelasticity tester "MCR-300" (manufactured by Pysica) at a 20°C environment, by increasing the shear rate from 10 to 1000 and reading the viscosity at a shear rate of 200.

[0093] The surface tension of the radiation-curable inkjet composition according to this embodiment at 20°C is preferably 20 mN / m or more and 40 mN / m or less. 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 nozzle surface that has been treated with a liquid-repellent coating. As a result, the composition is ejected from the nozzle in a normal and appropriate amount, and flight deviation and scattering of the composition can be further reduced, making it suitable for use in inkjet recording devices. The surface tension can be measured by using an automatic surface tension meter "CBVP-Z" (manufactured by Kyowa Interface Science Co., Ltd.) to check the surface tension when a platinum plate is wetted with the radiation-curable inkjet composition in an environment of 20°C.

[0094] 1.5. Method for producing the composition The production (preparation) of a radiation-curable inkjet composition is carried out by mixing each component contained in the composition and stirring to ensure that the components are thoroughly and uniformly mixed. In this embodiment, it is preferable that the preparation of the radiation-curable inkjet composition includes a step in the preparation process in which a mixture of a polymerization initiator and at least a portion of the polymerizable compound is subjected to at least one of ultrasonic treatment and heating treatment. This reduces 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 it may contain all the components contained in the radiation-curable inkjet composition. The polymerizable compound contained in the mixture only needs to be at least a portion of the polymerizable compound contained in the radiation-curable inkjet composition.

[0095] 2. Ink Set An ink set according to one embodiment of the present invention includes a cyan ink composition, a magenta ink composition, a yellow ink composition, a black ink composition, and the above-mentioned radiation-curable inkjet composition.

[0096] Even if an image with increased color gamut coverage is formed using an ink set that comprises a special ink containing a specific pigment as a colorant, cracking of the printed coating is likely to occur when such printed materials are installed outdoors. On the other hand, if an image is formed without using a special ink containing a specific pigment as a colorant in the ink set, it is not possible to increase the color gamut coverage. In contrast, according to the ink set of this embodiment, the color gamut coverage can be increased by including at least one specific pigment as a colorant in the radiation-curable inkjet composition that constitutes the ink set, and the stretchability of the coating film can be improved by including a predetermined amount or more of a monofunctional polymerizable compound relative to the total amount of polymerizable compounds (100% by mass), thereby preventing cracking of the printed coating film (coating film cracks) when installed outdoors. In other words, according to the ink set of this embodiment, it is possible to provide an ink set that can expand the color gamut and protect the expanded color gamut.

[0097] The cyan ink composition, magenta ink composition, yellow ink composition, and black ink composition included in the ink set according to this embodiment will be described below. Note that the radiation-curable inkjet composition included in the ink set according to this embodiment is as described above and will therefore not be described further.

[0098] 2.1. Cyan Ink Composition The ink set according to this embodiment includes a cyan ink composition. The components that may be included in the cyan ink composition are described below.

[0099] 2.1.1. Colorants The cyan ink composition included in the ink set according to this embodiment preferably contains a colorant. The colorant used in the cyan ink composition is not particularly limited, but examples 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, 60.

[0100] <Other colorants> The cyan ink composition included in the ink set according to this embodiment may also contain colorants other than those described above. Such colorants may be pigments or dyes.

[0101] Both inorganic and organic pigments can be used as pigments.

[0102] As inorganic pigments, carbon blacks (CI (Colour Index Generic Name) 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.

[0103] Examples of organic pigments include azo pigments such as insoluble azo pigments, condensed azo pigments, azo lakes, and chelate 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; aniline black; and daylight fluorescent pigments.

[0104] More specifically, the black pigments used are carbon black, such as No. 2300, No. 900, MCF88, No. 33, No. 40, No. 45, No. 52, MA7, MA8, MA100, No. 2200B, etc. (all manufactured by Mitsubishi Chemical Corporation), Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, etc. (all manufactured by 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 Examples include the 1400 (manufactured by CABOT JAPAN KK), 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, and Special Black 4 (all manufactured by Degussa).

[0105] Examples of white pigments include CI Pigment White 6, 18, and 21.

[0106] Examples of yellow pigments include CI Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 16, 17, 24, 34, 35, 37, 53, 55, 65, 73, 74, 75, 81, 83, 93, 94, 95, 97, 98, 99, 108, 109, 110, 113, 114, 117, 120, 124, 128, 129, 133, 138, 139, 147, 151, 153, 154, 155, 167, 172, and 180.

[0107] Magenta-based pigments include CI Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 40, 41, 42, 48(Ca), 48(Mn), 57(Ca), 57:1, 88, 112, 114, 122, 123, 144, 146, 149, 150, 166, 168, 170, 171, 175, 176, 177, 178, 179, 184, 185, 187, 202, 209, 219, 224, 245, or CI Pigment Violet. Numbers 19, 23, 32, 33, 36, 38, 43, and 50 can be cited.

[0108] In addition, pigments other than 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.

[0109] The above pigments may be used individually or in combination of two or more. When using the above pigments, the average particle size is preferably 300 nm or less, and more preferably between 50 nm and 200 nm. When the average particle size is within the above range, the reliability of the cyan ink composition, such as discharge stability and dispersion stability, is further improved, and images with superior quality can be formed.

[0110] As dyes, there are no particular limitations, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used. For example, as dyes, 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, 142, 144, Examples include 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.

[0111] The above dyes may be used individually or in combination of two or more.

[0112] The lower limit of the colorant content is preferably 1% by mass or more, and more preferably 2% by mass or more, relative to the total amount (100% by mass) of the cyan ink composition. The upper limit of the colorant content is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, relative to the total amount (100% by mass) of the cyan ink composition. When the colorant content is within the above range, the coverage of the color gamut may be further improved.

[0113] 2.1.2. Other Ingredients The components other than colorants that may be contained in the cyan ink composition included in the ink set according to this embodiment are the same as those in the radiation-curable inkjet composition described above, so their explanation will be omitted.

[0114] 2.2. Magenta ink composition The ink set according to this embodiment includes a magenta ink composition. The components that may be included in the magenta ink composition are described below.

[0115] 2.2.1. Colorants The magenta ink composition included in the ink set according to this embodiment preferably contains a colorant. The colorants used in the magenta ink composition are not particularly limited, but examples include CI Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 40, 41, 42, 48(Ca), 48(Mn), 57(Ca), 57:1, 88, 112, 114, 122, 123, 144, 146, 149, 150, 166, 168, 170, 171, 175, 176, 177, 178, 179, 184, 185, 187, 202, 209, 219, 224, 245, or CI Pigment Violet. Numbers 19, 23, 32, 33, 36, 38, 43, and 50 can be cited.

[0116] The magenta ink composition included in the ink set according to this embodiment may also contain colorants other than those described above, such as those that can be contained in the cyan ink composition described above, and the same applies to the content and other aspects, so no further explanation is given.

[0117] 2.2.2. Other Ingredients The components other than colorants that the magenta ink composition included in the ink set according to this embodiment may contain are the same as those in the radiation-curable inkjet composition described above, so their explanation will be omitted.

[0118] 2.3. Yellow Ink Composition The ink set according to this embodiment includes a yellow ink composition. The components that may be contained in the yellow ink composition are described below.

[0119] 2.3.1. Colorants The yellow ink composition included in the ink set according to this embodiment preferably contains a colorant. The colorant used in the yellow ink composition is not particularly limited, but examples include CI Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 16, 17, 24, 34, 35, 37, 53, 55, 65, 73, 74, 75, 81, 83, 93, 94, 95, 97, 98, 99, 108, 109, 110, 113, 114, 117, 120, 124, 128, 129, 133, 138, 139, 147, 151, 153, 154, 155, 167, 172, and 180.

[0120] The yellow ink composition included in the ink set according to this embodiment may also contain colorants other than those described above, such as those that can be contained in the cyan ink composition described above, and the same applies to the content and other aspects, so no further explanation is given.

[0121] 2.3.2. Other Ingredients The components other than colorants that the yellow ink composition included in the ink set according to this embodiment may contain are the same as those in the radiation-curable inkjet composition described above, so their explanation will be omitted.

[0122] 2.4. Black Ink Composition The ink set according to this embodiment includes a black ink composition. The components that may be included in the black ink composition are described below.

[0123] 2.4.1. Colorants The black ink composition included in the ink set according to this embodiment preferably contains a colorant. There are no particular restrictions on the colorants used in the black ink composition, but for example, carbon blacks such as furnace black, lamp black, acetylene black, and channel black (CI Pigment Black 7) can be used. More specifically, carbon blacks used for black include No. 2300, No. 900, MCF88, No. 33, No. 40, No. 45, No. 52, MA7, MA8, MA100, No. 2200B, etc. (all manufactured by Mitsubishi Chemical Corporation), Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700, etc. (all manufactured by Carbon Columbia), Rega1 400R, Rega1 330R, Rega1 660R, Mogul L, Monarch 700, Monarch 800, Monarch Examples include the 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc. (manufactured by CABOT JAPAN KK), 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, and Special Black 4 (all manufactured by Degussa).

[0124] The black ink composition included in the ink set according to this embodiment may also contain colorants other than those described above, such as those that can be contained in the cyan ink composition described above, and the same applies to the content and other aspects, so no further explanation is given.

[0125] 2.4.2. Other Ingredients The components other than colorants that the black ink composition included in the ink set according to this embodiment may contain are the same as those in the radiation-curable inkjet composition described above, so their explanation will be omitted.

[0126] 3. 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.

[0127] 3.1 Preparation of inkjet composition First, the colorant, dispersant, and a portion of each monomer 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 a polymerizable compound. Next, the remaining monomer, polymerization initiator, polymerization inhibitor, and slip agent were placed in a stainless steel container, a mixing tank, to obtain the composition shown in Tables 1 to 3 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, the mixture was filtered through a 5 μm membrane filter to obtain the inkjet compositions for each example.

[0128] The values ​​for each component shown in the examples in Tables 1 to 3 below represent mass percentages. The ratios listed in Tables 1 to 3 below represent the mass ratio of each component. In Tables 1 to 3 below, "vinyl compound" refers to an N-vinyl compound, and is indicated with "○" when applicable. In Table 3 below, "Cy" refers to the cyan ink composition, "Ma" refers to the magenta ink composition, "Ye" refers to the yellow ink composition, "Bk" refers to the black ink composition, and "CMYK composition" refers to the cyan ink composition, magenta ink composition, yellow ink composition, and black ink composition.

[0129] Note that the "Tg (°C) of monomer" in Tables 1 to 3 below is the weighted average of the glass transition temperatures of the monomers included in each example.

[0130] [Table 1]

[0131] [Table 2]

[0132] [Table 3]

[0133] Further explanations are provided for each component shown in Tables 1 to 3 above. <Monomer> • NVC (product name "V-CAP", manufactured by ISP Japan, N-vinylcaprolactam) • VMOX (manufactured by BASF, vinylmethyloxazolidinone) • THFA (product name "V#150", manufactured by Osaka Organic Chemical Industry Co., Ltd., tetrahydrofurfuryl acrylate) • DCPA (product name "FA-511AS", manufactured by Hitachi Chemical Co., Ltd., dicyclopentenyl acrylate) • IBXA (product name, manufactured by Osaka Organic Chemical Industry Co., Ltd., isobornyl acrylate) • PEA (product name "Viscote #192", manufactured by Osaka Organic Chemical Industry Co., Ltd., phenoxyethyl acrylate) • ACMO (product name, manufactured by KJ Chemicals Co., Ltd., acryloylmorpholin) • BZA (product name "V#160", manufactured by Osaka Organic Chemical Industry Co., Ltd., benzyl acrylate) • VEEA (product name, manufactured by Nippon Shokubai Co., Ltd., 2-(2-vinyloxyethoxy)ethyl acrylate) • DPGDA (product name "APG-100", manufactured by Shin-Nakamura Chemical Co., Ltd., dipropylene glycol diacrylate) <Polymerization initiator> • 819 (Product name "Omnirad 819", manufactured by IGM Resins BV, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide) • TPO (product name "Speedcure TPO", manufactured by Lambson, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide) <Polymerization inhibitors> • MEHQ (product name, manufactured by Kanto Chemical Co., Ltd., hydroquinone monomethyl ether) <Slip agent> • BKY-UV3500 (product name, manufactured by Bic Chemie Japan, polyether-modified polydimethylsiloxane)

[0134] <Colorants> • PO36 (CI Pigment Orange 36) • PO38 (CI Pigment Orange 38) • PO43 (CI Pigment Orange 43) • PO64 (CI Pigment Orange 64) PO71 (CI Pigment Orange 71) PO13 (CI Pigment Orange 13) • PR177 (CI Pigment Red 177) • PR179 (CI Pigment Red 179) • PR224 (CI Pigment Red 224) • PR254 (CI Pigment Red 254) • PR255 (CI Pigment Red 255) • PR175 (CI Pigment Red 175) • PV23 (CI Pigment Violet 23) PV32 (CI Pigment Violet 32) PV37 (CI Pigment Violet 37) PV39 (CI Pigment Violet 39) PG7 (CI Pigment Green 7) PG36 (CI Pigment Green 36) PB15:6 (CI Pigment Blue 15:6) PB25 (CI Pigment Blue 25) PB60 (CI Pigment Blue 60) PB15:3 (CI Pigment Blue 15:3) • PR122 (CI Pigment Red 122) • PY155 (CI Pigment Yellow 155) • Carbon black (carbon black pigment) <Dispersant> • Solsperse 36000 (product name, manufactured by Lubrizol, polymer dispersant)

[0135] 3.2. Evaluation Method 3.2.1. Evaluation of color weather resistance Using an inkjet printer "PX-G5000" (manufactured by Seiko Epson Corporation), each inkjet composition obtained above was filled into its respective nozzle row. Printing was performed on a PVC film (manufactured by 3M Corporation, product name "IJ180-10") at room temperature and atmospheric pressure, adjusting the duty cycle so that the ink dot diameter was medium and the initial OD value was 0.5, 1.0, and the maximum value. At the same time, an irradiation intensity of 100 mW / cm² was applied from a UV-LED in an ultraviolet irradiation device mounted next to the carriage. 2 To achieve this, the first irradiation was performed at a wavelength of 385 nm, followed by an irradiation intensity of 1000 mW / cm². 2 The accumulated light intensity is 700 mJ / cm². 2 The image was cured by a second irradiation at a wavelength of 395 nm. In this way, a record with the image printed on a PVC film was produced.

[0136] Subsequently, the obtained records were placed in the chamber of a xenon weather meter (manufactured by Suga Test Instruments Co., Ltd.), and a cycle test was conducted under the test conditions shown in Table 4 below: "40 minutes of light irradiation" → "20 minutes of light irradiation + water precipitation" → "60 minutes of light irradiation" → "60 minutes of water precipitation". This cycle test was carried out continuously for 12 weeks, and the records were removed after 12 weeks. For each removed record, the OD value was measured using a Gretag densitometer (manufactured by Gretag Macbeth), and the remaining OD value percentage (%) was determined. Of the three types of records with initial OD values ​​of 0.5, 1.0, and the maximum value, the record with the lowest remaining percentage was selected for evaluation. Weather resistance was judged based on the following criteria. (Evaluation Criteria) A: OD value retention rate of 90% or more B: OD value retention rate is 80% or more but less than 90% C: OD value retention rate is 70% or more but less than 80% D: OD value retention rate less than 70%

[0137] [Table 4]

[0138] 3.2.2. Evaluation of paint film cracks In "3.2.1. Evaluation of Color Weather Resistance" above, the coating on the recorded material was visually inspected after a 12-week continuous cycle test, and evaluated based on the following evaluation criteria. (Evaluation Criteria) A: No paint peeling. B: Cracks and paint peeling present.

[0139] 3.2.3. Evaluation of Smoothness (Color Development) The coating film of the recording material prepared in "3.2.1. Evaluation of Color Weather Resistance" above was measured for cross-sectional roughness Rz (μm) using an interference microscope and evaluated based on the following evaluation criteria. Note that the smaller the cross-sectional roughness Rz (μm), the better the gloss and therefore the superior the color development. (Evaluation Criteria) A: 0.85 or less B: Over 0.85 and less than 1.00 C:1.00 or more

[0140] 3.2.4. Evaluation of Color Gamut Coverage Improvement Using the inkjet printer "PX-G5000" (manufactured by Seiko Epson Corporation), the inkjet compositions of each example or comparative example obtained above were combined with the CMYK inkjet composition and filled into the nozzle row. A solid pattern image was printed on a PVC film (manufactured by 3M Ltd., product name "IJ180-10") at room temperature and atmospheric pressure, with the ink dots being medium-sized and the film thickness of the printed material being 10 μm. At the same time, an irradiation intensity of 100 mW / cm² was applied from a UV-LED in an ultraviolet irradiation device mounted next to the carriage. 2 To achieve this, the first irradiation was performed at a wavelength of 385 nm, followed by an irradiation intensity of 1000 mW / cm². 2 The accumulated light intensity is 700 mJ / cm². 2 The image was cured by a second irradiation at a wavelength of 395 nm. In this way, a record with the image printed on a PVC film was produced.

[0141] Furthermore, using the inkjet printer "PX-G5000" (manufactured by Seiko Epson Corporation), the CMYK inkjet compositions obtained above were filled into the nozzle rows, and a record was produced in the same manner as described above.

[0142] The coverage rate on the Pantone® color chart was measured for these two recordings, and the degree to which the coverage rate of each example and comparative example improved compared to a recording made using only CMYK inkjet ink compositions was determined according to the evaluation criteria below. Note that the color gamut coverage rate is derived from the pigment. (Evaluation Criteria) A: 5% or more B: 3% or more but less than 5% C: 2% to less than 3% D: 0% or more and less than 2%

[0143] 3.2.5. Evaluation of stretchability Each inkjet composition obtained above was coated onto a PVC film (product name "JT5829R", manufactured by MACtac) to a thickness of 10 μm using a bar coater. Then, a metal halide lamp (manufactured by iGraphics) was used to inflate the film at 400 mJ / cm². 2 A coating film was formed by curing with the energy described above. The release paper was peeled off the PVC film on which the above coating film was formed, and test specimens were prepared by cutting them into strips 1 cm wide and 8 cm long. For each test specimen, the elongation rate as a measure of flexibility was measured using a tensile testing machine (product name "TENSILON", manufactured by ORIENTEC). The elongation rate was defined as the value at which a crack occurred when pulled at 5 mm / min. This value was calculated using the formula {(length at crack - length before stretching) / length before stretching × 100}. The evaluation criteria are shown below. (Evaluation Criteria) A: Over 300% B: 250% or more, less than 300% C: 200% or more, less than 250% D: Less than 200%

[0144] 3.2.6. Evaluation of abrasion resistance The cured coating film prepared in "3.2.5. Evaluation of Stretchability" above was evaluated using a micro-scratch test in accordance with JIS R3255. For measurement, an ultra-thin film scratch tester (product name "CSR-5000", manufactured by Nanotec Corporation) 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 while applying a load during micro-scratching. 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

[0145] 3.3. Evaluation Results The results of the evaluation tests are shown in Tables 1 to 3 above.

[0146] Based on the evaluation results above, each embodiment was able to increase the color gamut coverage while preventing cracking of the printed coating (coating cracks) when installed outdoors.

[0147] In contrast, each of the comparative examples failed to achieve both high color gamut coverage and prevention of cracking of the printed coating when installed outdoors. Specifically, in Comparative Example 1, the monofunctional polymerizable compound was not within the specified range, so coating cracking could not be prevented. Also, in Comparative Examples 2 and 3, the color gamut coverage could not be improved because specific pigments were not used.

[0148] The following conclusions can be drawn from the embodiments described above.

[0149] One embodiment of a radiation-curable inkjet composition is: The polymerizable compound contains 78% by mass or more of a monofunctional polymerizable compound relative to the total amount of the polymerizable compound. The colorants include at least one selected from the group consisting of CI Pigment Orange 36, CI Pigment Orange 38, CI Pigment Orange 43, CI Pigment Orange 64, CI Pigment Orange 71, CI Pigment Red 177, CI Pigment Red 179, CI Pigment Red 224, CI Pigment Red 254, CI Pigment Red 255, CI Pigment Violet 23, CI Pigment Violet 32, CI Pigment Violet 37, CI Pigment Violet 39, CI Pigment Green 7, CI Pigment Green 36, CI Pigment Blue 15:6, CI Pigment Blue 25, and CI Pigment Blue 60.

[0150] In one embodiment of the above radiation-curable inkjet composition, The aforementioned colorant may include CI Pigment Orange 43 or CI Pigment Red 254.

[0151] In one embodiment of the above radiation-curable inkjet composition, The content of the N-vinyl compound as the polymerizable compound may be 5% by mass or less relative to the total amount of the polymerizable compound.

[0152] In one embodiment of the above radiation-curable inkjet composition, The polymerizable compounds may include 90% by mass or more of the monofunctional polymerizable compounds relative to the total amount of the polymerizable compounds.

[0153] In one embodiment of the above radiation-curable inkjet composition, The weighted average of the glass transition temperatures (Tg) of each homopolymer in the polymerizable compound, weighted by the mass ratio of each polymerizable compound's content, may be 42°C or higher.

[0154] One form of an ink set is, The present invention comprises a cyan ink composition, a magenta ink composition, a yellow ink composition, a black ink composition, and a radiation-curable inkjet composition according to the above embodiment.

[0155] 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 comprising: a polymerizable compound containing 78% by mass or more of a monofunctional polymerizable compound relative to the total amount of the polymerizable compound; a colorant containing at least one selected from the group consisting of C.I. Pigment Red 177, C.I. Pigment Red 179, C.I. Pigment Red 224, C.I. Pigment Red 254, C.I. Pigment Red 255, C.I. Pigment Blue 15:6, C.I. Pigment Blue 25, and C.I. Pigment Blue 60; a weighted average of the glass transition temperatures (Tg) of each homopolymer in the polymerizable compound, weighted by the mass ratio of the respective polymerizable compounds, is 42°C or higher; and the colorant content is 1% by mass or more and 20% by mass or less; Cyan ink composition and Magenta ink composition and Yellow ink composition and An ink set containing a black ink composition.

2. The ink set according to claim 1, wherein the colorant includes C.I. Pigment Red 254.

3. The ink set according to claim 1 or claim 2, wherein the content of the N-vinyl compound as the polymerizable compound is 5% by mass or less relative to the total amount of the polymerizable compound.

4. The ink set according to any one of claims 1 to 3, wherein the polymerizable compound contains 90% by mass or more of the monofunctional polymerizable compound based on the total amount of the polymerizable compound.

5. The ink set according to any one of claims 1 to 4, wherein the polymerizable compound comprises an N-vinyl compound, and the N-vinyl compound comprises vinylmethyloxazolidinone.

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