Ink for ink-jet recording and ink-jet recording method

Abstract

Provided is an ink for inkjet recording, an inkjet recording method, and an ink cartridge. The ink for inkjet recording contains: a polymerizable monomer (A); a polymerization initiator (B); a siloxane compound (C) containing a main chain and a side chain, the main chain containing a structural unit containing a Si-O bond, the side chain containing at least one of an ethyleneoxy unit and a propyleneoxy unit and a polymerizable group, the ratio of the total number of moles of the ethyleneoxy unit and the propyleneoxy unit to the total number of moles of the structural unit containing a Si-O bond, the ethyleneoxy unit, and the propyleneoxy unit being 30% or greater; and a near-infrared absorbing pigment (D).

Description

Technical Field

[0001] This invention relates to an ink for inkjet recording and an inkjet recording method. Background Technology

[0002] In recent years, research has been conducted on inks containing near-infrared absorbing pigments.

[0003] For example, in Patent Document 1, a photocurable ink composition for recording images with high infrared absorption rate and excellent lightfastness after photocuring is disclosed. The photocurable ink composition contains particles of a specific squartzite pigment as a near-infrared absorbing pigment, a free radical polymerizable monomer, a free radical polymerization initiator, and a pigment sensitizer. The volume average particle size of the squartzite pigment particles is 10 nm to 400 nm.

[0004] Patent Document 1: International Publication No. 2020 / 202628 Summary of the Invention

[0005] The technical problem to be solved by the invention

[0006] Inks containing near-infrared absorbing pigments are sometimes used for recording near-infrared absorbing images for security or traceability purposes. These near-infrared absorbing images are sometimes recorded as Dot Code (two-dimensional code) patterns and read by infrared illumination.

[0007] On the other hand, in recent years, there has been an increased chance of alcohols, such as ethanol, adhering to images in image recordings. For example, alcohols are sometimes used as cleaning agents for wiping during the processing of image recordings for purposes such as cleaning and disinfection. Furthermore, alcohols can sometimes adhere to images during the material transport process of image recordings.

[0008] However, when alcohol adheres to an infrared absorption image, it may be difficult to read the infrared absorption image.

[0009] In the above cases, from the point of view of ensuring readability even when alcohol is attached, alcohol resistance is sometimes required for near-infrared absorption images.

[0010] One aspect of the present invention is to provide an inkjet recording ink and an inkjet recording method capable of recording near-infrared absorption images with excellent alcohol resistance.

[0011] means for solving technical problems

[0012] The present invention includes the following methods.

[0013] <1> An inkjet recording ink, comprising:

[0014] Polymerizable monomer (A);

[0015] Polymerization initiator (B);

[0016] A siloxane compound (C) comprising a main chain and side chains, said main chain comprising structural units containing Si-O bonds, said side chains comprising at least one of ethylene oxide units and propylene oxide units and polymerizable groups, wherein the total molar number of ethylene oxide units and propylene oxide units is at least 30 mol% of the total molar number of the structural units containing Si-O bonds, ethylene oxide units, and propylene oxide units; and

[0017] Near-infrared absorbing pigment (D).

[0018] <2> The ink for inkjet recording as described in <1>, wherein,

[0019] The SP value of polymerizable monomer (A) is 18.0 MPa. 1 / 2 the following.

[0020] <3> The ink for inkjet recording according to <1> or <2>, wherein,

[0021] The content of siloxane compounds (C) is 0.5% to 3.0% by mass relative to the total amount of inkjet recording ink.

[0022] <4> Inkjet recording ink according to any one of <1> to <3>, wherein,

[0023] The mass ratio of the polymerizable monomer (A) to the siloxane compound (C) is 26.0–300.

[0024] <5> Inkjet recording ink according to any one of <1> to <4>, wherein,

[0025] The proportion of monofunctional polymerizable monomers in polymerizable monomer (A) is less than 50% by mass.

[0026] <6> Inkjet recording ink according to any one of <1> to <5>, wherein,

[0027] Near-infrared absorbing pigment (D) contains squaric acid onyx pigment represented by the following formula 1.

[0028] [Chemical Formula 1]

[0029]

[0030] In Formula 1, ring A and ring B independently represent aromatic rings or heteroaromatic rings, respectively, X A and X B Each independently represents a monovalent substituent, G A and G BEach of these groups independently represents a monovalent substituent, and kA represents 0 to n. A Integers, kB represents 0 to n B an integer, n A and n B They represent G that can be substituted on ring A or ring B, respectively. A and G B The maximum number of integers, X A With G A They can bond together to form a ring, X B With G B They can bond together to form a ring, and when G A and G B When multiple G exist, A Each other and G B They can also bond with each other to form a ring structure.

[0031] <7> Inkjet recording ink according to any one of <1> to <6>, wherein,

[0032] The siloxane compound (C) comprises a siloxane compound (CA) represented by the following formula CA.

[0033] [Chemical Formula 2]

[0034]

[0035] In formula CA,

[0036] Rp represents a polymerizable group.

[0037] L1 represents a divalent linker group.

[0038] x represents an integer greater than or equal to 1.

[0039] y represents an integer greater than or equal to 0.

[0040] m and n each independently represent integers greater than or equal to 0.

[0041] The sum of m and n is an integer greater than or equal to 1.

[0042] In formula CA, the value A calculated by the formula “((m+n) / (x+y+m+n))×100” is 30 or higher.

[0043] In formula CA, the arrangement of structural units labeled with subscript x and structural units labeled with subscript y can be either a block copolymer arrangement or a random copolymer arrangement.

[0044] In formula CA, the arrangement of structural units labeled with subscript m and structural units labeled with subscript n can be either a block copolymer arrangement or a random copolymer arrangement.

[0045] <8> The ink for inkjet recording according to any one of <1> to <7> further contains pigment derivatives.

[0046] <9> The ink for inkjet recording according to any one of <1> to <8> further contains an acrylic resin.

[0047] <10> An inkjet recording method, which uses inkjet recording ink as described in any one of <1> to <9>.

[0048] The inkjet recording method includes:

[0049] The process of spraying the aforementioned ink for inkjet recording onto a substrate using an inkjet recording method; and

[0050] The process of irradiating the inkjet recording ink ejected onto the aforementioned substrate with active energy rays.

[0051] Invention Effects

[0052] According to one aspect of the present invention, an inkjet recording ink and an inkjet recording method are provided that are capable of recording near-infrared absorption images with excellent alcohol resistance. Detailed Implementation

[0053] The ink for inkjet recording and the inkjet recording method of the present invention will be described in detail below.

[0054] In this specification, the numerical range represented by “~” indicates the range included by taking the values ​​before and after “~” as the minimum and maximum values, respectively.

[0055] In the numerical ranges described in this specification, the upper or lower limit value recorded in a certain numerical range can be replaced with the upper or lower limit value of other numerical ranges described in different stages. Furthermore, the upper or lower limit value recorded in a certain numerical range described in this specification can also be replaced with the value shown in the embodiments.

[0056] In this specification, when multiple substances corresponding to each component are present in the composition, unless otherwise specified, the amount of each component in the composition refers to the total amount of the multiple substances present in the composition.

[0057] In this specification, a combination of two or more preferred methods is a more preferred method.

[0058] In this specification, the term "process" includes not only independent processes, but also processes that can not be clearly distinguished from other processes, as long as the intended purpose of the process can be achieved.

[0059] In this specification, "(meth)acrylate" is a concept that includes both acrylate and methacrylate, "(meth)acrylic acid" is a concept that includes both acrylic acid and methacrylic acid, and "(meth)acryloyl" is a concept that includes both acryloyl and methacryloyl.

[0060] In this specification, "near-infrared radiation" refers to electromagnetic waves with a maximum absorption wavelength of 700nm to 2500nm.

[0061] [Inkjet recording ink]

[0062] The inkjet recording ink (hereinafter, simply referred to as "ink") of the present invention contains:

[0063] Polymerizable monomer (A);

[0064] Polymerization initiator (B);

[0065] A siloxane compound (C) comprising a main chain and side chains, said main chain comprising structural units containing Si-O bonds, said side chains comprising at least one of ethylene oxide units and propylene oxide units and polymerizable groups, wherein the total molar number of ethylene oxide units and propylene oxide units is at least 30 mol% of the total molar number of the structural units containing Si-O bonds, ethylene oxide units, and propylene oxide units; and

[0066] Near-infrared absorbing pigment (D).

[0067] The ink of this invention may contain other components as needed.

[0068] The ink according to the present invention is capable of recording near-infrared absorption images with excellent alcohol resistance.

[0069] The reasons for this effect are speculated to be as follows.

[0070] As mentioned above, from the point of view, readability is ensured even when alcohol adheres to near-infrared absorbing images recorded using inks containing near-infrared absorbing pigments, alcohol resistance is sometimes required.

[0071] In this regard, the ink of the present invention is an ink containing a near-infrared absorbing pigment (D).

[0072] It is an ink containing polymerizable monomers (A) and polymerization initiators (B).

[0073] It is an ink containing siloxane compounds (C).

[0074] Siloxane compounds (C) are compounds that consist of a main chain and side chains.

[0075] The main chain contains structural units with Si-O bonds (hereinafter also referred to as "Si-O units").

[0076] The side chain contains at least one of an ethylene oxide unit and an propylene oxide unit (hereinafter also referred to as a "specific AO unit") and a polymerizable group.

[0077] Furthermore, the siloxane compound (C) is a compound in which the total molar number of ethyleneoxy units and propyleneoxy units is greater than or equal to the total molar number of Si-O units, ethyleneoxy units and propyleneoxy units (hereinafter also referred to as "molar ratio [specific AO unit / (Si-O unit + specific AO unit)]") is 30 mol% or more.

[0078] In this invention,

[0079] The structural unit containing Si-O bonds is represented by the following Si-O unit.

[0080] The ethyleneoxy unit represents the following EO unit,

[0081] The propylene oxide unit represents the PO unit described below.

[0082] [Chemical Formula 3]

[0083]

[0084] In Si-O, EO, and PO units, * indicates a bonding position.

[0085] When the ink of the present invention is applied to a substrate, the main chain of the siloxane compound (C) containing Si-O units is disposed near the surface of the ink film in the ink of the present invention applied to the substrate (hereinafter also referred to as "ink film").

[0086] This Si-O unit has the property of repelling alcohols.

[0087] Furthermore, it is believed that in the aforementioned ink film, the side chains of the siloxane compound (C) (i.e., side chains containing specific AO units and polymerizable groups) are disposed inside the ink film. It is believed that through the reaction of the polymerizable groups in these side chains with the polymerizable monomers present inside the ink film, the Si-O units of the siloxane compound (C) are fixed near the surface of the ink film.

[0088] In this embodiment, the molar ratio [specific AO unit / (Si-O unit + specific AO unit)] in the siloxane compound (C) is 30 mol% or more. This molar ratio [specific AO unit / (Si-O unit + specific AO unit)] corresponds to the proportion of the side chain in the total siloxane compound (C). It is believed that by making this molar ratio [specific AO unit / (Si-O unit + specific AO unit)] 30 mol% or more, the reaction between the polymerizable monomers inside the ink film and the polymerizable groups on the side chains of the siloxane compound (C) is promoted. As a result, the Si-O units on the main chain of the siloxane compound (C) are firmly fixed near the surface of the ink film.

[0089] The ink film is cured by polymerization of polymerizable monomer (A) to form a near-infrared absorption image.

[0090] It is believed that Si-O units are also firmly fixed near the surface of the near-infrared absorption image formed by curing the above-mentioned ink film.

[0091] As a result, it is believed that the alcohol resistance of near-infrared absorption images can be maintained stably (e.g., even if the surface of the near-infrared absorption image is rubbed).

[0092] Near-infrared absorption images are preferably Dot Code (two-dimensional code) images.

[0093] Typically, Dot Code images have a larger specific surface area (i.e., the proportion of the air interface) compared to solid films. Therefore, Dot Code images are susceptible to polymerization inhibition caused by oxygen, resulting in insufficient surface curing and consequently reduced alcohol resistance.

[0094] In contrast, the ink according to the present invention can effectively improve alcohol resistance even when the near-infrared absorption image is a Dot Code image, through the action of the siloxane compound (C).

[0095] Next, the components that may be contained in the ink of the present invention will be described.

[0096] <Polymerizable Monomer (A)>

[0097] The ink of the present invention contains a polymerizable monomer (A).

[0098] In this invention, polymerizable monomer (A) refers to all polymerizable monomers that may be contained in the ink.

[0099] The polymerizable monomer (A) can be just one polymerizable monomer or two or more polymerizable monomers.

[0100] In this invention, a monomer refers to a compound with a molecular weight of less than 1000. A polymerizable monomer refers to a compound having polymerizable groups and a molecular weight of less than 1000.

[0101] The molecular weight of the polymerizable monomer is preferably 100 or more and less than 1000, more preferably 100 to 800, and even more preferably 150 to 700. The molecular weight of the polymerizable monomer is calculated based on the types and numbers of atoms constituting the polymerizable monomer.

[0102] Examples of polymerizable monomers include photopolymerizable monomers that polymerize by light irradiation and thermopolymerizable monomers that polymerize by heating or infrared irradiation. Examples of photopolymerizable monomers include polymerizable monomers having free radical polymerizable groups capable of free radical polymerization (i.e., free radical polymerizable monomers) and polymerizable monomers having cationic polymerizable groups capable of cationic polymerization (i.e., cationic polymerizable monomers).

[0103] The polymerizable monomer is preferably a photopolymerizable monomer, and more preferably a free radical polymerizable monomer.

[0104] The preferred free radical polymerizable monomer is an olefin unsaturated monomer having an olefin unsaturated group as a free radical polymerizable group.

[0105] As olefin unsaturated monomers, examples include monofunctional and polyfunctional olefin unsaturated monomers.

[0106] Monofunctional olefin unsaturated monomers refer to monomers having one olefin unsaturated group, such as monofunctional (meth)acrylates, monofunctional (meth)acrylamides, monofunctional aromatic vinyl compounds, monofunctional vinyl ethers, and monofunctional N-vinyl compounds.

[0107] Examples of monofunctional (meth)acrylates include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, tert-octyl methacrylate, isoamyl methacrylate, decyl methacrylate, isodecyl methacrylate, lauryl methacrylate, octadecyl methacrylate, isooctadecyl methacrylate, cyclohexyl methacrylate, 4-n-butylcyclohexyl methacrylate, 4-tert-butylcyclohexyl methacrylate, borneol methacrylate, isoborneol methacrylate, and 2-ethylhexyl methacrylate. Diethylene glycol (meth)acrylate, butoxyethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, 4-bromobutyl (meth)acrylate, cyanoethyl (meth)acrylate, benzyl (meth)acrylate, butoxymethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-(2-methoxyethoxy)ethyl (meth)acrylate, 2-(2-butoxyethoxy)ethyl (meth)acrylate, ethyl carbitol (meth)acrylate, 2,2,2-tetrafluoroethyl (meth)acrylate, 1H,1H,2H,2H-perfluorodecyl (meth)acrylate, 4-butylphenyl (meth)acrylate, phenyl (meth)acrylate, 2,4-butyl (meth)acrylate5-Tetramethylphenyl ester, 4-chlorophenyl acrylate, 2-phenoxymethyl acrylate, 2-phenoxyethyl acrylate, glycidyl acrylate, glycidyl acrylate, glycidyl acrylate, glycidyl acrylate, glycidyl acrylate, propyl acrylate, tetrahydrofurfuryl acrylate, 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl acrylate Butyl acrylate, 4-hydroxybutyl acrylate, 3-hydroxybutyl acrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminopropyl acrylate, trimethoxysilyl propyl acrylate, trimethylsilyl propyl acrylate, polyethylene oxide monomethyl ether (meth)acrylate, polyethylene oxide (meth)acrylate, polyethylene oxide monoalkyl ether (meth)acrylate, dipropylene glycol dimethacrylate Alcohol (meth)acrylates, polyoxypropylene monoalkyl ether (meth)acrylates, 2-methacryloyloxyethyl succinic acid, 2-methacryloyloxyhexahydrophthalic acid, 2-formyloxyethyl-2-hydroxypropyl phthalate, (meth)acrylate butoxydiethylene glycol ester, (meth)acrylate trifluoroethyl ester, perfluorooctyl ethyl (meth)acrylate, (meth)acrylate 2-hydroxy-3-phenoxypropyl ester, ethylene oxide (EO) modified phenol (meth)acrylate, EO modified cresol (meth)acrylate Esters, EO-modified nonylphenol (meth)acrylate, propylene oxide (PO)-modified nonylphenol (meth)acrylate, EO-modified 2-ethylhexyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenoxyethyl (meth)acrylate, dicyclopentenyl (meth)acrylate, 3-ethyl-3-oxetanebutylmethyl (meth)acrylate, phenoxyethylene glycol (meth)acrylate, phenoxyethylene glycol (meth)acrylate, and cyclic trimethylolpropane methyl acetal (meth)acrylate.

[0108] Examples of monofunctional (meth)acrylamides include (meth)acrylamide, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N-propyl (meth)acrylamide, N-n-butyl (meth)acrylamide, N-tert-butyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, and (meth)acryloylmorpholine.

[0109] Examples of monofunctional aromatic vinyl compounds include styrene, dimethylstyrene, trimethylstyrene, isopropylstyrene, chloromethylstyrene, methoxystyrene, acetoxystyrene, chlorostyrene, dichlorostyrene, bromostyrene, methyl vinyl benzoate, 3-methylstyrene, 4-methylstyrene, 3-ethylstyrene, 4-ethylstyrene, 3-propylstyrene, 4-propylstyrene, 3-butylstyrene, 4-butylstyrene, 3-hexylstyrene, 4-hexylstyrene, 3-octylstyrene, 4-octylstyrene, 3-(2-ethylhexyl)styrene, 4-(2-ethylhexyl)styrene, allylstyrene, isopropylstyrene, butenylstyrene, octenylstyrene, 4-tert-butoxycarbonylstyrene, and 4-tert-butoxystyrene.

[0110] Examples of monofunctional vinyl ethers include, for example, methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, n-butyl vinyl ether, tert-butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, lauryl vinyl ether, cyclohexyl vinyl ether, cyclohexylmethyl vinyl ether, 4-methylcyclohexylmethyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, ethoxyethoxyethyl vinyl ether, methoxy polyethylene glycol vinyl ether, tetrahydrofurfuryl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexylmethyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chloroethyl vinyl ether, chlorobutyl vinyl ether, chloroethoxyethyl vinyl ether, phenylethyl vinyl ether, and phenoxy polyethylene glycol vinyl ether.

[0111] Examples of monofunctional N-vinyl compounds include, for example, N-vinyl-ε-caprolactam and N-vinylpyrrolidone.

[0112] From the perspective of improving curability, monofunctional olefinic unsaturated compounds are preferably compounds with cyclic structures. Examples of monofunctional olefinic unsaturated compounds with cyclic structures include cyclohexyl methacrylate, 4-n-butylcyclohexyl methacrylate, 4-tert-butylcyclohexyl methacrylate, borneol acrylate, isoborneol acrylate, benzyl methacrylate, 4-butylphenyl methacrylate, phenyl methacrylate, 2,4,5-tetramethylphenyl methacrylate, 4-chlorophenyl methacrylate, 2-phenoxymethyl methacrylate, 2-phenoxyethyl methacrylate, dicyclopentenyl methacrylate, dicyclopentenyloxyethyl methacrylate, dicyclopentyl methacrylate, (3-ethyl-3-oxetanebutylmethyl) methacrylate, phenoxyethylene glycol (meth)acrylate, and cyclic trimethylolpropane methyl acetal (meth)acrylate, among other monofunctional (meth)acrylates with cyclic structures.

[0113] Monofunctional aromatic vinyl compounds;

[0114] Cyclohexyl vinyl ether, cyclohexyl methyl vinyl ether, 4-methylcyclohexyl methyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenoxyethyl vinyl ether, phenyl ethyl vinyl ether, phenoxy polyethylene glycol vinyl ether and other monofunctional vinyl ethers with cyclic structures;

[0115] Monofunctional N-vinyl compounds with cyclic structures, such as N-vinyl-ε-caprolactam and N-vinylpyrrolidone.

[0116] From the viewpoint of image abrasion resistance and solvent resistance, monofunctional olefinic unsaturated compounds are preferably compounds with high glass transition temperatures (Tg). Examples of monofunctional olefinic unsaturated compounds with a cyclic structure and high Tg include isobornyl (meth)acrylate (Tg 97°C).

[0117] Polyfunctional olefin unsaturated monomers refer to monomers having two or more olefin unsaturated groups, such as polyfunctional (meth)acrylates and polyfunctional vinyl ethers.

[0118] Examples of multifunctional (meth)acrylates include, for example, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butanediol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, and neopentyl glycol. Di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, hexanediol di(meth)acrylate, heptaethylenediol di(meth)acrylate, EO-modified neopentanediol di(meth)acrylate, PO-modified neopentanediol di(meth)acrylate, EO-modified hexanediol di(meth)acrylate, PO-modified hexanediol di(meth)acrylate, octanediol di(meth)acrylate, nonanediol di(meth)acrylate, decanediol di(meth)acrylate Acrylates, dodecanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, glycerol di(meth)acrylate, pentaerythritol di(meth)acrylate, ethylene glycol diglycidyl ether di(meth)acrylate, diethylene glycol diglycidyl ether di(meth)acrylate, tricyclodecanediethanol di(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane EO addition tri... (Meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tri(meth)acryloyloxyethoxytrimethylolpropane, glycerol polyglycidyl ether poly(meth)acrylate, tri(2-acryloyloxyethyl)isocyanurate and 2-(2-ethyleneoxyethoxy)ethyl(meth)acrylate.

[0119] Examples of multifunctional vinyl ethers include, for example, 1,4-butanediol divinyl ether, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, 1,4-cyclohexanediethanol divinyl ether, bisphenol A epoxy alkyl divinyl ether, bisphenol F epoxy alkyl divinyl ether, trimethylolethane trivinyl ether, trimethylolpropane trivinyl ether, and ditrimethylolpropane tetraethylene ether. Alkenyl ethers, glycerol trivinyl ethers, pentaerythritol tetravinyl ethers, dipentaerythritol pentavinyl ethers, dipentaerythritol hexavinyl ethers, EO addition trimethylolpropane trivinyl ethers, PO addition trimethylolpropane trivinyl ethers, EO addition di-trimethylolpropane tetravinyl ethers, PO addition di-trimethylolpropane tetravinyl ethers, EO addition pentaerythritol tetravinyl ethers, PO addition pentaerythritol tetravinyl ethers, EO addition dipentaerythritol hexavinyl ethers, and PO addition dipentaerythritol hexavinyl ethers.

[0120] From the viewpoint of improving curability, the polyfunctional olefinic unsaturated monomer is preferably a compound containing oxygen atoms, and the ratio of the number of oxygen atoms to the number of carbon atoms in one molecule is preferably 0.2 or more, more preferably 0.3 or more. The upper limit of the ratio is not particularly limited, for example, it is 0.5. Examples of compounds with an oxygen-to-carbon ratio of 0.2 or more in one molecule include, for example, polyethylene glycol diacrylate.

[0121] Furthermore, the polymerizable monomers can be commercially available products as described in works such as Shinzo Yamashita's "Crosslinking Agent Handbook" (TAISEISHA, 1981); Kiyoshi Kato's "UV / EB Curing Handbook (Raw Materials)" (Polymer Journal, 1985); RadTech Japan's "Application and Market of UV / EB Curing Technology," page 79 (CMC Publishing Co., Ltd., 1989); and Eiichiro Ryuzan's "Polyester Resin Handbook" (NIKKAN KOGYO SHIMBUN, LTD., 1988).

[0122] As the polymerizable monomer (A), the ink of the present invention preferably contains a multifunctional polymerizable monomer, more preferably a monofunctional polymerizable monomer and a multifunctional polymerizable monomer. By containing a multifunctional polymerizable monomer in the ink, images with excellent curability can be recorded. Furthermore, by containing a multifunctional polymerizable monomer in the ink, the phenomenon of unreacted polymerizable monomers migrating from the image record to the outside (so-called migration) can be suppressed. In particular, it is excellent for use as a packaging material in the food packaging and cosmetic packaging fields where the safety of the substrate is strictly required.

[0123] From the viewpoint of curability, the proportion of the multifunctional polymerizable monomer in the polymerizable monomer (A) contained in the ink is preferably 50% by mass or more, and more preferably 60% by mass or more.

[0124] Furthermore, the upper limit of the proportion of multifunctional polymerizable monomers in the polymerizable monomers contained in the ink is not particularly limited and can be 100% by mass.

[0125] From the viewpoint of further improving the alcohol resistance of near-infrared absorption images, the proportion of monofunctional polymerizable monomers in the polymerizable monomers (A) contained in the ink is preferably 50% by mass or less, more preferably 40% by mass or less.

[0126] Furthermore, the proportion of monofunctional polymerizable monomers in the polymerizable monomers contained in the ink can be 0 by mass.

[0127] The polymerizable monomer (A) accounts for 50% or more by mass in the total amount of the ink of the present invention, more preferably 60% or more by mass, and even more preferably 70% or more by mass.

[0128] The upper limit of the polymerizable monomer (A) in the total amount of the ink of the present invention also depends on the amount of other components, such as 95% by mass, 90% by mass, etc.

[0129] Furthermore, from the viewpoint of further improving the alcohol resistance of near-infrared absorption images, the mass ratio of the content of the polymerizable monomer (A) to the content of the siloxane compound (C) in the ink of the present invention (hereinafter, the mass ratio [polymerizable monomer (A) / siloxane compound (C)]] is preferably 26.0 to 300, more preferably 26.0 to 200, and even more preferably 27.0 to 200.

[0130] In this invention, from the viewpoint of improving readability and solvent resistance after a wiping test, the glass transition temperature (Tg) of the polymerizable monomer (A) is preferably 30°C or higher, more preferably 60°C or higher. In particular, the proportion of the polymerizable monomer with a glass transition temperature of 30°C or higher in the polymerizable monomer (A) is preferably 90% by mass or higher, more preferably 92% by mass or higher. The upper limit of the above proportion is not particularly limited, for example, it is 100% by mass. If the proportion of the polymerizable monomer with a glass transition temperature of 30°C or higher in the polymerizable monomer (A) is 90% by mass or higher, the readability after the wiping test is further improved. For example, isobornyl (meth)acrylate (Tg: 97°C) can be cited as a polymerizable monomer with a Tg of 30°C or higher.

[0131] Furthermore, the glass transition temperature (Tg) of the polymerizable monomer (A) refers to the glass transition temperature when the polymerizable monomer (A) is a homopolymer. Homopolymers with a weight-average molecular weight of 10,000 to 20,000 are obtained by adding any polymerization initiator to the polymerizable monomer (A). The glass transition temperature (Tg) of the homopolymer with a weight-average molecular weight of 10,000 to 20,000 is used as the glass transition temperature of the polymerizable monomer (A). The glass transition temperature (Tg) of the homopolymer varies according to the weight-average molecular weight, but within the range of 10,000 to 20,000 weight-average molecular weight, the change in Tg due to the difference in weight-average molecular weight is negligible. Additionally, the weight-average molecular weight refers to the value determined by gel permeation chromatography (GPC). In the GPC-based assay, an HLC-8020GPC (manufactured by TOSOH CORPORATION) was used as the assay apparatus. Three TSKgel Super Multipore HZ-H (4.6mm ID × 15cm, manufactured by TOSOH CORPORATION) columns were used as the eluent, and THF (tetrahydrofuran) was used. The sample concentration was set to 0.45% by mass, the flow rate to 0.35 ml / min, the sample injection volume to 10 μl, and the assay temperature to 40°C. An RI detector was used for the measurement. Calibration curves were constructed based on eight samples from TOSOH CORPORATION's "Standard Samples TSK Standard, Polystyrene": "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000", and "n-propylbenzene".

[0132] The glass transition temperature (Tg) was determined using a differential scanning calorimeter (DSC) in accordance with ASTM D3418-8. For example, the glass transition temperature (Tg) was determined using a differential scanning calorimeter (product name "EXSTAR6220") manufactured by SII NanoTechnology Inc., under standard measurement conditions.

[0133] From the viewpoint of further improving the alcohol resistance of near-infrared absorption images, the SP value of the polymerizable monomer (A) is preferably 23.0 MPa. 1 / 2 Hereinafter, 20.0 MPa is more preferred. 1 / 2 Hereinafter, 18.0 MPa is further preferred. 1 / 2 Hereinafter, 17.6 MPa is further preferred. 1 / 2 the following.

[0134] In this invention, the SP value of the polymerizable monomer (A) refers to the Hansen solubility parameter. The Hansen solubility parameter is derived from the solubility parameter imported by Hildebrand and consists of three components: dispersion term δd, polarity term δp, and hydrogen bonding term δh, and is represented in three-dimensional space.

[0135] The SP value δ of the polymerizable monomer (A) is calculated using the following formula S.

[0136] SP value (δ) [MPa 1 / 2 ]=(δd 2 +δp 2 +δh 2 ) 1 / 2 ……(S)

[0137] In addition, the dispersion term δd, polarity term δp, and hydrogen bonding term δh were calculated using HSPiP (version 4.1.07) software.

[0138] The following shows the dispersion term δd, polarity term δp, hydrogen bonding term δh, and SP value for MPDDA (3-methyl-1,5-pentanediol diacrylate), DPGDA (dipropylene glycol diacrylate), IBOA (isobornyl acrylate), TCDDMDA (tricyclodecanediethanol diacrylate), TMTPA (trimethylolpropane triacrylate), ACMO (acryloylmorpholine), EOTMPTA (trimethylolpropane EO addition triacrylate), and PEA (phenoxyethyl acrylate).

[0139] [Chemical Formula 4]

[0140]

[0141] Furthermore, when the ink contains two or more polymerizable monomers (A), the SP value of the polymerizable monomers (A) is calculated using the following method. First, the weighted average of the dispersion, polarity, and hydrogen bonding terms of the polymerizable monomers (A) contained in the ink is calculated as δd, δp, and δh. Then, based on the calculated δd, δp, and δh, the SP value is calculated using the above formula S.

[0142] When the ink contains two or more polymerizable monomers (A), δd is calculated using the following formula F1. In formula F1, δd... m W represents the dispersed terms of the polymerizable monomer (A) consisting of m terms (m being an integer greater than 1). m This indicates the percentage (by mass) of the polymerizable monomer (A) in item m above relative to the total amount of ink.

[0143] δd=Σδd m W m / ΣWm ...(F1)

[0144] Similarly, when the ink contains two or more polymerizable monomers (A), δp and δh are calculated using the following formulas F2 and F3.

[0145] δp=Σδp m W m / ΣW m ...(F2)

[0146] δh=Σδh m W m / ΣW m ...(F3)

[0147] In equation F2, δp m Represents the polarity term of the polymeric monomer (A) for each of the m terms (m represents an integer greater than 1).

[0148] In equation F3, δh m This represents the hydrogen bond term of the polymerizable monomer (A) in the form of m terms (m represents an integer greater than or equal to 1).

[0149] <Polymerization Initiator (B)>

[0150] The ink of the present invention contains a polymerization initiator (B).

[0151] In this invention, polymerization initiator (B) refers to all polymerization initiators that may be contained in the ink.

[0152] The polymerization initiator (B) can be a single compound or two or more compounds.

[0153] When the polymerizable monomer (A) in the ink of the present invention contains a free radical polymerizable monomer, the polymerization initiator (B) preferably contains a free radical polymerization initiator.

[0154] Examples of free radical polymerization initiators include alkyl phenyl ketone compounds, acylphosphine compounds, aromatic ononium salt compounds, organic peroxides, thio compounds, hexaaryl biimidazole compounds, ketoxime ester compounds, borate compounds, azadinium compounds, metallocene compounds, active ester compounds, compounds with carbon-halogen bonds, and alkylamine compounds.

[0155] The polymerization initiator is preferably selected from at least one of the group consisting of acylphosphine compounds and thio compounds, more preferably selected from at least one of the group consisting of acylphosphine oxide compounds and thioxanone compounds, and more preferably consists of acylphosphine oxide compounds and thioxanone compounds.

[0156] If the polymerization initiator contains acylphosphine oxide compounds and thioxanone compounds, the readability after the transfer test and the readability after the wipe test are improved.

[0157] Examples of acylphosphine oxide compounds include monoacylphosphine oxide compounds and diacylphosphine oxide compounds, with diacylphosphine oxide compounds being preferred.

[0158] Examples of monoacylphosphine oxide compounds include, for example, isobutyryl diphenylphosphine oxide, 2-ethylhexanoyl diphenylphosphine oxide, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, o-toluyl diphenylphosphine oxide, p-tert-butylbenzoyl diphenylphosphine oxide, 3-pyridylcarbonyl diphenylphosphine oxide, acryloyl diphenylphosphine oxide, benzoyl diphenylphosphine oxide, and neopentyl phenylphosphine. Vinyl ester, adipyl bis(diphenylphosphine oxide), neopentyl diphenylphosphine oxide, p-toluyl diphenylphosphine oxide, 4-(tert-butyl)benzoyl diphenylphosphine oxide, terephthalyl bis(diphenylphosphine oxide), 2-methylbenzoyl diphenylphosphine oxide, neodecanoyl diphenylphosphine oxide, 2-methyl-2-ethylhexanoyl diphenylphosphine oxide, 1-methyl-cyclohexanoyl diphenylphosphine oxide, methyl neopentyl phenylphosphine and isopropyl neopentyl phenylphosphine.

[0159] Examples of diacylphosphine oxide compounds include, for example, bis(2,6-dichlorobenzoyl)phenylphosphine oxide, bis(2,6-dichlorobenzoyl)-2,5-dimethylphenylphosphine oxide, bis(2,6-dichlorobenzoyl)-4-ethoxyphenylphosphine oxide, bis(2,6-dichlorobenzoyl)-4-propylphenylphosphine oxide, bis(2,6-dichlorobenzoyl)-2-naphthylphosphine oxide, and bis(2,6-dichlorobenzoyl) -1-Naphthylphosphine oxide, bis(2,6-dichlorobenzoyl)-4-chlorophenylphosphine oxide, bis(2,6-dichlorobenzoyl)-2,4-dimethoxyphenylphosphine oxide, bis(2,6-dichlorobenzoyl)decylphosphine oxide, bis(2,6-dichlorobenzoyl)-4-octylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,5-dimethylphosphine oxide Bis(2,6-dichloro-3,4,5-trimethoxybenzoyl)-2,5-dimethylphenylphosphine oxide, Bis(2,6-dichloro-3,4,5-trimethoxybenzoyl)-4-ethoxyphenylphosphine oxide, Bis(2-methyl-1-naphthoyl)-2,5-dimethylphenylphosphine oxide, Bis(2-methyl-1-naphthoyl)-4-ethoxyphenylphosphine oxide, Bis(2-methyl-1-naphthoyl) 2-Naphthylphosphine oxide, bis(2-methyl-1-naphthoyl)-4-propylphenylphosphine oxide, bis(2-methyl-1-naphthoyl)-2,5-dimethylphenylphosphine oxide, bis(2-methoxy-1-naphthoyl)-4-ethoxyphenylphosphine oxide, bis(2-chloro-1-naphthoyl)-2,5-dimethylphenylphosphine oxide and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide.

[0160] The preferred acylphosphine oxide compound is bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (product name "Omnirad 819", manufactured by IGM Resins BV), 2,4,6-trimethylbenzoyl diphenylphosphine oxide (product name "Omnirad TPO H", manufactured by IGM Resins BV), or (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide (product name "Omnirad TPO-L", manufactured by IGM Resins BV).

[0161] Examples of thioxanthone compounds include thioxanthone, 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-dichlorothioxanthone, 2-dodecylthioxanthone, 2,4-diethylthioxanthone, 2,4-dimethylthioxanthone, 1-methoxycarbonylthioxanthone, 2-ethoxycarbonylthioxanthone, 3-(2-methoxyethoxycarbonyl)thioxanthone, 4-butoxycarbonylthioxanthone, 3-butoxycarbonyl-7-methylthioxanthone, 1-cyano-3-chlorothioxanthone, 1-ethoxycarbonyl-3-chlorothioxanthone, 1-ethoxycarbonyl-3-ethoxythioxanthone, 1-ethoxycarbonyl-3-aminothioxanthone, 1-ethoxycarbonyl-3-phenylsulfonylthioxanthone, 3,4-bis[2-(2-methoxyethoxy)ethoxycarbonyl]thioxanthone, and 1-ethoxycarbonyl -3-(1-methyl-1-morpholinylethyl)thioxanthone, 2-methyl-6-dimethoxymethylthioxanthone, 2-methyl-6-(1,1-dimethoxybenzyl)thioxanthone, 2-morpholinylmethylthioxanthone, 2-methyl-6-morpholinylmethylthioxanthone, n-allylthioxanthone-3,4-dicarboxylic acid imide, n-octylthioxanthone-3,4-dicarboxylic acid imide, N-(1,1,3,3-tetramethylbutyl)thioxanthone-3,4-dicarboxylic acid imide, 1-phenoxythioxanthone, 6-ethoxycarbonyl-2-methoxythioxanthone, 6-ethoxycarbonyl-2-methylthioxanthone, thioxanthone-2-polyethylene glycol ester and 2-hydroxy-3-(3,4-dimethyl-9-oxo-9H-thioxanthone-2-yloxy)-N,N,N-trimethyl-1-propaneammonium chloride.

[0162] Thioxanone compounds can be commercially available. Examples of commercially available products include the SPEEDCURE series manufactured by Lambson Limited (e.g., SPEEDCURE 7010, SPEEDCURE 7010L, SPEEDCURE CPTX, and SPEEDCURE ITX).

[0163] When the polymerization initiator (B) contains an acylphosphine oxide compound and a thioxanthone compound, the ratio of the content of the acylphosphine oxide compound to the content of the thioxanthone compound, on a mass basis, is preferably 2 to 10, more preferably 3 to 7.

[0164] From the viewpoint of further improving the alcohol resistance of near-infrared absorption images, the content of polymerization initiator (B) relative to the total amount of ink is preferably 5% by mass or more, more preferably 10% by mass or more. The upper limit of the polymerization initiator content is not particularly limited, for example, it is 30% by mass.

[0165] When the polymerization initiator (B) contains an acylphosphine oxide compound, from the viewpoint of further improving the alcohol resistance of the near-infrared absorption image, the content of the acylphosphine oxide compound relative to the total amount of ink is preferably 5% to 15% by mass, more preferably 8% to 12% by mass.

[0166] When the polymerization initiator (B) contains a thioxanthone compound, from the viewpoint of further improving the alcohol resistance of the near-infrared absorption image, the content of the thioxanthone compound relative to the total amount of ink is preferably 0.5% to 5% by mass, more preferably 1% to 3% by mass.

[0167] <Siloxane Compounds (C)>

[0168] The ink of this invention contains a siloxane compound (C).

[0169] As described above, the siloxane compound (C) is a compound comprising a main chain containing Si-O units and a side chain containing a specific AO unit (i.e., at least one of EO and PO units) and a polymerizable group, and is a compound with a molar ratio of [specific AO unit / (Si-O unit + specific AO unit)] (i.e., the ratio of the total number of moles of specific AO units to the total number of moles of Si-O units and specific AO units) of 30 mol% or more.

[0170] The siloxane compound (C) contained in the ink of the present invention may be only one type or two or more types.

[0171] As described above, by making the molar ratio of the siloxane compound (C) [specific AO unit / (Si-O unit + specific AO unit)] 30 mol% or more, the alcohol resistance of the near-infrared absorption image is improved.

[0172] From the viewpoint of improving the alcohol resistance of the obtained near-infrared absorption image, the molar ratio of the siloxane compound (C) [specific AO unit / (Si-O unit + specific AO unit)] is preferably 50 mol% or more, more preferably 51 mol% or more, even more preferably 60 mol% or more, and even more preferably 70 mol% or more.

[0173] From the viewpoint of improving the alcohol resistance of the obtained near-infrared absorption image, the upper limit of the molar ratio [specific AO unit / (Si-O unit + specific AO unit)] in the siloxane compound (C) is preferably 95 mol%, more preferably 90 mol%.

[0174] In the siloxane compound (C), the total amount of Si-O units and specific AO units relative to the total amount of the siloxane compound (C) is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 80% by mass or more.

[0175] The molecular weight of the siloxane compound (C) is preferably 1000 or higher.

[0176] The molecular weight of the siloxane compound (C) is more preferably 1,000 to 100,000, even more preferably 1,000 to 50,000, and even more preferably 1,000 to 30,000.

[0177] The main chain of siloxane compounds (C) contains Si-O units.

[0178] The proportion of Si-O units in the main chain of the siloxane compound (C) is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 80% by mass or more.

[0179] The terminal end of the main chain in the siloxane compound (C) is preferably trimethylsilyl (-Si(CH3)3).

[0180] The main chain in a siloxane compound (C) is preferably represented by the following formula CA1.

[0181] [Chemical Formula 5]

[0182]

[0183] In formula CA1,

[0184] x represents an integer greater than or equal to 1.

[0185] y represents an integer greater than or equal to 0.

[0186] * indicates the bonding position with the side chain.

[0187] In formula CA1, the arrangement of structural units labeled with subscript x (i.e., Si-O units bonded to side chains) and structural units labeled with subscript y (i.e., Si-O units not bonded to side chains) can be either block copolymers or random copolymers.

[0188] The side chains of the siloxane compound (C) contain a specific AO unit (i.e., at least one of an ethyleneoxy unit and a propyleneoxy unit) and a polymerizable group.

[0189] As a polymerizable group, it is preferably a free radical polymerizable group, more preferably an olefinic unsaturated group, and even more preferably (meth)acryloyl.

[0190] As a side chain in a siloxane compound (C), a side chain represented by the following formula CA2 is preferred.

[0191] [Chemical Formula 6]

[0192]

[0193] In equation CA2,

[0194] Rp represents a polymerizable group.

[0195] L1 represents a divalent linker group.

[0196] * indicates the bonding position with the main chain.

[0197] m and n each independently represent integers greater than or equal to 0.

[0198] The sum of m and n is an integer greater than or equal to 1.

[0199] In formula CA2, the arrangement of structural units labeled with subscript m (i.e., EO units) and structural units labeled with subscript n (i.e., PO units) can be either block copolymers or random copolymers.

[0200] As Rp, it is preferably a free radical polymerizable group, more preferably an olefinic unsaturated group, and even more preferably (meth)acryloyl group.

[0201] As the divalent linking group represented by L1, it is preferably a single bond or an alkylene group having 1 to 10 carbon atoms, more preferably an alkylene group having 1 to 10 carbon atoms, even more preferably an alkylene group having 1 to 6 carbon atoms, and even more preferably an alkylene group having 2 to 4 carbon atoms.

[0202] In formula CA2, the arrangement of structural units marked with subscript m (i.e., ethyleneoxy units) and structural units marked with subscript n (propyleneoxy units) can be either block copolymers or random copolymers.

[0203] That is, structural units marked with subscript m (i.e., ethyleneoxy units) or structural units marked with subscript n (propyleneoxy units) can be bonded to the polymerizable group represented by Rp.

[0204] The siloxane compound (C) preferably comprises a siloxane compound (CA) represented by the following formula CA.

[0205] [Chemical Formula 7]

[0206]

[0207] In formula CA,

[0208] Rp represents a polymerizable group.

[0209] L1 represents a divalent linker group.

[0210] x represents an integer greater than or equal to 1.

[0211] y represents an integer greater than or equal to 0.

[0212] m and n each independently represent integers greater than or equal to 0.

[0213] The sum of m and n is an integer greater than or equal to 1.

[0214] In formula CA, the value A calculated by the formula “((m+n) / (x+y+m+n))×100” is 30 or higher.

[0215] In formula CA, the arrangement of structural units labeled with subscript x and structural units labeled with subscript y can be either a block copolymer arrangement or a random copolymer arrangement.

[0216] In formula CA, the arrangement of structural units labeled with subscript m and structural units labeled with subscript n can be either a block copolymer arrangement or a random copolymer arrangement.

[0217] In formula CA, Rp is preferably a free radical polymerizable group, more preferably an olefinic unsaturated group, and even more preferably (meth)acryloyl.

[0218] In formula CA, the divalent linking group represented by L1 is preferably a single bond or an alkylene group having 1 to 10 carbon atoms, more preferably an alkylene group having 1 to 10 carbon atoms, even more preferably an alkylene group having 1 to 6 carbon atoms, and even more preferably an alkylene group having 2 to 4 carbon atoms.

[0219] In formula CA, the value A calculated by the formula “((m+n) / (x+y+m+n))×100” is 30 or higher.

[0220] Value A corresponds to the molar ratio mentioned above: [specific AO unit / (Si-O unit + specific AO unit)].

[0221] By setting the value A to 30 or higher, the alcohol resistance of the obtained near-infrared absorption image is further improved.

[0222] From the viewpoint of further improving the alcohol resistance of the obtained near-infrared absorption image, the value A is preferably 50 or more, more preferably 51 or more, and even more preferably 70 or more.

[0223] The upper limit of value A is preferably 95, and more preferably 90.

[0224] Siloxane compounds (C) may be commercially available products.

[0225] Commercially available products include, for example, BYKUV-3500 (BYK JAPAN KK.); TEGORAD 2010, 2011, 2100, 2200N, 2250, 2300 (Evonik Industries AG); etc.

[0226] These commercially available products all belong to the category of siloxane compounds (CA) represented by the formula CA.

[0227] The content of siloxane compound (C) in the ink of the present invention is preferably 0.1% to 5.0% by mass relative to the total amount of ink, more preferably 0.3% to 3.0% by mass, and even more preferably 0.5% to 1.5% by mass.

[0228] When the content of siloxane compound (C) is 0.05% by mass or more, the alcohol resistance of near-infrared absorption images is further improved.

[0229] When the content of siloxane compound (C) is less than 5% by mass, foaming during ink ejection is further suppressed, and the ejectibility of the ink is further improved.

[0230] <Near-infrared absorbing pigment (D)>

[0231] The ink of this invention contains a near-infrared absorbing pigment (D).

[0232] In this invention, near-infrared absorbing pigment (D) refers to all near-infrared absorbing pigments that may be contained in the ink.

[0233] Near-infrared absorbing pigments (D) can be a single compound or two or more compounds.

[0234] As a near-infrared absorbing pigment (D), it preferably includes at least one selected from the group consisting of squaric acid pigment, anthocyanin, phthalocyanine pigment, perylene pigment, pyrrolopyrrole pigment, anthraquinone pigment and diamine pigment.

[0235] As a squaric acid pigment, for example, a squaric acid pigment represented by Formula 1 described later can be used.

[0236] As an anthocyanin pigment, anthocyanin 1 shown in the examples described later can be used.

[0237] Furthermore, as anthocyanin pigments, compounds described in publicly available documents such as Japanese Patent Application Publication No. 2021-91809 and International Publication No. 2016 / 186050 can also be used.

[0238] As a phthalocyanine pigment, for example, commercially available products such as EX COLOR IR-14 manufactured by NIPPON SHOKUBAI CO.,LTD. can be used.

[0239] Furthermore, as phthalocyanine pigments, compounds described in publicly available documents such as Japanese Patent Application Publication No. 2013-151675 (paragraph 0050) can also be used.

[0240] As perylene pigments, commercially available products such as BASF's Lumogen IR788 and BASF's Lumogen IR765 can be used.

[0241] As a pyrrolopyrrole pigment, for example, the compound (A-1) shown in the examples described later can be used.

[0242] Furthermore, as a pyrrolopyrrole pigment, compounds described in publicly available documents such as International Patent Publication No. 2016 / 035695, Japanese Patent Application Publication No. 2009-263614, and International Patent Publication No. 2017 / 130825 can be used.

[0243] The near-infrared absorbing pigment (D) further preferably contains squartzite pigment, and even more preferably contains squartzite pigment represented by the following Formula 1.

[0244] [Chemical Formula 8]

[0245]

[0246] In Formula 1, ring A and ring B independently represent aromatic rings or heteroaromatic rings, respectively, X A and X B Each independently represents a monovalent substituent, G A and G B Each of these groups independently represents a monovalent substituent, and kA represents 0 to n. A Integers, kB represents 0 to n B an integer, n A and n B They represent G that can be substituted on ring A or ring B, respectively. A and G B The maximum number of integers, X A With G A They can bond together to form a ring, X B With G B They can bond together to form a ring, and when G A and G B When multiple G exist, A Each other and G B They can also bond with each other to form a ring structure.

[0247] (G A and G B )

[0248] In Equation 1, G A and G B Each can be used to represent a monovalent substituent independently.

[0249] As a result of G A or G BThe monovalent substituents represented include, for example, halogen atoms, cyano, nitro, alkyl, alkenyl, ynyl, aryl, heteroaryl, aralkyl, and -OR. 10 -COR 11 -COOR 12 -OCOR 13 -NR 14 R 15 -NHCOR 16 -CONR 17 R 18 -NHCONR 19 R 20 -NHCOOR 21 -SR 22 -SO2R 23 -SO2OR 24 -NHSO2R 25 and SO2NR 26 R 27 .

[0250] R 10 ~R 27 Each can be independently represented by a hydrogen atom, an aliphatic group, an aromatic group, or a heterocyclic group.

[0251] -COOR 12 R 12 In the case of hydrogen atoms (i.e., carboxyl groups), hydrogen atoms can dissociate (i.e., carbonate groups) or remain in a salt state.

[0252] Furthermore, -SO2OR 24 R 24 In the case of hydrogen atoms (i.e., sulfonyl), hydrogen atoms can dissociate (i.e., sulfonate group) or be in a salt state.

[0253] Examples of halogen atoms include fluorine, chlorine, bromine, and iodine.

[0254] The alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 15, and even more preferably 1 to 8. The alkyl group can be any of straight-chain, branched, or cyclic, preferably straight-chain or branched.

[0255] The alkenyl group preferably has 2 to 20 carbon atoms, more preferably 2 to 12, and especially preferably 2 to 8. The alkenyl group can be any of linear, branched, or cyclic, preferably linear or branched.

[0256] The number of carbon atoms in the alkynyl group is preferably 2 to 40, more preferably 2 to 30, and particularly preferably 2 to 25. The alkynyl group can be any of straight-chain, branched, or cyclic, preferably straight-chain or branched.

[0257] The aryl group preferably has 6 to 30 carbon atoms, more preferably 6 to 20, and even more preferably 6 to 12.

[0258] The alkyl portion of the aralkyl group is the same as the alkyl group described above. The aryl portion of the aralkyl group is the same as the aryl group described above. The number of carbon atoms in the aralkyl group is preferably 7 to 40, more preferably 7 to 30, and even more preferably 7 to 25.

[0259] The heteroaryl group is preferably a monocyclic or fused ring, more preferably a monocyclic or fused ring with 2 to 8 fusion numbers, and more preferably a monocyclic or fused ring with 2 to 4 fusion numbers. The number of heteroatoms in the ring constituting the heteroaryl group is preferably 1 to 3. The heteroatoms in the ring constituting the heteroaryl group are preferably nitrogen, oxygen, or sulfur atoms. The heteroaryl group is preferably a 5-membered or 6-membered ring. The number of carbon atoms in the ring constituting the heteroaryl group is preferably 3 to 30, more preferably 3 to 18, and even more preferably 3 to 12. Examples of heteroaryl groups include pyridine rings, piperidine rings, furan rings, furfuran rings, thiophene rings, pyrrole rings, quinoline rings, morpholine rings, indole rings, imidazole rings, pyrazole rings, carbazole rings, phenothiazine rings, phenotoxazine rings, indoleline rings, thiazole rings, pyrazine rings, thiadiazine rings, benzoquinoline rings, and thiadiazine rings.

[0260] As alkyl, alkenyl, alkynyl, aralkyl, aryl, and heteroaryl groups, they may have substituents or be unsubstituted.

[0261] Examples of substituents include those described in paragraph 0030 of Japanese Patent Application Publication No. 2018-154672. Examples of substituents include alkyl, aryl, amino, alkoxy, aryloxy, aromatic heterocyclic alkyl, acyl, alkoxycarbonyl, aryloxycarbonyl, acyloxy, acylamino, alkoxycarbonylamino, aryloxycarbonylamino, sulfonylamino, alkylthio, arylthio, aromatic heterocyclic thio, sulfonyl, hydroxyl, mercapto, halogen atom, cyano, sulfonyl, and carboxyl. Preferably, the substituent is alkyl, aryl, alkoxy, aryloxy, aromatic heterocyclic alkyl, acyl, alkoxycarbonyl, aryloxycarbonyl, acyloxy, alkoxythio, arylthio, aromatic heterocyclic thio, sulfonyl, hydroxyl, mercapto, halogen atom, cyano, sulfonyl, or carboxyl.

[0262] Furthermore, the "number of carbon atoms" in the substituent refers to the "total number of carbon atoms" of the substituent. For details on each substituent, please refer to paragraphs 0031 to 0035 of Japanese Patent Application Publication No. 2018-154672.

[0263] (X A and X B )

[0264] X A and X B Each can be used to represent a monovalent substituent independently.

[0265] X A and X B The substituents are preferably groups with active hydrogen, more preferably -OH, -SH, -COOH, -SO3H, or -NR. X1 R X2 -NHCOR X1 -CONR X1 R X2 -NHCONR X1 R X2 -NHCOOR X1 -NHSO2R X1 -B(OH)2 or PO(OH)2, more preferably -OH, -SH or NR X1 R X2 .

[0266] R X1 and R X2 Each can be represented independently by a hydrogen atom or a monovalent substituent. Examples of substituents include alkyl, alkenyl, ynyl, aryl, and heteroaryl groups. Alkyl groups are preferred. Alkyl groups are preferably straight-chain or branched. Detailed information on alkyl, alkenyl, ynyl, aryl, and heteroaryl groups is available in section G. A and G B The meaning of the scope described in the text is the same.

[0267] (Ring A and Ring B)

[0268] Ring A and ring B represent aromatic rings or heteroaromatic rings independently, respectively.

[0269] Aromatic rings and heteroaromatic rings can be monocyclic or fused rings.

[0270] Examples of aromatic and heteroaromatic rings include benzene rings, naphthyl rings, pentanene rings, indene rings, azulene rings, heptene rings, indene rings, perylene rings, pentanebenzene rings, acenaphthene rings, phenanthrene rings, anthracene rings, and tetrabenzene rings. Rings, triphenylene rings, fluorene rings, biphenyl rings, pyrrole rings, furan rings, thiophene rings, imidazole rings, oxazole rings, thiazole rings, pyridine rings, pyrazine rings, pyrimidine rings, pyridazine rings, indazine rings, indole rings, benzofuran rings, benzothiophene rings, isobenzofuran rings, quinazine rings, quinoline rings, phthalazine rings, naphthidine rings, quinoxazoline rings, quinoxazoline rings, isoquinoline rings, carbazole rings, phenanthridine rings, acridine rings, phenanthrene-rhein rings, thiamethoxam rings, benzopyran rings, xanthan rings, phenoxazoline rings, phenothiazine rings, and phenothiazine rings.

[0271] Among them, ring A and ring B are preferably aromatic rings, and more preferably benzene rings or naphthalene rings.

[0272] The aromatic ring may be unsubstituted or substituented. G is an example of a substituent. A and GB The substituents described in the text.

[0273] X A With G A X B With G B They can bond together to form a ring, and when G A and G B When multiple rings exist separately, they can bond together to form a ring. The rings are preferably 5-membered or 6-membered rings. The rings can be monocyclic or heterocyclic.

[0274] When X A With G A X B With G B G A Each other or G B When they bond together to form a ring, they can bond directly to form a ring, or they can bond together with a divalent linker selected from the group consisting of alkylene, -CO-, -O-, -NH-, -BR-, and combinations thereof.

[0275] X A With G A X B With G B G A Each other or G B They are preferably bonded together to form a ring.

[0276] R represents a hydrogen atom or a monovalent substituent. G is an example of a substituent. A and G B The substituents described herein are preferably alkyl or aryl.

[0277] (kA and kB)

[0278] kA represents 0~n A Integers, kB represents 0 to n B an integer, n A Let n be the largest integer that can be replaced on ring A. B This represents the largest integer that can be replaced on the B-ring.

[0279] kA and kB are each preferably 0 to 4, more preferably 0 to 2, and especially preferably 0 to 1. Furthermore, it is preferable to exclude the case where kA and kB simultaneously represent 0 (zero).

[0280] From the viewpoint of lightfastness, the squaric acid pigment represented by Formula 1 is preferably the squaric acid pigment represented by Formula 2 below.

[0281] [Chemical Formula 9]

[0282]

[0283] In Equation 2, R 1 and R 2 Each can be used to represent a monovalent substituent independently.

[0284] R 3 and R 4 Each can be used to represent a hydrogen atom or an alkyl group independently.

[0285] X 1 and X 2 Each independently represents an oxygen atom or -N(R) 5 )-.

[0286] R 5 It represents a hydrogen atom, alkyl group, aryl group, or heteroaryl group.

[0287] X 3 and X 4 They can be used to represent carbon atoms or boron atoms independently.

[0288] t and u in X 3 and X 4 When it is a boron atom, it represents 1; in X... 3 and X 4 When it represents a carbon atom, it is represented as 2.

[0289] Y 1 Y 2 Y 3 and Y 4 Each of these represents a monovalent substituent independently. Y 1 With Y 2 and Y 3 With Y 4 They can bond together to form a ring.

[0290] When Y 1 Y 2 Y 3 and Y 4 When multiple of them exist separately, they can also bond together to form a ring.

[0291] p and s independently represent integers from 0 to 3, and q and r independently represent integers from 0 to 2.

[0292] (R 1 and R 2 )

[0293] R 1 With R 2 They can be the same or different, but the same is preferred. Furthermore, when t and u are 2, the two Rs... 1 2 R 2 They can be the same or different, but being the same is preferred.

[0294] As a result of R 1 and R 2 The monovalent substituents represented can be exemplified by those related to G. A and G B The same monovalent substituent. Where R 1 and R 2 The preferred group is aryl. The aryl group may have a monovalent substituent or may be unsubstituted. The number of carbon atoms in the aryl group is preferably 6 to 30, more preferably 6 to 20, and even more preferably 6 to 14.

[0295] (Y 1 Y 2 Y 3 and Y 4 )

[0296] As a result of Y 1 Y 2 Y 3 and Y 4 The monovalent substituents represented can be exemplified by those related to G. A and G B The same monovalent substituent.

[0297] (p, q, r, and s)

[0298] p, q, r, and s are preferably 0. That is, in Equation 2, Y is preferably absent. 1 Y 2 Y 3 and Y 4 .

[0299] (X 1 and X 2 )

[0300] X 1 With X 2 They can be the same or different, but the same is preferred. X 1 and X 2 Preferably -N(R) 5 )-.

[0301] (R 5 )

[0302] By R 5 The alkyl, aryl, and heteroaryl groups indicated may be unsubstituted or have monovalent substituents. Examples of monovalent substituents include those related to G. A and G B The same monovalent substituent.

[0303] The alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 10, even more preferably 1 to 4, and particularly preferably 1 to 2. The alkyl group can be straight-chain or branched.

[0304] The number of carbon atoms in the aryl group is preferably 6 to 20, more preferably 6 to 12.

[0305] The heteroaryl group can be monocyclic or polycyclic. The number of heteroatoms in the ring constituting the heteroaryl group is preferably 1 to 3. The heteroatoms in the ring constituting the heteroaryl group are preferably nitrogen, oxygen, or sulfur atoms. The number of carbon atoms in the ring constituting the heteroaryl group is preferably 3 to 30, more preferably 3 to 18, and even more preferably 3 to 12.

[0306] R 5 Preferably, it is a hydrogen atom, a methyl group, or an ethyl group; more preferably, it is a hydrogen atom or a methyl group; and even more preferably, it is a hydrogen atom.

[0307] (X 3 and X 4 )

[0308] X 3 and X 4 They can be the same or different, but the same is preferred. X 3 and X 4 Boron atoms are preferred.

[0309] (R 3 and R 4 )

[0310] By R 3 and R 4 The alkyl group represented preferably has 1 to 4 carbon atoms, more preferably 1 or 2. The alkyl group can be straight-chain or branched. Examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, and isobutyl. 3 and R 4 Each of the following is preferably a hydrogen atom, a methyl group, or an ethyl group, more preferably a hydrogen atom or a methyl group, and even more preferably a hydrogen atom.

[0311] The molecular weight of the squaric acid pigment represented by Formula 1 is preferably 100 to 2,000, more preferably 150 to 1,000.

[0312] The squaric acid pigment represented by Formula 1 is described in detail in Japanese Patent Application Publication No. 2011-2080101, and the compound described therein is preferably used as the squaric acid pigment in this invention.

[0313] The squaric acid pigment represented by Formula 1 and the squaric acid pigment represented by Formula 2 can be tautomers of each other. Tautomers can be described, for example, by reference to paragraph 0034 of International Publication No. 2016-136783.

[0314] The following are specific examples of squaric acid pigments represented by Formula 1 or Formula 2 above (compounds S-1 to S-45).

[0315] However, the squaric acid onium pigments represented by Formula 1 or Formula 2 are not limited to the specific examples below. Hereinafter, "Me" represents methyl and "Ph" represents phenyl.

[0316] [Chemical Formula 10]

[0317]

[0318] [Chemical Formula 11]

[0319]

[0320] [Chemical Formula 12]

[0321]

[0322] [Chemical Formula 13]

[0323]

[0324] [Chemical Formula 14]

[0325]

[0326] [Chemical Formula 15]

[0327]

[0328] From the viewpoint of improving readability and readability over time, the squaric acid pigment represented by Formula 1 is preferably compound S-1, S-3, S-7, S-37, S-41, S-42, S-43, S-44 or S-45.

[0329] The near-infrared absorbing pigment (D) is preferably dispersed in the ink in the form of particles. From the viewpoint of lightfastness, the volume average particle size of the near-infrared absorbing pigment (D) is preferably 10 nm or more, more preferably 15 nm or more, even more preferably 20 nm or more, and particularly preferably 50 nm or more. Furthermore, from the viewpoint of dispersibility and ejectibility, the volume average particle size of the near-infrared absorbing pigment (D) is preferably 400 nm or less, more preferably 300 nm or less, and even more preferably 200 nm or less.

[0330] When near-infrared absorbing pigment (D) is coated with a dispersant or the like, the volume average particle size of the near-infrared absorbing pigment (D) refers to the volume average particle size in the coated state.

[0331] The volume average particle size can be determined using the Zetasizer Nano ZS (manufactured by Malvern Panalytical Ltd) as the measuring device, by dynamic light scattering.

[0332] Near-infrared absorbing pigments (D) are preferably dispersed using a disperser. Examples of dispersers include, for example, bead mills, ball mills, sand mills, attritors, roller mills, agitators, Henschel mixers, colloid mills, ultrasonic homogenizers, pearl mills, jet mills, and paint mixers.

[0333] The content of near-infrared absorbing pigment (D) relative to the total amount of ink is preferably 0.1% to 20% by mass, more preferably 0.1% to 10% by mass, and even more preferably 0.3% to 7% by mass.

[0334] <Dispersant>

[0335] The ink of the present invention preferably contains at least one dispersant.

[0336] The dispersant has the function of dispersing near-infrared absorbing pigments (D).

[0337] The weight-average molecular weight of the dispersant is preferably 100,000 or less, more preferably 75,000 or less, and even more preferably 50,000 or less. If the weight-average molecular weight of the dispersant is 100,000 or less, the diffusion rate of the dispersant in the dispersion medium is increased, and thus an image recorder with excellent readability can be obtained.

[0338] The weight-average molecular weight of the dispersant is preferably 1000 or more, more preferably 2000 or more, and even more preferably 3000 or more. If the weight-average molecular weight of the dispersant is 1000 or more, the compatibility with the dispersion medium will not become too high, and the near-infrared absorbing pigment represented by Formula 1 can be stably dispersed by the dispersant.

[0339] Weight-average molecular weight refers to the value determined by gel permeation chromatography (GPC). In the GPC-based determination, the apparatus used was an HLC-8020GPC (manufactured by TOSOH CORPORATION), with three TSKgel Super Multipore HZ-H (4.6mm ID × 15cm, manufactured by TOSOH CORPORATION) columns as the eluent and THF (tetrahydrofuran) as the eluent. The sample concentration was set to 0.45% by mass, the flow rate to 0.35 ml / min, the sample injection volume to 10 μl, and the measurement temperature to 40°C. Measurements were performed using an RI detector. Calibration curves were constructed based on eight samples from TOSOH CORPORATION's "Standard Samples TSK Standard, Polystyrene": "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000", and "n-propylbenzene".

[0340] The dispersant is preferably a polymer, which can be any of random polymers, block polymers, and graft polymers.

[0341] From the viewpoint of readability over time, the dispersant is preferably a block polymer. The block polymer, for example, has an adsorption block and a dispersion medium affinity block. The adsorption block has an adsorption group that adsorbs onto the near-infrared absorbing pigment represented by Formula 1, and the dispersion medium affinity block has a functional group that has an affinity for the dispersion medium. In the block polymer, the adsorption group has low shielding and high mobility, thus the adsorption rate to the near-infrared absorbing pigment represented by Formula 1 is fast. Therefore, if the dispersant is a block polymer, the readability is further improved. Furthermore, the adsorption group aggregates in the block polymer, thus the adsorption force on the near-infrared absorbing pigment represented by Formula 1 is high. Therefore, if the dispersant is a block polymer, the readability over time is further improved.

[0342] The dispersant preferably has basic or acidic functional groups. When the ink contains pigment derivatives described later, a combination of a dispersant with basic functional groups and a pigment derivative with acidic functional groups, or a combination of a dispersant with acidic functional groups and a pigment derivative with basic functional groups, is preferred. If the ink contains a dispersant with basic functional groups and a pigment derivative with acidic functional groups, the pigment derivative is easily adsorbed onto the dispersant through acid-base interaction. Similarly, if the ink contains a dispersant with acidic functional groups and a pigment derivative with basic functional groups, the pigment derivative is easily adsorbed onto the dispersant through acid-base interaction.

[0343] The near-infrared absorbing pigment represented by Formula 1 can be stably dispersed in the ink through the spatial repulsion between the dispersants, resulting in improved stability over time. Consequently, readability is improved after a period of time.

[0344] Examples of basic functional groups include amino, amide, and imino groups. A dispersant may have only one basic functional group or two or more.

[0345] Examples of acidic functional groups include carboxyl and sulfonyl groups. Dispersants may have only one type of acidic functional group or two or more.

[0346] When the dispersant is a dispersant with basic functional groups, from the viewpoint of improving readability and readability over time, the base value of the dispersant is preferably 15 mg KOH / g or more, more preferably 20 mg KOH / g or more, and even more preferably 25 mg KOH / g or more. The upper limit of the base value of the dispersant is not particularly limited, for example, it is 40 mg KOH / g.

[0347] In this invention, the alkalinity is determined by the perchloric acid method as specified in JIS K 2501:2003. Furthermore, the alkalinity is obtained as the number of milligrams (mg) of hydrochloric acid or perchloric acid and equivalent potassium hydroxide required to neutralize all alkaline components contained in 1g of the sample.

[0348] When the dispersant is a dispersant with acidic functional groups, from the viewpoint of improving readability and readability over time, the acid value of the dispersant is preferably 15 mg KOH / g or more, more preferably 20 mg KOH / g or more, and even more preferably 25 mg KOH / g or more. The upper limit of the acid value of the dispersant is not particularly limited, for example, it is 40 mg KOH / g.

[0349] In this invention, the acid value is determined by the method described in JIS K0070:1992. Furthermore, the acid value is obtained as the number of milligrams (mg) of potassium hydroxide required to neutralize all acid components contained in 1g of the sample.

[0350] Dispersants can be commercially available products. Examples of commercially available products include, for instance, The Lubrizol Corporation's SOLSPERSE (registered trademark) series (e.g., SOLSPERSE 16000, 21000, 32000, 35000, 41000, 41090, 43000, 44000, 46000, 54000, 55000, 71000, etc.), BYK-Chemie GmbH's DISPERBYK (registered trademark) series (e.g., DISPERBYK 102, 110, 111, 118, 170, 190, 194N, 2001, 2013, 2015, 2090, 2096, etc.), and Evonik Industries AG's TEGO (registered trademark) Dispers series (e.g., TEGO Dispers). 610, 610S, 630, 651, 655, 750W, 755W, etc.), Kusumoto Chemicals, Ltd.'s DISPARLON (registered trademark) series (e.g., DA-375, DA-1200, etc.), KYOEISHA CHEMICAL Co.,LTD's FLOREN series (e.g., WK-13E, G-700, G-900, GW-1500, GW-1640, WK-13E, etc.), BASF's EFKA (registered trademark) series (e.g., EFKA PX 4701, EFKA PX 4731, EFKA PX 4732, etc.).

[0351] From the viewpoint of improving readability and readability over time, the content of dispersant relative to the total amount of ink is preferably 0.7% to 5% by mass, more preferably 0.8% to 4% by mass.

[0352] The ratio of the content of the dispersant to the content of the near-infrared absorbing pigment represented by Formula 1 is preferably 0.1 to 20 by mass, more preferably 0.2 to 5, and even more preferably 0.5 to 5.

[0353] Regarding the SP value of the dispersant, as long as the difference between the SP value of the polymerizable monomer and the SP value of the dispersant is 3.8 MPa... 1 / 2 ~16.0MPa 1 / 2 The value of SP is not particularly limited. From the viewpoint of dispersion stability, the preferred SP value of the dispersant is 21 MPa. 1 / 2 ~34MPa 1 / 2 More preferably 24MPa 1 / 2 ~34MPa 1 / 2 .

[0354] The SP value of the dispersant can be calculated, for example, using the formula of KWSUH and JMCORBETT (Journal of Applied Polymer Science, 12, 2359, 1968).

[0355] SP value = {(V ml ) 1 / 2 ×δH+(V mh ) 1 / 2 ×δD} / {(V ml ) 1 / 2 +(V mh ) 1 / 2}

[0356] V ml V mh δH and δD are calculated by substituting the titration amount H (mL) at the cloud point when 0.5 g (solid component) of the dispersant is dissolved in 10 mL of a good solvent at a test temperature of 20 °C and n-hexane is added, and the titration amount D (mL) at the cloud point when 0.5 g (solid component) of the dispersant is dissolved in 10 mL of a good solvent at a test temperature of 20 °C and deionized water is added, into the following formula.

[0357] V ml = (molar volume of good solvent) × (molar volume of n-hexane) / {(1-V H )×(molar volume of n-hexane)+V H ×(molar volume of good solvent)}

[0358] V mh = (molar volume of good solvent) × (molar volume of deionized water) / {(1-V D )×(molar volume of deionized water)+V D ×(molar volume of good solvent)}

[0359] V H =H / (10+H)

[0360] V D =D / (10+D)

[0361] δH = (SP value of good solvent) × 10 / (10 + H) + (SP value of n-hexane) × H / (10 + H)

[0362] δD = (SP value of good solvent) × 10 / (10 + D) + (SP value of deionized water) × D / (10 + D)

[0363] In addition, the molar volume of n-hexane is 130.3 mL / mol, and the molar volume of deionized water is 18 mL / mol.

[0364] Furthermore, the SP value of n-hexane is 7.27 (cal / cm³). 3 ) 1 / 2 The SP value of deionized water is 23.39 (cal / cm³). 3 ) 1 / 2 .

[0365] The good solvent used to dissolve the above-mentioned dispersant is not particularly limited as long as it is a solvent capable of dissolving the dispersant, and can be appropriately selected. For example, acetone can be cited as a good solvent.

[0366] The molar volume of acetone is 74.4 mL / mol, and the SP value of acetone is 9.72 (cal / cm³). 3 ) 1 / 2 .

[0367] When using acetone as a good solvent, substitute 74.4 into "molar volume of good solvent" and 9.72 into "SP value of good solvent" in the above formula.

[0368] The SP values ​​for each solvent were calculated using HSPiP (version 4.1.07) software.

[0369] The molar volume (mL / mol) of each solvent is obtained by dividing the molecular weight (g / mol) by the density (g / mL).

[0370] Furthermore, the unit of the obtained SP value is (cal / cm). 3 ) 1 / 2 According to 1 (cal / cm 3 ) 1 / 2 ≈2.05MPa 1 / 2 It can change the unit from (cal / cm) 3 ) 1 / 2 Convert to MPa 1 / 2 .

[0371] In the ink of this invention, the difference between the SP value of the polymerizable monomer and the SP value of the dispersant is 3.8 MPa. 1 / 2 ~16.0MPa 1 / 2 Additionally, the difference mentioned above refers to the absolute value of the value obtained by subtracting one SP value from another.

[0372] It can be inferred that if the difference in the above SP values ​​is 3.8 MPa 1 / 2 Therefore, the dispersant is less likely to detach from the surface of the near-infrared absorbing pigment represented by Formula 1, thus improving the dispersion stability of the near-infrared absorbing pigment represented by Formula 1. On the other hand, it can be inferred that if the difference in the above SP values ​​is 16.0 MPa... 1 / 2The dispersant adsorbed on the surface of the near-infrared absorbing pigment represented by Formula 1 diffuses appropriately, preventing the near-infrared absorbing pigment represented by Formula 1 from easily agglomerating. As a result, an image recorder with excellent readability can be obtained. Furthermore, in the ink of the present invention, the near-infrared absorbing pigment represented by Formula 1 can be stably dispersed for a long time by the dispersant, resulting in an image recorder with excellent readability even after a period of time.

[0373] From the perspective of improving readability and readability over time, the difference in the above-mentioned SP values ​​is preferably 4.5 MPa. 1 / 2 ~15.5MPa 1 / 2 More preferably 5.0 MPa 1 / 2 ~15.2MPa 1 / 2 .

[0374] <Pigment Derivatives>

[0375] The ink of the present invention preferably also contains at least one pigment derivative.

[0376] Pigment derivatives are compounds that have a structure derived from pigments within their molecules and have a molecular weight of less than 1000.

[0377] If the ink contains pigment derivatives, these derivatives function through π-π interactions between the pigment derivatives and the near-infrared absorbing pigment represented by Formula 1, and also through acid-base interactions between the pigment derivatives and the dispersant. Therefore, the near-infrared absorbing pigment represented by Formula 1 is further and more stably dispersed by the dispersant, improving the ink's stability over time. Consequently, readability improves over time.

[0378] Pigment derivatives preferably have basic or acidic functional groups.

[0379] Examples of basic functional groups include amino, amide, and imino groups. Pigment derivatives may have only one basic functional group or two or more.

[0380] Examples of acidic functional groups include carboxyl and sulfonyl groups. Pigment derivatives may have only one type of acidic functional group or more than two types.

[0381] Pigment derivatives having acidic functional groups are preferably represented by the following formula 3.

[0382] P-[R 10 -X 10 ]m……(3)

[0383] In Equation 3, P represents pigment residue, and R 10 X represents a divalent linker group. 10 Each group represents a carboxyl group or a sulfonyl group independently. m represents the largest integer that can be substituted for P.

[0384] (P)

[0385] For example, P can be represented by residues of diketopyrrolopyrrole pigments; azo pigments such as azo, diazo, and polyazo; phthalocyanine pigments; anthraquinone pigments such as diaminodianthraquinone, anthraquinone, flavin, anthraquinone, indigoanthraquinone, pirathrone, and violetone; quinacrine pigments; dioxazine pigments; violet ketone pigments; perylene pigments; thioindigo pigments; isoindoline pigments; isoindolineone pigments; quinoline ketone pigments; reducing pigments; and metal complex pigments.

[0386] From the viewpoint of improving readability and readability over time, P is preferably a residue of a diketopyrrolopyrrole pigment, a phthalocyanine pigment, an anthraquinone pigment, or a dioxazine pigment, and more preferably a diketopyrrolopyrrole pigment, a phthalocyanine pigment, or an anthraquinone pigment.

[0387] (R 10 )

[0388] As R 10 Examples include those selected from alkylene, arylene, -O-, -S-, -C=O-, and -NR. 30 -、-CONR 30 -、-SO2NR 30 -NR 30 CO-, -NR 30 SO2- includes divalent groups in the group, divalent groups formed by combining two or more of these, and single bonds. R 30 It represents a hydrogen atom or an alkyl group.

[0389] Among them, R 10 Single bonds are preferred.

[0390] (X 10 )

[0391] X 10 Preferably sulfonated. Multiple X 10 They can be the same or different, but the same is preferred.

[0392] (m)

[0393] m is preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 3.

[0394] The pigment derivative contained in the ink can be one or two types.

[0395] From the viewpoint of improving readability and readability over time, the content of pigment derivatives relative to the total amount of ink is preferably 0.005% to 0.1% by mass.

[0396] From the viewpoint of improving readability and readability over time, the content of pigment derivatives relative to the total amount of near-infrared absorbing pigments represented by Formula 1 is preferably 0.12% to 15% by mass, more preferably 0.15% to 12% by mass.

[0397] The ink of the present invention may also contain the following other components.

[0398] (polymerization inhibitor)

[0399] The ink of the present invention preferably contains a polymerization inhibitor. The polymerization inhibitor contained in the ink may be one type or two types.

[0400] Examples of polymerization inhibitors include hydroquinone compounds, phenothiazines, catechols, alkylphenols, alkyl bisphenols, zinc dimethyl dithiocarbamate, copper dimethyl dithiocarbamate, copper dibutyl dithiocarbamate, copper salicylate, thiodipropionate, mercaptobenzimidazole, phosphites, nitrosamine compounds, hindered amine compounds, and nitrosyl free radicals.

[0401] The polymerization inhibitor is preferably selected from at least one of the group consisting of nitrosamine compounds, hindered amine compounds, hydroquinone compounds and nitrosyl free radicals, more preferably selected from at least one of the group consisting of nitrosamine compounds, hydroquinone compounds and nitrosyl free radicals, and even more preferably includes nitrosamine compounds, hydroquinone compounds and nitrosyl free radicals.

[0402] Examples of nitrosamine compounds include, for example, aluminum salt of N-nitroso-N-phenylhydroxylamine and N-nitroso-N-phenylhydroxylamine. The preferred nitrosamine compound is aluminum salt of N-nitroso-N-phenylhydroxylamine.

[0403] Hindered amine compounds are compounds that have an intramolecular hindered amine structure. Examples of hindered amine compounds include those described in Japanese Patent Application Publication No. 61-91257. Preferably, the hindered amine compound is a derivative of 2,2,6,6-tetramethylpiperidine having a structure in which all hydrogens at the 2- and 6-carbon positions of piperidine are substituted with methyl groups. Examples of hindered amine compounds include 4-benzoyloxy-2,2,6,6-tetramethylpiperidine and 1-(3,5-di-tert-butyl-4-hydroxyphenylpropionyloxyethyl)-4-(3,5-di-tert-butyl-4-hydroxyphenylpropionyloxy)-2,2,6,6-tetramethylpiperidine.

[0404] Examples of hydroquinone compounds include hydroquinone, methylhydroquinone, tert-butylhydroquinone, and p-methoxyphenol. Among these, p-methoxyphenol is preferred.

[0405] Examples of nitrosyl radicals include 2,2,6,6-tetramethylpiperidin-1-oxy (TEMPO) and 2,2,6,6-tetramethyl-4-hydroxypiperidin-1-oxy (TEMPOL). The nitrosyl radical is preferably 2,2,6,6-tetramethyl-4-hydroxypiperidin-1-oxy (TEMPOL).

[0406] From the viewpoint of improving the long-term stability of ink, the content of the polymerization inhibitor relative to the total amount of ink is preferably 1% by mass or more, more preferably 1.5% by mass or more. The upper limit of the polymerization inhibitor content is not particularly limited, but from the viewpoint of polymerizability, 5% by mass is preferred.

[0407] When the polymerization inhibitor contains a nitrosamine compound, from the viewpoint of improving the long-term stability of the ink, the content of the nitrosamine compound relative to the total amount of ink is preferably 0.5% to 5% by mass, more preferably 0.5% to 2% by mass.

[0408] When the polymerization inhibitor contains a hydroquinone compound, from the viewpoint of improving the long-term stability of the ink, the content of the hydroquinone compound relative to the total amount of ink is preferably 0.1% to 5% by mass, more preferably 0.5% to 2% by mass.

[0409] (Sensitizer)

[0410] When the ink of the present invention contains a polymerization initiator, a sensitizer may be included together with the polymerization initiator. If the ink contains a sensitizer, the curability is improved, especially when using an LED light source. Furthermore, the sensitizer also helps to improve the lightfastness of the ink.

[0411] Sensitizers are substances that absorb specific active energy rays and become electronically excited. When an electronically excited sensitizer comes into contact with a photopolymerization initiator, it produces electron transfer, energy transfer, and heat generation. This, in turn, promotes the chemical change of the photopolymerization initiator.

[0412] Examples of sensitizers include, for example, ethyl 4-(dimethylamino)benzoate (EDB), anthraquinone, 3-acylcoumarin derivatives, terphenyl, styrene ketone, 3-(aroylmethylene)thiazoline, camphorquinone, eosin, rhodamine, erythrosine, compounds represented by general formula (i) as described in Japanese Patent Application Publication No. 2010-24276, and compounds represented by general formula (I) as described in Japanese Patent Application Publication No. Hei 6-107718.

[0413] When the ink contains a sensitizer, the content of the sensitizer relative to the total amount of ink is preferably 1.0% to 15.0% by mass, more preferably 1.5% to 10.0% by mass, and even more preferably 2.0% to 6.0% by mass.

[0414] (Organic solvents)

[0415] The ink of the present invention may contain at least one organic solvent.

[0416] Examples of organic solvents include ketones such as acetone, methyl ethyl ketone, and diethyl ketone; alcohols such as methanol, ethanol, 2-propanol, 1-propanol, 1-butanol, and tert-butanol; chlorinated solvents such as chloroform and dichloromethane; aromatic solvents such as benzene and toluene; ester solvents such as ethyl acetate, butyl acetate, isopropyl acetate, ethyl lactate, butyl lactate, and isopropyl lactate; ether solvents such as diethyl ether, tetrahydrofuran, and dioxane; glycol ether solvents such as ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, and propylene glycol monomethyl ether; and glycol ether acetate solvents such as propylene glycol monomethyl ether acetate.

[0417] When the ink of the present invention contains organic solvents, the content of organic solvents relative to the total amount of ink is preferably 5% by mass or less, more preferably 2% by mass or less. The ink of the present invention may be composed of no organic solvents (i.e., the content of organic solvents relative to the total amount of ink is 0% by mass).

[0418] (resin)

[0419] The ink of the present invention preferably contains resin.

[0420] If the ink contains resin, near-infrared absorption images with better alcohol resistance can be obtained.

[0421] The resin described here does not have the function of dispersing near-infrared absorbing pigments (D), unlike the dispersants mentioned above. Furthermore, the resin described here does not have polymerizable groups, unlike the polymerizable monomers (A) mentioned above.

[0422] Examples of resins include acrylic resins, cellulose derivatives, epoxy resins, polyesters, polyurethanes, polyamides, polyvinyl chloride, polyimides, phenolic resins, and silicone resins.

[0423] From the perspective of dispersion stability, acrylic resin is preferred.

[0424] That is, the ink of the present invention preferably contains acrylic resin.

[0425] In this invention, "acrylic resin" refers to a polymer containing structural units derived from (meth)acrylic acid compounds.

[0426] (Meth)acrylic acid compounds are compounds having an acryloyl group (CH2=CH-C(=O)-) or a methacryloyl group (CH2=C(CH3)-C(=O)-).

[0427] Examples of (meth)acrylic acid compounds include (meth)acrylic acid, (meth)acrylates, and (meth)acrylamide.

[0428] The acrylic resin is preferably a polymer containing structural units derived from (meth)acrylate, more preferably a polymer containing structural units derived from (meth)acrylate, and even more preferably poly(meth)acrylate.

[0429] From the viewpoint of improving the alcohol resistance of near-infrared absorption images, the content of acrylic resin relative to the total amount of ink is preferably 0.5% to 2% by mass.

[0430] From the viewpoint of improving the alcohol resistance of near-infrared absorption images, when the total amount of polymerizable monomer (A) is set to 100 parts by mass, the content of acrylic resin is preferably 0.40 parts by mass to 1.70 parts by mass.

[0431] From the viewpoint of ink ejection properties when ink is ejected by inkjet recording, the weight-average molecular weight of the resin is preferably 5,000 to 100,000, more preferably 10,000 to 75,000.

[0432] From the perspective of ejectibility, the content of components with a molecular weight of 1000 or higher in the total ink is preferably less than 6.5% by mass relative to the total amount of ink.

[0433] From an ejectibility perspective, there is no particular limit to the lower limit of the content of components with a molecular weight of 1000 or higher in the total ink. The content of components with a molecular weight of 1000 or higher in the total ink can be 0.5% by mass or higher, 1.0% by mass or higher, or 2.0% by mass or higher.

[0434] The ink of the present invention may also contain surfactants other than siloxane compounds, ultraviolet absorbers, co-sensitizers, antioxidants, anti-fading agents, conductive salts, and other additives. Regarding additives, please refer appropriately to publicly available documents such as Japanese Patent Application Publication No. 2011-225848 and Japanese Patent Application Publication No. 2009-209352.

[0435] <Physical Properties>

[0436] The viscosity of the ink of the present invention is preferably 10 mPa·s to 50 mPa·s, more preferably 10 mPa·s to 30 mPa·s, and even more preferably 10 mPa·s to 25 mPa·s. The viscosity is a value measured using a viscometer at 25°C. For example, the viscosity is measured using a VISCOMETER TV-22 type viscometer (manufactured by Toki Sangyo Co., Ltd.).

[0437] The surface tension of the ink of the present invention is preferably 20 mN / m to 45 mN / m, more preferably 20 mN / m to 30 mN / m. The surface tension is a value measured using a surface tension meter at 25°C. For example, the surface tension is measured using a DY-700 (manufactured by Kyowa Interface Science Co., Ltd.).

[0438] [Inkjet Recording Method]

[0439] The inkjet recording method of the present invention includes: a step of spraying the ink of the present invention onto a substrate by inkjet recording (hereinafter also referred to as the "ink spraying step"); and a step of irradiating the ink sprayed onto the substrate with active energy rays (hereinafter also referred to as the "active energy ray irradiation step").

[0440] (Ink ejection process)

[0441] In the inkjet recording method of the present invention, firstly, the ink of the present invention is sprayed onto the substrate by inkjet recording.

[0442] [Substrate]

[0443] The substrate is not particularly limited as long as it can form an ink image; examples include paper, cloth, wood, metal, and plastic.

[0444] As for paper, examples include high-quality paper, coated paper, art paper, and other conventional printing papers and inkjet recording papers, all of which are primarily composed of cellulose. Furthermore, paper can be coated with oil-based or water-based varnishes.

[0445] The substrate can be either a permeable or non-permeable substrate. "Non-permeable" means it absorbs very little or no water from the ink; specifically, it means the water absorption rate is 10.0 g / m³. 2 The following properties.

[0446] In the inkjet recording method of the present invention, in particular, when a non-permeable substrate is used as the substrate, an image with excellent curing properties can be obtained.

[0447] The shape of the non-permeable substrate is not particularly limited; it can be any of the following: three-dimensional shape such as a bottle, sheet, or film.

[0448] Examples of non-permeable substrates include metals (e.g., aluminum), plastics (e.g., polyvinyl chloride, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl alcohol acetal), and glass.

[0449] The non-permeable substrate preferably includes thermoplastic resins such as polyvinyl chloride, polyethylene terephthalate, and polypropylene.

[0450] Non-permeable substrates can be surface treated.

[0451] Examples of surface treatments include corona treatment, plasma treatment, flame treatment, heat treatment, abrasion treatment, light irradiation treatment (e.g., ultraviolet irradiation treatment) and flame treatment.

[0452] Corona treatment can be performed, for example, using a Corona Master (manufactured by Shinko Electric & Instrumentation Co., Ltd., PS-10S). The conditions for corona treatment can be appropriately selected based on the type of non-permeable substrate and the composition of the ink. Corona treatment can be performed, for example, under the following conditions.

[0453] • Processing voltage: 10~15.6kV

[0454] Processing speed: 30~100mm / s

[0455] Furthermore, the substrate can be a transparent substrate or a substrate laminated from polyethylene or polypropylene.

[0456] Examples of transparent substrates include glass, quartz, and plastics (e.g., cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, acrylic resins, chlorinated polyolefin resins, polyethersulfone resins, polyethylene terephthalate (PET), polyethylene naphthalate, nylon, polyethylene, polystyrene, polypropylene, polycyclic olefin resins, polyimide resins, polycarbonate resins, polyvinyl alcohol acetal, etc.). The transparent substrate can be one layer or two or more layers.

[0457] [Inkjet recording method]

[0458] The inkjet recording method is not particularly limited. As long as it can record images, it is not particularly restricted. It can be any known method, such as charge control method that uses electrostatic induction to eject ink, on-demand inkjet method that uses the vibration pressure of piezoelectric elements (pressure pulse method), acoustic inkjet method that converts electrical signals into sound beams to irradiate ink and uses radiation pressure to eject ink, and thermal inkjet method that heats ink to form bubbles and uses the resulting pressure (Bubble Jet (registered trademark)).

[0459] As an inkjet recording method, it is particularly effective to utilize the following inkjet recording method: by using the method described in Japanese Patent Application Publication No. 54-59936, the ink subjected to heat energy undergoes a rapid volume change, and the ink is ejected from the nozzle by the force generated by the change of state.

[0460] Furthermore, regarding the inkjet recording method, one can refer to the method described in paragraphs 0093 to 0105 of Japanese Patent Application Publication No. 2003-306623.

[0461] Examples of inkjet heads used in inkjet recording include multi-pass methods that use short, column printheads to scan and record simultaneously across the width of the substrate, and single-pass methods that use row printheads with recording elements arranged over an entire area corresponding to one side of the substrate.

[0462] In a single-pass method, by scanning the substrate in a direction intersecting the arrangement direction of the recording elements, a pattern can be formed on the entire surface of the substrate, eliminating the need for a transport system such as a carriage that scans short printheads. Furthermore, since complex scanning control of the carriage movement and the substrate is unnecessary, only the substrate moves, thus enabling higher recording speeds compared to multi-pass methods. Therefore, in the inkjet recording method of the present invention, ink is preferably ejected in a single-pass manner.

[0463] The ink ejected from the inkjet head is preferably 1 pL (picoliter) to 100 pL, more preferably 3 pL to 80 pL, and even more preferably 3 pL to 20 pL.

[0464] (Active energy ray irradiation process)

[0465] In the inkjet recording method of the present invention, it is preferable to irradiate the ink ejected onto the substrate with active energy rays. In the ink, polymerizable monomers are polymerized and cured by irradiation with active energy rays. Examples of active energy rays include alpha rays, gamma rays, X-rays, ultraviolet rays, visible light, and electron beams. From the viewpoint of safety and cost, the active energy rays are preferably ultraviolet light (hereinafter also referred to as "UV") or visible light, and more preferably ultraviolet light.

[0466] The preferred exposure dose of active energy rays is 20 mJ / cm. 2 ~10000J / cm 2 More preferably 100 mJ / cm 2 ~7000mJ / cm 2The irradiation time is preferably 0.01 seconds to 120 seconds, more preferably 0.1 seconds to 90 seconds. The irradiation conditions and basic irradiation method are applicable to the irradiation conditions and methods disclosed in Japanese Patent Application Publication No. 60-132767. Specifically, it is preferable to provide light sources on both sides of the head unit of the ink ejection device and to scan the head unit and the light sources in a so-called multi-pass manner or to use other light sources without accompanying drive.

[0467] As a light source for ultraviolet (UV) irradiation, mercury lamps, gas lasers, and solid-state lasers are mainly used, with mercury lamps, metal halide lamps, and UV fluorescent lamps being the most well-known. Furthermore, replacing them with GaN (gallium nitride) based semiconductor UV light-emitting devices would be very useful for industry and the environment. UV-LEDs (light-emitting diodes) and UV-LDs (laser diodes) are small in size, have long lifespans, high efficiency, and low cost, making them promising candidates for UV irradiation light sources. Specifically, metal halide lamps, high-pressure mercury lamps, medium-pressure mercury lamps, low-pressure mercury lamps, or UV-LEDs are preferred light sources for UV irradiation.

[0468] As a UV-LED, for example, a purple LED (manufactured by NICHIA CORPORATION) with a main emission spectrum having wavelengths between 365 nm and 420 nm can be cited. As an LED with a shorter wavelength, U.S. Patent No. 6,084,250 discloses an LED capable of emitting ultraviolet light with wavelengths between 300 nm and 370 nm.

[0469] Furthermore, by combining multiple UV-LEDs, it is possible to irradiate ultraviolet light in different wavelength ranges. The peak wavelength of the ultraviolet light is preferably 200nm to 405nm, more preferably 220nm to 400nm, and even more preferably 340nm to 400nm.

[0470] After the ink ejection process, the ink is irradiated with active energy rays in an environment with an oxygen concentration of less than 1 vol%, thereby inhibiting polymerization due to oxygen inhibition and improving curability. The lower limit of the oxygen concentration is not particularly limited. By setting the irradiation environment to a vacuum or replacing it with a gas other than air (e.g., nitrogen), the oxygen concentration can practically be set to 0. The oxygen concentration in the active energy ray irradiation process is preferably 0.01 vol% to 1 vol%, more preferably 0.1 vol% to 1 vol%.

[0471] Methods for controlling the oxygen concentration in the irradiation environment include, for example, setting the inkjet recording device to a closed system and creating a nitrogen or carbon dioxide environment, and methods for circulating an inert gas such as nitrogen. Methods for supplying nitrogen include, for example, using a nitrogen cylinder and using a device that separates only nitrogen from the air by utilizing the difference in permeability of oxygen and nitrogen to a hollow fiber membrane. Methods for supplying carbon dioxide include, for example, using a carbon dioxide cylinder. Inert gases refer to conventional gases such as N2, H2, and CO2, and rare gases such as He, Ne, and Ar. From the viewpoints of safety, availability, and cost, N2 is preferred as the inert gas.

[0472] Furthermore, the active energy ray irradiation process may include: irradiating ink sprayed onto a substrate with a first active energy ray to semi-cur the ink film (i.e., the film formed by the ink applied to the substrate) (hereinafter also referred to as the "first irradiation process"); and irradiating the semi-cured ink film with a second active energy ray to formally cure it (hereinafter also referred to as the "second irradiation process").

[0473] After the process of semi-curing the ink film, the formal curing process is carried out, thereby improving the readability after the wiping test and the readability after the sealing test.

[0474] In this invention, the situation where only a portion of the polymerizable monomers in the ink film are polymerized is referred to as "semi-curing," and the irradiation with active energy rays used for semi-curing is also referred to as "pinning exposure." Furthermore, in this invention, the situation where all the polymerizable monomers in the ink film are actually polymerized is referred to as "formal curing," and the irradiation with active energy rays used for formal curing is also referred to as "formal exposure."

[0475] In the first irradiation step, at least a portion of the polymerizable monomers in the ink film are polymerized by irradiating the ink film with a first active energy ray. In the second irradiation step, all the polymerizable monomers in the ink film are polymerized by irradiating the ink film with a second active energy ray.

[0476] In the first irradiation process, only a portion of the polymerizable monomers in the ink film are polymerized, thus reducing the amount of active energy rays exposed compared to the case where only formal exposure is performed.

[0477] The preferred exposure dose for the first active energy ray is 2 mJ / cm². 2 ~5000mJ / cm 2 More preferably 20 mJ / cm 2 ~5000mJ / cm 2 The irradiation time is preferably 0.01 seconds to 20 seconds, more preferably 0.1 seconds to 10 seconds.

[0478] The preferred exposure dose for the second active energy ray is 20 mJ / cm². 2 ~10000J / cm 2 More preferably 100 mJ / cm 2 ~7000mJ / cm 2 .

[0479] The irradiation time is preferably 0.01 seconds to 120 seconds, and more preferably 0.1 seconds to 90 seconds.

[0480] The reaction rate of the ink film after pinning exposure is preferably 10% to 80%.

[0481] The reaction rate of the ink film after formal exposure is preferably more than 80% and less than 100%, more preferably 85% to 100%, and even more preferably 90% to 100%.

[0482] In addition, the reaction rate of the ink film refers to the polymerization rate of polymerizable monomers in the ink film, as determined by high performance liquid chromatography.

[0483] The reaction rate of the ink film was calculated using the following method.

[0484] Prepare a substrate that has been irradiated with active energy rays to obtain an ink film. Cut a 20mm × 50mm sample piece from the area of ​​the substrate where the ink film is present. Immerse the cut sample piece in 10 mL of THF (tetrahydrofuran) for 24 hours to obtain a leachate of the ink. Calculate the amount of polymerizable monomer (hereinafter referred to as "monomer amount after irradiation X1") from the obtained leachate using high performance liquid chromatography.

[0485] In addition, prepare a substrate that has not been irradiated with active energy rays, and perform the same operation as described above to calculate the amount of polymerizable monomer (hereinafter referred to as "monomer amount X0 when not irradiated").

[0486] Based on the monomer amount X1 after irradiation and the monomer amount X0 before irradiation, the reaction rate (%) of the ink film is calculated using the following formula.

[0487] Ink reaction rate (%) = ((monomer amount before irradiation X0 - monomer amount after irradiation X1) / monomer amount before irradiation X0) × 100

[0488] When both the first and second irradiation steps are included, the time from the moment the ink lands on the substrate to the moment it is irradiated by the first active energy ray is preferably within 0.5 seconds. Immediate semi-curing after landing suppresses ink diffusion on the substrate, improving readability. However, the time from the moment the ink lands on the substrate to the moment it is irradiated by the second active energy ray is not particularly limited.

[0489] Furthermore, excluding the semi-curing process (i.e., only the formal curing process), the time from the moment the ink lands on the substrate to the moment it is irradiated by the active energy rays is preferably less than 1 second. By performing formal curing immediately after landing, ink diffusion on the substrate is suppressed, and readability is improved.

[0490] (Other processes)

[0491] The inkjet recording method of the present invention may include steps other than the ink ejection step and the active energy ray irradiation step. For example, a drying step following the ink ejection step, where the ink ejected onto the substrate is dried, can be included. The drying method and drying temperature in the drying step can be appropriately adjusted.

[0492] Example

[0493] The following are embodiments of the present invention, but the present invention is not limited to the following embodiments.

[0494] The detailed contents of each component contained in the inks of the examples and comparative examples are as follows.

[0495] In addition, Speedcure 7010L (manufactured by Lambson Limited) and FLORSTAB UV12 (manufactured by Kromachem Ltd) were used in the preparation of the ink. Speedcure 7010L is a mixture of Speedcure 7010 and EOTMPTA, with a mixing ratio of 1:1 by mass. In the table, Speedcure 7010 is listed in the polymerization initiator column, and EOTMPTA is listed in the polymerizability monomer column.

[0496] Furthermore, FLORSTAB UV12 is a mixture of N-nitroso-N-phenylhydroxylamine aluminum salt and PEA at a ratio of 1:9. In the table, N-nitroso-N-phenylhydroxylamine aluminum salt is listed under the polymerization inhibitor column, and PEA is listed under the polymerizability monomer column.

[0497] [Examples 1-22, Comparative Examples 1-2]

[0498] Inks with the compositions shown in Tables 1 to 3 below were prepared.

[0499] A dispersion is prepared by using near-infrared absorbing pigments, dispersants, pigment derivatives, and a portion of polymerizable monomers, and the resulting dispersion is mixed with other components to prepare ink.

[0500] The detailed information about the components in the ink is as follows.

[0501] <Near-infrared absorbing pigment (D)>

[0502] Compounds S-1, S-3, and S-7, which are squaric acid pigments, are described in specific examples of squaric acid pigments represented by Formula 1 or Formula 2.

[0503] As a perylene pigment, BASF's "Lumogen IR788" was used.

[0504] As a phthalocyanine pigment, “EX COLOR IR-14” manufactured by NIPPON SHOKUBAI CO.,LTD. was used.

[0505] Anthocyanin 1, as anthocyanin pigment, and compound (A-1), as pyrrolopyrrole pigment, are pigment compounds with the following structures, respectively.

[0506] [Chemical Formula 16]

[0507]

[0508] <Pigment Derivatives>

[0509] SOLSPERSE 12000S…manufactured by The Lubrizol Corporation. A copper phthalocyanine synergist with a sulfonyl group.

[0510] <Dispersant>

[0511] SOLSPERSE 71000…manufactured by The Lubrizol Corporation. A graft polymer with basic functional groups. Weight-average molecular weight 52890, SP value 21.74 MPa. 1 / 2 .

[0512] <Siloxane Compounds (C)>

[0513] TEGORAD 2200N, 2250, 2300, 2010… are all manufactured by Evonik Industries AG and are siloxane compounds (CA) represented by the formula CA. The x, y, m, and n in formula CA are shown in Tables 1 to 3. In all compounds, Rp in formula CA is an acryloyl group.

[0514] • BYKUV-3500……Manufactured by BYK JAPAN KK. It is a siloxane compound (CA) represented by the formula CA. The x, y, m, and n in formula CA are shown in Tables 1 to 3. Rp in formula CA represents an acryloyl group.

[0515] • TEGORAD 2500……Manufactured by Evonik Industries AG. A comparative siloxane compound with a specific AO unit ratio of less than 30 mol%. The x, y, m, and n in formula CA are shown in Tables 1 to 3. Rp in formula CA represents an acryloyl group.

[0516] <Polymerizable Monomer (A)>

[0517] MPDDA…Product name “SR341” (manufactured by Sartomer Company, Inc.), 3-methyl-1,5-pentanediol diacrylate, SP value: 17.60 MPa 1 / 2 Tg: 105℃.

[0518] • DPGDA… Product name “DPGDA” (manufactured by DAICEL-ALLNEX LTD.), dipropylene glycol diacrylate, SP value: 17.73 MPa 1 / 2 Tg: 104℃.

[0519] • IBOA… Product name “SR506NS” (manufactured by Sartomer Company, Inc.), isobornyl acrylate, SP value: 17.10 MPa 1 / 2 Tg: 97℃.

[0520] • TCDDMDA… Product name “SR833S” (manufactured by Sartomer Company, Inc.), tricyclodecanediethanol diacrylate, SP value: 17.85 MPa 1 / 2 Tg: 186℃

[0521] • EOTMPTA…trimethylolpropane EO addition triacrylate, SP value: 17.72 MPa 1 / 2 Tg: 90℃.

[0522] • PEA...Phenoxyethyl acrylate, SP value: 19.44 MPa 1 / 2 FLORSTAB UV12 (manufactured by Kromachem Ltd) contains 90% by mass, Tg: 5℃.

[0523] • CTFA… Cyclic trimethylolpropane methyl acetal acrylate, SP value: 19.0 MPa 1 / 2 Tg: 33.2℃

[0524] 4-HBA…4-Hydroxybutyl acrylate, SP value: 21.0 MPa 1 / 2 Tg: -32℃

[0525] The glass transition temperature (Tg) of each polymerizable monomer was determined using the Tg of each polymerizable monomer as a homopolymer with a weight average molecular weight of 10,000 to 20,000. The glass transition temperature (Tg) was measured using a differential scanning calorimeter (product name "EXSTAR6220") manufactured by SII NanoTechnology Inc.

[0526] The SP values ​​of the polymerizable monomers were calculated based on the above formulas S and F1 to F3. The dispersion term δd, polar term δp, and hydrogen bonding term δh of each polymerizable monomer contained in the ink are recorded in Tables 1 to 3, and are values ​​calculated using HSPiP (version 4.1.07) software.

[0527] <Polymerization Initiator (B)>

[0528] • Omnirad 819…… Manufactured by IGM Resins BV. Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0529] • Omnirad TPO-L……manufactured by IGM Resins BV. (2,4,6-Trimethylbenzoyl)ethoxyphenylphosphine oxide.

[0530] <Sensitizer>

[0531] • Speedcure7010……Manufactured by Lambson Limited. 1,3-Di({α-[1-chloro-9-oxo-9H-thioxanth-4-yl)oxy]acetylpoly[oxy(1-methylethylene)]}oxy)-2,2-bis({α-[1-methylethylene)]}oxymethyl)propane.

[0532] <Polymerization Inhibitor>

[0533] •UV-12……N-Nitrosino-N-phenylhydroxylamine aluminum salt: 10% by mass contained in FLORSTAB UV12 (manufactured by Kromachem Ltd).

[0534] <Image Recording>

[0535] The prepared ink was filtered using a 5μm filter.

[0536] The filtrate was filled into the ink cartridge of the inkjet recording device (product name "DMP-2850", manufactured by Fujifilm Corporation), and a 3% dot image was recorded on the substrate under the conditions of nozzle temperature of 25°C, resolution of 600 dpi (dots per inch) and jet volume of 10 pL.

[0537] PET (polyethylene terephthalate) film was used as the substrate. Then, an LED light (product name "PELUV CURE UNIT", manufactured by Printed Electronics) was used at an exposure of 250 mW / cm². 2 The image was recorded by irradiating it with ultraviolet light (wavelength 395nm).

[0538] <Evaluation>

[0539] (Image's alcohol resistance)

[0540] The obtained images were evaluated for alcohol resistance.

[0541] The results are shown in Tables 1 to 3.

[0542] Using a cotton swab soaked in a 75% ethanol aqueous solution, the images in the image record obtained by the above image recording were wiped with constant force. Twenty locations were randomly selected from the images obtained by this wiping operation, and it was determined whether they could be read using an IR detector.

[0543] Readability was evaluated based on the number of readable sections. The evaluation criteria are as follows. The highest grade for alcohol resistance is AAA.

[0544] AAA: Readable at positions 18 to 20.

[0545] AA: Readable at positions 15 to 17.

[0546] A: It can be read from position 10 to 14.

[0547] B: Readable at positions 5 to 9.

[0548] C: Readable at positions 1 to 4.

[0549] D: Failed to read.

[0550] (Image readability)

[0551] Furthermore, it was determined whether the images in the obtained image recordings possessed the capability to be read using an IR (infrared) detector, i.e., IR readability.

[0552] As a result, the images in the image recordings of each embodiment and each comparative example have IR readability.

[0553] [Table 1]

[0554]

[0555] [Table 2]

[0556]

[0557] [Table 3]

[0558]

[0559] As shown in Table 1, in the various embodiments using inks containing a polymerizable monomer (A), a polymerization initiator (B), a specific AO unit (i.e., the ratio of the total molar number of ethylene oxide units and propylene oxide units to the total molar number of structural units containing Si-O bonds, ethylene oxide units and propylene oxide units) of 30 mol% or more (C), and a near-infrared absorbing pigment (D), the recorded images exhibited excellent alcohol resistance.

[0560] In Comparative Example 1, which used ink that did not contain siloxane compounds, and in Comparative Example 2, which used ink containing a specific AO unit at a rate of less than 30 mol% instead of siloxane compound (C), the alcohol resistance of the recorded images was reduced compared to the respective examples.

[0561] Based on the results of all embodiments, from the viewpoint of further improving the alcohol resistance of the image, the SP value of the polymerizable monomer (A) is preferably 18.0 MPa. 1 / 2 the following.

[0562] Based on the results of Examples 2 and 13, from the viewpoint of further improving the alcohol resistance of the image, the content of siloxane compound (C) relative to the total amount of ink is preferably 3.0% by mass or less.

[0563] Based on the results of Examples 10 and 11, it is known that, from the viewpoint of further improving the alcohol resistance of the image, the content of siloxane compound (C) relative to the total amount of ink is preferably 0.5% by mass or more.

[0564] Based on the results of Examples 14-17, from the viewpoint of further improving the alcohol resistance of the image, the proportion of the monofunctional polymerizable monomer in the polymerizable monomer (A) is preferably 50% by mass or less.

[0565] [Examples A to E]

[0566] The inks with the compositions shown in Table 4 below were prepared.

[0567] A dispersion is prepared by using near-infrared absorbing pigments, dispersants, pigment derivatives, and a portion of polymerizable monomers, and the resulting dispersion is mixed with other components to prepare ink.

[0568] The details of each component in the ink are shown in the descriptions of Examples 1 to 22.

[0569] In the inks of Examples A to E, the following acrylic resins were also used.

[0570] <Acrylic Resin>

[0571] • Acrylic resin… Product name “Dianal BR-113”, manufactured by Mitsubishi Chemical Corporation, polymethyl methacrylate, weight average molecular weight (Mw) 30000

[0572] • Acrylic resin… Product name “Dianal BR-110”, manufactured by Mitsubishi Chemical Corporation, polymethyl methacrylate, weight average molecular weight (Mw) 72000

[0573] • Acrylic resin… Product name “Dianal MB-2660”, manufactured by Mitsubishi Chemical Corporation, polymethyl methacrylate, weight average molecular weight (Mw) 65000

[0574] <Image Recording>

[0575] Using the ink prepared above, image recordings were obtained in the same manner as in Examples 1 to 22.

[0576] <Evaluation>

[0577] (Image of alcohol resistance (using 75% ethanol aqueous solution))

[0578] The obtained images were subjected to the same alcohol resistance evaluation as that performed in Examples 1 to 22.

[0579] The results are shown in Table 4.

[0580] For comparison, the results of Example 20 described above are also shown in Table 4.

[0581] (Image of alcohol resistance (using 95% ethanol aqueous solution))

[0582] The obtained images were evaluated for alcohol resistance (using 95% ethanol aqueous solution) in the same manner as the alcohol resistance evaluation performed in Examples 1-22, except that the 75% ethanol aqueous solution was changed to a 95% ethanol aqueous solution.

[0583] The alcohol resistance of the image in Example 20 described above was also evaluated in the same manner (using 95% ethanol aqueous solution).

[0584] The results are shown in Table 4.

[0585] (Image readability)

[0586] Furthermore, it was determined whether the images in the obtained image recordings possessed the capability to be read using an IR (infrared) detector, i.e., IR readability.

[0587] As a result, the images in each image record of Examples A to E have IR readability.

[0588] [Table 4]

[0589]

[0590] As shown in Table 4, in Examples A to E, as in Examples 1 to 22, the recorded images exhibited excellent alcohol resistance.

[0591] Furthermore, by comparing Example 20 with Examples A to E, it can be confirmed that when the ink contains acrylic resin (Examples A to E), the alcohol resistance is further improved.

[0592] [Examples F to I]

[0593] The inks with the compositions shown in Table 5 below were prepared.

[0594] These inks were prepared in the same manner as the inks of Example 20, except that the type of siloxane compound (C) was changed, as shown in Table 5.

[0595] The details of each component in the ink (including the types of siloxane compounds (C)) are shown in the descriptions of Examples 1 to 22.

[0596] <Image Recording>

[0597] Using the ink prepared above, an image recorder was obtained in the same manner as in Example 20.

[0598] <Evaluation>

[0599] (Image of alcohol resistance (using 95% ethanol aqueous solution))

[0600] The obtained images were evaluated for alcohol resistance (using 95% ethanol aqueous solution) in the same manner as the alcohol resistance evaluation performed in Examples 1-22, except that the 75% ethanol aqueous solution was changed to a 95% ethanol aqueous solution.

[0601] The alcohol resistance of the image in Example 20 described above was also evaluated in the same manner (using 95% ethanol aqueous solution).

[0602] The results are shown in Table 4.

[0603] (Image readability)

[0604] Furthermore, it was determined whether the images in the obtained image recordings possessed the capability to be read using an IR (infrared) detector, i.e., IR readability.

[0605] As a result, the images in each image record of Examples F to I have IR readability.

[0606] [Table 5]

[0607]

[0608] Based on the results of Examples F to G and Example 20 shown in Table 5, from the viewpoint of improving the alcohol resistance of the image, "(m+n) / (x+y+m+n)*100" (i.e., value A) is preferably 50 mol% or more, and more preferably 51 mol% or more. Furthermore, as described above, value A corresponds to the aforementioned molar ratio [specific AO unit / (Si-O unit + specific AO unit)].

[0609] The disclosures of Japanese Patent Application No. 2021-161313, filed on September 30, 2021, and Japanese Patent Application No. 2022-132501, filed on August 23, 2022, are incorporated herein by reference in their entirety.

[0610] All documents, patent applications and technical standards described in this specification are incorporated herein by reference to the same extent as the specific documents, patent applications and technical standards which are incorporated herein by reference.

Claims

1. An ink for inkjet recording, comprising: Polymerizable monomer (A); Polymerization initiator (B); A siloxane compound (C) comprising a main chain and side chains, the main chain comprising structural units containing Si-O bonds, the side chains comprising at least one of ethylene oxide units and propylene oxide units and polymerizable groups, wherein the total molar number of the ethylene oxide units and the propylene oxide units is at least 30 mol% relative to the total molar number of the structural units containing Si-O bonds, the ethylene oxide units, and the propylene oxide units; and Near-infrared absorbing pigment (D). The mass ratio of the polymerizable monomer (A) to the siloxane compound (C) is 26.0 to 300. The content of the polymerization initiator (B) is 5% by mass or more relative to the total amount of the inkjet recording ink. The content of the siloxane compound (C) is 0.05% by mass or more relative to the total amount of the inkjet recording ink. The near-infrared absorbing pigment (D) comprises a squaric acid onyx pigment represented by Formula 1 below. In Formula 1, ring A and ring B independently represent aromatic rings or heteroaromatic rings, respectively, X A and X B Each independently represents a monovalent substituent, G A and G B Each of these groups independently represents a monovalent substituent, and kA represents 0 to n. A Integers, kB represents 0 to n B an integer, n A and n B They represent G that can be substituted on ring A or ring B, respectively. A and G B The maximum number of integers, X A With G A They may bond together to form a ring or not, X B With G B They may bond together to form a ring or not, and when G A and G B When multiple G exist, A Each other and G B They may bond together to form a ring structure or not. The SP value of the polymerizable monomer (A) is 18.0 MPa. 1 / 2 the following.

2. The ink for inkjet recording according to claim 1, wherein, The content of the siloxane compound (C) is 0.5% to 3.0% by mass relative to the total amount of inkjet recording ink.

3. The ink for inkjet recording according to claim 1, wherein, The monofunctional polymerizable monomer accounts for less than 50% by mass of the polymerizable monomer (A).

4. The ink for inkjet recording according to claim 1, wherein, The siloxane compound (C) comprises a siloxane compound (CA) represented by the following formula CA. In formula CA, Rp represents a polymerizable group. L1 represents a divalent linker group. x represents an integer greater than or equal to 1. y represents an integer greater than or equal to 0. m and n each independently represent integers greater than or equal to 0. The sum of m and n is an integer greater than or equal to 1. In formula CA, the value A calculated using the formula "((m+n) / (x+y+m+n))×100" is 30 or higher. In formula CA, the arrangement of structural units labeled with subscript x and structural units labeled with subscript y is either a block copolymer arrangement or a random copolymer arrangement. In formula CA, the arrangement of structural units labeled with subscript m and structural units labeled with subscript n is either a block copolymer arrangement or a random copolymer arrangement.

5. The ink for inkjet recording according to claim 1, wherein, The inkjet recording ink also contains pigment derivatives.

6. The ink for inkjet recording according to claim 1, wherein, The inkjet recording ink also contains acrylic resin.

7. An inkjet recording method, wherein the inkjet recording ink according to any one of claims 1 to 6 is used. The inkjet recording method includes: The process of spraying ink for inkjet recording onto a substrate using an inkjet recording method; and A process of irradiating inkjet recording ink ejected onto the substrate with active energy rays.

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