Ink for inkjet recording and inkjet recording method

Abstract

The present invention provides an ink for inkjet recording and an inkjet recording method. The inkjet recording ink comprises a near-infrared absorbing pigment represented by the following formula 1, a polymerizable monomer, a polymerization initiator, and a dispersant. The content of the polymerizable monomer is 50% by mass or more relative to the total amount of the inkjet recording ink, and 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 Omit ring A, ring B, and X in formula 1. A 、X B , G A , G B , kA and kB.

Description

Technical Field

[0001] The present invention relates to an ink for inkjet recording and an inkjet recording method. Background Art

[0002] Near-infrared absorbing dyes that absorb infrared rays but do not actually absorb visible light are expected to be used in the field of inks because of their invisibility.

[0003] For example, Japanese Patent Application Laid-Open No. 2019-001983 describes an inkjet ink containing a squarylium dye, a dispersant, an organic solvent, and water.

[0004] Furthermore, there is known a method of recording an image by adding a polymerizable compound to ink and curing the ink with active energy rays. Summary of the Invention

[0005] Technical issues to be solved by the invention

[0006] However, as described in Japanese Patent Application Laid-Open No. 2019-001983, when the squarylium dye is dispersed with a dispersant, readability is insufficient.

[0007] The present invention has been made in light of such circumstances, and according to an embodiment of the present invention, provides an inkjet recording ink and an inkjet recording method capable of obtaining an image recorded material having excellent readability and readability after aging.

[0008] Means for solving technical problems

[0009] The present invention includes the following aspects.

[0010] <1> An inkjet recording ink comprising a near-infrared absorbing pigment represented by the following formula 1, a polymerizable monomer, a polymerization initiator, and a dispersant, wherein the content of the polymerizable monomer is 50% by mass or more relative to the total amount of the inkjet recording ink, and 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 .

[0011] [Chemical Formula 1]

[0012]

[0013] In Formula 1, Ring A and Ring B each independently represent an aromatic ring or an aromatic heterocycle, and X A and X B Each independently represents a monovalent substituent, G A and G B Each independently represents a monovalent substituent, kA represents 0 to n A Integer, kB represents 0~n Binteger, n A and n B represents G that can be substituted on ring A or ring B respectively A and G B The largest integer number, X A With G A Can bond with each other to form a ring, X B With G B Can bond with each other to form a ring, G A and G B When there are multiple, G A Each other and G B They can be bonded to each other to form a ring structure.

[0014] <2> according to <1> The ink for inkjet recording, wherein

[0015] The weight average molecular weight of the dispersant is 50,000 or less.

[0016] <3> according to <1> or <2> The ink for inkjet recording, wherein

[0017] The dispersant is a block polymer.

[0018] <4> according to <1> to <3> The inkjet recording ink described in any one of the preceding claims further comprises a pigment derivative.

[0019] <5> according to <1> to <4> The inkjet recording ink described in any one of the preceding claims further comprises a siloxane compound.

[0020] <6> according to <5> The ink for inkjet recording, wherein

[0021] The siloxane compound includes a siloxane compound having a polymerizable group.

[0022] <7> according to <6> The ink for inkjet recording, wherein

[0023] The content of the siloxane compound having a polymerizable group is 0.5% by mass to 3% by mass based on the total amount of the inkjet recording ink.

[0024] <8> according to <1> to <7> The ink for inkjet recording according to any one of the preceding claims, wherein

[0025] The polymerization initiator includes an acylphosphine oxide compound and a thioxanthone compound.

[0026] <9> according to <1> to <8> The ink for inkjet recording according to any one of the preceding claims, wherein

[0027] The ratio of the polymerizable monomer having a glass transition temperature of 30° C. or higher in the polymerizable monomer is 90% by mass or higher.

[0028] <10> An inkjet recording method using <1> to <9> The ink for inkjet recording according to any one of the preceding claims, wherein the inkjet recording method comprises:

[0029] a step of ejecting ink for inkjet recording onto a substrate by an inkjet recording method; and

[0030] A step of irradiating the inkjet recording ink ejected onto the substrate with active energy rays.

[0031] Effects of the Invention

[0032] According to an embodiment of the present invention, there are provided an inkjet recording ink and an inkjet recording method capable of obtaining an image recorded material having excellent readability and readability after aging. DETAILED DESCRIPTION

[0033] Hereinafter, the inkjet recording ink and the inkjet recording method of the present invention will be described in detail.

[0034] In this specification, the numerical range expressed using "to" indicates a range including the numerical values ​​described before and after "to" as the minimum value and the maximum value, respectively.

[0035] In the numerical ranges described in this specification, the upper limit or lower limit described in a certain numerical range may be replaced by the upper limit or lower limit of another numerical range described in another stage. In addition, in the numerical ranges described in this specification, the upper limit or lower limit described in a certain numerical range may be replaced by the value shown in the Examples.

[0036] In this specification, when a plurality of substances corresponding to each component are present in a composition, the amount of each component in the composition refers to the total amount of the plurality of substances present in the composition unless otherwise specified.

[0037] In this specification, a combination of two or more preferred embodiments is a more preferred embodiment.

[0038] In this specification, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes as long as the intended purpose of the process can be achieved.

[0039] In this specification, "(meth)acrylate" is a concept encompassing both acrylate and methacrylate. Furthermore, "(meth)acrylic acid" is a concept encompassing both acrylic acid and methacrylic acid.

[0040] In this specification, “readability after a certain period of time” refers to the readability of an image recorded material obtained using ink after a predetermined period of time (for example, one week) has passed since its preparation.

[0041] [Inkjet Recording Ink]

[0042] The inkjet recording ink of the present invention (hereinafter referred to as "ink") comprises a near-infrared absorbing pigment represented by the following formula 1, a polymerizable monomer, a polymerization initiator, and a dispersant. The content of the polymerizable monomer is 50% by mass or more relative to the total amount of the inkjet recording ink, and 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 .

[0043] [Chemical Formula 2]

[0044]

[0045] In Formula 1, Ring A and Ring B each independently represent an aromatic ring or an aromatic heterocycle, and X A and X B Each independently represents a monovalent substituent, G A and G B Each independently represents a monovalent substituent, kA represents 0 to n A Integer, kB represents 0~n B integer, n A and n B represents G which can be substituted for ring A or ring B respectively A and G B The largest integer, X A With G A Can bond with each other to form a ring, X B With G B Can bond with each other to form a ring, G A and G B When there are multiple, G A Each other and G B They can be bonded to each other to form a ring structure.

[0046] As an ink containing a squarylium dye, for example, Japanese Patent Application Laid-Open No. 2019-001983 describes an inkjet ink containing a squarylium dye, a dispersant, an organic solvent, and water.

[0047] On the other hand, there is known a method of recording an image by adding a polymerizable monomer to ink and curing the ink with active energy rays.

[0048] Simply combining a squarylium dye and a polymerizable monomer to form an ink yields insufficient readability and time-lapse readability. The present inventors conducted extensive research and discovered that by including a near-infrared absorbing dye represented by Formula 1, a polymerizable monomer, a polymerization initiator, and a dispersant, the content of the polymerizable monomer is 50% by mass or more relative to the total amount of the inkjet recording ink, and 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 reason why the ink of the present invention can provide an image recorded material with excellent readability and readability after a certain period of time is presumably as follows.

[0049] The ink involved in the present invention contains a near-infrared absorbing pigment represented by Formula 1 and a dispersant. The near-infrared absorbing pigment represented by Formula 1 is dispersed in the ink by adsorbing the dispersant on the surface of the near-infrared absorbing pigment represented by Formula 1. The surface of the near-infrared absorbing pigment represented by Formula 1 is almost neutral, so it is not easy to adsorb the dispersant. The present inventors have found that the compatibility between the dispersant and the dispersion medium contributes to the readability of the obtained image record. In the ink of the present invention, the content of the polymerizable monomer is 50% by mass or more relative to the total amount of the ink for inkjet recording. Therefore, as a dispersion medium, the present inventors focused on the difference between the SP value of the polymerizable monomer that accounts for the majority of the ink involved in the present invention and the SP value of the dispersant. It is speculated that if the difference in the above-mentioned SP value is 3.8MPa 1 / 2 If the above SP value difference is 16.0 MPa, the dispersant is unlikely to be separated from the surface of the near-infrared absorbing pigment represented by Formula 1, and the readability of the obtained image record is improved. 1 / 2 The dispersant adsorbed onto the surface of the near-infrared absorbing pigment represented by Formula 1 diffuses appropriately, making it difficult for the near-infrared absorbing pigment represented by Formula 1 to aggregate with one another. As a result, it is believed that the readability of the resulting image record is improved. Furthermore, in the ink of the present invention, the dispersant enables the near-infrared absorbing pigment represented by Formula 1 to be stably dispersed for a long period of time, resulting in an image record with excellent readability over time.

[0050] Next, each component contained in the ink according to the present invention will be described.

[0051] (Near-infrared absorbing pigment)

[0052] The ink according to the present invention contains a near-infrared absorbing pigment represented by Formula 1. The near-infrared absorbing pigment represented by Formula 1 contained in the ink may be one kind or two or more kinds.

[0053] [Chemical Formula 3]

[0054]

[0055] In Formula 1, Ring A and Ring B each independently represent an aromatic ring or an aromatic heterocycle, and X A and X B Each independently represents a monovalent substituent, G A and G B Each independently represents a monovalent substituent, kA represents an integer from 0 to nA, and kB represents an integer from 0 to nB. nA represents G A The largest integer that can be substituted for ring A, nB represents G B The largest integer that can be substituted into ring B. X A With G A or X B With G B They can be bonded to each other to form a ring, G A and G B When there are multiple Gs bonded to ring A, A and multiple Gs bonded to ring B B They may be bonded to each other to form a ring structure.

[0056] 〔G A and G B 〕

[0057] G A and G B Each independently represents a monovalent substituent.

[0058] Examples of the monovalent substituent include a halogen atom, a cyano group, a nitro group, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, an aralkyl group, -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 .

[0059] R 10 ~R 27 Each independently represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group.

[0060] In addition, -COOR 12 R 12 In the case of a hydrogen atom (ie, a carboxyl group), the hydrogen atom may be dissociated (ie, a carbonate group) or in the form of a salt. 24 R 24 In the case of a hydrogen atom (ie, a sulfo group), the hydrogen atom may be dissociated (ie, a sulfonate group) or may be in the form of a salt.

[0061] Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

[0062] The number of carbon atoms in the alkyl group is preferably 1 to 20, more preferably 1 to 15, and even more preferably 1 to 8. The alkyl group may be linear, branched, or cyclic, but is preferably linear or branched.

[0063] The number of carbon atoms in the alkenyl group is preferably 2 to 20, more preferably 2 to 12, and particularly preferably 2 to 8. The alkenyl group may be linear, branched, or cyclic, but is preferably linear or branched.

[0064] 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 may be linear, branched, or cyclic, but is preferably linear or branched.

[0065] The number of carbon atoms in the aryl group is preferably 6-30, more preferably 6-20, and even more preferably 6-12.

[0066] 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.

[0067] The heteroaryl group is preferably a monocyclic or fused ring, more preferably a monocyclic or fused ring having 2 to 8 fused rings, and even more preferably a monocyclic or fused ring having 2 to 4 fused rings. The number of heteroatoms constituting the heteroaryl group's ring is preferably 1 to 3. The heteroatoms constituting the heteroaryl group's ring are preferably nitrogen, oxygen, or sulfur atoms. The heteroaryl group is preferably a 5-membered or 6-membered ring. The number of carbon atoms constituting the heteroaryl group's ring is preferably 3 to 30, more preferably 3 to 18, and even more preferably 3 to 12. Examples of the heteroaryl group include a pyridine ring, a piperidine ring, a furan ring, a furfuran ring, a thiophene ring, a pyrrole ring, a quinoline ring, a morpholine ring, an indole ring, an imidazole ring, a pyrazole ring, a carbazole ring, a phenothiazine ring, a phenoxazine ring, an indoline ring, a thiazole ring, a pyrazine ring, a thiadiazine ring, a benzoquinoline ring, and a thiadiazole ring.

[0068] The alkyl group, alkenyl group, alkynyl group, aralkyl group, aryl group, and heteroaryl group may have a substituent or may be unsubstituted.

[0069] As a substituent, the substituents described in paragraph 0030 of Japanese Patent Application Laid-Open No. 2018-154672 can be mentioned. As a substituent, alkyl, aryl, amino, alkoxy, aryloxy, aromatic heterocyclic oxy, acyl, alkoxycarbonyl, aryloxycarbonyl, acyloxy, acylamino, alkoxycarbonylamino, aryloxycarbonylamino, sulfonylamino, alkylthio, arylthio, aromatic heterocyclic sulfonyl, sulfonyl, hydroxyl, sulfydryl, halogen atom, cyano, sulfo and carboxyl can be mentioned. Among them, the substituent is preferably alkyl, aryl, alkoxy, aryloxy, aromatic heterocyclic oxy, acyl, alkoxycarbonyl, aryloxycarbonyl, acyloxy, alkylthio, arylthio, aromatic heterocyclic sulfonyl, sulfonyl, hydroxyl, sulfydryl, halogen atom, cyano, sulfo or carboxyl.

[0070] In addition, the “number of carbon atoms” in a substituent refers to the “total number of carbon atoms” of the substituent. For details of each substituent, reference can be made to the substituents described in paragraphs 0031 to 0035 of JP-A-2018-154672.

[0071] 〔X A and X B 〕

[0072] X A and X B Each independently represents a monovalent substituent.

[0073] X A and X B The substituent in is preferably a group having active hydrogen, more preferably -OH, -SH, -COOH, -SO3H, -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 .

[0074] R X1 and R X2 Each independently represents a hydrogen atom or a monovalent substituent. Examples of the substituent include alkyl, alkenyl, alkynyl, aryl, and heteroaryl groups. Among them, the substituent is preferably an alkyl group. The alkyl group is preferably linear or branched. The details of the alkyl, alkenyl, alkynyl, aryl, and heteroaryl groups are similar to those of G A and G B The meaning of the scope described in has the same meaning.

[0075] [Ring A and Ring B]

[0076] Ring A and Ring B each independently represent an aromatic ring or an aromatic heterocyclic ring.

[0077] The aromatic ring and aromatic heterocyclic ring may be a single ring or a condensed ring.

[0078] Examples of the aromatic ring and aromatic heterocyclic ring include a benzene ring, a naphthalene ring, a pentalene ring, an indene ring, an azulene ring, a heptalene ring, an indenene ring, a perylene ring, a pentacene ring, an acenaphthylene ring, a phenanthrene ring, an anthracene ring, a tetracene ring, ring, triphenylene ring, fluorene ring, biphenyl ring, pyrrole ring, furan ring, thiophene ring, imidazole ring, oxazole ring, thiazole ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, indolizine ring, indole ring, benzofuran ring, benzothiophene ring, isobenzofuran ring, quinolizine ring, quinoline ring, phthalazine ring, naphthyridine ring, quinoxaline ring, quinoxazoline ring, isoquinoline ring, carbazole ring, phenanthridine ring, acridine ring, phenanthroline ring, thianthrene ring, benzopyran ring, xanthene ring, phenoxathiol ring, phenothiazine ring and phenazine ring.

[0079] Among them, ring A and ring B are preferably aromatic rings, more preferably benzene rings or naphthalene rings.

[0080] The aromatic ring may be unsubstituted or may have a substituent. Examples of the substituent include G A and G B The substituents described in .

[0081] X A With G A 、X B With G B Can bond with each other to form a ring, G A and G B When there are multiple of each, they may be bonded to each other to form a ring. The ring is preferably a 5-membered ring or a 6-membered ring. The ring may be a monocyclic ring or a heterocyclic ring.

[0082] X A With G A 、X B With G B , G A Each other or G B When they are bonded to each other to form a ring, they may be directly bonded to form a ring, or they may be bonded to form a ring via a divalent linking group selected from the group consisting of alkylene, -CO-, -O-, -NH-, -BR-, and combinations thereof. A With G A 、X B With G B , G A Each other or G B They are preferably bonded to each other via -BR to form a ring.

[0083] R represents a hydrogen atom or a monovalent substituent. As the substituent, G A and G B The substituents described in are preferably alkyl or aryl groups.

[0084] 〔kA and kB〕

[0085] kA represents an integer from 0 to nA, kB represents an integer from 0 to nB, nA represents the maximum integer that can be substituted on ring A, and nB represents the maximum integer that can be substituted on ring B.

[0086] kA and kB are each independently preferably 0 to 4, more preferably 0 to 2, and particularly preferably 0 to 1. Furthermore, it is preferred that kA and kB are not simultaneously 0 (zero).

[0087] From the viewpoint of light resistance, the near-infrared absorbing pigment represented by Formula 1 is preferably a compound represented by Formula 2 below.

[0088] [Chemical Formula 4]

[0089]

[0090] In formula 2, R 1 and R 2 Each independently represents a monovalent substituent.

[0091] R 3 and R 4 Each independently represents a hydrogen atom or an alkyl group.

[0092] X 1 and X 2 Each independently represents an oxygen atom or -N(R 5 )-.

[0093] R 5 represents a hydrogen atom, an alkyl group, an aryl group or a heteroaryl group.

[0094] X 3 and X 4 Each independently represents a carbon atom or a boron atom.

[0095] t and u in X 3 and X 4 When it is a boron atom, it represents 1. 3 and X 4 When it is a carbon atom, it means 2.

[0096] Y 1 、Y 2 、Y 3 and Y 4 Each independently represents a monovalent substituent. 1 With Y 2 and Y3 With Y 4 They may be bonded to each other to form a ring.

[0097] Y 1 、Y 2 、Y 3 and Y 4 When a plurality of them exist, they may be bonded to each other to form a ring.

[0098] p and s each independently represent an integer of 0 to 3, and q and r each independently represent an integer of 0 to 2.

[0099] 〔R 1 and R 2 〕

[0100] R 1 With R 2 They may be the same or different, but are preferably the same. 1 , 2 R 2 They may be the same or different, but are preferably the same.

[0101] As R 1 and R 2 The monovalent substituent represented by G includes A and G B The same monovalent substituent. 1 and R 2 An aryl group is preferably an aryl group. 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.

[0102] 〔Y 1 、Y 2 、Y 3 and Y 4 〕

[0103] As Y 1 、Y 2 、Y 3 and Y 4 The monovalent substituent represented by G includes A and G B The same monovalent substituent.

[0104] [p, q, r, and s]

[0105] p, q, r and s are preferably 0. That is, in Formula 2, it is preferred that Y does not exist. 1 、Y 2 、Y 3 and Y 4 .

[0106] 〔X 1and X 2 〕

[0107] X 1 With X 2 They may be the same or different, but are preferably the same. 1 and X 2 Preferably -N(R 5 )-.

[0108] 〔R 5 〕

[0109] By R 5 The alkyl, aryl and heteroaryl groups represented by may be unsubstituted or may have a monovalent substituent. Examples of the monovalent substituent include A and G B The same monovalent substituent.

[0110] The number of carbon atoms in the alkyl group is preferably 1 to 20, more preferably 1 to 10, further preferably 1 to 4, and particularly preferably 1 to 2. The alkyl group may be linear or branched.

[0111] The aryl group preferably has 6 to 20 carbon atoms, more preferably 6 to 12 carbon atoms.

[0112] The heteroaryl group may be monocyclic or polycyclic. The number of heteroatoms constituting the heteroaryl ring is preferably 1 to 3. The heteroatoms constituting the heteroaryl ring are preferably nitrogen, oxygen, or sulfur atoms. The number of carbon atoms constituting the heteroaryl ring is preferably 3 to 30, more preferably 3 to 18, and even more preferably 3 to 12.

[0113] R 5 It is preferably a hydrogen atom, a methyl group or an ethyl group, more preferably a hydrogen atom or a methyl group, and still more preferably a hydrogen atom.

[0114] 〔X 3 and X 4 〕

[0115] X 3 and X 4 They may be the same or different, but are preferably the same. 3 and X 4 Preferred is a boron atom.

[0116] 〔R 3 and R 4 〕

[0117] By R 3 and R 4 The number of carbon atoms of the alkyl group represented by is preferably 1 to 4, more preferably 1 or 2. The alkyl group may be linear or branched. Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, and isobutyl. 3 and R4 Each independently preferably is a hydrogen atom, a methyl group or an ethyl group, more preferably a hydrogen atom or a methyl group, and still more preferably a hydrogen atom.

[0118] The molecular weight of the near-infrared absorbing pigment represented by Formula 1 is preferably 100 to 2,000, more preferably 150 to 1,000.

[0119] The near-infrared absorbing dye represented by Formula 1 is described in detail in JP-A-2011-2080101, and the compound described therein can be preferably used as the squarylium dye in the present invention.

[0120] The near-infrared absorbing pigment represented by Formula 1 and the near-infrared absorbing pigment represented by Formula 2 may be tautomers of each other. For example, the description of paragraph 0034 of International Publication No. 2016-136783 can be referred to for tautomers.

[0121] Specific examples of near-infrared absorbing pigments represented by Formula 1 or Formula 2 are shown below (Specific Examples B-1 to B-40). However, the present invention is not limited to the following compounds. In the formula, "Me" represents a methyl group, "Ph" represents a phenyl group, and "Ac" represents an acetyl group.

[0122] [Chemical Formula 5]

[0123]

[0124] [Chemical Formula 6]

[0125]

[0126] [Chemical Formula 7]

[0127]

[0128] [Chemical Formula 8]

[0129]

[0130] [Chemical Formula 9]

[0131]

[0132] [Chemical Formula 10]

[0133]

[0134] From the viewpoint of improving readability and readability after a certain period of time, the near-infrared absorbing dye represented by Formula 1 is preferably Specific Example B-1, B-3, B-7, B-37, B-41, B-42, B-43, B-44, or B-45.

[0135] The near-infrared absorbing pigment represented by Formula 1 is preferably dispersed in the ink in the form of particles. From the perspective of light resistance, the volume average particle size of the near-infrared absorbing pigment represented by Formula 1 is preferably 10 nm or larger, more preferably 15 nm or larger, further preferably 20 nm or larger, and particularly preferably 50 nm or larger. Furthermore, from the perspective of dispersibility and ejectability, the volume average particle size of the near-infrared absorbing pigment represented by Formula 1 is preferably 400 nm or smaller, more preferably 300 nm or smaller, and further preferably 200 nm or smaller.

[0136] When the near-infrared absorbing dye is coated with a dispersant or the like, the volume average particle size of the near-infrared absorbing dye refers to the volume average particle size in the coated state.

[0137] The volume average particle size can be measured by a dynamic light scattering method using Zetasizer Nano ZS (manufactured by Malvern Panalytical Ltd.) as a measuring device.

[0138] The near-infrared absorbing pigment is preferably dispersed using a disperser. Examples of the disperser include a circulating bead mill, a bead mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, and a paint shaker.

[0139] The content of the near-infrared absorbing pigment represented by Formula 1 is preferably 0.1 to 20% by mass, more preferably 0.1 to 10% by mass, and further preferably 0.3 to 7% by mass, relative to the total amount of the ink.

[0140] (polymerizable monomer)

[0141] The ink according to the present invention contains a polymerizable monomer. The polymerizable monomer contained in the ink may be one type or two or more types.

[0142] In the present invention, a monomer refers to a compound having a molecular weight of less than 1000. A polymerizable monomer refers to a compound having a polymerizable group and a molecular weight of less than 1000.

[0143] 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.

[0144] Examples of polymerizable monomers include photopolymerizable monomers that undergo polymerization by irradiation with light and thermally polymerizable monomers that undergo polymerization by irradiation with heat or infrared rays. Examples of photopolymerizable monomers include polymerizable monomers having a radical polymerizable group capable of undergoing free radical polymerization (i.e., a radical polymerizable monomer) and polymerizable monomers having a cationic polymerizable group capable of undergoing cationic polymerization (i.e., a cationic polymerizable monomer). Among these, the polymerizable monomer is preferably a photopolymerizable monomer, and more preferably a radical polymerizable monomer.

[0145] The radical polymerizable monomer is preferably an ethylenically unsaturated monomer having an ethylenically unsaturated group. Examples of the ethylenically unsaturated monomer include monofunctional ethylenically unsaturated monomers and polyfunctional ethylenically unsaturated monomers.

[0146] The monofunctional ethylenically unsaturated monomer refers to a monomer having one ethylenically unsaturated group, and examples thereof include monofunctional (meth)acrylates, monofunctional (meth)acrylamides, monofunctional aromatic vinyl compounds, monofunctional vinyl ethers, and monofunctional N-vinyl compounds.

[0147] Examples of the monofunctional (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, tert-octyl (meth)acrylate, isoamyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, octadecyl (meth)acrylate, isooctadecyl (meth)acrylate, cyclohexyl (meth)acrylate, 4-n-butylcyclohexyl (meth)acrylate, 4-tert-butylcyclohexyl (meth)acrylate, bornyl (meth)acrylate, isobornyl (meth)acrylate, 2-ethylhexyl 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, 2,4,5-tetramethylphenyl (meth)acrylate, 4-chlorophenyl (meth)acrylate, 2-phenoxymethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, glycidyl (meth)acrylate, glycidyloxybutyl (meth)acrylate, glycidyloxyethyl (meth)acrylate, glycidyloxypropyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate Butyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, diethylaminopropyl (meth)acrylate, trimethoxysilylpropyl (meth)acrylate, trimethylsilylpropyl (meth)acrylate, polyethylene oxide monomethyl ether (meth)acrylate, polyethylene oxide (meth)acrylate, polyethylene oxide monoalkyl ether (meth)acrylate, dipropylene glycol Alcohol (meth)acrylate, polypropylene oxide monoalkyl ether (meth)acrylate, 2-methacryloyloxyethyl succinic acid, 2-methacryloyloxyhexahydrophthalic acid, 2-formyloxyethyl-2-hydroxypropyl phthalate, butoxydiethylene glycol (meth)acrylate, trifluoroethyl (meth)acrylate, perfluorooctylethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, ethylene oxide (EO) modified phenol (meth)acrylate, EO modified cresol (meth)acrylate Ester, EO modified nonylphenol (meth)acrylate, propylene oxide (PO) modified nonylphenol (meth)acrylate, EO modified 2-ethylhexyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, (3-ethyl-3-oxetanylmethyl) (meth)acrylate, phenoxyethylene glycol (meth)acrylate, phenoxyethylene glycol (meth)acrylate and cyclic trimethylolpropane formal (meth)acrylate.

[0148] Examples of the monofunctional (meth)acrylamide 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-methylol (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, and (meth)acryloylmorpholine.

[0149] Examples of the monofunctional aromatic vinyl compound include styrene, dimethylstyrene, trimethylstyrene, isopropylstyrene, chloromethylstyrene, methoxystyrene, acetoxystyrene, chlorostyrene, dichlorostyrene, bromostyrene, methyl vinylbenzoate, 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, isopropenylstyrene, butenylstyrene, octenylstyrene, 4-tert-butoxycarbonylstyrene, and 4-tert-butoxystyrene.

[0150] Examples of the monofunctional vinyl ether include 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, cyclohexyl methyl vinyl ether, 4-methylcyclohexyl methyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenyloxyethyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, butoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, ethoxyethoxyethyl vinyl ether, methoxypolyethylene glycol vinyl ether, tetrahydrofurfuryl vinyl ether, 2-hydroxyethyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxymethylcyclohexyl methyl vinyl ether, diethylene glycol monovinyl ether, polyethylene glycol vinyl ether, chloroethyl vinyl ether, chlorobutyl vinyl ether, chloroethoxyethyl vinyl ether, phenylethyl vinyl ether, and phenoxypolyethylene glycol vinyl ether.

[0151] Examples of the monofunctional N-vinyl compound include N-vinyl-ε-caprolactam and N-vinylpyrrolidone.

[0152] From the viewpoint of improving curability, the monofunctional ethylenically unsaturated compound is preferably a compound having a ring structure. Examples of the monofunctional ethylenically unsaturated compound having a ring structure include cyclohexyl (meth)acrylate, 4-butylphenyl (meth)acrylate, 4-tert-butylcyclohexyl (meth)acrylate, bornyl (meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate, 4-butylphenyl (meth)acrylate, phenyl (meth)acrylate, 2,4,5-tetramethylphenyl (meth)acrylate, 4-chlorophenyl (meth)acrylate, 2-phenoxymethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentyl (meth)acrylate, (3-ethyl-3-oxetanylmethyl) (meth)acrylate, phenoxyethylene glycol (meth)acrylate, and cyclic trimethylolpropane formal (meth)acrylate.

[0153] Monofunctional aromatic vinyl compounds;

[0154] Monofunctional vinyl ethers having a ring structure, such as cyclohexyl vinyl ether, cyclohexyl methyl vinyl ether, 4-methylcyclohexyl methyl vinyl ether, benzyl vinyl ether, dicyclopentenyl vinyl ether, 2-dicyclopentenyloxyethyl vinyl ether, phenylethyl vinyl ether, and phenoxypolyethylene glycol vinyl ether;

[0155] Monofunctional N-vinyl compounds having a ring structure, such as N-vinyl-ε-caprolactam and N-vinylpyrrolidone.

[0156] The polyfunctional ethylenically unsaturated monomer refers to a monomer having two or more ethylenically unsaturated groups, and examples thereof include polyfunctional (meth)acrylates and polyfunctional vinyl ethers.

[0157] Examples of the polyfunctional (meth)acrylate include 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. Di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, hexanediol di(meth)acrylate, heptanediol di(meth)acrylate, EO-modified neopentyl glycol di(meth)acrylate, PO-modified neopentyl glycol 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, tricyclodecane dimethanol di(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane EO addition tris(meth)acrylate (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-vinyloxyethoxy)ethyl(meth)acrylate.

[0158] Examples of the polyfunctional vinyl ethers include 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-cyclohexanedimethanol divinyl ether, bisphenol A alkylene oxide divinyl ether, bisphenol F alkylene oxide divinyl ether, trimethylolethane trivinyl ether, trimethylolpropane trivinyl ether, ditrimethylolpropane tetravinyl ether, and the like. vinyl ether, glycerol trivinyl ether, pentaerythritol tetravinyl ether, dipentaerythritol pentavinyl ether, dipentaerythritol hexavinyl ether, EO addition trimethylolpropane trivinyl ether, PO addition trimethylolpropane trivinyl ether, EO addition ditrimethylolpropane tetravinyl ether, PO addition ditrimethylolpropane tetravinyl ether, EO addition pentaerythritol tetravinyl ether, PO addition pentaerythritol tetravinyl ether, EO addition dipentaerythritol hexavinyl ether and PO addition dipentaerythritol hexavinyl ether.

[0159] From the viewpoint of improving curability, the polyfunctional ethylenically unsaturated monomer is preferably a compound having oxygen atoms, and the ratio of the number of oxygen atoms to the number of carbon atoms contained 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, and is, for example, 0.5. As a compound having a ratio of the number of oxygen atoms to the number of carbon atoms contained in one molecule of 0.2 or more, for example, polyethylene glycol diacrylate can be cited.

[0160] Furthermore, the polymerizable monomer may be a commercially available product described in “Handbook of Cross-linking Agents” compiled by Shinzo Yamashita (TAISEISHA, 1981); “Handbook of UV / EB Curing (Raw Materials)” compiled by Kiyoshi Kato (Polymer Publishing Association, 1985); “Application and Market of UV·EB Curing Technology” compiled by RadTech Japan, page 79 (1989, CMC Publishing Co., Ltd.); “Handbook of Polyester Resins” written by Eiichiro Ryuyama (1988, NIKKAN KOGYO SHIMBUN, LTD.), etc.

[0161] The ink of the present invention preferably contains a polyfunctional polymerizable monomer as a polymerizable monomer, and more preferably contains both a monofunctional and a polyfunctional polymerizable monomer. The inclusion of a polyfunctional polymerizable monomer in the ink enables the recording of an image with excellent curability. Furthermore, the inclusion of a polyfunctional polymerizable monomer in the ink suppresses the transfer of unreacted polymerizable monomer from the image recorded material to the outside (so-called migration). This ink is particularly well-suited for use as packaging materials in the food and cosmetics packaging fields, where substrate safety is strictly required.

[0162] From the perspective of curability, the proportion of the polyfunctional polymerizable monomer in the total polymerizable monomers contained in the ink is preferably 50% by mass or greater, and more preferably 60% by mass or greater. Furthermore, the upper limit of the proportion of the polyfunctional polymerizable monomer in the total polymerizable monomers contained in the ink is not particularly limited and may be 100% by mass.

[0163] In the present invention, from the viewpoint of improving the readability and solvent resistance after the wiping test, the glass transition temperature (Tg) of the polymerizable monomer is preferably 30°C or more, more preferably 60°C or more. In particular, the proportion of the polymerizable monomer having a glass transition temperature of 30°C or more in the polymerizable monomer is preferably 90% by mass or more, more preferably 92% by mass or more. The upper limit of the above ratio is not particularly limited, for example, 100% by mass. If the proportion of the polymerizable monomer having a glass transition temperature of 30°C or more in the polymerizable monomer is 90% by mass or more, the readability after the wiping test is further improved. As a polymerizable monomer having a Tg of 30°C or more, for example, isobornyl (meth)acrylate (Tg: 97°C) can be cited.

[0164] In addition, the glass transition temperature (Tg) of a polymerizable monomer refers to the glass transition temperature when the polymerizable monomer is a homopolymer. A homopolymer with a weight average molecular weight of 10,000 to 20,000 is obtained by adding any polymerization initiator to the polymerizable monomer. The glass transition temperature (Tg) of a homopolymer with a weight average molecular weight of 10,000 to 20,000 is adopted as the glass transition temperature of the polymerizable monomer. The glass transition temperature (Tg) of the homopolymer changes according to the weight average molecular weight, but in the range of 10,000 to 20,000, the variation of Tg caused by the difference in weight average molecular weight is negligible. In addition, the weight average molecular weight refers to the value measured by gel permeation chromatography (GPC). In the measurement based on GPC, HLC (registered trademark) -8020GPC (manufactured by TOSOH CORPORATION) was used as a measuring apparatus, 3 TSKgel (registered trademark) SuperMultipore HZ-H (4.6 mm ID × 15 cm, manufactured by TOSOH CORPORATION) were used as columns, and THF (tetrahydrofuran) was used as an eluent. In addition, the sample concentration was set to 0.45% by mass, the flow rate was set to 0.35 ml / min, the sample injection amount was set to 10 μl, and the measurement temperature was set to 40 ° C., and the measurement was performed using an RI detector. The calibration curve was prepared based on 8 samples of "Standard Sample TSK Standard, Polystyrene" manufactured by TOSOH CORPORATION: "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000" and "n-propylbenzene".

[0165] The glass transition temperature (Tg) is measured using a differential scanning calorimeter (DSC) in accordance with ASTM D3418-8. For example, the glass transition temperature (Tg) is measured using a differential scanning calorimeter manufactured by SII NanoTechnology Inc. (product name "EXSTAR6220") under conventional measurement conditions.

[0166] The content of the polymerizable monomer is 50% by mass or more, more preferably 60% to 95% by mass, and even more preferably 70% to 90% by mass, relative to the total amount of the ink. When the content of the polymerizable monomer is 50% by mass or more, the resulting image record has excellent readability.

[0167] Regarding the SP value of the polymerizable monomer, the difference between the SP value of the polymerizable monomer and the SP value of the dispersant described below is sufficient to be 3.8 MPa. 1 / 2 ~16.0MPa 1 / 2 The value of is not particularly limited. From the viewpoint of curability and dispersion stability, the SP value of the polymerizable monomer is preferably 15.0 MPa. 1 / 2 ~30.0MPa 1 / 2 , more preferably 17.0 MPa 1 / 2 ~20.0MPa 1 / 2 .

[0168] In the present invention, the SP value of a polymerizable monomer refers to the Hansen solubility parameter. The Hansen solubility parameter is a solubility parameter introduced by Hildebrand that is divided into three components: a dispersion term δd, a polar term δp, and a hydrogen bonding term δh, and expressed in a three-dimensional space.

[0169] The SP value δ of the polymerizable monomer is set to a value calculated using the following formula A.

[0170] SP value (δ) [MPa 1 / 2 ]=(δd 2 +δp 2 +δh 2 ) 1 / 2 ...(A)

[0171] In addition, the dispersion term δd, polar term δp, and hydrogen bond term δh were calculated using HSPiP (version 4.1.07) software.

[0172] Table 1 shows the dispersion term δd, polarity term δp, hydrogen bonding term δh and SP values ​​of MPDDA (3-methyl-1,5-pentanediol diacrylate), DPGDA (dipropylene glycol diacrylate), IBOA (isobornyl acrylate), TCDDMDA (tricyclodecane dimethanol diacrylate), TMPTA (trimethylolpropane triacrylate), ACMO (acryloylmorpholine), EOTMPTA (trimethylolpropane EO addition triacrylate) and PEA (phenoxyethyl acrylate).

[0173] [Table 1]

[0174]

[0175] When the ink contains two or more polymerizable monomers, the SP value of each polymerizable monomer is calculated using the following method. First, the weighted average of the dispersion term, polar term, and hydrogen bonding term of the polymerizable monomers in the ink is calculated as δd, δp, and δh. The SP value is then calculated using the above-mentioned formula A based on the calculated δd, δp, and δh.

[0176] When the ink contains two or more polymerizable monomers, δd is calculated using the following formula B1. In formula B1, δd m represents the dispersion term of the polymerizable monomer m items (m represents an integer greater than or equal to 1) in the polymerizable monomer, W m The content ratio (mass %) of the polymerizable monomer in the above item m relative to the total amount of the ink.

[0177] δd=∑δd m W m / ∑W m ...(B1)

[0178] Similarly, when the ink contains two or more polymerizable monomers, δp and δh are calculated by the following formulas B2 and B3.

[0179] δp=∑δp m W m / ∑W m ...(B2)

[0180] δh=∑δh m W m / ∑W m ...(B3)

[0181] In formula B2, δp m The polarity term of the polymerizable monomer represents m terms (m represents an integer of 1 or greater) in the polymerizable monomer.

[0182] In formula B3, δh mThe hydrogen bonding term of the polymerizable monomer represents m terms (m represents an integer of 1 or greater) in the polymerizable monomer.

[0183] (Dispersant)

[0184] The ink according to the present invention contains a dispersant. The dispersant has a function of dispersing the squarylium dye represented by Formula 1.

[0185] The weight average molecular weight of the dispersant is preferably 100,000 or less, more preferably 75,000 or less, and further preferably 50,000 or less. Furthermore, the weight average molecular weight of the dispersant is preferably 1,000 or more, more preferably 2,000 or more, and further preferably 3,000 or more. 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, thereby obtaining an image record having excellent readability. On the other hand, if the weight average molecular weight of the dispersant is 1,000 or more, the compatibility with the dispersion medium does not become too high, and the near-infrared absorbing pigment represented by Formula 1 can be stably dispersed by the dispersant.

[0186] The weight-average molecular weight refers to the value measured by gel permeation chromatography (GPC). In the measurement based on gel permeation chromatography (GPC), HLC (registered trademark) -8020GPC (manufactured by TOSOH CORPORATION) was used as a measuring device, 3 TSKgel (registered trademark) Super Multipore HZ-H (4.6 mm ID × 15 cm, manufactured by TOSOH CORPORATION) were used as columns, and THF (tetrahydrofuran) was used as an eluent. In addition, the sample concentration was set to 0.45% by mass, the flow rate was set to 0.35 ml / min, the sample injection amount was set to 10 μl, and the measurement temperature was set to 40 ° C, and the measurement was performed using an RI detector. The calibration curve was prepared based on 8 samples of "standard sample TSK standard, polystyrene" manufactured by TOSOH CORPORATION: "F-40", "F-20", "F-4", "F-1", "A-5000", "A-2500", "A-1000" and "n-propylbenzene".

[0187] The dispersant is preferably a polymer, and the polymer may be any of a random polymer, a block polymer, and a graft polymer.

[0188] Wherein, from the viewpoint of readability after time, dispersant is preferably block polymer.Block polymer, for example, has adsorption block and dispersion medium affinity block, and the adsorption block has the adsorption group adsorbed on the near infrared absorbing pigment represented by Formula 1, and the dispersion medium affinity block has the functional group with affinity to dispersion medium. In block polymer, the shielding property of adsorption group is low and mobility is high, therefore the adsorption speed to the near infrared absorbing pigment represented by Formula 1 is fast. Therefore, if dispersant is block polymer, then readability is further improved. Moreover, adsorption group is gathered in block polymer, therefore the adsorption power to the near infrared absorbing pigment represented by Formula 1 is high. Therefore, if dispersant is block polymer, then readability is further improved after time.

[0189] The dispersant preferably has a basic functional group or an acidic functional group. When the ink contains the pigment derivative described later, a combination of a dispersant with a basic functional group and a pigment derivative with an acidic functional group or a combination of a dispersant with an acidic functional group and a pigment derivative with a basic functional group is preferred. If the ink contains a combination of a dispersant with a basic functional group and a pigment derivative with an acidic functional group, the pigment derivative is easily adsorbed on the dispersant through acid-base interaction. Similarly, if the ink contains a combination of a dispersant with an acidic functional group and a pigment derivative with a basic functional group, the pigment derivative is easily adsorbed on the dispersant through acid-base interaction. Due to the spatial repulsion between the dispersants, the near-infrared absorbing pigment represented by Formula 1 can be stably dispersed in the ink, and the stability over time is improved. As a result, the readability is improved over time.

[0190] Examples of the basic functional group include an amino group, an amide group, and an imine group. The dispersant may have only one basic functional group or may have two or more basic functional groups.

[0191] Examples of the acidic functional group include a carboxyl group and a sulfonic group. The dispersant may have only one type of acidic functional group or may have two or more types.

[0192] When the dispersant has a basic functional group, the base number of the dispersant is preferably 15 mgKOH / g or greater, more preferably 20 mgKOH / g or greater, and even more preferably 25 mgKOH / g or greater, from the perspective of improving readability and readability over time. The upper limit of the base number of the dispersant is not particularly limited, but is, for example, 40 mgKOH / g.

[0193] In the present invention, the base number is a value measured by the perchloric acid method specified in JIS K 2501: 2003. The base number 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 1 g of a sample.

[0194] When the dispersant has an acidic functional group, the acid value of the dispersant is preferably 15 mgKOH / g or greater, more preferably 20 mgKOH / g or greater, and even more preferably 25 mgKOH / g or greater, from the perspective of improving readability and readability over time. The upper limit of the acid value of the dispersant is not particularly limited, but is, for example, 40 mgKOH / g.

[0195] In the present invention, the acid value is a value measured by the method described in JIS K0070: 1992. The acid value is obtained as the number of milligrams (mg) of potassium hydroxide required to neutralize all acid components contained in 1 g of a sample.

[0196] The dispersant may be a commercially available product. Examples of commercially available products include the SOLSPERSE (registered trademark) series of The Lubrizol Corporation (e.g., SOLSPERSE 16000, 21000, 32000, 35000, 41000, 41090, 43000, 44000, 46000, 54000, 55000, 71000, etc.), the DISPERBYK (registered trademark) series of BYK-Chemie GmbH (e.g., DISPERBYK 102, 110, 111, 118, 170, 190, 194N, 2001, 2013, 2015, 2090, 2096, etc.), and the TEGO (registered trademark) Dispers series of Evonik Industries AG (e.g., TEGO Dispers 610, 610S, 630, 651, 655, 750W, 755W, etc.), DISPARLON (registered trademark) series of Kusumoto Chemicals, Ltd. (e.g., DA-375, DA-1200, etc.), FLOREN series of KYOEISHA CHEMICAL Co., LTD. (e.g., WK-13E, G-700, G-900, GW-1500, GW-1640, WK-13E, etc.), EFKA (registered trademark) series of BASF (e.g., EFKA PX 4701, EFKAPX 4731, EFKA PX 4732, etc.).

[0197] From the viewpoint of improving readability and readability after aging, the content of the dispersant is preferably 0.7% by mass to 5% by mass, more preferably 0.8% by mass to 4% by mass, relative to the total amount of the ink.

[0198] 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, more preferably 0.2 to 5, and even more preferably 0.5 to 5, based on mass.

[0199] Regarding the SP value of the dispersant, 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 From the viewpoint of dispersion stability, the SP value of the dispersant is preferably 21 MPa. 1 / 2 ~34MPa 1 / 2 , more preferably 24 MPa 1 / 2 ~34MPa 1 / 2 .

[0200] The SP value of the dispersant is calculated, for example, by the following formula of KWSUH and JMCORBETT (Journal of Applied Polymer Science, 12, 2359, 1968).

[0201] SP value = {(V ml ) 1 / 2 ×δH+(V mh ) 1 / 2 ×δD} / {(V ml ) 1 / 2 +(V mh ) 1 / 2}

[0202] V ml 、V mh , δH, and δD are values ​​calculated by substituting the titration amount H (mL) at the cloud point when 0.5 g (solid content) of the dispersant is dissolved in 10 mL of a good solvent at a measuring temperature of 20°C and n-hexane is added thereto, and the titration amount D (mL) at the cloud point when 0.5 g (solid content) of the dispersant is dissolved in 10 mL of a good solvent at a measuring temperature of 20°C and deionized water is added thereto into the following formula.

[0203] 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)}

[0204] 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)}

[0205] V H =H / (10+H)

[0206] V D =D / (10+D)

[0207] δH = (SP value of good solvent) × 10 / (10+H) + (SP value of n-hexane) × H / (10+H)

[0208] δD = (SP value of good solvent) × 10 / (10+D) + (SP value of deionized water) × D / (10+D)

[0209] In addition, the molar volume of n-hexane is 130.3 mL / mol, and the molar volume of deionized water is 18 mL / mol. In addition, the SP value of n-hexane is 7.27 (cal / cm 3 ) 1 / 2 The SP value of deionized water is 23.39 (cal / cm 3 ) 1 / 2 .

[0210] The good solvent for dissolving the dispersant is not particularly limited as long as it can dissolve the dispersant, and can be appropriately selected. Examples of the good solvent include acetone.

[0211] The molar volume of acetone is 74.4 mL / mol, and the SP value of acetone is 9.72 (cal / cm 3 ) 1 / 2 .

[0212] When acetone is used as the good solvent, 74.4 is substituted into the "molar volume of the good solvent" and 9.72 is substituted into the "SP value of the good solvent" in the above formula.

[0213] The SP value of each solvent was calculated using HSPiP (version 4.1.07) software.

[0214] The molar volume (mL / mol) of each solvent is a value obtained by dividing the molecular weight (g / mol) by the density (g / mL).

[0215] The unit of the obtained SP value is (cal / cm 3 ) 1 / 2 According to 1 Ability to change the unit from (cal / cm 3 ) 1 / 2 Convert to MPa 1 / 2 .

[0216] In the ink of the present 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 The above-mentioned difference refers to the absolute value of the value obtained by subtracting one SP value from another SP value.

[0217] It is estimated that if the difference in the above SP values ​​is 3.8 MPa 1 / 2 If the above SP value difference is 16.0 MPa, the dispersant is unlikely to be separated from the surface of the near-infrared absorbing pigment represented by Formula 1, and the dispersion stability of the near-infrared absorbing pigment represented by Formula 1 is improved. 1 / v The dispersant adsorbed onto the surface of the near-infrared absorbing pigment represented by Formula 1 diffuses appropriately, making it difficult for the near-infrared absorbing pigment represented by Formula 1 to aggregate with one another. As a result, an image record with excellent readability can be obtained. Furthermore, in the ink of the present invention, the dispersant enables the near-infrared absorbing pigment represented by Formula 1 to be stably dispersed for a long period of time, resulting in an image record with excellent readability over time.

[0218] From the viewpoint of improving readability and readability after a certain period of time, the difference in the SP value is preferably 4.5 MPa. 1 / 2 ~15.5MPa 1 / 2 , more preferably 5.0 MPa 1 / 2 ~15.2MPa 1 / 2 .

[0219] (Pigment derivatives)

[0220] The ink according to the present invention preferably further contains a pigment derivative.

[0221] The pigment derivative refers to a compound having a structure derived from a pigment in the molecule and having a molecular weight of less than 1,000.

[0222] When a pigment derivative is included in an ink, π-π interactions between the pigment derivative and the near-infrared absorbing pigment represented by Formula 1 are effective, while acid-base interactions between the pigment derivative and the dispersant are effective. Therefore, the near-infrared absorbing pigment represented by Formula 1 is further stably dispersed by the dispersant, improving the ink's stability over time. Consequently, readability improves over time.

[0223] The pigment derivative preferably has a basic functional group or an acidic functional group.

[0224] Examples of the basic functional group include an amino group, an amide group, and an imine group. The pigment derivative may have only one basic functional group or two or more basic functional groups.

[0225] Examples of the acidic functional group include a carboxyl group and a sulfo group. The pigment derivative may have only one type of acidic functional group or may have two or more types.

[0226] The pigment derivative having an acidic functional group is preferably represented by Formula 3 below.

[0227] P-[R 10 -X 10 ]m……(3)

[0228] In formula 3, P represents the pigment residue, R 10 represents a divalent linking group, X 10 Each independently represents a carboxyl group or a sulfo group. m represents the maximum integer that can be substituted by P.

[0229] 〔P〕

[0230] Examples of P include diketopyrrolopyrrole pigments; azo pigments such as azo, disazo, and polyazo; phthalocyanine pigments; anthraquinone pigments such as diaminodianthraquinone, anthrapyrimidine, flavonol, anthraquinone, indanthrone, pyrathrone, and ionone; quinacridone pigments; dioxazine pigments; perinone pigments; perylene pigments; thioindigo pigments; isoindoline pigments; isoindolinone pigments; quinophthalone pigments; reduced pigments, and residues of metal complex pigments.

[0231] Among them, from the viewpoint of improving readability and readability over time, P is preferably a residue of a diketopyrrolopyrrole dye, a phthalocyanine dye, an anthraquinone dye, or a dioxazine dye, and more preferably a diketopyrrolopyrrole dye, a phthalocyanine dye, or an anthraquinone dye.

[0232] 〔R 10 〕

[0233] As R 10 For example, there can be mentioned a group selected from the group consisting of alkylene, arylene, -O-, -S-, -C=O-, -NR 30 -、-CONR 30 -,-SO2NR 30 、-NR 30 CO-、-NR 30 A divalent group in the group of SO2-, a divalent group formed by combining two or more of these, and a single bond. 30 represents a hydrogen atom or an alkyl group.

[0234] Among them, R 10 It is preferably a single bond.

[0235] 〔X 10 〕

[0236] X 10 Preferably it is a sulfo group. 10 They may be the same or different, but are preferably the same.

[0237] 〔m〕

[0238] m is preferably 1-10, more preferably 1-5, and even more preferably 1-3.

[0239] The pigment derivative contained in the ink may be one kind or two or more kinds.

[0240] From the viewpoint of improving readability and readability over time, the content of the pigment derivative is preferably 0.005% by mass to 0.1% by mass relative to the total amount of the ink.

[0241] From the viewpoint of improving readability and readability over time, the content of the pigment derivative is preferably 0.12 to 15 mass %, more preferably 0.15 to 12 mass %, relative to the total amount of the near-infrared absorbing pigment represented by Formula 1.

[0242] (Polymerization initiator)

[0243] The ink of the present invention preferably contains a polymerization initiator. The polymerization initiator contained in the ink may be one or more. When the ink of the present invention contains a free radical polymerizable monomer as a polymerizable monomer, the polymerization initiator is preferably a free radical polymerization initiator.

[0244] Examples of the radical polymerization initiator include alkylphenone compounds, acylphosphine compounds, aromatic onium salt compounds, organic peroxides, thio compounds, hexaarylbiimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having a carbon-halogen bond, and alkylamine compounds.

[0245] Among them, the polymerization initiator is preferably at least one selected from the group consisting of acylphosphine compounds and thio compounds, more preferably at least one selected from the group consisting of acylphosphine oxide compounds and thioxanthone compounds, and even more preferably contains acylphosphine oxide compounds and thioxanthone compounds.

[0246] When the polymerization initiator contains an acylphosphine oxide compound and a thioxanthone compound, the readability after the transfer test and the readability after the wiping test are improved.

[0247] Examples of the acylphosphine oxide compound include monoacylphosphine oxide compounds and bisacylphosphine oxide compounds, and bisacylphosphine oxide compounds are preferred.

[0248] Examples of the monoacylphosphine oxide compound include isobutyryldiphenylphosphine oxide, 2-ethylhexanoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide, o-toluoyldiphenylphosphine oxide, p-tert-butylbenzoyldiphenylphosphine oxide, 3-pyridylcarbonyldiphenylphosphine oxide, acryloyldiphenylphosphine oxide, benzoyldiphenylphosphine oxide, and pivaloylphenylphosphine oxide. 1-Methyl-2-cyclohexanoyldiphenylphosphine oxide, methyl pivaloylphenylphosphine oxide, and isopropyl pivaloylphenylphosphine oxide.

[0249] Examples of the bisacylphosphine oxide compound include 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)-2-naphthylphosphine oxide. -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-dimethoxyphenylphosphine oxide phenylphosphine 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.

[0250] Among them, the acylphosphine oxide compound is preferably bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (product name "Omnirad 819", manufactured by IGM Resins BV), 2,4,6-trimethylbenzoyldiphenylphosphine 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).

[0251] Examples of the thioxanthone compound 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, 1-ethoxycarbonyl- thioxanthone, 2-methyl-6-(1,1-dimethoxybenzyl)thioxanthone, 2-morpholinomethylthioxanthone, 2-methyl-6-morpholinomethylthioxanthone, n-allylthioxanthone-3,4-dicarboximide, n-octylthioxanthone-3,4-dicarboximide, N-(1,1,3,3-tetramethylbutyl)thioxanthone-3,4-dicarboximide, 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-thioxanthon-2-yloxy)-N,N,N-trimethyl-1-propanaminium chloride.

[0252] The thioxanthone compound may be a commercially available product, and examples of the commercially available product include the SPEEDCURE series manufactured by Lambson Limited (for example, SPEEDCURE 7010, SPEEDCURE CPTX, and SPEEDCURE ITX).

[0253] When the polymerization initiator 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 is preferably 2 to 10, more preferably 3 to 7, based on mass.

[0254] From the perspective of improving readability and readability after time, the content of the polymerization initiator is preferably 5% by mass or more, more preferably 10% by mass or more, relative to the total amount of the ink. The upper limit of the content of the polymerization initiator is not particularly limited, and is, for example, 30% by mass.

[0255] When the polymerization initiator contains an acylphosphine oxide compound, the content of the acylphosphine oxide compound is preferably 5 to 15 mass %, more preferably 8 to 12 mass % relative to the total amount of the ink from the viewpoint of improving readability and readability over time.

[0256] When the polymerization initiator contains a thioxanthone compound, the content of the thioxanthone compound is preferably 0.5% to 5% by mass, more preferably 1% to 3% by mass, relative to the total amount of the ink, from the viewpoint of improving readability after a transfer test and readability after a wiping test.

[0257] The ink according to the present invention may further contain the following other components.

[0258] (Siloxane compound)

[0259] The ink of the present invention preferably contains at least one siloxane compound. Siloxane compounds act as surfactants in inks. When a siloxane compound is included in the ink, it tends to be localized near the air interface of the ink film during curing. This improves readability after a rub test.

[0260] The siloxane compound is preferably an organo-modified polysiloxane. Organo-modified polysiloxane refers to a polysiloxane in which an organic group is introduced into a portion of the methyl groups of polydimethylsiloxane. The position where the organic group is introduced may be the terminal of the polydimethylsiloxane or a side chain.

[0261] Examples of the organo-modified polysiloxane include polyether-modified polydimethylsiloxane, phenyl-modified polydimethylsiloxane, alcohol-modified polydimethylsiloxane, alkyl-modified polydimethylsiloxane, aralkyl-modified polydimethylsiloxane, fatty acid ester-modified polydimethylsiloxane, epoxy-modified polydimethylsiloxane, amino-modified polydimethylsiloxane, amino-modified polydimethylsiloxane, and mercapto-modified polydimethylsiloxane.

[0262] The siloxane compound preferably includes a siloxane compound having a polymerizable group. As described above, when the ink contains a siloxane compound having a polymerizable group, the siloxane compound having a polymerizable group tends to be localized near the air interface of the ink film during ink curing. This promotes polymerization near the air interface of the ink film, improving readability after a close fit test and after a transfer test.

[0263] The molecular weight of the siloxane compound having a polymerizable group is 1000 or more, and is different from the polymerizable monomer.

[0264] In the siloxane compound having a polymerizable group, the number of polymerizable groups possessed by the siloxane compound is not particularly limited, and is, for example, 1 to 5. The polymerizable groups possessed by the siloxane compound are preferably of the same type as the polymerizable groups possessed by the polymerizable monomer contained in the ink. Specifically, the polymerizable groups are preferably free radical polymerizable groups, more preferably ethylenically unsaturated groups, and even more preferably (meth)acryloyl groups.

[0265] The siloxane compound having a polymerizable group is preferably an organo-modified polysiloxane into which an organic group containing a polymerizable group is introduced.

[0266] The siloxane compound having a polymerizable group may be a commercially available product, for example, TEGORAD 2100 from Evonik Industries AG.

[0267] When the ink of the present invention contains a siloxane compound, the content of the siloxane compound is preferably 0.01% to 5% by mass, more preferably 0.05% to 3% by mass, and even more preferably 0.05% to 1.5% by mass, relative to the total amount of the ink. In particular, the content of the siloxane compound having a polymerizable group is preferably 0.1% to 5% by mass, more preferably 0.5% to 3% by mass, relative to the total amount of the ink. When the siloxane compound content is 5% or less, foaming is less likely to occur during ink ejection, resulting in excellent ejection properties. As a result, image records with excellent readability can be obtained. On the other hand, when the siloxane compound content is 0.1% or more by mass, polymerization near the air interface of the ink film is promoted, improving readability after a close fit test and after a transfer test.

[0268] (Polymerization Inhibitor)

[0269] The ink according to the present invention preferably contains a polymerization inhibitor. The polymerization inhibitor contained in the ink may be one type or two or more types.

[0270] Examples of the polymerization inhibitor include hydroquinone compounds, phenothiazines, catechols, alkylphenols, alkylbisphenols, zinc dimethyldithiocarbamate, copper dimethyldithiocarbamate, copper dibutyldithiocarbamate, copper salicylate, thiodipropionate, mercaptobenzimidazole, phosphites, nitrosamine compounds, hindered amine compounds, and nitrosyl radicals.

[0271] Among them, the polymerization inhibitor is preferably at least one selected from the group consisting of nitrosamine compounds, hindered amine compounds, hydroquinone compounds and nitrosyl radicals, more preferably at least one selected from the group consisting of nitrosamine compounds, hydroquinone compounds and nitrosyl radicals, and even more preferably contains nitrosamine compounds, hydroquinone compounds and nitrosyl radicals.

[0272] Examples of the nitrosamine compound include N-nitroso-N-phenylhydroxylamine aluminum salt and N-nitroso-N-phenylhydroxylamine. Among them, the nitrosamine compound is preferably N-nitroso-N-phenylhydroxylamine aluminum salt.

[0273] A hindered amine compound is a compound having a hindered amine structure within the molecule. Examples of hindered amine compounds include the compounds described in Japanese Patent Application Laid-Open No. 61-91257. Among these, the hindered amine compound is preferably a derivative of 2,2,6,6-tetramethylpiperidine having a structure in which all hydrogen atoms at the 2- and 6-carbon positions of piperidine are replaced by 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.

[0274] Examples of the hydroquinone compound include hydroquinone, methylhydroquinone, tert-butylhydroquinone, and p-methoxyphenol. Among them, p-methoxyphenol is preferred as the hydroquinone compound.

[0275] Examples of the nitrosyl radical include 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) and 2,2,6,6-tetramethyl-4-hydroxypiperidin-1-oxyl (TEMPOL). Among them, the nitrosyl radical is preferably 2,2,6,6-tetramethyl-4-hydroxypiperidin-1-oxyl (TEMPOL).

[0276] From the perspective of improving the temporal stability of the ink, the content of the polymerization inhibitor is preferably 1% by mass or more, and more preferably 1.5% by mass or more, relative to the total amount of the ink. The upper limit of the polymerization inhibitor content is not particularly limited, but from the perspective of polymerizability, it is preferably 5% by mass.

[0277] When the polymerization inhibitor contains a nitrosamine compound, the content of the nitrosamine compound is preferably 0.5% to 5% by mass, more preferably 0.5% to 2% by mass, relative to the total amount of the ink, from the viewpoint of improving the temporal stability of the ink.

[0278] When the polymerization inhibitor contains a hydroquinone compound, the content of the hydroquinone compound is preferably 0.1 to 5 mass %, more preferably 0.5 to 2 mass %, relative to the total amount of the ink, from the viewpoint of improving the temporal stability of the ink.

[0279] (Sensitizer)

[0280] When the ink of the present invention contains a photopolymerization initiator, it may also contain a sensitizer. The inclusion of a sensitizer improves curability, particularly when using an LED light source. Furthermore, the sensitizer helps improve the light resistance of the ink.

[0281] Sensitizers are substances that absorb specific active energy rays and become electronically excited. When the electronically excited sensitizer comes into contact with the photopolymerization initiator, it causes electron transfer, energy transfer, and heat generation, thereby accelerating the chemical transformation of the photopolymerization initiator.

[0282] As sensitizers, for example, there can be mentioned ethyl 4-(dimethylamino)benzoate (EDB), anthraquinone, 3-acylcoumarin derivatives, terphenyl, styryl ketone, 3-(aroylmethylene)thiazoline, camphorquinone, eosin, rhodamine, erythrosine, compounds represented by the general formula (i) described in Japanese Patent Application Publication No. 2010-24276, and compounds represented by the general formula (I) described in Japanese Patent Application Publication No. 6-107718.

[0283] When the ink contains a sensitizer, the content of the sensitizer 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, relative to the total amount of the ink.

[0284] The ink according to the present invention may contain at least one organic solvent.

[0285] Examples of the organic solvent 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; chlorine-based solvents such as chloroform and dichloromethane; aromatic solvents such as benzene and toluene; ester-based solvents such as ethyl acetate, butyl acetate, isopropyl acetate, ethyl lactate, butyl lactate, and isopropyl lactate; ether-based solvents such as diethyl ether, tetrahydrofuran, and dioxane; glycol ether-based solvents such as ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, and propylene glycol monomethyl ether; and glycol ether acetate-based solvents such as propylene glycol monomethyl ether acetate.

[0286] When the ink of the present invention contains an organic solvent, the content of the organic solvent is preferably 5% by mass or less, and more preferably 2% by mass or less, relative to the total amount of the ink. The ink of the present invention may contain no organic solvent (i.e., the content of the organic solvent is 0% by mass relative to the total amount of the ink).

[0287] The ink of the present invention may further contain additives other than the siloxane compound, such as surfactants, ultraviolet absorbers, co-sensitizers, antioxidants, anti-fading agents, and conductive salts. For additives, reference may be made to publicly known documents such as Japanese Patent Application Publication No. 2011-225848 and Japanese Patent Application Publication No. 2009-209352.

[0288] <Physical properties>

[0289] 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 at 25°C using a viscometer. For example, the viscosity can be measured using a VISCOMETER TV-22 viscometer (manufactured by Toki Sangyo Co., Ltd.).

[0290] The surface tension of the ink of the present invention is preferably 20 mN / m to 45 mN / m, more preferably 23 mN / m to 30 mN / m. The surface tension is a value measured at 25°C using a surface tensiometer. For example, the surface tension can be measured using a DY-700 (manufactured by Kyowa Interface Science Co., Ltd.).

[0291] [Inkjet Recording Method]

[0292] The inkjet recording method involved in the present invention includes: a process of ejecting the ink involved in the present invention onto a substrate by an inkjet recording method (hereinafter also referred to as the "ink ejecting process"); and a process of irradiating the ink ejected onto the substrate with active energy rays (hereinafter also referred to as the "active energy ray irradiation process").

[0293] (Ink ejection process)

[0294] In the inkjet recording method of the present invention, first, the ink of the present invention is discharged onto a substrate by an inkjet recording method.

[0295] 〔Base material〕

[0296] The substrate is not particularly limited as long as an ink image can be formed thereon, and examples thereof include paper, cloth, wood, metal, and plastic.

[0297] Examples of the paper include conventional printing papers and inkjet recording papers containing cellulose as a main component, such as premium paper, coated paper, and art paper. Furthermore, the paper may be provided with an oily varnish or an aqueous varnish.

[0298] The substrate may be permeable or non-permeable. "Non-permeable" means that it absorbs little or no water contained in the ink, and specifically, the amount of water absorbed is 10.0 g / m2 or less.

[0299] In the inkjet recording method according to the present invention, particularly when a non-permeable substrate is used as the substrate, an image having excellent curability can be obtained.

[0300] The shape of the impermeable substrate is not particularly limited, and may be any of a three-dimensional shape such as a bottle, a sheet, and a film.

[0301] Examples of the impermeable substrate 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, and polyvinyl acetal), and glass.

[0302] Among them, the impermeable substrate preferably comprises a thermoplastic resin such as polyvinyl chloride, polyethylene terephthalate, or polypropylene.

[0303] The impermeable substrate may be surface treated.

[0304] Examples of the surface treatment include corona treatment, plasma treatment, heat treatment, abrasion treatment, light irradiation treatment (for example, ultraviolet irradiation treatment), and flame treatment.

[0305] Corona treatment can be performed using, for example, Corona Master (PS-10S, manufactured by Shinko Filtration & Instrumentation Co., Ltd.). The conditions for the corona treatment can be appropriately selected depending on the type of the non-permeable substrate, the composition of the ink, etc. The corona treatment can be performed under the following conditions, for example.

[0306] Processing voltage: 10~15.6kV

[0307] Processing speed: 30-100 mm / s

[0308] Furthermore, the substrate may be a transparent substrate or a substrate laminated with polyethylene or polypropylene.

[0309] Examples of the transparent substrate 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, polycycloolefin resins, polyimide resins, polycarbonate resins, and polyvinyl acetal). The transparent substrate may be a single layer or may be two or more layers.

[0310] [Inkjet recording method]

[0311] There is no particular limitation on the inkjet recording method as long as it is a method that can record images. It can be a well-known method, such as a charge control method that uses electrostatic induction force to eject ink, a drop-on-demand inkjet method (pressure pulse method) that uses the vibration pressure of a piezoelectric element, an acoustic inkjet method that converts an electrical signal into a sound beam to irradiate the ink and uses radiation pressure to eject the ink, and a thermal inkjet (Bubble Jet (registered trademark)) method that heats the ink to form bubbles and uses the generated pressure.

[0312] As an inkjet recording method, the following inkjet recording method can be particularly effectively used: using the method described in Japanese Patent Application Laid-Open No. 54-59936, the ink subjected to thermal energy undergoes a rapid volume change, and the ink is ejected from the nozzle by the force generated by the state change.

[0313] Furthermore, regarding the inkjet recording method, reference can also be made to the method described in paragraphs 0093 to 0105 of Japanese Patent Application Laid-Open No. 2003-306623.

[0314] As inkjet heads used for inkjet recording, there are a multi-pass method that uses short column heads to record while scanning the heads in the width direction of the substrate, and a single-pass method that uses a row head with recording elements arranged in the entire area corresponding to one side of the substrate.

[0315] In the single-pass method, the substrate is scanned in a direction intersecting the arrangement of the recording elements, enabling pattern formation across the entire surface of the substrate. This eliminates the need for a transport system such as a carriage that scans a short, small printhead. Furthermore, since complex control of the carriage's movement and the substrate's scanning is unnecessary, only the substrate moves, enabling faster recording speeds compared to multi-pass methods. Therefore, in the inkjet recording method of the present invention, ink ejection in a single pass is preferred.

[0316] The ejection amount of 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.

[0317] (Active Energy Ray Irradiation Step)

[0318] In the inkjet recording method of the present invention, the ink ejected onto the substrate is preferably irradiated with active energy rays. The polymerizable monomers in the ink are polymerized and cured by irradiation with active energy rays. Examples of active energy rays include α-rays, γ-rays, X-rays, ultraviolet rays, visible light rays, and electron beams. Among these, from the perspectives of safety and cost, the active energy rays are preferably ultraviolet rays (hereinafter also referred to as "UV") or visible light rays, and more preferably ultraviolet rays.

[0319] The exposure dose of active energy rays is preferably 20 mJ / cm 2 ~10000J / cm 2 , more preferably 100 mJ / cm 2 ~7000mJ / cm 2 The irradiation time is preferably 0.01 to 120 seconds, more preferably 0.1 to 90 seconds. The irradiation conditions and basic irradiation method can be applied to the irradiation conditions and irradiation method disclosed in Japanese Patent Application Laid-Open 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 source in a so-called multi-pass manner or to perform the irradiation using another light source that is not driven.

[0320] Mercury lamps, gas lasers, and solid-state lasers are the main sources of ultraviolet light. Mercury lamps, metal halide lamps, and ultraviolet fluorescent lamps are widely known. Furthermore, the use of GaN (gallium nitride)-based semiconductor ultraviolet light-emitting devices is also very useful for industrial and environmental reasons. UV-LEDs (light-emitting diodes) and UV-LDs (laser diodes) are expected to be used as ultraviolet light sources due to their compact size, long lifespan, high efficiency, and low cost. Preferred ultraviolet light sources include metal halide lamps, high-pressure mercury lamps, medium-pressure mercury lamps, low-pressure mercury lamps, or UV-LEDs.

[0321] Examples of UV-LEDs include violet LEDs (manufactured by Nichia Corporation) whose main emission spectrum has a wavelength between 365 nm and 420 nm. As an LED with an even shorter wavelength, U.S. Patent No. 6,084,250 discloses an LED capable of emitting ultraviolet light with a wavelength between 300 nm and 370 nm. Furthermore, by combining multiple UV-LEDs, it is possible to irradiate ultraviolet light in different wavelength regions. The peak wavelength of ultraviolet light is preferably between 200 nm and 405 nm, more preferably between 220 nm and 400 nm, and even more preferably between 340 nm and 400 nm.

[0322] After the ink ejection process, irradiation with active energy rays in an environment with an oxygen concentration of 1% by volume or less can suppress polymerization inhibition due to oxygen and improve 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 (for example, nitrogen), the oxygen concentration can be effectively reduced to 0. The oxygen concentration during the active energy ray irradiation process is preferably 0.01% by volume to 1% by volume, and more preferably 0.1% by volume to 1% by volume.

[0323] As a method for controlling the oxygen concentration of the irradiation environment, for example, a method of setting the inkjet recording device to a closed system and setting it to a nitrogen environment or a carbon dioxide environment and a method of circulating an inert gas such as nitrogen can be cited. As a method for supplying nitrogen, for example, there is a method of using a nitrogen cylinder and a method of using the following device: a device that utilizes the difference in the permeability of oxygen and nitrogen to the hollow yarn membrane to separate only nitrogen from the air. As a method for supplying carbon dioxide, for example, a method of using a carbon dioxide cylinder can be cited. Inert gas refers to conventional gases such as N2, H2, CO2 and rare gases such as He, Ne, Ar. Among them, from the viewpoint of safety, availability and cost, inert gas is preferably N2.

[0324] Furthermore, the active energy ray irradiation step may include: a step of irradiating the ink ejected onto the substrate with a first active energy ray to semi-cure the ink film (i.e., the film formed by the ink applied to the substrate) (hereinafter also referred to as the "first irradiation step"); and a step of irradiating the semi-cured ink film with a second active energy ray to formally cure it (hereinafter also referred to as the "second irradiation step").

[0325] After performing the step of semi-curing the ink film, the main curing step is performed, whereby the readability after the wiping test and the readability after the adhesion test are improved.

[0326] In the present invention, polymerizing only a portion of the polymerizable monomers in the ink film is referred to as "semi-curing," and irradiation with active energy rays for semi-curing is also referred to as "pinning exposure." Furthermore, in the present invention, polymerizing substantially all of the polymerizable monomers in the ink film is referred to as "main curing," and irradiation with active energy rays for main curing is also referred to as "main exposure."

[0327] In the first irradiation step, the ink film is irradiated with the first active energy ray to polymerize at least a portion of the polymerizable monomers in the ink film. In the second irradiation step, the ink film is irradiated with the second active energy ray to polymerize substantially all of the polymerizable monomers in the ink film.

[0328] In the first irradiation step, only a portion of the polymerizable monomers in the ink film is polymerized, so the exposure dose of the active energy rays is reduced compared to the case where only the main exposure is performed.

[0329] The exposure dose of the first active energy ray is preferably 2 mJ / cm 2 ~5000mJ / cm 2 , more preferably 20 mJ / cm 2 ~5000mJ / cm 2 The irradiation time is preferably 0.01 to 20 seconds, more preferably 0.1 to 10 seconds.

[0330] The exposure dose of the second active energy ray is preferably 20 mJ / cm 2 ~10000J / cm 2 , more preferably 100 mJ / cm 2 ~7000mJ / cm 2 The irradiation time is preferably 0.01 to 120 seconds, more preferably 0.1 to 90 seconds.

[0331] The reaction rate of the ink film after pin exposure is preferably 10% to 80%.

[0332] The reaction rate of the ink film after the main exposure is preferably more than 80% and 100% or less, more preferably 85% to 100%, and even more preferably 90% to 100%.

[0333] The reaction rate of the ink film refers to the polymerization rate of the polymerizable monomer in the ink film determined by high performance liquid chromatography.

[0334] The reaction rate of the ink film was calculated by the following method.

[0335] Prepare a substrate on which an ink film has been irradiated with active energy rays. Cut a 20 mm x 50 mm sample piece from the area of ​​the substrate where the ink film is present. Immerse the sample piece in 10 mL of THF (tetrahydrofuran) for 24 hours to obtain an eluate containing the ink. The amount of polymerizable monomer in this eluate is calculated using high-performance liquid chromatography (hereinafter referred to as "post-irradiation monomer amount X1").

[0336] Separately, a substrate in which the ink film was not irradiated with active energy rays was prepared, and the same operation as above was performed except that the substrate was prepared, and the amount of the polymerizable monomer was calculated (hereinafter referred to as "monomer amount before irradiation X0").

[0337] The reaction rate (%) of the ink film was calculated from the monomer amount X1 after irradiation and the monomer amount X0 before irradiation using the following formula.

[0338] Reaction rate of ink (%) = ((monomer amount before irradiation X0 - monomer amount after irradiation X1) / monomer amount before irradiation X0) × 100

[0339] 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 with the first active energy ray is preferably less than 0.5 seconds. By semi-curing the ink immediately after landing, ink diffusion on the substrate is suppressed, improving readability. The time from the moment the ink lands on the substrate to the moment it is irradiated with the second active energy ray is not particularly limited.

[0340] Furthermore, when a semi-curing step is not included (i.e., only a full curing step is performed), the time from the moment the ink lands on the substrate to the moment it is irradiated with active energy rays is preferably less than 1 second. By performing full curing immediately after landing, ink diffusion on the substrate is suppressed, thereby improving readability.

[0341] (Other processes)

[0342] The inkjet recording method of the present invention may include other steps in addition to the ink ejection step and the active energy ray irradiation step. Examples of such other steps include a drying step for drying the ink ejected onto the substrate after the ink ejection step. The drying method and drying temperature in the drying step can be adjusted as appropriate.

[0343] Example

[0344] Hereinafter, examples of the present invention will be described, but the present invention is not limited to the following examples.

[0345] The details of the components contained in the inks of the Examples and Comparative Examples are as follows. Speedcure 7010L (manufactured by Lambson Limited) and FLORSTAB UV12 (manufactured by Kromachem Ltd.) were used in the preparation of the inks. 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 polymerizable monomer column. Furthermore, FLORSTAB UV12 is a mixture of N-nitroso-N-phenylhydroxylamine aluminum salt and PEA, with a mixing ratio of 1:9. In the table, N-nitroso-N-phenylhydroxylamine aluminum salt is listed in the polymerization inhibitor column, and PEA is listed in the polymerizable monomer column.

[0346] <Pigment>

[0347] Compound B-1...Squarylium pigment

[0348] Compound B-3...Squarylium pigment

[0349] Compound B-7... Squarylium pigment

[0350] Compound B-37... Squarylium pigment

[0351] Compound B-41... Squarylium pigment

[0352] Compound B-43... Squarylium pigment

[0353] Compound B-44...Squarylium pigment

[0354] Compound P-1...pyrrolopyrrole boron pigment

[0355] The structural formula of each pigment is as follows: Wherein, "Ph" represents a phenyl group.

[0356] [Chemical Formula 11]

[0357]

[0358] [Chemical Formula 12]

[0359]

[0360] <Pigment derivatives>

[0361] Pigment derivative 1 having an acidic functional group: SOLSPERSE 5000S (manufactured by The Lubrizol Corporation), copper phthalocyanine having a sulfonic group

[0362] Pigment derivative 2 having an acidic functional group: SOLSPERSE 12000S (manufactured by The Lubrizol Corporation), copper phthalocyanine having a sulfonic group

[0363] Pigment derivatives having a basic functional group...the following compound S-1

[0364] [Chemical Formula 13]

[0365]

[0366] <Dispersant>

[0367] Graft polymer 1 having an acidic functional group: Product name: SOLSPERSE 55000 (manufactured by The Lubrizol Corporation), weight average molecular weight: 55,000, SP value: 21.65 MPa 1 / 2

[0368] Graft polymer 2 having an acidic functional group: Product name: SOLSPERSE 41000 (manufactured by The Lubrizol Corporation), weight average molecular weight: 47,000, SP value: 30.99 MPa 1 / 2

[0369] Graft polymer 1 having a basic functional group: Product name: SOLSPERSE 32000 (manufactured by The Lubrizol Corporation), weight average molecular weight: 59,000, SP value: 18.62 MPa 1 / 2

[0370] Graft polymer 2 having a basic functional group: Product name: EFKA PX 4731 (manufactured by BASF), weight average molecular weight: 24,000, SP value: 20.10 MPa 1 / 2

[0371] Graft polymer 3 having a basic functional group: Product name: SOLSPERSE 71000 (manufactured by The Lubrizol Corporation), weight average molecular weight: 52890, SP value: 21.74 MPa 1 / 2

[0372] Graft polymer 4 having a basic functional group: Product name: BYKJET-9151 (manufactured by BYK-Chemie GmbH), weight average molecular weight: 22810, SP value: 25.89 MPa 1 / 2

[0373] Block polymer 1 having a basic functional group: Product name: EFKA PX 4701 (manufactured by BASF), weight average molecular weight: 22,000, SP value: 32.73 MPa 1 / 2

[0374] Block polymer 2 having a basic functional group: Product name: "DISPERBYK 191" (manufactured by BYK-Chemie GmbH), weight average molecular weight: 12,000, SP value: 33.55 MPa 1 / 2

[0375] Block polymer 1 having an acidic functional group: Product name: DISPERBYK-2001 (manufactured by BYK-Chemie GmbH), weight average molecular weight: 3500, SP value: 22.68 MPa 1 / 2

[0376] The SP value of the dispersant was calculated using the following formula of KWSUH and JMCORBETT (Journal of Applied Polymer Science, 12, 2359, 1968).

[0377] SP value = {(V m1 ) 1 / 2 ×δH+(V mh) 1 / 2 ×δD} / {(V m1 ) 1 / 2 +(V mh ) 1 / 2}

[0378] V m1 、V mh , δH, and δD are calculated by substituting the titer H (mL) at the cloud point when 0.5 g (solid content) of the dispersant is dissolved in 10 mL of acetone at a measurement temperature of 20°C and n-hexane is added thereto, and the titer D (mL) at the cloud point when 0.5 g (solid content) of the dispersant is dissolved in 10 mL of acetone at a measurement temperature of 20°C and deionized water is added thereto into the following formula.

[0379] V m1 =74.4×130.3 / {(1-V H )×130.3+V H ×74.4}

[0380] V mh =74.4×18 / {(1-V D )×18+V D ×74.4}

[0381] V H =H / (10+H)

[0382] V D =D / (10+D)

[0383] δH=9.72×10 / (10+H)+7.27×H / (10+H)

[0384] δD=9.72×10 / (10+D)+23.39×D / (10+D)

[0385] The SP values ​​of acetone, hexane and deionized water were calculated using HSPiP (version 4.1.07) software.

[0386] The unit of the obtained SP value is (cal / cm 3 ) 1 / 2 According to 1 Change the unit from (cal / cm 3 ) 1 / 2 Convert to MPa 1 / 2 .

[0387] <Polymerizable Monomer>

[0388] MPDDA: Product name: "SR341" (manufactured by Sartomer Company, Inc.), 3-methyl-1,5-pentanediol diacrylate, SP value: 17.60 MPa 1 / 2 , Tg: 105℃

[0389] DPGDA... Product name "DPGDA" (manufactured by DAICEL-ALLNEX LTD.), dipropylene glycol diacrylate, SP value: 17.73 MPa 1 / 2 , Tg: 104℃

[0390] IBOA: Product name: "SR506NS" (manufactured by Sartomer Company, Inc.), isobornyl acrylate, SP value: 17.10 MPa 1 / 2 , Tg: 97℃

[0391] TCDDMDA: Product name "SR833S" (manufactured by Sartomer Company, Inc.), tricyclodecane dimethanol diacrylate, SP value: 17.85 MPa 1 / 2 , Tg: 186℃

[0392] TMPTA……Product name “TMPTA” (manufactured by DAICEL-ALLNEX LTD.), trimethylolpropane triacrylate, SP value: 17.43 MPa 1 / 2 , Tg: 27℃

[0393] ACMO…Product name “ACMO” (manufactured by Rahn AG), acryloylmorpholine, SP value: 22.39 MPa 1 / 2 , Tg: 145℃

[0394] EOTMPTA...Trimethylolpropane EO addition triacrylate, SP value: 17.72MPa 1 / 2 , 50% by mass contained in Speedcure7010L (manufactured by Lambson Limited), Tg: 90°C

[0395] PEA……phenoxyethyl acrylate, SP value: 19.44MPa 1 / 2 , 90 mass% contained in FLORSTAB UV12 (manufactured by Kromachem Ltd.), Tg: 5°C.

[0396] The glass transition temperature (Tg) of each polymerizable monomer is the Tg of a homopolymer having a weight average molecular weight of 10,000 to 20,000. The glass transition temperature (Tg) is a value measured using a differential scanning calorimeter manufactured by SII NanoTechnology Inc. (product name "EXSTAR6220").

[0397] The SP value of the polymerizable monomer was calculated using the following equations A and B1 to B3. The dispersion term, polar term, and hydrogen bonding term of each polymerizable monomer contained in the ink are shown in Table 1. The dispersion term δd, polar term δp, and hydrogen bonding term δh were calculated using HSPiP (version 4.1.07) software.

[0398] SP value (δ) [MPa 1 / 2 ]=(δd 2 +δp 2 +δh 2 ) 1 / 2 ...(A)

[0399] δd=∑δd m W m / ∑W m ...(B1)

[0400] δp=∑δp m W m / ∑W m ...(B2)

[0401] δh=∑δh m W m / ∑W m ...(B3)

[0402] In formula B1, δd m The term "m" represents the dispersed amount of the polymerizable monomer (m represents an integer of 1 or greater) in the polymerizable monomer.

[0403] In formula B2, δp m The polarity term of the polymerizable monomer represents m terms (m represents an integer of 1 or greater) in the polymerizable monomer.

[0404] In formula B3, δh m The hydrogen bonding term of the polymerizable monomer represents m terms (m represents an integer of 1 or greater) in the polymerizable monomer.

[0405] In formulas B1 to B3, W m The content ratio (mass %) of the polymerizable monomer in the above item m relative to the total amount of the polymerizable monomers is shown.

[0406] Tables 2 to 6 show the calculated SP values ​​of the polymerizable monomers.

[0407] <Polymerization Initiator>

[0408] Omnirad 819 (manufactured by IGM Resins BV): Bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide

[0409] Omnirad TPO-L (manufactured by IGM Resins BV): (2,4,6-trimethylbenzoyl)ethoxyphenylphosphine oxide

[0410] Speedcure 7010: 1,3-bis({α-[1-chloro-9-oxo-9H-thioxanthen-4-yl)oxy]acetylpoly[oxy(1-methylethylene)]}oxy)-2,2-bis({α-[1-methylethylene)]}oxymethyl)propane, 50% by mass contained in Speedcure 7010L (manufactured by Lambson Limited)

[0411] <Siloxane Compound>

[0412] BYK-307 (manufactured by BYK Co., LTD): Polysiloxane without polymerizable groups

[0413] TEGORAD 2100 (manufactured by Degussa AG): Polysiloxane having a polymerizable group

[0414] <Polymerization Inhibitor>

[0415] N-nitroso-N-phenylhydroxylamine aluminum salt: 10% by mass contained in FLORSTAB UV12 (manufactured by Kromachem Ltd.)

[0416] MEHQ: p-Methoxyphenol

[0417] [Example 7]

[0418] The components were mixed to the following composition and pre-dispersed using a stirrer for 30 minutes. The mixture was then dispersed using a batch bead mill (product name "Easy Nano RMB," manufactured by AIMEX Co., Ltd.) at 1000 rpm (rotational speed / minute) for 4.5 hours using 0.5 mm diameter zirconia beads. Filtration was performed using a 67 μm filter cloth and a 5 μm filter to obtain Dispersion Liquid A1.

[0419] <Composition>

[0420] Compound B-1: 4% by mass

[0421] Pigment derivative with acidic functional group 1...0.02 mass%

[0422] · Block polymer with basic functional groups 1...4% by mass

[0423] MPDDA……91.98 mass%

[0424] Next, the components were mixed to the following composition to prepare ink.

[0425] <Composition>

[0426] · The above dispersion A1 ... 25 mass%

[0427] DPGDA: 25% by mass

[0428] IBOA: 12% by mass

[0429] TCDDMDA: 17% by mass

[0430] TMPTA: 5% by mass

[0431] ·PEA…4% by mass

[0432] Omnitad 819……4% by mass

[0433] ·TPO-L……6% by mass

[0434] FLORSTAB UV12……1% by mass

[0435] MEHQ: 1% by mass

[0436] [Examples 1 to 6, 8 to 25, Comparative Examples 1 to 6]

[0437] A dispersion was prepared in the same manner as in Example 7, except that the content of each component contained in the ink was changed to the content (mass %) described in Tables 2 to 5, thereby preparing an ink.

[0438] <Image Record>

[0439] Each ink prepared in the Examples and Comparative Examples was filtered using a 5 μm filter. The filtrate was filled into an ink cartridge attached to an inkjet recording device (product name "DMP-2850", manufactured by Fujifilm Corporation). A 3% dot image was recorded on a substrate under the conditions of a nozzle temperature of 25°C, a resolution of 600 dpi (dots per inch), and a jet volume of 10 pL. A PET (polyethylene terephthalate) film was used as the substrate. Subsequently, an LED lamp (product name "PEL UV CURE UNIT", manufactured by PRINTED ELECTRONICS) was used at an exposure of 250 mW / cm 2, irradiated with ultraviolet light (wavelength 395nm), and obtained an image record.

[0440] Using each ink prepared in the examples and comparative examples, evaluations were performed on readability, readability after time, readability after the transfer test, readability after the adhesion test, and readability after the wiping test. The evaluation results are shown in Tables 2 to 5. In addition, in Tables 2 to 5, "SP value difference" refers to the difference between the calculated SP value of the polymerizable monomer and the SP value of the dispersant. Furthermore, "the proportion of monomers having a Tg of 30°C or higher" refers to the proportion of polymerizable monomers having a glass transition temperature of 30°C or higher in all polymerizable monomers. In Comparative Example 6, the curing property was insufficient, and the readability after the transfer test, the readability after the adhesion test, and the readability after the wiping test could not be evaluated, so it is recorded as "-" in Table 5.

[0441] [Readability]

[0442] Twenty locations were randomly selected from the image records obtained and their readability was determined using an IR detector. Readability was evaluated based on the number of readable locations. The evaluation criteria were as follows.

[0443] A: It can be read at 15 to 20 locations.

[0444] B: Can be read at 10 to 14 locations.

[0445] C: Can be read at 5 to 9 locations.

[0446] D: Unable to read at any one location or readable at 1 to 4 locations.

[0447] [Readability after time]

[0448] After the ink was prepared, the sealed container containing the ink was left to stand at 50°C for one week. After one week, the ink was filtered using a 5 μm filter. The filtrate was filled into an ink cartridge included with an inkjet recording device (product name "DMP-2850", manufactured by Fujifilm Corporation), and an image record was obtained using the same method as described above.

[0449] Twenty locations were randomly selected from the image records and their readability was determined using an IR detector. Readability was evaluated over time based on the number of readable locations. The evaluation criteria were as follows.

[0450] A: It can be read at 15 to 20 locations.

[0451] B: Can be read at 10 to 14 locations.

[0452] C: Can be read at 5 to 9 locations.

[0453] D: Unable to read at any one location or readable at 1 to 4 locations.

[0454] [Readability after transfer test]

[0455] A photographic substrate (product name: "Premium Glossy Photo Paper," manufactured by Fujifilm Corporation) was superimposed on the resulting image record. A load of 5N was applied to the photographic substrate for 3 seconds. After the photographic substrate was peeled off, 20 locations were randomly selected from the image record and evaluated for readability using an IR detector. Readability was evaluated after the transfer test based on the number of readable locations. The evaluation criteria were as follows.

[0456] A: It can be read at 15 to 20 locations.

[0457] B: Can be read at 10 to 14 locations.

[0458] C: Can be read at 5 to 9 locations.

[0459] D: Unable to read at any one location or readable at 1 to 4 locations.

[0460] [Readability after the fit test]

[0461] The adhesive surface of a tape (product name "CT405AP-12," manufactured by Nichiban Co., Ltd.) was applied to the resulting image recorded material. After the tape was removed, 20 locations were randomly selected from the image recorded material and evaluated for readability using an IR detector. Readability was evaluated after the adhesion test based on the number of readable locations. The evaluation criteria were as follows.

[0462] A: It can be read at 15 to 20 locations.

[0463] B: Can be read at 10 to 14 locations.

[0464] C: Unable to read at any location or readable at 1 to 9 locations.

[0465] [Readability after wiping test]

[0466] The resulting image record was placed on a woven cloth and rubbed 15 times with a 200g load. Twenty locations were randomly selected from the rubbed image record and evaluated for readability using an IR detector. Readability was evaluated after the adhesion test based on the number of readable locations. The evaluation criteria were as follows.

[0467] A: It can be read at 15 to 20 locations.

[0468] B: Can be read at 10 to 14 locations.

[0469] C: Can be read at 5 to 9 locations.

[0470] D: Unable to read at any one location or readable at 1 to 4 locations.

[0471]

[0472]

[0473]

[0474]

[0475] As shown in Tables 2 to 5, it can be seen that in Examples 1 to 25, since the near-infrared absorbing pigment represented by Formula 1, the polymerizable monomer, the polymerization initiator, and the dispersant are included, the content of the polymerizable monomer is 50% by mass or more relative to the total amount of the inkjet recording ink, and 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 , thus, an image record with excellent readability and readability after time can be obtained.

[0476] It is understood that in Comparative Example 1, since the near-infrared absorbing dye represented by Formula 1 is not included, readability and readability after a certain time period are poor.

[0477] It can be seen that in Comparative Examples 2 to 4, the difference between the SP value of the polymerizable monomer and the SP value of the dispersant is less than 3.8 MPa. 1 / 2 , so the readability is poor after a period of time.

[0478] It can be seen that in Comparative Example 5, the difference between the SP value of the polymerizable monomer and the SP value of the dispersant exceeds 16.0 MPa. 1 / 2 , so the readability and readability after a period of time are poor.

[0479] It is understood that in Comparative Example 6, since the content of the polymerizable monomer is less than 50% by mass, the readability and the readability after a certain period of time are poor.

[0480] It can be seen that in Example 3, the molecular weight of the dispersant is 50,000 or less, and the readability is excellent compared to Example 1.

[0481] It is found that in Example 5, the dispersant is a block polymer, and the readability after the passage of time is superior to that in Example 3.

[0482] It is found that Example 7, which contains a pigment derivative, has better readability after a period of time than Example 5.

[0483] It can be seen that Example 9, which contains a siloxane compound, has better readability after the wiping test than Example 7.

[0484] It is found that Examples 11 to 13, which contain a siloxane compound having a polymerizable group, are superior to Example 9 in readability after the transfer test and readability after the adhesion test.

[0485] In particular, it was found that in Example 13, the content of the siloxane compound having a polymerizable group was 0.5% to 3% by mass relative to the total amount of the ink, and that the results were generally excellent compared to Examples 11 and 12.

[0486] It was found that Example 15, which contained an acylphosphine oxide compound and a thioxanthone compound, had superior readability after the transfer test compared to Example 13.

[0487] It is found that in Example 17, the ratio of the polymerizable monomer having a glass transition temperature of 30° C. or higher in the polymerizable monomer is 90% by mass or higher, and the readability after the wiping test is superior to that of Example 15.

[0488] [Example 26]

[0489] The same ink as that used in Example 24 was introduced into the No. 6 throttle valve of a single-pass inkjet printer ("Jet Press 540WV" manufactured by FUJIFILM Corporation).

[0490] A PET (polyethylene terephthalate) film was prepared as a substrate, and the ink was ejected from the inkjet head of the inkjet printer to form an image with a dot ratio of 3% on the substrate in a single pass.

[0491] The ink application conditions were set to 600 dpi×600 dpi, a single-pass method, and a substrate transport speed of 50 m / min.

[0492] Next, the ink applied to the substrate was irradiated with active energy rays A for 0.1 seconds from the time the ink landed as exposure for the main curing. Active energy rays A are ultraviolet rays with a peak wavelength of 385 nm. The exposure dose of active energy rays A was set to 6600 mJ / cm 2 The image records obtained were evaluated for readability, readability after aging, readability after a transfer test, readability after a close contact test, and readability after a wiping test using the above-mentioned evaluation methods. All evaluation results were A.

[0493] [Example 27]

[0494] In the same manner as in Example 26, ink was applied to the substrate.

[0495] Next, the ink applied to the substrate was sequentially irradiated with a first active energy ray as exposure for semi-curing and a second active energy ray as exposure for full curing. The time from the time the ink landed to the irradiation of the first active energy ray was 0.1 seconds, and the time from the time the ink landed to the irradiation of the second active energy ray was 2.0 seconds. Both the first and second active energy rays were ultraviolet rays with a peak wavelength of 385 nm. The exposure dose of the first active energy ray was set to 350 mJ / cm 2 The second active energy ray exposure was set to 6600 mJ / cm 2 The image records obtained were evaluated for readability, readability after aging, readability after a transfer test, readability after a close contact test, and readability after a wiping test using the above-mentioned evaluation methods. All evaluation results were A.

[0496] In addition, regarding the invention of Japanese Patent Application No. 2020-153118 filed on September 11, 2020, the entirety of the invention is incorporated into this specification by reference. Furthermore, all documents, patent applications, and technical standards described in this specification are incorporated into this specification by reference to the same extent as if each document, patent application, or technical standard was specifically and individually described as being incorporated by reference.

Claims

1. An ink for inkjet recording, comprising: A near-infrared absorbing pigment represented by the following formula (2); polymerizable monomers; polymerization initiator; and dispersants, The polymerizable monomer is a compound having an ethylenically unsaturated group and a molecular weight of less than 1000, The dispersant has an acidic functional group or a basic functional group, The content of the polymerizable monomer is 50% by mass or more relative to the total amount of the inkjet recording ink. 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 , In formula (2), R 1 and R 2 Each independently represents a monovalent aromatic group, R 3 and R 4 Each independently represents a hydrogen atom or an alkyl group, X 1 and X 2 Each independently represents an oxygen atom or -N(R 5 )-, R 5 represents a hydrogen atom, an alkyl group, an aryl group or a heteroaryl group, X 3 and X 4 each independently represents a carbon atom or a boron atom, t and u in X 3 and X 4 When it is a boron atom, it represents 1. 3 and X 4 When it is a carbon atom, it means 2. p, q, r and s are 0, Y 1 、Y 2 、Y 3 and Y 4 Does not exist.

2. The inkjet recording ink according to claim 1, wherein The weight average molecular weight of the dispersant is 1,000 to 50,000.

3. The inkjet recording ink according to claim 1 or 2, wherein The dispersant is a block polymer. 4 . The ink for inkjet recording according to claim 1 , further comprising a pigment derivative. 5 . The inkjet recording ink according to claim 1 , further comprising a siloxane compound.

6. The ink for inkjet recording according to claim 5, wherein The siloxane compound includes a siloxane compound having a polymerizable group.

7. The inkjet recording ink according to claim 6, wherein The content of the siloxane compound having a polymerizable group is 0.5% by mass to 3% by mass based on the total amount of the inkjet recording ink.

8. The inkjet recording ink according to claim 1 or 2, wherein The polymerization initiator includes an acylphosphine oxide compound and a thioxanthone compound.

9. The inkjet recording ink according to claim 1 or 2, wherein The ratio of the polymerizable monomer having a glass transition temperature of 30° C. or higher in the polymerizable monomer is 90% by mass to 100% by mass.

10. An inkjet recording method using the inkjet recording ink according to any one of claims 1 to 9, the inkjet recording method comprising: a step of ejecting the inkjet recording ink onto a substrate by an inkjet recording method; and a step of irradiating the inkjet recording ink ejected onto the substrate with active energy rays.

Images