Near-infrared absorbing composition, ink, inkjet recording ink, and printed matter

Abstract

To provide a near-infrared absorbing composition capable of forming a coating having high invisibility and near-infrared absorbing ability and excellent light resistance and further having small quality variation, and an infrared absorbing ink or an inkjet recording ink using the same, further a printed matter in which a near-infrared absorbing image is printed using these inks.SOLUTION: The above-mentioned problems are solved by a near-infrared absorbing composition obtained by dispersing in an aqueous solvent an indigo compound (A) having a maximum absorption wavelength in the wavelength range of more than 800 nm and not more than 1,050 nm.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a near-infrared absorbing composition, an ink prepared from the composition, an ink for ink-jet recording, and a printed matter using the same. [Background technology]

[0002] Near-infrared absorbing dyes are generally dyes that have an absorption band in the near-infrared region of 700 nm to 1300 nm, and are mainly used in optical filters for semiconductor light receiving elements having the function of absorbing and cutting near-infrared rays, near-infrared cut filters for electronic devices, near-infrared filters for photography, near-infrared absorbing films and near-infrared absorbing plates that cut off heat rays for energy saving, near-infrared absorbing films for agricultural use for the purpose of selectively utilizing sunlight, recording media that utilize the heat absorbed by near-infrared rays, protective glasses, spectacles, sunglasses, near-infrared cut cosmetics, heat-blocking films, electrophotographic photoreceptors, materials for laser welding, materials for laser marking, etc. They are also useful as noise cut filters for CCD cameras and filters for CMOS image sensors.

[0003] It has also been proposed to be used in the field of security printing. In recent years, technology has been attracting attention for recording invisible information, which is not visible under normal visual conditions, on documents and securities such as stock certificates, bonds, checks, gift certificates, lottery tickets, and commuter passes, and then optically reading that information. Such technology is extremely useful in security management and is effective in increasing the added value of documents and strengthening counterfeit prevention measures for securities.

[0004] One method for recording invisible information is to use an image forming material that uses a dye that absorbs in the near infrared region of 700nm to 1300nm, which is invisible to the human eye. Although this invisible information cannot be seen by the human eye, it can be detected by a silicon light receiving element (CCD, CMOS, etc.).

[0005] Representative dyes that have absorption in the near infrared region of 700nm to 1300nm include phthalocyanine dyes, cyanine dyes, diimonium dyes, squarylium dyes, and croconium dyes. Among these, phthalocyanine dyes and cyanine dyes are particularly representative. Each has its own distinctive characteristics, and phthalocyanine dyes have a relatively robust structure and therefore good resistance to various types of light, but have poor transparency and invisibility due to absorption in the visible light region due to a structure called the soret band. On the other hand, cyanine dyes are generally used in a dissolved state as dyes, and therefore have very high transparency and invisibility, but have extremely poor resistance to various types of light, especially light resistance. Diimonium dyes, squarylium dyes, and croconium dyes also have characteristics similar to those of cyanine dyes. As described above, there is currently no near-infrared absorbing dye that simultaneously satisfies the requirements for invisibility and fastness, and there is a demand for the development of a material that has strong absorption in the near-infrared region, high invisibility, and sufficient fastness.

[0006] Patent Documents 1 to 4 describe examples of water-based near-infrared absorbing paints and inks. However, the near-infrared absorbing paints and inks using naphthalocyanine, diimmonium, and croconium-based dyes described in these documents are not sufficient in terms of durability and invisibility. Patent Document 5 describes examples of water-based near-infrared absorbing paints and inks with improved durability and invisibility. However, the near-infrared absorbing paints and inks using diketopyrrolopyrrole-based dyes described in this document have a problem in that the number of steps in the production of the dye structure is large, making stable production difficult. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2002-187955 A [Patent Document 2] Japanese Patent Application Publication No. 9-263717 [Patent Document 3] JP 2002-309131 A [Patent Document 4] JP 2002-146254 A [Patent Document 5] JP 2010-222557 A Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a near-infrared absorbing composition capable of forming a coating film having high invisibility, near-infrared absorbing ability, and excellent light resistance and further having small quality variation, and a near-infrared absorbing ink and inkjet recording ink using the same. Another object of the present invention is to provide a printed matter on which a near-infrared absorbing image is printed using the ink. [Means for solving the problem]

[0009] As a result of intensive research by the present inventors to solve the above problems, they have found that the above problems can be solved by a near-infrared absorbing composition, an ink, an ink for inkjet recording, and a printed matter having the following configurations.

[0010] That is, the present invention relates to a near infrared absorbing composition obtained by dispersing in an aqueous solvent an indigo compound (A) having a maximum absorption wavelength in the wavelength range of more than 800 nm and not more than 1,050 nm.

[0011] The present invention also relates to the near infrared absorbing composition, wherein the indigo compound (A) is a compound represented by the following general formula (1): General formula (1) [ka] [In the formula, X1~X 24each independently represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent, an alkoxyl group which may have a substituent, an aryloxy group which may have a substituent, an arylalkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an alkylthio group which may have a substituent, an arylthio group which may have a substituent, an amino group, an alkylamino group which may have a substituent, an arylamino group which may have a substituent, a cyano group, a halogen atom, a nitro group, a hydroxyl group, -SO3H; -COOH; and monovalent to trivalent metal salts of these acidic groups; and alkylammonium salts. X1 to X 24 Two adjacent groups among the groups represented by the formula: may be linked to form a 5- or 6-membered ring together with the carbon atoms to which they are bonded. M represents a metal atom.

[0012] The present invention also relates to the near infrared absorbing composition, wherein the indigo compound (A) is a compound represented by the following general formula (2): General formula (2) [ka] [where, X 25 ~X 40 each independently represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent, an alkoxyl group which may have a substituent, an aryloxy group which may have a substituent, an arylalkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an alkylthio group which may have a substituent, an arylthio group which may have a substituent, an amino group, an alkylamino group which may have a substituent, an arylamino group which may have a substituent, a cyano group, a halogen atom, a nitro group, a hydroxyl group, -SO3H; -COOH; and monovalent to trivalent metal salts of these acidic groups; and alkylammonium salts. X 25 ~X 40 Two adjacent groups among the groups represented by the following formula (I) may be linked to form a 5- or 6-membered ring together with the carbon atoms to which they are bonded.

[0013] The present invention also relates to an ink containing the near-infrared absorbing composition.

[0014] The present invention also relates to an ink for ink-jet recording, which contains the near-infrared absorbing composition.

[0015] The present invention also relates to a printed matter having a near-infrared absorbing image printed thereon using the ink.

[0016] The present invention also relates to a printed matter on which a near-infrared absorbing image is printed using the ink for ink-jet recording. Effect of the Invention

[0017] According to the present invention, it is possible to provide a near-infrared absorbing composition capable of forming a coating film having high invisibility, near-infrared absorbing ability, and excellent light resistance and further having small quality variation, and a near-infrared absorbing ink and an inkjet recording ink using the same. Furthermore, according to the present invention, it is possible to provide a printed matter on which a near-infrared absorbing image is printed using these inks. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The terms used in this specification are defined below. When "(meth)acryloyl", "(meth)acrylic", "(meth)acrylic acid", "(meth)acrylate", or "(meth)acrylamide" is used, it means "acryloyl and / or methacryloyl", "acrylic and / or methacrylic", "acrylic acid and / or methacrylic acid", "acrylate and / or methacrylate", or "acrylamide and / or methacrylamide", respectively, unless otherwise specified. "CI" in this specification means Color Index (CI). Colorants include pigments and dyes. "Having a maximum absorption wavelength in the range of more than 800 nm to 1050 nm" means that the absorption spectrum of the compound in solution has a wavelength that shows maximum absorbance in the specified wavelength range. The measurement solvent used to measure the absorption spectrum of the compound in solution is not particularly limited, and examples thereof include chloroform, methanol, dimethyl sulfoxide, N-methylpyrrolidone, and tetrahydrofuran. In this specification, N-methylpyrrolidone is used as the measurement solvent unless otherwise specified.

[0019] <Visible light> In this specification, "visible light" means light with a wavelength of 400 nm or more and 700 nm or less.

[0020] <Near infrared> In this specification, "near infrared" refers to light with a wavelength of more than 700 nm and not exceeding 1300 nm.

[0021] <Near infrared absorbing composition> The near infrared absorbing composition of the present invention is prepared by dispersing in an aqueous solvent an indigo compound (A) having a maximum absorption wavelength in the wavelength range of more than 800 nm and not more than 1,050 nm.

[0022] <Indigo compound (A) having a maximum absorption wavelength in the wavelength range of more than 800 nm and not more than 1050 nm> The indigo compound (A) contained in the near infrared absorbing composition of the present invention has a maximum absorption wavelength in the range of more than 800 nm to 1050 nm. The indigo compound (A) in the present invention (hereinafter, also simply referred to as indigo compound (A)) is a compound having a structure represented by the following general formula (3). The indigo compound (A) can be used as a near infrared absorbing dye.

[0023] General formula (3) [ka]

[0024] General formula (4) [ka] In the formula, R1 and R2 each independently represent a group represented by general formula (4) or a metal atom which may have a ligand. X 41 ~X 52 each independently represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent, an alkoxyl group which may have a substituent, an aryloxy group which may have a substituent, an arylalkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an alkylthio group which may have a substituent, an arylthio group which may have a substituent, an amino group, an alkylamino group which may have a substituent, an arylamino group which may have a substituent, a cyano group, a halogen atom, a nitro group, a hydroxyl group, -SO3H; -COOH; and monovalent to trivalent metal salts of these acidic groups; and alkylammonium salts. X 41 ~X 52 Two adjacent groups among the groups represented by the following formula (I) may be linked to form a 5- or 6-membered ring together with the carbon atoms to which they are bonded.

[0025] (Metal atom which may have a ligand) Examples of the metal atom that may have a ligand include Cu, Zn, Co, Ni, Ru, Pd, Pt, Mn, and Sn. Divalent metal atoms are preferred, and Zn and Pd are more preferred. When Zn or Pd is used as the metal atom, the indigo compound (A) has low absorption in the visible light region.

[0026] The ligand of the ligand-bearing metal atom is not particularly limited, and examples thereof include β-diketonato ligands, olefins, conjugated ketones, nitriles, amines, carboxylate ligands, carbon monoxide, phosphines, phosphinites, phosphonites, phosphites, ligands represented by general formula (5), and ligands represented by general formula (6). The ligand may be a chelate ligand. Among these, the ligands represented by general formula (5) or general formula (6) are preferred because they provide stable compounds, and the ligand represented by general formula (6) is particularly preferred.

[0027] General formula (5) [ka] [X 53 , X 54 each independently represents an alkyl group which may have a substituent or an aryl group which may have a substituent.]

[0028] General formula (6) [ka] [X 55 ~X 62 each independently represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent, an alkoxyl group which may have a substituent, an aryloxy group which may have a substituent, an arylalkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an alkylthio group which may have a substituent, an arylthio group which may have a substituent, an amino group, an alkylamino group which may have a substituent, an arylamino group which may have a substituent, a cyano group, a halogen atom, a nitro group, a hydroxyl group, -SO3H; -COOH; and monovalent to trivalent metal salts of these acidic groups; and alkylammonium salts. X 55 ~X 62 Two adjacent groups among the groups represented by the following formula (I) may be linked to form a 5- or 6-membered ring together with the carbon atoms to which they are bonded.

[0029] Among the compounds represented by general formula (3), those represented by general formula (1) or general formula (2) are preferred because of their small quality variation, and those represented by general formula (1) are more preferred.

[0030] General formula (1) [ka]

[0031] General formula (2) [ka] [In the formula, X1~X 40 each independently represents a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent, an alkoxyl group which may have a substituent, an aryloxy group which may have a substituent, an arylalkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an alkylthio group which may have a substituent, an arylthio group which may have a substituent, an amino group, an alkylamino group which may have a substituent, an arylamino group which may have a substituent, a cyano group, a halogen atom, a nitro group, a hydroxyl group, -SO3H; -COOH; and monovalent to trivalent metal salts of these acidic groups; and alkylammonium salts. X1 to X 40 Two adjacent groups among the groups represented by the formula: may be linked to form a 5- or 6-membered ring together with the carbon atoms to which they are bonded. M represents a metal atom.

[0032] Examples of the "alkyl group" of the alkyl group which may have a substituent include linear or branched alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, neopentyl, n-hexyl, n-octyl, stearyl, and 2-ethylhexyl. Examples of the "alkyl group having a substituent" include trichloromethyl, trifluoromethyl, 2,2,2-trifluoroethyl, 2,2-dibromoethyl, 2,2,3,3-tetrafluoropropyl, 2-ethoxyethyl, 2-butoxyethyl, 2-nitropropyl, benzyl, 4-methylbenzyl, 4-tert-butylbenzyl, 4-methoxybenzyl, 4-nitrobenzyl, and 2,4-dichlorobenzyl.

[0033] Examples of the "aryl group" of the aryl group which may have a substituent include a phenyl group, a naphthyl group, and anthryl group. Examples of the "substituted aryl group" include a p-methylphenyl group, a p-bromophenyl group, a p-nitrophenyl group, a p-methoxyphenyl group, a 2,4-dichlorophenyl group, a pentafluorophenyl group, a 2-aminophenyl group, a 2-methyl-4-chlorophenyl group, a 4-hydroxy-1-naphthyl group, a 6-methyl-2-naphthyl group, a 4,5,8-trichloro-2-naphthyl group, an anthraquinonyl group, and a 2-aminoanthraquinonyl group.

[0034] Examples of the "alkoxyl group" in the alkoxyl group which may have a substituent include straight-chain or branched alkoxyl groups such as a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a tert-butoxy group, a neopentyloxy group, a 2,3-dimethyl-3-pentyloxy group, an n-hexyloxy group, an n-octyloxy group, a stearyloxy group, and a 2-ethylhexyloxy group. Examples of the "substituted alkoxyl group" include a trichloromethoxy group, a trifluoromethoxy group, a 2,2,2-trifluoroethoxy group, a 2,2,3,3-tetrafluoropropoxy group, a 2,2-ditrifluoromethylpropoxy group, a 2-ethoxyethoxy group, a 2-butoxyethoxy group, a 2-nitropropoxy group, and a benzyloxy group.

[0035] Examples of the "aryloxy group" of the aryloxy group which may have a substituent include a phenoxy group, a naphthoxy group, an anthryloxy group, etc., and examples of the "aryloxy group having a substituent" include a p-methylphenoxy group, a p-nitrophenoxy group, a p-methoxyphenoxy group, a 2,4-dichlorophenoxy group, a pentafluorophenoxy group, a 2-methyl-4-chlorophenoxy group, etc.

[0036] Examples of the "arylalkyl group which may have a substituent" include a benzyl group, a 2-phenylpropane-yl group, a styryl group, a diphenylmethyl group, and a triphenylmethyl group.

[0037] Examples of the "cycloalkyl group" of the cycloalkyl group which may have a substituent include a cyclopentyl group, a cyclohexyl group, an adamantyl group, etc. Examples of the "cycloalkyl group having a substituent" include a 2,5-dimethylcyclopentyl group, a 4-tert-butylcyclohexyl group, etc.

[0038] Examples of the "alkylthio group" of the alkylthio group which may have a substituent include a methylthio group, an ethylthio group, a propylthio group, a butylthio group, a pentylthio group, a hexylthio group, an octylthio group, a decylthio group, a dodecylthio group, and an octadecylthio group. Examples of the "substituted alkylthio group" include a methoxyethylthio group, an aminoethylthio group, a benzylaminoethylthio group, a methylcarbonylaminoethylthio group, and a phenylcarbonylaminoethylthio group.

[0039] Examples of the "arylthio group" of the arylthio group which may have a substituent include a phenylthio group, a 1-naphthylthio group, a 2-naphthylthio group, and a 9-anthrylthio group. Examples of the "substituted arylthio group" include a chlorophenylthio group, a trifluoromethylphenylthio group, a cyanophenylthio group, a nitrophenylthio group, a 2-aminophenylthio group, and a 2-hydroxyphenylthio group.

[0040] Examples of the "alkylamino group" in the alkylamino group which may have a substituent include a methylamino group, an ethylamino group, a propylamino group, a butylamino group, a pentylamino group, a hexylamino group, a heptylamino group, an octylamino group, a nonylamino group, a decylamino group, a dodecylamino group, an octadecylamino group, an isopropylamino group, an isobutylamino group, an isopentylamino group, a sec-butylamino group, a tert-butylamino group, a sec-pentylamino group, a tert-pentylamino group, a tert-octylamino group, a neopentylamino group, a cyclopropylamino group, a cyclobutylamino group, a cyclopentylamino group, a cyclohexylamino group, a cycloheptylamino group, a cyclooctylamino group, a cyclododecylamino group, a 1-adamantamino group, and a 2-adamantamino group.

[0041] Examples of the "arylamino group" of the arylamino group which may have a substituent include an anilino group, a 1-naphthylamino group, a 2-naphthylamino group, an o-toluidino group, a m-toluidino group, a p-toluidino group, a 2-biphenylamino group, a 3-biphenylamino group, a 4-biphenylamino group, a 1-fluoreneamino group, a 2-fluoreneamino group, a 2-thiazoleamino group, a p-terphenylamino group, and the like.

[0042] Examples of halogen atoms include fluorine, chlorine, bromine, and iodine.

[0043] Examples of the acidic group include -SO3H and -COOH, and examples of the monovalent to trivalent metal salts of these acidic groups include sodium salts, potassium salts, magnesium salts, calcium salts, iron salts, aluminum salts, etc. Examples of the alkyl ammonium salts of the acidic group include ammonium salts of long-chain monoalkylamines such as octylamine, laurylamine, and stearylamine, and quaternary alkyl ammonium salts such as palmityl trimethyl ammonium, lauryl trimethyl ammonium, dilauryl dimethyl ammonium, and distearyl dimethyl ammonium salts.

[0044] X1~X 52 , X55 ~X 62 Among the groups represented by the formula (I), two adjacent groups may be linked together to form a 5-membered or 6-membered ring together with the carbon atoms to which they are bonded. The 5-membered or 6-membered ring may have a substituent. Examples of such 5-membered rings include a cyclopentene ring, a cyclopentadiene ring, an imidazole ring, a thiazole ring, a pyrazole ring, an oxazole ring, an isoxazole ring, a thiophene ring, a furan ring, and a pyrrole ring, and examples of the 6-membered ring include a cyclohexane ring, a cyclohexene ring, a cyclohexadiene ring, a benzene ring, a pyridine ring, a piperazine ring, a piperidine ring, a morpholine ring, a pyrazine ring, a pyrone ring, and a pyrrolidine ring.

[0045] Among the above substituents, X1 to X 52 , X 55 ~X 62 Preferred examples of the substituent include a hydrogen atom, a methyl group, a methoxy group, a fluorine atom, a chlorine atom, and a bromine atom. Among these, a hydrogen atom, a chlorine atom, and a bromine atom are more preferred, since they result in an indigo compound (A) that has less absorption in the visible light region.

[0046] (Method of synthesizing indigo compound (A)) The indigo compound (A) can be synthesized using the compound represented by the general formula (7) as a raw material.

[0047] General formula (7) [ka]

[0048] In general formula (7), X 63 ~X 70 is X1~X 52 , X 55 ~X 62 is synonymous with.

[0049] The compound represented by general formula (7) can be obtained according to the synthesis method described in JP-A-2012-224593.

[0050] The indigo compound (A) can be obtained by reacting the compound represented by the general formula (7) with a boron compound or a metal complex, and adding a Lewis acid such as titanium tetrachloride or aluminum chloride as necessary.

[0051] The reaction temperature is not particularly limited, but is preferably in the range of 25 to 170°C, and more preferably 40 to 130°C.

[0052] The reaction solvent is not particularly limited, but is preferably one in which the intermediate and the boron compound or metal complex are soluble, specific examples of which include tetrahydrofuran, toluene, xylene, bromobenzene, and N-methylpyrrolidone.

[0053] When a boron compound is used, the borinic acid esters are preferred, with 2-aminoethyl diphenylborinate being particularly preferred.

[0054] The reaction time is not particularly limited, but the progress of the reaction may be confirmed by MALDI TOF-MS spectrometry or a spectrophotometer to confirm the disappearance of the raw materials.

[0055] In the production of the compound represented by the general formula (1), the compound represented by the general formula (8) may be produced as a by-product. The presence of the by-product can be confirmed by TOF-MS spectroscopy.

[0056] General formula (8) [ka] [where, X 71 ~X 102 is X1~X 52 , X 55 ~X 62 M represents a metal atom.

[0057] In the present invention, examples of the indigo compound (A) include the following compounds, but the present invention is not limited thereto. [ka]

[0058] [ka]

[0059] [ka]

[0060] [ka]

[0061] The particle size of the indigo compound (A) in the present invention may be controlled by using a known dissolution-precipitation method such as acid pasting. Specifically, the particle size of the indigo compound (A) can be controlled by dissolving the indigo compound (A) in a good solvent, mixing the good solvent with a large excess of a poor solvent to precipitate the indigo compound (A), and filtering or distilling off the solvent.

[0062] Here, the good solvent is not particularly limited as long as it can dissolve the indigo compound (A), and examples of the good solvent include inorganic acids (sulfuric acid, fuming sulfuric acid, chlorosulfonic acid, hydrochloric acid, phosphoric acid, etc.) and their aqueous solutions, organic acids (dichloroacetic acid, methanesulfonic acid, etc.), inorganic bases (sodium hydroxide, potassium hydroxide, calcium hydroxide, etc.) and their aqueous solutions, organic bases (triethylamine, diazabicycloundecene, sodium methoxide, etc.), alcohol solvents (methanol, n-propanol, tert-amyl alcohol, etc.), ketone solvents (methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.), ether solvents (tetrahydrofuran, propylene glycol, etc.), and the like. Examples of the good solvent include dimethyl sulfoxide, hexamethylene sulfoxide, sulfolane, etc., ester solvents (ethyl acetate, n-butyl acetate, ethyl lactate, etc.), amide solvents (N,N-dimethylformamide, 1-methyl-2-pyrrolidone, etc.), aromatic hydrocarbon solvents (toluene, xylene, etc.), aliphatic hydrocarbon solvents (octane, etc.), nitrile solvents (acetonitrile, etc.), halogen solvents (carbon tetrachloride, dichloromethane, etc.), ionic liquids (1-ethyl-3-methylimidazolium tetrafluoroborate, etc.), and carbon disulfide solvents. The amount of the good solvent used is not particularly limited as long as it is an amount that can dissolve the indigo compound (A), but from the viewpoint of industrial economy, it is preferably 100 to 5000 parts by mass, more preferably 500 to 3000 parts by mass, relative to 100 parts by mass of the indigo compound (A).

[0063] The temperature when dissolving the indigo compound (A) is preferably from -10 to 200°C, more preferably from -10 to 130°C, and further preferably from -10 to 100°C.

[0064] The poor solvent is not particularly limited as long as it precipitates the indigo compound (A) when mixed with a solution containing the indigo compound (A) dissolved in a good solvent, and suitable examples include aqueous solvents (water, hydrochloric acid, aqueous sodium hydroxide solution, etc.) From the viewpoint of industrial economy, the amount of the poor solvent used is preferably 50 to 5000 parts by mass, more preferably 100 to 3000 parts by mass, relative to 100 parts by mass of the solution containing the indigo compound (A).

[0065] The deposition temperature is preferably from -10 to 150°C, more preferably from -5 to 130°C, and further preferably from 0 to 100°C.

[0066] The method of mixing the indigo compound (A) solution with the poor solvent is not particularly limited, and any method may be used as long as the indigo compound (A) can be precipitated. For example, the indigo compound (A) particles can be precipitated by a method of injecting the indigo compound (A) solution into ice water prepared in advance, or a method of continuously injecting the solution into running water using an apparatus such as an aspirator.

[0067] The particle size of the indigo compound (A) in the present invention may be controlled using a known solvent salt milling method. Specifically, a clay-like mixture consisting of at least three components, the indigo compound (A), a water-soluble inorganic salt, and a water-soluble solvent, is strongly kneaded using a kneader or the like. The kneaded mixture is put into water and stirred with various stirrers to form a slurry. The obtained slurry is filtered to remove the water-soluble inorganic salt and the water-soluble solvent, thereby controlling the particle size of the indigo compound (A).

[0068] Examples of the water-soluble inorganic salt that can be used include sodium chloride, sodium sulfate, and potassium chloride. These inorganic salts are used in an amount ranging from 1 to 20 times by mass of the indigo compound (A). When the amount of the inorganic salt is 1 or more times by mass, the indigo compound (A) can be sufficiently finely divided. When the amount of the inorganic salt is 20 or less by weight, it is preferable from the viewpoint of productivity because it does not require a great deal of effort to remove the water-soluble inorganic salt and the water-soluble solvent after kneading and at the same time, the amount of the indigo compound (A) that can be treated at one time does not decrease.

[0069] In solvent salt milling, heat is often generated during kneading, so from the viewpoint of safety, it is preferable to use a water-soluble solvent having a boiling point of about 120 to 250° C. Examples of the water-soluble solvent include 2-(methoxymethoxy)ethanol, 2-butoxyethanol, 2-(isopentyloxy)ethanol, 2-(hexyloxy)ethanol, ethylene glycol, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene glycol monomethyl ether, liquid polyethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, and low molecular weight polypropylene glycol.

[0070] The amount of the water-soluble solvent used is preferably 5 to 1,000 parts by mass, more preferably 50 to 500 parts by mass, per 100 parts by mass of the indigo compound (A). By appropriately selecting the amount of the water-soluble solvent used, the kneaded product can have a viscosity suitable for the solvent salt milling treatment.

[0071] The kneading temperature during the solvent salt milling is preferably from −10° C. to 300° C., and more preferably from 30° C. to 90° C. The kneading time during the solvent salt milling is preferably from 0.1 to 100 hours, and more preferably from 3 to 24 hours.

[0072] <Water-based solvent> The near infrared absorbing composition of the present invention contains an aqueous solvent. In the present invention, the term "aqueous solvent" means a solvent consisting of a liquid containing at least water. In the present invention, in addition to water, alcohol-based solvents, glycol ether-based solvents, polyalkylene glycol-based solvents, etc. can be suitably used as the aqueous solvent. In addition, these aqueous solvents other than water refer to those that have a solubility in water of 5 g / 100 gH2O or more at 25°C and 1 atm, and are liquid. In addition, among the pH adjusters described later, those that satisfy the above conditions are also included in the aqueous solvent.

[0073] In the near infrared absorbing composition of the present invention, the content of the aqueous solvent having a boiling point of 240° C. or higher under 1 atmospheric pressure is preferably 8% by mass or less (may be 0% by mass) based on the total amount of the near infrared absorbing composition. In particular, from the viewpoint of obtaining a printed matter having excellent drying properties, image quality, and abrasion resistance on a non-permeable substrate such as a plastic substrate, the content of the aqueous solvent having a boiling point of 240° C. or higher under 1 atmospheric pressure is more preferably 5% by mass or less (may be 0% by mass), further preferably 2% by mass or less (may be 0% by mass), and particularly preferably 1% by mass or less (may be 0% by mass).

[0074] The boiling point at 1 atmospheric pressure can be measured using a thermal analysis device such as a DSC (differential scanning calorimetry).

[0075] Examples of aqueous solvents other than water having a boiling point of 240° C. or higher under 1 atmospheric pressure include glycerin, 3-methyl-1,5-pentanediol, 1,6-hexanediol, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol, triethylene glycol, tripropylene glycol, tetrapropylene glycol, 2-pyrrolidone, ε-caprolactone, polyethylene glycol 200, polyethylene glycol 400, polyethylene glycol 600, and the like.

[0076] The water-based solvent used in the present invention preferably has a weighted average boiling point at 1 atmosphere of 100 to 235°C, more preferably 120 to 210°C, and particularly preferably 120 to 195°C. In addition, in consideration of the image quality on non-permeable substrates such as plastic substrates, it is particularly suitable to have a boiling point of 120 to 180°C. If the weighted average boiling point of the water-based solvent at 1 atmosphere is 100°C or higher, the ejection stability from the inkjet head is improved. If the weighted average is 235°C or lower, there is no drying failure on the recording medium, and the remaining water-based solvent does not cause bleeding between water-based ink droplets, improving the image quality, and the adhesion to non-permeable substrates such as plastic substrates and the abrasion resistance of the printed matter are also improved. In addition, the calculation of the weighted average boiling point includes the water-based solvent having a boiling point of 240°C or higher at 1 atmosphere. The weighted average value of the boiling points at 1 atmospheric pressure is a value obtained by adding together the product of the boiling points at 1 atmospheric pressure calculated for each water-soluble organic solvent and the mass ratio thereof to the total amount of aqueous solvents.

[0077] From the viewpoint of keeping the weighted average value of the boiling points of the aqueous solvents within the above range, the blending amount of the aqueous solvents having a boiling point of 100 to 220°C at 1 atmospheric pressure is preferably 50 mass % or more, more preferably 70 mass % or more, and particularly preferably 85 mass % or more, based on the total amount of the aqueous solvents in the near infrared absorbing composition.

[0078] Examples of aqueous solvents other than water that can be suitably used in the present invention include: Examples of monohydric alcohol solvents include ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, 3-butanol, isobutanol, 3-methoxy-1-butanol, and 3-methoxy-3-methyl-1-butanol. Examples of dihydric alcohol solvents (diol solvents) include ethylene glycol, 1,2-propanediol (propylene glycol), 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,2-hexanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, and 3-methyl-1,3-butanediol. Trihydric or higher alcohol solvents (polyol solvents) include 1,2,4-butanetriol and diglycerin. Examples of glycol ether solvents include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol monohexyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monoisobutyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl butyl ether, triethylene glycol methyl butyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, triethylene glycol methyl ethyl ether, tetraethylene glycol butyl methyl ether, propylene glycol monomethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, propylene glycol dimethyl ether, and tripropylene glycol dimethyl ether. Examples of polyalkylene glycol solvents include dipropylene glycol, Examples of chain amide solvents include N,N-dimethylformamide, N,N-dimethyl-β-methoxypropionamide, N,N-dimethyl-β-ethoxypropionamide, N,N-dimethyl-β-butoxypropionamide, N,N-dimethyl-β-pentoxypropionamide, N,N-dimethyl-β-hexoxypropionamide, N,N-dimethyl-β-heptoxypropionamide, N,N-dimethyl-β-2-ethylhexoxypropionamide, N,N-dimethyl-β-octoxypropionamide, N,N-diethyl-β-butoxypropionamide, N,N-diethyl-β-pentoxypropionamide, N,N-diethyl-β-hexoxypropionamide, N,N-diethyl-β-heptoxypropionamide, and N,N-diethyl-β-octoxypropionamide. Cyclic amide solvents include N-methylpyrrolidone and N-ethylpyrrolidone. Cyclic carbamate solvents include 3-methyl-2-oxazolidinone and 3-ethyl-2-oxazolidinone. These include, but are not limited to,

[0079] The aqueous solvent other than water used in the present invention is preferably an aqueous solvent having one or two hydroxyl groups, from the viewpoint of obtaining a printed matter having excellent image quality and drying property, having excellent compatibility with binder resins and surfactants, and further obtaining a near-infrared absorbing composition having a low viscosity and excellent discharge stability. Among them, an aqueous solvent having two hydroxyl groups, i.e., a diol-based solvent, is particularly preferably selected.

[0080] Among the diol solvents, it is preferable to use one or more alkanediols having at least 2 to 5 carbon atoms, more preferably an alkanediol having 3 to 4 carbon atoms, and particularly preferably an alkanediol having 3 carbon atoms.

[0081] The content of the aqueous solvent other than water used in the present invention is preferably 1 to 30% by mass based on the total amount of the near infrared absorbing composition, more preferably 3 to 27% by mass or less, and particularly preferably 5 to 25% by mass or less, from the viewpoint of ensuring ejection stability on an inkjet head and obtaining printed matter having excellent adhesion, drying properties, and image quality even on non-penetrating substrates.

[0082] <Dispersion resin> The near infrared absorbing composition of the present invention may contain a dispersing resin. The type of dispersion resin is not particularly limited, and for example, acrylic resin, styrene acrylic resin, maleic acid resin, styrene maleic acid resin, olefin maleic acid resin, urethane resin, ester resin (polycondensation product of polyvalent carboxylic acid and polyhydric alcohol), etc. can be used, but is not limited thereto. Among them, in terms of the large material selectivity and ease of synthesis, it is preferable to use one or more selected from the group consisting of acrylic resin, styrene acrylic resin, urethane resin, and ester resin. In addition, from the viewpoint of improving the dispersion stability and ejection stability of the ink, it is preferable to use the same type of resin as the binder resin described later.

[0083] The above-mentioned dispersion resins can be synthesized by known methods or commercially available products can be used. There are no particular limitations on the structure, and resins having, for example, a random structure, a block structure, a comb structure, a star structure, etc. can be used. Furthermore, either a water-soluble resin or a water-insoluble resin can be selected as the dispersion resin. The term "water-insoluble resin" refers to a dispersion resin that is not transparent to the naked eye when mixed with 1% by mass of water at 25°C.

[0084] In the present invention, when a water-soluble resin is used as the dispersion resin, the acid value is preferably 50 to 450 mgKOH / g, more preferably 100 to 400 mgKOH / g. Particularly preferably 150 to 350 mgKOH / g. By setting the acid value within the above range, it is possible to maintain the dispersion stability of the indigo compound (A) and to stably eject it from the inkjet head. It is also possible to maintain the ejection stability on the inkjet head. Furthermore, it is preferable in that the solubility of the dispersion resin in water can be ensured and the interaction between the dispersion resins becomes favorable, thereby suppressing the viscosity of the dispersion liquid.

[0085] On the other hand, when a water-insoluble resin is used as the dispersing resin, its acid value is preferably 0 to 100 mgKOH / g, more preferably 5 to 90 mgKOH / g, and even more preferably 10 to 80 mgKOH / g. If the acid value is within the above range, a printed matter having excellent drying properties and abrasion resistance can be obtained.

[0086] The acid value of the resin in this specification can be measured by potentiometric titration using a known device, for example, AT-610 manufactured by Kyoto Electronics Manufacturing Co., Ltd.

[0087] In the near infrared absorbing composition of the present invention, it is preferable to introduce an aromatic group into the dispersion resin from the viewpoint of improving the adsorption ability to the indigo compound (A) and ensuring dispersion stability. As a result, even if the indigo compound (A) is finely dispersed, it is possible to ensure the dispersion stability and discharge stability of the near infrared absorbing composition over a long period of time. Examples of the aromatic group include, but are not limited to, a phenyl group, a naphthyl group, an anthryl group, a tolyl group, a xylyl group, a mesityl group, and an anisyl group. Among them, a phenyl group and a tolyl group are preferable from the viewpoint of ensuring sufficient dispersion stability.

[0088] From the viewpoint of achieving a balance between the dispersion stability, printing quality, and drying properties of the ink containing the indigo compound (A), the content of the aromatic ring-containing monomer is preferably 5 to 75 mass % relative to the total amount of the dispersion resin, more preferably 5 to 65 mass %, and even more preferably 10 to 50 mass %.

[0089] In addition to the aromatic group, it is particularly preferable to introduce an alkyl group having 8 to 36 carbon atoms into the dispersion resin. By making the alkyl group have 8 to 36 carbon atoms, it is possible to reduce the viscosity of the dispersion liquid, improve the dispersion stability of the ink containing the indigo compound (A), and stabilize the ejection. The number of carbon atoms in the alkyl group is more preferably 10 to 30, and even more preferably 12 to 24. As long as the alkyl group has 8 to 36 carbon atoms, either a straight chain or a branched chain can be used, but a straight chain is preferable. Examples of linear alkyl groups include ethylhexyl (C8), lauryl (C12), myristyl (C14), cetyl (C16), stearyl (C18), arachyl (C20), behenyl (C22), lignoceryl (C24), cerotoyl (C26), montanyl (C28), melissyl (C30), dotriacontanyl (C32), tetratriacontanyl (C34), and hexatriacontanyl (C36).

[0090] From the viewpoint of achieving both low viscosity of the dispersion and abrasion resistance of the printed matter, the content of the monomer containing an alkyl chain having 8 to 36 carbon atoms is preferably 5 to 60 mass %, more preferably 10 to 55 mass %, and particularly preferably 15 to 50 mass %, relative to the total amount of the dispersion resin.

[0091] In addition, when a water-soluble resin is used as the dispersion resin, it is preferable that the acid group in the resin is neutralized with a base in order to increase the solubility in the near infrared absorbing composition. Whether the amount of base added is excessive or not can be confirmed, for example, by preparing a 10% by mass aqueous solution of the dispersion resin and measuring the pH of the aqueous solution. From the viewpoint of improving the dispersion stability of the near infrared absorbing composition containing the indigo compound (A), the pH of the aqueous solution is preferably 7 to 11, more preferably 7.5 to 10.5.

[0092] Examples of the base for neutralizing the dispersion resin include, but are not limited to, organic amine solvents such as triethylamine, monoethanolamine, diethanolamine, N-methyldiethanolamine, dimethylaminoethanol, diethylaminoethanol, and aminomethylpropanol; aqueous ammonia; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; and alkali metal carbonates such as lithium carbonate, sodium carbonate, sodium bicarbonate, and potassium carbonate.

[0093] When a water-soluble resin is used as the dispersing resin, the weight-average molecular weight is preferably in the range of 1,000 to 50,000, more preferably in the range of 5,000 to 40,000, further preferably in the range of 10,000 to 35,000, and particularly preferably in the range of 15,000 to 30,000. By having the weight-average molecular weight in the above range, the indigo compound (A) is stably dispersed in water, and viscosity adjustment when applied to the near-infrared absorbing composition is easy to perform. When the weight-average molecular weight is 1,000 or more, the dispersing resin is difficult to dissolve in the aqueous solvent added to the near-infrared absorbing composition, so that the adsorption of the dispersing resin to the indigo compound (A) is strengthened, and the dispersion stability is improved. When the weight-average molecular weight is 50,000 or less, the viscosity during dispersion is suppressed low, and the dispersion stability of the near-infrared absorbing composition and the ejection stability from the inkjet head are improved, enabling stable printing over a long period of time.

[0094] The blending amount of the dispersion resin is preferably 1 to 100% by mass relative to the blending amount of the indigo compound (A). By setting the ratio of the dispersion resin within the above range, the viscosity of the dispersion liquid is suppressed, and the dispersion stability and discharge stability of the near infrared absorbing composition are improved. The ratio of the indigo compound (A) to the dispersion resin is more preferably 2 to 50% by mass, and particularly preferably 4 to 45% by mass.

[0095] <Dispersion aid> In the near infrared absorbing composition of the present invention, a dispersion aid may be used in combination from the viewpoint of significantly improving the dispersion stability and ejection stability of the indigo compound (A) and also improving the color reproducibility of printed matter by enabling fine dispersion of the indigo compound (A). The dispersion aid is a material that contributes to improving the adsorption rate of the dispersion resin or surfactant to the indigo compound (A). In the present invention, any conventionally known material can be used as the dispersion aid, and in particular, a compound called a dye derivative can be preferably used.

[0096] <Ink and inkjet recording ink> The ink and inkjet recording ink of the present invention contain the near infrared absorbing composition of the present invention. The ink and inkjet recording ink of the present invention may also contain a binder resin, a surfactant, etc. Each component contained in the ink and inkjet recording ink of the present invention will be described below.

[0097] <Binder resin> In the ink of the present invention, a binder resin can be used to improve the scratch resistance of the printed matter. Two or more types of binder resins may be used in combination.

[0098] In this specification, the term "binder resin" refers to a resin used to bind a layer of a printed matter (printed layer, ink layer) to a recording medium. The ink of the present invention may contain a dispersion resin, but the dispersion resin and the binder resin are distinguished by their adsorption rate to the indigo compound (A). That is, a resin whose adsorption rate to the indigo compound (A) is 50% by mass or more relative to the total amount of the mixture is determined to be a dispersion resin, and a resin whose adsorption rate is less than 50% by mass is determined to be a binder resin.

[0099] In addition, as a method for confirming whether the resin present in the ink is the binder resin in this specification, there is a method for measuring the adsorption rate to the indigo compound (A). For example, the ink diluted with water as necessary is subjected to a centrifugal separation process (e.g., 30,000 rpm for 4 hours) to separate the indigo compound (A) from the supernatant. When the solid content in the supernatant is measured, if the solid content is greater than 50 mass% of the total amount of the resin contained in the ink, the resin is determined to be a binder resin.

[0100] Generally, water-soluble resins and resin particles are known as the form of binder resin for inks, and in the present invention, either one may be selected and used, or both may be used in combination. For example, resin particles have a higher molecular weight than water-soluble resins, and can improve the abrasion resistance of printed matter and also provide excellent image quality. In addition, inks using water-soluble resins as binder resins have excellent ejection stability. In this specification, the term "water-soluble resin" refers to a resin that is not the water-insoluble resin described above, that is, a 25°C / 1% by mass water mixture of the target resin is transparent to the naked eye.

[0101] The types of binder resins used in the present invention include acrylic resins, styrene-acrylic resins, urethane resins, urethane-acrylic composite resins, styrene-butadiene resins, vinyl chloride resins, styrene-maleic acid resins, ester resins, olefin resins, etc. Among them, from the viewpoint of obtaining an ink excellent in dispersion stability and ejection stability, it is preferable to use one or more resins selected from the group consisting of acrylic resins, styrene-acrylic resins, urethane resins, urethane-acrylic composite resins, and olefin resins. In general, urethane resins, urethane-acrylic composite resins, and olefin resins have low glass transition temperatures, and are therefore preferably selected from the viewpoint of adhesion to non-permeable substrates such as plastic substrates and image quality.

[0102] The glass transition temperature of the binder resin can be selected according to the required properties, for example, as follows: Specifically, in order to obtain an ink that improves the ejection stability and the abrasion resistance of the printed matter and is also excellent in drying properties and blocking resistance (the phenomenon in which a printed layer sticks to another recording medium when the recording medium is overlaid after printing), the glass transition temperature is preferably 60 to 140°C, more preferably 70 to 135°C, and particularly preferably 80 to 130°C.

[0103] On the other hand, when the ink of the present invention is used for non-permeable substrates such as plastic substrates, from the viewpoints of image quality and adhesion, it is preferable to use one or more resins selected from the group consisting of urethane resins, urethane-acrylic composite resins, and olefin resins, and / or one or more resins selected from the group consisting of acrylic resins and styrene-acrylic resins having a glass transition temperature of -120 to 45°C (preferably -80 to 25°C, and more preferably -60 to 15°C).

[0104] The glass transition temperature is a value measured using a DSC (differential scanning calorimeter), and can be measured, for example, as follows. Approximately 2 mg of a sample obtained by drying a resin is weighed on an aluminum pan, and the aluminum pan is set as a test container in a holder in a DSC measuring device (for example, DSC-60Plus manufactured by Shimadzu Corporation). Then, measurement is performed under a temperature rise condition of 5°C / min, and the temperature of the baseline shift read from the obtained DSC chart is defined as the glass transition temperature in this specification.

[0105] Furthermore, from the viewpoints of adhesion to plastic substrates, scratch resistance of printed matter, and blocking resistance, it is preferable that the binder resin contains an olefin resin and one or more resins selected from an acrylic resin, a styrene-acrylic resin, a urethane resin, and a urethane-acrylic composite resin.

[0106] The binder resin may be synthesized by a known method or may be a commercially available product. There is no particular limitation on the structure of the binder resin, and resins having, for example, a random structure, a block structure, a comb structure, a star structure, etc. may be used.

[0107] When a water-soluble resin is used as the binder resin in the present invention, the weight average molecular weight thereof is preferably from 5,000 to 50,000, more preferably from 8,000 to 45,000, and even more preferably from 10,000 to 40,000, from the viewpoints of ensuring ejection stability from an inkjet nozzle and obtaining printed matter having excellent adhesion and abrasion resistance to various recording media.

[0108] The weight-average molecular weight of the binder resin in the present invention can be measured by a conventional method. For example, the weight-average molecular weight in this specification is determined as a polystyrene-equivalent value measured using a GPC measuring device (HLC-8120GPC manufactured by Tosoh Corporation) equipped with a TSKgel column manufactured by Tosoh Corporation and an RI detector, and using THF as a developing solvent.

[0109] The content of the binder resin relative to the total amount of the ink is preferably 1 to 15 mass %, more preferably 2 to 12 mass %, and even more preferably 4 to 10 mass % in terms of solid content. By setting the amount of the binder resin within the above range, it is possible to obtain an ink that is excellent in the abrasion resistance and drying properties of printed matter, as well as in image quality, without decreasing the dispersion stability and ejection stability.

[0110] <Surfactant> In the present invention, it is preferable to contain one or more surfactants, from the viewpoint that by using it in combination with a binder resin, an ink excellent in ejection stability, image quality of printed matter, and drying property can be obtained. Generally, various surfactants are known according to the purpose, such as acetylenic diol-based, acetylenic alcohol-based, siloxane-based, acrylic-based, fluorine-based, polyoxyalkylene-based, etc., and the ink of the present invention preferably contains an acetylenic diol-based and / or siloxane-based surfactant.

[0111] Examples of acetylene diol surfactants that can be used in the present invention include, but are not limited to, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 2,5,8,11-tetramethyl-6-dodecyne-5,8-diol, hexadec-8-yne-7,10-diol, 6,9-dimethyl-tetradec-7-yne-6,9-diol, 7,10-dimethylhexadec-8-yne-7,10-diol, and ethylene oxide and / or propylene oxide adducts thereof.

[0112] Examples of siloxane surfactants that can be suitably used in the present invention include siloxane surfactants having one or more ethylene oxide groups and / or one or more propylene oxide groups at the side chain and / or at both ends of the polydimethylsiloxane chain. Specific examples include 8032ADDITIVE, FZ-2104, FZ-2120, FZ-2122, FZ-2162, FZ-2164, FZ-2166, FZ-2404, FZ-7001, FZ-7002, FZ-7006, L-7001, L-7002, SF8427, SF8428, SH3748, SH3749, SH3771M, SH3772M, SH 3773M, SH3775M, SH8400, BYK-331, BYK-333, BYK-345, BYK-346, BYK-347, BYK-348, BYK-349, BYK-UV3500, BYK-UV3510, BYK-UV3530, BYK-UV3570 manufactured by BYK-Chemie, TEGO manufactured by Evonik Wet250, TEGOWet260, TEGOWet270, TEGOWet280, TEGOGlide410, TEGOGlide432, TEGOGlide435, TEGOGlide440, TEGOGlide450, KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-640, KF-642, KF-643, KF-644, KF-945, KF-6011, KF-6012, KF-6015, KF-6017, KF-6020, KF-6204, X-22-4515 manufactured by Shin-Etsu Chemical Co., Ltd., and the Silface SAG series manufactured by Nissin Chemical Co., Ltd.

[0113] Furthermore, examples of polyoxyalkylene surfactants that can be suitably used in the present invention include compounds represented by the following general formula (9).

[0114] General formula (9): RO-(EO)m-(PO)nH

[0115] In the above general formula (9), R represents an alkyl group having 8 to 22 carbon atoms, an alkenyl group having 8 to 22 carbon atoms, an alkylcarbonyl group having 8 to 22 carbon atoms, or an alkenylcarbonyl group having 8 to 22 carbon atoms. The above R may have a branched structure. EO represents an ethylene oxide group, and PO represents a propylene oxide group. m represents the average number of moles of EO added and is a number from 2 to 50, and n represents the average number of moles of PO added and is a number from 0 to 50. When n is not 0, the order of addition of (EO)m and (PO)n does not matter, and the addition may be in blocks or randomly.

[0116] The surfactant that can be used in the present invention is preferably one that has a hydrophobic group and a hydrophilic group separated in the molecule, and therefore, among the surfactants exemplified above, those having a hydrophilic ethylene oxide group are particularly preferably selected.

[0117] From the viewpoints of increasing the affinity with the binder resin, obtaining an ink having excellent dispersion stability and ejection stability, and obtaining printed matter having excellent image quality without bleeding or uneven shading, it is preferable to use a surfactant having an HLB value of 0 to 5, and it is particularly preferable to contain a surfactant having an HLB value of 0 to 4.

[0118] In particular, from the viewpoint of obtaining printed matter having excellent image quality with little bleeding between ink droplets and little unevenness in shading on non-permeable substrates such as plastic substrates, in addition to dispersion stability and ejection stability, it is preferable to use a surfactant having an HLB value of 0 to 5 (preferably 0 to 4) in combination with a surfactant having an HLB value of 6 to 18 (preferably 7 to 18, particularly preferably 8 to 16).

[0119] The HLB (Hydrophile-Lipophile Balance) value is one of the parameters that indicate the hydrophilicity and hydrophobicity of a material; the smaller the value, the more hydrophobic the material is, and the larger the value, the more hydrophilic the material is. There are various known methods for calculating the HLB value from a chemical structure, and various known methods for measuring the HLB value. In the present invention, when the structure of a compound is clearly known, such as an acetylene diol surfactant or a polyoxyalkylene surfactant, the HLB value is calculated using the Griffin method. The Griffin method is a method for calculating the HLB value using the molecular structure and molecular weight of the target material, using the following formula (10).

[0120] Equation (10): HLB value = 20 x (sum of molecular weights of hydrophilic parts) ÷ (molecular weight of material)

[0121] On the other hand, when a compound with an unknown structure is included, such as a siloxane-based surfactant, the HLB value of the surfactant can be experimentally determined by the following method described on page 324 of "Surfactant Handbook" (edited by Nishi Ichiro et al., Sangyo Tosho Co., Ltd., 1960). Specifically, 0.5 g of the surfactant is dissolved in 5 mL of ethanol, and the solution is titrated with a 2% by mass aqueous phenol solution while stirring at 25°C, and the end point is when the solution becomes turbid. When the amount of the aqueous phenol solution required to reach the end point is A (mL), the HLB value can be calculated by the following formula (11).

[0122] Equation (11): HLB value = 0.89 x A + 1.11

[0123] The content of the surfactant in the ink of the present invention is preferably 0.2 to 4 mass % relative to the total amount of the ink, and more preferably 0.5 to 2 mass %.

[0124] <Water> The water contained in the ink of the present invention is preferably ion-exchanged water (deionized water) rather than ordinary water containing various ions, and its content is preferably in the range of 20 to 90% by mass of the total mass of the ink.

[0125] <Other ingredients> In addition to the above-mentioned components, the ink of the present invention may contain a pH adjuster, if necessary, to obtain an ink having desired physical properties. Examples of compounds that can be used as pH adjusters include: Alkanolamines include triethylamine, monoethanolamine, diethanolamine, N-methyldiethanolamine, dimethylaminoethanol, diethylaminoethanol, and aminomethylpropanol. Other nitrogen-containing compounds include ammonia water, monoethylamine, diethylamine, triethylamine, cyclohexylamine, benzylamine, urea, and piperidine. Alkali metal hydroxides include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Alkali metal carbonates include lithium carbonate, sodium carbonate, sodium bicarbonate, and potassium carbonate. Acidic compounds include hydrochloric acid, sulfuric acid, acetic acid, citric acid, maleic acid, maleic anhydride, succinic acid, tartaric acid, malic acid, phosphoric acid, boric acid, fumaric acid, malonic acid, ascorbic acid, and glutamic acid. The pH adjusters may be used alone or in combination of two or more thereof.

[0126] The blend amount of the pH adjuster is preferably 0.01 to 5 mass % relative to the total amount of the ink, more preferably 0.1 to 3 mass %, and most preferably 0.2 to 1.5 mass %.

[0127] In addition to the above components, additives such as antifoaming agents, preservatives, and ultraviolet absorbers can be added to the ink of the present invention as necessary to obtain ink with desired physical properties. The amount of these additives added is preferably 0.01 to 10% by mass based on the total mass of the ink.

[0128] It is preferable that the ink of the present invention does not substantially contain a polymerizable monomer.

[0129] <pKa values ​​of nitrogen-containing compounds> As described above, the ink of the present invention can contain a nitrogen-containing compound as a water-soluble organic solvent and / or a pH adjuster. However, depending on the nitrogen-containing compound used, it may adversely affect the dispersion stability and ejection stability, so in the present invention, it is preferable to limit the amount of the nitrogen-containing compound.

[0130] Specifically, the total amount of the chain amide solvent, cyclic amide solvent, and cyclic carbamate solvent is preferably 3% by mass or less (may be 0% by mass) relative to the total amount of the ink, and more preferably 1% by mass or less (may be 0% by mass). Although the detailed reason is unclear, when a large amount of these compounds is added, the dispersion stability and ejection stability tend to deteriorate.

[0131] Furthermore, even if it is a compound other than the above, the total amount of nitrogen-containing compounds having a pKa value at 25° C. of 2 or less (preferably, the pKa value is 4 or less) or 10 or more (preferably, the pKa value is 9.5 or more) is preferably 3% by mass or less (may be 0% by mass) relative to the total amount of the ink, and particularly preferably 1% by mass or less (may be 0% by mass). This is because these compounds are strongly acidic or basic, and may also adversely affect the dispersion stability and ejection stability.

[0132] The pKa value of the present invention can be measured by a known method, for example, potentiometric titration. Examples of nitrogen-containing compounds having a pKa value of 2 or less at 25° C. include urea (pKa value=0.2), and examples of nitrogen-containing compounds having a pKa value of 10 or more at 25° C. include cyclohexylamine (pKa value=10.6), monoethylamine (pKa value=10.7), diethylamine (pKa value=11.0), triethylamine (pKa value=10.7), and piperidine (pKa value=11.2).

[0133] <Specific metal atoms> The near infrared absorbing composition of the present invention may contain small amounts of metal components including Li, Na, Mg, K, Cs, Co, Ca, Fe, Si and Zr (hereinafter also referred to as specific metal atoms) other than the constituent components of the indigo compound (A). If a large amount of metal components including these specific metal atoms is present, the dispersion stability may be impaired and the heat resistance may be reduced.

[0134] The total content of the specific metal atoms in the metal components contained in the near infrared absorbing composition of the present invention is preferably 1 to 1000 mass ppm, more preferably 300 mass ppm or less, and particularly preferably 200 mass ppm or less, based on the entire near infrared absorbing composition. The lower limit of the total amount of the specific metal atoms is not particularly limited, but is preferably 1 mass ppm or more, more preferably 5 mass ppm or more, based on the entire near infrared absorbing composition.

[0135] The content of each specific metal atom contained in the near infrared absorbing composition of the present invention is preferably 100 ppm by mass or less, and more preferably 50 ppm by mass or less, based on the entire near infrared absorbing composition.

[0136] Methods for removing various raw materials contained in the near-infrared absorbing composition or metal atoms that have been mixed in from the equipment during the manufacturing process include methods using water washing as described in JP 2010-83997 A, JP 2018-36521 A, JP H07-198928 A, JP H08-333521 A, JP 2009-7432 A, and the like, and methods for removing magnetic foreign matter using a magnet as described in JP 2011-48736 A, and the like. One or more of these methods can be used as appropriate.

[0137] The content of specific metal atoms can be measured by inductively coupled plasma emission spectrometry (ICP).

[0138] <Method of producing near-infrared absorbing composition and ink> The near infrared absorbing composition and ink of the present invention, which are composed of the above-mentioned components, can be manufactured by a known method. In particular, in order to obtain a near infrared absorbing composition and ink excellent in dispersion stability and ejection stability, a manufacturing method in which a dispersion containing an indigo compound (A) is manufactured in advance, and then the dispersion, a binder resin, a surfactant, etc. are mixed is preferably selected. An example of a manufacturing method for the near infrared absorbing composition and ink of the present invention will be described below, but as mentioned above, the manufacturing method is not limited to the following.

[0139] (1) Preparation of dispersion (1-1) Dispersion treatment method using water-soluble dispersion resin When a water-soluble resin is used as the dispersion resin, the dispersion resin and water, and if necessary, a water-soluble organic solvent are mixed and stirred to prepare a dispersion resin aqueous solution. The indigo compound (A) is added to the dispersion resin aqueous solution, and after mixing and stirring (premixing), a dispersion treatment is performed using a dispersing machine. Thereafter, centrifugation, filtration, and adjustment of the solid content are performed as necessary to obtain a dispersion liquid.

[0140] (1-2) Dispersion treatment using a water-insoluble dispersing resin When producing a dispersion of an indigo compound (A) coated with a water-insoluble dispersion resin, the dispersion resin is dissolved in an organic solvent such as methyl ethyl ketone beforehand, and the dispersion resin is neutralized as necessary to prepare a dispersion resin solution. The indigo compound (A) and water are added to the dispersion resin solution, and the mixture is mixed and stirred (premixed), and then a dispersion treatment is performed using a dispersing machine. The organic solvent is then removed by distillation under reduced pressure, and centrifugal separation, filtration, and solid content adjustment are performed as necessary to obtain a dispersion.

[0141] In the above methods (1-1) and (1-2), the dispersing machine used in dispersing the indigo compound (A) may be any commonly used dispersing machine, such as a ball mill, a roll mill, a sand mill, a bead mill, a Nanomizer, etc. Among the above, a bead mill is preferably used, and specifically, it is commercially available under the trade names of Super Mill, Sand Grinder, Agitator Mill, Grain Mill, Dyno Mill, Pearl Mill, Cobol Mill, etc.

[0142] In the above methods (1-1) and (1-2), the particle size distribution of the dispersion can be controlled by adjusting the size of the grinding media of the dispersing machine, changing the material of the grinding media, increasing the packing rate of the grinding media, changing the shape of the stirring member (agitator), increasing the dispersion treatment time, classifying the dispersion treatment with a filter or centrifuge, and combinations of these methods. In order to keep the indigo compound (A) within a suitable particle size range, it is preferable that the diameter of the grinding media of the dispersing machine is 0.1 to 3 mm. In addition, glass, zircon, zirconia, and titania are preferably used as the material of the grinding media.

[0143] (2) Preparation of ink To the dispersion obtained above, a binder resin, a surfactant, a water-soluble organic solvent, water, and, if necessary, the pH adjuster and other additives listed above are added, and the mixture is stirred and mixed. If necessary, the mixture may be stirred and mixed while being heated in the range of 40 to 100°C.

[0144] (3) Removal of coarse particles Coarse particles contained in the mixture are removed by a method such as filtration separation or centrifugation to obtain an ink. As a method for filtration separation, a known method can be appropriately used, but when a filter is used, the pore size is preferably 0.3 to 5 μm, more preferably 0.5 to 3 μm. When performing filtration, a single type of filter may be used, or multiple types may be used in combination.

[0145] <Ink characteristics> The ink of the present invention is preferably adjusted to have a viscosity of 3 to 20 mPa·s at 25°C. This viscosity range allows stable ejection characteristics to be exhibited from heads having normal frequencies of 4 to 10 KHz to high-frequency heads of 10 to 70 KHz. In particular, by setting the viscosity at 25°C to 4 to 10 mPa·s, stable ejection can be achieved even when used with an inkjet head having a design resolution of 600 dpi or more. The above viscosity can be measured by a conventional method. Specifically, it can be measured using 1 mL of ink using an E-type viscometer (TVE25L type viscometer manufactured by Toki Sangyo Co., Ltd.).

[0146] Furthermore, from the viewpoints of making the ink capable of being stably discharged and obtaining printed matter with excellent image quality, the ink of the present invention preferably has a static surface tension of 18 to 35 mN / m, and particularly preferably 20 to 32 mN / m, at 25° C. The static surface tension refers to the surface tension measured by the Wilhelmy method in an environment of 25° C., and can be measured, for example, using CBVP-Z manufactured by Kyowa Interface Science Co., Ltd. and a platinum plate.

[0147] Furthermore, from the viewpoint of obtaining excellent image quality by quickly orienting the surfactant after landing on the recording medium and obtaining suitable wettability on the recording medium, the ink of the present invention preferably has a dynamic surface tension at 10 milliseconds, as measured by the maximum bubble pressure method, of 26 to 36 mN / m, more preferably 28 to 36 mN / m, and particularly preferably 30 to 36 mN / m. Note that the dynamic surface tension in this specification can be measured in an environment of 25°C using, for example, a bubble pressure dynamic surface tensiometer BP100 manufactured by Kruss.

[0148] In order to obtain a printed matter having high invisibility, the ink of the present invention has an average secondary particle diameter (D50) of 40 to 500 nm, more preferably 50 to 400 nm, and particularly preferably 60 to 300 nm. In order to keep the average secondary particle diameter within the above-mentioned preferred range, the dispersion treatment process may be controlled as described above. The average secondary particle diameter (D50) of the indigo compound (A) refers to the median diameter measured by dynamic light scattering using a particle size distribution measuring instrument (e.g., Microtrac UPAEX-150 manufactured by Microtrac-Bell).

[0149] <Ink-pretreatment liquid set> The ink of the present invention can also be used in the form of an ink-pretreatment liquid set in combination with a pretreatment liquid containing an aggregating agent. By applying a pretreatment liquid containing an aggregating agent onto a recording medium, a layer (ink aggregation layer) can be formed in which the solid components contained in the ink are intentionally aggregated. By landing the ink on the ink aggregation layer, bleeding between ink droplets and color unevenness can be prevented, and the image quality of the printed matter can be significantly improved. Furthermore, depending on the material used in the pretreatment liquid, the adhesion, abrasion resistance, and blocking resistance of the printed matter can also be improved.

[0150] In this specification, the term "flocculant" refers to a component that can disrupt the dispersion state of the indigo compound (A) and resin fine particles contained in the ink, causing them to flocculate, and / or can insolubilize the water-soluble resin and thicken the ink. From the viewpoint of significantly improving image quality, the flocculant used in the pretreatment liquid to be combined with the ink of the present invention preferably contains one or more types selected from metal salts and cationic polymer compounds. Of these, from the viewpoint of obtaining excellent image quality, it is preferable to use a metal salt as the flocculant, and Ca 2+ , Mg 2+ , Zn 2+ , Al 3+ It is particularly preferred that the pretreatment liquid contains a salt of a polyvalent metal ion selected from the group consisting of: When a metal salt is used as the flocculant, the content thereof is preferably 2 to 30 mass %, and more preferably 3 to 25 mass %, based on the total amount of the pretreatment liquid.

[0151] The pretreatment liquid may contain other suitable additives such as organic solvents, surfactants, pH adjusters, antifoaming agents, preservatives, etc. Specific usable materials are the same as those for the ink described above.

[0152] From the viewpoint of obtaining a printed matter having excellent image quality when used in combination with the ink of the present invention, the static surface tension of the pretreatment liquid is preferably 20 to 45 mN / m, more preferably 23 to 40 mN / m, and particularly preferably 25 to 37 mN / m. The static surface tension of the pretreatment liquid can be measured in the same manner as the static surface tension of the ink.

[0153] <Inkjet recording method> The ink of the present invention is used in a recording method in which it is ejected from an ink-jet head and applied onto a recording medium.

[0154] As the pass system in the inkjet recording method, either a single pass system in which ink is ejected onto the recording medium only once for recording, or a serial system in which ejection and recording are performed while a short shuttle head is reciprocally scanned in a direction perpendicular to the conveying direction of the recording medium may be adopted. However, in the case of a serial system, it is necessary to adjust the ejection timing taking into account the movement of the inkjet head, and deviation of the landing position is likely to occur. Therefore, when printing the ink of the present invention, a single pass system, particularly a pass system in which the recording medium passes under a fixed inkjet head, is preferably used.

[0155] There are no particular limitations on the method of ejecting ink, and any known method can be used, such as the drop-on-demand method (pressure pulse method) that utilizes the vibration pressure of a piezoelectric element, or the thermal inkjet (bubble jet [registered trademark]) method that heats the ink to form bubbles and utilizes the resulting pressure.

[0156] The amount of ink droplets ejected from the inkjet head is preferably 0.2 to 30 picoliters, and more preferably 1 to 20 picoliters, from the standpoint of greatly reducing the drying load and improving image quality.

[0157] It is preferable that the ink of the present invention is provided with a drying mechanism for drying the ink on the recording medium after the ink is applied onto the recording medium by an inkjet printing method. The drying method used in the drying mechanism includes a heat drying method, a hot air drying method, a microwave drying method, a drum drying method, and the like.

[0158] In the present invention, from the viewpoint of preventing bumping of the liquid components in the ink and obtaining printed matter with excellent image quality, it is preferable that the drying temperature be 35 to 100°C when a heat drying method is adopted, and that the hot air temperature be 50 to 250°C when a hot air drying method is adopted.

[0159] The drying methods may be used alone, or a combination of two or more may be used in succession, or may be used simultaneously. For example, by using the heat drying method and the hot air drying method in combination, the ink can be dried more quickly than when each method is used alone.

[0160] <Recording Media> The recording medium on which the ink of the present invention is printed is not particularly limited, and any known recording medium can be used. Among them, non-permeable or poorly permeable substrates are preferred, and the ink of the present invention can be used particularly preferably for non-permeable substrates. In this specification, the permeability of a recording medium is determined by the amount of water absorption measured by a dynamic scanning absorptiometer. Specifically, the amount of water absorption of pure water in a contact time of 100 msec, measured by the following method, is 1 g / m 2 Recording media with a permeability of less than 1 to 10 g / m are considered "non-permeable substrates". 2 The recording medium having the above structure is called a "hardly permeable substrate."

[0161] The amount of water absorbed by a recording medium can be measured, for example, under the following conditions: A dynamic scanning absorptivity meter, KM500win manufactured by Kumagai Riki Kogyo Co., Ltd., is used to measure the amount of transferred pure water under the conditions of 23°C and 50% RH using a recording medium approximately 15 to 20 cm square. Measurement method: Spiral Method ·Measurement start radius: 20mm Measurement end radius: 60mm ·Contact time: 10~1,000msec Number of sampling points: 19 (measured at approximately equal intervals relative to the square root of contact time) Scanning distance: 7mm Rotating table speed switching angle: 86.3 degrees Headbox conditions: width 5mm, slit width 1mm

[0162] Examples of non-permeable or poorly permeable substrates include plastic substrates such as polyvinyl chloride, polyethylene terephthalate (PET), polypropylene, polyethylene, nylon, polystyrene, and polyvinyl alcohol; coated paper substrates such as coated paper, art paper, and cast paper; metal substrates such as aluminum, iron, stainless steel, and titanium; and glass substrates. The above substrates may have a smooth or uneven surface, and may be transparent, semi-transparent, or opaque. In addition, two or more of these recording media may be laminated together. Furthermore, a peelable adhesive layer may be provided on the opposite side of the printed surface, and an adhesive layer may be provided on the printed surface after printing. The shape of the recording medium used in the inkjet recording method of the present invention may be in the form of a roll or a sheet.

[0163] It is also preferable to subject the non-permeable substrates or poorly permeable substrates exemplified above to a surface modification method such as corona treatment or plasma treatment, since this improves the wettability of the ink of the present invention, improves image quality and drying properties, and also improves abrasion resistance and adhesion due to the uniformity of the surface of the printed matter.

[0164] <Coating treatment> The printed surface of a printed matter produced using the ink of the present invention may be subjected to a coating treatment, if necessary. Specific examples of the coating treatment include coating / printing of a coating composition, and lamination processing using a dry lamination method, a solventless lamination method, an extrusion lamination method, etc., and any of these may be selected, or both may be combined.

[0165] When a coating treatment is performed on a printed matter by coating / printing a coating composition, the coating / printing method may be either a method of printing without contacting the recording medium, such as inkjet printing, or a method of printing by bringing the coating composition into contact with the recording medium. When the method of printing without contacting the recording medium is selected, the coating composition may be an ink (clear ink) that does not substantially contain a colorant component, which is obtained by removing the pigment from the aqueous inkjet ink of the present invention. It is preferable to use a fluorine-based ink. EXAMPLES

[0166] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to these. In addition, "parts" means "parts by mass" and "%" means "% by mass".

[0167] Before describing the examples, each measurement method will be described.

[0168] (Method of identifying compounds) The compounds used in the present invention were identified by infrared absorption spectroscopy and MALDI TOF-MS spectroscopy. The MALDI TOF-MS spectroscopy was performed using a Bruker Daltonics MALDI mass spectrometer AutoflexIII, and the compounds were identified by the agreement of the molecular ion peak of the mass spectrum in the positive mode obtained with the mass number obtained by calculation.

[0169] (Maximum absorption wavelength of indigo compound (A)) The maximum absorption wavelength of the indigo compound (A) was measured by dissolving the indigo compound (A) in a 10 ppm solution in N-methylpyrrolidone, and then measuring the wavelength showing the maximum absorbance in the absorption spectrum in the range of 400 to 1300 nm using a UV-Vis-NIR spectrophotometer U-4150 (manufactured by Hitachi High-Technologies Corporation).

[0170] (Indigo compounds (a1-1) to (a4-1)) Indigo compounds (a1-1) to (a4-1) represented by the following structural formulas were synthesized in the same manner as described in JP 2012-224593 A. The maximum absorption wavelengths of the indigo compounds (a1-1) to (a4-1) were 1000 nm, 1040 nm, 1015 nm, and 1005 nm, respectively.

[0171] [ka]

[0172] (Indigo compounds (a5-1) to (a7-1)) Indigo compounds (a5-1) to (a7-1) represented by the following structural formulas were synthesized in the same manner as described in JP 2013-87233 A. The maximum absorption wavelengths of the indigo compounds (a5-1) to (a7-1) were 905 nm, 835 nm, and 890 nm, respectively.

[0173] [ka]

[0174] (Indigo compound (a8-1)) In a reaction vessel, 10.7 parts of aniline, 120 parts of bromobenzene, and 25.7 parts of diazabicyclooctane were added and stirred. Then, 95.2 parts of a 1 mol / l toluene solution of titanium tetrachloride was added dropwise. After the dropwise addition, 10.0 parts of indigo were added and refluxed for 10 hours. After the reaction was completed, methanol was added and filtered to obtain a green powder. This was separated with dichloromethane and water, and the organic layer was concentrated to obtain 14.6 parts of compound (1-1).

[0175] [Compound (1-1)] [ka]

[0176] In a reaction vessel, 13.5 parts of compound (1-1), 22.0 parts of zinc acetate (II) dihydrate, and 120 parts of N-methylpyrrolidone were mixed and stirred, and the mixture was heated and stirred at 50°C for 5 hours. The reaction solution was cooled to 30°C while stirring, and poured into 500 parts of methanol while stirring to obtain a blue slurry. This slurry was filtered, washed with 500 parts of methanol, and dried to obtain 11.1 parts of indigo compound (a8-1). The maximum absorption wavelength of the indigo compound (a8-1) was 830 nm.

[0177] (a8-1) [ka]

[0178] (Indigo compound (a9-1)) The same procedure as in the synthesis of compound (1) was carried out except that 10.0 parts of indigo used in the synthesis of compound (1) was changed to 22.0 parts of Bat Blue 5, to obtain 24.4 parts of compound (2).

[0179] [Compound (2)] [ka]

[0180] The same procedure as in the synthesis of indigo compound (a8-1) was carried out except that 13.5 parts of compound (1) used in the synthesis of indigo compound (a8-1) was replaced with 23.9 parts of compound (2), to obtain 23.5 parts of indigo compound (a9-1). The maximum absorption wavelength of indigo compound (a9-1) was 838 nm.

[0181] (a9-1) [ka]

[0182] (Indigo compound (a10-1)) The same procedure as in the synthesis of compound (1) was carried out except that 10.7 parts of aniline used in the synthesis of compound (1) was changed to 12.3 parts of p-toluidine, to obtain 14.9 parts of compound (3).

[0183] [Compound (3)] [ka]

[0184] In a reaction vessel, 14.0 parts of compound (3), 22.0 parts of zinc acetate (II) dihydrate, and 120 parts of tetrahydrofuran were mixed and stirred, and the mixture was heated and stirred at 40°C for 5 hours. The reaction solution was cooled to 30°C while stirring, and poured into 500 parts of methanol while stirring to obtain a blue slurry. This slurry was filtered, washed with 500 parts of methanol, and dried to obtain 11.1 parts of indigo compound (a10-1). The maximum absorption wavelength of the indigo compound (a10-1) was 833 nm.

[0185] (a10-1) [ka]

[0186] (Indigo compound (a11-1)) The same procedure as in the synthesis of compound (1) was carried out, except that 10.7 parts of aniline used in the synthesis of compound (1) was changed to 14.2 parts of 3-methoxyaniline, to obtain 17.3 parts of compound (4).

[0187] [Compound (4)] [ka]

[0188] The same procedure as in the synthesis of indigo compound (a8-1) was carried out except that 13.5 parts of compound (1) used in the synthesis of indigo compound (a8-1) was replaced with 14.5 parts of compound (4), to obtain 12.3 parts of indigo compound (a11-1). The maximum absorption wavelength of indigo compound (a11-1) was 835 nm.

[0189] (a11-1) [ka]

[0190] (Indigo compound (a12-1)) In a reaction vessel, 13.5 parts of compound (1), 19.0 parts of nickel (II) acetate tetrahydrate, and 120 parts of N-methylpyrrolidone were mixed and stirred, and the mixture was heated and stirred at 100°C for 5 hours. The reaction solution was cooled to 30°C while stirring, and poured into 500 parts of methanol while stirring to obtain a blue slurry. This slurry was filtered, washed with 500 parts of methanol, and dried to obtain 11.5 parts of indigo compound (a12-1). The maximum absorption wavelength of the indigo compound (a12-1) was 820 nm.

[0191] (a12-1) [ka]

[0192] (Compound (b1-1)) Compound (b1-1) represented by the following structural formula was synthesized in the same manner as described in JP 2010-222557 A. The maximum absorption wavelength was 780 nm in chloroform.

[0193] Compound (b1-1) [ka]

[0194] (Compound (b2-1)) Compound (b2-1) represented by the following structural formula was synthesized in the same manner as described in Japanese Patent No. 6751762. The maximum absorption wavelength was 850 nm in chloroform.

[0195] Compound (b2-1) [ka]

[0196] The indigo compounds (a1-1) to (a12-1) and the compounds (b1-1) to (b2-1) were produced three times by repeating the same production method. Hereinafter, for example, the compound (a1-1) produced three times by repeating the same production method will be represented as (a1-1), (a1-2), and (a1-3), and the same applies to the other compounds.

[0197] <Production of near-infrared absorbing composition> In producing the near infrared absorbing composition, a dispersant was prepared.

[0198] (Preparation of dispersant [C-1] solution) A reaction vessel equipped with a gas inlet tube, a thermometer, a condenser, and a stirrer was charged with 93.4 parts of butanol and substituted with nitrogen gas. The reaction vessel was heated to 110°C, and a mixture of 30 parts of acrylic acid, 35 parts of styrene, 35 parts of lauryl methacrylate, and 6 parts of V-601 (manufactured by Wako Pure Chemical Industries) as a polymerization initiator was dropped over 2 hours to carry out a polymerization reaction. After the dropwise addition, the reaction was carried out at 110°C for 3 hours, and then 0.6 parts of V-601 was added, and the reaction was continued at 110°C for another 1 hour. After that, the reaction system was cooled to room temperature, and 39 parts of dimethylaminoethanol were added to neutralize, and then 100 parts of water were added. Then, the mixed solution was heated to 100°C or higher to distill off butanol, and then the solid content was adjusted to 30% using water to obtain an aqueous solution of dispersant [C-1] (solid content 30%). The weight average molecular weight and acid value of the dispersant [C-1], measured by the methods described above, were 16,000 and 230, respectively.

[0199] [Example 1] (Near infrared absorbing composition (D-1)) 20.0 parts of indigo compound (a1-1) was mixed with 200.0 parts of ion-exchanged water and 2.0 parts of sodium salt of special aromatic sulfonic acid formalin condensate (Demol SN-B, manufactured by Kao Corporation), and the mixture was dispersed in an Eiger mill for 3 hours to obtain a near-infrared absorbing composition (D-1).

[0200] [Examples 2 to 36, Comparative Examples 1 to 6] (Near infrared absorbing compositions (D-2) to (D-36), (D-73) to (D-78)) Near infrared absorbing compositions (D-2) to (D-36) and (D-73) to (D-78) were obtained in the same manner as for the near infrared absorbing composition (D-1), except that the indigo compound (a1-1) was changed to a compound described in Tables 1-1 and 1-2.

[0201] [Example 37] (Near infrared absorbing composition (D-37)) 20.0 parts of the indigo compound (a1-1), 60.0 parts of ion-exchanged water, and 20.0 parts of the dispersant [C-1] solution were pre-dispersed using a disperser, and then main dispersion was carried out for 2 hours using a 0.6 L Dyno Mill filled with 1800.0 parts of zirconia beads having a diameter of 0.5 mm, to obtain a near infrared absorbing composition (D-37).

[0202] [Examples 38 to 72, Comparative Examples 7 to 12] Near infrared absorbing compositions (D-38) to (D-72) and (D-79) to (D-84) were obtained in the same manner as for the near infrared absorbing composition (D-37), except that the indigo compound (a1-1) was changed to a compound described in Tables 1-1 and 1-2.

[0203] [Table 1-1]

[0204] [Table 1-2]

[0205] <Production of inkjet recording ink> In producing the inkjet recording ink, a binder resin was produced.

[0206] (Preparation of binder resin [E-1] solution) In a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser, 40 parts of ion-exchanged water and 0.2 parts of Aqualon KH-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a surfactant were charged, and 1% of a pre-emulsion in which 40 parts of 2-ethylhexyl acrylate, 50 parts of methyl methacrylate, 7 parts of styrene, 2 parts of dimethylacrylamide, 1 part of methacrylic acid, 53 parts of ion-exchanged water, and 1.8 parts of Aqualon KH-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a surfactant were mixed in advance was further added. After the internal temperature was raised to 60°C and the atmosphere was fully replaced with nitrogen, 10% of 10 parts of a 5% aqueous solution of potassium persulfate and 20 parts of a 1% aqueous solution of anhydrous sodium bisulfite were added to initiate polymerization. After the reaction system was kept at 60°C for 5 minutes, the remaining pre-emulsion, the 5% aqueous solution of potassium persulfate, and the remaining 1% aqueous solution of anhydrous sodium bisulfite were added dropwise over 1.5 hours while maintaining the internal temperature at 60°C, and stirring was continued for another 2 hours. After confirming that the conversion rate exceeded 98% by measuring the solid content, the temperature was cooled to 30°C. Diethylaminoethanol was added to adjust the pH to 8.5, and the solid content was further adjusted to 40% with ion-exchanged water to obtain a resin microparticle water dispersion. The solid content was determined by the residue after baking at 150°C for 20 minutes. The obtained resin microparticle water dispersion was used as a binder resin [E-1] solution.

[0207] [Example 101] (Inkjet recording ink (F-1)) 40.3 parts of the near infrared absorbing composition (D-1) were mixed with 10 parts of glycerin, 10 parts of triethylene glycol, 10 parts of triethylene glycol monobutyl ether, 0.2 parts of triethanolamine, and 1 part of an acetylene glycol surfactant (Olfine E1010, manufactured by Nissin Chemical Industry Co., Ltd.), and stirred at 35°C for 1 hour. The remainder was mixed with ultrapure water (resistivity of 18 MΩ·cm or more) to make the total amount 100 parts. The mixture was then filtered through a 1.0 μm filter to obtain the inkjet recording ink (F-1) of the present invention.

[0208] [Examples 102 to 136, Comparative Examples 101 to 106] (Inkjet recording inks (F-2) to (F-36), (F-73) to (F-78)) Inkjet recording inks (F-2) to (F-36) and (F-73) to (F-78) were obtained in the same manner as in the production of the inkjet recording ink (F-1), except that the near-infrared absorbing composition (D-1) was changed to a near-infrared absorbing composition shown in Table 2.

[0209] [Example 137] 20 parts of the near infrared absorbing composition (D-37), 40 parts of triethylene glycol monomethyl ether, 27.5 parts of ion-exchanged water, and 12.5 parts of the fixing resin [E-1] solution were mixed to obtain an inkjet recording ink (F-37).

[0210] [Examples 138 to 172, Comparative Examples 107 to 112] Inkjet recording inks (F-38) to (F-72) and (F-79) to (F-84) were obtained in the same manner as in the production of the inkjet recording ink (F-37), except that the near-infrared absorbing composition (D-37) was changed to a near-infrared absorbing composition shown in Table 2.

[0211] (Evaluation of invisibility and near-infrared absorption of ink for inkjet recording) The inkjet recording inks (F-1) to (F-84) were loaded into a black ink cartridge for an inkjet printer PM-A700 (product name, manufactured by EPSON Corporation), and a solid image was printed on photo glossy paper (EPSON PM Photo Paper <Glossy> (KA420PSK, EPSON) (product name)) with the color setting set to "black," and the inks were evaluated by the following method. A solid image was printed on photo glossy paper, and the image obtained was measured using a reflection spectrodensitometer (X-rite 939, manufactured by X-Rite Inc.) to determine ΔE in formula (I) and R in formula (II). 0≦ΔE≦15 (I) (100-R)≧75 (II) [In formula (I), ΔE is represented by the following formula (III):

[0212]

number

[0213] L1, a1, b1, L2, a2, and b2 can be obtained using a reflection spectrodensitometer. L1, a1, b1, L2, a2, and b2 in the present invention are measured using an X-Rite 939 reflection spectrodensitometer manufactured by X-Rite Inc. The evaluation criteria are as follows: ⊚: very good level, ◯: good level, and ×: not suitable for practical use. <<Invisibility>> ◎: ΔE less than 10 ○: ΔE 10 or more, less than 15 ×:ΔE 15 or more <<Near infrared absorption ability>> ◎:(100-R) 80 or more ○: (100-R) 75 or more, less than 80 ×: (100-R) Less than 75

[0214] (Evaluation of light resistance of inkjet recording ink) The test pieces obtained in the same manner as those prepared for evaluating the invisibility and near-infrared absorption ability were placed in a light resistance tester (TOYOSEIKI "SUNTEST CPS+") and left for 24 hours. At this time, the irradiance was 47 mW / cm 2 The test was carried out using a broadband light of 300 to 800 nm. Images before and after the light fastness test were measured using a reflection spectrodensitometer (X-rite 939, manufactured by X-Rite Inc.) to determine R in formula (II). The remaining rate relative to that before light irradiation was determined, and the light fastness was evaluated according to the following criteria. The remaining rate was calculated using the following formula. Survival rate = (100-R) after irradiation ÷ (100-R) before irradiation × 100 ◎: Residual rate is 95% or more ○: Residual rate is 90% or more, but less than 95% ×: Residual rate is less than 90%

[0215] (Quality variation evaluation) The criteria for evaluating quality variation are as follows: ◯: In the evaluations of invisibility, near-infrared absorbing ability, and light fastness, the evaluations of inks prepared by repeatedly producing the same compound were all the same. ×: In the evaluations of invisibility, near-infrared absorbing ability, and light fastness, inks produced by repeatedly producing the same compound had one or more different evaluations.

[0216] [Table 2-1]

[0217] [Table 2-2]

[0218] The inkjet recording inks of the present invention all had good invisibility, near-infrared absorptivity, and lightfastness, and showed little variation in quality when repeatedly produced, whereas the inkjet recording inks of the comparative examples showed variation in quality when repeatedly produced.

[0219] From the above results, it is found that the near-infrared absorbing composition of the present invention has small quality variation. Furthermore, printed matter using an inkjet recording ink prepared from the near-infrared absorbing composition of the present invention has good invisibility, near-infrared absorbing ability, and light fastness, and these qualities can be stably supplied.

Claims

1. A near-infrared absorbing composition comprising an indigo compound (A) having a maximum absorption wavelength in the wavelength range of more than 800 nm to 1,050 nm, dispersed in an aqueous solvent.

2. 2. The near infrared absorbing composition according to claim 1, wherein the indigo compound (A) is a compound represented by the following general formula (1): General formula (1) 【Chemistry 1】 [In the formula, X １ ~X ２４ each independently represents a hydrogen atom, an optionally substituted alkyl group, an optionally substituted aryl group, an optionally substituted alkoxyl group, an optionally substituted aryloxy group, an optionally substituted arylalkyl group, an optionally substituted cycloalkyl group, an optionally substituted alkylthio group, an optionally substituted arylthio group, an amino group, an optionally substituted alkylamino group, an optionally substituted arylamino group, a cyano group, a halogen atom, a nitro group, a hydroxyl group, -SO 3 H; —COOH; and monovalent to trivalent metal salts of these acidic groups; and alkylammonium salts. １ ~X ２４ Two adjacent groups among the groups represented by the formula (I) may be linked to form a 5- or 6-membered ring together with the carbon atoms to which they are bonded. M represents a metal atom.

3. 2. The near infrared absorbing composition according to claim 1, wherein the indigo compound (A) is a compound represented by the following general formula (2): General formula (2) 【Chemistry 2】 [In the formula, X ２５ ~X ４０ each independently represents a hydrogen atom, an optionally substituted alkyl group, an optionally substituted aryl group, an optionally substituted alkoxyl group, an optionally substituted aryloxy group, an optionally substituted arylalkyl group, an optionally substituted cycloalkyl group, an optionally substituted alkylthio group, an optionally substituted arylthio group, an amino group, an optionally substituted alkylamino group, an optionally substituted arylamino group, a cyano group, a halogen atom, a nitro group, a hydroxyl group, -SO 3 H; —COOH; and monovalent to trivalent metal salts of these acidic groups; and alkylammonium salts. ２５ ~X ４０ Two adjacent groups among the groups represented by the following formula (I) may be linked to form a 5- or 6-membered ring together with the carbon atoms to which they are bonded.

4. An ink comprising the near infrared absorbing composition according to any one of claims 1 to 3.

5. An ink for ink-jet recording, comprising the near-infrared absorbing composition according to any one of claims 1 to 3.

6. A printed matter having a near-infrared absorbing image printed thereon using the ink according to claim 4.

7. A printed matter on which a near-infrared absorbing image is printed using the ink for ink-jet recording according to claim 5.

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