Azo-iron complex dye, ink composition containing the same, and method for producing the azo-iron complex dye

Abstract

[Problem] To provide an azo iron complex dye which does not contain harmful heavy metals, exhibits sufficient solubility in organic solvents for practical use, and exhibits a good black color. [Solution] This azo iron complex dye contains a disazo-monoazo iron complex represented by chemical formula (1) (In chemical formula (1), R1 and R2 are each independently a straight chain or branched chain alkyl group having 3-10 carbon atoms, R3 is an electron-withdrawing group, R4 is a straight chain or branched chain alkyl group having 1-5 carbon atoms or a straight chain or branched chain alkoxy group having 1-5 carbon atoms, R5 is a nitro group, a sulfoamide group or a halogen atom, R6 is a hydrogen atom, a straight chain or branched chain alkyl group having 1-8 carbon atoms, a nitro group or a halogen atom, R7 is a hydrogen atom or a straight chain or branched chain alkyl group having 3-12 carbon atoms, and A+ is a monovalent cation).

Description

[Technical Field]

[0001] The present invention relates to an azo-iron complex dye, an ink composition containing the same, and a method for producing the azo-iron complex dye. [Background technology]

[0002] Ink compositions are used to print or write on recording media using inkjet printers, writing instruments, and recorders. Ink compositions for continuous inkjet (CIJ) printers, which are widely used in the industrial field, are formulated to have high electrical conductivity due to the fact that CIJ printers charge and deflect the ink composition while ejecting it onto a recording medium. They are also formulated to ensure good ink adhesion even on smooth, non-absorbent surfaces such as glass, metal, and plastic plates. These ink compositions contain a colorant, an organic solvent, and a resin that acts as a fixing agent and is soluble in the organic solvent.

[0003] Examples of colorants contained in ink compositions include pigments and dyes. Among colorants, black colorants are in particularly high demand. However, while black pigments are less susceptible to discoloration due to light or heat, they have poor color development and may aggregate in the ink composition, resulting in poor storage stability. Black dyes have high solubility in organic solvents and excellent color development and storage stability. However, black dyes deteriorate and discolor due to heat and light, resulting in poor heat resistance and light fastness. For this reason, metal complex dyes, which exhibit a black color and have high heat resistance and light fastness like black pigments while maintaining the inherent high solubility of black dyes in organic solvents, are used as black colorants.

[0004] Furthermore, as organic solvents contained in ink compositions, in addition to the conventionally used ketone-based organic solvents such as acetone and methyl ethyl ketone, alcohol-based organic solvents such as ethanol and propylene glycol, and ether-based organic solvents such as propylene glycol monoalkyl ethers are also used from the viewpoints of environmental conservation and ensuring safety for the human body.

[0005] Known black dyes with excellent solubility in alcohol-based organic solvents include amine salts of azochrome complex dyes. Specific examples of such azochrome complex dyes include CISOLVENT BLACK 23, 27, 28, 29, 35, and 45. Patent Document 1 also describes azochrome complex dyes that are black and soluble in acetone.

[0006] However, because azochrome complex dyes contain chromium, a harmful heavy metal, their use is being discouraged from the viewpoints of environmental conservation and human safety. Therefore, metal complex dyes that have the favorable properties of metal complex dyes but do not contain harmful heavy metals such as chromium are being investigated.

[0007] As one example of such studies, Patent Document 2 proposes a mixed dye containing three types of disazo compounds and iron complexes as specific complex-forming agents. Patent Document 3 also describes polyazo iron complex dyes. However, these iron complex dyes are not black, but rather brown or reddish-brown. Patent Document 4, on the other hand, describes a monoazo iron complex salt compound. This monoazo iron complex salt compound is black-purple, which is not as black as the azo chrome complex dye. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 51-023518 [Patent Document 2] Japanese Patent Application Publication No. 5-247360 [Patent Document 3] Special Publication No. 47-044530 [Patent Document 4] Japanese Patent Application Publication No. 63-4992 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an azo iron complex dye that does not contain harmful heavy metals, has sufficient solubility in organic solvents for practical use, and exhibits a good black color, an ink composition containing the same, and a method for producing the azo iron complex dye. [Means for solving the problem]

[0010] The azo iron complex dye that has been developed to achieve the above object is represented by the following chemical formula (1): [ka] (In chemical formula (1), R 1 and R 2 are each independently a linear or branched alkyl group having 3 to 10 carbon atoms, and R 3 teeth It is bonded to the para position relative to the azo group on the same aromatic ring and is selected from a cyano group, a nitro group, an acetyl group, a sulfoamide group, and a halogen atom. is an electron-withdrawing group, R 4 is a linear or branched alkyl group having 1 to 5 carbon atoms or a linear or branched alkoxy group having 1 to 5 carbon atoms, and R 5 is a nitro group, a sulfonamide group, or a halogen atom, and R 6 is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, a nitro group, or a halogen atom; R 7 is a hydrogen atom or a linear or branched alkyl group having 3 to 12 carbon atoms, and A + is a monovalent cation. ) includes disazo-monoazo iron complexes represented by the formula:

[0011] The azo iron complex dye is 3 but , the above cyano group, The aforementioned nitro group, The aforementioned acetyl group, The aforementioned a sulfoamide group, and The above-mentioned atom is selected from a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. The electron-withdrawing group may be selected from halogen atoms.

[0012] The azo iron complex dye is, for example, represented by the following chemical formula (2): [ka] (In chemical formula (2), R5 ~R 7 and A + is the same as chemical formula (1).

[0013] Azo iron complex dyes are represented by the following chemical formula (3): [ka] (In chemical formula (3), R 1 ~R 4 and A + is the same as chemical formula (1).

[0014] The azo iron complex dye is, for example, a dye in which the monovalent cation is an alkali metal ion, an ammonium ion, or a compound represented by the following chemical formula (4): [ka] (In chemical formula (4), R 8 is a linear or branched alkyl group having 1 to 18 carbon atoms, and R 9 and R 10 are each independently a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms.

[0015] The azo iron complex dye may have peak area ratios of 20-70:5-80:0-50 in chromatograms obtained by measuring the disazo-monoazo iron complex, the monoazo-monoazo iron complex, and the disazo-disazo iron complex by high performance liquid chromatography at a wavelength of 254 nm, respectively.

[0016] The ink composition of the present invention contains any of the azo iron complex dyes described above and an organic solvent.

[0017] The ink composition may be for use in an inkjet printer.

[0018] The method for producing the azo iron complex dye of the present invention is a method for producing an azo iron complex dye represented by the following chemical formula (5): [ka] (In chemical formula (5), R 1 and R 2 are each independently a linear or branched alkyl group having 3 to 10 carbon atoms, and R 3 teeth It is bonded to the para position relative to the azo group on the same aromatic ring and is selected from a cyano group, a nitro group, an acetyl group, a sulfoamide group, and a halogen atom. is an electron-withdrawing group, R 4 is a linear or branched alkyl group having 1 to 5 carbon atoms or a linear or branched alkoxy group having 1 to 5 carbon atoms, and a disazo dye represented by the following chemical formula (6): [ka] (In chemical formula (6), R 5 is a nitro group, a sulfonamide group, or a halogen atom, and R 6 is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, a nitro group, or a halogen atom; R 7 is a hydrogen atom or a linear or branched alkyl group having 3 to 12 carbon atoms; and an iron complexation step of heating a monoazo dye represented by the formula (I) with an iron-containing agent in a solvent to obtain an azo-iron complex anion; and an ion exchange step of reacting the azo iron complex anion with an alkali metal solution and / or an ammonium compound to introduce a cation to be combined with the azo iron complex anion, thereby obtaining a compound represented by the following chemical formula (1): [ka] (In chemical formula (1), R 1 ~R 4 is the same as chemical formula (5), and R 5 ~R 7 is the same as chemical formula (6), and A + is a monovalent cation.) to obtain a disazo-monoazo iron complex represented by

[0019] In the method for producing the azo iron complex dye, for example, the disazo dye and the monoazo dye are used in a molar ratio of 2:8 to 8:2 in the iron complex forming step. [Effects of the Invention]

[0020] The azo iron complex dye of the present invention does not contain harmful heavy metals such as chromium or cobalt, and therefore contributes to environmental conservation and is highly safe for humans compared to azo chromium complex dyes. Furthermore, the azo iron complex dye contains an azo iron complex having a specific structure, which allows it to exhibit a higher blackness than conventional azo iron complex dyes. Furthermore, the azo iron complex dye of the present invention has practical solubility stability in various organic solvents, such as ketone organic solvents, alcohol organic solvents, and ether organic solvents.

[0021] The ink composition of the present invention contains the above-described azo iron complex dye, and therefore is highly safe for the environment and the human body. It also adheres firmly to and does not easily peel off from recording media, whether the recording media is ink-absorbent or ink-non-absorbent. Therefore, the ink composition can be widely used as a black colorant for various media, such as inkjet printers, writing instruments, and recorders.

[0022] According to the method for producing an azo iron complex dye of the present invention, by appropriately selecting the substituent bonded to the benzene ring of the ligand of the azo iron complex and the cation bonded to the azo iron complex anion, and by adjusting the molar ratio of the disazo dye that forms the disazo ligand and the monoazo dye that forms the monoazo ligand, it is possible to produce an azo iron complex dye that combines high solubility in various organic solvents with high blackness. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a graph showing the visible absorption spectrum of azo iron complex dye A-1 in Example 1 to which the present invention is applied. [Figure 2] 1 is a graph showing the visible absorption spectrum of azo iron complex dye A-2 in Example 2 according to the present invention. [Figure 3]1 is a graph showing the visible absorption spectrum of azo iron complex dye A-3 in Example 3 according to the present invention. [Figure 4] 1 is a graph showing the visible absorption spectrum of azo iron complex dye A-4 in Example 4 according to the present invention. [Figure 5] 1 is a graph showing the visible absorption spectrum of azo iron complex dye A-5 in Example 5 according to the present invention. [Figure 6] 1 is a graph showing the visible absorption spectrum of azo iron complex dye A-6 in Example 6 according to the present invention. [Figure 7] 1 is a graph showing the visible absorption spectrum of azo iron complex dye A-7 in Example 7 according to the present invention. [Figure 8] 1 is a graph showing the visible absorption spectra of azo iron complex dye A-1 in Example 1 to which the present invention is applied, and azo iron complex dyes B-1 to B-3 in Comparative Examples 1 to 3 to which the present invention is not applied. DETAILED DESCRIPTION OF THE INVENTION

[0024] The present invention will be described in detail below, but the scope of the present invention is not limited to these embodiments. In this specification, the symbol "to" is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit, in principle.

[0025] (Azo iron complex dye) The azo iron complex dye of the present invention is represented by the following chemical formula (1): [ka] (In chemical formula (1), R 1 and R 2 are each independently a linear or branched alkyl group having 3 to 10 carbon atoms, and R 3 is an electron-withdrawing group, and R 4 is a linear or branched alkyl group having 1 to 5 carbon atoms or a linear or branched alkoxy group having 1 to 5 carbon atoms, and R 5 is a nitro group, a sulfonamide group, or a halogen atom, and R 6is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, a nitro group, or a halogen atom; R 7 is a hydrogen atom or a linear or branched alkyl group having 3 to 12 carbon atoms, and A + is a monovalent cation. ) includes disazo-monoazo iron complexes represented by the formula:

[0026] As can be seen from the above chemical formula (1), the disazo-monoazo iron complex contained in the azo iron complex dye of the present invention has a structure in which trivalent iron and an azo iron complex anion containing azo ligands in which a disazo dye and a monoazo dye are combined in a molar ratio of 1:2 are bonded to a monovalent cation.

[0027] In chemical formula (1), R 1 and R 2is a straight-chain or branched-chain alkyl group having 3 to 10 carbon atoms. Specifically, it is an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, an n-hexyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 2,2-dimethylbutyl group, a 2,3-dimethylbutyl group, an n-heptyl group, a 2-methylhexyl group, a 3-methylhexyl group, a 2,2-dimethylpentyl group, a 2,3-dimethylpentyl group, a 2,4-dimethylpentyl group, a 3,3-dimethylpentyl group, a 3-ethylpentyl group, a 2,2,3-trimethylbutyl group, an n-octyl group, a 2-methylheptyl group, a 3-methylheptyl group, Examples of the alkyl group include 4-methylheptyl, 2,2-dimethylhexyl, 2,3-dimethylhexyl, 2,4-dimethylhexyl, 2,5-dimethylhexyl, 3,3-dimethylhexyl, 3,4-dimethylhexyl, 2-ethylhexyl, 3-ethylhexyl, 2,2,3-trimethylpentyl, 2,2,4-trimethylpentyl, 2,3,3-trimethylpentyl, 2,3,4-trimethylpentyl, 2-methyl-3-ethylpentyl, 3-methyl-3-ethylpentyl, 2,2,3,3-tetramethylbutyl, n-nonyl, n-decyl, and lauryl. Of these, n-butyl, isobutyl, sec-butyl, tert-butyl, isopentyl, and 2-ethylhexyl are preferred.

[0028] In chemical formula (1), R 3 is an electron-withdrawing group, specifically a cyano group, a nitro group, an acetyl group, a sulfoamide group, and a halogen atom. The halogen atom includes fluorine, chlorine, bromine, and iodine. R 3 When R is an electron-withdrawing group, the deep color deepening effect of the azo iron complex dye is enhanced, and a deep black color sufficient for practical use is obtained. 3 is bonded at the para position relative to the azo group on the same aromatic ring, which is preferable in terms of deep color development.

[0029] Such a disazo-monoazo iron complex is specifically represented by the following chemical formula (7): [ka] (In chemical formula (7), R 1 ~R 7 and A + is the same as chemical formula (1).

[0030] In chemical formula (1), R 4 is a linear or branched alkyl group having 1 to 5 carbon atoms, or a linear or branched alkoxy group having 1 to 5 carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, and a neopentyl group, and examples of the alkoxy group include a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, a tert-butoxy group, an n-pentyloxy group, an isopentyloxy group, and a neopentyloxy group.

[0031] Such a disazo-monoazo iron complex is specifically represented by the following chemical formula (8): [ka] (In chemical formula (8), R 1 ~R 7 and A + is the same as chemical formula (1).

[0032] In chemical formula (1), R 5 R is an electron-withdrawing substituent such as a nitro group, a sulfoamide group, or a halogen atom. Examples of the halogen atom include fluorine, chlorine, bromine, and iodine. 5 is preferably bonded to the 4th or 5th position relative to the azo group on the aromatic ring to which it is bonded, since this further improves the blackness of the disazo-monoazo iron complex and allows for a black color deep enough for practical use.

[0033] In chemical formula (1), R 6is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, a nitro group, or a halogen atom. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, an n-hexyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 2,2-dimethylbutyl group, a 2,3-dimethylbutyl group, an n-heptyl group, a 2-methylhexyl group, a 3-methylhexyl group, a 2,2-dimethylpentyl group, a 2,3-dimethylpentyl group, a 2,4-dimethylpentyl group, a 3,3-dimethylpentyl group, a 3-ethylpentyl group, a 2,2,3-trimethylbutyl group, an n-octyl Examples of halogen atoms include 2-methylheptyl, 3-methylheptyl, 4-methylheptyl, 2,2-dimethylhexyl, 2,3-dimethylhexyl, 2,4-dimethylhexyl, 2,5-dimethylhexyl, 3,3-dimethylhexyl, 3,4-dimethylhexyl, 2-ethylhexyl, 3-ethylhexyl, 2,2,3-trimethylpentyl, 2,2,4-trimethylpentyl, 2,3,3-trimethylpentyl, 2,3,4-trimethylpentyl, 2-methyl-3-ethylpentyl, 3-methyl-3-ethylpentyl, and 2,2,3,3-tetramethylbutyl. Examples of halogen atoms include fluorine, chlorine, bromine, and iodine.

[0034] Specifically, such a disazo-monoazo iron complex is represented by the following chemical formula (9a): [ka] (In chemical formula (9a), R 1 ~R 7 and A + is the same as chemical formula (1).) and the following chemical formula (9b) [ka] (In chemical formula (9b), R 1 ~R 7 and A + is the same as chemical formula (1).

[0035] In chemical formula (1), R 7 is a hydrogen atom or a straight-chain or branched-chain alkyl group having 3 to 12 carbon atoms. Examples of this alkyl group include n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, 2-methylpentyl, 3-methylpentyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, n-heptyl, 2-methylhexyl, 3-methylhexyl, 2,2-dimethylpentyl, 2,3-dimethylpentyl, 2,4-dimethylpentyl, 3,3-dimethylpentyl, 3-ethylpentyl, 2,2,3-trimethylbutyl, n-octyl, tert-octyl, 2-methylheptyl, 3 4-methylheptyl group, 4-methylheptyl group, 2,2-dimethylhexyl group, 2,3-dimethylhexyl group, 2,4-dimethylhexyl group, 2,5-dimethylhexyl group, 3,3-dimethylhexyl group, 3,4-dimethylhexyl group, 2-ethylhexyl group, 3-ethylhexyl group, 2,2,3-trimethylpentyl group, 2,2,4-trimethylpentyl group, 2,3,3-trimethylpentyl group, 2,3,4-trimethylpentyl group, 2-methyl-3-ethylpentyl group, 3-methyl-3-ethylpentyl group, 2,2,3,3-tetramethylbutyl group, n-nonyl group, n-decyl group, lauryl group, and dodecyl group. Of these, tert-butyl, isopentyl, hexyl, n-octyl, tert-octyl, 2-ethylhexyl, n-nonyl, n-decyl and dodecyl groups are preferred.

[0036] Specifically, such a disazo-monoazo iron complex is represented by the following chemical formula (10a): [ka] (In chemical formula (10a), R 1 ~R 7 and A + is the same as chemical formula (1).) The following chemical formula (10b) [ka] (In chemical formula (10b), R 1 ~R 7 and A + is the same as chemical formula (1).) The following chemical formula (10c): [ka] (In chemical formula (10c), R 1 ~R 7 and A + is the same as chemical formula (1).) and the following chemical formula (10d): [ka] (In chemical formula (10d), R 1 ~R 7 and A + is the same as chemical formula (1).

[0037] In chemical formula (1), A + is a monovalent cation. This monovalent cation can be hydrogen ion, alkali metal ion, ammonium ion (NH4 + ), and monovalent alkyl group-containing ammonium ions. The disazo-monoazo iron complex may contain only one or more of these monovalent cations. Among these, ammonium ions and monovalent alkyl group-containing ammonium ions are preferred. As the alkali metal ion, lithium ions (Li + ), sodium ions (Na + ), and potassium ions (K + The alkali metal ions may be derived from a pH adjuster used in the synthesis of the disazo-monoazo iron complex. Only one type of monovalent cation may be bonded to the iron complex anion, or multiple types may be bonded to the iron complex anion.

[0038] The monovalent alkyl group-containing ammonium ion is represented by the following chemical formula (4): [ka] It is expressed as:

[0039] In chemical formula (4), R 8 is a linear or branched alkyl group having 1 to 18 carbon atoms, and R 9 and R 10 are each independently a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms. 7 The alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, 2-methylpentyl, 3-methylpentyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, n-heptyl, 2-methylhexyl, 3-methylhexyl, 2,2-dimethylpentyl, 2,3-dimethylpentyl, 2,4-dimethylpentyl, 3,3-dimethylpentyl, 3-ethylpentyl, 2,2,3-trimethylbutyl, n-octyl, 2-methylheptyl, and 3-methylheptyl. Examples of alkyl groups include 4-methylheptyl, 2,2-dimethylhexyl, 2,3-dimethylhexyl, 2,4-dimethylhexyl, 2,5-dimethylhexyl, 3,3-dimethylhexyl, 3,4-dimethylhexyl, 2-ethylhexyl, 3-ethylhexyl, 2,2,3-trimethylpentyl, 2,2,4-trimethylpentyl, 2,3,3-trimethylpentyl, 2,3,4-trimethylpentyl, 2-methyl-3-ethylpentyl, 3-methyl-3-ethylpentyl, and 2,2,3,3-tetramethylbutyl, n-nonyl, n-decyl, undecyl, lauryl, and stearyl. Among these, a straight or branched chain alkyl group having 7 to 18 carbon atoms is preferred, a branched chain alkyl group having 8 to 15 carbon atoms is more preferred, and a branched chain alkyl group having 11 to 14 carbon atoms is even more preferred.

[0040] In chemical formula (4), R 9 and R 10Specific examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, n-heptyl, and n-octyl groups, with methyl being preferred.

[0041] The disazo-monoazo iron complex essentially contained in the azo iron complex dye of the present invention has an amino group (—NR in chemical formula (1)) bonded to a dialkyl group having a specific range of carbon atoms. 1 R 2 ) and electron-withdrawing groups (same -R 3 ) and the same electron-withdrawing group (same -R 5 and / or -R 6 ) and a monoazo ligand having the same structure, the azo iron complex dye is deep-colored and absorbs wavelengths in the visible light range, resulting in a deep black color that is sufficient for practical use.

[0042] Furthermore, the aromatic ring of the disazo ligand is composed only of arylene groups, and does not contain a naphthalene ring, which would otherwise be bulky and result in a high molecular weight. Therefore, this azo iron complex dye has a lower molecular weight than azo iron complex dyes having a naphthalene ring-containing disazo ligand, and therefore exhibits high color development even in small amounts.

[0043] Furthermore, this disazo-monoazo iron complex contains, as a cation, an alkali metal ion, an ammonium ion, and / or a monovalent alkyl-containing ammonium ion having an alkyl group with a specific carbon number within a specific range, thereby improving the solubility of the azo iron complex anion that produces a black color. Therefore, the azo iron complex dye of the present invention exhibits a practically high level of solubility in alcohol-based organic solvents such as ethanol and ethylene glycol and ketone-based organic solvents such as methyl ethyl ketone, making it suitable for use in ink compositions. Furthermore, due to its high solubility stability, it does not precipitate or precipitate in organic solvents. Therefore, this azo iron complex dye is suitable for ink compositions, particularly ink compositions for continuous inkjet printers. Furthermore, the azo iron complex dye does not contain chromium or cobalt, which are heavy metals harmful to the environment and human body, thereby contributing to environmental conservation and ensuring safety to the human body.

[0044] The azo iron complex dye of the present invention preferably contains, in addition to the disazo-monoazo iron complex represented by chemical formula (1), a monoazo-monoazo iron complex having only a monoazo ligand, which is the ligand possessed by the disazo-monoazo iron complex, and / or a disazo-disazo iron complex having only a disazo ligand.

[0045] This monoazo-monoazo iron complex has the following chemical formula (2): [ka] (In chemical formula (2), R 5 ~R 7 and A + is the same as chemical formula (1).

[0046] The disazo-disazo iron complex is represented by the following chemical formula (3): [ka] (In chemical formula (3), R 1 ~R 4 and A + is the same as chemical formula (1).

[0047] When the azo iron complex dye contains a disazo-monoazo iron complex (DM form), a monoazo-monoazo iron complex (MM form), and a disazo-disazo iron complex (DD form), the molar ratio of these can be expressed as the peak area ratio in a chromatogram obtained by measurement by high-performance liquid chromatography at a specific wavelength, for example, 254 nm. Specifically, the DM:MM:DD ratio is preferably 20-70:5-80:0-50, more preferably 20-65:5-80:0-50, even more preferably 20-60:20-80:0-30, and even more preferably 20-55:20-80:0-15. The lower limit of the DD form may be 1 instead of 0. The above values ​​are calculated by rounding off the peak area ratio to one decimal place. For example, the lower limit of 0 for the DD isomer encompasses values ​​exceeding 0.0, ie, 0.1 to 0.4.

[0048] The azo iron complex dye preferably contains, in addition to a disazo-monoazo iron complex, which is an asymmetric azo iron complex, a symmetric azo iron complex dye such as a monoazo-monoazo iron complex having only monoazo ligands and / or a disazo-disazo iron complex having only disazo ligands, because by adjusting the ratio of each azo iron complex in the azo iron complex within an appropriate range, the blackness, solubility, and dissolution stability of the azo iron complex dye, as well as the electrical conductivity required for an ink composition for a continuous ink jet (CIJ) printer, can be appropriately and arbitrarily adjusted.

[0049] The azo iron complex dye of the present invention is suitable for use in ink compositions for CIJ printers. In this case, the electrical conductivity K of the azo iron complex dye is preferably 300 to 2200 μS / cm, and more preferably 600 to 2000 μS / cm. When the electrical conductivity is within this range, the charge of the ink composition for CIJ printers containing the azo iron complex dye can be stably and freely controlled, thereby improving the ejection stability of the ink composition. The electrical conductivity K is measured by inserting the electrodes of an electrical conductivity meter into a 6% by mass methyl ethyl ketone solution of the azo iron complex dye and immersing it therein.

[0050] The alkali metal ion content of the azo iron complex dye is preferably 1000 ppm or less, and more preferably 500 ppm or less, which can reduce the surface tension of the ink composition, making the ink composition suitable for use in CIJ printers.

[0051] Furthermore, additives such as leveling agents and anti-repellents contained in CIJ ink compositions often contain silicone compounds or silicone surfactants, and when the alkali metal ion content of the azo iron complex dye is within the above range, it is possible to suppress the formation of complexes between these silicone compounds and silicone surfactants and the alkali metal ions, thereby preventing clogging of the printer head and improving the ejection stability of the CIJ printer ink composition.

[0052] In order to obtain the azo iron complex dye containing the azo iron complex represented by the chemical formulas (1) to (3), it is preferable to employ a production method including the following first to fifth steps. Step 1: A step of obtaining a disazo dye using a diazo coupling reaction Step 2: A step of obtaining a monoazo dye using a diazo coupling reaction The third step is to form an iron complex by reacting the mixture of disazo dye and monoazo dye to obtain an azo-iron complex dye. Step 4: Changing and preparing the cation of the azo iron complex dye 5th process: Filtering, washing, drying and pulverizing the azo iron complex dye According to this manufacturing method, a high-purity azo-iron complex dye can be obtained. Each step will be described in detail below.

[0053] Step 1: A step of obtaining a disazo dye using a diazo coupling reaction The first step is to obtain a disazo dye that can serve as a disazo ligand in an azo iron complex.

[0054] (1-1: Synthesis of monoazo compounds) First, as shown in the following chemical formula (11), a specific aromatic amine is diazotized by a known method, and then subjected to a diazo coupling reaction with 2-aminophenol by a conventional method to obtain a monoazo compound, which is an intermediate for a disazo dye. [ka] (In chemical formula (11), R 3 and R 4 is the same as chemical formula (1).

[0055] In the reaction of chemical formula (11), specifically, an aqueous solution of aminobenzene (diazo component) having an electron-withdrawing substituent group diluted with hydrochloric acid and sodium nitrite (for example, a 40% by mass aqueous solution) are added to ion-exchanged water or a mixed solvent of ion-exchanged water and a lower alcohol, and the mixture is stirred at a temperature of 0 to 5°C for 1 to 3 hours to diazotize the aminobenzene and obtain a diazotized solution. Excess nitrous acid is decomposed with sulfamic acid or the like.

[0056] Next, an aminophenol having a substituent suitable for forming a metal complex, such as a hydroxyl group, is dissolved or finely dispersed in an aqueous solution diluted with hydrochloric acid. The diazotization solution is added dropwise to the solution, and the mixture is stirred at room temperature or a low temperature for several hours in a hydrophilic solvent or a water-lower alcohol solvent to carry out a diazo coupling reaction, yielding a solution containing a monoazo compound. The monoazo compound is filtered and washed with water to obtain a wet cake of the monoazo compound. This wet cake can be used in the next step, the synthesis of a disazo dye, after drying, or as a solution containing the monoazo compound.

[0057] (1-2: Synthesis of disazo dyes) The monoazo compound obtained by the above synthesis is diazotized by a known method as shown in the following chemical formula (12), and then subjected to a diazo coupling reaction with an aminophenol compound having a specific alkylamino group by a conventional method to obtain a solution containing a disazo dye. [ka] (In chemical formula (12), R 1 ~R 4 is the same as chemical formula (1).

[0058] In the reaction of chemical formula (12), specifically, for example, an aqueous solution prepared by diluting the monoazo compound obtained in the synthesis of the monoazo compound with hydrochloric acid and sodium nitrite (for example, a 40% by mass aqueous solution) are added to ion-exchanged water or a mixed solvent of ion-exchanged water and a lower alcohol, and the mixture is stirred at a temperature of 0 to 5°C for 1 to 3 hours to diazotize the aminobenzene and obtain a diazotized solution. Excess nitrous acid is decomposed with sulfamic acid or the like.

[0059] Next, an aminophenol having a substituent suitable for forming a metal complex, such as a hydroxyl group, is dissolved or finely dispersed in an alkaline aqueous solution. The diazotization solution is added dropwise to the resulting solution, and the mixture is stirred at room temperature or a low temperature for several hours in a hydrophilic solvent or a water-lower alcohol solvent to carry out a diazo coupling reaction, yielding a solution containing a disazo dye. The disazo dye is filtered and washed with water to obtain a disazo dye wet cake. This wet cake can be used in the subsequent iron complexation step after drying, or as a wet cake, or as a disazo dye-containing solution.

[0060] Step 2: A step of obtaining a monoazo dye using a diazo coupling reaction The second step is to obtain a monoazo dye that can serve as a monoazo ligand in an azo iron complex.

[0061] First, an aromatic amine having an electron-withdrawing group such as a nitro group or a halogen atom is diazotized by a known method to obtain a diazotized solution. Specifically, for example, an aqueous solution of an aminobenzene (diazo component) having an electron-withdrawing substituent group diluted with hydrochloric acid and sodium nitrite (e.g., a 40% by weight aqueous solution) are added to ion-exchanged water or a mixed solvent of ion-exchanged water and a lower alcohol, and the mixture is stirred at a temperature of 0 to 5°C for 1 to 3 hours to diazotize the aminobenzene and obtain a diazotized solution. Excess nitrous acid is decomposed with sulfamic acid or the like.

[0062] Next, as shown in the following chemical formula (13), the diazo compound in the diazotized solution obtained above and 2-naphthol are subjected to a diazo coupling reaction in a conventional manner to obtain a monoazo dye. [ka] (In chemical formula (13), R 5 ~R 7 is the same as chemical formula (1).

[0063] The reaction of chemical formula (13) is specifically carried out as follows. 2-Naphthol is dissolved or finely dispersed in an alkaline aqueous solution, and the diazotization solution is added dropwise to the solution. A diazotization coupling reaction is carried out in a hydrophilic solvent or a water-lower alcohol solvent while stirring at room temperature or a low temperature for several hours to obtain a solution containing a monoazo dye. The monoazo dye is filtered and washed with water to obtain a monoazo dye wet cake. This wet cake may be used in the next step, the iron complexation step, after drying, or may be used as the wet cake or as the monoazo dye-containing solution.

[0064] The third step is to form an iron complex by complexing the mixture of the disazo dye and the monoazo dye with iron to obtain an azo-iron complex. The third step is an iron complexation step in which the disazo dye and monoazo dye obtained in the previous step are ironized to obtain an azo iron complex (azo iron complex anion).

[0065] The disazo dye obtained in the first step and the monoazo dye obtained in the second step are charged in a molar ratio of, for example, 2:8 and mixed to obtain a mixed dye. This mixed dye is dispersed or dissolved in a solvent, and an iron-containing agent is added, followed by heating and stirring at 80 to 140°C for 1 to 5 hours. As a result, as shown in chemical formula (14) below, the iron-containing reaction proceeds, and the disazo dye and monoazo dye are coordinated to the iron atom, obtaining a mixture of a disazo-monoazo iron complex represented by chemical formula (1), a monoazo-monoazo iron complex represented by chemical formula (2), and a disazo-disazo iron complex represented by chemical formula (3). [ka] (In chemical formula (14), R 1 ~R 7 is the same as chemical formula (1), and X + is any cation.)

[0066] The mixing ratio of the disazo dye to the monoazo dye is preferably 2:8 to 8:2 in molar ratio, and specific examples of mixing ratios include 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, and 8:2. Of these, a ratio of disazo dye:monoazo dye=2:8 to 5:5 is preferred because it provides high blackness and high solubility in the organic solvent contained in the ink composition.

[0067] Examples of the solvent used in the iron complexation step include water, a water-organic solvent mixed solution, and an organic solvent, among which a water-organic solvent mixed solvent is preferred. Examples of the organic solvent include alcohol-based solvents, glycol-based solvents, amide-based solvents, ether-based solvents, ketone-based solvents, sulfoxide-based solvents, and aromatic hydrocarbon-based solvents, among which alcohol-based solvents, glycol-based solvents, amide-based solvents, and sulfoxide-based solvents are preferred.

[0068] Specific examples of preferred organic solvents include alcohol-based solvents such as ethanol, n-propanol, isopropanol, n-butanol, isobutanol, amyl alcohol, benzyl alcohol, cyclohexanol, and diacetone alcohol; glycol alkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, and dipropylene glycol monoethyl ether; glycol acetates such as ethylene glycol monoacetate and propylene glycol monoacetate; glycol-based solvents such as glycols such as ethylene glycol, diethylene glycol, trimethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, and butanediol; and amide-based solvents such as N-methylformamide, N,N-dimethylformamide, N-ethylformamide, N,N-diethylformamide, N-methylacetamide, and N,N-dimethylacetamide. Examples of sulfoxide solvents include sulfolane, 3-methylsulfolane, dimethyl sulfoxide, etc. Among these, amide solvents are preferred.

[0069] Examples of iron-forming agents used in the iron complexation step include ferric sulfate, ferrous sulfate, ferric chloride, ferrous chloride, ferric nitrate, iron acetate, and iron lactate. The amount of iron-forming agent is preferably 1 / 2 to 2 equivalents, more preferably 1 / 2 to 2 / 3, relative to the total equivalents of the disazo dye and monoazo dye. The iron-forming reaction is preferably carried out at a temperature appropriate for the type of solvent used, while heating (including reflux stirring). The iron-forming reaction may be carried out in the presence of additives such as a reaction accelerator or pH adjuster. By adjusting the pH by adding an acid or base, any cation X combined with the azo iron complex anion during the reaction can be easily obtained. + to the desired cation A +The cation can be prepared as, for example, a hydrogen ion, a sodium ion, a potassium ion, an ammonium ion, a monovalent alkyl group-containing ammonium ion, or a mixture thereof.

[0070] In the third step, the disazo dye obtained in the first step and the monoazo dye obtained in the second step are mixed together, followed by the ferric reaction. However, the third step is not limited to this. Alternatively, a disazo dye or a monoazo dye may be added to the solvent, followed by the monoazo dye or disazo dye, and then an ferric agent may be added to carry out the ferric reaction with trivalent iron. Alternatively, a disazo dye or a monoazo dye may be added to the solvent, followed by the ferric agent to carry out the ferric reaction, followed by the monoazo dye or disazo dye, followed by the ferric agent if necessary to carry out the ferric reaction with trivalent iron. In this case, the excess azo dye that has previously undergone the ferric reaction and another azo dye added later undergo an ferric reaction to produce a disazo-monoazo iron complex.

[0071] The disazo dye and the monoazo dye may each be used alone, or a mixture of two or more dyes having different substituents or different bonding positions of the substituents may be used, for example, a mixture of one disazo dye and two monoazo dyes, or a mixture of two disazo dyes and one monoazo ligand.

[0072] Step 4: Changing and preparing the cation of the azo iron complex dye The fourth step is a step of changing or preparing the cation of the azo iron complex dye, which is an ion exchange step in which the cation of the azo iron complex dye obtained in the step of converting the azo dye mixture into an iron complex using, for example, an alkali metal solution, an ammonium solution, and / or a monovalent amine having an alkyl group having 3 to 18 carbon atoms, is exchanged for a desired cation.

[0073] For example, if the cations of the azo-iron complex dye obtained in the above step are hydrogen ions or alkali metal ions, these cations are exchanged with an ammonium cation exchange agent. This cation exchange reaction yields an azo-iron complex dye with ammonium cations introduced, as shown in the following chemical formula (15). [ka] (In chemical formula (15), R 1 ~R 7 is the same as chemical formula (1), and R 8 ~R 10 is the same as chemical formula (4), and X + is any cation.)

[0074] The ammonium forming agent may be an aqueous ammonium solution or a monovalent amine compound having an alkyl group having a carbon number of 3 to 18. The ammonium forming agent may be used alone or in combination.

[0075] By adjusting the conditions, such as the amount of acid, base, and ammonium cation exchange agent used for cation exchange and the reaction temperature, it is possible to obtain an azo iron complex having mixed cations. It is possible to obtain an azo iron complex in which 86 mol % or more, especially 90 mol % or more of the cations in the mixed cation are the desired ammonium ions.

[0076] The cation exchange reaction in Step 4 can be carried out simultaneously or sequentially with the iron-containing reaction in Step 3. Step 4 may also be carried out by adding an ammonium-containing agent together with an organic solvent when preparing the ink composition.

[0077] 5th process: Filtering, washing, drying and pulverizing the azo iron complex dye The fifth step is carried out as necessary after the third or fourth step, and optionally includes a filtering step, a washing step, a drying step, and a pulverizing step.

[0078] The filtration step is a step in which the reaction solution containing the azo-iron complex dye obtained in the third step, the iron complexation step (or the subsequent alkali treatment) or the ion exchange step, is separated into a solid azo-iron complex dye and the solvent by filtration to obtain a wet cake of the azo-iron complex dye. Filtration methods include heavy-pressure filtration methods such as paper filtration, bag filtration, and centrifugation; vacuum filtration using filters such as Nutsche filters, Moore filters, disc filters, drum filters, and Oliver filters; and pressure filtration methods such as filter presses, closed leaf filters, and closed multistage filters.

[0079] After the filtration step, a washing step may be carried out. The wet cake of the azo iron complex or azo iron complex dye is thoroughly washed with a washing liquid. Examples of the washing liquid include water and organic solvents, with water being preferred. This wet cake may be used as an intermediate in the next step.

[0080] After the washing step, a drying step may be performed to dry the wet cake of the azo iron complex dye. If necessary, a further drying step may be performed. The dried azo iron complex dye in the form of clumps is crushed or pulverized using a known pulverizer to a desired particle size.

[0081] In the azo iron complex dye of the present invention, the disazo ligand and monoazo ligand contained in the disazo-monoazo iron complex (DM form), the monoazo-monoazo iron complex (MM form), and the disazo-disazo iron complex (DD form), respectively, as well as specific examples of azo iron complex dyes in which these ligands are combined, are described in more detail below.

[0082] (disazo ligand) The disazo ligand (D ligand) which is the ligand of the azo iron complex dye of the present invention is specifically represented by the following chemical formula (16). [ka] (In chemical formula (16), R 1 and R 2 is the same as chemical formula (1), and R 3a ~R 3cone of R is an electron-withdrawing group selected from a cyano group, a nitro group, an acetyl group, a sulfoamide group, and a halogen atom, and the others are hydrogen atoms; 4a ~R 4c one of which is a linear or branched alkyl group having 1 to 5 carbon atoms or a linear or branched alkoxy group having 1 to 5 carbon atoms, and the others are hydrogen atoms.

[0083] In chemical formula (16), R 1 , R 2 , R 3a ~R 3c , and R 4a ~R 4c Specific substituents are shown in Table 1.

[0084] [Table 1]

[0085] (monoazo ligand) The monoazo ligand (M ligand) of the azo iron complex dye of the present invention is specifically represented by the following chemical formula (17). [ka] (In chemical formula (17), R 5a and R 5b are each independently a hydrogen atom, a nitro group, a sulfonamide group, or a halogen atom, and R 6a and R 6b are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, a nitro group, or a halogen atom; R 7a ~R 7f are each independently a hydrogen atom or a linear or branched alkyl group having 3 to 12 carbon atoms.) 5a and R 5b and R 6a and R 6b and R are preferably not all the same substituents at the same time. 7a ~R 7f It is preferred that one of these groups is an alkyl group and the others are all hydrogen atoms.

[0086] In chemical formula (17), R 5a , R 5b , R 6a , R 6b , and R 7a ~R 7f Specific substituents are shown in Table 2.

[0087] [Table 2]

[0088] The azo iron complex dye of the present invention contains at least a disazo-monoazo iron complex (DM form) in which one mole of each of at least one disazo ligand (D ligand) represented by the above chemical formula (16) and having a substituent, for example, as shown in Table 1, and at least one monoazo ligand (M ligand) represented by the above chemical formula (17) and having a substituent, for example, as shown in Table 2, is coordinated to an iron atom.

[0089] In addition to the DM form, the azo iron complex dye may also include a monoazo-monoazo iron complex (MM form) represented by the aforementioned chemical formula (17), specifically shown in Table 2, in which two moles of at least one M ligand are coordinated to one mole of iron atoms, and a disazo-disazo iron complex (DD form) represented by the aforementioned chemical formula (16), specifically shown in Table 1, in which two moles of at least one D ligand having a substituent are coordinated to one mole of iron atoms. The ratio of each azo iron complex species in such azo iron complex dyes, the D and M ligand species they possess, and the mixing ratio of the disazo dye (D dye) to the monoazo dye (M dye) required to obtain each azo iron complex dye are shown in Table 3. In Table 3, the symbols in the D and M ligand columns correspond to those in Tables 1 and 2.

[0090] [Table 3]

[0091] (Ink composition) The ink composition of the present invention contains an azo iron complex dye and an oil-based liquid medium as an organic solvent. The content of the azo iron complex dye in the ink composition is preferably 3 to 25% by mass, more preferably 5 to 15% by mass, and even more preferably 5 to 10% by mass. Examples of the organic solvent include ketone organic solvents, alcohol organic solvents, and ether organic solvents, with ketone organic solvents and alcohol organic solvents being preferred.

[0092] Examples of ketone organic solvents include lower alkyl ketones such as acetone, methyl ethyl ketone, dipropyl ketone, methyl isobutyl ketone, and methyl isopropyl ketone; and cyclic ketones such as cyclohexanone. Among these, methyl ethyl ketone is suitable for ink compositions for continuous inkjet printers because of its excellent solubility of resins, dispersibility of pigments, conductivity, and ink drying properties.

[0093] Alcohol-based organic solvents include lower alkyl alcohols such as methanol, ethanol, propanol, and isopropanol and butanol; and glycols such as dioxane, ethylene glycol, diethylene glycol, and triethylene glycol.

[0094] Examples of the ether-based organic solvent include glycol ethers and esters thereof. Specific examples of glycol ethers include ethylene glycol alkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monoisobutyl ether, ethylene glycol monophenyl glycol, ethylene glycol monobenzyl glycol, ethylene glycol dimethyl ether, and ethylene glycol diethyl ether; diethylene glycol alkyl ethers such as diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monophenyl glycol, diethylene glycol monobenzyl glycol, diethylene glycol dimethyl ether, and diethylene glycol diethyl ether; triethylene glycol alkyl ethers such as diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisopropyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monophenyl glycol, diethylene glycol monobenzyl glycol, diethylene glycol dimethyl ether, and diethylene glycol diethyl ether; triethylene glycol alkyl ethers such as propylene glycol monomethyl ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether, and triethylene glycol diethyl ether; propylene glycol alkyl ethers such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, and propylene glycol monophenyl ether; dipropylene glycol alkyl ethers such as dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monopropyl ether, and dipropylene glycol monopropyl ether; and tripropylene glycol alkyl ethers such as tripropylene glycol monomethyl ether and tripropylene glycol monobutyl ether.

[0095] In addition to the above, examples of the organic solvent include ester-based organic solvents such as ethyl acetate, ethyl propionate, ethyl lactate, propyl acetate, and butyl acetate; and aromatic hydrocarbon-based organic solvents such as toluene and xylene.

[0096] The organic solvents may be used alone or in combination of two or more kinds.

[0097] The ink composition of the present invention may contain a resin soluble in the above organic solvent. Specific examples of such a resin include cellulose-based resins, styrene-acrylic resins, terpene-phenol resins, polyvinyl butyral resins, ketone resins, maleic acid-based resins, rosin resins, acrylic resins, styrene-maleic acid resins, polyvinyl acetal resins, polyvinyl alcohol resins, rosin ester-based resins, silicone resins, phenolic resins, coumarone-indene resins, novolac resins, aldehyde resins, polyester resins, polyamide resins, polyimide resins, terpene resins, alkyd resins, urethane resins, acetal resins, epoxy resins, urea resins, melamine resins, and xylene resins. These resins may be used alone or in combination of two or more.

[0098] Specific examples of the cellulose-based resin include nitrocellulose; lower acyl group-substituted cellulose such as cellulose propionate, cellulose butyrate, cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate; lower alkyl group-substituted cellulose such as methyl cellulose and ethyl cellulose; cellulose nitrate; and hydroxypropyl cellulose.

[0099] These cellulose resins come in a variety of types, varying in the degree of hydroxyl group substitution and molecular weight. The cellulose resin is appropriately selected depending on the viscosity required for the ink composition. Examples include cellulose esters in which the hydroxyl groups of the cellulose resin are fully or partially modified with one or more esters having 2 to 8 carbon atoms, preferably 2 to 5 carbon atoms. Specifically, lower acyl group-substituted cellulose derivatives such as cellulose acetate propionate and cellulose acetate butyrate are preferred. Particularly preferred cellulose acetate butyrates have acetyl and butyryl substitution degrees of 2 to 20% and 32 to 53%, respectively. Furthermore, particularly preferred cellulose acetate propionates have acetyl and propionyl substitution degrees of 0.5 to 10% and 35 to 55%, respectively. The degree of substitution is defined as 100% when all three hydroxyl groups in one glucose unit are substituted.

[0100] The styrene-acrylic resin is a copolymer of a styrene-based monomer and an acrylic-based monomer, and preferably has an acid value of 120 or less and a molecular weight of 3,000 to 30,000. Examples of the styrene-based monomer include styrene, α-methylstyrene, and vinyltoluene. Examples of the acrylic-based monomer include acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, butyl acrylate, butyl methacrylate, amyl acrylate, amyl methacrylate, hexyl acrylate, hexyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, and 2-hydroxypropyl methacrylate.

[0101] Styrene-acrylic resins are commercially available, and examples thereof include JONCRYL® 68, 586, and 611 (manufactured by BASF), HIAMER® SBM-100, and HIAMER SAM-955 (manufactured by Sanyo Chemical Industries, Ltd.), and NICALITE® NC-6531 and NICALITE NC-6100 (manufactured by Nippon Carbide Corporation).

[0102] Terpene phenolic resins are copolymers of terpenes such as α-pinene, β-pinene, and dipentene with phenols such as phenol and bisphenol. Monomers are selected based on the requirements of the ink composition, and the molar ratio of each monomer is determined. Terpene phenolic resins are commercially available, such as YP90 and YP90L; YS Polystar S145, #2100, #2115, #2130, T80, T100, T115, T130, and T145; and Mighty Ace G125 and G150 (all manufactured by Yasuhara Chemical Co., Ltd.).

[0103] Polyvinyl butyral resin is a copolymer of polyvinyl alcohol and butyralaldehyde. The degree of butyralization, the content of hydroxyl groups and acetyl groups, and the degree of polymerization are set according to the requirements of the ink composition. From the viewpoints of the viscosity of the ink composition and solubility in solvents, it is preferable that the polyvinyl butyral resin has a relatively low degree of polymerization. Polyvinyl butyral resins are commercially available, and examples thereof include S-LEC (registered trademark) BL-1, BL-2, BL-3, BL-S, BM-1, BM-2, BM-5, BM-S, BH-3, BH-S, BX-1, BX-2, BX-5, BX-10, BX-55, and BX-L (manufactured by Sekisui Chemical Co., Ltd.); and Denka Butyral #2000-L, #3000-1, #3000-2, #3000-4, #3000-K, #4000-1, #4000-2, #5000-A, and #6000-C (manufactured by Denka Company Limited).

[0104] The ketone resin is a copolymer of a ketone compound and formaldehyde, and is preferably a polymer compound having an average molecular weight of 3,000 or more. The ketone resin may be chemically modified, such as by hydrogenation and / or end group modification. Ketone resins are commercially available, and examples thereof include Hilac (registered trademark) 111 and 222 (manufactured by Showa Denko Materials Inc.) and K-90 (manufactured by Arakawa Chemical Industries, Ltd.).

[0105] The maleic acid resin is preferably a rosin-modified maleic acid resin. The rosin-modified maleic acid resin is a polyester of rosin, maleic acid, and a polyhydric alcohol. Rosin-modified maleic acid resins are commercially available, such as Beccasite (registered trademark) P-720 and J-896 (manufactured by DIC Corporation) and Tespol (registered trademark) 1101, 1103, 1104, 1105, 1150, 1151, 1152, 1155, 1158, and 1161 (manufactured by Showa Denko Materials Co., Ltd.).

[0106] The ink composition of the present invention is suitable for use in inkjet printers, preferably industrial inkjet printers, and particularly charge-controlled continuous inkjet (CIJ) printers. Ink compositions for CIJ printers may contain a charge control agent to obtain the desired charge amount. In the ink composition of the present invention, the azo iron complex dye has high electrical conductivity, imparting a sufficient charge amount to the ink composition, so that a charge control agent is generally not required. On the other hand, when a particularly high charge amount is required for the ink composition, the ink composition may contain a charge control agent.

[0107] Charge control agents include conductive salts, such as salts of alkali metals such as lithium, sodium, and potassium; salts of alkaline earth metals such as magnesium and potassium; ammonium salts, and quaternary ammonium salts. Specific examples include perchlorates, thiocyanates, formates, acetates, sulfates, sulfonates, propionates, trifluoroacetates, triflates (trifluoromethanesulfonates), hexafluorophosphates, hexafluoroantimonates, tetrafluoroborates, picrates, and carboxylates, as well as tetrabutylammonium hexafluorophosphate, tetrabutylammonium bromide, and tetraphenylboron quaternary ammonium salts. Alkali metal halides and alkaline earth metal halides are also included. Examples of such halides include fluorides, chlorides, bromides, and iodides. The content of the charge control agent in the ink composition is 0.1 to 10% by mass, preferably 0.1 to 5% by mass, and more preferably 0.3 to 3% by mass.

[0108] The ink composition for a CIJ printer may contain a wetting agent to form droplets of a desired size when ejected from the nozzle of the CIJ printer. Examples of the wetting agent include surfactants, such as anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants.

[0109] Examples of anionic surfactants include fatty acid salts, alkyl sulfate salts, alkylaryl sulfonates, alkylnaphthalenesulfonates, dialkylsulfonates, dialkylsulfosuccinates, alkyl diaryl ether disulfonates, alkyl phosphates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylaryl ether sulfates, naphthalenesulfonate formalin condensates, polyoxyethylene alkyl phosphate salts, glycerol borate fatty acid esters, and polyoxyethylene glycerol fatty acid esters.

[0110] Cationic surfactants include alkylamine salts, quaternary ammonium salts, alkylpyridinium salts, and alkylimidazolium salts.

[0111] Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, polyoxyethylene oxypropylene block copolymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkylamines, fluorine-based nonionic surfactants, and silicone-based nonionic surfactants.

[0112] Amphoteric surfactants include alkyl betaines, alkyl amine oxides, and phosphatidyl cholines.

[0113] The ink composition of the present invention may contain a pH adjuster to suppress changes in the ink composition such as precipitation or sedimentation of dyes, etc., and deterioration in storage stability such as discoloration, etc. The pH adjuster is not particularly limited as long as it is added for the above purposes and can control the pH of the ink within the range of 7 to 8.

[0114] Specific examples of the pH adjuster include aliphatic substituted amines such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, and tripropylamine, and alkanolamines such as methanolamine, dimethanolamine, trimethanolamine, ethanolamine, diethanolamine, triethanolamine, propanolamine, dipropanolamine, and tripropanolamine. From the viewpoint of suppressing discoloration, alkanolamines such as triethanolamine are particularly preferred.

[0115] In addition to or in place of the charge control agent and humectant, the ink composition may contain additives to improve print quality, ink fixation, and the solution stability of the azo-iron complex dye, and to impart a desired viscosity and surface tension. Such additives include antifoaming agents, chemical stabilizers, UV stabilizers, and stabilizers that inhibit corrosion by salts; and biocides such as bactericides and fungicides.

[0116] The method for producing the ink composition will be described below. The azo-iron complex dye, organic solvent, resin, and optional additives are placed in a sealed container and stirred. These are mixed and dissolved uniformly, and then filtered through a membrane filter. The mixed solution may be heated as needed.

[0117] Ink compositions are used in CIJ printers as follows: The ink composition stored in an ink tank is sucked out by a pump and flows through a flow path toward the printer head. Droplets of the ink composition are ejected from a nozzle at the end of the printer head. The ink composition droplets become charged by passing through a charging electrode, and then pass through a deflection electrode. The ink composition droplets are deflected in a predetermined pattern to depict the desired characters or figures, and reach the print medium that passes beyond the deflection electrode. This results in characters and other images being printed on the print medium. For example, lot numbers and dates such as the date of manufacture or expiration date are printed on the print medium.

[0118] Examples of print media include slips, cardboard boxes, product packaging, and plastic bottles, which are made of plastics such as polyolefins like polyethylene and polypropylene, polyvinyl chloride, polyesters like polyamide and PET, polycarbonate, polyacetal, polyacrylate, polyurethane, polyether, polystyrene, and polyimide.

[0119] The ink composition of the present invention can be used with a CIJ printer to print on glass, such as soda-lime glass and boron silicate glass; the above-mentioned plastics; and metals, such as aluminum, iron, tin, and copper. When the printing medium is metal, good printing can be achieved by pretreating the metal surface by sandblasting or pickling.

[0120] The ink composition is also suitable as an ink for a writing instrument. When the ink composition is used as an ink for a writing instrument, specifically as an ink for a marking pen, the content of the azo iron complex dye is 5 to 10 mass %, and when used as an ink for a ballpoint pen, the content is 15 to 25 mass %. [Example]

[0121] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In these examples, % means % by mass.

[0122] (Preparation Example 1: Synthesis of Disazo Dye D-1) 118.0 g (1.0 mol) of p-aminobenzonitrile and 339 g of 35% hydrochloric acid were added to 592.0 g of ion-exchanged water, cooled to −3° C. in an ice bath, and 178 g of a 40% aqueous solution of sodium nitrite was gradually added to carry out a diazotization reaction, yielding a diazonium salt solution.

[0123] In a separate beaker, 123.0 g (1.0 mol) of 2-amino-p-cresol and 104.0 g of 35% hydrochloric acid were added to 412 g of ion-exchanged water and dissolved. 4 g of 1-butanol and 140 g of ice were added and cooled to 2°C, and the previously prepared diazonium salt solution was slowly added dropwise. The pH was adjusted to 4.9 with 20% aqueous sodium hydroxide, and the precipitate was filtered under reduced pressure. After washing with ion-exchanged water, 664 g of a wet cake of the monoazo compound represented by the following chemical formula (18) was obtained.

[0124] [ka]

[0125] 304 g (0.42 mol) of the monoazo compound wet cake obtained earlier was added to 402 g of ion-exchanged water and stirred to disperse. 49 g of 48% potassium hydroxide aqueous solution was gradually added. After stirring for 30 minutes, 126 g of ion-exchanged water and 84 g of ice were added, and the mixture was stirred for another 30 minutes. After stirring was completed, 75 g of 40% sodium nitrite aqueous solution was added and stirred for 5 minutes. Next, 153 g of 35% hydrochloric acid was added dropwise using a dropping funnel. After the dropwise addition, the mixture was stirred for approximately 1 hour to obtain a diazonium salt solution.

[0126] In a separate beaker, 88 g (0.40 mol) of N,N-dibutyl-aminophenol and 133 g of 48% aqueous potassium hydroxide solution were added to 1332 g of methanol and stirred under ice cooling to dissolve. The previously obtained diazonium salt solution was added dropwise to the mixture and stirred for 12 hours. The precipitate was filtered under reduced pressure and washed with ion-exchanged water to obtain 409 g of a wet cake. This was dried at 80 °C to obtain 163.6 g of disazo dye D-1, represented by the following chemical formula (19):

[0127] [ka]

[0128] (Preparation Example 2: Synthesis of Disazo Dye D-2) 107.5 g (0.78 mol) of p-nitroaniline and 290 g of 35% hydrochloric acid were added to 200.0 g of ion-exchanged water, and the mixture was heated to 65°C while stirring. After stirring for 1 hour, the mixture was cooled to -3°C in an ice bath. 138.5 g of a 40% aqueous solution of sodium nitrite was gradually added to the mixture, and a diazotization reaction was carried out to obtain a diazonium salt solution.

[0129] In a separate beaker, 96.0 g (0.78 mol) of 2-amino-p-cresol and 81.0 g of 35% hydrochloric acid were added to 500 g of ion-exchanged water and dissolved. 4 g of 1-butanol and 140 g of ice were added, and the mixture was cooled to 2°C in an ice bath. The previously prepared diazonium salt solution was then slowly added dropwise. The pH was adjusted to 4.8 with 20% aqueous sodium hydroxide, and the precipitate was filtered under reduced pressure. After washing with ion-exchanged water, 163.1 g of a wet cake of the monoazo compound represented by the following chemical formula (20) was obtained.

[0130] [ka]

[0131] 162 g (0.60 mol) of the monoazo compound wet cake obtained above and 147.5 g of 35% hydrochloric acid were added to 1643 g of N,N-dimethylformamide, and the mixture was heated to 60°C with stirring to dissolve. After visually confirming that no lumps were present, the mixture was cooled to 20°C in an ice bath. 105.7 g of a 40% aqueous sodium nitrite solution was gradually added, and the mixture was stirred at room temperature for 2 hours to obtain a diazonium salt solution.

[0132] In a separate beaker, 131.7 g (0.60 mol) of N,N-dibutyl-aminophenol and 133 g of 48% potassium hydroxide aqueous solution were added to 1200 g of methanol and stirred under ice cooling to dissolve. The previously obtained diazonium salt solution was added dropwise to the mixture and stirred for 12 hours. The precipitate was filtered under reduced pressure and washed with ion-exchanged water to obtain 409 g of a wet cake. This was dried at 80 °C to obtain 75.2 g of disazo dye D-2, represented by the following chemical formula (21).

[0133] [ka]

[0134] (Preparation Example 3: Synthesis of Disazo Dye D-3) 172 g (1.00 mol) of p-aminobenzenesulfonamide and 271 g of 35% hydrochloric acid were added to 600.0 g of ion-exchanged water and cooled to -3°C in an ice bath. 179.3 g of 40% aqueous sodium nitrite solution was gradually added to the mixture. 2.4 g of urea was then added to carry out the diazotization reaction, yielding a diazonium salt solution.

[0135] In a separate beaker, 123.4 g (1.00 mol) of 2-amino-p-cresol and 125.0 g of 35% hydrochloric acid were added to 440 g of ion-exchanged water and dissolved. 4 g of 1-butanol and 140 g of ice were added, and the mixture was cooled to 2°C in an ice bath. The previously prepared diazonium solution was then slowly added dropwise. The pH was adjusted to 4.8 with 20% aqueous sodium hydroxide, and the precipitate was filtered under reduced pressure. After washing with ion-exchanged water, 719.5 g of a wet cake of the monoazo compound represented by the following chemical formula (22) was obtained.

[0136] [ka]

[0137] 700 g (0.90 mol) of the monoazo compound wet cake obtained above was dispersed in 700 g of ion-exchanged water, and then 82.7 g of 48% aqueous sodium hydroxide solution was gradually added and stirred for 1 hour. 700 g of ice was added in an ice bath, and the mixture was cooled to 1°C, and then 162.0 g of 40% aqueous sodium nitrite solution was gradually added. After stirring for a while, 300 g of ice was added, and 287.0 g of 35% hydrochloric acid was gradually added thereto. The mixture was stirred at room temperature for 2 hours to obtain a diazonium salt solution.

[0138] In a separate beaker, 193.2 g (0.88 mol) of N,N-dibutyl-aminophenol and 217.5 g of 48% aqueous sodium hydroxide solution were added to 690 g of methanol and stirred under ice cooling until dissolved. The previously obtained diazonium salt solution was added dropwise and stirred for 12 hours. After adjusting the pH to 4.0 using 35% hydrochloric acid, the mixture was heated to 35°C and stirred for 1 hour. The precipitate was filtered under reduced pressure and washed with ion-exchanged water to obtain 441.1 g of a wet cake. This was dried at 80°C to obtain 175.2 g of disazo dye D-3, represented by the following chemical formula (23):

[0139] [ka]

[0140] (Preparation Example 4: Synthesis of disazo dye D-4) 67.6 g (0.50 mol) of 4-acetaminophenone and 114.6 g of 35% hydrochloric acid were added to 688.0 g of ion-exchanged water and cooled to -3°C in an ice bath. 90.6 g of 40% aqueous sodium nitrite solution was gradually added to the mixture to carry out the diazotization reaction. After stirring for 1 hour, 1.9 g of thiourea was added to obtain a diazonium salt solution.

[0141] In a separate beaker, 61.6 g (0.50 mol) of 2-amino-p-cresol and 52.1 g of 35% hydrochloric acid were added to 1111 g of methanol and dissolved. After cooling to 5°C in an ice bath, the previously prepared diazonium solution was slowly added dropwise. The precipitate was filtered under reduced pressure, washed with ion-exchanged water, and dried at 80°C to obtain 56.3 g of a monoazo compound represented by the following chemical formula (24).

[0142] [ka]

[0143] 56.0 g (0.18 mol) of the monoazo compound obtained above and 45.4 g of 35% hydrochloric acid were added to 415 g of N,N-dimethylformamide solution, and 84 g of ice was added in an ice bath to cool to 2° C. 32.6 g of 40% aqueous sodium nitrite solution was slowly added thereto and stirred for 1 hour, and 1.8 g of sulfamic acid was added thereto to obtain a diazonium salt solution.

[0144] In a separate beaker, 40.6 g (0.18 mol) of N,N-dibutyl-aminophenol and 79.1 g of 20% aqueous sodium hydroxide solution were added to 612.1 g of methanol and stirred under ice cooling to dissolve. The previously obtained diazonium salt solution was added dropwise to the mixture and stirred for 3 hours. The precipitate was filtered under reduced pressure, washed with methanol, and dried at 80 °C to obtain 15.9 g of disazo dye D-4, represented by the following chemical formula (25).

[0145] [ka]

[0146] (Preparation Example 5: Synthesis of monoazo dye M-1) 7.5 g (0.05 mol) of 5-nitro-2-aminophenol and 13.6 g of 35% hydrochloric acid were dissolved in 50.0 g of isopropanol, and 8.0 g of a 40% aqueous sodium nitrite solution was gradually added in an ice bath to diazotize the mixture, thereby obtaining a diazonium salt solution.

[0147] 200 g of water was placed in another beaker, and 26.1 g of a 20% aqueous solution of sodium hydroxide was added, followed by 6.6 g of 2-naphthol, which was dispersed. The previously prepared diazonium salt was added dropwise to this dispersion, and the mixture was allowed to react for 3 hours. The pH was then adjusted to 2.8, and the precipitated monoazo compound was filtered and washed with water to obtain 82.5 g of a wet cake of monoazo dye M-1, represented by the following chemical formula (26):

[0148] [ka]

[0149] (Preparation Example 6: Synthesis of monoazo dye M-2) 7.5 g (0.05 mol) of 4-nitro-2-aminophenol and 13.6 g of 35% hydrochloric acid were dissolved in 50.0 g of isopropanol, and 8.0 g of a 40% aqueous sodium nitrite solution was gradually added in an ice bath to diazotize the mixture, thereby obtaining a diazonium salt solution.

[0150] In another beaker, 200 g of water was added, 26.1 g of 20% aqueous sodium hydroxide solution was added, and 6.6 g (0.05 mol) of 2-naphthol was added and dispersed. The diazonium salt prepared earlier was added dropwise to this dispersion and allowed to react for 3 hours. The pH was then adjusted to 2.8, and the precipitated monoazo compound was filtered and washed with water to obtain 81.8 g of a wet cake of monoazo dye M-2 represented by the following chemical formula (27).

[0151] [ka]

[0152] (Preparation Example 7: Synthesis of monoazo dye M-3) 7.0 g (0.05 mol) of 4-chloro-2-aminophenol and 13.6 g of 35% hydrochloric acid were dissolved in 50.0 g of isopropanol, and 8.0 g of a 40% aqueous sodium nitrite solution was gradually added in an ice bath to diazotize the mixture, thereby obtaining a diazonium salt solution.

[0153] In another beaker, 200 g of water was placed, 26.1 g of 20% aqueous sodium hydroxide solution was added, and 6.6 g (0.05 mol) of 2-naphthol was added and dispersed. The diazonium salt prepared earlier was added dropwise to this dispersion and allowed to react for 3 hours. The pH was then adjusted to 2.8, and the precipitated monoazo compound was filtered and washed with water to obtain 80.1 g of a wet cake of monoazo dye M-3 represented by the following chemical formula (28). [ka]

[0154] (Preparation Example 8: Synthesis of monoazo dye M-4) 7.0 g (0.05 mol) of 4-chloro-2-aminophenol and 13.6 g of 35% hydrochloric acid were dissolved in 50.0 g of isopropanol, and 8.0 g of a 40% aqueous sodium nitrite solution was gradually added in an ice bath to diazotize the mixture, thereby obtaining a diazonium salt solution.

[0155] In another beaker, 200 g of water was added, 26.1 g of 20% aqueous sodium hydroxide solution was added, and 6.6 g (0.05 mol) of 2-naphthol was added and dispersed. The diazonium salt prepared earlier was added dropwise to this dispersion and allowed to react for 3 hours. The pH was then adjusted to 2.8, and the precipitated monoazo compound was filtered and washed with water to obtain 80.1 g of a wet cake of monoazo dye M-3 represented by the following chemical formula (29). [ka]

[0156] (Preparation Example 9: Synthesis of monoazo dye M-5) 34.0 g (0.24 mol) of 4-chloro-2-aminophenol and 82.2 g of 35% hydrochloric acid were dissolved in 182.0 g of isopropanol, and 48.9 g of a 40% aqueous sodium nitrite solution was gradually added in an ice bath to diazotize the mixture, thereby obtaining a diazonium salt solution.

[0157] In another beaker, 182 g of isopropanol was placed, 107.2 g of 20% aqueous sodium hydroxide solution was added, and 60.7 g (0.24 mol) of 6-tert-octyl-2-naphthol was dissolved. The diazonium salt prepared above was added dropwise to this solution, and the reaction was allowed to proceed for 2 hours. The precipitate was then filtered, washed with water, and dried to obtain 93.5 g of monoazo dye M-5 represented by the following chemical formula (30). [ka]

[0158] Example 1: Synthesis of azo iron complex dye A-1 5.3 g (0.011 mol) of the disazo dye D-1 obtained in Preparation Example 1 and 22.1 g (water content 40%, 0.043 mol) of the wet cake of the monoazo dye M-1 obtained in Preparation Example 5 were added to 120 g of N,N-dimethylformamide solution and stirred at 55°C for 1 hour (disazo dye:monoazo dye = 2:8 mol). 12.4 g (0.013 mol) of a 41% aqueous solution of ferric sulfate was added dropwise thereto, and after the addition, the temperature was raised to 120°C and stirred for 3 hours. After the reaction was completed, the solution was allowed to cool to room temperature, and 9.0 g of a 20% aqueous solution of sodium hydroxide was added thereto to adjust the pH to 10.0. The reaction solution was then diluted with 5% tert-alkyl (C 12 ~C 14 103.6 g of an aqueous solution of a primary amine (manufactured by The Dow Chemical Company; trade name: PRIMENE 81-R) was gradually added, and the mixture was heated and stirred at 40°C for 1 hour. The precipitate was then filtered, washed with water, and dried to obtain 23.1 g of azo iron complex dye A-1, which contains a disazo-monoazo iron complex (DM form) represented by the following chemical formula (31DM), a monoazo-monoazo iron complex (MM form) represented by the following chemical formula (31MM), and a disazo-disazo iron complex (DD form) represented by the following chemical formula (31DD).

[0159] [ka]

[0160] [ka]

[0161] [ka]

[0162] (Absorbance measurement) A solution of azo iron complex dye A-1 was prepared in methyl ethyl ketone to a concentration of 10 mg / 1000 ml (10 ppm). The absorbance of this solution was measured using an ultraviolet-visible spectrophotometer (Shimadzu Corporation; product name UV-1700). The visible absorption spectrum of azo iron complex dye A-1 is shown in Figure 1. A solution containing azo iron complex dye A-1 at a 5% concentration exhibited a sufficiently black color.

[0163] (Measurement of electrical conductivity) A 6% solution of azo iron complex dye A-1 in methyl ethyl ketone was prepared and measured using a conductivity meter (manufactured by Eutech Instruments; product name: CyberScan CON100). The resulting electrical conductivity K was 1530 μS / cm. Furthermore, a 6% solution of azo iron complex dye A-1 in methyl ethyl ketone was prepared and measured using a conductivity meter (manufactured by Knick; product name: Conducell 4USF-PG120). The resulting electrical conductivity K was 1530 μS / cm.

[0164] (Measurement of alkali metal ion content) The alkali metal ion (Na ion) content in the azo-iron complex dye was measured using an atomic absorption spectrophotometer (Varian Technologies Japan Limited; product name: SpectrAA-220FS). As a result, the alkali metal ion content was found to be 1000 ppm or less.

[0165] Example 2: Synthesis of azo iron complex dye A-2 9.69 g (0.020 mol) of the disazo dye D-1 obtained in Preparation Example 1 and 10.6 g (water content 42%, 0.020 mol) of the wet cake of the monoazo dye M-2 obtained in Preparation Example 6 were added to 100 g of N,N-dimethylformamide solution and stirred at 55°C for 1 hour (disazo dye:monoazo dye = 5:5 mol). 9.5 g (0.010 mol) of a 41% aqueous solution of ferric sulfate was added dropwise thereto, and after the addition, the temperature was raised to 120°C and stirred for 3 hours. After the reaction was completed, the solution was allowed to cool to room temperature, and 9.0 g of a 20% aqueous solution of sodium hydroxide was added thereto to adjust the pH to 10.1. The reaction solution was then diluted with 5% tert-alkyl (C 12 ~C14 80.6 g of an aqueous solution of a primary amine (manufactured by The Dow Chemical Company; trade name: PRIMENE 81-R) was gradually added, and the mixture was heated and stirred at 40°C for 1 hour. The precipitate was then filtered, washed with water, and dried to obtain 15.6 g of azo iron complex dye A-2 containing the DM form represented by the following chemical formula (32DM), the MM form represented by the following chemical formula (32MM), and the DD form represented by the following chemical formula (32DD).

[0166] [ka]

[0167] [ka]

[0168] [ka]

[0169] The absorbance, electrical conductivity, and alkali metal ion content of azo iron complex dye A-2 were measured in the same manner as for azo iron complex dye A-1. The visible absorption spectrum of azo iron complex dye A-2 is shown in Figure 2. A solution containing azo iron complex dye A-2 at a 5% concentration exhibited a sufficiently black color. The electrical conductivity K of azo iron complex dye A-2 was 908 μS / cm, and the alkali metal ion content was less than 1000 ppm.

[0170] (Example 3: Synthesis of azo iron complex dye A-3) 5.33 g (0.011 mol) of the disazo dye D-1 obtained in Preparation Example 1 and 21.9 g (40% water content, 0.044 mol) of the wet cake of the monoazo dye M-3 obtained in Preparation Example 7 were added to 100 g of N,N-dimethylformamide solution and stirred at 55°C for 1 hour (disazo dye:monoazo dye = 2:8 mol). 12.9 g (0.013 mol) of a 41% aqueous solution of ferric sulfate was added dropwise thereto, and after the addition, the temperature was raised to 120°C and stirred for 3 hours. After the reaction was completed, the solution was allowed to cool to room temperature, and 9.0 g of a 20% aqueous solution of sodium hydroxide was added to adjust the pH to 10.2. The reaction solution was then diluted with 5% tert-alkyl (C 12 ~C 14 103.0 g of an aqueous solution of a primary amine (manufactured by The Dow Chemical Company; trade name: PRIMENE 81-R) was gradually added, and the mixture was heated and stirred at 40°C for 1 hour. The precipitate was then filtered, washed with water, and dried to obtain 17.8 g of azo iron complex dye A-3 containing the DM form represented by the following chemical formula (33DM), the MM form represented by the following chemical formula (33MM), and the DD form represented by the following chemical formula (33DD).

[0171] [ka]

[0172] [ka]

[0173] [ka]

[0174] The absorbance, electrical conductivity, and alkali metal ion content of azo iron complex dye A-3 were measured in the same manner as for azo iron complex dye A-1. The visible absorption spectrum of azo iron complex dye A-3 is shown in Figure 3. A solution containing azo iron complex dye A-3 at a 5% concentration exhibited a sufficiently black color. The electrical conductivity K of azo iron complex dye A-3 was 1260 μS / cm, and the alkali metal ion content was less than 1000 ppm.

[0175] Example 4: Synthesis of azo iron complex dye A-4 5.55 g (0.011 mol) of disazo dye D-2 obtained in Preparation Example 2 and 21.9 g (water content 40%, 0.043 mol) of wet cake of monoazo ligand M-2 obtained in Preparation Example 6 were added to 100 g of N,N-dimethylformamide solution and stirred at 55°C for 1 hour (disazo dye:monoazo dye = 2:8 mol). 12.4 g (0.013 mol) of 41% aqueous ferric sulfate solution was added dropwise, and after the addition, the temperature was raised to 120°C and stirred for 3 hours. After the reaction was completed, the solution was allowed to cool to room temperature, and 9.0 g of 20% aqueous sodium hydroxide solution was added to adjust the pH to 10.1. The reaction solution was then diluted with 5% tert-alkyl (C 12 ~C 14 102.8 g of an aqueous solution of a primary amine (manufactured by The Dow Chemical Company; trade name: PRIMENE 81-R) was gradually added, and the mixture was heated and stirred at 40°C for 1 hour. The precipitate was then filtered, washed with water, and dried to obtain 16.5 g of azo iron complex dye A-4 containing the DM form represented by the following chemical formula (34DM), the MM form represented by the following chemical formula (34MM), and the DD form represented by the following chemical formula (34DD).

[0176] [ka]

[0177] [ka]

[0178] [ka]

[0179] The absorbance, electrical conductivity, and alkali metal ion content of azo iron complex dye A-4 were measured in the same manner as for azo iron complex dye A-1. The visible absorption spectrum of azo iron complex dye A-4 is shown in Figure 4. A solution containing azo iron complex dye A-4 at a 5% concentration exhibited a sufficiently black color. The electrical conductivity K of azo iron complex dye A-4 was 1275 μS / cm, and the alkali metal ion content was less than 1000 ppm.

[0180] Example 5: Synthesis of azo iron complex dye A-5 12.9 g (0.024 mol) of the disazo dye D-3 obtained in Preparation Example 3 and 18.7 g (40% water content, 0.036 mol) of the wet cake of the monoazo dye M-2 obtained in Preparation Example 6 were added to 120 g of N,N-dimethylformamide solution and stirred at 55°C for 1 hour (disazo dye:monoazo dye = 4:6 mol). 15.0 g (0.015 mol) of a 41% aqueous solution of ferric sulfate was added dropwise thereto, and after the addition, the temperature was raised to 120°C and stirred for 3 hours. After the reaction was completed, the solution was allowed to cool to room temperature, and 9.0 g of a 20% aqueous solution of sodium hydroxide was added to adjust the pH to 9.9. The reaction solution was then diluted with 5% tert-alkyl (C 12 ~C 14 125.3 g of an aqueous solution of a primary amine (manufactured by The Dow Chemical Company; trade name: PRIMENE 81-R) was gradually added, and the mixture was heated and stirred at 40°C for 1 hour. The precipitate was then filtered, washed with water, and dried to obtain 15.9 g of azo iron complex dye A-5 containing the DM form represented by the following chemical formula (35DM), the MM form represented by the following chemical formula (35MM), and the DD form represented by the following chemical formula (35DD).

[0181] [ka]

[0182] [ka]

[0183] [ka]

[0184] The absorbance, electrical conductivity, and alkali metal ion content of azo iron complex dye A-5 were measured in the same manner as for azo iron complex dye A-1. The visible absorption spectrum of azo iron complex dye A-5 is shown in Figure 5. A solution containing azo iron complex dye A-5 at a 5% concentration exhibited a sufficiently black color. The electrical conductivity K of azo iron complex dye A-5 was 920 μS / cm, and the alkali metal ion content was less than 1000 ppm.

[0185] Example 6: Synthesis of azo iron complex dye A-6 5.3 g (0.011 mol) of disazo dye D-1 obtained in Preparation Example 1, 11.2 g (40% water content, 0.022 mol) of wet cake of monoazo dye M-1 obtained in Preparation Example 5, and 11.6 g (42% water content, 0.022 mol) of wet cake of monoazo dye M-2 obtained in Preparation Example 6 were added to 120 g of N,N-dimethylformamide solution and stirred at 55°C for 1 hour (disazo dye:monoazo dye 1:monoazo dye 2 = 2:4:4 mol). 12.4 g (0.013 mol) of 41% aqueous ferric sulfate solution was added dropwise, and after the addition, the temperature was raised to 120°C and stirred for 3 hours. After the reaction was completed, the solution was allowed to cool to room temperature, and the pH was adjusted to 10.1 by adding 9.0 g of 20% aqueous sodium hydroxide solution. The reaction solution was then diluted with 5% tert-alkyl (C 12 ~C 14 100.4 g of an aqueous solution of a primary amine (manufactured by The Dow Chemical Company; trade name: PRIMENE 81-R) was gradually added, and the mixture was heated and stirred at 40°C for 1 hour. The precipitate was then filtered, washed with water, and dried to obtain 14.4 g of azo iron complex dye A-6 containing the DM form represented by the following chemical formula (36DM), the MM form represented by the following chemical formula (36MM), and the DD form represented by the following chemical formula (36DD).

[0186] [ka]

[0187] [ka]

[0188] [ka]

[0189] The absorbance, electrical conductivity, and alkali metal ion content of azo iron complex dye A-6 were measured in the same manner as for azo iron complex dye A-1. The visible absorption spectrum of azo iron complex dye A-6 is shown in Figure 6. As can be seen from the figure, a solution containing azo iron complex dye A-6 at a 5% concentration exhibited a sufficiently black color. Furthermore, the electrical conductivity K of azo iron complex dye A-6 was 1450 μS / cm, and the alkali metal ion content was less than 1000 ppm.

[0190] Example 7: Synthesis of azo iron complex dye A-7 12.9 g (0.024 mol) of disazo dye D-3 obtained in Preparation Example 5, 32.0 g (water content 40%, 0.056 mol) of wet cake of monoazo dye M-4 obtained in Preparation Example 8, 200 g of ion-exchanged water, 12 g of n-butanol, and 48 g of 20% aqueous sodium hydroxide solution were added and stirred at 70°C for 30 minutes (disazo dye:monoazo dye = 3:7 mol). 20.0 g (0.021 mol) of 41% aqueous ferric sulfate solution was added dropwise thereto, and after the addition, the temperature was raised to 90°C and stirred for 3 hours. After the reaction was completed, the reaction solution was allowed to cool to room temperature, and 5% tert-alkyl (C 12 ~C 14 191.3 g of an aqueous solution of a primary amine (manufactured by The Dow Chemical Company; trade name: PRIMENE 81-R) was gradually added, and the mixture was heated and stirred at 40°C for 1 hour. The precipitate was then filtered, washed with water, and dried to obtain 40.2 g of azo iron complex dye A-7 containing the DM form represented by the following chemical formula (37DM), the MM form represented by the following chemical formula (37MM), and the DD form represented by the following chemical formula (37DD).

[0191] [ka]

[0192] [ka]

[0193] [ka]

[0194] The absorbance, electrical conductivity, and alkali metal ion content of azo iron complex dye A-7 were measured in the same manner as for azo iron complex dye A-1. The visible absorption spectrum of azo iron complex dye A-7 is shown in Figure 7. A solution containing azo iron complex dye A-7 at a concentration of 5% exhibited a sufficiently black color. The electrical conductivity K of azo iron complex dye A-7 was 826 μS / cm, and the alkali metal ion content was less than 1000 ppm.

[0195] (Comparative Example 1: Synthesis of azo iron complex dye B-1) 42.5 g of the wet cake of monoazo dye M-2 obtained in Preparation Example 6 (water content 42%, 0.080 mol), 120 g of ion-exchanged water, and 5.7 g of n-butanol were added to 12.5 g of 20% aqueous sodium hydroxide solution and stirred at 90°C for 1 hour (disazo dye:monoazo dye = 0:10 mol). 40.7 g (0.042 mol) of 41% aqueous ferric sulfate solution was added dropwise thereto, and after the addition, the temperature was raised to 90°C and stirred for 3 hours. After the reaction was completed, the solution was allowed to cool to room temperature, and 9.0 g of 20% aqueous sodium hydroxide solution was added to adjust the pH to 10.1. The reaction solution was then diluted with 5% tert-alkyl (C 12 ~C 14 100.4 g of an aqueous solution of a primary amine (manufactured by The Dow Chemical Company; trade name: PRIMENE 81-R) was gradually added, and the mixture was heated and stirred at 40°C for 1 hour. The precipitate was then filtered, washed with water, and dried. As a result, 27.4 g of azo iron complex dye B-1 consisting solely of a monoazo-monoazo iron complex, as represented by the following chemical formula (38MM), was obtained.

[0196] [ka]

[0197] The absorbance, electrical conductivity, and alkali metal ion content of azo iron complex dye B-1 were measured in the same manner as for azo iron complex dye A-1. A solution containing azo iron complex dye B-1 at a concentration of 5% was brownish-red. The electrical conductivity K of azo iron complex dye B-1 was 1450 μS / cm, and the alkali metal ion content was less than 1000 ppm.

[0198] Comparative Example 2: Synthesis of azo iron complex dye B-2 21.9 g of the wet cake of disazo dye D-1 obtained in Preparation Example 1 (water content 42%, 0.026 mol) and 2.9 g of urea were added to 100 g of N,N-dimethylformamide solution and stirred at 50°C for 1 hour (disazo dye:monoazo dye = 10:0 mol). 6.33 g (0.007 mol) of 41% aqueous ferric sulfate solution was added dropwise thereto, and after the addition, the temperature was raised to 120°C and stirred for 3 hours. After the reaction was completed, the solution was allowed to cool to room temperature, and 5.0 g of 20% aqueous sodium hydroxide solution was added to adjust the pH to 10.9. The reaction solution was then diluted with 5% tert-alkyl (C 12 ~C 14 80.1 g of an aqueous solution of a primary amine (manufactured by The Dow Chemical Company; trade name: PRIMENE 81-R) was gradually added, and the mixture was heated and stirred at 35°C for 2 hours. The precipitate was then filtered, washed with water, and dried. As a result, 9.41 g of azo-iron complex dye B-2 consisting solely of a disazo-disazo-iron complex was obtained, as represented by the following chemical formula (39DD).

[0199] [ka]

[0200] The absorbance, electrical conductivity, and alkali metal ion content of azo iron complex dye B-2 were measured in the same manner as azo iron complex dye A-1. When azo iron complex dye B-2 was dissolved at a concentration of 5%, it exhibited a sufficiently black color. However, azo iron complex dye B-2 had poor dissolution stability, and precipitates were observed after leaving it to stand overnight (8 hours). Furthermore, the electrical conductivity K of azo iron complex dye B-2 immediately after dissolution was 165 μS / cm, and the alkali metal ion content was less than 1000 ppm.

[0201] (Comparative Example 3: Azo Iron Complex Dye B-3) Five parts by mass of the azo iron complex dye B-1 obtained in Comparative Example 1 and five parts by mass of the azo iron complex dye B-2 obtained in Comparative Example 2 were ground and mixed using a laboratory mini blender (manufactured by AS ONE Corporation) to obtain 9.9 g of azo iron complex dye B-3, which is a mixture of azo iron complex dye B-1 and azo iron complex dye B-2.

[0202] The absorbance, electrical conductivity, and alkali metal ion content of azo iron complex dye B-3 were measured in the same manner as for azo iron complex dye A-1. A solution containing azo iron complex dye B-3 at a concentration of 5% exhibited a reddish-black color. The electrical conductivity K of azo iron complex dye B-1 was 979 μS / cm, and the alkali metal ion content was less than 1000 ppm.

[0203] (Comparison of visible absorption spectra) The visible absorption spectra of the azo iron complex dye A-1 obtained in Example 1 and the azo iron complex dyes B-1 to B-3 obtained in Comparative Examples 1 to 3 are shown in Figure 8. The visible absorption spectrum of the azo iron complex dye B-1 is stronger than that of the azo iron complex dye A-1 in the range of 400 nm to 550 nm, indicating that the azo iron complex dye B-1 exhibits a strong reddish hue.

[0204] The visible absorption spectrum of the azo iron complex dye B-2 shows strong absorption in the long wavelength region, particularly above 550 nm, which indicates that the azo iron complex dye B-2 exhibits a strong blue hue.

[0205] The visible absorption spectrum of azo iron complex dye B-3 was almost identical to that of azo iron complex dye A-1. However, as mentioned above, azo iron complex dye A-1 exhibited a practically sufficient black color, while azo iron complex dye B-3 exhibited a reddish black color. A detailed comparison of the two spectra revealed that the visible absorption spectrum of azo iron complex dye B-3 was higher than that of azo iron complex dye A-1 in the 400-550 nm range, but the absorbance in the 600-650 nm range was comparable. This indicates that the MD isomers contained only in azo iron complex dye A-1 contribute significantly to the black color.

[0206] (Confirmation of the composition of azo iron complex dye) The azo iron complex dyes A-1 to A-7 to which the present invention is applied contain at least three types of azo iron complexes: DM, DD, and MM. The relative abundance ratios (molar ratios) of these in the azo iron complex dyes can be determined from the peak area ratios in the chromatogram obtained by measurement at a specific wavelength using high-performance liquid chromatography (HPLC; Shimadzu Corporation, Prominence). For the azo iron complex dyes A-1 to C-6 obtained in Examples 1 to 7 and the azo iron complex dye B-1 obtained in Comparative Examples 1 to 3, 1 mg of each azo iron complex dye was dissolved in 10 ml of dimethylformamide solution and measured under the following measurement conditions. The results are shown in Table 4. High-performance liquid chromatography: Column: L-COLUMN ODS2 4.6 x 250 mm, 5 μm Column temperature: 40℃ Mobile phase: Solution A: Tetrahydrofuran (HPLC grade, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) / acetonitrile (manufactured by the same company) = 3 / 2 Solution B: ultrapure water / 10 mM tetraethylammonium (Waters) = 500 / 7.5 Gradient: Solution A / Solution B 50:50 → 70:30 Measurement wavelength: UV at 254nm

[0207] [Table 4]

[0208] (Solubility evaluation) Azo iron complex dyes A-1 to A-7 obtained in Examples 1 to 7 and azo iron complex dyes B-1 to B-3 obtained in Comparative Examples 1 to 3 were added to methyl ethyl ketone and ethanol, respectively, to prepare azo iron complex dye solutions at concentrations of 5%, 10%, 15%, and 20%, and ultrasonically dispersed for 10 minutes. The azo iron complex dye solutions were then vacuum filtered through a membrane filter (pore size 1 μm, PTFE). The concentration at which no undissolved matter remained on the membrane filter was determined to be the maximum azo iron complex dye concentration. The hue of the 5% azo iron complex dye solution in methyl ethyl ketone was also visually observed. The results are shown in Table 5.

[0209] [Table 5]

[0210] By applying the present invention, the azo iron complex dyes of the examples, which essentially contain a disazo-monoazo iron complex, exhibited a practical black hue in a 5% methyl ethyl ketone solution. In particular, azo iron complex dyes A-1, A-2, and A-6, in which the disazo ligand has a cyano group and the monoazo ligand has a nitro group, respectively, exhibited high solubility in both methyl ethyl ketone and ethanol. Azo iron complex dye A-5, in which the disazo ligand has a sulfoamide group and the monoazo ligand has a nitro group, respectively, and azo iron complex dye A-7, in which the disazo ligand and the monoazo ligand have sulfoamide groups, exhibited slightly lower electrical conductivity and a slightly redder hue, but exhibited very high solubility in both methyl ethyl ketone and ethanol. The azo iron complex dye A-3, in which the monoazo ligand has chlorine as a substituent, showed low solubility in ethanol, but high solubility in methyl ethyl ketone at 10%, which is higher than the practical concentration of 6%.

[0211] In a comparative example outside the scope of the present invention, azo iron complex dye B-1, consisting solely of a monoazo-monoazo iron complex, exhibited good solubility but exhibited a reddish-brown hue rather than black. Azo iron complex dye B-2, consisting solely of a disazo-disazo iron complex, exhibited a practically acceptable black color but exhibited low solubility in both methyl ethyl ketone and ethanol. Furthermore, it exhibited poor solubility stability in ethanol, and precipitates were observed when an ethanol solution of azo iron complex dye B-2 was allowed to stand for approximately 10 minutes. A methyl ethyl ketone solution of azo iron complex dye B-3, which was a simple mixture of azo iron complex dye B-1 consisting solely of a monoazo-monoazo iron complex and azo iron complex dye B-2 consisting solely of a disazo-disazo iron complex, exhibited only a reddish black color, and precipitates were observed when the ethanol solution was allowed to stand for approximately 10 minutes.

[0212] (Ink Example 1) Six parts by mass of a cellulose-based resin, one part by mass of lithium nitrate, and three parts by mass of azo iron complex dye A-1 were added to 70 parts by mass of methyl ethyl ketone, 10 parts by mass of ethanol, and 10 parts by mass of isopropyl alcohol, and the mixture was stirred and dissolved. The mixed solution was then filtered through a 1.0 μm filter to obtain the ink composition of Example 1. This ink composition was filled into an ink cartridge, and printed using an inkjet printer to obtain a black print. The print was a deep black with no fading. Based on this, the print density and ink ejection stability of the ink composition of Ink Example 1 were evaluated to be good.

[0213] (Ink Example 2) An ink composition of Ink Example 2 was obtained in the same manner as Ink Example 1, except that azo iron complex dye A-2 was used instead of azo iron complex dye A-1. Using this ink composition, a black print was obtained in the same manner as Ink Example 1. The print was a deep black with no fading. From this, the print density and ink ejection stability of the ink composition of Ink Example 2 were evaluated to be good.

[0214] (Ink Example 3) An ink composition of Ink Example 3 was obtained in the same manner as Ink Example 1, except that azo iron complex dye A-5 was used instead of azo iron complex dye A-1. Using this ink composition, a black print was obtained in the same manner as Ink Example 1. The print was a deep black with no fading. From this, the print density and ink ejection stability of the ink composition of Ink Example 3 were evaluated to be good.

[0215] (Ink Example 4) An ink composition of Ink Example 4 was obtained in the same manner as Ink Example 1, except that azo iron complex dye A-6 was used instead of azo iron complex dye A-1 and 0.5 parts by mass of triethanolamine was added as a pH adjuster. A black print was obtained using this ink composition in the same manner as Ink Example 1. The print was a deep black with no fading. Based on this, the print density and ink ejection stability of the ink composition of Ink Example 4 were evaluated to be good.

[0216] (Ink comparison example 1) An ink composition of Comparative Ink 1 was obtained in the same manner as Ink Example 1, except that azo iron complex dye B-1 was used instead of azo iron complex dye A-1. When this ink composition was used to print on a print medium in the same manner as Ink Example 1, a light brown print with no hiding power was obtained.

[0217] (Comparative Ink Example 2) An ink composition of Comparative Ink 2 was obtained in the same manner as Ink Example 1, except that azo iron complex dye B-2 was used instead of azo iron complex dye A-1. However, this ink composition produced a precipitate after standing for about 10 minutes. This precipitate was removed by filtration. When the ink composition was used to print on a print medium in the same manner as Ink Example 1, a light black print was obtained.

[0218] (Comparative Ink Example 3) An ink composition of Comparative Ink 3 was obtained in the same manner as Ink Example 1, except that azo iron complex dye B-3 was used instead of azo iron complex dye A-1. When this ink composition was used to print on a print medium in the same manner as Ink Example 1, a light brown print with no hiding power was obtained. [Industrial Applicability]

[0219] The azo iron complex dye of the present invention and the ink composition containing the same are used as inks for ink jet printers, writing instruments, and recorders. The method for producing the azo iron complex dye of the present invention is used to produce the azo iron complex.

Claims

1. The following chemical formula (1) 【Chemistry 1】 (In chemical formula (1), R １ and R ２ are each independently a linear or branched alkyl group having 3 to 10 carbon atoms, and R ３ is an electron-withdrawing group selected from a cyano group, a nitro group, an acetyl group, a sulfoamide group, and a halogen atom, and is bonded to the para position of the azo group on the same aromatic ring; R ４ is a linear or branched alkyl group having 1 to 5 carbon atoms or a linear or branched alkoxy group having 1 to 5 carbon atoms, and R ５ is a nitro group, a sulfoamide group, or a halogen atom, and R ６ is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, a nitro group, or a halogen atom; R ７ is a hydrogen atom or a linear or branched alkyl group having 3 to 12 carbon atoms, and A ＋ is a monovalent cation.

2. The R ３ is the electron-withdrawing group selected from the group consisting of the cyano group, the nitro group, the acetyl group, the sulfonamide group, and the halogen atom selected from the group consisting of a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

3. The following chemical formula (2) 【Chemistry 2】 (In chemical formula (2), R ５ ~R ７ and A ＋ is the same as chemical formula (1).

4. The following chemical formula (3) 【Transformation 3】 (In chemical formula (3), R １ ~R ４ and A ＋ is the same as chemical formula (1).

5. The monovalent cation is selected from alkali metal ions, ammonium ions, and cations represented by the following chemical formula (4): 【Chemistry 4】 (In chemical formula (4), R ８ is a linear or branched alkyl group having 1 to 18 carbon atoms; R ９ and R １０ are each independently a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms.

6. The azo iron complex dye according to claim 4, wherein the disazo-monoazo iron complex, the monoazo-monoazo iron complex, and the disazo-disazo iron complex have peak area ratios of 20-70:5-80:0-50 in chromatograms obtained by measurement at a wavelength of 254 nm by high performance liquid chromatography, respectively.

7. An ink composition comprising the azo iron complex dye according to claim 1 and an organic solvent.

8. 8. The ink composition according to claim 7, which is for use in an ink jet printer.

9. The following chemical formula (5) 【Transformation 5】 (In chemical formula (5), R １ and R ２ are each independently a linear or branched alkyl group having 3 to 10 carbon atoms, and R ３ is an electron-withdrawing group selected from a cyano group, a nitro group, an acetyl group, a sulfoamide group, and a halogen atom, and is bonded to the para position of the azo group on the same aromatic ring; R ４ is a linear or branched alkyl group having 1 to 5 carbon atoms or a linear or branched alkoxy group having 1 to 5 carbon atoms; and a disazo dye represented by the following chemical formula (6): 【Transformation 6】 (In chemical formula (6), R ５ is a nitro group, a sulfoamide group, or a halogen atom, and R ６ is a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, a nitro group, or a halogen atom; R ７ is a hydrogen atom or a linear or branched alkyl group having 3 to 12 carbon atoms; and an iron-complexing step of heating a monoazo dye represented by the formula (I) with an iron-complexing agent in a solvent to obtain an azo-iron complex anion; and an ion exchange step of reacting the azo iron complex anion with an alkali metal solution and / or an ammonium compound to introduce a cation to be combined with the azo iron complex anion, thereby obtaining a compound represented by the following chemical formula (1). 【Transformation 7】 (In chemical formula (1), R １ ~R ４ is the same as chemical formula (5), and R ５ ~R ７ is the same as chemical formula (6), and A ＋ is a monovalent cation.

10. 10. The method for producing an azo iron complex dye according to claim 9, wherein in the iron complex formation step, the disazo dye and the monoazo dye are mixed in a molar ratio of 2:8 to 8:2.

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